Preparation and characterization of three-dimensionally ordered mesoporous titania microparticles as anode material for lithium ion battery

Synthesis of TiO2 Nanobelt Bundles Decorated with TiO2 Nanoparticles and Aggregates and Their Use as Anode Materials for Lithium-Ion Batteries

TiO₂ nanobelt bundles decorated with TiO₂ aggregates were prepared using an easy and scalable hydrothermal method at various temperatures (170, 190, 210, and 230 °C). It was demonstrated that the synthesis temperature is a key parameter to tune the number of aggregates on the nanobelt surface. Prepared TiO₂ aggregates and nanobelt bundles were used to design anode materials in which the aggregates regulated the pore size and connectivity of the interconnected nanobelt bundle structure. A galvanostatic technique was employed for the electrochemical characterization of TiO₂ samples. Using TiO₂ as a model material due to its small volume change during the cycling of lithium-ion batteries (LIBs), the relationship between the morphology of the anode materials and the capacity retention of the LIBs on cycling is discussed. It was clearly found that the size and connectivity of the pores and the specific surface area had a striking impact on the Li insertion behavior, lithium storage capability, and cycling performance of the batteries. The initial irreversible capacity was shown to increase as the specific surface area increased. As the pore size increased, the ability of the mesoporous anatase to release strain was stronger, resulting in better cycling stability. The TiO₂ powder prepared at a temperature of 230 °C displayed the highest discharge and charge capacities (203.3 mAh/g and 140.8 mAh/g) and good cycling stability.

Scalable synthesis of smooth PS@TiO2 core-shell and TiO2 hollow spheres in the (sub) micron size range: understanding synthesis and calcination parameters

Hollow spheres made from titanium dioxide (TiO2) are interesting structures because of their high surface area and low density, combined with semiconducting properties of the TiO2. However, the synthesis is still challenging because of the high reactivity of the titania precursors. Here, we present a simple, reproducible, and scalable way to synthesize TiO2 hollow spheres in the micrometer/sub-micrometer size range comprising three steps: synthesis of polystyrene template particles, growth of TiO2 shells, and calcination to hollow spheres. We investigate the importance of adjusting the seed particle surface functionalization via the appropriate choice of comonomer during the dispersion polymerization. An aging step and a calcination process at low temperatures are mandatory to retain the particle integrity during the seed particle removal. We provide a detailed characterization of each step of this process including electron microscopy, small angle X-ray scattering, and simultaneous thermal analysis.

The State of Research Regarding Ordered Mesoporous Materials in Batteries

Ordered mesoporous materials, porous materials with a pore size of 2-50 nm which are prepared via the sol-gel process using surfactant molecular aggregates as a template to assemble channels through the interfacial action of organic and inorganic substances, have recently triggered a heated debate. In addition to applications in the catalytic cracking of heavy oils and residues, the manufacturing of graft materials, the purification of water, the conversion of automobile exhaust, biochips, and the treatment of environmental pollutants via photocatalysts, ordered mesoporous materials have drawn substantial attention in the field of electrochemical energy storage due to advantages such as large specific surface area, uniform and continuously adjustable pore size, and orderly arrangement. Here, a general summary and appraisal of the study of ordered mesoporous materials for batteries in recent years is given, including the synthesis methods, meso/nanostructural features, and electrochemical capabilities of such materials.

Porous-Nickel-Scaffolded Tin-Antimony Anodes with Enhanced Electrochemical Properties for Li/Na-Ion Batteries

The energy and power densities of rechargeable batteries urgently need to be increased to meet the ever-increasing demands of consumer electronics and electric vehicles. Alloy anodes are among the most promising candidates for next-generation high-capacity battery materials. However, the high capacities of alloy anodes usually suffer from some serious difficulties related to the volume changes of active materials. Porous supports and nanostructured alloy materials have been explored to address these issues. However, these approaches seemingly increase the active material-based properties and actually decrease the electrode-based capacity because of the oversized pores and heavy mass of mechanical supports. In this study, we developed an ultralight porous nickel to scaffold with high-capacity SnSb alloy anodes. The porous-nickel-supported SnSb alloy demonstrates a high specific capacity and good cyclability for both Li-ion and Na-ion batteries. Its capacity retains 580 mA h g^-1 at 2 A g^-1 after 100 cycles in Li-ion batteries. For a Na-ion battery, the composite electrode can even deliver a capacity of 275 mA h g^-1 at 1 A g^-1 after 1000 cycles. This study demonstrates that combining the scaffolding function of ultralight porous nickel and the high capacity of the SnSb alloy can significantly enhance the electrochemical performances of Li/Na-ion batteries.

Fabrication of three-dimensional ordered macroporous spinel CoFe2O4 as efficient bifunctional catalysts for the positive electrode of lithium-oxygen batteries

Three-dimensionally ordered macroporous (3DOM) CoFe₂O₄ (CFO) catalysts were prepared by using the colloidal crystal templating method to be used as bifunctional catalysts of Li-O₂ battery positive electrodes. In order to study the relationship between the macropore diameter and charge/discharge behavior, 3DOM CFO catalysts with two different pore diameters of 140 and 60 nm were prepared. The physicochemical properties of the 3DOM CFO catalysts were investigated by scanning electron microscopy, X-ray diffraction, transmission electron microscopy, X-ray photoelectron spectroscopy, and X-ray absorption spectroscopy. When the 3DOM CFO catalyst with a pore diameter of 140 nm (CFO@140) was used in the O₂-electrode of Li-O₂ batteries, it exhibited a substantially enhanced discharge capacity (ca. 11 658.5 mA h g^-1) in the first cycle. Moreover, the Li-O₂ cells with the CFO@140 catalyst showed cycling stability over 47 cycles at a limited capacity of 500 mA h g^-1 with a reduced potential polarization of 1.13 V, as compared with that with Ketjen Black carbon and the 3DOM CFO of 60 nm pore diameter (CFO@60). Their high cycling stability, low overpotential, high round-trip efficiency, and high rate performance suggest that these 3DOM CFO catalysts could be promising O₂-electrode catalysts for next-generation lithium-oxygen batteries.

Lithium adsorption performance of a three-dimensional porous H2TiO3-type lithium ion-sieve in strong alkaline Bayer liquor

A three-dimensional porous H₂TiO₃-type lithium ion-sieve prepared by polystyrene colloidal microspheres template was applied to selectively adsorb Li⁺ ions from the strong alkaline Bayer liquor.

Electrode materials with tailored facets for electrochemical energy storage

In recent years, the design and morphological control of crystals with tailored facets have become hot spots in the field of electrochemical energy storage devices. For electrode materials, morphologies play important roles in their activities because their shapes determine how many facets of specific orientation are exposed and therefore available for surface reactions. This review focuses on the strategies for crystal facet control and the unusual electrochemical properties of electrode materials bound by tailored facets. Here, electrode materials with tailored facets include transition metal oxides such as SnO₂, Co₃O₄, NiO, Cu₂O, and MnO₂, elementary substances such as Si and Au, and intercalation compounds such as Li₄Ti₅O₁₂, LiCoO₂, LiMn₂O₄, LiFePO₄, and Na_0.7MnO₂ for various applications of Li-ion batteries, aqueous rechargeable lithium batteries, Na-ion batteries, Li-O₂ batteries and supercapacitors. How these electrode materials with tailored facets affect their electrochemical properties is discussed. Finally, research opportunities as well as the challenges in this emerging research frontier are highlighted.

3D interconnected hierarchically macro-mesoporous TiO2 networks optimized by biomolecular self-assembly for high performance lithium ion batteries

A 3D interconnected hierarchically macro-mesoporous TiO₂ network optimized by the mediation of biomolecular self-assembly has been used for high performance lithium storage.

MoO2 nanocrystals interconnected on mesocellular carbon foam as a powerful catalyst for vanadium redox flow battery

MoO₂ nanocrystals on mesocellular carbon foam are used for a high performance vanadium redox flow battery. This improves the slow reaction of the VO²⁺/VO²⁺ redox couple, inducing high efficiencies with high specific capacity.

Cyclic voltammogram on ridge/pore array architectured electrode inspired by butterfly-wings

Porous architectured electrodes are intensely investigated for promoting electrochemical performance. Besides the high surface area, mass transport plays an irreplaceable role in the architecture assisting effect, which is, however, far beyond expression due to the complexity and irregularity of various electrode materials. Here, we took advantage of elaborate architectures from butterfly wings and obtained carbon electrode with ridge/pore array hierarchical architecture (ridge/pore-C) using a carbonizing-graphite coating method. A basic one-electron transfer process using the redox couple ferri/ferrocyanide as a benchmark under cyclic voltammetric conditions was conducted. The peak potential separation for ridge/pore-C was decreased by 117 mV compared to its non-architectured counterpart, with obvious enhancement of peak current density, indicating prominent beneficial impact on electrochemical responses. Further finite element simulation demonstrated the additional lateral diffusion within the ridge domain and partial thin layer diffusion within the pore array domain of ridge/pore-C, and simultaneously verified the experimental results. By constructing and investigating the well-organized porous architecture for affecting cyclic voltammogram, this work provides a prototype and cost-effective method for structural design of efficient electrodes by drawing inspiration from nature.

Hydrogen titanate constructed by ultrafine nanobelts as advanced anode materials with high-rate and ultra-long life for lithium-ion batteries

The electrochemical performance of hydrogen titanate has been successfully and significantly improved by novel morphology engineering and heat treatment strategies.

Crystallinity-controlled titanium oxide-carbon nanocomposites with enhanced lithium storage performance

Nanocomposites of crystalline-controlled TiO(2) -carbon are prepared by a novel one-step approach and applied in anodes of lithium ion batteries. In our nanocomposite anodes, the Li(+) capacity contribution from the TiO(2) phase was enormous, above 400 mAh g(-1) (Li(1+x) TiO(2) , x>0.2), and the volumetric capacity was as high as 877 mAh cm(-3) with full voltage utilization to 0 V versus Li/Li(+) , which resulted in higher energy density than that of state-of-the-art titania anodes. For the first time, it was clearly revealed that the capacity at 1.2 and 2.0 V corresponded to Li(+) storage at amorphous and crystalline TiO(2) , respectively. Furthermore, improvements in the rate capability and cycle performance were observed; this was attributed to resistance reduction induced by higher electrical/Li(+) conduction and faster Li(+) diffusion.

Small quantities of cobalt deposited on tin oxide as anode material to improve performance of lithium-ion batteries

In this report, we present a hybrid structure involving a small quantity of Co element uniformly deposited on porous SnO(2) spheres as stable and high capacity anode materials for lithium-ion batteries. Specifically, Co element deposited on SnO(2) nanomaterials exhibited an exceptional reversible capacity of 810 mA h g(-1) after 50 cycles which is higher than the pure SnO(2) electrode. Based on the experiments results, a possible mechanism for the change of this structure during lithium ion insertion/extraction was proposed. The minute quantity of Co element uniformly deposited on SnO(2) spherical structure could prevent Sn aggregation during charging-discharging, and high porosity of the spherical structure allowed the volume expansion during lithium ion alloying/dealloying. The SnO(2) deposited with small quantities of Co element as electrode facilitated improved performance of lithium ion batteries with higher energy densities.

Kinetic, Isotherm and Thermodynamic Analysis on Adsorption of Cr(VI) Ions from Aqueous Solutions by Synthesis and Characterization of Magnetic-Poly(divinylbenzene-vinylimidazole) Microbeads

The magnetic-poly(divinylbenzene-1-vinylimidazole) [m-poly(DVB-VIM)] microbeads (average diameter 53-212 μm) were synthesized and characterized; their use as adsorbent in removal of Cr(VI) ions from aqueous solutions was investigated. The m-poly(DVB-VIM) microbeads were prepared by copolymerizing of divinylbenzene (DVB) with 1-vinylimidazole (VIM). The m-poly(DVB-VIM) microbeads were characterized by N(2) adsorption/desorption isotherms, ESR, elemental analysis, scanning electron microscope (SEM) and swelling studies. At fixed solid/solution ratio the various factors affecting adsorption of Cr(VI) ions from aqueous solutions such as pH, initial concentration, contact time and temperature were analyzed. Langmuir, Freundlich and Dubinin-Radushkvich isotherms were used as the model adsorption equilibrium data. Langmuir isotherm model was the most adequate. The pseudo-first-order, pseudo-second-order, Ritch-second-order and intraparticle diffusion models were used to describe the adsorption kinetics. The apparent activation energy was found to be 5.024 kJ mol(-1), which is characteristic of a chemically controlled reaction. The experimental data fitted to pseudo-second-order kinetic. The study of temperature effect was quantified by calculating various thermodynamic parameters such as Gibbs free energy, enthalpy and entropy changes. The thermodynamic parameters obtained indicated the endothermic nature of adsorption of Cr(VI) ions. Morever, after the use in adsorption, the m-poly(DVB-VIM) microbeads with paramagnetic property were separeted via the applied magnetic force. The magnetic beads could be desorbed up to about 97% by treating with 1.0 M NaOH. These features make the m-poly(DVB-VIM) microbeads a potential candidate for support of Cr(VI) ions removal under magnetic field.

Enhanced Li storage performance of ordered mesoporous MoO2 via tungsten doping

Ordered mesoporous tungsten-doped MoO(2) was synthesized by a nanocasting method. The Li storage performance of mesoporous MoO(2) is significantly improved by tungsten doping, which exhibits a reversible capacity of 700 mA h g(-1), better cycling and rate performance. This material combines the advantages of the high theoretical capacity of MoO(2) and the better electroactivity of WO(2).

From synthetic montroseite VOOH to topochemical paramontroseite VO2 and their applications in aqueous lithium ion batteries

Synthetic montroseite VOOH has been successfully prepared via a simple template-free hydrothermal route on a large scale for the first time-after sixty years of delay. The as-obtained sample shows a hierarchical morphology of urchin-like nanoarchitecture with hollow interiors consisting of well-crystalline nanorods standing vertically on the shell surface. Time-dependent experiments illustrated that these hierarchical hollow nanourchins were formed through the hydrolysis-driven Kirkendall effect coupled with a new-phased vanadium oxyhydroxide V(10)O(14)(OH)(2) precursor templated approach. Meanwhile, the as-obtained VOOH hollow nanourchins could convert topochemically to paramontroseite VO(2) without altering the size and original appearance during the annealing process due to the extreme structural similarity revealed by crystal structure analysis. Furthermore, the improved electrochemical performance of both montroseite VOOH and paramontroseite VO(2) hierarchical hollow structures toward Li uptake and release verifies their potential applications as anode materials in aqueous lithium ion batteries. These improved electrochemical properties could be ascribed to the synergetic effect of the microscopic tunneled crystal structure and macroscopic hollow morphological features, which provide the easy infiltration of electrolyte, short diffusion lengths for lithium ions and electron transport as well as sufficient void space to buffer the volume change.

Ordered mesoporous metallic MoO2 materials with highly reversible lithium storage capacity

Highly ordered mesoporous crystalline MoO(2) materials with bicontinuous Ia3d mesostructure were synthesized by using phosphomolybdic acid as a precursor and mesoporous silica KIT-6 as a hard template in a 10% H(2) atmosphere via nanocasting strategy. The prepared mesoporous MoO(2) material shows a typical metallic conductivity with a low resistivity ( approximately 0.01Omega cm at 300 K), which makes it different from all previously reported mesoporous metal oxides materials. Primary test found that mesoporous MoO(2) material exhibits a reversible electrochemical lithium storage capacity as high as 750 mA h g(-1) at C/20 after 30 cycles, rendering it as a promising anode material for lithium ion batteries.

Brookite titania photocatalytic nanomaterials: Synthesis, properties, and applications

Phase-pure brookite TiO2 and its activity has been obscured for its difficulty of synthesis. Hence, we introduced the method of preparation and property of phase-pure brookite TiO2 and prepared phase-pure brookite TiO2 by hydrothermal method using Ti(SO4)2 as precursor. Phase formation was achieved by hydrothermal treatment at 180 °C after different synthesis time. The physical and photophysical properties of samples were characterized by X-ray diffraction (XRD), transmission electron microscopy (TEM), UV–vis diffraction (UV–vis/DRS), and Raman spectroscopy. The dependence of the photocatalytic activities on synthesis time and correlations with the physical properties of brookite samples was examined in detail. In the case of mineralization of rhodamine B (Rh B), the sample with the narrowest bandgap and the lowest photoluminescence (PL) intensity (at hydrothermal synthesis time 36 h) showed the best photodecolorization activity. Proposed decolorization mechanism was elucidated in the light of the UV–vis spectra of the analyzed degradation products and frontier electron density (FED) theory. The results indicated that photocatalytic decolorization by brookite TiO2 is a highly effective way to remove Rh B under near-visible light irradiation.

Fabrication and electrochemical characterization of TiO2 three-dimensional nanonetwork based on peptide assembly

The three-dimensional network of TiO(2) hollow nanoribbons designed from a peptide assembly using atomic layer deposition is demonstrated as a promising Li secondary battery electrode in this study. The nanoribbon network ensures effective transport of electrons and Li ions due to (i) a well-connected network of nanoribbons and (ii) the hollow structure of each nanoribbon itself, into which Li ions in the electrolyte can readily diffuse. The improved specific capacity, rate capability, and cyclability of the nanonetwork show that the utilization of a nanonetwork of individual hollow ribbons can serve as a promising strategy toward the development of high-performance electrode for Li secondary batteries.