Scalable liquid-crystalline MXene films via bio-inspired surface bridging strategy for enhancing electrochemical performance

Abstract

The discovery of liquid crystal (LC) phases in dispersions of two-dimensional (2D) materials has opened new opportunities for developing aligned three-dimensional (3D) macrostructures, enabling advancements in energy-storage applications. However, achieving suitable mechanical, electrical, and electrochemical reliability in films, a type of macrostructure, remains challenging due to the inherent self-restacking of MXene sheets and the lack of a proper fabrication protocol for large-scale film formation. Here, we demonstrate a sequential surface bridging strategy for MXene sheets utilizing their LC properties and further boosting both the mechanical and electrochemical properties by facilitating in situ polymerization of norepinephrine between the MXene interlayers. The LC MXene ink, with strong cross-linking connections via synergistic hydrogen and/or covalent bonding, provides high alignment levels in sheets, expanded interlayer structures, and excellent processability for large-area film formation. Consequently, LC MXene/poly(norepinephrine) hybrid films have expanded the range of applications from symmetric electrochemical capacitors to asymmetric Zn-ion hybrid capacitors, achieving a specific capacity of 92.9 mAh/g at 0.2 A/g and an energy density of 55.6 Wh/kg at a power density of 83.6 W/kg. This innovative LC-based self-assembly of MXene with a bio-inspired organic polymer not only addresses the self-restacking issue but also paves the way for high-performance MXene-based hybrid films for next-generation energy-storage devices.