JPH10302839A - Nonaqueous electrolyte secondary battery, its separator, and their manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To uniformly diffuse lithium ions in the whole electrode to the utmost and increase capacity. SOLUTION: A lithium foil laminated film 50 obtained by holding a metal lithium foil 52 in a base film 51 is piled up on a separator 30, and they are passed between a pair of transfer rollers 53 to press them. After that, by peeling off the base film 51, the separator 30 on which the very thin metal lithium foil 52 is transferred is produced. The separator 30 is interposed between a positive plate 10 and a negative plate 20 so that the metal lithium foil 52 faces the negative plate 20, and they are wound to form an electrode body.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery, a separator thereof, and a method for producing the same.

[0002]

2. Description of the Related Art For example, a non-aqueous electrolyte secondary battery which performs charging and discharging by a reversible reaction of absorbing lithium ions released from one between a positive electrode and a negative electrode into the other has the following structure. It is known. For example, an electrode mixture containing a lithium-containing oxide of a transition metal is applied to a metal aluminum foil to produce an electrode plate for a positive electrode, and an electrode mixture containing a layered carbon material is applied to a copper foil to form a negative electrode. To manufacture electrode plates. Then, by winding these positive and negative electrode plates with a separator interposed therebetween, an electrode body having a spiral multilayer structure is manufactured, and this is accommodated in a battery can together with a non-aqueous electrolyte.

In this type of secondary battery, apart from lithium ions contributing to a reversible reaction, there are lithium ions irreversibly incorporated into each electrode, and it is necessary to supply lithium ions in advance before initial charging to increase the capacity. Desirable for.

As a technique for supplying lithium ions to an electrode body in advance, there is a technique described in, for example, JP-A-7-94211. In this method, a metal lithium foil is pressure-bonded to a copper foil on the outermost peripheral portion of the negative electrode plate on which the electrode mixture has not been applied.

However, in the above-mentioned manufacturing method, metallic lithium is present only in a part of the outermost periphery of the electrode body, so that lithium ions can be uniformly supplied to the entire electrode body. In addition, there is a limit to the increase in capacity due to non-uniform ion concentration. In the above manufacturing method, it is conceivable that a large amount of metallic lithium is present by increasing the thickness of the metallic lithium foil so that lithium ions can be distributed to the whole. However, in this case, the lithium ion concentration on the outer peripheral side of the electrode body becomes excessive. In addition, metallic lithium is precipitated during the battery reaction, which causes problems such as a decrease in capacity.

Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery capable of diffusing lithium as uniformly as possible throughout the entire electrode body and enabling a large capacity, a separator thereof, and a method of manufacturing these. There.

[0006]

The non-aqueous electrolyte secondary battery according to the first aspect of the present invention is obtained by laminating electrode plates for a positive electrode and a negative electrode with a separator interposed therebetween. The feature is that the lithium source material is stacked.

According to a second aspect of the present invention, there is provided a method for manufacturing a non-aqueous electrolyte secondary battery, comprising stacking electrode plates for a positive electrode and a negative electrode via a separator. Where the lithium foil is transferred to the separator surface by peeling off the base film after pressing the lithium foil laminate film formed by laminating the lithium foil on the base film, and laminating the electrode plate with the separator interposed therebetween. It has features.

According to a third aspect of the present invention, there is provided a method of manufacturing a separator for a non-aqueous electrolyte secondary battery, comprising laminating electrode plates for a positive electrode and a negative electrode with a separator interposed therebetween. It is characterized in that the lithium foil is transferred to the surface by peeling off the base film after the lithium foil laminate film formed by laminating the lithium foil on the film is pressed.

According to a fourth aspect of the present invention, there is provided a method of manufacturing a separator for a non-aqueous electrolyte secondary battery, wherein the lithium foil laminated film is formed by rolling a lithium foil between two base films with a lithium foil interposed therebetween. It is characterized in that it is manufactured by rolling lithium foil thinly by applying pressure between rollers.

[0010]

According to the first aspect of the present invention, since the lithium source material is superimposed on the separator, lithium is uniformly diffused into the electrode mixture applied to the electrode plate, and an appropriate amount of lithium is dispersed. Can be supplied, and the capacity of the secondary battery can be increased.

By the way, when the lithium foil is overlaid on a wide area of the separator, it may be necessary to make the lithium foil considerably thin in order not to supply lithium excessively. Then, since the tensile strength of the lithium foil is greatly reduced, the lithium foil is broken by a slight tension, and it becomes very difficult to laminate the lithium foil. In this regard, in the manufacturing method of claim 2 and claim 3, since the lithium foil is transferred to the separator using the lithium foil laminated film in which the lithium foil is laminated on the base film, the lithium foil is laminated when the lithium foil is laminated. An acting tension or the like can be received by the base film. As a result, it is possible to manufacture a separator and a non-aqueous electrolyte secondary battery to which a necessary minimum amount of lithium is supplied by making the lithium foil thinner as necessary. The thickness of the lithium foil is preferably in the range of 0.1 μm to 50 μm. If the thickness is less than 0.1 μm, the replenishment of irreversible lithium ions tends to be insufficient. This is because it is easy to decrease.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is an exploded view of a completed nonaqueous electrolyte secondary battery. As is well known, a spirally laminated electrode body 40 is formed by winding a positive electrode plate 10 and a negative electrode plate 20 via a separator 30 made of, for example, a polyethylene nonwoven fabric. It is housed in a battery can 41. The battery can 41 has a cylindrical container-shaped negative electrode case 42 with an opening opening formed in the positive electrode cap 43.
Although not shown, for example, ethylene carbonate (EC), diethyl carbonate (DEC) and dimethyl carbonate (DMC) are contained in the inside 2:
A non-aqueous electrolyte obtained by adding 1 mol / l lithium hexafluorophosphate to a mixed solution mixed at a ratio of 1: 2 is filled. The positive electrode lead 11 extends from the positive electrode plate 10 and is electrically connected to the positive electrode cap 43, and the negative electrode lead 21 extends from the negative electrode plate 20 and is connected to the negative electrode case 42.

As shown in FIG. 2, the positive electrode plate 10 has a current collector 12 made of aluminum foil having a thickness of, for example, 20 μm.
The positive electrode mixture 13 is held on both surfaces. For example, polyvinylidene fluoride as a binder and acetylene black as a conductive material are added to lithium cobalt oxide (LiCoO2), which is a lithium-containing oxide of a transition metal, and kneaded so as to form a paste. Then, it is applied to both surfaces of the current collector 12, dried and rolled, and cut into a predetermined width to form a tape. In addition, the positive electrode lead 11 is located at the winding start end of the positive electrode plate 10 and is connected to the current collector 12 on which the positive electrode mixture 13 is not applied.

On the other hand, as shown in FIG. 3, the negative electrode plate 20 is formed by holding a negative electrode mixture 23 on both surfaces of a current collector 22 made of copper foil having a thickness of, for example, 12 μm. In this method, a paste obtained by kneading graphite powder together with a binder is applied to both surfaces of the current collector 22, dried and rolled, and cut into a predetermined width to form a tape. The negative electrode lead 21 is located at the end of the negative electrode plate 20 and is connected to a current collector 22 to which the negative electrode mixture 23 is not applied.

The separator 30 is made of, for example, a nonwoven fabric made of polyethylene. When the electrode 30 is manufactured, the lithium foil 52 is laminated on one surface thereof.
This separator 30 is manufactured using a lithium foil laminated film 50. That is, as shown in FIG. 4, the lithium foil laminated film 50 is obtained by laminating a metal lithium foil 52 having a thickness of, for example, about 0.1 μm to 50 μm on a base film 51. As the base film 51, a material having releasability and tensile strength enough to easily peel off the metal lithium foil 52 is preferable. In this embodiment, a film of trimethylpentene 1 (for example, a release film CE manufactured by Sumitomo Bakelite Co., Ltd.)
LE-E911A).

Further, in order to manufacture the lithium foil laminated film 50, a metal lithium foil having a thickness capable of being handled is sandwiched between two base films 51,
This is passed between rolling rolls to roll the metal lithium foil to a desired thickness, and then one of the base films 51 is peeled off. Since metallic lithium is a soft metal, it can be easily rolled.

Then, as shown in FIG. 5, the lithium foil laminated film 50 is placed on the separator 30 described above, and this is passed between a pair of transfer rolls 53 and pressed.
At the exit side of the roll 53, the base film 51 is peeled off and wound. Then, since the surface of the separator 30 is porous, the metallic lithium foil 52 is pressed into the surface so as to bite into the surface, and the metallic lithium foil 52
It is transferred to the side. Thus, the separator 30 having the extremely thin metal lithium foil 52 laminated on the surface is manufactured.

Thereafter, the separator 30 described above is sandwiched between the positive electrode plate 10 and the negative electrode plate 20 with the lithium foil 52 side facing the negative electrode plate 20 and wound into a roll to produce an electrode body 40. The battery is completed by enclosing it in the can 41 together with the electrolytic solution.

According to this manufacturing method, since the metal lithium foil 52 is laminated almost all over the separator 30,
At the time of initial charging, lithium ions are mixed with the electrode mixture 2 of the negative electrode plate 20.
3, and a sufficient amount of irreversible lithium ions can be occluded in the graphite. Of course, since the metal lithium foil 52 is sufficiently thin so as not to be excessive, repeated charging and discharging may cause excessive lithium to precipitate and inactivate, thereby reducing the capacity or causing a gap between the positive and negative electrodes. Short-circuiting can be reliably prevented. Even if the metal lithium foil 52 is considerably thinned in this way, since it is held by the base film 51, the tension or the like acting when the metal lithium foil 52 is laminated on the separator 30 is reduced. It can be received on the base film 51. This means that the metal lithium foil 52 can be thinned and the necessary minimum amount of lithium for precharge can be laminated.

<Other Embodiments> The present invention is not limited to the embodiments described above and illustrated in the drawings. For example, the following embodiments are also included in the technical scope of the present invention. In addition to the following, various changes can be made without departing from the scope of the invention.

(1) In the above embodiment, the case where a metal lithium foil is used as the lithium foil has been described, but this may be a lithium alloy foil or another lithium compound. May be any lithium source material that can supply lithium. Of course, the lithium source material is not limited to being continuously laminated, and the lithium foil may be intermittently laminated on the separator surface as needed.

(2) In the above embodiment, the separator 30 is provided between the positive electrode plate 10 and the negative electrode plate 20 by the lithium foil 52.
Although the electrode body 40 was manufactured by sandwiching the negative electrode plate 20 so that the side faces the negative electrode plate 20 and winding it in a roll shape, the present invention is not limited to this.
The lithium foil 52 may be sandwiched between the positive electrode plate 10 and the positive electrode plate 10, and may be alternately contacted with the positive electrode plate 10 and the negative electrode plate 20.

(3) In the above embodiment, the electrode body has a three-piece structure in which the positive electrode plate 10 and the negative electrode plate 20 are wound with the separator 30 interposed therebetween. 1 formed with the electrode mixture layer of the negative electrode, respectively.
The present invention may be applied to an electrode body having a structure in which two electrode plates are wound together with a separator, and further to an electrode body having a structure in which one electrode plate in which a separator layer is integrated in advance is wound. Is also good.

(4) In the above embodiment, the present invention is applied to a secondary battery of a type in which lithium ions are released and inserted between a positive electrode and a negative electrode. However, the present invention is not limited to this, and the reversible reaction of ionization and deposition of metallic lithium is applied. The present invention can be applied to a secondary battery using the same. In this case, the lithium foil may be directly in contact with the current collector without forming the electrode mixture layer on the current collector. In addition, it goes without saying that the present invention can be widely applied to not only cylindrical batteries but also square or button-type nonaqueous electrolyte secondary batteries.

(5) In the above embodiment, a film of trimethylpentene 1 (TRX) was used as the base film. However, the present invention is not limited to this. For example, polypropylene, polyethylene, polyethylene terephthalate, polyimide, polyvinyl chloride, or a wax-based release film Pattern paper and the like can be widely used.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a nonaqueous electrolyte secondary battery showing one embodiment of the present invention.

FIG. 2 is an enlarged sectional view of a positive electrode plate.

FIG. 3 is an enlarged sectional view of a negative electrode plate.

FIG. 4 is an enlarged sectional view of a lithium foil laminated film.

FIG. 5 is a cross-sectional view showing a transfer process of a lithium foil.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Positive electrode plate 20 ... Negative electrode plate 30 ... Separator 40 ... Electrode body 50 ... Lithium foil laminated film 51 ... Base film 52 ... Metal lithium foil (lithium source material)

Claims (4)

[Claims] 1. A non-aqueous electrolyte secondary battery obtained by laminating electrode plates for a positive electrode and a negative electrode via a separator,
A non-aqueous electrolyte secondary battery, wherein a lithium source material is stacked on the separator. 2. A method for producing a non-aqueous electrolyte secondary battery comprising a positive electrode and a negative electrode laminated on each other with a separator interposed therebetween, comprising a lithium foil laminated film comprising a base film and a lithium foil laminated on the base film. Non-aqueous electrolyte secondary battery characterized in that the lithium foil is transferred to the surface of the separator by peeling off the base film after being pressed on the separator, and the electrode plate is laminated with the separator interposed therebetween. Manufacturing method. 3. A method for producing a separator for a non-aqueous electrolyte secondary battery, comprising laminating each of a positive electrode electrode plate and a negative electrode plate via a separator, wherein the lithium foil laminate comprises a lithium foil laminated on a base film. A method for producing a separator for a non-aqueous electrolyte secondary battery, comprising transferring a lithium foil to a surface by peeling the base film after laminating and pressing a film. 4. The lithium foil laminated film,
4. The non-aqueous solution according to claim 3, wherein said lithium foil is thinly rolled by sandwiching a lithium foil between two base films and passing them between rolling rollers to apply pressure. A method for producing a separator for an electrolyte secondary battery.