Mesostructured niobium-doped titanium oxide-carbon (Nb-TiO₂-C) composite as an anode for high-performance lithium-ion batteries

다국어 초록 (Multilingual Abstract)

<P><B>Abstract</B></P> <P>Mesostructured niobium (Nb)-doped TiO<SUB>2</SUB>-carbon (Nb-TiO<SUB>2</SUB>-C) composites are synthesized by a hydrothermal process for application as anode materials in Li-ion batteries. The composites have a hierarchical porous structure with the Nb-TiO<SUB>2</SUB> nanoparticles homogenously distributed throughout the porous carbon matrix. The Nb content is controlled (0–10 wt%) to investigate its effect on the physico-chemical properties and electrochemical performance of the composite. While the crystalline/surface structure varied with the addition of Nb (<I>d</I>-spacing of TiO<SUB>2</SUB>: 0.34–0.36 nm), the morphology of the composite remained unaffected. The electrochemical performance (cycle stability and rate capability) of the Nb-TiO<SUB>2</SUB>-C composite anode with 1 wt% Nb doping improved significantly. First, a full cut-off potential (0–2.5 V <I>vs</I>. Li/Li<SUP>+</SUP>) of Nb-doped composite anode (1 wt%) provides a higher energy utilization than that of the un-doped TiO<SUB>2</SUB>-C anode. Second, Nb-TiO<SUB>2</SUB>-C composite anode (1 wt%) exhibits an excellent long-term cycle stability (100% capacity retention, 297 mAh/g at 0.5 C after 100 cycles and 221 mAh/g at 2 C after 500 cycles) and improved rate-capability (192 mAh/g at 5 C), respectively (1 C: 150 mA/g). The superior electrochemical performance of Nb-TiO<SUB>2</SUB>-C (1 wt%) could be attributed to the synergistic effect of improved electronic conductivity induced by optimal Nb doping (1 wt%) and lithium-ion penetration (high diffusion kinetics) through unique pore structures.</P> <P><B>Highlights</B></P> <P> <UL> <LI> Mesostructured porous nanocomposites of Nb-doped TiO<SUB>2</SUB> and carbon are prepared. </LI> <LI> The composites are prepared hydrothermally and used as anodes for Li-ion battery. </LI> <LI> Highly conductive porous carbon and optimized Nb doping (1 wt%) act synergistically. </LI> <LI> ∼100% capacity retention (221 mAh/g) after 500 cycles is realized. </LI> <LI> Good rate capability with a high capacity (192 mAh/g) at 5 C is achieved. </LI> </UL> </P>