A Mo5N6 electrocatalyst for efficient Na2S electrodeposition in room-temperature sodium-sulfur batteries
Chao Ye, Huanyu Jin, Jieqiong Shan, Yan Jiao, Huan Li, Qinfen Gu, Kenneth Davey, Haihui Wang, Shi‐Zhang Qiao
Abstract
Abstract 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 Mo 5 N 6 cathode material that enables efficient Na 2 S electrodeposition to achieve an initial discharge capacity of 512 mAh g −1 at a specific current of 1 675 mA g −1 , and a final discharge capacity of 186 mAh g −1 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 Na 2 S 2 dissociation free energy for Mo 5 N 6 . This promotes Na 2 S electrodeposition, and thereby favours long-term cell cycling performance.