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

Abstract

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 Al_mNi_n(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.