Improved electrochemical performance of Li(Ni0.6Co0.2Mn0.2)O2 at high charging cut-off voltage with Li1.4Al0.4Ti1.6(PO4)3 surface coating*

Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 has been surface-modified by the lithium-ion conductor Li 1.4 )Al 0.4 )Ti 1.6 )(PO 4 ) 3 via a facile mechanical fusion method. The annealing temperature during coating process shows a strong impact on the surface morphology and chemical composition of Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 . The 600-°C annealed material exhibits the best cyclic stability at high charging cut-off voltage of 4.5 V ( versus Li + /Li) with the capacity retention of 90.9% after 100 cycles, which is much higher than that of bare material (79%). Moreover, the rate capability and thermal stability are also improved by Li 1.4 )Al 0.4 )Ti 1.6 )(PO 4 ) 3 coating. The enhanced performance can be attributed to the improved stability of interface between Li(Ni 0.6 Co 0.2 Mn 0.2 )O 2 and electrolyte by Li 1.4 )Al 0.4 )Ti 1.6 )(PO 4 ) 3 modification. The results of this work provide a possible method to design reliable cathode materials to achieve high energy density and long cycle life.