Plasma-assisted coating of nanosized SnO2 on LiNi0.5Co0.2Mn0.3O2 cathodes for enhanced cyclic stability of lithium-ion batteries

Layered Ni-rich cathode materials, LiNixCoyMnzO2, are regarded as the most promising cathode materials due to their high energy density. However, their poor cyclic stability at high voltage significantly limits their commercial application. To address this problem, a series of SnO2-x surface-modified LiNi0.5Co0.2Mn0.3O2 cathode materials is prepared by a one-step plasma-assisted milling strategy. The conductive SnO2 nanograins are homogeneously coated on the surface of LiNi0.5Co0.2Mn0.3O2 microsized particles under the interaction of plasma and mechanical energy. As a result, the electrode consisting of milled LiNi0.5Co0.2Mn0.3O2 coated with 3 wt % SnO2 exhibits a high initial Coulombic efficiency of 82.7% and a good capacity retention of 92.3% after 150 cycles. This is superior to the other milled control materials and a commercial LiNi0.5Co0.2Mn0.3O2 electrode with an initial Coulombic efficiency of 77.4% and a capacity retention of 87.1% after 150 cycles. It is demonstrated that the synergistic effect of high energy plasma and milling-induced oxygen vacancies in the SnO2-x surface protection layers of the LiNi0.5Co0.2Mn0.3O2 cathode enable greatly increased conductivity of the active materials and stable interfaces between the electrolyte and electrode. These factors are beneficial to provide a higher discharge capacity and enhanced cyclic stability in the 3 wt % SnO2 coated LiNi0.5Co0.2Mn0.3O2 cathode.