Oxygen‐modulated metal nitride clusters with moderate binding ability to insoluble Li2Sx for reversible polysulfide electrocatalysis

Abstract

Abstract Multiphase sulfur redox reactions with advanced homogeneous and heterogeneous electrochemical processes in lithium–sulfur (Li–S) batteries possess sluggish kinetics. The slow kinetics leads to significant capacity decay during charge/discharge processes. Therefore, electrocatalysts with adequate sulfur‐redox properties are required to accelerate reversible polysulfide conversion in cathodes. In this study, we have fabricated an oxygen‐modulated metal nitride cluster (C‐MoNx‐O) that has a moderate binding ability to the insoluble Li2Sx for reversible polysulfide electrocatalysis. A Li–S battery equipped with C‐MoNx‐O electrocatalyst displayed a high discharge capacity of 875 mAh g−1 at 0.5 C. The capacity decay rate of each cycle was only 0.10% after 280 cycles, which is much lower than the control groups (C‐MoOx: 0.16%; C‐MoNx: 0.21%). Kinetic studies and theoretical calculations suggest that C‐MoNx‐O electrocatalyst presents a moderate binding ability to the insoluble Li2S2 and Li2S when compared to the C‐MoOx and C‐MoNx surfaces. Thus, the C‐MoNx‐O can effectively immobilize and reversibly catalyze the solid–solid conversion of Li2S2–Li2S during charge–discharge cycling, thus promoting reaction kinetics and eliminating the shuttle effect. This study to design oxygen‐doped metal nitrides provides innovative structures and reversible solid–solid conversions to overcome the sluggish redox chemistry of polysulfides.

Keywords

• electrocatalysts
• lithium–sulfur batteries
• metal nitride
• reversible polysulfide catalysis
• shuttle effects