The preparation of PANI/CA composite electrode material for supercapacitors and its electrochemical performance

Polyaniline (PANI)/carbon aerogel (CA) composite electrode materials were prepared by chemical oxidation polymerization. The morphology of PANI/CA composite was examined by scanning electron microscopy. The results showed that PANI was uniformly deposited onto the surface of porous CA and filled big inner pores of the CA. Electrochemical performance of the composite electrode was studied by cyclic voltammograms and galvanostatic charge/discharge measurements. The results indicated that the PANI/CA composite electrode had much better electrochemical performance, high reversibility, and high charge/discharge properties than CA. Moreover, the results based on cyclic voltammograms showed that the composite material has a high specific capacitance of 710.7 F g⁻¹, while the capacitance of CA electrode was only 143.8 F g⁻¹. Besides, the supercapacitor using the PANI/CA composite as electrode active material showed a stable cycle life in the potential range of −0.2–0.8 V.     

PVC–PMMA composite electrospun membranes as polymer electrolytes for polymer lithium-ion batteries

Composite nanofibrous membranes based on poly (vinyl chloride) (PVC)?Cpoly (methyl methacrylate) (PMMA) were prepared by electrospinning and then they were soaked in liquid electrolyte to form polymer electrolytes (PEs). The introduction of PMMA into the PVC matrix enhanced the compatibility between the polymer matrix and the liquid electrolyte. The composite nanofibrous membranes prepared by electrospinning involved a fully interconnected pore structure facilitating high electrolyte uptake and easy transport of ions. The ion conductivity of the PEs increased with the increase in PMMA content in the blend and the ion conductivity of the polymer electrolyte based on PVC?CPMMA (5:5, w/w) blend was 1.36?×?10^?3 S cm^?1 at 25?°C. The polymer electrolyte based on PVC?CPMMA (5:5, w/w) blend presented good electrochemical stability up to 5.0?V (vs. Li/Li⁺) and good interfacial stability with the lithium electrode. The promising results showed that nanofibrous PEs based on PVC?CPMMA were of great potential application in polymer lithium-ion batteries.     

The effects of crystal structure of the precursor MnO2 on electrochemical properties of spinel LiMn2O4

Journal of Solid State Electrochemistry - The spinel LiMn2O4 samples for lithium-ion battery have been synthesized through one-step solid-state method using four different polymorphs of MnO2, e.g.,...     

Effect of MgF2 coating on the electrochemical performance of LiMn2O4 cathode materials

Spinel LiMn₂O₄ cathode materials were coated with 1.0, 3.0 and 5.0?wt.% of MgF₂ by precipitation, followed by heat treatment at 400?°C for 5?h in air. The effects of MgF₂ coating on the structural and electrochemical properties of LiMn₂O₄ cathodes were investigated using XRD, SEM, and electrochemical tests. XRD and SEM results show that no significant bulk structural differences are observed between the coated and pristine LiMn₂O₄. The charge–discharge tests show that the discharge capacity of LiMn₂O₄ decreases slightly, but the cyclability of LiMn₂O₄ is clearly improved when the amount of the MgF₂ coated was increased to 3.0?wt.%. The 3.0?wt.% MgF₂-coated LiMn₂O₄ exhibits capacity retention of 80.1 and 76.7 % after 100 cycles at room temperature (25?°C) and elevated temperature (55?°C) at a rate of 1?C, respectively, much higher than those of the bare LiMn₂O₄ (70.1 and 61.6 %). The improvement of electrochemical performance is attributed to the suppression of Mn dissolution into the electrolyte via the MgF₂ coating layer.     

Effects of complexants on [Ni1/3Co1/3Mn1/3]CO3 morphology and electrochemical performance of LiNi1/3Co1/3Mn1/3O2

LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials for the application of lithium ion batteries were synthesized by carbonate co-precipitation routine using different ammonium salt as a complexant. The structures and morphologies of the precursor [Ni_1/3Co_1/3Mn_1/3]CO₃ and LiNi_1/3Co_1/3Mn_1/3O₂ were investigated through X-ray diffraction, scanning electron microscope, and transmission electron microscopy. The electrochemical properties of LiNi_1/3Co_1/3Mn_1/3O₂ were examined using charge/discharge cycling and cyclic voltammogram tests. The results revealed that the microscopic structures, particle size distribution, and the morphology properties of the precursor and electrochemical performance of LiNi_1/3Co_1/3Mn_1/3O₂ were primarily dependent on the complexant. Among all as-prepared LiNi_1/3Co_1/3Mn_1/3O₂ cathode materials, the sample prepared from Na₂CO₃–NH₄HCO₃ routine using NH₄HCO₃ as the complexant showed the smallest irreversible capacity of 19.5 mAh g⁻¹ and highest discharge capacity of 178.4 mAh g⁻¹ at the first cycle as well as stable cycling performance (98.7% of the initial capacity was retained after 50 cycles) at 0.1 C (20 mA g⁻¹) in the voltage range of 2.5–4.4 V vs. Li⁺/Li. Moreover, it delivered high discharge capacity of over 135 mAh g⁻¹ at 5 C (1,000 mA g⁻¹).     

基础有机化学教学改革的探索与实践

当今世界的新知识层出不穷,有机化学已经广泛渗透到生命科学、材料科学、环境科学、能源科学等众多学科领域。有机化学作为化学学科中最活跃的领域,发展十分迅速、内容越来越多,加上在教学上追求自身的系统性和完整性,使得教学体系中有限的课堂容量与不断膨胀的课程内容之间的矛盾日益突出,因此,进行基础有机化学教学改革已是日益重要、日趋紧迫的工作。1　教学改革的设想　　(1)转变教育教学观念,更新教学思想,重新认真审定教育教学目标,制定教学计划,在改革中创新教学模式,提高教学质量。在充分酝酿的前提下,我们确定了“厚基础、高素…     

呸啶衍生物的合成及抑菌性

呸啶是一种多核含氮杂环化合物,在工业和生物活性研究领域研究中发挥着重要作用。 长期以来,由于含氮杂环的存在,广大研究者们对呸啶化合物进行了大量的研究。 本文以1,8-萘二胺和醛为原料,设计合成了一系列呸啶衍生物(4a~4g和6),并通过红外光谱、核磁共振氢谱、核磁共振碳谱和高分辨质谱对其结构进行了表征。 其中化合物4a~4g和6的结构进行了单晶衍射测定。 单晶衍射结果显示,化合物4b和6的晶体均属于属于单斜晶系,P2₁/n空间群。 此外,还对目标化合物进行了抑菌试验,结果表明,化合物4b~4g和6对所测试的植物性病菌具有广谱的抑菌活性,说明呸啶衍生物在将来的抗菌生物领域具有很好应用前景。 研究结果还表明,抑菌性并不具有明显的取代基效应。     

The preparation and performance of flocculent polyaniline/carbon nanotubes composite electrode material for supercapacitors

Polyaniline (PANI)/carbon nanotubes (CNTs) composite electrode material was prepared by in situ chemical polymerization. The structure and morphology of PANI/CNTs composite are characterized by Fourier infrared spectroscopy, scanning electron microscope, and transmission electron microscopy. It has been found that a flocculent PANI was uniformly deposited on the surface of CNTs. The supercapacitive behaviors of the PANI/CNTs composite materials are investigated with cyclic voltammetry, galvanostatic charge/discharge, impedance, and cycle life measurements. The results show that the PANI/CNTs composite electrodes have higher specific capacitances than CNT electrodes and better stability than the conducting polymers. The capacitance of PANI/CNTs composite electrode is as high as 837.6 F g⁻¹ measured by cyclic voltammetry at 1 mV s⁻¹. Besides, the capacitance retention of coin supercapacitors remained 68.0% after 3,000 cycles.