Elastic MXene conductive layers and electrolyte engineering enable robust potassium storage

Abstract

The precisely engineered structures of materials greatly influence the manifestation of their properties. For example, in the process of alkali metal ion storage, a carefully designed structure capable of accommodating inserted and extracted ions will improve the stability of material cycling. The present study explores the uniform distribution of self-grown carbon nanotubes to provide structural support for the conductive and elastic MXene layers of Ti₃C₂T_x-Co@NCNTs. Furthermore, a compatible electrolyte system has been optimized by analyzing the solvation structure and carefully regulating the component in the solid electrolyte interphase (SEI) layer. Mechanistic studies demonstrate that the decomposition predominantly controlled by FSI⁻ leads to the formation of a robust inorganic SEI layer enriched with KF, thus effectively inhibiting irreversible side reactions and major structural deterioration. Confirming our expectations, Ti₃C₂T_x-Co@NCNTs exhibits an impressive reversible capacity of 260 mA h g⁻¹, even after 2000 cycles at 500 mA g⁻¹ in 1 M KFSI (DME), surpassing most MXene-based anodes reported for PIBs. Additionally, density functional theory (DFT) calculations verify the superior electronic conductivity and lower K⁺ diffusion energy barriers of the novel superstructure of Ti₃C₂T_x-Co@NCNTs, thereby affirming the improved electrochemical kinetics. This study presents systematic evaluation methodologies for future research on MXene-based anodes in PIBs.