Lithium ion polymer electrolytes

• US 6,413,676 B1
• Filed: 06/28/1999
• Issued: 07/02/2002
• Est. Priority Date: 06/28/1999
• Status: Expired due to Fees

• Current Assignee: Alfred J. Longhi Jr, Government of the United States of America
• Original Assignee: Lithium Werks Technology BV
• Inventors: Munshi, M. Zafar A.
• Primary Examiner(s): WEINER, LAURA S
• Application Number:
  US09/340,944
• Time in Patent Office: 1,100 Days
• Field of Search: 429/306, 429/309, 429/300, 429/303, 429/314, 429/316, 429/310
• US Class Current: 429/306
• CPC Class Codes: H01M 10/0525 Rocking-chair batteries, i.e. batteries with lithium insertion or intercalation in both electrodes; Lithium-ion batteries
• CPC Class Codes: H01M 10/0565 Polymeric materials, e.g. gel-type or solid-type
• CPC Class Codes: H01M 10/0585 of accumulators having only flat construction elements, i.e. flat positive electrodes, flat negative electrodes and flat separators
• CPC Class Codes: H01M 4/04 Processes of manufacture in general
• CPC Class Codes: H01M 4/131 Electrodes based on mixed oxides or hydroxides, or on mixtures of oxides or hydroxides, e.g. LiCoOx
• CPC Class Codes: H01M 4/133 Electrodes based on carbonaceous material, e.g. graphite-intercalation compounds or CFx
• CPC Class Codes: H01M 4/134 Electrodes based on metals, Si or alloys
• CPC Class Codes: H01M 4/137 Electrodes based on electro-active polymers
• CPC Class Codes: H01M 4/622 being polymers
• CPC Class Codes: H01M 4/661 Metal or alloys, e.g. alloy coatings H01M4/669 take precedence
• CPC Class Codes: H01M 4/667 in the form of layers, e.g. coatings
• CPC Class Codes: H01M 4/668 Composites of electroconductive material and synthetic resins
• CPC Class Codes: H01M 6/10 with wound or folded electrodes
• CPC Class Codes: H01M 6/168 by additives
• CPC Class Codes: H01M 6/188 Processes of manufacture
• CPC Class Codes: H01M 6/40 Printed batteries , e.g. thin film batteries
• CPC Class Codes: Y02E 60/10 Energy storage using batteries
• CPC Class Codes: Y02P 70/50 Manufacturing or production processes characterised by the final manufactured product
• CPC Class Codes: Y02T 10/70 Energy storage systems for electromobility, e.g. batteries
• CPC Class Codes: Y10T 29/49108 Electric battery cell making
• CPC Class Codes: Y10T 29/49115 : including coating or impregnating

Abstract

A dimensionally stable, highly resilient, hybrid copolymer solid-solution electrolyte-retention film for use in a lithium ion battery in one preferred embodiment has a predominantly amorphous structure and mechanical strength despite contact with liquid solvent electrolyte. The film is a thinned (stretched), cast film of a homogeneous blend of two or more polymers, one of which is selected for its pronounced solvent retention properties. A very high surface area inorganic filler dispersed in the blend during formation thereof serves to increase the porosity of the film and thereby enhance electrolyte retention. The film is soaked in a solution of liquid polymer with liquid organic solvent electrolyte and lithium salt, for absorption thereof. Use of a cross-linked liquid polymer enhances trapping of molecules of the electrolyte into pores of the film. The electrolyte film is sandwiched between flexible active anode and cathode layers to form the lithium ion battery. Novel methods are provided for forming the electrodes, the polymer substrate, and other elements of the battery.

Claims

1. A thin film solid polymer electrolyte for a lithium ion battery, comprising:

a solid base polymer material of less than about 25 microns in thickness, comprising a hybrid copolymer of at least two polymers homogeneously blended in non-discrete phase and dissolved in solid solution with a solvent,

one of said two polymers being polyvinylidene fluoride (PVDF), selected from a polar group having pronounced solvent retention properties, and

the other of said two polymers being selected from a second group to provide properties of enhanced strength and improved processing capability of said solid base polymer material, said second group consisting of polyester (PET), polypropylene (PP), polyethylene napthalate (PEN), polycarbonate (PC), polyphenylene sulfide (PPS), and polytetrafluoroethylene (PTFE), or a combination of two or more members thereof; and

a liquid electrolyte solution containing a lithium salt absorbed within pores of said solid base polymer material.

2. The thin film solid polymer electrolyte of claim 1, wherein:

said solid base polymer material further includes a high surface area inorganic filler to create porosity therein and to enhance the mechanical stability of the thin film solid polymer electrolyte.

3. The thin film solid polymer electrolyte of claim 2, wherein:

said inorganic filler consists of one of fumed silica or alumina.

4. The thin film solid polymer electrolyte of claim 3, wherein:

said inorganic filler is in a concentration range from about 0.1% to about 30% by weight dispersed in said solid solution.

5. The thin film solid polymer electrolyte of claim 1, wherein:

said other of the at least two polymers has a concentration in said solid solution which is selected to provide a desired property, including one or more of said enhanced strength, said improved processing capability, and enhanced thermal stability at elevated temperature, of said solid base polymer material.

6. The thin film solid polymer electrolyte of claim 1, wherein:

the ratio of said at least two polymers in said solid solution is selected to provide a desired property, including one or more of said enhanced strength, said improved processing capability, and enhanced thermal stability at elevated temperature, of said solid base polymer material.

7. The thin film solid polymer electrolyte of claim 1, wherein:

said one of the at least two polymers has a concentration in said solid solution of from 1% to 99%, and the remainder being the other of the at least two polymers.

8. The thin film solid polymer electrolyte of claim 1, wherein:

said other of the at least two polymers is PP.

9. The thin film solid polymer electrolyte of claim 1, wherein:

said other of the at least two polymers is PEN.

10. A lithium ion battery, comprising:

the solid polymer electrolyte of claim 1.