Freestanding carbon nanofibers encapsulating MOF-derived NiSe with in-situ porous carbon protective layer for sodium storage

NiSe is considered to be an effective sodium storage electrode material due to its eminent theoretical capacity and ultra-long-term cycle life. Nonetheless, the large volume fluctuation and slow reaction kinetics cause NiSe to exhibit poor rate performance and cycle stability. Furthermore, the conventional electrode preparation technique necessitates the use of conductive and binder chemicals, resulting in poor electrochemical performance. To address these issues, freestanding NiSe-based electrodes (NiSe@C@NCNFs) are successfully fabricated via electrospinning Ni-MOF precursors and subsequent selenization reactions that NiSe nanoparticles are in-situ protected by MOF-derived porous carbon, thus ensuring the long-term cycling stability for sodium storage. Furthermore, the unique electrode structure design can improve the anode-electrolyte interface contact, short-ening the sodium ionic transport path and quickening reaction kinetics. According to corresponding kinetics analysis, the sodiation/desodiation process of NiSe@C@NCNFs is a dominant surface pseudo-capacitance pro -cess, guaranteeing their prominent rate capability.