The serious limitations of MnO2 are poor electrical conductivity and low utilization rate of electrochemical active area. These problems have seriously limited the application of MnO2 aqueous zinc‐ion batteries (AZIBs). Herein, preparing MnO2 uniformly loaded on carbon nanotubes with good electrical conductivity can greatly improve the poor electrical conductivity of MnO2. Moreover, by introducing oxygen vacancy, the surface capacitance, the reaction kinetics, and the electrochemical performance of MnO2 is increased. The specific capacity of the Vo‐MnO2/CNT material is 314 mAh g−1, at 0.2 A g−1, and capacity retention of 81% is achieved after 1000 cycles. In particular, the prepared device presents a distinct energy density of 416.2 Wh kg−1. As a result, the capacity as well as the cycle stability is effectively improved compared with the original MnO2.

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Suffering from the sluggish kinetics resulting from the inferior conductivity of manganese dioxide (MnO 2 ), many endeavors have been devoted to promoting the electrochemical performance of MnO 2 . Doping heteroatoms into host materials has emerged as an effective strategy to generate lattice vacancies for fast diffusion of ions/electrons in MnO 2 -based materials for supercapacitors (SCs). To eliminate the use of dangerous solvents and the severe reaction conditions used in previous reports, in this work, we first obtain N-doped MnO 2 (N−MnO 2 ) nanosheets with abundant oxygen vacancies simultaneously by a mild hydrothermal reaction. Thus, thanks to the mutual effect of N doping and oxygen vacancies, the capability of ion diffusion for N−MnO 2 /NGCF (NGCF represents N-doped single-wall carbon nanotube cross-linked graphene composite film) has increased an order of magnitude (1.68 × 10 −11 cm 2 s −1 compared with 8.42 × 10 −13 cm 2 s −1 for MnO 2 /NGCF) and shows superior rate capability, where at 30 A g −1 a capacitance retention of 51.7% remains, i.e., 185.1 F g −1 , compared with 44% at 15 A g −1 for MnO 2 /NGCF. In addition, we apply ex situ X-ray diffraction (XRD) and scanning electron microscopy (SEM) to verify the fact that nitrogen doping with abundant vacancies will benefit reversible intercalation/stripping of Na + by triggering the phase change from MnO 2 to MnOOH for N−MnO 2 compared with MnO 2 with adsorption/desorption during the charge−discharge process, which has never been discussed before. Excitingly, an asymmetric supercapacitor (ASC), fabricated by N−MnO 2 /NGCF as a cathode and MnO 2 /NGCF as an anode, delivers a maximum energy and power density of 75.3 Wh kg −1 and 18.1 × 10 3 W kg −1 , respectively. This work provides an approach to design self-standing advanced N-doped MnO 2 and a deeper insight into the mode of reaction of MnO 2 in neutral electrolyte for aqueous SCs.

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