Free-standing hybrid films comprising of ultra-dispersed titania nanocrystals and hierarchical conductive network for excellent high rate performance of lithium storage

Abstract

The construction of advanced electrode materials is key to the field of energy storage. Herein, a free-standing anatase titania (TiO 2 ) nanocrystal/carbon nanotube (CNT) film is reported using a simple and scalable sol-gel method, followed by calcination. This unique free-standing film comprises ultra-small TiO 2 nanocrystals (~ 5.9 nm) and super-aligned CNTs, with ultra-dispersed TiO 2 nanocrystals on the surfaces of the CNTs. On the one hand, these TiO 2 nanocrystals can significantly decrease the diffusion distance of the charges and on the other hand, the cross-linked CNTs can act as a three-dimensional (3D) conductive network, allowing the fast transport of electrons. In addition, the film is free-standing, without requiring electrode fabrication and additional conductive agents and binders. Owing to these above synergistic effects, the film is directly used as an anode in Li-ion batteries, and delivers a high discharge capacity of ~ 105 mAh•g −1 at high rate of 60 C (1 C = 170 mA•g −1 ) and excellent cycling performance over 2,500 cycles at 30 C. These results indicate that the free-standing anatase TiO 2 nanocrystal/CNT film affords a superior performance among the various TiO 2 materials and can be a promising anode material for fast-charging Li-ion batteries. Moreover, the TiO 2 /CNT film exhibits an areal capacity of up to 2.4 mAh•cm −2 , confirming the possibility of its practical use.

In Situ Conformal Carbon Coating for Constructing Hierarchical Mesoporous Titania/Carbon Spheres as High-Rate Lithium-Ion Battery Anodes

“…On the other hand, current efforts to improve the electrical conductivity of TiO 2 generally include deliberately introducing exotic conductive supports or extra additives being changed into conductive agents. − Conductive supports or their precursors, for example, graphene oxide (GO), ,,,, graphite oxide, and carbon nanotubes (CNTs) ,,, need to be fabricated in advance. Additives, for example, octylamine, glucose, organic precursor, pyrrole, and silver acetate are introduced to obtain conductive agents in the preparation process.…”

Rapid Preparation of Uniform High-Crystallized Mesoporous Titania Spheres without High-Temperature Treatment

“…Figure e presents the galvanostatic curves of the mesoporous TiO 2 spheres prepared in the mixed ethanol/water solution at a current density of 1 C (1 C = 170 mA/g) in the voltage range of 1.0–3.0 V for the first three cycles at room temperature. The discharge curves are divided into three stages. ,, (I) First stage is a sudden drop of voltage from open-circuit voltage to ∼1.75 V. This stage is the formation of the solid solution containing tetragonal anatase ( I 4 1 / amd ) and Li-poor tetragonal Li x TiO 2 ( I 4 1 / amd ) after a small amount of Li + ions inserted into TiO 2 . (II) The second stage is a voltage plateau region at ∼1.7 V, involving the coexistence of Li-rich orthorhombic Li 0.5 TiO 2 ( Imma ) and Li-poor tetragonal Li x TiO 2 ( I 4 1 / amd ) accompanied by the continuous insertion of Li + ions.…”

“…As one of the most important inorganic materials, titania (TiO 2 ) is widely used in various fields, including energy conversion, , energy storage, , photocatalysis, , and electrocatalysis. , To optimize the application performance, various types of TiO 2 samples have been prepared, such as TiO 2 nanotubes, , TiO 2 nanowires, , TiO 2 nanoparticles/nanocrystals, − mesoporous TiO 2 , , and TiO 2 -based composites. , Among them, mesoporous TiO 2 materials are the most promising candidates for various applications, due to their abundant and hierarchical porous structure and high-surface area. − For example, due to the high specific surface area, the Caruso group has demonstrated that the mesoporous TiO 2 beads can improve the light harvesting with a large accessible surface for dye loading, thus promoting the photon-to-current conversion efficiency of dye-sensitized solar cells compared to P25 nanoparticles. The Snaith group has prepared mesoporous TiO 2 single crystals which provide highly accessible surfaces and high conductivities .…”

Carbon Nanostructures Decorated with Titania: Morphological Control and Applications

“…MWCNTs have been widely studied as templates for titania nanostructures, as can be seen from the many entries in Table 1; thus, only a few studies are discussed here. With a sol-gel process in ethanol using a tetrabutyl titanate precursor, it was possible to decorate CNTs with titania nanocrystals, and the materials were used to obtain a film for potential applications as a battery anode [119]. When the same precursor was used in alkaline aqueous solutions with wider, hydroxylated CNTs (average diameter of 50 nm), nanowires were obtained instead, which entangled with CNTs in a network and were envisaged for the same application [126].…”