Effect of Hf-doping on electrochemical performance of anatase TiO2 as an anode material for lithium storage.

ABSTRACT: Hafnium-doped titania (Hf/Ti?=?0.01; 0.03; 0.05) had been facilely synthesized via a template sol-gel method on carbon fibre. Physico-chemical properties of the as-synthesized materials were characterized by X-ray diffraction, Raman spectroscopy, scanning electron microscopy, energy-dispersive X-ray analysis, scanning transmission electron microscopy, X-ray photoelectron spectroscopy, thermogravimetry analysis and Brunauer-Emmett-Teller measurements. It was confirmed that Hf4+ substitute in the Ti4+ sites, forming Ti1-x Hf x O2 (x?=?0.01; 0.03; 0.05) solid solutions with an anatase crystal structure. The Ti1-x Hf x O2 materials are hollow microtubes (length of 10-100?µm, outer diameter of 1-5?µm) composed of nanoparticles (average size of 15-20?nm) with a surface area of 80-90?m2?g-1 and pore volume of 0.294-0.372?cm3?g-1. The effect of Hf ion incorporation on the electrochemical behaviour of anatase TiO2 in the Li-ion battery anode was investigated by galvanostatic charge/discharge and electrochemical impedance spectroscopy. It was established that Ti0.95Hf0.05O2 shows significantly higher reversibility (154.2?mAh?g-1) after 35-fold cycling at a C/10 rate in comparison with undoped titania (55.9?mAh?g-1). The better performance offered by Hf4+ substitution of the Ti4+ into anatase TiO2 mainly results from a more open crystal structure, which has been achieved via the difference in ionic radius values of Ti4+ (0.604 Å) and Hf4+ (0.71 Å). The obtained results are in good accord with those for anatase TiO2 doped with Zr4+ (0.72 Å), published earlier. Furthermore, improved electrical conductivity of Hf-doped anatase TiO2 materials owing to charge redistribution in the lattice and enhanced interfacial lithium storage owing to increased surface area directly depending on the Hf/Ti atomic ratio have a beneficial effect on electrochemical properties.

SUBMITTER: Gnedenkov SV 

PROVIDER: S-EPMC6030266 | biostudies-literature | 2018 Jun

REPOSITORIES: biostudies-literature