Synergistic enhancement in energy storage in lithium/sodium ion batteries using engineered composites of MXenes and carbon nanohorns

Abstract

The synthetic procedures and re-stacking of MXenes have been major challenges, driving research toward developing a facile and sustainable solution for their applications in energy storage devices. Considering these key issues, this study outlines a hydrofluoric acid-free synthesis of an MXene (Sf-MXene) and investigates the influence of carbon nanohorns (CNHs) when added in different proportions on interfacial and electrochemical properties in Li/Na-ion batteries. BET, XRD, Raman, XPS, and FE-SEM were conducted to understand the chemical and physical properties of the materials. Impedance and cyclic voltammetry were conducted on CR 2025 Li/Na-half cells to evaluate the electrochemical performance. Furthermore, to elucidate the complex interfacial properties, distribution of relaxation times (DRT) analysis was conducted. A better performance in terms of specific capacity and cycling stability was observed in Sf-MXene/CNH 4 : 1 based Li and Na-ion anodic half cells in comparison with Sf-MXene/CNH 3 : 2 and Sf-MXene based Li/Na-ion anodic half cells. Further DRT studies revealed a reduced total polarization resistance post cyclic voltammetry in Sf-MXene/CNH 4 : 1, improving ion kinetics in Li-ion anodic half cells. Sf-MXene/CNH 3 : 2 was shown to increase the SEI and interfacial resistance, calculated through DRT and impedance studies, thereby resulting in poorer electrochemical performance. Furthermore, Li-ion anodic half-cells showed easier ion transport and higher capacity than their Na counterparts due to the facile diffusion of lithium ions in the active materials employed in this study. Postmortem XPS studies were conducted to evaluate the nature of the solid electrolyte interphase.