Nb₂O₅ nanocrystals decorated graphene composites as anode materials for high-performance dual-ion batteries

Niobium oxide (Nb₂O₅) is a promising material in photocatalytic, solar cell, electronic like electron field emitters, and especially lithium-ion batteries (LIBs) because of its adjustable morphologies, controllable crystal type, stable structure, and environmental friendliness. However, its low electrical conductivity lowers the rate performance and limits the practical applications in LIBs. Herein, we present a one-step solid-state synthesis of orthogonal Nb₂O₅ nanocrystals/graphene composites (Nb₂O₅/G) as high-performance anode materials in LIBs. Benefiting from the nanoscale crystalline structure Nb₂O₅ and highly-conductive graphene substrate, the as-prepared Nb₂O₅/G exhibits excellent electrochemical performances. Impressively, a reversible structural phase transition between orthogonal Nb₂O₅ and tetragonal Li_1−xNbO₂ (0 < x < 1) was verified by ex-situ transmission electron microscopy (TEM) and X-ray photoelectron spectroscopy (XPS). After coupling with graphite cathode based on PF₆-intercalation/deintercalation mechanisms, Nb₂O₅/G∥graphite dual-ion batteries (DIBs) full cell delivers good electrochemical performance in terms of cyclic performance and rate capability. We believe this work can provide a clear route towards developing advanced transition metal oxide/graphene composite anode and a comprehension of its electrochemical reaction mechanism.