<i>d</i>-Spacing Effect on the Electrochemical Performance of MXene in Room Temperature Ionic Liquid Electrolyte

MXenes exhibit excellent capacitance at high rates in aqueous electrolytes specially in H₂SO₄ aqueous electrolyte, but in a narrow potential window, which limits the energy density. Moreover, oxidation of Ti₃C₂ under high anodic potentials in aqueous electrolytes further limits its use to cathodes of asymmetric devices. Organic electrolyte and room temperature ionic liquids (RTIL) provide larger potential window, leading higher energy density. In this work, different intercalants were introduced in-between Ti₃C₂T_z, producing different interlayer spacing (d-spacing). RTIL were employed as electrolytes to investigate the d-spacing effects on electrochemical performance for three-electrode system. As a result, intercalated Ti₃C₂T_z, provides much broader operating window of 3.2 V, showing much higher specific capacitances of 257 F/g, energy and power densities of 256 Wh/kg and 46000 W/kg, respectively, and cycling stability than pristine Ti₃C₂T_z. In addition, the electrochemical performance, ions dynamics were investigated by ex situ X-ray diffraction (XRD), broadband dielectric spectroscopy (BDS) and quasi elastic neutron scattering (QENS) spectra.