GRAPHITE POWDER FOR LITHIUM ION SECONDARY BATTERY NEGATIVE ELECTRODE AND MANUFACTURE OF THE GRAPHITE POWDER

摘要

PROBLEM TO BE SOLVED: To enhance filling properties and improve discharge capacity and charge/discharge efficiency by consisting of a powder mixed with a graphite powder obtained from a bulk mesophase and a graphite powder obtained from a mesophase spherular and setting a bulk density to a specific value or above. SOLUTION: For a graphite powder, both a bulk mesophase and a mesophase spherular re used for a raw material and the resulting graphite powders from these are mixed to a have a bulk density of 1.35 g/cm3 or above. Average grain size of the bulk mesophase powder is preferably 20-40 μm and average grain size of the mesophase spherular is 10 μm or under. When two kinds of the graphite powders obtained these are mixed, filling properties are excellent because the spherical graphite powders having a small grain size are tightly filled in the spaces between the irregular graphite powders of a large grain size. A compounding ratio when mixing is that the graphite powder obtained from the bulk mesophase powder is preferably 75-98 wt.% and the graphite powder obtained from the mesophase spherular is 2-25 wt.%.