Regulating interfacial behavior via reintegration the Helmholtz layer structure towards ultra-stable and wide-temperature-range aqueous zinc ion batteries

Abstract

Aqueous zinc-ion batteries are recognized as a potential candidate in large-scale energy storage devices. However, parasitic reactions on interfaces have severely limited their further development due to sticky de-solvation process of Zn(H₂O)₆²⁺. Acetylacetone (Hacac) is proposed as a tri-functional additive by altering the solvation structure to address detrimental interface issues. Specifically, the acetyl groups induced by decomposition of Hacac inhibit dendrite growth, by-product aggregation on anode via guiding ordered deposition of zinc ions and suppressing water decomposition in internal Helmholtz plane (IHP). Meanwhile, the acetyl groups remarkably alleviate by-product aggregation and maintain the cathode structure by accelerating zinc ion transfer and inhibiting disintegration of water in IHP. With the addition of 0.5 wt% Hacac, Zn metal maintains a high coulombic efficiency of 99.9 % after 2000 cycles at 10 mA cm⁻² and 1 mAh cm⁻², with superior longevity of 5200 h at 1 mA cm⁻² with 0.5 mAh cm⁻² for Zn|Zn cells. As expected, the assembled Zn|NH₄V₄O₁₀ batteries exhibit an outstanding capacity retention of 90 % up to 22,000 cycles at 10 A/g. As a highly efficient strategy, the reframing of Helmholtz layer structure via electrolyte additive could be broadened to address general interfacial issues in advanced energy storage systems.