JPH0122708B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a rechargeable organic electrolyte battery for use in mobile DC power supplies, backup power supplies, and the like. Conventional configurations and their problems Conventionally, high energy density batteries using lithium as the active material for the negative electrode, so-called lithium batteries, have used a mixture of carbon fluoride and carbon black, or manganese dioxide and carbon black, or manganese dioxide and carbon black as the positive electrode. Using a mixture with a binder, lithium metal is used as the negative electrode, propylene carbonate or γ-butyrolactone in which lithium perchlorate or lithium borofluoride is dissolved in the electrolyte, or these and 1.2 dimethoxyethane (hereinafter referred to as DME). A mixed solution is used. However, in the case of this system, it is used as a primary battery, and charging is not possible at this stage. On the other hand, a rechargeable DC power battery using lithium metal uses activated carbon fiber as the positive electrode, lithium metal as the negative electrode, and propylene carbonate or γ-butyrolactone in which lithium perchlorate or lithium borofluoride is dissolved as the electrolyte, or these. A system using a mixed solution of 1,2-dimethoxyethane and 1,2-dimethoxyethane has been devised. In this type of battery, the positive electrode is a polarizable electrode that mainly utilizes charge in the electric double layer on the surface of activated carbon for charging and discharging, and the negative electrode mainly consists of redox reactions of metallic lithium. Generally, the electric capacity of an electric double layer is extremely small compared to a normal battery active material, so the activated carbon positive electrode is rate-limiting for the electric capacity of a battery. Therefore, the effective surface area and conductivity of the activated carbon that forms the electric double layer, as well as the contact resistance between the metal current collector and the activated carbon and the storage case, are extremely important factors in terms of battery characteristics. Among these, the role of the metal current collector is to lower the internal resistance of the battery and to stabilize the long-term charge/discharge cycle characteristics. In order to further improve the effect of this metal current collector, it is common to weld the metal current collector to the case. One way to do this is, for example, by thermally spraying aluminum metal onto activated carbon fiber cloth to provide an aluminum layer on one side of the activated carbon fiber cloth, and then spot-welding this to the case on top of the activated carbon fiber cloth, or by incorporating an aluminum lath plate. There is one in which a part of the activated carbon of the activated carbon molded body is scraped off to expose a part of the lath plate, and the exposed part is spot welded to the case. The former, thermally sprayed aluminum, has excellent conductivity, but it is expensive and the welding strength when welded to the case is not necessarily high, and the activated carbon layer may sometimes separate from the case.
There were variations in welding strength. In the latter case, when part of the activated carbon is scraped off and spot welded, the welding strength to the case is strengthened, but a part of the activated carbon is lost, resulting in a decrease in electric capacity. Purpose of the Invention The present invention provides a rechargeable organic electrolyte battery that uses activated carbon as a positive electrode and lithium metal as a negative electrode, by effectively attaching a metal current collector to the case without reducing the electrical capacity. The purpose of this invention is to reduce variations in charge/discharge cycle characteristics and to provide a battery at low cost. Structure of the Invention In order to achieve the above object, the present invention is such that a metal current collector is welded to a case in advance, and an activated carbon electrode is placed on the metal current collector. By doing this, the current collector can be perfectly welded to the case, and the activated carbon electrode will not be scraped, so the capacitance will not decrease. Moreover, since assembly can be performed easily and inexpensively, mass production is also easy. As the current collector here, a screen, lath, punched metal, etc. made of aluminum, nickel, titanium, stainless steel, etc. can be used. As the activated carbon electrode, it is possible to use activated carbon fiber cloth punched out to a desired size, or an activated carbon powder molded body molded with a binder such as fluororesin or SBR. DESCRIPTION OF EXAMPLES The present invention will be explained below with reference to Examples. (Example 1) The figure shows a cross-sectional view of the structure of a coin-shaped rechargeable lithium battery to which the present invention is applied. Its manufacture was carried out as follows. First, as the positive electrode current collector 5, punch out a lath plate of aluminum metal to a size of 14.0 mm in diameter.
A welded fixing part 5' was formed by electric welding to the center of the inner bottom surface of the positive electrode case 1 made of 20.0 mm stainless steel. Then, an activated carbon fiber cloth with a surface area of 1500 m ² and a thickness of 0.8 mm was punched out to a size of 14.0 mm in diameter, and placed on the electrically welded aluminum lath plate to obtain a positive electrode 4. Next, a lithium metal having a thickness of 0.5 mm and a size of 12 mm was used as the negative electrode 7, and this was pressure-bonded to the inner surface of the sealing plate 2. A polypropylene nonwoven fabric is used as the separator 6, and propylene carbonate is used as the electrolyte.
DME at a volume ratio of 1:1, lithium perchlorate dissolved in this mixed solution at a concentration of 1 mol/mole is prepared, and after adding it to the separator 6 and the activated carbon fiber cloth of the positive electrode 4, The plate 2 and the case 1 were coupled together via a sealing ring 3, and the battery was further sealed. Let this be A. The completed battery will have a diameter of 20 mm and a thickness of 1.6 mm. (Example 2) A battery was produced in the same manner as in Example 1 except that a titanium lath plate was used as a metal current collector. Let this be B. (Example 3) A battery was produced in the same manner as in Example 1 except that an aluminum lath plate was used as a metal current collector. Let this be C. (Example 4) An aluminum lath plate was used as a metal current collector, and it was welded using a laser welding method.
A battery was produced in the same manner as in Example 1 except for welding to the case. Let this be D. As a comparative example, aluminum was thermally sprayed onto the same activated carbon fiber cloth as in Example 1, the activated carbon fiber cloth was inserted so that the aluminum surface was in contact with the inner surface of the case, and the activated carbon fiber cloth and the case were sandwiched using the electrode of a spot welding machine. Welded. The battery was constructed in the same manner as in Example 1 in other respects. Let this be E. Prepare 10 each of these batteries A to E, and 1mA
The battery was repeatedly charged and discharged for 1 hour, and the internal resistance in the charged state after 1000 cycles and the discharge capacity from 3V to 1.5V at 1mA discharge were measured. The results are shown in the table below.

[Table] As is clear from the table, even after 1000 cycles, the internal resistance of all of the products A to D according to the present invention was lower than that of the conventional product, and the discharge capacity was also large. This is because the variation σ is small and indicates that stable quality was obtained. On the other hand, the comparison product E has some parts that are significantly inferior, so the variation is large and the average value is also shifted in a negative direction. From these facts, the effects of the present invention are obvious. In the above embodiment, the metal current collector is welded at one location, but it is more reliable to weld at several locations. Furthermore, almost the same effect as in Example 1 was obtained when an activated carbon powder molded body made into pellets using fluororesin as a binder was used instead of activated carbon fibers. Furthermore, the shape of the battery is not limited to a coin shape, but can also be applied to a button shape or a cylindrical shape. Effects of the Invention As described above, the rechargeable lithium battery of the present invention can be manufactured more easily and inexpensively than conventional ones, and can stably withstand long-term charging and discharging, and its range of applications is extremely wide. It is.

[Brief explanation of drawings]

The figure is a sectional view of a coin-shaped rechargeable organic electrolyte battery according to an embodiment of the present invention. 1... Positive electrode case, 2... Sealing plate, 3... Sealing ring, 4... Positive electrode, 5... Positive electrode current collector, 5'...
...Electric welding part of positive electrode current collector, 6...Separator,
7...Negative pole.

Claims (1)

[Claims] 1. An organic electrolyte battery comprising a positive electrode case 1, a polarizable positive electrode 4, and a negative electrode 7 made of lithium metal, wherein the polarizable positive electrode 4 is made of activated carbon containing an organic electrolyte. A metal current collector 5 is welded to the inner bottom of the positive electrode case 1, and the metal current collector 5 is a rechargeable organic battery on which activated carbon containing the organic electrolyte is placed. electrolyte battery. 2. The rechargeable organic electrolyte battery according to claim 1, wherein the metal current collector 5 is made of any one of titanium, nickel, stainless steel, and aluminum.