锂离子电池硅/石墨/无定形碳复合阳极材料的制备及电化学性能表征

提出并制备了一种优化结构的硅/石墨/无定形碳复合材料,材料主要通过对硅、石墨和蔗糖的混合物进行超细粉碎和热解制备,硅基材料的电化学性能得到有效改善。研究了硅/石墨/无定形碳材料的形貌、电化学性能、循环稳定性,并对硅含量进行了优化。结果表明,将纳米硅材料负载在石墨碳基体上,结合高温热解技术,可以有效提高阳极材料的电化学性能。以石墨为缓冲基体、具备导电网络和非晶碳涂层的硅/石墨/无定形碳材料表现出良好的电化学性能。硅/石墨/无定形碳材料的非晶碳涂层可以明显降低硅与电解液之间接触损耗的可能性,并通过释放硅体积变化产生的应力来帮助保持材料的稳定性。     

硅与氮化钛纳米复合材料作为锂离子电池负极的吸放锂性能研究

采用直流电弧等离子体方法合成了硅与氮化钛纳米复合材料,利用XRD,TEM等手段研究了其微观结构.结果显示,得到的纳米颗粒由Si和TiN以及部分Cu0.1Si1.9Ti组成,其形状为球形,颗粒尺寸大多分布在10～50 nm之间.用恒流充放电的方法研究了其作为锂离子电池负极的电化学行为,在锂的嵌入硅镍纳米颗粒的过程中,Si充当活性中心,而其中的TiN和Cu0.1Si1.9Ti作为惰性成分,不与Li反应,充当缓冲基体及导电剂的作用.当电流密度为150 mA·g-1时,电极的循环稳定性最好,首次可逆容量为737 mAh·g-1,20次循环后容量仍为542 mAh·g-1.在0.05～0.8V的电位区间的循环稳定性是最好的.     

Electrospinning-Enabled Si/C Nanofibers with Dual Modification as Anode Materials for High-Performance Lithium-Ion Batteries

In this work,silicon@reduced graphene oxide/pyrolytic carbon nanofibers(Si@RGO/C NFs) composite with double modified layer is prepared through electrospinning,stabilization and carbonization.In this composite,polyethylene oxide-polypropylene oxide-polyethylene oxide(P123,a non-ionic surfactant) is introduced as the dispersant,which can make silicon nanoparticles evenly dispersed in electrospinning solution to prevent it from agglomeration.Graphene modified layer can buffer the volumetric expansion of silicon nanoparticles,prevent direct contact between silicon and electrolyte as well as enhance the electrical conductivity.Moreover,carbon fibers synthesized by electrospinning can encapsulate silicon@graphene composite internally to form a double modified layer.This composite with double modified layer can further alleviate the volume change of silicon nanoparticles and avoid direct contact between silicon and electrolyte to form a stable interface.Owing to the above-mentioned merits,the Si@RGO/C NFs composite exhibits excellent cyclic stability and superior rate performance.Particularly,it maintains a specific capacity of 929 mA h g~(-1) with the retention ratio of 83.1% after 100 cycles at 0.5 A g~(-1) and delivers an outstanding rate capability of 1003 mA h g~(-1) at 2 A g~(-1).     

Silicon/flake graphite/carbon anode materials prepared with different dispersants by spray-drying method for lithium ion batteries

Silicon/flake graphite/carbon (Si/FG/C) composites were synthesized with different dispersants via spray drying and subsequent pyrolysis, and effects of dispersants on the characteristics of the composites were investigated. The structure and properties of the composites were determined by X-ray diffractometry (XRD), scanning electron microscopy (SEM) and electrochemical measurements. The results show that samples have silicon/flake graphite/amorphous carbon composite structure, good spherical appearances, and better electrochemical performance than pure nano-Si and FG/C composites. Compared with the Si/FG/C composite using washing powder as dispersant, the Si/FG/C composite using sodium dodecyl benzene sulfonate (SDBS) as dispersant has better electrochemical performance with a reversible capacity of 602.68 mA·h/g, and a capacity retention ratio of 91.58 % after 20 cycles.     

Development of High Efficient Composite Anodes

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锂离子电池用石墨负极材料改性研究进展

石墨是目前商业化锂离子电池应用最广的负极材料,日益增长的市场需求对石墨负极材料的储锂性能提出了更高的要求。概述了锂离子电池的工作原理和石墨嵌锂机制,针对石墨负极材料理论比容量(372 mA.h/g)较低和电解液兼容性较差等问题,总结了近年来石墨负极材料的改性手段,主要分为表面改性和结构调控等2类,其中表面改性技术包括氧化和卤化处理,特点是通过调控界面化学性质,可增强石墨结构的稳定性,促进稳定SEI膜的形成,但对于石墨储锂容量的提升非常有限;结构调控包括剥层法和缺陷构筑法,特点是通过扩大石墨层间距、降低石墨维度及在石墨结构上构筑缺陷,从而增加锂离子的活性位点,提供更多锂离子扩散通道,缓解循环过程中的体积变化,改善石墨与电解液的相容性,显著提升石墨的储锂性能。最后对石墨负极材料的未来发展趋势进行了展望。     

复合变质对不同镁量原位Mg2Si/Al复合材料组织的影响

在不同镁含量铸造Mg2Si/Al-Si复合材料过程中,加入混合稀土氧化物与CaCO3作为变质剂,并采用光学显微镜研究了复合变质对组织的影响.结果表明,变质剂加入量与镁的加入量有关.0.2%的混合稀土氧化物与0.3%的CaCO3使Al-10%Mg-20%Si的初生Mg2Si尺寸由原来的75μm减小到25μm左右,变质效果显著,并初步探讨了其变质机理.     

超声波对原位Mg_2Si／Al复合材料中初生Mg_2Si形态的影晌

采用光学显微镜和场发射扫描电镜,研究超声波对原位Mg2Si／A1复合材料中初生Mg_2Si形态的影响。研究结果表明：超声波处理使初生Mg2Si的晶粒尺寸从150μm降低到20μm,初生Mg_2Si形态发生改变。在二维形貌中,未实施超声波振动处理的初生Mg_2Si晶粒生长为含有空腔的粗大颗粒,共晶组织生长于其中,相应的三维形态为含有漏斗状空腔的八面体和十四面体。超声波处理后的初生Mg_2Si晶粒变成细小、实心三维形态的颗粒,颗粒棱角已发生钝化效应。     

超声波对原位Mg2Si/Al复合材料中初生Mg2Si形态的影响

采用光学显微镜和场发射扫描电镜,研究超声波对原位 Mg2Si/Al 复合材料中初生 Mg2Si 形态的影响。研究结果表明：超声波处理使初生Mg2Si的晶粒尺寸从150μm降低到20μm,初生Mg2Si形态发生改变。在二维形貌中,未实施超声波振动处理的初生Mg2Si晶粒生长为含有空腔的粗大颗粒,共晶组织生长于其中,相应的三维形态为含有漏斗状空腔的八面体和十四面体。超声波处理后的初生Mg2Si晶粒变成细小、实心三维形态的颗粒,颗粒棱角已发生钝化效应。     

高硅碳比灰铸铁形成机理的探讨

本文综述了近年来学术界对高硅碳比灰铸铁形成理论方面的研究成果。     

Synthesis and electrochemical performance of Co3O4/C composite anode for lithium ion batteries

The Co3O4/acetylene black composite anodes were successfully prepared by combination of oxalate precipitation and pyrolysis of the precipitate. The composite and its precursor were characterized by thermo-gravimetric analysis(TGA), differential thermal analysis(DTA), X-ray diffractometry(XRD), scanning electronic microscopy(SEM) and electrochemical measurements. The effects of carbon content and calcination temperature on properties of the composite were investigated in detail. The cycling performance of the Co3O4 anode is improved remarkably by the addition of carbon. As the calcination temperature rises in the range of 300-450 ℃, the crystallinity of the composites increases, but their reversible capacity and cycling stability decrease. Being charged/discharged at a current density of 0.1C rate, the optimized Co3O4/C composite anode shows a large initial reversible capacity of 757 mA-h/g, and a capacity of 743 mA-h/g is observed after 10 cycles.     

Synthesis and Electrochemical Performance of Li2MnSiO4/C as Cathode Materials with High Capacity for Lithium ion Batteries

在三元液相体系中合成了球形Li2MnSiO4/C 复合正极材料,XRD、SEM和电化学性能测试对材料进行了表征。XRD测试表明Li2MnSiO4 具有正交结构,对应Pmn21空间群。SEM显示所得样品为小于1 μm的球形颗粒。将Li2MnSiO4/C 组装成扣式电池进行电化学测试的结果表明,在1.5~4.6 V,该样品的初始充电容量达310 mAh/g,放电容量高至 286 mAh/g,为理论比容量的85.9%;循环30 次后放电比容量为142 mAh/g。     

熔融渗硅对二维编制炭/炭复合材料摩擦特性的影响

为了改善航空刹车副用炭／炭复合材料的摩擦磨损性能，对二维编制C／C复合材料的摩擦机理进行了深入的研究；对比了试样渗Si后及渗Si前的实验结果，着重研究了试样不同的渗Si量对摩擦磨损行为及特性的影内。结果发现渗Si的试样比没有渗Si试样摩擦曲线线型好，并且摩擦试验过程中的振动现象也得到了解决。但摩擦因数随着所生成SiC含量的增加，由0．35→0.32→0．28呈下降趋势；磨损量随着所生成SiC含量的增加而增大；当有大量的不均匀的SiC颗粒生成时，C／C复合材料的摩擦表面将会被剥落，并从材料的微观性能及摩擦机理方面给予了深入的分析。     

铸态球墨铸铁硅碳比的研究

研究了砂型铸态球铁中硅碳比对组织及性能的影响，总结出获得高塑、韧性铸态球铁的最佳硅碳比范围，并对球铁一次结晶石墨化过程中硅与碳两元素的相互作用进行了初步探讨，并提出将球铁中的硅碳比作为单独的成分因素。     

高Si／C值铸铁的性能及其应用

本文研究了高Si/C比铸铁的机械、铸造与切削加工性能,并系统提出了推广、应用该种铸铁的一些意见。     

原位反应自生MgO/Mg2Si增强镁基复合材料的热力学和动力学研究

对SiO2与Mg反应的热力学分析计算，在Mg的熔化温度范围内，Mg与SiO2反应生成MgO和Mg2Si。通过真空感应炉中氩气保护，在纯Mg熔体中加入SiO2原位反应自生MgO／Mg2Si增强镁基复合材料，并采用XRD、OM、ESEM、EDAX等对反应生成相的种类、形态、大小和分布等进行研究。结果表明：800℃在Mg中加入SiO2可原位反应生成Mg2Si和MgO增强相，Mg2Si为多角形和细条状，在Mg基体中分布均匀；MgO为细小的粒子状，在熔体中分布不均匀，大多则是聚集在坩蜗底部；机械搅拌可有效削弱反应添加物SiO2的动力学沉降过程，改善原住反应的动力学条件，促使反应生成的MgO在熔体中分布均匀.初步建立起SiO2与Mg反应的宏观动力学模型。     

Si/MgO composite anodes for Li-ion batteries

A Si/MgO composite anode material was prepared by a simple magnesium reduction process using silicon oxide and magnesium as starting reactants.The feasibility of this process is discussed from the thermodynamic viewpoint.The resultant composite material is mainly composed of Si and MgO components.MgO,acting as a buffer layer,can accommodate the large volume change of active Si during the charge/discharge process,thus the cycling stability is improved.Electrochemical tests demonstrate that the first charge and discharge capacities of the synthesized Si/MgO composite anode are ca.1380 and 1046 mAh g-1,respectively,with an initial coulomb efficiency of ca.76%.The magnesium reduction process provides a novel idea for the synthesis of Si-based anode materials.     

Influence of high intensity ultrasonic vibration on microstructure of in-situ synthesized Mg2Si/Mg composites

Coarse and agglomerated primary Mg2Si phase in in-situ synthesized Mg2Si/Mg composite with 4%Si was treated in remelting process by means of high intensity ultrasonic vibration. The effects of ultrasonic vibration duration and temperature on size, morphology and distribution of the primary Mg2Si were studied. The evolution mechanism was discussed. The microstructures of the composites were investigated by means of optical microscopy （OM） and scanning electronic, microscopy （SEM）. The components were inspected with energy dispersion spectrum （EDS） and X-ray diffraction （XRD）. The results indicate that ultrasonic vibration does not alter two constituents of the composites, but changes the size and distribution of aggregated primary Mg2Si particles. The size of primary Mg2Si particles decreases with the increase of vibration duration and vibrating temperature. High intensity ultrasonic has little effects on the primary Mg2Si morphology. The high intensity ultrasonic vibration is an effective means to prepare well-proportioned in-situ synthesized magnesium matrix composites.     

钇掺杂LiFePO4锂离子电池正极材料的制备与性能

用固相法合成LiFe1-xYxPO4 (x=0, 0.01, 0.02, 0.03, 0.04)锂离子电池正极材料,采用X射线衍射仪、扫描电子显微镜、粉末比电阻法和充放电性能测试表征材料的晶体结构、微观形貌、电子电导率和电化学性能。结果表明,少量的钇掺杂并未改变材料的晶体结构,但改善了材料的微观结构,提高其电子电导率,改善可逆容量和电化学性能。在10 mA/g的电流密度下,LiFe0.97Y0.03PO4首次放电容量可达146.54 mAh/g。     

碳／碳复合材料表面羟基磷灰石生物涂层的研究进展

综述了C／C复合材料表面HAp涂层的制备工艺研究进展，指出涂层与基体的结合是目前该材料存在的主要问题。在总结前人解决问题的基础上，提出了采用水热电沉积解决此问题的新方案。最后，展望了C／C复合材料表面HAp生物涂层的研究重点和发展趋势。