▎ 摘　　要

The hierarchical nickel chloride/reduced graphene oxide (NiCl2-rGO) aerogels are synthesized via a facile hydrothermal and freeze-drying methods using low-cost nickel chloride hexahydrate (NiCl2.6H2O) as raw material. The NiCl2-rGO hybrid aerogel structure enables the uniform distribution of lamellar NiCl2 on the threedimensional (3D) cross-linked conductive graphene sheets. When employed as cathode for sodium-nickel chloride (Na-NiCl2) batteries, the as-obtained NiCl2-rGO aerogels exhibit excellent electrochemical performance with high reversible capacities (116 mAh g-1 after 50 cycles, 128 mAh g-1 in a fixed capacity window (20%-80% state of charge (SOC)) after 50 cycles), and a ultra-low polarization (0.05 V in the fixed capacity window). The outstanding performance of NiCl2-rGO aerogels can be attributed to the excellent conductivity of graphene. Moreover, the strong contact between NiCl2 and graphene sheets can effectively promote the transfer of electrons. Compared with traditional tubular Na-NiCl2 batteries, the molar ratio of Ni/NaCl of NiCl2-rGO aerogels can be decreased from 1.8 to the stoichiometric ratio (0.5). To the best of our knowledge, this work paves a perspective way for the first time to develop charged-state NiCl2-based cathodes with splendid performance for Na-NiCl2 batteries.