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Design of Nickel-based cation-disordered rock-salt oxides: The effect of transition metal (M = V, Ti, Zr) substitution in LiNi0.5M0.5O2 binary systems

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Abstract

Cation-disorderedoxides have been ignored as positive electrode material for a long time, due tostructurally limited lithium insertion/extraction capabilities. In this work, acase study is carried outon nickel based cation-disordered Fm-3m LiNi0.5M0.5O2 positive electrode materials.The present investigation targets tailoring the electrochemical properties fornickel basedcation-disordered rock-salt by electronic considerations. The compositionalspace for binary LiM+3O2 with metals active for +3/+4 redoxcouples are extended to ternary oxides with LiA0.5B0.5O2 with A=Ni+2 and B=Ti+4 , Zr+4 and V+4 in order to assess the impact of the differenttransition metal in the isostructural oxides. The direct synthesis of variousnew unknownternary nickel based Fm-3m cation-disordered rock-salt positiveelectrode materials ispresented with a particular focus on the LiNi0.5V0.5O2 system. This positive electrode materialfor Li ion batteries displays an average voltage of ~ 2.55 V and a highdischarge capacity of264 mAhg-1 corresponding to 0.94 Li. For appropriate cut-off voltages, a long cyclelife is achieved. The charge compensation mechanism is probed by XANES,confirming thereversible oxidation and reduction of V4+/V5+. The enhancement in theelectrochemical performanceswithin the presented compounds stresses the importance of mixedcationdisordered transitionmetal oxides with different electronic configuration.