We prepared K+ ions and –O functional group co-modified V2CTX MXene (VCT-K) and further incorporated it with single-walled carbon nanotube (SWCNT), obtaining freestanding V2CTX composite films (VCT-K@C) with the 3D conductive network. Significantly, K+ ions were introduced into V2CTX MXene to stabilize the interlayer structure and prevent the aggregation of nanosheets, the terminal group of –O was controllably modified on the surface of MXene to improve the Li+ ions storage reversible capacities and the SWCNT acted as the bridge between MXene nanosheets to opens up the channels for ion/electron transportation in the longitudinal direction.

One-dimensional Sb2S3 nanorods with the longitudinal distribution are used as a sacrificial template in this work by a simple electrostatic spinning method. After heat treatment, abundant longitudinal distribution channels within flexible carbon nanofibers are obtained. Meanwhile, Sb ultra-small nanoparticles can be in-situ embedded within N, S co-doped carbon matrix (N,S,Sb-CNFs). Owing to the N, S, Sb co-modification and the well-designed one-dimensional mesoporous carbon substrate, the N,S,Sb-CNFs hybrids achieve better interfacial contact with electrolyte, ameliorated electrical conductivity and distinct kinetic promotion.

The two dimensional (2D) Ti3C2 MXene with controllable terminal groups was introduced into 1D carbon nanofibers to form a 3D conductive network by the electrospinning strategy. In such Ti3C2 MXene and carbon matrix composites (named KTi- 400@CNFs), the 2D nanosheet structure endows Ti3C2 MXene with more active sites for Li+ ion storage, and the carbon framework is favorable to the conductivity of the composites. Impressively, Ti–O–C bonds are formed at the interface be tween Ti3C2 MXene and the carbon framework.

We prepared rose-like VS2 nanosheets which have decent specific capacities, metallic conductivity, and open enough channels and further incorporated them into a single-walled carbon nanotube (SWCNT) network, achieving a C−V chemical bonded freestanding VS2@SWCNT (C-VS2) composite. Such chemical bonding in the composites builds a bridge for rapid electron transfer and ion diffusion in the longitudinal direction from one layer to another layer.

We rationalized the facile construction of N, S co-doped Sb and carbon nanofibers (Sb@N,S-CNFs) with longitudinal tunnels through a tetrafunctional template-assisted strategy, taking into account the overall structural and compositional considerations. The pyrolysis of Sb2S3 nanorod template and the volatilization of Sb results in the formation of void space and Sb nanorods in longitudinal tunnels as well as the doping of Sb nanodots and sulfur in carbon fiber matrix. This well-designed multilevel structure optimized for favorable annealing time not only effectively mitigates large volume changes, but also greatly improves the diffusion kinetics of ions and electrons, thus resulting in much improved rate performance (219 mAh g−1 at 4 A g−1) and cycling stability (85.1% capacity retention after 1000 cycles at 2 A g−1) in half cells as well as a favorable rate capability and cycling performance in full cells matched with Na3V2(PO4)2O2F cathode.