Interlayer-engineered MXene Nanosheets confining CoGa-LDH enable ultrafast charge transfer kinetics for high-energy potassium-ion supercapacitors.

Two-dimensional MXenes, with their accordion-like morphology and facile exfoliation into monolayers, offer an ideal platform for immobilizing electroactive materials. However, composites fabricated from MXenes through conventional methods exhibit inhomogeneous dispersion, sluggish charge redistribution, and poor interfacial coupling, limiting their potassium-ion storage performance. Herein, an interlayer-engineered CoGa-LDH/MXene heterostructure is fabricated via Peltier effect-driven rotational hydrothermal synthesis with tunable Co/Ga ratios. This approach ensures atomic-level confinement of layered double hydroxide (LDH) within MXene interlayers while strengthening interfacial coupling and ion transport kinetics. The resulting heteroarchitecture synergizes the high pseudocapacitance of CoGa-LDH and the metallic conductivity of MXene, enabling ultrafast ion/electron transport and suppressing self-aggregation. Optimized Co1Ga1-LDH/MXene delivers a remarkable specific capacitance of 1345.3 F/g and exceptional cyclability (85.13 % retention after 6000 cycles), surpassing most reported LDH-based supercapacitors. Density functional theory (DFT) calculations reveal that the heterointerface enhances K+-ion adsorption energy and modulates charge distribution, accelerating redox kinetics. When the Co1Ga1-LDH/MXene composite is assembled into an asymmetric supercapacitor (ASC), the device achieves an energy density of 77.4 Wh/kg at 1125 W/kg, with sustained performance under rigorous cycling. This work elucidates the confinement engineering of MXene-based compounds and their potassium storage mechanisms, providing critical references for high-energy-density supercapacitors in alkaline systems.