Defect Promoted Capacity and Durability of N‐MnO2–x Branch Arrays via Low‐Temperature NH3 Treatment for Advanced Aqueous Zinc Ion Batteries

Abstract Defect engineering (doping and vacancy) has emerged as a positive strategy to boost the intrinsic electrochemical reactivity and structural stability of MnO 2 ‐based cathodes of rechargeable aqueous zinc ion batteries (RAZIBs). Currently, there is no report on the nonmetal element doped MnO 2 cathode with concomitant oxygen vacancies, because of its low thermal stability with easy phase transformation from MnO 2 to Mn 3 O 4 (≥300 °C). Herein, for the first time, novel N‐doped MnO 2– x (N‐MnO 2– x ) branch arrays with abundant oxygen vacancies fabricated by a facile low‐temperature (200 °C) NH 3 treatment technology are reported. Meanwhile, to further enhance the high‐rate capability, highly conductive TiC/C nanorods are used as the core support for a N‐MnO 2– x branch, forming high‐quality N‐MnO 2– x @TiC/C core/branch arrays. The introduced N dopants and oxygen vacancies in MnO 2 are demonstrated by synchrotron radiation technology. By virtue of an integrated conductive framework, enhanced electron density, and increased surface capacitive contribution, the designed N‐MnO 2– x @TiC/C arrays are endowed with faster reaction kinetics, higher capacity (285 mAh g −1 at 0.2 A g −1 ) and better long‐term cycles (85.7% retention after 1000 cycles at 1 A g −1 ) than other MnO 2 ‐based counterparts (55.6%). The low‐temperature defect engineering sheds light on construction of advanced cathodes for aqueous RAZIBs.