JPS59169075A - High temperature type battery - Google Patents

Abstract

PURPOSE:To provide a battery using a separator having good wettability to molten salt and sufficient porosity by using Li or Li alloy as a negative electrode, metal sulfide such as iron sulfide or iron disulfide as a positive electrode, and placing porous magnesia powder between them. CONSTITUTION:Metal sulfide such as iron sulfide or iron disulfide is used in a positive electrode 1, Li or Li alloy is in a negative electrode 3, and porous magnesia powder 2 is filled between them. The porous magnesia powder is prepared in such a way that, for example, magnesium nitrate solution corresponding to 2wt% magnesia is added to densified magnesia having a mean particle size of 0.3mu and they are formed in glanule by a extruding method, then burned. Thereby, a separator which is low cost, easy to handle, and has good wettability to molten salt and sufficient porosity is obtained. A battery is assembled by using this separator.

Description

[Detailed Description of the Invention] The present invention uses negative @i I: lithium or lithium alloy, iron sulfide, 71i* iron oxide, etc. for the positive electrode, and a porous NNO I screw for the separator. It is suitable for molten salt batteries using particles.

Conventionally, in high-temperature batteries that use molten salt, the separator material has various characteristics such as stability at around 500°C, which is the operating temperature of the battery, corrosion resistance in molten water, and reactivity with active materials. Therefore, boron nitride and magnesia are being considered. A separator made of boron nitride is made porous by converting boron nitride into ferrite. Although this felt separator exhibits a large porosity of just under 90% and fully satisfies the characteristics required for battery separators such as electrical insulation, it is difficult to make felt to make the separator porous. In addition to being very expensive, there were problems in that the retention of the active material was insufficient. In addition, boron nitride does not wet with molten salt as it is, so after making boron nitride into felt, magnesia is precipitated on the surface of the fiber using magnesium nitrate, which produces magnesia through thermal decomposition, to improve its wettability with molten salt. This required a processing step to improve the quality of the product.

Since magnesia has not been refined to date, attempts have been made to use magnesia powder in separators. However, separators using powder have a small porosity of around 50%, and as a result, the utilization rate of active materials in batteries remains at a low value. Moreover, when assembling a battery, it is inconvenient to handle because it is a powder, and requires processing such as pressure molding together with electrolyte powder to form a plate.

The present invention improves these drawbacks and provides a battery using a separator that is inexpensive, easy to handle, has good wettability to molten salt, and has sufficient porosity.

Examples thereof will be described in detail below.

Porous magnesia particles were produced using heavy magnesia with an average particle size of 0.3 μm and magnesium nitrate as raw materials.

First, 2% by weight of an aqueous magnesium nitrate solution (calculated as magnesia) is added to heavy magnesia, and the extrusion granulation method is used to form granules.The granules are fired at 1000°C to make them porous and easy to handle. Particles with sufficient strength were obtained.

Next, a lithium iron sulfide battery according to the present invention as shown in FIG. 1 was constructed using these two porous particles having a particle size of 100 to 150 microns, and a discharge test was conducted.

In the figure, (1) is a positive electrode that uses iron sulfide as an active material, with 15% by weight of iron sulfide powder with grain size of 50 to 300 μ and electrolyte of lithium chloride and potassium chloride with grain size of 50 to 150 μ. After adding it and charging it into a honeycomb-shaped W electric body, it was B-formed at 100 MPa at room temperature.
It is plate-shaped. The surface of the electrode plate has a 200-mesh stainless steel 1'V net for holding the active material. 2) is a separator formed by filling porous magnesia particles according to the present invention between poles;
is a negative electrode using a lithium-aluminum alloy as an active material. Like the positive electrode, the negative electrode also has a honeycomb-shaped current collector.
It is a plate-shaped body filled with 15% by weight of lithium-aluminum alloy powder with a particle size of 50μ to 300μ and electrolyte powder with a particle size of 50μ to 100μ, and press-formed at room temperature at 100 MPa. The negative electrode also has a 200-mesh stainless steel net for holding the active material. Electric M
A 54% by weight lithium chloride-potassium chloride molten salt was used for the quality. The operating temperature of the battery was 470°C. Note that the capacity of the positive electrode was 25Δh, and the capacity of the negative electrode was 1.3 times that of the positive electrode.

The porosity of the separator formed by pouring porous magnesia particles according to the present invention between the poles is as large as 79%, and its pore distribution is as shown in Figure 2.
There are pores around μ and micropores of 0.1 μ or less.

The former pores are caused by the gaps between particles.
Although the latter minute pores are distributed inside the powder, the gaps between the particles are small depending on the particle size of the active material, and it can be seen that the separator layer can sufficiently hold the active material.

In a battery test, a battery using porous magnesia particles according to the present invention showed a high utilization rate of positive electrode active material at 2.5Δ charging/discharging of 83%. Porosity 46 with similar configuration
In a battery using a magnesia powder separator with a porosity of 89%, the active material usage rate was only 64%, and in a battery using a boron nitride felt separator with a porosity of 89%, the value was 8696, which is equivalent to the value of the porosity of the separator made by the present invention. There was one.

As is clear from the following description and examples, the present invention improves the drawbacks of conventional separators, uses an inexpensive magnesium compound as a raw material, is porous, and has a molten salt wettability.
An advantageous aspect of the present invention is to provide a molten salt battery using a separator that can sufficiently retain an active material.

The battery according to the present invention also has the advantage that it can be assembled by a simple process of inserting the positive and negative electrode plates into the battery case and then pouring porous magnesia grains between the electrodes.

[Brief explanation of drawings]

FIG. 1 is a sectional view showing an embodiment of a battery according to the present invention, and FIG. 2 is a pore distribution diagram of a separator using porous magnesia particles according to the present invention, measured by mercury intrusion method. 1... Positive electrode, 2... Porous magnesia particles are used.

Claims (1)

[Claims] A high-temperature battery characterized by using lithium or lithium alloy for the negative electrode, metal sulfide for the positive electrode, and having porous magnesia particles interposed between the electrodes.