Improving Electrochemical Cycling Stability of Ni‐rich LiNi 0.91 Co 0.06 Al 0.03 O 2 Cathode Materials through H 3 BO 3 and Y 2 O 3 Composite Coating

The nickel‐rich LiNi 0.91 Co 0.06 Al 0.03 O 2 cathode material has attracted wide attention due to its high energy density and appropriate thermal stability; however, its practical application has been greatly restricted by exorbitant residual LiOH/Li 2 CO 3 and poor cycling performance. In this work, we have reduced the residual LiOH/Li 2 CO 3 by washing the LiNi 0.91 Co 0.06 Al 0.03 O 2 fabricated through a high‐temperature solid‐state method and improved the cycling performance with a composite coating process. The results show that the amount of residual LiOH/Li 2 CO 3 in the washed materials is significantly decreased, which is very favorable for the processability of materials. LiNi 0.91 Co 0.06 Al 0.03 O 2 with 0.1 wt% composite coating exhibits optimum properties: the discharge capacity reaches 217.4 mAh/g at 0.1 C, the cycling retention still remains at 93.7 % after 100 cycles at 1 C, and the cycling retention of the soft‐packing battery remains as high as 81.7 % after 800 cycles at 1 C. The excellent electrochemical performances are attributed to the synergistic effect of excellent fluidity of H 3 BO 3 and outstanding stability of Y 2 O 3 , mitigating the interface reaction between electrolyte and cathode material.