Abstract: Improved stabilized spinel battery cathode material and methods of treating particles of spinel battery cathode material to produce a protective coating of battery-inactive lithium metal oxide on the particles are provided. The methods basically comprise mixing the spinel particles with a particulate reactant selected from a lithium salt, a lithium metal oxide or a mixture of a lithium salt and a metal oxide and then heating the resultant particulate mixture for a time and temperature to react the particulate reactant with the spinel particles whereby a protective coating of lithium metal oxide is formed on the spinel particles and the lithium content of the spinel adjacent to the coating is increased a limited amount.

Abstract: A series of electroactive insertion compounds, LiM.sub.y.sup.II M.sub.z.sup.III Mn.sub.l.sup.III Mn.sub.q.sup.IV O.sub.4 (0<y+z.ltoreq.0.5, y+z+l+q=2), where M=any transition metal or combination of metals, for application in non-aqueous batteries, capacitors, and superconducting materials, are disclosed. These newly synthesized compounds are unique in that they contain at least two mixed valence elements, thereby allowing the reversible intercalation of lithium cations at potentials near 4.7-5.1 V vs. lithium. Also disclosed are novel copper insertion compounds of the formula LiM.sub.y Cu.sub.0.5-y Mn.sub.1.5 O.sub.4 (0.ltoreq.y.ltoreq.0.49), where M=one or more metals or transition metals. Such materials have also been found to be remarkably stable at this voltage upon repeated cycling.