Oxygen-deficient Niobium Oxide in Carbon Matrix as Anode for Lithium-Ion Battery

Lithium-ion batteries (LIBs) have been extensively investigated as high performance rechargeable batteries for portable electronic devices and electric vehicles (EVs). However, the current LIB technology is handicapped by several critical disadvantages for EV applications including short cycling life and safety hazard resulting from dynamic solid electrolyte interface (SEI) formed at low working potential. Spinel lithium titanate (Li₄Ti₅O₁₂), anatase titanium dioxide (TiO₂) and niobium pentoxide (Nb₂O₅) have been considered to be as promising anode materials for rechargeable LIBs owing to the considerable safety advantage that their redox potentials match to the lowest unoccupied molecular orbital (LUMO) of the organic liquid-carbonate electrolyte, which prevents the growth of lithium dendrites and the decomposition of electrolyte. Unfortunately, their intrinsic poor electric conductivities, poor lithium ion conductivities, and the capacity decay resulted from pulverization during charge-discharge processes limit their practical use in LIBs, especially for Nb₂O₅ (σ∼3×10⁻⁶ S·cm⁻¹).

   Herein, we report a one-step facile hydrothermal synthesis of Nb₂O₅/carbon matrix using glucose as the carbon source. After post-heat treatment under H₂ gas, the glucose is carbonized to form carbon matrix and Nb₂O₅ nanocrystals are homogeneously immersed in carbon matrix. The stoichiometric Nb₂O₅ insulator becomes to oxygen-deficient niobium oxide semiconductor, and this carbon matrix can efficiently prevent niobium oxide nanocrystals from pulverization during the charge-discharge processes, resulting in improved recyclability. In addition, the carbon matrix and oxygen-deficient niobium oxide can effectively enhance the electronic conductivity and lithium ion conductivity of our electrode material, which results in enhanced rate performance and cycle durability. We believe that such a kind of niobium oxide/carbon matrix structure provides a new design toward high cycle durability niobium oxide based anode materials.