A MoN electrocatalyst for efficient NaS electrodeposition in room-temperature sodium-sulfur batteries.

Metal sulfides electrodeposition in sulfur cathodes mitigates the shuttle effect of polysulfides to achieve high Coulombic efficiency in secondary metal-sulfur batteries. However, fundamental understanding of metal sulfides electrodeposition and kinetics mechanism remains limited. Here using room-temperature sodium-sulfur cells as a model system, we report a MoN cathode material that enables efficient NaS electrodeposition to achieve an initial discharge capacity of 512 mAh g at a specific current of 1 675 mA g, and a final discharge capacity of 186 mAh g after 10,000 cycles. Combined analyses from synchrotron-based spectroscopic characterizations, electrochemical kinetics measurements and density functional theory computations confirm that the high d-band position results in a low NaS dissociation free energy for MoN. This promotes NaS electrodeposition, and thereby favours long-term cell cycling performance.