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

Abstract

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.