Graphite material for negative electrode of lithium ion secondary battery having lattice strain and lithium ion secondary battery

摘要

Provided is a carbon material for negative electrode capable of suppressing capacity degradation due to repeated charge and discharge cycles, storage while being charged or floating charge. A graphite material having lattice distortion for lithium-ion secondary battery negative electrode is obtained by a manufacturing method comprising the steps of: pulverizing and classifying a raw coke composition obtained from a heavy-oil composition undergone coking by delayed coking process, the raw coke composition having a H/C atomic ratio that is a ratio of hydrogen atoms H and carbon atoms C of 0.30 to 0.50 and having a micro-strength of 7 to 17 mass% to obtain powder of the raw coke composition; giving compressive stress and shear stress to the powder of the raw coke composition so that average circularity is 0.91 to 0.97 to obtain round powder; heating the round powder to obtain a carbonized composition; and graphitizing the carbonized composition. The graphite material has a size of a crystallite Lc(112) of 4 nm to 30 nm, the size being calculated from a (112) diffraction line obtained by X-ray wide-angle diffractometry, and has lattice distortion in the range from 0.001 to 0.085, the lattice distortion being calculated from a (004) diffraction line and a (006) diffraction line.