A 3D crinkled MXene/TiO₂ heterostructure with interfacial coupling for ultra-fast and reversible potassium storage

MXenes have been regarded as a rising star of energy storage materials due to their excellent physiochemical properties. However, MXene always suffers from a re-stacking issue and long transport path along the planar direction, resulting in limited exposure of K⁺ adsorption sites and unsatisfactory potassium storage performance. Herein, a crumpled MXene/TiO₂ (CM/TiO₂) heterostructure is constructed as an anode of potassium-ion batteries (PIBs) by a facile solvothermal route. The CM/TiO₂ heterostructure with strong interfacial coupling provides abundant open pores and transport channels, providing efficient electron transfer and rapid ion diffusion capabilities. Taking advantage of the structural superiority and chemical coupling, the CM/TiO₂ electrode exhibits a reversible capacity of 101.5 mA h g⁻¹ at 1 A g⁻¹ after 400 cycles. The improved kinetics of the MXene/TiO₂ heterostructure are systematically investigated by using theoretical calculations and experimental analysis. When coupled with an AC cathode, the fabricated CM/TiO₂//AC potassium-ion hybrid capacitor exhibits decent electrochemical performance, revealing great potential for practical application. Our work sheds new light on the structure engineering of MXene-based electrode materials for energy storage devices.