Metal-Nitrogen Batteries: Emerging and Promising Models for Energy Conversion/Storage System and Simultaneous NH Synthesis.

The new type of metal-nitrogen (MN/NO/NO /NO ) batteries, transforming the traditional electrical-energy-input catalytic system into an electrical-energy-output type and simultaneously achieving the electrosynthesis of ammonia, attracts more attention. Despite being at the early research stage, recent encouraging advancements in combining NH synthesis and energy conversion/storage in such M-nitrogen batteries are meaningfully summarized. This review presents the battery system's components (including anode metals, cathode catalysts, and the involving reaction processes), and briefly introduces separators and electrolytes, while comparing their electrochemistry and electrocatalytic performance. Three categories of M-nitrogen batteries are delineated: three-phase MN batteries solely for N fixation, MN/NO batteries, and two-phase MNO /NO batteries for NH synthesis. Additionally, strategies for enhancing performance of M-nitrogen batteries are discussed, highlighting on design for electrodes materials, methods for reaction pathways, optimization for device, and outlook for practical use. Finally, suggestions and prospects of the future development of this battery system are put forward, envisioning a scenario toward high-energy-density and superior performance M-nitrogen batteries. This review offers a reference for design of electrocatalytic materials in reduction reactions of nitrogen-containing reactants for green ammonia production, gives a clue for new battery devices for energy conversion/storage, and will boost the efficient and green nitrogen circular economy.