U.S. patent application number 16/359725 was filed with the patent office on 2019-07-11 for methods of applying printable lithium compositions for forming battery electrodes.
The applicant listed for this patent is FMC Lithium USA Corp.. Invention is credited to Kenneth Brian Fitch, William Arthur Greeter, JR., Jian Xia, Marina Yakovleva.
Application Number | 20190214631 16/359725 |
Document ID | / |
Family ID | 67139926 |
Filed Date | 2019-07-11 |
United States Patent
Application |
20190214631 |
Kind Code |
A1 |
Fitch; Kenneth Brian ; et
al. |
July 11, 2019 |
METHODS OF APPLYING PRINTABLE LITHIUM COMPOSITIONS FOR FORMING
BATTERY ELECTRODES
Abstract
A method for depositing lithium on a substrate to form an
electrode is provided. The method includes applying a printable
lithium composition comprised of lithium metal powder, a polymer
binder compatible with the lithium metal powder, a rheology
modifier compatible with the lithium metal powder and a solvent
compatible with the lithium metal powder and with the polymer
binder, to a substrate.
Inventors: |
Fitch; Kenneth Brian;
(Cherryville, NC) ; Yakovleva; Marina; (Gastonia,
NC) ; Greeter, JR.; William Arthur; (Dallas, NC)
; Xia; Jian; (Belmont, NC) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
FMC Lithium USA Corp. |
Philadelphia |
PA |
US |
|
|
Family ID: |
67139926 |
Appl. No.: |
16/359725 |
Filed: |
March 20, 2019 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
62464521 |
Feb 28, 2017 |
|
|
|
62691819 |
Jun 29, 2018 |
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H01M 10/052 20130101;
H01M 10/0585 20130101; H01M 2004/027 20130101; H01M 10/0525
20130101; H01M 4/139 20130101; H01M 4/0404 20130101; H01M 4/0409
20130101; H01M 4/0414 20130101; H01M 4/485 20130101; H01M 4/364
20130101; H01M 4/622 20130101; H01M 4/134 20130101; H01M 4/0411
20130101; H01M 10/0565 20130101; H01M 4/602 20130101; H01M 4/382
20130101; H01M 4/624 20130101; H01M 4/1395 20130101 |
International
Class: |
H01M 4/1395 20060101
H01M004/1395; H01M 4/38 20060101 H01M004/38; H01M 4/62 20060101
H01M004/62; H01M 4/134 20060101 H01M004/134; H01M 4/04 20060101
H01M004/04; H01M 10/0585 20060101 H01M010/0585; H01M 10/052
20060101 H01M010/052 |
Claims
1. A method for depositing lithium on a substrate to form an
electrode comprising applying a printable lithium composition
comprised of lithium metal powder, a polymer binder compatible with
the lithium metal powder, a rheology modifier compatible with the
lithium metal powder and a solvent compatible with the lithium
metal powder and with the polymer binder, to a substrate.
2. The method of claim 1, wherein applying the printable lithium
composition to the substrate comprises printing the printable
lithium composition onto the substrate with a slot die print
head.
3. The method of claim 2 further including loading the printable
lithium composition to the print head.
4. The method of claim 2 further including loading the printable
lithium composition into a cartridge, loading the cartridge into a
dispenser attached to a slot die print head, and mounting the slot
die head onto a printer for printing the printable lithium
composition onto the substrate.
5. The method of claim 1, wherein applying the printable lithium
composition to the substrate comprises extruding the printable
lithium composition onto the substrate.
6. The method of claim 5, wherein extruding the printable lithium
composition onto the substrate comprises inserting the printable
lithium composition into an extruder and extruding the printable
lithium composition out of a nozzle.
7. The method of claim 5, wherein extruding the printable lithium
composition onto the substrate comprises extruding the printable
lithium composition onto the substrate as a pattern.
8. The method of claim 1, wherein applying the printable lithium
composition comprises applying coating to a roller and passing the
substrate through the roller.
9. The method of claim 1, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition onto an anode.
10. The method of claim 9 further including the step of forming a
battery comprised of the printed anode.
11. The method of claim 9, wherein applying the printable lithium
composition onto an anode comprises applying the printable lithium
composition onto a current collector at a thickness between about
10 microns to about 200 microns.
12. The method of claim 1, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition as a monolithic coating forming an anode for a
solid-state battery.
13. The method of claim 1, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition to a solid electrolyte for a solid-state
battery.
14. The method of claim 1, wherein the printable lithium
composition includes a solvent compatible with the lithium powder
and with the polymer binder.
15. A method for depositing lithium on a substrate to form an
electrode comprising printing a printable lithium composition
comprised of lithium metal powder, a polymer binder compatible with
the lithium metal powder, a rheology modifier compatible with the
lithium powder and a solvent compatible with the lithium powder and
with the polymer binder, to a substrate with a slot die print
head.
16. The method of claim 15 further including loading the printable
lithium composition into a cartridge, loading the cartridge into a
dispenser attached to a slot die print head, and mounting the slot
die head onto a printer for printing the printable lithium
composition onto the substrate.
17. The method of claim 15, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition onto an anode, cathode, solid electrolyte,
current collector, or carrier material.
18. The method of claim 17 further including the step of forming a
battery comprised of the anode, cathode, solid electrolyte, current
collector, or carrier material.
19. A method for depositing lithium on a substrate to form an
electrode comprising extruding a printable lithium composition
comprised of lithium metal powder, a polymer binder compatible with
the lithium metal powder, a rheology modifier compatible with the
lithium powder and the polymer binder, and a solvent compatible
with the lithium powder and with the polymer binder, onto a
substrate.
20. The method of claim 19, wherein extruding the printable lithium
composition onto the substrate comprises inserting the printable
lithium composition into an extruder and extruding the printable
lithium composition out of a nozzle.
21. The method of claim 19, wherein extruding the printable lithium
composition onto the substrate comprises extruding the printable
lithium composition onto the substrate as a pattern.
22. The method of claim 19, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition onto an anode, cathode, solid electrolyte,
current collector, or carrier material.
23. The method of claim 22 further including the step of forming a
battery comprised of the anode, cathode, solid electrolyte, current
collector, or carrier material.
24. A method for depositing lithium on a substrate to form an
electrode comprising roller coating a substrate with a printable
lithium composition comprised of lithium metal powder, a polymer
binder compatible with the lithium metal powder, a rheology
modifier compatible with the lithium powder and the polymer binder,
and a solvent compatible with the lithium powder and with the
polymer binder.
25. The method of claim 24, wherein roller coating the substrate
comprises applying coating to a roller and passing the substrate
over the roller.
26. The method of claim 24, wherein applying the printable lithium
composition to the substrate comprises applying the printable
lithium composition onto an anode, cathode, solid electrolyte,
current collector, or carrier material.
27. The method of claim 26 further including the step of forming a
battery comprised of the anode, cathode, solid electrolyte, current
collector, or carrier material.
Description
RELATED APPLICATION
[0001] The following application claims priority to U.S.
Provisional No. 62/646,521 filed Mar. 22, 2018, and U.S.
Provisional No. 62/691,819 filed Jun. 29, 2018, the disclosures of
which are incorporated by reference in their entireties.
FIELD OF THE INVENTION
[0002] The present invention relates to a method for applying a
printable lithium composition suitable for formation of electrodes
suitable for use in a wide variety of energy storage devices,
including batteries and capacitors.
BACKGROUND OF THE INVENTION
[0003] Lithium and lithium-ion secondary or rechargeable batteries
have found use in certain applications such as in cellular phones,
camcorders, and laptop computers, and even more recently, in larger
power application such as in electric vehicles and hybrid electric
vehicles. It is preferred in these applications that the secondary
batteries have the highest specific capacity possible but still
provide safe operating conditions and good cyclability so that the
high specific capacity is maintained in subsequent recharging and
discharging cycles.
[0004] Although there are various constructions for secondary
batteries, each construction includes a positive electrode (or
cathode), a negative electrode (or anode), a separator that
separates the cathode and anode, an electrolyte in electrochemical
communication with the cathode and anode. For secondary lithium
batteries, lithium ions are transferred from the anode to the
cathode through the electrolyte when the secondary battery is being
discharged, i.e., used for its specific application. During the
discharge process, electrons are collected from the anode and pass
to the cathode through an external circuit. When the secondary
battery is being charged, or recharged, the lithium ions are
transferred from the cathode to the anode through the
electrolyte.
[0005] Historically, secondary lithium batteries were produced
using non-lithiated compounds having high specific capacities such
as TiS.sub.2, MoS.sub.2, MnO2, and V.sub.2O.sub.5, as the cathode
active materials. These cathode active materials were coupled with
a lithium metal anode. When the secondary battery was discharged,
lithium ions were transferred from the lithium metal anode to the
cathode through the electrolyte. Unfortunately, upon cycling, the
lithium metal developed dendrites that ultimately caused unsafe
conditions in the battery. As a result, the production of these
types of secondary batteries was stopped in the early 1990s in
favor of lithium-ion batteries.
[0006] Lithium-ion batteries typically use lithium metal oxides
such as LiCoO.sub.2 and LiNiO.sub.2 as cathode active materials
coupled with an active anode material such as a carbon-based
material. It is recognized that there are other anode types based
on silicon oxide, silicon particles and the like. In batteries
utilizing carbon-based anode systems, the lithium dendrite
formation on the anode is substantially avoided, thereby making the
battery safer. However, the lithium, the amount of which determines
the battery capacity, is totally supplied from the cathode. This
limits the choice of cathode active materials because the active
materials must contain removable lithium. Also, delithiated
products corresponding to Li.sub.xCoO.sub.2, Li.sub.xNiO.sub.2
formed during charging and overcharging are not stable. In
particular, these delithiated products tend to react with the
electrolyte and generate heat, which raises safety concerns.
[0007] New lithium-ion cells or batteries are initially in a
discharged state. During the first charge of lithium-ion cell,
lithium moves from the cathode material to the anode active
material. The lithium moving from the cathode to the anode reacts
with an electrolyte material at the surface of the graphite anode,
causing the formation of a passivation film on the anode. The
passivation film formed on the graphite anode is a solid
electrolyte interface (SEI). Upon subsequent discharge, the lithium
consumed by the formation of the SEI is not returned to the
cathode. This results in a lithium-ion cell having a smaller
capacity compared to the initial charge capacity because some of
the lithium has been consumed by the formation of the SEI. The
partial consumption of the available lithium on the first cycle
reduces the capacity of the lithium-ion cell. This phenomenon is
called irreversible capacity and is known to consume about 10% to
more than 20% of the capacity of a lithium ion cell. Thus, after
the initial charge of a lithium-ion cell, the lithium-ion cell
loses about 10% to more than 20% of its capacity.
[0008] One solution has been to use stabilized lithium metal powder
to pre-lithiate the anode. For example, lithium powder can be
stabilized by passivating the metal powder surface with carbon
dioxide such as described in U.S. Pat. Nos. 5,567,474, 5,776,369,
and 5,976,403, the disclosures of which are incorporated herein in
their entireties by reference. The CO.sub.2-passivated lithium
metal powder can be used only in air with low moisture levels for a
limited period of time before the lithium metal content decays
because of the reaction of the lithium metal and air. Another
solution is to apply a coating such as fluorine, wax, phosphorus or
a polymer to the lithium metal powder such as described in U.S.
Pat. Nos. 7,588,623, 8,021,496, 8,377,236 and U.S. Patent
Publication No. 2017/0149052, for example.
[0009] There, however, remains a need for processes and
compositions for applying lithium metal powder to various
substrates to provide electrodes for capacitors, lithium-ion cells
and other lithium metal batteries.
SUMMARY OF THE INVENTION
[0010] To this end, the present invention provides methods for
depositing lithium on a substrate to form an electrode by applying
a printable lithium composition to the substrate. The printable
lithium composition may be applied by various means, including
printing, extruding, spraying, and coating.
[0011] The printable lithium composition of the present invention
comprises a lithium metal powder, a polymer binder, wherein the
polymer binder is compatible with the lithium powder, and a
rheology modifier compatible with the lithium powder and the
polymer binder. A solvent may be included in the printable lithium
composition, wherein the solvent is compatible with the lithium
powder and compatible with (e.g., able to form suspension or to
dissolve in) the polymer binder. The solvent may be included as a
component during the initial preparation of the printable lithium
composition, or added later after the printable lithium composition
is prepared.
BRIEF DESCRIPTION OF THE DRAWINGS
[0012] FIG. 1 is a schematic of one embodiment of a printable
lithium composition coated onto a substrate;
[0013] FIG. 2 is a schematic of one embodiment of a printable
lithium composition extruded onto a substrate;
[0014] FIG. 3 is a schematic of one embodiment of a printable
lithium composition printed onto a substrate using a slot die;
[0015] FIG. 4 is a plan view of a printable lithium composition
printed onto a substrate;
[0016] FIG. 5 is a temperature and pressure profile for the
reactivity testing of SLMP/styrene butadiene/toluene printable
lithium composition; and
[0017] FIG. 6 is a plot showing the cycle performance for a pouch
cell with printable lithium derived thin lithium film as the anode
vs. commercial thin lithium foil.
DETAILED DESCRIPTION OF THE INVENTION
[0018] The foregoing and other aspects of the present invention
will now be described in more detail with respect to the
description and methodologies provided herein. It should be
appreciated that the invention can be embodied in different forms
and should not be construed as limited to the embodiments set forth
herein. Rather, these embodiments are provided so that this
disclosure will be thorough and complete, and will fully convey the
scope of the invention to those skilled in the art.
[0019] The terminology used in the description of the invention
herein is for the purpose of describing particular embodiments only
and is not intended to be limiting of the invention. As used in the
description of the embodiments of the invention and the appended
claims, the singular forms "a", "an" and "the" are intended to
include the plural forms as well, unless the context clearly
indicates otherwise. Also, as used herein, "and/or" refers to and
encompasses any and all possible combinations of one or more of the
associated listed items.
[0020] The term "about," as used herein when referring to a
measurable value such as an amount of a compound, dose, time,
temperature, and the like, is meant to encompass variations of 20%,
10%, 5%, 1%, 0.5%, or even 0.1% of the specified amount. Unless
otherwise defined, all terms, including technical and scientific
terms used in the description, have the same meaning as commonly
understood by one of ordinary skill in the art to which this
invention belongs.
[0021] As used herein, the terms "comprise," "comprises,"
"comprising," "include," "includes" and "including" specify the
presence of stated features, integers, steps, operations, elements,
and/or components, but do not preclude the presence or addition of
one or more other features, integers, steps, operations, elements,
components, and/or groups thereof.
[0022] As used herein, the term "consists essentially of" (and
grammatical variants thereof), as applied to the compositions and
methods of the present invention, means that the
compositions/methods may contain additional components so long as
the additional components do not materially alter the
composition/method. The term "materially alter," as applied to a
composition/method, refers to an increase or decrease in the
effectiveness of the composition/method of at least about 20% or
more.
[0023] All patents, patent applications and publications referred
to herein are incorporated by reference in their entirety. In case
of a conflict in terminology, the present specification is
controlling.
[0024] In accordance with the present invention, a method for
applying a printable lithium composition is provided. In one
embodiment, the printable lithium composition is electrochemically
active and may be used to form an anode by applying or depositing
the printable lithium composition on an anode conductive or carrier
material (e.g., copper or polymer or ceramic films). The printable
lithium composition comprises a lithium metal powder, one or more
polymer binders, one or more rheology modifiers and may further
include a solvent or co-solvent.
[0025] In another embodiment, the printable lithium composition may
be applied or deposited to prelithiate an anode or cathode. The
prelithiated anode or cathode may be incorporated into an energy
storage device such as a capacitor or battery. The battery may be
comprised of liquid electrolytes. In another embodiment, the
battery may be comprised of solid electrolytes to form a
solid-state battery. In another embodiment, the printable lithium
composition may be used applied or deposited to form a monolithic
lithium metal anode for use in conventional and solid-state
batteries.
[0026] In yet another embodiment, the printable lithium composition
may be applied or deposited so as to form a solid electrolyte for a
solid-state battery, and includes combining the printable lithium
composition with a polymer or ceramic material to form a solid
electrolyte.
[0027] In one embodiment, the active anode material and the
printable lithium composition are provided together and extruded
onto the current collector (e.g., copper, nickel, etc.). For
instance, the active anode material and printable lithium
composition may be mixed and co-extruded together. Examples of
active anode materials include graphite, graphite-SiO,
graphite-SnO, SiO, hard carbon and other lithium ion battery and
lithium ion capacitor anode materials. In another embodiment, the
active anode material and the printable lithium composition are
co-extruded to form a layer of the printable lithium composition on
the current collector. The deposition of the printable lithium
composition including the above extrusion technique may include
depositing as wide variety patterns (e.g., dots, stripes),
thicknesses, widths, etc. For example, the printable lithium
composition and active anode material may be deposited as a series
of stripes, such as described in US Publication No. 2014/0186519
incorporated herein by reference in its entirety. The stripes would
form a 3D structure that would account for expansion of the active
anode material during lithiation. For example, silicon may expand
by 300 to 400 percent during lithiation. Such swelling potentially
adversely affects the anode and its performance. By depositing the
printable lithium as a thin stripe in the Y-plane as an alternating
pattern between the silicon anode stripes, the silicon anode
material can expand in the X-plane alleviating electrochemical
grinding and loss of particle electrical contact. Thus, the
printing method can provide a buffer for expansion. In another
example, where the printable lithium formulation is used to form
the anode, it could be co-extruded in a layered fashion along with
the cathode and separator, resulting in a solid-state battery.
[0028] In one embodiment, the printable lithium composition may be
applied to a substrate or a preformed anode by coating the
substrate with a roller. One example is a gravure coating device,
such as one described in U.S. Pat. No. 4,948,635 herein
incorporated by reference in its entirety. In the example shown in
FIG. 1, a pair of spaced rollers 12, 12' support the substrate 10
as it advances toward a gravure roller 14. A nozzle is utilized to
apply the coating material to the gravure roller 14 while a doctor
blade 16 is utilized to remove excess coating from the gravure
roller 14. The gravure roller 14 contacts the substrate 10 as it
travels through the gravure roller to apply the ink composition.
The gravure roller can be designed to print various patterns on the
surface of the substrate; for example, lines or dots.
[0029] In another embodiment, the printable lithium composition may
be applied to a substrate by extruding the printable lithium
composition onto the substrate from an extruder. One example of an
extruder is described in U.S. Pat. No. 5,318,600 herein
incorporated by reference in its entirety. In such an embodiment,
high pressure forces the printable lithium composition through an
extrusion nozzle to coat the exposed surface area of the substrate.
As seen in FIG. 2, the ink composition 20 is contained within a
container 22. A high pressure forces the ink composition 20 through
an extrusion nozzle 24 to coat the exposed surface area of the
substrate 10. One example of such an extruding apparatus may be
mounted upon a suitable table and includes the hydraulic cylinder
having a high pressure oil feed inlet and an oil outlet. The
hydraulic cylinder typically contains a piston that drives the
piston head into engagement with the upper end of the extrusion
plunger 26.
[0030] In another embodiment, the printable lithium composition may
be applied to a substrate by printing the printable lithium
composition onto the substrate. Slot die print heads may be used to
print monolithic, stripe or other patterns of the printable lithium
composition onto the substrate. One example of a compatible printer
utilizing a slot die print head is described in U.S. Pat. No.
5,494,518 herein incorporated by reference in its entirety. As seen
in FIGS. 3 and 4, a slot coating die typically comprises a slot
coating die head 30 through which the ink composition 20 is
extruded onto the substrate 10, as the substrate 10 is moved past
the slot coating die head 30. FIG. 4 illustrates one example of a
slot coating wherein the ink composition 20 having a coating width
C.sub.w and gaps between each strip designated as C.sub.G. Both
C.sub.w and C.sub.G may vary depending on the configuration of the
slot coating die head 30.
[0031] In another embodiment, a conventional carbon anode may be
prelithiated by depositing the printable lithium composition on the
carbon anode. This will obviate the problem associated with carbon
anodes in which upon initial charging of the cell when lithium is
intercalated into the carbon some irreversibility occurs due to
some lithium and cell electrolyte being consumed resulting in an
initial capacity loss.
[0032] In one embodiment, the printable lithium composition may be
used to pre-lithiate an anode as described in U.S. Pat. No.
9,837,659 herein incorporated by reference in its entirety. For
example, the method includes disposing a layer of printable lithium
composition adjacent to a surface of a pre-fabricated/pre-formed
anode. The pre-fabricated electrode comprises an electroactive
material. In certain variations, the printable lithium composition
may be applied to the carrier/substrate via a deposition process. A
carrier substrate on which the layer of printable lithium
composition may be disposed may be selected from the group
consisting of: polymer films (e.g., polystyrene, polyethylene,
polyethyleneoxide, polyester, polypropylene,
polypolytetrafluoroethylene), ceramic films, copper foil, nickel
foil, or metal foams by way of non-limiting example. Heat may then
be applied to the printable lithium composition layer on the
substrate or the pre-fabricated anode. The printable lithium
composition layer on the substrate or the pre-fabricated anode may
be further compressed together, under applied pressure. The
heating, and optional applied pressure, facilitates transfer of
lithium onto the surface of the substrate or anode. In case of
transfer to the pre-fabricated anode, pressure and heat can result
in mechanical lithiation, especially where the pre-fabricated anode
comprises graphite. In this manner, lithium transfers to the
electrode and due to favorable thermodynamics is incorporated into
the active material.
[0033] In one embodiment, the printable lithium composition may be
incorporated within the anode as described in US Publication No.
2018/0269471 herein incorporated by reference in its entirety. For
example, the anode can comprise an active anode composition and the
printable lithium composition, and any electrically conductive
powder if present. In additional or alternative embodiments, the
printable lithium composition is placed along the surface of the
electrode. For example, the anode can comprise an active layer with
an active anode composition and a printable lithium composition
source layer on the surface of active layer. In an alternative
configuration, the printable lithium composition source layer is
between the active layer and a current collector. Also, in some
embodiments, the anode can comprise printable lithium composition
source layers on both surfaces of the active layer.
[0034] In one embodiment, the printable lithium composition may be
incorporated into a three-dimensional electrode structure as
described in US Publication No. 2018/0013126 herein incorporated by
reference in its entirety. For example, the printable lithium
composition may be incorporated into a three-dimensional porous
anode, porous current collector or porous polymer or ceramic film,
wherein the printable lithium composition may be deposited
therein.
[0035] In some embodiments, an electrode prelithiated with the
printable lithium composition can be assembled into a cell with the
electrode to be preloaded with lithium. A separator can be placed
between the respective electrodes. Current can be allowed to flow
between the electrodes. For example, an anode prelithiated with the
printable lithium composition of the present invention may be
formed into a second battery such as described in U.S. Pat. No.
6,706,447 herein incorporated by reference in its entirety.
[0036] In one embodiment, the printable lithium composition is
deposited or applied to an active anode material on a current
collector namely to form a prelithiated anode. Suitable active
anode materials include graphite and other carbon-based materials,
alloys such as tin/cobalt, tin/cobalt/carbon, silicon-carbon,
variety of silicone/tin based composite compounds, germanium-based
composites, titanium based composites, elemental silicon, and
germanium. The anode materials may be a foil, mesh or foam.
Application may be via spraying, extruding, coating, printing,
painting, dipping, and spraying.
[0037] Anodes prelithiated using the printable lithium composition
may be incorporated into various types of batteries. For example,
the prelithiated anodes may be incorporated into batteries as
disclosed in U.S. Pat. Nos. 7,851,083, 8,088,509, 8,133,612,
8,276,695, and 9,941,505, which are incorporated herein by
reference in their entireties. Printing the printable lithium
composition on an anode material may be an alternative to smearing
lithium as disclosed in U.S. Pat. No. 7,906,233 incorporated herein
by reference in its entirety.
[0038] The cathode is formed of an active material, which is
typically combined with a carbonaceous material and a binder
polymer. The active material used in the cathode is preferably a
material that can be lithiated. Preferably, non-lithiated materials
such as MnO.sub.2, V.sub.2O.sub.5, MoS.sub.2, metal fluorides or
mixtures thereof, Sulphur and sulfur composites can be used as the
active material. However, lithiated materials such as
LiMn.sub.2O.sub.4 and LiMO.sub.2 wherein M is Ni, Co or Mn that can
be further lithiated can also be used. The non-lithiated active
materials are preferred because they generally have higher specific
capacities, lower cost and broader choice of cathode materials in
this construction that can provide increased energy and power over
conventional secondary batteries that include lithiated active
materials.
[0039] In one embodiment, the printable lithium composition may be
used to prelithiate a capacitor, such as an anode in a lithium-ion
capacitor as described in US Publication No. 2017/0301485 herein
incorporated by reference. For example, the anode can be
constructed using hard carbon, soft carbon or graphite. The anode
may then be attached to a current collector before or during having
a printable lithium composition layer coated on the top surface of
the anode. The printable lithium composition may also be used to
prelithiate an energy storage device such as a lithium-ion
capacitor as described in U.S. Pat. No. 9,711,297 herein
incorporated by reference in its entirety.
[0040] In one embodiment, the printable lithium composition may be
used to prelithiate a hybrid battery/capacitor as described in US
Publication No. 2018/0241079 herein incorporated by reference in
its entirety. The term "hybrid electrode" refers to an electrode
that includes both battery electrode materials and capacitor
electrode materials. In one embodiment, the hybrid cathode may
comprise a blend of higher energy materials, such as battery
cathode materials, and high power materials, such as capacitor
cathode materials. For example, lithium-ion battery cathode
materials may be combined with ultracapacitor or supercapacitor
cathode materials. To complete the hybrid lithium-ion cell
assembly, the hybrid cathode may be disposed against an anode
electrode with a polyolefin separator in between the electrodes and
is placed in a confined packaging, such as an energy storage device
container, e.g. housing. The electrode stack is filled and
contacted with a suitable electrolyte, such as a solvent containing
a lithium-ion electrolyte salt and optionally including an
electrolyte additive. The energy storage device package can be
sealed.
[0041] The anode used in combination with the hybridized cathode
can comprise elemental metal, such as elemental lithium. A method
for prelithiation is direct addition of the printable lithium
composition to the electrode formulation. This printable lithium
composition uniformly integrated into the electrode formulation can
then be used to form an electrode film, in a dry process, which can
then be laminated onto a current collector, such as a metal foil,
to form the electrode, such as an anode. The printable lithium
composition can be also applied to the current collector prior to
the lamination with the dry electrode. Embodiments herein can allow
for a homogenous, and in some embodiments, dry, and/or particulate
material, to be used as a raw material in the anode and hybridized
cathode. Some embodiments herein can avoid the need for two
separate layers on each electrode (such as a "battery material"
layer and a "capacitor material" layer), which can avoid the need
to introduce manufacturing complexity and added production cost. In
further embodiments, the pre-doped electrode is a hybrid cathode.
It will be understood that the elemental metal and related concepts
described herein with respect to an energy storage device with
lithium may be implemented with other energy storage devices, and
other metals.
[0042] As disclosed in US application Ser. No. ______ (Attorney
Matter ID. 073396.1116, filed concurrently with this application)
and hereby incorporated by reference in its entirety, the printable
lithium composition comprises a lithium metal powder, one or more
polymer binders, one or more rheology modifiers and may further
include a solvent or co-solvent. The polymer binder may be
compatible with the lithium metal powder. The rheology modifier may
be compatible with the lithium metal powder and the polymer binder.
The solvent may be compatible with the lithium metal powder and
with the polymer binder.
[0043] The lithium metal powder may be in the form of a finely
divided powder. The lithium metal powder typically has a mean
particle size of less than about 80 microns, often less than about
40 microns and sometimes less than about 20 microns. The lithium
metal powder may be a low pyrophoricity stabilized lithium metal
power (SLMP.RTM.) available from FMC. The lithium metal powder may
also include a substantially continuous layer or coating of
fluorine, wax, phosphorus or a polymer or the combination thereof
(as disclosed in U.S. Pat. Nos. 5,567,474, 5,776,369, and
5,976,403). Lithium metal powder has a significantly reduced
reaction with moisture and air.
[0044] The lithium metal powder may also be alloyed with a metal.
For example, the lithium metal powder may be alloyed with a Group
I-VIII element. Suitable elements from Group IB may include, for
example, copper, silver, or gold. Suitable elements from Group IIB
may include, for example, zinc, cadmium, or mercury. Suitable
elements from Group IIA of the Periodic Table may include
beryllium, magnesium, calcium, strontium, barium, and radium.
Elements from Group IIIA that may be used in the present invention
may include, for example, boron, aluminum, gallium, indium, or
thallium. Elements from Group IVA that may be used in the present
invention may include, for example, carbon, silicon, germanium,
tin, or lead. Elements from Group VA that may be used in the
present invention may include, for example, nitrogen, phosphorus,
or bismuth. Suitable elements from Group VIIIB may include, for
example, nickel, palladium, or platinum.
[0045] The polymer binder is selected so as to be compatible with
the lithium metal powder. "Compatible with" or "compatibility" is
intended to convey that the polymer binder does not violently react
with the lithium metal powder resulting in a safety hazard. The
lithium metal powder and the polymer binder may react to form a
lithium-polymer complex, however, such complex should be stable at
various temperatures. It is recognized that the amount
(concentration) of lithium and polymer binder contribute to the
stability and reactivity. The polymer binder may have a molecular
weight of about 1,000 to about 8,000,000, and often has a molecular
weight of 2,000,000 to 5,000,000. Suitable polymer binders may
include one or more of poly(ethylene oxide), polystyrene,
polyisobutylene, natural rubbers, butadiene rubbers,
styrene-butadiene rubber, polyisoprene rubbers, butyl rubbers,
hydrogenated nitrile butadiene rubbers, epichlorohydrin rubbers,
acrylate rubbers, silicon rubbers, nitrile rubbers, polyacrylic
acid, polyvinylidene chloride, polyvinyl acetate, ethylene
propylene diene termonomer, ethylene vinyl acetate copolymer,
ethylene-propylene copolymers, ethylene-propylene terpolymers,
polybutenes. The binder may also be a wax.
[0046] The rheology modifier is selected to be compatible with the
lithium metal powder and the polymer binder. The rheology modifier
provides rheology properties such as viscosity and flow under shear
conditions. The rheology modifier may also provide conductivity,
improved capacity and/or improved stability/safety depending on the
selection of the rheology modifier. To this end, the rheology
modifier may be the combination of two or more compounds so as to
provide different properties or to provide additive properties.
Exemplary rheology modifiers may include one or more of carbon
black, carbon nanotubes, graphene, silicon nanotubes, graphite,
hard carbon and mixtures, fumed silica, titanium dioxide, zirconium
dioxide and other Group IIA, IIIA, IVB, VB and VIA
elements/compounds and mixtures or blends thereof. Other additives
intended to increase lithium ion conductivity can be used; for
example, electrochemical device electrolyte salts such as lithium
perchlorate (LiClO.sub.4), lithium hexafluorophosphate
(LiPF.sub.6), lithium nitrate (LiNO.sub.3), lithium bis(oxalate)
borate (LiBOB), and lithium trifluoromethanesulfonimide
(LiTFSI).
[0047] Solvents compatible with lithium may include acyclic
hydrocarbons, cyclic hydrocarbons, aromatic hydrocarbons,
symmetrical ethers, unsymmetrical ethers, cyclic ethers, alkanes,
sulfones, mineral oil, and mixtures, blends or cosolvents thereof.
Examples of suitable acyclic and cyclic hydrocarbons include
n-hexane, n-heptane, cyclohexane, and the like. Examples of
suitable aromatic hydrocarbons include toluene, ethylbenzene,
xylene, isopropylbenzene (cumene), and the like. Examples of
suitable symmetrical, unsymmetrical and cyclic ethers include
di-n-butyl ether, methyl t-butyl ether, tetrahydrofuran, glymes and
the like. Commercially available isoparaffinic synthetic
hydrocarbon solvents with tailored boiling point ranges such as
Shell Sol.RTM. (Shell Chemicals) or Isopar.RTM. (Exxon) are also
suitable.
[0048] The polymer binder and solvents are selected to be
compatible with each other and with the lithium metal powder. In
general, the binder or solvent should be non-reactive with the
lithium metal powder or in amounts so that any reaction is kept to
a minimum and violent reactions are avoided. The binder and solvent
should be compatible with each other at the temperatures at which
the printable lithium composition is made and will be used.
Preferably the solvent (or co-solvent) will have sufficient
volatility to readily evaporate from the printable lithium
composition (e.g., in slurry form) to provide drying of the
printable lithium composition (slurry) after application.
[0049] The components of the printable lithium composition may be
mixed together as a slurry or paste to have a high concentration of
solid. Thus the slurry/paste may be in the form of a concentrate
with not all of the solvent necessarily added prior to the time of
depositing or applying. In one embodiment, the lithium metal powder
should be uniformly suspended in the solvent so that when applied
or deposited a substantially uniform distribution of lithium metal
powder is deposited or applied. Dry lithium powder may be dispersed
such as by agitating or stirring vigorously to apply high sheer
forces.
[0050] In another embodiment, a mixture of the polymer binder,
rheology modifier, coating reagents, and other potential additives
for the lithium metal powder may be formed and introduced to
contact the lithium droplets during the dispersion at a temperature
above the lithium melting point, or at a lower temperature after
the lithium dispersion has cooled such as described in U.S. Pat.
No. 7,588,623 the disclosure of which is incorporated by reference
in its entirety. The thusly modified lithium metal may be
introduced in a crystalline form or in a solution form in a solvent
of choice. It is understood that combinations of different process
parameters could be used to achieve specific coating and lithium
powder characteristics for particular applications.
[0051] Conventional pre-lithiation surface treatments require
compositions having very low binder content and very high lithium;
for example, see U.S. Pat. No. 9,649,688 the disclosure of which is
incorporated by reference in its entirety. However, embodiments of
the printable lithium composition in accordance with the present
invention can accommodate higher binder ratios, including up to 20
percent on dry basis. Various properties of the printable lithium
composition, such as viscosity and flow, may be modified by
increasing the binder and modifier content up to 50% dry basis
without loss of electrochemical activity of lithium. Increasing the
binder content facilitates the loading of the printable lithium
composition and the flow during printing. For example, in one
embodiment the printable lithium composition comprises about 70%
lithium metal powder and about 30% polymer binder and rheology
modifiers. In another embodiment, the printable lithium composition
may comprise about 85% lithium metal powder and about 15% polymer
binder and rheology modifiers.
[0052] An important aspect of printable lithium compositions is the
rheological stability of the suspension. Because lithium metal has
a low density of 0.534 g/cc, it is difficult to prevent lithium
powder from separating from solvent suspensions. By selection of
lithium metal powder loading, polymer binder and conventional
modifier types and amounts, viscosity and rheology may be tailored
to create the stable suspension of the invention. A preferred
embodiment shows no separation at greater than 90 days. This can be
achieved by designing compositions with very high zero shear
viscosity in the range of 1.times.10.sup.4 cps to 1.times.10.sup.7
cps. It is however very important to the application process that
the compositions, when exposed to shear, exhibit viscosity
characteristics in the ranges claimed.
[0053] The resulting printable lithium composition preferably may
have a viscosity at 10 s.sup.-1 about 20 to about 20,000 cps, and
often a viscosity of about 100 to about 10,000 cps. At such
viscosity, the printable lithium composition is a flowable
suspension or gel. The printable lithium composition preferably has
an extended shelf life at room temperature and is stable against
metallic lithium loss at temperatures up to 60.degree. C., often up
to 120.degree. C., and sometimes up to 180.degree. C. The printable
lithium composition may separate somewhat over time but can be
placed back into suspension by mild agitation and/or application of
heat.
[0054] In one embodiment, the printable lithium composition
comprises on a solution basis about 5 to 50 percent lithium metal
powder, about 0.1 to 20 percent polymer binder, about 0.1 to 30
percent rheology modifier and about 50 to 95 percent solvent. In
one embodiment, the printable lithium composition comprises on a
solution basis about 15 to 25 percent lithium metal powder, about
0.3 to 0.6 percent polymer binder having a molecular weight of
4,700,000, about 0.5 to 0.9 percent rheology modifier, and about 75
to 85 percent solvent. Typically, the printable lithium composition
is applied or deposited to a thickness of about 10 microns to 200
microns prior to pressing. After pressing, the thickness can be
reduced to between about 1 to 50 microns. Examples of pressing
techniques are described, for example, in U.S. Pat. Nos. 3,721,113
and 6,232,014 which are incorporated herein by reference in their
entireties.
[0055] In another embodiment, the printable lithium composition may
be applied or deposited to prelithiate an anode or cathode of a
solid-state battery. For example, the printable lithium composition
may be used to form a monolithic lithium metal anode for use in a
solid-state battery, including solid-state batteries as described
in U.S. Pat. Nos. 8,252,438 and 9,893,379 and incorporated herein
by reference in their entireties.
[0056] In another embodiment, the printable lithium composition may
be used to form or in conjunction with a solid electrolyte for use
in a solid-state battery. For instance, the printable lithium
composition may be deposited on a variety of solid-state
electrolytes as described in U.S. Pat. No. 7,914,930 herein
incorporated by reference in its entirety. One example of a
solid-state secondary battery may include a positive electrode
capable of electrochemically absorbing and desorbing lithium; a
negative electrode capable of electrochemically absorbing and
desorbing lithium, the negative electrode including an active
material layer that comprises an active material, the active
material layer being carried on a current collector; and a
non-aqueous electrolyte. A method includes the steps of: reacting
lithium with the active material of the negative electrode by
bringing the printable lithium composition into contact with a
surface of the active material layer of the negative electrode; and
thereafter combining the negative electrode with the positive
electrode to form an electrode assembly.
[0057] The following examples are merely illustrative of the
invention and are not limiting thereon.
EXAMPLES
Example 1
[0058] 10 g of solution styrene butadiene rubber (S-SBR Europrene
Sol R 72613) is dissolved in 90 g toluene (99% anhydrous, Sigma
Aldrich) by stirring at 21.degree. C. for 12 hours. 6 g of the 10
wt % SBR (polymer binder) in toluene (solvent) is combined with 0.1
g carbon black (Timcal Super P) (rheology modifier) and 16 g of
toluene and dispersed in a Thinky ARE 250 planetary mixer for 6
minutes at 2000 rpm. 9.3 g of stabilized lithium metal powder
(SLMP.RTM., FMC Lithium Corp.) having polymer coating of 20 to 200
.mu.m and d50 of 20 .mu.m is added to this suspension and dispersed
for 3 minutes at 1000 rpm in a Thinky mixer. The printable lithium
is then filtered through 180 .mu.m opening stainless steel mesh.
The printable lithium suspension is then doctor blade coated on to
a copper current collector at a wet thickness of 2 mil (.about.50
.mu.m). FIG. 6 is a plot showing the cycle performance for a pouch
cell LMP with printable lithium derived thin lithium film as the
anode vs. commercial thin lithium foil.
Example 2
[0059] 10 g of 135,000 molecular weight ethylene propylene diene
terpolymer (EPDM) (Dow Nordel IP 4725P) is dissolved in 90 g
p-xylene (99% anhydrous, Sigma Aldrich) by stirring at 21.degree.
C. for 12 hours. 6 g of the 10 wt % EPDM (polymer binder) in
p-xylene (solvent) is combined with 0.1 g TiO2 (Evonik Industries)
(rheology modifier) and 16 g of toluene and dispersed in a Thinky
ARE 250 planetary mixer for 6 minutes at 2000 rpm. 9.3 g of
stabilized lithium metal powder (SLMP.RTM., FMC Lithium Corp.)
having polymer coating of 20 to 200 .mu.m and d50 of 20 .mu.m is
added to this suspension and dispersed for 3 minutes at 1000 rpm in
a Thinky mixer. The printable lithium is then filtered through 180
.mu.m opening stainless steel mesh. The printable lithium
composition is then doctor blade coated on to a copper current
collector at a wet thickness of 2 mil (.about.50 .mu.m).
Shelf Life Stability
[0060] Printable lithium components must be selected to ensure
chemical stability for long shelf life at room temperature and
stability at elevated temperature for shorter durations such as
during transport or during the drying process. The printable
lithium composition stability was tested using calorimetry. 1.5 g
SLMP was added to a 10 ml volume Hastelloy ARC bomb sample
container. 2.4 g of 4% SBR binder solution was added to the
container. The container was fitted with a 24-ohm resistance heater
and a thermocouple to monitor and control sample temperature. The
bomb sample set-up was loaded into a 350 ml containment vessel
along with insulation. An Advance Reactive Screening Systems Tool
calorimeter by Fauske Industries was used to assess the
compatibility of the printable lithium solutions during a constant
rate temperature ramp to 190.degree. C. The temperature ramp rate
was 2.degree. C./min and the sample temperature was held at
190.degree. C. for 60 minutes. The test was conducted under 200 psi
Argon pressure to prevent boiling of the solvent. FIG. 5 shows the
temperature and pressure profiles for the reactivity testing of a
SLMP/styrene butadiene/toluene printable lithium composition.
Printing Performance
[0061] The quality of the printable lithium composition with regard
to printability is measured by several factors, for example,
consistency of flow which directly impact one's ability to control
lithium loading on a substrate or an electrode surface. An
effective means of measuring flow is Flow Conductance which is an
expression of the loading per square centimeter in relation to the
factors which control the loading--the pressure during extrusion
and the speed of the printer head. It can most simply be thought of
as the inverse of flow resistance.
[0062] The expression is used to allow comparisons between prints
of varying pressures and speeds, and changes in Flow Conductance
can alert one to non-linear relationships of flow with pressure.
These are important for scaling the loading for a printable lithium
up or down depending on the need of the anode or cathode. An ideal
printable lithium composition would behave in a linear fashion to
changes in extrusion pressure.
[0063] To test printability, a printable lithium composition is
filtered through 180 .mu.m opening stainless steel mesh and loaded
into a Nordson EFD 10 ml syringe. The syringe is loaded into a
Nordson EFD HP4x syringe dispenser and attached to a slot die print
head. The slot die print head is equipped with a 100 .mu.m-300
.mu.m thick shim with channel openings designed to deliver the
desired printable lithium composition loading. The slot die head is
mounted on a Loctite 300 Series robot. The print head speed is set
to 200 mm/s and the printing pressure is between 20 and 200 psi
argon, depending on shim and channel design. The print length is 14
cm. In an example printing trial experiment, the printable lithium
composition was printed 30 times from a single syringe at dispenser
settings ranging from 80 psi to 200 psi. For this print trial
experiment, the flow conductance average was 0.14
mg s * cm 2 * lbf in 2 ##EQU00001##
with standard deviation of 0.02. Although this printable
composition does not behave in a perfectly linear fashion, the
composition flow response to changes in dispenser pressure is
predictable to allow one skilled in the art to fine tune lithium
loading to the desired level. Thus, at fixed dispenser pressure
conditions the loading of lithium can be controlled very
consistently. For example, for a print of 0.275
mAh cm 2 ##EQU00002##
lithium metal, the CV is about 5%.
Electrochemical Testing
[0064] The pre-lithiation effect of printable lithium composition
can be evaluated by printing the required amount of printable
lithium onto the surface of prefabricated electrodes. The
pre-lithiation lithium amount is determined by testing the anode
material in half-cell format and calculating the lithium required
to compensate for the first cycle losses due to formation of SEI,
or other side reactions. To calculate the necessary amount of
printable lithium, the capacity as lithium metal of the composition
must be known and is approximately 3600 mAh/g dry lithium basis for
the compositions used as examples.
[0065] The pre-lithiation effect is tested using Graphite-SiO/NCA
pouch cells. The Graphite-SiO anode sheet has the following
formulation: artificial graphite (90.06%)+SiO (4.74%)+carbon black
(1.4%)+SBR/CMC (3.8%). The capacity loading of the electrode is
3.59 mAh/cm.sup.2 with 87% first cycle CE (columbic efficiency).
The printable lithium is applied onto a Graphite-SiO anode at 0.15
mg/cm.sup.2 lithium metal. The electrode is dried at 80.degree. C.
for 100 min followed by lamination at a roller gap approximately
75% of the thickness of the electrode. A 7 cm.times.7 cm electrode
is punched from the printable lithium treated anode sheet. The
positive electrode has the following formulation: NCA (96%)+carbon
black (2%)+PVdF (2%). The positive electrode is 6.8 cm.times.6.8 cm
with capacity loading of 3.37 mAh/cm.sup.2. The NCA cathode has 90%
first cycle CE. The anode to cathode capacity ratio is 1.06 and the
baseline for full cell first cycle CE is 77%. Single layer pouch
cells are assembled and 1M LiPF.sub.6/EC+DEC (1:1) is used as the
electrolyte. The cells are pre-conditioned for 12 hours at
21.degree. C. and then the formation cycle is conducted at
40.degree. C. The formation protocol is 0.1 C charge to 4.2V,
constant voltage to 0.01 C and 0.1 C discharge to 2.8V. In the
described test 89% first cycle CE was demonstrated.
[0066] Although the present approach has been illustrated and
described herein with reference to preferred embodiments and
specific examples thereof, it will be readily apparent to those of
ordinary skill in the art that other embodiments and examples may
perform similar functions and/or achieve like results. All such
equivalent embodiments and examples are within the spirit and scope
of the present approach.
* * * * *