Positive electrode, lithium-ion secondary battery, and method of producing positive electrode

A positive electrode for a lithium-ion secondary battery, the positive electrode comprising at least:

• a positive electrode current collector;
• and
• a positive electrode active material layer,
• the positive electrode active material layer being formed on a surface of the positive electrode current collector,
• the positive electrode current collector comprising an aluminum foil and a porous film,
• the porous film covering and directly contacting a surface of the aluminum foil,
• the positive electrode active material layer covering and directly contacting a surface of the porous film,
• the porous film containing at least aluminum oxide,
• the porous film having a thickness not smaller than 10 nm and not greater than 800 nm,
• the porous film having a dynamic hardness not lower than 5 and not higher than 200,
• the porous film is obtained by bringing the aluminum foil into contact with superheated steam, and
• the porous film has an average pore size of 80 nm to 2000 nm.