Non-metal anion doping construction of the durable cathode with optimized oxygen vacancies in aqueous zinc-ion batteries
Huiying Gao, Xie Jinfeng, Shirui Zhang, Mei Chengjia, Jun Liu, Du Haiqiong, Zhao Chengsi, Ni Weihai, He Huang, Xueqiang Qi
Abstract
Aqueous zinc-ion batteries have already shown promising prospects in electronic devices, owing to their environmentally benign nature and high safety. Manganese dioxide is studied as one kind of cathode material, however, it typically displays slow kinetics and unstable crystal structures. Defect engineering introduces active sites in MnO<sub>2</sub>, while metal ion doping increases material's molar mass, which offers rare zinc storage contribution. To find a feasible doping strategy with optimized oxygen vacancies is highly desirable. Herein, the incorporation of nitrogen-doped MnO<sub>2</sub> (NMO) with lower electronegativity as the cathode enabled the realization of reversible aqueous zinc-ion batteries. The structural stability and electrochemical properties of NMO were enhanced by nitrogen doping. NMO exhibited a smaller charge transfer resistance than pristine MnO<sub>2</sub> (279.6 Ω vs. 484.5 Ω). Cyclic voltammetry curves displayed that the incorporation of nitrogen doping could decrease the polarization, which provided a good basis for optimizing electrode kinetics. Specifically, the battery displayed a promising specific discharge capacity of 153.1 mAh·g<sup>–1</sup> at 0.5 A·g<sup>–1</sup> after 100 cycles. And at the current density of 1 A·g<sup>–1</sup>, the capacity retention of NMO after 1600 cycles was 1.72 times that of pristine MnO<sub>2</sub>. This study proposed a feasible idea for modifying non-metal hole sites in the cathode materials of zinc-based batteries, providing deep insights for future practical application of energy storage systems.