Recent progress in surface coating of cathode materials for lithium ion secondary batteries

The cathode serves as a key component in a lithium ion secondary battery, and its property significantly affects the battery performance. Thus, numerous researches have been carried out to develop both synthesis processes and modification methods of cathodes. Among different commonly used strategies for improving battery electrochemical performance, the cathode surface coating is an extremely useful and widely used one. However, the intrinsic mechanism of cathode coating is not completely clear, and thus a more comprehensive study is urgently needed. To meet this goal, in this review, we summarize the recent advances in the coating materials and technologies as well as the corresponding mechanisms for cathodes. Firstly, the characteristics of physicochemical properties for various common coating materials and their effects on the electrochemical performances of cathodes are introduced. Secondly, the effects of coating methods on cathode properties are discussed. Thirdly, the research status and recent progresses of cathodes with different crystal structures are reviewed respectively. The studies indicate that the structural characteristics of the cathode material play a very important role when selecting the coating material and the coating technology which should be carefully considered. Finally, the existing challenges and future directions to cathode surface coating are also suggested. (C) 2017 Elsevier B.V. All rights reserved.