JP2001266927A - Wound battery - Google Patents

Abstract

(57) [Problem] To provide a battery excellent in characteristics with high efficiency per volume of a wound body. SOLUTION: In a wound battery in which a battery element in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator is housed in a battery can, a positive electrode conductive tab joined to the positive electrode and a negative electrode are joined. Both of the negative electrode conductive tabs are mounted near the ends of the winding start side of the positive electrode and the negative electrode of the winding body, with an interval therebetween, and on the winding start side, There is a portion where the electrode active material layer of the positive electrode is not applied, and the end on the winding start side of the negative electrode is located at a portion facing the portion where the electrode active material layer of the positive electrode is not applied. The current collector at the beginning of the winding of the negative electrode, which faces the surface on which the positive electrode active material layer is not formed, with the separator interposed therebetween, prevents deposition of the battery reactant formed beyond the end of the facing positive electrode. Negative electrode active material for A wound battery provided with a portion where no negative electrode active material layer is formed except for a layer.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a sealed battery having a wound battery element, and more particularly to a wound battery having a small thickness of a wound body and high reliability even during overcharge.

[0002]

2. Description of the Related Art Various types of batteries are used as power supplies for small electronic devices, such as lithium-ion secondary batteries, which are small and large-capacity sealed batteries, as power supplies for mobile phones, notebook computers, camcorders and the like. Non-aqueous electrolyte batteries are used. As these non-aqueous electrolyte batteries, batteries having a cylindrical or square structure are used. In a lithium-ion battery used as a power source for a small electronic device, an active material is applied to each of a positive electrode current collector and a negative electrode current collector, and then wound with a separator interposed therebetween. What is stored and sealed is used.

[0003] As such batteries, there are used a cylindrical battery in which a wound body is accommodated in a cylindrical battery can and a square battery in which a wound battery is accommodated in a rectangular battery can. In the battery storage section, small or thin devices are used due to the problem that the ineffective volume becomes large with the cylindrical battery or the diameter of the cylindrical battery is limited by the thickness of the battery storage section. , A prismatic battery is widely used.

FIG. 3 is a partially cutaway perspective view illustrating a prismatic battery. The prismatic battery 1 is formed by winding a positive electrode 2 coated with a positive electrode active material and a negative electrode 3 coated with a negative electrode active material with a separator 4 interposed therebetween to form a wound body 5 of a battery element. The battery is sealed by welding the upper battery header 7 to the battery can 2 after injecting the electrolyte. FIG. 4 is a diagram illustrating a development view of a wound body of the battery element. In the case of a battery in which the positive electrode terminal is at the upper center of the battery can, the wound body is formed by joining a positive electrode conductive tab 8 to the positive electrode 2 coated with the positive electrode active material, and connecting the negative electrode 3 to the negative electrode 3 coated with the negative electrode active material. After the conductive tab 9 is joined, the separator 4 made of a microporous film is interposed, and winding is performed using a winding device in a winding direction 10 indicated by an arrow, starting from the side on which the positive electrode tab is provided. We manufacture wound bodies.

FIG. 5 is a cross-sectional view illustrating a wound body housed in a battery can of a rectangular battery. FIG. 5 (A)
FIG. 5 is a cross-sectional view of the upper part of the wound body. After the wound body 5 is housed in the battery can, the positive conductive tab 8 is conductively connected to the header portion of the upper part of the battery can. No.6 is welded to the wall. FIG. 5B is a diagram illustrating a central portion of the wound body. In a battery using a positive electrode and a negative electrode that dope and dedope lithium, such as a lithium ion battery, excessive lithium is deposited on the negative electrode surface during overcharge, or lithium crystals grow abnormally and the A non-coated portion 11 on which the positive electrode active material is not applied is formed in the center of the wound body of the positive electrode 2 so as not to break through and short-circuit with the positive electrode. 8 are joined.

Further, in order to reduce the current density of the negative electrode at a portion facing the end of the positive electrode coated with the active material, to prevent abnormal deposition of lithium on the surface of the negative electrode, A negative electrode active material is applied to a portion of the negative electrode that is wider than a portion facing the portion where the positive electrode active material is applied. When such a battery is charged and discharged, the electrode active material layer repeatedly expands and contracts during charging and discharging, as shown in FIG. 5C, a space where the active material layer does not exist at the center of the wound body. Causes large distortion.

Further, a negative electrode active material layer which does not contribute to the battery reaction is present at the beginning of the winding of the wound body, and the thickness of the wound body of the electrode is increased, and the electrode is locally deformed by the deformation of the wound body. There is a problem in that the distance between the electrodes becomes short, a portion where current concentrates is formed, lithium is precipitated, and the reliability at the time of overcharging is reduced.

[0008]

SUMMARY OF THE INVENTION The present invention relates to a wound type battery having a battery element in which a positive electrode and a negative electrode are stacked with a separator interposed therebetween and wound, wherein a positive electrode active material at the center of the wound body is provided. It is an object of the present invention to provide a battery having excellent characteristics in which the thickness of the wound body is prevented from being increased due to the deformation of the wound body caused by the presence of the non-coated portion, or the reliability during overcharge is prevented from being reduced.

[0009]

SUMMARY OF THE INVENTION An object of the present invention is to provide a wound type battery in which a battery element in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator is accommodated in a battery can, and wherein Both the joined positive electrode conductive tab and the connected negative electrode conductive tab are attached to the wound body near the winding start side ends of the positive electrode and the negative electrode with an interval therebetween. At the beginning of the winding, there is a portion where the electrode active material layer of the positive electrode is not applied, and at the end of the winding of the negative electrode, the electrode active material layer of the positive electrode is applied. The current collector at the beginning of the winding of the negative electrode, which is located on the portion opposite to the portion where the positive electrode active material layer is not formed and faces the surface on which the positive electrode active material layer is not formed via a separator, has the end of the positive electrode facing the opposite end. Battery reaction formed beyond It can be solved by winding type battery where the anode active material layer except for the negative electrode active material layer is provided with a portion which is not formed for preventing the precipitation of quality. In addition, the portion where the negative electrode active material is not formed is formed by applying a single-sided coating to the beginning of winding of the wound body from the portion of the negative electrode active material layer formed to prevent deposition of the battery reactant. The wound type battery according to the above. A wound battery as described above wherein the battery reactant is lithium.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION In a wound type battery according to the present invention, by providing a positive electrode tab and a negative electrode tab at the beginning of winding of a wound body, both conductive tabs are present near the center of the wound body. ing. Thereby, each conductive tab can prevent the joint portion from being destroyed by the impact at the time of falling, and furthermore, by forming a single-sided coated portion of the active material layer on the current collector at the beginning of the winding, Eliminating the active material layer that does not contribute to the battery reaction, reducing the thickness of the wound body,
It is possible to prevent the wound body from being deformed due to repeated charging and discharging of the battery.

FIG. 1 is a view for explaining a battery according to an embodiment of the present invention, and a lithium ion secondary battery will be described as an example. FIG. 1A is a diagram showing a cross section perpendicular to the winding axis of the wound body, and FIG. 1B is a diagram showing a developed view of members constituting the wound body. Each of the positive electrode conductive tab 8 provided on the positive electrode 2 and the negative electrode conductive tab 9 provided on the negative electrode 3 is provided at an end near the winding start portion of the negative electrode 3 and the positive electrode 2, and is wound via the separator 4. Since the wire is wound in the direction of the winding direction 10, the interval between the positive electrode conductive tab and the negative electrode conductive tab and their positions in the wound body can be accurately defined at the beginning of winding. As a result, even if there is a delicate difference in the characteristics of the members such as the positive electrode, the negative electrode, and the separator, and even if the manner of applying the force during winding changes, the positive electrode conductive tab and the negative electrode conductive tab may be changed. Or the variation in the distance from the center or the distance from the center can be made extremely small.

In the positive electrode 2, a non-coated portion 11 on which no positive electrode active material layer is formed on both surfaces is formed at a winding start portion, and a positive electrode conductive tab 8 is attached to the non-coated portion. . Further, as shown in 3A showing one surface of the negative electrode 3, when the wound body is manufactured, the positive electrode active material layer 2 of the positive electrode is formed.
The negative electrode active material layer 3a is formed on the surface opposite to the surface on which the negative electrode active material is applied, beyond the end position 12 corresponding to the end of the positive electrode active material layer 2a. A negative conductive tab 9 is attached. Further, as shown on the other surface 3b of the negative electrode, the negative electrode active material layer 3a is formed on the other surface also at the beginning of the winding of the wound body.

FIG. 2 is a view for explaining the central portion of the wound body of the battery according to the embodiment of the present invention shown in FIG. Positive electrode 2
The positive electrode conductive tab 8 is attached to the winding start portion of the wound body, and the non-coated portion 11 where the positive electrode active material layer 2a is not formed is formed at the winding start portion. In the negative electrode 3, a negative electrode active material layer 3 a is formed on a surface of the positive electrode 2 opposite to the positive electrode active material layer 2 a.
“a” is also present in a portion beyond the end of the positive electrode active material layer 2a, and prevents deposition of lithium due to concentration of current on a surface facing the end of the positive electrode.

A negative electrode active material layer 3a is formed on the other surface of the negative electrode 3 from the beginning of the winding, and the negative electrode active material layer 3a is formed on only one surface of the negative electrode 3 at the center. A one-sided application part 3b is provided. The negative electrode conductive tab 9 is joined to a portion where the negative electrode active material 3a is not applied. As a result, the thickness of the negative electrode at the beginning of winding of the wound body is reduced, and the thickness of the wound body can be reduced.

Further, since the active material layer is formed only on one surface of the negative electrode at the beginning of the winding, the central portion of the wound body is provided with a current collector to which the active material is not applied, a positive electrode conductive tab,
Since the battery can be filled with the negative electrode conductive tab and the separator, a high-quality battery can be obtained without distortion even when repeatedly charged and discharged.

[0016] In the battery of the present invention, since the conductive connection portion with the outside is provided on the lid on both the positive electrode side and the negative electrode side, even when an impact due to a drop is applied, the impact destroys the joint at the joint. Since it does not act in the direction, it does not affect the joint between the conductive tab and the lid, and the joint is not destroyed by impact. Further, the battery of the present invention can be applied to both cases where the battery can also serves as the negative electrode terminal and where the battery can also serves as the positive electrode terminal. Further, the wound type battery of the present invention includes:
The present invention can be applied to any of a square battery and a cylindrical battery.

[0017]

According to the battery of the present invention, the variation in the distance between the positive electrode conductive tab and the negative electrode conductive tab and the distance from the center is reduced, and the wound power generator suitable for an assembling operation using an automatic assembling apparatus or the like. The element can be obtained, and a battery of stable quality can be manufactured. In addition, since a portion where the negative electrode active material layer is provided only on one side is formed at the beginning of the winding of the wound body, the winding is performed. A battery with a thin circular body can be obtained. Further, since the wound body is stable, a battery with a small amount of deformation of the battery element and excellent characteristics can be obtained even when the battery is repeatedly charged and discharged. Furthermore, since both the positive electrode conductive tab and the negative electrode conductive tab attached to the winding body of the battery element were joined to the upper lid of the battery can and the external connection terminal provided on the lid, the impact applied by dropping the battery or the like caused A highly reliable battery in which the conductive connection portion is not broken can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a battery according to one embodiment of the present invention.

FIG. 2 is a diagram illustrating a central portion of a wound body of the battery according to the embodiment of the present invention shown in FIG. 1;

FIG. 3 is a partially broken perspective view illustrating a prismatic battery.

FIG. 4 is a diagram illustrating a development view of a wound body of a battery element.

FIG. 5 is a diagram illustrating a wound body housed in a battery can of a square battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Rectangular battery, 2 ... Positive electrode, 2a ... Positive electrode active material layer, 3
, A negative electrode, 3a, a negative electrode active material layer, 3A, one surface of a negative electrode, 3B, another surface of the negative electrode, 4, a separator,
5 ... wound body, 6 ... battery can, 7 ... battery header, 8 ... positive electrode conductive tab, 9 ... negative electrode conductive tab, 10 ... winding direction, 11 ...
Non-applied part, 12 ... end position

Claims (1)

[Claims] 1. A wound type battery in which a battery element in which a strip-shaped positive electrode and a strip-shaped negative electrode are wound via a separator is accommodated in a battery can, a positive electrode conductive tab joined to the positive electrode and a negative electrode. Both of the joined negative electrode conductive tabs are attached to the wound body near the ends of the winding start side of the positive electrode and the negative electrode, with a space therebetween, and at the winding start side. There is a portion where the electrode active material layer of the positive electrode is not applied, and the end on the winding start side of the negative electrode is located in a portion facing the portion where the electrode active material layer of the positive electrode is not applied. At the same time, the current collector at the beginning of the winding of the negative electrode facing the surface on which the positive electrode active material layer is not formed via a separator prevents the deposition of the battery reactant formed beyond the end of the facing positive electrode. Negative active material for A wound type battery provided with a portion where no negative electrode active material layer is formed except for a layer.