Anchoring stable aqueous-CCl4 interface via wettability-tailored membrane electrode for durable seawater-based Zn-Cl2 flow batteries

Zinc-chlorine (Zn-Cl 2 ) battery with high discharge voltage, attractive theoretical energy density and inherently low-cost active materials provides affordable and scalable solutions for stationary energy storage. However, the Zn-Cl 2 battery suffers from rapid capacity decay and low coulombic efficiency (CE), primarily due to uncontrolled overflow of Cl 2 gas from the electrolyte. Solvents with high chlorine solubility like CCl 4 combine high chlorine storage capacity, delivering a theoretical volumetric capacity of up to 97 Ah L −1 , but at the cost of suffering from water-oil interfacial instability. In this work, we designed a wettability-tailored membrane electrode with CNT and Pt nanoparticle that stabilizes the two-phase interface and exhibits electrocatalytic activity. Moreover, leveraging the abundant and low-cost chloride in seawater, we replace deionized water with seawater. When using a seawater-based electrolyte, the Zn-Cl 2 flow battery delivers 600 stable cycles (over 220 h) with an average CE of 88.37%. Notably, it maintains 1420 stable cycles (over 544 h) at 0 °C, accompanied by an average CE of 91.94% and a capacity retention of 94.1%. This work establishes a new paradigm for the design of interface regulation strategies in Zn-Cl 2 flow batteries, providing a feasible approach for high-capacity, seawater-based energy storage systems suitable for coastal low-temperature applications.