Prediction of Halogenated MXenes as Electrode Materials for Halide-Ion Batteries.

Exploring and developing new rechargeable halide-ion batteries plays an important role in the advancement and growth of the ion battery family. Here, we systematically explored the feasibility of single-layer MXenes and their hydrogenated derivatives as electrode materials for halide-ion batteries via first-principles theory. The calculated results indicate that halide ions (T ions) can be stably and efficiently adsorbed on the surfaces of MX and MXH, with theoretical specific capacities ranging from 227 to 497 mAh g. The diffusion barriers of the T ion on MXenes are from 0.55 to 0.10 eV, comparable to those of the Li ion in graphite and LiCoO. The electronegativity of halide anions displays significant impacts on their discharge voltage plateaus on MX, with the highest voltage up to 5.60 V for the F ion. As a comparison, the hydrogenation of MXH with less surface activity raises a 2-3 V voltage reduction. All MXene-based full cells of TTiC|TTiCH (where = 0-2 and = 2-0) and TTiN|TTiNH (where = 0-2 and = 2-0) demonstrated high full battery specific energies for F-, Cl-, and Br-ion batteries, up to 462 Wh kg. These results demonstrate the potential of new halide-ion battery designs, paving the way for future research and innovation in battery technology.