锂离子电池微晶石墨复合材料的制备及电性能研究

动力锂离子电池对负极材料的综合性能和成本提出更高的要求。本文以微晶石墨为原料,X-8沥青作为包覆剂和黏结剂,通过一体化粉碎整形和二次造粒制得一种复合微晶石墨,其首次可逆比容量和库伦效率分别达到354.4 mA·h/g和92.2%。在LiFePO_4/C电池体系中,1 200次循环后电池的容量保持率达到91%。     

天然微晶石墨提纯工艺及可逆储锂性能

天然微晶石墨含量丰富,晶粒微小,表现为各向同性,是制备锂离子电池负极材料的极好原料,但其纯度不高,利用盐酸和氟硅酸对浮选后微晶石墨进行混酸提纯处理.实验结果表明:当液固比为2:1、HF体积分数为50％、提纯时间为3 h、提纯温度为70℃时固定碳含量最高,达99％;结合XRD、SEM、EDS和Raman分析可知,混酸提纯后微晶石墨纯度提高,层间距变小,结晶度提高;提纯后的微晶石墨首次放电比容量为778.9 mAh/g,首次库伦效率增加到61.3％,循环性能、充放电效率和倍率性能均提高,阻抗值均降低.     

天然石墨球形化工艺研究

随着国产电池对汞含量的限制和低汞化的要求,天然石墨作为制备低汞、无汞电池的优质导电材料,与我国"绿色"碱锰电池得到了同步发展,但要求石墨粉体粒度范围窄、振实密度大.作者利用微细粒子复合化设备对鳞片石墨和微晶石墨的球形化工艺进行了较深入地研究.结果表明球形化处理后,鳞片石墨和微晶石墨的形状均有较大的改善,球形度得到较大幅度的提高,其中鳞片石墨长径比与整形前的长径比相比分别降低了32.75%和48.94%,振实密度提高了85%以上,而且成球率高.     

单颗粒人造石墨负极材料的制备及储锂性能研究

随着低碳经济的快速推进,人造石墨技术得到飞速的发展。国内外学者对人造石墨的包覆、石墨化、电化学及储锂机理进行了大量的研究,取得了丰硕的成果,但对粒度大小对电化学及储锂特性的影响研究较少。针对这一问题,从表面形貌、粒度分布、首次库伦效率和充放电比容量、循环测试几个方面,对单颗粒人造石墨的颗粒大小对储能特性的影响进行研究,所得研究成果具有一定的理论和实践价值。     

锂离子电池用硅-石墨/炭复合负极材料的电化学性能研究（英文）

以纳米硅、石墨和马铃薯淀粉为原料制备硅-石墨/炭复合负极材料,探讨复合材料的制备工艺对其电化学性能的影响,并采用扫描电镜和X-射线衍射法对材料的颗粒形貌和微晶结构进行表征。研究表明:当复合材料中m(Si)/m(graphite)为1∶4,球磨时间为10 h时,复合材料经20次循环后其可逆容量仍为466 mA·h/g,显示出良好的电化学性能,进一步分析表明纳米硅和石墨均对复合材料的可逆容量做出贡献,而且复合材料中含量较高的石墨的颗粒形貌和微晶结构对其电化学性能起关键性作用。     

电解液PS含量对锂离子电池性能的影响

考察了电解液中PS添加剂含量对锂离子电池初始容量及内阻、高温储存性能、倍率性能、常温循环性能的影响。电解液中PS添加剂含量对于电池初始容量及内阻影响不大。电解液中PS添加剂含量越高,电池的高温储存性能越好。而随着电解液中PS添加剂含量的增加,电池的倍率性能和常温循环性能均有所下降。综合考虑,电解液中PS添加剂含量为1%时,电池性能较优。     

锂离子电池炭负极材料的研究概况

综述了作为锂离子电池炭负极材料的石墨类、非石墨类、纳米材料等方面的研究成果，介绍了上述各种材料的特点。通过对石墨类材料的改性，在炭材料中形成纳米级孔、洞、通道等都可能提高锂的可逆贮量和减少不可逆容量损失，有利于负极比容量的提高，从而有利于进一步提高锂离子电池的比能量。     

微晶石墨高温焙烧制备高纯石墨研究

以青海都兰某微晶石墨浮选精矿为原料,通过高温焙烧制备高纯石墨。利用XRF、XRD、SEM-EDS等分析原料成分、物相、形貌,系统考查焙烧温度与时间对石墨含碳量和回收率的影响。以含碳量为目标优化了焙烧时间、NaOH/石墨配料比、盐酸浓度、酸浸温度、酸浸时间等参数。结果表明,焙烧温度1 000℃,焙烧时间为20 min,NaOH与石墨矿的质量比为0.75,盐酸浓度为0.6 mol/L,酸浸温度为40℃,酸浸时间为60 min条件下,固定碳含量提高到99.898%,回收率为64.32%。高温碱熔酸浸法是用微晶石墨制备高纯石墨的有效方法,为微晶石墨的高效利用开辟新途径。     

威宁无烟煤基石墨制备及其电化学性能研究

以贵州威宁无烟煤为原料，通过物理提纯可制备低灰(1.60%)无烟煤，探究了不同石墨化温度对无烟煤基石墨微观结构的影响，并进一步考察了威宁无烟煤石墨化样品用作锂离子电池负极材料的电化学性能。研究表明：随热处理终温的升高，煤基石墨样品石墨化度和石墨晶体结构有序度逐渐提高，在2 800℃下所得煤基石墨石墨化度可达96.99%。煤基石墨的首次可逆容量和库伦效率随石墨化终温升高而逐渐提高，煤基石墨WN-2800在0.1C(1C=372 mAh/g)电流密度下首次可逆容量和库伦效率分别可达293.5 mAh/g、86.8%。煤基石墨WN-2800在1C电流密度下经过100次循环后，可逆容量为241.0 mAh/g,且库伦效率始终接近100%。煤基石墨WN-2800表现出较优异的综合电化学性能。本研究表明，威宁无烟煤可作为制备高性能煤基人造石墨的优质原料。     

精制石油焦基负极材料的电化学性能研究

以精制石油焦为原料,经球磨、炭化和石墨化制备负极材料,并组装成扣式电池.考察影响电化学性能的石墨化关键性能,包括表面形貌、比表面积、粒度分布、石墨化度、元素组成等,进行充放电、循环伏安、交流阻抗测试.结果表明,首次嵌锂容量为349.2 mAh/g,首次库伦效率为78％;500次循环后,容量上升为440.6 mAh/g,...     

Characterization of silicon- and carbon-based composite anodes for lithium-ion batteries

In recent years development of active materials for negative electrodes has been of great interest. Special attention has been focused on the active materials possessing higher reversible capacity than that of conventional graphite. In the present work the electrochemical performance of some carbon/silicon-based materials has been analyzed. For this purpose various silicon-based composites were prepared using such carbon materials as graphite, hard carbon and graphitized carbon black. An analysis of charging-discharging processes at electrodes based on different carbon materials has shown that graphite modified with silicon is the most promising anode material. It has also been revealed that the irreversible capacity mainly depends on the content of Si. An optimum content of Si has been determined with taking into account that high irreversible capacity is not suitable for practical application in lithium-ion batteries. This content falls within the range of 8-10 wt%.The reversible capacity of graphite modified with 8 wt% carbon-coated Si was as high as 604 mAh g⁻¹. The irreversible capacity loss with this material was as low as 8.1%. The small irreversible capacity of the material allowed developing full lithium-ion rechargeable cells in the 2016 coin cell configuration. Lithium-ion batteries based on graphite modified with silicon show gravimetric and volumetric specific energy densities which are higher by approximately 20% than those for a lithium-ion battery based on natural graphite.     

新型导电复合材料性能的研究

以石墨与环氧树脂为原料通过模压成型得到一种新型导电复合材料,考察了石墨粒径、环氧树脂含量及固化时间对导电复合材料性能的影响。试验结果表明,石墨粒径的减小有利于复合材料强度的提高;环氧树脂含量的增加使复合材料的强度明显提高,而导电性能却下降;并且探讨了复合材料性能随不同固化时间而变化的情况．得到了最佳固化时间。     

Electrochemical, textural and microstructural effects of mechanical grinding on graphitized petroleum coke for lithium and sodium batteries

A graphitized coke material obtained from petroleum residua was mechanically ground at different milling times between 0 and 100 h. Electrochemical reactions with both lithium and sodium are significantly altered as a function of grinding time. Short-time ball milling of graphite (1 and 5 h) induces a limited decrease in particle size and an increase in microstrain content. Simultaneously, alkali metal intercalation and electrolyte decomposition are hindered, and thus the irreversible and reversible capacities decrease. For longer milling time (up to 100 h), average crystallite size decreases and particles adopt a lamellar shape. Simultaneously, the irreversible capacity increases and correlates with an increase of the resistance, as obtained by impedance spectroscopy. Ex-situ XRD shows that extensively ground graphite samples need a higher discharge specific capacity to reach the formation of n-stages as compared to non-ground graphite, this being indicative of lithium incorporation in energetically different sites to the interlayer space. Sodium storage capacity increases with prolonged grinding time. This effect is shown here for the first time for graphitized cokes.     

沥青包覆石墨用作锂离子电池负极材料的研究

锂离子电池因其质量轻，能量密度高等优良性能，是近几年来电化学界研究的热点。但锂离子电池用石墨作负极还存在一些问题，需要对石墨改性处理。本文介绍了石墨的一种改性方法：沥青包覆石墨法，可有效降低石墨的比表面积，从而大幅度提高了石墨负极材料的首次可逆容量和库仑效率，改善电池的循环性能等。     

Optimising the performance of SiC-based varistors through composition and microstructure control

SiC varistors are employed as surge arrestors in high power/high energy niche applications. Using a model formulation based on 50 % SiC and 50 % clay plus graphite, the effects of SiC grain size, composition and graphite content were investigated. Disc and toroidal samples were sintered at 1130 °C under a reducing atmosphere; products were ～70–75 % dense. The main phases detected by SEM and XRD were SiC, SiO₂ (quartz), mullite, graphite and porosity. With increasing graphite content (zero to 11 wt%) the non-linear coefficient (α) decreased from 5.9 to 2.7, the breakdown field E_b decreased from 3346 to 36 V cm^?1, and bulk electrical resistivity fell by three orders of magnitude. As SiC grain size reduced from 120 μm to 10 μm, non-linear coefficients (α) almost doubled (3.7–6.3) and breakdown field (E_b) increased by an order of magnitude (226–2656 V cm^?1) as a result of increasing numbers of resistive grain boundaries between the device electrodes. The impurity content of SiC grains had a modest impact on electrical properties. The resistance of grain boundary regions was typically one to two orders of magnitude larger than that of grain cores.     

Ball-milling: the behavior of graphite as a function of the dispersal media

The ball-milling in liquid media leads to well organized, thin and highly anisometric graphite (HAG) crystals. The presence in the milling container of a liquid, which acts as a lubricant and decreases the violence of the shocks, is relevant. Two liquids are used: n-dodecane and water. With dodecane, inert towards graphite and the metal of the milling tools, the powder consists of pure graphite whereas with water, the graphite particles are covered with nanocrystallites (15 nm) of a magnetic compound: the maghemite (γ Fe₂O₃). The electrochemical properties of those powders are interesting. The highly anisometric graphite leads to an irreversible capacity around half of that for the initial graphite powder, in contradiction with previous results claiming that higher the surface area, the higher the irreversible capacity. In fact, milling in the presence of dodecane provokes essentially a cleavage, which increases the global area, but does not drastically change the number of edge carbon atoms, responsible for the increase of the large irreversible capacity. The graphite–maghemite composites present a high capacity, partly reversible by oxidation–reduction between iron and wustite (FeO). This reaction is made possible by the nanometric size of the particles, and therefore their high reactivity.     

含水量对粗对苯二甲酸熟化的影响

研究了高温下含水量对粗对苯二甲酸晶体粒度和固液两相中杂质浓度的影响,结果表明:熟化能增加对苯二甲酸晶体的平均粒径,但含水量变化对熟化过程影响不明显。含水量的减小有利于固相和液相中4-CBA浓度的降低,但此含水量存在一个阈值,低于此含水量对杂质的减少速率影响微小。     

MgO掺杂8YSZ陶瓷性能的研究

以MgO为添加剂,制备8YSZ陶瓷材料,研究MgO掺杂对材料致密化、显微结构、相组成和抗弯强度的影响。结果表明:引入MgO添加剂后有利于材料的致密化。当MgO含量较少时,MgO固溶于基体中,当MgO≥7wt%时,8YSZ基体中出现第二相。添加少量MgO,晶粒尺寸增大,当出现第二相时,晶粒尺寸略有减小。材料的致密化使其具有良好的抗弯强度。     

球磨粉的特点及其对炭素制品性能的影响

研究了球磨粉的特点和普通球磨粉与超细粉的差别,并根据不同粒度焦炭的吸附性计算出其粘结剂的最佳需要量。结果表明,-0.075mm球磨粉需要粘结剂量是2～1mm焦炭需要粘结剂量的3.8倍,是4～2mm焦炭需要粘结剂量的4.2倍。同时还计算了由不同粒度焦炭构成的糊料的真密度,-0.075mm球磨粉构成糊料的真密度低于0.5～0.15mm及0.15～0.075mm焦炭构成糊料的真密度,但明显高于4～2mm焦炭构成糊料的真密度。-0.075mm球磨粉的含量对炭素制品的性能有明显的影响,其含量适宜时,炭素制品的体积密度、抗折强度及弹性模量最高,电阻率最低。     

粒度对煤燃烧和热解动力学影响的量化研究

以六方石墨原子簇模拟纳米煤颗粒,采用量子化学AM1方法,研究了粒度对煤燃烧和热解动力学参数的影响规律.结果表明,粒度对煤粒燃烧和热解动力学参数有显著影响,Ea随着煤粒粒径的减小而减小,R则随粒径减小而增大,并且Ea和lnR均与粒径的倒数呈线性关系,这些影响规律与文献报道的实验结果一致.