Regulating membrane ion clusters to alleviate ammonia crossover in thermally regenerative batteries

In all-aqueous thermally regenerative ammonia battery (ATRB), ammonia crossover from anolyte to catholyte causes self-discharge, resulting in capacity decay. Based on the transport mechanism of small molecules in Nafion membranes, recast membranes were fabricated via solution casting to regulate their microstructure and alleviate ammonia crossover. Compared with the commercial Nafion membrane, the recast membrane demonstrated smaller and more dispersed ionic cluster structures along with enhanced dimensional stability, achieving a 53.6% reduction in ammonia permeability and a 2.9-fold increase in discharge capacity. Experimental results confirmed that ammonia transport predominantly occurs through hydrophilic ionic cluster channels within the membrane. Thermal treatment effectively regulates the membrane's microstructure, with the 130 °C-treated recast membrane exhibiting the lowest ammonia permeability, attributed to its minimized ionic cluster size. This study provides a simple and efficient strategy for alleviation of ammonia crossover in ATRB.