The present invention includes compositions and methods of making cation-substituted and fluorine-substituted spinel cathode compositions by firing a LiMn.sub.2-y-zLi.sub.yM.sub.zO.sub.4 oxide with NH.sub.4HF.sub.2 at low temperatures of between about 300 and 700.degree. C. for 2 to 8 hours and a .eta. of more than 0 and less than about 0.50, mixed two-phase compositions consisting of a spinel cathode and a layered oxide cathode, and coupling them with unmodified or surface modified graphite anodes in lithium ion cells.
STATEMENT OF FEDERALLY FUNDED RESEARCH
This invention was made with U.S. Government support under Contract No. DE-AC03-76SF00098 (Subcontract No. 6712770) awarded by the U.S. Department of Energy. The government may have certain rights in this invention.