Electrochemical Energy Storage in MXene Materials

The growing demand for portable electronics and electric vehicles requires energy storage devices with higher power density and faster charging rates than conventional lithium-ion batteries can provide. Pseudocapacitive materials offer an alternative mechanism combining battery-like energy density with capacitor-like power performance, though their long-term cycling stability remains problematic. Two-dimensional transition metal carbides and nitrides (MXenes) have emerged as promising candidates due to their metallic conductivity and surface redox chemistry.

This study investigates the electrochemical behavior of Ti₃C₂Tₓ MXene in aqueous electrolytes with systematic variation of pH and interlayer spacing. Electrodes were fabricated by vacuum filtration of delaminated MXene flakes, with thickness controlled between 2 and 20 micrometers. Cyclic voltammetry and galvanostatic charge-discharge measurements were conducted in three-electrode configuration.

Specific capacitance of 517 F/g was achieved at 2 mV/s scan rate in 1 M H₂SO₄, with 85% retention after 10,000 cycles at 10 A/g. Rate capability testing demonstrated 63% capacitance retention when scan rate increased from 2 to 100 mV/s.

These results indicate that proton intercalation dominates charge storage in acidic media, while ion intercalation in neutral electrolytes shows inferior kinetics. The exceptional cycling stability suggests that MXene surface termination groups prevent structural degradation during repeated intercalation. Optimization of interlayer spacing through cation pillaring represents a promising strategy for enhancing rate performance in next-generation electrochemical energy storage devices.