A rechargeable aqueous zinc/sodium manganese oxides battery with robust performance enabled by Na2SO4 electrolyte additive

Rechargeable aqueous Zn ion batteries (ZIBs) have recently attracted immense interest for large-scale energy storage systems stemming from their high natural abundance, environmental benignity, and high safety. However, the frustrating structural degradation in the cathode and the inherent Zn dendrite growth on the anode severely hinder the progress for future application. Herein, we report a zinc/sodium manganese oxides (denoted as Zn/NMO) battery with pre-inserted Na+ ions and crystal water in the cathode interlayer, which greatly facilitates cations diffusion without serious structural distortion. More importantly, Na2SO4 additive in ZnSO4-based electrolyte can eliminate Zn dendrites by modifying the deposited pattern of Zn2+ ions. Consequently, the Zn/NMO battery exhibits a high capacity (367.5 mAh g−1 at 0.65 C) and super long-term cyclic stability (only 0.007% capacity fading after 10000 cycles at 6.5 C). Besides, operando and ex situ electrochemical characterizations demonstrate that the formation of byproducts in the cathode surface leads to improved capacity and low Coulombic efficiency during the electrochemical activation process. Density functional theory (DFT) calculation further reveals the interface reaction mechanism, in which the solvation energy of electrolyte ions is responsible for the H+/Zn2+ insertion/extraction in the cathode material.