Facile scalable multilevel structure engineering makes Ti0.667Nb1.333O4 a new promising lithium-ion battery anode

Abstract

Titanium/Niobium oxide-based lithium-ion battery anodes are characterized by their excellent safety features, superior rate capability and high theoretical capacity. However, the intrinsic poor electron conductivity of the metal oxides significantly limits anode performance. In this work, Ti0.667Nb1.333O4 (TNO4) has been synthesized and utilized as the lithium-ion battery anode for the first time. A facile scalable multilevel structure engineering in terms of electronic, morphology, and surface structures is applied to TNO4, leading to an effective performance improvement. The electronic structure, in regard to the band gap and lithium-ion diffusion energy barrier, is well tuned by a stoichiometric atomic substitution of titanium by niobium. The reduced band gap (0.38 eV vs. 3.10 eV) and increased energy barrier along the c-axis (0.13 eV vs. 0.04 eV) accelerate electrochemical kinetics and increase actual capacities. In combination with particle size reduction and surface carbon composition, the electrochemical performance is further improved. The lithiation/delithiation mechanism of the TNO4 anode is investigated by in situ X-ray diffraction (XRD) and density functional theory (DFT) computations. In situ transmission electron microscopy (TEM) is applied to reveal the structure change upon lithiation and delithiation, where a limited volume change is observed. Differential electrochemical mass spectrometry (DEMS) shows a slight gassing process of TNO4/carbon.