JPS6027151B2 - Lithium-iodine solid electrolyte battery - Google Patents

Description

Detailed Description of the Invention The present invention relates to the improvement of a lithium-iodine solid electrolyte battery in which metallic lithium is used as a negative electrode active material and iodine or an iodine complex is used as a positive electrode active material. The purpose is to provide a battery with less increase in internal resistance during battery storage by covering it with sodium hydroxide or using a lithium negative electrode.

A lithium-iodine group electrolyte battery, which uses lithium as the negative electrode active material and iodine or an iodine body as the positive electrode active material, can produce lithium-ion conductive iodine on the contact surface by simply contacting lithium and iodine or an iodine body directly. A solid electrolyte layer mainly composed of lithium chloride is formed, and this layer acts as an isolation layer and does not cause internal short circuits, making it possible to easily construct a high energy density battery with an electromotive force of about 3.0 volts. have.

According to A.A. Schneider et al., the terminal voltage VT during discharge of this battery is expressed by the following equation.

VT: V side (R.

i+Rti2) Vemf is electromotive force, R.

is the internal resistance before discharge, i is the magnitude of the discharge current, and t is the discharge elapsed time. That is, the discharge characteristics of this battery are determined by the solid electrolyte layer that is formed on the contact surface between the lithium negative electrode and the iodine or iodine rust positive electrode during battery construction and grows during battery storage.

It is governed by the pot resistance (R) before discharge and the internal resistance (R) due to the solid electrolyte layer that grows during discharge. Growth of the solid electrolyte during battery storage appears to be due to battery self-discharge due to diffusion of iodine from the positive electrode through the solid electrolyte layer to the lithium negative electrode. In addition, the growth rate follows a law similar to the corrosion phenomenon of metals, and R. It is said to be the perfect time. This growth rate, especially when stored at a high temperature of about 45 qo or higher, causes an increase in the diffusion rate of iodine, resulting in significant storage deterioration of the battery, which is one of the difficulties in putting this battery into practical use. The present invention eliminates these drawbacks by using a lithium negative electrode whose surface in contact with an iodine or iodine body positive electrode is coated with lithium hydroxide, and provides a lithium-iodine battery with little increase in internal resistance during storage. It is something.

Hereinafter, the present invention will be explained in detail with reference to examples thereof.

Figure 1 shows an outer diameter of 11.6 mm used to see the effects of the present invention.
FIG. 2 is a half-cut cross-sectional view of a lithium-iodine battery with a thickness of 2.5 mm.

1 is a metallic lithium negative electrode, 2 is a particle size that allows 75% of 1 part by weight of iodine-added charge transfer rust to pass through a 325-mesh sieve, in which 1 iodine is fixedly added to each molecule of 1-butylpyridinium iodide. Si02 gel 0 for chromatography
．． 3 is a negative electrode current collector/sealing plate made of general-purpose stainless steel; 4 is a chromium content of 3;
5 is an insulator made of resin such as polypropylene.

According to the present invention, 6 is a lithium hydroxide layer covering the surface of the metal lithium electrode in contact with the iodine-based positive electrode.

This layer is placed on the lithium negative electrode 1 and the peripheral body 5 in the recess of the sealing board 3 in a closed container dehumidified with phosphorus pentoxide.
After arranging the negative electrode module to form a negative electrode module, the negative electrode module is treated with a salt-containing aqueous solution such as a saturated lithium chloride aqueous solution until the relative humidity in the atmosphere at 20 oo is 11.
% in a closed container and leave for 2 to 30 minutes to form. The lithium hydroxide layer thus formed has a white porous appearance with a thickness of about 20 to 100 microns. In a conventional lithium-iodine battery, a lithium iodide solid electrolyte layer is formed at position 6 in FIG. 1 during battery construction, and as shown in FIG. As shown in 8, as iodine progresses, it grows on the iodine-based positive electrode 2 side, and during battery storage, iodine, which is the positive electrode agent, diffuses and moves to the lithium negative electrode 1 side through the lithium iodide layer. , self-discharge reaction (
2L+12→4il), and as shown by 7, it also grows on the lithium negative electrode side.

However, in the battery of the present invention, as shown in FIG. 2, the portion corresponding to 9 in FIG. Since the diffusion movement of iodine is small and the growth of the lithium iodide layer on the negative electrode side is small, the internal resistance increases only slightly during storage of the battery.

Such a situation is illustrated by a battery storage test shown in FIG. 4, which was conducted to examine the effects of the present invention.

Battery A has the structure shown in FIG. 1, and is a conventional lithium-iodine battery in which 6 is a lithium iodide layer.
is a lithium-iodine battery according to the present invention in which 6 is a lithium hydroxide layer formed by leaving it in an atmosphere of 20 oo and 11% relative humidity for 5 minutes. For batteries A and B, changes over time in internal resistance under storage at 6000°C and 25°C are shown.

The internal resistance was measured by discharging the battery for several seconds with a direct current such that the battery voltage did not fall below 2.4V at 2,500 volts, and determining the value of the potential drop at that time and the value of the DC current flowing. Battery electromotive force was 2.80 volts for battery A and 2.90 volts for battery B. The electromotive force of battery B has decreased for 3 months (60q0) due to battery storage.
It becomes 2.87 volts at 6 months (60℃) and 2.85 volts after 6 months (at 60°C). As is clear from FIG. 4, the battery B having the lithium hydroxide layer according to the present invention has a higher internal resistance value immediately after construction than the conventional battery A, but the internal resistance value R increases with the passage of storage time. It is small out of the relationship of time. This indicates that the lithium hydroxide layer effectively acts as a barrier for the diffusion and movement of iodine. The free energy of formation of LiOH is -106.1 Kcal/mole
・°C (value according to the Electrochemical Society's Nawa Electrochemical Handbook), which is -64. Gender cal/mole・00(Li/
The absolute value is large compared to the electromotive force of L, 1/12 battery (calculated from the electromotive force of 2.80 V), and since LiOH exists relatively stably even in iodine, it acts as a barrier for the diffusion and movement of 12. In addition, as in the embodiment of the present invention, the LiOH layer formed on the metal lithium plate is porous, allowing some degree of penetration of the iodine-based positive electrode and diffusion movement of 12. (Owens et al.) proposes that a Li-ion conductive solid electrolyte such as Lil Ni 20 is formed, and it is possible to effectively suppress the increase in internal resistance without causing any trouble during battery discharge. The present inventors believe that.

LiL due to the reaction of LiOH and 12 during battery storage
- The generation of 20 volts and the like is almost certain, since the electromotive force of the battery according to the present invention gradually decreases from 2.90 volts during battery storage.

[Brief explanation of drawings]

Fig. 1 is a front view showing the main parts of a battery according to an embodiment of the present invention, Fig. 2 is a diagram showing the state of the main parts during storage and discharging, and Fig. 3 is a diagram showing the main parts of a conventional battery. FIG. 4 is a diagram showing states during storage and discharging, and is a diagram comparing changes in internal resistance during battery storage. 1... Negative electrode, 2... Positive electrode, 6...
Lithium hydroxide layer. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Scope of Claims] 1. A lithium-iodine solid electrolyte comprising a positive electrode using iodine or an iodine complex as an active material, and a lithium negative electrode with sodium hydroxide formed on the surface in contact with the front positive electrode. battery. 2. The lithium-iodine solid electrolyte battery according to claim 1, wherein the positive electrode active material is an iodine-added 1-butylpyridinium charge transfer complex.