The effect of Al substitution on the reactivity of delithiated LiNi((0.5-z))Mn((0.5-z))A1(2z)O(2) with nonaqueous electrolyte

The high-temperature reactions between 1 M LiPF6 ethylene carbonate:diethyl carbonate and Al-doped LiNi(0.5-z)Mn(0.5-z)Al2zO2 charged to 4.3 V are studied by accelerating rate calorimetry and compared with those of charged LiNi1/3Mn1/3Co1/3O2 and spinel LiMn2O4. Simultaneous Al substitution for Ni and Mn in LiNi0.5Mn0.5O2 improves the thermal stability. The maximum self-heating rate attained and the specific capacity decrease as the Al content increases. Materials with z>0.03 are less reactive with electrolyte than spinel LiMn2O4 at all temperatures studied. There is a range of compositions near z=0.05 that show excellent promise as materials which are both safer and more energy dense than spinel LiMn2O4. (C) 2008 The Electrochemical Society.