Method of making polymeric electrolytic cell separator membrane

• US 5,607,485 A
• Filed: 05/19/1995
• Issued: 03/04/1997
• 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: Schmutz, Caroline N., Gozdz, Antoni S., Tarascon, Jean-Marie, Warren, Paul C.
• Primary Examiner(s): Maples, John S.
• Application Number:
  US08/445,446
• Time in Patent Office: 655 Days
• Field of Search: 429/254, 29/623.1, 29/623.5
• US Class Current: 29/623.5
• 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 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 plasticizer or plasticizer mixture comprising such solvents as ethylene carbonate, propylene carbonate, dimethyl carbonate, and dibutyl phthalate. The film may be used in such form or after extracting of the retained plasticizer 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 plasticizer or replace plasticizer previously extracted from the polymeric matrix.

Claims

1. A method of making an electrolytic cell which comprises arranging, in sequence, a positive electrode element, a separator element, and a negative electrode element characterized in that

a) said separator element is prepared by:

1) mixing at least one copolymer of vinylidene fluoride and hexafluoropropylene with 20 to 70% by weight of a plasticizer compatible with said copolymer; and

2) forming the resulting mixture into a self-supporting film,

c) at least a portion of said plasticizer is extracted from said self-supporting film with an extracting solvent which is substantially a non-solvent for said copolymer,

d) said extracting solvent is removed from said film, and

e) a conductivity-effective amount of an electrolyte salt is homogeneously distributed throughout said film by replacing the extracted plasticizer with a solution of said salt.

2. A method of making a separator element for an electrolytic cell characterized in that

a) at least one copolymer of vinylidene fluoride and hexafluoropropylene is mixed with 20 to 70% by weight of a plasticizer compatible with said copolymer,

b) the resulting mixture is formed into a self-supporting film

c) at least a portion of said plasticizer is extracted from said self-supporting film with an extracting solvent which is substantially a non-solvent for said copolymer,

d) said extracting solvent is removed from said film, and

e) a conductivity-effective amount of an electrolyte salt is homogeneously distributed throughout said film by replacing the extracted plasticizer with a solution of said salt.