JPH0355029B2 - - 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 indium, In, Nb _1-y In _y S _2+1.5y (y: 0.01~
0.1) and which exhibits good charge/discharge cycle characteristics.

Function Nb _1-y In _y , which is a novel positive electrode material according to the present invention
S _2+1.5y is Nb ⁴⁺ of NbS ₂ (ion radius is 0.63 Å)
By partially substituting In ³⁺ (ion radius: 0.81 Å), distortion of the crystal due to the movement of Cu ⁺ ions into and out of the SS layer is reduced, and Cu ⁺ ions can be stored between the SS layers. During battery discharge, the discharge capacity can be increased crystallographically or electrostatically.

A solid electrolyte secondary battery using the positive electrode material has a high capacity and can provide 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 Nb _0.98 In _0.02 S _2.03 positive electrode. Figure 2
When a solid electrolyte secondary battery with a diameter of 7 mm and having the cross-sectional structure shown in is discharged at a constant current value of 100 μA at 20°C, the change in battery voltage is expressed as the x value, that is, the change in Cu from the negative electrode as the discharge progresses. ⁺ ions are occluded between the layers of the positive electrode, and the positive electrode is expressed as Cu _x Nb _0.98 In _0.02 S _2.03 , and this x value is 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, as discharge progresses, and this decrease continues until x is around 0.28, and a plateau appears when x exceeds 0.30.

Curve b indicates that y=0 for the positive electrode material, i.e.
This shows the battery voltage when a battery using NbS ₂ containing no In was discharged in the same way as battery a. The manner in which the battery voltage decreases when x is between 0 and 0.28 is as follows from curve b for a battery using NbS ₂ as a positive electrode shown as a comparative example, and curve a for a battery using Nb _0.98 In _0.02 S _2.03 as a positive electrode according to the present invention. is more gradual.

That is, Nb _1-y In _y S _2+1.5y (y: 0.01 to 0.10)
can maintain a single layered crystal structure until x is around 0.28, and can smoothly import and remove Cu ⁺ ions until x is around 0.28.

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 Nb _1-y In _y
It is inferior to 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.

Nb _1-y In _y , a novel positive electrode material according to the present invention
S _2+1.5y is produced by gradually feeding sulfur vapor into a quartz glass container containing a mixture of metallic Nb powder, metallic In powder, or Nb and In alloy powder in a predetermined ratio, and heating the reaction at 900℃. Or, as a simpler method,
Mix NbS ₂ powder and In ₂ S ₃ powder at a predetermined ratio,
It can also be obtained by molding pellets of about 7 mmφ under a pressure of about 3 tons, vacuum-sealing them in a quartz glass tube at a pressure of 0.1 Torr or less, and heating and reacting 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.
Nb _1-y In _y S _2+1.5y of 0.10, 0.20, and 0.30 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): Nb _1-y In _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+RbCu ₄ I _1.5 Cl _3.5
(Weight ratio 1:3.4:1.2)...0.075gr The above cathode powder, solid electrolyte powder, and anode powder are pressed into three layers under a pressure of about 3 tons to form L battery pellets, and then the cathode and anode 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.
1 is a positive electrode layer, 2 is a solid electrolyte layer, 3 is a negative electrode layer, 4
5 is a current collector, 5 is an electrode lead, and 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
This figure 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 at 0.01, 0.02, 0.01, 0.02,
It can be seen that the battery using Nb _1-y In _y S _2+1.5y containing 0.05 and 0.10 as the positive electrode has excellent cycle characteristics.

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, Nb _1-y In _y S _2+1.5y is used as the positive electrode material.
Solid electrolyte secondary batteries, which are composed of a Cu-based negative electrode and a Cu ⁺ ion conductive solid electrolyte, have low polarization, that is, a gradual drop in battery voltage during discharge, and excellent charging properties.・Gives discharge characteristics.

[Brief explanation of drawings]

Fig. 1 is a diagram showing voltage changes during discharging of a solid electrolyte secondary battery according to an embodiment of the present invention, Fig. 2 is a cross-sectional view showing the structure of the battery, and Fig. 3 is a diagram showing charging and discharging of the same battery. Cycle characteristic diagram, FIG. 4 is a charge/discharge cycle characteristic diagram 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 Consists of a negative electrode mainly composed of copper, a Cu ⁺ ion conductive solid electrolyte, and a positive electrode mainly composed of a sulfide represented by Nb _1-y In _y S _{2 + 1.5y} (y: 0.01 to 0.1) A solid electrolyte secondary battery characterized by: