Temperature-dependent solid electrolyte interphase reactions drive performance in lithium-mediated nitrogen reduction to ammonia

Abstract

The solid electrolyte interphase (SEI) is a vital component to control mass transport and selectivity in the lithium-mediated reduction of N₂ to NH₃ (Li-N₂R). Finding strategies that generate the optimal SEI, a complex network of organic and inorganic species, can potentially improve Li-N₂R performance. Here, we unravel structure-property relationships of the SEI by correlating its composition with the NH₃ Faradaic efficiency (FE_NH3). By modifying the reaction temperature, we alter electrolyte decomposition reactions and observe changes in the SEI that explain FE_NH3 trends between electrolyte solvents. We quantify a complex reaction environment at elevated temperatures where SEI formation is counteracted by etching reactions. This trade-off leads to temporal fluctuations of FE_NH3, but the maximal FE_NH3 can reach up to 40%, the highest value reported for batch cells at ambient pressure thus far. Our work underscores the potential of novel electrolytes that steer SEI selectivity and, ultimately, improve Li-N₂R performance.