SECONDARY BATTERY

A secondary battery includes a negative electrode, a positive electrode, and an electrolytic solution. The negative electrode includes a negative electrode active material layer. The positive electrode includes a positive electrode active material layer. The positive electrode active material layer has a same dimension as a dimension of the negative electrode active material layer in a width direction. The positive electrode active material layer includes a reaction active part in which charging and discharging reactions proceed, and a reaction less-active part in which the charging and discharging reactions proceed less easily than in the reaction active part. The reaction less-active part includes one end part, another end part, or both of the positive electrode active material layer in the width direction.