US Patent 11658280 Lithium secondary battery and card with built-in battery

Provided is a lithium secondary battery including: a positive electrode plate which is a lithium complex oxide sintered plate; a negative electrode layer containing carbon; a separator interposed between the positive electrode plate and the negative electrode layer; and an electrolytic solution with which the positive electrode plate, the negative electrode layer, and the separator are impregnated, wherein the positive electrode plate has a thickness of 70 to 120 μm, the negative electrode layer has a thickness of 90 to 170 μm, the lithium secondary battery has a rectangular flat plate shape with each side having a length of 20 to 55 mm, the lithium secondary battery has a thickness of 350 to 500 μm, and the lithium secondary battery has an energy density of 200 to 300 mWh/cm