Preparation and electrochemical performance of manganese oxide/carbon nanotubes composite as a cathode for rechargeable lithium battery with high power density

Manganese oxide/carbon nanotubes (MO/CNTs) composite was prepared by hydrothermally reducing KMnO₄ with CNTs, where the used CNTs are of dual role, i.e., they serve as reductant during reaction and the remaining CNTs act as conducting agent in the composite. This composite was characterized by X-ray diffraction and scanning electron microscopy techniques. In addition, the electrochemical performances of the composite were investigated, which suggested an excellent rate-capability of this material; e.g., it delivered a high discharge capacity as 131 mAh g^− 1 at a high current density of 4 A g^− 1 (20 C), and high capacity at low discharge current density, e.g., about 209 mAh g^− 1 at 0.2 C rate. Therefore, such a MO/CNTs composite is promising in high power application of lithium battery and electrochemical capacitor.     

Potentiodynamical co-deposited manganese oxide/carbon composite for high capacitance electrochemical capacitors

Manganese oxide/carbon composite materials were prepared by introducing the carbon powders into the potentiodynamical anodic co-deposited manganese oxide in 0.5 mol L^− 1 MnSO₄ and 0.5 mol L^− 1 H₂SO₄ mixed solution at 40 °C. The surface morphology and structure of the composite material were examined by scanning electron microscope and X-ray diffraction. Cyclic voltammetry tests and electrochemical impedance measurements were applied to investigate the performance of the composite electrodes with different ratios of manganese oxide and carbon. These composite materials with rough surface, which consisted of approximately amorphous manganese oxide, were confirmed to possess the ideal capacitive property. The highest specific capacitance of manganese oxide/carbon composite electrode was up to 410 F g^− 1 in 1.0 mol L^− 1 Na₂SO₄ electrolyte at the scan rate 10 mV s^− 1. The synthesized composite materials exhibited ideal capacitive behavior indicating a promising electrode material for electrochemical supercapacitors.     

Preparation and characterization of TiO2/ZnO composite coating on carbon steel surface and its anticorrosive behavior in seawater

The TiO₂/ZnO composite coatings with various atomic ratios of Ti to Zn were prepared on carbon steel surface via sol–gel process followed by thermal treatment at different temperature. The as-prepared coatings were characterized through X-ray diffraction method, scanning electron microscopy, energy dispersive X-ray spectroscopy, and their anticorrosive behaviors in sterilized seawater were electrochemically assessed. The obtained coatings were quite thin even for the 8-layer samples. The thermal treatment at 500 °C led to severe oxidation of the steel substrate. The incorporation of ZnO avoided crack formation and refined the particles of the composite coatings. The electrochemical measurements of both the potentiodynamic polarization curves and electrochemical impedance spectroscopy revealed a substantial protection of the coatings for the substrate. In particular, the 8-layer TiO₂/ZnO composite coatings with atomic molar ratios of Ti to Zn of 1/1 and 1/3 after thermal treatment at 500 °C showed better anticorrosive performances than others.     

Effect of copper doping on physical properties of nanocrystallized SnS zinc blend thin films grown by chemical bath deposition

SnS: Cu thin films have been successfully prepared on Pyrex substrates using low cost chemical bath deposition (CBD) technique with different copper doped concentration (y = [Cu]/[Sn] = 5%, 6%, 8%, 9% and 10%). The structure, the surface morphology and the optical properties of the SnS:Cu films were studied by X-ray diffraction (XRD), atomic force microscopy (AFM) and spectrophotometer measurements, respectively. To obtain a thickness of the order of 780 ± 31 nm for absorber material in solar cell devices, a system of multilayer has been prepared. It is found that the physical properties of tin sulphide are affected by Cu-doped concentration. In fact, X-ray diffraction study showed that better cristallinity in zinc blend structure with preferential orientations (111)^ZB and (200)^ZB, was obtained for y equal to 6%. According to the AFM analysis we can remark that low average surface roughness (RMS)value of SnS(ZB) thin film obtained with Cu-doped concentrations equal to y = 6%, is about of 54 nm. Energy dispersive spectroscopy (EDS) showed the existence of Cu in the films. Optical analyses by means of transmission T(λ) and reflection R(λ) measurements show 1.51 eV as a band gap value of SnS:Cu(6%) which is nearly equal to the theoretical optimum value of 1.50 eV for efficient light absorption. On the other hand, Cu-doped tin sulphide exhibits a high absorption coefficient up to 2 × 10⁶ cm⁻¹, indicating that SnS:Cu can be used as an absorber thin layer in photovoltaic structure such as SnS:Cu/ZnS/SnO₂:F and SnS:Cu/In₂S₃/SnO₂:F, where ZnS and In₂S₃ are chemically deposited in a previous studies.     

Carbon nanotubes anchored with SnO2 nanosheets as anode for enhanced Li-ion storage

The carbon nanotubes (CNTs) anchored with SnO₂ nanosheets were prepared using a hydrothermal method. The as-prepared products were characterized by X-ray diffraction, fourier transform infrared spectroscopy, thermogravimetric analyses, field emission scanning electron microscope and transmission electron microscope. The electrochemical performances of SnO₂ nanosheets/CNTs composite were measured by galvanostatic charge/discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the SnO₂ nanosheets/CNTs composite maintains high lithium storage capacity and good cycling stability. The designed structure plays key role in improving electrochemical performance. The CNTs anchored with SnO₂ nanosheets will be an ideal candidate of anode material for lithium ion batteries.     

High-performance visible-light-driven SnS₂/SnO₂ nanocomposite photocatalyst prepared via in situ hydrothermal oxidation of SnS₂ nanoparticles

SnS?/SnO? nanocomposites with tunable SnO? contents were prepared via in situ hydrothermal oxidation of SnS? nanoparticles in 0.375-4.5 mass% H?O? aqueous solutions at 180 °C for 0-12 h. The structure, composition and optical properties of the as-prepared SnS?/SnO? nanocomposites were characterized by X-ray diffraction, transmission electron microscopy, high-resolution transmission electron microscopy, Brunauer-Emmett-Teller (BET) surface area analysis, energy-dispersive X-ray spectroscopy, X-ray photoelectron spectroscopy, and UV-vis diffuse reflectance spectra. Furthermore, their photocatalytic properties were tested for the degradation of methyl orange in water under visible light (λ > 420 nm) irradiation. It was found that the as-prepared SnS?/SnO? nanocomposites with suitable SnO? content not only demonstrated superior photocatalytic activity to both SnS? nanoparticles and physically mixed SnS?/SnO? composite nanoparticles, but also had remarkable photocatalytic stability. The tight attachment of SnO? nanoparticles to SnS? nanoparticles, which can facilitate interfacial electron transfer and reduce the self-agglomeration of two components, was considered to play an important role in achieving the high photocatalytic performances exhibited by the as-prepared SnS?/SnO? nanocomposites.     

Biomass-derived nitrogen-rich porous carbon composite for supercapacitor application

In this study, egg proteins are used as a nitrogen source for the synthesis of nitrogen-rich carbonaceous material through hydrothermal carbonization (HTC) for the electrochemical energy storage application. The composite of activated carbon with egg-derived protein (AC/EDP) is prepared by mixing untreated egg proteins in the aqueous dispersion of activated carbon, followed by HTC at 220 °C for 12 h in a Teflon-lined autoclave. The resultant composite is then directed to chemical activation with KOH and thermal activation at a temperature ranging from 500 to 700 °C. The nitrogen-doped activated carbon exhibited a microporous and mesoporous structure with a high specific surface area of 1660 m² g^?1, confirmed through BET analysis. The composite morphology was analyzed through scanning and high-resolution transmission electron microscopy. X-ray photoelectron spectroscopy indicates the presence of a considerable amount of pyrrolic, pyridinic, and quaternary nitrogen in AC/EDP, which improved the electrochemical performance. The composite activated at 700 °C exhibited the highest capacitance of 263 F g^?1 at a current density of 0.2 A g^?1. The highest energy density and power density values are 32 Wh kg^?1 and 7920 W kg^?1, respectively. The AC/EDP exhibited high cyclic stability, and the capacitance retention observed after 10,000 cycles is 98%.

     

Structural, optical, and electrical properties of tin sulfide thin films grown by spray pyrolysis

Tin sulfide (SnS) thin films have been prepared by spray pyrolysis (SP) technique using tin chloride and N, N-dimethylthiourea as precursor compounds. Thin films prepared at different temperatures have been characterized using several techniques. X-ray diffraction studies have shown that substrate temperature (T_s) affects the crystalline structure of the deposited material as well as the optoelectronic properties. The calculated optical band gap (E_g) value for films deposited at T_s = 320-396 °C was 1.70 eV (SnS). Additional phases of SnS₂ at 455 °C and SnO₂ at 488 °C were formed. The measured electrical resistivity value for SnS films was ∼ 1 × 10⁴ Ω-cm.     

纳米纤维素/碳纤维-聚苯胺/碳纳米管电极的制备

目的以纳米纤维素/碳纤维复合膜为导电基底,制备纳米纤维素/碳纤维-聚苯胺/碳纳米管超级电容器电极。方法利用超声处理和真空抽滤制备纳米纤维素/碳纤维复合膜;利用原位聚合法制备聚苯胺和聚苯胺/碳纳米管复合材料;通过真空抽滤法制备纳米纤维素/碳纤维-聚苯胺电极和纳米纤维素/碳纤维-聚苯胺/碳纳米管电极。结果在纳米纤维素/碳纤维复合膜中,碳纤维形成了互穿导电网络结构,是良好的超级电容器电极导电基体;纳米纤维素/碳纤维-聚苯胺/碳纳米管电极具有良好的电化学性能,在扫描速率为5 mV/s的条件下,质量比电容为380.74 F/g,且在1000次循环测试后,电容保留率为88.05%。结论以纳米纤维素/碳纤维导电复合膜作为基体制备的纳米纤维素/碳纤维-聚苯胺/碳纳米管电极具有良好的电化学性能,可以作为超级电容器电极。     

Photovoltaic structures using chemically deposited tin sulfide thin films

Chemically deposited thin films of tin sulfide forms in two crystalline structures depending on the bath compositions used: orthorhombic, SnS(OR), and zinc-blende, SnS(ZB). These films posses p-type electrical conductivity and have band gaps of 1.2 and 1.7 eV, respectively. The photovoltaic structure: SnO₂:F/CdS/SnS(ZB)/SnS(OR) with evaporated Ag-electrode reported here shows an open circuit voltage (V_OC) of 370 mV, a short circuit current density (J_SC) of 1.23 mA/cm², fill factor of 0.44 and conversion efficiency of 0.2% under 1 kW/m² illumination intensity. We present an evaluation for improvement in the light generated current density when the two types of SnS absorber films are used. Different evaporated electrode materials were tested, from which Ag-electrode was chosen for this work. The results given above were obtained with SnS(ZB) film of 0.1 µm and SnS(OR) film of 0.5 µm in thickness.     

Chemical bath deposition of SnS films with different crystal structures

SnS (stannous sulfide) films were prepared by chemical bath deposition in which a novel chelating reagent ammonium citrate was used. The film has a zinc blende structure or orthorhombic structure which is determined by the pH value of the deposition solution (zinc blende structure at pH = 5 and orthorhombic structure at pH = 6). The reason for this result may be that SnS films prepared at different pH values have different deposition mechanisms, which results in different structures. The prepared SnS films are all smooth and well adhered. The optical bandgaps of the SnS films are determined to be 1.75 eV and 1.12 eV for zinc blende structure and orthorhombic structure, respectively.     

预歧化处理的高性能锂离子电池SiO/C负极材料

以SiO和蔗糖为原料,SiO经高温歧化反应处理后,通过机械球磨、喷雾干燥、高温热解工艺制备出具有优异电化学性能的锂离子电池SiO/C负极材料。经XRD、FTIR、XPS、SEM、TEM结构分析表明,歧化反应处理的片状SiO包含非晶态SiO和纳米晶相Si、SiO_2,蔗糖热解形成的无定形碳包覆在细片状SiO的表面,组成球形SiO/C颗粒。电化学测试结果表明,预歧化处理的SiO/C复合材料的首次放电容量为1 314.6mAh/g,首次库伦效率达到71%;100周循环后的放电容量为851.2mAh/g,容量保持率达到78.5%,循环稳定性远高于未经歧化处理的SiO/C复合材料。电化学性能的提高归因于SiO预歧化反应及热解碳包覆。     

Effects of annealing temperature on electrochemical performance of SnSx embedded in hierarchical porous carbon with N-carbon coating by in-situ structural phase transformation as anodes for lithium ion batteries

Tuned tin chalcogenides rooted in hierarchical porous carbon(HPC)with N-carbon coating layers are prepared by thermal shock under various temperatures(denoted as HPC-SnS2-PAN-Various T).With the increase of annealing temperature,the morphology and phase structure of SnS2,as well as the cyclization degree of polyacrylonitrile(PAN),are significantly changed,which leads to the formation of rod-like SnS and ordered structure of conductive N-carbon layer.By combining HPC,N-carbon coating derived from the cyclization of PAN,with 1D SnS nanorods generated from structural phase transformation of SnS2,the optimized composite(HPC-SnS2-PAN-500)as anode for lithium ion batteries(LIBs)provides buffer space for volume changes during alloying/dealloying process,builds a highly conductive network as well as decreases irreversible capacity from solid electrolyte interphase and enhances the ion/electron transport.Attributed to the above merits from composition regulation and architecture modification by sulfur depletion and PAN cyclization,this target anode exhibits an extraordinary cycling stability with a high specific capacity of 652.5 mA h/g at 0.5 A/g after 900 cycles.It suggests that rod-like SnS embedded in HPC with cyclized PAN layers by thermal treatment approach renders a potential structural design of anode materials for LIBs.     

碳前驱体对LiFePO_4/C复合材料的形貌及电化学性能的影响

采用葡萄糖、环氧树脂、酚醛树脂为碳源制备了LiFePO4/C复合材料。利用X射线衍射、扫描电镜等方法对复合材料进行研究。结果表明,葡萄糖获得了碳包覆复合材料,而环氧树脂、酚醛树脂则得到了碳芯结构复合材料。碳芯结构复合材料的电化学性能优于碳包覆复合材料,电流密度为15mA/g时,试样C、D的放电容量分别为165、167mAh/g;电流密度为600mA/g时,试样C、D的放电容量分别为139.4、145.5mAh/g,经过50循环后容量保持率分别高达99.2%、99.5%。     

超声电沉积锡基碳纳米管复合材料制备工艺研究

采用了超声电沉积工艺制备了锡基碳纳米管复合材料,作为锂离子电池负极,研究其电化学性能.采用了正交实验研究了电沉积操作条件对材料电化学性能的影响,并依据实验结果给出了初步的解释,同时总结出最佳电沉积操作条件,在此基础上,制备出了性能最优的锂离子电池锡基碳纳米管复合材料负极.     

碳源对液相法制备Li3V2（PO4）3/C的影响

以4种不同种类的有机物(柠檬酸、水杨酸、聚丙烯酸、蔗糖)为碳源,通过液相反应合成Li3V2(PO4)3/C复合材料。研究了不同碳源对复合材料的晶型结构、形貌及电化学性能的影响。结果表明,碳源对Li3V2(PO4)3/C材料的晶型结构没有影响,但对电化学性能影响较明显,其中采用柠檬酸为碳源制得的Li3V2(PO4)3/C复合材料电化学性能最好。进一步研究了柠檬酸的加入量对复合材料的电化学性能的影响,发现当柠檬酸加入量为钒与碳的物质的量比为1∶4时,样品的平均粒径较小,电化学性能最好,0.1C首次放电比容量为123.59mAhg-1,0.5C首次放电比容量也高达117.27mAhg-1,循环10次后,仍保持在117.19mAhg-1,容量几乎没有衰减,10C时比容量仍有105.43mAhg-1。     

Synthesis and electrochemical performance of a simple and low-cost sulfur/porous carbon composite cathode for rechargeable lithium sulfur battery

The sugar and phenolic resin were used as source materials to prepare porous carbons labeled as PC1 and PC2 respectively, which were activated by chemical methods with CaCO₃ as active agent. Sulfur/porous carbon composites were synthesized by thermally treating a mixture of sublimed sulfur and porous carbon. The morphology, structure, and electrochemical performance of the composite were investigated by scanning electron microscopy, Brunauer–Emmett–Teller, and a variety of electrochemical techniques. The electrochemical measurements show that the SPC2 electrode presents a more favorable electrochemical kinetics than the SPC1 electrode. In comparison with SPC1, it is shown that the rate of Li⁺ diffusion with SPC2 is significantly higher and the charge transfer resistance is much lower. The PC2 with high surface area (735.2 m² g⁻¹) and large pore volume (1.56 cm³ g⁻¹) not only increases the electronic conductivity of composites, but also facilitates transfer of the Li ion in the composite electrode.     

Effects of MoS2 doping on the electrochemical performance of FeF3 cathode materials for lithium-ion batteries

Orthorhombic structure FeF₃ was synthesized by a liquid-phase method. The FeF₃/MoS₂ for the application of cathode material of lithium-ion battery was prepared through mechanical milling with molybdenum bisulfide. The structure and morphology of the FeF₃/MoS₂ were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of FeF₃/MoS₂ was studied by charge/discharge, cyclic voltammetry and electrochemical impedance spectra measurements. The results show that the prepared FeF₃/MoS₂ was typical orthorhombic structure, uniform surface morphology, better particle-size distribution and excellent electrochemical performances. The initial discharge capacity of FeF₃/MoS₂ was 169.6 mAh·g^− 1 in the voltage range of 2.0-4.5 V, at room temperature and 0.1 C charge-discharge rate. After 30 cycles, the capacity retention is still 83.1%.     

High electrochemical activity from hybrid materials of electrospun tungsten oxide nanofibers and carbon black

Tungsten oxide (WO₃) nanofibers were prepared by oxidizing the electrospun ammonium metatungstate (AMT) and polyvinyl pyrrolidone (PVP) composite fibers. The WO₃ nanofibers with controllable diameters ranging from 80 to 130 nm were obtained by electrospinning different AMT/PVP mixture solutions. Electrochemical activity of the WO₃ nanofibers was measured in 0.5 M sulfuric acid solution. Cyclic voltammetry tests show that the WO₃ nanofibers have electrochemical activity which is closely related to hydrogen oxidation in fuel cells and the electrochemical activity could be greatly enhanced by the addition of carbon black. The hybrid materials of the WO₃ nanofibers and carbon black with the WO₃:C mass ratio of 10:1 possess high electrochemical activity with an anodic peak current density of 11.2 mA/cm², even higher than the commercial 20 wt% Pt/C catalyst. The electrospun WO₃ nanofibers may be promising electrocatalysts or catalyst supports for hydrogen oxidation in fuel cells due to the simplicity in production and high electrochemical activity.     

Effect of carbon content and calcination temperature on the electrochemical performance of lithium iron phosphate/carbon composites as cathode materials for lithium-ion batteries

Lithium iron phosphate/carbon (LiFePO₄/C) composites were prepared by a convenient method with water-soluble phenol-formaldehyde resin as the carbon precursor. The morphology, crystalline structure, thermal stability, and composition of as-prepared LiFePO₄/C composites were investigated by scanning electron microscopy, X-ray diffraction, thermogravimetric analysis, and Raman spectrometry. Their electrochemical performance was examined based on cyclic voltammogram with a LAND battery testing system while the effect of carbon content and calcination temperature was highlighted. Results show that carbon content and calcination temperature dramatically influence the discharge capacities and rate performance of LiFePO₄/C composites. The optimal calcination temperature is 700 °C, and the optimal carbon content (mass fraction) is 8.7%. The LiFePO₄/C composite prepared under the optimal conditions exhibits an initial room temperature discharge capacity of 150.2 mA h g^?1 at a 0.2 C rate and a constant discharge capacity of about 105.7 mA h g^?1 at a 20.0 C rate after 50 cycles, showing promising potential as a novel cathode material for lithium ion batteries.