PROCESS FOR PRODUCTION OF POSITIVE ELECTRODE ACTIVE MATERIAL FOR LITHIUM SECONDARY BATTERY, POSITIVE ELECTRODE ACTIVE MATERIAL, AND LITHIUM SECONDARY BATTERY

摘要

A process for the production of a positive electrode active material capable of bringing about, when used as a positive electrode, a lithium secondary battery which is stable for a long period and which exhibits improved charge and discharge characteristics.  The process can dispense with the step of firing a precursor prepared by subjecting various metal salts to liquid- or solid-phase reaction, said metal salts being starting materials necessary for producing a positive electrode active material which consists of a positive electrode material containing different kinds of divalent metals as the constituents.  Thus, the process makes it possible to produce a positive electrode active material by simple synthesis, and the process can give a positive electrode active material powder having a larger particle diameter than that of a conventional positive electrode active material powder. The process comprises mixing together multiple kinds of olivine-type lithium M phosphate powders different in the kind of M (M is divalent metal), sintering the obtained mixed powder either in an inert atmosphere or in a vacuum to conduct solution treatment and thus synthesize a positive electrode material which consists of a single compound containing the multiple kinds of divalent metals as constituents, and then pulverizing the positive electrode material into a powder having a mean particle diameter of 1 µm or above.