U.S. patent application number 13/336459 was filed with the patent office on 2012-04-19 for solid state battery.
This patent application is currently assigned to POLYPLUS BATTERY COMPANY. Invention is credited to Bruce D. Katz, Yevgeniy S. Nimon, Steven J. Visco.
Application Number | 20120094188 13/336459 |
Document ID | / |
Family ID | 46328943 |
Filed Date | 2012-04-19 |
United States Patent
Application |
20120094188 |
Kind Code |
A1 |
Visco; Steven J. ; et
al. |
April 19, 2012 |
SOLID STATE BATTERY
Abstract
Disclosed are ionically conductive membranes for protection of
active metal anodes and methods for their fabrication. The
membranes may be incorporated in active metal negative electrode
(anode) structures and battery cells. In accordance with the
invention, the membrane has the desired properties of high overall
ionic conductivity and chemical stability towards the anode, the
cathode and ambient conditions encountered in battery
manufacturing. The membrane is capable of protecting an active
metal anode from deleterious reaction with other battery components
or ambient conditions while providing a high level of ionic
conductivity to facilitate manufacture and/or enhance performance
of a battery cell in which the membrane is incorporated.
Inventors: |
Visco; Steven J.; (Berkeley,
CA) ; Nimon; Yevgeniy S.; (Danville, CA) ;
Katz; Bruce D.; (Orinda, CA) |
Assignee: |
POLYPLUS BATTERY COMPANY
Berkeley
CA
|
Family ID: |
46328943 |
Appl. No.: |
13/336459 |
Filed: |
December 23, 2011 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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12907819 |
Oct 19, 2010 |
8114171 |
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13336459 |
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12475403 |
May 29, 2009 |
7838144 |
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12907819 |
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11824574 |
Jun 29, 2007 |
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12475403 |
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10772228 |
Feb 3, 2004 |
7390591 |
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11824574 |
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10731771 |
Dec 5, 2003 |
7282302 |
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10772228 |
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10686189 |
Oct 14, 2003 |
7282296 |
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10731771 |
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60418899 |
Oct 15, 2002 |
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60511710 |
Oct 14, 2003 |
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60518948 |
Nov 10, 2003 |
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Current U.S.
Class: |
429/312 ;
429/306 |
Current CPC
Class: |
H01M 6/185 20130101;
Y02P 70/50 20151101; H01M 6/18 20130101; H01M 6/187 20130101; Y02E
60/10 20130101; H01M 2300/008 20130101; Y10T 29/49115 20150115;
H01M 6/182 20130101; H01M 10/056 20130101; H01M 10/0562 20130101;
H01M 10/0565 20130101; H01M 2300/0071 20130101; H01M 6/188
20130101; H01M 10/0525 20130101; H01M 6/181 20130101; H01M 50/46
20210101; H01M 2300/0094 20130101; Y10T 29/49108 20150115; H01M
50/403 20210101; H01M 2300/0065 20130101; H01M 50/409 20210101 |
Class at
Publication: |
429/312 ;
429/306 |
International
Class: |
H01M 10/0565 20100101
H01M010/0565 |
Claims
1. A solid state battery, comprising: a solid anode comprising
lithium; a solid cathode comprising a material selected from the
group consisting of metal oxide based cathodes, metal sulfide based
cathodes and active sulfur cathodes; a solid protective membrane
having lithium ion conductivity of at least 10.sup.-7 S/cm on the
first surface of the anode, the membrane being substantially
impervious, chemically compatible with lithium on a surface in
contact with the anode, and chemically compatible with the cathode
on an opposite second surface; and a solid polymer electrolyte
disposed between the second surface of the protective membrane and
the cathode.
2. The battery cell of claim 1, wherein the anode is lithium
metal.
3. The battery cell of claim 1, wherein the anode is a lithium
metal alloy.
4. The battery cell of claim 1, wherein the solid protective
membrane is monolithic.
5. The battery cell of claim 1, wherein the solid protective
membrane comprises a composite comprising, a first component in
contact with the anode, the first component being conductive to
lithium ions chemically compatible with lithium, and a second
component in contact with the first component, the second component
being substantially impervious, conductive to lithium ions and
chemically compatible with the first material component and the
cathode.
6. The battery cell of claim 5, wherein the first component
comprises a material selected from the group consisting of
Li.sub.3N, Li.sub.3P and LiI, LiBr, LiCl, LiF, LiPON.
7. The battery cell of claim 5, wherein the first component is an
in situ composite reaction product of lithium with one selected
from the group consisting of metal nitride, silicon nitride, metal
halide, metal phosphide, red phosphorus, a wetting layer coated on
LiPON.
8. The battery cell of claim 5, wherein the substantially
impervious ionically conductive layer comprises a material selected
from the group consisting of glassy or amorphous active metal ion
conductors, ceramic active metal ion conductors, and glass-ceramic
active metal ion conductors.
9. The battery cell of claim 1, wherein the solid polymer
electrolyte comprises polyethylene oxide (PEO).
10. The battery cell of claim 1, wherein the cathode is a lithiated
metal oxide based cathode.
11. The battery cell of claim 10, wherein, the lithiated metal
oxide based cathode is selected from the group consisting of
Li.sub.xCoO.sub.2, Li.sub.xNiO.sub.2, Li.sub.xMn.sub.2O.sub.4 and
LiFePO.sub.4.
12. The battery cell of claim 1, wherein the cathode is an
unlithiated metal oxide based cathode.
13. The battery cell of claim 12, wherein the cell is a secondary
cell and the unlithiated metal oxide based cathode is selected from
the group consisting of AgxV.sub.2O.sub.5, CuxV.sub.2O.sub.5,
V.sub.2O.sub.5 and V.sub.6O.sub.13.
14. The battery cell of claim 12, wherein the cell is a primary
cell and the unlithiated metal oxide based cathode is selected from
the group consisting of AgxV.sub.2O.sub.5, CuxV.sub.2O.sub.5,
V.sub.2O.sub.5 and V.sub.6O.sub.13, MnO.sub.2, CuO,
Ag.sub.2CrO.sub.4 and MoO.sub.3.
15. The battery cell of claim 1, wherein, the cathode is a metal
sulfide based cathode.
16. The battery cell of claim 15, wherein the cell is a secondary
cell and the metal sulfide based cathode is selected from the group
consisting of FeS.sub.2 and TiS.sub.2.
17. The battery cell of claim 15, wherein the cell is a primary
cell and the unlithiated metal sulfide based cathode is selected
from the group consisting of FeS and CuS.
18. The battery cell of claim 1, wherein the cathode is an active
sulfur cathode.
19. The battery cell of claim 18, wherein the active sulfur cathode
is selected from the group consisting of elemental sulfur,
polysulfides and combinations thereof.
20. The battery cell of claim 1, wherein the cathode is a
PEO/carbon/metal-oxide type cathode.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 12/907,819, filed Oct. 19, 2010, titled IN
SITU FORMED IONICALLY CONDUCTIVE MEMBRANES FOR PROTECTION OF ACTIVE
METAL ANODES AND BATTERY CELLS, now pending; which is a
continuation of U.S. patent application Ser. No. 12/475,403, filed
May 29, 2009, titled PROTECTIVE COMPOSITE BATTERY SEPARATOR AND
ELECTROCHEMICAL DEVICE COMPONENT WITH RED PHOSPHORUS, now U.S. Pat.
No. 7,838,144, issued Nov. 23, 2010; which is a continuation of
U.S. patent application Ser. No. 11/824,574, filed Jun. 29, 2007,
titled IONICALLY CONDUCTIVE MEMBRANES FOR PROTECTION OF ACTIVE
METAL ANODES AND BATTERY CELLS, now abandoned; which is a
continuation of U.S. patent application Ser. No. 10/772,228, filed
Feb. 3, 2004, titled IONICALLY CONDUCTIVE MEMBRANES FOR PROTECTION
OF ACTIVE METAL ANODES AND BATTERY CELLS, now U.S. Pat. No.
7,390,591, issued Jun. 24, 2008; which is a continuation-in-part of
U.S. patent application Ser. No. 10/731,771 filed Dec. 5, 2003,
titled IONICALLY CONDUCTIVE COMPOSITES FOR PROTECTION OF ACTIVE
METAL ANODES, now U.S. Pat. No. 7,282,302, issued Oct. 16, 2007;
which is a continuation-in-part of U.S. patent application Ser. No.
10/686,189 filed Oct. 14, 2003, titled IONICALLY CONDUCTIVE
COMPOSITES FOR PROTECTION OF ACTIVE METAL ANODES, now U.S. Pat. No.
7,282,296, issued Oct. 16, 2007; which claims priority to U.S.
Provisional Patent Application No. 60/418,899 filed Oct. 15, 2002,
titled IONICALLY CONDUCTIVE COMPOSITES FOR PROTECTION OF ANODES AND
ELECTROLYTES.
[0002] This application also claims priority through prior
application Ser. No. 10/772,228 in its chain of priority to U.S.
Provisional Patent Application No. 60/511,710 filed Oct. 14, 2003,
titled IONICALLY CONDUCTIVE COMPOSITES FOR PROTECTION OF ACTIVE
METAL ELECTRODES IN CORROSIVE ENVIRONMENTS and U.S. Provisional
Patent Application No. 60/518,948 filed Nov. 10, 2003, titled
BI-FUNCTIONALLY COMPATIBLE IONICALLY COMPOSITES FOR ISOLATION OF
ACTIVE METAL ELECTRODES IN A VARIETY OF ELECTROCHEMICAL CELLS AND
SYSTEMS.
[0003] Each of these prior applications is incorporated herein by
reference in its entirety and for all purposes.
BACKGROUND OF THE INVENTION
[0004] 1. Field of the Invention
[0005] The present invention relates generally to separators and
electrode structures for use in batteries. More particularly, this
invention relates to ionically conductive membranes for protection
of active metal anodes from deleterious reaction with air, moisture
and other battery components, battery cells incorporating such
protected anodes and methods for their fabrication.
[0006] 2. Description of Related Art
[0007] The low equivalent weight of alkali metals, such as lithium,
render them particularly attractive as a battery electrode
component. Lithium provides greater energy per volume than the
traditional battery standards, nickel and cadmium. Unfortunately,
no rechargeable lithium metal batteries have yet succeeded in the
market place.
[0008] The failure of rechargeable lithium metal batteries is
largely due to cell cycling problems. On repeated charge and
discharge cycles, lithium "dendrites" gradually grow out from the
lithium metal electrode, through the electrolyte, and ultimately
contact the positive electrode. This causes an internal short
circuit in the battery, rendering the battery unusable after a
relatively few cycles. While cycling, lithium electrodes may also
grow "mossy" deposits which can dislodge from the negative
electrode and thereby reduce the battery's capacity.
[0009] To address lithium's poor cycling behavior in liquid
electrolyte systems, some researchers have proposed coating the
electrolyte facing side of the lithium negative electrode with a
"protective layer." Such protective layer must conduct lithium
ions, but at the same time prevent contact between the lithium
electrode surface and the bulk electrolyte. Many techniques for
applying protective layers have not succeeded.
[0010] Some contemplated lithium metal protective layers are formed
in situ by reaction between lithium metal and compounds in the
cell's electrolyte which contact the lithium. Most of these in situ
films are grown by a controlled chemical reaction after the battery
is assembled. Generally, such films have a porous morphology
allowing some electrolyte to penetrate to the bare lithium metal
surface. Thus, they fail to adequately protect the lithium
electrode.
[0011] Various pre-formed lithium protective layers have been
contemplated. For example, U.S. Pat. No. 5,314,765 (issued to Bates
on May 24, 1994) describes an ex situ technique for fabricating a
lithium electrode containing a thin layer of sputtered lithium
phosphorus oxynitride ("LiPON") or related material. LiPON is a
glassy single ion conductor (conducts lithium ion) which has been
studied as a potential electrolyte for solid state lithium
microbatteries that are fabricated on silicon and used to power
integrated circuits (See U.S. Pat. Nos. 5,597,660, 5,567,210,
5,338,625, and 5,512,147, all issued to Bates et al.).
[0012] Work in the present applicants' laboratories has developed
technology for the use of glassy or amorphous protective layers,
such as LiPON, in active metal battery electrodes. (See, for
example, U.S. Pat. Nos. 6,025,094, issued Feb. 15, 2000, 6,402,795,
issued Jun. 11, 2002, 6,214,061, issued Apr. 10, 2001 and
6,413,284, issued Jul. 2, 2002, all assigned to PolyPlus Battery
Company). Despite this progress, alternative protective layers and
structures that could also enhance active metal, particularly
lithium metal, battery performance continue to be sought. In
particular, protective layers that combine the characteristics of
high ionic conductivity and chemical stability to materials and
conditions on either side of the protective layer are desired.
SUMMARY OF THE INVENTION
[0013] The present invention provides ionically conductive
membranes for decoupling the active metal anode and cathode sides
of an active metal electrochemical cell, and methods for their
fabrication. The membranes may be incorporated in active metal
negative electrode (anode) structures and electrochemical devices
and components, including battery and fuel cells. The membranes are
highly conductive for ions of the active metal, but are otherwise
substantially impervious. They are chemically stable on one side to
the active metal of the anode (e.g., lithium), and on the other
side to the cathode, other battery cell components such as solid or
liquid phase electrolytes, including organic or aqueous liquid
electrolytes, ambient conditions and other environments corrosive
to the active metal of the anode if directly contacted with it. The
membrane is capable of protecting an active metal anode from
deleterious reaction with other battery components or ambient
conditions and decoupling the chemical environments of the anode
and cathode enabling use of anode-incompatible materials, such as
solvents and electrolytes, on the cathode side without deleterious
impact on the anode, and vice versa. This broadens the array of
materials that may be used in active metal electrochemical cells
and facilitates cell fabrication while providing a high level of
ionic conductivity to enhance performance of an electrochemical
cell in which the membrane is incorporated.
[0014] The membrane may have any suitable composition, for example,
it may be a monolithic material chemically compatible with both the
anode and cathode environments, or a composite composed of at least
two components of different materials having different chemical
compatibilities, one chemically compatible with the anode
environment and the other chemically compatible with the cathode
environment.
[0015] Composite membranes may be composed of a laminate of
discrete layers of materials having different chemical
compatibility requirements, or it may be composed of a gradual
transition between layers of the materials. By "chemical
compatibility" (or "chemically compatible") it is meant that the
referenced material does not react to form a product that is
deleterious to battery cell operation when contacted with one or
more other referenced battery cell components or manufacturing,
handling or storage conditions. A first material layer (or first
layer material) of the composite is ionically conductive, and
chemically compatible with an active metal electrode material.
Chemical compatibility in this aspect of the invention refers both
to a material that is chemically stable and therefore substantially
unreactive when contacted with an active metal electrode material.
It may also refer to a material that is chemically stable with air,
to facilitate storage and handling, and reactive when contacted
with an active metal electrode material to produce a product that
is chemically stable against the active metal electrode material
and has the desirable ionic conductivity (i.e., a first layer
material). Such a reactive material is sometimes referred to as a
"precursor" material. A second material layer of the composite is
substantially impervious, ionically conductive and chemically
compatible with the first material. Additional layers are possible
to achieve these aims, or otherwise enhance electrode stability or
performance. All layers of the composite have high ionic
conductivity, at least 10.sup.-7 S/cm, generally at least 10.sup.-6
S/cm, for example at least 10.sup.-5 S/cm to 10.sup.-4 S/cm, and as
high as 10.sup.-3 S/cm or higher so that the overall ionic
conductivity of the multi-layer protective structure is at least
10.sup.-7 S/cm and as high as 10.sup.-3 S/cm or higher.
[0016] A wide variety of materials may be used in fabricating
protective composites in accordance with the present invention,
consistent with the principles described above. For example, the
first layer, in contact with the active metal, may be composed, in
whole or in part, of active metal nitrides, active metal
phosphides, active metal halides or active metal phosphorus
oxynitride-based glass. Specific examples include Li.sub.3N,
Li.sub.3P, LiI, LiBr, LiCl, LiF and LiPON. Active metal electrode
materials (e.g., lithium) may be applied to these materials, or
they may be formed in situ by contacting precursors such as metal
nitrides, metal phosphides, metal halides, red phosphorus, iodine,
nitrogen or phosphorus containing organics and polymers, and the
like with lithium. The in situ formation of the first layer may
result from an incomplete conversion of the precursors to their
lithiated analog. Nevertheless, such incomplete conversions meet
the requirements of a first layer material for a protective
composite in accordance with the present invention and are
therefore within the scope of the invention.
[0017] A second layer of the protective composite may be composed
of a material that is substantially impervious, ionically
conductive and chemically compatible with the first material or
precursor and environments normally corrosive to the active metal
of the anode, including glassy or amorphous metal ion conductors,
such as a phosphorus-based glass, oxide-based glass,
phosphorus-oxynitride-based glass, sulpher-based glass,
oxide/sulfide based glass, selenide based glass, gallium based
glass, germanium-based glass or boracite glass (such as are
described D. P. Button et al., Solid State Ionics, Vols. 9-10, Part
1, 585-592 (December 1983); ceramic active metal ion conductors,
such as lithium beta-alumina, sodium beta-alumina, Li superionic
conductor (LISICON), Na superionic conductor (NASICON), and the
like; or glass-ceramic active metal ion conductors. Specific
examples include LiPON, Li.sub.3PO.sub.4.Li.sub.2S.SiS.sub.2,
Li.sub.2S.GeS.sub.2.Ga.sub.2S.sub.3, Li.sub.2O.11Al.sub.2O.sub.3,
Na.sub.2O.11Al.sub.2O.sub.3, (Na,
Li).sub.1+xTi.sub.2-xAl.sub.x(PO.sub.4).sub.3
(0.6.ltoreq.x.ltoreq.0.9) and crystallographically related
structures, Na.sub.3Zr.sub.2Si.sub.2PO.sub.12,
Li.sub.3Zr.sub.2Si.sub.2PO.sub.12, Na.sub.5ZrP.sub.3O.sub.12,
Na.sub.5TiP.sub.3O.sub.12, Na.sub.3Fe.sub.2P.sub.3O.sub.12,
Na.sub.4NbP.sub.3O.sub.12, Li.sub.5ZrP.sub.3O.sub.12,
Li.sub.5TiP.sub.3O.sub.12, Li.sub.3Fe.sub.2P.sub.3O.sub.12 and
Li.sub.4NbP.sub.3O.sub.12, and combinations thereof, optionally
sintered or melted. Suitable ceramic ion active metal ion
conductors are described, for example, in U.S. Pat. No. 4,985,317
to Adachi et al., incorporated by reference herein in its entirety
and for all purposes.
[0018] A particularly suitable glass-ceramic material for the
second layer of the protective composite is a lithium ion
conductive glass-ceramic having the following composition:
TABLE-US-00001 Composition mol % P.sub.2O.sub.5 26-55% SiO.sub.2
0-15% GeO.sub.2 + TiO.sub.2 25-50% in which GeO.sub.2 0-50%
TiO.sub.2 0-50% ZrO.sub.2 0-10% M.sub.2O.sub.3 0-10%
Al.sub.2O.sub.3 0-15% Ga.sub.2O.sub.3 0-15% Li.sub.2O 3-25%
and containing a predominant crystalline phase composed of
Li.sub.1+x(M,Al,Ga).sub.n(Ge.sub.1-yTi.sub.y).sub.2-x(PO.sub.4).sub.3
where X.ltoreq.0.8 and 0.ltoreq.Y.ltoreq.1.0, and where M is an
element selected from the group consisting of Nd, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm and Yb and/or
Li.sub.1+x+yQ.sub.xTi.sub.2-xSi.sub.yP.sub.3-yO.sub.12 where
0<X.ltoreq.0.4 and 0.ltoreq.Y.ltoreq.0.6, and where Q is Al or
Ga. The glass-ceramics are obtained by melting raw materials to a
melt, casting the melt to a glass and subjecting the glass to a
heat treatment. Such materials are available from OHARA
Corporation, Japan and are further described in U.S. Pat. Nos.
5,702,995, 6,030,909, 6,315,881 and 6,485,622, incorporated herein
by reference.
[0019] Either layer may also include additional components. For
instance, a suitable active metal compatible layer (first layer)
may include a polymer component to enhance its properties. For
example, polymer-iodine complexes like poly(2-vinylpyridine)-iodine
(P2VP-I.sub.2), polyethylene-iodine, or tetraalkylammonium-iodine
complexes can react with Li to form a LiI-based film having
significantly higher ionic conductivity than that for pure LiI.
Also, a suitable first layer may include a material used to
facilitate its use, for example, the residue of a wetting layer
(e.g., Ag) used to prevent reaction between vapor phase lithium
(during deposition) and LiPON when LiPON is used as a first layer
material.
[0020] In solid state embodiments, a suitable second layer may
include a polymer component to enhance its properties. For example,
a glass-ceramic active metal ion conductor, like the glass-ceramic
materials described above, may also be combined with polymer
electrolytes to form flexible composite sheets of material which
may be used as second layer of the protective composite. One
important example of such a flexible composite material has been
developed by OHARA Corp. (Japan). It is composed of particles of a
Li-ion conducting glass-ceramic material, such as described above,
and a solid polymer electrolyte based on PEO-Li salt complexes.
OHARA Corp. manufactures this material in the form of sheet with a
thickness of about 50 microns that renders it flexible while
maintaining its high ionic conductivity. Because of its relatively
high ionic conductivity (better than 4*10.sup.-5 S/cm at room
temperature in the case of the OHARA product) and stability toward
metallic Li, this type of composite electrolyte can be used at room
temperature or elevated temperatures in fully solid-state
cells.
[0021] In addition, the layers may be formed using a variety of
techniques. These include deposition or evaporation (including
e-beam evaporation) of layers of material, such as Li.sub.3N or an
ionically conductive glass. Also, as noted above, the active metal
electrode adjacent layer may be formed in situ from the
non-deleterious reaction of one or more precursors with the active
metal electrode. For example, a Li.sub.3N layer may be formed on a
Li anode by contacting Cu.sub.3N with the Li anode surface, or
Li.sub.3P may be formed on a Li anode by contacting red phosphorus
with the Li anode surface.
[0022] The invention encompasses protected anode structures with
fully-formed protective layers and battery separators incorporating
ambient stable precursors, each of which may be handled or stored
in normal ambient atmospheric conditions without degradation prior
to incorporation into a battery cell. Battery cells and methods for
making composites and battery cells are also provided.
[0023] These and other features of the invention are further
described and exemplified in the detailed description below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0024] FIG. 1 is a schematic illustration of an active metal
battery cell incorporating an ionically conductive protective
membrane in accordance with the present invention.
[0025] FIGS. 2A and B are schematic illustrations of ionically
conductive protective membrane battery separators in accordance
with the present invention.
[0026] FIG. 3A is a schematic illustration of an active metal anode
structure incorporating an ionically conductive protective laminate
composite membrane in accordance with the present invention.
[0027] FIG. 3B is a schematic illustration of an active metal anode
structure incorporating an ionically conductive protective graded
composite membrane in accordance with the present invention.
[0028] FIGS. 4A-B, 5 and 6A-B are schematic illustrations of
alternative methods of making an electrochemical device structure
incorporating an ionically conductive protective membrane in
accordance with the present invention.
[0029] FIGS. 7A-B and 8A-D are plots of data illustrating the
performance benefits of ionically conductive protective membranes
in accordance with the present invention.
DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS
[0030] Reference will now be made in detail to specific embodiments
of the invention. Examples of the specific embodiments are
illustrated in the accompanying drawings. While the invention will
be described in conjunction with these specific embodiments, it
will be understood that it is not intended to limit the invention
to such specific embodiments. On the contrary, it is intended to
cover alternatives, modifications, and equivalents as may be
included within the spirit and scope of the invention as defined by
the appended claims. In the following description, numerous
specific details are set forth in order to provide a thorough
understanding of the present invention. The present invention may
be practiced without some or all of these specific details. In
other instances, well known process operations have not been
described in detail so as not to unnecessarily obscure the present
invention.
[0031] When used in combination with "comprising," "a method
comprising," "a device comprising" or similar language in this
specification and the appended claims, the singular forms "a,"
"an," and "the" include plural reference unless the context clearly
dictates otherwise. Unless defined otherwise, all technical and
scientific terms used herein have the same meaning as commonly
understood to one of ordinary skill in the art to which this
invention belongs.
INTRODUCTION
[0032] The present invention provides ionically conductive
membranes for decoupling the active metal anode and cathode sides
of an active metal electrochemical cell, and methods for their
fabrication. The membranes may be incorporated in active metal
negative electrode (anode) structures and electrochemical devices
and components, including battery and fuel cells. The membranes are
highly conductive for ions of the active metal, but are otherwise
substantially impervious. They are chemically stable on one side to
the active metal of the anode (e.g., lithium), and on the other
side to the cathode, other battery cell components such as solid or
liquid phase electrolytes, including organic or aqueous liquid
electrolytes, and preferably to ambient conditions. The membrane is
capable of protecting an active metal anode from deleterious
reaction with other battery components or ambient conditions and
decoupling the chemical environments of the anode and cathode
enabling use of anode-incompatible materials, such as solvents and
electrolytes, on the cathode side without deleterious impact on the
anode, and vice versa. This broadens the array of materials that
may be used in active metal electrochemical cells and facilitates
cell fabrication while providing a high level of ionic conductivity
to enhance performance of an electrochemical cell in which the
membrane is incorporated.
[0033] The membrane may have any suitable composition, for example,
it may be a monolithic material chemically compatible with both the
anode and cathode environments, or a composite composed of at least
two components of different materials having different chemical
compatibilities, one chemically compatible with the anode
environment and the other chemically compatible with the cathode
environment.
[0034] Composite membranes may be composed of at least two
components of different materials having different chemical
compatibility requirements. The composite may be composed of a
laminate of discrete layers of materials having different chemical
compatibility requirements, or it may be composed of a gradual
transition between layers of the materials. By "chemical
compatibility" (or "chemically compatible") it is meant that the
referenced material does not react to form a product that is
deleterious to battery cell operation when contacted with one or
more other referenced battery cell components or manufacturing,
handling or storage conditions.
[0035] A first material layer of the composite is both ionically
conductive and chemically compatible with an active metal electrode
material. Chemical compatibility in this aspect of the invention
refers to a material that is chemically stable and therefore
substantially unreactive when contacted with an active metal
electrode material. Active metals are highly reactive in ambient
conditions and can benefit from a barrier layer when used as
electrodes. They are generally alkali metals such (e.g., lithium,
sodium or potassium), alkaline earth metals (e.g., calcium or
magnesium), and/or certain transitional metals (e.g., zinc), and/or
alloys of two or more of these. The following active metals may be
used: alkali metals (e.g., Li, Na, K), alkaline earth metals (e.g.,
Ca, Mg, Ba), or binary or ternary alkali metal alloys with Ca, Mg,
Sn, Ag, Zn, Bi, Al, Cd, Ga, In. Preferred alloys include lithium
aluminum alloys, lithium silicon alloys, lithium tin alloys,
lithium silver alloys, and sodium lead alloys (e.g., Na.sub.4Pb). A
preferred active metal electrode is composed of lithium. Chemical
compatibility also refers to a material that may be chemically
stable with oxidizing materials and reactive when contacted with an
active metal electrode material to produce a product that is
chemically stable against the active metal electrode material and
has the desirable ionic conductivity (i.e., a first layer
material). Such a reactive material is sometimes referred to as a
"precursor" material.
[0036] A second material layer of the composite is substantially
impervious, ionically conductive and chemically compatible with the
first material. By substantially impervious it is meant that the
material provides a sufficient barrier to battery electrolytes and
solvents and other battery component materials that would be
damaging to the electrode material to prevent any such damage that
would degrade electrode performance from occurring. Thus, it should
be non-swellable and free of pores, defects, and any pathways
allowing air, moisture, electrolyte, etc. to penetrate though it to
the first material. Preferably, the second material layer is so
impervious to ambient moisture, carbon dioxide, oxygen, etc. that
an encapsulated lithium alloy electrode can be handled under
ambient conditions without the need for elaborate dry box
conditions as typically employed to process other lithium
electrodes. Because the composite protective layer described herein
provides such good protection for the lithium (or other active
metal), it is contemplated that electrodes and
electrode/electrolyte composites of this invention may have a quite
long shelf life outside of a battery. Thus, the invention
contemplates not only batteries containing a negative electrode,
but unused negative electrodes and electrode/electrolyte laminates
themselves. Such negative electrodes and electrode/electrolyte
laminates may be provided in the form of sheets, rolls, stacks,
etc. Ultimately, they may be integrated with other battery
components to fabricate a battery. The enhanced stability of the
batteries of this invention will greatly simplify this fabrication
procedure.
[0037] In addition to the protective composite laminate structure
described above, a protective composite in accordance with the
present invention may alternatively be a functionally graded layer,
as further described below.
[0038] It should be noted that the first and second materials are
inherently ionically conductive. That is, they do not depend on the
presence of a liquid electrolyte or other agent for their ionically
conductive properties.
[0039] Additional layers are possible to achieve these aims, or
otherwise enhance electrode stability or performance. All layers of
the composite have high ionic conductivity, at least 10.sup.-7
S/cm, generally at least 10.sup.-6 S/cm, for example at least
10.sup.-5 S/cm to 10.sup.-4 S/cm, and as high as 10.sup.-3 S/cm or
higher so that the overall ionic conductivity of the multi-layer
protective structure is at least 10.sup.-7 S/cm and as high as
10.sup.-3 S/cm or higher.
[0040] Protective Membranes and Structures
[0041] FIG. 1 illustrates an ionically conductive protective
membrane in accordance with the present invention in context as it
would be used in an active metal battery cell 120, such as a
lithium-sulfur battery, in accordance with the present invention.
The membrane 100 is both ionically conductive and chemically
compatible with an active metal (e.g., lithium) electrode (anode)
106 on one side, and substantially impervious, ionically conductive
and chemically compatible with an electrolyte 110 and/or cathode
112 on the other side. The ionic conductivity of the membrane is at
least 10.sup.-7 S/cm, generally at least 10.sup.-6 S/cm, for
example at least 10.sup.-5 S/cm to 10.sup.-4 S/cm, and as high as
10.sup.-3 S/cm or higher. The active metal anode 106 in contact
with the first side of the protective membrane is connected with a
current collector 108 composed of a conductive metal, such as
copper, that is generally inert to and does not alloy with the
active metal. The other side of the membrane 100, is (optionally)
in contact with an electrolyte 110. Alternatively, in some
embodiments, the protective membrane 100 may itself be the sole
electrolyte of the battery cell. Adjacent to the electrolyte is the
cathode 112 with its current collector 114.
[0042] The protective membrane may be a composite composed of two
or more materials that present sides having different chemical
compatibility to the anode and electrolyte and/or cathode,
respectively. The composite is composed of a first layer of a
material that is both ionically conductive and chemically
compatible with an active metal electrode material. The composite
also includes second layer of a material that is substantially
impervious, ionically conductive and chemically compatible with the
first material and the cathode/electrolyte environment.
[0043] As described further below, given the protection afforded by
the protective membranes of the present invention, the electrolytes
and/or cathodes combined with the protected anodes of the present
invention may include a wide variety of materials including, but
not limited to, those described in the patents of PolyPlus Battery
Company, referenced herein below.
[0044] FIG. 2A illustrates a protective membrane composite battery
separator in accordance with one embodiment of the present
invention. The separator 200 includes a laminate of discrete layers
of materials with different chemical compatibilities. A layer of a
first material or precursor 202 is ionically conductive and
chemically compatible with an active metal. In most cases, the
first material is not chemically compatible with oxidizing
materials (e.g., air, moisture, etc). The first layer, in contact
with the active metal, may be composed, in whole or in part, of
active metal nitrides, active metal phosphides, active metal
halides or active metal phosphorus oxynitride-based glasses.
Specific examples include Li.sub.3N, Li.sub.3P, LiI, LiBr, LiCl and
LiF. In at least one instance, LiPON, the first material is
chemically compatible with oxidizing materials. The thickness of
the first material layer is preferably about 0.1 to 5 microns, or
0.2 to 1 micron, for example about 0.25 micron.
[0045] As noted above, the first material may also be a precursor
material which is chemically compatible with an active metal and
reactive when contacted with an active metal electrode material to
produce a product that is chemically stable against the active
metal electrode material and has the desirable ionic conductivity
(i.e., a first layer material). Examples of suitable precursor
materials include metal nitrides, red phosphorus, nitrogen and
phosphorus containing organics (e.g., amines, phosphines, borazine
(B.sub.3N.sub.3H.sub.6), triazine (C.sub.3N.sub.3H.sub.3)) and
halides. Some specific examples include P (red phosphorus),
Cu.sub.3N, SnN.sub.x, Zn.sub.3N.sub.2, FeN.sub.x, CoN.sub.x,
aluminum nitride (AlN), silicon nitride (Si.sub.3N.sub.4) and
I.sub.2, Br.sub.2, Cl.sub.2 and F.sub.2. Such precursor materials
can subsequently react with active metal (e.g., Li) to form Li
metal salts, such as the lithium nitrides, phosphides and halides
described above. In some instances, these first layer material
precursors may also be chemically stable in air (including moisture
and other materials normally present in ambient atmosphere), thus
facilitating handling and fabrication. Examples include metal
nitrides, for example Cu.sub.3N.
[0046] Also, a suitable active metal compatible layer may include a
polymer component to enhance its properties. For example,
polymer-iodine complexes like poly(2-vinylpyridine)-iodine
(P2VP-I.sub.2), polyethylene-iodine, or with
tetraalkylammonium-iodine complexes can react with Li to form a
LiI-based film having significantly higher ionic conductivity than
that for pure LiI.
[0047] The ionic conductivity of the first material is high, at
least 10.sup.-7 S/cm, generally at least about 10.sup.-5 S/cm, and
may be as high as 10.sup.-3 S/cm or higher.
[0048] Adjacent to the first material or precursor layer 202 is a
second layer 204 that is substantially impervious, ionically
conductive and chemically compatible with the first material or
precursor, including glassy or amorphous metal ion conductors, such
as a phosphorus-based glass, oxide-based glass,
phosphorus-oxynitride-based glass, sulpher-based glass,
oxide/sulfide based glass, selenide based glass, gallium based
glass, germanium-based glass or boracite glass (such as are
described D. P. Button et al., Solid State Ionics, Vols. 9-10, Part
1, 585-592 (December 1983); ceramic active metal ion conductors,
such as lithium beta-alumina, sodium beta-alumina, Li superionic
conductor (LISICON), Na superionic conductor (NASICON), and the
like; or glass-ceramic active metal ion conductors. Specific
examples include LiPON, Li.sub.3PO.sub.4.Li.sub.2S.SiS.sub.2,
Li.sub.2S.GeS.sub.2.Ga.sub.2S.sub.3, Li.sub.2O.11Al.sub.2O.sub.3,
Na.sub.2O.11Al.sub.2O.sub.3, (Na,
Li).sub.1+xTi.sub.2-xAl.sub.x(PO.sub.4).sub.3
(0.6.ltoreq.x.ltoreq.0.9) and crystallographically related
structures, Na.sub.3Zr.sub.2Si.sub.2PO.sub.12,
Li.sub.3Zr.sub.2Si.sub.2PO.sub.12, Na.sub.5ZrP.sub.3O.sub.12,
Na.sub.5TiP.sub.3O.sub.12, Na.sub.3Fe.sub.2P.sub.3O.sub.12,
Na.sub.4NbP.sub.3O.sub.12, Li.sub.5ZrP.sub.3O.sub.12,
Li.sub.5TiP.sub.3O.sub.12, Li.sub.3Fe.sub.2P.sub.3O.sub.12 and
Li.sub.4NbP.sub.3O.sub.12, and combinations thereof, optionally
sintered or melted. Suitable ceramic ion active metal ion
conductors are described, for example, in U.S. Pat. No. 4,985,317
to Adachi et al., incorporated by reference herein in its entirety
and for all purposes.
[0049] A particularly suitable glass-ceramic material for the
second layer of the protective composite is a lithium ion
conductive glass-ceramic having the following composition:
TABLE-US-00002 Composition mol % P.sub.2O.sub.5 26-55% SiO.sub.2
0-15% GeO.sub.2 + TiO.sub.2 25-50% in which GeO.sub.2 0-50%
TiO.sub.2 0-50% ZrO.sub.2 0-10% M.sub.2O.sub.3 0-10%
Al.sub.2O.sub.3 0-15% Ga.sub.2O.sub.3 0-15% Li.sub.2O 3-25%
and containing a predominant crystalline phase composed of
Li.sub.1+x(M,Al,Ga).sub.x(Ge.sub.1-yTi.sub.y).sub.2-x(PO.sub.4).sub.3
where X.ltoreq.0.8 and 0.ltoreq.Y.ltoreq.1.0, and where M is an
element selected from the group consisting of Nd, Sm, Eu, Gd, Tb,
Dy, Ho, Er, Tm and Yb and/or
Li.sub.1+x+yQ.sub.x(Ti.sub.2-x(Si.sub.yP.sub.3-yO.sub.12 where
0<X.ltoreq.0.4 and 0.ltoreq.Y.ltoreq.0.6, and where Q is Al or
Ga. The glass-ceramics are obtained by melting raw materials to a
melt, casting the melt to a glass and subjecting the glass to a
heat treatment. Such materials are available from OHARA
Corporation, Japan and are further described in U.S. Pat. Nos.
5,702,995, 6,030,909, 6,315,881 and 6,485,622, incorporated herein
by reference.
[0050] The high conductivity of some of these glasses, ceramics and
glass-ceramics (ionic conductivity in the range of about 10.sup.-5
to 10.sup.-3 S/cm or greater) may enhance performance of the
protected lithium anode, and allow relatively thick films to be
deposited without a large penalty in terms of ohmic resistance.
[0051] Also, for solid state applications, a suitable second layer
may include a polymer component to enhance its properties. For
example, a glass-ceramic active metal ion conductor, like the
glass-ceramic materials described above, may also be combined with
polymer electrolytes to form flexible composite sheets of material
which may be used as second layer of the protective composite. One
important example of such a flexible composite material has been
developed by OHARA Corp. (Japan). It is composed of particles of a
Li-ion conducting glass-ceramic material, such as described above,
and a solid polymer electrolyte based on PEO-Li salt complexes.
OHARA Corp. manufactures this material in the form of sheet with a
thickness of about 50 microns that renders it flexible while
maintaining its high ionic conductivity. Because of its relatively
high ionic conductivity (better than 4*10.sup.-5 S/cm at room
temperature in the case of the OHARA product) and stability toward
metallic Li, this type of composite electrolyte can be used at room
temperature or elevated temperatures in fully solid-state
cells.
[0052] The composite barrier layer should have an inherently high
ionic conductivity. In general, the ionic conductivity of the
composite is at least 10.sup.-7 S/cm, generally at least about
10.sup.-6 to 10.sup.-5 S/cm, and may be as high as 10.sup.-4 to
10.sup.-3 S/cm or higher. The thickness of the first precursor
material layer should be enough to prevent contact between the
second material layer and adjacent materials or layers, in
particular, the active metal of the anode with which the separator
is to be used. For example, the first material layer may have a
thickness of about 0.1 to 5 microns; 0.2 to 1 micron; or about 0.25
micron.
[0053] The thickness of the second material layer is preferably
about 0.1 to 1000 microns, or, where the ionic conductivity of the
second material layer is about 10.sup.-7 S/cm, about 0.25 to 1
micron, or, where the ionic conductivity of the second material
layer is between about 10.sup.-4 about 10.sup.-3 S/cm, about 10 to
1000 microns, preferably between 1 and 500 microns, and more
preferably between 10 and 100 microns, for example 20 microns.
[0054] When the first material layer is a precursor material
chemically stable in air, for example Cu.sub.3N or LiPON, the
protective composite battery separator may be handled or stored in
normal ambient atmospheric conditions without degradation prior to
incorporation into a battery cell. When the separator is
incorporated into a battery cell, the precursor layer 202 is
contacted with an active metal (e.g., lithium) electrode. The
precursor reacts with the active metal to form an ionically
conductive material that is chemically compatible with the active
metal electrode material. The second layer is contacted with an
electrolyte to which a cathode and current collector is or has been
applied. Alternatively, the second layer acts as the sole
electrolyte in the battery cell. In either case, the combination of
the two layers in the protective composite protects the active
metal electrode and the electrolyte and/or cathode from deleterious
reaction with one another.
[0055] In addition to the protective composite laminates described
above, a protective composite in accordance with the present
invention may alternatively be compositionally and functionally
graded, as illustrated in FIG. 2B. Through the use of appropriate
deposition technology such as RF sputter deposition, electron beam
deposition, thermal spray deposition, and or plasma spray
deposition, it is possible to use multiple sources to lay down a
graded film. In this way, the discrete interface between layers of
distinct composition and functional character is replaced by a
gradual transition of from one layer to the other. The result, as
with the discrete layer composites described above, is a
bi-functionally compatible ionically conductive composite 220
stable on one side 214 to lithium or other active metal (first
material), and on the other side 216 substantially impervious and
stable to ambient conditions, and ultimately, when incorporated
into a battery cell, to the cathode, other battery cell components
(second material). In this embodiment, the proportion of the first
material to the second material in the composite may vary widely
based on ionic conductivity and mechanical strength issues, for
example. In many, but not all, embodiments the second material will
dominate. For example, suitable ratios of first to second materials
may be 1-1000 or 1-500, for example about 1 to 200 where the second
material has greater strength and ionic conductivity than the first
(e.g., 2000 .ANG. of LiPON and 20-30 microns of OHARA
glass-ceramic). The transition between materials may occur over any
(e.g., relatively short, long or intermediate) distance in the
composite. Other aspects of the invention apply to these graded
protective composites substantially as to the discrete-layered
laminate protective composites, for example, they may be used in
the electrode and cell embodiments, etc.
[0056] FIG. 3A illustrates an encapsulated anode structure
incorporating a protective laminate composite in accordance with
the present invention. The structure 300 includes an active metal
electrode 308, e.g., lithium, bonded with a current collector 310,
e.g., copper, and a protective composite 302. The protective
composite 302 is composed of a first layer 304 of a material that
is both ionically conductive and chemically compatible with an
active metal electrode material, but not chemically compatible with
oxidizing materials (e.g., air). For example, the first layer, in
contact with the active metal, may be composed, in whole or in
part, of active metal nitrides, active metal phosphides or active
metal halides. Specific examples include Li.sub.3N, Li.sub.3P, LiI,
LiBr, LiCl and LiF. The thickness of the first material layer is
preferably about 0.1 to 5 microns, or 0.2 to 1 micron, for example
about 0.25 micron.
[0057] Active metal electrode materials (e.g., lithium) may be
applied to these materials, or they may be formed in situ by
contacting precursors such as metal nitrides, metal phosphides,
metal halides, red phosphorus, iodine and the like with lithium.
The in situ formation of the first layer may be by way of
conversion of the precursors to a lithiated analog, for example,
according to reactions of the following type (using P, Cu.sub.3N,
and PbI.sub.2 precursors as examples):
[0058] 1. 3Li+P.dbd.Li.sub.3P (reaction of the precursor to form
Li-ion conductor);
[0059] 2(a). 3Li+Cu.sub.3N.dbd.Li.sub.3N+3 Cu (reaction to form
Li-ion conductor/metal composite);
[0060] 2(b). 2Li+PbI.sub.2=2 LiI+Pb (reaction to form Li-ion
conductor/metal composite).
[0061] First layer composites, which may include electronically
conductive metal particles, formed as a result of in situ
conversions meet the requirements of a first layer material for a
protective composite in accordance with the present invention and
are therefore within the scope of the invention.
[0062] A second layer 306 of the protective composite is composed
of a substantially impervious, ionically conductive and chemically
compatible with the first material or precursor, including glassy
or amorphous metal ion conductors, such as a phosphorus-based
glass, oxide-based glass, phosphorus-oxynitride-based glass,
sulpher-based glass, oxide/sulfide based glass, selenide based
glass, gallium based glass, germanium-based glass or boracite
glass; ceramic active metal ion conductors, such as lithium
beta-alumina, sodium beta-alumina, Li superionic conductor
(LISICON), Na superionic conductor (NASICON), and the like; or
glass-ceramic active metal ion conductors. Specific examples
include LiPON, Li.sub.3PO.sub.4.Li.sub.2S.SiS.sub.2,
Li.sub.2S.GeS.sub.2.Ga.sub.2S.sub.3, Li.sub.2O.11Al.sub.2O.sub.3,
Na.sub.2O.11Al.sub.2O.sub.3, (Na, Li).sub.1+xTi.sub.2-
xAl.sub.x(PO.sub.4).sub.3 (0.6.ltoreq.x.ltoreq.0.9) and
crystallographically related structures,
Na.sub.3Zr.sub.2Si.sub.2PO.sub.12,
Li.sub.3Zr.sub.2Si.sub.2PO.sub.12, Na.sub.5ZrP.sub.3O.sub.12,
Na.sub.5TiP.sub.3O.sub.12, Na.sub.3Fe.sub.2P.sub.3O.sub.12,
Na.sub.4NbP.sub.3O.sub.12, Li.sub.5ZrP.sub.3O.sub.12,
Li.sub.5TiP.sub.3O.sub.12, Li.sub.3Fe.sub.2P.sub.3O.sub.12 and
Li.sub.4NbP.sub.3O.sub.12, and combinations thereof, optionally
sintered or melted. Suitable ceramic ion active metal ion
conductors are described, for example, in U.S. Pat. No. 4,985,317
to Adachi et al., incorporated by reference herein in its entirety
and for all purposes. Suitable glass-ceramic ion active metal ion
conductors are described, for example, in U.S. Pat. Nos. 5,702,995,
6,030,909, 6,315,881 and 6,485,622, previously incorporated herein
by reference and are available from OHARA Corporation, Japan.
[0063] The ionic conductivity of the composite is at least
10.sup.-7 S/cm, generally at least 10.sup.-6 S/cm, for example at
least 10.sup.-5 S/cm to 10.sup.-4 S/cm, and as high as 10.sup.-3
S/cm or higher. The thickness of the second material layer is
preferably about 0.1 to 1000 microns, or, where the ionic
conductivity of the second material layer is about 10.sup.-7 S/cm,
about 0.25 to 1 micron, or, where the ionic conductivity of the
second material layer is between about 10.sup.-4 about 10.sup.-3
S/cm, 10 to 1000 microns, preferably between 1 and 500 micron, and
more preferably between 10 and 100 microns, for example 20
microns.
[0064] When the anode structure is incorporated in a battery cell,
the first layer 304 is adjacent to an active metal (e.g., lithium)
anode and the second layer 306 is adjacent to an electrolyte or,
where the second layer is the sole electrolyte in the battery cell,
a cathode.
[0065] Either layer may also include additional components. For
instance, a suitable first active metal compatible layer 304 may
include a polymer component to enhance its properties. For example,
polymer-iodine complexes like poly(2-vinylpyridine)-iodine
(P2VP-I.sub.2), polyethylene-iodine, or with
tetraalkylammonium-iodine can react with Li to form a LiI-based
film having significantly higher ionic conductivity than that for
pure LiI. Also, for solid state applications, a suitable second
layer 306 may include a polymer component to enhance its
properties. For example, a glass-ceramic active metal ion conductor
like that available from OHARA Corporation, described above, may be
fabricated within a polymer matrix that renders it flexible while
maintaining its high ionic conductivity (available from OHARA
Corporation, Japan).
[0066] In addition, the layers may be formed using a variety of
techniques. These include deposition or evaporation (including
e-beam evaporation) of layers of material, such as Li.sub.3N or an
ionically conductive glass. Also, as noted above, the active metal
electrode adjacent layer may be formed in situ from the
non-deleterious reaction of one or more precursors with the active
metal electrode. For example, a Li.sub.3N layer may be formed on a
Li anode by contacting Cu.sub.3N with the Li anode surface, or
Li.sub.3P may be formed on a Li anode by contacting red phosphorus
with the Li anode surface.
[0067] As noted above with regard to the protective membrane
separator structures described in connection with FIGS. 2A and B,
in addition to the protective composite laminates described above,
a protective composite in accordance with the present invention may
alternatively be compositionally and functionally graded, as
illustrated in FIG. 3B. Through the use of appropriate deposition
technology such as RF sputter deposition, electron beam deposition,
thermal spray deposition, and or plasma spray deposition, it is
possible to use multiple sources to lay down a graded film. In this
way, the discrete interface between layers of distinct composition
and functional character is replaced by a gradual transition of
from one layer to the other. The result, as with the discrete layer
composites described above, is a bi-functionally compatible
ionically conductive composite 320 stable on one side 314 to
lithium or other active metal (first material), and on the other
side 316 substantially impervious and stable to the cathode, other
battery cell components and preferably to ambient conditions
(second material).
[0068] As noted with reference to the graded separator in FIG. 2B,
in this embodiment the proportion of the first material to the
second material in the composite may vary widely based on ionic
conductivity and mechanical strength issues, for example. In many,
but not all, embodiments the second material will dominate. For
example, suitable ratios of first to second materials may be 1-1000
or 1-500, for example about 1 to 200 where the second material has
greater strength and ionic conductivity than the first (e.g., 2000
.ANG. of LiPON and 20-30 microns of OHARA glass-ceramic). The
transition between materials may occur over any (e.g., relatively
short, long or intermediate) distance in the composite.
[0069] Also, an approach may be used where a first material and
second material are coated with another material such as a
transient and/or wetting layer. For example, an OHARA glass ceramic
plate is coated with a LiPON layer, followed by a thin silver (Ag)
coating. When lithium is evaporated onto this structure, the Ag is
converted to Ag--Li and diffuses, at least in part, into the
greater mass of deposited lithium, and a protected lithium
electrode is created. The thin Ag coating prevents the hot (vapor
phase) lithium from contacting and adversely reaction with the
LiPON first material layer. After deposition, the solid phase
lithium is stable against the LiPON. A multitude of such
transient/wetting (e.g., Sn) and first layer material combinations
can be used to achieve the desired result.
[0070] Thus, the invention encompasses protected anode structures
with fully-formed protective layers and battery separators
incorporating ambient stable precursors, each of which may be
handled or stored in normal ambient atmospheric conditions without
degradation prior to incorporation into a battery cell. Battery
cells and methods for making separators, anode structures and
battery cells are also provided.
[0071] Battery Cells
[0072] Protected active metal anodes as described herein may be
incorporated into a variety of battery cell structures. These
includes fully solid state battery cells and battery cells with gel
and liquid electrolyte systems, including, but not limited to,
those described in the patents of PolyPlus Battery Company,
referenced herein.
[0073] Solid and Gel State Batteries
[0074] A solid state battery cell in accordance with the present
invention may include a protected anode as described herein against
a polymer electrolyte such as polyethylene oxide (PEO), and a
PEO/carbon/metal-oxide type cathode.
[0075] Alternatively, gel-state electrolytes in which non-aqueous
solvents have been gelled through the use of a gelling agent such
as polyacrylonitrile (PAN), polyethylene oxide (PEO),
polyvinylidene fluoride (PVDF), or polymerizable monomers that are
added to the non-aqueous solvent system and polymerized in situ by
the use of heat or radiation may be used.
[0076] Examples of suitable solid and gel state electrolytes and
batteries incorporating them are described, for example, in U.S.
Pat. No. 6,376,123, issued Apr. 23, 2002 and titled RECHARGEABLE
POSITIVE ELECTRODES, assigned to PolyPlus Battery Company, the
assignee of the present application, which is incorporated herein
by reference in its entirety and for all purposes.
[0077] Liquid Electrolytes
[0078] One of the main requirements of the liquid electrolyte
system for all Li-metal and Li-ion battery cells is its
compatibility with the anode material. The liquid electrolytes of
existing Li-metal and Li-ion cells are not thermodynamically stable
toward Li metal, Li alloys, and Li--C compounds, but rather
kinetically stable due to formation of a solid electrolyte
interface (SEI) protecting the anode surface from a continuous
reaction with components of the electrolyte. Therefore, only a very
limited spectrum of aprotic solvents and supporting salts is
suitable for use in Li-metal and Li-ion batteries with an
unprotected anode. In particular, the binary, ternary or
multicomponent mixtures of alkyl carbonates or their mixtures with
ethers are used as solvents, and LiPF.sub.6 is generally used as a
supporting salt in electrolytes for Li-ion batteries.
[0079] The main component of these solvent mixtures is ethylene
carbonate (EC). It has been shown that without the presence of EC
in the electrolyte, the SEI formed does not provide enough
protection for anode surface, and cell's cyclability is very poor.
However, EC has a high melting point of 35.degree. C. and a high
viscosity that limits the rate capability and the cell's low
temperature performance. Another important disadvantage of existing
Li-ion batteries is the irreversible capacity loss during the first
charge associated with in situ formation of the SEI.
[0080] Protection of the anode with an ionically conductive
protective membrane in accordance with the present invention allows
for use of a very wide spectrum of solvents and supporting salts in
rechargeable and primary batteries with Li metal anodes. The
protected anode is completely decoupled from the electrolyte, so
electrolyte compatibility with the anode is no longer an issue;
solvents and salts which are not kinetically stable to Li can be
used. Improved performance can be obtained with conventional liquid
electrolytes, as noted above and as described, for example, in U.S.
Pat. No. 6,376,123, previously incorporated herein by reference.
Moreover, the electrolyte solution can be composed of only low
viscosity solvents, such as ethers like 1,2-dimethoxy ethane (DME),
tetrahydrofuran (THF), 2-methyltetrahydrofuran, 1,3-dioxolane
(DIOX), 4-methyldioxolane (4-MeDIOX) or organic carbonates like
dimethylcarbonate (DMC), ethylmethylcarbonate (EMC),
diethylcarbonate (DEC), or their mixtures. Also, super low
viscosity ester solvents or co-solvents such as methyl formate and
methyl acetate, which are very reactive to unprotected Li, can be
used. As is known to those skilled in the art, ionic conductivity
and diffusion rates are inversely proportional to viscosity such
that all other things being equal, battery performance improves as
the viscosity of the solvent decreases. The use of such electrolyte
solvent systems significantly improves battery performance, in
particular discharge and charge characteristics at low
temperatures.
[0081] Ionic Liquids
[0082] Ionic liquids are organic salts with melting points under
100 degrees, often even lower than room temperature. The most
common ionic liquids are imidazolium and pyridinium derivatives,
but also phosphonium or tetralkylammonium compounds are also known.
Ionic liquids have the desirable attributes of high ionic
conductivity, high thermal stability, no measurable vapor pressure,
and non-flammability. Representative ionic liquids are
1-Ethyl-3-methylimidazolium tosylate (EMIM-Ts),
1-Butyl-3-methylimidazolium octyl sulfate (BMIM-OctSO4),
1-Ethyl-3-methylimidazolium hexafluorophosphate, and
1-Hexyl-3-methylimidazolium tetrafluoroborate. Although there has
been substantial interest in ionic liquids for electrochemical
applications such as capacitors and batteries, they are unstable to
metallic lithium and lithiated carbon. However, protected lithium
anodes as described in this invention are isolated from direct
chemical reaction, and consequently lithium metal batteries using
ionic liquids can be developed as an embodiment of the present
invention. Such batteries should be particularly stable at elevated
temperatures.
[0083] Cathodes
[0084] Another important advantage associated with the use of
ionically conductive protective membranes in accordance with the
present invention in battery cells is that both lithiated
intercalation compounds and unlithiated intercalation compounds can
be used as cathode materials. As a result, protection of the anode
with ionically conductive composite materials allows for use of a
variety of 2, 3, 4 and 5 V cathodes suitable for fabrication of
primary and rechargeable batteries for a wide range of
applications. Examples of lithiated metal oxide based cathodes
suitable for rechargeable cells with protected Li anodes in
accordance with the present invention include: Li.sub.xCoO.sub.2,
Li.sub.xNiO.sub.2, Li.sub.xMn.sub.2O.sub.4 and LiFePO.sub.4.
Examples of unlithiated metal oxide or sulfide based cathodes
suitable for use both for primary and rechargeable cells with
protected Li anodes in accordance with the present invention
include: AgxV.sub.2O.sub.5, CuxV.sub.2O.sub.5, V.sub.2O.sub.5,
V.sub.6O.sub.13, FeS.sub.2 and TiS.sub.2. Examples of metal oxide
based cathodes suitable for primary cells with protected Li anodes
in accordance with the present invention include: MnO.sub.2, CuO,
Ag.sub.2CrO.sub.4 and MoO.sub.3. Examples of metal sulfide based
positive electrodes for primary cells with protected Li anodes in
accordance with the present invention include: CuS and FeS.
[0085] In addition, active sulfur cathodes including elemental
sulfur and polysulfides, as described in the patents of PolyPlus
Battery Company cited and incorporated by reference below are
suitable cathodes for protected lithium metal anode battery cells
in accordance with the present invention.
[0086] Fabrication Techniques
[0087] Materials and techniques for fabrication of active metal
battery cells are described, for example, in U.S. Pat. Nos.
5,686,201 and 6,376,123 issued to Chu on Nov. 11, 1997. Further
description of materials and techniques for fabrication of active
metal battery cells having anode protective layers are described,
for example, in U.S. patent application Ser. No. 09/139,601, filed
Aug. 25, 1998 (now U.S. Pat. No. 6,214,061, issued Apr. 10, 2001),
titled ENCAPSULATED LITHIUM ALLOY ELECTRODES HAVING BARRIER LAYERS,
and naming May-Ying Chu, Steven J. Visco and Lutgard C. DeJonge as
inventors; U.S. patent application Ser. No. 09/086,665 filed May
29, 1998 (now U.S. Pat. No. 6,025,094, issued May 15, 2000), titled
PROTECTIVE COATINGS FOR NEGATIVE ELECTRODES, and naming Steven J.
Visco and May-Ying Chu as inventors; U.S. patent application Ser.
No. 09/139,603 filed Aug. 25, 1998 (now U.S. Pat. No. 6,402,795,
issued Jun. 11, 2002), titled "PLATING METAL NEGATIVE ELECTRODES
UNDER PROTECTIVE COATINGS," and naming May-Ying Chu, Steven J.
Visco and Lutgard C. DeJonghe as inventors; U.S. patent application
Ser. No. 09/139,601 filed Aug. 25, 1998 (now U.S. Pat. No.
6,214,061, issued Apr. 10, 2001), titled "METHOD FOR FORMING
ENCAPSULATED LITHIUM ELECTRODES HAVING GLASS PROTECTIVE LAYERS,"
and naming Steven J. Visco and Floris Y. Tsang as inventors. The
active metal electrode may also be an active metal alloy electrode,
as further described in U.S. patent application Ser. No. 10/189,908
filed Jul. 3, 2002 (now U.S. Pat. No. 6,991,662, issued Jan. 31,
2006), titled "ENCAPSULATED ALLOY ELECTRODES," and naming Steven J.
Visco, Yevgeniy S. Nimon and Bruce D. Katz as inventors. The
battery component materials, including anodes, cathodes,
separators, protective layers, etc., and techniques disclosed
therein are generally applicable to the present invention and each
of these patent applications is incorporated herein by reference in
its entirety for all purposes.
[0088] In particular, a protective membrane in accordance with the
present invention may be formed using a variety of methods. These
include deposition or evaporation. Protective membrane composites
of the present invention may be formed by deposition or evaporation
(including e-beam evaporation) of the first layer of material or
precursor on the second layer of material. Also, as noted above and
described further below, the first layer may be formed in situ from
the non-deleterious reaction of one or more precursors with an
active metal electrode or material, by deposition or evaporation of
lithium on the precursor, by direct contact of the precursor with a
lithium metal (e.g., foil), or by plating of the precursor with
lithium through a second layer material. In some embodiments, the
second layer material may also be formed on the first layer
material, as described further below.
[0089] Referring to FIG. 4A, a first method for forming a
protective membrane composite in accordance with the present
invention is shown. A first layer, that is a highly ionically
conductive active metal chemically compatible material, is directly
deposited onto a second layer material, that is a substantially
impervious, ionically conductive material, for example, a highly
ionically conductive glass or glass-ceramic material such as LiPON
or an OHARA glass-ceramic material described above. This can be
done by a variety of techniques including RF sputtering, e-beam
evaporation, thermal evaporation, or reactive thermal or e-beam
evaporation, for example. In the particular example illustrated in
the figure, lithium is evaporated in a nitrogen plasma to form a
lithium nitride (Li.sub.3N) layer on the surface of a glass-ceramic
material such as the OHARA material described above. This is
followed by evaporation of lithium metal onto the Li.sub.3N film.
The Li.sub.3N layer separates the lithium metal electrode from the
second material layer, but allows Li ions to pass from the Li
electrode through the glass. Of course, other active metal, and
first and second layer materials, as described herein, may be used
as well.
[0090] Alternatively, referring to FIG. 4B, a second method for
forming a protective membrane composite in accordance with the
present invention is shown. The ionically conductive chemically
compatible first layer material is formed in situ following
formation of a precursor layer on the second layer material. In the
particular example illustrated in the figure, a surface of a
glass-ceramic layer, for example one composed of the OHARA material
described above, is coated with red phosphorus, a precursor for an
active metal (in this case lithium) phosphide. Then a layer of
lithium metal is deposited onto the phosphorus. The reaction of
lithium and phosphorus forms Li.sub.3P according to the following
reaction: 3Li+P.dbd.Li.sub.3P. Li.sub.3P is an ionically conductive
material that is chemically compatible with both the lithium anode
and the glass-ceramic material. In this way, the glass-ceramic (or
other second layer material) is not in direct contact with the
lithium electrode. Of course, other active metal, first layer
precursor and second layer materials, as described herein, may be
used as well. Alternative precursor examples include CuN.sub.3,
which may be formed as a thin layer on a second layer material
(e.g., glass-ceramic) and contacted with a Li anode in a similar
manner according to the following reaction:
3Li+Cu.sub.3N.dbd.Li.sub.3N+3 Cu; or lead iodide which may be
formed as a thin layer on a polymer electrolyte and contacted with
a Li anode in a similar manner according to the following reaction:
2Li+PbI.sub.2=2 LiI+Pb.
[0091] In another alternative, illustrated in FIG. 5, a protective
membrane composite in accordance with the present invention may
alternatively be compositionally and functionally graded so that
there is a gradual transition of from one layer to the other. For
example, a plasma spray operation with two spray heads, one for the
deposition of a first component material, such as Li.sub.3N,
Cu.sub.3N, Li.sub.3P, LiPON, or other appropriate material, and the
other for the deposition of a second component material, such as an
OHARA glass-ceramic, may be used. The first plasma spray process
begins laying down a layer of pure glass-ceramic material, followed
by a gradual decrease in flow as the second plasma spray torch is
gradually turned on, such that there is a gradient from pure
glass-ceramic to a continuous transition from glass-ceramic to pure
LiPON or Li.sub.3N, etc. In this way, one side of the membrane is
stable to active metal (e.g., lithium, sodium, etc.) and the other
side is substantially impervious and stable to the cathode, other
battery cell components and preferably to ambient conditions.
Electron beam deposition or thermal spray deposition may also be
used. Given the parameters described herein, one or skill in the
art will be able to use any of these techniques to form the graded
composites of the invention.
[0092] To form a protected anode, lithium is then bonded to the
graded membrane on the first layer material (stable to active
metal) side of the graded protective composite, for example by
evaporation of lithium onto the protective composite as described
above. It may also be desirable to add a bonding layer on top of
the lithium stable side of the graded composite protective layer,
such as Sn, Ag, Al, etc., before applying lithium.
[0093] In any of the forgoing methods described with reference to
FIGS. 4A-B and 5, rather than forming a lithium (or other active
metal) layer on the first layer material or precursor, the first
layer material or precursor of the protective composite may be
contacted with the lithium by bonding metallic lithium to the
protective interlayer material or precursor, for example by direct
contact with extruded lithium metal foil.
[0094] In a further embodiment, a suitable substrate, e.g., having
a wetting layer, such as a film of tin on copper, may be coated
with a first layer material precursor, e.g., Cu.sub.3N. This may
then be coated with a second layer material, e.g., a (ionically)
conductive glass. An active metal electrode may then be formed by
plating the tin electrode with lithium (or other active metal),
through the first and second layer materials. The Cu.sub.3N
precursor is also converted to Li.sub.3N by this operation to
complete the protective composite in accordance with the present
invention on a lithium metal electrode. Details of an active metal
plating process are described in commonly assigned U.S. Pat. No.
6,402,795, previously incorporated by reference.
[0095] With regard to the fabrication methods described above it is
important to note that commercial lithium foils are typically
extruded and have numerous surface defects due to this process,
many of which have deep recesses that would be unreachable by
line-of-sight deposition techniques such as RF sputter deposition,
thermal and E-beam evaporation, etc. Another issue is that active
metals such as lithium may be reactive to the thin-film deposition
environment leading to further deterioration of the surface during
the coating process. This typically leads to gaps and holes in a
membrane deposited onto the surface of an active metal electrode.
However, by inverting the process, this problem is avoided; lithium
is deposited on the protective membrane rather than the protective
membrane being deposited on lithium. Glass and glass-ceramic
membranes can be made quite smooth either by melt-casting
techniques, cut and polish methods, or a variety of known methods
leading to smooth surfaces (lithium is a soft metal that cannot be
polished). Single or multiple smooth, gap-free membranes may then
be deposited onto the smooth surface. After deposition is complete,
active metal can be deposited onto the smooth surface by
evaporation, resulting is a active meta/protective membrane
interface that is smooth and gap-free. Alternatively, a transient
bonding layer such as Ag can be deposited onto the protective
membrane such that extruded lithium foil can be joined to the
membrane by pressing the foil against the Ag layer.
[0096] Also as noted above, in an alternative embodiment of the
invention the first layer may include additional components. For
instance, a suitable first layer may include a polymer component to
enhance its properties. For example, polymer-iodine complexes like
poly(2-vinylpyridine)-iodine (P2VP-I.sub.2), polyethylene-iodine,
or tetraalkylammonium-iodine can react with Li to form an ionically
conductive LiI-based film that is chemically compatible with both
an active metal and a second layer material as described herein.
Without intending to be bound by theory, it is expected that the
use of polymer-iodine charge transfer complexes can lead to
formation of composites containing LiI and polymer and having
significantly higher ionic conductivity than that for pure LiI.
Other halogens may also be used in this manner, for example in
bromine complexes.
[0097] Referring to FIG. 6A, a first embodiment of this aspect of
the present invention is shown. A polymer layer and a layer of
iodine are coated on a second layer material surface and allowed to
react forming polymer-iodine complex.
[0098] According to this method, a thin layer of polymer may be
applied to the second material layer (e.g., conductive glass) using
brushing, dipping, or spraying. For example, a conductive glass
layer may be coated with a thin (e.g., 0.5 to 2.0 micron,
preferably 0.1 to 0.5 micron) layer of P2VP in this way.
[0099] One technique for applying an iodine coating is sublimation
of crystalline iodine that can be achieved at room temperature
(e.g., about 20 to 25.degree. C.) in a reactor placed in the dry
box or in a dry room. A sublimed layer of iodine can be made very
thin (e.g., 0.05 to 1.0 microns and the rate of sublimation can be
adjusted by varying the temperature or distance between the
substrate and source of iodine.
[0100] Alternatively, high concentrations (e.g., 50 to 100 g/liter
of iodine can be dissolved in an organic solvent, such as
acetonitrile and n-heptane. Dissolved iodine can be coated on the
conductive glass surface by such methods as dip coating, spraying
or brushing, among others. In this case, treatment conditions can
be easily changed by varying the length of coating treatment and
iodine concentrations. Examples of iodine sources for this
technique include metal iodides are AgI and PbI.sub.2, which are
known to be used as the cathode materials in solid-state batteries
with Li anode and LiI-based solid electrolyte.
[0101] Then, lithium (or other active metal) is contacted with the
polymer-iodine complex on the conductive glass (or other second
layer material), for example by evaporation or pressing onto the
glass coated with this complex. The result is a LiI-containing
composite protective barrier layer on the Li anode.
[0102] Referring to FIG. 6B, an alternative embodiment of this
aspect of the present invention is shown. A conductive glass (or
other second layer material) surface is coated with a thin layer of
iodine, such as by a technique described above, that can react with
Li forming LiI layer (A).
[0103] Active metal, for example lithium foil, can be coated with a
thin layer of polymer (B), for example as described above, and then
contacted with the iodine layer on the glass. After assembly,
iodine reacts with the polymer layer and, as a result,
LiI-containing composite protective barrier layer with reduced
impedance is formed.
EXAMPLES
[0104] The following examples provide details illustrating
advantageous properties, in particular very low impedance, of
composite membrane protective structures in accordance with the
present invention on lithium electrodes. These examples are
provided to exemplify and more clearly illustrate aspects of the
present invention and are in no way intended to be limiting.
Example 1
Impedance Measurements Using LIPON in Composite Protective
Layer
[0105] Approximately 0.75 microns of LiPON was RF sputter-deposited
onto copper foil samples in a MRC 8671 Sputter Deposition system.
Some of the copper foil samples were coated with an additional
layer of Cu.sub.3N (approximately 0.9 microns) by RF Magnetron
sputtering of a copper target in a nitrogen environment. One
LiPON/Cu sample was transferred to a vacuum evaporator, and
approximately 3 to 7 microns of lithium metal was evaporated
directly onto the LiPON surface. Another Cu.sub.3N/LiPON/Cu sample
was coated with a similar thickness of lithium. The impedance for
the unprotected LiPON/Cu sample is shown in FIG. 7A; the
evaporation of lithium onto the LiPON surface led to a dramatic
rise in the resistance of the sample, which is undesirable for
electrochemical devices. The beneficial effects of the protective
Cu.sub.3N film can be seen in FIG. 7B; the impedance is
dramatically lower in this case.
Example 2
Impedance Measurements Using Glass-Ceramic Active Metal Ion
Conductor (OHARA) in Composite Protective Layer
[0106] Samples of Li.sup.+ conductive glass-ceramic plates were
received from OHARA Corporation. Approximately 3 to 7 microns of
lithium was evaporated directly onto the OHARA glass-ceramic plate.
The deleterious reaction of lithium with the electrolyte is seen in
FIG. 8A; the impedance of the sample is quite large, approximately
40,000 .OMEGA.cm.sup.2. A film of Cu.sub.3N (about 0.9 microns
thick) was RF Magnetron sputter-deposited onto a second sample of
glass-ceramic plate, with subsequent evaporation of about 3 to 7
microns of lithium. The beneficial effect of the Cu.sub.3N film can
be seen in FIG. 8B; the impedance of the glass-ceramic is
dramatically improved relative to the plate without the Cu.sub.3N
film. Superimposition of FIGS. 8A and 8B in FIG. 8C further
illustrates the dramatic improvement in performance for the
Cu.sub.3N protected plate. The ionically conductive nature of the
protective film is seen in 8D, where lithium is moved across the
Li/Cu.sub.3N/glass interface; this is presumably due to conversion
of the ionically insulating Cu.sub.3N film to highly conductive
Li.sub.3N+Cu.
CONCLUSION
[0107] Although the foregoing invention has been described in some
detail for purposes of clarity of understanding, it will be
apparent that certain changes and modifications may be practiced
within the scope of the appended claims. It should be noted that
there are many alternative ways of implementing both the process
and compositions of the present invention. Accordingly, the present
embodiments are to be considered as illustrative and not
restrictive, and the invention is not to be limited to the details
given herein.
[0108] All references cited herein are incorporated by reference
for all purposes.
* * * * *