Water plays a key role in the nitrogen conversion pathway in lithium-nitrogen batteries

Lithium-nitrogen batteries can deliver high energy densities using environmentally friendly and abundant nitrogen as a resource. Ac-cording to previous studies, the nitrogen conversion pathway is ex-pected to consist of formation and decomposition of lithium nitride. However, the reaction deserves more attention prior to forming a consensus. The thermodynamic equilibrium reaction potential for lithium nitride is low, 0.44 V, versus Li/Li+, which is far from the higher operational experimental potentials. In this work, with a se-ries of characterizations from macro-to microscale in initial and sub-sequent cycles, we reveal that trace water in the electrolyte would promote the nitrogen reduction reaction at a higher working poten-tial in the discharge process. We invoke a reaction in the water -containing battery where formation of lithium amide and lithium hydroxide is key. This finding suggests a new nitrogen conversion pathway in lithium-nitrogen batteries and will provide insight for further studies on metal-nitrogen batteries.