A simple way to enhance graphite as cathode for dual-ion batteries: An in-situ formed coating layer of hydrolysate from ZIF-8

Dual-ion batteries (DIB) have drawn much attention because of their advantages such as low cost, high energy density, and high power density. Graphite has been considered as one of the most promising cathode materials for DIBs due to its low cost, good electron conductivity, environment friendliness and unique two-dimensional layered structure. However, graphite still suffers from limited cycling stability caused by the structural collapse of graphite, resulting from the repeated intercalation/deintercalation of anions, solvent co-intercalation, and electrolyte decomposition on the electrode/electrolyte interface. In this work, the electrochemical performances of graphite cathode are significantly enhanced through a simple way by in-situ coating of the hydrolysate Zn 5 (HMIM) 4 (MIM) 6 (OH) 4 (labeled as ZnHM) derived from ZIF-8, which was performed in aqueous solution at room temperature. It is found that a capacity retention as high as 84 % with the discharge capacity of 65 mA h g −1 after 1000 cycles at 100 mA g −1 was achieved. More importantly, ca. 70 % of the initial discharge capacity is retained even after 3000 cycles at 500 mA g −1 . These remarkable electrochemical properties are attributed to the coating layers of ZnHM on graphite surface, which inhibit the co-intercalation of solvent molecules, keep the structural stability of graphite, and hinder the decomposition of electrolyte.