JPH012252A - thin wall magnesium battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

[Detailed Description of the Invention] As electronic technology develops, electronic devices such as computers and radios tend to become ultra-small and ultra-thin. Demand for thin-walled batteries has been rapidly increasing.

The present invention relates to an ultra-thin magnesium battery that can be built into a thin IC card such as a bank card or credit card.

Highly pure magnesium has poor workability and is difficult to form into electrodes, so it is not used as a battery electrode material5, but magnesium-based alloys are often used as anode materials for electric sliding doors. Ta.

For example, it is known that there is a magnesium dry battery that uses an alloy of magnesium with a small amount of aluminum and zinc added to the negative electrode of the battery, and that it is possible to obtain a terminal voltage of 2 V or more. Furthermore, dry batteries that use magnesium alloy as the negative electrode not only have high voltage, but also have good heavy load discharge characteristics at low temperatures such as -50℃.Batteries that are combined with copper chloride are especially suitable for use in SOS lamps and SO3 transmitters during maritime disasters. In addition to sonar buoys, it has been used in model airplanes, radiosondes, fishing gear, etc.

A magnesium dry battery with a negative electrode made of a magnesium alloy containing small amounts of aluminum and zinc and a positive electrode made of manganese dioxide has a capacity that is approximately three times that of a battery that uses a zinc negative electrode, and a discharge duration that is 2.5 times longer than that of a normal zinc negative electrode battery. It is said to be five times longer. This shows that magnesium is extremely suitable as a negative electrode material for batteries.

However, magnesium cannot meet the demands of the era of thinner batteries, and ultra-thin batteries with a thickness of 0.51 or less are made using lithium oxide, which uses lithium foil with a thickness of about 1 mm as the negative electrode. Batteries have been used.

The reason for this is that it is extremely difficult to produce foil by plastic processing of magnesium or magnesium alloys, and the processing yield is low, making it difficult to make it a target for industrial production.

In general, it is known that metals with a crystal structure consisting of a close-packed hexagonal lattice are more difficult to plastically work than metals with a body-centered cubic lattice or a face-centered cubic lattice, and magnesium is suitable for such difficult-to-work materials. A typical example is good (a well-known metal).

When magnesium is cast by a conventional casting method using a cooling mold, the ingot consists of a polycrystalline body containing isocycle islands. In such an ingot, columnar crystals grow on the outer periphery in a line substantially perpendicular to the surface, forming a columnar crystal zone. Casting defects such as segregation of impurities, cavities, and air bubbles occur inside the ingot. Such an ingot cannot be cold rolled.

It is known that hot working is possible when small amounts of manganese and zinc are added to magnesium. However, even in this case, the presence of grain boundaries (crackling of edges of the entrained plate or foil occurs), resulting in extremely low yields and difficulty in using it as an industrial means of producing magnesium foil, making it difficult to produce thin-walled magnesium batteries. I couldn't do that.

In order to manufacture ultra-thin magnesium batteries, 0.1-
It is necessary to find a method for producing thin magnesium foil that is no better than ugly.To do this, one possible method is to create a thin plate-shaped ingot during casting, then slightly roll it to finish it into foil.

To cast thin metal strips, there is a method of supplying molten metal onto the surface of a cooled rotating roll and rapidly solidifying it, but this cannot be applied to manufacturing magnesium foil for electrodes. , the metal strip is made of polycrystalline material, and when such a metal strip is rolled, countless minute holes are generated, and breakage easily occurs during processing, making it impossible to obtain a sound and thin foil. Can not.

The present inventor heated the mold to a temperature higher than the solidification temperature of the cast metal,
When rolling a magnesium ingot cast by the heated mold continuous casting method, in which the cooling of the cast metal is not done by removing heat from the mold, but by bringing a coolant into direct contact with the solidified ingot, cracks and We have experimentally discovered that a magnesium foil without pinholes and without any coagulation grain boundaries is extremely easy to obtain, and that the magnesium foil thus obtained is excellent as a negative electrode for thin batteries. completed.

Magnesium is an abundant resource and the material is cheaper than lithium used in conventional ultra-thin batteries, so ultra-thin batteries with magnesium negative electrodes will be widely used in the future.
It is believed that this will greatly contribute to the development of the electronic industry.

Example A graphite heating mold with a hollow cross section of lsm x 30 mm at the outlet was used, the temperature of the inner wall of the mold was maintained at 651'C or higher, and the ingot was cooled only outside the open end of the mold. A strip-shaped ingot with a width of 30 mm was continuously cast.

The obtained band-shaped ingot consisted of many columnar crystals near the solidification start end, but was a complete single crystal at about 500 s+m from the solidification start end. By rolling this single-crystal ingot, it was possible to easily form a sound foil with no pinholes and a thickness of 0.1 mm without any edge cracking.

This foil was used as the negative electrode of the battery, and M, O! A battery with a thickness of 0.511111 mm and having a cross section as shown in FIG.

That is, in Fig. 1, ■ is a negative electrode (anode) made of magnesium foil, and a separator ■ containing an electrolyte containing M, B, etc. as main components is placed between it and the positive electrode (cathode) of M, O□. It's in between. ■■ is a battery cover made of stainless steel, which constitutes a fish species terminal and a positive terminal, respectively. ■■ is an insulating material seal.

A high voltage of 2.1V was obtained with this ultra-thin battery. Magnesium, which does not have coagulation grain boundaries, does not cause corrosion and the surface reacts uniformly and is consumed, so there is little loss of battery capacity due to natural discharge, and after storage for one year at 20°C, the battery capacity decreases by only 1. It was only %.

[Brief explanation of drawings]

FIG. 1 is a longitudinal section showing an example of an ultra-thin battery using magnesium foil. 1. Magnesium negative electrode 2, M-O as positive electrode 3, Separator 4, Negative electrode terminal 5, Positive electrode terminal 6, Insulating material seal

Claims (1)

[Scope of Claims] A dry battery using a magnesium foil as a negative electrode, characterized in that the magnesium foil is made by processing an ingot obtained by a hot mold continuous casting method. battery.