U.S. patent application number 11/371861 was filed with the patent office on 2006-08-24 for solid polymeric electrolytes for lithium batteries.
Invention is credited to Charles A. Angell, Xiaoguang Sun, Wu Xu.
Application Number | 20060189776 11/371861 |
Document ID | / |
Family ID | 26906913 |
Filed Date | 2006-08-24 |
United States Patent
Application |
20060189776 |
Kind Code |
A1 |
Angell; Charles A. ; et
al. |
August 24, 2006 |
Solid polymeric electrolytes for lithium batteries
Abstract
Novel conductive polyanionic polymers and methods for their
preparation are provided. The polyanionic polymers comprise
repeating units of weakly-coordinating anionic groups chemically
linked to polymer chains. The polymer chains in turn comprise
repeating spacer groups. Spacer groups can be chosen to be of
length and structure to impart desired electrochemical and physical
properties to the polymers. Preferred embodiments are prepared from
precursor polymers comprising the Lewis acid borate tri-coordinated
to a selected ligand and repeating spacer groups to form repeating
polymer chain units. These precursor polymers are reacted with a
chosen Lewis base to form a polyanionic polymer comprising weakly
coordinating anionic groups spaced at chosen intervals along the
polymer chain. The polyanionic polymers exhibit high conductivity
and physical properties which make them suitable as solid polymeric
electrolytes in lithium batteries, especially secondary lithium
batteries.
Inventors: |
Angell; Charles A.; (Mesa,
AZ) ; Xu; Wu; (Tempe, AZ) ; Sun;
Xiaoguang; (Tempe, AZ) |
Correspondence
Address: |
QUARLES & BRADY LLP
RENAISSANCE ONE
TWO NORTH CENTRAL AVENUE
PHOENIX
AZ
85004-2391
US
|
Family ID: |
26906913 |
Appl. No.: |
11/371861 |
Filed: |
March 7, 2006 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10311644 |
Sep 19, 2003 |
7012124 |
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PCT/US01/19338 |
Jun 16, 2001 |
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11371861 |
Mar 7, 2006 |
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60212230 |
Jun 16, 2000 |
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60290864 |
May 14, 2001 |
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Current U.S.
Class: |
528/4 ;
429/122 |
Current CPC
Class: |
H01M 2300/0085 20130101;
H01M 10/052 20130101; C08G 65/328 20130101; C08G 65/338 20130101;
Y02E 60/10 20130101; C08G 79/10 20130101; Y02T 10/70 20130101; H01M
10/0565 20130101; C08G 79/08 20130101; H01M 2300/0082 20130101 |
Class at
Publication: |
528/004 ;
429/122 |
International
Class: |
C08G 79/08 20060101
C08G079/08 |
Goverment Interests
[0002] Financial assistance for this project was provided by U.S.
Government through the National Science Foundation under Grant
Number CHE-9808678 and the Department of Energy under Grant Nos.
DEFG0393ER14378-003 and DEFG0395ER45541. Therefore the United
States Government may own certain rights to this invention.
Claims
1. A Lewis acid-containing polymer comprising repeat units having
the formula: [AL].sub.p wherein A is a Lewis acid group having the
formula ##STR3## wherein X is a Group III element; Y.sub.1 is a
ligand bound to X; O is a ligand bound to X and to the polymer
chain L; L is a polymeric chain chemically linked to a ligand in
said Lewis Acid and wherein L comprises a determined number of
spacer groups and has the formula: L=(Z).sub.n wherein Z is a
spacer group; and n is the number of each said spacer groups and
wherein Z is the same or different in each occurrence; and p is the
number of repeat units in the polymer.
2-78. (canceled)
Description
[0001] This application claims priority rights based on U.S.
Provisional Application 60/212,230, filed Jun. 16, 2000 and
60/290,864 filed May 14, 2001. The above-identified provisional
applications are hereby incorporated by reference.
INTRODUCTION
[0003] 1. Technical Field
[0004] The present invention relates to novel polyanionic polymers
having high conductivity suitable for use in solid polymeric
electrolytes in lithium batteries, especially secondary lithium
batteries.
[0005] 2. Background
[0006] Lithium batteries supply energy to a growing number of
portable electrochemical devices and are a promising energy source
for larger applications such as electric automobiles. Accordingly,
lithium batteries are the subject of intense research and the
effort to improve performance continues.
[0007] A major area of interest has been in the field of
electrolytes for lithium cells where a solid electrolyte with high
ionic conductivity, wide electrochemical stability window and good
lithium ion transport number has been the goal. Electrolytes are
generally prepared by dissolving a highly-conductive salt in a
polymer, usually an ether polymer, to make solid polymeric
electrolytes (SPE). Examples of the "salt-in-polymer" approach
include the electrolytes disclosed in U.S. Pat. No. 5,849,432, U.S.
Pat. No. 5,824,433, U.S. Pat. No. 5,660,947, and U.S. Pat. No.
6,235,433.
[0008] A "polymer-in-salt" approach has also been attempted. In
this approach, chain polymers are added as a dilute component to
impart solidity to molten alkali metal salt mixtures of high
conductivity (1). Unfortunately it has been difficult to find
simple salts of lithium that are stable and liquid at room
temperature. Examples of the polymer-in-salt approach include U.S.
Pat. No. 5,962,169, U.S. Pat. No. 5,855,809, U.S. Pat. No.
5,786,110, U.S. Pat. No. 5,506,073 and U.S. Pat. No. 5,484,670.
[0009] The need for conductive polymers continues to spur the
development of new materials. Polymeric films which contain weakly
coordinating anionic groups are promising candidates as SPE as they
would have good decoupling characteristics and thus high transport
number for cations. Batteries and other electronic devices could be
made much smaller and lighter by exploiting these films (2).
[0010] Attempts have been made to polymerize molten salts into
solid films, but the reported conductivity of these films is not
high at room temperature (3,4). Other highly conductive polymers
have been made by linking anionic imide groups in a polymer and
then forming complexes with the anionic groups using Lewis acids
such as AlCl.sub.3 and BF.sub.3 (5). The AlCl.sub.3-complexed
polymers exhibit very high conductivities, 10.sup.-3.8 Scm.sup.-1,
and good electrochemical characteristics, but are not suitable for
commercial use because the potential volatility of AlCl.sub.3 and
BF.sub.3 makes them environmentally unsafe (5). Nevertheless, the
high conductivity of the Lewis acid/Lewis base pairs makes them
promising candidates as SPE if this problem were solved.
[0011] Despite continuing discoveries of highly conductive
electrolytic salts, and advances in polymerizing these salts, solid
polymer electrolytes for lithium batteries are still needed.
Especially sought are weakly coordinating anionic materials that
can be fabricated into films with high conductivity.
[0012] 3. Relevant literature [0013] 1. C. A. Angell, K. Xu, S. S.
Zhang and M. Videa, "Variations on the Salt-Polymer Electrolyte
Theme for Flexible Solid Electrolytes", Solid State Ionics, 86-88,
17-28 (1996). [0014] 2. C. A. Angell, C. Liu and G. Sanchey,
"Rubbery Solid Electrolytes with Dominant Catronic Transport and
High Ambient Conductivity", Nature, 362, 137-139, Mar. 11, 1993.
[0015] 3. J. R. MacCallum and C. A. Vincent (Eds.), Polymer
Electrolytes Reviews, Vol. 1, Elsevier, London, 1987. [0016] 4. H.
Ohno, "Molten Salt Type Polymer Electrolytes", Electrochimica Acta,
46, 1407-1411 (2001). [0017] 5. S. S. Zhang, Z. Chang, K. Xu and C.
A. Angell, "Molecular and Anionic Polymer System with
Micro-Decoupled Conductivities", Electrochimica Acta, 45, 12-29
(2000).
SUMMARY OF THE INVENTION
[0018] It has been discovered that certain Lewis acids can be
readily incorporated into polymeric chains. These stable polymers
can be readily converted into conductive polymers by addition of a
suitable Lewis base. Stable polymers of Lewis acids and methods for
preparing the polymers are provided.
[0019] The polymers comprise repeating units of Lewis acid groups
chemically bound within chain polymers which in turn comprise
repeating spacer groups. The length and number of spacer groups are
chosen to position the Lewis acids in the chain at desired
repeating intervals.
[0020] In the provided method for preparing the subject polymers,
certain Lewis acids comprising a Group III element coordinated to
three ligands (i.e., under-coordinated) are contacted with polymer
chains having end groups reactive with two of the ligands. A Lewis
acid-containing chain polymer comprising repeating spacer groups
results. In a preferred method wherein the Lewis acid-containing
polymer comprises a borate group, the starting material is a
boronic acid and spacer groups are linked by reaction with hydroxyl
groups on the boronic acid.
[0021] The Lewis acid-containing polymers can be readily converted
into excellent ionic conductors by reacting them with a weakly
associating Lewis base anion, as a negatively charged species,
charge compensated by any cation of choice. Examples of conductive
polyanionic polymers are given.
[0022] Physical properties of the polyanionic polymers can be
modified by addition of co-polymers, plasticizers, solvents,
ceramic particles and cross-linking which allows them to be formed
into conductive films and otherwise fabricated.
[0023] Resultant polymeric products are useful as solid polymeric
electrolytes for batteries, especially lithium batteries.
BRIEF DESCRIPTION OF THE FIGURES
[0024] FIGS. 1A and 1B give the conductivities of polyanionic
polymers formed by addition of certain anionic Lewis bases to a
preferred Lewis-acid-containing polymer. The Lewis acid is borate
bound to the ligand methoxy-oligo(ethylene glycol).sub.8
(MEG.sub.8). The polymer chain comprises repeat spacer groups
ethylene glycol (Egn). The Lewis bases are anionic components of
the following salts: [0025] lithium
bis(trifluoromethanesulfonyl)imide [LiN(SO.sub.2CF.sub.3).sub.2,
LiTFSI or LiImide] [0026] lithium trifluoromethanesulfonate
(LiSO.sub.3CF.sub.3) [0027] lithium thiocyanate (LiSCN) [0028]
sodium cyanide (NaCN) [0029] lithium methoxide (LiOCH.sub.3) [0030]
lithium 2,2,2-trifluoroethoxide (LiOCH.sub.2CF.sub.3) [0031]
lithium sulfide (Li.sub.2S)
[0032] FIG. 1A illustrates 1:1 (mol) Li salts-P(MEG.sub.mEG.sub.nB)
complexes wherein m is 8 and n is 9.
[0033] FIG. 1B illustrates 1:1 (mol) Li salts-P(MEG.sub.mEG.sub.nB)
complexes wherein m is 8 and n is 14.
[0034] FIGS. 2A-2D illustrate a study of a preferred embodiment of
the present polyanionic polymer having the formula poly lithium
[methoxy-oligo(ethylene glycol).sub.m oligo(ethylene glycol).sub.n
bis(trifluoromethane sulfonyl)imido borate], (herein abbreviated as
P[Li+(MEG.sub.mEG.sub.n TFSIB)-] where m represents the length of
the branch m and is 1-12 and n represents the length of spacer
chain and is 2-14 and TFSI is bis(trifluoromethanesulfonyl)imide.
The figures illustrate the effect of the length of branching ligand
and the effect of spacer chain length on the conductivity of the
polyanionic polymer at various temperatures.
[0035] FIG. 2A illustrates 1:1 (mol) P[Li(MEG.sub.mEG.sub.9 TFSIB)]
complexes wherein m is 1, 3, 8, or 12.
[0036] FIG. 2B illustrates 1:1 (mol) P[Li(MEG.sub.8EG.sub.nTFSIB)
complexes wherein n is 2, 5, 9 or 14.
[0037] FIG. 2C illustrates 1:1 (mol) LiTFSI-P(MEG.sub.3EG.sub.nB)
complexes wherein n is 2, 5, 9 or 14.
[0038] FIG. 2D illustrates P[Li(PhEGnTFSIB)]phenyl borate complexes
with different values of repeating spacer groups and ratios of salt
to polymer. The conductivity of the imide salt is given for
comparison.
[0039] 3A-C illustrate a study of a preferred embodiment of the
present polyanionic polymer having the formula
{lithium[polymethoxy-oligo(ethylene glycol).sub.m oligo(ethylene
glycol).sub.n trifluoromethane sulfanates borate}, (herein
abbreviated as P[Li(MEG.sub.mEG.sub.nCF.sub.3SO.sub.3B)] where m
represents the length of the branch chain and is 1-12 and n
represents the length of spacer chain and is 2-14. The figures
illustrate the effect of the length of branching ligand and the
effect of spacer chain length on the conductivity of the
polyanionic polymer at various temperatures.
[0040] FIG. 3A illustrates the cooling curve of 1:1 (mol)
P[Li(MEG.sub.mEG.sub.nCF.sub.3SO.sub.3B)] complexes wherein m is 1,
3, 8, or 12.
[0041] FIG. 3B illustrates the cooling curve of 1:1 (mol)
P[Li(MEG.sub.mEG.sub.nCF.sub.3SO.sub.3B)] complexes wherein n is 2,
5, 9 or 14.
[0042] FIG. 3C illustrates the cooling curve of 1:1 (mol)
P[Li(MEG.sub.mEG.sub.nCF.sub.3SO.sub.3B)] complexes wherein n is 2,
5, 9 or 14.
[0043] FIG. 4 illustrates the conductivity of a preferred
embodiment of the present polyanionic polymer having the formula:
poly{lithium[phenyl-oligo(ethylene glycol).sub.14
cyanomethyleneborate], (herein abbreviated as
P[Li(PhEG14CNCH.sub.2B)] in the presence of different percentages
of plasticizer (1:1 o/w ethylene carbonate/propylene carbonate) at
various temperatures. This compound comprises Lewis acid borate
with ligand phenyl, spacer groups ethylene glycol and the anionic
Lewis base CH.sub.2CN.sup.- with counterion lithium.
[0044] FIG. 5 illustrates the conductivity of a preferred
embodiment of the present polyanionic polymer having the formula
{poly{lithium[oligo((dimethyl siloxane-co-tetra ethylene
glycol)-phenyl bis(trifluoromethanesulfonyl)imidoborate]} in the
presence of different percentages of plasticizer (1:1 o/w ethylene
carbonate/propylene carbonate) at various temperatures.
[0045] This compound comprises Lewis acid borate with ligand
phenyl, spacer groups oligoether siloxane and the anionic Lewis
base TFSI.sup.- and counterion lithium.
[0046] FIG. 6 illustrates the conductivity at various temperatures
of preferred embodiment of the present polyanionic polymers having
the formula poly {lithium[phenyl-oligo(ethylene glycol).sub.n
cyanoborate]} or poly {sodium[phenyl-oligo(ethylene glycol).sub.n
cyanoborate]} (herein abbreviated as P[Li(PBEG.sub.nCN)] or P[NaPB
EG.sub.n)] wherein n is 5 (for 200), 9 (for 400), or 14 (for 600)).
These polyanionic polymers comprise borate with phenyl ligand and
ethylene glycol spacer units of different length with the Lewis
base CN.sup.- and with Na.sup.+ or Li.sup.+ as counterions.
[0047] FIGS. 7A and 7B illustrate the conductivities of LiSCN
complexes of Lewis-acid containing polymers wherein n is 2, 5, 9 or
14.
[0048] FIG. 7A illustrates the conductivity at various temperatures
of LiSCN--P(MEG8EG.sub.nB) wherein n is 2, 5, 9 or 14 with various
ratio of salt to polymer.
[0049] FIG. 7B illustrates the conductivity at various temperatures
of LiSCN-[phenyl-oligo(ethylene glycol).sub.n borate] at various
ratios of salt to polymer wherein n=3, 5 or 7.
[0050] FIG. 8 illustrates the conductivity at various temperatures
of NaCN--P(MEG.sub.8EG.sub.nB) wherein n is 3, 7 or 9 with 1:1
ratio of salt to polymer.
[0051] FIGS. 9A-9D illustrate the conductivity at various
temperatures of the cross-linked polymer of
LiOCH.sub.2CF.sub.3--P(MEG.sub.3EG.sub.nB) with various amounts of
plasticizer and n equals 2 to 14.
[0052] FIG. 9A illustrates
LiOCH.sub.2CF.sub.3--P(MEG.sub.3EG.sub.2B.
[0053] FIG. 9B illustrates
LiOCH.sub.2CF.sub.3--P(MEG.sub.3EG.sub.5B.
[0054] FIG. 9C illustrates
LiOCH.sub.2CF.sub.3--P(MEG.sub.3EG.sub.9B.
[0055] FIG. 9D illustrates
LiOCH.sub.2CF.sub.3--P(MEG.sub.3EG.sub.14B.
[0056] FIGS. 10A and 10B illustrate the electrochemical
characteristics of the anionic polymers
LiTFSI-P(MEG.sub.8EG.sub.14B).
[0057] FIG. 10A illustrates the Li deposition-stripping of 1:1
(mol) LiTFSI-P(MEG.sub.8EG.sub.14B).
[0058] FIG. 10B illustrates the electrochemical stability window of
1:1 (mol) LiTFSI-P(MEG.sub.8EG.sub.14B).
[0059] FIGS. 11A and 11B illustrate the electrochemical
characteristics of the anionic polymers
LiSO.sub.3CF.sub.3--P(MEG.sub.8EG.sub.14B).
[0060] FIG. 11A illustrates the Li deposition-stripping of 1:1
(mol) LiSO.sub.3CF.sub.3--P(MEG.sub.8EG.sub.14B).
[0061] FIG. 11B illustrates the electrochemical stability window of
1:1 (mol) LiSO.sub.3CF.sub.3--P(MEG.sub.8EG.sub.14B).
DESCRIPTION OF PREFERRED EMBODIMENTS
[0062] Novel polymeric compositions incorporating Lewis acids are
provided wherein the Lewis acids comprise a Group III element and
three ligands bound to the Group III element. The Lewis acid groups
are positioned in the polymer chain by means of spacer groups of
determined length and structure: Methods for forming the Lewis-acid
polymers are given. The polymers find use as precursors in the
formation of conductive polyanionic polymers.
[0063] Polyanionic polymers are provided which exhibit high
conductivity. They are prepared by combining the Lewis
acid-containing polymers with certain salts of a Lewis base. The
resultant polymers comprise polyanionic groups whose strength of
attraction for counterion is dependent on the bonding strength
between the Lewis acid group and the chosen Lewis base. Polyanionic
polymers prepared by addition of an anionic Lewis base which
associates weakly with the Lewis acid-containing polymers to form
weakly coordinating anionic groups and exhibit good decoupling and
good conductivity are provided. Certain other polyanionic polymers
formed by addition of an anionic Lewis base which binds strongly to
the Lewis acids to exhibit weak decoupling and hence relatively
poor, but strictly single ion, conductivity, but good ion
transport, are provided. Compounds with intermediate bonding
strengths are also provided.
[0064] The anionic polymers can be modified by the addition of
plasticizers, co-polymers and by cross-linking to make a
polyanionic polymeric network. The modified polyanionic polymers
can be formed into films and find use as electrolytes in
electrochemical devices employing lithium batteries.
[0065] The Lewis acids in the present polymers comprise a Group III
element, preferably boron or aluminum, most preferably boron. A
Lewis acid is defined as a group, which is capable of accepting
electrons in a chemical reaction. As may be observed by their
position in the periodic chart, the Group III elements contain 3
electrons in their outer orbits, and so even after bonding to three
ligands (total 6 electrons), they still have the capacity to accept
another ligand. The Lewis acid groups will, for the most part, be
tri-coordinated boron groups wherein two ligands are oxygen atoms
or other functional groups capable of linking the central Group III
element into the polymer chain.
[0066] In preferred embodiments, two oxygen atoms chemically link
the Lewis acid group into the backbone of the polymer chain. The
third ligand in some instances is phenyl, substituted phenyl,
preferably 2,4-difluorodiphenyl or 3,5-diflurodiphenyl, alkyl,
substituted alkyl or alkoxy. As used herein, the term "substituted"
means halo, alkyl, alkoxy or phenyl.
[0067] In certain preferred instances the ligand on the Lewis acid
group, preferably a borate, is alkoxy-oligo(alkene glycol).sub.m
(hereinafter termed XG.sub.m), preferably methoxy-oligo(ethylene
glycol).sub.m (hereinafter termed MEG.sub.m) or
butoxy-oligo(propyleneglycol).sub.m (hereinafter termed BPG.sub.m)
wherein m is 1-45.
[0068] The present polymers comprise repeating units of Lewis acids
separated by polymer chain groups. The polymer chains in turn
comprise repeating spacer groups which may be the same or different
in each occurrence. The number, length and structure of the spacer
groups determine the intervals between the Lewis acid groups in the
polymer chain. They also determine the flexibility of the chains
and the mechanical strength and other physical characteristics of
the polymer. The spacer groups may be chosen to provide optimal
physical characteristics to the polymer. The spacing of the weakly
coordinating anionic moieties in the polymers at regular,
determined intervals in the polymer chain gives them a consistency
of electrical and mechanical characteristics that may not be
obtainable in simple mixtures. In certain instances the spacer
groups are polyethers, preferably repeating groups of polyethylene
glycol (hereinafter termed (EG).sub.n or polypropylene glycol
(hereinafter termed (PG).sub.n). Other ethers may likewise be
employed.
[0069] In certain other instances the spacer groups are
polysiloxanes having the formula
Si[(CR.sub.3).sub.2]--O(CR.sub.2CR.sub.2O).sub.n. Other chemical
groups that can be linked to the Lewis acid group by the method of
the present invention are likewise suitable spacer groups. In
certain instances the spacer groups comprise a chemical group
suitable for causing further reaction of the polymer chain with
other polymers or with a solid surface--a chromatography bead, for
example.
[0070] Table 1 illustrates the effect of the nature and length of
the spacer groups and the ligand on the physical state and
appearance of Lewis acid-containing polymers wherein the Lewis acid
group is a borate bound to a ligand comprising branching groups
MEG.sub.m or BPG.sub.m having different repeat values m. In these
examples, the spacer groups are oligo(ethylene glycol) (EG.sub.n)
or oligo(polyethylene glycol) (PG.sub.n) having different repeat
values of n. TABLE-US-00001 TABLE 1 APPEARANCE OF LEWIS
ACID-CONTAINING POLYMERS HAVING THE FORMULAE a.
poly[methoxy-oligo(ethylene glycol).sub.m oligo(ethylene
glycol).sub.n borate], where m represents the length of the branch
and is 1, 3, 8 or 12 and n represents the length of spacer chain
and is 2, 5, 9, or 14. This compound is herein abbreviated as
P(MEG.sub.mEG.sub.nB). b. poly[methoxy-oligo(ethylene glycol).sub.m
oligo(propylene glycol).sub.n borate] where m represents the length
of the branch and is 8 and n represents the length of spacer chain
and is 13. This compound is herein abbreviated as
P(MEG.sub.mPG.sub.nB). c. poly[butoxy-oligo(propylene glycol).sub.m
oligo(propylene glycol).sub.n borate], where m represents the
length of the branch and is 5 and n represents the length of spacer
chain and is 9. This compound is herein abbreviated as
P(BPG.sub.mEG.sub.nB). Branch Spacer Brach Spacer type type length
length (Y.sub.1) (Z) (m) (n) Appearance MEG EG 1 9 Gel (brittle
rubber) 3 2 Gel (brittle rubber) 5 Soft rubber 9 Rubber 14 Rubber 8
2 Viscous liquid 5 Viscous liquid 9 Very viscous liquid 14 Very
viscous liquid 12 9 Very viscous liquid PG 8 13 Very viscous liquid
BPG EG 5 9 Rubber
The Lewis acid polymers of the subject invention will have one of
the formulae: [AL].sub.p
[0071] wherein [0072] A is a Lewis acid group having the formula
##STR1## [0073] wherein X is a Group III element; [0074] Y.sub.1 is
a ligand bound to X; [0075] O is a ligand bound to X and to the
polymer chain L; [0076] L is a polymeric chain chemically linked to
a ligand in said Lewis Acid and wherein L comprises a determined
number of spacer groups and has the formula: L=(Z).sub.n [0077]
wherein [0078] Z is a spacer group; and [0079] n is the number of
each said spacer groups [0080] and wherein Z is the same or
different in each occurrence; and [0081] p is the number of repeat
units in the polymer.
[0082] In preferred embodiments of the Lewis-acid containing
polymer, [0083] X is aluminum or boron, most preferably boron.
[0084] The ligand Y.sub.1 is selected from the group comprising
phenyl, substituted phenyl, alkyl, substituted alkyl, alkoxy and
substituted alkoxy. As used herein, the term "substituted" means
halo, alkyl, alkoxy, alkylene glycol, or phenyl. Most usually
Y.sub.1 is phenyl, fluoro-substituted phenyl preferably
2,4-difluorophenyl or 3,5-difluorophenyl, and CH.sub.3. In certain
preferred instances, Y.sub.1 is alkoxy-oligo(alkylene glycol) and
preferrably methoxy-oligo(ethylene glycol).sub.m or
butoxy-oligo(propylene glycol).sub.m wherein m is 1-45. [0085] Z is
preferably chosen from the group comprising alkyl, R-substituted
alkyl, alkoxy and R-substituted alkoxy wherein R is selected from
the group comprising hydrogen, halo, alkyl, alkoxy, phenyl and
substituted phenyl. In other instances, Z is a polysiloxane having
the formula Si [(CR.sub.3).sub.2]--O(CR.sub.2CR.sub.2O).sub.n
wherein n is independently 2 to about 50, preferably 2 to about 20,
and R is hydrogen or alkyl. [0086] Z most preferably is a polyether
having the formula [(O(CR.sub.2).sub.aCR.sub.2].sub.n wherein n is
from 2 to about 100, most preferably 2 to about 20, a is zero to
about 20 and R is hydrogen, halo, alkyl or R-substituted alkyl
wherein R is halo, alkyl or phenyl. [0087] p is a number from about
1 to about 100.
[0088] In these preferred embodiments the ether groups may be the
same or different in each occurrence.
[0089] The same symbol may be present a plurality of times, each of
the incidents may be the same or different.
[0090] In certain preferred embodiments of the Lewis
Acid-containing polymers, X is boron, Y.sub.1 is phenyl, alkyl or
alkoxy, most preferably poly[methoxy-oligo(ethylene glycol).sub.m
or poly[butoxy-oligo(propylene glycol).sub.m wherein m is 1-20 and
spacer groups are (OCH.sub.2CH.sub.2).sub.n wherein n is from 1 to
about 25. In these preferred embodiments, m is about 1-45 and the
repeat unit has a molecular weight up to about 2000.
[0091] The subject Lewis acid-containing polymer may be prepared by
contacting a Lewis acid group comprising a Group III element
coordinated to three ligands with a polymer having a reactive group
capable of combining with at least one, most preferably two, of
said ligands under conditions whereby the ligand and the reactive
group react to form the Lewis acid-containing polymer and a small
molecule. In preferred methods for forming Lewis acid-containing
polymers comprising borate, a starting material may be a
commercially available boronic acid such as phenyl boronic acid or
methyl boronic acid (Aldrich Chemical Company). The substituted
boronic acid is contacted with a chain polymer having repeat spacer
groups preferably polyether groups and having reactive hydroxyl
groups. In this preferred method, a chain polymer which comprises
repeat units of phenyl- or alkyl-substituted boron and the spacer
groups bound to oxygen groups on the boron is formed, and the small
molecule which is formed is water.
[0092] In other instances the substituted boronic acid may be
prepared from boric acid and then this substituted boronic acid is
further reacted with a suitable spacer group. In these instances,
novel ligands may be prepared which are chosen to have desired
chemical properties to affect the electron density of the Lewis
acid and the resultant Lewis acid-containing polymer. In a
preferred embodiment, polymers may be prepared by combining
un-substituted Lewis acid, preferably boric acid, with an ether
group with one terminal reactive hydroxyl group and one terminal
alkoxyl group to form a boronic acid, and then reacting the
substituted boronic acid with a poly(alkylene glycol) spacer group.
The resultant polymer comprises a tri-substituted borate group
wherein one ligand is an alkoxy group of the formula
--(OCR.sub.2CR.sub.2).sub.nOCR.sub.3 wherein R is hydrogen or alkyl
and the other two ligands are spacer groups of the formula
--(OCR.sub.2CR.sub.2).sub.n wherein n is 1-50, preferably 1-20 and
most preferably 3, 5, 9 or 14.
[0093] It is to be understood that in those instances herein,
wherein n is given an integral value, it may be that the actual
repeat value is somewhat less or more, but the integral value is
reported for convenience. Thus, e.g. when n is 14, the actual value
may be about 13.6.
[0094] Certain other boronic acids that are suitable Lewis acids in
the present method comprise alkyl and R-substituted alkyl wherein R
is alkyl, ether, phenyl or halo. In these preparations, reaction
conditions are controlled to allow mono-ligand formation and to
assure that two remaining hydroxyl borate groups remain available
for subsequent combination with spacer groups.
[0095] The Lewis acid-containing polymers are precursors in the
formation of conductive polyanionic polymers of the present
invention. The subject polyanionic polymers are prepared by adding
a salt of a Lewis base to the Lewis acid-containing polymer. In the
reaction, the anionic Lewis base, which is defined as a chemical
group capable of donating electrons in a reaction, combines with
under-coordinated Lewis acids in the polymer. In those instances
wherein the Lewis acid-containing polymers comprise borate, the
anionic Lewis base combines with under-coordinated boron in the
Lewis acid group and essentially becomes the fourth ligand. A
polyanionic polymer results.
[0096] In certain instances, the anionic Lewis base may bind
strongly to the Lewis acid moiety and will produce a polyanionic
polymer which has relatively poor conductivity, but high Li.sup.+
transport number (close or equal to unity). In other instances, the
Lewis base may associate weakly with the Lewis acid and produce a
polymer which has good conductivity but lower Li.sup.+ transport
number. The Lewis base used to make the polyanionic polymer may be
chosen to produce the product desired. For application as polymeric
electrolytes in lithium batteries, the main parameters to consider
are high conductivity, wide electrochemical stability window
(>4.5 V) and mechanical strength. The lithium ion transport
number is also important for this application, and the higher the
better.
[0097] Polyanionic polymers prepared from the Lewis acid polymers
have one of the formulae: [M].sup.+k.sub.b[AL].sup.-q.sub.p
[0098] wherein
[0099] AL is a repeat unit in the chain wherein: [0100] A is an
anionic group comprising a Lewis acid bound to or associated with a
Lewis base and having one of the formulae: ##STR2## [0101] wherein
X is a Group III element; [0102] Y.sub.1 is a ligand bound to X;
[0103] Y.sub.2 is a ligand bound to X or associated with X wherein
Y.sub.1 and Y.sub.2 and are the same or different in each
occurrence; [0104] L is a polymeric chain group chemically linked
to oxygen in said anionic group and wherein L comprises a
determined number of spacer groups and has the formula: L=(Z).sub.n
[0105] wherein [0106] Z is a spacer group; and [0107] n is the
number of each said spacer groups [0108] and wherein Z is the same
or different in each occurrence; and [0109] p is the number of
repeat units in the polymer. [0110] q is the charge on the anion;
[0111] M.sup.+ is a cation or cationic group; [0112] b is the
number of cations; [0113] k is the charge on the cation; and [0114]
bk equals pq.
[0115] The counterion M.sup.+k is a cation or a cationic group
selected from the group comprising hydrogen, Group I metals, Group
II metals, NR.sub.4 and PR.sub.4 wherein R is hydrogen, alkyl, or
halo, and k is one to three. In certain instances wherein the
polyanionic polymer is used as an electrolyte in a lithium battery,
the counterion is most favorably lithium. In those embodiments
wherein the polyanionic polymer is incorporated into an ion
exchange system, the cation is preferably a Group I metal or Group
II metal, most preferably sodium, potassium, and calcium. FIG. 6
illustrates the conductivity of certain preferred polymers in the
presence of different cations.
[0116] Y.sub.1, X and Z are defined as previously.
[0117] Lewis base Y.sub.2 is an anionic group capable of donating
electrons to the Lewis acid group in the chain and forming a stable
entity with the chain. The Lewis base may be an organic or an
inorganic anion. In certain instances the Lewis base is an imide,
preferably a sulfonyl-substituted imide wherein substituted
sulfonyl is preferably --SO.sub.2(CR.sub.2).sub.aCR.sub.3 wherein a
is zero to about 4 and R is alkyl, hydrogen or halo preferably
fluoro. In certain other instances, the Lewis base is an alkoxide,
preferably methoxide, or an R-substituted alkoxide wherein R is
alkyl or halo, most preferably fluoro. In yet other instances, the
Lewis base Y.sub.2 is cyanide, thiocyanate or a sulfide. In certain
preferred instances the Lewis base Y.sub.2 is an R-substituted
alkyl wherein R is cyanide, thiocyanide, SO.sub.2 or halo. In
certain preferred instances R is a halo-substituted alkyl
sulfonate.
[0118] In certain other instances Lewis base Y.sub.2 is a phenyl or
aryl or R-substituted phenyl wherein R is alkyl, alkoxide or halo,
preferrably fluoro. Other anionic Lewis bases which bind to or
associate with tri-coordinated X in the Lewis acid-containing
polymer to form stable polyanionic polymers are also suitable
[0119] Lewis base Y.sub.2 in preferred embodiments may be selected
from the group comprising bis(trifluoromethanesulfonyl)imide
[.sup.-N(SO.sub.2CF.sub.3).sub.2 or TFSI.sup.-],
bis(pentafluoroethanesulfonyl)imide
[N(SO.sub.2CF.sub.2CF.sub.3).sub.2 or BETI.sup.-],
trifluoromethanesulfonate (CF.sub.3SO.sub.3.sup.-), cyanide
(CN.sup.-), methoxide (.sup.-OCH.sub.3), 2,2,2-trifluoroethoxide
(.sup.-OCH.sub.2CF.sub.3), thiocyanate (SCN.sup.-), sulfide
(S.sup.-2), phenyl(Ph.sup.-), methyl phenyl, butylphenyl and
cyanomethyl (.sup.-CH.sub.2CN). FIGS. 1-6 illustrate the
conductivity of certain of these preferred embodiments.
[0120] In certain preferred embodiments of the conductive
polyanionic polymers, X is boron, O is oxygen, Y.sub.1 is
methoxy-oligo(ethylene glycol) (MEG.sub.m) or
butoxy-oligo(propylene glycol) (BPG.sub.m) having different repeat
values m, Z is oligo(ethylene glycol) (EG.sub.n) or oligo(propylene
glycol) having different repeat values of n from 1 to about 20, and
Y.sub.2 is CN.sup.-, SCN.sup.-, CF.sub.3SO.sub.3.sup.-, or
TFSI.sup.- most preferably TFSI.sup.- or CF.sub.3SO.sub.3.sup.-.
FIGS. 2 and 3 give the conductivity of these polymers
respectively.
[0121] The physical properties of certain preferred polyanionic
polymers are given in Table 2. In Table 2 the illustrated
polyanionic polymers are complexes formed between certain anionic
Lewis bases and Lewis acid-containing polymers having one of the
formulae P(MEG.sub.mEG.sub.nB), P(MEG.sub.mPG.sub.nB) or
P(BPG.sub.mEG.sub.nB). These formulae have been described more
fully hereinabove (in the legend of Table 1). The polyanionic
polymers in Table 2 were prepared with 1:1 mol ratio of boron to
anion. TABLE-US-00002 TABLE 2 APPEARANCE OF POLYANIONIC POLYMERS
COMPRISING COMPLEXES OF CERTAIN ANIONIC LEWIS BASES AND LEWIS
ACID-CONTAINING POLYMERS Polymer Branch Spacer Branch Spacer length
length Li salt type type (m) (n) Appearance LiTFSI MEG EG 1 9
Viscous liquid 3 9 8 2 5 9 14 12 9 PG 8 13 BPG EG 5 9
LiSO.sub.3CF.sub.3 MEG EG 3 2 5 9 14 8 2 5 9 14 LiSCN MEG EG 8 2
Very viscous liquid 5 Viscous liquid 9 14 NaCN MEG EG 8 2 Greasy
mass 5 Viscous liquid 9 14 LiOCH.sub.3 MEG EG 8 9 Soft rubber 14
LiOCH.sub.2CF.sub.3 MEG EG 8 9 Soft rubber 14 Li.sub.2S MEG EG 8 9
Greasy mass 14
[0122] The present polyanionic polymers exhibit high conductivity
as illustrated in FIGS. 1-9 and Table 3. This property makes them
especially suitable for incorporation into electrochemical devices
and especially in lithium batteries.
[0123] Table 3 illustrates conductivities at 25.degree. C. of
certain preferred polyanionic polymers comprising the Lewis acid
tri-coordinated borate wherein ligand Y.sub.1 is MEG.sub.m, Z is
EG.sub.n and Lewis base Y.sub.2 is imide (TFSI.sup.-) or
CF.sub.3SO.sub.3.sup.-. In Table 3 the polyanionic polymers have
the formulae P(MEG.sub.mEG.sub.nB), P(MEG.sub.mPG.sub.nB) or
P(BPG.sub.mEG.sub.nB). These formulae have been described more
fully hereinabove (in the legend of Table 1). The polyanionic
polymers in Table 3 were prepared with 1:1 mol ratio of boron to
anion. These preferred compounds are exemplary of the
conductivities required for use as electrolytes in electrochemical
devices. TABLE-US-00003 TABLE 3 CONDUCTIVITIES AT AMBIENT
TEMPERATURE OF POLYANIONIC POLYMERS COMPRISING COMPLEXES OF CERTAIN
ANIONIC LEWIS BASES AND LEWIS ACID-CONTAINING POLYMERS Polymer
Branch Spacer Branch Spacer Conductivity type type length length at
25.degree. C. Li salt (Y.sub.1) (Z) (m) (n) (Scm.sup.-1) LiTFSI MEG
EG 1 9 1.6 .times. 10.sup.-5 3 2 3.0 .times. 10.sup.-6 5 1.5
.times. 10.sup.-5 9 3.7 .times. 10.sup.-5 14 5.3 .times. 10.sup.-5
8 2 3.4 .times. 10.sup.-5 5 5.6 .times. 10.sup.-5 9 6.2 .times.
10.sup.-5 14 7.6 .times. 10.sup.-5 12 9 6.6 .times. 10.sup.-5 PG 8
13 2.6 .times. 10.sup.-5 BPG EG 5 9 3.7 .times. 10.sup.-5
LiSO.sub.3CF.sub.3 MEG EG 3 2 1.9 .times. 10.sup.-6 5 9.9 .times.
10.sup.-6 9 1.5 .times. 10.sup.-5 14 3.0 .times. 10.sup.-5 8 2 1.2
.times. 10.sup.-5 5 2.7 .times. 10.sup.-5 9 3.8 .times. 10.sup.-5
14 4.8 .times. 10.sup.-5 LiSCN MEG EG 8 2 5.5 .times. 10.sup.-6 5
1.2 .times. 10.sup.-5 9 1.7 .times. 10.sup.-5 14 1.7 .times.
10.sup.-5 NaCN MEG EG 8 2 3.1 .times. 10.sup.-7 5 1.6 .times.
10.sup.-6 9 1.7 .times. 10.sup.-6 14 1.2 .times. 10.sup.-6
LiOCH.sub.3 MEG EG 8 9 9.9 .times. 10.sup.-7* 14 7.2 .times.
10.sup.-7* LiOCH.sub.2CF.sub.3 MEG EG 8 9 8.3 .times. 10.sup.-7* 14
5.4 .times. 10.sup.-7 Li.sub.2S MEG EG 8 9 5.8 .times. 10.sup.-7 14
8.6 .times. 10.sup.-7 *The conductivity values were measured at
75.degree. C.
[0124] These preferred compounds are exemplary of the
conductivities required for use as electrolytes in electrochemical
devices.
[0125] Certain polyanionic polymers wherein the Lewis
acid-containing polymers comprise phenyl as Y.sub.1 and are
complexed to preferred Lewis base anions exhibit the glass
transitions temperatures and physical appearance illustrated in
Table 4. The conductivities are also illustrated in Table 4 and
FIGS. 2D, 6 and 7B. In Table 4 the formulae PBEG.sub.n indicates P
is phenyl, B is borate and EG is spacer group ethylene glycol and
has repeat number n wherein TREG is triethylene glycol and n is 3,
200 equals 5, 400 equals 9, 600 equals 14 and 1000 equals 23. The
ratio of Lewis base anion to borate ion is indicated in
parentheses. TABLE-US-00004 TABLE 4 The Glass Transition
Temperatures (Tg), Ambient Conductivities and Physical Appearance
of Different Boron Containing Polyethers + Salt Complexes Log
.sigma..sub.RT Appearance Compositions T.sub.g (.degree. C.)
(S.cm.sup.-1) at 25.degree. C. PBTREG:LiCN(B:CN = 4) -40 -- Viscous
liquid PBTREG:LiCN(B:CN = 1) -23.4 -5.60 Viscous liquid
PB200EG:NaCN (B:CN = 2) -14.5 -5.20 Viscous liquid PB200EG:NaCN
(B:CN = 1) -7.5 -5.37 Viscous liquid PB400EG:NaCN(B:CN = 2) -59.5
-4.98 Viscous liquid PB400EG:NaCN(B:CN = 1) -58 -4.56 Viscous
liquid PB400EG:LiIm(B:Im = 2) -44 -4.75 Viscous liquid
PB400EG:LiIm(B:Im = 1) -37.8 -5.20 Viscous liquid PB400EG:LiCN(B:CN
= 1) -50 -4.87 Viscous liquid PB600EG:NaCN(B:CN = 2) -57.3 -4.86
Viscous liquid PB600EG:NaCN(B:CN = 1) -46.5 -5.09 Viscous liquid
PB600EG:LiIm(B:Im = 2) -56 -4.54 Viscous liquid PB600EG:LiIm(B:Im =
1) -47 -4.70 Viscous liquid PB1000EG:NaCN(B:CN = 2) -62.5 -6.00
Crystalline PB1000EG:NaCN(B:CN = 1) -61 -5.76 Crystalline
[0126] In an important aspect of the present invention, methods for
preparing the novel polyanionic chain polymers are given. In the
methods, a precursor polymer comprising repeating Lewis acid groups
linked into polymer chains comprising repeating spacer groups is
contacted with a Lewis base under conditions whereby the Lewis base
either bonds to the Lewis acid to form an anionic group or the
Lewis base associates with the Lewis acid group to form an anionic
trap. The counter ion on the supplied Lewis base becomes the
counter ion on the resulting anionic polymer. The counter ion may
be later exchanged for a different cation by known methods.
[0127] The subject polyanionic polymers comprising the Lewis bases
disclosed herein exhibit a wide range of bonding strength with the
Lewis acids. The order of binding strength is approximately as
follows, wherein Ph.sup.- represents the strongest binding: [0128]
Ph.sup.->CH.sub.3O.sup.->CF.sub.3CH.sub.2O.sup.->S.sup.2->CN.-
sup.->SCN.sup.->CF.sub.3SO.sub.3.sup.->TFSI.sup.-
[0129] The corresponding polyanionic polymers may be expected to
exhibit a similar order of conductivities from low to high as
illustrated herein.
[0130] Although these embodiments illustrate the nature of Lewis
bases that are suitable to form conductive polyanionic polymers,
this list is not intended to be inclusive. Indeed it is an
important aspect of the present invention that a method and means
are provided whereby polyanionic polymers of a desired conductivity
or transport number can be prepared.
[0131] Certain modifications can be made to the present conductive
polymers to enhance their mechanical properties so they can be more
readily formed into films or otherwise fabricated into components
suitable for use in secondary lithium batteries. Certain properties
of the present polymers indicate their suitability for such
purposes. They are soluble in certain solvents and plasticizers,
which is a prerequisite for film formation. They may be
cross-linked to form polyanionic composites, and these cross-linked
composites are likewise soluble or swollen in plasticizers. The
polymeric chains in the present polymers may be chosen to be
reactive with other polymers so that they may be mixed with, bonded
to, or otherwise incorporated into suitable non-ionic chain
polymers, ionic chain polymers comprising other ionic groups,
polymer networks or block-co-polymers. These modifications have
been illustrated in the following examples. Certain similar
modifications will be apparent to one skilled in the polymer
arts.
[0132] In an important aspect of the present invention, the
polyanionic chain polymers are cross-linked to form a polyanionic
polymeric network. Any suitable cross-linking agent may be used,
but most preferably the string polymers are chemically crosslinked
with lithium boron hydride. Cross-linked polymers exhibit greater
mechanical strength than the simple polymer chains.
[0133] In yet a further important aspect of the present invention,
the polyanionic chain polymers are dissolved in solvents,
preferably polar solvents, for example tetrahydrofuran (THF),
acetonitrile and acetone. This advantageous property of the
polyanionic polymers of the present invention makes them suitable
for fabrication into films and coatings.
[0134] In a related aspect of the present invention, the
polyanionic chain polymers incorporating weakly coordination
anionic groups may be affixed to a solid surface and incorporated
into an ion-exchange system. The spacer groups may be chosen to
provide a tethering group for bonding to a surface such as an ion
exchange resin bead or a porous membrane. In these applications the
exchange capacity of the polymer may be determined by the charge
density (length of spacer chain between anionic sites and charge of
anionic site) and also the strength of bonding between the Lewis
acid and the chosen anionic Lewis base.
[0135] In yet another aspect of the present invention, a method is
given for increasing the conductivity of the polyanionic polymers
wherein certain plasticizers are added to the polymers. Although it
is not intended that the present invention be bound by a
description of the mechanism of the plasticization effect, it is
proposed that the local mobility of the polymeric chain is
increased by the plasticizers and as a result the conductivity is
increased.
[0136] In an advantageous embodiment of the invention, the anionic
chain polymers and the cross-linked network polymers comprise
certain plasticizers that enhance the conductivity of the polymer.
The plasticized polymers and cross-linked polymers can be formed
into conductive films by methods known in the art. Preferred
plasticizers are carbonate and non-carbonate plasticizers. Suitable
carbonate plasticizers are, for example, ethylene carbonate (EC),
propylene carbonate (PC), butylene carbonate (BC),
dimethylcarbonate (DMC) and diethyl carbonate (DEC). Suitable
non-carbonate plasticizers are 1,2-dimethoxyethane (DME) and
1,2-diethoxyethane (DEE), dimethylsulfoxide (DMSO), dimethylsulfone
(DMS), ethylmethylsulfone (EMS), .gamma.-butyrolactone (BL).
Preferred plasticizers comprise mixtures of carbonate plasticizer,
preferably mixtures of ethylene carbonate and propylene carbonate
(EC-PC), ethylene carbonate and dimethyl carbonate (EC-DMC), and
propylene carbonate and dimethylxyethane (PC-DME).
[0137] The above-mentioned polyanionic polymers and cross-linked
polymers and those embodiments wherein the polymers are dissolved
in solvents or comprise plasticizers can be employed advantageously
as solid polymeric electrolytes in most any type of electrochemical
device. Most specifically the polyanionic polymers of the present
invention are suitable SPE for electrochemical devices comprising
lithium and in particular, lithium rechargeable batteries. The
polyanionic polymers can be incorporated in electrochemical cells
and lithium batteries, especially rechargeable lithium
batteries.
[0138] These and other features, aspects and advantages of the
present invention will become better understood with reference to
the following descriptive examples.
EXAMPLE 1
[0139] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid comprises a
tri-coordinated boron group wherein one ligand is phenyl and two
ligands are oxygen linked to the polymeric chain containing
repeating spacer units of ethylene glycol. This compound has the
formula poly[phenyl-oligo(ethylene glycol).sub.n borate] wherein n
is 3 to 23.
[0140] Phenylboronic acid [PhB(OH).sub.2] was refluxed with
poly(ethylene glycol) (PEG), chosen from triethylene glycol,
PEG200, PEG400, PEG600 or PEG 100, in toluene. (In these Examples,
the use of triethylene glycol results in a value of n=3; for
PEG200, n is 5; for PEG400, n is 9; for PEG600, n is 14 and for
PEG1000, n is 23.) The water produced in the condensation reaction
was collected and measured to determine the extent of the reaction.
When the amount of recovered water indicated that reaction was
complete, the solution was filtered and the solvent was removed on
a rotary evaporator. The product was further dried by overnight
evacuation at 100.degree. C. in a vacuum oven. The product was a
viscous liquid or crystal solid, depending on the PEG used.
EXAMPLE 2
[0141] This example illustrates the preparation of a Lewis
acid-containing polymer as in Example 1 but wherein the polymer has
repeat spacer groups of different chain lengths of propylene
glycol. This compound has the formula poly[phenyl-oligo(propylene
glycol).sub.n borate] wherein n is 7 to 17.
[0142] Phenylboronic acid was reacted with polypropylene glycol
(PPG) as in Example 1. The PPG used was chosen from PPG425 (gives
n=7), PPG725 (gives n=13), or PPG1000 (gives n=17). The result was
a viscous liquid.
EXAMPLE 3
[0143] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid comprises a
tri-coordinated boron group wherein one ligand is methyl and two
ligands are oxygen linked to the polymeric chain containing
repeating spacer units of ethylene glycol. This compound has the
formula poly[methyl-oligo(ethylene glycol).sub.n borate] wherein n
is 14.
[0144] Methyl boronic acid [CH.sub.3B(OH).sub.2] was refluxed with
PEG600 in toluene as described in Example 1. The result was a
viscous liquid.
EXAMPLE 4
[0145] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid comprises a
tri-coordinated boron group wherein one ligand is
2,4-difluorophenyl or 3,5-difluorophenyl and two ligands are oxygen
linked to the polymeric chain containing repeating spacer units of
ethylene glycol. This compound has the formula
poly[2,4-difluorophenyl-oligo(ethylene glycol).sub.n borate] or
poly[3,5-difluorophenyl-oligo(ethylene glycol).sub.n borate]
wherein n is 9.
[0146] 2,4-difluorophenylboronic acid or 3;5-difluorophenylboronic
acid was refluxed with PEG400 in toluene as described in Example 1.
The result was a viscous liquid.
EXAMPLE 5
[0147] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid group comprises
borate with a first ligand methoxy-oligo(ethylene glycol).sub.m and
two ligand oxygens bound to the spacer groups oligo(ethylene
glycol).sub.n. These compounds have the formula
poly[methoxy-oligo(ethylene glycol).sub.m oligo(ethylene
glycol).sub.n borate], wherein m represents the length of the
branch and is 1-12 and n represents the length of spacer chain and
is 2-14. This polymer is herein abbreviated as
P(MEG.sub.mEG.sub.nB).
[0148] (1) In a dry flask equipped with stirring bar, water
separation apparatus, condenser and CaCl.sub.2 drying tube, were
placed 0.02 mol boric acid, 0.02 mol poly(ethylene
glycol)monomethyl ether with molecular weight chosen from 76 (gives
m=1), 164 (gives m=3), 350 (gives m=8) and 550 (gives m=12), and
some anhydrous benzene. The reaction mass was stirred and heated in
an oil bath of about 100.degree. C. until a clear solution was
obtained. The benzene solution was cooled to room temperature and
the amount of water removed from the reaction mass was
measured.
[0149] (2) 0.02 mol poly(ethylene glycol) with molecular weight
chosen from 106 (gives n=2), 200 (gives n=5), 400 (gives n=9) and
600 (gives n=14), was added quickly into the above reaction
solution. The mixture solution was stirred and heated again in the
oil bath of 110-120.degree. C. until no more water was released
(about 3 days). After the reaction was complete, the amount of
water produced was measured in order to calculate the
polymerization degree. The solvent in the viscous reaction mass was
evaporated on a rotary evaporator at reduced pressure. The residual
polymer was then dried in a vacuum oven at about 90.degree. C. at
high vacuum for 2 days, and kept in a dry glove box after
drying.
[0150] The physical appearances of these polymers are given in
Table 1.
EXAMPLE 6
[0151] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid group comprises
borate with a first ligand methoxy-oligo(ethylene glycol).sub.m and
two ligand oxygens bound to the spacer groups oligo(propylene
glycol).sub.n. These compounds have the formula
poly[methoxy-oligo(ethylene glycol).sub.m oligo(propylene
glycol).sub.n borate], wherein m represents the length of the
branch and is 1-12 and n represents the length of spacer chain and
is 7-17. This polymer is herein abbreviated as
P(MEG.sub.mPG.sub.nB).
[0152] Boric acid was reacted with poly(ethylene glycol)monomethyl
ether with molecular weight of 350 (gives m=8) in anhydrous
benzene, and then with polypropylene glycol 725 (gives n=13) as
described in Example 5. The physical appearances of these polymers
are given in Table 1.
EXAMPLE 7
[0153] This example illustrates the preparation of the Lewis
acid-containing polymer wherein the Lewis acid group comprises
boron bound to three ligands. The first ligand is
butoxy-oligo(propylene glycol).sub.m and the other two ligands are
oxygens bound to oligo(ethylene glycol).sub.n. The formula for
these compounds is poly[butoxy-oligo(propylene glycol).sub.m
oligo(ethylene glycol).sub.n borate], wherein m represents the
length of the branch and is 1-12 and n represents the length of
spacer chain and is 2-14. This polymer is herein abbreviated as
P(BPG.sub.mEG.sub.nB).
[0154] Boric acid was reacted with poly(propylene glycol)mono-butyl
ether with molecular weight of 340 (gives m=5) in anhydrous
benzene, and then with polyethylene glycol 400 (gives n=9) as
described in Example 5. The physical appearance of the polymer is
given in Table 1.
EXAMPLE 8
[0155] This example illustrates the preparation of a Lewis
acid-containing polymer wherein the Lewis acid group comprises
boron bound to three ligands. The first ligand is phenyl and the
other two ligands are oxygens bound to dimethyl
siloxane-co-tetraethylene glycol. The formula for these compounds
is poly[oligo(dimethyl siloxane-co-tetraethylene
glycol)phenylborate]. This polymer is herein abbreviated as
P(DMS-co-TEG-co-PBA). P[DMS.sub.iEG.sub.4).sub.nPB].
[0156] To a flame dried 500 ml three-neck flask equipped with
condenser, thermometer and dropping funnel was added 23.9 g (0.123
mole) tetraethylene glycol. The flask was heated to 100.degree. C.
and 18.0 g (0.123 mole) bis(dimethylamino)dimethyl silane was added
dropwise under vigorous stirring. After the addition the reaction
was continued at the same temperature while a lot of gas
(dimethylamine) was bubbling out of the solution. When the gas
evolution was nearly ceased (about 2 hours), 250 ml benzene was
added to the reaction flask and followed by adding 15 g
phenylboronic acid. The azeotropic distillation process was begun.
The reaction was continued for 24 hours, and then the solution was
filtered and evaporated to remove the solvent. A viscous product
was obtained. It was further dried at 70.degree. C. in the vacuum
oven for one day.
EXAMPLE 9
[0157] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 1. The
polyanionic polymer has the repeat unit
--[O--B.sup.-(Ph).sub.2--(OCH.sub.2CH.sub.2).sub.n]-- wherein n is
14, and the counter ion is lithium.
[0158] The polymer from Example 1 was dissolved in dry ether, and
cooled to 0-5.degree. C. Phenyllithium in ether was added dropwise.
After addition, the solution was stirred overnight. Then the
solvent was removed by evaporation and a fluffy rubber was
obtained. The product has a glass transition temperature of 219K.
The conductivity was low, 3.6.times.10.sup.-8 Scm.sup.-1 at
25.degree. C.
EXAMPLE 10
[0159] This example illustrates the preparation of an
anion-trapping polymer electrolyte from the Lewis acid-containing
polymer of Example 1. The polymer has the ethylene glycol repeat
unit with 9 and 14, and the counter ion is lithium.
[0160] The polymer from Example 1 was reacted with lithium imide.
The product was a viscous liquid and the physical properties and
conductivities are shown in Table 4 and FIG. 2D. The conductivities
of these polymers are given in FIG. 2D.
EXAMPLE 11
[0161] This example illustrates the preparation of a polyanionic
polymer electrolyte from the Lewis acid-containing polymer of
Example 1. The polyanionic polymer has the repeat unit
--[O--B.sup.-(Ph)(CN)--(OCH.sub.2CH.sub.2).sub.n]-- wherein n is 3
and 9, and the counter ion is lithium.
[0162] The polymer from Example 1 was stirred with lithium cyanide
in anhydrous THF at room temperature for 6 hours. After that the
undissolved salt was filtered off and the solvent in the filtrate
was evaporated on a rotary evaporator at reduced pressure. The
product was further dried in a vacuum oven at 100.degree. C. for
one day and a viscous liquid was obtained. The properties of the
polyanionic polymers are listed in Table 4. The conductivities of
these polymers are given in FIGS. 6 and 7B.
EXAMPLE 12
[0163] This example illustrates the preparation of a polyanionic
polymer electrolyte from the Lewis acid-containing polymer of
Example 1. The polyanionic polymer has the repeat unit
--[O--B.sup.-(Ph)(CN)--(OCH.sub.2CH.sub.2).sub.n]-- wherein n is 5
to 23, and the counter ion is sodium.
[0164] The polymer from Example 1 was stirred with sodium cyanide
in anhydrous THE as described in Example 11. The properties and
conductivities of the polyanionic polymers are shown in Table 4 and
FIG. 6. The conductivities of these polymers are given in FIG.
6.
EXAMPLE 13
[0165] This example illustrates the preparation of a polyanionic
polymer electrolyte from the Lewis acid-containing polymer of
Example 1. The polyanionic polymer has the repeat unit
--[O--B.sup.-(Ph)(SCN)--(OCH.sub.2CH.sub.2).sub.n]-- wherein n is 9
and 14, and the counter ion is lithium.
[0166] The polymer from Example 1 was stirred with lithium
thiocyanate in anhydrous THF at room temperature to get a clear
solution. The solvent was then evaporated on a rotary evaporator at
reduced pressure. The product was further dried in a vacuum oven at
100.degree. C. for one day and a viscous liquid was obtained. The
properties and conductivities of the polyanionic polymers are shown
in Table 4 and FIG. 7B. The conductivities of these polymers are
given in FIG. 7B.
EXAMPLE 14
[0167] This example illustrates the preparation of a polyanionic
polymer electrolyte from the Lewis acid-containing polymer of
Example 1. The polyanionic polymer has the ethylene glycol repeat
unit of 9 and 14, and the counter ion is lithium.
[0168] (1) Lithium sulfide and sublimed sulfur were stirred in
anhydrous DME at room temperature till all solid dissolved to yield
lithium polysulfide (Li.sub.2S.sub.8).
[0169] (2). The polymer from Example 1 was dissolved in DME and
combined with lithium polysulfide solution in DME at room
temperature with shaking. Polymer precipitate was formed out of the
solution. It was collected and dried in a vacuum oven at
100.degree. C. for one day. A sticky solid was obtained. The
properties of the polyanionic polymers are listed in Table 4.
EXAMPLE 15
[0170] This example illustrates the preparation of an
anion-trapping polymer from the Lewis acid-containing polymer of
Examples 5-7. The polymer comprises imide complexed to a
substituted borate. Spacer groups are ethylene glycol, and the
counter ion is lithium.
[0171] About 2 g of various polymers from Examples 5-7 (wherein the
length of MEG was 1-12, the length of BPG was 5, the number of
spacer groups EG was 2-14 and PG was 13) was weighed in a dry glove
box and dissolved in anhydrous tetrahydrofuran (THF). A
quantitative amount of LiTFSI was added into the solution. The
mixture was shaken occasionally to dissolve the salt and to make
the solution homogeneous. The solvent in the clear solution was
evaporated down on a rotavapor at reduced pressure. The residual
was dried in a vacuum oven at about 90.degree. C. at high vacuum
for 2 days, and kept in a dry glove box after drying. The products
were viscous liquids (see Table 2). The conductivities of these
polymers are given in FIGS. 1A, 1B, 2A, 2B, and 2C. The
conductivities at 25.degree. C. of the complexes wherein the ligand
Y.sub.1 on the Lewis acid was MEG.sub.m or BPG.sub.m of determined
lengths and spacer group Z was oligo(ethylene glycol).sub.n
(EG.sub.n) or oligo(propylene glycol).sub.n (PG.sub.n) at
determined lengths were listed in Table 3.
EXAMPLE 16
[0172] This example illustrates the preparation of an
anion-trapping polymer from the Lewis acid-containing polymer of
Example 5. The polymer comprises LiSO.sub.3CF.sub.3 complexed to a
substituted borate. Spacer groups are ethylene glycol.
[0173] The complexes were prepared as in Example 15 by mixing
various polymers from Example 5 (wherein the length of MEG.sub.m
was 3 and 8 and the length of spacer groups EG.sub.n was 2-14) and
LiSO.sub.3CF.sub.3 in anhydrous tetrahydrofuran (THF). The products
were viscous liquids (see Table 2). The conductivities of these
polymers are given in FIGS. 1A, 1B, 3A, 3B, and 3C. The
conductivities at 25.degree. C. of the complexes wherein the ligand
Y.sub.1 on the Lewis acid was MEG.sub.m or BPG.sub.m of determined
lengths and spacer group Z was oligo(ethylene glycol).sub.n
(EG.sub.n) or oligo(propylene glycol).sub.n (PG.sub.n) at
determined lengths were listed in Table 3.
EXAMPLE 17
[0174] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5.
Polymers from Example 5 (wherein the length of MEG.sub.m was 8 and
the length of spacer groups was 2 to 14) were reacted with lithium
thiocyanate (LiSCN), as described in Example 15. The conductivities
of the polymers are given in FIGS. 1A, 1B and 7A.
EXAMPLE 18
[0175] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5 wherein
the length of MEG was 8 and the number of spacer groups was 9.
[0176] Polymers from Example 5 were reacted with lithium cyanide
(LiCN) as described in Example 11. The products were dried in a
vacuum oven at 90.degree. C. for 2 days.
EXAMPLE 19
[0177] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5.
Polymers from Example 5 (wherein the length of MEG.sub.m was 8 and
the length of spacer groups was 2 to 14) were refluxed with sodium
cyanide (NaCN) in anhydrous THF for 2 days, followed by the
filtration of undissolved salt, evaporation of solvent and drying
as described in Example 18. The conductivities of the polymers are
given in FIGS. 1A, 1B and 8.
EXAMPLE 20
[0178] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5.
Polymers from Example 5 (wherein the length of MEG.sub.m was 8 and
the length of spacer groups was 9 and 14) were reacted with lithium
methoxide (LiOCH.sub.3), as described in Example 15. The
conductivities of the polymers are given in FIGS. 1A and 1B.
EXAMPLE 21
[0179] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5.
Polymers from Example 5 (wherein the length of MEG.sub.m was 8 and
the length of spacer groups was 9 and 14) were reacted with lithium
2,2,2-trifluoroethoxide (LiOCH.sub.2CF.sub.3), as described in
Example 15. The conductivities of the polymers are given in FIGS.
1A and 1B.
EXAMPLE 22
[0180] This example illustrates the preparation of a polyanionic
polymer from the Lewis acid-containing polymer of Example 5.
Polymers from Example 5 (wherein the length of MEG.sub.m was 8 and
the length of spacer groups was 9 and 14) were reacted with lithium
sulfide (Li.sub.2S), as described in Example 19. The conductivities
of the polymers are given in FIGS. 1A and 1B.
EXAMPLE 23
[0181] This example illustrates the synthesis of cyanomethyllithium
(LiCH.sub.2CN) and the preparation of a polyanionic polymer from
the Lewis acid-containing polymer from Example 1.
[0182] (1) To the flame dried 250 ml flask equipped with condenser,
thermometer and dropping funnel was added 10 ml dry ether and 0.6 g
acetonitrile. The system was cooled to 0-5.degree. C. and 5.84 ml
butyllithium (2.5 m in hexane) diluted with 10 ml dry ether was
added dropwise. After addition the solution was stirred for 6
hours.
[0183] (2) 10 g polymer from Example 1 wherein the ethylene glycol
repeat unit is 9 (i.e., PB600EG) in 10 ml THF was added slowly to
the reaction solution. The solution was stirred for another 4 hours
before evaporating the solvent. The product was sticky solid, and
its conductivity was measured by pressing it between two stainless
steel electrodes. The conductivity was measured and is given in
FIG. 4.
EXAMPLE 24
[0184] This example illustrates the preparation of a polyanionic
polymer prepared from the Lewis acid-containing polymer of Example
8.
[0185] The polymer from Example 8 was stirred with Li imide in
anhydrous THF as described in Example 15. The molar ratio of boron
in polymer from Example 8 to the anion of Lewis base (i.e., B:Im)
was 2. The properties of the polyanionic polymer electrolytes were
listed in Table 4 and FIG. 2D.
EXAMPLE 25
[0186] This example illustrates the plasticization of a polyanionic
polymer prepared in Example 23. The plasticizing effect was
measured by using EC/PC (1/1, o/w) as the plasticizer.
[0187] The polyanionic polymer electrolyte from Example 23 was
mixed well with different amount of EC/PC (1/1, o/w). The
conductivities of the plasticized electrolytes are given in FIG.
4.
EXAMPLE 26
[0188] This example illustrates the plasticization of an
anion-trapping polymer prepared in Example 24. The anion-trapping
polymer electrolyte from Example 24 was mixed well with different
amount of EC/PC (1/1, o/w) as described in Example 25. The
conductivities of the plasticized electrolytes are given in FIG.
5.
EXAMPLE 27
[0189] This example illustrates the preparation of a cross-linked
polyanionic polymer from the Lewis-acid-containing polymers of
Example 5. Lithium borohydride (LiBH.sub.4) was used as a
crosslinker.
[0190] Polymers from Example 5 (wherein the length of MEG.sub.m was
3 and the length of spacer groups was 2 to 14) was dissolved in
anhydrous THF. LiOCH.sub.2CF.sub.3 was added and stirred to allow
all salt to dissolve. The solution was then vigorously stirred and
cooled to -78.degree. C. in a dry ice-acetone bath. A certain
amount of LiBH.sub.4 in THF solution was added dropwise. After
addition, the reaction mass was stirred at room temperature
overnight. The solvent of the clear solution was evaporated down on
a rotavapor under reduced pressure and the residual was dried in a
vacuum oven at 90.degree. C. for 2 days. The product was glass,
stiff rubber and soft rubber depending on the length of the spacer.
The room temperature conductivities of these crosslinked
polyanionic electrolytes are 3.8.times.10.sup.-7 Scm.sup.-1 for the
spacer length n=9 and 2.3.times.10.sup.-7 Scm.sup.-1 for the spacer
length n=14.
EXAMPLE 28
[0191] This example illustrates the plasticization of a polyanionic
polymer prepared in Example 27. The crosslinked polyanionic polymer
electrolytes from Example 27 were mixed well with different amount
of EC/PC (1/1, o/w) as described in Example 25. The conductivities
of the plasticized electrolytes are given in FIGS. 9A and 9D.
EXAMPLE 29
[0192] This example illustrates the method for measuring the
conductivity of the polyanionic polymers of Examples 9-28.
[0193] Conductivities of the polyanionic polymers prepared in
Examples 9-28 were determined by a.c. impedance measurement as a
function of temperature using a HP 4192A LF Impedance Analyzer in a
frequency range from 5 Hz to 13 MHz, with dip-type cells containing
two parallel platinum discs or block-type cells containing two
stainless steel block electrodes. The cell constants of the
dip-type cells were from 0.7 to 1.3 cm.sup.-1, calibrated by 0.1M
KCl aqueous solution.
EXAMPLE 30
[0194] This example illustrates the electrochemical properties of
an anion-trapping polymer electrolyte from Example 15 wherein the
length of MEG.sub.m was 8 and the length of spacer groups was 14,
and the lithium salt was LiTFSI. The cyclic voltammograms were
measured at room temperature on an EG&G
potentiostat/galvanostat model 273, with a three-electrode dip-cell
with stainless steel wire as working electrode and lithium metal as
counter and reference electrodes. The scan rate was 5 mVs.sup.-1.
The cyclic voltammetric results were given in FIGS. 10A and
10B.
EXAMPLE 31
[0195] This example illustrates the electrochemical properties of
an anion-trapping polymer electrolyte from Example 16 wherein the
length of MEG.sub.m was 8 and the length of spacer groups was 14,
and the lithium salt was LiSO.sub.3CF.sub.3. The cyclic
voltammograms were measured as described in Example 30 and the
results were given in FIGS. 11A and 11B.
[0196] Those skilled in the art will appreciate that numerous
changes and modifications may be made to the preferred embodiments
of the invention and that such changes and modifications may be
made without departing from the spirit of the invention. It is
therefore intended that the appended claims cover all such
equivalent variations as fall within the true spirit and scope of
the invention.
* * * * *