A substance includes an oxide including at least one element selected from the group including cobalt Co, nickel Ni, manganese Mn, iron Fe, and copper Cu; and silicon Si chemically bonded to the surface of the oxide. Also, a battery includes a cathode, an anode, and an electrolyte, wherein the cathode includes an oxide including at least one selected from the group including cobalt Co, nickel Ni, manganese Mn, iron Fe, and copper Cu; and a substance including silicon Si chemically bonded to the surface of the oxide.