U.S. patent application number 12/373945 was filed with the patent office on 2009-11-12 for multilayer material based on active lithium, method of preparation and applications in electrochemical generators.
This patent application is currently assigned to Hydro-Quebec. Invention is credited to Martin Dontigny, Michel Gauthier, Michel Petitclerc, Karim Zaguib.
Application Number | 20090280410 12/373945 |
Document ID | / |
Family ID | 38952123 |
Filed Date | 2009-11-12 |
United States Patent
Application |
20090280410 |
Kind Code |
A1 |
Zaguib; Karim ; et
al. |
November 12, 2009 |
MULTILAYER MATERIAL BASED ON ACTIVE LITHIUM, METHOD OF PREPARATION
AND APPLICATIONS IN ELECTROCHEMICAL GENERATORS
Abstract
A method for preparing a multilayer material based on active
lithium, by depositing a film of active lithium on a protective
layer at a sufficient speed so that substantially no oxidation of
the lithium occurs, and/or during a sufficient time for the
adhesion of the lithium to develop after contact with the
protective layer. The multilayer material, when incorporated in an
electrochemical battery as an anode, has excellent impedance
stability and no formation of dendrites during the cycling.
Batteries where the anode is the multilayer material are
particularly efficient in terms of their coulomb efficiency.
Inventors: |
Zaguib; Karim; (Longueuil,
CA) ; Dontigny; Martin; (Notre-Dame-du-Mont-Carmel,
CA) ; Petitclerc; Michel; (Sainte-Julie, CA) ;
Gauthier; Michel; (La Prairie, CA) |
Correspondence
Address: |
BUCHANAN, INGERSOLL & ROONEY PC
POST OFFICE BOX 1404
ALEXANDRIA
VA
22313-1404
US
|
Assignee: |
Hydro-Quebec
Montreal
CA
|
Family ID: |
38952123 |
Appl. No.: |
12/373945 |
Filed: |
July 17, 2007 |
PCT Filed: |
July 17, 2007 |
PCT NO: |
PCT/CA07/01254 |
371 Date: |
January 15, 2009 |
Current U.S.
Class: |
429/220 ;
427/126.1; 427/126.3; 429/223; 429/231.9 |
Current CPC
Class: |
C23C 28/34 20130101;
C23C 28/322 20130101; H01M 4/661 20130101; H01M 4/625 20130101;
H01M 4/131 20130101; H01M 4/0402 20130101; H01M 4/525 20130101;
C23C 28/345 20130101; C23C 28/321 20130101; C23C 8/10 20130101;
H01M 10/0565 20130101; H01M 4/505 20130101; Y02E 60/10 20130101;
H01M 4/1391 20130101; C23C 28/00 20130101; H01M 10/052 20130101;
H01M 4/366 20130101; H01M 4/0407 20130101; C23C 28/324 20130101;
C23C 4/11 20160101 |
Class at
Publication: |
429/220 ;
429/231.9; 429/223; 427/126.1; 427/126.3 |
International
Class: |
H01M 4/38 20060101
H01M004/38; H01M 4/58 20060101 H01M004/58; B05D 5/12 20060101
B05D005/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jul 18, 2006 |
CA |
2,552,282 |
Claims
1-48. (canceled)
49. A method for preparing a multilayer material which comprises at
least one layer of active lithium, said method comprising a step of
depositing a film of active lithium on a protective layer at a
sufficient speed so that substantially no oxidation of the lithium
occurs, and/or during a sufficient time for the adhesion of the
lithium to develop after contact with the protective layer.
50. The method as claimed in claim 49, wherein the layer of active
lithium consists essentially of lithium which has a degree of
purity higher than 99%, or of a lithium alloy comprising less than
3000 ppm of impurities.
51. The method as claimed in claim 49, wherein the layer of active
lithium carries on one or each of its surfaces, a passivation layer
which is such that the ratio "thickness of the passivation
layer"/"thickness of the layer of active lithium" is between
2.10.sup.-5 and 1.10.sup.-3.
52. The method as claimed in claim 49, wherein the passivation
layer comprises at least one lithium compound from the group
consisting of Li.sub.2O, Li.sub.2CO.sub.3, LiOH, and
Li.sub.2S.sub.2O.sub.4; wherein the Li.sub.2O, Li.sub.2CO.sub.3 and
LiOH are formed in a dry atmosphere.
53. The method as claimed in claim 49, wherein a protective layer
is deposited on each of the surfaces of the film of active lithium,
the two protective layers consisting essentially of an
ion-conducting material.
54. The method as claimed in claim 49, wherein the film of active
lithium is deposited on a protective layer consisting essentially
of an ion-conducting material.
55. The method as claimed in claim 49, wherein the film of active
lithium is deposited on a protective layer consisting essentially
of an ion-conducting material and a protective layer consisting
essentially of an electron-conducting material is deposited on the
free surface of the film of active lithium.
56. The method as claimed in claim 49, wherein the method is
implemented in a dry air atmosphere, in an anhydrous chamber with a
dew point between -45 and 55.degree. C. and a relative humidity
between 0.7 and 2.2%.
57. The method as claimed in claim 49, wherein the protective layer
is deposited in 1 to 15 seconds.
58. The method as claimed in claim 49, wherein an ion-conducting
protective layer comprises at least two sublayers, consisting
essentially of, independently of one another, a material which has
an ion conduction higher than 10.sup.-4S.cm.sup.2, and which is
selected from ceramics, glasses, polymers, and polymers containing
a ceramic filler.
59. The method as claimed in claim 49, wherein the material
constituting the protective layer consists essentially of a ceramic
of the nonstoichiometric lithium phosphorus oxynitride type
(LIPON).
60. The method as claimed in claim 49, wherein the protective layer
consists essentially of a ceramic or of a glass with a thickness
equal to or less than 1 .mu.m, of a solution of an ionic compound
in a polymer, of a polymer carrying ionic groups, of a polymer
containing a ceramic, of a polymer with a thickness between 1 and
100 .mu.m, or of an electron conducting material.
61. A multilayer material obtained as claimed in claim 49,
comprising at least one layer of active lithium and one protective
layer adhering to one another, wherein the lithium layer is a layer
of active lithium which carries, on at least one of its surfaces, a
continuous or discontinuous passivation layer having an average
thickness of less than 50 .ANG., and wherein said at least one
protective layer consists essentially of an ion-conducting
material.
62. The multilayer material as claimed in claim 61, wherein the two
surfaces of the layer of active lithium carry an ion-conducting
protective layer.
63. The multilayer material as claimed in claim 61, wherein one of
the surfaces of the layer of active lithium adheres to a protective
layer consisting essentially of an ion-conducting material, and the
other surface of the layer of active lithium adheres to a
protective layer consisting essentially of an electron-conducting
material.
64. An electrochemical generator comprising at least one cathode,
one electrolyte and at least one anode, wherein the anode comprises
a multilayer material as claimed in claim 61.
65. The generator as claimed in claim 64, wherein it comprises at
least one assembly comprising the following elements, in the order
indicated: a collector; a cathode material; a polymer electrolyte,
or a separator impregnated with a gel electrolyte or a separator
impregnated with a liquid electrolyte; the multilayer material
forming the anode; wherein said multilayer material comprises a
layer of active lithium between a metal protective layer and a
nonmetallic protective layer, consisting essentially of a material
selected from ceramics of the LIPON type, ionic glasses, conducting
polymers, polymers containing ceramic fillers, and polymers made
conducting by the addition of a solution of an ionic compound in a
liquid solvent, the nonmetallic protective layer being in contact
with the electrolyte.
66. The generator as claimed in claim 64, wherein it comprises at
least one assembly comprising the following elements, in the order
indicated: a collector; a cathode material; a polymer electrolyte;
the multilayer material forming the anode; an electrolyte; a
cathode; a collector; wherein said multilayer material comprises a
layer of lithium between two protective layers, each consisting
essentially of, independently of one another, a material selected
from LIPON, ionic glasses, conducting polymers and polymers
containing ceramic fillers, and polymers made conducting by the
addition of a solution of an ionic compound in a liquid
solvent.
67. The generator as claimed in claim 64, wherein the lithium film
of the multilayer is in contact with a nickel or copper support
which serves as a current collector.
Description
FIELD OF THE INVENTION
[0001] The present invention relates to a method for preparing a
multilayer material based on active lithium, a method for its
preparation, and its use in electrochemical batteries.
RELATED ART
[0002] Lithium metal batteries in which the electrolyte is a
polymer electrolyte have the advantage of supplying an energy
density by weight and volume that is higher than that of Li-ion
batteries, thanks to the capacitance of the lithium metal anode
which is 3700 mAh/g. This value is 10 times higher than that of an
anode based on graphite (LiC.sub.6) or 20 times higher than that of
an anode of the titanium spinel (Li.sub.4Ti.sub.5O.sub.12)
type.
[0003] On the other hand, during the charging of high current
lithium batteries, in which the lithium is electrodeposited, a
potential formation of dendrites on the lithium surface may occur
fairly rapidly after a few cycles of use. These dendrites may
perforate the separator (in which the electrolyte is impregnated)
and touch the cathode.
[0004] One solution to this problem of instability is proposed in
U.S. Pat. No. 6,214,061. It consists in protecting a film of
lithium forming the anode of a battery by a protective layer
consisting of a vitreous ion-conducting material, for example glass
or a lithium phosphorus oxynitride, designated by LIPON. The
protective layer is deposited on a substrate, the lithium layer is
then deposited on the protective layer, and a current collector is
finally deposited on the lithium layer.
[0005] The protective layer and the lithium layer are deposited by
cathode sputtering or by vapor deposition. This technique yields
good results. However, it requires operation under vacuum for the
deposition of the protective layer and of the lithium layer,
demanding more complicated and more costly devices at the
industrial level.
[0006] The use of a thin film of lithium is important in lithium
metal polymer batteries, because it serves to optimize the excess
lithium, by comparison with the capacitance of the cathode.
[0007] The technology for obtaining thin films of lithium metal by
lamination is described in CA-A-2 099 524 and CA-A-2 099 526 in the
name of Hydro-Quebec.
[0008] CA-A-2 099 524 describes a method for laminating a lithium
strip for obtaining a lithium film between 10 and 100 .mu.m thick.
This method is characterized by the fact that at the discharge end
of the roll mill and after a single passage, in the presence of a
lubricant, the roll mill film remains adhering to the surface of
one of the working rolls up to a given point on a portion of the
circumference of this roll beyond the meeting point of the two
rolls. Although the film obtained thereby can be used in an
electrochemical generator, it has a passivation layer with a
non-negligible thickness.
[0009] CA-A-2 099 526 describes additives for lubricants usable in
the lamination of lithium strips in thin films, which improves
their performance. These additives are represented by the general
formula L-A-B where L is a hydrocarbon radical acting as a
lubricant segment, B denotes an oligomer segment serving as a
solvate segment for the metal salts, and A is a chemical bond
joining the hydrocarbon radical to the oligomer segment.
SUMMARY
[0010] It is an object of the present invention to propose a method
for preparing electrochemical batteries which have an anode whereof
the active material is a thin film of lithium, which can be
implemented at atmospheric pressure, that is in the most convenient
industrial conditions, and which yields batteries in which said
lithium film adheres perfectly to the elements of the battery
adjacent to it and does not form dendrites during operation.
[0011] This is why the present invention relates to a method for
preparing a multilayer comprising at least one film of lithium, the
multilayer obtained, and its use as an anode in an electrochemical
battery.
[0012] The inventive method is suitable for preparing a multilayer
material comprising at least one layer of active lithium, and it is
characterized in that it comprises a step of depositing a film of
active lithium on a protective layer at a sufficient speed so that
substantially no oxidation of the lithium occurs, and/or during a
sufficient time for the adhesion of the lithium to develop after
contact with the protective layer.
[0013] The multilayer material according to the invention comprises
at least one layer of active lithium which carries a protective
layer on at least one of its surfaces, said protective layer
consisting or consisting essentially of an ion-conducting
material.
[0014] A multilayer material of the invention, when incorporated in
an electrochemical battery as an anode, has excellent impedance
stability, with no formation of dendrites during cycling.
[0015] The batteries of which the anode comprise a multilayer
material of the invention are particularly efficient in terms of
their coulomb efficiency.
BRIEF DESCRIPTION OF THE DRAWINGS
[0016] FIGS. 1A and 1B: show the variation in thickness of a
passivation film of lithium (E, in .ANG.) on the y-axis, as a
function of exposure time in a dry air atmosphere (T, in seconds)
on the x-axis, for a lithium film obtained according to the
invention; FIG. 1A is an enlarged view of the zone T=0 to 1 of FIG.
1B.
[0017] FIG. 2: shows the method for applying the protective film to
the lithium, which serves to maintain the thickness of the
passivation layer of lithium constant over time; the curves E (in
.ANG.) as a function of T (in seconds) show the variation in
thickness of the passivation layer, before (left-hand curve) and
after the deposition of two protective layers (right-hand curve);
Li denotes a film of standard lithium, Li* denotes a film of active
lithium; P denotes the protective material (glass or ceramic); No.
1 and No. 2 respectively denote the 1.sup.st and the 2.sup.nd step
of the process.
GENERAL DESCRIPTION OF THE INVENTION
[0018] A first object of the invention relates to a method for
preparing a multilayer material which comprises at least one layer
of active lithium, said method comprising a step of depositing a
film of active lithium on a protective layer at a sufficient speed
so that substantially no oxidation of the lithium occurs, and/or
during a sufficient time for the adhesion of the lithium to develop
after contact with the protective layer.
[0019] The layer of active lithium consists or consists essentially
of lithium which has a degree of purity higher than 99%, or of a
lithium alloy comprising less than 3000 ppm of impurities. Such a
layer has good adhesion properties.
[0020] In one embodiment, the layer of active lithium carries on
one or each of its surfaces, a passivation layer which is such that
the ratio "thickness of the passivation layer"/"thickness of the
layer of active lithium" is between 2.105 and 1.10.sup.-3.
[0021] In another embodiment, the thickness of the passivation
layer is zero.
[0022] The passivation layer comprises at least one lithium
compound from the group consisting of Li.sub.2O, Li.sub.2CO.sub.3,
LiOH, and Li.sub.2S.sub.2O.sub.4. Li.sub.2O, Li.sub.2CO.sub.3 and
LiOH are formed in a dry atmosphere, Li.sub.2S.sub.2O.sub.4 is
formed in the presence of SO.sub.2.
[0023] It is particularly preferred to effect the deposition of the
film of active lithium on the protective layer by lamination. The
conditions for carrying out a lithium deposition on a support layer
by lamination, especially the additives used, in particular the
lubricants, are described in CA-A-2 099 524 and CA-A-2 099 526.
[0024] When the multilayer material is intended for use as a
two-sided anode in a battery, a protective layer is deposited on
each of the surfaces of the film of lithium, the two protective
layers consisting or consisting essentially of an ion-conducting
material.
[0025] When the multilayer material is intended for use as a
one-sided anode in a battery, the film of active lithium is
deposited on a protective layer consisting or consisting
essentially of an ion-conducting material. It is advantageous to
deposit, on the other surface of the film of active lithium, a
protective layer consisting or consisting essentially of an
electron conducting material which may act as a current collector
for the anode.
[0026] The deposition of the lithium layer by lamination allows
operation at atmospheric pressure. The multilayer material is
preferably prepared in a dry air atmosphere, in an anhydrous
chamber characterized by a dew point between -45 and 55.degree. C.,
which is between 0.7 and 2.2%, and preferably at -50.degree. C. at
1.3% relative humidity.
[0027] A protective layer may be deposited in 1 to 15 seconds.
[0028] When the multilayer material comprises two protective layers
on either side of the layer of active lithium, the second
protective layer may be deposited on the film of active lithium at
the same time as the first protective layer is deposited on the
other free surface of the lithium film. The second layer may also
be deposited after the deposition of the first layer, preferably
less than 15 seconds after.
[0029] The material used to form a protective layer has an ion
conduction higher than 10.sup.-4S.cm.sup.2, and is selected from
ceramics, glasses, polymers, and mixtures thereof.
[0030] An ion-conducting protective layer may comprise at least two
sublayers, consisting or consisting essentially of, independently
of one another, a material which has an ion conduction higher than
10.sup.-4S.cm.sup.2, and which is selected from ceramics, glasses,
and polymers optionally containing a ceramic filler.
[0031] A protective layer of ceramic advantageously consists or
consists essentially of a ceramic of the nonstoichiometric lithium
phosphorus oxynitride type. This type of ceramic is generally
designated by the name LIPON. In the context of the present
invention, the compound Li.sub.3.3PO.sub.3.9N.sub.0.17 and similar
compounds are preferably used. A detailed presentation of LIPON
compounds of their use, particularly for the preparation of thin
films for all-solid batteries, is provided in "Micro Power
Sources", K. Zaghib and S. Surampudi, Proceedings Volume 2000-03,
pp. 70 to 79, published by The Electrochemical Society.
[0032] A LIPON ceramic layer may be deposited on a substrate by
cathode sputtering, laser or plasma ablation, for example from a
Li.sub.3PO.sub.4 target. The substrate for the deposition of the
protective film may be a film of propylene or of a PP-PE-PP
copolymer serving as a separator in the generator. The substrate
may further be a 1/2 cell and consists of a collector, a cathode
and an electrolyte, the LIPON layer being deposited on the
electrolyte layer. The protective layer may also be formed on any
substrate carrying a film of PP, said film being removable by
peeling after formation of the protective layer, and deposition of
the lithium film on the protective layer.
[0033] A protective layer may further consist or consists
essentially of glass.
[0034] A protective layer consisting or consisting essentially of a
ceramic or of a glass preferably has a thickness equal to or lower
than 1 .mu.m.
[0035] A protective layer may consist or consists essentially of a
solution of an ionic compound in a polymer or of a polymer carrying
ionic groups. The polymer may further contain a ceramic.
[0036] A protective layer of the polymer type preferably has a
thickness of 1 to 100 .mu.m.
[0037] For the protective layer consisting or consisting
essentially of a polymer to have good mechanical strength, it is
preferable to select either a high molecular weight polymer which
has an intrinsic mechanical strength, or a polymer which has
crosslinkable groups and to which a crosslinkage imparts the
mechanical strength. Polyethers or polyvinyls are particularly
preferred.
[0038] Polymers usable as a material constituting a protective
layer may be selected from polymers with 3 branches and polymers
with 4 branches.
[0039] Polymer with 3 branches means a polymer having 3 branches in
the form of a three-branched comb, like those described in
"Relationship between Structural Factor of Gel Electrolyte and
Characteristics of Electrolyte and Lithium-ion Polymer Battery
Performances", by Hiroe Nakagawa et al, The 44.sup.th Symposium in
Japan, Nov. 4-6, 2003, abstract 3D26. The 3 substantially parallel
branches of these polymers are preferably fixed to the center and
to the two ends of a small skeleton, preferably comprising 3 atoms,
more particularly 3 carbon atoms in the chain. In the case of a
chain with 3 carbon atoms, each of the atoms is connected to a
branch.
[0040] Among these polymers with 3 branches, those which have an
average molecular weight (M.sub.W) of between 1,000 and 1,000,000
are preferred, more particularly those having an average molecular
weight of between 5,000 and 100,000.
[0041] Polymer with four branches means a polymer in the form of a
four-branched comb. WO-03/063287 describes a preferred family of
polymers with four branches. The 4 substantial parallel branches of
these polymers are fixed respectively between the two ends
(preferably symmetrically on the chain) and at the two ends of a
small chain preferably having 4 atoms, which are preferably 4
carbon atoms. In the case of a chain having 4 carbon atoms, each
atom is connected to a branch.
[0042] Among these four-branched polymers, those having hybrid
terminal groups are preferred, more particularly hybrid acrylate
(preferably methacrylate) and alkoxy (preferably alkoxy with 1 to 8
carbon atoms, in particular methoxy or ethoxy), or vinyl groups, at
least one branch of said four-branched polymer (and preferably at
least two branches) being capable of giving rise to a
crosslinkage.
[0043] Another family of polymers with four branches, useful for
the present invention, is described in columns 1 and 2 of U.S. Pat.
No. 6,190,804. This document is incorporated by reference in the
present application.
[0044] The polymer is preferably a star polyether which has at
least four branches having terminal groups containing the following
functions: acrylate or methacrylate and alkoxy, allyloxy and/or
vinyloxy, at least one, and preferably at least two of these
functions being active for crosslinkage. It has a voltage stability
much higher than 4.
[0045] An example of a polyether with 4 branches is a
tetrafunctional polymer preferably having a high molecular weight
and having the formula (1):
##STR00001##
where: [0046] R.sup.1 and R.sup.2 each represent a hydrogen atom or
a lower alkyl (preferably having 1 to 7 carbon atoms); [0047]
R.sup.3 represents a hydrogen atom or a methyl group; [0048] m and
n each represent a whole number higher than or equal to 0; [0049]
in each high molecular weight chain, m+n>35; [0050] each of the
groups R.sup.1, R.sup.2, R.sup.3 and each of the parameters m and n
may be identical or different in the 4 high molecular weight
chains.
[0051] Among these polymers with four branches, those which have an
average molecular weight between 1,000 and 1,000,000, preferably
between 5,000 and 100,000, are particularly advantageous.
[0052] Vinyl polymers of the ethylene glycol (EG) type, and more
particularly those described in EP-A-1 249 461 (DKS), are also
advantageous as protective materials, in particular those having an
average molecular weight between 600 and 2,500.
[0053] Polymers of this family may advantageously be obtained by
reacting ethylene oxide and 2,3-epoxy-1-propanol with
HO--(--CH.sub.2CH.sub.2O--).sub.4--H) or by reacting
2,3-epoxy-1-propanol with ethylene glycol. This step is followed by
the grafting of polymerizable and/or nonpolymerizable functional
groups at each end of the skeleton and of the side chains of the
polymer. Compounds having one or more groups carrying an active
hydrogen and alkoxy groups may also be used in the form of monomers
which are crosslinked in situ, during the preparation of the
protective layer.
[0054] The hydroxyl group is an example of a group carrying an
active hydrogen.
[0055] Compounds having 1 to 5 hydroxyl groups are preferred. The
monomethylether of triethyleneglycol, ethyleneglycol, glycerin,
diglycerin, pentaerythritol and derivatives thereof are specific
examples of compounds having one or more groups carrying an active
hydrogen.
[0056] CH.sub.3ONa, t-BuOK and derivatives thereof are specific
examples of precursor alkoxides of alkoxy groups.
[0057] The polyether polymers used as a material for the protective
layer have a structural unit represented by the formula (1) and the
structural unit represented by the formula (2) and/or the
structural unit represented by the formula (3). The number of units
having formula (1) in a molecule is between 1 and 22,800,
preferably between 5 and 11,400, and more particularly between 10
and 5,700. The total number of units having formula (2) and/or
formula (3) is between 1 and 13,600, preferably between 5 and
6,800, and more preferably between 10 and 3,400.
##STR00002##
[0058] (Meth)acrylate groups, allyl groups and vinyl groups are
examples of polymerizable functional groups grafted at each
molecular end. Alkyl groups and functional groups comprising boron
atoms are examples of nonpolymerizable functional groups. Among
alkyl groups, alkyl groups having 1 to 6 carbon atoms are
preferred, particularly those having 1 to 4 carbon atoms, and more
particularly the methyl group.
[0059] Examples of functional groups comprising boron atoms include
those presented by the following formulas (4) or (5)
##STR00003##
[0060] The groups R.sup.11 and R.sup.12 in formula (4) and the
groups R.sup.21, R.sup.22 and R.sup.23 in the formula (5) may be
identical or different, and alkyl, alkoxy, aryl, alkenyl, alkynyl,
aralkyl, cycloalkyl, cyano, hydroxyl, formyl, aryloxy, alkylthio,
arylthio, acyloxy, sulfonyloxy, amino, alkylamino, arylamino,
carbonamino, oxysulfonylamino, sulfonamide, oxycabonylamino, ureid,
acyl, oxycarbonyl, carbamoyl, sulfonyl, sulfinyl, oxysulfonyl,
sulfamoyle, carboxylate, sulfonate or phosphonate group, a
heterocyclic group, or a --B(R.sup.a)(R.sup.b),
--OB(R.sup.a)(R.sup.b) or OSi(R.sup.a)(R.sup.b)(R.sup.c) group in
which (R.sup.a), (R.sup.b) and (R.sup.c) each represent a hydrogen,
a halogen, an alkyl, alkoxy, aryl, alkenyl, alkynyl, aralkyl,
cycloalkyl, cyano, hydroxyl, formyl, aryloxy, alkylthio, arylthio,
acyloxy, sulfonamide, oxycarbonylamino, ureid, acyl, oxycarbonyl,
carbamoyl, sulfonyl, sulfinyl, oxysulfonyl, sulfamoyle,
carboxylate, sulfonate, phosphonate, heterocyclic group or
derivatives thereof. R.sup.11, and R.sup.12 in the formula (4) and
R.sup.21 and R.sup.22, R.sup.23 in the formula (5) may be joined
together to form a ring, and the ring may have substitutes. Each
group may also be substituted by substitutable groups. X.sup.+ in
the formula (5) represents an alkali metal ion, preferably a
lithium ion.
[0061] The ends of the molecular chains in the polyether polymer
may all be polymerizable functional groups, nonpolymerizable
functional groups, or both.
[0062] The average molecular weight (Mw) of a polyether polymer is
not especially limited, but it is usually about 500 and 2 million,
and advantageously about 1,000 up to 1.5 million.
[0063] The polymers of these preferred families are also
advantageously selected from polymers which are crosslinkable by
ultraviolet, infrared, heat treatment and/or electron beam
(EBeam).
[0064] When a protective layer is intended to form the collector of
the anode, it consists or consists essentially of an
electron-conducting material. The electron-conducting material may
be of metal, selected from Ni, Cu and stainless steel.
[0065] A metal protective layer may be obtained by a physical or
chemical vapor deposition method, preferably with a thickness of
100 to 150 .ANG.. It may also be obtained from a free metal strip,
preferably having a thickness of 10 to 15 .mu.m.
[0066] Preferably, a metal protective layer has a surface
resistivity lower than 1 .OMEGA./cm.sup.2.
[0067] A second object of the invention relates to the multilayer
material obtained by the inventive method.
[0068] A multilayer material according to the invention comprises
at least one layer of active lithium and one protective layer
adhering to one another, characterized in that the lithium layer is
a layer of active lithium which carries, on at least one of its
surfaces, a continuous or discontinuous passivation layer having an
average thickness of less than 50 .ANG., and in that said at least
one protective layer consists or consists essentially of an
ion-conducting material.
[0069] When the multilayer material is intended to form a two-sided
anode of an electrochemical battery, the two surfaces of the layer
of active lithium carry an ion-conducting protective layer. The two
protective layers may consist or consists essentially of the same
material or of different materials.
[0070] When the multilayer material is intended to form a one-sided
anode of an electrochemical battery, one of the surfaces of the
layer of active lithium adheres to a protective layer consisting or
consisting essentially of an ion-conducting material, and the other
surface of the layer of active lithium adheres to a protective
layer consisting or consisting essentially of an electron
conducting material.
[0071] In a multilayer material obtained by the inventive method,
the adhesiveness between the lithium layer and the protective
layer, measured by the method ASTM No. D3359, is higher than 4, on
a scale from 1 to 5.
[0072] The protective layers prevent the exposure to an atmosphere
from causing the formation or growth of a lithium passivation
layer.
[0073] A multilayer material consisting or consisting essentially
of a layer of active lithium between two metal protective layers
preferably has an application in areas other than electrochemical
generators.
[0074] A third object of the invention relates to an
electrochemical battery comprising at least one cathode, an
electrolyte, and at least one multilayer material of the invention
as an anode. The multilayer material of the invention may
advantageously be incorporated in various types of electrochemical
battery.
[0075] The battery may be a one-sided battery or a two-sided
battery. The battery may be in the form of an all-solid battery, a
liquid electrolyte battery or a gel electrolyte battery.
[0076] A one-sided battery comprises at least one assembly
comprising the following elements, in the order indicated: [0077] a
collector; [0078] a cathode material; [0079] a polymer electrolyte,
or a separator impregnated with a gel electrolyte or a separator
impregnated with a liquid electrolyte; [0080] a multilayer
material; said multilayer material comprises a layer of active
lithium between a metal protective layer and a nonmetallic
protective layer, consisting or consisting essentially of a
material selected from ceramics of the LIPON type, ionic glasses,
conducting polymers, polymers containing ceramic fillers, and
polymers made conducting by the addition of a solution of an ionic
compound in a liquid solvent, the nonmetallic protective layer
being in contact with the electrolyte.
[0081] A two-sided battery comprises at least one assembly
comprising the following elements, in the order indicated:
[0082] a collector;
[0083] a cathode material;
[0084] a polymer electrolyte;
[0085] a multilayer material;
[0086] an electrolyte;
[0087] a cathode;
[0088] a collector;
said multilayer material comprises a layer of lithium between two
protective layers, each consisting or consisting essentially of,
independently of one another, a material selected from LIPON, ionic
glasses, conducting polymers and polymers containing ceramic
fillers, and polymers made conducting by the addition of a solution
of an ionic compound in a liquid solvent.
[0089] The electrolyte of a battery according to the invention may
be a polymer electrolyte, a separator impregnated with a gel
electrolyte, or a separator impregnated with a liquid
electrolyte.
[0090] The cathode of a battery according to the invention consists
or consists essentially of a material which comprises an active
cathode material, and/or an electron conductor and/or a polymer,
and/or a lithium salt and/or a binder.
[0091] The active material of the cathode may be selected from
LiV.sub.3O.sub.8, V.sub.2O.sub.5, LiCoO.sub.2, LiMn.sub.2O.sub.4,
LiMn.sub.13Co.sub.1/3Mn.sub.1/3O.sub.2, and mixtures thereof.
[0092] The polymer is preferably a polyether.
[0093] The electron conductor consists of Ketjen carbon, Shawinigan
carbon, graphite, carbon fibers, vapor-deposited carbon fibers, and
mixtures of at least two thereof.
[0094] The lithium salt is preferably selected from lithium
bis-trifluoromethanesulfonylimide (LiTFSI), lithium
bis-fluorosulfonylimide (LiFSI), lithium dicyanotriazole (LiDCTA),
lithium bis-pentafluoroethanesulfonylimide (LiBETI), LiPF.sub.6,
LiBF.sub.4, LiBOB, and mixtures thereof.
[0095] The binder is preferably selected from the group consisting
of PVDF, PTFE, and water soluble binders (WSB), such as a SBR
rubber for example.
[0096] The collector of the cathode preferably consists or consists
essentially of aluminum optionally coated with carbon.
[0097] In an advantageous embodiment, the anode of the generator
according to the invention is a multilayer material which has a
metal protective layer, consisting or consisting essentially of Ni
or Cu, this protective layer forming the collector of the
anode.
[0098] When the lithium film of the multilayer is in contact with a
nickel or copper support, said support serves as a current
collector. The electrolyte of a generator according to the
invention may be a liquid or gel electrolyte which impregnates a
separator consisting of a polypropylene (PP) or a sequenced
copolymer of polypropylene and ethylene (PP-PE-PP).
[0099] The gel electrolyte may be obtained from a composition
comprising at least one polymer having crosslinkable groups, at
least one lithium salt or at least one liquid solvent and at least
one crosslinking agent. The polymer is advantageously a polyether
or a mixture of four-branched polyethers or polyethylene glycol,
preferably having an average molecular weight MW of between 2,000
and 10,000, more particularly between 2,500 and 8,000. The lithium
salt may be selected from those mentioned above for the cathode
material. The liquid solvent is a polar aprotic solvent selected
from ethyl carbonate (EC), propylene carbonate (PC), dimethyl
carbonate (DMC), methyl and ethyl carbonate (EMC), diethyl
carbonate (DEC), .gamma.-butyrolactone (GBL), vinyl carbonate (VC)
and from molten salts having a SP lower than 50 .ANG., and mixtures
thereof.
[0100] A fourth object of the invention relates to a method for
preparing a battery of which the anode is made from active lithium,
using a multilayer material of the invention as the anode
material.
[0101] A generator according to the invention can be prepared by
depositing a layer of glass or ceramic adjacent to a layer of
active lithium, on a half-cell consisting or consisting essentially
of a cathode film and an electrolyte film.
[0102] When the electrolyte of a generator according to the
invention is a polymer gel electrolyte, a crosslinkable polymer is
preferably used, and it is crosslinked by UV, IR or electron beam
irradiation, or by heating or by a combination of both, after
having deposited it on a substrate. The crosslinkable polymer may
be selected from crosslinkable polymers defined for the material
constituting the protective layer. It is particularly advantageous
to carry out the crosslinkage within the generator, after having
sealed it.
DESCRIPTION OF PREFERENTIAL EMBODIMENTS OF THE INVENTION
All-Solid Battery
[0103] For preparing an all-solid battery, a layer of ceramic
(constituting the protective layer) is deposited on a substrate
consisting of a half-cell, by plasma sputtering (including nitrogen
gases) from a source of LIPON (lithium-phosphorus-nitrogen)
prepared by the method described in New Power Source, PV 2000-03,
by K Zaghib and Surampudi, pages 16 to 30 and pages 70 to 80. The
half-cell comprises a cathode and a solid polymer electrolyte
(SPE).
[0104] The LIPON layer deposited advantageously has a thickness of
about 1 .mu.m. The half-cell consists of the superimposition of a
collector, a cathode forming material, and the SPE electrolyte. The
protective layer is deposited on the SPE layer of the
half-cell.
[0105] The cathode material consists of an active cathode material
(for example LiV.sub.3O.sub.8), a binder and optionally a material
imparting ion conduction and a material imparting electron
conduction. The binder may be a polymer of the polyether type. The
material imparting ion conduction is a lithium salt, for example
LiTFSI. The material imparting electron conductivity may be a high
specific surface area carbon. The cathode has a thickness of 45
.mu.m.
[0106] The SPE electrolyte consists of a solution of LiTFSi in a
polyether type of polymer, and its thickness is advantageously
between 20 and 30 .mu.m. A film of lithium is then deposited on the
LIPON film. The starting lithium is a commercial extruded film 250
.mu.m thick, which has a passivation layer more than 50 .ANG.
thick.
[0107] This lithium film is laminated between two stainless steel
rolls in a Class 1,000 type anhydrous chamber, to obtain a 50 .mu.m
thick film of lithium. The rolling is preferably carried out in the
presence of a lubricant and/or an additive preferably selected from
those described in CA-A-2 099 526.
[0108] This 50 .mu.m thick film is actively deposited on the SPE
surface, that is very rapidly and before the lithium is passivated
by the air. The deposition is preferably carried out in less than 2
seconds.
[0109] It has thus been discovered that, if this operating mode is
carried out in a predefined time, it unexpectedly avoids the rapid
growth of the passivation film, which is generally formed of
lithium carbonate Li.sub.2CO.sub.3 and oxide Li.sub.2O and LiOH,
and it provides a very strong adhesiveness of the layer of active
lithium to the protective layer.
[0110] The deposition of active lithium on the LIPON, by the method
of the invention, thereby serves to minimize the thicknesses of the
Li.sub.2CO.sub.3 and Li.sub.2O layers, thereby substantially
improving the long-term cyclability of the all-solid battery. By
thus lowering the impedance of the battery, excellent performance
is obtained, particularly in use with high currents.
[0111] The deposition of the film of active lithium on the LIPON
layer results in the inhibition of the formation of dendrites
thanks to the presence of the hard and solid layer of LIPON on the
lithium.
Liquid Electrolyte Battery
[0112] A liquid electrolyte battery according to the invention
comprises a cathode, a separator impregnated with an electrolyte, a
protective layer, and an anode consisting of a film of active
lithium.
[0113] The cathode may be made from a composite, similar to the one
described for the all-solid battery.
[0114] The separator may be made from polypropylene (PP) or a
PP-PPE-PP for example of the CELGARD type.
[0115] The electrolyte is advantageously a solution of lithium salt
(for example LiTFSI) in a solvent (for example a mixture of
ethylene carbonate and diethylene carbonate).
[0116] The film of active lithium is obtained by laminating a film
of commercial lithium.
[0117] For assembling a battery, the LIPON film is deposited on one
of the faces of the separator by cathode sputtering, the active
lithium is rapidly deposited on the free-face of the LIPON, and a
film of cathode material is then deposited on the free face of the
separator.
Gel Electrolyte Battery
[0118] According to this particular embodiment of the invention, a
cathode is fabricated from a composition prepared by mixing 82% of
LiFePO.sub.4 (produced by Phostech) with 3% by weight of Ketjen
black, 3% of graphite, 12% of PVDF in the presence of the solvent
NMP, at the rate of 20% by weight, of the total weight of the
powders previously mixed.
[0119] The solution is spread on an aluminum carbon collector, and
the solvent is evaporated. A film is obtained having a thickness of
45 microns, with a porosity of 73%. The cathode is calendered until
a porosity of 40% is obtained.
[0120] A ceramic film of the LIPON type having a thickness of 1
.mu.m is deposited on a film of Celgard 3501.RTM., and a film of
active lithium is then deposited on the free surface of the LIPON
film, by lamination of an extruded lithium.
[0121] The cathode is then deposited on the free face of the
Celgard 3501.RTM. film.
[0122] The assembly thus produced is introduced into a flexible
aluminum bag, together with a mixture of precursors of the gel
electrolyte, and the bag is then sealed. The mixture of precursors
consists of 95% by weight of a polyether (which is preferably of
the four-branched type), a mixture of 1 M LiTFSi+0.5 M
LiPF.sub.6+EC+GBL (1:3 by volume), and 1,000 ppm of Pekadox 16.RTM.
as crosslinkage initiator.
[0123] The battery was sealed by the technique described in
WO2004/068610 relative to a rechargeable electrochemical generator,
and more particularly in example 2 of the document.
[0124] The battery is maintained at 60.degree. C. for one hour.
This step is necessary to form the gel in the pores present on the
surface of the electrode material, of the Celgard and in the LIPON
pores. The batteries prepared by implementing this method are
functional at ambient temperature.
[0125] It has been found unexpectedly that lithium, owing to its
particular chemical reactivity, develops an excellent adhesion with
glasses and ceramics immediately after its lamination.
EXAMPLES
[0126] The examples below are provided for illustration and are
nonlimiting for the object of the invention.
Example 1
[0127] A half-cell is prepared consisting of a current collector, a
cathode material and a solid polymer electrolyte SPE.
[0128] The cathode material consists of LiV.sub.3O.sub.8, a
polyether binder, LiTFSI and a high specific surface area carbon.
The cathode has a thickness of 45 .mu.m.
[0129] The electrolyte SPE consists of a solution of LiTFSi in a
polyether type of polymer, and its thickness is between 20 and 30
.mu.m.
[0130] A film of metal lithium having a thickness of 250 .mu.m is
obtained by extrusion, and then manually laminated with a jeweler's
roll mill for 2 seconds. A lithium film having a thickness of 55
.mu.m is thus obtained, with a passivation film on its furnace of
which the thickness is 25 .ANG..
[0131] This film is extremely sticky and adheres to the assembly on
the LiV.sub.3O.sub.8/SPE cell. The half-cell has an impedance of
6.OMEGA., which is much lower, hence more advantageous, than the
impedance of 12.OMEGA. of a cell containing a standard lithium film
at the same measurement temperature of 60.degree. C.
Example 2
[0132] A film of methyl lithium having a thickness of 250 .mu.m is
obtained by extrusion. It is then laminated with a jeweler's roll
mill, at ambient temperature for 2 seconds. A film of active
lithium, having a thickness of 55 .mu.m, is thus obtained, and it
has a passivation layer having a thickness of 45 .ANG.. This film
was evaluated on the same day in an XPS analyzer. The thickness
measured for the Li.sub.2O layer is 255 .ANG..
[0133] A film of active lithium which remained for one week in an
anhydrous chamber has a Li.sub.2O layer having a thickness of 250
.ANG. and a Li.sub.2CO.sub.3 layer having a thickness of 125
.ANG..
[0134] These values should be compared with those of the commercial
lithium from FMC, in which the Li.sub.2O layer has a thickness of
400 .ANG. and the Li.sub.2CO.sub.3 has a thickness of 150
.mu.m.
Example 3
[0135] A half-current collector/cathode material/SPE cell is
prepared by the method of example 1.
[0136] A LIPON layer is deposited by sputtering on the SPE face of
the half-cell, from a Li.sub.3PO.sub.4 target. It has a thickness
of 900 nm and an adhesiveness, measured by ASTM method number
D3359, of 5/5.
Example 4
[0137] A LiV.sub.3O.sub.8/SPE/LIPON/lithium type battery was
prepared by the following process.
[0138] On the SPE face of a half-cell "current collector/cathode
material/SPE" prepared by the procedure in example 1, a layer of
LIPON having a thickness of 1 .mu.m was deposited by cathode
sputtering.
[0139] A film of lithium was then deposited on the LIPON film, from
a commercial extruded film having a thickness of 250 .mu.m, and
which has a passivation layer more than 50 .ANG. thick. This film
of commercial lithium was laminated between two stainless steel
rolls in a Class 1,000 type anhydrous chamber, to obtain a 50 .mu.m
thick lithium film.
[0140] This 50 .mu.m thick film was actively deposited on the SPE
surface, in less than 2 seconds, and a current collector was then
deposited on the lithium film.
[0141] The battery thereby produced has a capacitance of 5 mAh. It
was cycled in C/3 discharge and charged to a constant potential of
3.1 volts for 1 hour. The capacitance and coulomb efficiency are
stable during the 100 cycles. A 3% loss of capacitance is measured
after 100 cycles, but the coulomb efficiency remains between 99.9
and 100%.
[0142] A LiV.sub.3O.sub.8/SPE/lithium battery, prepared with a
similar half "current collector/cathode material/SPE" cell and with
a standard lithium, was cycled in C/3 in discharge and charged in 2
C to a constant potential of 3.1 volts for 1 hour. After 10 cycles,
the capacitance dropped by 30% and the coulomb efficiency by
50%.
[0143] In conclusion, the preceding examples demonstrate the very
low thickness of the passivation layer in the multilayer materials
of the invention, and the exceptional adhesion of the lithium to
its protective layer.
[0144] Furthermore, the batteries incorporating a multilayer
material of the invention are characterized by a low impedance and
by an outstanding coulomb efficiency in charge/discharge.
[0145] Although the present invention has been described with the
help of specific embodiments, it is understood that several
variations and modifications may be grafted to said practices, and
it is the object of the present invention to cover such
modifications, uses or adaptations of the present invention,
generally following the principles of the invention and including
any alternative to the present description which becomes known or
conventional in the field of activity in which the present
invention applies, and which may be applied to the essential
elements mentioned above, in agreement with the scope of the
following claims.
* * * * *