Direct Synthesis of Carbon-Doped TiO2-Bronze Nanowires as Anode Materials for High Performance Lithium-Ion Batteries

High-Performance Lithium-Ion Batteries with High Stability Derived from Titanium-Oxide- and Sulfur-Loaded Carbon Spherogels

This study presents a novel approach to developing high-performance lithium-ion battery electrodes by loading titania-carbon hybrid spherogels with sulfur. The resulting hybrid materials combine high charge storage capacity, electrical conductivity, and core-shell morphology, enabling the development of next-generation battery electrodes. We obtained homogeneous carbon spheres caging crystalline titania particles and sulfur using a template-assisted sol-gel route and carefully treated the titania-loaded carbon spherogels with hydrogen sulfide. The carbon shells maintain their microporous hollow sphere morphology, allowing for efficient sulfur deposition while protecting the titania crystals. By adjusting the sulfur impregnation of the carbon sphere and varying the titania loading, we achieved excellent lithium storage properties by successfully cycling encapsulated sulfur in the sphere while benefiting from the lithiation of titania particles. Without adding a conductive component, the optimized material provided after 150 cycles at a specific current of 250 mA g-1 a specific capacity of 825 mAh g-1 with a Coulombic efficiency of 98%.

Electrospun Nanotubular Titania and Polymeric Interfaces for High Energy Density Li-Ion Electrodes

In the current study, for the first time, electrospinning of nanotubular structures was developed for Li-ion battery high energy density applications. For this purpose, titania-based nanotubular materials were synthesized and characterized. Before electrospinning with PVDF to obtain a self-standing electrode, the nanotubes were modified to obtain the best charge-transferring structure. In the current study, for the first time, the effects of various thermal treatment temperatures and durations under an Ar-controlled atmosphere were investigated for Li⁺ diffusion. Electrochemical impedance spectroscopy, cyclic voltammograms, and galvanostatic intermittent titration technique showed that the fastest charge transfer kinetics belongs to the sample treated for 10 h. After optimization of electrospinning parameters, a fully nanotube-embedded fibrous structure was achieved and confirmed by scanning electron microscopy and transmission electron microscopy. The obtained flexible electrode was pressed at ambient and 80 °C to improve the fiber volume fraction. Finally, the galvanostatic charge/discharge tests for the electrospun electrode after 100 cycles illustrated that the hot-pressed sample showed the highest capacity. The polymeric network enabled the omission of metallic current collectors, thus increasing the energy density by 14%. The results of electrospun electrodes offer a promising structure for future high-energy applications.

TiO2 as an Anode of High-Performance Lithium-Ion Batteries: A Comprehensive Review towards Practical Application

Lithium-ion batteries (LIBs) are undeniably the most promising system for storing electric energy for both portable and stationary devices. A wide range of materials for anodes is being investigated to mitigate the issues with conventional graphite anodes. Among them, TiO2 has attracted extensive focus as an anode candidate due to its green technology, low volume fluctuations (<4%), safety, and durability. In this review, the fabrication of different TiO2 nanostructures along with their electrochemical performance are presented. Different nanostructured TiO2 materials including 0D, 1D, 2D, and 3D are thoroughly discussed as well. More precisely, the breakthroughs and recent developments in different anodic oxidation processes have been explored to identify in detail the effects of anodization parameters on nanostructure morphology. Clear guidelines on the interconnected nature of electrochemical behaviors, nanostructure morphology, and tunable anodic constraints are provided in this review.

Carbon-Doped TiNb2O7 Suppresses Amorphization-Induced Capacity Fading

The limited capacity of graphite anodes in high-performance batteries has led to considerable interest in alternative materials in recent years. Due to its high capacity, titanium niobium oxide (TiNb₂O₇, TNO) with a Wadsley-Roth crystallographic sheared structure holds great promise as a next-generation anode material, but a comprehensive understanding of TNO's electrochemical behavior is lacking. In particular, the mechanism responsible for the capacity fading of TNO remains poorly elucidated. Given its metastable nature (as an entropy-stabilized oxide) and the large volume change in TNO upon lithiation and delithiation, which has long been overlooked, the factors governing capacity fading warrant investigation. Our studies reveal that the structural weakness of TNO is fatal to the long-term cycling stability of TNO and that the capacity fading of TNO is driven by amorphization, which results in a significant increase in impedance. While nanostructuring can kinetically boost lithium intercalation, this benefit comes at the expense of capacity fading. Carbon doping in TNO can effectively suppress the critical impedance increase despite the amorphization, providing a possible remedy to the stability issue.

One-step preparation of C-doped TiO2 nanotubes with enhanced photocatalytic activity by a water-assisted method

In this paper, C-doped TiO₂ nanotubes were prepared in one-step by adding sucrose to water-assisted crystallization solution. The photocatalytic activity was obviously enhanced due to the decrease of the energy band gap after doping.

Recent Advances in Synthesis and Applications of Carbon-Doped TiO2 Nanomaterials

TiO2 has been widely used as a photocatalyst and an electrode material toward the photodegradation of organic pollutants and electrochemical applications, respectively. However, the properties of TiO2 are not enough up to meet practical needs because of its intrinsic disadvantages such as a wide bandgap and low conductivity. Incorporation of carbon into the TiO2 lattice is a promising tool to overcome these limitations because carbon has metal-like conductivity, high separation efficiency of photogenerated electron/hole pairs, and strong visible-light absorption. This review would describe and discuss a variety of strategies to develop carbon-doped TiO2 with enhanced photoelectrochemical performances in environmental, energy, and catalytic fields. Emphasis is given to highlight current techniques and recent progress in C-doped TiO2-based materials. Meanwhile, how to tackle the challenges we are currently facing is also discussed. This understanding will allow the process to continue to evolve and provide facile and feasible techniques for the design and development of carbon-doped TiO2 materials.

Nitrogen-doped TiO2(B) nanobelts enabling enhancement of electronic conductivity and efficiency of lithium-ion storage

To enhance the intrinsic electrical conductivities of TiO₂(B) nanobelts, nitrogen(N)-doped TiO₂(B) nanobelts (N-TNB) were prepared in this study by a facile and cost-effective hydrothermal method using urea as the nitrogen source with TiO₂ (P25) nanoparticles. x-ray photoelectron spectroscopy confirmed that the N-atoms preferentially occupied up to ∼0.516 atom% in the interstitial sites of the N-TNB and the maximum concentration of substituted-N bonds in the N-TNB was ∼0.154 atom%, thereby the total concentration of doped nitrogen elements of ∼0.67 atom% improved the high intrinsic electrical conductivity and ionic diffusivity of the TiO₂(B) nanobelts. The as-prepared N-TNB electrode delivered the highest specific capacity of 133.9 mAh g^-1 in the first cycle, with an exceptional cyclic capacity retention at an ultrafast current rate of 1000 mA g^-1; this is not less than 51% after 500 cycles and represents an excellent rate capability of ∼37 mAh g^-1 at an ultra-high rate of 40 C. These values are among the best ever reported on comparison of the delivered highest discharge capacity of N-TNB at 1000 mA g^-1 and high-rate capabilities of its Li⁺ ion storage with the literature data for N-TNB (∼231.5 mAh g^-1 at a very low current density of 16.75 mA g^-1, ∼0.1 C) of similar materials used in sodium-ion batteries. This implies the potential feasibility of these N-TNB as high-capacity anode materials for next-generation, high-energy-density, electrochemical energy-storage devices.

Nanostructured anode materials

Throughout the lithium ion battery (LIB) history, since they were mass produced by Sony in 1991, graphite-based materials have been the anode material of choice. There have been enormous efforts to search for ways of tapping higher energy with alternative anode materials to work in LIBs. Yet, those materials have always been subjected to detrimental mechanisms that hinder their applications in LIBs. Will nanotechnology and nanostructured anode materials change the energy storage technologies markedly in the future?

Homogeneous growth of TiO2-based nanotubes on nitrogen-doped reduced graphene oxide and its enhanced performance as a Li-ion battery anode

The pursuit of a promising replacement candidate for graphite as a Li-ion battery anode, which can satisfy both engineering criteria and market needs has been the target of researchers for more than two decades. In this work, we have investigated the synergistic effect of nitrogen-doped reduced graphene oxide (NrGO) and nanotubular TiO₂ to achieve high rate capabilities with high discharge capacities through a simple, one-step and scalable method. First, nanotubes of hydrogen titanate were hydrothermally grown on the surface of NrGO sheets, and then converted to a mixed phase of TiO₂-B and anatase (TB) by thermal annealing. Specific surface area, thermal gravimetric, structural and morphological characterizations were performed on the synthesized product. Electrochemical properties were investigated by cyclic voltammetry and cyclic charge/discharge tests. The prepared anode showed high discharge capacity of 150 mAh g^-1 at 1 C current rate after 50 cycles. The promising capacity of synthesized NrGO-TB was attributed to the unique and novel microstructure of NrGO-TB in which long nanotubes of TiO₂ have been grown on the surface of NrGO sheets. Such architecture synergistically reduces the solid-state diffusion distance of Li⁺ and increases the electronic conductivity of the anode.

Self-Reconstructed Formation of a One-Dimensional Hierarchical Porous Nanostructure Assembled by Ultrathin TiO2 Nanobelts for Fast and Stable Lithium Storage

Owing to their unique structural advantages, TiO₂ hierarchical nanostructures assembled by low-dimensional (LD) building blocks have been extensively used in the energy-storage/-conversion field. However, it is still a big challenge to produce such advanced structures by current synthetic techniques because of the harsh conditions needed to generate primary LD subunits. Herein, a novel one-dimensional (1D) TiO₂ hierarchical porous fibrous nanostructure constructed by TiO₂ nanobelts is synthesized by combining a room-temperature aqueous solution growth mechanism with the electrospinning technology. The nanobelt-constructed 1D hierarchical nanoarchitecture is evolves directly from the amorphous TiO₂/SiO₂ composite fibers in alkaline solutions at ambient conditions without any catalyst and other reactant. Benefiting from the unique structural features such as 1D nanoscale building blocks, large surface area, and numerous interconnected pores, as well as mixed phase anatase-TiO₂(B), the optimum 1D TiO₂ hierarchical porous nanostructure shows a remarkable high-rate performance when tested as an anode material for lithium-ion batteries (107 mA h g^-1 at ∼10 A g^-1) and can be used in a hybrid lithium-ion supercapacitor with very stable lithium-storage performance (a capacity retention of ∼80% after 3000 cycles at 2 A g^-1). The current work presents a scalable and cost-effective method for the synthesis of advanced TiO₂ hierarchical materials for high-power and stable energy-storage/-conversion devices.

Enhanced degradation of ciprofloxacin by graphitized mesoporous carbon (GMC)-TiO2 nanocomposite: Strong synergy of adsorption-photocatalysis and antibiotics degradation mechanism

In order to achieve remarkable synergy between adsorption and photocatalysis for antibiotics elimination from water, in this study, a graphitized mesoporous carbon (GMC)-TiO₂ nanocomposite was successfully synthesized by an extended resorcinol-formaldehyde (R-F) method. In the composite, the lamellar GMC nanosheets possessed large specific surface area and mesoporous structure, and could adsorb and enrich antibiotics effectively. This could not only reduce the antibiotic concentration in water shortly, but also greatly increase the chances for antibiotics to contact with and be degraded by photocatalysts and active species. Interestingly, GMC could also facilitate the transportation of photogenerated electrons to further improve the photocatalytic efficiency of TiO₂, and 15 mg/L ciprofloxacin (CIP) could be totally mineralized in 1.5 h. Meanwhile, the biological inhibition of reaction solution on luminescence bacteria decreased obviously with antibiotics degradation until non-toxicity, reinforcing the thorough elimination of antibiotics. Besides, from the viewpoint of organic chemistry, several plausible CIP degradation pathways were established using HPLC-MS technique, and an interesting intermediate with five-membered ring structure was firstly proposed, which is helpful to deeply understand CIP degradation. Strong synergy between adsorption and photocatalysis, along with quick and efficient antibiotics elimination, double confirm the great potential of GMC-TiO₂ nanocomposite for practical antibiotic wastewater purification.

Sn-Doped Rutile TiO2 Hollow Nanocrystals with Enhanced Lithium-Ion Batteries Performance

Hollow structures and doping of rutile TiO₂ are generally believed to be effective ways to enhance the performance of lithium-ion batteries. Herein, uniformly distributed Sn-doped rutile TiO₂ hollow nanocrystals have been synthesized by a simple template-free hydrothermal method. A topotactic transformation mechanism of solid TiOF₂ precursor is proposed to illustrate the formation of rutile TiO₂ hollow nanocrystals. Then, the Sn-doped rutile TiO₂ hollow nanocrystals are calcined and tested as anode in the lithium-ion battery. They deliver a highly reversible specific capacity of 251.3 mA h g^-1 at 0.1 A g^-1 and retain ∼110 mA h g^-1 after 500 cycles at a high current rate 5 A g^-1 (30 C), which is much higher than most of the reported work.

High-Performance Li-Ion Capacitor Based on an Activated Carbon Cathode and Well-Dispersed Ultrafine TiO2 Nanoparticles Embedded in Mesoporous Carbon Nanofibers Anode

A novel Li-ion capacitor based on an activated carbon cathode and a well-dispersed ultrafine TiO₂ nanoparticles embedded in mesoporous carbon nanofibers (TiO₂@PCNFs) anode was reported. A series of TiO₂@PCNFs anode materials were prepared via a scalable electrospinning method followed by carbonization and a postetching method. The size of TiO₂ nanoparticles and the mesoporous structure of the TiO₂@PCNFs were tuned by varying amounts of tetraethyl orthosilicate (TEOS) to increase the energy density and power density of the LIC significantly. Such a subtle designed LIC displayed a high energy density of 67.4 Wh kg^-1 at a power density of 75 W kg^-1. Meanwhile, even when the power density was increased to 5 kW kg^-1, the energy density can still maintain 27.5 Wh kg^-1. Moreover, the LIC displayed a high capacitance retention of 80.5% after 10000 cycles at 10 A g^-1. The outstanding electrochemical performance can be contributed to the synergistic effect of the well-dispersed ultrafine TiO₂ nanoparticles, the abundant mesoporous structure, and the conductive carbon networks.

Three-Dimensional Branched TiO2 Architectures in Controllable Bloom for Advanced Lithium-Ion Batteries

Three-dimensional branched TiO2 architectures (3D BTA) with controllable morphologies were synthesized via a facile template-free one-pot solvothermal route. The volume ratio of deionized water (DI water) and diethylene glycol in solvothermal process is key to the formation of 3D BTA assembled by nanowire-coated TiO2 dendrites, which combines the advantages of 3D hierarchical structure and 1D nanoscale building blocks. Benefiting from such unique structural features, the BTA in full bloom achieved significantly increased specific surface areas and shortened Li(+) ion/electrons diffusion pathway. The lithium-ion batteries based on BTA in full bloom exhibited remarkably enhanced reversible specific capacity and rate performance, attributing to the high contact area with the electrolyte and the short solid state diffusion pathway for Li(+) ion/electrons promoting lithium insertion and extraction.