Understanding the Zeta Potential in Regulating Zn Deposition Kinetics for Zn-Ion Batteries.

Abstract

Severe Zn²⁺ concentration polarization at the anode/electrolyte interface induces inhomogeneous electric field distribution on the Zn anode surface in aqueous zinc-ion batteries (AZIBs), causing dendrite growth and formation of "dead zinc". Colloidal electrolytes are used to regulate Zn plating/stripping behavior. However, there is a lack of systematic and fundamental understanding of the adsorption capacity of colloidal particles for Zn²⁺ and Zeta potential (ZP) in optimizing Zn deposition kinetics. Herein, the ZP of oxide nanoparticles (ONPs, i.e., MgO, SiO₂, Al₂O₃) and the adsorption energy for Zn²⁺ are studied to evaluate their effects on enhancing the cyclic stability of AZIBs. A Gum Arabic (GA) coating strategy on the ONPs surface is executed to eliminate the interference of the surface chemical environment for Zn²⁺ adsorption energy. Therefore, the screening principle for ONPs based on ZP is established when they are used in colloidal electrolytes. Specifically, the SiO₂ colloidal electrolyte (4Z-S) with the ZP of -28.6 mV facilitates rapid Zn deposition kinetics. Accordingly, zinc electrodes in 4Z-S electrolyte realize a high coulombic efficiency (CE) of 99.7% and long-term life of 3400 h at 5 mA cm^-2. A 145 mAh Zn||I₂ pouch cell achieves a high capacity retention of 94.8% after 1000 cycles, implying promising practical application.