Multi-Pleated Alkalized Ti 3 C 2 T x MXene-Based Sandwich-Like Structure Composite Nanofibers for High-Performance Sodium/Lithium Storage.

The volume expansion of CoFe 2 O 4 anode poses a significant challenge in the commercial application of lithium/sodium-ion batteries (LIBs/SIBs). However, metal-organic-frameworks (MOF) offer superior construction of heterostructures with refined interfacial interactions and lower ion diffusion barriers in Li/Na storage. In this study, the CoFe 2 O 4 @carbon nanofibers derived from MOF are produced through electrospinning, in situ growth followed by calcination, which are then confined within an MXene-confined MOF-derived porous CoFe 2 O 4 @carbon composite architecture under alkali treatment. The CoFe 2 O 4 nanofibers anchor on the alkalized MXene that is decorated with the NaOH solution to form a multi-pleated structure. The sandwich-like structure of the composite effectively alleviates the volume expansion and shortens the Li/Na-ion diffusion path, which displays high capacity and outstanding rate performance as anode materials for LIBs/SIBs. As a consequence, the obtained CoFe 2 O 4 @carbon@alkalized MXene composite anode shows satisfied rate performance at current density of 10 A g -1 for LIBs (318 mAh·g -1 ) and 5 A g -1 for SIBs (149 mAh g -1 ). The excellent cycling performance is further demonstrated at a high current density, where it maintains a discharge capacity of 807 mAh g -1 at 2 A g -1 after 400 cycles for LIBs and 130 mAh g -1 at 1 A g -1 even after 1000 cycles for SIBs.