Abstract: MXene electrodes serve as ideal candidates for aqueous supercapacitors due to their superior rapid charge transport properties. However, pristine MXene suffers from tight sheet restacking resembling soil compaction, which inevitably leads to blocked ion channels and obscured active sites. Additionally, the susceptibility of active Ti sites to oxidative degradation severely restricts the high-rate energy storage performance and long-term cycling stability. To address these bottlenecks, this study constructs a MXene-DFBA biomimetic composite electrode via the Schiff base covalent reaction between 3,4-difluorobenzaldehyde (DFBA) and aminated MXene (MXene-NH₂). Drawing inspiration from the synergistic physiological characteristics of plant root hairs involving loose channel construction, barrier protection, and nutrient enrichment, the MXene-DFBA composite is endowed with a triple biomimetic synergistic effect to expand interlayer spacing, inhibit oxidative degradation, and induce the formation of a localized built-in electric field (BIEF). Benefiting from this biomimetic mechanism, the charge storage capability and reaction kinetics of the MXene-DFBA electrode are significantly optimized. The MXene-DFBA material delivers a specific capacitance of 52.8 F g^-1 at 0.5 A g^-1. The assembled aqueous symmetric supercapacitor achieves a maximum energy density of 4.08 Wh kg^-1 and a maximum power density of 4526 W kg^-1. Furthermore, the device exhibits exceptional long-term stability with a capacitance retention of 95.7% after 100000 cycles, outperforming most reported supercapacitors. This work provides a novel biomimetic design strategy for the construction of high-stability and high-performance MXene-based energy storage devices.

Key words: Plant root hair biomimicry, MXene, 3,4-Difluorobenzaldehyde, Built-in electric field, Aqueous potassium-ion supercapacitor