In situ built nanoconfined Nb2O5 particles in a 3D interconnected Nb2C MXene@rGO conductive framework for high-performance potassium-ion batteries

Abstract

Exploring novel anode materials with excellent electrochemical performance is of great significance for the development of potassium-ion batteries (KIBs). Here, a 3D interconnected Nb₂C/rGO conductive framework with in situ generated Nb₂O₅ nanoparticles (Nb₂O₅/Nb₂C/rGO) is successfully constructed by a simple one-step hydrothermal method and subsequent freeze-drying and annealing treatments. The unique structure formed by the intimate contact of the three components has a 3D conductive network, abundant pores and a large specific surface area, which can not only inhibit the self-restacking of Nb₂C nanosheets and the agglomeration of Nb₂O₅ nanoparticles and alleviate the volume change during the charge–discharge process, but also expose more active sites and provide unimpeded channels for the diffusion of K⁺ and infiltration of the electrolyte. Meanwhile, Nb₂O₅ nanoparticles produced by in situ oxidation of surface Nb₂C and the residual subsurface Nb₂C with a low potassium ion diffusion barrier and a high conductivity can shorten the diffusion distance and promote the diffusion kinetics of electrons/ions. Benefiting from the elaborately designed structure and synergistic effects of three different components, as an anode for KIBs, the resulting Nb₂O₅/Nb₂C/rGO exhibits a superior specific capacity of 410.6 mA h g⁻¹ after 100 cycles at 0.1 A g⁻¹, an exceptional rate performance of 159.0 mA h g⁻¹ at 5 A g⁻¹, a capacity retention of 88.8% and a coulombic efficiency over 99.8% after 1000 cycles at 2.0 A g⁻¹. Moreover, Nb₂O₅/Nb₂C/rGO also shows a good potassium storage performance in a KIB full-cell. Furthermore, the combined potassium storage mechanism of K⁺ intercalation/deintercalation is revealed by CV and in/ex situ analyses. This work can provide more meaningful guidance for the rational design and construction of anode materials for high-performance KIBs.