Improving electrochemical performance of LiNi0.8Co0.1Mn0.1O2 cathode via polyanionic TiP2O7 coating

Abstract

Safety issues of common rechargeable Li-ion batteries (LIB) necessitate urgent development of alternative high-performance electrode materials. Lithiated nickel-rich oxides (LiNi_1-x-yMn_xCo_yO₂) are promising LIB cathode materials, but they suffer from structural instabilities causing major capacity loss. To address this issue, here we use a robust ethanol-based wet coating process to coat a LiNi_0.8Co_0.1Mn_0.1O₂ LIB cathode material with polyanionic compound TiP₂O_7. The coating layer does not affect the phase structure of LiNi_0.8Co_0.1Mn_0.1O₂ and ensures a remarkable electrochemical performance, evidenced by the high initial Coulombic efficiency, durable cyclic stability, and excellent rate performance. The mechanisms leading to the achieved improvements are related to the effects of the coating layer which improved the Li⁺ diffusion capability and the electrochemical polarization. The TiP₂O₇ layer protects the electrode from the electrolyte by suppressing side reactions such as HF acidic attack and the associated dissolution of transition metal ion. Moreover, the unique three-dimensional (XO_n)^m- framework of the TiP₂O₇ polyanion provides plentiful accommodation sites and channels for the Li-ions diffusion. The demonstrated approach opens new avenues for practical applications of electrochemically active coatings in diverse energy storage devices and systems.