Synthesis of Nitrogen‐Doped KMn8O16 with Oxygen Vacancy for Stable Zinc‐Ion Batteries

Abstract The development of MnO 2 as a cathode for aqueous zinc‐ion batteries (AZIBs) is severely limited by the low intrinsic electrical conductivity and unstable crystal structure. Herein, a multifunctional modification strategy is proposed to construct N‐doped KMn 8 O 16 with abundant oxygen vacancy and large specific surface area (named as N‐KMO) through a facile one‐step hydrothermal approach. The synergetic effects of N‐doping, oxygen vacancy, and porous structure in N‐KMO can effectively suppress the dissolution of manganese ions, and promote ion diffusion and electron conduction. As a result, the N‐KMO cathode exhibits dramatically improved stability and reaction kinetics, superior to the pristine MnO 2 and MnO 2 with only oxygen vacancy. Remarkably, the N‐KMO cathode delivers a high reversible capacity of 262 mAh g −1 after 2500 cycles at 1 A g −1 with a capacity retention of 91%. Simultaneously, the highest specific capacity can reach 298 mAh g −1 at 0.1 A g −1 . Theoretical calculations reveal that the oxygen vacancy and N‐doping can improve the electrical conductivity of MnO 2 and thus account for the outstanding rate performance. Moreover, ex situ characterizations indicate that the energy storage mechanism of the N‐KMO cathode is mainly a H + and Zn 2+ co‐insertion/extraction process.