MXene based heterostructure engineered via molten salt modification: toward high-capacity and long-life zinc-iodine batteries

The scalable synthesis of high-quality MXenes with minimal layer stacking remains a critical challenge for their practical applications. Here, we report a modified molten salt-assisted strategy to construct a 3D porous Ti 3 C 2 T x @K 2 Ti 8 O 17 heterostructure, simultaneously addressing MXene restacking and enhancing electrochemical performance. By exfoliating Ti 3 C 2 T x in a LiCl-AlCl 3 molten salt medium followed by in-situ KOH-induced transformation, K 2 Ti 8 O 17 nanoflakes are uniformly embedded between MXene layers, acting as permanent spacers to inhibit aggregation while creating a conductive, catalytic network. As a proof of concept, the engineered Ti 3 C 2 T x @K 2 Ti 8 O 17 heterostructure is implemented as a multifunctional separator for zinc-iodine batteries (ZIBs), the optimized ZIBs demonstrates exceptional cycling stability with ultralow capacity decay (0.0008% per cycle at 50 C over 7000 cycles) and remarkable rate capability (137.4 mAh g − 1 at 50 C), far outperforming commercial polypropylene separator based ZIBs. The excellent performances of the ZIBs can be attributed to the following factors: (1) iodine redox kinetics is significantly accelerated by the conductive MXene matrix, (2) polyiodide shuttle effects are suppressed through chemisorption on K 2 Ti 8 O 17 spacers, and (3) electrolyte permeability is improved by the hierarchically porous architecture. This strategy combines strong adsorption with fast electrochemical reactions, providing a simple and effective solution for optimizing the performance of Zn-I 2 batteries.