Engineering Fe–N Coordination Structures for Fast Redox Conversion in Lithium–Sulfur Batteries

Abstract

Critical drawbacks, including sluggish redox kinetics and undesirable shuttling of polysulfides (Li 2 Sn, n = 4–8), seriously deteriorate the electrochemical performance of high‐energy‐density lithium–sulfur (Li–S) batteries. Herein, these challenges are addressed by constructing an integrated catalyst with dual active sites, where single‐atom (SA)‐Fe and polar Fe 2 N are co‐embedded in nitrogen‐doped graphene (SA‐Fe/Fe 2 N@NG). The SA‐Fe, with plane‐symmetric Fe‐4N coordination, and Fe 2 N, with triangular pyramidal Fe‐3N coordination, in this well‐designed configuration exhibit synergistic adsorption of polysulfides and catalytic selectivity for Li 2 Sn lithiation and Li 2 S delithiation, respectively. These characteristics endow the SA‐Fe/Fe 2 N@NG‐modified separator with an optimal polysulfides confinement–catalysis ability, thus accelerating the bidirectional liquid–solid conversion (Li 2 Sn↔Li 2 S) and suppressing the shuttle effect. Consequently, a Li–S battery based on the SA‐Fe/Fe 2 N@NG separator achieves a high capacity retention of 84.1% over 500 cycles at 1 C (pure S cathode, S content: 70 wt%) and a high areal capacity of 5.02 mAh cm−2 at 0.1 C (SA‐Fe/Fe 2 N@NG‐supported S cathode, S loading = 5 mg cm−2). It is expected that the outcomes of the present study will facilitate the design of high‐efficiency catalysts for long‐lasting Li–S batteries.