Construction of waffle-like NS-ZIF@V2CTx heterostructures for high-performance potassium-ion batteries

Abstract

V₂CT_x MXenes have attracted much attention in the field of metal-ion batteries due to their flexible interlayer spacing and high electronic conductivity. Unfortunately, lamellar V₂CT_x suffers from the self-stacking phenomenon during charging and discharging processes. Herein, alternately stacked waffle-like NS-ZIF@V₂CT_x heterostructures with numerous exposed active sites, enhanced electrical conductivity and superior structural stability have been fabricated and utilized as anodes in potassium-ion batteries. The ultrathin porous ZIF nanosheets in the waffle-like NS-ZIF@V₂CT_x heterostructures were transformed from the ZIF nanoparticles through an innovative solvothermal reaction. This material exhibits a large specific discharge capacity of 278 mAh g⁻¹ over a 200-lap cycling test at 100 mA g⁻¹, while the electrode still maintains 100 mAh g⁻¹ after 2000 cycles at a current density of 500 mAh g⁻¹. The dense nano-network increases the interlayer spacing of V₂CT_x MXene and impedes the self-stacking phenomenon of V₂CT_x, thereby accelerating the diffusion and transport efficiency of electrons and ions. The waffle-like lightweight structures can increase the energy density of potassium-ion batteries. Ex situ characterization and electrochemical kinetics tests have been performed to verify the superiority of the waffle-like nanostructure. This study provides an inspired structure design strategy for developing MXene and MOF hybrid composites in the field of metal-ion battery research.