Yakun Tang

Multimodal porous CNT@TiO2 nanocables with superior performance in lithium-ion batteries

Multimodal porous CNT@TiO2 core–sheath coaxial nanocables have been constructed by a sol–gel method and post-calcination in the presence of polymer nanotubes acting as a template and carbon source. The composite exhibits excellent electrochemical properties, attaining a high discharge capacity of 231 mA h g−1 at 1000 mA g−1 for up to 110 cycles.

Porous CNT@Li4Ti5O12 coaxial nanocables as ultra high power and long life anode materials for lithium ion batteries

Porous CNT@Li4Ti5O12 core–sheath coaxial nanocables were designed using a sol–gel method combined with a following low temperature reflux process and a short post-annealing in the presence of bamboo-like polymer nanotubes acting as a template and a carbon source. As anodes for lithium ion batteries, coaxial nanocables exhibit a high reversible capacity of 322.5 mA h g−1 at 200 mA g−1 after 200 cycles. They also have excellent rate capability and superior long-term cycling stability at high current density, which could attain a high discharge capacity of 198.7 mA h g−1 at 2000 mA g−1 for up to 2000 cycles. Compared with the Li4Ti5O12 nanoparticles, the enhanced electrochemical performance of the CNT@Li4Ti5O12 nanocomposites benefits from the shortened Li+ diffusion distance, large contact surface area, high conductivity, and good structure stability of the coaxial nanocables, which simultaneously solves the major problems on the loss of electrical contact and the aggregation of particles for Li4Ti5O12 anodes. The material with a nanocable structure is a potential candidate for developing advanced electrochemical energy storage systems with high power and long life.

High-yield bamboo-like porous carbon nanotubes with high-rate capability as anodes for lithium-ion batteries

Bamboo-like porous carbon nanotubes (BCNTs) are prepared on a large scale through the pyrolysis of bamboo-like highly crosslinked polydivinylbenzene nanotubes. As anode materials for lithium-ion batteries, the BCNTs exhibit excellent electrochemical performance, attaining a high discharge capacity of 335 mA h g−1 at a current of 100 mA g−1. Even at a higher charge–discharge rate of 1000 mA g−1, a high discharge capacity of 230 mA h g−1 can be obtained for up to 300 cycles, which indicates the material has an excellent high-rate performance and cycle stability due to the separated hollow compartment structure and rich micropores on the surface of the BCNTs with the high BET surface area of 490.8 m2 g−1.

Sandwich-Like CNT@Fe3O4@C Coaxial Nanocables with Enhanced Lithium-Storage Capability

Through the combined method of a low-temperature reflux and calcination, porous sandwich-like CNT@Fe3O4@C coaxial nanocables were cleverly constructed, which exhibited a favorable specific capacity of 724.8 mA h g-1 at 1000 mA g-1, a satisfying rate performance and admirable Coulombic efficiency (ca. 100%) for anodes of lithium-ion batteries. Due to the enlarged contact surface area, shortened Li+ diffusion distance, hierarchical porosity, reasonable structural design and good structural stability, the electrochemical performance of the CNT@Fe3O4@C nanocomposites was greatly enhanced in comparison with the traditional iron oxide anodes. So, it is a good candidate for anode materials with high performance.

Anatase/rutile titania anchored carbon nanotube porous nanocomposites as superior anodes for lithium ion batteries

Anatase/rutile titania anchored carbon nanotube (TiO2@CNT) porous nanocomposites are fabricated using TiCl3 and polymer nanotubes as the titanium and carbon sources, respectively, by a hydrothermal process with subsequent heat treatment. As anodes for lithium ion batteries, the electrochemical performance of the nanocomposites is highly dependent on the crystal phase and content of TiO2. Compared with anatase TiO2/C nanocomposites, the TiO2@CNT nanocomposites exhibit high reversible capacity, excellent rate capability and superior long-term cycling stability at high current densities. The enhanced electrochemical performance of the nanocomposites results from the shortened Li+ diffusion distance, large contact surface area and sufficient conductivity. In addition, the crystal interface effect of mixed-phase TiO2 could improve the dispersion rate of electrons, which is conducive to the rapid transport of Li+ and the electrons.

Rational design of hybrid porous nanotubes with robust structure of ultrafine Li4Ti5O12 nanoparticles embedded in bamboo-like CNTs for superior lithium ion storage

Robust hybrid porous bamboo-like carbon nanotubes (CNTs), with ultrafine Li4Ti5O12 nanoparticles homogeneously embedded, are synthesized by a facile sol–gel process, combined with subsequent heat treatment. The nanohybrids exhibit a reversible capacity as high as 582.4 mA h g−1 at 0.2 A g−1 after 500 cycles, together with excellent rate capability and long-term cycling stability at high current densities. A high discharge capacity of 114.2 mA h g−1 at 5 A g−1 is attained for up to 3000 cycles. The superior electrochemical performance of the nanohybrids is attributed to their structure rather than their composition. Their exceptional electrochemical performance benefits from the high electrical conductivity of the porous carbon matrix, which not only provides continuous three-dimensional electron transportation routes but also simultaneously solves the major problems of pulverization, loss of electrical contact, and particle aggregation of Li4Ti5O12 anode. In addition, the highly dispersive, ultrafine Li4Ti5O12 nanoparticles greatly shorten the diffusion paths for both electrons and ions. Such a structure not only preserves all the advantages of one-dimensional nanostructures, but also offers potential for a high packing density of electrode materials. Surely, this strategy can be widely extended to other anode materials.

In Situ Chelating Synthesis of Hierarchical LiNi1/3Co1/3Mn1/3O2 Polyhedron Assemblies with Ultralong Cycle Life for Li‐Ion Batteries

Layered lithium transition-metal oxides, with large capacity and high discharge platform, are promising cathode materials for Li-ion batteries. However, their high-rate cycling stability still remains a large challenge. Herein, hierarchical LiNi1/3 Co1/3 Mn1/3 O2 polyhedron assemblies are obtained through in situ chelation of transition metal ions (Ni2+ , Co2+ , and Mn2+ ) with amide groups uniformly distributed along the backbone of modified polyacrylonitrile chains to achieve intimate mixing at the atomic level. The assemblies exhibit outstanding electrochemical performances: superior rate capability, high volumetric energy density, and especially ultralong high-rate cyclability, due to the superiority of unique hierarchical structures. The polyhedrons with exposed active crystal facets provide more channels for Li+ diffusion, and meso/macropores serve as access shortcuts for fast migration of electrolytes, Li+ and electrons. The strategy proposed in this work can be extended to fabricate other mixed transition metal-based materials for advanced batteries.

One-dimensional controllable crosslinked polymers grafted with N-methyl-D-glucamine for effective boron adsorption

In this research, a series of one-dimensional controllable crosslinked polymers with the different mass ratios of 4-vinylbenzychloride (VBC) and divinyl benzene (DVB) was prepared via cationic polymerization, and the polymers were grafted with the functional group N-methyl-D-glucamine (NMDG) for boron removal. The optimum polymeric mass ratio and a series of boron adsorption performances were studied. The maximum adsorption capacity was 18.15 mg g−1, of which 94% was retained after 4 cycles. Meanwhile, different pH values had negligible effect on the boron adsorption capacity, which was favorable for the removal of boron from its aqueous solution in a wide pH window. In addition, a magnetic adsorbent was prepared by the combination of Fe3O4 nanoparticles and the polymer, which provided an effective way to collect and recover adsorbents from their aqueous solutions.

Pseudocapacitive Behaviors of Li2FeTiO4/C Hybrid Porous Nanotubes for Novel Lithium-Ion Battery Anodes with Superior Performances

Hybrid nanotubes of cation disordered rock salt structured Li2FeTiO4 nanoparticles embedded in porous CNTs were developed. Such unique hybrids with continuous 3D electron transportation paths and isolated small particles have been shown to be an ideal architecture that brought out enhanced electrochemical performances. Meanwhile, they exhibited improved extrinsic capacitive characteristics. In addition, we demonstrate a successful example to use cathode active material as anode for lithium-ion batteries (LIBs). More importantly, our hybrids had much superior electrochemical performances than most of the reported Li4Ti5O12-based nanocomposites. Therefore, it is concluded that Li2FeTiO4 can be a prospective anode material for LIBs.

Solid-state photochromic behavior of pyrazolone 4-phenylthiosemicarbazones

Solid-state photochromic materials have attracted much more attention due to their actual potential applications in photoactive devices. Here, three new compounds (1-phenyl-3-methyl-4-(3-fluoro/chloro/bromobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazones) were synthesized, which exhibited reversible solid state photochromic properties upon UV/Vis light irradiation. Their photochromic properties, first-order kinetics and fatigue resistance were investigated by time-dependent UV-Vis absorption spectroscopy. The results showed that their fatigue resistance and addressability were enhanced with the increase in the electron-withdrawing ability of the substituents on the phenyl group at the 4-position of the pyrazolone ring. Thus, 1-phenyl-3-methyl-4-(3-fluorobenzal)-5-hydroxypyrazole 4-phenylthiosemicarbazone exhibited good photochromic properties and high fatigue resistance. Based on single crystal X-ray diffraction and FT-IR analyses, the photochromic mechanism involved intra/intermolecular proton transfer.