<scp>Fe₃O₄</scp>/Fe/<scp>FeS</scp> Tri‐Heterojunction Node Spawning N‐Carbon Nanotube Scaffold Structure for High‐Performance Sodium‐Ion Battery

Abstract

The Fe‐based anode of sodium‐ion batteries attracts much attention due to the abundant source, low‐cost, and high specific capacity. However, the low electron and ion transfer rate, poor structural stability, and shuttle effect of NaS 2 intermediate restrain its further development. Herein, the Fe 3 O 4 /Fe/FeS tri‐heterojunction node spawned N‐carbon nanotube scaffold structure (FHNCS) was designed using the modified MIL‐88B(Fe) as a template followed by catalytic growth and sulfidation process. During catalytic growth process, the reduced Fe monomers catalyze the growth of N‐doped carbon nanotubes to connect the Fe 3 O 4 /Fe/FeS tri‐heterojunction node, forming a 3D scaffold structure. Wherein the N‐doped carbon promotes the transfer of electrons between Fe 3 O 4 /Fe/FeS particles, and the tri‐heterojunction facilitates the diffusion of electrons at the interface, to organize a 3D conductive network. The unique scaffold structure provides more active sites and shortens the Na + diffusion path. Meanwhile, the structure exhibits excellent mechanical stability to alleviate the volume expansion during circulation. Furthermore, the Fe in Fe 3 O 4 /Fe heterojunction can adjust the d‐band center of Fe in Fe 3 O 4 to enhance the adsorption between Fe 3 O 4 and Na 2 S intermediate, which restrains the shuttle effect. Therefore, the FHNCS demonstrates a high specific capacity of 436 mAh g −1 at 0.5 A g −1 , 84.7% and 73.4% of the initial capacities are maintained after 100 cycles at 0.5 A g −1 and 1000 cycles at 1.0 A g −1 . We believe that this strategy gives an inspiration for constructing Fe‐based anode with excellent rate capability and cycling stability.