Tunable Electrocatalytic Behavior of Sodiated MoS₂ Active Sites toward Efficient Sulfur Redox Reactions in Room-Temperature Na-S Batteries.

Abstract

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 MoS₂ 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 MoS₂ active sites play a key role in catalyzing polysulfide redox reactions, especially the conversion from long-chain Na₂ S_n (4 ≤ n ≤ 8) to short-chain Na₂ S₂ and Na₂ S. Significantly, the electrocatalytic activity of MoS₂ can be tunable via adjusting the discharge depth. It is remarkable that the sodiated MoS₂ exhibits much stronger binding energy and electrocatalytic behavior compared to MoS₂ sites, effectively enhancing the formation of the final Na₂ S product. Consequently, the S cathode achieves superior electrochemical performance in RT Na-S batteries, delivering a high capacity of 774.2 mAh g^-1 after 800 cycles at 0.2 A g^-1 , and an ultrahigh capacity retention with a capacity decay rate of only 0.0055% per cycle over 2800 cycles.