JPS6031067B2 - Manufacturing method of battery positive electrode - Google Patents

Description

Detailed Description of the Invention The present invention relates to a method for manufacturing a positive electrode of a battery, particularly an organic electrolyte battery using a light metal as a negative electrode active material and cupric oxide as a positive electrode active material, which is easy to manufacture and has discharge characteristics. The purpose of this invention is to provide a positive electrode suitable for a button-type organic electrolyte battery with excellent energy density and high energy density.

Conventionally, an organic electrolyte in which a solute such as lithium perchlorate or lithium borofluoride is dissolved in an organic solvent such as propyl carbonate or y-butyrolactone is used.
Organic electrolyte batteries are known in which a light metal such as lithium, magnesium, or aluminum is used as a negative electrode and a metal halide or oxide is used as a positive electrode.

Generally, a battery is composed of a positive electrode, a negative electrode, a separator, an electrolytic solution, and a battery container that encloses them.

The capacity of this battery cannot take any size or shape; it generally has a predetermined volume and shape for incorporation into a device. It is desirable that high energy can be extracted. In recent years, with the development of thin watches and calculators, there has been a strong demand for primary batteries with particularly high energy and excellent discharge characteristics. In button-type batteries with lithium as the negative electrode and cupric oxide as the positive active material, cupric oxide has no conductivity, so conductive materials such as acetylene black and ethylene tetrafluoride-propylene hexafluoride are used. A pellet-shaped positive electrode was used that was press-molded with a binder such as a polymer added.

However, since a conductive material and a binder are used, the filling amount of second oxidized steel as an active material decreases, resulting in a decrease in discharge capacity, and a high energy density battery cannot be expected. On the other hand, it is possible to increase the packing density by minimizing the conductive particles and binder, but in this battery system, the positive electrode swells with the discharge reaction, so if the packing density is increased too much, it will cause problems at the end of discharge. This has the drawback of causing the battery container to bulge and putting pressure on the pond parts of the equipment in which it is used, so it is necessary to fill the battery container with a filling amount that minimizes the bulge. Therefore, in the case of an appropriate filling amount, the cupric oxide pellet used as the positive electrode will have a reduced thickness due to the pressure molding of the powder, an increase in the distance between the electrodes, and a reduction in the contact with the mass concentrator. Causes defects. From the above points, it is recommended to insert a liquid-retaining metal porous body 7 as a substrate into the back surface of the negative electrode 3 or the positive electrode 5 as shown in FIG. 3 or 4, or to use a material such as polypropylene as shown in FIG. A battery was constructed by inserting a nonwoven fabric 7' between the two electrodes.

However, when such a spacer is inserted, the amount of active material is disadvantageously reduced by the volume thereof. Also,
Inserting a nonwoven fabric 7' or the like between the positive and negative electrodes will cause a decrease in discharge voltage due to an increase in internal resistance, since the specific conductivity of the impregnated organic electrolyte is about two orders of magnitude lower than that of an aqueous solution. There was a drawback that the voltage rise at the initial stage of discharge was slow. In addition, as a method for manufacturing a positive electrode plate made only of oxidized steel with good electrical conductivity, copper oxide and alkali metal oxides, such as Li20
There is a method of making the alkali metal by firing a mixture with oxidized steel and Na20 to drop the alkali metal into oxidized steel. Although a porous positive electrode with excellent electrical conductivity can be obtained by this method, it has the following drawbacks.

That is, the melting point of the alkali metal oxide is quite high, for example, Li20 has a melting point of 170,000 or more. Therefore, when an alkali metal is dissolved in oxidized steel, both the oxidized steel and the alkali metal oxide are solid, and a solid phase-solid reaction occurs. The distribution of alkali metal oxides on the surface of oxidized steel tends to be non-uniform because it is a solid, so it is necessary to repeat the cycle of heating and crushing several times. In Samurai Publication No. 51-12272y, the oxidized steel is first heated once in order to eliminate the alkali metals, and the obtained hard shell is passed through a 200-mesh sieve once, and then heated again. A molded sakio positive electrode plate is obtained. The present invention is characterized in that lithium carbonate is used in place of this secondary lithium oxide.

The melting point of lithium carbonate is 618°C, and above this temperature, lithium carbonate becomes a liquid. A mixture of lithium carbonate and oxidized steel is heated to a temperature higher than the melting point of lithium carbonate, the melting point of oxidized steel (10
When 2 is heated to a temperature below C), lithium carbonate first melts and uniformly wets the surface of the oxidized steel, and then the reaction between lithium carbonate and copper oxide proceeds gradually, and lithium oxide is formed. It becomes solid solution oxidized steel. According to this method, the distribution of lithium is more uniform than in the secondary method,
Heating once is sufficient. Therefore, by using lithium carbonate, it is possible to obtain a positive electrode plate with good electrical conductivity and sufficient strength by uniformly dissolving lithium into solid solution by simply heating a mixed molded body of lithium carbonate and copper oxide once. Can be done. Examples of the present invention will be described below.

First, cupric oxide powder and lithium carbonate powder were mixed at a molar ratio of 2:2, and the mixture was mixed with a diameter of 4.2 mm and a thickness of 1.5 mm. It was shaped like a disc on the side of the ship. The porosity of this molded body was 37%. Next, this molded body was placed in the atmosphere at a temperature of 80°C.
The product was fired at 0 qo for 5 hours to cause the cupric oxide and lithium carbonate to react and bind together, thereby obtaining a porous positive electrode. The porosity of the positive electrode is
If the pellet before firing has a porosity of 40% or more, it will easily collapse during handling after molding, so it is desirable to have a porosity of 40% or less. In addition, with a porosity of 35% or less,
The thickness of the pellet is reduced, and when it is incorporated into a battery, the contact with the case, which also serves as the positive terminal, is unstable. Addition of lithium carbonate powder is difficult when using only cupric oxide powder, as the pellet after sintering tends to crumble and is difficult to handle. By adding lithium carbonate and sintering, it reacts with cupric oxide, The lithium metal oxide solidifies into cupric oxide, which significantly increases electrical conductivity, and the pellet after solidification becomes strong enough to be handled.

Figure 1 shows the amount of lithium carbonate in the mixture and the electrical conductivity of the resulting precipitated porous material.

It shows the relationship between (Q and skin), and the lithium carbonate content is 1
．． The electrical conductivity is maximum in the range of 5 to 3.0 mol%. Regarding the firing temperature, in the example, firing was performed at 800 qo, but the melting points of lithium carbonate and cupric oxide are 618 qo and 1026 qo, respectively, and below 618 qo, the electrical conductivity is low and the competitive bond is not sufficient. Ta.

Moreover, at 1026 qo or more, cupric oxide melted and did not exist as pellets. 618oC~102o
There was no big difference in the range of , and both electrical conductivity and sperm competition were good.

In the battery using the porous positive electrode obtained in the above manner, the distance between the electrodes is set to a maximum of 4 mm, and the positive electrode itself has a liquid-retaining property to maximize the surface contact of the electrolyte. , the reaction surface area is increased, and it is expected that the radiation fin characteristics will be improved and stabilized, and a high-energy density battery with excellent discharge capacity can be expected because it does not contain any substrates such as lead-in capacitors, binding materials, or liquid-containing materials.

FIG. 2 shows a lithium battery using the above-mentioned positive electrode.

Reference numeral 1 denotes an upper case made of stainless steel, and a packing 2 made of polypropylene is inserted around its periphery.

A disk-shaped metal lithium negative electrode 3 having a diameter of 4.6 mm and a thickness of 0.9 mm is crimped onto the inner surface of the upper case 1, and a separator 4 made of a microporous film made of polypropylene,
After inserting the porous positive electrode 5 of the present invention, an electrolytic solution consisting of propylene carbonate in which 1 mole of lithium perchlorate is dissolved is injected, and the stainless steel lower case 6 is aligned with the packing 2, and the opening of the lower case is It is caulked and sealed. Battery A with the above configuration, and batteries B, C, D with conventional configurations shown in Figures 3, 4, and 5, each using a positive electrode made of oxidized second node powder, and batteries similar to Figure 2. The composition is 100 parts by weight of cupric oxide, 5 parts of guide fin material, and 7 parts of binder.
FIG. 6 shows the discharge characteristics when a constant resistance discharge of 2 and 0 and 1 and 0 was performed for a battery E using a positive electrode formed from a mixture of 2 and 0 parts by weight.

As is clear from FIG. 6, the battery using the positive electrode according to the present invention has good voltage stability and is about 15% better in discharge time than the conventional product. As described above, the present invention provides a positive electrode that is easy to manufacture, has excellent discharge characteristics, and provides a button-shaped organic electrolyte battery that has particularly high energy density.

[Brief explanation of the drawing]

Fig. 1 shows the relationship between the content of lithium carbonate in a mixture of cupric oxide and lithium carbonate and the electrical conductivity of the obtained positive electrode, and Fig. 2 shows the relationship between the content of lithium carbonate in a mixture of cupric oxide and lithium carbonate and the electrical conductivity of the obtained positive electrode. FIGS. 3 to 5 are longitudinal sectional views of subordinate batteries, and FIG. 6 shows discharge characteristics of various batteries. Figure 1 Figure 2 Figure 3 Figure 4 Figure 5 Figure 6

Claims (1)

[Claims] 1. A mixture of cupric oxide powder and lithium carbonate is molded, and the molded body is sintered at a temperature below the melting point of cupric oxide and above the melting point of lithium carbonate to form cupric oxide powder. A method for producing a positive electrode for a battery, characterized by obtaining a porous copper body. 2. The content of lithium carbonate in the mixture is 1.5 to 3.
The method for producing a positive electrode for a battery according to claim 1, wherein the content is 0 mol%. 3. The method for producing a battery positive electrode according to claim 1 or 2, wherein the molded body has a porosity of 35 to 40%.