Impact of Al or Mg substitution on the Thermal Stability of Li[sub 1.05]Mn[sub 1.95−z]M[sub z]O[sub 4] (M=Al or Mg)

Single phase Al or Mg-substituted ( or Mg) (, 0.05, 0.1, 0.15, 0.2) samples were synthesized by a two-step solid-state reaction. Electrochemical studies confirmed that Al or Mg substitution reduced the reversible specific capacity of . The effects of Al or Mg substitution on the thermal stability of charged samples in the presence of a 1 M ethylene carbonate:diethyl carbonate electrolyte were studied by accelerating rate calorimetry. The results showed that Al or Mg substitution has little effect on improving the thermal stability of . This is in contrast to the layered lithium transition-metal oxides (e.g., , , , and ), where Al substitution significantly lowers the kinetics of the reactions of the charged electrode materials with electrolyte.