Fe₃O₄/Fe/FeS 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 NaS2 intermediate restrain its further development. Herein, the Fe3O4/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 Fe3O4/Fe/FeS tri‐heterojunction node, forming a 3D scaffold structure. Wherein the N‐doped carbon promotes the transfer of electrons between Fe3O4/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 Fe3O4/Fe heterojunction can adjust the d‐band center of Fe in Fe3O4 to enhance the adsorption between Fe3O4 and Na2S 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.

SnO/SnO2 Heterojunction Nanoparticles Anchored on Graphene Nanosheets for Lithium Storage

“…22 Lattice fringing is unclear and subject to measurement errors due to the abundance of defects that develop with the formation of heterojunctions and the optical opacity of the heterojunction particles. 23 Figure S3a,b also shows the generation of heterojunctions with distinct interfaces in the (002), (200) lattice of SnO as well as the ( 200) and (211) lattices of SnO 2 . This demonstrates that SnO/SnO 2 @G has abundant heterogeneous interfaces, unique interconnected porous structure, and a highly conductive graphene matrix, which facilitates the SnO/SnO 2 heterostructures to promote charge transport, enrich storage sites, prevent aggregation, and buffer volume expansion during the cycling process.…”

“…The heterointerface between SnO and SnO 2 nanocrystals was distinguished by a white dashed line . Lattice fringing is unclear and subject to measurement errors due to the abundance of defects that develop with the formation of heterojunctions and the optical opacity of the heterojunction particles Figure S3a,b also shows the generation of heterojunctions with distinct interfaces in the (002), (200) lattice of SnO as well as the (200) and (211) lattices of SnO 2 .…”