Improvement of superior cycle performance of LiNi0.8Co0.15Al0.05O2 cathode for lithium-ion batteries by multiple compound modifications

Structural degradation and side reaction in cathode materials have been regarded as the main issues that compromise the capacity and cycle stability of Ni-rich LiNi 0.8 Co 0.15 Al 0.05 O 2 . Herein, an inside-out modification method was reported to stabilize internal structure and restrain side reactions of LiNi 0.8 Co 0.15 Al 0.05 O 2 , composing of doping Mg inside the layer structure and coating Al 2 O 3 outside the cathode materials particles. Through dual protection strategies, an unprecedented capacity retention as high as 99% after 100   cycles and 95% after 250   cycles (from 178 to 168.9   mAh   g −1 ) was achieved at 1.0C, which are much more superior among LiNi 0.8 Co 0.15 Al 0.05 O 2 cathodes using previously reported modification methods. X-ray diffraction results indicated that Al and Mg ions were successfully introduced into the bulk materials and exhibited excellent hexagonal structure. This work highlights that the multiple modified method is a promising strategy to enhance the cycling performance of LiNi 0.8 Co 0.15 Al 0.05 O 2 , and these enhancements can be attributed to the protection from “inside” to “outside” of LiNi 0.8 Co 0.15 Al 0.05 O 2 particles, which suppress phase transition and cation mixing inside the materials, and reduce side effects outside the particles, thus allows for rapid electron transport during the electrochemical Li + insertion/extraction reaction.