A detailed investigation of the structural and electrochemical impact of lithium and fluorine substitutions on the 4.7 V LiMn1.5Ni0.5O4−δ (LMNO) positive electrode for Li-ion batteries was accomplished. Impact of subsequent transition metal substitution on the tetrahedral 8a sites was also investigated relative to rate and elevated temperature cycling stability. Significantly improved cycling in excess of 600 cycles was established for an anion modified spinel relative to an optimized benchmark material at 60 °C.