Rational construction of NiSe/FeSe heterostructures with a stable solid-electrolyte interphase film for highly durable Na-ion batteries.

Heterostructured anode materials have garnered significant attention in recent years due to their ability to optimize interfacial structures between different components. This design not only facilitates the formation of stable solid-electrolyte interphase (SEI) films but also enhances the overall electrochemical performance, including battery capacity and cycle stability. In this study, a novel N-doped carbon-modified NiSe/FeSe heterostructure combined with carbon nanotubes (NC@NFS/CNTs) composite was successfully synthesized via co-precipitation and gas-phase selenization. This material was subsequently applied as an anode for Na-ion batteries (NIBs). Based on the synergistic effect of the interfacial properties of the heterostructure and the highly conductive nature of CNTs, the NC@NFS/CNTs composite exhibited excellent electrochemical stability and superior long-term durability. The battery retains a capacity of 332.4 mAh g after 5000 charge/discharge cycles a current density of 5 A g. Moreover, the capacity retention rate remains as high as 77 % even after 10,000 cycles at an ultra-high current density of 40 A g. Ex-situ XPS and XRD analyses, along with low-temperature EIS tests, demonstrate that the Na storage properties of the NC@NFS/CNTs electrode are significantly enhanced. This improvement is primarily attributed to the heterojunction structure and the presence of highly conductive phases (CNTs and N-doped carbon layers), which effectively improve the electrode's kinetic performance and enhance the stability of the SEI film.