P-induced oxygen-deficient P-Ni2MnO4−x@rGO with enhanced energy density for supercapacitor

The intrinsically poor electrical conductivity and relatively low utilization efficiency of transition metal oxides limit their broad application in energy storage. Herein, engineering O vacancies and P doping have been employed by phosphorization treatment to boost the electrochemical performances of reduced graphene oxide (rGO)-wrapped P-Ni2MnO4−x (P-Ni2MnO4−x @rGO). The O vacancies and P doping not only improve the intrinsic electron conductivity but also create additional active sides. In addition, direct intimate contact between P-Ni2MnO4−x and rGO provides conducting framework for charge transfer. Thus, the utilization efficiency and the reaction activity of P-Ni2MnO4−x @rGO can be significantly improved. Benefiting from above advantages, P-Ni2MnO4−x @rGO electrode exhibits a maximum specific capacitance of 1344.7 F g−1 at 1 A g−1 and good rate capability. Moreover, the assembled asymmetric supercapacitor P-Ni2MnO4−x @rGO//hollow carbon sphere shows a high energy density of 87.5 W h kg−1 at a power density of 294.0 W kg−1, and it has an excellent cycling performance with 94.9% capacity retention at 5 A g−1 after 10000 cycles. The outstanding performances of P-Ni2MnO4−x @rGO make it become a competitive candidate for high-performance supercapacitors.