Surface engineering of LiNi0.8Mn0.1Co0.1O2 towards boosting lithium storage: Bimetallic oxides versus monometallic oxides

Although conventional monometallic oxide coating on lithium nickel cobalt manganese oxide (NCM) cathode materials has been extensively investigated, there are still many issues, such as low electrical conductivity, poor mechanical properties and inferior chemical stability, that need to be addressed. Indeed, because of the single nature of monometallic oxides, it is difficult to achieve the synergistic effect of various properties. In this work, NiCo2O4 were rationally grown on the surface of commercial LiNi0.8Mn0.1Co0.1O2 (NCM811) to obtain a bimetallic oxide coated NCM811 as cathode material for Lithium ion batteries (LIBs). This cleverly designed coating with a higher electronic and ionic conductivity, better bulk modulus, and an outstanding interfacial stability, could improve the capacity retention to 90.97% after 200 cycles at 100 mA g(-1) and enhance the initial coulombic efficiency (CE) to 82.92%. The electrochemical characterization further clarifies the indisputable benefits of NiCo2O4 coating to enhancement of the cathode performance. Moreover, the theoretical calculations provide more explanations in three aspects, including mechanical stability, chemical stability and electrical properties, confirming the superiority of NiCo2O4 bimetallic oxide coating with multiple properties over the monometallic one. More importantly, this study has profound implications in the design of bimetallic and polymetallic oxide coatings for electrode materials, and even other bimetallic coatings, such as sulfides and selenides, in the future.