Lithium-ion secondary battery and method of manufacturing the same

A method of manufacturing a lithium-ion secondary battery that includes a positive electrode, a negative electrode, and a non-aqueous electrolyte, the positive electrode including a positive active material layer containing a positive active material, and the negative electrode including a negative active material layer containing a negative active material,

• the method comprising:
• obtaining a BET specific surface area of the positive active material;
• and
• adding an inorganic phosphate compound to the positive active material layer to adjust an amount of the inorganic phosphate compound to 0.02 g/m2 to 0.225 g/m2 per unit surface area based on the BET specific surface area of the positive active material, wherein
• the inorganic phosphate compound includes at least one of an alkali metal, an alkaline earth metal, and a hydrogen atom, and
• the lithium-ion secondary battery is configured to allow an open-circuit voltage of the lithium-ion secondary battery to increase to 4.3 V or higher in terms of metal lithium.