JPH0123898B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to organic electrolyte batteries, and more particularly to a method for producing an anode using manganese dioxide as an anode active material.

When manganese dioxide is used as an anode active material in an organic electrolyte battery, the water contained therein has a negative effect on cathode active materials such as lithium, so it is necessary to heat-treat the manganese dioxide to remove the water content. Conventionally, the method for heat treatment of this anode was to mix and mold manganese dioxide, a conductive additive, and a binder to make an anode, and then place the anode in a sealed furnace and heat treat it at a predetermined temperature. There is. However, when an anode heat-treated in a sealed furnace is used, the internal resistance of the battery is high, resulting in performance problems.

As a result of various studies on this increase in internal resistance, the present inventors found that when an anode is heat-treated in a sealed furnace, some of the conductive additives and binders mixed in the anode undergo thermal changes. It was revealed that this is due to the formation of modified products. In other words, phosphorous graphite is used as a conductive aid, but it has functional groups such as carboxyl groups at the ends of its crystal lattice, and it is also known that organic substances are attached to the surface of phosphorous graphite. Furthermore, although a synthetic resin is usually used as a binder, the functional groups, attached organic substances, and a part of the binder are thermally decomposed during heat treatment. The resulting modified product is incorporated into the battery while remaining attached to the anode, and the modified product is dissolved in an electrolytic solution containing an organic solvent, and transferred to the cathode side through the separator, forming a coating on the surface of the cathode. appears and inhibits the discharge reaction.

An object of the present invention is to provide a method for manufacturing an anode for an organic electrolyte battery that overcomes the drawbacks of the prior art and has excellent discharge performance.

To achieve this objective, the present invention provides a heat treatment process in which an anode made of a mixture of manganese dioxide, a conductive additive, and a binder is heated to convert manganese dioxide into an intermediate between γ and β forms. It is characterized by performing a predetermined heat treatment while sequentially supplying and discharging steam inside.

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a diagram showing an organic electrolyte battery according to an embodiment of the present invention.

100 parts by weight of electrolytic manganese dioxide and 10 parts by weight of phosphorous graphite
An anode 1 made of a mixture of 1 part by weight and 1 part by weight of polytetrafluoroethylene is inserted into the bottom of an anode can 2, and an electrolyte absorber 3 made of a nonwoven polypropylene fabric is placed thereon. The anode 1 and the electrolyte absorber 3 are each impregnated with a predetermined amount of an electrolyte in which 1 mole of lithium perchlorate is dissolved in a solvent in which propylene carbonate and dimethoxyethane are mixed at a volume ratio of 1:1. let

A cathode terminal plate 5 is fitted into the opening of the anode can 2 via a gasket 4 made of polypropylene.
A stainless steel net 6 is welded to the inner surface of the cathode terminal plate 5, and a cathode 7 made of metallic lithium is pressed onto this.The cathode 7 faces the anode 1 with the separator 3 in between.

Next, a method for manufacturing the anode 1 will be explained with reference to FIGS. 2 to 4.

The anode 1, which is formed by mixing electrolytic manganese dioxide (γ-type MnO ₂ ), a conduction aid, and a binder in a predetermined ratio as described above and press-molding the mixture, is placed in a heat-resistant cassette 8 shown in FIG. 3. . A plurality of through holes 9 are provided in the outer peripheral wall of the cassette 8 to improve air circulation, and inside the cassette 8, as shown in FIG. A large number of anodes 10 and anodes 1 are stored so as to be alternately stacked on top of each other.

The cassette 8 containing the anode 1 is stacked on a perforated plate 13 installed in the inner chamber 12 of the electric furnace 11, as shown in FIG. In this inner chamber 12,
An air supply pipe 14, an exhaust pipe 15, and a thermocouple 16 are inserted, respectively, and a heater 18 is arranged on the peripheral wall 17 of the electric furnace 11. This heater 18
The temperature inside the furnace in the inner chamber 12 is maintained at approximately 400°C,
Air 20 is sent from the air supply pipe 14 into the interior chamber 12 by a blower 19 at a rate of 1/min. This air 20 is sent to a humidifier 21 before being sent to the electric furnace 11.
The high humidity air with a relative humidity of 70 to 95% is sent into the interior room 12. This high-humidity air 20 is heated by a heater 18, passes through a perforated plate 13, flows along the surface of an anode 1 housed in a cassette 8, and is discharged from an exhaust pipe 15. By performing this heat treatment for 4 hours, the crystal structure of manganese dioxide becomes an intermediate between the γ type and the β type. After the heat treatment is completed, dry air that has passed through a compressed air dehumidifier (not shown) is sent into the interior chamber 12 to cool the anode 1.

The heat treatment temperature of the anode is suitably about 250-430°C, preferably about 370-430°C. In the above embodiment, the oxygen-containing gas (air) and moisture were supplied together to the anode, but they can also be supplied through separate systems. In addition to air, the oxygen-containing gas may be oxygen gas alone or a mixture of oxygen gas and other gases such as nitrogen gas. Further, when the oxygen concentration in the manganese dioxide heat treatment atmosphere is high, only moisture in the form of steam may be supplied to the anode by a humidifying means. It is preferable to supply and discharge moisture continuously during the heat treatment of manganese dioxide.
May be intermittent.

When performing heat treatment while supplying a mixed gas of oxygen gas and nitrogen gas into the heated atmosphere of the anode, the anode is treated with various oxygen concentrations in the supplied gas, and the open circuit voltage of the lithium battery assembled using these anodes is determined. Figure 5 shows the change in internal resistance, and Figure 6 shows the change in internal resistance.The number of samples for each type of battery was 30. Curve A in the figure is the supply gas without humidification, curve B
shows the case where humidified supply gas is used. Note that in both figures, the upper end of a line segment extending parallel to the vertical axis in the figure indicates the highest value, and the lower end indicates the lowest value, and the longer the length of the line segment, the greater the dispersion. The circle marked in the middle of the line segment indicates the average value.

As is clear from FIG. 5, by humidifying the supplied gas, the open circuit voltage of each battery is lowered by about 0.1V, but the variation in voltage is very small except for the one with 0% oxygen by volume. Furthermore, as is clear from FIG. 6, by humidifying the supplied gas, the internal resistance of the battery is extremely reduced and the variation is also reduced.

The theoretical basis for why the internal resistance decreases when a specified heat treatment is performed while supplying moisture to the anode using a humidifying means is not clear, but it is possible that thermal decomposition products of conductive aids and binders mixed in the anode It is thought that this is because it dissolves in the supplied moisture and is carried away from the anode along with the moisture.

The present invention has the above-described configuration, and can produce an anode for an organic electrolyte battery having excellent performance.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of essential parts of a lithium battery using an anode made according to an embodiment of the present invention, and FIG. 2 is a schematic configuration diagram of an electric furnace used in an embodiment of the present invention.
Fig. 3 is a perspective view of a heat treatment cassette used in the electric furnace, Fig. 4 is a sectional view showing the state in which the anode is housed in the cassette, and Figs. 5 and 6 are lithium FIG. 2 is an open circuit voltage characteristic diagram and an internal resistance characteristic diagram of a battery. 1...Anode, 11...Electric furnace, 14...Air supply pipe, 15...Exhaust pipe, 19...Blower, 20...
...Highly humid air, 21...humidifier.

Claims (1)

[Claims] 1. An anode is made by mixing and molding manganese dioxide having a γ-type crystal structure, a conductive additive, and a binder.
An organic electrolyte battery characterized in that, in the heat treatment step of heating the anode to convert the manganese dioxide into an intermediate between γ-type and β-type, a predetermined heat treatment is performed while sequentially supplying and discharging water vapor into the heat treatment atmosphere. Manufacturing method for anodes.