JPH10270069A - Rectangular battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rectangular battery with a high capacity and its manufacture. SOLUTION: A battery has a generating element formed with two windings, for which a multiplex sheet A with at least two long sheets laminated is wound in the same direction or in mutually opposite directions with both longitudinal ends as winding start ends in such a manner that winding internal stress arising in winding is left. In this way the angular battery is easily formed. Still, an initial facing space between a positive electrode collector and a negative electrode collector is kept for a long time because the winding internal stress is left in the generating element, so that the battery can show stable capability and a long life.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic battery and a method of manufacturing the same, and more particularly to a prismatic battery having a nonaqueous liquid electrolyte, for example, a prismatic battery suitable for a prismatic lithium secondary battery and a prismatic battery thereof. It relates to a manufacturing method.

[0002]

2. Description of the Related Art Various electric devices, especially portable personal computers and telephones, are required to be further reduced in weight and size, and from this requirement, batteries used for them can be accommodated in a compact small storage space. The development of prismatic batteries is needed. A power generating element composed of positive and negative bipolar sheets used in a prismatic battery is usually of a rectangular or flat type.

FIG. 9 is a perspective view of a power generating element E used in a conventional prismatic lithium secondary battery. In FIG. 9, 1 is a positive electrode sheet piece, and 2 is a negative electrode sheet piece. The power generating element body E, not shown, is a positive / negative bipolar sheet 1, 2
A separator is interposed between the pieces, and the positive and negative bipolar sheets 1,
2 and three pieces of the separator as one set, and a multiplicity of sets are laminated with further separators interposed between each set, and one positive electrode sheet and two negative electrode sheets Are electrically connected to each other. In a secondary battery such as a lithium secondary battery, the battery capacity is proportional to the amount of the positive electrode active material of the positive electrode sheet. Therefore, when the thickness of the positive electrode active material layer of the positive electrode sheet is increased, the amount of the positive electrode active material per unit area of the positive electrode sheet is increased. Capacity can be secured. However, in practice, a normal positive electrode active material layer has poor electric conductivity, so that if it is thick, the electric resistance becomes excessively large, and the battery action is conversely reduced. For this reason, a method has been adopted in which the number of stacked sets is increased to ensure the required battery capacity by making the positive electrode active material layer thinner and increasing the electrode area. However, when the number of stacked sets is increased, the number of electrical connections by the connection wires 4 which requires a lot of work is increased, and mass production of batteries becomes difficult.

FIG. 10 is a perspective view of another power generating element E used for a conventional prismatic lithium secondary battery, and the power generating element E includes a positive electrode sheet, a negative electrode sheet, and a separator. As shown in the sectional view of FIG. 11, the long aggregate sheet A is wound on a flat core body FC, and then the core body FC is removed. In this power generation element body E, a necessary electrode area and a battery capacity can be secured by increasing the number of windings by using the long aggregate sheet A, so that the problem of the laminate shown in FIG. There is no. However, the power generating element E composed of the flat wound body has the following problems.

[0005] In general, when the distance between the positive electrode sheet and the negative electrode sheet in the power generating element body increases, the electrical resistance between the positive electrode current collector and the negative electrode current collector increases, and a normal battery function is obtained. I can't play it. For this purpose, for example, a cylindrical power generating element body used for a cylindrical battery is obtained by winding a set sheet similar to the long set sheet A under a relatively large tension on a columnar core. Thus, the internal stress based on the winding tension at the time of winding remains in each sheet in the set sheet after winding. Even after the core is removed, each sheet in the collective sheet always shrinks and tries to close due to the residual internal stress, and as a result, the facing distance between the positive electrode current collector and the negative electrode current collector is maintained so as not to be large. Is done. By the way, as described with reference to FIG. 11, when the long collective sheet A is wound on the flat core member FC, the ends of the core member FC of both ends FC1 and FC2 of the obtained flat wound member are obtained. Although the above-mentioned internal stress is likely to remain in the respective sheet portions E1 and E2 located at both ends where the turn is made, even after the removal of the core body, the internal stress applied to the intermediate portion E3 hardly remains. A large capacity battery cannot be obtained because the facing distance between the positive electrode current collector and the negative electrode current collector in the portion tends to be wide.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a prismatic battery having a high capacity and a method for manufacturing the same.

[0007]

The present invention has the following features. (1) A power generation element body comprising a two-turn body wound with both ends in the longitudinal direction of a collective sheet formed by laminating at least long sheets of a positive electrode and a negative electrode constituting the power generation element body as winding ends. Characteristic square battery. (2) The above two windings are wound in the same direction as each other
(1) The prismatic battery according to the above. (3) The above-mentioned (1), wherein the two winding bodies are wound in opposite directions.
The prismatic battery as described. (4) The prismatic battery according to any one of the above (1) to (3), wherein each of the two winding bodies has a cylindrical shape or an elliptical cylindrical shape. (5) At least a long sheet of the positive electrode and the negative electrode constituting the power generating element body is wound on a core body while applying a tension while winding both ends in the longitudinal direction as winding ends. In obtaining a wound body, at the winding start end of each sheet at both ends in the longitudinal direction of the aggregated sheet so that the difference in length between each sheet in the non-wound aggregated sheet portion between the two wound bodies is reduced. A method for manufacturing a prismatic battery, comprising winding the battery with a difference.

[0008]

The power generating element body used in the present invention is formed of a two-winding body which is wound with both ends in the longitudinal direction of a long collective sheet constituting the power generating element body as winding start ends. Therefore, since all parts other than the extremely short non-wound collective sheet portion connecting between the two-wound bodies are in the wound state, internal stress based on the winding tension at the time of winding remains and this residual internal The stress keeps the interval between the positive electrode current collector and the negative electrode current collector from becoming large. Further, since the power generating element body is formed of a two-turn body of a long collective sheet, its cross section is nearly flat, so that a prismatic battery can be manufactured.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, the present invention will be described in more detail with reference to the drawings.

FIG. 1 is a perspective view of a power generating element used in an embodiment of the present invention, and FIG. 2 is a top view for schematically explaining a method of manufacturing the power generating element shown in FIG. FIG.
FIG. 4 is a perspective view of another power generating element used in the embodiment of the present invention, and FIG. 4 is a top view for schematically explaining a method of manufacturing the power generating element shown in FIG. 3. 5 to 8 are top views of the embodiment of the present invention.

As shown in FIG. 2, a power generating element body E shown in FIG. 1 is composed of a long aggregate sheet A in which four sheets of a separator, a positive electrode sheet, a negative electrode sheet, and a separator are sequentially laminated. It is obtained by winding the cores S and S 'in the same winding direction while applying tension to the cores S and S' with the ends A1 and A1 'as the winding ends, respectively, and then pulling out the cores S and S'. Then, the power generation element body E
Is composed of two wound bodies A2 and A2 'having the same winding direction, and both wound bodies A2 and A2' are connected by a non-wound portion C located substantially at the center of the aggregated sheet A in the longitudinal direction. Having.

As shown in FIG. 4, a power generating element body E shown in FIG. 3 has a core sheet S having a long sheet A similar to that described above, with its both ends A1 and A1 'in the longitudinal direction as winding ends. And S 'are wound in opposite winding directions as shown by arrows while applying tension, and then each core S, S' is pulled out. Thus, the power generating element body E is composed of two winding bodies A2 and A2 'whose winding directions are opposite to each other, and the two winding bodies A2 and A2' are non-winding members located substantially at the center of the aggregate sheet A in the longitudinal direction. It has a structure connected by a part C.

5 to 8, K denotes a battery can,
E is a power generation element body. In the embodiment of FIG. 5, the power generating element body E shown in FIG. 1 is used, while in the embodiment of FIG. 6, the power generating element body E shown in FIG. 3 is used. Have been. In the embodiment of FIG.
The power generating element E has two winding bodies A2 and A2 'having the same winding direction and an elliptical cross section, whereas in the embodiment shown in FIG. Each of the two winding bodies A2 and A2 ', which are opposite to each other and have an elliptical cross section, is used. The winding bodies A2 and A2' are housed in a flat battery can K having a side wall having an arc-shaped cross section on the upper surface. ing. 7 and 8 in which a power generating element E composed of two winding bodies A2 and A2 'having an elliptical cross section is housed in a flat battery can K having a side wall having an arc-shaped cross section on the upper surface. The example is effective in obtaining a flatter prismatic battery.

The power generating element body E having the winding bodies A2 and A2 'having an elliptical cross section used in the embodiments of FIGS.
In the manufacturing process of the power generating element body E having the winding bodies A2 and A2 'having a circular cross section shown in FIGS. 1 and 3, the cores S and S' are obtained by removing the cores S and S 'and compressing the cores S from both sides. Alternatively, it can also be obtained by winding an ellipse using a core having an elliptical cross section instead of the cores S and S ′.

The use of the power generating element body E having the winding bodies A2 and A2 'having an elliptical cross section is effective in obtaining a flatter rectangular battery, but in the case of an excessively flat elliptical shape, FIG. The same problem as the conventional example described above, that is, the problem that the residual winding internal stress in the portion corresponding to E3 in FIG. 11 tends to decrease or disappear, occurs, so that the elliptical cross-sectional shapes of the winding bodies A2 and A2 'are generated. The ratio of the major axis to the minor axis is 3
It is preferable that the shape be an elliptical shape within a range of 2 times or less, particularly 2.5 times or less, or a pseudo-elliptical shape corresponding thereto.

1 to 4, the aggregate sheet A includes at least a positive electrode sheet and a negative electrode sheet. In addition, in the case of using a solid electrolyte sheet or a liquid electrolyte, at least one separator, usually two sheets, is used. Including. Therefore, a collective sheet A formed by laminating a number of these constituent sheets is wound around the cores S, S 'from both ends as shown in FIGS. And the point C in FIGS.
The length between the winding ends of the two-winding body at the center in the longitudinal direction or the vicinity thereof, that is, the length of the non-rolled portion C between the constituent sheets of the collective sheet A is slightly larger or smaller. In particular, when winding is performed in opposite directions as shown in FIG. 4, there is a large difference between the constituent sheet located outside the set sheet A and the constituent sheet located inside the set sheet A, and the inside constituent sheet becomes slack. In the present invention, the slack of a part of the sheet at the non-winding portion C has no adverse effect on the power generation function of the power generation element E. However, in the case where it is necessary to prevent the occurrence of the slack of the partial component sheet due to easy handling of the power generating element body E as an intermediate in the battery manufacturing process or other reasons, the aggregate sheet to be used is A is wound in the desired winding direction and the slack length of the constituent sheet generated in the non-wound portion C is known in advance, and the length of each sheet from the winding start end of the collective sheet A to the non-wound portion C It is preferable to provide a difference corresponding to each slack length. For example, the length of the component sheet having a large amount of slack is shortened in advance. Thus, it is possible to prevent or reduce the occurrence of the slack of the constituent sheet in the non-wound portion C.

The positive electrode sheet and its positive electrode active material and the positive electrode current collector, which can be constituent elements of the aggregate sheet A, the negative electrode sheet and its negative electrode active material and the negative electrode current collector, the separator, and the electrolyte are the nonaqueous electrolyte lithium secondary battery. Conventionally known batteries in the field of secondary batteries can be used. Hereinafter, some examples of typical or preferable members will be described.

The positive electrode active material is LiCoO ₂ , LiNiO
Composite oxides of Li such as ₂ and a transition metal element belonging to Group 9 to 10 of the periodic table, LiMnO ₂ , Li _X Mn _(2-Y) M _Y
O ₄ (M is B, P, Al, etc.) Li-Mn based composite oxide such as, and the like V ₂ O _5. The negative electrode active material includes various Li-based alloys and carbon materials such as natural or artificial graphite. The binder for the positive electrode active material or the negative electrode active material is polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, ethylene-propylene-diene-based polymer, or the like. The positive electrode sheet and the positive electrode sheet can be formed by applying a mixed composition comprising an active material and a binder to one or both surfaces of a current collector, sufficiently drying, and rolling. Examples of the separator include porous sheets made of other thermoplastic polymers such as polyolefins such as polyethylene, polypropylene, and polybutene having excellent electrical insulation properties, nylon, polyester, polyvinyl chloride, and polyvinylidene fluoride.

[0019]

As described above, the prismatic battery of the present invention is composed of two wound bodies and employs a power generating element having a substantially flat cross section, so that the prismatic battery can be easily formed. In addition, since the initial facing distance between the positive electrode current collector and the negative electrode current collector is maintained for a long time due to residual internal stress in the power generating element, the battery function is stable and the life is long. Therefore, the prismatic battery of the present invention is extremely useful as a power source for various electric devices, particularly portable personal computers and telephones.

[Brief description of the drawings]

FIG. 1 is a perspective view of a power generating element used in an embodiment of the present invention.

FIG. 2 is a top view for schematically explaining a method of manufacturing the power generating element body shown in FIG.

FIG. 3 is a perspective view of another power generating element used in the embodiment of the present invention.

FIG. 4 is a top view for schematically explaining a method of manufacturing the power generating element body shown in FIG.

FIG. 5 is a top view of the embodiment of the present invention.

FIG. 6 is a top view of another embodiment of the present invention.

FIG. 7 is a top view of another embodiment of the present invention.

FIG. 8 is a top view of another embodiment of the present invention.

FIG. 9 is a perspective view of a power generating element used in a conventional prismatic lithium secondary battery.

FIG. 10 is a perspective view of another power generating element used in a conventional prismatic lithium secondary battery.

11 is an explanatory diagram of a method for manufacturing the power generating element body shown in FIG.

[Explanation of symbols]

 E Power generation element body A Assembly sheet A1, A1 'Both ends A2, A2' of assembly sheet A Wound body of power generation element body C Non-wound portion S, S 'core of power generation element body E

Claims (5)

[Claims] 1. A power generating element body comprising a two-winding body formed by winding at least two longitudinal ends of a collective sheet formed by laminating long sheets of a positive electrode and a negative electrode constituting a power generating element body. A prismatic battery characterized by the above. 2. The prismatic battery according to claim 1, wherein the two windings are wound in the same direction. 3. The prismatic battery according to claim 1, wherein the two windings are wound in opposite directions. 4. The prismatic battery according to claim 1, wherein each of the two winding bodies has a cylindrical shape or an elliptical cylindrical shape. 5. An assembly sheet comprising at least a long sheet of a positive electrode and a long sheet of a negative electrode constituting a power generating element body, each of which is wound on a core body while applying winding tension with both ends in the longitudinal direction as winding ends. In order to obtain a two-rolled body, the winding of each sheet at both ends in the longitudinal direction of the aggregated sheet so that the difference in length between the sheets in the non-wound aggregated sheet portion between the two-winded bodies becomes small. A method for manufacturing a prismatic battery, comprising winding a battery with a difference at an end.