JPH06260155A - Square form lithium battery - Google Patents

Abstract

PURPOSE:To achieve excellent producibility and enhance the reliance upon sealing by inserting a group of electrodes in a battery can from the same side as the direction of electrode stacking, and sealing the can. CONSTITUTION:A group of electrodes 5 formed by winding band electrodes in an eliptical form or in a rectangle whose corners are made in an arc of circle, or a group of electrodes 5 formed by stacking electrodes in the strip form, is inserted in a battery can, which is sealed with a sealing plate. The method of sealing is of double wind fastening, and the sealing plate is positioned so that it applies a pressure to the group of electrodes in the same direction as the electrode stacking. For example, the group of electrodes 5 formed by winding positive electrodes, negative electrodes, and separators in an eliptical form is inserted in a battery can 3 (of stainless steel plate of 0.3mm in thickness) in the same direction as the electrode stacking, and the sealing plate 4 (stainless steel plate of 0.3mm in thickness) and the can 3 are sealed by the double wind fastening system. This achieves excellent producibility and enhances the reliance upon sealing.

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 have become smaller and lighter, there has been an increasing demand for small, lightweight batteries with high energy density. A lithium battery is promising as a battery that meets these requirements.

Positive electrode active materials for lithium batteries include manganese dioxide, spinel manganese, lithium cobalt oxide,
Various sulfides and oxides are used, including transition metal oxides such as lithium nickel oxide. As the negative electrode active material, lithium alloys such as metallic lithium, Li—Al alloys and Li—Pb alloys, and carbon materials that absorb and release lithium ions have been studied.

As the electrolyte, an organic electrolytic solution such as lithium perchlorate, lithium trifluorotrimethanesulfonate, lithium hexafluorophosphate dissolved in an organic solvent of propylene carbonate or ethylene carbonate, or an organic or inorganic electrolyte These solid electrolytes are often used.

The battery case has a cylindrical shape or a rectangular shape. The most commonly used cylindrical type has low space efficiency when storing equipment, and the prismatic type has high space efficiency. However, the prismatic battery has a problem that it is difficult to seal it.

As a sealing method, there are a crimp type in which a sealing plate is caulked with a battery case through a resin packing, and a welding type in which a battery case and a sealing plate are welded and sealed. The crimp type is used for coin type batteries and cylindrical type batteries, and has an advantage that it can be mass-produced at low cost. As for the prismatic battery, the crimp type cannot secure sufficient airtightness, and thus the welding type using a YAG laser is mainly used. This sealing method has drawbacks such as an expensive laser device and a slow sealing speed.

When the battery is sealed by the welding method,
A general method is to insert an electrode group in which strip-shaped electrodes are stacked in a direction perpendicular to the electrode stacking direction from the upper surface of a battery can and then seal the upper surface with a sealing plate. This is because the shorter the welding distance is, the higher the productivity is, so that the sealing plate is welded to the top surface of the battery can, which has the smallest area.However, when the electrode group is inserted from the top surface of the battery case as described above. Had the following various problems. That is, in order to facilitate the insertion, it is necessary to make the size of the electrode group relatively smaller than the inner size of the battery can. As a result, there is a problem that the electrode group becomes loose after insertion. When an appropriate pressing force is not applied to the electrode plate group, the electrode reaction often occurs nonuniformly, resulting in a significant decrease in battery performance or a large variation in battery performance. Further, in this insertion method, the step of electrically connecting the collector terminal provided on the sealing plate and the electrode group becomes complicated, and the electrode substance is easily attached to the sealing surface when the electrode group is inserted. There were also problems such as reduced reliability.

[0008]

According to the present invention, an electrode group formed by winding a strip-shaped electrode into an elliptical shape or a rectangular shape whose corners are arcuate or an electrode group formed by laminating strip-shaped electrodes is a battery. In a prismatic lithium battery which is inserted into a can and sealed with a sealing plate, or a rectangular lithium battery whose corners are arcuate, the sealing method is a double winding sealing, and the sealing plate is in the same direction as the electrode stacking direction on the electrode group. An object of the present invention is to solve the above problems by using a prismatic lithium battery characterized by being positioned so as to apply a compressive force.

[0009]

In the prismatic lithium battery of the present invention, the sealing method is not the conventional welding method but the double winding method used for canning and beverage cans. By using this method, the sealing speed can be significantly increased without impairing the airtightness. Moreover, since the sealing speed does not depend on the sealing distance, the sealing surface can be freely selected. Therefore, in the prismatic lithium battery of the present invention, the electrode group is inserted and sealed in the battery can from the same direction as the electrode stacking direction.

In this case, the sealing plate is arranged in parallel with the stacked electrodes. Therefore, the compression force applied to the electrode group can be easily made appropriate. In addition, since the battery can have a large opening in the battery can for inserting the electrode group (since the dimensional difference between the electrode group and the opening does not affect the pressure of the electrode), the electrode group and the battery terminal are electrically connected. Workability at the time of mechanical connection is remarkably improved. Further, since the opening is large, the problem that the active material or the like adheres to the sealing portion is reduced.

In the lithium battery of the present invention, strip-shaped positive electrode plates and negative electrode plates may be alternately laminated to form an electrode group, or the positive electrode plates and the negative electrode plates may be formed with separators in between. Alternatively, it may be formed by winding it into an elliptical shape or a rectangular shape whose corners are arcuate.

[0012]

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. An electrode group 5 formed by winding the positive electrode, the negative electrode, and the separator in an elliptical shape is shown in FIG.
m ^t) to be inserted from the lamination direction in the same direction of the electrode was sealed by a sealing plate 4 (stainless steel plate 0.3 mm ^t) and the battery can 3 double seamed scheme. The battery size is 1.5 cm in thickness (D), 10 cm in width (W), and height (H).
Was 10 cm. 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.

Next, as an example of a conventional battery, as shown in FIG. 2, a battery similar to the battery (A) of the present invention except that an electrode is inserted from the upper surface of the battery can and the upper surface is sealed with a YAG laser. Is called (A).

Table 1 shows the average sealing speeds of these batteries. Further, these batteries were stored in an atmosphere of 45 ° C. and a humidity of 95% for one month and then subjected to a charge / discharge test. The change in discharge capacity in that case is also shown in Table 1. From these results, it is apparent that the prismatic lithium battery of the present invention is more excellent in productivity and is inferior to the conventional welding type in sealing reliability.

[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, in the present invention, the prismatic battery includes a battery in which the corners of the prismatic battery are arcuate and a battery in which the corners of the prismatic battery are cut out. Therefore, for example, a battery having a shape as shown in FIG. 3 is also included in the prismatic battery, and the present invention can be applied.

Further, the electrolytic solution which is a lithium ion conductive material 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.

[0020]

As described above, the prismatic lithium battery of the present invention is excellent in mass productivity and reliability, and its industrial value is extremely large.

[Brief description of drawings]

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

FIG. 2 is a diagram showing a conventional prismatic lithium battery.

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

[Explanation of symbols]

 3 Battery can 4 Sealing plate 5 Electrode group

Claims (1)

[Claims] 1. An electrode group is formed by winding a strip-shaped electrode into an elliptical shape or a rectangular shape whose corners are arcuate, or is formed by stacking strip-shaped electrodes, and the electrode group is a battery can. The battery can is double-sealed with a sealing plate, and the sealing plate is positioned so as to apply a compressive force to the electrode group in the same direction as the electrode stacking direction. A prismatic lithium battery characterized by.