Nickel phosphite (Ni11(HPO3)8(OH)6) superstructures assembled by nanotubes are synthesized under mild hydrothermal conditions with the sodium salt of polystyrene sulfonic acid. More importantly, Ni11(HPO3)8(OH)6 superstructures are applied as electrode materials for supercapacitors. Benefitting from their novel superstructures, in a three-electrode system, Ni11(HPO3)8(OH)6 superstructure electrodes show a good specific capacitance (1876 F g−1 at 0.625 A g−1), good rate capability, and excellent cycling properties (95 % of the initial specific capacitance at 6.25 A g−1 after 2000 cycles) in 3.0 M KOH. Additionally, asymmetric Ni11(HPO3)8(OH)6–graphene nanosheet supercapacitors are also designed. The specific energy of a cell in 3.0 M KOH reaches about 28.6 Wh kg−1 at 92.5 W kg−1.