Method of manufacturing an organic electrolyte electrochemical cell of unitary structure

Inactive Publication Date: 2001-07-19
SAFT FINANCE S AR L
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

[0007] An object of the present invention is to provide a method of making an electrochemical cell of unitary structure which minimizes variations in dimensions.

Problems solved by technology

Because of the risk of leakage, such cells are ill-suited to consumer portable equipment.
However, over time electrical contact between the various components of the generator degrades, particularly if gas is given off.
Pressing is performed at a temperature of at least 150.degree. C., causing the copolymer to melt completely and thus leading to a non-porous material.
That method suffers from the drawback of giving rise to large changes in dimensions during manufacture of the cell.
During extraction, the structure collapses, thus leading to a dense material.
Thereafter impregnation leads to the VDF-HFP copolymer swelling in the presence of the electrolyte solvent.
Such changes in dimensions give rise to tightening and unsticking phenomena that are harmful to the electrical continuity of the resulting cell.

Method used

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  • Method of manufacturing an organic electrolyte electrochemical cell of unitary structure
  • Method of manufacturing an organic electrolyte electrochemical cell of unitary structure

Examples

Experimental program
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Effect test

example 1

[0058] EXAMPLE 1

[0059] The method of the invention was used to make a button type lithium rechargeable electrochemical cell A as shown in FIG. 1.

[0060] The anode 1 was made of a porous layer 2 deposited on a copper collector 3. The porous layer 2 contained graphite as its electrochemically active material, and a binder which was polyvinylidene fluoride (PVDF).

[0061] The cathode 4 was made up of a porous layer 5 deposited on an aluminum collector 6. The porous layer 5 contained a mixed nickel and lithium oxide as its electrochemically active material and a binder constituted by polyvinylidene fluoride (PVDF).

[0062] A polymer solution was prepared contained 50% by weight of PVDF, 60% by weight of triethylphosphate (TEP) as solvent, and 25% by weight of tetrahydrofuran (THF) which acts as a diluant to adjust the viscosity of the solution. The solution was spread in the form of a film on an inert support, e.g. an aluminum sheet, a plate of glass or of PTFE, etc. . . .

[0063] The THF was ...

example 2

[0068] EXAMPLE 2

[0069] A button type lithium rechargeable electrochemical cell B was made in accordance with the invention having electrodes analogous to those of Example 1 and containing the same electrolyte, however it was made in a different manner.

[0070] After being fabricated, the electrodes were dried under a vacuum at 120.degree. C. and then covered in respective films of solution containing 15% by weight PVDF, 60% by weight triethylphosphate (TEP) as volatile solvent, and 25% by weight tetrahydrofuran (THF).

[0071] After the THP had been evaporated off, the film was immersed in a non-solvent which was water, thereby causing the polymer to precipitate. A porous PVDF membrane was thus obtained which was dried in air.

[0072] The electrodes had their faces covered in the polymer film placed together and they were maintained under pressure at a temperature of 95.degree. C. for 10 seconds. The assembly obtained in that way was placed in a cup closed by a cover to form the button typ...

example 3

[0073] EXAMPLE 3

[0074] A button type lithium rechargeable electrochemical cell C was made in accordance with the invention, having electrodes analogous to those of Example 1 and containing the same electrolyte, but it was made in a different manner.

[0075] After being fabricated, the electrodes were dried under a vacuum at 120.degree. C, and then covered in respective films of a solution containing 25% by weight PVDF and 87.5% TEP.

[0076] After being allowed to drip dry, each electrode was immersed for 20 minutes in water which is a strong non-solvent in order to cause the polymer to precipitate. The electrode was then dried in air, initially at 35.degree. C. and then at 120.degree. C. to remove all traces of water. This produced a very adhesive layer of solid PVDP having a thickness of 50 .mu.m and porosity of 75%.

[0077] The faces of the electrodes carrying the polymer films were put together and the electrodes were held together under pressure at a temperature of 95.degree. C. for 1...

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Abstract

The present invention provides a method of manufacturing an organic electrolyte electrochemical cell comprising at least one electrochemical couple made up of two electrodes sandwiching a solid film of porous polymer containing said electrolyte, each electrode comprising a porous layer containing an electrochemically active material and a binder, the method comprising the following steps: ü a polymer is put into solution in a solvent and said solution is spread in the form of a film on a support; ü said film of solution is immersed in a volatile is non-solvent that is miscible with said solvent in order to precipitate said polymer and said polymer film is dried to eliminate said non-solvent; and ü said couple made up of said polymer film placed between said electrodes and in contact therewith, and impregnated with said electrolyte, is compressed while being heated to a temperature less than or equal to the temperature at which said polymer film starts to melt so as to obtain incomplete melting of said polymer, said electrodes becoming unseparable after cooling.

Description

[0001] The present invention relates to a method of manufacturing an organic electrolyte electrochemical cell of structure that is unitary, i.e. in with the various component elements are connected together so as to form a single whole.[0002] Organic electrolyte cells, in particular lithium cells are presently the subject of rapid and major development because of the high energy density they make available and because of their long lifetime. They are particularly suitable for use in objects of small dimensions.[0003] Traditional cells are made up of solid electrodes sandwiching a porous separator containing liquid electrolyte. Because of the risk of leakage, such cells are ill-suited to consumer portable equipment.[0004] As a result cells have been proposed that include an electrolyte that is made solid by being immobilized in a polymer matrix. However, over time electrical contact between the various components of the generator degrades, particularly if gas is given off. In order t...

Claims

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Application Information

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IPC IPC(8): H01M4/04H01M4/131H01M4/133H01M4/62H01M6/16H01M6/18H01M6/22H01M10/04H01M10/0525H01M10/0565H01M10/0566H01M10/058H01M10/36
CPCH01M4/04H01M4/131H01M4/133H01M4/621H01M6/168H01M6/188H01M10/0525H01M10/0565H01M10/0566H01M10/058Y02E60/122Y10T29/49112Y10T29/49115Y02E60/10Y02P70/50
InventorANDRIEU, XAVIERBOUDIN, FRANCOIS
OwnerSAFT FINANCE S AR L