ABSTRACT Development of advanced anodes for sodium‐ion batteries (SIBs) remains challenging due to the sluggish kinetics and severe volume expansion. Here, we report the rational design of bimetallic Co/Cu sulfides embedded in N/S‐doped carbon matrices, via chemical vapor sulfurization of MOF precursor. The optimized CuCo 2 S 4 electrode achieves exceptional sodium storage performance, delivering a high capacity of 573.3 mA h g −1 at 0.2 A g −1 and maintaining 504.2 mA h g −1 at 5 A g −1 after 3000 cycles with 85.6% capacity retention. Interestingly, the CuCo 2 S 4 and the other Cu/Co mixed sulfides obtained after Cu incorporation show greatly enhanced sodium storage capacity, cycling stability, and rate capability, as compared with the single metal sulfides (CoS x or CuS x ). DFT calculations reveal that CuCo 2 S 4 displays smaller energy barriers for Na + migration and higher polysulfide adsorption capability than those for CoS 1.035 . The synergistic interaction of bimetallic Co/Cu sulfides greatly enhances the redox reactivity with fast Na + transport kinetics, lower charge transfer resistance, and suppressed polysulfide shuttle effect during cycling, which corroboratively contributes to the superior cycling performance of CoCuS‐2. Moreover, the CoCuS‐2||Na 3 V 2 (PO 4 ) 3 full cell demonstrates good cycling performance, delivering 255.9 mA h g −1 at 1 A g −1 after 700 cycles with 80.9% capacity retention.
Chai et al. (Tue,) studied this question.