Phosphorus-doped TiO2mesoporous nanocrystals for anodes in high-current-rate lithium ion batteries

Limited by the intrinsic low electronic conductivity and inferior electrode kinetics, the use of TiO2as an anode material for lithium ion batteries (LIBs) is hampered. Nanoscale surface-engineering strategies of morphology control and particle size reduction have been devoted to increase the lithium storage performances. It is found that the ultrafine nanocrystal with mesoporous framework plays a crucial role in achieving the excellent electrochemical performances due to the surface area effect. Herein, a promising anode material for LIBs consisting of phosphorus-doped TiO2mesoporous nanocrystals (P-TMC) with ultrafine size of 2-8 nm and high specific surface area (234.164 m2g-1) has been synthesized. It is formed through a hydrothermal process and NaBH4assisted heat treatment for anatase defective TiO2(TiO2-x) formation followed by a simple gas phosphorylation process in a low-cost reactor for P-doping. Due to the merits of the large specific surface area for providing more reaction sites for Li+ions to increase the storage capacity and the presence of oxygen vacancies and P-doping for enhancing material's electronic conductivity and diffusion coefficient of ions, the as-designed P-TMC can display improved electrochemical properties. As a LIB anode, it can deliver a high reversible discharge capacity of 187 mAh g-1at 0.2 C and a good long cycling performance with ∼82.6% capacity retention (101 mAh g-1) after 2500 cycles at 10 C with an average capacity loss of only 0.007% per cycle. Impressively, even the current rate increases to 100 times of the original rate, a satisfactory capacity of 104 mAh g-1can be delivered, displaying good rate capacity. These results suggest the P-TMC a viable choice for application as an anode material in LIB applications. Also, the strategy in this work can be easily extended to the design of other high-performance electrode materials with P-doping for energy storage.

Improved Lithium Storage Performance of a TiO2 Anode Material Doped by Co

TiO₂ is a promising anode material for lithium-ion batteries (LIBs) due to its low cost, suitable operating voltage, and excellent structural stability. The inherent poor electron conductivity and low ion diffusion coefficient, however, severely limit its application in lithium storage. Here, Co-doped TiO₂ is synthesized by a hydrothermal method as an anode material since Co@TiO₂ possesses a large specific surface area and high electronic conductivity. Thanks to the Co dopants, the ion diffusion and electron transport are both greatly improved, which is very beneficial for cycle stability, coulombic efficiency (CE), reversible capacity, and rate performance. As a result, Co@TiO₂ shows a high reversible capacity of 227 mAh g^-1 at 3 C, excellent rate performance, and cycling stability with a capacity of about 125 mAh g^-1 at 10C after 600 cycles (1 C = 170 mA g^-1).

Ustinov A, Sergienko VI. Effect of Hf-doping on electrochemical performance of anatase TiO2 as an anode material for lithium storage

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.

Superior shuttling of lithium and sodium ions in manganese-doped titania @ functionalized multiwall carbon nanotube anodes

In order to improve the electrochemical kinetics of anatase titania (TiO₂), Mn-doped TiO₂ incorporated with functionalized multiwall carbon nanotubes (MWCNTs) has been prepared by a modified hydrothermal method and tested for both lithium (LIB) and sodium-ion battery (SIB) anodes. The size of the TiO₂ particles is controlled to ∼35-40 nm, with almost even distribution on the MWCNTs surface. The nanostructuring and appropriate doping of cost-effective manganese into the TiO₂ host improved the electrochemical performance in terms of high rate capability and specific capacity for both the rechargeable battery systems. For the LIBs, the charge capacity of the 5% Mn-TiO₂/MWCNT anode is 226.3 mA h g^-1 in the first cycle, and is retained at 176.4 mA h g^-1 after 80 cycles as compared with the SIBs, in which the charge capacity is 152.1 mA h g^-1 in the first cycle, and is retained at 121.4 mA h g^-1 after 80 cycles. After testing the electrodes at a high current rate of 20C, the nanocomposite electrode can still demonstrate charge capacities of 131.2 and 117.2 mA h g^-1 at a 0.1C rate for LIBs and SIBs, respectively. The incorporation of Mn-ions (2+, 4+) is found to play a crucial role in terms of defects and vacancy creation, increasing conduction band electrons and lattice expansion to facilitate alkali metal ion diffusion for superior electrochemical performance. The combination of heteroatom doping and use of a highly conductive additive in the form of MWCNTs has resulted in excellent electrode integrity, high ion accessibility, and fast electron transport. Its outstanding cycling stability and remarkable rate performance make the 5% Mn-TiO₂/MWCNT a promising anode material for high-performance LIBs and SIBs.

Solar-driven photocatalytic treatment of diclofenac using immobilized TiO2-based zeolite composites

The study is aimed at evaluating the potential of immobilized TiO2-based zeolite composite for solar-driven photocatalytic water treatment. In that purpose, TiO2-iron-exchanged zeolite (FeZ) composite was prepared using commercial Aeroxide TiO2 P25 and iron-exchanged zeolite of ZSM5 type, FeZ. The activity of TiO2-FeZ, immobilized on glass support, was evaluated under solar irradiation for removal of diclofenac (DCF) in water. TiO2-FeZ immobilized in a form of thin film was characterized for its morphology, structure, and composition using scanning electron microscopy/energy-dispersive x-ray spectroscopy (SEM/EDX). Diffuse reflectance spectroscopy (DRS) was used to determine potential changes in band gaps of prepared TiO2-FeZ in comparison to pure TiO2. The influence of pH, concentration of hydrogen peroxide, FeZ wt% within the composite, and photocatalyst dosage on DCF removal and conversion efficiency by solar/TiO2-FeZ/H2O2 process was investigated. TiO2-FeZ demonstrated higher photocatalytic activity than pure TiO2 under solar irradiation in acidic conditions and presence of H2O2.

Fe, S co-doped anatase TiO2 nanotubes as anodes with improved electrochemical performance for lithium ion batteries

Fe, S co-doped TiO₂ nanotubes are synthesized by a sol–gel and subsequent chemical process, exhibiting improved electrochemical performance for LIBs.