NONAQUEOUS-ELECTROLYTE SECONDARY BATTERY

摘要

This invention provides a nonaqueous-electrolyte secondary battery that inhibits change in the structure of a positive-electrode active material under high voltages, allowing both a high capacity and a long service life. Said nonaqueous-electrolyte secondary battery is characterized by the provision of the following: a positive electrode containing a positive-electrode active material that stores and releases lithium ions; a negative electrode containing a negative-electrode active material that stores and releases lithium ions; and a nonaqueous electrolyte. This nonaqueous-electrolyte secondary battery is also characterized in that: the positive-electrode active material is a cobalt complex oxide that contains magnesium in a lithium layer; magnesium is present in said lithium layer after the battery has been charged to a lithium-based potential of at least 4.53 V; and a magnesium-containing compound is present on the negative electrode in an amount that is between 4.5 mol% and 10 mol%, inclusive, of the amount of magnesium in the positive electrode.