Simultaneously enhanced electrochemical performance and air stability of Ni‐rich cathode with a modified washing process

Abstract Water washing has been regarded as one of the most effective strategies to remove surface residual lithium of nickel‐rich layered oxides for lithium‐ion batteries (LIBs). However, the loss of lattice lithium during the water washing process deteriorates the electrochemical performances and air stability. Herein, washing the LiNi 0.90 Co 0.08 Al 0.02 O 2 (NCA) with ammonium dihydrogen phosphate (NH 4 H 2 PO 4 ) solution has been proposed to simultaneously enhance electrochemical performances and air stability, in which in‐situ generated Li 3 PO 4 coating layer on surface of NCA can suppress the loss of lattice lithium. Besides, as a fast ionic conductor, Li 3 PO 4 coating layer on NCA can prevent the direct contact with electrolyte/air. As a result, the NH 4 H 2 PO 4 solution washed NCA cathode can deliver a high capacity of 131.9 mAh·g −1 at 10.0C rate as well as impressive cycle stability with a capacity retention of 83.1% after 100 cycles at 1.0C, much higher than those of water washed NCA (WS‐NCA) electrode. After exposed in air for 7 days, the NH 4 H 2 PO 4 solution washed NCA electrode can more effectively maintain the structural integrity as well as the electrochemical performances than water‐washed NCA. This work provides a simple and effective approach to enhance the cycle stability and air stability of Nickel‐rich cathode materials.