NON-AQUEOUS ELECTROLYTE SECONDARY BATTERY

A non-aqueous electrolyte secondary battery including a positive electrode, a separator, a negative electrode facing the positive electrode, with the separator interposed; and a liquid electrolyte. The positive electrode includes a composite oxide containing lithium as a first metal, and a second metal other than lithium. In the composite oxide, the second metal contains Ni, a content of Ni in the second metal is 90 at% or more, and a content of Co in the second metal is 10 at% or less. The liquid electrolyte contains at least one cation X selected from the group consisting of Na, K, Rb, Cs, Fr, Mg, Ca, Sr, Ba, and Al, and an oxalate complex anion Y.