Coal-derived two-dimensional MNb2O6 (M = Mn, Fe, Co)/C hybrids with superior lithium storage performance

Abstract

Rational design of electrode materials with fast reaction kinetics, improved safety, and reversible ion (de)intercalation capability is crucial for advancing high-performance lithium-ion batteries (LIBs). In this study, two-dimensional (2D) MNb₂O₆ (M = Mn, Fe, Co)/C nanohybrids were synthesized by a molten-salt-assisted method using Heishan coal as both the carbon source and structural carrier. Owing to the favorable interfacial interaction between coal-based carbon and the compounds generated by the lower melting point of Fe(NO₃)₃ and Nb₂O₅, FeNb₂O₆/C (FeNO/C) nanosheets with a uniformly dispersed structure were obtained. These nanosheets exhibit excellent cycling stability of 632.1 mAh g⁻¹ after 600 cycles at 0.4 A g⁻¹, a competitive Li⁺ diffusion rate, reversible Li⁺ (de)intercalation capability, and robust structural integrity. Notably, the LiFePO₄∥FeNO/C full battery also demonstrates favorable performance. Unlike FeNO/C, the tremella-like CoNb₂O₆/C (CoNO/C) exhibits enhanced electrochemical behavior through an amorphous phase transformation mechanism. Overall, the strong performances of these samples validate the rational design of 2D M–Nb–O/coal-based carbon hybrid nanostructures with superior structural stability and integrity, providing a valuable reference for the development of similar materials.