Understanding the Reversible Reactions of Li-N₂ Battery Catalyzed With SnO₂

Metal–N₂ battery can be applied in both energy storage and electrochemical nitrogen reduction reaction (NRR); however, there has been only extraordinarily little study on metal–N₂ battery since its electrochemical reversibility still needs further proofs. And its electrochemical performances also need to be enhanced. Herein, we investigated the discharge–charge reactions between Li anode and N₂ cathode via designing an efficient catalyst of nanosized SnO₂ particles dispersed on N-doped carbon nanosheets (SnO₂@NC) for the Li-N₂ battery, with good cyclic stability and a high specific capacity of 0.25 mA h (~500 mA h g⁻¹) at a large current density of 1000 mA g⁻¹. The electrochemical reversibility of both NRR in the discharge process and nitrogen extraction reaction in the charge process for Li-N₂ battery is discussed. Time-of-flight secondary ion mass spectrometry results imply that the SnO₂@NC can effectively promote the adsorption of N₂ and the activation of NRR in the discharge process. Furthermore, ex situ X-ray photoelectron spectroscopy and Fourier transform infrared tests are performed to study the electrochemical reversibility of Li-N₂ battery. It can be proved that the formation and decomposition of discharging product Li₃N are electrochemical reversible during cycling in our deigned Li-N₂ battery system with SnO₂@NC catalyst.