Fig. 7.

Structural characterization and electrochemical performance analysis of MXene as electrode material in KIB: a–c SEM images of Ti₃AlC₂ MAX phase, Ti₃C₂ MXene nanosheets (MNSs) obtained by etching the precursor MAX phase with 40% HF solution and KOH-treated Ti₃C₂ MNSs (a-Ti₃C₂), respectively. d XRD spectra stack of Ti₃AlC₂, Ti₃C₂ and a-Ti₃C₂. e SEM image of Ti₃C₂ MXene nanoribbons (MNRs) at low magnification. f Corresponding image at high-magnification g TEM image of MNRs h XPS spectra of Ti₃AlC₂, Ti₃C₂, and a-Ti₃C₂ showing the free C and K peaks. i–k HRTEM images of the Ti₃C₂ MNRs at different positions (“A” and “B”) and varying thicknesses (8, 16, and 22 nm). l XPS spectra of the 3 samples showing the O 1s peak. m–q Elemental mapping of Ti, C, K, O and F regions of the a-Ti₃C₂ sample, respectively. r CV of the a-Ti₃C₂ MNRs for KIB collected at a scan rate of 0.1 mV s⁻¹. s GCD curves of the sample obtained at different given current rates. t Rate capability of the a-Ti₃C₂ sample. u Cycling performance at 200 mA g⁻¹ and coulombic efficiency for the a-Ti₃C₂ sample [145]. Copyright 2018 Elsevier