Polymeric electrolytic cell separator membrane

• US 5,418,091 A
• Filed: 08/23/1993
• Issued: 05/23/1995
• Est. Priority Date: 03/05/1993
• Status: Expired due to Term

• Current Assignee: Valence Technology Incorporated (Lithium Werks B.V.)
• Original Assignee: Bell Communications Research, Inc. (Telefonaktiebolaget LM Ericsson)
• Inventors: Gozdz, Antoni S., Tarascon, Jean-Marie, Warren, Paul C., Schmutz, Caroline N.
• Primary Examiner(s): Maples, John S.
• Application Number:
  US08/110,262
• Time in Patent Office: 638 Days
• Field of Search: 429/192, 429/194, 429/191, 429/252, 429/254, 429/251, 264/344
• US Class Current: 429/252
• CPC Class Codes: C08J 2327/16 Homopolymers or copolymers of vinylidene fluoride
• CPC Class Codes: C08J 9/28 by elimination of a liquid phase from a macromolecular composition or article, e.g. drying of coagulum
• CPC Class Codes: H01M 10/05 Accumulators with non-aqueous electrolyte H01M10/39 takes precedence
• CPC Class Codes: H01M 10/052 Li-accumulators
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 2300/0085 Immobilising or gelification of electrolyte
• CPC Class Codes: H01M 50/426 Fluorocarbon polymers
• CPC Class Codes: H01M 6/181 with polymeric electrolytes
• CPC Class Codes: H01M 6/32 activated through external addition of electrolyte or of electrolyte components
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y10T 29/49115 including coating or impregnating

Abstract

A flexible polymeric film useful as an interelectrode separator or electrolyte member in electrolytic devices, such as rechargeable batteries, comprises a copolymer of vinylidene fluoride with 8 to 25% hexafluoropropylene. The film may be cast or formed as a self-supporting layer retaining about 20% to 70% of a high-boiling solvent or solvent mixture comprising such solvents as ethylene carbonate, propylene carbonate, dimethyl carbonate, and dibutyl phthalate. The film may be used in such form or after leaching of the retained solvent with a film-inert low-boiling solvent to provide a separator member into which a solution of electrolytic salt is subsequently imbibed to displace retained solvent or replace solvent previously leached from the polymeric matrix.

Claims

1. A separator membrane useful for preparing an electrolytic cell

characterized in that said membrane is substantially devoid of pores and electrolytic salt and comprises a composition initially comprising a polymeric material and 20 to 70% by weight of a compatible plasticizer therefor and from which composition at least a portion of said plasticizer has been removed, said membrane thereby being in a preconditioned state conducive to absorption of electrolytic solution.

2. A separator membrane according to claim 1

characterized in that said polymeric material comprises a copolymer of vinylidene fluoride with 8 to 25% by weight hexafluoropropylene.

3. A separator membrane according to claim 1

characterized in that said plasticizer is selected from the group consisting of ethylene carbonate, propylene carbonate, dimethyl carbonate, diethoxyethane, dibutyl phthalate, diethyl carbonate, dimethoxyethane, dipropyl carbonate, and mixtures thereof.

4. A separator membrane according to claim 1

characterized in that said copolymer contains 12 to 20% by weight hexafluoropropylene.

5. A separator membrane according to claim 4

characterized in that said copolymer contains 12 to 15% by weight hexafluoropropylene.

6. A separator membrane according to claim 1

characterized in that said plasticizer has been removed from said composition by extraction with a low-boiling extracting solvent which is substantially a non-solvent for said polymeric material.

7. A separator membrane according to claim 1

characterized in that said composition comprises up to about 20% by weight of an inorganic filler selected from the group consisting of alumina and silica.

8. A rechargeable battery cell assembly comprising a positive electrode, a negative electrode, and a separator membrane disposed therebetween

characterized in that said membrane is substantially devoid of pores and electrolytic salt and comprises a composition initially comprising a polymeric material and 20 to 70% by weight of a compatible plasticizer therefor and from which composition at least a portion of said plasticizer has been removed, said membrane thereby being in a preconditioned state conducive to absorption of electrolytic solution.

9. A rechargeable battery cell assembly according to claim 8

characterized in that said polymeric material comprises a copolymer of vinylidene fluoride with 8 to 25% by weight hexafluoropropylene.

10. A rechargeable battery cell assembly according to claim 8

characterized in that said plasticizer has been removed from said composition by extraction with a low-boiling extracting solvent which is substantially a non-solvent for said polymeric material.

11. A rechargeable battery cell assembly according to claim 8

characterized in that said composition comprises up to about 20% by weight of an inorganic filler selected from the group consisting of alumina and silica.