Carbon powder for use in cathode materials of non-aqueous secondary battery

Abstract

The invention provides low cost carbon powder which does not decompose propylene carbonate to be used as a negative electrode material of a low temperature-operable nonaqueous secondary battery. The carbon powder obtained by depositing low temperature fired carbon originating in pitch on a part of the surface of natural graphite powder is made by mixing the natural graphite powder with pitch powder of a carbon precursor in a solid state and heating at 900-1,500 deg C to carbonize the pitch. The quantity of the pitch powder is controlled so that the ratio V2 / V1 of the pore volume (V1) of poreshaving 2-50 nm pore diameter to the pore volume (V2) of pores having 50-200 nm pore diameter in the pore distribution curve determined by analyzing nitrogen desorption side isotherm of the resultant carbon powder by the BJH method is >=1.

Description

technical field

[0001] The present invention relates to an inexpensive carbon powder in which carbon with a low degree of graphitization is adhered to a part of the surface of a natural graphite powder, and particularly relates to a carbon powder suitable for a negative electrode material for a nonaqueous secondary battery. Background technique

[0002] Lithium-ion secondary batteries are rapidly spreading as power sources for portable electronic devices and the like. The negative electrode material of non-aqueous secondary batteries typified by lithium ion secondary batteries is carbon powder. Due to the demand for high capacity of small batteries, negative electrode materials are also seeking high capacity. In current non-aqueous secondary batteries, artificial graphite powder that has been graphitized is mainly used as a negative electrode material. Since the capacity per unit volume is further increased, the fillability of the electrode is improved, that is, the densit...