A computational study of the high voltage LixCoyMn4-yO8 cathode material

We present a theoretical investigation of a family of promising cathode mat erials, the spinel phases LixCoyMn4-yO8 where 0 less than or equal to x les s than or equal to 2 and 0 less than or equal to y less than or equal to 4. A combination of atomistic static lattice simulations and high quality ele ctronic structure calculations has been used to investigate the effects of cation ordering, the structural changes during lithium insertion and the un usually high cell voltages that have been measured in these materials. An a nalysis of the calculated electronic structures indicates that the generati on of discharge voltages over 5 V is linked to the reduction of cobalt atom s in the structure. The involvement of oxygen p states is also a possibilit y.