JPS59127376A - Solid electrolyte battery - Google Patents

Abstract

PURPOSE:To increase discharge utility of lithium by forming a negative electrode by mixing lithium powder and solid electrolyte powder in a specific ratio. CONSTITUTION:Lithium powder and solid electrolyte powder are mixed in a specified ratio and pressed in a desired shape to form a negative electrode. The negative electrode is stacked with a solid electrolyte layer and they are bonded together by pressing. Lithium nitride family such as LiN, Li3N-LiI, Li3N-LiI- LiOH are preferable as solid electrolyte. Same or different material is used in solid electrolyte used in the negative electrode and that used in the solid electrolyte layer. A mixing ratio of lithium powder and solid electrolyte powder which form a negative electrode is a range of 1:0.7-1:1.8, preferably 1:1-1:1.2.

Description

DETAILED DESCRIPTION OF THE INVENTION The object of the present invention is to improve the discharge characteristics of solid electrolyte batteries using lithium as a negative active material.

Conventional solid electrolyte batteries use lithic cum plates as negative electrodes, but as discharge progresses, a gap 1'' is created between the negative electrode and the solid electrolyte layer, reducing the discharge utilization rate of the negative electrode. The drawback is that sufficient discharge performance cannot be obtained. This is because the discharge reaction of this type of battery is such that lithium gradually ionizes from the side facing the positive electrode on the negative electrode side, passes through the solid electrolyte layer, moves to the positive electrode side, reacts with the positive electrode active material, and produces discharge products on the positive electrode side. However, the negative electrode discharge consumption F
, 'rK, and the solid electrolyte has no elasticity at all, so the solid electrolyte layer cannot follow and deform as the negative electrode wears out due to discharge.

Therefore, it is necessary to pressurize the negative electrode to maintain contact between the negative electrode and the solid electrolyte at all times, but in small and thin batteries, it is difficult to provide such pressurizing means inside the battery. .

In view of these circumstances, the inventors of the tree have conducted various studies and have determined the theoretical volume ratio of lithium powder and isoelectrolyte powder (
volume ratio calculated using theoretical density) is 1. : 0.
7 to 1: Constructing a negative electrode from a mixture of 1.8 discovered that the discharge utilization rate of lithium was improved and a solid electrolyte battery with good discharge characteristics could be obtained, leading to the completion of the present invention. .

In other words, in the great invention, even if the lyticum near the solid electrolyte layer disappears as the discharge progresses, the solid electrolyte 11 dispersed in the negative electrode remains.
By making it possible for lithium ions to migrate to the positive electrode side, the discharge utilization rate of lithium is improved, and a solid electrolyte battery with good discharge characteristics can be obtained. More specifically, in the present invention, by increasing the substantial contact area between lithium and the electrolyte, the current per unit area is reduced, and as a result, the diffusion rate of lithium and the depletion rate of lithium consumed at the interface are reduced. It is thought that this makes it difficult for lithium to peel off and improves the negative electrode utilization rate.

The lithium powder is preferably a fine powder with a mesh size of 60 mesh or more, and the solid electrolyte powder used in the shredded negative electrode is also preferably a fine powder with a mesh size of 60 mesh or more.

Then, the negative electrode (after mixing these lithium powders and solid electrolyte powder in a predetermined ratio, about 0.1 to 1t/α2
Pressure molded into a predetermined shape at a pressure of Note that, after the negative electrode and the solid electrolyte layer are each preformed, the negative electrode and the solid electrolyte layer can also be integrally formed by overlapping them and performing main molding.

Solid electrolytes include Li, gN, Li5N-LiI,
A lithium oxide type material such as Li5N-Lil-LiOH is preferred, and the solid electrolyte used for the negative electrode and the solid electrolyte constituting the solid electrolyte layer may be the same or different.

The mixing ratio of the lithium powder constituting the negative electrode and the solid electrolyte layer powder is preferably in the range of 1:0.7 to 1:1.8 in terms of theoretical volume ratio, and preferably in the range of 1-1 to 1:1.2. . child.

This is because when the amount of solid electrolyte powder added is less than 0.7 in theoretical volume ratio to lithium powder, the effect of mixing the solid electrolyte into the negative electrode is not fully exhibited, and on the other hand, when it exceeds 1.8. This is because the absolute amount of lithium in the negative electrode decreases.

Next, the present invention will be explained with reference to examples.

Example 1 Lithium powder (140 mesh pass) and Li5N-Li
1 powder (60 mesh baths) at a theoretical volume ratio of 1=1, thoroughly mixed, and used as a negative electrode.

100q of Li5N-LiI is used as a solid electrolyte layer, 450Jv of a mixture of lead iodide and carbonyl nickel (mixing ratio is 4:1 in theoretical volume ratio) is used as a positive electrode, and 21q of a mixture of the lithium powder and Li3N-Li I powder is used as a negative electrode. A starting element was formed using a pressure bonding method, and a solid electrolyte battery having a diameter of [myt] and a thickness of about 1 inch as shown in Fig. 1 was assembled. In FIG. 1, (1) is a negative electrode composed of a mixture of lithium powder and Li5N-Lil powder as described above, (2) is a positive electrode, (3) is a solid electrolyte layer, and (4) is a positive electrode.
(5) is a positive current collector plate, (6) is a ceramic ring, and (7) is a brazing material.

When this upper pond was discharged with a constant flow of 130 μA at 20° C., the characteristics shown by curve A in the Kotobuki 2 diagram were obtained.

Examples 2 to 5 and Comparative Examples 1 to 6 Lithium powder (140 mesonupas) Li3N L
il powder (60 mesh passes) at a theoretical volume ratio of 1:01
0.2.0.4.0.5.0.6.0.7.1.2.1
, 4.1.8.2.0 and thoroughly mixed. This is used for the negative electrode.

Li3 N -Li I 1001v was used as a solid electrolyte, mixed powder 450 Misaki of lead iodide and carbonyl nickel similar to that in Example 1 was used as a positive electrode, and the lithium powder and Li were used as a positive electrode.
Weigh out the amount of the mixture with 3N-LI I powder so that the amount of lithium is 5.1811v (equivalent to 20mAh),
Using this as a negative electrode, a power generation element was formed by a pressure bonding method.
I assembled a similar battery.

These batteries were discharged at a constant current of 130 μA at 20°C.

An important characteristic of the negative electrode is the volume of the negative electrode required to discharge a certain electric capacity, and the smaller this value is, the better. In order to compare each battery with this characteristic, the above discharge results are shown in Figure 8. The vertical axis is the volume per unit electric capacity of lithium in the negative electrode divided by the negative electrode utilization rate, and the horizontal axis is the lithium/electrolyte. The theoretical volumetric mixing ratio (1:x) of

As is clear from FIG. 3, the addition of Li3N-LiI reduces the volume of the negative electrode required to ensure a constant discharge capacity compared to the case of lithium alone (ie, 1:0). This effect is most noticeable when Li
The amount of 5N-LiI added is 1:1 by volume to lithium.
0.7 or more, and the amount of Li5N-LiI added is 1:1
~1: The effect is especially great at 1.2, and the effect decreases when it is higher than that. This is thought to be due to a decrease in the absolute lithium content in the negative electrode.

In addition, in the case of lithium alone (comparative example 1), 20"C,3
The discharge characteristics at constant current discharge of 0 μA are shown by curve ``B'' in FIG.

Example 6 A battery was manufactured in the same manner as in Example 1 except that the solid electrolyte added to the negative i-ball was replaced with Li3N.

Got 'ill! When the cell was discharged at a constant current of 18θμ at 20°C, results similar to curve A in FIG. 2 were obtained.

Example 7 The solid electrolyte added to the negative electrode was Li3N -LiI -L
A battery was manufactured in the same manner as in Example 1 except that iOH was used instead.

When the obtained battery was discharged at a constant current of 20"0130 μA, results similar to curve A in FIG. 2 were obtained.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an example of a completely completed solid electrolyte battery, and FIG. 2 is a discharge characteristic diagram of the solid electrolyte battery of the present invention and a conventional solid electrolyte battery. FIG. 8 is a diagram showing the relationship between the mixing ratio of lithium and Li, Nt, and it in the negative electrode and the volume per unit electric capacity of lithicium/negative electrode utilization rate. (1)...Negative electrode, (2)...Positive electrode, (3)...
・Solid electrolyte layer, patent applicant Hitachi Maxell Co., Ltd. 71 Figure 72 Discharge capacity (mAh) Yoshi 3 (1:χ)

Claims (1)

[Claims] 1. A solid body comprising a negative electrode using lithium as an active material, a positive electrode placed in a position VC opposite to the negative electrode, and a solid electrolyte layer interposed between the negative electrode and the positive electrode. A solid 7U electrolyte battery for use in an electrolyte battery, characterized in that the negative electrode is composed of a mixture of lithium powder and solid electrolyte powder in a theoretical volume ratio of 0.7 to 1:1.8. 2. The solid electrolyte battery according to claim 1, wherein the solid electrolyte comprises Li3N, Li5N-Lil, or LIy, NLII-LIOH.