Facile synthesis of Ni11(HPO3)8(OH)6/rGO nanorods with enhanced electrochemical performance for aluminum-ion batteries.

The electrochemical behaviors of the ultrashort nickel phosphite nanorods supported on reduced graphene oxide (Ni11(HPO3)8(OH)6/rGO nanorods), as a candidate for cathodic applications in aluminum-ion batteries, are firstly investigated. Ni11(HPO3)8(OH)6/rGO nanorods are synthesized by a facile solvothermal process. Ni11(HPO3)8(OH)6 and Ni11(HPO3)8(OH)6/rGO cathodes both possess very high initial discharge capacities of 132.4 and 182.0 mA h g-1 at a current density of 200 mA g-1, respectively. In addition, the long-term cycling stability of the Ni11(HPO3)8(OH)6/rGO cathode is further evaluated, exhibiting a discharge capacity of 49.2 mA h g-1 even over 1500 cycles. More importantly, the redox reaction mechanism of the Ni11(HPO3)8(OH)6 cathode for aluminum-ion batteries revealed that Ni11(HPO3)8(OH)6 is partially substituted with Al3+ to form AlmNin(HPO3)8(OH)6 and metallic Ni in the nanorod-like Ni11(HPO3)8(OH)6 cathodes during the discharge process. These findings are of great significance for the further development of novel materials for aluminum-ion batteries.