Non-aqueous electrolyte secondary battery active material powder and a non-aqueous electrolyte secondary battery

Excellent non-aqueous electrolyte secondary battery active material reversible with sodium salt, and provides a non-aqueous electrolyte secondary battery using the same. The positive electrode active material in the composite metal oxide containing Na, oxide containing Mn and Ni, and holds the ionic radius of the large Na and stable crystal structure, reversible storage and release reaction of Na ions in charging and discharging particularly excellent in gender, further, the negative electrode active material is a compound having at least one aromatic carboxylic acid sodium salt structure hardly occur metal deposition of Na, is suitable excellent reversibility of charge-discharge reaction.