A positive electrode includes a positive electrode current collector and a positive electrode mixture layer disposed on the current collector. The positive electrode mixture layer includes a lithium transition metal composite oxide containing 50 mol % or more Ni relative to the total number of moles of metal element or elements except Li, a conductive carbon material, and an adhesion improver capable of attaching to the lithium transition metal composite oxide and the carbon material. The adhesion improver contains a Lewis acidic group, a Lewis basic group, and an aromatic ring-containing hydrophobic group.