Novel olivine and spinel LiMAsO4 (M = 3d-metal) as positive electrode materials in lithium cells

New olivines LiMAsO₄ (M = Mn, Fe, Co, and Ni) have been tested as positive electrode in lithium cells. Under the used experimental conditions we did not succeed to remove lithium ions from LiFeAsO₄, LiMnAsO₄ or LiNiAsO₄. More work is needed in order to verify whether the lack of electrochemical activity is intrinsic to these materials, or it is due to kinetical limitations such as particle size and poor conductivity. On the contrary lithium ions could be reversibly deinserted/inserted from/into LiCoAsO₄ at average voltages of 4.8 and 4.6 V respectively; the delithiated compound maintaining the olivine structural framework.The high pressure polymorph of LiMAsO₄ (M = Fe, Co, Ni) crystallizing with the spinel structure did not show any electrochemical activity potentially useful in rechargeable lithium batteries.