Electronic structure regulation of Fe3C neighbored Fe-N4 ensembles enables optimized redox-cascade electrocatalysis for high-performance lithium-sulfur batteries

An integrated electrocatalyst consisting of Fe 3 C nanoparticles and adjacently atomic-dispersed Fe is rationally developed to realize optimized redox-cascade electrocatalysis . Fe 3 C-FeSAC with dual active sites provide strong anchoring ability for LiPSs and continuously catalyze the stepwise conversion of polysulfides during the entire discharge and charge process. • The successful construction of Fe 3 C nanoparticles and neighbored Fe-N 4 ensembles. • FeSAC and Fe 3 C exhibit synergistic promotion on the adsorption-diffusion-conversion towards LiPSs . • An efficient redox-cascade electrocatalysis strategy towards precise match of catalytic process is proposed. The large-scale commercialization of lithium-sulfur batteries with high energy density is mainly hindered by sluggish polysulfides conversion kinetics and severe shuttle effect. Single-atomic catalyst with monofunctional active sites can hardly promote the overall polysulfides redox reaction due to the multi-step and multi-phase conversion of sulfur species. To address this issue, an integrated electrocatalyst consisting of Fe 3 C nanoparticles and adjacently atomic-dispersed Fe is developed to facilitate the entire redox-cascade polysulfides conversion process. The enhanced electron delocalization of Fe 3d orbital can effectively modulate the electronic structure and strengthen the d-p hybridization with polysulfides to promote the conversion reaction kinetics. Furthermore, the redox-cascade conversion mechanism is uncovered that FeSAC serve as highly active sites to promote the initial solid–liquid reduction reaction from S 8 to Li 2 S 4 , while the subsequent liquid–solid reactions as a rate-determining step during the entire discharge process is facilitated by Fe 3 C. For the reverse charge process, Fe 3 C presents highly catalytic ability to reduce the energy barrier for Li 2 S dissociation, thus realizing the entire tandem conversion of sulfur species. Consequently, Fe 3 C-FeSAC/CNS exhibits an impressive initial capacity of 857 mAh g −1 with an exceptional attenuation rate of 0.043 % per cycle over 750 cycles at 4 C and high-rate capability of 756 mAh g −1 at 5 C. This work proposes a novel strategy to develop a multifunctional catalyst for bidirectional tandem catalysis process, enabling high-performance lithium-sulfur batteries.