中间相炭微球用作锂离子电池阳极的充放电性能研究

中间相炭微球（ＭＣＭＢｓ）是一种性能优异的锂离子电池阳极用炭材料。研究了经不同温度热处理的ＭＣＭＢｓ 的微观结构与充放电性能的相关性。经７００ ℃～１ ０００ ℃炭化热处理的ＭＣＭＢｓ,随着热处理温度的提高其充放电性能变好,而经１ ７００ ℃～２ ８００ ℃热处理的ＭＣＭＢｓ 的充放电性能变化与此相反。经７００ ℃热处理的ＭＣＭＢ的放电容量为４２５ ｍ Ａｈ／ｇ,超过了石墨的理论容量３７６ ｍ Ａｈ／ｇ,这是由于其内部的微孔起到了锂离子储存“仓库”的作用。     

中间相炭微球的制备及嵌锂性能考察

为了获得更高嵌锂性能的锂离子电池负极用炭材料,以质量分数为3 7%吡啶不溶物的煤焦油为原料,在450℃下自生压热缩聚制备中间相炭微球(MCMB),采用恒电流充放电技术研究所得MCMB的充放电性能.研究发现:随着MCMB平均球径的增加,首次充放电可逆容量从246mA·h/g增至540mA·h/g,首次充放电效率先增加后减小;本实验条件下平均球径为8 9μm的MCMB的充放电性能最好.     

锂离子二次电池用涂炭石墨阳极

开发了一种新型涂炭天然石墨，由这种材料制备的锂离子电池阳极材料显示了卓越的电化学性能。通过应用该涂炭技术，使得PC基电解液的电池效率得到了明显改善。     

中间相炭微球热处理用作锂离子电池负极材料

介绍了热处理工艺对中间相炭微球(MCMB)微观结构的影响及其热处理后用作锂离子电池的电化学性能.指出MCMB经2500 ℃以上高温处理虽然具有良好的充放性能,但是其理论充放电仅为372mAh/g,而MCMB经500～1500 ℃热处理后虽然具有高达1190mAh/g的首次充电容量,但是循环性能极差.而在过渡金属化合物存在下MCMB经低于1000 ℃低温修饰处理可获得充放容量高于500mAh/g、循环性能良好的锂离子电池负极材料,为轻量化、高容量锂离子电池负极材料的开发提供了新的发展方向.     

中间相炭微球作用锂离子电池阳极的充放电性能研究

中间相炭微球（ＭＣＭＢｓ）是一种性能优异的锂离子电池阳极用炭材料。研究了经不同温度热处理的ＭＣＭＢｓ的微观结构与充放电性能的相关性。经７００℃￣１０００℃炭化热处理的ＭＣＭＢｓ，随着热处理温度的提高充放电性能变好，而经１７００￣２８００℃热处理的ＭＣＭＢｓ的充放电性能变化与此相反。经７００℃热处理的ＭＣＭＢ的放电容量为４２５ｍＡｈ／ｇ，超过了石墨的理论容量３７６ｍＡｈ／ｇ，这是由于 内部的微也 到     

中间相炭微球(MCMB)的制备与应用

综述了中间相炭微球制备和应用的国内外研究现状,分析了现有工艺中存在的问题,提出了需要解决的几个关键问题。     

锂离子电池用中间相炭微球的低温表面修饰

采用CoCl2对中间相炭微球进行低温表面修饰,进行了表征和性能测量,并研究对其性能的影响.结果表明,低温热处理中间相炭微球仍以低温炭结构为主,但是微球表面的碳微晶尺寸比内部的大;低温表面热处理能够明显提高中间相炭微球的可逆容量,在不降低充电容量的情况下将首次库仑效率从52.2%提高到87.2%,并改善了循环性能.低温表面修饰使中间炭微球表面碳结构的有序化程度增强,有效地缓解了碳表面的不可逆电化学反应.     

碳纳米管/中间相炭微球复合材料锂离子电池负极材料研究

采用热缩聚法(温度为420℃、反应时间为2 h)制备出碳纳米管/中间相炭微球复合材料。研究了碳纳米管添加量对中间相炭微球的形成和形貌的影响,以及对碳纳米管/中间相炭微球复合材料充放电性能的影响。实验结果表明,5%(质量分数)的碳纳米管添加量有利于中间相炭微球的形成,碳纳米管/中间相炭微球复合材料作为负极材料的锂离子电池充放电容量可达到337 mAh/g,20次循环后容量仍保持88%。     

由中间相炭微球制备高密度各向同性炭

以中间相炭微球（ＭＣＭＢ）为原料，在常温下压制成型。所用ＭＣＭＢ由不同一次吡啶不溶物含量的煤焦油在不同的条件下聚合后通过热过滤及吡啶抽提分离而得。考察了不同原料、成型压力、热处理温度及升温速率对炭制品的密度及收缩率的影响。１０００℃下炭化后炭制品的表观密度最高达１．７５ｇ／ｃｍ３。     

乳液法制备中间相炭微球的研究

为制备高性能中间相炭微球(MesocarbonMicrobeads,简称MCMB),选用三种不同中间相含量的石油渣油沥青为原料(中间相体积含量:PP185%,PP290%,PP3100%),采用乳液法制备中间相沥青微球(MesophasePitchMi crobeads,简称MPMB),再经预氧化和炭化处理,制得圆整度好、收率高、球径分布窄的中间相炭微球。利用扫描电子显微镜(SEM)考察了MPMB的微观形貌,同时还利用激光粒度分析仪测定了MPMB的粒度分布。研究了乳液法制备MPMB的影响因素,研究结果表明:(1)耐高温硅油适宜作为乳液法的导热分散介质;(2)不同中间相含量的沥青制备微球时有其适宜的处理温度和时间(PP1:320℃,30min;PP2:330℃,30min;PP3:355℃,30min),且制得的微球收率(收率:PP1相似文献   

Facile synthesis of rutile TiO2/carbon nanosheet composite from MAX phase for lithium storage

Titanium oxide (TiO₂), with excellent cycling stability and low volume expansion, is a promising anode material for lithium-ion battery (LIB), which suffers from low electrical conductivity and poor rate capability. Combining nano-sized TiO₂ with conductive materials is proved an efficient method to improve its electrochemical properties. Here, rutile TiO₂/carbon nanosheet was obtained by calcinating MAX (Ti₃AlC₂) and Na₂CO₃ together and water-bathing with HCl. The lamellar carbon atoms in MAX are converted to 2D carbon nanosheets with urchin-like rutile TiO₂ anchored on. The unique architecture can offer plentiful active sites, shorten the ion diffusion distance and improve the conductivity. The composite exhibits a high reversible capacity of 247 mA h g⁻¹, excellent rate performance (38 mA h g⁻¹ at 50 C) and stable cycling performance (0.014% decay per cycle during 2000 cycles) for lithium storage.     

原位生长纳米炭纤维/硅复合材料及其储锂性能

采用催化化学气相沉积法在微米硅颗粒表面原位生长纳米炭纤维得到纳米炭纤维/硅复合材料.利用SEM,TEM和XRD表征了复合材料的表面形态和微观结构,并考察了其作为锂离子电池负极材料的循环性能.电化学测试表明:与纳米纤维/硅机械混合物相比,原位生长纳米炭纤维/硅复合材料具有更高的可逆容量(1042mAh/g)和更好的循环稳定性.根据SEM和交流阻抗分析结果,分析了纳米炭纤维/硅复合材料在充放电过程中的结构演变机制,其优异的电化学性能主要来源于原位生长纳米炭纤维与硅颗粒之间良好的接触性能.     

Nitrogen-doped amorphous carbon coated mesocarbon microbeads as excellent high rate Li storage anode materials

A composite anode material consisting of a stable inner core of mesocarbon microbeads and a porous nitrogen-doped amorphous carbon shell active for lithium storage is prepared. The thin birnessite MnO₂ nanosheets hydrothermally deposited on mesocarbon microbeads are in situ replaced by polypyrrole, which is then transformed to nitrogen-doped amorphous carbon layer by calcination in nitrogen atmosphere. The surface modified mesocarbon microbeads exhibit average discharge capacities of 444 and 103?mA?h?g^?1 at the current densities of 0.1 and 3?A?g^?1, respectively, obvious higher than the corresponding values of the bare sample, 371 and 60?mA?h?g^?1. Moreover, the composite anode maintains a discharge capacity of 306?mA?h?g^?1 after 500 cycles at 1?A?g^?1, suggesting an excellent cycle stability. It is believed that the nitrogen-doped amorphous carbon layer has provided additional lithium storage capacity and stabilized the structure integrity of mesocarbon microbeads. This work demonstrates that the capacity and rate performance of commercial graphitic carbons can be much improved by simply introducing a nitrogen-doped carbon coating layer active for Li storage, making them attractive for high power Li-ion batteries.     

Electrodeposition of amorphous silicon anode for lithium ion batteries

Amorphous silicon has been successfully electrodeposited on copper using a SiCl₄ based organic electrolyte under galvanostatic conditions. The electrodeposited silicon films were characterized for their composition, morphology and structural characteristics using glancing angle X-ray diffraction (GAXRD), scanning electron microscopy (SEM), and Raman spectroscopy. GAXRD and Raman analyses clearly confirm the amorphous state of the deposited silicon film. The deposited films were tested for possible application as anodes for Li-ion battery. The results indicate that this binder free amorphous silicon anode exhibits a reversible capacity of ∼1300 mAh g⁻¹ with a columbic efficiency of >99.5% up to 100 cycles. Impedance measurements at the end of each charge cycle show a non-variable charge transfer resistance which contributes to the excellent cyclability over 100 cycles observed for the films. This approach of developing thin amorphous silicon films directly on copper eliminates the use of binders and conducting additives, rendering the process simple, facile and easily amenable for large scale manufacturing.     

Polycrystalline SnO2 nanowires coated with amorphous carbon nanotube as anode material for lithium ion batteries

One-dimensional (1D) SnO₂ nanowires, coated by in situ formed amorphous carbon nanotubes (a-CNTs) with a mean diameter of ca. 60 nm, were synthesized by annealing the anodic alumina oxide (AAO) filled with a sol of SnO₂. X-ray diffraction (XRD) and selected area electron diffraction (SAED) patterns revealed that the prepared SnO₂ nanowires exist in polycrystalline rutile structure. The coating of carbon nanotubes has some defects on the wall after the internal SnO₂ nanoparticles were removed. The 1D SnO₂ nanowires present a reversible capacity of 441 mAh/g and an excellent cycling performance as an anode material for lithium ion batteries. This suggests that 1D nanostructured materials have great promise for practical application.     

锂离子电池负极材料中间相炭微球的表面镀镍修饰研究

采用化学镀的方法在石墨化中间相炭微球的表面镀覆金属镍,采用扫描电镜对镀覆后的炭微球进行了表面分析,采用X-射线衍射的方法对镀镍炭微球进行了物相分析,将镀覆后的中间相炭微球用于锂离子电池负极材料,并进行了不同倍率的充放电分析及交流阻抗研究。结果表明,在不使用活化剂和敏化剂的情况下,金属镍仍然能够沉积在炭微球的表面;炭微球的大电流放电性能大大提高,在2C放电电流下的放电容量提高了23%,镀镍后交换电流密度增大并且SEI膜电阻减小,炭微球的反应活性大大提高。     

High throughput production of nanocomposite SiOx powders by plasma spray physical vapor deposition for negative electrode of lithium ion batteries

Nanocomposite Si/SiO_x powders were produced by plasma spray physical vapor deposition (PS-PVD) at a material throughput of 480 g h⁻¹. The powders are fundamentally an aggregate of primary ∼20 nm particles, which are composed of a crystalline Si core and SiO_x shell structure. This is made possible by complete evaporation of raw SiO powders and subsequent rapid condensation of high temperature SiO_x vapors, followed by disproportionation reaction of nucleated SiO_x nanoparticles. When CH₄ was additionally introduced to the PS-PVD, the volume of the core Si increases while reducing potentially the SiO_x shell thickness as a result of the enhanced SiO reduction, although an unfavorable SiC phase emerges when the C/Si molar ratio is greater than 1. As a result of the increased amount of Si active material and reduced source for irreversible capacity, half-cell batteries made of PS-PVD powders with C/Si = 0.25 have exhibited improved initial efficiency and maintenance of capacity as high as 1000 mAh g⁻¹ after 100 cycles at the same time.     

Diffusion of lithium ions and diffusion-induced stresses in a phase separating electrode under galvanostatic and potentiostatic operations: Phase field simulations

Phase separation in an electrode of a lithium ion battery, which is a phenomenon where an active electrode material is separated into Li-rich and Li-poor phases, exists widely in many active materials and has significant impacts on the diffusion of lithium ions and diffusion-induced stresses. A phase field model is developed to study the phase separation. Firstly, the influences of various energies, such as the free energy of uniform Li-ion concentration, gradient energy and elastic energy, on phase separation are discussed. Secondly, the impacts of charge operation, e.g. galvanostatic and potentiostatic, on Li-ion diffusion and diffusion-induced stresses in a planar phase separating electrode are investigated. Calculations are also made for single phase electrodes based on Fick’s law for comparison. The obtained simulation results show that the Li-ion diffusion in a phase separating electrode depends significantly on the phase separating profile and movement of phase boundary, but it is not sensitive to charge operation. The diffusion-induced stresses also separate into high and low stress regions. Finally, based on the diffusion process and diffusion-induced stress, it is suggested that phase separation should be avoided for the sake of fast charging and mechanical reliability.     

Closely packed Si@C and Sn@C nano-particles anchored by reduced graphene oxide sheet boosting anode performance of lithium ion batteries

Both silicon and tin are promising anodes for new generation lithium ion batteries due to high lithium storage capacities (theoretically 4200 mA h g-1 and 992 mA h g-1,respectively).However,their large volumetric expansions (both are above 300 ％) usually lead to poor cycling stability.In this case,we synthesized closely packed Si@C and Sn@C nano-particles anchored by reduced graphene oxide (denoted as Si@C/Sn@C/rGO) by the way of solution impregnation and subsequent hydrogenation reduction.Sn particles with a diameter of 100 nm are coated by carbon and surrounded by Si@C particles around 40 nm in average diameter through the high-resolution transmission electron microscopy.Expansions of Si and Sn are alleviated by carbon shells,and reduced graphene oxide sheets accommodate their volume changes.The prepared Si@C/Sn@C/rGO electrode delivers an enhanced initial coulombic efficiency (78％),rate capability and greatly improved cycle stability (a high reversible capacity of nearly 1000 mA h g-1 is achieved after 300 cycles at a current density of 1000 mA g-1).It can be believed that packing Sn@C nano-particles with Si@C relieves the volume expansion of both and releases the expansion stresses.Sn@C particles enhance anode process kinetics by reducing charge transfer resistance and increasing lithium ion diffusion coefficient.The present work provides a viable strategy for facilely synthesizing silicon-tin-carbon composite anode with long life.