JPH0122709B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a secondary battery in which all battery power generation elements are solid.

Structure of conventional examples and their problems Batteries whose power generation elements are all solid, that is, batteries that use a solid electrolyte and solid positive and negative electrode materials, are smaller and smaller than conventional batteries that use liquid electrolytes. It is easy to make it thin, and it is difficult to cause electrolyte shortening, so it is easy to separate the cells, and it is convenient for stacking. Furthermore, the battery container containing the power generation element has the advantage that an inexpensive plastic package can be used instead of the metal container normally used in batteries using liquid electrolytes.

However, since all of the power generating elements are provided in solid form, the electrical contact between each element of the battery becomes loose as the battery charges and discharges, due to changes in the volume of the positive or negative electrode as the battery charges and discharges. However, there is a drawback that internal resistance and polarization increase, resulting in a decrease in battery performance. The internal stress within the positive or negative electrode that occurs during charge/discharge reactions in a solid electrolyte battery is difficult to relax within the positive or negative electrode due to deformation of the positive or negative electrode, such as in a positive or negative electrode that contains a liquid electrolyte. This stress is concentrated at the contact portion between the positive and negative electrodes and the current collector, and in some cases, at the contact portion between the positive electrode or the negative electrode and the solid electrolyte layer acting as a separator.
Normally, in solid electrolyte batteries, an appropriate amount of solid electrolyte is coexisting in the positive and negative electrodes in order to reduce polarization of the positive and negative electrodes, so the elastic properties of the positive and negative electrodes and the solid electrolyte are similar. ,
Deterioration in battery performance due to damage to the contact portion between the positive electrode or the negative electrode and the solid electrolyte layer is generally smaller than deterioration due to poor contact between the current collector and the electrode.

Purpose of the Invention The purpose of the present invention is to provide a solid electrolyte secondary battery that prevents poor contact between elements due to changes in the volume of positive and negative electrodes associated with charging and discharging reactions, and has excellent repeated charging and discharging performance. do.

Structure of the invention By using a conductive flexible carbon film in which carbon fibers are dispersed in synthetic rubber as a current collecting material, it is possible to effectively absorb and release the internal stress generated inside the battery during charging and discharging reactions of the battery. do.

DESCRIPTION OF EMBODIMENTS Example 1 FIG. 1 shows a cross-sectional structure of an embodiment of a solid electrolyte secondary battery according to the present invention. 1 is a positive electrode layer made of a mixture of positive electrode active material Cu _0.1 Tis ₂ and _{solid electrolyte} RbCu ₄ I _1.5 Cl _{3.5 ;} 2 is a negative electrode active material Cu and _solid electrolyte RbCu ₄ I _1.5 Cl ₃ a negative electrode layer consisting of a mixture of _.5 ;
3 is a solid electrolyte layer (RbCu ₄ I ₁ . ₅ Cl ₃ . ₅ ), 4 is an electrode lead, and 5 is a plastic package. 6 is a current collector film made of carbon film according to the present invention. This carbon film uses styrene-butadiene rubber (SBR) as a synthetic rubber, and is made by dispersing carbon fibers with a length of 30 to 100 μ and a wire diameter of 7 to 8 μ. The film has a sheet resistance value of approximately 1Ω.

A current collector film is placed on the positive electrode 1 side and the negative electrode side 2 of a battery pellet with a diameter of 7 mmφ and a thickness of about 1.5 mm obtained by press-molding three layers: a positive electrode layer, a solid electrolyte layer, and a negative electrode layer. 6 at about 80℃ for 5 to 6 seconds.
Pressure bonding is performed at a pressure of approximately 20 kg/cm ² , and then electrode leads are placed on each current collector surface, and heat and pressure bonding is performed at approximately 140° C. for 10 to 15 seconds. After a current collector film 6 and an electrode lead 4 are provided on the battery pellet, the battery is constructed by covering the battery pellet with a room temperature curing epoxy resin 5 containing SiC filler.

Figure 2 shows the battery voltages Vct and Vdt at the end of charging and discharging in each cycle when such a battery is repeatedly charged and discharged at a constant current value of 100 μA at room temperature in 0.2 mAh increments. The horizontal axis represents the number of discharge cycles. In this diagram, battery A
is a battery equipped with a carbon film current collector in which carbon fibers are dispersed in synthetic rubber according to the present invention, and battery B is a battery equipped with an epoxy resin current collector, which is conventionally used for the MnO _2- electrode current collector in a laminated dry cell. The only difference is that it has a current collector obtained by applying and baking conductive carbon paint, which is made by dispersing acetylene black powder and carbon powder, on the positive and negative electrode sides of the battery pellet. This is a solid electrolyte secondary battery having a cross-sectional structure similar to that shown in .

For battery A, Vc't and Vdt hardly change from their initial values even after 300 charge/discharge cycles, but for battery B, Vct gradually increases compared to the initial values from around the 150th cycle. and Vdt begins to decrease. Battery A having the carbon film according to the present invention is a battery with extremely good charge/discharge cycle characteristics.

Example 2 FIG. 3 shows a cross-sectional structure of a stacked solid electrolyte secondary battery which is another example of the solid electrolyte secondary battery according to the present invention. In FIG. 3, the same numbers as in FIG. 1 indicate the same battery elements.

Cell pellet 3 with a diameter of 7 mmφ and a thickness of approximately 1.5 mm
It is made up of an accumulation of ke.

Figure 4 shows the battery shown in Figure 3 at room temperature.
Vct and Vdt in each cycle when charging and discharging are repeated at 0.2mAh with a constant current of 100μA,
It is shown against the number of discharge cycles. In this figure, battery C is a battery equipped with a carbon film in which carbon fibers are dispersed in synthetic rubber according to the present invention, and battery D is a battery equipped with a carbon film in which carbon fibers are dispersed in synthetic rubber (butadiene styrene rubber). This battery has the same cross-sectional structure as the one shown in Figure 3, except that it uses a carbon film as a current collector.Battery E has the same cross-sectional structure as the one shown in _Fig . The only difference is that it has a current collector obtained by applying and baking a conductive carbon paint made by dispersing acetylene black powder and carbon powder in an epoxy resin, as shown in Figure 3. This is a stacked solid electrolyte secondary battery that has a cross-sectional structure similar to that of the previous battery.

For battery C, Vct and Vdt hardly change from their initial values even after 300 charge/discharge cycles, but for battery D they gradually change from about the 100th cycle, and for battery E from about the 45th cycle. Vct increases and Vdt begins to decrease.

Example 3 FIG. 5 shows the cross-sectional structure of yet another example of the solid electrolyte secondary battery according to the present invention. 7 _is positive electrode active material _Ag0.1TiS2 and _solid electrolyte
a positive electrode layer consisting of a mixture of RbAg ₄ I ₅ (SiO ₂ dispersion);
8 is negative electrode active material Ag and solid electrolyte RbAg ₄ I ₅ (SiO ₂
The negative electrode layer 9 is a solid electrolyte layer RbAg ₄ I ₅ (SiO ₂ dispersed). Others, Figure 5
Inside, the same numbers as in FIGS. 1 and 3 indicate the same battery components. The size of the battery pellet is 7 mmφ and 1.2 mm thick.

FIG. 6 shows the battery shown in FIG. 5 at room temperature.
The battery voltages Vct and Vdt at the end of charging and discharging in each cycle are shown against the number of charging/discharging cycles when charging and discharging are repeated at 0.1 mAh at a constant current of 20 μA. In this diagram, battery F
is a battery equipped with a carbon film current collector in which carbon fibers are dispersed in synthetic rubber according to the present invention, and Battery G is conventionally used as a MnO _2- electrode current collector in a laminated dry cell. The solid electrolyte 2 differs only in that it has a current collector obtained by applying and baking a conductive carbon paint made by dispersing acetylene black and carbon powder in an epoxy resin. Next battery.

For battery F, Vct and Vdt hardly change from their initial values even after 300 charge/discharge cycles, but for battery G, Vct gradually increases and Vdt decreases from around the 180th cycle. Begin to.

According to the present invention, since the current collectors of the positive and negative electrodes are composed of thermocompression-adhesive flexible conductive films made of synthetic rubber with carbon fibers dispersed therein, changes in volume of the positive and negative electrodes due to charge/discharge reactions are absorbed. However, a solid electrolyte secondary battery that can maintain good contact at all times and has excellent charge/discharge cycle characteristics can be realized.

[Brief explanation of drawings]

Figure 1 is a cross-sectional view showing the structure of a solid electrolyte secondary battery, Figure 2 is a graph showing the charge/discharge cycle characteristics of the battery, and Figure 3 is a cross-sectional view showing the structure of a stacked solid electrolyte secondary battery. Figure 4 is a graph showing the charge/discharge cycle characteristics of the battery, Figure 5 is a cross-sectional view showing the structure of a solid electrolyte secondary battery, and Figure 6 is a graph showing the charge/discharge cycle characteristics of the battery. It is. 1... Positive electrode layer, 2... Negative electrode layer, 3... Solid electrolyte layer, 6... Current collector.

Claims (1)

[Scope of Claims] 1. A solid electrolyte secondary battery comprising a solid positive electrode 1, a solid negative electrode 2, a solid electrolyte 3, and a current collector 6 for positive and negative electrodes, comprising: Reference numeral 6 refers to a solid electrolyte secondary battery comprising a conductive carbon film, wherein the film is made of synthetic rubber with carbon fibers dispersed therein.