Nanoreactors Encapsulating Built‐in Electric Field as a “Bridge” for Li–S Batteries: Directional Migration and Rapid Conversion of Polysulfides

Abstract Lithium–sulfur batteries (Li–S) are recognized as the next generation of secondary batteries due to their satisfactory theoretical specific capacity and energy density. However, a series of problems such as disordered migration behavior, sluggish redox kinetics, and serious shuttle effect of lithium polysulfides (LiPSs) greatly limit the commercial application. Herein, nanoreactors encapsulate heterostructure to guarantee sulfur conversion in the hosts where the heterostructure consists of FeP with moderate adsorption ability, excellent catalytic active and low work function, and Fe 3 O 4 with strong adsorption ability and high work function. This rational configuration of heterostructure controls the direction of the interface built‐in electric field (BIEF) between catalyst and adsorbent, realizing the successive “trapping‐directional migration‐conversion” reaction mechanism to sulfur species. Thanks to BIEF as a bridge to connect the trapping site and catalytic site, Fe 3 O 4 /FeP@C─S cathode delivers an ultrahigh initial specific capacity of 1402 mAh g −1 at 0.1 C and remains more than 450 mAh g −1 at 5 C after 350 cycles. Even with a sulfur loading of 5.20 mg cm −2 , it displayed the initial specific capacity of 970 mAh g −1 . This work provided an effective strategy to design high‐performance electrocatalysts for commercial Li–S batteries.