Operando Raman and DFT Analysis of (De)lithiation in Fast-Charging, Shear-Phase H-Nb₂O₅

Niobium-based compounds with Wadsley-Roth crystallographic shear structures show promise as fast lithium storage materials in micrometer sizes without the need for nanostructure engineering. However, the lithium storage mechanism underlying their unique electrochemical properties has yet to be understood. Herein, we characterized the evolution of vibration bands in operando Raman spectra of the representative shear phase, H-Nb₂O₅, during lithiation in order to correlate the lithiation-induced structural variations of H-Nb₂O₅ with the electrochemical properties. Complemented by DFT calculations, the lithium storage mechanism was unraveled, including the preference for adsorption sites, the resultant electronic structure, and specific pathways for lithium transport. This work provides insight into the lithium storage mechanism in shear structure Nb₂O₅, which is believed to be useful for knowledge-based design of niobium-based compounds as high-rate lithium storage materials.