Boosting the electrochemical performance of LiCoO2 by triple-phase interface via “island-bridge” shaped surface coating

Surface coating as an effective strategy has been extensively utilized to enhance the surface/interface stability of cathode for lithium-ion batteries. As widely recognized, the electrochemical performance of coated cathode is greatly dependent on the properties of coating layer. Rational design on the structure and composition of coating layer becomes crucial. Here, a unique "island-bridge" shaped Zr-based coating layer has been constructed through a facile synthetic protocol. This coating layer composes of several high-crystalline ZrO2 nanoparticles and a thin low-crystalline zirconium hydroxide layer that connects these nanoparticles, forming a typical "island-bridge" structure. The successful formation of such a unique coating layer was demonstrated to be related to the usage amount of Zr source and the calcined temperature. The novel "island-bridge" coating has been successfully applied to modify the surface of LiCoO2, showing excellent capability on improving the electrochemical performance. The unique "island-bridge" structure coating induces the formation of a triple-phase interface, namely island-cathode-bridge interface. Theoretical calculation suggests that such an island-cathode-bridge triple-phase interface can effectively reduce the Li+ diffusion energy, leading to favorable Li+ transportation kinetics and suppressed cathode-electrolyte interface evolution. Furthermore, this "island-bridge" layer can well prevent direct contact between LiCoO2 and electrolyte, enhancing the surface/interface stability, resulting in improved cyclic performance. This work provides new insights into the rational design of surface coating for high-energy density cathodes.