Fast and extensive intercalation chemistry in Wadsley-Roth phase based high-capacity electrodes

Abstract

Wadsley-Roth (W-R) structured oxides featured with wide channels represent one of the most promising material families showing compelling rate performance for lithium-ion batteries. Herein, we report an in-depth study on the fast and extensive intercalation chemistry of phosphorus stabilized W-R phase PNb9O25 and its application in high energy and fast-charging devices. We explore the intercalation geometry of PNb9O25 and identify two geometrical types of stable insertion sites with the total amount much higher than conventional intercalation-type electrodes. We reveal the ion transportation kinetics that the Li ions initially diffuse along the open type III channels and then penetrate to edge sites with low kinetic barriers. During the lithiation, no remarkable phase transition is detected with nearly intact host phosphorous niobium oxide backbone. Therefore, the oxide framework of PNb9O25 keeps almost unchanged with all the fast diffusion channels and insertion cavities well-maintained upon cycling, which accomplishes the unconventional electrochemical performance of W-R structured electrodes.