Tunable Electrocatalytic Behavior of Sodiated MoS Active Sites toward Efficient Sulfur Redox Reactions in Room-Temperature Na-S Batteries.

Room-temperature (RT) sodium-sulfur (Na-S) batteries hold great promise for large-scale energy storage due to the advantages of high energy density, low cost, and resource abundance. The research progress on RT Na-S batteries, however, has been greatly hindered by the sluggish kinetics of the sulfur redox reactions. Herein, an elaborate multifunctional architecture, consisting of N-doped carbon skeletons and tunable MoS sulfiphilic sites, is fabricated via a simple one-pot reaction followed by in situ sulfurization. Beyond the physical confinement and chemical binding of polarized N-doped carbonaceous microflowers, the MoS active sites play a key role in catalyzing polysulfide redox reactions, especially the conversion from long-chain Na S (4 ≤ n ≤ 8) to short-chain Na S and Na S. Significantly, the electrocatalytic activity of MoS can be tunable via adjusting the discharge depth. It is remarkable that the sodiated MoS exhibits much stronger binding energy and electrocatalytic behavior compared to MoS sites, effectively enhancing the formation of the final Na S product. Consequently, the S cathode achieves superior electrochemical performance in RT Na-S batteries, delivering a high capacity of 774.2 mAh g after 800 cycles at 0.2 A g , and an ultrahigh capacity retention with a capacity decay rate of only 0.0055% per cycle over 2800 cycles.