Multilayered MXene electrodes in deep eutectic solvent ionic liquid electrolyte for supercapacitor applications

Numerous studies have shown that two-dimensional titanium carbide (Ti₃C₂T_x), a MXene family member, has promising electrochemical characteristics for energy storage. Ti₃C₂T_x, made by selective etching of A layers in MAX phases, is suitable to various applications owing to its high surface area, hydrophilic surfaces, variable interlayer spacing, and strong electrical conductivity. Its supercapacitor performance has received attention because it has the potential to bridge high-power capacitors with high-energy batteries. This work compares the potential window and capacitance performance of multilayered (ml-) Ti₃C₂T_x in non-aqueous ionic liquid electrolyte (Ethaline) to alkaline (KOH) and neutral (Na₂SO₄) electrolytes. LiF + HCl etching method was used to produce ml-Ti₃C₂T_x, which was tested in three potential windows: positive (0 to +0.6 V), negative (0 to -1.2 V), and combined positive-negative (+0.5 to -1.2 V). The areal capacitance of ml-Ti₃C₂T_x in Ethaline was determined as 40 mF/cm² within a narrow potential window (0.6 V) and increased to 356 mF/cm² within a wider potential window (1.7 V) at a scan rate of 5 mV/s. Aqueous KOH and Na₂SO₄ electrolytes were unsuitable for MXene based energy storage with 1.7 V potential window due to degradation and low activity. SEM-EDS, XRD, TEM, FTIR and CV indicated effective synthesis, functionalization, and electrochemical activity of ml-Ti₃C₂T_x. Surface modifications, such as O-H and C-O vibrational bands, demonstrate the importance of electrolyte interactions in improving performance. It was shown that ionic liquid electrolytes like Ethaline can improve energy storage. This study advances high-performance supercapacitors by widening the potential window and enhancing charge storage processes, meeting the growing demand for efficient and sustainable energy.