A lithium ion battery includes an anode and a cathode. The cathode includes a lithium, manganese, nickel, and oxygen containing compound. An electrolyte is disposed between the anode and the cathode. A protective layer is deposited between the cathode and the electrolyte. The protective layer includes pure lithium phosphorus oxynitride and variations that include metal dopants such as Fe, Ti, Ni, V, Cr, Cu, and Co. A method for making a cathode and a method for operating a battery are also disclosed.
STATEMENT REGARDING FEDERALLY SPONSORED RESEARCH
 This invention was made with government support under contract No. DE-AC05-00OR22725 awarded by the U.S. Department of Energy. The government has certain rights in this invention.