Intercalation of Small Organic Molecules into Ti₃C₂T_x MXene Cathodes for Flexible High-Volume-Capacitance Zn-Ion Microsupercapacitor

The delamination of 2D Ti₃C₂T_x MXene endows the injection of various ions and small organic molecules into its layers, thus leading to a tunable distance between layers and adjustable electrochemical properties. A suitable selection of intercalators needs to be considered according to the relevant metal-ion-based energy storage device because of the different radii of metal ions such as Li⁺, Na⁺, Mg²⁺ Zn²⁺, etc. Herein, the intercalation of N,N-dimethylacetamide (DMAC), acetonitrile (ACN), dimethyl sulfoxide (DMSO), LiCl (H₂O) into Ti₃C₂T_x cathodes and their electrochemical performance comparisons by fabricating Zn-ion microsupercapacitors (MSCs) is reported. Studies found that an increased calculated interlayer space of 3.42, 7.47, 7.79, 8.3 Å is obtained for the H₂O, DMSO, ACN, DMAC intercalated Ti₃C₂T_x cathodes, and a decreased calculated binding energy of −0.03, −0.78, −1.91, and −3.06 eV is obtained for the Ti₃C₂T_x-H₂O, Ti₃C₂T_x-DMSO, Ti₃C₂T_x-ACN, and Ti₃C₂T_x-DMAC, respectively. The highest interlayer space, lowest binding energy, and amide groups make the DMAC intercalated Ti₃C₂T_x-based MSC exhibit volumetric capacitance of 1873 F cm⁻³ at a scan rate of 5 mV s⁻¹, much higher than 1103 F cm⁻³ for Ti₃C₂T_x-H₂O, 1313 F cm⁻³ for Ti₃C₂T_x-ACN, 544 F cm⁻³ for Ti₃C₂T_x-DMSO. The superior flexibility that results in invariable capacitance under 5000 bending cycles, together with the lighting test of the fabricated MSC, demonstrates its application in the wearable integrated system.