Magnesium substitution to improve the electrochemical performance of layered Li₂MnO₃ positive-electrode material

Li₂MnO₃ has received lots of attention due to its large theoretical capacity. However, its application is obstructed by low practical capacity and poor cycling stability. Here, a new tactic of magnesium substitution for partial lithium to improve the electrochemical performance of Li₂MnO₃ by a traditional solid state reaction is presented. Sample with only 1% magnesium content delivers a large initial discharge capacity of 307.5 mAh g⁻¹ which is much superior than the 241.9 mAh g⁻¹ of pristine Li₂MnO₃. The cycling performance also get improved that the capacity retention is 84.5% for Li_1.98Mg_0.01MnO₃ but only 77.7% for pristine counterpart after 30 cycles at 0.1 C. Moreover, the effective suppression of voltage decay has been achieved because of improved kinetic properties and leads to a tremendous progress in the energy density which is as much as 944 Wh kg⁻¹ for Li_1.98Mg_0.01MnO₃ compared with 747.1 Wh kg⁻¹ of Li₂MnO₃. These achievements attained by Mg-doping make Li₂MnO₃ a promising positive-electrode material for the next generation of lithium ion batteries.