Improved electrochemical performance of layered Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ cathode material via VPO₅ coating

Li-excess Mn-based cathodes are thought to be viable cathode materials for next-generation lithium-ion batteries by reason of high discharge capacity and cheap price. However, the initial lattice oxygen loss and structural degradation lead to serious voltage decay and capacity fading in cycling, which significantly restricts their practical usage. Herein, VPO₅ is coated on spherical Li_1.2Ni_0.13Co_0.13Mn_0.54O₂ (LNCMO) by a simple wet chemical method. The VPO₅ layer shows good effect in inhibiting the initial irreversible O₂ release, increasing the structural stability of LNCMO, and suppressing side reactions at the interface of electrolyte and electrode. It turns out that the 2 wt% VPO₅-coated LNCMO possesses a discharge capacity of 289.8 mAh g⁻¹ at 0.1C with improved coulombic efficiency from 70.3 to 85.8%. The capacity retention is 80.8% after 200 cycles at 1C with average discharge voltage declines from 3.97 to 2.95 mV per cycle. This work shows that VPO₅ surface layer can effectively improve the cycling performances of LNCMO and provides an idea to modify Li-excess Mn-based cathode materials.