Enhanced kinetics and stability for aqueous Zn battery enabled by low-cost additive chemistry

Rechargeable aqueous zinc(Zn) batteries are a sustainable alternative to lithium-based energy storage devices due to their high safety, low cost, and scalability. Unfortunately, the Zn/Zn2+ redox chemistry is significantly plagued by undesirable interface caused by the instability of water, which directly dictates the low Zn reversibility and dendrite growth behavior. Here, we report an aqueous electrolyte in which low-cost ammonium dihydrogen phosphate is utilized as an electrolyte additive to enable the in-situ construction of phosphate-based interphase on the Zn-metal surface. Importantly, such interphase not only effectively eliminates water-related parasitic reactions and enables a highly reversible Zn deposition/dissolution, as demonstrated by its high Coulombic efficiency of 99.3 %, but also contributes a dendrite-free Zn morphology. Apart from the improved stability of the Zn anode, the addition of NH4H2PO4 also grants the enhanced reaction kinetics of Zn2+, bringing a lower Zn2+ de-solvation energy barrier and much-improved rate performance. Benefiting from the synergistic factors, excellent cycling performances of the Zn0.25V2O5·nH2O (ZVO)/Zn batteries are guaranteed. Additionally, a 31.2 mAh ZVO/Zn pouch cell also demonstrates a stable long life of 400 cycles, and capacity retention of 67.8 % is also retained. The low-cost and efficient electrolyte strategy points out a promising direction for practical Zn batteries.