Micro-supercapacitors of exceptionally high capacitance fabricated using intrinsically stable MXene inks via electrohydrodynamic jet printing

Abstract

MXenes hold tremendous promise as printable conductive inks for microelectronic devices, due to their excellent electrical conductivity and solution processability. However, their oxidation susceptibility and poor dispersion in organic solvents hinder the development of highly viscous, organic-based MXene inks, necessary for making micro-supercapacitors via the high-resolution Electrohydrodynamic (EHD) jet-printing technique. Herein, we present a robust solution by developing alkylated 3,4-dihydroxy-L-phenylalanine (ADOPA) functionalized MXene (ADS-MXene), blended with carboxymethyl cellulose (CMC) in a hybrid organic solvent, to form a stable ADS-MXene((CMC)) ink. This ink demonstrated high electrical conductivity (3400 S cm(-1)), optimal viscosity (similar to 4 x10 (3) cP), oxidation resistance and highly stable dispersion for up to 3 months. Utilizing an EHD jet printing process especially optimized for this ink composition, we successfully fabricated ultrahigh-resolution interdigitated micro-supercapacitor electrodes with a line width and gap of 80 mu m, achieving an outstanding areal cell density of 6 cells cm(-)(2). These electrodes experimentally exhibited superior volumetric capacitance of 2013 F cm(-)(3), the highest reported to date for a MXene printed micro-supercapacitor device. This remarkable capacitance was further validated using density functional theory (DFT) calculations, which revealed pronounced charge transfer between ADOPA and MXene, contributing to said stability. Beyond record device metrics, ADS-MXene((CMC)) establishes a reproducible ink process operating window for stable EHD printing, advancing standardization efforts for MXene inks. This approach overcomes longstanding critical processing barriers and opens new avenues for high resolution, ultrahigh capacitance micro-supercapacitors, indispensable for next-generation microelectronics