JPH0355026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to an all-solid-state solid electrolyte secondary battery using a solid electrolyte having high ionic conductivity at room temperature.

Conventional technology Batteries using solid electrolytes that have high ionic conductivity at room temperature can be made into an all-solid state, so they are highly reliable with essentially no leakage and extremely low self-discharge during storage. It becomes a sexual battery.

As for such batteries, primary batteries, whose life spans end after one discharge, have conventionally been proposed. However, when the battery is used as a power source in the field of microelectronics, which is characterized by miniaturization of electric circuit elements, the battery is naturally required to be small. As batteries become smaller, their capacity decreases, so secondary batteries, which can be used repeatedly, are becoming more useful in place of primary batteries, which expire after a single discharge.

A necessary requirement when constructing a secondary battery is that the positive electrode material and the negative electrode material have the ability to perform a reversible electrochemical reaction during charging and discharging of the battery.

In particular, metal chalcogenides are used as positive electrode materials in batteries using liquid electrolytes, and metal chalcogenides are used as negative electrode materials.
It has long been known that the use of alkali metals such as Li is useful. This metal chalcogenide has a layered crystal structure, and when the battery is discharged, the alkali metal ions released from the negative electrode are occluded between the layers, and when the battery is charged, the alkali metal ions are released from the interlayers, resulting in a reversible battery reaction. It has the feature of being able to do the following.

Problems to be Solved by the Invention It is possible to use the metal chalcogenide described above as a positive electrode material for an all-solid-state secondary battery that has a copper-based negative electrode and a Cu ⁺ conductive solid electrolyte. As a person skilled in the art would easily think, it was not known at all which types of metal chalcogenides and to what extent Cu ⁺ ions can be freely transferred between the layers.

Means for Solving the Problems The present invention consists of a negative electrode mainly composed of Cu, a Cu ⁺ ion conductive solid electrolyte, and a part of NbS ₂ as a positive electrode material, which allows Cu ⁺ ions to be freely transferred between the layers. A new compound with a layered crystal structure substituted with chromium, Cr, and with Cu inserted in advance, Cu _x Nb _1-y Cr _y S _2+1.5y (x: 0.05-0.15, y: 0.01
-0.10) and exhibits good charge/discharge cycle characteristics.

Function Cu _x Nb _1-y, a novel positive electrode material according to the present invention
Cr _y S _2+1.5y is Nb ⁴⁺ of NbS ₂ (ion radius is 0.63 Å)
By partially substituting Cr ³⁺ (ion radius: 0.55 Å) and at the same time inserting Cu between the S-S layers,
To reduce the crystal distortion caused by the insertion and removal of Cu ⁺ into and out of the SS layer, and to increase the amount of Cu ⁺ that can be stored between the SS layers, that is, the discharge capacity during battery discharge, either crystallically or electrostatically. I can do it.

A solid electrolyte secondary battery using the positive electrode material can have high capacity and good charge/discharge cycle characteristics.

Examples Example 1 Curve a in Figure 1 uses RbCu ₄ I _1.5 Cl _3.5 as the Cu ⁺ ion conductive solid electrolyte, and is composed of a negative electrode mainly composed of Cu and a Cu _0.1 Nb _0.95 Cr _0.05 S _2.08 positive electrode. The change in battery voltage when a solid electrolyte secondary battery with the cross-sectional structure shown in Figure 2 is charged at 100 μA until x = 0 and then discharged at a constant current of 100 μA at 20°C is shown below. , x values are shown on the horizontal axis. As can be seen from this curve a, the battery voltage shows a monotonous decrease as x increases, that is, the discharge progresses, and this decrease continues until x is around 0.30, and a plateau appears when x exceeds 0.30. Moreover, it is gentler than the curve b showing the discharge characteristics of a battery using NbS ₂ as a positive electrode in which x=0 and y=0 shown as a comparative example.

That is, Cu _x Nb _1-y Cr _y S _2+1.5y (x: 0.05~
0.15, y: 0.01-0.10) can maintain a single layered crystal structure until x is around 0.30, and Cu ⁺
Ions can be taken in and out smoothly.

For NbS ₂ , the plateau of the cell voltage is x=
It starts to appear around 0.25, the battery voltage is lower than a, and the ease of introducing and removing Cu ⁺ ions is Cu _x Nb _1-y
It is inferior to Cr _y S _2+1.5y .

Curve a in FIG. 3 shows a battery similar to the battery according to the invention and exhibiting the characteristics shown in FIG.
This shows the relationship between the battery voltage at the end of each cycle and the number of charge/discharge cycles when charging and discharging are repeated at 20℃ and 100μA between 0.25 and 20℃, and the number of charge/discharge cycles is good. give.

Cu _x Nb _1-y, a novel positive electrode material according to the present invention
Cr _y S _2+1.5y is metal Nb powder, metal Cr powder, metal
A mixture of Cu powder at a specified ratio, or
It can be obtained by gradually feeding sulfur vapor into a quartz glass container containing an alloy powder of Nb, Cr, and Cu and heating it at 900℃, or as a simpler method, combining NbS ₂ powder and Cr ₂ S ₃ powder and
The mixture is mixed with Cu powder at a predetermined ratio and formed into pellets of approximately 7 mm diameter under a pressure of approximately 3 tons, which is vacuum sealed in a quartz glass tube at a pressure of 0.1 Torr or less.
It can also be obtained by heating reaction at 900°C for about 72 hours.

Example 2 The y value is 0.01, 0.02, 0.05, depending on the amount of raw material charged.
0.10, 0.20, and 0.30 Cu _0.1 Nb _1-y Cr _y S _2+1.5y were synthesized, and a solid electrolyte battery with a diameter of 7 mm and having a cross-sectional structure shown in FIG. 2 was constructed using these as positive electrode materials.

Positive electrode (powder): Cu _0.1 Nb _1-y Cr _y S _2+1.5y +RbCu ₄ I _1.5
Cl _3.5 (weight ratio 2:3)...0.06gr Solid electrolyte (powder): RbCu ₄ I _1.5 Cl _3.5 ...0.05gr Negative electrode (powder): Cu+Cu _1.59 S+PbCu ₄ I _1.5 Cl _3.5
(Weight ratio 1:3.4:1.2)...0.075gr The above positive electrode powder, solid electrolyte powder, and negative electrode powder are pressed into three layers under a pressure of about 3 tons to form battery pellets, and then the positive electrode and negative electrode sides are conductive. A battery was fabricated by thermocompressing a current collector made of carbon film and an electrode lead, and then coating the entire battery with epoxy resin. Figure 2 shows a cross-sectional view of the solid electrolyte secondary battery made in this way, where 1 is a positive electrode layer, 2 is a solid electrolyte layer, 3 is a negative electrode layer, 4 is a current collector, and 5 is an electrode lead. , 6 is a resin package.

Figure 4 shows the battery made in this way.
℃, the value of x ranges from 0 to 0.25 at a constant current value of 100μA
It shows the relationship between the battery voltage at the end of discharge of each cycle and the number of charging/discharging cycles when charging and discharging is performed.According to the present invention, Cr is 0.01 as a y value,
It can be seen that batteries using Cu _0.1 Nb _1-y Cr _y S _2+1.5y containing 0.02, 0.05, and 0.10 as the positive electrode have excellent cycle characteristics.

Example 3 The amount of Cu inserted in advance is x=0.05, 0.1,
0.15, Cu _x Nb _0.95 Cr _0.05 S _2.08 , and use these as positive electrode materials.The structure shown in Figure 2 has a diameter of 7 mm.
A solid electrolyte battery was constructed. solid electrolyte material,
The weight and composition of the negative electrode material, positive electrode, negative electrode, and solid electrolyte are the same as in Example 2. The method of assembling the battery is also the same as in Example 2.

Figure 5 shows the battery made in this way.
It shows the relationship between the battery voltage at the end of each cycle and the number of charge/discharge cycles when charging and discharging at a constant current value of 100 μA and x in the range of 0 to 0.25. Provides excellent cycle characteristics of over 100 cycles.

In addition, in the examples of the present invention, RbCu ₄ I _1.5 Cl _3.5 was used as the Cu ⁺ ion conductive solid electrolyte, but
Other Cu ⁺ ion conductive solid electrolytes, e.g.
RbCu ₄ I _1.25 Cl _3.75 , Rb _0.75 K _0.25 Cu ₄ I _1.5 Cl _3.5 , CuBr
It goes without saying that the same effects as the present invention can be obtained by using a solid electrolyte to which a quaternary ammonium salt such as hexamethylenetetramine is added.
Furthermore, as a negative electrode mainly composed of Cu,
In addition to the mixture of Cu _1.59 S + Cu ⁺ ion-conductive solid electrolyte, mixtures of Cu + Cu ⁺ ion-conductive solid electrolyte and mixtures of Cu ₅ Mo ₆ S ₈ + Cu ⁺ ion-conductive solid electrolyte can also be used. It goes without saying that the same effect as the invention can be obtained.

Effects of the invention According to the present invention, Cu _x Nb _1-y Cr _y is used as a positive electrode material.
A solid electrolyte secondary battery, which has S _2+1.5y and is composed of a Cu-based negative electrode and a Cu ⁺ ion conductive solid electrolyte, has low polarization, that is, a gradual drop in battery voltage during discharge. , and provides excellent charge/discharge characteristics.

[Brief explanation of drawings]

Figure 1 is a voltage change diagram during discharge of a solid electrolyte secondary battery according to an embodiment of the present invention, Figure 2 is a sectional view showing the structure of the battery, and Figure 3 is a diagram of the charge/discharge cycle characteristics of the battery. , FIG. 4 is a diagram showing the charging/discharging cycle characteristics of the same battery, and FIG. 5 is a diagram showing the charging/discharging cycle characteristics of the same battery. a...Battery of an example of the present invention, b...Battery of a comparative example, 1...Positive electrode layer, 2...Solid electrolyte layer, 3
...Negative electrode layer.

Claims (1)

[Claims] 1 Negative electrode mainly made of copper, Cu ⁺ ion conductive solid electrolyte, and Cu _x Nb _1-y with Cu inserted in advance
Sulfide represented by Cr _y S _2+1.5y (where y:
0.01 to 0.10, x: 0.05 to 0.15).