JPH0534788B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD The present invention relates to a charging/discharging method for solid electrolyte secondary batteries. Structures of conventional examples and their problems In general, secondary batteries have characteristics specific to the battery system determined by the electrochemical properties such as the positive electrode active material, negative electrode active material, reversibility of the electrolyte, overvoltage, and decomposition voltage. It has a charging/discharging limit voltage or quantity of electricity beyond which the repeated charging/discharging characteristics are extremely degraded. In other words, nickel-cadmium batteries and lead-acid batteries, which are typical examples of conventional secondary batteries, have been studied for many years, and the current charging and discharging limit voltages and electricity amount unique to each battery system have been determined. A discharge method has been adopted. In order to put a secondary battery composed of a new positive electrode active material, negative electrode active material, and electrolyte into practical use, the charging/discharging limit voltage or amount of electricity unique to this battery system must be determined, and the charging/discharging method unique to this battery system must be determined. It is an essential requirement to provide On the other hand, unlike conventional nickel-cadmium batteries that use liquid electrolytes, solid electrolyte secondary batteries that use solid electrolytes do not leak in principle and can be made smaller and thinner very easily. , has been attracting attention as a small power source for the microelectronics field, which has achieved remarkable power and energy savings in recent years. Among these solid electrolyte secondary batteries, Cu _x TiS ₂ and Cu _x TiCr _y
An interlayer compound such as S _2+1.5y is used as a positive electrode active material, and Cu
Secondary batteries that use ionic conductive solid electrolytes have excellent battery characteristics because the positive electrode active material has excellent reversibility, and the ionic conductivity of the solid electrolyte is high enough to be comparable to organic electrolytes and is chemically stable. It is now attracting attention as a solid electrolyte secondary battery that is promising. The battery reaction of the solid electrolyte secondary battery is negative electrode; Cu discharge ---→ ←-- charging Cu +e positive electrode; Cu _x TiS ₂ Cu _x TiCr _g S _2+1.5y +δCu +δe discharge ---→ ←-- charging Cu _x Although expressed as +δTiS ₂ Cu _x +δTiCr _g S _2+1.5y , the reaction at the negative electrode is a dissolution precipitation reaction of copper (Cu), and there is no particular restriction on its reversibility. The reaction at the positive electrode is a reaction in which Cu enters and exits between the S and S layers of TiS or TiCr _y S _2+1.5 y, but the reversibility of this reaction is not known at all, and therefore there is a possibility that the battery will not perform well. It is difficult to determine the charge/discharge limits that provide repeatability characteristics, which is an obstacle to putting the solid electrolyte secondary battery into practical use. OBJECTS OF THE INVENTION An object of the present invention is to provide a charging/discharging method that provides good repeated charging/discharging characteristics for a solid electrolyte secondary battery. Structure of the Invention A solid electrolyte secondary battery to which the present invention is applied is a Cu
Positive electrode mainly composed of Cu _x TiS ₂ , Cu _x TiCr _y S _2+1.5y
(0=x<0.2, 0.01<y<0.2) A positive electrode mainly composed of a compound selected from the group of RbCu ₄ I _1.5 Cl _3.5 ,
It is composed of a Cu ion conductive solid electrolyte such as RbCu ₄ I _1.25 Cl _3.75 . When using the battery, the charging limit battery voltage should be 0.60 + i _c R _c (volts) or less, and the discharging limit battery pressure should be 0.33 - i _d R _d
(Vault) Charging and discharging should be repeated to satisfy the above conditions. Here, i _c and _d are charging and discharging current values, respectively, and the unit is ambare. R _c and R _d are the DC internal resistance values of the battery during charging and discharging, respectively, in ohms. The battery voltages V _{cp and} V dp when the charging or discharging current is reduced to 9/10 for approximately 100 milliseconds while the battery is being charged or discharged, and the battery voltages V _cc and V _dc just before the current is reduced _. From this, R _c = 10・(V _cc −V _cp /i _c R _d = 10・(V _dp −V _dc /i _d ). This is the limit voltage in the sense that discharge is performed below the voltage value, and the discharge limit battery voltage is the limit voltage in the sense that discharge is performed above this voltage.Description of Examples Solid electrolyte with the configuration shown below A secondary battery is constructed and the present invention is applied. Example 1 Electrolyte: 0.05 gr of RbCu ₄ I _1.5 Cl _3.5 Negative electrode mixture: 4.75 parts by weight of a mixture of 80% by weight Cu powder and 20% by weight Cu ₂ S and the electrolyte 0.2gr of 1.25 parts by weight mixture Positive electrode mixture: 2 parts by weight of Cu _0.1 TiS ₂ and the electrolyte 3
The above materials were pressure molded into three layers at a pressure of 2 tons/cm ² to assemble a battery with a diameter of 7 mm and a pressure of about 1 mm. These batteries were subjected to nine types of charge/discharge cycle tests shown in the following table a at room temperature with constant current pulses of 90 μA for 100 milliseconds once every 60 seconds, typically at 100 μA.
I did ~h. The same table shows the undischarged and uncharged battery voltages in the first cycle. The DC internal resistance of the batteries used in Table 1 for each test a to h shows almost no change during charging or discharging, and remains almost the same at room temperature over all the cycles tested.
R _c R _d is 220Ω.

【table】

[Table] Figure 1 shows the results in each cycle test from a to h.
It shows the relationship between the number of cycles and the undischarged voltage (solid line) and the charged unvoltage (broken line), and according to the charging/discharging method of the present invention, the charging limit voltage is 0.60 + 10 ^-4 ·
220 = 0.622 volt or less and the discharge limit voltage is
It can be seen that the charge/discharge cycle tests a, b, c, d, and e, in which the voltage was 0.33−10 ⁻⁴ ·220 = 0.308 volt or higher, provided good repeated charge/discharge characteristics that could withstand practical use. In addition, when the charging voltage or discharging voltage exceeds the limit voltage indicated by the present invention at the end of the cycle test in d and e, the charging and discharging voltages are suddenly repeated.
It can be seen that the discharge characteristics deteriorate. Example 2 Electrolyte: 0.05gr of RbCu ₄ I _1.5 Cl _3.5 Negative electrode mixture: 0.2gr of a mixture of 4.75 parts by weight of a mixture of 80% by weight Cu powder and 20% by weight of Cu ₂ S and 1.25 parts by weight of the electrolyte Positive electrode mixture: Cu A mixture of 2 parts by weight of _0.05 TiCr _0.025 S _2.0375 and 3 parts by weight of the electrolyte was press-molded into 3 layers with 0.06 gr of the above materials at a pressure of 2 tons/cm ² to form a battery with a diameter of 7 mm and a pressure of approximately 1 mm. Assembled. These batteries at room temperature, typically 100μA, 60
Nine types of charge/discharge cycle tests shown in the table below are performed using a constant current pulse of 90 μA for 100 milliseconds once every second.
I did steps a′ to h′. The same table shows the undischarged and uncharged battery voltages in the first cycle. The DC internal resistance of the batteries used in Table 2 for each test a' to h' hardly changes during charging or discharging, and remains almost the same at room temperature over all the cycles tested.
R _c R _d is 220Ω.

[Table] Figure 2 shows the relationship between the number of cycles, discharge and no-voltage (solid line), and charge and no-voltage (dashed line) in each cycle test from a' to h'. , the charging limit voltage is 0.60+10 ^-4・220=
0.622 volt or less and discharge limit voltage is 0.33−
It can be seen that the charge/discharge cycle tests a, b, c, d, and e, in which the voltage is 10 ^-4 · 220 = 0.308 volts or more, provide good repeated charge/discharge characteristics that can withstand practical use. Furthermore, in d and e, it can be seen that when the charging voltage or discharging voltage exceeds the limit voltage indicated by the present invention at the end of the cycle test, the charging/discharging characteristics rapidly deteriorate repeatedly. Effects of the Invention According to the present invention, a solid electrolyte secondary battery can exhibit good repeated charge/discharge characteristics.

[Brief explanation of drawings]

Figure 1 shows the number of charging/discharging cycles and battery voltage characteristics during charging/discharging, showing the effects of the charging/discharging method of an embodiment of the present invention, and Figure 2 shows the characteristics of the battery voltage during charging/discharging. It is a relationship diagram.

Claims (1)

[Claims] 1. A negative electrode mainly made of metallic copper, Cu _x TiS ₂ , Cu _x
A positive electrode mainly composed of a compound selected from the group of TiCr _y S _2+1.5y (0x<0.2, 0.01<y<0.2) and Cu
When charging and discharging a solid electrolyte secondary battery composed of an ionically conductive solid electrolyte, the charging limit battery voltage is 0.60.
A charging/discharging method for a solid electrolyte _secondary battery, characterized in that the discharge limit battery voltage is 0.33−i _d R d or more and the discharge limit battery voltage is 0.33 ₋ i d R _d or more. However, i _c and i _d are the charging and discharging current values (in amperes), respectively, and R _c and R _d are the charging and discharging current values, respectively.
DC internal resistance value of battery during discharge (unit: ohm)
The value given by R _c = 10・(V _cc −V _cp /i _c R _d =10・(V _dp −V _dc /i _d) , V _cp and V _dp are during charging and discharging, This is the battery voltage (in volts) when the charging current value or discharging current value is reduced by 9/10 for approximately 100 milliseconds, and V _cc and V _dc are the battery voltages (in volts) before the reduction. .