Enhanced Li-ion diffusion improves N₂-to-NH₃ current efficiency at 100 mA cm^-2.

Abstract

Electrochemical lithium (Li)-mediated nitrogen (N₂) reduction could enable production of ammonia (NH₃) at ambient temperatures and pressures, offering a route to reduce carbon emissions in the chemical sector. However, NH₃ productivity is often limited by sluggish Li-ion desolvation and diffusion at the solid electrolyte interphase (SEI). Here, we present a concerted desolvation:diffusion layered SEI architecture that provides abundant Li-ion flux for efficient N₂ conversion toward NH₃ production at high current densities. The SEI comprises stacked inorganic layers with low ion-binding affinity and high ion-conductivity functionalities that increase Li-ion flux by two orders of magnitude. This design strategy achieved N₂ electroreduction in a 2 M lithium difluoro(oxalato)borate electrolyte with a Faradaic efficiency of 98% and an energy efficiency of 21% for NH₃ production at 100 milliamperes per square centimeter (mA cm^-2). The system sustained an 80% Faradaic efficiency over 40 hours, after which performance declined.