Intrinsic Ion Concentration Difference Induced Antipolyelectrolyte Effect for Promoting Stability of Zn Anodes

Aqueous zinc-ion batteries have gained significant attention due to their high safety and low cost. However, the cation concentration gradient at the anode/electrolyte interface often causes serious Zn dendrites and side reactions. Herein, cross-linked ion channels were constructed on the anode surface by the antipolyelectrolyte effect of zwitterionic polymer carboxymethyl chitosan (CMCHS) molecules, which is induced by the transient ion concentration difference at the initial Zn²⁺ deposition process. The CMCHS channels endow the anode surface with homogeneous ions and electron distributions. Simultaneously, CMCHS molecules enter into Zn²⁺ solvation structures and H₂O molecules are removed, limiting the activity of solvated H₂O molecules. Therefore, the dendrite growth and water activity are significantly suppressed, resulting in the excellent electrochemical performance of Zn anodes. An average Coulombic efficiency of 99.58% is achieved, which is much superior to the case in the conventional ZnSO₄ electrolyte. To illustrate the feasibility of the CMCHS-contained electrolyte, Zn||V₂O₅ full batteries were assembled and exhibited enhanced electrochemical performance.