超级电容器有机低温电解液的制备及电化学性能研究

超级电容器低温性能的好坏与其电极材料及电解液密切相关,通过电化学测试研究了以活性炭和石墨烯为电极材料,1mol·L-1不同体积含量丙酸甲酯(MP)的SBP-BF4/(PC+DMC+MP)体系为电解液的超级电容不同温度时的电化学性能,分析发现,MP有助于提升有机电解液的低温性能,MP溶剂体积分数为33％的活性炭超级电容可...     

纳米碳材料的超级电容器性能测试

通过扫描电子显微镜、透射电子显微镜和拉曼对纳米碳材料进行表征。测试结果表明,样品纳米碳具有较高的纯度。循环伏安、充放电及循环等电化学性能测试表明,纳米碳电极的比电容较高,循环稳定性较好,且具有良好的电化学性能。     

环丁砜混合有机电解液在超级电容器中的应用

将环丁砜作为耐高温、高压添加剂加入到TEA-BF4/AN体系电解液中,应用于商品化100 F活性炭基双电层超级电容器。通过恒流充放电、高温浮充测试对比了添加环丁砜前后两种电解液体系的电化学性能。发现添加环丁砜后的电解液超级电容器具有明显优势,在2.85 V,70℃条件下浮充1512小时,容量保持率高达80%。     

透明超级电容器电极的制备及其电化学性能研究

超级电容器因其充电速度快、使用寿命长、无污染以及免维护等特征,已经受到了越来越多国内外研究者的关注。本文研究了使用氧化铟锡-聚对苯二甲酸乙二醇酯(ITO-PET)导电薄膜和氧化石墨烯制备透明电极的方法。采用电沉积法将氧化石墨烯沉积到ITO-PET透明导电薄膜的表面制备得到电极材料,并研究其性能。     

炭基非对称型超级电容器的研究进展

基于碳材料的超级电容器因其高功率密度、快速充放电能力而在电化学储能技术领域发挥着重要的作用,但是较低的能量密度严重限制其发展应用。相较于常规对称型超级电容器,非对称型超级电容器可以充分利用理论工作电压窗口,大幅拓宽工作电压进而提升整体能量密度。本文简单介绍了非对称型超级电容器的优势与分类,以及在电极电位拓宽策略方面的最新研究进展,为未来开发新型超级电容器提供参考方向。     

超级电容器用solvent-in-salt型电解液的研究进展

Solvent-in-salt (SIS)型电解液作为一类新型超浓缩电解液,主要由水或者有机溶剂和易溶盐组成,具有溶液溶剂化程度小、自由溶剂分子少、电化学窗口宽、电化学稳定性高等特点,在超级电容器中显示了独特的优势并展现了良好的应用前景。本文重点综述了SIS型电解液的原理和优势,梳理了近年来SIS作为超级电容器电解液的研究进展,总结了其存在的问题,同时展望了SIS型电解液未来的发展方向。     

超级电容器用煤基活性炭研究

为了研究煤基活性炭电极对超级电容器性能的影响规律,根据超级电容器的工作原理,阐述了比表面积、孔径分布、表面官能团、石墨化程度、灰分及粒度对电化学性能的影响。研究表明适宜的中孔比例和粒度有利于电解液的扩散;含氧和含氮官能团可以改善电极的表面润湿性;无定型炭结构孔隙更发达,更适合作为活性炭材料;降低灰分可以提高电极的充放电特性和倍率特性。     

用于超级电容器的煤基活性炭电极材料的研究进展

活性炭电极材料广泛的应用于超级电容器中,制备活性炭的前驱体种类繁多,其中煤炭是优质的活性炭前驱体,它的含碳量高、储量丰富且价格低廉。以煤为前驱体制备活性炭可以拓宽煤的应用领域,提高煤炭附加值。综述了最新煤基活性炭电极材料的研究进展,分析了煤基活性炭性质对超级电容器电性能的影响,最后对煤基活性炭未来的研究方向以及发展前景提出了展望。     

Mechanochemical preparation of polydiphenylamine and its electrochemical performance in hybrid supercapacitors

A simple mechanochemical route for the synthesis of high quality inorganic anion doped polydiphenylamines (PDPAs) is reported in this article. Elemental analysis performed for the PDPAs indicated the presence of dopant anions in the polymeric chain. PDPA prepared in the presence of 96 wt% H₂SO₄ (PDPA–H₂SO₄) was found to be better doped than the other polymeric salts. Spectroscopic profiles of the polymers showed that the PDPAs were in a doped conducting state. The X-ray diffraction (XRD) pattern of the as-prepared polymeric powders revealed the presence of more crystalline phases in PDPA–H₂SO₄. Field emission scanning electron microscopic (FESEM) images highlighted the formation of inorganic anion doped PDPA particles with different sizes (80–100 nm). Electrochemical studies performed for the polymeric particles depicted the redox behavior and good electrochemical activity of PDPA salts. Thermogravimetric analysis (TGA)/differential thermal analysis (DTA) proved that all the PDPA salts were thermally stable up to 300 °C. The electrochemical performance of PDPA–H₂SO₄ in hybrid supercapacitors was evaluated due to its superior physicochemical properties. The maximum specific capacitance of the hybrid supercapacitor constructed out of PDPA–H₂SO₄ powder was found to be 108 F g⁻¹.     

Excellent performance MWCNTs-GONRs/Ni(OH)2 electrode for outstanding supercapacitors

Due to the unconventional properties of MWCNTs-GONRs (multiwalled carbon nanotubes-graphene oxide nanoribbons), we have tried to use it as a carbon resource for supercapacitors. MWCNTs-GONRs/Ni(OH)₂ electrode was obtained by hydrothermal method. Velvet α-Ni(OH)₂ was prepared above NF (nickel-foam) loaded with MWCNTs-GONRs. This layered design can effectively promote the diffusion of ions and increase the active site for MWCNTs-GONRs/Ni(OH)₂ electrode, thus enhancing the electrochemical performance. The electrode exhibits extraordinary electrochemical performances in electrochemical testing, such as supernal specific capacitance (1713.2 F g⁻¹) and prominent working time. In addition, supercapacitors was assembled with MWCNTs-GONRs/Ni(OH)₂ and active carbon as materials. Which represents a prominent energy density (41.23 Wh kg⁻¹), high power (6.80 kW kg⁻¹) and prominent cycling stability property (95.18%, 3000 times). The electrode prepared in this work provides a clue to enlighten people for energy storage.     

Solvothermal synthesis of porous MnCo2O4.5 spindle-like microstructures as high-performance electrode materials for supercapacitors

This study presents the facile preparation of novel MnCo₂O_4.5 microspindles (MSs) for the first time through a rapid solvothermal method combined with subsequent calcination of the precursor at 450 °C for 4 h in air. The MnCo₂O_4.5 MSs have an average length of 4–5 µm and diameter of 2–4 µm, respectively, achieving a specific surface area as high as 83.3 m² g⁻¹. In addition, the size and morphology of the MnCo₂O_4.5 microstructures could be easily tuned by some parameters including reaction time, volume ratio of ethanol to water, and dosage of urea. The electrochemical performance was further evaluated in three-electrode system, detailed electrochemical characterizations revealed that such MnCo₂O_4.5 MSs exhibited both high specific capacitance of 343 F g⁻¹ at a current density of 0.5 A g⁻¹ and excellent cycling performance of 81.3% capacitance retention after 5000 cycles at a current density of 4 A g⁻¹ in 2 M of KOH electrolyte, which made it a potential electrode material for an advanced supercapacitor. Furthermore, the present synthetic method is simple and can be extended to the synthesis of other electrode materials based on transition metal oxides.     

Enhancing the electrochemical performance of d-Mo2CTx MXene in lithium-ion batteries and supercapacitors by sulfur decoration

With the development of the energy industry, electrochemical energy storage technology is increasingly involved in developing innovations in the field. The materials of the electrode have a significant influence on the performance of energy storage devices. For this purpose, two-dimensional MXene with excellent electrical conductivity, mechanical strength, and a variety of possible surface-active terminations are attracting much attention. In the present work, S-decorated d-Mo₂CT_x (d-Mo₂CT_x--S) is designed. The first-principles calculations reveal that it may possess good energy storage characteristics. Due to the decoration with S, unique morphology and structure are obtained, conferring stability, optimized Li⁺ storage, improved charge transport, and lithium-ion adsorption capabilities. Compared with d-Mo₂CT_x, d-Mo₂CT_x--S exhibits higher discharge capacity (623 mAh g⁻¹ at 1 A g⁻¹) as lithium-ion electrode material and higher specific capacitance (561 F g⁻¹ at 1 A g⁻¹). As a supercapacitor, the material also shows excellent cyclic stability (20,000 charge-discharge cycles). This work may inspire the exploration of other MXene and new surface functionalization methods to improve the performance of MXene as electrode materials for new energy devices.     

Facile synthesis of three dimensional flower-like Co3O4@MnO2 core-shell microspheres as high-performance electrode materials for supercapacitors

In this work, we reported the synthesis of three dimensional flower-like Co₃O₄@MnO₂ core-shell microspheres by a controllable two-step reaction. Flower-like Co₃O₄ microspheres cores were firstly built from the self-assembly of Co₃O₄ nanosheets, on which MnO₂ nanosheets shells were subsequently grown through the hydrothermal decomposition of KMnO₄. The MnO₂ nanosheets shells were found to increase the electrochemical active sites and allow faster redox reaction kinetics. Based on these advantages, when used as an electrode for supercapacitors, the prepared flower-like Co₃O₄@MnO₂ core-shell composite electrode demonstrated a significantly enhanced specific capacitance (671 F g⁻¹ at 1 A g⁻¹) as well as improved rate capability (84% retention at 10 A g⁻¹) compared with the pristine flower-like Co₃O₄ electrode. Moreover, the optimized asymmetric supercapacitor device based on the flower-like Co₃O₄@MnO₂//active carbon exhibited a high energy density of 34.1 W h kg⁻¹ at a power density of 750 W kg⁻¹, meaning its great potential application for energy storage devices.     

Facile synthesis and strongly microstructure-dependent electrochemical properties of graphene/manganese dioxide composites for supercapacitors

Graphene has attracted much attention since it was firstly stripped from graphite by two physicists in 2004, and the supercapacitor based on graphene has obtained wide attention and much investment as well. For practical applications of graphene-based supercapacitors, however, there are still many challenges to solve, for instance, to simplify the technological process, to lower the fabrication cost, and to improve the electrochemical performance. In this work, graphene/MnO₂ composites are prepared by a microwave sintering method, and we report here a relatively simple method for the supercapacitor packaging, i.e., dipping Ni-foam into a graphene/MnO₂ composite solution directly for a period of time to coat the active material on a current collector. It is found that the microwave reaction time has a significant effect on the microstructure of graphene/MnO₂ composites, and consequently, the electrochemical properties of the supercapacitors based on graphene/MnO₂ composites are strongly microstructure dependent. An appropriately longer microwave reaction time, namely, 15 min, facilitates a very dense and homogeneous microstructure of the graphene/MnO₂ composites, and thus, excellent electrochemical performance is achieved in the supercapacitor device, including a high specific capacitance of 296 F/g and a high capacitance retention of 93% after 3,000 times of charging/discharging cycles.

PACS

81.05.ue; 78.67.Sc; 88.80.fh     

Electrochemical performance of spherical LiCoO2 with high stability in neutral aqueous electrolyte

Layer-structured lithium cobalt oxide (LCO) is one of promising electrode materials for secondary aqueous lithium-ion batteries, yet the effect of structural proton insertion in LCO in neutral aqueous electrolytes cannot be ignored. Present study investigates the electrochemical performance of polycrystalline spherical LCO in neutral aqueous saturated Li₂SO₄ solution. Herein, we for the first time demonstrate the dependence of LCO stability on the discharge cutoff potential. The applied LCO electrodes show good cycling stability within the potential window of 0.65–1.1 V vs. SCE, while electrochemical impedance spectrum (EIS) analysis detects no sign of proton intercalation. Moreover, the spherical LCO free from the proton intercalation exhibits a superior rate capability with 78% discharge capacity retention at 80 C. The lithium-ion chemical diffusion coefficient being seven times than that of irregular shaped LCO sample can be responsible for such significant rate capability. The cyclability testing depicts the better performance of spherical LCO in comparison with the counterpart, especially in terms of electrode activation time. Post cycling electrode characterization displays that the discharge capacity fading of LCO mainly results from the crystal grain deformation due to high potential cycling and can be alleviated by reducing the depth of charge.     

In situ synthesis of integrated dodecahedron NiO/NiCo2O4 coupled with N-doped porous hollow carbon capsule for high-performance supercapacitors

NiO and NiCo₂O₄ exhibit excellent synergistic effects and broad application prospects in electrochemical applications. However, the apparent interfacial instability between NiO and NiCo₂O₄ limits ion transport kinetics, charge/ion transfer, and electrochemical stability. In response, we developed and designed an integrated dodecahedron NiO/NiCo₂O₄ by a facile in-situ calcination method. Moreover, by utilizing the porous hollow structure of nitrogen-doped carbon capsules (N-Cc) as a conductive network, the N-Cc_x@NiO/NiCo₂O₄ heterostructures with stable interface structure, excellent electrolyte adsorption, and electron transfer pathways were carefully designed. The N-Cc_1.0@NiO/NiCo₂O₄ heterostructures are found to deliver an outstanding specific capacitance of 658.8 F g⁻¹, and a high energy density of 101.40 Wh kg⁻¹ at a power density of 775.03 W kg⁻¹, along with capacitance retention of more than 93.5% after 8000 cycles. Based on the DFT calculations and electrochemical experimental results, this work provides an effective in situ route for the construction of high-performance metal oxide heterostructure electrode materials for new energy storage devices.     

Characterization and performance of hydrous manganese oxide prepared by electrochemical method and its application for supercapacitors

Hydrous manganese oxide was deposited on graphite substrates at anodic potentials of 0.5-0.95 V versus saturated calomel electrode (SCE) in 0.25 M Mn(CH₃COO)₂ solution at 25 °C. Morphology of manganese oxide prepared was examined by scanning electron microscopy (SEM). Manganese oxide deposited at various anodic potentials was evaluated by cyclic voltammetry with various potential scan rates in different electrolytes. Results indicated that the pseudocapacitive behaviors of manganese oxide were excellent both in 2 M KCl and 2 M (NH₄)₂SO₄ solutions at room temperature. Manganese oxide deposited at 0.5 V versus SCE showed better capacitive behaviors, the specific capacitances were 275 F/g in 2 M KCl solution and 310 F/g in 2 M (NH₄)₂SO₄ solution, respectively. Besides, better electrochemical reversibility could be obtained in 2 M KCl solution.     

Study on electrochemical performance of porous integrated PANI-Fe in supercapacitors

The iron-coordinated polyaniline (PANI-Fe) integrated nanomaterials was prepared by chemical oxidative and in-situ electrochemical polymerization, which was applied to supercapacitor electrodes. The N–Fe coordination bond is formed between FeCl₃ and the N of quinone diimine to enhance the interaction of the polyaniline molecular chain. The PANI-Fe electrode material forms a crosslinked porous fiber framework through two-step oxidation, which greatly improves the energy storage capacity of PANI-Fe. PANI-Fe achieves higher capacitance of 642 F g⁻¹ at 1 A g⁻¹ than PANI of 310 F g⁻¹, and maintains high capacitance retention of 82.4 % when the current density increases from 1 to 10 A g⁻¹. According to first-principles calculations, the Fermi energy (N(E)) of PANI-Fe drop down to 0.265 eV from 0.901 eV of PANI, which proves that its conductivity is improved. The change of the electrostatic potential of PANI-Fe indicates that the formation of the N–Fe coordination bond can improve the carrier transport behavior. PANI-Fe has a smaller HOMO-LUMO energy gap than PANI, indicating that the formation of N–Fe coordination bonds can increase the electrical activity of PANI.