Suppression of Halide Ions Crossover in Zn-halide Batteries by 2D MXene Membranes

A significant challenge in the practical application of Zn-halide batteries is their rapid self-discharge caused by the migration of halide species from the positive electrode to the metallic Zn. These highly oxidizing anions react with the deposited Zn, leading to its dissolution and the consequent loss of capacity. To address this issue, selective membranes such as Nafion or polyolefin separators are commonly used to mitigate anion crossover. However, aside from their high costs, these membranes often fail to prevent the transport of corrosive halides. Recently, there has been growing interest in utilizing Ti3C2Tx (MXene) for membrane applications. The negatively charged surface of MXene sheets and their ability to form free-standing films stable in halide electrolytes make them promising candidates for selective membranes. This study demonstrates the effective use of MXene membranes to mitigate the crossover of halide ions (Cl−, Br−, and I−). The ion transport mechanism was elucidated through a systematic electrochemical analysis combined with measurements of the physical properties of the electrolyte solutions and atomistic insights from ab-initio molecular dynamics simulations. Compared to Nafion, the developed MXene membrane exhibits a significantly improved anion selectivity, highlighting its potential as a compelling choice for use in batteries utilizing halide-ion based electrolytes.