High-Temperature Stable Anatase Titanium Oxide Nanofibers for Lithium-Ion Battery Anodes

Facile Synthesis of Pre-Lithiated LiTiO2 Nanoparticles for Quick Charge and Long Lifespan Anode in Lithium-Ion Batteries

Titanium dioxide (TiO2) has been widely used as an alternative anodic material for lithium-ion batteries (LIBs) due to its ultrahigh capacity retention and long cycle lifespan. However, the restriction of lithium insertion, intrinsically poor electronic conductivity, and sluggish lithium ionic kinetics of bulk TiO2 hinder their specific capacity and rate performance. Herein, LiTiO2 nanoparticles (NPs) are synthesized via a facile ball milling method by the reaction of anatase TiO2 with LiH. The as-prepared LiTiO2 NPs have strong structural stability and a "zero strain" effect during the repeated intercalation/deintercalation, even at low potential. As anodic materials for LIBs, LiTiO2 NPs exhibit a superior rate performance of ∼100 mA h g-1 at 10C (3350 mA g-1) with a capacity retention of 100% after 1000 cycles, which is 5 times higher than that of the original commercial anatase TiO2 powder. The higher specific capacity of LiTiO2 NPs is attributed to the increased conversion of Ti3+ to Ti2+ on the porous surface of LiTiO2 NPs, which provides a more capacitive contribution. This study not only provides a new fabrication approach toward Ti-based anodes for ultrafast LIBs but also underscores the potential importance of embedding lithium into transition metal oxides as a strategy for boosting their electrochemical performance.

Effect of Ni Doping Content on Phase Transition and Electrochemical Performance of TiO2 Nanofibers Prepared by Electrospinning Applied for Lithium-Ion Battery Anodes

Titanium dioxide (TiO₂), as a potential anode material applied for lithium-ion batteries (LIBs), is constrained due to its poor theoretical specific capacity (335 mAh·g⁻¹) and low conductivity (10⁻⁷-10⁻⁹ S·cm⁻¹). When compared to TiO₂, NiO with a higher theoretical specific capacity (718 mAh·g⁻¹) is regarded as an alternative dopant for improving the specific capacity of TiO₂. The present investigations usually assemble TiO₂ and NiO with a simple bilayer structure and without NiO that is immersed into the inner of TiO₂, which cannot fully take advantage of NiO. Therefore, a new strategy was put forward to utilize the synergistic effect of TiO₂ and NiO, namely doping NiO into the inner of TiO₂. NiO-TiO₂ was fabricated into the nanofibers with a higher specific surface area to further improve their electrochemical performance due to the transportation path being greatly shortened. NiO-TiO₂ nanofibers are expected to replace of the commercialized anode material (graphite). In this work, a facile one-step electrospinning method, followed by annealing, was applied to synthesize the Ni-doped TiO₂ nanofibers. The Ni doping content was proven to be a crucial factor affecting phase constituents, which further determined the electrochemical performance. When the Ni doping content was less than 3 wt.%, the contents of anatase and NiO were both increased, while the rutile content was decreased in the nanofibers. When the Ni doping content exceeded 3 wt.%, the opposite changes were observed. Hence, the optimum Ni doping content was determined as 3 wt.%, at which the highest weight fractions of anatase and NiO were obtained. Correspondingly, the obtained electronic conductivity of 4.92 × 10⁻⁵ S⋅cm⁻¹ was also the highest, which was approximately 1.7 times that of pristine TiO₂. The optimal electrochemical performance was also obtained. The initial discharge and charge specific capacity was 576 and 264 mAh·g⁻¹ at a current density of 100 mA·g⁻¹. The capacity retention reached 48% after 100 cycles, and the coulombic efficiency was about 100%. The average discharge specific capacity was 48 mAh·g⁻¹ at a current density of 1000 mA·g⁻¹. Approximately 65.8% of the initial discharge specific capacity was retained when the current density was recovered to 40 mA·g⁻¹. These excellent electrochemical results revealed that Ni-doped TiO₂ nanofibers could be considered to be promising anode materials for LIBs.

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

TiO₂ is regarded as a prospective electrode material owing to its excellent electrochemical properties such as the excellent cycling stability and the high safety. However, its low capacity and low electronic conductivity greatly restrict the further improvement in electrochemical performance. A new strategy was put forward to solve the above defects involved in TiO₂ in which the low capacity was enhanced by nanomerization and porosity of TiO₂, and the low electronic conductivity was improved by introducing Ag with a high conductivity. One-dimensional mesoporous Ag nanoparticles-embedded TiO₂ nanofibers (Ag@TiO₂ nanofibers) were successfully synthesized via a one-step electrospinning process combined with subsequent annealing treatment in this study. The microstructure and morphology of mesoporous TiO₂@Ag nanofibers were confirmed by X-ray diffraction, scanning electron microscopy, transmission electron microscopy, and nitrogen adsorption–desorption. TiO₂ nanofibers mainly consisted of a large amount of anatase TiO₂, accompanied with traces of rutile TiO₂. Ag nanoparticles were uniformly distributed throughout TiO₂ nanofibers and promoted the transformation of TiO₂ from the anatase to the rutile. The corresponding electrochemical performances are measured by galvanostatic charge-discharge, cycle stability, rate performance, cycle voltammetry, and electrochemical impedance spectroscopy measurements in this research, with pristine TiO₂ nanofibers as the reference. The results indicated that the introduction of Ag nanoparticles into TiO₂ nanofibers significantly improved the diffusion coefficient of Li ions (5.42 × 10⁻⁹ cm²⋅s⁻¹ for pristine TiO₂, 1.96 × 10⁻⁸ cm²⋅s⁻¹ for Ag@TiO₂), and the electronic conductivity of TiO₂ (1.69 × 10⁻⁵ S⋅cm⁻¹ for pristine TiO₂, and 1.99 × 10⁻⁵ S⋅cm⁻¹ for Ag@TiO₂), based on which the comprehensive electrochemical performance were greatly enhanced. The coulombic efficiency of the Ag@TiO₂ nanofibers electrode at the first three cycles was about 56%, 93%, and 96%, which was higher than that without Ag (48%, 66%, and 79%). The Ag@TiO₂ nanofibers electrode exhibited a higher specific discharge capacity of about 128.23 mAh⋅g⁻¹ when compared with that without Ag (72.76 mAh·g⁻¹) after 100 cycles at 100 mA·g⁻¹. With the current density sharply increased from 40 mA·g⁻¹ to 1000 mA·g⁻¹, the higher average discharge capacity of 56.35 mAh·g⁻¹ was remained in the electrode with Ag, when compared with the electrode without Ag (average discharge capacity of about 12.14 mAh·g⁻¹). When the current density was returned to 40 mA·g⁻¹, 80.36% of the initial value was returned (about 162.25 mAh·g⁻¹) in the electrode with Ag, which was evidently superior to that without Ag (about 86.50 mAh·g⁻¹, only 55.42% of the initial value). One-dimensional mesoporous Ag@TiO₂ nanofibers can be regarded as a potential and promising candidate as anode materials for lithium ion batteries.

Lamellar-like Electrospun Mesoporous Ti-Al-O Nanofibers

Ceramic oxides nanofibers are promising materials as catalysts, electrodes and functional materials. In this report, a unique lamellar-like mesoporous structure was realized for the first time in a new system based on titania and alumina. The final structure was found to be highly dependent on the process conditions which are outlined herein. In view of the similar architecture we recently obtained with Fe-Al-O fibers, the pore formation mechanism we outline herein is general and is applicable to additional systems.

Photoelectrocatalytic effect of unbalanced RF magnetron sputtered TiO2 thin film on ITO-coated patterned SiO2 nanocone arrays

Highly increased photocurrent response of unbalanced RF magnetron sputtered TiO₂ thin film on ITO-coated patterned SiO₂ nanocone arrays.