两种硫含量控制方法对锂硫电池性能的影响

采用高导电性碳材料和商业活性炭分别作为硫的载体,与单质硫混合后进行热处理制得SP/S和CAC/S硫碳复合材料,利用热重测试、循环伏安、交流阻抗和恒流充放电测试等分析方法,研究了正极中电极材料厚度、硫碳复合比例对电池电化学性能的影响.结果表明:适当增加电极材料厚度可以有效地改善Super-P材料电极综合电化学性能;通过改变硫碳复合比例,提高硫含量则对活性炭材料锂硫电池电极的性能提升有着显著的效果.其中,含硫量为63.60%的CAC/S正极材料首次放电比容量达到908.8 m Ah/g,活性物质利用率为54.2%,100圈循环后放电容量为594.1 m Ah/g,容量保持率达到65.4%.     

GO@S复合正极的制备及其在锂硫电池中的应用

采用Hummers法和熔融扩散法结合的方法制备了氧化石墨烯@硫(GO@S)复合正极材料,研究了此复合正极对锂硫电池电化学性能的影响.测试结果表明,GO@S复合正极大幅度提高了电池的比容量、有效改善了电池的倍率性能和循环稳定性.在0.1 C倍率下,初始放电容量高达1 044 mA·h/g;0.5 C倍率下经过100次的充放电循环后,库伦效率为96%,容量保持率为78.5%.     

S/石墨烯复合材料的水热法制备及其电化学性能研究

采用水热法制备了S/石墨烯复合材料,并利用XRD,SEM,TEM等手段考察了其微观结构及形貌特征,发现石墨烯呈现多层状,与硫复合后能将其充分包覆。以复合材料为正极、锂为负极组装成扣式电池进行CV,EIS及充放电等电化学性能测试。结果表明:添加石墨烯后硫正极的可逆性明显改善,多次充放电后电池内阻有所增加,在0.3mA/cm2电流密度下放电,首次放电比容量为1 145mAh/g,经30次充放电循环后仍可稳定在500mAh/g。     

玉米芯基多孔碳的制备及其在锂硫电池中的应用

锂硫电池理论比容量高、成本低、环境友好,但硫正极仍面临导电性差、容量衰减快、体积膨胀等问题。采用生物质废弃物玉米芯作为碳源,KOH为活化剂,通过不同工艺制备了三种多孔碳材料。利用XRD、SEM、BET等对多孔碳产品的物相形貌等进行表征后发现,采用一次活化工艺所制备的多孔碳材料具有大量相互贯通的孔道结构,故具有高的比表面积(1 578.64 m~2/g)与较大的孔容(0.93 cm~3/g)。覆硫后用于锂硫电池正极,可作为三维导电骨架显著提高硫正极的导电率,并对单质硫表现出较高的吸附性能。电化学测试表明改性正极材料首次放电比容量为1 050.7 mAh/g,50周循环后容量保持率为50.4%。综合对比表明,一次活化工艺为利用此类生物质废弃物制备多孔碳材料提供了优化方案。     

介孔碳的制备及其对锂硫电池性能的影响

文章采用硬模板法制备了介孔碳,与单质硫混合制备了锂硫电池正极材料,采用BET、XRD、FESEM等测试手段对材料的性能进行表征,并研究了以介孔碳、导电石墨和碳纳米管为导电基体的锂硫电池的电化学性能。结果表明,硫/介孔碳复合材料为正极的电池在0.1C的放电倍率下首次放电比容量为1 389mA·h/g,0.2C倍率下首次放电比容为1 313mA·h/g,100次循环后,库仑效率保持在95%以上,其电化学性能在3种复合材料中最优。     

多孔碳的模板比例对锂硫电池性能的影响

文章采用不同质量比的葡萄糖和碳酸钙模板制备了3种多孔碳,再与单质硫复合成3种硫碳正极材料;测试计算了3种多孔碳的比表面积和孔径分布,观测分析了硫碳复合材料的形貌结构,测试了电池的电化学性能。研究结果表明:当葡萄糖与碳酸钙的质量比为4∶4时,制备的多孔碳与硫复合后装配的电池电化学性能最优;在0.2C的放电倍率下锂硫电池首次放电容量为1 480 mA·h/g,100次循环后仍能保持在630mA·h/g,库伦效率接近100%。     

多壁碳纳米管涂层修饰苘麻基生物碳/硫复合正极材料的制备及对锂硫电池性能的影响

锂硫(Li-S)电池因高理论能量密度在众多新型电池中受到广泛关注,但存在硫正极导电性差、多硫化物的穿梭等问题,制约其商业应用。针对上述问题,本次试验制备苘麻基生物碳(AC),通过熔融扩散法与升华硫(S)复合形成碳/硫复合材料(AC@S),并使用碳涂层法在正极材料表面涂覆多壁碳纳米管(MWCNTS)作为Li-S电池正极片与隔膜之间的夹层,进一步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Li-S电池的容量和循环性能。AC@S+MWCNTs电池首次放电容量为1 242.8 mAh·g^-1,循环150次后仍保持982.4 mAh·g^-1,相同条件下比AC@S高出275.0 mAh·g^-1。将MWCNTS涂层与正极材料结合设计工艺简单,成本低,且可提高材料导电性、抑制多硫化物的穿梭效应,表现出良好的循环性能和库伦效率,是一种解决Li-S电池穿梭效应的有效途径。     

无粘结剂的柔性硫/碳纤维布电极的制备及电化学性能研究

以碳布为基底,通过浸渍法成功制备了柔性硫/碳纤维布电极.制备的柔性硫/碳纤维布电极无需添加导电剂和粘接剂,可直接用作硫正极极片组装电池,大大简化了电池制备工艺.电化学测试结果表明,硫含量为56.77%(质量分数)的硫/碳纤维布电极展现出了最好的电化学性能,即在0.1A/g电流密度下的可逆放电比容量达1 394mAh/g;充放电循环测试100次后,可逆放电容量仍然维持在733mAh/g.电化学性能的提高主要归因于碳纤维本身的导电性、柔韧性以及大量碳纤维相互交错互联的导电网络.     

基于Co-N-C改性隔膜的高性能锂硫电池

设计制备了一种钴嵌入式叶片状氮掺杂碳(Co-N-C)材料改性隔膜用于锂硫电池,借助高分散单质钴提供的活性位点实现对正极侧中间产物多硫化物的化学锚定,抑制其溶解导致的穿梭效应;利用氮掺杂碳材料的微纳结构加快离子传输速率,提高电化学反应动力学,使改性隔膜实现吸附-催化协同作用。实验结果表明,采用此改性隔膜组装的锂硫电池,首圈比容量高达1408 mAh/g,且在1 C倍率下稳定循环400圈,衰减率仅为每圈0.05%,电池性能明显提升。     

Cu_2SC复合材料的原位电化学制备及其储锂性能测试

以葡萄糖为碳源,硫代硫酸钠为硫源,一锅法原位复合制备S/C复合材料前驱体,然后在充放电循环过程中原位电化学法制备得到了Cu2S/C复合材料,并对其作为锂离子电池正极材料的电化学储锂性能进行了研究.充放电测试结果表明,Cu2S/C复合材料具有良好的循环性能,首次可逆容量为255.4mAh·g-1,100次循环后容量仍保持在252.3mAh·g-1,容量衰减很少.同时,分别在0.2,0.5和1C(1C=337mA·g-1)电流密度下进行充放电性能测试,容量分别为232.8,207.6,183.8mAh·g-1,呈现出较好的倍率性能.     

Markedness and its Interpretation in Language Use

Language markedness is a common phenomenon in languages, and is reflected from hearing, vision and sense, i.e. the variation in the three aspects such as phonology, morphology and semantics. This paper focuses on the interpretation of markedness in language use following the three perspectives, i.e. pragmatic interpretation, psychological interpretation and cognitive interpretation, with an aim to define the function of markedness.     

Features of Women's language

Language is a means of verbal communication. People use language to communicate with each other. In the society, no two speakers are exactly alike in the way of speaking. Some differences are due to age, gender, statue and personality. Above all, gender is one of the obvious reasons. The writer of this paper tries to describe the features of women＇s language from these perspectives： pronunciation, intonation, diction, subjects, grammar and discourse. From the discussion of the features of women＇s language, more attention should be paid to language use in social context. What＇s more, the linguistic phenomena in a speaking community can be understood more thoroughly.     

An Analysis of Catherine＇s Character——Wuthering Heights

Wuthering Heights, Emily Bronte＇s only novel, was published in December of 1847 under the pseudonym Ellis Bell. The book did not gain immediate success, but it is now thought one of the finest novels in the English language. Catherine is the key character of this masterpiece, because everybody and everything center on her though she had a short life. We can understand this masterpiece better if we know Catherine well.     

Lower Paleozoic oil relationships within Williston Basin, Canada

The Williston Basin is a significant petroleum province, containing oil production zones that include the Middle Cambrian to Lower Ordovician, Upper Ordovician, Middle Devonian, Upper Devonian and Mississippian and within the Jurassic and Cretaceous. The oils of the Williston Basin exhibit a wide range of geochemical characteristics defined as "oil families", although the geochemical signature of the Cambrian Deadwood Formation and Lower Ordovician Winnipeg reservoired oils does not match any "oil family". Despite their close stratigraphic proximity, it is evident that the oils of the Lower Palaeozoic within the Williston Basin are distinct. This suggests the presence of a new "oil family" within the Williston Basin. Diagnostic geochemical signatures occur in the gasoline range chromatograms, within saturate fraction gas chromatograms and biomarker fingerprints. However, some of the established criteria and cross-plots that are currently used to segregate oils into distinct genetic families within the basin do not always meet with success, particularly when applied to the Lower Palaeozoic oils of the Deadwood and Winnipeg Formation.     

低渗透非均质砂岩油藏启动压力梯度研究

理论推导与室内实验相结合,建立了低渗透非均质砂岩油藏启动压力梯度确定方法。首先借助油藏流场与电场相似的原理,推导了非均质砂岩油藏启动压力梯度计算公式。其次基于稳定流实验方法,建立了非均质砂岩油藏启动压力梯度测试方法。结果表明:低渗透非均质砂岩油藏的启动压力梯度确定遵循两个等效原则。平面非均质油藏的启动压力梯度等于各级渗透率段的启动压力梯度关于长度的加权平均;纵向非均质油藏的启动压力梯度等于各渗透率层的启动压力梯度关于渗透率与渗流面积乘积的加权平均。研究成果可用于有效指导低渗透非均质砂岩油藏的合理井距确定,促进该类油藏的高效开发。     

On Tragic Consciousness In The Works By Ernest Hemingway

As an American modern novelist who were famous in the literary world, Hemingway was not a person who always followed the trend but a sharp observer. At the same time, he was a tragedy maestro, he paid great attention on existence, fate and end-result. The dramatis personae's tragedy of his works was an extreme limit by all means tragedy on the meaning of fearless challenge that failed. The beauty of tragedy was not produced on the destruction of life, but now this kind of value was in the impact activity. They performed for the reader about the tragedy on challenging for the limit and the death.     

Achieving Unusual States of Matter Under High Pressure

正The periodicity of the elements and the non-reactivity of the inner-shell electrons are two related principles of chemistry,rooted in the atomic shell structure.Within compounds,Group I elements,for example,invariably assume the+1 oxidation state,and their chemical properties differ completely from those of the p-block elements.These general rules govern our understanding of chemical structures and reactions.Using first principles calcula-     

Exchange-Correlation and Electronic Excitation Energies from Pairing Matrix Fluctuations

We have developed an adiabatic connection to formulate the ground-state exchange-correlation energy in terms of pairing matrix linear fluctuations.This formulation of the exchange-correlation energy opens a new channel for density functional approximations based on the many-body perturbation theory.We illustrate the potential of such approaches with an approximation based on the particle-particle Random Phase Approximation(pp-RPA).This re-     

Density Functional Theory for the Response of Periodic Systems to Electric Fields Based on the Vector Potential Approach

正The electronic and nuclear(structural/vibrational)response of 1D-3D nanoscale systems to electric fields gives rise to a host of optical,mechanical,spectral,etc.properties that are of high theoretical and applied interest.Due to the computational difficulty of treating such large systems it is convenient to model them as infinite and periodic(at least,in first approximation).The fundamental theoretical/computational problem in doing so is that     

Call for Papers

<正>"The Journal of Shanghai Normal University:Mathematics"is published by Shanghai Normal University as regular issues of The Journal of Shanghai Normal University each year from 2014 in English.The editors-in-chief of the issues are professors Yuhao Cong and Maoan Han.The Journal of Shanghai Normal University was started in 1958 with