Manipulating the Solvation Structure and Interface via a Bio-Based Green Additive for Highly Stable Zn Metal Anode

The practical application of aqueous zinc-ion batteries (AZIBs) is limited by serious side reactions, such as the hydrogen evolution reaction and Zn dendrite growth. Here, the study proposes a novel adoption of a biodegradable electrolyte additive, γ-Valerolactone (GVL), with only 1 vol.% addition (GVL-to-H₂O volume ratio) to enable a stable Zn metal anode. The combination of experimental characterizations and theoretical calculations verifies that the green GVL additive can competitively engage the solvated structure of Zn²⁺ via replacing a H₂O molecule from [Zn(H₂O)₆]²⁺, which can efficiently reduce the reactivity of water and inhibit the subsequent side reactions. Additionally, GVL molecules are preferentially adsorbed on the surface of Zn to regulate the uniform Zn deposition and suppress the Zn dendrite growth. Consequently, the Zn anode exhibits boosted stability with ultralong cycle lifespan (over 3500 h) and high reversibility with 99.69% Coulombic efficiency. The Zn||MnO₂ full batteries with ZnSO₄-GVL electrolyte show a high capacity of 219 mAh g^-1 at 0.5 A g^-1 and improved capacity retention of 78% after 550 cycles. This work provides inspiration on bio-based electrolyte additives for aqueous battery chemistry and promotes the practical application of AZIBs.