羟基化多壁碳纳米管掺杂抑制锂硫电池的穿梭效应

为了抑制锂硫电池的“穿梭效应”,改善锂硫电池的电化学性能。正极片掺杂羟基化多壁碳纳米管（MWCNTs—OH）,利用亲水性羟基官能团对多硫化物的吸附作用,阻止多硫化物的扩散,增加有效物质的利用率,抑制穿梭效应的产生,提高锂硫电池的容量和循环性能。利用TEM、SEM和EDS等进行结构和性能表征。电化学测试结果表明,掺杂MWCNTs—OH的锂硫电池,放电容量明显提高。在0.1 C倍率,首次放电比容量达到1 281 mAh/g,首次库伦效率接近96.7%,循环10次后比容量还保持在882 mAh/g。在0.2 C、0.5 C和1 C倍率下充放电时,电池首次放电比容量分别达到794.2 mAh/g、712.2 mAh/g和557.3 mAh/g,显示出极佳的倍率性。      

无粘结剂三维石墨烯-硫正极的电化学性能研究

为提高电极中硫的负载量,采用水热法和热处理法制备了锂硫电池用无粘结剂三维石墨烯-硫正极材料,用比表面积测试仪、电子扫描电镜、电化学工作站以及电池测试系统对电极的比表面积、微观表面形貌和电化学性能进行了表征.结果表明:所制备的无粘结剂三维石墨烯-硫电极的最高放电比容量为517.3 mAh/g,50次循环后,放电比容量仍能保持在448.9 mAh/g,表现出较高的比容量和良好的循环性能.     

豆渣活性炭孔结构对锂硫电池性能的影响

以固体废弃物豆渣为原料,采用化学活化法制备了不同孔结构的活性炭,并以活化后的碳材料负载硫作为锂硫电池的正极材料。采用X射线衍射、扫描电镜、热重和比表面分析仪对复合材料进行结构、形貌和孔径分析,通过充放电性能测试对锂硫电池进行电化学性能分析。电化学测试结果表明,DZC/S-5复合材料在0.1C电流密度下首次放电比容量可达1 238.9mA/h,经过100次循环后,比容量保持了871.3mAh/g,平均每循环仅衰减了0.29%,库伦效率约95%,表现了最佳的电化学性能。     

切割方向对桦木衍生的取向微通道生物质炭锂硫电池隔膜性能的影响

生物源材料由于来源丰富、可循环使用、无污染, 并且能够实现多功能化而引起了广泛关注。本研究利用大自然中广泛分布的桦木树干为原料, 通过不同取向切割、去木质素和碳化等过程得到具有相应取向的微孔道结构的生物质炭, 并用作锂硫电池的隔层。生物质炭的比表面积为267.7 m ²/g, 有大量的微孔及介孔。测试结果表明: 沿与电极平面呈45°方向切割所得的生物质炭的电化学性能最好。在0.2C(1C=1650 mA/g)下该生物质炭隔层制备的锂硫电池初始比容量为979.4 mAh/g, 200次循环后保留有625.4 mAh/g, 每圈容量损失率仅为0.18%。该生物质炭隔层可以有效地吸附和阻挡多硫化锂, 减小充放电过程中产生的穿梭效应, 并且桦木的微通道结构和类蒸腾特性可以有效地提高电池的比容量、循环稳定性, 有利于锂硫电池的商业化应用。     

利用二硫苏糖醇夹层抑制锂硫电池的穿梭效应

为了抑制锂硫电池的穿梭效应,改善锂硫电池的电化学性能,尝试以二硫苏糖醇(DTT)为剪切剂,对高阶多硫化物进行剪切以阻止其溶解。将二硫苏糖醇(DTT)掺入多壁碳纳米管(MWCNTs)纸中,制得DTT夹层,将该DTT夹层置于锂硫扣式半电池正极片和隔膜之间,正极片的载硫面密度约为2 mg/cm2。SEM观察结果证实DTT均匀分散在MWCNTs纸的表面和空隙中。电化学测试结果表明引入DTT夹层结构的锂硫电池在0.05C倍率首次放电比容量达到1 288 mAh/g,首次库伦效率接近100%,在0.5C、2C、4C倍率下充放电时的比容量分别达到650mAh/g、600mAh/g、410mAh/g。DTT夹层结构的引入可有效剪切高阶多硫化物并阻止其迁移到锂负极,从而抑制穿梭效应,改善锂硫电池的循环稳定性和库伦效率。     

香蒲活性炭用于锂硫电池正极材料

通过香蒲绒的热解和KOH活化制备香蒲活性炭。香蒲活性炭的BET比表面积和孔容积分别为1 913. 7 m~2/g和0. 893 cm~3/g,主要为孔径约2 nm的微、介孔。当其用于锂硫电池正极时,碳基质的微介孔可以高度分散和负载非导电性硫,并有效持硫、抑制多硫化物的扩散;同时孔壁可以较快地进行电子输运。因此硫/香蒲活性炭复合材料具有较好的循环性能和倍率容量,0. 12C下首次放电容量可达1 150. 1 m Ah/g,100次循环后比容量为663. 3 m Ah/g。不同倍率测试表明,复合电极均具有较好的循环稳定性,1C下可逆容量约600 m Ah/g。     

氧化炭黑/Ni_3S_2-S正极材料在Li-S电池中的应用研究

制备了氧化炭黑与Ni_3S_2复合材料作为导电客体的硫正极材料,并研究了基于此硫正极的锂硫电池的电化学性能。研究结果证明,Ni_3S_2作为共同导电客体材料可以使锂硫电池具有更好的倍率性能和循环稳定性。在1C的充放电倍率下,锂硫电池在300次循环后可逆容量为595mAh/g;其中,首次放电比容量达到1163mAh/g。     

花瓣状纳米硫和球状纳米硫的制备及性能

锂硫电池因能量密度高、环境友好,被认为是最有希望的新一代能源储存装置。但是,多硫化物穿梭效应和体积膨胀等问题是锂硫电池目前所面临的巨大挑战。通过化学合成法制备了不同形貌且具有稳定规则结构的纳米硫,为电池在充放电过程中提供更多的活性位点,有效减少正极活性物质的损失,使电池的电化学性能得到提升。结果表明,花瓣状纳米硫材料在0.1C的电流密度下有740.72 mAh/g的初始容量,100次循环后容量保持在362.07 mAh/g;球状纳米硫材料在0.1C的电流密度下初始容量为825.30 mAh/g,100次循环后容量保持在418.06 mAh/g,每圈的容量衰减率仅为0.493%。     

二硫苏糖醇/多壁碳纳米管阻隔层抑制锂硫电池的穿梭效应

二硫苏糖醇(DTT)作为剪切剂,对高阶多硫化物进行剪切阻止其溶解,抑制穿梭效应的产生。以二硫苏糖醇(DTT)和多壁碳纳米管(MWCNTs)复合薄膜作为锂硫电池正极片与隔膜之间的阻隔层,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。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DTT/MWCNTs阻隔层的锂硫电池在0.2 C倍率首次放电比容量达到1 674 mAh/g,活性物质的利用率达到99.9%。在1 C充放电300次循环后,容量依然保持在780 mAh/g,是首次放电容量1 094 mAh/g的71.3%,且库伦效率保持在95.3%以上。在5 C和10 C倍率下充放电,电池比容量分别达到597和214 mAh/g。     

逐步炭化法制备锂-硫电池正极碳/硫复合材料的研究

提出一种逐步炭化法,以稀硫酸、蔗糖和单质硫为原料,制备碳/硫复合正极材料。扫描电镜、透射电镜结果显示:复合材料为粒度分布均匀的核壳结构球体,直径约为3μm;单质硫均匀填充在球体内部。此种结构有利于提高其电化学性能。在0.1C倍率下碳/硫复合正极材料首次放电比容量为1065mAh/g,60次循环之后,放电比容量趋于稳定,150次循环后的比容量仍可达到510mAh/g,库仑效率始终保持在90%以上。表明逐步炭化法可以制备适宜的锂硫电池正极材料。     

Preparation and electrochemical properties of biochar from pyrolysis of pomelo peel via different methods

Dried pomelo peel waste was employed as raw material and heated separately via three different thermal treatment methods which are vacuum tube furnace (700?°C, 300?～?1 × 10^?5?Pa), muffle furnace (300?°C in air) and hydrothermal treatment in an oven (200?°C, sealed). Therefore, three kinds of amorphous porous carbon were obtained and named as S1, S2 and S3, respectively. XRD, SEM, EDS, specific surface area and pore size analyzer have been used to characterize the morphology, composition and porosity of the biochar materials which show 3 dimensional porous framework morphologies, but only S1 possesses highest specific surface area (464.96m²/g) among the 3 biochar materials. The electrochemical properties were characterized via galvanostatic charge/discharge method, cyclic voltammetry (CV) and AC impedance. After 100 cycles of charge and discharge process, the specific capacity of the biochar S1 maintained 297.0mAh/g. The specific capacity of S2 was 103.3mAh/g and the specific capacity of S3 is 106.0mAh/g. Thus, S1 exhibits a high specific surface area and excellent electrochemical performance which may have potential application due to low cost of the biochar prepared from pomelo peel wastes.     

基体碳材料对锂硫电池性能影响的研究

采用乙炔黑、土状石墨、Cabot Vulcan XC-72炭黑、Cabot Bp2000超级导电炭黑作为硫载体制备了一系列含硫复合材料。通过X射线粉末晶体衍射(XRD)、扫描电子显微镜(SEM)、比表面积分析(BET)等分析测试手段对材料的物理性能进行表征,利用电池测试系统对材料的电化学性能进行了测试。结果表明基体材料表面结构、孔径分布及比表面积等因素都对复合材料的电化学性能造成影响,综合性能最好的基体材料为BP2000超级导电炭黑,其初始放电比容量高达1385.1mAh/g,在室温下经过30次循环之后电池放电比容量仍保持在1080.2mAh/g,容量保持率高达78%。     

煤基球形多孔碳用于锂离子电池负极材料的性能研

因具有较短的锂离子扩散路径、大的比表面积等优势, 球形碳材料在锂离子电池负极材料中展露出良好的应用前景。研究以新疆库车产煤为原料, 采用电弧放电法及化学活化法制备出了具有多孔结构的煤基球形碳。通过X射线衍射(XRD)、扫描电镜(SEM)、拉曼光谱(Raman)、氮气吸脱附法和恒电流充放电等测试手段对材料结构、形貌和电化学性能进行了表征。结果表明, 在100 mA/g的电流密度下, 煤基球形多孔碳的首次放电比容量可达到1188.9 mAh/g, 远高于商业石墨负极372 mAh/g的理论比容量。此外, 该材料还表现出了良好的循环稳定性, 经历200圈循环后的放电比容量为844.9 mAh/g。煤基球形多孔碳优异的电化学性能得益于活化过程所产生的分级孔道结构能为锂离子提供更多储存空间, 从而提高了电极的容量及循环稳定性。     

Controllable Interlayer Spacing of Sulfur‐Doped Graphitic Carbon Nanosheets for Fast Sodium‐Ion Batteries

The electrochemical behaviors of current graphitic carbons are seriously restricted by its low surface area and insufficient interlayer spacing for sodium‐ion batteries. Here, sulfur‐doped graphitic carbon nanosheets are reported by utilizing sodium dodecyl sulfate as sulfur resource and graphitization additive, showing a controllable interlayer spacing range from 0.38 to 0.41 nm and a high specific surface area up to 898.8 m² g^?1. The obtained carbon exhibits an extraordinary electrochemical activity for sodium‐ion storage with a large reversible capacity of 321.8 mAh g^?1 at 100 mA g^?1, which can be mainly attributed to the expanded interlayer spacing of the carbon materials resulted from the S‐doping. Impressively, superior rate capability of 161.8 mAh g^?1 is reserved at a high current density of 5 A g^?1 within 5000 cycles, which should be ascribed to the fast surface‐induced capacitive behavior derived from its high surface area. Furthermore, the storage processes are also quantitatively evaluated, confirming a mixed storage mechanism of diffusion‐controlled intercalation behavior and surface‐induced capacitive behavior. This study provides a novel route for rationally designing various carbon‐based anodes with enhanced rate capability.     

S‐Doped Carbon Fibers Uniformly Embedded with Ultrasmall TiO2 for Na+/Li+ Storage with High Capacity and Long‐Time Stability

Building a rechargeable battery with high capacity, high energy density, and long lifetime contributes to the development of novel energy storage devices in the future. Although carbon materials are very attractive anode materials for lithium‐ion batteries (LIBs), they present several deficiencies when used in sodium‐ion batteries (SIBs). The choice of an appropriate structural design and heteroatom doping are critical steps to improve the capacity and stability. Here, carbon‐based nanofibers are produced by sulfur doping and via the introduction of ultrasmall TiO₂ nanoparticles into the carbon fibers (CNF‐S@TiO₂). It is discovered that the introduction of TiO₂ into carbon nanofibers can significantly improve the specific surface area and microporous volume for carbon materials. The TiO₂ content is controlled to obtain CNF‐S@TiO₂‐5 to use as the anode material for SIBs/LIBs with enhanced electrochemical performance in Na⁺/Li⁺ storage. During the charge/discharge process, the S‐doping and the incorporation of TiO₂ nanoparticles into carbon fibers promote the insertion/extraction of the ions and enhance the capacity and cycle life. The capacity of CNF‐S@TiO₂‐5 can be maintained at ≈300 mAh g^?1 over 600 cycles at 2 A g^?1 in SIBs. Moreover, the capacity retention of such devices is 94%, showing high capacity and good stability.     

High-Energy Interlayer-Expanded Copper Sulfide Cathode Material in Non-Corrosive Electrolyte for Rechargeable Magnesium Batteries

Rechargeable magnesium batteries (RMB) have been regarded as an alternative to lithium-based batteries because of their abundant elemental resource, high theoretical volumetric capacity, and multi-electron redox reaction without the dendrite formation of magnesium metal anode. However, their development is impeded by their poor electrode/electrolyte compatibility and the strong Coulombic effect of the multivalent Mg²⁺ ions in cathode materials. Herein, copper sulfide material is developed as a high-energy cathode for RMBs with a non-corrosive Mg-ion electrolyte. Given the benefit of its optimized interlayer structure, good compatibility with the electrolyte, and enhanced surface area, the as-prepared copper sulfide cathode exhibits unprecedented electrochemical Mg-ion storage properties, with the highest specific capacity of 477 mAh g⁻¹ and gravimetric energy density of 415 Wh kg⁻¹ at 50 mA g⁻¹, among the reported cathode materials of metal oxides, metal chalcogenides, and polyanion-type compounds for RMBs. Notably, an impressive long-term cycling performance with a stable capacity of 111 mAh g⁻¹ at 1 C (560 mA g⁻¹) is achieved over 1000 cycles. The results of the present study offer an avenue for designing high-performance cathode materials for RMBs and other multivalent batteries.     

Enhanced hydrogen storage capacity of nanosized copper loaded active carbons treated under CO2

A kind of composites with nanosized Cu loaded on activated active carbons was prepared. The materials were characterized by X-ray diffraction (XRD) patterns, transmission electron microscope (TEM) and nitrogen adsorption. The highest surface area of 2746 m2/g was obtained for the optimized activated active carbon. TEM image and size distribution analyses show that the ball-like Cu(0) particles are dispersed homogeneously in the composites with diameters of 10-30 nm. The electrochemical hydrogen storage properties were determined and an optimized discharge capacity of 605.5 mAh/g was gotten, which corresponds to 2.24 wt% of hydrogen uptake capacity.     

负载ZnS的介孔炭复合硫正极材料的制备及性能研究

为了获得高性能的锂硫电池正极材料, 采用先超声分散再进行热处理的方法制备了负载ZnS的介孔炭复合材料(ZnS/MC), 进而用热复合法获得负载有ZnS的介孔炭复合硫正极材料(ZnS/MC/S)。XRD、SEM、EDS和N2吸附脱附等温线表明, 当ZnS含量低于17wt%时, 通过超声波分散, ZnS可以均匀负载到介孔炭中; 但热处理或提高ZnS含量时ZnS会发生聚集, 形成闪锌矿型ZnS晶相。循环伏安测试表明, ZnS对多硫离子的氧化起促进作用; 充放电测试表明, ZnS/MC/S电极的初始放电比容量为1354.6 mAh/g, 首次充放电库仑效率为98.7%; 50次循环后容量仍有650 mAh/g。     

Large reversible Li storage of graphene nanosheet families for use in rechargeable lithium ion batteries

The lithium storage properties of graphene nanosheet (GNS) materials as high capacity anode materials for rechargeable lithium secondary batteries (LIB) were investigated. Graphite is a practical anode material used for LIB, because of its capability for reversible lithium ion intercalation in the layered crystals, and the structural similarities of GNS to graphite may provide another type of intercalation anode compound. While the accommodation of lithium in these layered compounds is influenced by the layer spacing between the graphene nanosheets, control of the intergraphene sheet distance through interacting molecules such as carbon nanotubes (CNT) or fullerenes (C60) might be crucial for enhancement of the storage capacity. The specific capacity of GNS was found to be 540 mAh/g, which is much larger than that of graphite, and this was increased up to 730 mAh/g and 784 mAh/g, respectively, by the incorporation of macromolecules of CNT and C60 to the GNS.