High-Donor Electrolyte Additive for Stable Aqueous Zinc Batteries

As one of the emerging secondary batteries, rechargeable aqueous zinc-ion batteries (AZIBs) are prevailing over conventional lithium-ion batteries counterparts in terms of low cost, environmental benignity, and intrinsic safety. Metallic zinc anode is highly prized due to its low redox potential, high theoretical capacity, earth-abundance, and water compatibility. Despite these attractive merits, critical issues of unstable Zn chemistry in conventional aqueous electrolytes such as dendrite growth, hydrogen evolution and side reactions would inevitably provoke surface corrosion and damage the anode-electrolyte interface during battery operation. electrolyte engineering <i>via</i> introducing additives may become one of the most expedient solutions to achieve anti-side reactions and smooth deposition simultaneously. For parameter, Gutmann donor number (DN) reflects the intrinsic capacity of electron-donating, which can be used to indicate the solubility of intermediate products and the variation of the hydrogen-bonding network in aqueous electrolytes. A unique and facile strategy to improve Zn reversibility in aqueous batteries by tailoring electrolyte solvation structure with high-donor-number N, N-dimethyl acetamide (DMA) solvent additive. it is demonstrated that high-donor DMA additive with strong electron-donating ability can confine free water activity, replace the water in Zn2+ solvation sheath, and reshape hydrogen-bonding network of water, which is highly conducive to reducing the reaction activity. DMA additive is proven capable of replacing coordinated water molecules and participating in the solvated Zn²⁺ sheath, contributing to the restraint of dendrite growth and side reactions. The DMA-modified electrolyte enables remarkable suppression of water-involved hydrogen evolution and severe corrosion, which contributes to preferentially uniform deposition and ultralong cycling life of 4500 h at current density of 1 mA cm⁻² in symmetric cell, and high Coulombic efficiency of 99.6% in asymmetric cell. Besides, with solvation modulation, full batteries of Zn//VO₂ exhibit long-term cycling performance of 500 cycles and withstand subzero temperature condition. This regulation strategy employing high-donor solvents as additives thereby verifies the effectiveness of aqueous batteries.