石墨添加对中间相炭微球电化学性能的影响

以煤焦油沥青为原料，采用聚合法制备中间相炭微球。研究了不同天然鳞片石墨添加量在相同热处理条件下得到的中间相炭微球作为锂离子电池炭负极材料的电化学性能。研究结果表明，石墨的添加使中间相炭微球内部结构变的复杂，X衍射显示石墨的添加降低了炭微球的石墨化度和晶形尺寸。随石墨添加量的增加，电池的首次充放电容量和效率有所减小，三次循环后充放电效率趋于一致。     

添加剂对中间相炭微球结构的影响

以石油渣油为原料，分别添加2％的Nl10炭黑和2％的二茂铁制备中间相炭微球，考察了这两种添加剂对中间相炭微球结构的影响。实验结果表明，与添加炭黑制备的中间相炭微球相比，添加二茂铁制备的中间相炭微球结构规整，内部含有α-Fe粒子，在热处理过程中，α-Fe粒子对微球结构的石墨化转变具有催化作用。     

成核剂对中间相炭微球性能的影响

以煤液化沥青为原料,炭黑、石油焦、石墨和针状焦为成核剂,在410℃恒温5h条件下,采用热聚合法制备中间相炭微球,并研究四种成核剂在相同热处理条件下得到的中间相炭微球,作为锂离子电池负极材料的性能.结果表明:以炭黑和石墨为成核剂可以制备得到粒度分布均匀、表面形貌较好的中间相炭微球.由电性能测试结果可知,首次可逆容量和首次效率分别为353.9mAh/g与92.9%和346.5mAh/g与92.6%.对比商品化中间相炭微球指标,发现以炭黑和石墨为成核剂制备得到的中间相炭微球,其性能与国内同类产品的性能相近.     

锂在负极材料中的扩散行为对其大倍率充放电性能的影响

采用恒电位阶跃的方法,对锂在锂离子电池负极材料中的扩散系数进行测量,对天然石墨和中间相炭微球两种负极材料进行了大倍率充放电性能测试。结果表明,锂在两种负极材料中的扩散系数是不同的,锂在天然石墨中的扩散系数较小,只有1.90×10-11cm2/s,而锂中间相炭微球中的扩散系数较大,达4.25×10-9cm2/s,扩散系数大,电极的大电流充放电性能好,天然石墨在5 C放电下放电平台升高到0.3 V,放电容量急剧减小,而中间相炭微球在5 C放电下仍能保持0.2 V左右的放电平台,放电容量保持在234 mA.h/g。     

酚醛树脂对均相成核的中间相炭微球生成的作用

在QI含量很低的沥青中加入适量的酚醛树脂，可以改变沥青生成中间相炭微球的热缩聚反应，进而改变中间相炭微球的形貌与微观结构。酚醛树脂在沥青稠环芳烃分子热缩聚过程的初期形成共晶，在后期充当炭微球的交联剂的作用，使中间相炭微球的收率增加，尺寸变大，并影响了中间相炭微球的织构，红外光谱分析表明酚醛树脂已参与了中间相炭微球的形成；偏光显微镜、扫描电镜形象地表征出了中间相炭微球的微观织构以及酚醛树脂的作用。     

添加对甲苯磺酸对中间相炭微球制备的影响

以中温煤沥青为原料,在对甲苯磺酸(PTSA)不同添加量下,420℃恒温2h热缩聚制备中间相炭微球.利用元素分析、激光粒径分析、扫描电镜分析等手段对所得产物进行表征,研究了对甲苯磺酸添加量对中间相炭微球制备的影响.结果表明:在煤沥青中添加PTSA可以提高中间相炭微球的收率和C/H;中间相炭微球的平均粒径随PTSA添加量的增加呈先减小后增大的趋势;添加量约1%时,所得中间相炭微球粒径小,尺寸分布窄,球形度好.     

中间相炭微球制备高密高强炭/石墨材料的研究现状

为了对中间相炭微球制备高密高强炭／石墨材料的研究现状有所了解，并且对实验和实际生产起到指导作用，本文通过参阅大量中外文献，讨论了不同原料及制备方法制得的中间相炭微球、炭微球的球径、预氧化温度及时间、成型压力及时间、热处理温度及升温速率、保温时间对炭／石墨制品的力学性能及微观结构的影响。并对中间相炭微球制备高密高强炭／石墨材料中存在的问题和研究方向提出了自己的见解。     

芳烃共炭化对煤基中间相炭微球生成的影响

为研究芳烃共炭化对制备炭微球的影响,以中温沥青为原料,采用热缩聚法制备中间相炭微球,添加富芳烃组分蒽油,利用红外光谱表征原料结构,对生成的中间相炭微球进行元素分析、偏光分析以及粒度分析等,研究了不同蒽油添加量对中间相炭微球收率、C/H原子比、粒径等方面的影响。结果表明,最佳工艺操作条件为缩聚温度440℃,反应时间8 h。蒽油的存在可有效降低反应体系黏度,促进小球的长大和融并,适量添加蒽油可有效提高炭微球收率,使其粒度范围更加集中;而过量添加蒽油会降低原生喹啉不溶物的密度,不利于缩聚反应。蒽油添加量为5%时较合适,此时中间相炭微球收率为52.59%,C/H原子比为1.91,D10和D90分别为5.795和41.202μm。     

碳酸丙烯酯含量对中间相炭微球负极材料电化学性能的影响

碳酸丙烯酯(PC)溶剂具有极低的熔点和较高的介电常数,因此作为锂离子电池电解液溶剂,可以有效提高锂离子电池的低温性能。但由于PC易与锂离子在石墨负极表面发生共嵌入而破坏石墨结构,从而导致电池性能急剧变差。以结构稳定的中间相炭微球为负极,利用循环伏安、充放电循环测试和交流阻抗测试方法,研究了不同PC溶剂含量电解液对中间相炭微球电化学性能的影响。结果表明,中间相炭微球结构稳定,当PC含量增加到40%时仍未发生共嵌入现象。同时,随着PC含量的增加,中间相炭微球的循环性能逐步衰减。而PC含量为10%时,中间相炭微球具有最佳的循环性能,其与在不含PC溶剂的电解液中的循环性能相比,没有明显变化,循环100次后的放电比容量为207.1 m A·h/g,容量保持率为57.5%。     

热处理温度对锂离子电池用中间相炭微球结构及性能的影响

中间相炭微球作为一种重要的锂离子电池的负极材料,其结构直接关系到锂离子电池的充放电性能。以沥青为原料在惰性环境下,进行热缩聚反应,制备出中间相炭微球。采用XRD手段分别对炭化样品的和石墨化样品（热处理温度不同的炭微球）进行结构分析,又通过恒电流仪对他们的充放电性能进行了测试和结果比较。探讨了热处理温度对中间相炭微球结构及其性能的影响。     

煤焦油中吡啶不溶物及聚合条件对中间相炭微球收率,球径及其分布的影响

研究了煤焦油聚合制备中间相炭微球过程中，原料中PI的含量及聚合条件对中间相炭微球的球径及球径分布的影响。发现中间相炭微球的球径，随原料中PI的含量增加而减少，球径分布变窄，随聚合时间的延长，所产生的中间相炭微球球径增大，球径分布变宽。通过控制原料中一次PI的含量及聚合条件，获得较窄粒径分布的中间相沥青炭微球。     

Molten salt synthesis and antioxidation property of SiC-coated mesocarbon microbeads

Mesocarbon microbead (MCMB) is a prospective candidate as the raw material for nuclear graphite. However, the poor resistance to high-temperature oxidation limits its application. Herein, a dense SiC coating was prepared by molten salt synthesis on the surface of MCMB to improve its antioxidation performance. The effect of molten salt synthesis reaction time on the phase composition, microstructure, and antioxidation performance of the SiC-coated MCMB particles was investigated. A theoretical model was established to explain the SiC coating growth rule well, in conformity with the carbon vacancy diffusion mechanism in SiC coating. The SiC coating synthesized for 7 h with the thickness of .385 µm remarkably promoted the high-temperature antioxidation property of MCMB. The kinetics analysis indicated that the SiC coating obstructed the oxygen diffusion effectively during the oxidation process. The as-fabricated SiC-coated MCMBs with good oxidation resistance show great promise for application in nuclear industry and other antioxidative fields.     

商业化的锂离子电池石墨负极材料的研究进展

综述了锂离子电池石墨负极材料的研究进展,对MCMB、天然石墨与人造石墨、炭纤维为代表的石墨负极材料目前的研究和应用现状进行了详细的论述,并对石墨类炭负极的发展作了展望。     

Changes in the structure and functional groups produced during the fluorination of mesophase microbeads

The mesocarbon microbead (MCMB) fluorides with different fluorine contents were obtained in the temperature range of 100–110 °C in the presence of the mixed gas containing fluorine and nitrogen. The MCMB fluorides were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, X-ray photoelectron spectroscopy, scanning electron microscopy and elemental analysis. The results showed that the carbon lamination of the MCMBs was severely destroyed, which was indicated by a dramatic increase in the interlayer spacing of the resultant materials from 0.345 nm of the MCMBs to the range of 0.656 to 0.722 nm. Further studies on diversity of functional groups indicated that the whole fluorination reaction process comprises two steps: include a first diffusion of fluorine gas molecules inside the voids formed due to loose packing of MCMB molecules, and then fluorination. The two steps interacted with each other and jointly determined the apparent speed of the reaction. The original lamination structure of the MCMBs was completely destroyed for volume expansion of the resultant materials and diffusion of fluorine/nitrogen mixed gases. The final MCMB fluorides are themselves a conglomeration of particles with diameters ranging from 1 to 3 μm.     

Carbon foams with high compressive strength derived from mixtures of mesocarbon microbeads and mesophase pitch

Carbon foam with relatively high compressive strength and suitable thermal conductivity was prepared from mixtures of mesocarbon microbeads (MCMBs) and mesophase pitch, followed by foaming, carbonization and graphitization. The influence of addition amount of MCMB on the properties of as-prepared carbon foams was investigated in detail. Results showed that addition of MCMBs into mesophase pitch could significantly reduce the amount and length of cracks in carbon foams, which results in increase of compressive strength of carbon foams. Carbon foam with high compressive strength of 23.7 MPa and suitable thermal conductivity of 43.7 W/mK, was obtained by adding 50% MCMBs into mesophase pitch, followed by foaming, carbonization and graphitization.     

Densification of MCMB–SiC composites via two-step hot pressing

Mesocarbon microbead–SiC (MCMB–SiC) composites with 30 wt% MCMBs were densified using a two-step hot pressing method. Based on the pyrolysis of the initial MCMB powders, the effects of the pressing schedule on densification were investigated and the optimal first-step pressing temperature was determined. To reveal the influence of temperature on their microstructures, the raw MCMB powders were heat-treated at different temperatures in the range 400–1400 °C. The morphologies and degrees of carbonisation at different temperatures were additionally studied. The results showed that densification was mainly affected by the micro-gaps in the lamellar structure formed during the pyrolysis of the MCMBs. When the samples were first hot-pressed at a lower temperature and then at a higher temperature, the densification pressure required was effectively decreased. Furthermore, when the samples were first pressed at an appropriate temperature, the relative density of the composites was improved to a rather high value of 98.6%. The two-step hot pressing method was effective in fabricating dense C–SiC composites with high C content.     

不同尺寸MCMB石墨化性能的比较

采用X射线衍射方法分析了3种不同尺寸MCMB的石墨化性能。结果显示3种MCMB都具有良好的石墨化性能,但由于外形尺寸的不同,其石墨化性能具有明显的差别。     

炭化条件对针状焦结构的影响

以除去喹啉不溶物的中温煤沥青为原料,分别在不同的反应温度和保温时间下制备了中间相炭微球(MCMB);在磁场条件下制备了有序结构针状焦;通过扫描电镜(SEM)考察了不同反应条件下中间相炭微球和针状焦的形貌,讨论了中间相形成影响因素对针状焦结构的影响.结果表明,中间相形成阶段的反应温度、保温时间和体系黏度对针状焦的结构和性能具有重要影响,磁场对针状焦的流线型结构有促进作用.