Lattice matching and halogen regulation for synergistically induced large Li and Na storage by halogenated MXene VCCl.

Suffering from the formation of metal-ion dendrites and low storage capacity, MXene materials exhibit unsatisfactory performance in Li and Na storage. In this study, we demonstrate that the MXene VCCl structure can induce uniform Li and Na deposition. This is achieved through coherent heterogeneous interface reconstruction and regulated ion tiling by halogen surface termination. The high lattice matching (91% and 99%) between MXenes and Li/Na, along with positive Cl terminal regulation, guides Li/Na ions to nucleate uniformly on the VCCl MXene matrix and grow in a planar manner. Cl termination proves effective in regulating Li/Na ions due to its moderate adsorption and diffusion coefficients. Furthermore, upon adsorption onto the Cl-terminated VCCl monolayer, Li and Na clusters undergo dissociation, favoring uniform adsorption over cluster adsorption. VCCl MXenes exhibit impressive Li/Na storage capacities of 434.07 mA h g for Li and 217.03 mA h g for Na, surpassing the Li storage capacity of TiCCl by three-fold and the Na storage capacity of VC by 1.4 times. This study highlights the regulatory role of Cl surface terminals in dendrite formation and Li/Na ion deposition, with potential applications to other metal-ion storage electrodes.