Reconfiguring the Helmholtz plane with a trace polar additive for highly reversible zinc anodes

Abstract

The performance stability of aqueous zinc-ion batteries (AZIBs) is closely linked to the properties of the inner Helmholtz plane (IHP) at the zinc anode/electrolyte interface. Excessive reactive H₂O in the IHP significantly contributes to side reactions, including hydrogen evolution, passivation, and zinc dendrite formation. Here, a trace additive with abundant polar functional groups, thioacetamide (TAA), is introduced to modify the internal structure of the IHP and enhance the stability of zinc anodes. Both theoretical calculations and experiments demonstrate that TAA preferentially adsorbs onto the IHP at the zinc surface, reducing the decomposition of active H₂O and suppressing side reactions. TAA also facilitates the uniform deposition of Zn²⁺ ions on the (002) crystal plane, effectively preventing dendrite formation. Consequently, the addition of 10 mM TAA to the ZnSO₄ electrolyte significantly boosts the reversibility of zinc, achieving an improvement of nearly 13 times compared to the pure ZnSO₄ electrolyte. Furthermore, the Zn||V₆O₁₃ full cells with the optimized electrolyte maintain excellent stability after 2000 cycles at 3 A g⁻¹, surpassing the performance of the pure ZnSO₄ electrolyte.