Sulfur-based positive-electrode active material, positive electrode and lithium-ion secondary battery

Abstract

An object of the present invention is to provide a novel sulfur-based positive-electrode active material which can largely improve cyclability of a lithium-ion secondary battery, a positive electrode comprising the positive-electrode active material and a lithium-ion secondary battery comprising the positive electrode. The sulfur-based positive-electrode active material is one comprising: a carbon skeleton derived from a polymer composed of a monomer unit having at least one hetero atom-containing moiety, and sulfur incorporated into the carbon skeleton as the carbon skeleton is formed from the polymer by heat treatment.

Description

TECHNICAL FIELD[0001]The present invention relates to a novel sulfur-based positive-electrode active material which can be used on a lithium-ion secondary battery, a positive electrode comprising the sulfur-based positive-electrode active material and a lithium-ion secondary battery comprising the positive electrode.BACKGROUND ART[0002]Since a lithium-ion secondary battery, one type of nonaqueous electrolyte secondary batteries, has a large charging and discharging capacity, it has been used mainly as a battery for portable electronic devices. Moreover, the number of lithium-ion secondary batteries used as a battery for electric automobiles has been increasing, and enhancement of performance thereof is expected.[0003]Generally, materials comprising a rare metal such as cobalt or nickel are used as a positive-electrode active material of a lithium-ion secondary battery. However, due to the fact that rare metals are small in the distributed amount, not always easily available and addi...

AI Technical Summary

Benefits of technology

The present invention is related to a novel sulfur-based positive-electrode active material for lithium-ion batteries that can considerably improve the battery's capacity and cyclability. "Cyclability" refers to the ability of a battery to maintain its charging and discharging capacity even after repeated charging and discharging. A battery with a high capacity retention rate is considered to have excellent cyclability, while one with a low capacity retention rate is considered to have poor cyclability. The patent proposes a method for preparing a sulfur-based positive-electrode active material that can enhance the battery's performance.

Problems solved by technology

However, due to the fact that rare metals are small in the distributed amount, not always easily available and additionally expensive, a positive-electrode active material using a material that replaces a rare metal has been required.

Further, in the case of a positive-electrode active material comprising an oxidized compound, oxygen in the positive-electrode active material is released due to overcharging, or the like, and as a result, an organic electrolyte and a current collector are oxidized and burnt, which may cause firing, explosion, and the like.

However, the lithium-ion secondary battery using elemental sulfur as the positive-electrode active material has a problem that a battery capacity is deteriorated through repeated charging and discharging.

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