Dual function Li-reactive coating from residual lithium on Ni-rich NCM cathode material for Lithium-ion batteries

In this study, lithium phosphate (Li₃PO₄) is coated on the surface of Ni-rich LiNi_0.91Co_0.06Mn_0.03O₂ cathode material to enhance its cyclability and rate performance. The process is carried-out by achieving dual benefits, reduction of residual lithium compounds by converting them into Li₃PO₄ coating material. The 0.1 mol.% Li₃PO₄ (LiP) sample exhibits a capacity retention of 82% while the pristine NCM shows only 68.1% after 100 cycles. In addition, the LiP-0.1 NCM delivers high discharge capacities (161.9 mAh g^-1 at 3C, 144.3 mAh g^-1 at 4C and 94.6 mAh g^-1 at 5C) as compared to the pristine NCM (129.3 mAh g^-1 at 3C, 67.4 mAh g^-1 at 4C and 33.4 mAh g^-1 at 5C) in the voltage range of 3.0-4.3 V. In addition, the irreversible phase transition has also suppressed in the coated sample which is confirmed by cyclic voltammetry. Our study suggests that Li₃PO₄ coating reduces the polarization and acts as protecting layer between the electrode and electrolyte that results in the superior electrochemical performance.