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 (CIPs) and solvent-separated ion pairs (SSIPs), 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 simple displacement reaction to modify the adsorption properties of the Zn electrode, thereby influencing the composition of CIPs and SSIPs 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 at high deposition currents. Through a series of characterization studies 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 the 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.