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Structurally distorted MnO 2 is obtained via a simple Ni-doping treatment. The substantially accelerated electronic and ionic transfer kinetics contribute to an enhanced Na+ storage performance for supercapacitors applications. [Display omitted] • Structure distorted MnO 2 was prepared via Ni doping. • The Ni-MnO 2 shows high specific capacity and excellent rate performance. • Ni-MnO 2 exhibits delocalized electron and accelerated ionic transport kinetics. Manganese dioxide is a typical electrode material for supercapacitor due to its high theoretical capacitance and good environmental compatibility. However, the development of MnO 2 as electrode is limited by inferior conductivity, sluggish ionic transfer kinetics and poor cycling stability. Herein, we present a structure distortion strategy via Ni doping in MnO 2 to boost its Na+ storage performance. The as-obtained Ni-MnO 2 can deliver a high specific capacity of 379F g−1 at 1 A g−1, excellent rate performance of 281F g−1 at 20 A g−1, and a significantly enhanced cycling stability. In situ Raman results verify that Ni-MnO 2 with structure distortion can achieve a promising cycling life. Density functional theory results suggest that the structure distortion can efficiently modulate electron configuration by delocalizing electron. Furthermore, the Na+ diffusion energy barrier is remarkedly decreased in Ni-MnO 2 , thus accelerating ionic transport kinetics. An asymmetric supercapacitor based on Ni-MnO 2 cathode exhibits a high energy density of 114.6 Wh kg−1 at a power density of 3600 W kg−1. This work verifies the efficiency of structure distortion strategy on the improvement of Na ion storage performance in MnO 2 , which can be extended for the optimization of other electrode materials for energy storage. [ABSTRACT FROM AUTHOR]

Heterostructures of manganese oxides (MnO x , i.e., MnO and Mn 3 O 4) with carbon nitride (CN@MnO x) are prepared to boost the Na + storage capability of MnO x. Two different interfacial electric fields originated from the electronic redistribution at the interfaces of CN@MnO and CN@Mn 3 O 4 endow CN@MnO x with high reversible capacity of 305 F g−1 at 1 A g−1, ultrahigh rate capability of 223 F g−1 at 20 A g−1, and exceptional long-term cycling lifespan without significant capacity decay up to 5000 cycles at 1 A g−1. An asymmetric supercapacitor based on CN@MnO x electrode materials delivers a high energy density of 46.7 Wh kg−1 at a power density of 1000 W kg−1. Mechanism studies showed that the enhanced sodium ion storage performance in CN@MnO x is attributed to a dual-directional electronic modulation of MnO x , which simultaneously improve the electronic conductivity and accelerate the Na+ transfer kinetics. This work opens up a unique strategy to regulate the electronic structure of multi-phase electrode materials, and meanwhile provides new clues for the energy storage mechanism in multi-phase electrode materials. [Display omitted] • The electronic structure of multi-phase CN@MnO x is successfully regulated. • Dual electric fields are induced by dual-directional redistribution of charges. • The resultant CN@MnO x displays high capacity and significant rate capability. [ABSTRACT FROM AUTHOR]