Removing lithium residues via H3BO3 washing and concurrent in-situ formation of a lithium reactive coating on Ni-rich cathode materials toward enhanced electrochemical performance

Nickel-rich layered oxides are the most promising cathode materials for lithium-ion batteries owing to their high theoretical mass and volumetric energy densities. However, voltage attenuation caused by rupture of the secondary particle structure during charging and discharging severely precludes their practical application. Using LiNi0.8Co0.1Mn0.09Al0.01O2 (NCMA) as a model system, we developed a strategy that simultaneously removed inherent lithium residues and formed a boron-containing lithium compound coating using an H3BO3 solution and subsequent annealing. NCMA obtained after boric acid washing displayed a high specific capacity (220.6 and 200.8 mAh•g−1 at rates of 0.1 and 1 C, respectively) and good cycle stability (capacity retention of 85.66% after 200 cycles). This method removed excess LiOH and Li2CO3 and formed a stable coating on the material surface. Consequently, voltage attenuation caused by the disintegration of transition metals was prevented, while simultaneously enhancing the structural stability and electrochemical performance of the material.