Single‐Atom‐Dispersed FeNC/FeS ₂ Nanocluster for High‐Performance Sodium Metal Battery With Hybrid Electrochemical Behavior

ABSTRACT The rate capability and cycling stability of sodium metal batteries taking FeS 2 or sulfur as cathode are limited due to their low reaction kinetics and severe shuttle effect. Herein, we rationally design a novel single‐atom‐dispersed S 2 –FeNC/FeS 2 nanocluster heterojunction embedded in carbon spheres (SFNC/FeS 2 ) for the electrode material of sodium metal batteries. Interestingly, during the discharging process, the Na + is inserted into FeS 2 to generate Na 2 S, as well as the unique electrochemical reaction between S 2 –FeNC and Na + to form Na 2 S. Meanwhile, the FeNC can adsorb Na 2 S and catalyze the conversion from Na 2 S and Fe to FeS 2 or from Na 2 S and FeNC to S 2 –FeNC for suppressing the shuttle effect and promoting the distinct hybrid reversible electrochemical behavior, which improves performance tremendously. Notably, the SFNC/FeS 2 electrode delivers a specific capacity of 338.7 mAh g –1 after superlong 2000 cycles at a current density of 5.0 A g –1 and achieves a high energy density of 430.1 Wh Kg –1 at a current density of 0.05 A g –1 . This work presents a novel approach to studying sodium metal batteries with hybrid behavior for excellent high energy density and cycling stability.