In situ induced cation-vacancies in metal sulfides as dynamic electrocatalyst accelerating polysulfides conversion for Li-S battery

In-situ introduced the Fe-vacancies into FeS via one-step pyrolysis and verifies the feasibility of Fe 0.96 S@C host as catalyst and adsorbent toward polysulfides for the first time. Cation vacancy engineering is considered to be one of the effective methods to solve the issues of shuttling and sluggish redox kinetics of LiPSs owing to the intrinsic tunability of electronic structure. However, cation vacancies are few studied in the Li-S realm due to their complex and rigid preparation methods. In this work, one-step pyrolysis is reported to in situ introduce Fe-vacancies into iron sulfide (Fe 0.96 S) as a sulfur host. For this host structure, Fe 0.96 S is first employed as an adsorbent and catalyst in Li-S system. During the carbonization process, a tight contact structure of Fe 0.96 S crystal and carbon network (Fe 0.96 S@C) is in situ constructed, and the carbon layer as a conductor provides smooth electrons transfer pathways for redox reactions. Meanwhile, due to the introduction of Fe-vacancies in FeS crystal, the adsorption capability and catalytic effect for LiPSs have been substantially enhanced. Moreover, the presence of Fe 0.96 S crystal favors the mobility of electron and diffusion of Li + , which is revealed by the experiments and theoretical calculations. Through synergy respective advantages effect of Fe 0.96 S and carbon, the Fe 0.96 S@C-S cathode delivers high-rate capability at 5.0 C and stable long-life performance. Even under a high sulfur loading of 3.5 mg/cm 2 , the durable cyclic stability is still exhibited with the capacity retention of 93% over 400 cycles at 1.0 C, and the coulombic efficiency is ≥98%. Noting that this strategy greatly simplifies the synthetic process of currently known cation-vacancy materials and furnishes a universal mentality for designing both divinable and astonishing new cation-vacancy materials.