Enhancing the electrochemical performance of Co-less Ni-rich LiNi0.925Co0.03Mn0.045O2 cathode material via Co-modification with Li2B4O7 coating and B3+ doping

Abstract

Lithium tetraborate coating and boron doping are applied to the Co-less Ni-rich LiNi0.925Co0.03Mn0.045O2 (NCM) cathode material to improve the physical and electrochemical properties. Boric acid is transformed into lithium tetraborate through reacting with residual lithium compounds (LiOH/Li2CO3) on the surface of the NCM cathode material at 650 °C for 4 h. According to the calculation of density functional theory (DFT), it is more likely that boron ions are introduced into both transition metal ion sites and oxygen tetrahedral gap sites in the lattice of the cathode material surface. The modification sample displays an outstanding rate performance and cycling retention of 72.86% after 100 cycles compared to the bare NCM (59.65% after 100 cycles) at 1C under 55 °C. In addition, by comparing structure and morphology of the two samples after cycling, it is demonstrated that the synergic modification can improve the electrochemical properties of the material by effectively stabilizing the crystal structure and mitigating the erosion of the electrolyte.