Effect of Hf-doping on electrochemical performance of anatase TiO ₂ 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–xHfxO2 (x = 0.01; 0.03; 0.05) solid solutions with an anatase crystal structure. The Ti1–xHfxO2 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.

Synthesis of One-Dimensional Mesoporous Ag Nanoparticles-Modified TiO2 Nanofibers by Electrospinning for Lithium Ion Batteries

“…The electrochemical performance of Ag@TiO 2 nanofibers obtained in our research is also compared with that of TiO 2 composites reported in References [23,31,32,33,34,43,45,46]. As shown in Table 1, the comprehensive electrochemical performance obtained in our research is generally superior to that reported in the above-mentioned references.…”

“…Moreover, the addition also causes the sharp increase in current density of the TiO 2 nanofibers electrode at the same applied potential, which confirms that Ag contributes to the improvement in transfer rate of charges. The diffusion coefficient of samples can be calculated by the Randles-Sevcik equation (shown as following) [22,43]:Ip=0.4463×(F3/RT)1/2×n3/2×normalS×CLi×v1/2×normalDLi1/2 in which I p is the peak current (A), F is the Faraday constant (C⋅mol −1 ), R is the gas constant (J mol −1 ⋅K −1 ), T is the temperature (K), n is the number of electrons transferred, S is the contact area between the electrode and electrolyte (cm 2 ), С Li is the concentration of Li ion (mol⋅cm −3 ), ν is the scan rate (V⋅s −1 ), D Li is the diffusion coefficient (cm 2 ⋅s −1 ).…”

A review of scandium–hafnium doped TiO2 nanocrystals

“…The Hf doped TiO 2 -LIBs are low cost and environmentally friendly. Therefore Hf can be successfully doped into titanium source for improved power supply [21].…”

Biomass-Derived Graphitic Carbon Encapsulated Fe/Fe3C Composite as an Anode Material for High-Performance Lithium Ion Batteries

“…Therefore, the development of advanced anode materials is important to meet the ever-growing demand for high-performance LIBs. Some attractive transition metal sulfides, can provide high potential capacity by the conversion reaction or alloying process [3][4][5]. However, large volume changes during the lithiation and delithiation processes can cause rapid capacity fading and poor cycle life, which are serious drawbacks that hinder commercialization [6][7][8][9].…”