WO2010083330A1

WO2010083330A1 - Polymer compositions with oligomeric alkylene oxide pendants

Info

Publication number: WO2010083330A1
Application number: PCT/US2010/021070
Authority: WO
Inventors: Bing Hsieh
Original assignee: Seeo, Inc
Priority date: 2009-01-16
Filing date: 2010-01-14
Publication date: 2010-07-22

Abstract

A novel graft polymer composition with a vinyl or an ethylene oxide backbone and oligo-alkylene oxide pendants is disclosed. The synthesis of the graft polymers involves making a vinyl or ethylene oxide prepolymer containing alkene groups, which are then grafted with alkylene oxide containing pendants.

Description

POLYMER COMPOSITIONS WITH OLIGOMERIC ALKYLENE OXIDE PENDANTS

Inventors: Bing R. Hsieh

CROSS-REFERENCE TO RELATED APPLICATIONS

This application claims priority to U.S. Patent Provisional Application 61/145507, filed January 16, 2009, which is incorporated by reference herein.

BACKGROUND OF THE INVENTION Field of the Invention

[0001] This invention relates generally to high ionic conductivity polymer materials, and, more specifically, to high ionic conductivity polymer electrolytes with comb structures having a vinyl or an ethylene oxide backbone molecule and an alkylene oxide pendant chain.

[0002] 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. With this in mind, the idea of using a solid electrolyte with a lithium- based battery system has attracted great interest, and a variety of polymer-based electrolytes have been developed. While polyethylene oxide is a sufficiently conductive material as a liquid, its conductivity in solid form is too low to be practical for many applications. Other electrolytes containing polycarbonate or polysiloxane materials have also been developed. Although these materials offer reasonably good ionic conductivity, many are not solid at battery operating temperatures. Work continues to find even better polymer electrolyte materials which are solid at battery operating temperatures and have very good ionic conductivity. It would be useful to develop polymer electrolyte materials that have high room temperature conductivity (> 10^"4 S/cm) and low interfacial impedance.

DETAILED DESCRIPTION

[0003] The embodiments of the present invention relate to polymers with comb structures. These polymers have a vinyl and/or ethylene oxide backbone and a plurality of pendant chains grafted to the backbone. At least one pendant chain is an alkylene oxide-containing compound that is linked to the backbone through a silane, a siloxane or a sulfur group. These polymers can be used as electrolytes when combined with salts (e.g., lithium salts) to enhance their ionic conductivity. Such ionically-conductive polymers 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 highly ionically-conductive polymers with high ionic conductivity are desirable.

[0004] In one embodiment of the invention, polymer materials have a vinyl and/or substituted ethylene oxide backbone with alkylene oxide pendant groups.

[0005] The general structures of the polymer materials containing vinyl polymer backbones are shown below:

The general structures of the polymer materials containing substituted ethylene oxide backbones are shown below:

-(CH₂CHO)- -(CH₂CHO)- -(CH

wherein R is hydrogen or methyl; L is a linking group; X is sulfur, a silane, or a siloxane group; and EO is an oligo-alkylene oxide group. The L linking group can be a silane, a siloxane or a sulfur group. The polymer structures shown above can be used as homopolymers or can be incorporated as blocks in block copolymers.

[0006] The polymer materials are prepared by grafting alkylene oxide pendants onto a vinyl or an ethylene oxide prepolymer having alkene side groups. The general structures of the vinyl prepolymers that contain alkene side groups are shown below:

And the general structures of ethylene oxide prepolymers that contain alkene side groups are shown below:

-(CH

wherein R = H, CH₃

L = -(CH₂)_n- ; -O(CH₂)_n - ; -(CH₂)_n-O(CH₂)_m- ; -Ph-O-(CH₂)_n- ; -Ph-CH₂-O-(CH₂)_n- ; -C-O-(CH₂)_n-

In one arrangement, n and m are whole numbers that range from O to 8. In another arrangement, n is a whole number that ranges from 1 to 4. In one arrangement, the molecular weight of the prepolymers ranges from 20,000 to 500,000 Daltons. In another arrangement, the molecular weight of the prepolymers ranges from 50,000 to 200,000 Daltons.

[0007] Pendant compounds suitable for grafting onto the alkene side groups include, but are not limited to the following:

HS(CH₂J_nO(CH₂CH₂O)_n- CH₃

wherein n is an integer ranging from 2 to 50.

[0008] Another group of suitable pendant compounds contain polar groups such as cyano carbonate and ethylene carbonate. Some examples of these are shown below:

In one arrangement, the molar ratio of the alkylene oxide and the polar pendants ranges from about 98/2 to 70/30. Possible polar groups that can be used include, but are not limited to nitriles, perfluorocarbons, and alkyl carbonates, cyclic carbonates, nitro, amide, N- pyrrolidinone, N-succinimide, sulfolane, sulfoxide, phthalimide, sulfonyl, and sulfonic acids.

[0009] In one embodiment of the invention, the polymers disclosed herein are used as polymer electrolytes such as in electrochemical cells. The polymer electrolyte has a vinyl or ethylene oxide backbone, to which is attached alkylene oxide pendant chain and to which is added an electrolyte salt. In some arrangements, there are also polar group pendant chains attached to the backbone. In one embodiment of the invention, the electrolyte salt is a lithium salt.

[0010] There is no specific limitation to the salt that can be used with the polymers disclosed herein. Examples of useful salts include chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphates, sulfonamides, triflates, thiocynates, perchlorates, borates, or selenides of lithium, sodium, potassium, copper, silver, zinc, barium, lead, magnesium, calcium, ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum, tungsten or vanadium. Other useful salts include LiSCN, LiN(CN)2, LiC104, LiBF4, LiAsFo, LiPF6, LiCF3SO3, Li(CF3SO2)2N, Li(CF3SO2)3C, LiN(SO2C2F5)2, LiN(SO2CF3)2, LiN(SO2CF2CF3)2, lithium alkyl fluorophosphates, lithium oxalatoborate, as well as other lithium bis(chelato)borates having five to seven membered rings, lithium bis(trifluoromethane sulfone imide) (LiTFSI), LiPF3(C2F5)3, LiPF3(CF3)3, LiB(C2O4)2, and mixtures thereof.

[0011] In an exemplary embodiment, poly(4-pentenyl acrylate), obtained by free radical polymerization of the corresponding monomer, undergoes hydrosilylation with an ethylene- oxide-containing disiloxane in the presence of a Pt catalyst to give a polyacrylate with ethylene oxide pendants as shown below.

-

[0012] In an exemplary embodiment, a block copolymer of styrene and 4-pentenyl acrylate, obtained by living free radical polymerization of the two monomers, undergoes hydrosilylation with an ethylene-oxide-containing disiloxane in the presence of a Pt catalyst to give a block copolymer with ethylene oxide pendants.

[0013] In an exemplary embodiment, poly(3-butenyl vinyl ether), obtained by cationic polymerization of the corresponding monomer, undergoes hydrosilylation with an ethylene- oxide-containing disiloxane and a ethylene-carbonate-containing disiloxane in the presence of a Pt catalyst to give a polyvinyl ether with mixed pendants of ethylene oxide and ethylene carbonate.

[0014] In an exemplary embodiment, a block copolymer of styrene and allyl glycidyl ether, obtained by living anionic polymerization of the two monomers, undergoes hydro silylation with an ethylene-oxide-containing disiloxane in the presence of a Pt catalyst to give a block copolymer with both ethylene oxide and ethylene carbonate pendants.

[0015] 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.

Claims

WE CLAIM:

1. A polymer, comprising: a vinyl or ethylene oxide backbone; and a first pendant chain comprising an alkylene oxide group, the first pendant chain linked to the backbone through a silane, a siloxane or a sulfur group.

2. The polymer of Claim 1 wherein the vinyl backbone can be derived from prepolymers selected from the group consisting of:

R R R R

-(CH₂C)- -(CH₂C)- -(CH₂C)- -(CH₂C)- -(CH₂

wherein R is hydrogen or a methyl group and L is (CHi)_n, 0(CHi)_n, (CHi)_n-O(CHi)_1n,

O Ph-O(CHi)_n, Ph-CH₂O(CHi)_n, or -C-0-(CH₂)_n, and n and m are whole numbers that range from 0 to 8.

3. The polymer of Claim 1 wherein the ethylene oxide backbone can be derived from prepolymers selected from the group consisting of:

wherein L is (CH₂)_n, 0(CH₂)_n, (CH₂)_n-O(CH₂)_m, Ph-O(CH₂)_n, Ph-CH₂O(CH₂)_n,

O

Il or -C-0-(CH₂)_n, and n and m are whole numbers that range from 0 to 8.

4. The polymer of Claim 1 wherein the polymer has a structure selected from the group consisting of:

wherein R is hydrogen or methyl; L is a linking group; X is sulfur, a silane, or a siloxane group; EO is an oligo-alkylene oxide group.

5. The polymer of Claim 1 wherein the backbone has a molecular weight that ranges from 20,000 to 500,000 Daltons.

6. The polymer of Claim 1 wherein the backbone has a molecular weight that ranges from 50,000 to 200,000 Daltons.

7. The polymer of Claim 1, further comprising a second pendant chain comprising a polar group, the second pendant chain attached to the backbone.

8. The polymer of Claim 7 wherein the polar group is selected from the group consisting of cyano, sulfoxide, sulfonyl, and ethylene carbonate.

9. The polymer of Claim 7 wherein there are a plurality of alkylene oxide pendant chains and a plurality of polar group pendant chains attached to the backbone and the molar ratio between the alkylene oxide pendant chains and the polar pendant chains ranges from about 98/2 to 70/30.

10. A polymer electrolyte, comprising: a vinyl or ethylene oxide backbone; a first pendant chain comprising an alkylene oxide group, the first pendant chain attached to the backbone; and an electrolyte salt.

11. The polymer of Claim 10, further comprising a second pendant chain comprising a polar group, the second pendant group attached to the backbone.

12. The polymer electrolyte of Claim 10 wherein the electrolyte salt is a lithium salt.

13. The polymer electrolyte of Claim 10 wherein the electrolyte salt is selected from the group consisting of chlorides, bromides, sulfates, nitrates, sulfides, hydrides, nitrides, phosphates, sulfonamides, triflates, thiocynates, perchlorates, borates, or selenides of lithium, sodium, potassium, copper, silver, zinc, barium, lead, magnesium, calcium, ruthenium, tantalum, rhodium, iridium, cobalt, nickel, molybdenum, tungsten or vanadium.

14. The polymer electrolyte of Claim 10 wherein the electrolyte salt is selected from the group consisting of LiSCN, LiN(CN)₂, LiClO₄, LiBF₄, LiAsF₆, LiPF₆, LiCF₃SO₃, Li(CF₃SO₂)₂N, Li(CF₃SO₂)₃C, LiN(SO₂C₂Fs)₂, LiN(SO₂CF₃)₂, LiN(SO₂CF₂CF₃)₂, lithium alkyl fluorophosphates, lithium oxalatoborate, as well as other lithium bis(chelato)borates having five to seven membered rings, lithium bis(trifluoromethane sulfone imide) (LiTFSI), LiPF₃(C₂F₅)₃, LiPF₃(CF₃)₃, LiB(C₂O₄)₂, and mixtures thereof.