Suppression of Halide Ion Crossover in Zn–Halide Batteries by 2D MXene Membranes

A major challenge in Zn-halide batteries is rapid self-discharge caused by migration of halide ions to metallic Zn. Conventional Nafion or polyolefin separators, are commonly used to mitigate anion crossover, but they are costly and often ineffective in blocking corrosive halides. Recently, Ti₃C₂T_<i>x</i> (MXene) has emerged as a promising alternative due to its negatively charged surface and stability in halide electrolytes. This study demonstrates the effectiveness of MXene membranes in reducing halide ion (Cl^-, Br^-, and I^-) crossover and provides insights into the ion transport mechanism through systematic electrochemical studies, electrolyte property measurements, and <i>ab initio</i> molecular dynamics simulations. MXene membranes exhibit significantly improved anion selectivity compared to Nafion, making them an attractive candidate for halide-based battery applications. Their potential to enhance battery performance and stability offers a compelling solution for addressing self-discharge in Zn-halide batteries.