Boosting Aqueous Zn/MnO₂ Batteries via a Synergy of Edge/Defect-Rich Cathode and Dendrite-Free Anode

Aqueous Zn/MnO2 batteries exhibit huge potential for grid-scale energy storage but suffer from poor cycling stability derived from both structural instability of cathode and Zn dendrite growth of anode. Here, we report a high-performance aqueous Zn/MnO2 battery with ZnSO4-based electrolyte, comprising a nanoparticle-like cathode with abundant surface oxygen defects (MO-Vo) and a dendrite-free Zn anode. The transformation from nanowire (α-MnO2) to nanoparticle (MO-Vo) was found by tuning the annealing conditions in an argon flow. Moreover, the small size of MO-Vo nanoparticles can effectively promote the spatially uniform distribution of volume stress during carrier intercalation, boosting the structural stability of the MO-Vo cathode. Moreover, it was found that the intercalation pseudocapacitive behavior of Zn2+ in the MO-Vo cathode can be strongly boosted by tailoring the surface oxygen defect of MnO2 based on the calculations and experiments, thereby achieving enhanced cycling stability and redox kinetics. Additionally, the addition of K2SO4 additive into the electrolyte can tailor the deposition behavior of Zn2+, enabling stable Zn stripping/plating without dendrites. Therefore, the assembled Zn/MO-Vo batteries exhibit a high energy density and excellent long-term cyclability over 1400 cycles. Besides, the reaction mechanism of pseudocapacitive Zn2+ intercalation and H+ intercalation for the MO-Vo cathode was revealed via ex situ characterizations.