Lattice Matching and Halogen Regulation for Synergistically Induced Uniform Zinc Electrodeposition by Halogenated Ti₃C₂ MXenes

Dendrite growth and low Coulombic efficiency caused by uneven diffusion and electrodeposition of Zn²⁺ ions have emerged as a barrier to exploiting the Zn metal anode. 1 In this work, we demonstrate the stoichiometric halogenated MXenes (Ti₃C₂Cl₂, Ti₃C₂Br₂, and Ti₃C₂I₂) as an artificial layer that can induce uniform Zn deposition. 2 The efficient redistribution effect results from the coherent heterogeneous interface reconstruction and regulated ion tiling by halogen surficial termination. The synergetic effects of high lattice matching (90%) between the adopted MXenes and Zn, as well as the positive halogen regulation, guide Zn²⁺ ions to nucleate uniformly on the most extensive (000l) crystal plane of the MXene matrix and grow in a planar manner. 3 In terms of Zn ion regulation, Cl termination is found to be more effective than O/F, Br, and I due to its moderate adsorption and diffusion coefficient for Zn²⁺ ions. 4 The Ti₃C₂Cl₂–Zn anode achieves a life extension of over 12 times (840 h at 2 mA cm⁻²//1 mAh cm⁻²) over that of the bare Zn anode and serves more than 9000 cycles in a battery with a Ti₃C₂I₂ cathode at a high rate of 3 A g⁻¹. 5 Given the abundance of lattice parameters and terminations of MXene materials, the developed strategy is expected to be extended to other metal anode systems.