High-Voltage Symmetric Supercapacitor Based on 2D Titanium Carbide (MXene, Ti₂CT_x)/Carbon Nanosphere Composites in a Neutral Aqueous Electrolyte

The energy storage performance of one of the lightest-known MXenes, Ti 2 CT x (MX) combined with carbon nanospheres (CNS) has been investigated as a symmetric electrode system in an aqueous electrolyte (1 M Li 2 SO 4 ). The energy storage properties were interrogated using cyclic voltammetry (CV), galvanostatic cycling with potential limitation (GCPL), electrochemical impedance spectroscopy (EIS) and voltage-holding tests. The combined material (MX/CNS) demonstrated a higher specific capacity compared to each of the individual components. The material was fabricated with relatively high and low mass loadings, assembled into a symmetric device and performance compared. Specific capacitance, specific power and specific energy for the lower electrode mass loading of 180 F⋅g −1 , 37.6 kW⋅kg −1 and 14.1 W⋅h⋅kg −1 were all higher than 86 F⋅g −1 , 20.1 kW⋅kg −1 and 6.7 W⋅h⋅kg −1 for the higher mass loading. A wide voltage window of 1.5 V was obtained, but with limited long-term cycling behavior, suggesting the need for future improvement. Mathematical modelling and simulation of the supercapacitor showed good correlation with the experimental results, validating the model. The results reveal the potential of the Ti 2 CT x to be employed as a viable energy storage system for lightweight applications.