Gill‐Inspired Biomimetic Engineering Enables 100 000‐Cycle Stable Potassium Storage of MXene

ABSTRACT

MXene materials suffer from critical challenges including poor air stability, sheet restacking, sluggish K storage kinetics, and structural collapse during cycling. Inspired by biological interface functions, this work constructs an organic‐inorganic biomimetic MXene‐4‐MVA composite through chemical coupling between 4‐methylvaleric acid (4‐MVA) and the functionalized MXene surface. The 4‐MVA functions as a molecular pillar to expand interlayer spacing, expose active sites, and buffer volume deformation while forming a protective layer that inhibits MXene oxidation. Simultaneously, the interfacial charge redistribution induced by 4‐MVA modification generates an interfacial dipole effect, which regulates charge transfer behavior and K ⁺ adsorption kinetics. Experimental tests and density functional theory (DFT) calculations reveal that the organic modification regulates interfacial K adsorption behavior and ion transport characteristics. Consequently, the obtained MXene‐4‐MVA exhibits an excellent specific capacitance of 59.0 F g ⁻¹ at 0.5 A g ⁻¹ . The assembled aqueous symmetric MXene‐4‐MVA // MXene‐4‐MVA supercapacitor achieves an ultrahigh capacitance retention of 92.1% after 100 000 cycles at 5 A g ⁻¹ , exceeding the cycling stability of most state‐of‐the‐art supercapacitors. This study providing new insights for the design and preparation of highly stable MXene‐based energy storage electrodes.