A strategy of constructing spherical core-shell structure of Li_1.2Ni_0.2Mn_0.6O₂@Li_1.2Ni_0.4Mn_0.4O₂ cathode material for high-performance lithium-ion batteries

Serious decay of capacity and voltage for Li-rich layered cathode materials restrict their commercial application for Li-ion batteries. In this paper, a spherical core-shell structure, Li_1.2Ni_0.2Mn_0.6O₂@Li_1.2Ni_0.4Mn_0.4O₂ was in-situ prepared using hydrothermal method. SEM images as well as the analysis with XPS and EDS verified that the core-shell structure grows well. Electrochemical properties showed that the merits of the both materials have been preserved for high capacity of core material and high voltage as well as superior cycling stability of shell material. C/S-1/1 sample, whose mass proportion of core to shell is 1:1, exhibits the initial discharge capacity of 218 mAh·g⁻¹ with the highest operating voltage of 3.763 V at 0.1C between 2.0 and 4.8 V, splendid cycling stability with the capacity retention of 93.1% and high voltage retention value of 3.335 V after 100 cycles. The improvement of electrochemical performances are attributed to the stable Li_1.2Ni_0.4Mn_0.4O₂ protective shell, which is beneficial to improve the electrochemical kinetics, mitigate the morphology evolution and retard the layered-spinel phase transition by restraining the release of O₂ and weakening the electrode-electrolyte interfacial reaction.