石墨烯包覆碳纳米管-硫(CNT-S)复合材料及锂硫电池性能

针对锂硫电池研究与实际应用中遇到的主要问题, 本文通过一种简单有效的水热法还原氧化石墨烯对商用碳纳米管-硫(CNT-S)纳米复合材料进行包覆, 形成一种可有效抑制多硫聚合物扩散的石墨烯包覆结构。X射线衍射(XRD), 扫描电子显微镜(SEM)表征结果表明硫均匀地负载在碳纳米管上, 并且在CNT-S复合材料外表面包覆有一层石墨烯。电化学测试结果表明, 这种包覆结构能显著提高CNT-S复合材料的锂硫电池性能。     

微孔碳@硫复合材料的制备及其锂硫电池性能

针对锂硫电池研究中硫单质电导率低和多硫化锂易溶解于电解液的问题,制备了一种核壳结构的碳纳米管(CNT@C)作为硫载体,碳纳米管外壳包覆的碳层中的微孔能吸附多硫化锂,从而抑制多硫离子扩散.X射线衍射(XRD),透射电子显微镜(TEM)和扫描电子显微镜(SEM)表征结果表明硫均匀负载在核壳结构碳纳米管上.电化学测试结果表明这种核壳结构的复合材料有较高容量和良好的循环性能.     

石墨烯作为硫载体在锂硫电池中的研究进展

锂硫电池因其超高的理论能量密度以及硫资源丰富、成本低廉、无毒的优点,被认为是极具发展潜力与应用前景的新一代储能设备。然而,硫正极导电性差、体积膨胀以及穿梭效应严重等问题严重制约了其商业化应用。石墨烯具有高比表面积、高导电性和高柔韧性,并且易于进行表面化学修饰及组装,是一种理想的硫载体材料。本文主要综述了近年来三维石墨烯、表面化学修饰的石墨烯、石墨烯基复合材料以及石墨烯基柔性材料在锂硫电池正极中的研究现状,并展望了石墨烯作为硫载体在锂硫电池正极中的发展趋势。     

锂硫二次电池硫-碳纳米管正极的合成和性能

由单质硫与碳纳米管合成一种新型含碳复合材料.XRD、SEM、BET比表面和孔径分布表征观察硫-碳纳米管复合材料,循环伏安法和电池充放电测试材料的电化学性能.结果表明:以硫-碳纳米管作正极组装的2016型扣式电池有较好的电化学性能,其初始放电比容量达680mAh/g(室温),30次循环放电比容量仍稳定在500mAh/g.     

硫/石墨烯气凝胶的绿色可控制备及锂硫电池性能

以氧化石墨烯(GO)为碳前驱体,H2O2作为绿色氧化剂,H2S为还原剂和硫源,水热法制备了硫含量可控的硫/石墨烯气凝胶.通过调控加入到GO溶液中H2O2的用量使复合物中硫的质量分数在64％～ 84％间变动.将硫/石墨烯气凝胶用于锂硫电池正极材料,硫质量分数为70％的复合物表现了较好的锂硫电池性能,在0.1 A/g的电流...     

石墨烯包覆的硫填充碳纳米笼自支撑整体材料的制备及其锂硫电池性能研究

锂硫电池具有理论能量密度高、活性物质价廉、毒性低等优点,是最具发展潜力的高能量二次电池之一,其应用仍存在硫面载量小、循环寿命短和库伦效率低等难题.制备了石墨烯包覆的硫填充碳纳米笼自支撑整体材料,可直接用作锂硫电池正极,避免使用粘结剂、导电剂和集流体,当硫的面载量为3.8 mg·cm^-2时,锂硫电池展现出高的可逆比容量（1104 mAh·g^-1）、优异的循环稳定性（每圈容量衰减率仅为0.049%@1.0 A·g^-1）和>99.9%的库伦效率,其面积比容量（3.7 mAh·cm^-2）处于锂硫电池的先进水平.该电极的优异性能可归因于以下因素的协同作用：碳纳米笼的物理限域作用及石墨烯中含氧官能团的化学吸附作用有效抑制了活性物质的流失,微孔-介孔-大孔共存的分级孔结构和高导电性利于离子和电子的传输,纳米笼空腔填充有利于缓解体积膨胀造成的影响,整体材料的自支撑稳定结构有利于增加硫载量且维持电化学性能.本研究还提供了一种工艺简单、能有效提高面积比容量的硫正极制备方法.     

锂硫电池用石墨烯基材料的研究进展

锂硫电池因其理论能量密度高、资源丰富和环境友好等优势,被认为是最有发展前景的下一代电化学储能系统之一。然而,硫的绝缘性、充放电中间产物多硫化物的溶解和扩散、硫的体积膨胀以及锂负极安全性等问题,严重制约着锂硫电池的商业应用。石墨烯因其具有高导电、高柔性等诸多优异特性而被广泛研究,将其用于锂硫电池的正极载体、隔膜涂层和集流体中,以期实现高比能、高稳定性的锂硫电池。本文综述了石墨烯基材料,包括石墨烯、功能化石墨烯、掺杂石墨烯和石墨烯复合物,在锂硫电池中应用的研究进展,并展望了锂硫电池用石墨烯基材料的未来发展方向。     

金属氧化物用于锂硫电池硫正极材料改性的研究进展

锂硫电池因其能量密度高、原料丰富和价格低廉等优势而被认为是下一代的重要储能器件。但是,锂硫电池的发展仍面临诸多问题,包括多硫化物的穿梭效应、单质硫的导电性差、充电过程中硫体积膨胀导致的库仑效率差、容量快速衰减以及锂负极的腐蚀等。近年来,金属氧化物由于具有可吸附多硫化物、提高多硫化物之间的相互转化能力、形成3D形态纳米级结构及对主体材料与多硫化物之间的结合能发挥着关键作用等优点在锂硫电池正极材料的改性方面得到广泛应用。本文综述了多类金属氧化物(过渡金属氧化物、二元及多元金属氧化物、其他金属氧化物)在锂硫电池正极复合材料改性中的研究进展,并对金属氧化物在锂硫电池中的应用前景进行了展望。     

锂硫电池中的石墨烯掺杂

锂硫电池是以锂为负极,单质硫为正极的二次电池,具有高达1675 mA·h/g的比容量及2600 W·h/kg的比能量密度。理论上讲,相较于现有的锂离子电池,锂硫电池可使容量扩展5倍,这使其成为最有前景的锂离子电池。由于硫正极的绝缘性以及充放电过程中活性物质易溶于电解液,导致其可实现的能量密度远低于理论值。异原子掺杂石墨烯因具有优异的导电性,且对多硫化锂（LiPS）具有强的吸附作用而被广泛应用于锂硫电池,有效缓解了"穿梭效应",提高了电池的循环稳定性。本文主要从单原子掺杂、双原子掺杂两方面综述了异原子（如N,P,S,B）掺杂石墨烯在锂硫电池领域的研究现状,详细分析了其应用于锂硫电池的作用机理,并从掺杂量、掺杂形式、掺杂位置等方面对电池性能的提升进行了梳理和展望。     

功能碳基复合材料在锂硫电池正极中的应用

碳基复合材料由于结构可变、形貌可调、成分可控,能够展现出优异的理化特性,在能源存储和转化领域具有极大的应用潜力.其中,锂-硫电池作为高效的能源存储和转化器件,长期受困于硫(S)和硫化锂(Li2S)绝缘的瓶颈,亟需开发高导电的储硫载体帮助锂-硫电池实现可逆充放电.研究表明,碳基复合材料具有强的导电能力,且可以通过表/界面...     

基于氧化石墨烯的锂硫电池用聚乙烯隔膜的改性

通过简单刮涂法制备了氧化石墨烯(GO)涂覆改性的聚乙烯(PE)隔膜,并分析研究了GO的氧化程度对隔膜电学性能的影响。采用X射线光电子能谱分析(XPS)、扫描电子显微镜(SEM)、充放电实验、多硫化物透过性测试和交流阻抗等方法对GO及其改性隔膜的结构和性能进行了研究。结果表明:GO改性隔膜可以抑制锂硫电池的"穿梭效应";并且既具有较高的氧化程度,又具有较高的导电性的GO-4改性隔膜的电学性能最优;引入该隔膜的锂硫电池在0.2C条件下,首圈放电比容量为900.0mA·h/g,高于未改性PE隔膜的763.2mA·h/g。     

Sandwich-type functionalized graphene sheet-sulfur nanocomposite for rechargeable lithium batteries

A functionalized graphene sheet-sulfur (FGSS) nanocomposite was synthesized as the cathode material for lithium-sulfur batteries. The structure has a layer of functionalized graphene sheets/stacks (FGS) and a layer of sulfur nanoparticles creating a three-dimensional sandwich-type architecture. This unique FGSS nanoscale layered composite has a high loading (70 wt%) of active material (S), a high tap density of ～0.92 g cm(-3), and a reversible capacity of ～505 mAh g(-1) (～464 mAh cm(-3)) at a current density of 1680 mA g(-1) (1C). When coated with a thin layer of cation exchange Nafion film, the migration of dissolved polysulfide anions from the FGSS nanocomposite was effectively reduced, leading to a good cycling stability of 75% capacity retention over 100 cycles. This sandwich-structured composite conceptually provides a new strategy for designing electrodes in energy storage applications.     

锂硫电池用碳化钛涂层隔膜性能探究

为提高锂硫电池的比容量和循环性能,本文使用纳米碳化钛（TiC）作为涂层制备得到TiC/Celgard涂层隔膜,并探究其对锂硫电池性能的影响. 电化学性能测试结果表明,涂层隔膜能有效提高电池在不同倍率下的比容量以及电池的循环性能,在2C倍率下仍表现出650 mAh·g-1的比容量,0.5C循环100周容量仍能保持在843.1 mAh·g-1.     

锂硫电池多功能涂层隔膜的研究进展与展望

先进储能系统的开发对于满足电动汽车、便携式设备和可再生能源存储不断增长的需求至关重要. 锂硫（Li-S）电池具有比能量高、原材料成本低和环境友好等优点,是新型高性能电池研究领域中的热点. 然而,锂硫电池面向实际应用还存在许多问题,如可溶性多硫化物中间体的穿梭效应、锂枝晶生长以及锂硫电池在使用过程中的热稳定性和安全性等. 设计开发多功能涂层隔膜是改善锂硫电池上述不足的有效策略之一,在本综述中,详细论述了锂硫电池多功能涂层隔膜的研究进展. 包括聚合物材料、碳材料、氧化物材料、催化纳米粒子改性的功能化涂层隔膜及增强电池热稳定性、安全性的特种功能隔膜,对其作用特性进行了系统分析,并对未来研究发展提出展望.     

Using graphene/TiO2 nanocomposite as a new route for preparation of electroconductive,self-cleaning,antibacterial and antifungal cotton fabric without toxicity

A novel and efficient process is reported for fabrication of electroconductive, self-cleaning, antibacterial and antifungal cellulose textiles using a graphene/titanium dioxide nanocomposite. Cotton fabric was loaded with graphene oxide using a simple dipping coating method. The graphene oxide-coated cotton fabrics were then immersed in TiCl₃ aqueous solution as both a reducing agent and a precursor to yield a fabric coated with graphene/titanium dioxide nanocomposite. The crystal phase, morphology, microstructure and other physicochemical properties of the as-prepared samples were characterized by X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy, Fourier transform infrared spectroscopy, Raman spectroscopy and UV-Vis reflectance spectroscopy. Electrical resistance, self-cleaning performance, antimicrobial activity and cytotoxicity of treated fabrics were also assessed. The electrical conductivity of the graphene/titanium dioxide nanocomposite-coated fabrics was improved significantly by the presence of graphene on the surface of cotton fabrics. The self-cleaning efficiency of the treated fabrics was tested by degradation of methylene blue in aqueous solution under UV and sunlight irradiations. The results indicated that the decomposition rates of methylene blue were improved by the addition of graphene to the TiO₂ treatment on fabrics. Moreover, the graphene/titanium dioxide nanocomposite-coated cotton samples had negligible toxicity and possessed excellent antimicrobial activity.     

Green and facile microwave-assisted synthesis of TiO2/graphene nanocomposite and their photocatalytic activity for methylene blue degradation

TiO₂ (P25)/graphene nanocomposite photocatalyst have been successfully synthesized with P25 and different ratios of graphene oxide through a green and facile one-step microwave-assisted method. Graphene oxide was restored to graphene sheets and P25 was coated on it simultaneously during the reaction. The method offers easy access to the semiconductor/graphene nanocomposites with a uniform coating and strong interactions between semiconductor and the underlying graphene sheets. The prepared P25/graphene nanocrystals hybrid has superior photocatalytic activity in the degradation of methylene blue, showing an impressive photocatalytic enhancement over P25. The improved photocatalytic activities may be attributed to increased adsorptivity of dyes, extended light absorption range, and efficient charge separation properties of a two-dimensional graphene network.     

Towards understanding the effects of carbon and nitrogen-doped carbon coating on the electrochemical performance of Li4Ti5O12 in lithium ion batteries: a combined experimental and theoretical study

We investigate the effects of carbon coating, with and without nitrogen-dopants, on the electrochemical performance of a promising anode material Li(4)Ti(5)O(12) (LTO) in lithium ion battery applications. The comparative experimental results show that LTO samples coated with nitrogen-doped carbon derived from pyridine and an ionic liquid exhibit significant improvements in rate capability and cycling performance compared with a LTO sample coated by carbon derived from toluene and the pristine LTO sample. For the first time, we construct an atomistic model for the interface between the lithium transition metal oxide and carbon coating layers. Our first-principles calculations based on density functional theory reveal that at this interface there is strong binding between the graphene coating layer and the Ti-terminated LTO surface, which significantly reduces the chemical activity of LTO surfaces and stabilizes the electrode/electrolyte interface, providing a clue to solve the swelling problem for LTO-based batteries. More importantly, electron transfer from the LTO surface to graphene greatly improves the electric conductivity of the interface. Nitrogen-dopants in graphene coatings further increase the interfacial stability and electric conductivity, which is beneficial to the electrochemical performance in energy storage applications.     

Electrically conducting,transparent, graphene based nanocomposite coatings on flexible film substrate

Transparent, electrically conducting nanocomposite coated polyethylene terephthalate (PET) films are prepared using two types of bulk synthesized few layered graphene; namely reduced graphene oxide (rGO) and liquid exfoliated graphite (EG) dispersed in ultra high molecular weight polyethylene (UHMWPE). This study focuses on application of high concentration of such nanofillers (1: 1 to 2.5: 1 ratios with polymer) in order to develop a highly conducting but ultrathin coating for better transparency. The coated PET films are characterized for their surface morphology, electrical and optical properties. High resolution transmission electron microscopic (HRTEM) images and corresponding selected area electron diffraction (SAED) patterns confirm that the graphite has been exfoliated to few layer graphene using both the synthesis routes. Transmittance values of these coated films are measured in UV visible spectrum. The rGO based samples have high transmittance (~90–95%) compared to EG based samples (~40–50%). From current-voltage (I?V) graph and surface resistivity studies, it has been observed that rGO based samples are dielectric in nature similar to UHMWPE while EG based samples are electrically conducting and its conductivity increases with its concentration. EG based nanocomposite coated samples show much better electrical conductivities (resistance 338 to 66 kΩ at different concentrations of EG) than rGO based samples.     

Application of ZIF-8 coated with titanium dioxide in cathode material of lithium-sulfur battery

Lithium-sulfur batteries have become a potential candidate for a new generation of energy storage devices due to their extremely high theoretical capacity, but their shuttle effect and poor conductivity of sulfur and final discharge products hinder their commercial development. In this paper, ZIF-8 material with a large specific surface area was successfully prepared with metallic zinc as the central atom and dimethylimidazole. After sintering at 800 °C, the mesoporous carbon material was obtained, which increased its physical adsorption of sulfur. At the same time, titanium dioxide was coated on the mesoporous carbon material to obtain a core-shell structure with a specific surface area of up to 556.1 m²/g. The titanium dioxide coating well inhibits the occurrence of the shuttle effect and at the same time improves the cycle stability of the lithium-sulfur battery. The specific discharge capacity of the battery reaches 1351 mAh/g at 0.1 C.