JP3513195B2 - Electrochemical cell and method of manufacturing the same - Google Patents

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION This invention relates to electrochemical cells for lithium / solid polymer electrolyte batteries. More particularly, the present invention provides that the free end of the collector layer facing the electrolyte layer and / or the negative electrode layer, which has a side current collector and is based on the lithium cathode and the solid polymer electrolyte, is cut through the electrolyte layer. It relates to an electrochemical cell that includes a band of insulating material arranged to prevent electrical discharge and / or to prevent shorting the two electrode layers. The invention also relates to a method of manufacturing an electrochemical cell in which the free end of the collector layer is protected by a band of insulating material.

[0002]

BACKGROUND OF THE INVENTION The general principles of ACEP (Polymer Electrolyte Battery) type polymer electrolyte batteries and lithium anodes are described in US Pat.
No. 4,303,748. The preferred substances (copolymers, cross-linked polymers, salts, active substances for electrodes) used in these batteries as well as the process for their preparation are
It is disclosed in U.S. Pat. Nos. 4,578,326 and 4,758,487.

[0003]

The ACEP battery comprises a metal collector layer for the positive electrode (cathode), a film for the cathode, a film for the polymer electrolyte, a film for the negative electrode (lithium anode) and an insulating film. Each of these films typically has a thickness of 5 to 50 μm for a final total thickness of 100 to 150 μm.
It has a thickness of m 3 and requires a film about 30 m long, typically 15 cm wide to obtain a 100 Wh battery. Various types of possible assemblies for these various batteries are described in US Patent Application Publication No. 336,625 (June 6, 1988),
No. 337,522 (16 June 1988) and 342,538 (8 June 1988). A suitable type of assembly allows each of these films to be slightly offset so that the current generated by each of the electrodes is collected from the sides, as in a capacitor, rather than from the edges of the film. In a battery of this type, one end of the collector layer is used to collect the current generated from the anode. The other end, referred to below as the free end of the collector layer, is mounted opposite the electrolyte layer and / or the negative electrode layer and offset. Such an assembly gives rise to the following problems: The metal collector layer of the positive electrode (cathode) generally consists of a sheet of aluminum, nickel or other metal,
This collector layer, even with a small thickness, has a free cutting edge, which is directly contacted with the negative electrode layer or is cut through the assembly of the electrolyte layer and is composed of a relatively flexible polymer and therefore a lithium anode. There is a risk that the battery will be damaged due to a short circuit with.

[0004]

The invention proposes to arrange, for example, a band of insulating film which overlaps the free end of a metal collector layer between the collector layer of the positive electrode and the negative electrode layer. This band is stiffer than the electrolyte layer and more resistant to breaks near the free end of the collector layer. This insulating band also ensures insulation between the collector layer and the negative electrode layer when the electrolyte layer is shorter than the collector layer or when the collector layer is made of a material such as metallized polyester that electrochemically reacts with lithium. can do.

The base material for this insulating band is a film of insulating plasticizer which does not chemically or electrochemically react with the active materials of the battery (lithium, electrolyte, positive electrode) and does not deform at operating temperature or It is a tissue structure.
For example polypropylene, polyethylene, polyurethane,
Or any other known film of compatible plastic material can be used, and on the other hand a film which is not compatible with lithium [polyester, Teflon ™, FE
P (fluorinated polymer of ethylene and propylene), polyamide] can be used by making it compatible with a thin surface coating of polyethylene or polypropylene. Films or tissue structures of inorganic materials (glass fiber, boron nitride) can also be used. Capacitor grade polypropylene is particularly suitable because of its inert nature and the absence of impurities.

Also, in some cases, a thin coat layer of heat sealable adhesive on the sides of the metal collector layer is used to coat the insulative band to prevent the band from being displaced during manufacture. You can Also, the adhesive must be compatible with the active material of the battery and, for example, must be free of volatile products that can react with the battery and reduce battery performance. The adhesive must be heat-sealable so that it does not separate under acceptable temperatures for the battery material. Adhesives based on thermoplastic polyethylene or polyester are suitable. An example of a suitable heat-sealable insulating film is Transkote # 150 OPP, available from Transilwrap of Toronto, Canada, which provides plasticity to labels or originals. Used to give. This film of polypropylene, coated with a thermoplastic polyester adhesive and used in polymeric lithium batteries, showed a satisfactory charge / discharge cycle and no detrimental effect on the battery compared to batteries without insulating bands.

Generally, the thickness and width of the insulating band are appropriately selected to minimize the weight and volume of the insulating band in the battery, to facilitate setting during the manufacturing of the insulating band and to prevent excessive thickness. Try not to occur. 5-50 μm,
Bands, typically 25 μm thick and 3-12 mm wide, typically 6 mm wide, are generally satisfactory and have essential properties that the edges are well protected and will not move if the band is properly positioned. give.

As can be seen from the examples of either the collector layer alone, the cathode coated collector layer, or the cathode layer and the electrolyte layer coated collector layer, the placement of the bands was determined through various steps in the fabrication of the cell. It can be carried out.

In general, the invention comprises the superposition of a positive electrode layer, a solid polymer electrolyte layer, and a lithium negative electrode layer,
The positive electrode layer is in contact with the metal collector layer and the negative electrode layer is coated with an insulating film, the negative electrode layer and the metal collector layer are offset with respect to each other to allow side current collection, and then the collector is Electrochemical cell having a free end to be protected. The electrochemical cell includes a band of insulating material that does not react with the electrode and electrolyte materials and does not deform at operating temperatures. The band of the insulating material is arranged between the constituent layers of the cell, and when the collector layer and various layers containing the insulating material are laminated to form the cell, the band cuts the free end of the collector layer through the electrolyte layer. And / or shorting the two electrode layers. Also, if the electrolyte layer is shorter than the collector layer, or if the collector layer is made of a material such as a metallized polyester that electrochemically reacts with lithium, this insulating band provides insulation between the collector layer and the negative electrode layer. be able to.

In a preferred embodiment of the present invention, a band of insulating material is mounted between the electrolyte layer and the collector layer so that the free ends of the collector layers are superposed and the positive electrode layer and the band of insulating material are close to the collector layer. And place it.

In another preferred embodiment of the invention, the band of insulating material is heat sealable, whereby the portion of the band of insulating material that is in contact with the collector layer is heat sealed to the collector layer. can do.

In another preferred embodiment of the invention, the material of the electrolyte layer is slightly adhesive and the band of insulating material is not heat-sealable, so that the adhesion with the electrolyte layer is only ensured by the electrolyte layer. Nothing more. Preferably, a band of insulating material is placed on the electrolyte layer between the electrolyte layer and the negative electrode layer and the free ends of the collector layers are superposed and protected.

In another embodiment of the present invention, a non-heat-sealable band of insulative material is located under the electrolyte layer between the electrolyte layer and the collector layer, and the band of insulative material is free of the collector layer. The positive electrode layer and the band of the insulating material are placed close to each other so as to overlap with the end.

The band of insulating material has a thickness of about 5 .mu.m to 50 .mu.m, preferably about 25 .mu.m for heat sealable bands and about 8 .mu.m for non-heat sealable bands.

In another embodiment of the invention, a band of heat-sealable insulating material is heat-sealed on the collector layer using a heat-sealable or thermoplastic adhesive that is compatible with the elements of the cell. Stop. For example, the adhesive may be between about 1-10 μm, about 1-
It may have a thickness of 2 μm.

In another embodiment of the invention, the band of insulative material comprises polypropylene or polyethylene, or Teflon ™, FEP, polyester, or polyamide, with about 1 to 1 of polyethylene or polypropylene.
Coated with a thin layer of 2 μm.

In another example, the band of insulating material is between about 3 and.
It has a width of between 125 mm, for example about 6 mm.

In the present invention, the positive electrode layer, the solid polymer electrolyte layer, and the lithium negative electrode layer are laminated, the positive electrode layer is brought into contact with the metal collector layer, and the negative electrode layer is covered with an insulating film. It relates to a method of manufacturing an electrochemical cell in which the layers are offset with respect to each other to allow lateral current collection and further protect the free ends of the collector layers. According to this method, a band of an insulating material that does not react with the materials of the electrode, the collector and the electrolyte and does not deform at the operating temperature is arranged, thereby forming a cell by laminating various layers including a collector layer and an insulating film. If so, the band prevents the free end of the collector layer from being cut through the electrolyte layer and / or shorting the two electrode layers. As mentioned above, if the electrolyte layer is shorter than the collector layer, or if the collector layer is made of a material such as a metallized polyester that reacts electrochemically with lithium, this insulating band will be present between the collector layer and the negative electrode layer. It is also possible to secure insulation.

In another embodiment of the present invention, a band of insulating material is placed between the electrolyte layer and the collector layer, and the free ends of the collector layers are superposed, thereby separating the positive electrode layer and the band of insulating material. Bring them close together.

In another example, an electrolyte layer of slightly adhesive material and a band of non-heat-sealable insulating material are used and the band is applied over the layer of adhesive electrolyte.

In another embodiment of the invention, a band of insulating material is placed on the electrolyte layer, between the electrolyte layer and the negative electrode layer, and the free ends of the collector layers are superposed and protected.

In another example, an electrolyte layer of slightly adhesive material and a band of non-heat-sealable insulating material are used, the band being between the adhesive electrolyte layer and the positive electrode layer. Is provided under the layer of, and the free ends of the collector layers are overlapped and arranged near the positive electrode layer.

[0023]

Embodiments of the present invention will be described with reference to the drawings.
Referring to the drawings, and more particularly to FIG. 1, an electrochemical cell is shown to consist of a vanadium oxide based positive electrode layer 2 including a metal collector layer 1 of, for example, aluminum. Also shown is a lithium negative electrode layer 5 coated with a polypropylene insulating film 6. Electrolyte layer 3 disposed between two electrode layers 2 and 5 is U.S. Pat. No. 4,303,748, 4,578,526.
And a solid polymer as defined in 4,758,487. It can be seen that these various layers are offset to allow side current collection of the current (terminals + and-in the figure). With respect to the positive electrode layer 2 between the collector layer 1 and the electrolyte layer 3, a band 4 of insulating material, for example of polypropylene or other plastic material as described above, was arranged to overlap the free end of the collector. Also, if the electrolyte layer 3 is shorter than the collector layer 1 (not shown), or if the collector layer 1 is made of a material such as a metallized polyester that electrochemically reacts with lithium, the insulating band 4 is formed as the collector layer 1. Insulation can be ensured with the negative electrode layer 5.

Alternatively, as shown in FIG. 2, an insulating band 4 was placed in a similar position between the electrolyte layer 3 and the lithium negative electrode layer 5 but overlapping the free end of the collector layer. Next, as is apparent from FIG. 3, the side insulating band 4 is connected to the thin film 5 of lithium and the insulating film 6.
And collector layer 1, positive electrode layer 2 and solid polymer electrolyte layer 3
Stacked with half cells consisting of.

The present invention is shown by the following examples, but the invention is not limited thereto.

Example 1 An aluminum sheet having a width of 16 cm and a thickness of 15 μm was used as a coating support for the metal collector and the positive electrode. First, place this roll of aluminum sheet on the coating equipment.
It was transferred to a rolling mill composed of an iron roll heated to 85 ° C. and a silicone rubber roll. A thin band of 25 μm thick, 6 mm wide transcoat transilwrap is always laminated to one end of the aluminum sheet, so that 3 mm is located on the aluminum sheet and 3 mm is located outside the aluminum. The thermoplastic adhesive was melted as it passed through the mill and permanently bonded to the aluminum sheet at the exit of the mill. The aluminum sheet with protective bands along the edges of the sheet was then transferred in the mold direction of the machine. A solution of the vanadium oxide-based positive electrode is deposited on an aluminum sheet and the solvent is evaporated in a tunnel dryer to a thickness of 40 μm,
A thin film of a positive electrode having a width of 15 cm was obtained. Then an assembly consisting of an aluminum collector layer, a thin film of the positive electrode and a band for edge protection was placed in the center of this assembly with a thickness of 30
An electrolyte film having a thickness of 16 μm and a width of 16 cm was laminated with a lithium film having a thickness of 20 μm and a width of 16 cm which was deviated by about 2 mm with respect to aluminum, and a band for protecting an end portion of the aluminum was projected to the outside. A 16 cm 8 μm thick polypropylene film can be added last to be wound as a battery without shorting the electrode layers. The assembly thus formed constitutes an ACEP type cell with a current collector of 3.4V capable of laterally locating.

Example 2 First, a thin film of a positive electrode was formed on the aluminum collector and dried in a tunnel dryer, and a band of a transyl wrap was heat-sealed and laminated on one end of the aluminum layer. The desired battery was manufactured by repeating the method of Example 1.

Example 3 First, a thin film of the positive electrode was formed on the aluminum collector, and then an electrolyte film was laminated on the thin film of the positive electrode.
A film of "half-cell" (collector + positive electrode + electrolyte) is obtained,
Further three kinds of films: a half-cell, a 6 mm wide and 8 μm thick heat-sealable polypropylene band, and a lithium electrode film were laminated together to protect the edges of the aluminum layer. . After adding the insulating film to the lithium electrode layer, the desired battery was obtained. In this case, the slightly sticky electrolyte acts as an adhesive for the propylene band and prevents band migration.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an example electrochemical cell of the present invention including a band of insulating material.

FIG. 2 is a cross-sectional view of another example of the electrochemical cell of the present invention.

FIG. 3 shows the layers of the cell of the invention including an insulating band.

FIG. 4 is a diagram showing the behavior of the electrochemical cell of the present invention through charge / discharge cycles.

[Explanation of symbols]

1 Collector layer (aluminum metal collector layer) 2 Positive electrode layer (positive electrode layer based on vanadium oxide) 3 Electrolyte layer (solid polymer electrolyte layer) 4 Insulating material band (insulating band) 5 Negative electrode layer (lithium negative electrode layer) 6 Polypropylene insulating film

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-3-116661 (JP, A) JP-A-1-241767 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 6/18 H01M 10/38 H01M 10/40

Claims (2)

(57) [Claims] 1. A laminate comprising a positive electrode layer, a solid polymer electrolyte layer, and a lithium negative electrode layer, wherein the positive electrode layer is in contact with the metal collector layer and the negative electrode layer is covered with an insulating film, so that side current collection is achieved. An electrochemical cell in which the negative electrode layer and the collector layer are offset relative to each other to allow the collector layer to have a free end to be protected, which does not react with the electrode and electrolyte materials and An electrochemical cell in which a free end of the collector layer is protected by incorporating into the electrochemical cell a band of insulating material that does not deform at operating temperatures. 2. A method of manufacturing an electrochemical cell, comprising stacking a positive electrode layer, a solid polymer electrolyte layer and a lithium negative electrode layer, arranging the positive electrode layer in contact with a metal collector layer, the negative electrode layer being an insulating material. Of the negative electrode layer and the collector layer with respect to each other so as to form a side current collector, and does not react with the materials of the electrode layer, the collector layer and the electrolyte layer and the operating temperature of the cell. A method of manufacturing an electrochemical cell, wherein a free end of the collector layer is protected by arranging a band of an insulating material which is not deformed by the step between layers constituting the cell.