JPH0733376Y2 - Coin type lithium battery - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention relates to an improvement of a coin-type lithium battery.

2. Description of the Related Art As a conventional example, a sectional view of a coin type lithium battery is shown in FIG. In the figure, 1 is a stainless steel sealing plate which also serves as a negative electrode terminal, 2 is a polypropylene gasket, 3 is a stainless steel battery case, 4 is a sheet lithium of a negative electrode which is pressure-bonded to the uneven portion of the inner surface of the sealing plate 1, 5 Is a separator made of polypropylene non-woven fabric, 6 is mainly manganese dioxide, and is mixed with acetylene black as a conductive agent and styrene-butadiene as a binder, and is mixed and pressure-molded into a positive electrode mixture. 7 is a cross section L This is a dish-shaped positive electrode current collector having a conductive carbon coating formed on the contact surface with the positive electrode mixture 6. The electrolytic solution is obtained by dissolving lithium perchlorate in a mixed solvent of propylene carbonate and dimethoxyethane, and is impregnated in the separator 5 and the positive electrode mixture 6. In this configuration, current collection on the positive electrode side is performed by contact between the positive electrode mixture 6 and the inner surface of the positive electrode current collector 7, and contact between the bottom surface of the positive electrode current collector 7 and the inner bottom surface of the battery case 3. It has become. A cross-sectional view of the conventional example (2) is shown in FIG. 3. In the conventional example (2), a ring-shaped positive electrode collector having an L-shaped cross section with a large circular hole in the center instead of the dish-shaped collector. The configuration is the same as that of the conventional example (1) except that the electric body is used. Therefore, current collection on the positive electrode side is also performed by contact between the positive electrode mixture 6 and the inner surface of the positive electrode current collector 7, and contact between the bottom surface of the positive electrode current collector 7 and the inner bottom surface of the battery case 3.

Problems to be Solved by the Invention One of the most important points in the construction of a coin-type lithium battery is the current collecting method on the positive electrode side. However, in the conventional examples (1) and (2), since the current collecting effect is insufficient, there is a large variation in the internal resistance of the battery, and there is a problem that the voltage drops during discharge and the discharge time becomes short. . It is desirable that the contact pressure is as high as possible in order to improve the current collection effect on the positive electrode side. However, in the conventional example, the contact state between the positive electrode current collector 7 and the battery case 3 is caused by the variation in the thickness of the power generation component inside the battery. When the thickness of the component is greatly affected, the contact pressure becomes low, and abnormal internal resistance occurs due to poor contact. Further, when the gasket is strongly tightened at the time of sealing, the bottom of the battery case swells outward, so that a gap is created between the positive electrode current collector 7 and the battery case 3. This also causes an internal resistance abnormality. Further, in the case of the conventional example (2), since the contact area between the positive electrode mixture 6 and the positive electrode current collector 7 is small, contact failure between the positive electrode mixture and the positive electrode current collector is likely to occur. We have also tried to improve the contact by applying carbon to the surface of the positive electrode current collector in contact with the agent, but in the case of a ring-shaped positive electrode current collector, the area to be applied is small, so it is possible to apply it stably in the process. It is extremely difficult and has drawbacks in industrial production.

Means for Solving the Problems The present invention solves various problems in the above-mentioned conventional example all at once and facilitates industrial production of a battery of stable quality, and has a two-stage L-shaped cross section. In the dish-shaped positive electrode current collector, the concentric circular convex portion in the central portion on the side in contact with the battery case is reversely deformed from the battery case side toward the positive electrode side to bite the back side of the convex portion into an annular shape, and the convex portion Is a coin-type lithium battery in which the battery is brought into contact with the battery case under pressure.

This prevents the influence of the contact pressure drop due to the variation of the thickness of the components in the battery and the swelling of the battery case at the time of sealing, and it is always constant between the positive electrode current collector and the positive electrode mixture or between the positive electrode current collector and the battery case. The contact between them is improved by maintaining the pressure of. As a result, there is no abnormality in the internal resistance, and normal discharge is performed.

Embodiments The present invention will be described below with reference to embodiments.

FIG. 4 (a) is a top view of the positive electrode current collector of the present invention, and FIG.
Is a sectional view. FIG. 1 is a sectional view of a coin-type lithium battery to which the positive electrode current collector of the present invention is applied, which has the same configuration as the battery of the conventional example (1) except that the shape of the positive electrode current collector 7 is different. As shown in FIG. 4, the dish-shaped positive electrode current collector 7 of the present invention has a two-stage L-shaped cross section and a two-stage bottom, and a concentric circular convex portion 7 is formed in the central portion on the side in contact with the battery case. There is' When the positive electrode current collector 7 is installed in the battery case 3, the convex portion 7 ′ is pressed from the battery case side toward the positive electrode side to be inverted and deformed, and the back side of the convex portion is bite into an annular shape. At the same time, the convex portion is brought into contact with the battery case under pressure. For this reason, the contact pressure between the dish-shaped positive electrode current collector and the battery case can be improved by the spring effect of the convex portion returning to its original shape from the deformation. Also,
The contact state between the dish-shaped positive electrode current collector and the positive electrode can be improved by making the back side of the convex portion of the dish-shaped positive electrode current collector 7 bite into the positive electrode side. The material is made of stainless steel. Further, a conductive carbon paint is applied to the contact surface with the positive electrode composite to form a coating thereof.

Next, the battery of 16 mm in diameter and 2.0 mm in height shown in the conventional example (1), the conventional example (2), and the embodiment of FIG. Shown in the table. Table 2 shows the average value of the discharge duration of 30 KΩ for 10 samples and the number of abnormal discharges. The discharge abnormality mentioned here refers to a phenomenon in which the voltage temporarily and suddenly drops during discharge.

From these results, it is found that the battery of the present invention has a stable internal resistance at a lower level than that of the conventional example, and the discharge performance does not cause discharge abnormality and has a long duration. Recognize. In the positive electrode current collector 7 used in the embodiment of the present invention, the height of the convex portion 7'is 0.15 mm, but the same effect can be obtained by changing it according to the size of the battery.

Effect of the Invention As is clear from the above embodiment, the cross-sectional shape has a two-stage L shape.
Using a dish-shaped positive electrode current collector in the shape of a letter, the concentric circular convex part in the center of the side of the current collector that contacts the battery case is inverted and deformed from the battery case side toward the positive electrode side, and the back side of the convex part is In addition to making it bite into an annular shape, the convex portion is brought into contact with the battery case under pressure, so that the contact state between the dish-shaped positive electrode current collector and the positive electrode and the dish-shaped positive electrode current collector and the battery case should be good. It is possible to provide a coin-type lithium battery having low internal resistance and excellent discharge characteristics.

[Brief description of drawings]

FIG. 1 is a sectional view of a coin type lithium battery of the present invention, FIG.
FIG. 3 is a cross-sectional view of a conventional coin-type lithium battery, and FIGS. 4 (a) and 4 (b) are a top view and a cross-sectional view of the positive electrode current collector of the present invention before the convex portion is inverted. 1 ... Sealing plate, 2 ... Gasket, 3 ... Battery case,
4 ... Lithium, 5 ... Separator, 6 ... Positive electrode mixture,
7 ... Positive electrode current collector, 7 '... convex portion.

Claims (1)

[Scope of utility model registration request] 1. A negative electrode made of lithium and a positive electrode housed inside a dish-shaped positive electrode collector having a substantially L-shaped cross section are opposed to each other with a separator interposed therebetween, and these power generation components are connected to a battery case and a sealing plate. A coin-shaped lithium battery housed in a container comprising: a dish-shaped positive electrode current collector having a substantially L-shaped cross section, the dish-shaped positive electrode current collector having a two-stage bottom having a two-stage L-shaped cross-section. It is formed by pressing on the bottom surface of the case, and the concentric circular convex portion at the center of the side of the plate-shaped positive electrode current collector with the two-stage bottom that contacts the battery case is inverted and deformed toward the positive electrode side, The coin-shaped lithium battery in which the back side of the convex portion bites into a ring shape, and the convex portion is in contact with the battery case under pressure.