Anti-Self-Discharge Capability of Zn-Halogen Batteries Through an Entrapment-Adsorption-Catalysis Strategy Built Upon Separator.

Abstract

Aqueous Zn-halogen batteries (Zn-I₂/Br₂) suffer from grievous self-discharge behavior, resulting in irreversible loss of active cathode material and severe corrosion of zinc anode, which ultimately leads to rapid battery failure. Herein, an entrapment-adsorption-catalysis strategy is reported, leveraging Zn─Mn atom pairs-modified glass fiber separator (designated as ZnMn-NC/GF), to effectively mitigate the self-discharge phenomenon. The in situ Raman and UV experiments, along with theoretical calculations, confirmed the single-atom Mn sites are responsible for polyiodides adsorption, while Zn─Mn atom pairs facilitated the conversion of reaction intermediates. As a result, the utilization rate of cathode active species is enhanced through this ZnMn-NC/GF separator. The fully charged Zn-I₂ battery assembled with ZnMn-NC/GF maintained a Coulombic efficiency (CE) of 90.1% after being left for 120 h, as well as a capacity retention rate of 95.3% after 30000 cycles at a current density of 5 A g^-1. Additionally, the Zn-Br₂ battery designed with ZnMn-NC/GF separator can withstand more serious self-discharge problems of bromine species, with an average discharge voltage platform of 1.75 V at 0.5 A g^-1. The self-discharge problem of aqueous Zn-halogen batteries is significantly suppressed by this entrapment-adsorption-catalysis strategy, which can serve as a crucial reference for the advancement of high-performance aqueous Zn-halogen batteries.