Polydopamine derived carbon coated cobalt molybdenum layered double hydroxide as highly stable anode materials of sodium-ion battery

Two-dimensional layered double hydroxide (LDH) has promising open spaces for efficient Na+ + diffusion/ migration. Also, cobalt-based materials have high theoretical capacities and molybdenum incorporations can enhance electrical conductivity. Therefore, cobalt and molybdenum LDH is considered as an efficient anode material of sodium-ion battery (SIB). Nevertheless, volume expansion of LDH may limits the electrochemical performance of SIB. In this work, polydopamine (PDA) derived carbon coated cobalt molybdenum LDH (CoMoLDH) is synthesized via the hydrothermal, polymerization and carbonization processes as a novel anode material of SIB. Hydrothermal and polymerization durations are optimized to regular the morphology of CoMoLDH and achieve the suitable thickness of carbon layer. The optimal carbon coated CoMoLDH (CoMoLDHC-PDA) anode shows a high specific capacity of 779.9 mAh/g at 0.05 A/g. After 100 cycles, the CoMoLDH-C-PDA anodes still presents a specific capacity of 310.9 mAh/g corresponding to capacity retentions of 70.0%. High specific capacity, excellent rate performance and long-term cyclic ability of CoMoLDH-C-PDA are attributed to the higher Na+ + diffusion coefficient and smaller charge-transfer resistances. This study brings a blueprint for modifying novel bimetallic LDH with well-designed carbon coating, which is worthy to apply on other bimetallic LDH for enhancing rate performance and cycle life of SIB in the future.