An amorphous material, electrode and secondary battery

摘要

An amorphous carbon material, especially for an electrode of a lithium ion secondary battery, is characterized by an interlayer spacing d(002), obtained from the X-ray diffraction line assigned to the (002) plane of the carbon, of 0.345 nm to 0.356 nm, a ratio (Ps) of the number of carbon atoms involved in the layer structure to the total number of carbon atoms of from 0.54 to 0.85, and a ratio of total nitrogen:total carbon atoms in the amorphous carbon of 0.005:1 to 0.055:1. The amorphous carbon material is prepared by applying a heat treatment to an amorphous carbon material under vacuum or inert gas atmosphere for at least 30 minutes to provide the desired crystallite structure. The carbon material may take the form of carbon fiber material, especially short carbon fibers obtained by pulverizing larger carbon fibers. A lithium ion secondary battery containing an electrode comprising such an amorphous carbon material has a large discharge capacity and high charge-discharge cycle characteristics.