JPS60163383A - High temperature battery - Google Patents

Abstract

PURPOSE:To decrease the price of a battery and eliminate special operation such as vacuum pouring of electrolyte in battery assembly by manufacturing porous magnesia particles having a specified pore size by using low price magnesia, and using a filling layer of the particles as a separator. CONSTITUTION:Magnesia particles are manufactured by sintering heavy magnesia having a mean particle size of 0.3mum with magnesium nitrate. Magnesium nitrate solution corresponding to 2wt% as magnesia is added to heavy magnesia, and granules having a particle size of about 200mum are prepared and calcined at 600 deg.C to decompose magnesium nitrate and sintered at 1,000 deg.C to obtain porous particles having appropriate strength. Porous particles having a particle size of 100-150mu are filled between electrodes 1 and 3, and a porous magnesia plate 4 having a pore size of 20mum is placed on the particle layer. The periphery of the plate 4 is fixed to electrodes with a flange 5. Thereby, the price of battery is decreased and special operation such as vacuum pouring of electrolyte in battery assembly can be eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a high-temperature battery that can be used as a power source for electric vehicles or power storage.

A high-temperature battery is a battery that is operated by heating the battery above room temperature, for example, above the melting point of the electrolyte, and it has been reported that a high-temperature battery uses a second material for electrodes and partition walls. The most promising high-temperature batteries developed to date are alkali metals for the negative electrode.

This is a system in which a metal oxide or metal sulfide is used as an active material in the positive electrode.

In high-temperature batteries using these molten salts, the separator material is limited due to factors such as the operating temperature of the battery and the corrosive environment inside the battery, and boron nitride is used.

It has been reported that magnesia etc. can be used.

The characteristics required of a battery separator include chemical stability within the battery, as well as low internal resistance of the battery and high energy characteristics, so the separator must have a large porosity. Furthermore, in order to prevent whitening of the battery, the separator must have sufficient compressive strength to suppress deformation of the electrode plates after long-term operation. Separator price is also a major factor in separator selection.

In conventional batteries, boron nitride has been used as a separator material, and the boron nitride is made into fibers and then made into felt. Since this boron nitride and the weight of the separator are extremely small, when used in a battery, a battery exhibiting high energy characteristics can be obtained. However, since boron nitride does not get wet with molten salt, before incorporating the separator into the battery, a process is required to add magnesia to the felt using magnesium nitrate, which produces magnesia through thermal decomposition, to improve the smearing properties. I need. In addition, the boron nitride felt separator is easily deformed by compressive force, making it difficult to extend the life of the battery. The disadvantage is that the price is very high. Therefore, attempts have been made to use magnesia or the like, which has good wettability with molten salt, in the form of a powder for the separator.

This method of using powder for the separator is effective in mass production, easy to assemble the battery, and the price of the separator is lower than that of fiber.
-It is cheap +111i because it does not require much time. It has also been reported that a separator layer filled with powder has sufficient compressive strength. Therefore, expensive boron nitride film 1
~ Although 1νJ is expected to be used as a separator to replace the separator, since a packed layer of powder is used as a lever, the porosity is small at around 50%, and the energy characteristics of the battery remain at a low value, making it suitable for applications such as power storage. It is limited to power supplies used for low-rate discharge, and when injecting electrolyte, air bubbles in the pallet layer cause particles to rearrange, so vacuum injection is required, and external pressure etc. There was a problem with particle movement due to

The present invention (jl) improves these drawbacks, is inexpensive, has good wettability to molten salt, has sufficient porosity, does not require special operations such as vacuum injection during battery assembly, and does not require any special operations such as vacuum injection during assembly. The present invention provides a battery using a separator that does not cause particle rearrangement during operation and has high compressive strength.

FIG. 1 shows an embodiment of the battery σ according to the present invention. This is a cross-sectional view of J, and the embodiment will be described in detail below.

Porous magnesia particles having openings with a C1 average pore diameter of 0.1 μm were produced using inexpensive magnesia as a separator material, and a packed bed of these particles was used as a separator.

Porous magnesia particles were produced by sintering heavy magnesia having an average particle size of 0.3 μm into a porous state using magnesium nitrate as a binder.

First, 2% by weight of an aqueous magnesium nitrate solution (calculated as magnesia) was added to heavy magnesia, and the granules were made into granules of approximately 200 μm by extrusion granulation.
The particles were calcined at 00°C to thermally decompose magnesium nitrate, and then sintered at 1000°C to obtain porous particles with sufficient strength.

Next, as shown in FIG.
A porous magnesia plate (4) with a pore size of 20 μm is placed on top of the particle layer, and the peripheral part of the magnesia plate is spot welded to the battery case. ) was fixed.

In the figure, 13 (1) is a positive electrode that uses iron sulfide as the active material.
Iron sulfide powder with a particle size of 50μ to 300μ, electrolytic lithium chloride-potassium chloride with a particle size of 50μ to 150μ
After adding 15% by weight of particles having a particle size of μ and filling a honeycomb-shaped current collector, the mixture was press-molded at room temperature to form a plate. Note that a 325-mesh stainless steel net was provided on the surface of the electrode plate to hold the active material. (2) is a separator formed by filling porous magnesia particles according to the present invention between the electrodes;
3) uses a lithium-11-aluminum alloy as an active material.

It is a negative electrode.

Similar to the positive electrode, the negative electrode also has a honeycomb-shaped current collector with 50
It is a plate-shaped body filled with 15% by weight of lithium-aluminum alloy powder with a particle size of μ to 300 μ and electrolyte powder with a particle size of 50 μ to 100 μ, and press-formed at room temperature at 100 MPa. 7j retains active material even in negative electrode
It has a 325 mesh stainless steel screen. A 54% by weight lithium chloride-potassium chloride molten salt was used as the electrolyte. The operating temperature of the battery was 470°C. In addition,
The capacity of the positive electrode is 25A h, and the capacity of the negative electrode is 1.3
It was doubled.

A battery according to the present invention having a particle holder made of a porous 7gnesia plate on top of a separator particle layer and a battery without a particle holder were assembled and cycled with 2.5Δ charging and 5.0Δ discharging, and the battery characteristics were determined. compared.

For batteries without a particle holder, the Δh effect, which is the ratio of discharged electricity to charged IjM electricity, began to decrease after 85 cycles, and at 100 cycles an internal short circuit occurred in the battery, causing the battery to be dismantled. Upon investigation, it was found that the electrode plates had expanded abnormally above the separator layer and were in contact with each other. This is because during the injection of molten salt during the assembly process, the particles at the top of the separator layer moved to the top of the electrode plate along with air bubbles, and the filling rate of particles at the top of the separator layer decreased significantly, resulting in a decrease in the compression resistance of that part. This is thought to be due to the expansion of the electrode plate. Battery R:G according to the present invention does not have the problem of shortening the lifespan as mentioned above because the particles do not rearrange when the molten salt is injected, and it still maintains good battery characteristics even after 200 cycles. It shows.

As is clear from the above description and the examples in which magnesia powder was used in the separator, the present invention improves the drawbacks of conventional separators and provides a battery with a longer life span through a simple process. In the examples, magnesia was used as the separator material, but similar effects can be expected even if a powder of a substance that can withstand the environment inside the battery is used for the separator.

[Brief explanation of the drawing]

FIG. 1 is a sectional view showing an embodiment of a battery according to the present invention. 1...Positive electrode, 2...Separator, 3...Negative electrode, 4
... Particle holder:'X1 ] 3

Claims (1)

[Claims] 1. In high-temperature batteries that use alkali metals, alkaline earth metals, or alloys thereof for the negative electrode, metal oxides or metal sulfides for the positive electrode, and molten salt containing alkali metal or alkaline earth metal ions as the electrolyte. A high-temperature battery characterized in that particles made of an inorganic substance are interposed therebetween, and a particle holder is positioned on the surface of the particle layer facing the battery interior space.