Enhanced Electrochemical and Structural Stability of Ni-rich Cathode Material by Lithium Metaborate Coating for Lithium-Ion Batteries

A facile mechanical mixing-calcination method was employed to coat lithium metaborate onto LiNi_0.88Co_0.06Mn_0.03Al_0.03O₂ cathode. Physical characterizations revealed that the coating layer was uniformly spread on the surface of the material particles, and did not alter the structure and morphology. Electrochemical measurements indicated that the surface-modified cathode showed significantly improved cycling stability, both under room-temperature and high-temperature (50 °C). The coated sample delivered an initial discharge capacity of 211.0 mAh g⁻¹ at 0.1 C, and a capacity retention of 87.5 % after 300 cycles at 1 C rate under room-temperature. Meanwhile, it could maintain 97.2 % of initial capacity after 120 cycles at 1 C under 50 °C, which was much higher than the value of the pristine sample (only 37.2 %). The lithium-ion diffusion kinetics was analyzed by electrochemical impedance spectroscopy. The coated material exhibits lower surface resistance and charge-transfer resistance, as well as faster lithium-ion diffusion than the pristine one. The materials were also characterized after cycling. The surface-modified sample possessed more stable surficial and structural stability.