Emerging WS2/WSe2@graphene nanocomposites: synthesis and electrochemical energy storage applications

In recent years, tungsten disulfide(WS₂) and tungsten selenide(WSe₂) have emerged as favorable electrode materials because of their high theoretical capacity, large interlayer spacing, and high chemical activity; nevertheless, they have relatively low electronic conductivity and undergo large volume expansion during cycling, which greatly hinder them in practical applications. These drawbacks are addressed by combining a superior type of carbon material, graphene, with WS     

Facile synthesis of nanosheet-structured V2O5 with enhanced electrochemical performance for high energy lithium-ion batteries

Nanosheet-structured vanadium pentoxide (V₂O₅) has been fabricated by a sol-gel method. As revealed by the TEM, the as-synthesized V₂O₅ crystallites are composed of layer-by-layer stacked nanosheets. As a cathode material for lithium batteries, it exhibits much better electrochemical performance than the starting commercial V₂O₅ powders. A high specific discharge capacity of 264 mA h g^?1 can be obtained for the nanosheet-structured electrodes, which retains the capacity of 90% after 50 cycles. However, the commercial V₂O₅ only delivers a specific discharge capacity of 206 mA h g^?1 with a capacity retention of 64% after 50 cycles. Moreover, the nanosheet-structured V₂O₅ electrodes show much-improved C-rate capability. The superior cycling performance demonstrates that the nanosheet-structured V₂O₅ is a promising cathode material in lithium-ion battery applications.     

碳纳米管-导电聚合物复合材料与电化学储能

介绍了本研究组近年在电化学合成碳纳米管-导电聚合物多孔复合材料薄膜及其电化学电容性能和材料结构方面的主要研究结果.酸氧化制备表面带羟、羧基团的碳纳米管中性或弱酸性悬浊液,在其中溶入导电聚合物单体后,视情况决定是否添加电解质电解,在阳极上共沉积出复合材料薄膜,其电化学电容超过3 F·cm-2(vs.电极表观面积).考察各种实验结果,提出5种纳米管-聚合物相互作用机理及其对改善材料电化学电容性能的贡献.     

Metal-based inorganic nanocrystals for biological sonodynamic therapy applications:recent progress and perspectives

With the fast development of technology for the treatment of tumor and bacteria,photo-therapeutic strategies emerge as a kind of highly effective and common treatment,but the low tissue penetration depth of light limits their development.Sonodynamic therapy(SDT),as an efficient and non-invasive treatment,attracts more people’s attention due to the inherent property of high tissue penetration.The soft tissue penetration depth of ultrasound(US) can even reach more than 10 cm,which has great advant...     

Chemical synthesis and characterization of fluorinated polyphenylthiophenes: application to energy storage

Some fluorinated polyphenylthiophene have been chemically synthesized with good yields. The characterization of their positive and negative doping processes was performed by cyclic voltammetry and showed high capacities, but proved no real stability in cycling experiments. The application of the P-4-FPT as electroactive material in supercapacitor systems showed interesting properties in term of energy and power delivered.     

Enhancing electrochemical performances of small quinone toward lithium and sodium energy storage

Further application of organic quinone cathodes is restricted because they are inherent in poor conductivity and tend to dissolve in aprotic electrolytes.Salinization can work on the strong solubility of quinones.Herein,the ortho-disodium salt of tetrahydroxyquinone(o-Na₂THBQ)was selected to promote the electrochemical properties of tetrahydroxyquinone(THBQ).Reduced dissolution of o-Na₂THBQ in electrolyte after salinization(replacement of two H with two Na)contributed to enhanced electrochemical performance.In sodium-ion batteries(SIBs)in ester-based electrolyte,o-Na2THBQ cathodes at 50 mA·g^-1exhibited a reversible discharge capacity of 107 mAh·g^-1after 200 cycles.Ulteriorly,in ether-based electrolyte,reversible discharge capacities of 200.4,102.2,99.5 and 88 mAh·g^-1were obtained at 800,1600,3200 and 4800 mA·g^-1after 1000,2000,5000 and 8000 cycles,respectively.The ultraviolet absorption spectra and ex situ dissolution experiments of THBQ and o-Na₂THBQ showed that o-Na₂THBQ hardly dissolved in ether-based electrolyte.In lithium-ion batteries(LIBs),graphene was selected to further enhance the conductivity of o-Na2THBQ.At 50 mA·g^-1,o-Na₂THBQ and o-Na₂THBQ/Gr cathodes exhibited reversible discharge capacities of 124 and 131.5 mAh·g^-1after 200 cycles in ester-based electrolyte,respectively.At 50 mA·g^-1,PTPAn/o-Na₂THBQ electrodes in an all-organic Na/Li-ion battery showed reversible charge/discharge capacities of 51/50.3 and 33.8/33.1 mAh·g^-1after 200 cycles.     

Chemical synthesis and electrochemical analysis of nickel cobaltite nanostructures for supercapacitor applications

Nickel cobaltite (NiCo₂O₄) films containing nanorods and nanoflakes are synthesized on indium tin oxide (ITO) substrates by a chemical bath deposition method and calcination process at 300 °C for 3 h. The NiCo₂O₄/ITO films are used as electrodes for supercapacitor applications, and electrochemical properties of the NiCo₂O₄ nanostructures are examined by cyclic voltammetry and charge-discharge experiments. NiCo₂O₄ nanorods exhibit the largest specific capacitance, with a value of 490 F g⁻¹at energy and power densities of 45 Wh kg⁻¹ and 2 kW kg⁻¹, respectively. This is significantly better than the performance of NiCo₂O₄ nanoflakes. Cycle-life tests show that the specific capacitance of NiCo₂O₄ is stable even after 1000 cycles, indicating its high potential for supercapacitor applications. The low cost and environmental friendliness of NiCo₂O₄ nanorods, coupled with its high supercapacitor performance, offer advantages over other transition metal oxides used for supercapacitors.     

Co2P: A facile solid state synthesis and its applications in alkaline rechargeable batteries

The Co₂P crystals are successfully synthesized by a facile solid state reaction. Energy dispersive X-ray spectrum (EDS) results indicate a mol ratio of 0.6686-0.3314 for Co to P, confirming the stoichiometric ratio of Co₂P. Galvanostatic charge/discharge tests show that Co₂P exhibits a high maximum discharge capacity (C_max) of 223.5 mAh g⁻¹ and excellent cyclic properties with capacity retention of 97.9% (C₃₀₀/C_max) in the 300th cycle as an anode material in alkaline rechargeable batteries. Cyclic voltammetry (CV) and XRD tests during full charge/discharge processes confirm a quasi-reversible redox mechanism between Co(OH)₂ and Co resulting from the conversion of Co₂P. The simultaneously produced P plays an important role in the whole process - with the reaction and dissolution in the electrolyte, it brings many new interspaces in Co₂P body to enlarge the contact area between the active material and the electrolyte, and make the electrochemical process easier and faster.     

Graphite intercalation compounds as reagents in organic synthesis. An overview and some recent applications

Recent developments in the application of graphite intercalation compounds to organic synthesis are reviewed: chiral reductions, Fischer-Tropsch synthesis of low molecular weight hydrocarbons, fluorination of aromatic hydrocarbons, of β-diketones, of organosilicon and organogermanium derivatives, alkylation of nitriles and ketones, synthesis of aldehydes, preparation of protected Grignard reagents. New results are also given concerning the esterification of fatty and aromatic acids, the synthesis of 1,4-dioxane derivatives, of enol esters, the gem-difluorination of monoketones, the base-catalysed condensations of carbonyl derivatives. In all cases, the intercalated reagent is less aggressive and easier to handle than when its is non-intercalated. In a few instances, some regiospecificity is also shown, even if the precise mode of action is not always fully understood.     

Synthesis and electrochemical performance of Li3V2(PO4)3 by optimized sol-gel synthesis routine

Li₃V₂(PO₄)₃ samples were synthesized by sol-gel route and high temperature solid-state reaction. The influence of Li₃V₂(PO₄)₃ as cathode materials for lithium-ion batteries on electrochemical performances was investigated. The structure of Li₃V₂(PO₄)₃ as cathode materials for lithium-ion batteries and morphology of Li₃V₂(PO₄)₃ were characterized by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). Electrochemical performances were characterized by charge/discharge and AC impedance measurements. Li₃V₂(PO₄)₃ with smaller grain size shows better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of Li₃V₂(PO₄)₃ are attributed to the refined grains and enhanced electrical conductivity. AC impedance measurements also show that the Li₃V₂(PO₄)₃ synthesized by sol-gel route exhibits significantly decreased charge-transfer resistance and shortened migration distance of lithium ions.     

Soft-chemical synthesis and high-temperature electrochemical characteristics of VO2

1 Introduction In 1986, LVO (lithiated vanadium oxide) was first presented by FAUL et al[1?3] as positive electrode materials for thermal battery, which is a mixture of γ-LiV2O5 and VO2, but the morphology and crystallography of VO2 in the mixture were …     

粉末非晶硅制备及其气体氢化和电化学储氢性能研究

以Li13Si4为原料采用化学去锂化法制备了具有层状结构的非晶硅(α-Si)粉体并对α-Si进行球磨改性,研究了改性前后α-Si在H2中的氢化行为以及氢化处理对α-Si电极在质子传导离子液体中的电化学储氢性能影响。研究结果表明,球磨能明显减小α-Si粉体的颗粒尺寸,但易引入Fe和Cr金属杂质并形成Fe2Si与CrSi2。氢化时α-Si逐渐发生晶化,当氢化时间不少于8 h时,α-Si基本完全晶化,氢化后的SiHx结构由SiH、SiH2和SiH3三种成键模式组成。球磨改性有助于增加α-Si的初始吸氢量,随氢化时间延长,α-Si的吸氢量逐渐增大,其中经球磨和氢化2、5、8和58 h后的α-Si吸氢量分别达到(质量分数)0.38%、0.76%、0.91%和3.8%,其吸氢速率比较缓慢。α-Si电极在质子型离子液体中具有电化学吸放氢反应活性,但其放电容量偏低(42~163 mAh/g),其中球磨和氢化8 h的α-Si经20次充放电后具有最大放电容量163 mAh/g。球磨改性和适当的氢化处理(8 h)有利于提高α-Si电极的放电容量。     

钴酸锂的再生及其电化学性能

采用提取的含少量Co3O4的LiCoO2为原料,在不同温度下合成正极材料LiCoO2,烧结时间为12 h,并采用XRD和SEM技术研究合成的LiCoO2的晶相结构与微观形貌。结果发现:烧结温度对LiCoO2的晶体结构影响较大,烧结温度越高,LiCoO2的层状结构发育越完整。循环伏安曲线很好地反映了再生LiCoO2的脱/嵌锂行为。将LiCoO2样品做成电池进行电化学检测,结果发现,烧结温度为850℃的样品首次放电容量为151mA.h/g,30次循环之后,放电容量仍有141mA.h/g,表现出良好的电化学性能。     

Synthesis of Er2Ti2O7 nanocrystals and its electrochemical hydrogen storage behavior

Ultrafine Er₂Ti₂O₇ was synthesized at 700 °C within 2 h by a soft-chemistry route named citric acid sol–gel method (CAM). The obtained Er₂Ti₂O₇ with high dispersibility was square-like and the average size was about 70 nm. The prepared Er₂Ti₂O₇ nanocrystals in 6 M KOH aqueous solutions were investigated as a hydrogen storage material. It was found that the Er₂Ti₂O₇ powders would function as electrochemical hydrogen storage, showed fair electrochemical reversibility, and considerably high charge–discharge capacity. The reversible discharge capacity of the Er₂Ti₂O₇ electrode was found to exceed 320 mAh/g and adsorption capability of hydrogen is up to 1.27% at a current rate of 100 mA/g. In addition, the cycling ability and high rate capability of the Er₂Ti₂O₇ electrode are fairly good with only 4% capacity decay after 25 cycles. Cyclic voltammograms (CVs) were carried out to further examine the electrochemical hydrogen storage mechanism of Er₂Ti₂O₇.     

Structural and electrochemical hydrogen storage properties of Mg2Ni-based alloys

Four different methods, i.e. hydriding combustion synthesis + mechanical milling (HCS + MM), induction melting (followed by hydriding) + mechanical milling (IM(Hyd) + MM), combustion synthesis + mechanical milling (CS + MM) and induction melting + mechanical milling (IM + MM), were used to prepare Mg₂Ni-based hydrogen storage alloys used as the negative electrode material in a nickel-metal hydride (Ni/MH) battery. The structural and electrochemical hydrogen storage properties of the Mg₂Ni-based alloys have been investigated systematically. The XRD results indicate that the as-milled products show nanocrystalline or amorphous-like structures. Electrochemical measurements show that the as-milled hydrides exhibit higher discharge capacity and better electrochemical kinetic property than the as-milled alloys. Among the four different methods, the HCS + MM product possesses the highest discharge capacity (578 mAh g⁻¹), the best high rate dischargeability (HRD) and the highest exchange current density (58.8 mA g⁻¹). It is suggested that the novel method of HCS + MM is promising to prepare Mg-based hydrogen storage electrode alloy with high discharge capacity and activity.     

三元锂离子正极材料LiNi0.6Co0.2Mn0.2O2的控制合成与储能特性

采用草酸共沉淀法和高温固相法相结合的方法成功合成了LiNi0.6Co0.2Mn0.2O (NCM622)三元锂离子正极材料,通过先用水热合成草酸钴锰前驱体,然后再与镍盐、锂盐进行高温固相反应,避免了Ni2+、Co2+、Mn2+在草酸中沉淀不均匀的问题.X射线衍射(XRD)分析结果表明,该材料具有典型的类似α-NaFeO2的层状结构以及低的阳离子混排.电化学性能测试结果显示,相比于商业镍钴锰酸锂(NCM-商业),NCM622表现出优良的循环稳定性和倍率性能,在0.1C下经850℃处理的NCM-850试样的初始放电容量为184.1 mAh g-1,高于NCM-商业的175mAhg-1,在0.2C循环100圈以后NCM-850的容量保持率为88.6％而NCM-商业的保持率仅为47.8％.在5C下NCM-850仍然具有98.1mAhg-1的容量.这主要归因于材料拥有更稳定的晶体结构和更宽的离子扩散通道.     

Fabrication of highly ordered porous nickel phosphide film and its electrochemical performances toward lithium storage

Highly ordered porous Ni₃P film was successfully electrodeposited through a self-assembled monodisperse polystyrene sphere template on copper substrate after heat treatment. The spherical pores left in the film after the removal of polystyrene spheres are well-ordered and close-packed. The diameter of the pores arranged in the film is about 800 nm and the thickness of the wall connecting adjacent pores is 60 nm. As anode for lithium ion batteries, the nanostructured porous Ni₃P film exhibits improved capability and reversibility over the dense one. After 50 cycles, the reversible capacity of the porous Ni₃P film is 403 mAh g⁻¹ and 239 mAh g⁻¹ at 0.2 C and 2 C, maintaining 78.1% and 67.9% of the capacity in the 2nd cycle, respectively. The enhanced electrochemical performance of the porous film is attributed to the better contact between Ni₃P and electrolyte, which provides more sites for Li⁺ accommodation, shortens the diffusion length of Li⁺ and enhances the kinetics of electrode process. Moreover, the porous structure is stable and can sustain well even after 50 cycles.     

Atmospheric pressure pulsed-periodic source of high energy plasma flows and its applications

A new electromagnetic plasmadynamic system, pulsed-periodic plasmatron, operating at standard atmospheric pressure with high frequency has been developed. In this system plasma flow velocity reaches 3–5 ? 10³ m/s with temperature up to 15·10³ K. The results are presented on the use of the pulsed-periodic plasmatron for carbon steel (0, 45% C) surface layer hardening and boronized layer modification.