Iron selenide nanoparticles-encapsulated within bamboo-like N-doped carbon nanotubes as composite anodes for superior lithium and sodium-ion storage

Encapsulating the multifunctional nanostructures within a lightweight nanocarbon network is considered to be a promising strategy for developing state-of-the-art electrodes for alkali metal-ion batteries (AMIBs). Herein, the ultrafine FeSe₂ nanoparticles (NPs) were encapsulated within the bamboo-like N-doped carbon nanotubes (FeSe₂@CNTs) via a rationally in situ self-catalysis and subsequent chemical transformation, realizing a workable capacity and stable architecture. The 3D interactive CNT network provides a fast electron/ion conducting path, and constructs a solid electronic link between the CNTs and FeSe₂ NPs. The ultrafine dimension of FeSe₂ NPs ensures small volume change and short Li⁺/Na⁺ diffusion distance during charge and discharge. Profiting from the fast transport capability of both electrons and ions, the unique FeSe₂@CNTs exhibits outstanding host potential for Li⁺ storage with a capability of 397 mA h g⁻¹ at 10 A g⁻¹. Serving as anode for Na⁺ storage, the optimized electrode possesses excellent rate capability of 329 mA h g⁻¹ at 8 A g⁻¹. Additionally, the Li⁺/Na⁺ storage mechanisms are further revealed by in situ electrochemical techniques and density functional theory (DFT) calculations. The present work inspired a new window for developing high-performance hybrids towards various electrochemical energy applications.