MXene–carbon nanotube composite electrodes for high active mass asymmetric supercapacitors

Abstract

This article describes for the first time the fabrication of an asymmetric device, which is based on negative Ti₃C₂T_x (MXene)–multiwalled carbon nanotube (MCNT) electrodes and positive polypyrrole (PPy) coated MCNT electrodes. The approach involves the feasibility studies of new strategies for achieving enhanced electrochemical performance of high active mass (AM) MXene electrodes. Good material performance at high AM of 35 mg cm⁻² is linked to the application of multifunctional chelating dispersants for co-dispersion of Ti₃C₂T_x and MCNT and advanced water insoluble hydrophilic binders. The experimental results reveal the effect of the chemical structure of the dispersants and binders on electrode performance. Another important finding is the ability of achieving high capacitance of PPy-coated MCNT positive electrodes in a complementary potential range. The analysis of cyclic voltammetry data in Na₂SO₄ electrolyte for Ti₃C₂T_x–MCNT electrodes shows areal capacitance of 1.93 F cm⁻² which is substantially higher than literature results for pure Ti₃C₂T_x and Ti₃C₂T_x composites. Moreover, high capacitance is obtained at much lower electrical resistance. Especially important is the possibility of achieving higher capacitance equal to 0.94 F cm⁻² for the asymmetric supercapacitor in 0–1.6 V window, compared to literature data for symmetric supercapacitors with significantly lower capacitances in smaller voltage windows.