A metal-ion battery are provided. The disclosure provides a metal-ion battery. The metal-ion battery includes a positive electrode; a negative electrode, wherein the negative electrode is a metal or an alloy thereof, the metal is Cu, Fe, Zn, Co, In, Ni, Sn, Cr, La, Y, Ti, Mn, or Mo; a separator, wherein the positive electrode is separated from the negative electrode by the separator; and an electrolyte, disposed between the positive electrode and the negative electrode. The electrolyte includes ionic liquid, aluminum halide.