Electrode for nonaqueous electrolyte battery

Abstract

The following aspects (1) to (4) of the present invention can provide an electrode for nonaqueous electrolyte battery having excellent safety and charged storage properties and good high rate charge-discharge properties. (1) An electrode for nonaqueous electrolyte battery including a particulate active material having a porous film formed thereon. (2) An electrode for nonaqueous electrolyte battery including an active material having a filler held in pores. (3) An electrode for nonaqueous electrolyte battery including an active material which undergoes volumetric expansion and shrinkage during charge-discharge, having a filler held in pores. (4) The electrode for nonaqueous electrolyte battery according to aspect (1), wherein the porous film is an ionically-conductive film.

Description

TECHNICAL FIELD The present invention relates to an electrode for nonaqueous electrolyte battery. BACKGROUND OF THE INVENTION In recent years, with the development of electronic apparatus, the appearance of a novel high performance battery has been expected more and more. At present, as primary battery used as power supply for electronic apparatus there is mainly used manganese dioxide-zinc battery. As secondary battery used as power supply for electronic apparatus there is mainly used nickel battery such as nickel-cadmium battery, nickel-zinc battery and nickel-metal hydride battery or lead-acid battery. As the electrolyte solution for these batteries there is used an aqueous solution of alkali such as potassium hydroxide or an aqueous solution of sulfuric acid or the like. The theoretical decomposition voltage of water is 1.23 V. A battery system having an electromotive force of higher than this value is liable to decomposition of water that makes it difficult to stably store a...

AI Technical Summary

Benefits of technology

One aspect of the present invention concerns an electrode for nonaqueous electrolyte battery based on quite a novel principle comprising a particulate active material having a porous film formed thereon. Thus, a nonaqueous electrolyte battery excellent in safety, charged storage properties and high rate charge-discharge properties can be provided.

Another aspect of the present invention concerns an electrode for nonaqueous electrolyte battery based on quite a novel principle comprising an active material having a filler held in pores. Thus, a nonaqueous electrolyte battery excellent in safety, charged storage properties and high rate charge-discharge properties can be provided.

A further aspect of the present invention concerns an electrode for nonaqueous electrolyte battery based on quite a novel principle comprising an active material which undergoes volumetric expansion and shrinkage during charging and discharging, having a filler held in pores. Thus, a nonaqueous electrolyte battery excellent in safety, charged storage properties and high rate charge-discharge properties can be provided.

A still further aspect of the present invention concerns an electrode for nonaqueous electrolyte battery based on quite a novel principle comprising a particulate active material having a porous ionically-conductive film formed thereon. Thus, a nonaqueous electrolyte battery excellent in safety, charged storage properties and high rate charge-discharge properties can be provided.

Problems solved by technology

The theoretical decomposition voltage of water is 1.23 V. A battery system having an electromotive force of higher than this value is liable to decomposition of water that makes it difficult to stably store an electric energy.

A secondary battery comprising metallic lithium as a negative electrode is disadvantageous in that it is liable to internal short due to dendritic growth of metallic lithium and thus has a reduced life.

Further, since metallic lithium has a high reactivity, such a secondary battery can be hardly provided with a high safety.

The conventional batteries comprising a nonaqueous electrolyte solution are liable to vaporization of the electrolyte solution due to heat generation during shortcircuiting or other troubles, which causes a sudden rise in the inner pressure thereof.

As a result, the inner pressure of the battery shows a sudden further rise.

Accordingly, at present, the percent utilization of the carbon-based negative electrode is limited to less than 60% (LixC6, 0≦x<0.6) taking-into account the safety, making it impossible to obtain a practical battery having a high energy density.

Thus, the lithium-based battery has deteriorated charged storage properties.

However, polyether cannot provide a high ion conductivity while maintaining a sufficient mechanical strength.

Further, the ion conductivity of the polyether is drastically affected by temperature and thus cannot provide a sufficient ion conductivity at room temperature.

Thus, such a compound cannot be hardly used in lithium-based batteries.

However, no polymer electrolytes giving essential solution to the problem of diffusion of lithium ion have been reported.

Thus, the properties of nonaqueous batteries have not been sufficient as compared with that of aqueous batteries.

Accordingly, a lithium-based battery comprising an organic electrolyte solution is disadvantageous in that it is inferior to an aqueous battery in high rate charge-discharge properties.

This problem becomes very remarkable at low temperatures.

A lithium-based battery comprising a polymer electrolyte solution allows ion diffusion at a even lower rate than one comprising an organic electrolyte instead of electrolyte solution and thus is disadvantageous in that it is more inferior to a nonaqueous battery comprising an organic electrolyte solution in high rate charge-discharge properties.

However, such a lithium ionically-conductive inorganic solid electrolyte has some disadvantages.

In other words, it cannot provide a sufficient lithium ion conductivity.

Further, it lacks resistance to reduction-oxidation.

Moreover, the volumetric expansion and shrinkage of the active material during charge-discharge causes the active material to be peeled off the inorganic solid electrolyte.

Thus, such a lithium ionically-conductive inorganic solid electrolyte has never been put into practical use.

Since an organic electrolyte is combustible, a lithium-based battery comprising an organic electrolyte needs to be equipped with various safety elements such as safety valve, protective circuit and PTC element for the sake of safety, adding to cost.

Thus, a lithium-based battery has deteriorated charged storage properties.

A lithium-based battery comprising a polymer electrolyte instead of an electrolyte solution for the purpose of improving the safety and charged storage properties thereof is disadvantageous in that it allows ion diffusion in the electrolyte at a reduced rate and thus cannot perform charging and discharging at a high rate.

Such a lithium-based battery exhibits remarkably deteriorated high rate charge-discharge properties at low temperatures.

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