A general strategy to enhance the electrochemical activity and energy density of energy-storage materials through using sintering aids with redox activity: a case study of Mo4Nb26O77

Abstract

The solid-state reaction method for energy-storage material preparations is simple and cost effective, thereby being suitable for industrialization. However, its sintering temperatures are generally high, resulting in large-sized (>1 μm) primary particles with low electrochemical activity. Here, based on a Mo₄Nb₂₆O₇₇ model material, we explore a general modification of the solid-state reaction method through using sintering aids with redox activity and successfully prepare Mo₄Nb₂₆O₇₇ with submicron-sized (∼200 nm) primary particles at a low sintering temperature of only 700 °C. The resultant high electrochemical activity of Mo₄Nb₂₆O₇₇ and its additional Mo-based redox activity which originated from the MoO₃ sintering aid enable its large practical capacity of 366 mA h g⁻¹, which is the largest in the field of niobate anode materials. Mo₄Nb₂₆O₇₇ further exhibits a relatively low working potential since more Nb⁴⁺ ions are reduced to Nb³⁺ ions at low potentials. Additionally, Mo₄Nb₂₆O₇₇ has high rate performance and good cyclability when external Li⁺ ions mainly occupy the interstices between the (010) crystallographic planes of its open and stable shear ReO₃ crystal structure. Good low-temperature electrochemical properties are also achieved as a result of the high electrochemical activity. Therefore, this anode material has great practicability for high-performance Li⁺ storage.