JPH06260172A - Square form lithium battery - Google Patents

Abstract

PURPOSE:To lessen wastefull space likely generated inside of a battery can, enlarge the discharge capacity, and maintain excellent mass-producibility by furnishing a notch in a band-shaped electrode so that the angle part of a power generating element does not contact the battery can. CONSTITUTION:Notches (a) or (b) are provided in a band-shaped electrode, wherein the notch spacing is decided properly according to the length and thickness of the electrode so that the band-shaped electrode, when wound round, comes in one identical place. Similar notches are provided, if necessary, in the separator so as to suit the band-shaped electrode. When the electrode and separator provided with notches in this manner are wound round, a power generating element is produced whose angle part is notched in an arcuate form or triangularly. If this power generating element a, b is accommodated in a battery can, wasteful space likely generated in the can be decreased to allow enlargement of the discharge capacity of the resultant battery, and also sealing can be made in the double wind fastening system, so that an excellent mass- producibility as in conventional system can be maintained.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a prismatic lithium battery.

[0002]

2. Description of the Related Art As electronic devices are made smaller and lighter, light weight and high energy density batteries are required. Lithium batteries are the most promising batteries that meet this demand.

Batteries include cylinders and prisms. The most commonly used cylindrical type has low space efficiency when storing equipment, and the prismatic type has high space efficiency. Therefore, in recent years, there has been a great demand for prismatic batteries.

However, the prismatic battery has a problem in that it is inferior in productivity because a welding type sealing is used instead of a crimp type sealing which is generally used in a cylindrical shape. Moreover, since the conventional prismatic battery uses a power generation element in which strip-shaped electrode plates are laminated, there is a drawback that the electrode lamination process is complicated. Particularly in a lithium battery, the electrode thickness is thin and the number of electrodes is much larger than that in a nickel-cadmium battery or a nickel-hydrogen battery, so that the stacking process is significantly more complicated than other battery systems.

In order to solve these drawbacks of the conventional prismatic lithium battery, the inventor of the present invention has adopted a prismatic power generating element formed by winding a strip electrode into an elliptical shape, a rectangular shape or a shape in which two semi-circular arcs are connected by a straight line. We tried to seal the battery by inserting it into the battery case and using the double winding method used for canning and beverage cans. This method is overwhelmingly superior in productivity in manufacturing a power generation element as compared with a conventional method in which strip-shaped electrodes are laminated and each electrode is appropriately electrically joined to form a power generation element. In addition, if a double-winding sealing is used, the sealing speed can be increased to 1.5 times to 5 times that of the laser welding method.

However, it has been found that the double-winding sealing has a new problem that the corners of the surface to be sealed must be curved with a radius of at least 5 mm or more in order to increase the sealing speed. On the other hand, when the wound power generation element is inserted into the battery can, for example, in the case of a prismatic lithium battery as shown in FIG. 4, the corner R of the sealing surface may cause a useless space 6 in the battery can. all right. If the angle R of the battery can is reduced by slowing the sealing speed, this wasted space will be reduced, but productivity will be reduced and the original merit of this method will be lost.

[0007]

SUMMARY OF THE INVENTION According to the present invention, a band-shaped electrode and a separator are wound into an elliptical shape, a rectangular shape, or a shape in which two semi-circular arcs are connected by a straight line, and a power generating element is inserted into a battery can to form a dual structure. In a rectangular lithium battery sealed by a winding method, a rectangular lithium battery characterized in that a strip electrode and a separator, or a notch is provided in the strip electrode so that a corner of the power generation element does not come into contact with a battery can. A battery is used to solve the above drawbacks.

[0008]

In the prismatic lithium battery of the present invention, the strip electrodes and the strip separator are provided with notches as shown in FIGS. 1a and 1b, for example. The intervals of the notches are appropriately determined according to the length and thickness of the electrode so that they will be at the same place when the electrode is wound. When the electrode and the separator having such a cutout are wound, a power generation element is formed in which the corner portions are cut out in an arc shape or a triangular shape as shown in FIGS. When this power generating element is housed in a battery can, it is possible to significantly reduce the wasted space in the battery can as in the batteries (A) and (B) of FIG. As a result, the discharge capacity of the battery is increased and the energy density is improved.

[0009]

EXAMPLES The present invention will be described below with reference to preferred examples.

The positive electrode has a lithium cobalt composite oxide (Li
An xCoO ₂ ) electrode was used, and a graphite electrode was used as the negative electrode. The electrode and the separator are provided with a notch as shown in FIG. 1a, and two semi-circular arcs are wound in a straight line to form a shape shown in FIG.
Was used as a power generation element. Insert this power generation element into the battery can (resin-coated steel plate 0.22 mm ^t ) shown in FIG.
The sealing plate (resin-coated steel plate 0.22 mm ^t ) and the battery can were sealed by a double winding method. The size of the battery is 7.8 mm in thickness, 48 mm in width, and 40 mm in length.

The corners of the sealing surface have a radius of curvature of 7 mm. As the electrolytic solution, a solvent prepared by mixing ethylene carbonate and dimethyl carbonate in a volume ratio of 1: 1 and dissolving 1 mol / liter of lithium hexafluorophosphate was used. This battery is referred to as the prismatic lithium battery (A) of the present invention.

Next, a battery similar to the battery (A) except that the notch shape is the same as that of FIG. 1b is called a prismatic lithium battery (B) of the present invention.

Next, a battery similar to the battery (A) except that the separator is not provided with a notch is referred to as a prismatic lithium battery (C) of the present invention. In this case, if the space between the power generating element and the battery can is properly designed, the separator that remains when the power generating element is inserted into the battery can bends and escapes to the space, so that the sealing is not obstructed. Battery (C)
Has more productivity than the batteries (A) and (B) because the separator does not have a notch.

Next, a conventional prismatic lithium battery (a) in which notches are not provided in the electrode and the separator is shown in FIG.
Shown in.

Table 1 shows the discharge capacities of the above batteries. It can be seen that the batteries (A), (B) and (C) of the present invention having a small number of useless spaces 6 in the battery, that is, having a large electrode area, have a larger discharge capacity than the conventional battery (A).

[0016]

[Table 1] In the above examples, the case where the lithium cobalt composite oxide is used as the positive electrode active material has been described, but various materials such as manganese dioxide, lithium manganese oxide, vanadium pentoxide and lithium nickel oxide can be used. Further, although graphite is used as the negative electrode, in using the positive electrode of the present invention, the negative electrode active material is not basically limited, and other carbon materials, pure lithium, lithium alloys, etc. can be used.

Further, the electrolytic solution which is a lithium ion conductive substance and the solid ionic conductor are basically not limited, and those used in the conventional organic electrolytic solution secondary battery can be used. Examples of the organic solvent include cyclic esters such as ethylene carbonate which is an aprotic solvent and ethers such as tetrahydrofuran and dioxolane. These can be used alone or in a mixture of two or more thereof. As the solid ionic conductor, any substance having lithium ion conductivity can be used. A typical example thereof is polyethylene oxide. Also, the supporting electrolyte dissolved in such a non-aqueous solvent or solid ionic conductor is not basically limited. For example, L
One or more of iAsF ₆ , LiPF ₆ and LiCF ₃ SO ₃ can be used.

The prismatic lithium battery of the present invention includes a primary battery and a secondary battery.

[0019]

As described above, since the prismatic lithium battery of the present invention is excellent in mass productivity and has a large discharge capacity, its industrial value is extremely large.

[Brief description of drawings]

FIG. 1 is a diagram showing an example of electrodes of a prismatic lithium battery of the present invention.

FIG. 2 is a diagram showing an example of a power generation element of a conventional prismatic lithium battery.

FIG. 3 is a diagram showing an example of a prismatic lithium battery of the present invention.

FIG. 4 is a diagram showing a conventional prismatic lithium battery.

[Explanation of symbols]

 3 Battery can 4 Sealing plate 5 Power generation element 6 Wasted space

Claims (2)

[Claims] 1. A power generating element is formed by winding a strip-shaped electrode and a separator into an elliptical shape, a rectangular shape, or a shape in which two semi-circular arcs are connected by a straight line, and a battery can housing the power generating element is a double winding. A prismatic lithium battery sealed by a tightening method, characterized in that a notch is provided in the strip electrode so that a corner of the power generating element does not come into contact with a battery can. 2. A power generating element is formed by winding a strip-shaped electrode and a separator into an elliptical shape, a rectangular shape, or a shape in which two semi-circular arcs are connected by a straight line, and a battery can housing the power generating element is a double winding. A prismatic lithium battery sealed by a tightening method, characterized in that notches are provided in the strip electrodes and the separator so that the corners of the power generating element do not come into contact with the battery can.