Alkali ions pre-intercalated 3D crinkled Ti3C2Tx MXene architectures for advanced sodium storage

Two-dimensional (2D) materials, Ti3C2Tx MXene, have great potential for rapidly and stabilized sodium storage because of their excellent electrical conductivity and rich redox active sites. However, affected by the interaction of hydrogen bonds and van der Waals forces, Ti3C2Tx MXene nanosheets are prone to collapse and re-stacking, which is not conducive to the ions diffusion and electrons transport, affects the electrochemical performance. Herein, we prepared 3D wrinkled Ti3C2Tx MXene architectures with alkali ions (Na+, K+, Li+) pre-intercalation by continuous stirring treatment of Ti3C2Tx MXene in aqueous borohydride (NaBH4, KBH4, LiBH4) solution for sodium storage. This structure effectively enlarges the interlayer distance of Ti3C2Tx MXene nanosheets and shortens the sodium ion diffusion path. Benefitting from the superiority of the structure, Na+ pre-intercalated Ti3C2Tx MXene has the most excellent sodium storage performance, high reversible capacity of 256 mA h g−1 at 100 mA g−1 after 100 cycles, and amazing long-cycle stability of 168 mA h g−1 at 2000 mA g−1 after 6000 cycles. The density functional theory (DFT) calculation shows that the Ti3C2Tx MXene pre-intercalating with Na+ significantly reduces the diffusion energy barrier, greatly improves the embedding and diffusion kinetics of Na+. This novel three-dimensional wrinkled Ti3C2Tx MXene structure with alkali ions pre-intercalated can better broaden the application prospects of MXene-based materials in energy storage fields.