U.S. patent application number 16/998773 was filed with the patent office on 2021-02-25 for anodes for lithium-based energy storage devices.
This patent application is currently assigned to Graphenix Development, Inc.. The applicant listed for this patent is Graphenix Development, Inc.. Invention is credited to John C. Brewer, Paul D. Garman, Kevin Tanzil.
Application Number | 20210057755 16/998773 |
Document ID | / |
Family ID | 1000005060252 |
Filed Date | 2021-02-25 |
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United States Patent
Application |
20210057755 |
Kind Code |
A1 |
Brewer; John C. ; et
al. |
February 25, 2021 |
ANODES FOR LITHIUM-BASED ENERGY STORAGE DEVICES
Abstract
An anode for a lithium-based energy storage device such as a
lithium-ion battery is disclosed. The anode includes a current
collector having an electrically conductive layer and a surface
layer overlaying the electrically conductive layer. A lithium
storage layer is overlaying the surface layer and the surface layer
includes a metal chalcogenide having at least one of sulfur or
selenium. The metal chalcogenide may include a metal sulfide, a
metal polysulfide, a metal selenide, a metal polyselenide, or a
combination thereof. The metal chalcogenide may include a copper
sulfide or a copper polysulfide. The lithium storage may include a
total content of silicon, germanium, or a combination thereof of at
least 40 atomic %. The lithium storage layer may be a continuous
porous lithium storage layer having an average density from about
1.1 g/cm.sup.3 to about 2.25 g/cm.sup.3 and comprises at least 85
atomic % amorphous silicon.
Inventors: |
Brewer; John C.; (Rochester,
NY) ; Garman; Paul D.; (Pittsford, NY) ;
Tanzil; Kevin; (Rochester, NY) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
Graphenix Development, Inc. |
Williamsville |
NY |
US |
|
|
Assignee: |
Graphenix Development, Inc.
Williamsville
NY
|
Family ID: |
1000005060252 |
Appl. No.: |
16/998773 |
Filed: |
August 20, 2020 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
62889950 |
Aug 21, 2019 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/0565 20130101;
H01M 2300/0085 20130101; H01M 4/5815 20130101; H01M 2300/0082
20130101; H01M 4/0428 20130101; H01M 4/366 20130101; H01M 10/0568
20130101; H01M 10/0569 20130101; H01M 4/667 20130101; H01M 10/0525
20130101; H01M 2300/0028 20130101; H01M 4/48 20130101 |
International
Class: |
H01M 4/66 20060101
H01M004/66; H01M 10/0525 20060101 H01M010/0525; H01M 4/58 20060101
H01M004/58; H01M 4/36 20060101 H01M004/36; H01M 4/48 20060101
H01M004/48; H01M 4/04 20060101 H01M004/04; H01M 10/0568 20060101
H01M010/0568; H01M 10/0565 20060101 H01M010/0565; H01M 10/0569
20060101 H01M010/0569 |
Claims
1. An anode for an energy storage device comprising: a current
collector comprising an electrically conductive layer and a surface
layer overlaying the electrically conductive layer; and a lithium
storage layer overlaying the surface layer, wherein the surface
layer comprises a metal chalcogenide comprising at least one of
sulfur or selenium.
2. The anode of claim 1, wherein the metal chalcogenide comprises a
metal sulfide, a metal polysulfide, a metal selenide, or a metal
polyselenide.
3. The anode of claim 1, wherein the metal chalcogenide comprises a
transition metal sulfide, a transition metal polysulfide, a
transition metal selenide, or a transition metal polyselenide.
4. The anode of claim 3, wherein the transition metal is
copper.
5. The anode of claim 1, wherein the metal chalcogenide comprises a
copper sulfide or a copper polysulfide.
6. The anode of claim 1, wherein the surface layer further
comprises a metal oxide.
7. The anode of claim 1, wherein the surface layer comprises a
first sublayer overlaying the electrically conductive layer and a
second sublayer overlaying the first sublayer.
8. The anode of claim 7, wherein the first sublayer comprises at
least one of sulfur or selenium and the second sublayer comprises a
metal oxide.
9. The anode of claim 8, wherein the first sublayer comprises a
copper sulfide or a copper polysulfide.
10. The anode of claim 9, wherein the second sublayer comprises an
oxide of copper, an oxide of nickel, an oxide of titanium, or an
oxide of zinc.
11. The anode of claim 1, wherein the surface layer has an average
thickness in a range of 0.1 to 5.0 .mu.m.
12. The anode of claim 1, wherein the electrically conductive layer
comprises nickel, copper, stainless steel, titanium, conductive
carbon, or a combination thereof.
13. The anode of claim 1, wherein the lithium storage layer is a
continuous porous lithium storage layer.
14. The anode of claim 13, wherein the continuous porous lithium
storage layer has a total content of silicon, germanium, or a
combination thereof of at least 40 atomic %.
15. The anode of claim 13, wherein the continuous porous lithium
storage layer includes less than 10 atomic % carbon.
16. The anode of claim 13, wherein the continuous porous lithium
storage layer is substantially free of nanostructures.
17. The anode of claim 13, wherein the continuous porous lithium
storage layer has an average thickness from 4 .mu.m to 30
.mu.m.
18. The anode of claim 13, wherein the continuous porous lithium
storage layer comprises at least 85 atomic % amorphous silicon and
has a density in a range of 1.1 g/cm.sup.3 to 2.2 g/cm.sup.3.
19. A battery comprising the anode of claim 1 and a cathode.
20. The battery of claim 19, wherein the anode is prelithiated and
the cathode comprises sulfur, selenium, or both sulfur and
selenium.
Description
CROSS REFERENCE TO RELATED APPLICATION
[0001] This application claims the benefit of priority of U.S.
Provisional Application No. 62/889,950, filed Aug. 21, 2019, which
is incorporated herein by reference in its entirety for all
purposes.
TECHNICAL FIELD
[0002] The present disclosure relates to lithium ion batteries and
related energy storage devices.
BACKGROUND
[0003] Silicon has been proposed as a potential material for
lithium-ion batteries to replace the conventional carbon-based
anodes which have a storage capacity that is limited to .about.370
mAh/g. Silicon readily alloys with lithium and has a much higher
theoretical storage capacity (.about.3600 to 4200 mAh/g at room
temperature) than carbon-based anodes. However, insertion and
extraction of lithium into the silicon matrix causes significant
volume expansion (>300%) and contraction. This can result in
rapid pulverization of the silicon into small particles and
electrical disconnection from the current collector.
[0004] The industry has recently turned its attention to nano- or
micro-structured silicon to reduce the pulverization problem, i.e.,
silicon in the form of spaced apart nano- or micro-wires, tubes,
pillars, particles and the like. The theory is that making the
structures nano-sized avoids crack propagation and spacing them
apart allows more room for volume expansion, thereby enabling the
silicon to absorb lithium with reduced stresses and improved
stability compared to, for example, macroscopic layers of bulk
silicon.
[0005] Despite research into structured silicon approaches, such
batteries based solely on silicon have yet to make a large market
impact due to unresolved problems. A significant issue is the
manufacturing complexity and investment required to form these
anodes. For example, US 2015/0325852 describes silicon made by
first growing a silicon-based, non-conformal, porous layer on a
nanowire template by plasma-enhanced chemical vapor deposition
(PECVD) followed by deposition of a denser, conformal silicon layer
using thermal chemical vapor deposition (CVD). Formation of silicon
nanowires can be very sensitive to small perturbations in
deposition conditions making quality control and reproducibility a
challenge. Other methods for forming nano- or micro-structured
silicon use etching of silicon wafers, which is time-consuming and
wasteful. Further, the connection between silicon wires to a
current collector may be fragile and the structures may be prone to
break or abrade away when subjected to handling stresses needed to
manufacture a battery.
SUMMARY
[0006] There remains a need for anodes for lithium-based energy
storage devices such as Li-ion batteries that are easy to
manufacture, robust to handling, high in charge capacity, and
amenable to fast charging, for example, at least 1 C. These and
other needs are addressed by the embodiments described herein.
[0007] In accordance with an embodiment of this disclosure, an
anode for an energy storage device is provided that includes a
current collector having an electrically conductive layer and a
surface layer overlaying the electrically conductive layer; and a
lithium storage layer overlaying the surface layer, where the
surface layer includes a metal chalcogenide including at least one
of sulfur or selenium.
[0008] The present disclosure provides anodes for energy storage
devices that may have one or more of at least the following
advantages relative to conventional anodes: improved stability at
aggressive .gtoreq.1 C charging rates; higher overall areal charge
capacity; higher charge capacity per gram of silicon; improved
physical durability; simplified manufacturing process; and more
reproducible manufacturing process.
BRIEF DESCRIPTION OF DRAWINGS
[0009] FIG. 1 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0010] FIG. 2 is a cross-sectional view of a prior art anode having
nanostructures.
[0011] FIG. 3 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0012] FIG. 4 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0013] FIG. 5 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0014] FIG. 6 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0015] FIG. 7 is a cross-sectional view of an anode according to
some embodiments of the present disclosure.
[0016] FIG. 8 is a process flow diagram for preparing anodes
according to some embodiments of the present disclosure.
[0017] FIG. 9A is a schematic of apparatuses for roll-to-roll
processing of anodes according to some embodiments of the present
disclosure.
[0018] FIG. 9B is a schematic of apparatuses for roll-to-roll
processing of anodes according to another embodiment of the present
disclosure.
[0019] FIG. 10 is a cross-sectional view of a battery according to
some embodiments of the present disclosure.
[0020] FIG. 11 is a cross-sectional SEM of an anode according to
some embodiments of the present disclosure.
[0021] FIG. 12 show cycling performance data for an anode according
to some embodiments of the present disclosure.
[0022] FIG. 13 show cycling performance data for an anode according
to some embodiments of the present disclosure.
[0023] FIG. 14 show cycling performance data for an anode according
to some embodiments of the present disclosure.
DETAILED DESCRIPTION
[0024] It is to be understood that the drawings are for purposes of
illustrating the concepts of the disclosure and may not be to
scale. Various aspects of anodes of the present disclosure,
including deposition of lithium storage material, additional layers
and methods are described in co-pending U.S. patent application
Ser. Nos. 16/285,842, 16/909,008, 16/991,613, 16/991,623, and
16/991,626, the entire contents of which are incorporated by
reference for all purposes.
[0025] Anode Overview
[0026] FIG. 1 is a cross-sectional view according to some
embodiments of the present disclosure. Anode 100 includes an
electrically conductive current collector 101 and a lithium storage
layer 107. In this embodiment, the electrically conductive current
collector 101 includes a surface layer 105 provided over an
electrically conductive layer 103. In some embodiments, as
discussed later, the surface layer 105 may include a metal
chalcogenide material having at least one of sulfur or selenium,
optionally both sulfur and selenium. In some embodiments, the
electrically conductive layer 103 may be an electrically conductive
metal layer. The lithium storage layer 107 may be provided over
surface layer 105. In some embodiments, the top surface 108 of the
lithium storage layer 107 may corresponds to a top surface of anode
100. In some embodiments the lithium storage layer 107 is in
physical contact with the surface layer 105. In some embodiments,
the active material of the lithium storage layer may extend
partially into the surface layer. In some embodiments the
continuous porous lithium storage layer includes a material capable
of forming an electrochemically reversible alloy with lithium. In
some embodiments, the lithium storage layer is a continuous and/or
porous lithium storage layer (e.g., a continuous porous lithium
storage layer, discussed in more detail later). In some
embodiments, the lithium storage layer, optionally a continuous
and/or porous lithium storage layer, may include silicon,
germanium, tin, or alloys thereof. In some embodiments the lithium
storage layer, optionally a continuous and/or porous lithium
storage layer, includes at least 40 atomic % silicon, germanium, or
a combination thereof. In some embodiments, the lithium storage
layer, optionally a continuous and/or porous lithium storage layer,
may be provided by a chemical vapor deposition (CVD) process
including, but not limited to, a hot-wire CVD, or a plasma-enhanced
chemical vapor deposition (PECVD). In some embodiments, the CVD
lithium storage layer deposition may reduce a portion of the
surface layer to form metal. In some embodiments, the lithium
storage layer, optionally a continuous and/or porous lithium
storage layer may be provided by a physical vapor deposition (PVD)
process including but not limited to sputtering, e-beam, and
evaporation methods.
[0027] In the present disclosure, the lithium storage layer is
substantially free of nanostructures, e.g., in the form of
spaced-apart wires, pillars, tubes or the like, or in the form of
regular, linear vertical channels extending through the lithium
storage layer. FIG. 2 shows a cross-sectional view of a prior art
anode 170 that includes some non-limiting examples of
nanostructures, such as nanowires 190, nanopillars 192, nanotubes
194 and nanochannels 196 provided over a current collector 180. The
term "nanostructure" herein generally refers to an active material
structure (for example, a structure of silicon, germanium or their
alloys) having at least one cross-sectional dimension that is less
than about 2,000 nm, other than a dimension approximately normal to
an underlying substrate (such as a layer thickness) and excluding
dimensions caused by random pores and channels. Similarly, the
terms "nanowires", "nanopillars" and "nanotubes" refers to wires,
pillars and tubes, respectively, at least a portion of which, have
a diameter of less than 2,000 nm. "High aspect ratio"
nanostructures have an aspect ratio greater than 4:1, where the
aspect ratio is generally the height or length of a feature (which
may be measured along a feature axis aligned at an angle of 45 to
90 degrees relative to the underlying current collector surface)
divided by the width of the feature (which may be measured
generally orthogonal to the feature axis). In some embodiments, the
lithium storage layer is considered "substantially free" of
nanostructures when the anode has an average of fewer than 10
nanostructures per 1600 square microns (in which the number of
nanostructures is the sum of the number of nanowires, nanopillars,
and nanotubes in the same unit area), such nanostructures having an
aspect ratio of 4:1 or higher. Alternatively, there is an average
of fewer than 1 such nanostructures per 1600 square micrometers. In
some embodiments, the current collector may have a high surface
roughness or the surface layer may include nanostructures, but
these features are separate from the lithium storage layer.
[0028] In some embodiments, deposition conditions are selected in
combination with the surface layer so that the lithium storage
layers are relatively smooth providing an anode with diffuse or
total reflectance of at least 10% at 550 nm, alternatively at least
20% (measured at the lithium storage layer side). In some
embodiments, the anode may have lower reflectance than cited above,
for example, by providing a current collector having a rough
surface or by modifying deposition conditions of the lithium
storage layer.
[0029] The anode can be a continuous foil or sheet but may
alternatively be a mesh or have some other 3-dimensional structure.
In some embodiments, the anode is flexible.
[0030] In some embodiments as shown in FIG. 3, the current
collector 301 includes electrically conductive layer 303 and
surface layers (305a, 305b) deposited on either side of the
electrically conductive layer 303 and lithium storage layers (307a,
307b) are disposed on both sides to form anode 300. Surface layers
305a and 305b may be the same or different with respect to
composition, thickness, porosity, or some other property.
Similarly, lithium storage layers 307a and 307b may be the same or
different with respect to composition, thickness, porosity, or some
other property.
[0031] In some embodiments, the current collector has a mesh
structure and a representative cross section is shown in FIG. 4.
Current collector 401 includes surface layer 405 substantially
surrounding the inner, electrically conductive core 403, e.g., a
wire forming part of the mesh, the core acting as an electrically
conductive layer. A continuous porous lithium storage layer 407 is
provided over the surface layer to form anode 400. The mesh can be
formed from interwoven wires or ribbons of metal or conductive
carbon, formed by patterning holes into a substrate, e.g., a metal
or metal-coated sheet, or any suitable method known in the art.
[0032] Current Collector Current collector (101, 301, 401) includes
at least one surface layer (105, 305, 405), and may further include
a separate electrically conductive layer (103, 303, 403). In some
embodiments, the electrically conductive layer includes a metallic
material, e.g., titanium (and its alloys), nickel (and its alloys),
copper (and its alloys), or stainless steel. In some embodiments,
the electrically conductive layer includes an electrically
conductive carbon, such as carbon black, graphene, graphene oxide,
and graphite. In some embodiments the electrically conductive layer
may be in the form of a foil or sheet of conductive material, or
alternatively a layer deposited onto an insulating substrate. In
some embodiments the electrically conductive layer may have a
conductivity of at least 10.sup.3 S/m, or alternatively at least
10.sup.6 S/m, or alternatively at least 10.sup.7 S/m, and may
include inorganic or organic conductive materials or a combination
thereof.
[0033] In some embodiments, the electrically conductive layer has
an average thickness of at least 0.1 .mu.m, alternatively at least
1 .mu.m, alternatively at least 5 .mu.m. In some embodiments, the
electrically conductive substrate has an average thickness in a
range of 0.1 .mu.m to 1 .mu.m, alternatively 1 .mu.m to 2 .mu.m,
alternatively 2 .mu.m to 5 .mu.m, alternatively 5 .mu.m, to 10
.mu.m, alternatively 10 .mu.m to 15 .mu.m, alternatively 15 .mu.m
to 20 .mu.m, alternatively 20 .mu.m to 30 .mu.m, alternatively 30
.mu.m to 50 .mu.m, alternatively 50 .mu.m to 100 .mu.m, or any
combination of contiguous ranges thereof.
[0034] The metal chalcogenide material includes at least one of
sulfur or selenium, and in some embodiments may include both. The
metal chalcogenide material may include a metal sulfide, a metal
polysulfide, a metal selenide, or a metal polyselenide, or a
mixture thereof. A metal sulfide may generally refer to a compound
where the metal is associated with a sulfur atom in the form of
S.sup.2-. A metal polysulfide may generally refer to a compound
where the metal is associated with a chain of sulfur atoms in the
form of S.sub.n.sup.2 where n.gtoreq.2. Similarly, a metal selenide
may generally refer to a compound where the metal is associated
with a selenium atom in the form of Se'. A metal polyselenide may
generally refer to a compound wherein the metal is associated with
a chain of selenium atoms in the form of Se.sub.n.sup.2- where
n.gtoreq.2. In some embodiments, metal chalcogenides may have
complex structures. In some embodiments, the metal chalcogenide may
include a mixture of sulfur- and selenium-containing moieties. In
the present disclosure, a surface layer may be considered to
include: a metal sulfide so long as it includes a metal and least
one identifiable S.sup.2- species; or a metal selenide so long as
it includes a metal and at least one identifiable Se.sup.2-
species; or a metal polysulfide so long as it includes a metal and
at least one identifiable S.sub.n.sup.2- species with n.gtoreq.2;
or a metal polyselenide so long as it includes a metal and at least
one identifiable Se.sub.n.sup.2- species with n.gtoreq.2. A metal
chalcogenide including (S.sub.mSe.sub.p).sup.2- where m and p are
each at least 1, may be referred to as either a metal polysulfide
or a polyselenide for the purposes of this disclosure.
[0035] The chalcogenide may include a stoichiometric or
non-stoichiometric mixture of elements with respect to the metal
oxidation state. The surface layer may include a mixture of metal
chalcogenides having homogeneously or heterogeneously distributed
sulfur or selenium, mixtures of metals, or mixtures of metal
oxidation states. In some embodiments, the metal chalcogenide
material may include a transition metal sulfide, a transition metal
polysulfide, a transition metal selenide, a transition metal
polyselenide, or mixture thereof. The transition metal may be a
single transition metal or a mixture of transition metals. In some
embodiments, the metal chalcogenide material may include at least
one of Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Zn, Ga, or In.
[0036] In some embodiments, the metal chalcogenide material may
include a copper sulfide, a copper polysulfide, a copper selenide,
a copper polyselenide, or a mixture thereof. The copper of the
metal chalcogenide material may have an oxidation state of (I),
(II), or a mixture of both. In some embodiments, the surface layer
may include a copper chalcogenide according to formula 1:
Cu.sub.x[S.sub.mSe.sub.p] (1)
where 1.ltoreq.x.ltoreq.2, (m+p).gtoreq.1, and the average
oxidation state of Cu=2/x. In some embodiments, a surface layer may
include a copper chalcogenide of formula (1) in addition to some
Cu(0) metal.
[0037] In some embodiments, the surface layer may further include
one or more metal oxides. The metal element of the metal oxide may
be the same as that of the metal chalcogenide or different. In some
embodiments, the metal oxide may be a transition metal oxide. In
some embodiments, the metal oxide may include one or more of Ti, V,
Cr, Mn, Fe, Co, Ni Cu, Zn, Ga, or In. In some embodiments, the
metal oxide may include lithium, optionally in addition to another
metal. In some embodiments, the surface layer may include a
homogeneous or heterogeneous mixture of one or more metal
chalcogenides with one or more metal oxides.
[0038] In some embodiments, the surface layer may include an
oxygen-containing copper chalcogenide having the formula 2:
Cu.sub.x[(S.sub.mSe.sub.p).sub.yO.sub.(1-y)] (2)
where 1.ltoreq.x.ltoreq.2, (m+p).gtoreq.1, 0<y<1, and the
average oxidation state of Cu=2/x.
[0039] In some embodiments, the surface layer may include two or
more sublayers differing in chemical compositions. In some
embodiments, the surface layer may include two or more sublayers,
at least one of which includes a metal chalcogenide having at least
one of sulfur or selenium. For example, as shown in FIG. 5, anode
500 is similar to anode 100 and includes an electrically conductive
current collector 501 and a lithium storage layer 507. The
electrically conductive current collector 501 includes surface
layer 505 provided over an electrically conductive layer 503.
Surface layer 505 includes a first surface sublayer 505a overlaying
the electrically conductive layer 503 and a second surface sublayer
505b overlaying the first surface sublayer 505a. The second surface
sublayer 505b is interposed between the first surface sublayer 505a
and the lithium storage layer 507 In some embodiments, at least one
surface sublayer includes a sulfur- or selenium-containing metal
chalcogenide and one surface sublayer includes a metal oxide, e.g.,
a transition metal oxide. In some embodiments, a first surface
sublayer 505a including a sulfur- or selenium-containing metal
chalcogenide is disposed in contact with the electrically
conductive layer 503 and a second surface sublayer 505b including a
metal oxide is provided over the first sublayer 505a and in contact
with the lithium storage layer 507. In some embodiments, the second
surface sublayer having the metal oxide is thinner than the first
surface sublayer. In some embodiments, the current collector may
include a metallic copper foil, and a surface layer may include a
first surface sublayer of a copper sulfide or a copper polysulfide
in contact with the copper foil and a second surface sublayer of
titanium dioxide over first sublayer. In some embodiments, the
first surface sublayer may include a metal oxide and the second
surface sublayer may include a metal chalcogenide having at least
one of sulfur or selenium.
[0040] In some embodiments, the surface layer may include a metal
chalcogenide wherein the metal includes a mixture of a transition
metal and lithium.
[0041] In embodiments using an electrically conductive layer, the
surface layer should be sufficiently electrically conductive (e.g.,
is at least semi-conducting, or non-insulating) to allow transfer
of electrical charge between the electrically conductive layer and
the lithium storage layer. The surface layer may include dopants
that promote electrical conductivity.
[0042] In some embodiments, the surface layer has an average
thickness of at least 0.002 .mu.m, alternatively at least 0.005
.mu.m, alternatively at least 0.010 .mu.m, alternatively at least
0.020 .mu.m, alternatively at least 0.050 .mu.m, alternatively 0.1
.mu.m, alternatively at least 0.2 .mu.m, alternatively at least 0.5
.mu.m. In some embodiments, the surface layer has an average
thickness in a range of about 0.002 .mu.m to about 10 .mu.m,
alternatively, in a range of about 0.002 .mu.m to about 0.010
.mu.m, alternatively, in a range of about 0.010 .mu.m to about
0.050 .mu.m, alternatively, in a range of about 0.005 .mu.m to
about 0.10 .mu.m, alternatively, in a range of about 0.10 .mu.m to
about 0.20 .mu.m, alternatively in a range of about 0.20 .mu.m to
about 0.50 .mu.m, alternatively, in a range of about 0.50 .mu.m to
about 1.0 .mu.m, alternatively, in a range of about 1.0 .mu.m to
about 2.0 .mu.m, alternatively, in a range of about 2.0 .mu.m to
about 5.0 .mu.m, alternatively, in a range of about 5.0 .mu.m to
about 10 .mu.m, or any combination of contiguous ranges
thereof.
[0043] In some embodiments, a surface sublayer that includes a
metal oxide may have an average thickness of at least 0.002 .mu.m,
alternatively at least 0.005 .mu.m, alternatively at least 0.010
.mu.m, alternatively at least 0.020 .mu.m, alternatively at least
0.050 .mu.m, alternatively 0.1 .mu.m, alternatively at least 0.2
.mu.m, alternatively at least 0.5 .mu.m. In some embodiments, the
surface sublayer that includes a metal oxide may have an average
thickness in a range of about 0.002 .mu.m to about 0.010 .mu.m,
alternatively, in a range of about 0.002 .mu.m to about 0.005
.mu.m, alternatively, in a range of about 0.005 .mu.m to about 0.01
.mu.m, alternatively, in a range of about 0.010 .mu.m to about
0.050 .mu.m, alternatively, in a range of about 0.050 .mu.m to
about 0.1 .mu.m, alternatively, in a range of about 0.1 .mu.m to
about 0.5 .mu.m, alternatively, in a range of about 0.5 .mu.m to
about 1.0 .mu.m, alternatively, in a range of about 1.0 .mu.m to
about 2.0 .mu.m, or any combination of contiguous ranges
thereof.
[0044] In some embodiments, the surface layer or sublayer is formed
directly by atomic layer deposition (ALD), CVD, evaporation, or
sputtering.
[0045] In some embodiments, the electrically conductive layer is a
metal layer and the surface layer may be formed by treating a
portion of the electrically conductive metal layer with an agent to
form the metal chalcogenide, wherein at least some of metal
chalcogenide includes the metal(s) of the electrically conductive
layer. In some non-limiting examples, the reagent may be applied:
a) as a vapor, e.g., vaporized sulfur; b) from a reduced pressure
system, e.g., sulfur from a sulfur-valved cracker (VCC) effusion
cell; c) from a solution, e.g., liver of sulfur solution, or a
solution including one or more of a polysulfide salt, a thiosulfate
salt, or a polyselenide salt; d) by contact with a reactive sulfur-
or selenium-containing solid; or) by electrochemical reaction in a
solution comprising a sulfur or selenium source. Treating may
further include a heating step.
[0046] In some embodiments, a metal oxide precursor layer is first
formed on the electrically conductive layer and then treated to
form the surface layer. The metal oxide precursor layer may include
a precursor that includes a metal oxide. The precursor may then be
converted to the metal chalcogenide. In some embodiments, the metal
oxide precursor layer may be formed by a PVD process, a CVD
process, or an ALD process. In some embodiments, the metal oxide
precursor layer may be formed by partial oxidation of the
electrically conductive (metal) layer, for example, by thermal
oxidation in air or chemical or electrochemical oxidation in a
solution. In some embodiments the metal oxide precursor layer may
be formed from a metal oxide precursor composition. Some
non-limiting examples of metal oxide precursor compositions include
sol-gels (metal alkoxides), metal carbonates, metal acetates
(including organic acetates), metal hydroxides and metal oxide
dispersions. The metal oxide precursor composition may be thermally
treated to form the metal oxide precursor layer. Some or all of the
metal oxide precursor layer may be treated to cause sulfurization
or selenization to form the metal chalcogenide material, for
example, a metal sulfide, a metal polysulfide, a metal selenide, or
a metal polyselenide. In some embodiments, treatment of the metal
oxide precursor layer includes treatment with a solution, e.g., one
including one or more of a sulfide salt, a polysulfide salt, a
thiosulfate salt, a selenide salt, or a polyselenide salt. Treating
may further include a heating step. In some embodiments, not all of
the metal oxide of the metal oxide precursor layer is converted and
the surface layer may further include some metal oxide.
[0047] In some embodiments, a surface layer precursor composition
may be coated or printed over the electrically conductive layer 103
then treated to form surface layer 105. A few non-limiting examples
of metal chalcogenide precursor compositions include sulfide- or
selenide-sols, and sulfur- or selenide-containing organometallic
compounds. Treating may further include a heating step.
[0048] In some embodiments as mentioned above, forming the metal
chalcogenide may include a thermal treatment. Such treatment may
include exposure to a temperature of at least 50.degree. C.,
alternatively in a range of 50.degree. C. to 150.degree. C.,
alternatively in a range of 150.degree. C. to 250.degree. C.,
alternatively in a range of 250.degree. C. to 350.degree. C.,
alternatively in a range of 350.degree. C. to 450.degree. C., or
any combination of these ranges. Thermal treatment time depends on
many factors, but may optionally be at least 0.1 minute,
alternatively in a range of 1 to 240 minutes, to form the desired
surface layer. In some embodiments, thermal treatment may be
carried out using an oven, a tube furnace, infrared heating
elements, contact with a hot plate or exposure to a flash lamp. In
some embodiments, treatment may include exposure to reduced
pressure to form the metal chalcogenide, e.g., to drive off
solvents or volatile reaction products. The reduced pressure may be
less than 100 Torr, alternatively in a range of 0.1 to 100 Torr.
Exposure time to the reduced pressure may optionally be at least
0.1 minute, alternatively in a range of 1 to 240 minutes. In some
embodiments, both reduced pressure and thermal treatment may be
used. In some embodiments, the reduced pressure or thermal
treatment may initiate chemical reactions, drive off solvents, or
remove reaction byproducts.
[0049] In some embodiments, the metal chalcogenide may be provided
in a pattern over the electrically conductive layer in a manner
analogous to that disclosed in U.S. patent application Ser. No.
16/909,008 for metal oxides, the entire contents of which are
incorporated herein.
[0050] The current collector may have an electrically conductive
layer that includes two or more sublayers differing in chemical
composition. For example, the current collector may include
metallic copper foil as a first electrically conductive sublayer
with a second electrically conductive sublayer of metallic nickel
provided over the copper, and a surface layer of a nickel
chalcogenide over the metallic nickel. As mentioned previously, the
metallic copper and nickel may be in the form of alloys.
Lithium Storage Layer
[0051] A lithium storage layer includes a material capable of
reversibly incorporating lithium. A lithium storage layer may be
porous. In some embodiments, a lithium storage layer may include
silicon, germanium, tin, antimony, or a combination thereof. In
some embodiments, a lithium storage layer is substantially
amorphous. In some embodiments a lithium storage layer includes
substantially amorphous silicon. Such substantially amorphous
storage layers may include a small amount (e.g., less than 20
atomic %) of crystalline material dispersed therein. A lithium
storage layer may include dopants such as hydrogen, boron,
phosphorous, sulfur, fluorine, aluminum, gallium, indium, arsenic,
antimony, bismuth, nitrogen, or metallic elements. In some
embodiments a lithium storage layer may include porous
substantially amorphous hydrogenated silicon (a-Si:H), having,
e.g., a hydrogen content of from 0.1 to 20 atomic %, or
alternatively higher. In some embodiments, a lithium storage layer
may include methylated amorphous silicon. Note that, unless
referring specifically to hydrogen content, any atomic % metric
used herein for a lithium storage material or layer refers to all
atoms other than hydrogen.
[0052] In some embodiments, a lithium storage layer includes at
least 40 atomic % silicon, germanium or a combination thereof,
alternatively at least 50 atomic %, alternatively at least 60
atomic %, alternatively at least 70 atomic %, alternatively, at
least 80 atomic %, alternatively at least 90 atomic %. In some
embodiments, a lithium storage layer includes at least 40 atomic %
silicon, alternatively at least 50 atomic %, alternatively at least
60 atomic %, alternatively at least 70 atomic %, alternatively, at
least 80 atomic %, alternatively at least 90 atomic %.
[0053] In some embodiments, a lithium storage layer includes less
than 10 atomic % carbon, alternatively less than 5 atomic %,
alternatively less than 2 atomic %, alternatively less than 1
atomic %. In some embodiments, a lithium storage layer includes
less than 5% by weight of carbon-based binders, graphitic carbon,
graphene, graphene oxide, reduced graphene oxide, carbon nanotubes,
carbon black, and conductive carbon.
[0054] In some embodiments, a lithium storage layer may be a porous
lithium storage layer that includes voids or interstices (pores),
which may be random or non-uniform with respect to size, shape and
distribution. Such porosity does not result in, or result from, the
formation of any recognizable nanostructures such as nanowires,
nanopillars, nanotubes, nanochannels or the like. In some
embodiments, the pores are polydisperse. In some embodiments, when
analyzed by SEM cross section, 90% of pores larger than 100 .mu.m
in any dimension are smaller than about 5 .mu.m in any dimension,
alternatively smaller than about 3 .mu.m, alternatively smaller
than about 2 .mu.m. In some embodiments, the lithium storage layer
may include some pores that are smaller than 100 .mu.m in any
dimension, alternatively smaller than 50 .mu.m in any dimension,
alternatively smaller than 20 .mu.m in any dimension. In some
embodiments the lithium storage layer has an average density in a
range of 1.0-1.1 g/cm.sup.3, alternatively 1.1-1.2 g/cm.sup.3,
alternatively 1.2-1.3 g/cm.sup.3, alternatively 1.3-1.4 g/cm.sup.3,
alternatively 1.4-1.5 g/cm.sup.3, alternatively 1.5-1.6 g/cm.sup.3,
alternatively 1.6-1.7 g/cm.sup.3, alternatively 1.7-1.8 g/cm.sup.3,
alternatively 1.8-1.9 g/cm.sup.3, alternatively 1.9-2.0 g/cm.sup.3,
alternatively 2.0-2.1 g/cm.sup.3, alternatively 2.1-2.2 g/cm.sup.3,
alternatively 2.2-2.25 g/cm.sup.3, or any combination of contiguous
ranges thereof, and includes at least 40 atomic % silicon,
alternatively at least 50 atomic % silicon, alternatively at least
60 atomic % silicon, alternatively at least 70 atomic % silicon,
alternatively 80 atomic % silicon, alternatively at least 90 atomic
% silicon, alternatively at least 95 atomic % silicon.
[0055] In some embodiments, the lithium storage layer may be a
continuous lithium storage layer. In some embodiments, the lithium
storage layer may be both continuous and porous (a continuous
porous lithium storage layer). The majority of active material
(e.g., silicon, germanium, tin, antimony, or alloys thereof) of a
continuous lithium storage layer has substantial lateral
connectivity across portions of the current collector, such
connectivity extending around random pores and interstices (in the
case of a continuous porous lithium storage layer). Referring again
to FIG. 1, in some embodiments, "substantial lateral connectivity"
means that active material at one point X in the continuous lithium
storage layer 107 may be connected to active material at a second
point X' in the layer at a straight-line lateral distance LD that
is at least as great as the thickness T of the continuous lithium
storage layer, alternatively, a lateral distance at least 2 times
as great as the thickness, alternatively, a lateral distance at
least 3 times as great as the thickness. Not shown, the total path
distance of material connectivity, including circumventing pores in
the case of a continuous porous lithium storage layer, may be
longer than LD. In some embodiments, the continuous lithium storage
layer may be described as a matrix of interconnected silicon,
germanium, or alloys thereof, and in the case of a continuous
porous lithium storage layer, with random pores and interstices
embedded therein. In some embodiments, the continuous porous
lithium storage layer has a sponge-like form. In some embodiments,
about 75% or more of the surface layer surface is contiguous with
the first lithium storage layer, at least prior to electrochemical
formation. It should be noted that a continuous lithium storage
layer does not necessarily extend across the entire anode without
any lateral breaks and may include random discontinuities or cracks
and still be considered continuous.
[0056] In some embodiments, the lithium storage layer, optionally a
continuous and/or porous lithium storage layer, includes a
sub-stoichiometric oxide of silicon (SiO.sub.x), germanium
(GeO.sub.x) or tin (SnO.sub.x) wherein the ratio of oxygen atoms to
silicon, germanium or tin atoms is less than 2:1, i.e., x<2,
alternatively less than 1:1, i.e., x<1. In some embodiments, x
is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10,
alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95,
alternatively 0.95 to 1.25, alternatively 1.25 to 1.50.
[0057] In some embodiments, the lithium storage layer, optionally a
continuous and/or porous lithium storage layer, includes a
sub-stoichiometric nitride of silicon (SiN.sub.y), germanium
(GeN.sub.y), or tin (SnN.sub.y) wherein the ratio of nitrogen atoms
to silicon, germanium or tin atoms is less than 1.25:1, i.e.,
y<1.25. In some embodiments, y is in a range of 0.02 to 0.95,
alternatively 0.02 to 0.10, alternatively 0.10 to 0.50, or
alternatively 0.50 to 0.95, alternatively 0.95 to 1.25.
[0058] In some embodiments, the lithium storage layer, optionally a
continuous and/or porous lithium storage layer, includes a
sub-stoichiometric oxynitride of silicon (SiO.sub.xN.sub.y),
germanium (GeO.sub.xN.sub.y), or tin (SnO.sub.xN.sub.y) wherein the
ratio of total oxygen and nitrogen atoms to silicon, germanium or
tin atoms is less than 1:1, i.e., (x+y)<1. In some embodiments,
(x+y) is in a range of 0.02 to 0.95, alternatively 0.02 to 0.10,
alternatively 0.10 to 0.50, or alternatively 0.50 to 0.95.
[0059] In some embodiments, the above sub-stoichiometric oxides,
nitrides, or oxynitrides may be provided by a CVD process,
including, but not limited to, a PECVD process. The oxygen and
nitrogen may be provided uniformly within the lithium storage
layer, or alternatively the oxygen or nitrogen content may be
varied as a function of storage layer thickness.
[0060] In some embodiments, the lithium storage layer may include
two or more sublayers, optionally continuous and/or porous lithium
storage sublayers. For example, referring to FIG. 6, the lithium
storage layer 607 of anode 600 may include a plurality of lithium
storage sublayers (607a and 607b) having different physical
properties or chemical compositions, and independently selected
from any of the embodiments discussed above. Anode 600 includes a
current collector 601 including surface layer 605 disposed over
electrically conductive layer 603. Lithium storage sublayer 607a is
disposed over surface layer 605 and lithium storage sublayer 607b
is disposed over lithium storage sublayer 607a. For example,
lithium storage sublayer 607a may include amorphous silicon with
low oxygen content and lithium storage sublayer 607b may include a
suboxide of silicon, SiO.sub.x, with x in a range of 0.02 to 0.95.
Alternatively, the compositions of 607a and 607b could be reversed.
In another example, lithium storage sublayer 607a may include
amorphous silicon with low germanium and lithium storage sublayer
607b includes a higher atomic % germanium than 607a. In some
embodiments, the sublayers may have different amounts or types of
dopants. In some other embodiments, lithium storage sublayers 607a
and 607b have similar chemical compositions, but the density of
607a is higher than 607b. These are just a few non-limiting
examples. In some embodiments, the second lithium storage layer
includes sublayers, or both the first and second lithium storage
layers include sublayers. Many other combinations are possible.
Although two sublayers are shown in FIG. 6, three or more sublayers
may instead be used. In some embodiments, the sublayers may have
different lithium storage capacities in units of mAh/g or
mAh/cm.sup.2. In some embodiments, lithium storage sublayer 607a
has a higher lithium storage capacity than the upper lithium
layer(s) such as lithium storage sublayer 607b. In some
embodiments, lithium storage sublayer 607a has a lower lithium
storage capacity than the upper lithium layer(s) such as lithium
storage sublayer 607b.
[0061] In some embodiments, the lithium storage layer, optionally a
continuous and/or porous lithium storage layer, includes a gradient
of components, density, or porosity, or a combination thereof, as a
function of layer thickness. For example, the lithium storage layer
may include amorphous silicon having a density higher near the
surface layer than further away from the surface layer, or vice
versa.
[0062] The thickness or mass per unit area of the lithium storage
layer (optionally continuous and/or porous) depends on the storage
material, desired charge capacity and other operational and
lifetime considerations. Increasing the thickness typically
provides more capacity. If the lithium storage layer becomes too
thick, electrical resistance may increase and the stability may
decrease. In some embodiments, the anode may be characterized as
having an active silicon areal density of at least 0.5 mg/cm.sup.2,
alternatively at least 1.0 mg/cm.sup.2, alternatively at least 1.5
mg/cm.sup.2, alternatively at least 3 mg/cm.sup.2, alternatively at
least 5 mg/cm.sup.2. In some embodiments, the lithium storage
structure may be characterized as having an active silicon areal
density in a range of 0.5-1.5 mg/cm.sup.2, alternatively 1.5-2
mg/cm.sup.2, alternatively in a range of 2-3 mg/cm.sup.2,
alternatively in a range of 3-5 mg/cm.sup.2, alternatively in a
range of 5-10 mg/cm.sup.2, alternatively in a range of 10-15
mg/cm.sup.2, alternatively in a range of 15-20 mg/cm.sup.2, or any
combination of contiguous ranges thereof. "Active areal silicon
density" refers to the silicon in electrical communication with the
current collector that is available for reversible lithium storage
at the beginning of cell cycling, e.g., after anode
"electrochemical formation" discussed later. "Areal" of this term
refers to the surface area of the electrically conductive layer
over which active silicon is provided. In some embodiments, not all
of the silicon content is active silicon, i.e., some may be tied up
in the form of non-active silicides or electrically isolated from
the current collector.
[0063] In some embodiments the lithium storage has an average
thickness of at least 0.5 .mu.m, alternatively at least 1 .mu.m,
alternatively at least 3 .mu.m, alternatively at least 7 .mu.m. In
some embodiments, the lithium storage layer (optionally continuous
and/or porous) has an average thickness in a range of about 0.5
.mu.m to about 50 .mu.m. In some embodiments, the lithium storage
layer (optionally continuous and/or porous) comprises at least 85
atomic % amorphous silicon and has a thickness in a range of 0.5 to
1 .mu.m, alternatively 1-2 .mu.m, alternatively 2-4 .mu.m,
alternatively 4-7 .mu.m, alternatively 7-10 .mu.m, alternatively
10-15 .mu.m, alternatively 15-20 .mu.m, alternatively 20-25 .mu.m,
alternatively 25-30 .mu.m, alternatively 30-40 .mu.m, alternatively
40-50 .mu.m, or any combination of contiguous ranges thereof.
[0064] In some embodiments, the lithium storage layer (optionally
continuous and/or porous) includes silicon but does not contain a
substantial amount of crystalline silicides, i.e., the presence of
silicides is not readily detected by X-Ray Diffraction (XRD). Metal
silicides, e.g., nickel silicide, commonly form when silicon is
deposited at higher temperatures directly onto metal, e.g., nickel
foil. Metal silicides such as nickel silicides often have much
lower lithium storage capacity than silicon itself. In some
embodiments, the average atomic % of silicide-forming metallic
elements within the lithium storage layer are on average less than
35%, alternatively less than 20%, alternatively less than 10%,
alternatively less than 5%. In some embodiments, the average atomic
% of silicide-forming metallic elements within the lithium storage
layer are in a range of about 0.01% to about 10%, alternatively
about 0.05 to about 5%. In some embodiments, the atomic % of
silicide forming metallic elements in the lithium storage layer is
higher nearer the current collector than away from the current
collector.
[0065] Additional Lithium Storage Layers
[0066] The generally planar nature of some embodiments of the
present anode further allows simple coating of additional lithium
storage layers that are not continuous porous lithium storage
layers as described herein. For example, conventional lithium-ion
battery slurries based on carbon that may optionally further
include silicon particles, may be coated over the continuous porous
lithium storage layer of the present disclosure to further enhance
charge capacity. Coating methods may include curtain coating, slot
coating, spin coating, ink jet coating, spray coating or any other
suitable method.
CVD
[0067] CVD generally involves flowing a precursor gas, a gasified
liquid in terms of direct liquid injection CVD or gases and liquids
into a chamber containing one or more objects, typically heated, to
be coated. Chemical reactions occur on and near the hot surfaces,
resulting in the deposition of a thin film on the surface. This is
accompanied by the production of chemical by-products that are
exhausted out of the chamber along with unreacted precursor gases.
As would be expected with the large variety of materials deposited
and the wide range of applications, there are many variants of CVD
that may be used to form the lithium storage layer, the metal oxide
layer, an intermediate layer, a supplemental layer (see below) or
some other layer. It may be done in hot-wall reactors or cold-wall
reactors, at sub-torr total pressures to above-atmospheric
pressures, with and without carrier gases, and at temperatures
typically ranging from 100-1600.degree. C. in some embodiments.
There are also a variety of enhanced CVD processes, which involve
the use of plasmas, ions, photons, lasers, hot filaments, or
combustion reactions to increase deposition rates and/or lower
deposition temperatures. Various process conditions may be used to
control the deposition, including but not limited to, temperature,
precursor material, gas flow rate, pressure, substrate voltage bias
(if applicable), and plasma energy (if applicable).
[0068] As mentioned, the lithium storage layer (optionally
continuous and/or porous), e.g., a layer of silicon or germanium or
both, may be provided by plasma-enhanced chemical vapor deposition
(PECVD). Relative to conventional CVD, deposition by PECVD can
often be done at lower temperatures and higher rates, which can be
advantageous for higher manufacturing throughput. In some
embodiments, the PECVD is used to deposit a substantially amorphous
silicon layer (optionally doped) over the metal oxide layer. In
some embodiments, PECVD is used to deposit a substantially
amorphous continuous porous silicon layer over the metal oxide
layer.
[0069] PECVD
[0070] In PECVD processes, according to various implementations, a
plasma may be generated in a chamber in which the substrate is
disposed or upstream of the chamber and fed into the chamber.
Various types of plasmas may be used including, but not limited to,
capacitively-coupled plasmas, inductively-coupled plasmas, and
conductive coupled plasmas. Any appropriate plasma source may be
used, including DC, AC, RF, VHF, combinatorial PECVD and microwave
sources may be used. Some non-limiting examples of useful PECVD
tools include hollow cathode tube PECVD, magnetron confined PECVD,
inductively coupled plasma chemical vapor deposition (ICP-PECVD,
sometimes called HDPECVD, ICP-CVD or HDCVD), and expanding thermal
plasma chemical vapor deposition (ETP-PECVD).
[0071] PECVD process conditions (temperatures, pressures, precursor
gases, carrier gasses, dopant gases, flow rates, energies, and the
like) can vary according to the particular process and tool used,
as is well known in the art
[0072] In some implementations, the PECVD process is an expanding
thermal plasma chemical vapor deposition (ETP-PECVD) process. In
such a process, a plasma generating gas is passed through a direct
current arc plasma generator to form a plasma, with a web or other
substrate including the current collector optionally in an
adjoining vacuum chamber. A silicon source gas is injected into the
plasma, with radicals generated. The plasma is expanded via a
diverging nozzle and injected into the vacuum chamber and toward
the substrate. An example of a plasma generating gas is argon (Ar).
In some embodiments, the ionized argon species in the plasma
collide with silicon source molecules to form radical species of
the silicon source, resulting in deposition onto the current
collector. Example ranges for voltages and currents for the DC
plasma source are 60 to 80 volts and 40 to 70 amperes,
respectively.
[0073] Any appropriate silicon source may be used to deposit
silicon, including silane (SiH.sub.4), dichlorosilane
(H.sub.2SiCl.sub.2), monochlorosilane (H.sub.3SiC), trichlorosilane
(HSiCl.sub.3), silicon tetrachloride (SiCl.sub.4), and
diethylsilane. Depending on the gas(es) used, the silicon layer may
be formed by decomposition or reaction with another compound, such
as by hydrogen reduction. In some embodiments, the gases may
include a silicon source such as silane, a noble gas such as
helium, argon, neon, or xenon, optionally one or more dopant gases,
and substantially no hydrogen. In some embodiments, the gases may
include argon, silane, and hydrogen, and optionally some dopant
gases. In some embodiments the gas flow ratio of argon relative to
the combined gas flows for silane and hydrogen is at least 3.0,
alternatively at least 4.0. In some embodiments, the gas flow ratio
of argon relative to the combined gas flows for silane and hydrogen
is in a range of 3-5, alternatively 5-10, alternatively 10-15,
alternatively 15-20, or any combination of contiguous ranges
thereof. In some embodiments, the gas flow ratio of hydrogen gas to
silane gas is in a range of 0-0.1, alternatively 0.1-0.2,
alternatively 0.2-0.5, alternatively 0.5-1, alternatively 1-2,
alternatively 2-5, or any combination of contiguous ranges thereof.
In some embodiments, higher porosity silicon may be formed and/or
the rate of silicon deposition may be increased when the gas flow
ratio of silane relative to the combined gas flows of silane and
hydrogen increases. In some embodiments a dopant gas is borane or
phosphine, which may be optionally mixed with a carrier gas. In
some embodiments, the gas flow ratio of dopant gas (e.g., borane or
phosphine) to silicon source gas (e.g., silane) is in a range of
0.0001-0.0002, alternatively 0.0002-0.0005, alternatively
0.0005-0.001, alternatively 0.001-0.002, alternatively 0.002-0.005,
alternatively 0.005-0.01, alternatively 0.01-0.02, alternatively
0.02-0.05, alternatively 0.05-0.10, or any combination of
contiguous ranges thereof. Such gas flow ratios described above may
refer to the relative gas flow, e.g., in standard cubic centimeter
per minute (SCCM). In some embodiments, the PECVD deposition
conditions and gases may be changed over the course of the
deposition.
[0074] In some embodiments, the temperature at the current
collector during at least a portion of the time of PECVD deposition
is in a range of 100.degree. C. to 200.degree. C., alternatively
200.degree. C. to 300.degree. C., alternatively 300.degree. C. to
400.degree. C., alternatively 400.degree. C. to 500.degree. C.,
alternatively 500.degree. C. to 600.degree. C., alternatively
600.degree. C. to 700.degree. C. or any combination of contiguous
ranges thereof. In some embodiments, the temperature may vary
during the time of PECVD deposition. For example, the temperature
during early times of the PECVD may be higher than at later times.
Alternatively, the temperature during later times of the PECVD may
be higher than at earlier times.
[0075] Other Anode Features
[0076] The current collector may include one or more features to
ensure that a reliable electrical connection can be made. In some
embodiments, a supplemental layer 750 is provided over the surface
of the lithium storage layer, to form anode 700 as shown in FIG. 7.
In addition to supplemental layer 750, anode 700 includes an
electrically conductive current collector 701 and a lithium storage
layer 707. The electrically conductive current collector 701
includes a surface layer 705 provided over an electrically
conductive layer 703. In some embodiments, the supplemental layer
is a protection layer to enhance lifetime or physical durability.
The supplemental layer may be an oxide or nitride formed from the
lithium storage material itself, e.g., silicon dioxide, silicon
nitride, or silicon oxynitride in the case of silicon. A
supplemental layer may be deposited, for example, by ALD, CVD,
PECVD, evaporation, sputtering, solution coating, ink jet or any
method that is compatible with the anode. In some embodiments, a
supplemental layer is deposited in the same CVD or PECVD device as
the lithium storage layer. For example, stoichiometric silicon
dioxide or silicon nitride supplemental layer by be formed by
introducing an oxygen- or nitrogen-containing gas (or both) along
with the silicon precursor gas used to form the lithium storage
layer. In some embodiments the supplemental layer may include boron
nitride or silicon carbide. In some embodiments, a supplemental
layer may include a metal compound as described below.
[0077] In some embodiments, the one or more supplemental layers may
help stabilize the lithium storage layer by providing a barrier to
direct electrochemical reactions with solvents or electrolytes that
can degrade the interface. A supplemental layer should be
reasonably conductive to lithium ions and permit lithium ions to
move into and out of the lithium storage layer during charging and
discharging. In some embodiments, the lithium ion conductivity of a
supplemental layer is at least 10.sup.-9 S/cm, alternatively at
least 10.sup.-8 S/cm, alternatively at least 10'S/cm, alternatively
at least 10'S/cm. In some embodiments, the supplemental layer acts
as a solid-state electrolyte. In some embodiments, the supplemental
layer(s) are less electrically conductive than the lithium storage
structure so that little or no electrochemical reduction of lithium
ions to lithium metal occurs at the supplemental layer/electrolyte
interface. In addition to providing protection from electrochemical
reactions, a multiple supplemental layer structure embodiments may
provide superior structural support. In some embodiments, although
the supplemental layers may flex and may form fissures when the
lithium storage layer expands during lithiation, crack propagation
can be distributed between the layers to reduce direct exposure of
the lithium storage structure to the bulk electrolyte. For example,
a fissure in the second supplemental layer may not align with a
fissure in the first supplemental layer. Such an advantage may not
occur if just one thick supplemental layer is used. In an
embodiment, the second supplemental layer may be formed of a
material having higher flexibility than the first supplemental
layer.
[0078] In some embodiments, a supplemental layer may include
silicon nitride, e.g., substantially stoichiometric silicon nitride
where the ratio of nitrogen to silicon is in a range of 1.33 to
1.25. A supplemental layer comprising silicon nitride may have an
average thickness in a range of about 0.5 nm to 1 nm, alternatively
1 nm to 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to
20 nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,
alternatively 40 nm to 50 nm, or any combination of contiguous
ranges thereof. Silicon nitride may be deposited by an atomic layer
deposition (ALD) process or by a CVD process. In some embodiments,
the lithium storage layer includes silicon deposited by some type
of CVD process as described above, and at the end, a nitrogen gas
source is added to the CVD deposition chamber along with the
silicon source.
[0079] In some embodiments, a supplemental layer may include
silicon dioxide, e.g., substantially stoichiometric silicon dioxide
where the ratio of oxygen to silicon is in a range of 2.0 to 1.9. A
supplemental layer comprising silicon dioxide may have an average
thickness in a range of about 2 nm to 10 nm, alternatively 10 nm to
30 nm, alternatively 30 nm to 50 nm, alternatively 50 nm to 70 nm,
alternatively 70 nm to 100 nm, alternatively 100 nm to 150 nm,
alternatively 150 nm to 200 nm, or any combination of contiguous
ranges thereof. Silicon dioxide may be deposited by an atomic layer
deposition (ALD) process or by a CVD process. In some embodiments,
the lithium storage layer includes silicon deposited by some type
of CVD process as described above, and at the end, an
oxygen-containing gas source is added to the CVD deposition chamber
along with the silicon source.
[0080] In some embodiments, a supplemental layer may include
silicon oxynitride, e.g., a substantially stoichiometric oxynitride
of silicon (SiO.sub.xN.sub.y) wherein the sum of 0.5x and 0.75y is
in a range of 1.00 to 0.95. A supplemental layer comprising silicon
nitride may have an average thickness in a range of about 0.5 nm to
1 nm, alternatively 1 nm to 2 nm, alternatively 2 nm to 10 nm,
alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,
alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm,
alternatively 50 nm to 70 nm, alternatively 70 nm to 100 nm,
alternatively 100 nm to 150 nm, or any combination of contiguous
ranges thereof. In some embodiments, silicon oxynitride may be
provided by a CVD process, including but not limited to, a PECVD
process. The oxygen and nitrogen may be provided uniformly within
the lithium storage layer, or alternatively the oxygen or nitrogen
content may be varied as a function of position (e.g., height)
within the storage layer.
[0081] In some embodiments, silicon nitride, silicon dioxide, or
silicon oxynitride may be deposited by an atomic layer deposition
(ALD) process or by a CVD process. In some embodiments, the lithium
storage layer includes silicon deposited by some type of CVD
process as described above, and at the end, a nitrogen- and/or an
oxygen-containing gas source is added to the CVD deposition chamber
along with the silicon source.
[0082] In some embodiments a supplemental layer may include a metal
compound. In some embodiments, the metal compound includes a metal
oxide, metal nitride, or metal oxynitride, e.g., those containing
aluminum, titanium, vanadium, zirconium, or tin, or mixtures
thereof. In some embodiments, a supplemental layer including a
metal oxide, metal nitride, or metal oxynitride, may have an
average thickness of less than about 100 nm, for example, in a
range of about 0.5 nm to about 1 nm, alternatively about 1 nm to
about 2 nm, alternatively 2 nm to 10 nm, alternatively 10 nm to 20
nm, alternatively 20 nm to 30 nm, alternatively 30 nm to 40 nm,
alternatively 40 nm to 50 nm, or any combination of contiguous
ranges thereof. The metal oxide, metal nitride, or metal oxynitride
may include other components or dopants such as transition metals,
phosphorous or silicon.
[0083] In some embodiments, the metal compound may include a
lithium-containing material such as lithium phosphorous oxynitride
(LIPON), a lithium phosphate, a lithium aluminum oxide, or a
lithium lanthanum titanate. In some embodiments, the thickness of
supplemental layer including a lithium-containing material may be
in a range of 0.5 nm to 200 nm, alternatively 1 nm to 10 nm,
alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,
alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm,
alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or any
combination of contiguous ranges thereof.
[0084] In some embodiments the metal compound may be deposited by a
process comprising ALD, thermal evaporation, sputtering, or e-beam
evaporation. ALD is a thin-film deposition technique typically
based on the sequential use of a gas phase chemical process. The
majority of ALD reactions use at least two chemicals, typically
referred to as precursors. These precursors react with the surface
of a material one at a time in a sequential, self-limiting, manner.
Through the repeated exposure to separate precursors, a thin film
is deposited, often in a conformal manner. In addition to
conventional ALD systems, so-called spatial ALD (SALD) methods and
materials can be used, e.g., as described U.S. Pat. No. 7,413,982,
the entire contents of which are incorporated by reference herein
for all purposes. In certain embodiments, SALD can be performed
under ambient conditions and pressures and have higher throughput
than conventional ALD systems.
[0085] In some embodiments, the process for depositing the metal
compound may include electroless deposition, contact with a
solution, contact with a reactive gas, or electrochemical methods.
In some embodiments, a metal compound may be formed by depositing a
metallic layer (including but not limited to thermal evaporation,
CVD, sputtering, e-beam evaporation, electrochemical deposition, or
electroless deposition) followed by treatment to convert the metal
to the metal compound (including but not limited to, contact with a
reactive solution, contact with an oxidizing agent, contact with a
reactive gas, or a thermal treatment).
[0086] The supplemental layer may include an inorganic-organic
hybrid structure having alternating layers of metal oxide and
bridging organic materials. These inorganic-organic hybrid
structures are sometimes referred to as "metalcone". Such
structures can be made using a combination of atomic layer
deposition to apply the metal compound and molecular layer
deposition (MLD) to apply the organic. The organic bridge is
typically a molecule having multiple functional groups. One group
can react with a layer comprising a metal compound and the other
group is available to react in a subsequent ALD step to bind a new
metal. There is a wide range of reactive organic functional groups
that can be used including, but not limited to hydroxy, carboxylic
acid, amines, acid chlorides and anhydrides. Almost any metal
compound suitable for ALD deposition can be used. Some non-limiting
examples include ALD compounds for aluminum (e.g., trimethyl
aluminum), titanium (e.g., titanium tetrachloride), zinc (e.g.,
diethyl zinc), and zirconium (tris(dimethylamino)cyclopentadienyl
zirconium). For the purposes of the present disclosure, this
alternating sublayer structure of metal oxide/bridging organic is
considered a single supplemental layer of metalcone. When the metal
compound includes aluminum, such structures may be referred to as
an alucone. Similarly, when the metal compound includes zirconium,
such structures may be referred to as a zircone. Further examples
of inorganic-organic hybrid structures that may be suitable as a
supplemental layer may be found in U.S. Pat. No. 9,376,455, and US
patent publications 2019/0044151 and 2015/0072119, the entire
contents of which are incorporated herein by reference.
[0087] In some embodiments, a supplemental layer having a metalcone
may have a thickness in a range of 0.5 nm to 200 nm, alternatively
1 nm to 10 nm, alternatively 10 nm to 20 nm, alternatively 20 nm to
30 nm, alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm,
alternatively 50 nm to 100 nm, alternatively 100 to 200 nm, or any
combination of contiguous ranges thereof.
[0088] In some embodiments a supplemental layer (a first, a second,
or an additional supplemental layer) may include boron nitride or
silicon carbide and may have an average thickness of less than
about 100 nm, for example, in a range of about 0.5 nm to about 1
nm, alternatively about 1 nm to about 2 nm, alternatively 2 nm to
10 nm, alternatively 10 nm to 20 nm, alternatively 20 nm to 30 nm,
alternatively 30 nm to 40 nm, alternatively 40 nm to 50 nm, or any
combination of contiguous ranges thereof.
[0089] In some embodiments the anode is at least partially
pre-lithiated, i.e., the lithium storage layer and/or surface layer
includes some lithium prior to battery assembly, that is, prior to
combining the anode with a cathode in a battery cell. Note that
"lithiated storage layer" simply means that at least some of the
potential storage capacity of the lithium storage layer is filled,
but not necessarily all. In some embodiments, the lithiated storage
layer may include lithium in a range of 1% to 10% of the
theoretical lithium storage capacity of the lithium storage layer,
alternatively 10% to 20%, alternatively, 20% to 30%, alternatively
30% to 40%, alternatively 40% to 50%, alternatively 50% to 60%,
alternatively 60% to 70%, alternatively 70% to 80%, alternatively
80% to 90%, alternatively 90% to 100%, or any combination of
contiguous ranges thereof. In some embodiments, the surface layer
material may capture some of the lithium, and one may need to
account for such capture to achieve the desired lithium range in
the lithiated storage layer.
[0090] In some embodiments prelithiation may include depositing
lithium metal over the lithium storage layer, e.g., by evaporation,
e-beam or sputtering. Alternatively, prelithiation may include
contacting the anode with a reductive lithium organic compound,
e.g., lithium naphthalene, n-butyllithium or the like. In some
embodiments, prelithiation may include incorporating lithium by
electrochemical reduction of lithium ion in prelithiation
solution.
[0091] In some embodiments, prelithiation includes physical contact
of the lithium storage layer with a lithiation material. The
lithiation material may include a reducing lithium compound,
lithium metal or a stabilized lithium metal powder, any of which
may optionally be provided as a coating on a lithium transfer
substrate. The lithium transfer substrate may include a metal
(e.g., as a foil), a polymer, a ceramic, or some combination of
such materials, optionally in a multilayer format. In some
embodiments, such lithiation material may be provided on at least
one side of a current separator that faces the anode, i.e., the
current separator also acts as a lithium transfer substrate.
Stabilized lithium metal powders ("SLMP") typically have a
phosphate, carbonate or other coating over the lithium metal
particles, e.g. as described in U.S. Pat. Nos. 8,377,236,
6,911,280, 5,567,474, 5,776,369, and 5,976,403, the entire contents
of which are incorporated herein by reference. In some embodiments
SLMPs may require physical pressure to break the coating and allow
incorporation of the lithium into the lithium storage layer. In
some embodiments, other lithiation materials may be applied with
pressure and/or heat to promote lithium transfer into the lithium
storage layer, optionally through one or more supplemental layers.
In some embodiments a pressure applied between an anode and a
lithiation material may be at least 200 kPa, alternatively at least
1000 kPa, alternatively at least 5000 kPa. Pressure may be applied,
for example, by calendering, pressurized plates, or in the case of
a lithiation material coating on a current separator, by assembly
into battery having confinement or other pressurizing features.
[0092] In some embodiments, prelithiation includes thermally
treating the lithium storage layer during lithium incorporation,
after lithium incorporation, or both during and after. The thermal
treatment may assist in the incorporation of the lithium into the
lithium storage layer, for example by promoting lithium diffusion.
In some embodiments, thermally treating includes exposing the anode
to a temperature in a range of 50.degree. C. to 100.degree. C.,
alternatively 100.degree. C. to 150.degree. C., alternatively
150.degree. C. to 200.degree. C., alternatively 200.degree. C. to
250.degree. C., alternatively 250.degree. C. to 300.degree. C., or
alternatively 300.degree. C. to 350.degree. C. In some embodiments,
thermal treatment may be done under controlled atmosphere, e.g.,
under vacuum or argon atmosphere to avoid unwanted reactions with
oxygen, nitrogen, water or other reactive gases.
[0093] In some embodiments, prelithiation may soften the lithium
storage layer, for example, due to the formation of a
lithium-silicon alloy. This softening may cause problems in some
processes, for example, roll-to-roll processes whereby the softened
lithium storage layer begins to stick to rollers or to itself
during winding. In some embodiments providing at one or more
supplemental layers prior to prelithiation or after prelithiation,
the structural integrity and processability of the anode may be
substantially improved. In some embodiments, the supplemental
layer(s) may act as a harder interface with other surfaces to
prevent or reduce contact of such surfaces with the softened
lithium storage material.
[0094] In some embodiments, lithium metal may be deposited over the
lithium storage layer followed by deposition of lithium
ion-conducting layer. The anode may be thermally treated prior to
deposition of the lithium ion-conducting layer, after deposition of
the lithium ion-conducting layer, or both. In some embodiments, the
lithium metal is deposited directly onto the lithium storage layer.
In some embodiments, a supplemental layer, e.g., silicon nitride,
is deposited onto the lithium storage layer prior to deposition of
the lithium metal. In some embodiments, the lithium ion-conducting
layer may include a lithium-containing material, a metal oxide, or
a metalcone. Some non-limiting examples of lithium ion-conducting
layer materials include a lithium phosphorous oxynitride (UPON), a
lithium phosphate, a lithium aluminum oxide, a lithium lanthanum
titanate, and alucones. The lithium ion-conducting layer may
include multiple sublayers of different materials, e.g., selected
from the above list.
[0095] In some embodiments, the anode may be treated with a
reducing agent prior to final battery assembly. The reducing agent
may have an electrochemical potential sufficient to reduce at least
a portion of the metal chalcogenide. The reducing agent may include
an inorganic hydride, a substituted or unsubstituted borohydride,
an amine-borane, or an anionic organic aromatic compound. In some
embodiments, the reducing agent may be provided in a non-aqueous
solvent that is itself not reduced by the reducing agent and
applied under controlled conditions having low oxygen and
moisture.
[0096] Thermal treatments were discussed above with respect to
prelithiation and the surface layer, but in some embodiments the
anode may be thermally treated prior to battery assembly (after
deposition of the lithium storage coating is complete, but before
the anode is combined with a cathode in a battery cell), with or
without a prelithiation step. In some embodiments, thermally
treating the anode may improve adhesion of the various layers,
improve charge capacity, improve charging rates, or improve
electrical conductivity. In some embodiments, thermally treating
the anode may be done in a controlled environment, e.g., under
vacuum, argon, or nitrogen having a low oxygen and water content
(e.g., less than 100 ppm or partial pressure of less than 10 Torr,
alternatively less than 1 Torr, alternatively less than 0.1 Torr to
prevent degradation). Herein, "under vacuum" generally refers to a
reduced pressure condition wherein the total pressure of all gasses
(e.g. in a vacuum oven) is less than 10 Torr. Due to equipment
limitations, the vacuum pressure is typically greater than about
10.sup.-8 Torr. In some embodiments, anode thermal treatment may be
carried out using an oven, a tube furnace, infrared heating
elements, contact with a hot surface (e.g. a hot plate), or
exposure to a flash lamp. The anode thermal treatment temperature
and time depend on the materials of the anode. In some embodiments,
anode thermal treatment includes heating the anode to a temperature
of at least 50.degree. C., optionally in a range of 50.degree. C.
to 600.degree. C., alternatively 100.degree. C. to 250.degree. C.,
alternatively 250.degree. C. to 350.degree. C., alternatively
350.degree. C. to 450.degree. C., alternatively 450.degree. C. to
600.degree. C., alternatively 600.degree. C. to 700.degree. C.,
alternatively 700.degree. C. to 800.degree. C., or any combination
of contiguous ranges thereof. In some embodiments, the anode
thermal treatment time may be in a range of about 0.1 min to about
1 min, alternatively about 1 min to about 5 mins, alternatively
about 5 mins to about 10 mins, alternatively about 10 mins to about
30 minutes, alternatively about 30 mins to about 60 mins,
alternatively about 60 mins to about 90 mins, alternatively in a
range of about 90 mins to about 120 mins, or any combination of
contiguous ranges thereof.
[0097] As illustrated in FIG. 8, there are numerous process flow
options for fabricating anodes of the present disclosure. All of
the steps of FIG. 8 have been discussed in more detail above and
FIG. 8 is not an exhaustive list of all possibilities. In some
embodiments, at least Steps 801, 805 and 817 are required. In Step
801, a surface layer is formed on an electrically conductive layer,
e.g., an electrically conductive metal layer such as a metal foil
or metal mesh. In Step 805, one or more lithium storage layers are
deposited over or onto the surface layer. In an alternative
embodiment, prior to step 805, lithium metal may be deposited onto
the surface layer as shown in Step 803. In some cases, the anode
formed in Step 805 may be ready for assembly into a battery, Step
817.
[0098] In some embodiments, after Step 805, a prelithiation step
may be included, e.g., Step 807 where lithium metal may be
deposited onto the lithium storage layer(s). In some cases, the
anode from Step 807 may be ready to be assembled into a battery,
Step 817. In other embodiments as shown in Step 811, one or more
lithium ion-conducting layer(s) may be deposited onto the product
of Step 807 prior to battery assembly Step 817.
[0099] In some embodiments, after Step 805, one or more
supplemental layers may be deposited onto the lithium storage
layer(s), as shown in Step 809. In some cases, the anode from Step
809 may be ready for assembly into a battery, Step 817. In other
embodiments, a prelithiation step may be included, e.g. as shown in
Step 813 where lithium metal may be deposited over or onto the
supplemental layer(s). In some cases, the anode from Step 813 may
be ready for assembly into a battery, Step 817. In other
embodiments, one or more lithium ion-conducting layer(s) may be
deposited onto the product of Step 813 prior to battery assembly
Step 817.
[0100] In addition to the explicit steps shown in FIG. 8, thermal
treatments or other treatments may be performed between any of the
steps. Further, as mentioned, additional lithium storage layers
that are not lithium storage layers may be coated after Step 805.
In some embodiments one or more steps may be performed using
roll-to-roll coating methods wherein the electrically conductive
layer is in the form of a rolled film, e.g., a roll of metal
foil.
[0101] In some cases, as shown in schematic FIG. 9A, the
roll-to-roll processing may performed within a particular step
wherein the apparatus 901 for such step includes the necessary
processing hardware 903, e.g., for depositing, forming or treating
a layer, along with a loading tool 905 for holding a roll of film
906 to be processed, and a winding tool 907 to roll up the
processed film 908 after the step is complete. To carry out the
next step, the processed roll may be transferred to processing
apparatus 911, having its own processing hardware 913, loading tool
915, and winding tool 917. During transfer, the rolls may be kept
in a controlled environment, e.g., low oxygen or moisture,
depending on the step.
[0102] In some cases, the roll-to-roll processing may include
transfer of the film processed in one step directly to the next
step or apparatus as shown schematically in FIG. 9B. Processing
apparatus 921 is analogous to apparatus 901, but without the
winding tool. Apparatus 921 includes loading tool 925 for holding
the roll of film 926 to be processed and appropriate processing
hardware 923, e.g., for depositing, forming or treating a layer.
The processed film 928 from the first step moves to processing
apparatus 931 to receive another process step. Apparatus 931
includes the appropriate processing hardware 933, e.g., for
depositing, forming, or treating a layer, and a winding tool 937 to
roll up the processed film 938 after the next step is complete. Not
shown, the processed film 938 may instead move to yet another
processing apparatus without winding. Also, while drawn as separate
units, in some embodiments apparatus 921 and apparatus 931 may
share a common chamber. In some embodiments, a transition chamber
or zone may be provided between apparatus 921 and 931 designed to
avoid contamination of one process with another, or to act as a
film transport speed buffer if one process requires less time than
another.
[0103] Various combinations of the above embodiments may be
employed together, depending on the compatibility of one apparatus
interfacing with another. Fabrication equipment may further include
slitting stations.
[0104] Battery Features
[0105] The preceding description relates primarily to the
anode/negative electrode of a lithium-ion battery (LIB). The LIB
typically includes a cathode/positive electrode, an electrolyte and
a separator (if not using a solid-state electrolyte). Batteries can
be formed into multilayer stacks of anodes and cathodes with an
intervening separator. Alternatively, a single anode/cathode stack
can be formed into a so-called jelly-roll. Such structures are
provided into an appropriate housing having desired electrical
contacts.
[0106] In some embodiments, the battery may be constructed with
confinement features to limit expansion of the battery, e.g., as
described in US published applications 2018/0145367 and
2018/0166735, the entire contents of which are incorporated herein
by reference. In some embodiments a physical pressure is applied
between the anode and cathode, e.g., using a tensioned spring or
clip, a compressible film or the like. Confinement, pressure or
both may help ensure that the anode remains in active contact with
the current collector during formation and cycling, which may cause
expansion and contraction of the lithium storage layer.
[0107] FIG. 10 is a schematic cross-sectional view of a battery
according to some embodiments of the present disclosure. Battery
1090 includes top plate 1060, bottom plate 1062, anode side plate
1064, and cathode side plate 1066, which form part of a housing for
the stack of anodes 1000, cathodes 1040, and intervening separators
1030. Anodes are attached to an anode bus 1020 which is connected
to anode lead 1022 that extends through anode side plate 1064.
Cathodes are attached to a cathode bus 1050 which is connected to
cathode lead 1052 that extends through cathode side plate 1066.
Battery 1090 further includes electrolyte 1080 which fills the
space and saturates the separators 1030. Top compression member
1070 and lower compression member 1072 apply physical pressure
(arrows) between the anodes and cathodes. Compression members may
be compressible films, e.g., made from a porous polymer or
silicone. Alternatively, compression members may include an array
of compressible features, e.g., made from porous polymer or
silicone. Alternatively, the compression members may include
springs or an array of springs. Alternatively, compression members
may correspond to two sides of a compression clip or clamp. In some
embodiments, the separator may act as a compressible film. In some
embodiments the top and bottom plates may be formed a material
and/or structured to resist deformation thereby confining battery
swell.
[0108] Cathode
[0109] Positive electrode (cathode) materials include, but are not
limited to, lithium metal oxides or compounds (e.g., LiCoO.sub.2,
LiFePO.sub.4, LiMnO.sub.2, LiNiO.sub.2, LiMn.sub.2O.sub.4,
LiCoPO.sub.4, LiNi.sub.xCo.sub.yMnzO.sub.2,
LiNi.sub.XCo.sub.YAl.sub.ZO.sub.2, LiFe.sub.2(SO.sub.4).sub.3, or
Li.sub.2FeSiO.sub.4), carbon fluoride, metal fluorides such as iron
fluoride (FeF.sub.3), metal oxide, sulfur, selenium,
sulfur-selenium and combinations thereof. Cathode active materials
are typically provided on, or in electrical communication with, an
electrically conductive cathode current collector.
[0110] In some embodiments, a prelithiated anode of the present
disclosure is used with cathode including sulfur, selenium, or both
sulfur and selenium (collectively referred to herein as "chalcogen
cathodes"). In some embodiments, a prelithiated anode of the
present disclosure may be paired with a chalcogen cathode having an
active material layer, wherein the active material layer may
include a carbon material and a compound selected from the group
consisting of Se, Se.sub.yS.sub.x, Te.sub.yS.sub.x,
Te.sub.zSe.sub.yS.sub.x, and combinations thereof, where x, y and z
are any value between 0 and 1, the sum of y and x being 1, and the
sum of z, y and x being 1, the compound impregnated in the carbon
material, e.g., as described in US published application
2019/0097275, which is incorporated by reference herein for all
purposes. The compound may be present in an amount of 9-90% by
weight based on the total weight of the active material layer. In
some embodiments, the chalcogen cathode active material layer
further includes conductive carbon nanotubes to improve overall
conductivity and physical durability and may permit faster charging
and discharging. The presence of carbon nanotubes may further allow
thicker coatings that have greater flexibility thereby allowing
higher capacity.
[0111] Chalcogen cathodes are generally paired with lithium metal
anodes. However, lithium metal anodes are difficult to handle,
prone to degradation, and may further allow formation of dangerous
dendritic lithium that can lead to catastrophic shorts. In some
embodiments, prelithiated anodes of the present disclosure can
achieve equivalent energy storage capacity of a pure lithium anode,
but are much easier to handle and less prone to form dendritic
lithium, thus making them more compatible with chalcogen
cathodes.
[0112] Current Separator
[0113] The current separator allows ions to flow between the anode
and cathode but prevents direct electrical contact. Such separators
are typically porous sheets. Non-aqueous lithium-ion separators are
single layer or multilayer polymer sheets, typically made of
polyolefins, especially for small batteries. Most commonly, these
are based on polyethylene or polypropylene, but polyethylene
terephthalate (PET) and polyvinylidene fluoride (PVDF) can also be
used. For example, a separator can have >30% porosity, low ionic
resistivity, a thickness of .about.10 to 50 .mu.m and high bulk
puncture strengths. Separators may alternatively include glass
materials, ceramic materials, a ceramic material embedded in a
polymer, a polymer coated with a ceramic, or some other composite
or multilayer structure, e.g., to provide higher mechanical and
thermal stability. As mentioned, the separator may include a
lithiation material such as lithium metal, a reducing lithium
compound, or an SLMP material coated at least on the side facing
the anode.
[0114] Electrolyte
[0115] The electrolyte in lithium ion cells may be a liquid, a
solid, or a gel. A typical liquid electrolyte comprises one or more
solvents and one or more salts, at least one of which includes
lithium. During the first few charge cycles (sometimes referred to
as formation cycles), the organic solvent and/or the electrolyte
may partially decompose on the negative electrode surface to form
an SEI (Solid-Electrolyte-Interphase) layer. The SEI is generally
electrically insulating but ionically conductive, thereby allowing
lithium ions to pass through. The SEI may lessen decomposition of
the electrolyte in the later charging cycles.
[0116] Some non-limiting examples of non-aqueous solvents suitable
for some lithium ion cells include the following: cyclic carbonates
(e.g., ethylene carbonate (EC), fluoroethylene carbonate (FEC),
propylene carbonate (PC), butylene carbonate (BC) and vinylethylene
carbonate (VEC)), vinylene carbonate (VC), lactones (e.g.,
gamma-butyrolactone (GBL), gamma-valerolactone (GVL) and
alpha-angelica lactone (AGL)), linear carbonates (e.g., dimethyl
carbonate (DMC), methyl ethyl carbonate (MEC, also commonly
abbreviated EMC), diethyl carbonate (DEC), methyl propyl carbonate
(MPC), dipropyl carbonate (DPC), methyl butyl carbonate (NBC) and
dibutyl carbonate (DBC)), ethers (e.g., tetrahydrofuran (THF),
2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane (DME),
1,2-diethoxyethane and 1,2-dibutoxyethane), nitriles (e.g.,
acetonitrile and adiponitrile) linear esters (e.g., methyl
propionate, methyl pivalate, butyl pivalate and octyl pivalate),
amides (e.g., dimethyl formamide), organic phosphates (e.g.,
trimethyl phosphate and trioctyl phosphate), organic compounds
containing an S.dbd.O group (e.g., dimethyl sulfone and divinyl
sulfone), and combinations thereof.
[0117] Non-aqueous liquid solvents can be employed in combination.
Examples of these combinations include combinations of cyclic
carbonate-linear carbonate, cyclic carbonate-lactone, cyclic
carbonate-lactone-linear carbonate, cyclic carbonate-linear
carbonate-lactone, cyclic carbonate-linear carbonate-ether, and
cyclic carbonate-linear carbonate-linear ester. In some
embodiments, a cyclic carbonate may be combined with a linear
ester. Moreover, a cyclic carbonate may be combined with a lactone
and a linear ester. In some embodiments, the weight ratio, or
alternatively the volume ratio, of a cyclic carbonate to a linear
ester is in a range of 1:9 to 10:1, alternatively 2:8 to 7:3
[0118] A salt for liquid electrolytes may include one or more of
the following non-limiting examples: LiPF.sub.6, LiBF.sub.4,
LiClO.sub.4, LiAsF.sub.6, LiN(CF.sub.3SO.sub.2).sub.2,
LiN(C.sub.2F.sub.5SO.sub.2).sub.2, LiCF.sub.3SO.sub.3,
LiC(CF.sub.3SO.sub.2).sub.3, LiPF.sub.4(CF.sub.3).sub.2,
LiPF.sub.3(C.sub.2F.sub.5).sub.3, LiPF.sub.3(CF.sub.3).sub.3,
LiPF.sub.3 (iso-C.sub.3F.sub.7).sub.3,
LiPF.sub.5(iso-C.sub.3F.sub.7), lithium salts having cyclic alkyl
groups (e.g., (CF.sub.2).sub.2(S.sub.02).sub.2xLi and
(CF.sub.2).sub.3(SO.sub.2).sub.2xLi), and combinations thereof.
Common combinations include: LiPF.sub.6 and LiBF.sub.4; LiPF.sub.6
and LiN(CF.sub.3SO.sub.2).sub.2; and LiBF.sub.4 and
LiN(CF.sub.3SO.sub.2).sub.2.
[0119] In some embodiments, the total concentration of salt in a
liquid non-aqueous solvent (or combination of solvents) is at least
0.3 M, alternatively at least 0.7M. The upper concentration limit
may be driven by a solubility limit and operational temperature
range. In some embodiments, the concentration of salt is no greater
than about 2.5 M, alternatively no more than about 1.5 M.
[0120] In some embodiments, the battery electrolyte includes a
non-aqueous ionic liquid and a lithium salt.
[0121] A solid-state electrolyte may be used without the separator
because it serves as the separator itself. It is electrically
insulating, ionically conductive, and electrochemically stable. In
the solid electrolyte configuration, a lithium containing salt,
which could be the same as for the liquid electrolyte cells
described above, is employed but rather than being dissolved in an
organic solvent, it is held in a solid polymer composite. Examples
of solid polymer electrolytes may be ionically conductive polymers
prepared from monomers containing atoms having lone pairs of
electrons available for the lithium ions of electrolyte salts to
attach to and move between during conduction, such as
polyvinylidene fluoride (PVDF) or chloride or copolymer of their
derivatives, poly(chlorotrifluoroethylene),
poly(ethylene-chlorotrifluoro-ethylene), or poly(fluorinated
ethylene-propylene), polyethylene oxide (PEO) and oxymethylene
linked PEO, PEO-PPO-PEO crosslinked with trifunctional urethane,
poly(bis(methoxy-ethoxy-ethoxide))-phosphazene (MEEP), triol-type
PEO crosslinked with difunctional urethane,
poly((oligo)oxyethylene)methacrylate-co-alkali metal methacrylate,
polyacrylonitrile (PAN), polymethylmethacrylate (PMMA),
polymethylacrylonitrile (PMAN), polysiloxanes and their copolymers
and derivatives, acrylate-based polymer, other similar solvent-free
polymers, combinations of the foregoing polymers either condensed
or cross-linked to form a different polymer, and physical mixtures
of any of the foregoing polymers. Other less conductive polymers
that may be used in combination with the above polymers to improve
the strength of thin laminates include: polyester (PET),
polypropylene (PP), polyethylene naphthalate (PEN), polyvinylidene
fluoride (PVDF), polycarbonate (PC), polyphenylene sulfide (PPS),
and polytetrafluoroethylene (PTFE). Such solid polymer electrolytes
may further include a small amount of organic solvents listed
above. The polymer electrolyte may be an ionic liquid polymer. Such
polymer-based electrolytes can be coated using any number of
conventional methods such as curtain coating, slot coating, spin
coating, inkjet coating, spray coating or other suitable
method.
[0122] Additives may be included in the electrolyte to serve
various functions. For example, additives such as polymerizable
compounds having an unsaturated double bond may be added to
stabilize or modify the SEI. Certain amines or borate compounds can
act as cathode protection agents. Lewis acids can be added to
stabilize fluorine-containing anion such as PF.sub.6.sup.-. Safety
protection agents include those to protect overcharge, e.g.,
anisoles, or act as fire retardants, e.g., alkyl phosphates.
[0123] In some embodiments, a solid-state electrolyte may be vapor
deposited, solution-coated, melt-coated or a combination thereof.
Whether vapor deposited or coated from a solution or melt,
embodiments of the present disclosure are advantageous over
nanostructured devices. In the case of vapor deposited solid-state
electrolytes, anodes of the present disclosure do not have the
problem of physical "shadowing" that nano- or micro-structured
devices do. Shadowing will create non-uniform deposition of the
electrolyte. The anodes disclosed here generally do not have high
aspect ratio structures as described above, resulting in no or low
shadowing effects. Vapor deposited solid electrolytes can be
deposited uniformly and rapidly over anodes of the present
disclosure without resorting to slow atomic layer or other
conformal coating methods. In the case of solution or
melt-deposited solid-state electrolytes, anodes of the present
disclosure may be more robust to the stresses and shear forces
caused by the coating operation. High aspect ratio nano- or
micro-structures are susceptible to breakage from such forces.
[0124] In some embodiments, the original, non-cycled anode may
undergo structural or chemical changes during electrochemical
charging/discharging, for example, from normal battery usage or
from an earlier "electrochemical formation step". As is known in
the art, an electrochemical formation step is commonly used to form
an initial SEI layer and involves relatively gentle conditions of
low current and limited voltages. The modified anode prepared in
part from such electrochemical charging/discharging cycles may
still have excellent performance properties, despite such
structural and/or chemical changes relative to the original,
non-cycled anode.
EXAMPLES
Comparative Anode
[0125] A copper foil without a surface layer was prepared simply by
cleaning and wiping with isopropyl alcohol. The foil was placed in
a high-density plasma-enhanced chemical vapor deposition tool
(HDPECVD) using silane gas as the source of silicon and argon
carrier gas. Attempts to form a layer of amorphous silicon resulted
in a poorly adhered or non-adhered deposit that was unusable.
Anode 1 (Copper Sulfide Surface Layer)
[0126] A cleaned copper foil was immersed in an aqueous liver of
sulfur solution at room temperature until a surface layer including
a copper sulfide formed having an average thickness of about 0.5
.mu.m. The current collector was dipped in a solution of sodium
bicarbonate to neutralize the liver of sulfur, rinsed in DI water,
air-dried, and transferred to a high-density plasma-enhanced
chemical vapor deposition tool (HDPECVD). Amorphous silicon was
deposited over the surface layer at a loading of about 0.5
mg/cm.sup.2 to form the lithium storage layer. FIG. 11 is an SEM
cross section of Anode 1 showing a continuous porous amorphous
silicon layer 1107, about 3 .mu.m in thickness, overlaying the
.about.0.5 .mu.m surface layer (a copper sulfide) 1105, which in
turn, is overlaying the electrically conductive layer (copper metal
foil) 1103.
Anode 2 (Rough Copper Sulfide/TiO.sub.2 Surface Layer)
[0127] A clean copper foil was roughened using 600 grit silicon
carbide sandpaper and immersed in an aqueous liver of sulfur
solution at room temperature until a first surface sublayer
including a copper sulfide formed over the roughened foil, the
first surface sublayer having an average thickness of about 0.5
.mu.m. The current collector was dipped in a solution of sodium
bicarbonate to neutralize the liver of sulfur, rinsed in DI water,
air-dried and transferred to an ALD tool where 50 nm or amorphous
TiO.sub.2 was deposited onto the copper sulfide, thereby forming a
second surface sublayer. That is, the surface layer included copper
sulfide and TiO.sub.2 sublayers. Based on the method of making,
there may also exist some copper oxide between the copper sulfide
and TiO.sub.2. The current collector was placed in a high-density
plasma-enhanced chemical vapor deposition tool (HDPECVD). Amorphous
silicon was deposited over the surface layer at a loading of about
0.8 mg/cm.sup.2 to form the lithium storage layer.
Anode 3 (Copper Polysulfide/TiO.sub.2 Surface Layer)
[0128] A clean copper foil was placed in a muffle furnace and the
temperature was raised to between 200.degree. C. and 225.degree. C.
in air for about 180 minutes and cooled back to room temperature.
The partly oxidized foil was immersed in aqueous liver of sulfur
solution at room temperature until a first surface sublayer
including a copper polysulfide formed over the foil, the first
surface sublayer having an average thickness of about 0.5 .mu.m.
The current collector was dipped in a solution of sodium
bicarbonate to neutralize the liver of sulfur, rinsed in DI water
and air-dried. The surface layer further included some copper
oxide. The sample was transferred to an ALD tool and 50 nm or
amorphous TiO.sub.2 was deposited onto the copper polysulfide,
thereby forming a second surface sublayer. That is, the surface
layer included copper polysulfide and TiO.sub.2 sublayers. Based on
the method of making, there was also likely some copper oxide
between the copper sulfide and TiO.sub.2 sublayers. The current
collector was placed in a high-density plasma-enhanced chemical
vapor deposition tool (HDPECVD). Amorphous silicon was deposited
over the surface layer at a loading of about 0.8 mg/cm.sup.2 to
form the lithium storage layer. Half Cells
[0129] Half cells were constructed using a 1.27 cm diameter punch
of each anode. Lithium metal served as the counter electrode which
was separated from the test anode using Celgard.TM. separators. The
electrolyte solution included: a) 88 wt. % of 1.0 M LiPF.sub.6 in
3:7 EC:EMC (weight ratio); b) 10 wt. % FEC; and c) 2 wt. % VC.
Anodes first underwent a formation step. As is known in the art,
the formation step is used to form an initial SEI layer. Relatively
gentle conditions of low current and limited voltages may be used
to ensure that the anode is not overly stressed. The performance
cycling protocol included 3 C charging and C/3 discharging to
roughly a 20% state of charge. A 10-minute rest was provided
between charging and discharging cycles.
[0130] Plots of discharge capacity (mAh) and coulombic efficiency
(%) as a function of cycle # are shown in FIGS. 12-14. Anode 1
(FIG. 12) degrades more quickly than Anode 2 (FIG. 13) and Anode 3
(FIG. 14), but it should be noted that Anode 1 at least is
functional and much better than the comparative anode which did not
work at all. It appears that the metal oxide sublayer (Anode 2 and
Anode 3) may significantly improve cycling performance. Roughening
the copper foil (Anode 2) may also improve cycling performance.
Interestingly, both Anode 2 and Anode 3 show an initial dip in
discharge capacity, but the anodes recover and become stable with
cycling.
[0131] In some embodiments, the original, non-cycled anode may
undergo significant structural or chemical changes during
electrochemical charging/discharging, for example, from the
formation step and/or the usage cycling in a battery. Unexpectedly,
the anode formed from such electrochemical charging/discharging
cycles may still have excellent performance properties, despite
such structural and/or chemical changes.
[0132] Despite the industry's advocacy of micro- or nanostructured
silicon or other lithium storage materials, it has been found in
the present disclosure that highly effective anodes can be formed
without such features. Relative to comparable micro- or
nanostructured anodes, the anodes of the present disclosure may
have one or more of at least the following unexpected advantages:
comparable or improved stability at aggressive .gtoreq.1 C charging
rates; higher overall areal charge capacity; higher gravimetric
charge capacity; higher volumetric charge capacity; improved
physical durability; simplified manufacturing process; and/or a
more reproducible manufacturing process.
[0133] Although the present anodes have been discussed with
reference to batteries, in some embodiments the present anodes may
be used in hybrid lithium ion capacitor devices. Some non-limiting
representative embodiments are listed below.
[0134] 1. An anode for an energy storage device comprising:
[0135] a current collector comprising an electrically conductive
layer and a surface layer overlaying the electrically conductive
layer; and
[0136] a lithium storage layer overlaying the surface layer,
[0137] wherein the surface layer comprises a metal chalcogenide
comprising at least one of sulfur or selenium.
[0138] 2. The anode of embodiment 1, wherein the metal chalcogenide
comprises a metal sulfide, a metal polysulfide, a metal selenide,
or a metal polyselenide.
[0139] 3. The anode of embodiment 1 or 2, wherein the metal
chalcogenide comprises a transition metal sulfide, a transition
metal polysulfide, a transition metal selenide, or a transition
metal polyselenide.
[0140] 4. The anode of embodiment 3, wherein the transition metal
is copper.
[0141] 5. The anode according to any of embodiments 1-4, wherein
the metal chalcogenide comprises a copper sulfide or a copper
polysulfide.
[0142] 6. The anode according to any of embodiments 1-5, wherein
the surface layer further comprises a metal oxide.
[0143] 7. The anode according to any of embodiments 1-4, wherein
the surface layer comprises a first sublayer overlaying the
electrically conductive layer and a second sublayer overlaying the
first sublayer.
[0144] 8. The anode of embodiment 7, wherein the first sublayer
comprises at least one of sulfur or selenium and the second
sublayer comprises a metal oxide.
[0145] 9. The anode of embodiment 8, wherein the first sublayer
comprises a copper sulfide or a copper polysulfide.
[0146] 10. The anode of embodiment 9, wherein the second sublayer
comprises an oxide of copper, an oxide of nickel, an oxide of
titanium, an oxide of aluminum, or an oxide of zinc.
[0147] 11. The anode according to any of embodiments 1-10, wherein
the surface layer has an average thickness in a range of 0.1 to 5.0
.mu.m.
[0148] 12. The anode according to any of embodiments 1-11, wherein
the electrically conductive layer comprises nickel, copper,
stainless steel, titanium, conductive carbon, or a combination
thereof.
[0149] 13. The anode according to any of embodiments 1-12, wherein
the lithium storage layer is a continuous porous lithium storage
layer.
[0150] 14. The anode according to any of embodiments 1-13, wherein
the lithium storage layer has a total content of silicon,
germanium, or a combination thereof of at least 40 atomic %.
[0151] 15. The anode according to any of embodiments 1-14, wherein
the lithium storage layer includes less than 10 atomic %
carbon.
[0152] 16. The anode according to any of embodiments 1-15, wherein
the lithium storage layer is substantially free of
nanostructures.
[0153] 17. The anode according to any of embodiment 1-16, wherein
the lithium storage layer is a continuous porous lithium storage
layer comprising amorphous silicon having an areal density of at
least 0.2 mg/cm.sup.2 and the total content of silicon is at least
40 atomic %.
[0154] 18. The anode according to any of embodiment 1-17, wherein
the lithium storage layer has an average thickness from about 0.5
.mu.m to about 30 .mu.m.
[0155] 19. The anode according to any of embodiment 1-18, wherein
the lithium storage layer is a continuous porous lithium storage
layer comprising at least 85 atomic % amorphous silicon, wherein
the continuous porous lithium storage layer has a density in a
range of 1.1 g/cm.sup.3 to 2.2 g/cm.sup.3.
[0156] 20. A battery comprising the anode according to any of
embodiments 1-19 and a cathode.
[0157] 21. A method of making an anode for use in an energy storage
device, the method comprising:
[0158] providing a conductive current collector comprising an
electrically conductive layer and a surface layer overlaying the
electrically conductive layer, wherein the surface layer has an
average thickness of at least 0.1 .mu.m and comprises a metal
chalcogenide comprising at least one of sulfur or selenium; and
[0159] depositing a lithium storage layer onto the surface layer by
a CVD process.
[0160] 22. The method of embodiment 21 wherein the CVD process is a
PECVD process.
[0161] 23. The method of embodiment 21 or 22 wherein the lithium
storage layer has a total content of silicon, germanium, or a
combination thereof of at least 40 atomic %.
[0162] 24. The method according to any of embodiments 21-23,
wherein the lithium storage layer is a continuous porous lithium
storage layer comprising at least 85 atomic % amorphous silicon,
wherein the continuous porous lithium storage layer has a density
in a range of 1.1 g/cm.sup.3 to 2.2 g/cm.sup.3.
[0163] 25. The method according to any of embodiments 21-24,
wherein the electrically conductive layer comprises stainless
steel, nickel, copper, titanium, or conductive carbon.
[0164] 26. The method according to any of embodiments 21-25,
wherein the electrically conductive layer is a metal foil or a
metal mesh.
[0165] 27. The method according to any of embodiments 21-26,
wherein the metal chalcogenide comprises a metal sulfide, a metal
polysulfide, a metal selenide, or a metal polyselenide.
[0166] 28. The method according to any of embodiments 21-27,
wherein the metal chalcogenide comprises a transition metal
sulfide, a transition metal polysulfide, a metal transition
selenide, or a transition metal polyselenide.
[0167] 29. The method of embodiment 28, where in the transition
metal is copper.
[0168] 30. The method according to any of embodiments 21-29,
wherein the metal chalcogenide comprises a copper sulfide or a
copper polysulfide.
[0169] 31. The method according to any of embodiments 21-30,
further comprising forming the surface layer by treating the
electrically conductive layer with a solution comprising at least
one of a polysulfide salt, a thiosulfate salt, or a polyselenide
salt.
[0170] 32. The method according to embodiment 31, further
comprising heating the electrically conductive layer to a
temperature in a range of 100.degree. C. to 350.degree. C. after
treating the electrically conductive layer with the solution.
[0171] 33. The method according to any of embodiments 21-30,
further comprising forming the surface layer by first forming a
metal oxide precursor layer on the electrically conductive layer
followed by treating the metal oxide precursor layer with a
solution comprising at least one of a sulfide salt, a polysulfide
salt, a thiosulfate salt, a selenide salt, or a polyselenide salt
to at least partially convert a precursor comprising a metal oxide
in the metal oxide precursor layer to the metal chalcogenide.
[0172] 34. The method according to embodiment 33, further
comprising heating the electrically conductive layer after treating
to a temperature in a range of 100.degree. C. to 350.degree. C.
[0173] 35. The method according to any of embodiments 21-30,
further comprising forming the surface layer by depositing a metal
sulfide, a metal polysulfide, a metal selenide, or a metal
polyselenide onto the electrically conductive layer by a PVD
process, a CVD process, or an ALD process.
[0174] 36. The method according to any of embodiments 21-35,
wherein the surface layer further comprises a metal oxide.
[0175] 37. The method of embodiment 36, further comprising forming
the surface layer by depositing the metal oxide after forming a
metal sulfide, a metal polysulfide, a metal selenide, or a metal
polyselenide.
[0176] 38. The method of embodiment 37 wherein depositing the metal
oxide is by a PVD process, a CVD process, or an ALD process.
[0177] 39. The method according to any of embodiments 36-38,
wherein the metal oxide comprises a copper oxide, a nickel oxide, a
titanium oxide, an aluminum oxide, or a zinc oxide.
[0178] 40. The method according to any of embodiments 21-39,
wherein the surface layer comprises a first sublayer comprising a
copper sulfide or a copper polysulfide, and
[0179] the method further comprising depositing a second sublayer
over the first sublayer, the second sublayer comprising a copper
oxide, a nickel oxide, a titanium oxide, an aluminum oxide, or a
zinc oxide.
[0180] 41. The method of embodiment 40, wherein depositing the
second sublayer comprises depositing titanium dioxide by an ALD
process.
[0181] 42. A lithium-ion battery comprising a cathode and an anode
having a lithiated storage layer, wherein the anode is made by the
method according to any of embodiments 21-41.
[0182] 43. The lithium-ion battery of embodiment 42, wherein the
cathode comprises sulfur, selenium, or both sulfur and
selenium.
[0183] 44. The lithium-ion battery of embodiment 43, wherein the
cathode further comprises carbon nanotubes.
[0184] The specific details of particular embodiments may be
combined in any suitable manner without departing from the spirit
and scope of embodiments of the invention. However, other
embodiments of the invention may be directed to specific
embodiments relating to each individual aspect, or specific
combinations of these individual aspects.
[0185] The above description of example embodiments of the
invention has been presented for the purposes of illustration and
description. It is not intended to be exhaustive or to limit the
invention to the precise form described, and many modifications and
variations are possible in light of the teaching above.
[0186] In the preceding description, for the purposes of
explanation, numerous details have been set forth in order to
provide an understanding of various embodiments of the present
technology. It will be apparent to one skilled in the art, however,
that certain embodiments may be practiced without some of these
details, or with additional details.
[0187] Having described several embodiments, it will be recognized
by those of skill in the art that various modifications,
alternative constructions, and equivalents may be used without
departing from the spirit of the invention. Additionally, a number
of well-known processes and elements have not been described in
order to avoid unnecessarily obscuring the present invention.
Additionally, details of any specific embodiment may not always be
present in variations of that embodiment or may be added to other
embodiments.
[0188] Where a range of values is provided, it is understood that
each intervening value, to the tenth of the unit of the lower limit
unless the context clearly dictates otherwise, between the upper
and lower limits of that range is also specifically disclosed. Each
smaller range between any stated value or intervening value in a
stated range and any other stated or intervening value in that
stated range is encompassed. The upper and lower limits of these
smaller ranges may independently be included or excluded in the
range, and each range where either, neither, or both limits are
included in the smaller ranges is also encompassed within the
invention, subject to any specifically excluded limit in the stated
range. Where the stated range includes one or both of the limits,
ranges excluding either or both of those included limits are also
included.
[0189] As used herein and in the appended claims, the singular
forms "a", "an", and "the" include plural referents unless the
context clearly dictates otherwise. Thus, for example, reference to
"a method" includes a plurality of such methods and reference to
"the layer" includes reference to one or more layers and
equivalents thereof known to those skilled in the art, and so
forth. The invention has now been described in detail for the
purposes of clarity and understanding. However, it will be
appreciated that certain changes and modifications may be practiced
within the scope of the appended claims.
[0190] All publications, patents, and patent applications cited
herein are hereby incorporated by reference in their entirety for
all purposes. None is admitted to be prior art.
* * * * *