One-Step Synthesis of Co@C Composite as High-Performance Anode Material for Lithium-ion Batteries

A carbon-coated cobalt (Co@C) composite was synthesized by a one-step method using ionic liquid as carbon source and reducing agent. The Co@C composite exhibited a core-shell structure, in which the cobalt nanoparticles uniformly embedded in the carbon matrix. When used as the anode material for lithium ion batteries, the cobalt nanoparticles enhanced the kinetics of Li+ and electronic transport during the charge/discharge process. The Co@C composite material delivered a reversible capacity of 657.3 mAh g-1 after 60 cycles at a current density of 0.1C and exhibits improved rate performance when compared with pure carbon

Influence of Eu3+-Doped on Phase Transition Kinetics of Pseudoboehmite

The influence of Eu3+-doped on phase transition kinetics of pseudoboehmite has not been reported in the literature. Through dropping Eu(NO3)3 into pseudoboehmite colloidal solution, pseudoboehmite xerogel was produced using spray pyrolysis. The influence of Eu3+-doped on the mechanism of pseudoboehmite phase transition kinetics has been calculated and analyzed by TG/DSC, XRD, and Kissinger equation. Part of Eu3+ ion formed compound EuAl12O19, which existed between α-Al2O3 grains. Bulk diffusion of Al3+ was prevented from compound EuAl12O19. Therefore, phase transition kinetics rate of θ-Al2O3 → α-Al2O3 was slowed down, causing an increase of phase transition activation energy and elevation of phase transition temperature

Preparation of Carbon Encapsulated Core-Shell Fe@ CoFe2O4 Particles Through the Kirkendall Effect and Application as Advanced Anode Materials for Lithium-Ion Batteries

Carbon encapsulated core-shell Fe@CoFe2O4 nanoparticles (Fe@CoFe2O4@C) are produced by using Kirkendall effect method and used as the anode material for lithium-ion batteries. During the discharge process, Fe and Co particles are synthesized at the shell of the nanoparticles and are pulverized to smaller grains in the low potential regions. These pulverized particles not only increase the contact area between electrolyte and active materials, but also shortens the transfer distance of Li+ and electron, leading to an enhanced capacity. In addition, the structure stability and electrical conductivity of CoFe2O4 (CFO) shell are improved by the thin carbon layer coated on the surface of the shell. Due to this special structure, the Fe@CoFe2O4@C electrode exhibits excellent cycle performance, delivering a capacity of 1911 mA h g−1 after 500 cycles at 0.3 C (1 C = 1000 mA g−1). It also shows superior rate capacities of 760.8, 735.6, 672.2, and 596.5 mA h g−1 at the current densities of 1.0, 2.0, 5.0, and 10.0 C, respectively

One Step Hydrothermal Synthesis of Flower-shaped Co 3 O 4 Nanorods on Nickel Foam as Supercapacitor Materials and Their Excellent Electrochemical Performance

Flower-shaped Co3O4 nanorods directly grown on nickel foam(Co3O4/NF) were prepared by one step hydrothermal method at low temperature. Co3O4 nanorods are directly connected with the nickel foam, and no binder is needed as an additive, so the Co3O4/NF electrode has good electrical conductivity. This flower-shaped structure makes larger surface area of Co3O4 nanorods that exposes to the electrolyte, thus promoting the redox reaction. The Co3O4/NF electrode shows a high specific capacitance of 2005.34 F/g at the current density of 0.5 A/g and a high capacitance retention of 98.0% after 5000 cycles. The high superior capacitive performance with high specific capacitance and the excellent cyclic performance indicate that the one step hydrothermal method has great potential application in supercapacitors

Carbon Modified Porous Scale-like γ-Fe2O3 as Anode for High Performance Li-ion Batteries

Carbon modified porous γ-Fe2O3 particles (PFe2O3–C) are synthesized by a high temperature calcination method using sodium chloride as a template. During the nucleation and carbonation process, the Fe(NO3)3–C10H15N5 complex uniformly dispersed on the surface of NaCl particles which can limit its longitudinal growth, thus forming independent and homogeneous nanoparticles with a diameter of about 30 nm. Because of this special structure, the γ-Fe2O3 particles have a sufficient interspace between them, which can not only provide a large number of active sites for storing lithium ions, but also shorten diffusion length for lithium ion transport. The introduction of carbon can offer additional lithium ion storage and improve overall electrical conductivity. This PFe2O3–C electrode exhibits excellent rate performance (1139, 1067, and 972 mAh g−1 at 2, 5, and 10 C, respectively, 1 C = 924 mAh g−1) and cycle performance (up to 2100 mAh g−1 after 200 cycles at 0.3 C)

Nitrogen Doped Porous Onion Carbon Derived from Ionic Liquids as the Anode Materials for Lithium Ion Batteries with High Performance

A novel nitrogen doped porous onion carbon (NDPOC) material was prepared by using [HMIm]N(CN)2 as carbon and nitrogen source. The transmission electron microscopy (TEM) and scanning electron microscopy (SEM) revealed that the NDPOC had a uniform porous structure and was wrapped by onion structured carbon. When used as the anode material for lithium ion batteries, this material not only prevented the collapse and breakage of the pores, but also facilitated the lithium ion migration and electron transfer. The NDPOC anode showed excellent discharge specific capacity (805 mAh g−1 of 0.1C after 50 cycles), rate performance, and cycle stability (306 and 267 mAh g−1 at 5 and 10C after 300 and 500 cycles, respectively)

Pyrolysis Mechanism of Ionic Liquid Under Microwave Irradiation and the Formation of N-Doped Carbon

The pyrolysis mechanism of the ionic liquid [BMIm]N(CN)2 under microwave irradiation was discussed for the first time. The trimerization of the anion N(CN)− 2 and the formation of a framework were firstly caused by the microwave irradiation. And then the carbonization of the framework occurred when the temperature reached 330 °C. The pyrolysis product was graphitic nitrogendoped carbon and mainly originated from the anion N(CN)− 2. The nitrogen content and graphitization degree of the nitrogen-doped carbon was relied on the pyrolysis temperature

In Situ Coating on LiFePO 4 with Ionic Liquid as Carbon Source for High-Performance Lithium Batteries

LiFePO4/C materials were synthesized via an in situ coating on LiFePO4 with 1-butyl-3-methylimidazolium dicyanamide [BMIm][N(CN)2] as a carbon source. The electrode materials were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectra, Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM). The results revealed that 1–2 nm carbon films were successfully coated on the LiFePO4 particles. The electrochemical properties of LiFePO4/C composite were investigated by cyclic voltammetry (CV) curves, electrochemical impedance spectra (EIS), and electrochemical analysis. The test results showed that the LiFePO4/C composite possessed outstanding reversibility, cycle performance, and rate performance. The discharge capacities of LiFePO4/C were 161.5 mAh g−1 at 0.1 C and 143.6 mAh g−1 at 1 C, respectively. The excellent electrochemical properties of the LiFePO4/C electrode were mainly due to the thin, uniform, and highly graphitized carbon films

A Simple Synthesis of Nitrogen-Sulfur Co-Doped Porous Carbon Using Ionic Liquids as Dopant for High Rate Performance Li-Ion Batteries

A novel nitrogen‑sulfur co-doped porous carbon (NSPC) material was synthesized by using ionic liquids as the nitrogen and sulfur precursor. This material exhibited porous structure with high specific surface area (701 m2 g−1) and superior nitrogen and sulfur co-doping (4.66 and 1.83 wt%, respectively), The materials was used as anode materials for Lithium-ion batteries and showed a high reversible capacity of 987.7 mAh g−1 at a current density of 0.1 A g−1 and a good long cycle performance (337.5 mAh g−1 at 5 A g−1 after 5000 cycles). The NSPC\u27s superior electrochemical performance can be attributed to three points: (1) Excellent pore structure (surface area is 701 m2 g−1). (2) Nitrogen and sulfur co-doping (4.66 and 1.83 wt%, respectively). (3) Higher rate of capacitance contribution during process of charge and discharge

A new species of Sedum (Crassulaceae) from Mount Danxia in Guangdong, China

Sedum jinglanii, a new species of Crassulaceae from Mount Danxia in Guangdong, China, is described and illustrated. Phylogenetic analysis based on the internal transcribed spacer (ITS) region of nrDNA suggests that the new species belongs to S. sect. Sedum sensu Fu and Ohba (2001) in the “Flora of China”, and is sister to a clade comprising S. alfredi and S. emarginatum with high support values (SH-aLRT = 84, UFBS = 95) but is distantly related to S. baileyi. The new species is morphologically similar to S. alfredi but it can be distinguished from the latter in its opposite leaves (vs. alternate leaves), its usually wider leaves (0.4–1.2 cm vs. 0.2–0.6 cm), its usually shorter petals (3.4–4.5 mm vs. 4–6 mm), its shorter nectar scales (0.4–0.5 mm vs. 0.5–1 mm), its shorter carpels (1.5–2.6 mm vs. 4–5 mm), and its shorter styles (0.6–0.9 mm vs. 1–2 mm). The new species can be easily distinguished from S. emarginatum which both have opposite leaves by its short, erect or ascending rhizome (vs. long and prostrate rhizome in the latter), shorter petals (3.4–4.5 mm vs. 6–8 mm) and shorter carpels (1.5–2.6 mm vs. 4–5 mm). It can also be easily distinguished from S. baileyi by its short, erect or ascending rhizome (vs. long and prostrate rhizome) and its shorter style (0.6–0.9 mm vs. 1–1.5 mm)