Structural features of complete and partial activation of Li-rich cathodes studied by in-situ XRD

Li-rich oxides are materials shows a high specific discharge capacity which is achieved through a special charging procedure called activation. Still, these materials have the following disadvantages: a short cycle life and a drop of average discharge voltage. This paper describes the synthesis of Li 1.2 Ni 0.13 Co 0.13 Mn 0.54 O 2 (LMR) and its 5 at.%. K doping (LMRK) by the sol-gel method. A capacity of the produced materials equals to 232 mAh/g for LMR and 228 mAh/g for LMRK, respectively, under 0.1 С discharge current. The criterion of Li 2 MnO 3 phase complete activation was suggested following the results of studying charge/discharge curves and structural changes revealed with the use of in situ XRD method. This criterion has become a basis for determining the charge/discharge modes (current, voltage) required for Li 2 MnO 3 phase complete activation. It has been found out that elevated current increases the voltage at which complete activation occurs. K doping affects the material diffusion characteristics and results in an extra increase in voltage at which complete activation occurs. The obtained results can be used to study the activation of Li-rich cathodic materials and to select the optimum operation mode of lithium-ion batteries manufactured with the use of such materials.