Synthesis and electrochemical characterization of Fe and Ni substituted Li2MnO3—An effective means to use Fe for constructing 'Co-free' Li2MnO3 based positive electrode material

Equal amounts of Fe- and Ni-substituted Li2MnO3 (chemical formula: Li1+x[(Fe1/2Ni1/2)yMn1−y]1−xO2, 0 F m 3 ¯ m ). Electrochemical characterization as a positive electrode shows that the Li2O extraction region disappears above y = 0.6 on initial charging and that the energy density is decreased drastically above the composition on initial discharging. The optimized transition metal ratios are y = 0.4 and 0.5 because the initial average discharge voltage increases with y and the maximum initial cycle efficiency is attained. In the optimized composition, the Fe- and Ni-substituted Li2MnO3 is a 3.5 V class positive electrode, with similar charge and discharge profiles to those of the most attractive active material, NMC positive electrode (chemical formula: Li1+x[(Co1/2Ni1/2)yMn1−y]1−xO2, 0