Process of manufacturing porous separator for electrochemical power supply

• US 5,948,464 A
• Filed: 06/19/1996
• Issued: 09/07/1999
• Est. Priority Date: 06/19/1996
• Status: Expired due to Fees

• Current Assignee: IMRA America Incorporated (Aisin Corp.)
• Original Assignee: IMRA America Incorporated (Aisin Corp.)
• Inventors: Delnick, Frank M.
• Primary Examiner(s): Phasge, Arun S.
• Assistant Examiner(s): Parsons, Thomas H.
• Application Number:
  US08/767,468
• Time in Patent Office: 1,175 Days
• Field of Search: 429/189, 429/190, 429/194, 429/248, 429/249, 429/252, 429/191, 429/192, 429/193, 427/77, 427/243, 427/247
• US Class Current: 427/77
• CPC Class Codes: C25B 9/23 comprising ion-exchange membranes in or on which electrode material is embedded
• CPC Class Codes: H01G 9/02 Diaphragms; Separators
• CPC Class Codes: H01M 10/0436 Small-sized flat cells or batteries for portable equipment
• CPC Class Codes: H01M 50/403 Manufacturing processes of separators, membranes or diaphragms
• CPC Class Codes: H01M 50/426 Fluorocarbon polymers
• CPC Class Codes: H01M 50/434 Ceramics
• CPC Class Codes: H01M 50/46 Separators, membranes or diaphragms characterised by their combination with electrodes
• CPC Class Codes: H01M 50/489 Separators, membranes, diaphragms or spacing elements inside the cells, characterised by their physical properties, e.g. swelling degree, hydrophilicity or shut down properties
• CPC Class Codes: H01M 6/16 with organic electrolyte H01M6/18 takes precedence
• 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

Abstract

A method of forming a porous composite separator layer for an electrochemical cell comprising the steps of printing a thin layer of a separator precursor solution on the surface of one of the electrochemical cell electrodes, drying and curing the thin layer of separator precursor solution so that it transforms into a microporous composite separator structure. In the preferred embodiment, the separator precursor solution is formulated as an ink comprising a silica aerogel filler material dispersed in a solution of polymer binder which is dissolved in a suitable solvent. The process allows the manufacture of thin and flexible composite separators which are conformally bonded to the underlying electrodes.

Claims

1. A process for fabricating a porous composite separator for an electrochemical cell which includes an electrode, comprising the steps of:

disposing a solution of separator precursor on said electrode; and

transforming said solution of separator precursor so that said solution of separator precursor forms a porous composite separator that adheres to said electrode.

2. The process of claim 1, wherein the step of disposing a solution of separator precursor on said electrode comprises disposing a solution comprised of a solid particulate material, a polymer binder for said solid particulate material and a solvent to dissolve said polymer binder.

3. The process of claim 2, wherein said solution of separator precursor comprises a ratio of said polymer binder to said solid particulate material of between 5/95 and 35/65.

4. The process of claim 2, wherein said solution of separator precursor contains 60% to 75% by mass of said solvent.

5. The process of claim 2, wherein said solid particulate material comprises a material selected from the group consisting of silica aerogel, fumed silica, silica gel, silica hydrogel, silica xerogel, silica sol, colloidal silica, alumina, titania, magnesia, kaolin, talc, diatomaceous earth, calcium silicate, calcium carbonate, magnesium carbonate, and mixtures thereof.

6. The process of claim 2, wherein said polymer binder comprises a material selected from the group consisting of polyvinyl chloride, polyvinylidene fluoride-hexafluoropropylene copolymer and ethylene propylene hexadiene monomer.

7. The process of claim 2, wherein said solvent comprises 2(2-Butoxy Ethoxy) Ethyl Acetate.

8. The process of claim 1, wherein said step of disposing a solution of separator precursor on said electrode comprises using a printing technique to dispose said solution of precursor on said electrode.

9. The process of claim 1, wherein said step of transforming said solution of separator precursor on said electrode comprises:

first drying said solution of separator precursor to form a layer of separator material; and

subsequently curing said layer of separator material to form a porous separator layer.

10. The process of claim 9, wherein said step of drying comprises applying heat to said solution of separator precursor in a vacuum oven at a temperature of about 90-130°

C. so that said solution of separator precursor forms said layer of separator material.

11. The process of claim 9, wherein said step of curing comprises applying heat to said separator precursor in an convection oven at a temperature of about 190°

C. to 240°

C. so that said layer of separator material transforms into said layer of porous composite separator.

12. The process of claim 11, wherein said porous composite separator layer has a thickness in the range of 5 μ

to 100 μ

.

13. A process of forming a microporous separator for an electrochemical cell which includes an electrode, comprising:

printing a continuous layer of said separator on said electrode; and

drying said layer to form micropores therein.

14. The process of claim 13, wherein said step of drying comprises applying heat to said continuous layer of separator on said electrode in a vacuum oven at a temperature of about 90-130°

C.

15. The process of claim 13, further comprising curing said continuous layer of said separator by applying heat to said separator precursor in a convection oven at a temperature of about 190°

C. to 240°

C.

16. The process of claim 13, wherein said step of printing said continuous layer of said separator on said electrode comprises using either a stencil or a screen printing technique.

17. The process of claim 13, wherein said step of printing said continuous layer of said separator on said electrode comprises disposing a solution comprised of a solid particulate material, a polymer binder for said solid particulate material and a solvent to dissolve said polymer binder on said electrode.

18. A process of forming a microporous separator for an electrochemical cell which includes an electrode, comprising:

conformally bonding a continuous layer of said separator on said electrode; and

drying said layer to form micropores therein.

19. The process of claim 18, wherein the step of conformally bonding said continuous layer of said separator on said electrode comprises disposing a solution comprised of a solid particulate material, a polymer binder for said solid particulate material and a solvent to dissolve said polymer binder.

20. The process of claim 19, wherein said step of disposing said solution on said electrode comprises using a printing technique to dispose said solution on said electrode.