Synergistic Solvation and Nucleation Regulation for Enhanced Stability and Longevity in Aqueous Zinc-Ion Batteries with d-Pantothenic Acid Additive

Abstract

Aqueous zinc-ion batteries (AZIBs) have gained increasing attention for grid energy storage systems. However, ensuring the long-term reversible operation of the zinc anode remains a challenge due to dendrite growth and adverse side reactions during the charge and discharge cycles. This study investigates the use of d-pantothenic acid (D-PA) as an additive in 2 M ZnSO₄ aqueous electrolyte to enhance the cycling stability of the zinc anode in AZIBs. Experimental results and theoretical calculations demonstrate that D-PA reshapes the solvation structure of Zn²⁺ by partially replacing coordinated water molecules, ensuring the stability of Zn²⁺ transport. Furthermore, D-PA adsorbs on active sites of the zinc anode, increasing the surface overpotential (|η_s|), reducing the nucleation energy barrier, and decreasing the critical nucleus size (r_crit), thus ensuring uniform zinc deposition. This dual role of modifying the Zn²⁺ solvation shell and regulating Zn²⁺ nucleation effectively mitigates dendrite growth and suppresses side reactions, resulting in excellent stability of the zinc anode. Consequently, Zn||Zn symmetrical cells with the D-PA additive maintain stable operation for over 2000 h at 1.0 mA cm^–2 and 1.0 mA h cm^–2, and nearly 4000 h at 4.0 mA cm^–2 and 4.0 mA h cm^–2. Additionally, Zn||Cu asymmetric cells exhibit cycling stability over 300 cycles at 0.5 mA cm^–2 and 0.5 mA h cm^–2, with an average Coulombic efficiency of 99.29%. Moreover, Zn||V₂O₅ full cells containing the D-PA additive exhibit stable cycling performance over 1000 cycles at a current density of 1 A g^–1, maintaining a high capacity retention. Specifically, the initial capacity of the full cell is around 161.17 mA h g^–1, with approximately 62.7% capacity retention after 1000 cycles.