Abstract: Disclosed is a lithium-ion battery, where the lithium-ion battery includes a positive electrode active material, and the positive electrode active material includes lithium cobalt oxide particles doped with one or more elements of Al, Mg, Ti, Zr, Ni, Mn, Y, La, Sr, W, or Sc. When the lithium-ion battery is in an SOC of 0%, a molar ratio of an element lithium to an element cobalt in the positive electrode active material is A, and when the lithium-ion battery is in an SOC of 100%, a molar ratio of the element lithium to the element cobalt in the positive electrode active material is B, where 0.62?(A?B)?0.655. The lithium-ion battery provided in the present disclosure has good cycling performance at a high voltage.