Electrostatic Regulation of Zn2+ Ion Concentration on Electrodes and Its Impact on Electrochemical Performance

Abstract

The solvation structure of electrolytes, particularly the distribution and composition of contact ion pairs (CIP) and solvent-separated ion pairs (SSIP), is a prominent focus in battery research, serving as a critical determinant for understanding and interpreting battery electrochemical behavior. In this work, a phosphate-enriched protective layer (ZAP) was fabricated on the Zn electrode via a simply displacement reaction to modify the adsorption properties of the Zn electrode, thereby influencing the composition of CIP and SSIP at the electrode-electrolyte interface. Experimental results revealed that the ZAP layer significantly reduced the overpotential for Zn deposition, particularly in low-concentration electrolytes and under high deposition currents. Through a series of characterizations and theoretical calculations, it was found that the ion concentrations at the electrode-electrolyte interface played a pivotal role in governing interfacial electrochemistry, surpassing the influence of the CIP-to-SSIP ratio in the bulk electrolyte. Moreover, the ZAP layer could effectively suppress side reactions and enhance cycling stability of batteries. This study introduces a simple and cost-effective approach for protecting Zn anodes and emphasizes the critical importance of interfacial ion concentrations in electrochemical analysis.