Process for producing lithium borate compound

Abstract

A process for producing, by a relatively simple means, a lithium borate material which is useful as a positive-electrode material for lithium-ion secondary batteries, etc. and has improved cycle characteristics, capacity, etc., and excellent performances. The process is characterized by reacting one or more divalent-metal compounds comprising at least one compound selected from a group consisting of compounds of divalent iron and compounds of divalent manganese with boric acid and lithium hydroxide in a reducing atmosphere at 400-650 DEG C in the melt of a carbonate mixture comprising lithium carbonate and at least one alkali metal carbonate selected from a group consisting of potassium carbonate, sodium carbonate, rubidium carbonate, and cesium carbonate.

Description

technical field [0001] The present invention relates to a method for preparing a lithium borate-based compound useful as a positive electrode active material of a lithium-ion battery, and an application of the lithium borate-based compound obtained by the method. Background technique [0002] Lithium secondary batteries are small and have high energy density, and are widely used as power sources for portable electronic devices. As the positive electrode active material, LiCoO is mainly used 2 and other layered compounds. However, these compounds have the disadvantage that oxygen is easily desorbed at about 150° C. in a fully charged state, and in this case, an oxidative exothermic reaction of the non-aqueous electrolyte is likely to occur. [0003] In recent years, olivine phosphate compound LiMPO has been proposed as a positive electrode active material. 4 (LiMnPO 4 、LiFePO 4 、LiCoPO 4 Wait). The system is replaced by LiCoO 2 This kind of oxide is used as the 3-valen...

AI Technical Summary

Problems solved by technology

However, the solid-state reaction method requires a long-term reaction at a high temperature of 600°C or higher, and although the dopant element can be solid-dissolved, it involves problems such as crystal grain growth to 10 μm or larger and slow diffusion of ions.

Furthermore, since the reaction proceeds at a high temperature, there is a problem that doping elements that are not completely dissolved in the cooling process precipitate to generate impurities and increase the resistance.

Furthermore, due to heating to a high temperature, there is also a borate-based compound in which lithium deficiency and oxygen deficiency occur, and it is difficult to increase the capacity and improve the cycle characteristics.

Images