多级孔碳在锂硫电池正极中的研究进展

锂硫电池因其理论能量密度高、原材料丰富、成本低廉等优点而受到广泛关注。然而硫正极电导率低、体积膨胀、以及脱嵌锂过程中多硫化物产生的穿梭效应等问题限制了锂硫电池的商业化应用。其采用导电材料作为硫载体,一方面可缓解体积膨胀,另一方面可改善正极导电性,同时一定程度上限制多硫穿梭。多级孔碳由于具有导电性优良、结构稳定、孔径及形貌可控等优点,被认为是一种理想的硫载体。从锂硫电池的发展背景出发阐述了多级孔碳作为硫载体的研究意义,首先介绍了多级孔碳材料的制备方法如硬模板法、软模板法和活化法等,进一步介绍了碳材料中的微孔、介孔及大孔在锂硫电池中提升导电性、稳定结构和抑制多硫穿梭效应的作用机理,最后对多级孔碳作为硫载体推进锂硫电池的发展前景进行了展望。     

锂硫电池硫基碳正极材料及其改性研究进展

综述了锂硫电池存在的问题和碳纤维、碳纳米管、氧化石墨烯、多孔碳四种碳材料的性能以及其在锂硫电池正极中的应用,并探讨了碳材料原位掺杂非金属(C、N、O、B等)和复合各种金属化合物对材料的导电性和对多硫化物吸附性能的影响,以及对锂硫电池循环性能的影响。提出非金属掺杂多孔碳材料复合金属化物作为锂硫电池正极碳材料来降低多硫化物的穿梭效应以及反应过程中的体积膨胀,提高活性物质利用率,进而提高锂硫电池性能。     

多壁碳纳米管夹层抑制锂硫电池穿梭效应

以多壁碳纳米管（MWCNTs）薄膜作为锂硫电池正极片与隔膜之间的夹层,可抑制多硫化物的溶解和扩散,阻止穿梭效应,减小活性物质的损失,提高锂硫电池的容量和循环性能。本文利用透射电子显微镜（TEM）和扫描电镜（SEM）等进行结构和性能的表征。电化学测试结果表明,含MWCNTs夹层的锂硫电池在0.2C倍率首次放电比容量达到1352mA·h/g,首次库仑效率接近100%,循环20次后比容量还保持在1028mA·h/g。在1C、2C和5C倍率下充放电,电池比容量分别达到902mA·h/g、782mA·h/g和509mA·h/g。     

金属聚酞菁的合成与锂硫电池性能研究

为了抑制穿梭效应,采用固相合成法合成了聚酞菁镍(NiPPc)和聚酞菁铁(FePPc)。2种金属聚酞菁含有大量的M—N₄单元,增强了基体与多硫化物的化学吸附,抑制多硫化锂的溶解,提高固硫效果,而且能催化加速硫化锂与多硫化锂间的转化反应。丰富的氮杂原子也可增强载体与单质硫或多硫化物之间的相互作用,更有效地缓解穿梭效应,改善锂硫电池的性能。结果表明,S@FePPc在0.2 C的初始放电比容量为1 086 mAh/g, 200周循环后的容量保持率为41.7%,在2 C的大电流密度下的放电比容量仍达到536 mAh/g。     

锂硫电池电解质的研究

文章综述了锂硫电池有机液态、凝胶聚合物和全固态电解质的研究进展;阐述了锂硫电池电解质现阶段研究工作中存在的问题,并展望了锂硫电池电解质未来的研究方向。     

改善锂硫电池循环性能的研究进展

综述了制约锂硫电池循环性能的因素和正极、负极、电解质对锂硫电池循环性能改善的影响。介绍了制约锂硫电池循环性能的主要因素：不可逆硫化锂的形成、硫正极多孔结构的失效和电解液组分与锂负极的副反应。分别介绍了改善锂硫电池循环性能的途径：合适的黏合剂、碳材料、正极制备工艺,锂负极保护技术,合理组分的电解质,电池结构与设计。并在此基础上对今后的发展趋势进行了展望。     

锂硫电池隔膜改性研究进展

锂硫电池因其具有较高的理论比容量和高能量密度被誉为下一代动力电池的最佳候选之一。引起研究者们的广泛关注,成为新型锂电池研究热点。隔膜作为电池的重要组成部分,起到解决多硫化锂穿梭效应和抑制锂枝晶的作用,是提升电池各方面性能的关键。商业膜因其具有良好的机械性能和适用于连续生产以及较低的成本,目前现阶段对隔膜的研究主要集中在对商业隔膜Celgard系列的改性方面。本文主要从改性隔膜涂层的种类和作用机理方面综述了锂硫电池隔膜改性的最新研究现状。     

聚乙烯吡咯烷酮包覆硫/碳复合材料的制备及其电化学性能

采用液相化学沉积法,并引入聚乙烯吡咯烷酮（PVP）制备得到聚乙烯吡咯烷酮包覆硫/碳复合材料。采用热重分析（TGA）、扫描电子显微镜（SEM）、X射线衍射（XRD）、恒流充放电和循环伏安（CV）表征其物化性能和电化学性能,结果表明,聚乙烯吡咯烷酮可有效提高硫/碳复合材料的电化学性能。0.35 C充放电时,所得聚乙烯吡咯烷酮包覆硫/碳复合材料首次放电比容量达到1 415.3 mAh/g(按单质硫的质量计算),120次后比容量保留为903.3 mAh/g,容量保持率为63.8%;2 C充放电时,首次放电比容量可达到904 mAh/g,200次后比容量仍能保持在486.8 mAh/g。     

新型AB5型氧化合金/碳复合材料作为锂离子电池负极性能研究

对回收的废旧镍氢(MH-Ni)电池负极材料AB5型储氢合金进行改性再利用,经过高温氧化处理和添加改性石墨制成复合材料后,用于高性能锂离子电池负极材料.通过X射线衍射(XBD)和电子显微镜(SEM)对材料进行了简单表征,采用恒电流充放电仪对材料进行电化学性能测试.实验结果表明,所制得的AB5型氧化合金/碳复合材料的首次充...     

On Interlayer Stability and High-Cycle Simulator Performance of Diamond-Like Carbon Layers for Articulating Joint Replacements

Diamond like carbon (DLC) coatings have been proven to be an excellent choice for wear reduction in many technical applications. However, for successful adaption to the orthopaedic field, layer performance, stability and adhesion in physiologically relevant setups are crucial and not consistently investigated. In vitro wear testing as well as adequate corrosion tests of interfaces and interlayers are of great importance to verify the long term stability of DLC coated load bearing implants in the human body. DLC coatings were deposited on articulating lumbar spinal disks made of CoCr28Mo6 biomedical implant alloy using a plasma-activated chemical vapor deposition (PACVD) process. As an adhesion promoting interlayer, tantalum films were deposited by magnetron sputtering. Wear tests of coated and uncoated implants were performed in physiological solution up to a maximum of 101 million articulation cycles with an amplitude of ±2° and −3/+6° in successive intervals at a preload of 1200 N. The implants were characterized by gravimetry, inductively coupled plasma optical emission spectrometry (ICP-OES) and cross section scanning electron microscopy (SEM) analysis. It is shown that DLC coated surfaces with uncontaminated tantalum interlayers perform very well and no corrosive or mechanical failure could be observed. This also holds true in tests featuring overload and third-body wear by cortical bone chips present in the bearing pairs. Regarding the interlayer tolerance towards interlayer contamination (oxygen), limits for initiation of potential failure modes were established. It was found that mechanical failure is the most critical aspect and this mode is hypothetically linked to the α-β tantalum phase switch induced by increasing oxygen levels as observed by X-ray diffraction (XRD). It is concluded that DLC coatings are a feasible candidate for near zero wear articulations on implants, potentially even surpassing the performance of ceramic vs. ceramic.     

锂硫电池硫/炭复合正极材料的研究进展

锂硫电池具有高比能量密度、原料丰富且对环境友好等优势,成为当前最具有吸引力的二次电池体系之一.然而循环寿命低制约着其商业化进程.本文主要综述了几十年来国内外学者在硫/炭复合正极材料方面的研究现状,并对未来新型正极材料的研究方向进行了展望.     

Mass‐Production of Electrospun Carbon Nanofiber Containing SiOx for Lithium‐Ion Batteries with Enhanced Capacity

In this study, electrospun carbon nanofibers hybridized with silicon oxide (SiO_x) are prepared by using a syringeless electrospinning system of polyacrylonitrile (PAN) solution containing tetraethylorthosilicate (TEOS) via a sequential pyrolysis process. The syringeless electrospinning system provides a large number of composite nanofibers in a short time, and the obtained composite nanofibers exhibit uniform diameter and morphology. The composite nanofiber is converted into a carbon nanofiber containing SiO_x via a simple pyrolysis. The obtained SiO_x‐carbon nanofiber mat exhibits higher charge/discharge capacity than a general carbon nanofiber, and it provides more stable retention than single crystalline silicon materials. Thus, the mass‐production of a SiO_x‐carbon nanofiber from syringeless electrospinning is a promising method to produce anodic materials for Li‐ion batteries.     

锂离子电池Ni-Sn-Sb合金负极材料的制备及其电性能研究

采用化学还原-共沉积法制备了Ni-Sn-Sb三元合金材料,用XRD和SEM对其结构和形貌进行表征。根据充放电曲线、循环伏安和交流阻抗谱,探讨了合成电极的嵌/脱锂行为。研究表明:热处理后的Ni-Sn-Sb合金材料呈不均匀粒状结构;首次放电容量达到1 625 mAh.g-1,充电容量为628 mAh.g-1,循环20次后可逆容量仍有334mAh.g-1,库仑效率稳定在90%,具有较好的电化学性能。     

碳纳米管表面功能化研究进展

碳纳米管的表面功能化修饰已成为现代纳米领域的一大研究热点,对实现碳纳米管的独特约优越性起到基础性作用。文章筒述了碳纳米管（CNTs）的结构与制备方法,对碳纳米管常见的功能化修饰进行了综述,最后对碳纳米管改性高分子材料存在的问题和发展方向进行了展望。     

Engineering zirconium-based metal-organic framework-801 films on carbon cloth as shuttle-inhibiting interlayers for lithium-sulfur batteries

Lithium-sulfur batteries have been regarded as the next-generation rechargeable batteries due to their high theoretical energy density and specific capacity. Nevertheless, the shuttle effect of lithium polysulfides has hindered the development of lithium-sulfur batteries. Herein, a novel zirconium-based metal-organic framework-801 film on carbon cloth was developed as a versatile interlayer for lithium-sulfur batteries. This interlayer has a hierarchical porous structure, suitable for the immobilization of lithium polysulfides and accommodating volume expansion on cycling. Moreover, the MOF-801 material is capable of strongly adsorbing lithium polysulfides and promoting their catalytic conversion, which can be enhanced by the abundant active sites provided by the continuous structure of the MOF-801 films. Based on the above advantages, the lithium-sulfur battery, with the proposed interlayer, delivers an initial discharge capacity of 927 mAh·g^–1 at 1 C with an extremely low decay rate of 0.04% over 500 cycles. Additionally, a high area capacity of 4.3 mAh·cm^–2 can be achieved under increased S loading.     

煅烧条件对钛酸锂电化学性能的影响

采用固相法合成钛酸锂,着重考察了煅烧温度、煅烧时间对产物比表面积、振实密度及电化学性能的影响,确定了最佳合成工艺条件。实验结果表明：煅烧温度为850℃,煅烧时间为20 h时产品的循环性能比较好,初始容量达到163.8 mAh/g,20次循环后的容量仍可达160 mAh/g以上。