JPH1197055A - Non-cylindrical battery and manufacture of it - Google Patents

Abstract

PROBLEM TO BE SOLVED: To pressurize a wound electrode group over the whole circumference by arranging a deformable member having electrolyte resistance in the center part of winding of a wound electrode group, deforming it from one direction facing the wound electrode group side surface by pressurizing force, and pressing the wound electrode group in a direction perpendicular to the pressurizing direction. SOLUTION: A porous film made of polyethylene is interposed as a separator 13 between positive and negative electrodes, winding provided with a winding axis is used, and a wound electrode group 4 having the elliptical cross section is constituted. Since a cylindrical body is compressed and deformed together with the wound electrode group 4 into a flat shape when the wound electrode group 4 is inserted into a battery case 6, the wound electrode group 4 is pressed in the deformation direction 10. When the side surface of the prism battery case 6 is pressurized in such a direction that the wound electrode group 4 is formed into a further flat shape, the cylindrical body applies pressurizing force in the outer direction perpendicular to the pressurizing direction 9. Accordingly, insufficient pressurization of a part in which electrodes are laminated parallel to the pressurizing direction of the wound electrode group 4 is eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-cylindrical battery in which a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is accommodated in a non-cylindrical battery case, and a method of manufacturing the same. More specifically, the present invention relates to improvement of high-rate discharge performance of such a non-cylindrical battery.

[0002]

2. Description of the Related Art Conventionally, in order to accommodate a wound electrode group in a prismatic battery case, a substantially cylindrical wound electrode group is pressed to form a non-cylindrical shape having a cross section of an ellipse or an ellipse. And a method of accommodating a wound electrode group wound from the beginning into a non-cylindrical shape. In the former method, excessive pressure is applied when the wound electrode group is formed into a non-cylindrical shape, which causes a problem that the electrode active material falls off or the electrode itself breaks because it cannot withstand the pressure. According to the latter method, the former problem can be avoided. In order to realize the latter method, for example, as shown in JP-A-6-168736, there is a technique in which an electrode and a separator are wound using a plate-shaped shaft core, and the shaft core is removed after winding. .
In the wound electrode group obtained by the latter method, a space corresponding to the extracted axial center is formed at the center of the wound electrode. When this space is present, the pressure applied to the wound electrode group at the time of winding decreases, and as a result, a problem arises in that the force for pressing the electrodes after the battery is formed decreases. When the force to press the electrode weakens,
The adhesion between the electrode active material and the current collector is not good, and the high-rate discharge characteristics are deteriorated, or the active material is easily peeled from the current collector,
It falls off and the charge / discharge cycle performance is inferior. As a means for pressurizing the electrodes, an example of a prismatic battery using an electrode group in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween is disclosed in JP-A-5-13054.
No. 6,086,045. In this technique, the wall surface of the battery case facing the electrode stacking surface is curved inward to press the electrode group in the stacking direction, thereby improving the adhesion between the electrode active material and the current collector.

[0003]

However, in the technique disclosed in Japanese Patent Application Laid-Open No. Hei 5-13054, the electrode group is merely pressed in the direction in which the electrodes are stacked. Therefore, even if this technique is applied to the wound electrode group housed in the prismatic battery case, the wound electrode group is only pressed between the curved opposite wall surfaces, and is orthogonal to the pressing direction. Since no pressure is applied in the direction, the portion is under-pressed. An object of the present invention is to provide a non-cylindrical battery in which a non-cylindrical battery case accommodates a non-cylindrical wound electrode group having an elliptical or elliptical cross section. An object of the present invention is to provide a non-cylindrical battery that can be pressurized from the periphery.

[0004]

In order to solve the above-mentioned problems, a non-cylindrical battery according to the present invention comprises a positive electrode 11 and a negative electrode 1.
In a battery in which a wound electrode group 4 formed by winding the second electrode 2 via a separator 13 is accommodated in a non-cylindrical battery case 6, an electrolysis-resistant deformable member 1 is arranged at the center of the wound electrode group 4. In this state, the deformable member 1 is deformed by a pressing force received from one side of the side surface of the wound electrode group 4 and presses the wound electrode group 4 in a direction orthogonal to the pressing direction. It is characterized by the following. The deformable member 1 is arranged at the center of the wound over substantially the entire region from the upper end to the lower end of the wound electrode group 4. The deformable member 1 is disposed at the center of the wound electrode group (FIG. 3), and the wound electrode group is housed in the battery case by making the outer dimension of the wound electrode group larger than the inner dimension of the battery case. At times, the wound electrode group is pressurized and compressed from the side so that it can be housed in the battery case. The deformable member 1 is also flatly compressed and deformed together with the compression deformation of the wound electrode group, so that the deformable member 1 acts to press the wound electrode group from the inside (FIG. 5). As a specific example of the deformable member 1, a tubular body having an elliptical cross section as shown in FIG. 1 or a fluid (liquid, gas, sol, powder, or the like) (not shown) which can be stretched to have an electrolytic solution resistance. And those sealed in bags made of various materials. In addition, it is preferable that the deformable member is an elastic body from the viewpoint of repeating deformation and restoration. The material of the deformable member is preferably plastic or metal.

[0005] Further, a non-cylindrical battery according to the present invention, which is different from the above, for solving the above problems, comprises a positive electrode 11 and a negative electrode 1
2 is a battery in which a wound electrode group 4 formed by winding a separator 2 through a separator 13 is accommodated in a non-cylindrical battery case 6, and at least two flat members are substantially wound around the center of the wound electrode group 4. It is arranged on the same plane and a wedge member is arranged between the flat plate members. The flat plate member penetrates between the flat plate members by a pressing force that the wound electrode group 4 receives from a direction perpendicular to the flat surface of the flat plate member. The gap between the flat plate members is widened by the wedge member and the wound electrode group 4 is pressed. FIG.
The flat plate members 2a and 2b and the wedge member 3
An example is shown below. 2 with at least one side rounded
The two flat plate members 2a and 2b and the wedge member 3 are in a state where the rounded side surfaces of the two flat plate members are in contact with the side surfaces of the wedge member. The flat plate member and the wedge member are arranged at the center of the winding of the wound electrode group 4 in the above positional relationship (FIG. 4), and the outer dimension of the wound electrode group 4 is larger than the inner dimension of the battery case 6. ,
When the wound electrode group 4 is accommodated in the battery case 6, the wound electrode group 4 is pressurized and compressed from the side surface so that the wound electrode group 4 can be accommodated in the battery case 6. The compression of the wound electrode group 4 is performed from a direction perpendicular to the plane of the flat plate members 2a and 2b.
Penetrates between the plate members 2a, 2b, and the plate members 2a, 2b
It acts so as to press the wound electrode group 4 from the inside while increasing the interval (FIG. 6). The number, shape, and the like of the flat plate members 2a and 2b and the wedge member 3 can be changed within a range having the above-described operation.

The former (deformable member 1 in FIG. 1) is a non-cylindrical battery having a battery case 6 having a square cross section or a similar shape, but having a rectangular cross section as shown in FIG. 5 or a similar shape. But either is applicable. Even in the case where the cross section of the battery case 6 is a square or a shape similar thereto, it is possible to realize the above-described operation by changing the shape of the wound electrode group 4 before and after the battery case is accommodated. is there. The latter (the flat plate members 2a and 2b and the wedge member 3 in FIG. 2) is suitable for a battery having a prismatic shape in which the cross section of the battery case 6 is rectangular or a shape similar thereto. The similar shape is the same as that in FIG.
, Those with rounded side corners, oval or elliptical shapes.

When the prismatic battery is used in a state where it is pressurized from the outside of a pair of opposing wall surfaces, the wound electrode group 4 is pressurized and flattened. By making the flattening direction coincide with the flattening direction when the wound electrode group 4 is pressed into the battery case 6, the deformable member 1 is further flattened. Further, the interval between the flat plate members 2 a and 2 b is further increased by the intrusion of the wedge member 3. Thereby, the deformable member 1 applies a pressing force in the direction of flattening to the wound electrode plate group 4 from the inside thereof. Further, the flat plate members 2a and 2b apply a pressing force in a direction in which the member interval is widened to the wound electrode group 4 from the inside. Thereby, the adhesion between the current collector and the active material of the electrode plate is improved over the entire wound electrode group.

The deformable member 1 or the flat members 2a, 2
b and the wedge member 3 also serve as the axis or part of the axis during the step of winding the electrode, and after the winding step, the entire axis or part of the axis is cut off and left at the center of the wound to deform. There is no need to dispose the possible member 1 or the flat members 2a and 2b and the wedge member 3 in a later step, and the manufacturing process can be simplified. Further, the deformable member 1 or the flat plate members 2a and 2b and the wedge member 3
There is an advantage that the adhesiveness of the electrode group is improved.

The present invention is considered to be particularly effective for a prismatic battery in which the current collector is a conductive plate, foil, or film, and the active material uses a wound electrode group disposed on the current collector surface. . The reason is that the current collector with the three-dimensional structure is designed to have a higher active material holding capacity and a larger contact area between the active material and the current collector than the two-dimensional current collector (conductive plate, foil or film). This is because it is considered that there are few factors depending on the pressure of the electrode. A typical example of a battery having an electrode using a two-dimensional current collector is a lithium-ion secondary battery that is currently spreading. Among the positive electrodes of the lithium ion secondary battery, the active material composition is Li _x Mn _2-y A _y O ₄ (0.1
≦ x ≦ 1.1, 0 ≦ y ≦ 0.3, and A is at least one selected from transition metals). LiC
be inferior to oO ₂ are known. Therefore, the present invention is considered to be particularly effective in a prismatic lithium ion secondary battery using a wound electrode group having a manganese-based positive electrode.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The case where the non-cylindrical battery according to the present invention is a prismatic lithium ion secondary battery will be described below. The present invention is applicable to an electrode group wound in a non-cylindrical shape, and is not limited to the type of battery.

(Preparation Method of Positive Electrode) The positive electrode was prepared as follows. A 20 μm-thick aluminum foil is used as a conductive core material, and a positive electrode mixture slurry in which 88 parts by weight of lithium cobalt oxide (LiCoO ₂ ) powder and 4 parts by weight of polyvinylidene fluoride are dispersed in an N-methylpyrrolidone solvent is applied to both sides of the core material. I do. Then, it is dried and pressed by a roll press to a predetermined thickness to complete the positive electrode.

(Production Method of Negative Electrode) 90 parts by weight of spherical mesocarbon microbeads (particle diameter: 1 to 50 μm, d ₀₀₂ = 3.366 angstroms) on both surfaces of a copper core having a thickness of 20 μm as a conductive core. Then, a negative electrode mixture in which 10 parts by weight of polyvinylidene fluoride is dispersed in an N-methylpyrrolidone solvent is applied. After that, it is dried and pressed by a roll press to a predetermined thickness to complete the negative electrode.

(Preparation of Battery 1) A microporous polyethylene membrane was used as a separator, and was interposed between the positive and negative electrodes.
A wound electrode group 4 having an oval cross section is formed using a winding device having a wound axis (FIG. 3). At this time, the outer dimension on the minor diameter side of the wound electrode group 4 is slightly larger than the inner dimension of the battery case 6. The tubular body shown in FIG. 1 is arranged at the center of the wound electrode group. The cylindrical body has a nickel-plated thickness of 0.1 mm.
A 1 mm steel plate formed into a cylindrical shape was used. This cylindrical body slightly behaves like an elastic body against an external force. As for the method of arranging the cylindrical body at the center of the winding, the winding operation is performed by fitting the cylindrical body to the winding axis, and after the completion of the winding operation, as shown in FIG. An operation of extracting only the winding axis so that the body remains is performed. FIG. 5 shows a cross-sectional view in a state where the wound electrode group 4 shown in FIG. 3 is inserted into the prismatic battery case 6. It can be seen that the tubular body is deformed flat from the state of FIG. That is, when the wound electrode group 4 is inserted into the battery case 6, the cylindrical body is also compressed and deformed and flattened together with the wound electrode group 4, so that the wound electrode group 4 is also deformed in the deformation direction 10 in FIG. Pressed. Further, a pressing force due to the deformation of the cylindrical body also acts between the battery case wall surfaces 7 and 8 and the wound electrode group 4.

A battery cover made of stainless steel provided with an output terminal portion and an electrolyte inlet is sealed to the battery case 6 by laser welding. Thereafter, an electrolytic solution in which 1 mol / l of lithium hexafluorophosphate was dissolved in a mixed solvent (1: 1 volume ratio) of ethylene carbonate and dimethyl carbonate was injected, and then the injection port was sealed to form a prismatic battery. To complete. In this example, a stainless steel material is used for the battery case 6, but any other material may be used as long as it has a strength enough to withstand the pressure of the non-cylindrical electrode group in a normal use state.

In FIG. 5, it is assumed that the side surface of the prismatic battery case 6 is pressed in a direction to further flatten the wound electrode group 4 (in FIG. 5, the pressing direction 9 is an actual pressing direction 9). This is the direction that is most likely to be pressurized when using batteries.) Then, the cylindrical body applies a pressing force in an outer direction (deformation direction 10) orthogonal to the pressing direction 9. Therefore, the insufficient pressurization of the portion where the electrodes are stacked in parallel with the pressurizing direction of the wound electrode group 4 as described above is resolved.

(Fabrication of Battery 2) In another embodiment according to the present invention, the center of the wound electrode group 4 is disposed on the flat plate members 2a and 2b and the wedge member 3 shown in FIG. The flat plate members 2a and 2b made of polypropylene having a curved side surface are arranged so that the curved surfaces are adjacent to each other, and the columnar wedge member 3 made of polypropylene is arranged on an adjacent line. Flat plate members 2a, 2b
The wedge member 3 and the wedge member 3 are attached to the shaft center of the winding device in the above arrangement state, and the above-described positive electrode 11, negative electrode 12 and separator 13 are mounted.
Is wound. At this time, the outer dimension on the minor diameter side of the wound electrode group 4 is slightly larger than the inner dimension of the battery case 6. In this example, the flat plate members 2a and 2b and the wedge member 3 are all made of polypropylene, but other materials may be used as long as they have rigidity to withstand the winding pressure during winding. FIG. 4 shows a cross-sectional view of the wound non-columnar wound electrode group 4. The wound electrode group 4 is wound in a non-cylindrical shape around the flat plate members 2 a and 2 b and the wedge member 3. The process after being housed in the battery case 6 was the same as the manufacturing condition of the battery 1. FIG. 6 shows the wound electrode group 4 housed in the battery case 6. When the wound electrode group 4 of FIG. 4 is pressed into the battery case 6 made of stainless steel, the wound electrode group 4 is pressed from the pressing direction 9 by the wall surfaces 7 and 8 of the battery case 6. When this pressure is applied, the wedge member 3 enters between the flat plate members 2a and 2b and spreads the flat plate members 2a and 2b. As a result, the wound electrode group 4 is also pressed (pressed) in the deformation direction 10 from the inside thereof, and the adhesiveness of the active material / current collector of the electrode group is significantly improved.

In this embodiment, both the battery 1 and the battery 2 have a battery case 6.
Although the prismatic shape was used as the shape of the prism, for example, the same applies when using a non-cylindrical battery case such as a prismatic shape having rounded side corners, an oval or elliptical cross section. The effect can be obtained.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS As a comparison, a deformable member 1, a flat plate member 2
a, 2b and the batteries 1 and 2 except that the wedge member 3 is not provided.
Under the same conditions as above, a prismatic battery (conventional example) was produced. The following comparative study was conducted on the three types of batteries, Battery 1, Battery 2, and Conventional Example. FIG. 7 shows that each prismatic battery was fully charged 3 times.
It shows the discharge capacity when discharging at CmA. Here, the relative values are shown assuming that the discharge capacity of the conventional battery is 100%. Since the prismatic batteries (battery 1 and battery 2) of the present invention have a configuration in which the wound electrode group 4 can be pressed from almost the entire circumference as compared with the conventional example, it can be seen that the discharge capacity has been significantly improved.

FIG. 8 shows 1 CmA charge / discharge cycle characteristics of the prismatic batteries (battery 1 and battery 2) of the present invention. It can be seen that the prismatic batteries (battery 1 and battery 2) of the present invention have a configuration in which almost the entire wound electrode group 4 can be pressurized as compared with the conventional example, and thus have improved life characteristics.

[0020]

According to the present invention, in a non-cylindrical battery in which the non-cylindrical wound electrode group 4 is built in the battery case 6,
It was possible to provide a non-cylindrical battery capable of pressing the wound electrode group 4 almost all around. Thereby, high rate discharge characteristics and charge / discharge cycle life characteristics were improved.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an example of a deformable member used in a battery according to the present invention.

FIG. 2 shows a flat plate member 2a, 2a used in the battery according to the present invention.
FIG. 4 is a perspective view showing an example of a wedge member 3 with the reference numeral b.

FIG. 3 is a diagram showing a cross section of a wound electrode group according to the embodiment of the present invention.

FIG. 4 is a diagram showing a wound electrode group according to another embodiment of the present invention.

FIG. 5 is a diagram showing a cross section of the prismatic battery according to the embodiment of the present invention.

FIG. 6 is a diagram showing a cross section of a prismatic battery according to another embodiment of the present invention.

FIG. 7 is a diagram comparing discharge capacities when batteries are discharged at a high rate with relative values.

FIG. 8 is a diagram showing cycle characteristics of a battery.

[Explanation of symbols]

 1. Deformable members 2a, 2b. Flat plate member 3. Wedge member 4. 5. Wound electrode group Battery case 7,8. Battery case wall 9. Pressing direction 10. Deformation direction 11. Positive electrode 12. Negative electrode 13. Separator

Claims (9)

[Claims] 1. A battery in which a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is housed in a non-cylindrical battery case. The deformable member is deformed by a pressing force received from one direction facing the side surface of the wound electrode group, and is in a state of pressing the wound electrode group in a direction orthogonal to the pressing direction. Non-cylindrical battery characterized by the above-mentioned. 2. The non-cylindrical battery according to claim 1, wherein the deformable member is an elastic body. 3. The non-cylindrical battery according to claim 1, wherein the deformable member is a cylindrical body. 4. A battery in which a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is housed in a non-cylindrical battery case. And a wedge member is disposed between the flat plate members, and the flat plate member is disposed between the flat plate members by a pressing force that the wound electrode group receives from a direction perpendicular to the plane of the flat plate member. A non-cylindrical battery in which the distance between the flat plate members is widened by the penetrating wedge member and the wound electrode group is pressed. 5. The non-electrode according to claim 1, wherein the current collector of the positive electrode and / or the negative electrode is a conductive plate, foil or film, and the active material is disposed on the surface of the current collector. Cylindrical battery. 6. A method for producing a battery in which a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is accommodated in a non-cylindrical battery case. A step of arranging the deformable member and a step of pressing the wound electrode group from the opposite side surface in one direction and press-fitting the wound electrode group into the battery case. A method for manufacturing a non-cylindrical battery, wherein a member presses a wound electrode group in a direction orthogonal to the pressing force. 7. The method for producing a non-cylindrical battery according to claim 6, wherein the deformable member also serves as a shaft core or a part thereof in a winding step. 8. A method for manufacturing a battery in which a wound electrode group in which a positive electrode and a negative electrode are wound with a separator interposed therebetween is housed in a non-cylindrical battery case, wherein at least two flat plates are wound around the wound center of the wound electrode group. A step of arranging the members substantially on the same plane and arranging a wedge member between the plate members, and a step of press-fitting the wound electrode group into the battery case by pressing the wound electrode group from a direction perpendicular to the plane of the plate members. A method of manufacturing a non-cylindrical battery, wherein the pressing force causes a wedge member to enter between the flat plate members to widen the flat plate member interval, and presses the wound electrode group in a direction in which the flat plate member interval increases. 9. The method for manufacturing a non-cylindrical battery according to claim 8, wherein the flat plate member and the wedge member also serve as a shaft core or a part thereof in a winding step.