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.