U.S. patent application number 14/190042 was filed with the patent office on 2015-01-15 for electrochemical devices based on block copolymers.
This patent application is currently assigned to SEEO, INC. The applicant listed for this patent is SEEO, INC. Invention is credited to Hany Basam Eitouni, Bing R. Hsieh, Mohit Singh.
Application Number | 20150017547 14/190042 |
Document ID | / |
Family ID | 41797413 |
Filed Date | 2015-01-15 |
United States Patent
Application |
20150017547 |
Kind Code |
A1 |
Hsieh; Bing R. ; et
al. |
January 15, 2015 |
ELECTROCHEMICAL DEVICES BASED ON BLOCK COPOLYMERS
Abstract
The present invention relates generally to electrolyte
materials. According to an embodiment, the present invention
provides for a solid polymer electrolyte material that has high
ionic conductivity and is mechanically robust. An exemplary
material can be characterized by a copolymer that includes at least
one structural block, such as a vinyl polymer, and at least one
ionically conductive block with a siloxane backbone. In various
embodiments, the electrolyte can be a diblock copolymer or a
triblock copolymer. Many uses are contemplated for the solid
polymer electrolyte materials. For example, the novel electrolyte
material can be used in Li-based batteries to enable higher energy
density, better thermal and environmental stability, lower rates of
self-discharge, enhanced safety, lower manufacturing costs, and
novel form factors.
Inventors: |
Hsieh; Bing R.; (Pleasanton,
CA) ; Eitouni; Hany Basam; (Oakland, CA) ;
Singh; Mohit; (Berkeley, CA) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
SEEO, INC |
Hayward |
CA |
US |
|
|
Assignee: |
SEEO, INC
Hayward
CA
|
Family ID: |
41797413 |
Appl. No.: |
14/190042 |
Filed: |
February 25, 2014 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
13060944 |
Feb 25, 2011 |
8691928 |
|
|
PCT/US2009/054709 |
Aug 22, 2009 |
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14190042 |
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61091626 |
Aug 25, 2008 |
|
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Current U.S.
Class: |
429/309 |
Current CPC
Class: |
H01M 10/0565 20130101;
Y02E 60/10 20130101; H01M 10/0525 20130101; H01M 2300/0082
20130101; C08G 77/46 20130101 |
Class at
Publication: |
429/309 |
International
Class: |
H01M 10/0565 20060101
H01M010/0565; H01M 10/0525 20060101 H01M010/0525 |
Claims
1. An electrochemical device, comprising an electrolyte wherein the
electrolyte is a block copolymer, comprising: a first polymer block
comprising a thermoplastic polymer; and a second polymer block
comprising a siloxane-based polymer that has a siloxane backbone
and the following structure: ##STR00019## wherein x is an integer
with values ranging from 2 to 12, R is selected individually for
each siloxane repeat unit in the backbone, at least one R comprises
an oligoethylene-oxide-containing group, and m is an integer
ranging from about 2 to 2000; wherein the thermoplastic polymer
comprises a vinyl polymer; and salt.
2. The device of claim 1 wherein the salt comprises lithium.
3. The device of claim 1 wherein the salt is selected from the
group consisting of AgSO.sub.3CF.sub.3, NaSCN, NaSO.sub.3CF.sub.3,
KTFSI, NaTFSI, Ba(TFSI).sub.2, Pb(TFSI).sub.2, and
Ca(TFSI).sub.2.
4. The device of claim 1, wherein R is selected individually for
each siloxane repeat unit in the backbone, is selected from the
group consisting of oligoethylene-oxide-containing groups, highly
polar groups, ethylene carbonates, cyano groups, N-pyrrolidone
groups, and perfluoroalkyl groups, and at least one R comprises an
oligoethylene-oxide-containing group.
5. The device of claim 1, wherein the
oligoethylene-oxide-containing group is selected from the group
consisting of: --O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.iCH.sub-
.3
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub-
.2CH.sub.2O).sub.i--CH.sub.3
--O--(CH.sub.2CH.sub.2CH.sub.2O).sub.i--CH.sub.3
--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2CH.sub.2O).sub.i--CH.sub.3
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2CH.sub.2O).sub-
.i--CH.sub.3
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2C-
H.sub.2CH.sub.2O).sub.i--CH.sub.3
--O--(CH.sub.2CH.sub.2O).sub.i--(CH.sub.2CH.sub.2CH.sub.2O).sub.j--CH.sub-
.3 and
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(C-
H.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3 wherein i is
an integer in the range of about 1 to 8 and: ##STR00020## wherein X
is selected from the group consisting of:
--OSi(CH.sub.3).sub.2--(CH.sub.2CH.sub.2)-- --(CH.sub.2CH.sub.2)--
--(CH.sub.2).sub.3OCH.sub.2--;
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3OCH.sub.2-- and wherein i is
an integer in the range of about 1 to 8.
6. The device of claim 1 further comprising some R selected from
the group consisting of highly polar groups, ethylene carbonates,
cyano groups, N-pyrrolidone groups, and perfluoroalkyl groups.
7. The device of claim 4, wherein the ethylene carbonates are
selected from the group consisting of: ##STR00021## wherein X is
selected from the group consisting of:
--OSi(CH.sub.3).sub.2--(CH.sub.2CH.sub.2)-- --(CH.sub.2CH.sub.2)--
--(CH.sub.2).sub.3OCH.sub.2--
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3OCH.sub.2--; --OCH.sub.2;
and --OCH.sub.2CH.sub.2--
8. The device of claim 4, wherein the cyano groups are selected
from the group consisting of: ##STR00022## wherein n is an integer
in the range of about 1 to 10.
9. The device of claim 4, wherein the N-pyrrolidone group
comprises: ##STR00023## wherein n is an integer in the range of
about 1 to 8.
10. The device of claim 4, wherein the perfluroalkyl group
comprises: --(CH.sub.2).sub.m(CF.sub.2).sub.n-- wherein m and n are
integers that are selected independently and are each in the range
of about 1 to 8.
11. The device of claim 10 wherein the second block comprises a
random copolymer and the second R group is selected independently
from the group consisting of oligoethylene-oxide-containing groups,
highly polar groups, ethylene carbonates, cyano, N-pyrrolidone
groups, and perfluoroalkyl groups.
12. The device of claim 1, wherein only one kind of R group is
included in the polymer.
13. The device of claim 1, wherein only two different R groups are
included in the polymer.
14. The device of claim 13 wherein the second block comprises a
random copolymer and the second R group is selected independently
from the group consisting of oligoethylene-oxide-containing groups,
highly polar groups, ethylene carbonates, cyano, N-pyrrolidone
groups, and perfluoroalkyl groups.
15. The device of claim 1, wherein only three different R groups
are included in the polymer.
16. The device of claim 15 wherein the second block comprises a
random terpolymer and the second R group and the third R group is
each selected independently from the group consisting of
oligoethylene-oxide-containing groups, highly polar groups,
ethylene carbonates, cyano groups, N-pyrrolidone groups, and
perfluoroalkyl groups.
17. The device of claim 1 wherein the polysiloxane chain is
represented by: ##STR00024## wherein x is an integer with values
ranging from 2 to 12, integer m can each have any value between
about 2 and 2000, and n is an integer ranging from about 1 to
100.
18. The device of claim 1 wherein the polysiloxane chain is
represented by: ##STR00025## wherein x is an integer with values
ranging from 2 to 12, integer m can each have any value between
about 2 and 2000, and n is an integer ranging from about 1 to
100.
19. The device of claim 1 wherein the polysiloxane chain is
represented by: ##STR00026## wherein x is an integer with values
ranging from 2 to 12, integer m can each have any value between
about 2 and 2000, and n is an integer ranging from about 1 to
100.
20. An electrochemical device, comprising an electrolyte wherein
the electrolyte is a block copolymer, comprising: a first polymer
block comprising a thermoplastic polymer; and a second polymer
block comprising a siloxane-based polymer comprising: at least one
oligomeric ethylene oxide pendant group; and a polysiloxane having
one or more backbone silicons linked to a first side chain and one
or more backbone silicons linked to a second side chain, wherein
the first side chain comprises a poly(alkylene oxide) moiety, and
the second side chain includes a cyclic carbonate moiety; and
wherein the thermoplastic polymer comprises a vinyl polymer; and a
salt.
21. An electrochemical device, comprising an electrolyte wherein
the electrolyte is a block copolymer, comprising: a first polymer
block comprising a thermoplastic polymer; and a second polymer
block comprising a siloxane-based polymer comprising: at least one
oligomeric ethylene oxide pendant group; and a disiloxane that has
a backbone comprising: a first silicon linked to a first
substituent selected from a group consisting of a first side chain
that includes a cyclic carbonate moiety, a first side chain that
includes a poly(alkylene oxide) moiety, and a first crosslink that
links the disiloxane to a second siloxane and that includes a
poly(alkylene oxide) moiety; and a second silicon linked to a
second substituent selected from a group consisting of a second
side chain that includes a cyclic carbonate moiety and a second
side chain that includes a poly(alkylene oxide) moiety; and wherein
the thermoplastic polymer comprises a vinyl polymer; and a
salt.
22. The device of claim 21 wherein at least one of the silicon
atoms is linked to a side chain that includes a poly(alkylene
oxide) moiety or a cyclic carbonate moiety.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application is a continuation of U.S. patent
application Ser. No. 13/060,944, filed Feb. 25, 2011 and claims
priority to U.S. Provisional Patent Application 61/091,626, filed
Aug. 25, 2008 and to International Application PCT/US09/54709,
filed Aug. 22, 2009, all of which are incorporated by reference
herein.
BACKGROUND OF THE INVENTION
Field of the Invention
[0002] This invention relates generally to high ionic conductivity
block copolymer electrolytes, and, more specifically, to high ionic
conductivity block copolymer electrolytes in which one block is
made of polysiloxanes having ethylene oxide or other pendant groups
and another block is made of a polymer that provides a rigid
structure.
[0003] The increased demand for lithium secondary batteries has
resulted in research and development to improve the safety and
performance of these batteries. Many batteries employ liquid
electrolytes associated with high degrees of volatility,
flammability, and chemical reactivity. A variety of
polysiloxane-based electrolytes have been developed to address
these issues. Examples include polysiloxane materials that contain
pendant oligomeric ethylene oxide groups prepared from
poly(methylhydrosiloxanes), wherein the starting
polymethylhydrosiloxane reacts with a vinyl or hydroxyl oligomeric
ethylene oxide in the presence of a catalyst to give the respective
electrolyte. However, these polysiloxane-based electrolytes
typically have a low ionic conductivity that limits their use to
applications that do not require high rate performance. In
addition, these materials do not have adequate mechanical
properties to serve as an electrolyte without the use of a separate
mechanically rigid material. As a result, there is a need for
electrolytes that include polysiloxane-based electrolytes with an
increased ionic conductivity and improved mechanical
properties.
[0004] Highly conducting polymer electrolytes based on block
copolymers of styrene and ethylene oxide have been disclosed
previously, for example, in WO07142731 and WO07113236. The
approximate chemical structures of these polymers are shown below,
wherein m and n are the numbers of repeat units for the polystyrene
and polyethylene oxide blocks respectively.
##STR00001##
[0005] Such block copolymers have a unique lamella morphology that
results in both high modulus and relatively high ionic conductivity
at 80.degree. C. However, there is a strong need for polymer
electrode materials with high ionic conductivity
(10.sup.-4-10.sup.-5 S/cm) at room temperature. Known polymer
electrolyte materials with high room temperature ionic conductivity
include polysiloxanes and polyphosphazenes having oligomeric
ethylene oxide pendant groups (see Macromolecules 2005, 38,
5714-5720, which is included by reference herein). The remarkable
room temperature conductivity for these polymers has been ascribed
to their highly flexible inorganic backbones which produce an
amorphous polymer matrix with a very low glass transition
temperature. Being flexible and amorphous, these polymers have a
very low modulus and are prone to creep when used in a battery,
thus reducing the battery's lifespan.
[0006] The present invention relates to block copolymers that
include a siloxane-based polymer block and a structural polymer
block. These block copolymers can be combined with salts (such as
lithium salts) to create ionically conductive materials that are
solid at desirable operating temperatures for use in batteries and
the like.
DETAILED DESCRIPTION
[0007] The embodiments of the present invention relate to block
copolymers with both structural polymer blocks and siloxane-based
polymer blocks. The siloxane-based blocks can be combined with
salts (e.g., lithium salts) to enhance their ionic conductivity.
Such block copolymers, which are both ionically conductive and have
good mechanical properties, can be used advantageously for
batteries and other energy storage devices such as capacitors. The
skilled artisan will readily appreciate, however, that the
materials and methods disclosed herein will have application in a
number of other contexts where conductive polymers are desirable,
particularly where material properties such as high elastic modulus
and toughness are important.
[0008] In order to provide electrolyte materials with both high
conductivity and mechanical stability, a new class of electrolyte
materials based on block copolymers whose blocks include
thermoplastic polymers and oligo(ethylene oxide) grafted
polysiloxanes has been developed. As is well known to a person of
ordinary skill in the art, thermoplastic polymers include both semi
crystalline and glassy or amorphous polymers. Semicrystalline
polymers usually have both crystalline regions and amorphous or
glassy regions. The crystalline regions can represent only a small
fraction of the overall polymer volume or they can represent most
of the polymer volume and any fraction in between, morphology and
The mechanically rigid properties of thermoplastic polymers can
improve the mechanical properties of these electrolyte materials.
In one embodiment of the invention, the thermoplastic block
comprises a vinyl polymer. The vinyl polymer can include one or
more monomers such as ethylene, propylene, stryrene, vinyl
cyclohexane, vinyl pyridine, alkyl acrylate, methyl acrylate,
tetrafluroethylene, and acrylonitrile. In another embodiment of the
invention, the thermoplastic block comprises polydiene (containing
one or more monomers from butadiene, isoprene, etc.), polyamide
(e.g., nylon), polyimide, polysilane, and/or polyester (e.g.,
polycarbonate). The block copolymers can be diblocks or triblocks
with either ABA or BAB morphologies.
[0009] The general structures of the block copolymers are shown
below, wherein the R group is an ethylene oxide containing group,
and x and y are the numbers of repeat units of the polystyrene
block and the polysiloxane block, respectively.
##STR00002##
[0010] The range of x and y is from about 10 to 3000, and the R
groups can be selected from, but are not limited to, the following
structures:
[0011] --(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0012]
--(CH.sub.2).sub.2Si(CH.sub.3).sub.2OSi(CH.sub.3).sub.2--(CH.sub.2)-
.sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0013]
--(CH.sub.2).sub.2Si(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2C-
H.sub.2O).sub.i--CH.sub.3
[0014] --(CH.sub.2).sub.2Si(CH.sub.3).sub.2--O--(CH.sub.2CH.sub.2O
.sub.i--CH.sub.3
wherein i is an integer ranging from 1 to 20.
[0015] The new block copolymer electrolyte materials can be
obtained via a sequential anionic polymerization as shown in the
following scheme:
##STR00003##
[0016] Alternatively, the block copolymer electrolyte materials can
be obtained by a sequential anionic polymerization to give a
pre-block copolymer which is then grafted with a oligo(ethylene
oxide) pendant group, as illustrated below. In one embodiment of
the invention, this method has been used to prepare the novel
diblock copolymer electrolyte.
##STR00004##
Siloxane Block
[0017] In one embodiment of the invention, a block copolymer
contains a block that has a polysiloxane backbone to which pendant
groups can be grafted. The pendant groups have the following
structure, wherein x is an integer with values ranging from 2 to
12.
##STR00005##
The overall structure of the polymer block is:
##STR00006##
wherein x is an integer with values ranging from 2 to 12, R can be
selected individually for each siloxane repeat unit in the backbone
and m is an integer ranging from about 2 to 2000. In some
arrangements, there are some siloxane repeat units in the backbone
where structure (1) is absent. R can be an
oligoethylene-oxide-containing group. In one arrangement, at least
one R is an oligoethylene-oxide-containing group. R can also be a
highly polar group, such as an ethylene carbonate, a cyano group,
an N-pyrrolidone group, or a perfluoroalkyl group. In one
arrangement, the polymer block is a homopolymer when only one R
moiety is used for all repeat units. In another arrangement, the
polymer block is a random copolymer with only two different R
(R.sub.1, R.sub.2) moieties distributed randomly among the repeat
units. In another arrangement, the polymer block is a random
terpolymer with only three different R (R.sub.1, R.sub.2, R.sub.3)
moieties distributed randomly among the repeat units. In yet
another arrangement, there can be any number of different R
moieties attached randomly to the repeat units.
[0018] The polymer block structures described above can be
represented by the following formulas:
##STR00007##
wherein integers x.sub.1, x.sub.2, and x.sub.3 each have any value
ranging from 2 to 12, and integers m, n, o can each have any value
between about 2 and 2000. In another arrangement, m, n, o can each
have any value between about 10 and 1000.
[0019] Examples of oligoethylene-oxide-containing groups that are
suitable for R include, but are not limited to the following
groups:
[0020] --O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0021] --(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0022]
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i-
--CH.sub.3
[0023]
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.-
sub.2CH.sub.2O).sub.i--CH.sub.3
[0024] --O--(CH.sub.2CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0025]
--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0026]
--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.sub.2CH.sub.2CH.sub.2-
O).sub.i--CH.sub.3
[0027]
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3O--(CH.-
sub.2CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0028]
--O--(CH.sub.2CH.sub.2O).sub.i--(CH.sub.2CH.sub.2CH.sub.2O).sub.j---
CH.sub.3
[0029]
--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--OSi(CH.sub.3).sub.2--(C-
H.sub.2).sub.3O--(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0030]
--OSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2OSi(CH.sub.3).sub.2OSi(CH.s-
ub.3).sub.2--(CH.sub.2).sub.3O(CH.sub.2CH.sub.2O).sub.i--CH.sub.3
[0031]
--CH.sub.2CH.sub.2Si(CH.sub.3).sub.2--(CH.sub.2).sub.3O(CH.sub.2CH.-
sub.2O).sub.i--CH.sub.3
wherein i is an integer in the range of about 1 to 8.
[0032] Other oligoethylene-oxide-containing groups that are
suitable for R include, but are not limited to some that contain
double ethylene oxide strains such as:
##STR00008##
wherein X can be, but is not limited to:
[0033] --OSi(CH.sub.3).sub.2--(CH.sub.2CH.sub.2)--
[0034] --(CH.sub.2CH.sub.2)--
[0035] --(CH.sub.2).sub.3OCH.sub.2
[0036] --OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3OCH.sub.2--
and wherein i is an integer in the range of about 1 to 8.
[0037] Examples of ethylene-carbonate-containing groups that are
suitable for R include, but are not limited to the following
groups:
##STR00009##
wherein X can be, but is not limited to:
[0038] --OSi(CH.sub.3).sub.2--(CH.sub.2CH.sub.2)--
[0039] --(CH.sub.2CH.sub.2)--
[0040] --(CH.sub.2).sub.3OCH.sub.2--;
[0041] --OSi(CH.sub.3).sub.2--(CH.sub.2).sub.3OCH.sub.2--;
[0042] --OCH.sub.2; and
[0043] --OCH.sub.2CH.sub.2--
[0044] Examples of cyano groups that are suitable for R include,
but are not limited to the following groups:
##STR00010##
wherein n is an integer in the range of about 1 to 10.
[0045] Examples of N-pyrrolidone groups that are suitable for R
include, but are not limited to the following:
##STR00011##
wherein n is an integer in the range of about 1 to 8.
[0046] Examples of perfluroalkyl groups that are suitable for R
include, but are not limited to the following:
(CH.sub.2).sub.m(CF.sub.2).sub.n--F
wherein m and n are integers that are selected independently and
are in the range of about 1 to 8.
[0047] In one embodiment of the invention, the polysiloxane chain
is represented by:
##STR00012##
wherein x is an integer with values ranging from 2 to 12, integer m
can each have any value between about 2 and 2000, and n is an
integer ranging from about 1 to 100.
[0048] In another embodiment of the invention, the polysiloxane
chain is represented by:
##STR00013##
wherein x is an integer with values ranging from 2 to 12, integer m
can each have any value between about 2 and 2000, and n is an
integer ranging from about 1 to 100.
[0049] In yet another embodiment of the invention, the polysiloxane
chain is represented by:
##STR00014##
wherein x is an integer with values ranging from 2 to 12, integer m
can each have any value between about 2 and 2000, and n is an
integer ranging from about 1 to 100.
[0050] The polysiloxane polymers described above can be used as a
conductive block in a novel block copolymer electrolyte for
electrochemical devices.
[0051] Other ionically conductive polymers based on polysiloxanes
can also be used as the conducting blocks in the novel block
copolymers disclosed herein. Exemplary polysiloxane-based
electrolytes with good ionic conductivity are discussed below. All
references listed are included by reference herein for all
purposes.
[0052] Highly conducting polymer electrolytes based on
polysiloxanes have been disclosed by West, et al. U.S. Pat. No.
6,337,383 discloses solid polysiloxane polymers with multiple
oligooxyethylene side chains per silicon. The multiple
oligooxyethylene side chains are each connected directly to the
silicons, or they can be linked by a branching structure and then
jointly linked to the silicons.
[0053] In U.S. Patent Publication Number 2004/0248014, West et al.
disclose an electrolyte that includes a polysiloxane having one or
more backbone silicons linked to a first side chain and one or more
backbone silicons linked to a second side chain. The first side
chains include a poly(alkylene oxide) moiety and the second side
chains include a cyclic carbonate moiety.
[0054] In U.S. Patent Publication Number 2004/0214090, West et al.
disclose a cyclic siloxane polymer electrolyte having
poly(siloxane-g-ethylene oxides) with one or more poly(ethylene
oxide) side chains directly bonded to Si atoms.
[0055] In U.S. Pat. No. 6,887,619, West et al. disclose
cross-linked polysiloxane polymers having oligooxyethylene side
chains. Lithium salts of these polymers can be synthesized as a
liquid and then caused to solidify in the presence of elevated
temperatures to provide a solid electrolyte useful in lithium
batteries.
[0056] In U.S. Patent Publication Number 2005/0170254, West et al.
disclose disiloxanes that include a backbone with a first silicon
and a second silicon. The first silicon is linked to a first
substituent selected from a group consisting of: a first side chain
that includes a cyclic carbonate moiety; a first side chain that
includes a poly(alkylene oxide) moiety; and a first cross link
links the disiloxane to a second siloxane and that includes a
poly(alkylene oxide) moiety. The second silicon can be linked to a
second substituent selected from a group consisting of: a second
side chain that includes a cyclic carbonate moiety, and a second
side chain that includes a poly(alkylene oxide) moiety.
[0057] U.S. Patent Publication Number 2006/0035154 discloses an
electrolyte that includes one or more tetrasiloxanes. The
tetrasiloxanes have a backbone with two central silicons and two
terminal silicons. A first one of the silicons is linked to a side
chain that includes a poly(alkylene oxide) moiety. A second one of
the silicons is linked to a side chain that includes a
poly(alkylene oxide) moiety or to a side chain that includes a
cyclic carbonate moiety. When each of the central silicons is
linked to a side chain that includes a poly(alkylene oxide) moiety,
each of the central silicons is directly linked to the
poly(alkylene oxide) moiety.
[0058] Some of the West copolymers are polysiloxane materials that
contain pendant oligomeric ethylene oxide groups prepared mainly
from poly(methylhydrosiloxanes), as exemplified in the following
scheme, wherein the starting polymethylhydrosiloxane reacts with a
vinyl or hydroxyl oligomeric ethylene oxide in the presence of a
catalyst to give the electrolyte products:
##STR00015##
[0059] In one embodiment of the invention, polysiloxane polymers
are combined with a lithium salt. Lithium salts that can be used in
the polymers described herein are not limited, as long as they aid
lithium ion conduction in the polymer so it can be used as an
electrolyte. Examples of specific lithium salts include LiSCN,
LiN(CN).sub.2, LiClO.sub.4, LiBF.sub.4, LiAsF.sub.6, LiPF.sub.6,
LiCF.sub.3SO.sub.3, Li(CF.sub.3SO.sub.2).sub.2N,
Li(CF.sub.3SO.sub.2).sub.3C, LiN(SO.sub.2C.sub.2F.sub.5).sub.2,
lithium alkyl fluorophosphates, lithium oxalatoborate, as well as
other lithium bis(chelato)borates having five to seven membered
rings, LiPF.sub.3(C.sub.2F.sub.5).sub.3,
LiPF.sub.3(CF.sub.3).sub.3, LiB(C.sub.2O.sub.4).sub.2, and mixtures
thereof. In other embodiments of the invention, for other
electrochemistries, electrolytes are made by combining the
polysiloxane polymers with various kinds of salts. Examples
include, but are not limited to AgSO.sub.3CF.sub.3, NaSCN,
NaSO.sub.3CF.sub.3, KTFSI, NaTFSI, Ba(TFSI).sub.2, Pb(TFSI).sub.2,
and Ca(TFSI).sub.2.
[0060] Block copolymers that contain polysiloxane blocks, as
disclosed herein, are more ionically conducting than many other
polymer electrolytes that have been employed in batteries. It is
known that polymers with flexible backbone chains generally have
higher ionic conductivity than do polymers with stiff backbone
chains. In addition to having a flexible siloxane backbone chain,
the polymers disclosed herein have very flexible silicon-containing
side chains. Without wishing to be bound to any particular theory,
it may be that the increased flexibility of the side chains
increases the ionic conductivity of the polymer further than is
possible with stiffer side chain groups.
[0061] The basic method of making the polysiloxane polymer blocks
can be described generally as allowing a poly(methylvinylsiloxane)
to undergo a hydrosilylation reaction with hydrosilane compound(s)
in the presence of a metal catalyst. In one arrangement, a platinum
catalyst such as chloroplatinic acid and platinum
divinyltetramethyl disiloxane complex (also known as the Karstedt's
catalyst), platinum cyclovinylmethylsiloxane complex, or platinum
octanal/octanol complex is used.
##STR00016##
[0062] Examples of processes for synthesizing polysiloxane polymer
blocks with particular R groups are given below. The examples are
meant to be illustrative and not limiting.
EXAMPLE 1
[0063] A three-neck round flask was equipped with a magnetic
stirrer, two addition funnels, a nitrogen inlet, and a rubber
septum. Sodium hydride (60% dispersion in mineral oil) (46 g, 1.15
mol) and then inhibitor-free tetrahydrofuran (Aldrich 439215) (500
ml) were added into the flask. Triethylene glycol monomethyl ether
(156 ml, 0.976 mol) and allyl bromide (100 ml, 1.155 mol) were
placed separately into each of the two addition funnels to await
addition into the flask. The mixture was cooled with an ice-water
bath, and then the triethylene glycol monomethyl ether was added
dropwise from the funnel into the flask. The resulting mixture was
stirred at room temperature for at least two hours. The mixture was
cooled again with an ice-water bath before the allyl bromide was
added dropwise from the funnel into the flask. The resulting
mixture was stirred overnight at room temperature. The solid
(mostly NaBr) that had formed in the mixture was removed by suction
filtration. The solid was rinsed with tetrahydrofuran. The filtrate
was concentrated in vacuo (rotavap followed by pump under vacuum)
and then vacuum distilled (80-90.degree. C.) to give triethylene
glycol allyl methyl ether (structure shown below) as a colorless
liquid (169 g, 89%).
##STR00017##
[0064] A flask was equipped with a magnetic stirrer and an addition
funnel. 1,1,3,3-tetramethydisiloxane (500 g or 660 ml, 3.72 mol)
and toluene (300 ml) were added into the flask. Triethylene glycol
allyl methyl ether (2) (81.6 g, 0.4 mol), toluene (100 ml), and
platinum divinyltetramethyldisilane catalyst (2.1-2.4% platinum
concentration) (0.25) were placed in the addition funnel to await
addition into the flask. The disiloxane solution was heated to
60-70.degree. C., before adding the triethylene glycol allyl methyl
ether solution dropwise. The resulting solution was heated for a
total of 24 hours, cooled, and then concentrated in vacuo (rotavap
followed by pump under vacuum). The resulting liquid was
fractionally distilled under vacuum (bath temperature
130-200.degree. C. and pressure of 0.4-0.8 mm Hg) to give the
following fractions: first fraction: 35-93.degree. C. (unwanted
unknown materials); second fraction: 95-125.degree. C., (unwanted
unknown materials); third fraction: 125-145.degree. C. (58 g). The
third fraction was identified as the desired siloxane product, code
named 2SiC-4EO, with the following structure:
##STR00018##
[0065] Prepolymer I, poly(styrene-b-methylvinylsiloxane) having
about a 50:50 molar ratio of styrene to methylvinylsiloxane was
prepared via anionic polymerization as follows. High purity benzene
was further purified by treatment with sec-butyllithium using
1,1-diphenylethylene as the indicator. High purity tetrahydrofuran
was further purified by treatment with sodium using benzophenone as
the indicator. Styrene was purified by dibutylmagnesium treatment
and then transferred into a solvent transfer/storage flask with
high vacuum Teflon.RTM. valve involving a freeze and thaw technique
using a high vacuum line. Tetrahydrofuran was similarly transferred
in a solvent transfer/storage flask and moved into a glove box. A
more detailed description of the high vacuum line and purification
procedures can be found in U.S. Provisional Patent Application No.
60/988,085, which is included by reference herein. Dried benzene
(about 400 ml) was vacuum transferred into a 2 L reaction flask
with a high vacuum valve and a magnetic stirring bar using a
freeze-and-thaw technique. The reaction flask was moved into the
glove box, and sec-butyl lithium (0.4 ml) was added, followed by
addition of styrene (50 ml). The polymerization was allowed to
proceed overnight in the glove box (>12 hr), and then
hexamethylcyclotrisiloxane (2.0 g) was added through a powder
funnel, followed by addition of tetrahydrofuran (200 ml). The
yellow color of the polymerization solution disappeared after about
40 min. After an hour,
1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (50 ml) was added,
and the polymerization was allowed to proceed for about 22 h.
Excess trimethylchlorosilane (2.0 g) was added, and the resulting
solution was stirred for 24 h to ensure thorough termination. The
resulting solution was precipitated into magnetically stirring
methanol (2 L). The white precipitate was allowed to settle and
most of the solvent was decanted. Methanol (1000 ml) was added to
the precipitate and the resulting mixture was stirred for several
minutes. The solvent was decanted and the precipitate was dried by
blowing under nitrogen overnight, followed by vacuum drying for 24
hours to yield poly(styrene-b-vinylmethylsiloxane), a white powder
(86 g). The styrene/siloxane molar ratio was about 49/51 as
determined by NMR analysis.
[0066] Prepolymer II, poly(styrene-b-methylvinylsiloxane) having
about a 40:60 molar ratio of styrene to methylvinylsiloxane was
prepared similarly to the method described above, using the
following amounts of ingredients: benzene (about 500 ml), sec-butyl
lithium (0.4 ml), styrene (50 ml), hexamethylcyclotrisiloxane (2.0
g), tetrahydrofuran (250 ml),
1,3,5-trivinyl-1,3,5-trimethylcyclotrisiloxane (75 ml), and
trimethylchlorosilane (2.0 g). The empirical styrene/siloxane molar
ratio was about 36/64 as determined by NMR analysis.
[0067] Prepolymer I (2.0 g) and toluene (14 ml) were added into a
100 ml round flask equipped with a magnetic stirrer and then capped
with a tightly fitted rubber septum. The mixture was immersed in a
65.degree. C. oil bath and stirred until completely solubilized,
after which 2SiC-4EO (5 g) was added. Platinum
divinyltetramethyldisilane catalyst (2.0% platinum concentration)
(50 .mu.L) was then added, and the flask was capped with the septum
and heated at 65.degree. C. for 48 h. The mixture was diluted with
toluene (20 ml), and activated charcoal (0.25 g) was added. The
mixture was stirred at 65.degree. C. for several hours. The
activated charcoal was removed by filtration, and the filtrate was
concentrated in vacuo to yield a viscous liquid which was then
precipitated into hexane (150 ml) while stirring magnetically. The
solvent was decanted, hexane (75 ml) was added, and the mixture was
stirred about 1 min and then decanted. This procedure was repeated.
The wet solid was transferred into a sample vial and dried under
vacuum overnight to yield an ethylene oxide grafted
poly(styrene-b-methylvinylsiloxane) as a slightly rubbery solid
(3.6 g), identified as Polymer I. The molar ratio of
styrene/grafted Si/ungrafted Si was about 57/36/7 as determined by
NMR analysis.
[0068] Prepolymer II (2.0 g) and toluene (14 ml) were added into a
100 ml round flask equipped with a magnetic stirrer and then capped
with a tightly fitted rubber septum. The mixture was immersed in a
65.degree. C. oil bath, stirred until completely solubilized and
then 2SiC-4EO (5 g) was added. Platinum divinyltetramethyldisilane
catalyst (2.0% platinum concentration) (50 .mu.L) was then added,
and the flask was capped with the septum and heated at 65.degree.
C. for 48 h. The resulting solution was diluted with toluene (20
ml) and activated charcoal (0.25 g) was added and stirred at
65.degree. C. for several hours and then cooled. The activated
charcoal was removed by filtration, and the filtrate was
concentrated in vacuo to yield a viscous liquid which was then
precipitated into hexane (150 ml) while stirring magnetically. The
solvent was decanted, hexane (75 ml) was added, and the mixture was
stirred about 1 min and then decanted. This procedure was repeated
The wet solid was transferred into a sample vial and dried under
vacuum overnight to yield an ethylene oxide grafted
poly(styrene-b-methylvinylsiloxane) as soft gluey semi-solid (4.2
g), identified as Polymer II. The molar ratio of styrene/grafted
Si/ungrafted Si was about 44/50/6 as determined by NMR
analysis.
[0069] Prepolymer I (2.0 g) and anhydrous toluene (14 ml) were
added into a 100 ml round bottom flask equipped with a magnetic
stirrer and then capped with a tightly fitted rubber septum under
argon. The mixture was immersed in a 65.degree. C. oil bath,
stirred until complete solubilization and then degassed 2SiC-4EO (5
g) and platinum divinyltetramethyldisilane catalyst (2.0% Pt, 50
.mu.L) were then added via syringes. The resulting solution was
heated for 48 h and then diluted with toluene (20 ml) and activated
charcoal (0.25 g) was added. The resulting mixture was stirred at
65.degree. C. overnight and then cooled. The activated charcoal was
removed by filtration, and the filtrate with concentrated in vacuo
to yield a viscous liquid which was then precipitated into hexane
(150 ml) while stirring magnetically. The solvent was decanted,
hexane (75 ml) was added, and the mixture was stirred about 1 min
and then decanted. This procedure was repeated The wet solid was
transferred into a sample vial and dried under vacuum overnight to
yield an ethylene oxide grafted poly(styrene-b-methylvinylsiloxane)
as semi-solid (4.2 g), identified as Polymer III. The molar ratio
of styrene/grafted Si/ungrafted Si was about 52/47/1 as determined
by NMR analysis.
EXAMPLE 2
[0070] Polymer Electrolyte Solution Preparation: Polymer
electrolyte solutions were prepared under a controlled argon
atmosphere (<0.1 ppm moisture and oxygen gas). Each polymer
(Polymer I and Polymer III) was dissolved in separate quantities of
tetrohydrofuran (THF). A salt, lithium
bis(triflouromethylsulfone)imide (LiTFSI) was added to the polymer
solutions according to a ratio "r" determined by the ethylene oxide
(EO) content. The value "r" was defined for the purposes of this
procedure as the ratio of the concentrations of Li+ to EO. Values
of r ranging from 0.04 to 0.085 were tested on the samples. The
ratio of solute mass (polymer+salt) to total solution mass was
chosen to be in the range of 5-10 wt % dependent on the physical
properties of the polymer and the final state of the material
(i.e., as a free standing film or bulk polymer). The polymer+salt
(polymer electrolyte) in THF solution was agitated via a stir bar
until it became homogenous (i.e., polymer and salt completely
solvated in solution).
[0071] Preparation of Polymer Electrolyte: In order to test the
ionic conductivity of the polymer, the polymer electrolyte was
extracted from solution in any of the following three ways. [0072]
1) Free standing films on order of 30 to 100 um thickness were
obtained via drop casting (also known as free casting), wherein a
polymer electrolyte solution was poured onto a flat surface (e.g.,
aluminum foil sheet on a vacuum plate) at room temperature. The THF
solvent evaporated, leaving a cast film of the polymer electrolyte.
The film was then peeled off the flat surface in an argon
atmosphere and dried under vacuum at temperatures in the range of
65 to 110.degree. C. [0073] 2) The polymer electrolyte was cast
onto an aluminum foil. The electrolyte was not removed from the
foil; the electrolyte/foil bilayer was used in determining the
ionic conductivity of the polymer electrolyte. [0074] 3) THF was
extracted via roto-vac for initial removal of the majority of
solvent followed by an overnight dry under vacuum. The resulting
bulk polymer electrolyte was used for ionic conductivity
testing.
[0075] Test Cell Fabrication and Electrochemical Measurement: The
polymer electrolyte was placed into a symmetric cell with the
electrolyte sandwiched between identical or symmetric electrodes,
and impedance spectroscopy was performed. In some cells
non-blocking electrodes (lithium foil) were used. In some cells
blocking electrodes (aluminum foil or gold plated steel current
collectors) were used. All cells were constructed in an argon
atmosphere with oxygen gas content less than 0.1 ppm and controlled
moisture. [0076] 1) Freestanding polymer electrolyte films were
punched out in a coin shape. The films were pressed between
Teflon.RTM. sheets at 60.degree. C. at less than about 0.25 ton
total applied force. The polymer electrolyte film was sandwiched
between steel current collectors laminated with lithium foil and
pressed with light force at 60.degree. C. The steel/Li/polymer
electrolyte/Li/steel sandwich was placed in a Swagelok.RTM. cell.
[0077] 2) Polymer electrolyte/aluminum bilayers were punched out in
a coin shape. Two such bilayer coins were laminated together with
electrolyte sides facing one another to form an aluminum/polymer
electrolyte/aluminum sandwich. The sandwich was placed in a
Swagelok.RTM. cell. [0078] 3) Bulk polymer electrolyte was placed
in the aperture of an insulating spacer. The spacer and polymer
were pressed between Teflon.RTM. sheets to allow the polymer
electrolyte to fill the aperture completely. The polymer and spacer
were sandwiched between steel current collectors laminated with Li
foil. The Li/polymer electrolyte/Li sandwich was placed in a
Swagelok.RTM. cell.
[0079] Potentioelectrochemical impedance spectroscopy (PEIS) was
performed on each Swagelok.RTM. cell to determine the ionic
conductivity of the electrolytes. Ionic conductivity results are
shown below.
TABLE-US-00001 Ionic conductivity Polymer at 25.degree. C.
(Scm.sup.-1) I 5.4 .times. 10.sup.-6 III 2.6 .times. 10.sup.-5
[0080] This invention has been described herein in considerable
detail to provide those skilled in the art with information
relevant to apply the novel principles and to construct and use
such specialized components as are required. However, it is to be
understood that the invention can be carried out by different
equipment, materials and devices, and that various modifications,
both as to the equipment and operating procedures, can be
accomplished without departing from the scope of the invention
itself.
* * * * *