| Summary: | Niobium dioxide (NbO2) features a high theoretical capacity and an outstanding electron conductivity, which makes it a promising alternative to the commercial graphite negative electrode. However, studies on NbO2 based lithium-ion battery negative electrodes have been rarely reported. In the present work, NbO2 4 nanoparticles homogeneously embedded in carbon matrix are synthesized using a dental resin monomer (bisphenol A glycidyl dimethacrylate, Bis-GMA) as solvent and carbon source and niobium ethoxide (NbETO) as the precursor. Thermal polymerization and calcination under Ar/H2 atmosphere at 900 °C are applied, to synthesize the NbO2/carbon nanohybrid in a facile scalable way. It is revealed that a low Bis-GMA/NbETO mass ratio (from 1:1 to 1:2) enables the conversion of Nb (V) to Nb (IV) due to increased porosity induced by alcoholysis reaction between the NbETO and Bis-GMA. The fundamental mechanisms responsible for the formation of NbO2 are elaborated, which involve the reduction of Nb (V) by in situ generated carbon monoxide. The as-prepared NbO2/carbon nanohybrid delivers a reversible capacity of 225 mA h g-1 after 500 cycles at 1 C rate with the Coulombic efficiency of more than 99.4 % in the cycles. Various experimental and theoretical approaches including solid state NMR, ex situ XRD, differential electrochemical mass spectrometry, and density functional theory (DFT) are utilized to understand the fundamental lithiation/delithiation mechanisms of the NbO2/carbon nanohybrid. The results suggest that the NbO2/carbon nanohybrid bearing high capacity, long cycle life and low gas-evolution is promising for lithium storage applications.
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