纳米TiO2锂离子电池负极材料的溶剂热法制备及其电化学性能

本文采用溶剂热法,以四乙醇钛为主要原材料制备TiO2。结合X-射线衍射和扫描电镜等材料结构测试分析方法和恒电流充放电电化学测试技术,研究了添加表面活性剂聚乙烯吡咯烷酮(PVP)、溶剂热反应温度和高电导性气相生长碳纤维(VGCF)的添加对TiO2结构和电化学性能的影响。研究结果表明,本方法成功制备了纳米尺寸的锐钛矿TiO2,PVP的添加能改善TiO2颗粒的分散性。较低溶剂热反应温度下合成的TiO2颗粒尺寸较细,但团聚程度大,而较高的溶剂热反应温度使TiO2的颗粒尺寸长大,但团聚程度改善。通过添加表面活性剂、控制溶剂热温度和引入VGCF,本文获得的TiO2/C复合材料作为锂离子电池负极材料在1C、5C、10C和20C的放电倍率下容量分别可达220、180、150和120mAh/g,具有良好的倍率性能。     

三维多孔C球包覆纳米SnO2复合材料的电化学性能研究

以葡萄糖为碳源,锡酸钠为锡源,通过水热法制备了三维多孔C球包覆纳米SnO2复合材料。结果表明:样品的XRD谱线都出现SnO2的特征峰,多孔SnO2/C球尺寸为100nm左右,10～50nm的SnO2颗粒被均匀地包覆在约30nm的多孔碳层中。考察了水热时间对复合材料电化学性能的影响,在水热时间6h、烧结温度500℃、烧结保温时间2h的条件下,复合电极材料具有较高的可逆容量,首次可逆比容量为581.0mAh/g,首次放充电(嵌脱锂)效率为66.48%,经50次循环后,充电比容量保持在502.9mAh/g,循环效率为99.9%,具有较好的循环性能。     

锂电池负极材料氧化锡多孔疏松纳米球的制备、表征及电化学性能研究

在不使用模板和表面活性剂的前提下,利用水热法成功制备出了具有多孔疏松结构的SnO2纳米球,该球体是由无数个小的纳米颗粒组装而成的。运用X射线粉末衍射(XRD)、扫描电子显微镜(SEM)、透射电子显微镜(TEM)和选区电子衍射(SAED)等对所得产物的晶体结构和形貌进行了表征,同时也对其作为锂离子电池负极的电化学性能进行了系统的研究。     

纳米CuO/Cu负极材料的热氧化制备及其结构和电化学性能

采用纳米铜粉为原材料,通过直接在空气气氛中氧化的方法制备了含有微量Cu的纳米CuO/Cu复合材料作为锂离子电池负极材料。采用XRD、SEM、TEM等材料结构分析方法和恒电流充放电测试技术对在250～500℃不同氧化温度下获得产物的结构和电化学性能进行研究。研究结果表明,在250～500℃下氧化4小时,纳米Cu粉基本氧化为CuO,其含量在94wt.%以上,并保持初始Cu粉的纳米尺寸。经250～450℃氧化的产物中有微量的Cu（3～4wt.%）保留下来,而500℃氧化的样品中未发现有Cu。用该方法制备的纳米CuO/Cu作为锂离子电池负极材料表现出良好的循环稳定性,其中,经450℃氧化的材料表现出最     

SnO2/石墨烯锂离子电池负极材料的制备及其电化学行为研究

以氧化石墨和氯化亚锡为原料,采用原位合成法制得SnO2/石墨烯纳米复合材料。该方法不需外加还原剂,也避免了SnO2纳米粒子和石墨烯在机械混合过程中的团聚问题。XRD和TEM等的分析结果表明,纳米SnO2颗粒都均匀地分散在石墨烯表面,其中纳米SnO2的粒径和石墨烯的厚度分别为3~6 nm和1.5~2.0 nm。电化学测试结果表明:在200 mA/g电流密度下循环100次后,SnO2/石墨烯负极材料的嵌锂容量可稳定在552 mAh/g,容量保持率比单纯纳米SnO2提高了4.4倍;在40、400、800 mA/g的电流密度下,SnO2/石墨烯负极材料的放电容量可分别保持在724.5、426.0、241.3 mAh/g,表现出较好的倍率性能,该结果归因于石墨烯良好的导电性及其二维纳米结构。     

C/SnO2/TiO2纳米复合物的制备及其电化学性能研究

通过碳化吸附在SnO2/TiO2电极上的葡萄糖制备出C/SnO2/TiO2纳米复合电极材料。采用晶体粉末衍射仪(XRD)、场发射扫描电镜(SEM)、X射线能谱分析(EDS)等手段对复合电极进行了表征。将复合电极作为锂离子电池负极材料,通过循环伏安和计时电位法研究了其电化学性能。结果表明,在大的电流密度200μA·cm-2下循环30次后,放电容量仍保持在120.1μAh·cm-2。相比SnO2/TiO2电极,C/SnO2/TiO2复合电极电化学性能显著提高,交流阻抗谱图也显示C/SnO2/TiO2纳米复合材料拥有更低的电荷转移电阻。     

Sn(HPO4)2纳米片/Sn锂离子电池负极材料的制备及性能

随着移动便携式电子设备的更新换代,人们对于锂离子电池性能的提升有了更高的要求,而作为影响其储锂电化学性能的关键因素--负极材料,其最新研究动态已经成为人们广泛关注的热点。通过插层法将α-Sn(HPO₄)₂·H₂O剥离成Sn(HPO₄)₂纳米片(SNS),在保留其层状晶体结构的同时暴露出更多的储锂活性位点,并进一步利用化学镀法将剥离得到的SNS与具有高储锂比容量的金属Sn纳米颗粒进行复合。研究表明,制得的Sn/SNS复合材料具有显著优于SNS的综合储锂电化学性能,其中,Sn/SNS-Ⅲ在0.1 A/g电流密度下的比容量为475.7 mAh/g,在0.2 A/g电流密度下经过500次循环后比容量为449.5 mAh/g,在5 A/g电流密度下经过1000次循环后容量保持率仍为63.49%。这主要归因于均匀分布在SNS表面的Sn纳米颗粒(～10 nm)能够提供额外的储锂位点,同时SNS对Sn纳米颗粒的有效支撑能够抑制其团聚并缓解其在充放电过程中的体积膨胀,因此,Sn/SNS复合材料表...     

滤纸为模板制备中空SnO2纳米管锂离子电池负极材料

以植物纤维素(滤纸)为模板,制备了中空SnO2纳米管作为锂离子电池负极材料。通过XRD、SEM、TEM和HR TEM表征产物的组分、形貌和结构,表明合成材料是由粒度大小为5~15 nm SnO2粒子组装成的中空纳米管。同时,N2吸附/脱附测试表明此材料为疏松的介孔结构。材料在电流密度100 mA/g时,可逆容量稳定在580 mAh/g,60次循环后容量仍保持为550 mAh/g。制备的中空SnO2纳米管作为锂离子电池负极材料,具有较高的放电容量和良好的电化学循环性能。     

锂离子电池用聚萘负极材料的制备及电化学性能

采用3,4,9,10-二萘嵌苯四酸二酐(PTCTA)为原料,经高温自由基聚合、气相沉积、脱氢、石墨化工艺制得锂离子电池用聚萘(PPN)负极材料。通过X射线衍射、扫描电子显微镜、激光显微拉曼光谱等检测技术对PPN负极材料的结构和表面形貌进行了分析与表征,研究了PPN作为锂离子电池负极材料的电化学行为。结果表明,PPN负极材料具有类似石墨的多片层结构,电化学测试表明,PPN负极材料具有良好的循环稳定性和倍率性能;在50mA/g电流密度下,PPN负极材料首次放电比容量为368.4mAh/g,经过200圈循环之后,PPN负极材料的放电比容量仍保持在300.3mAh/g。结果显示PPN适用于做锂离子电池负极材料。     

Sb2S3基负极材料的制备及储能性能研究进展

由于在低电位范围内的合金化/脱合金化反应机制,硫化锑（Sb₂S₃）材料的理论放电比容量高达946 mA·h·g^-1,是一种有发展前景的锂/钠/钾离子电池负极材料。然而,在电化学反应过程中Sb₂S₃材料的聚集性和较差的导电性限制了离子/电子转移,导致了较差的电化学性能,严重阻碍了其实际应用。有必要对Sb₂S₃基负极材料的结构设计和储锂/钠/钾机制及近几年来的一些重要工作进行总结。本文综述了近年来Sb₂S₃基化合物材料的研究进展,主要包括合理的结构设计和/或与碳基材料结合等策略及所涉及的电化学反应机制,并提出了进一步改善Sb₂S₃化合物负极材料的展望。     

Facile synthesis and electrochemical properties of porous SnO2 micro-tubes as anode material for lithium-ion battery

Porous SnO₂ micro-tubes were synthesized by the thermal decomposition of SnC₂O₄ precursor. The morphology of SnC₂O₄ could be preserved after the controlled heat treatment and a lot of mesopores left due to the release of gases. The mesoporous nature with a range of 3-50 nm was characterized by BET method. SEM images showed that the obtained SnO₂ samples were rhombic tube-like with swallow-tailed nozzles. When the porous SnO₂ micro-tubes were used as anode materials for lithium-ion battery, they exhibited high lithium storage capacity and coulomb efficiency. In addition, CV results demonstrated that the formation of Li₂O at high voltage was partially reversible reactions.     

In situ synthesis of SnO2/graphene nanocomposite and their application as anode material for lithium ion battery

SnO₂/graphene nanocomposite was prepared via an in situ chemical synthesis method. The nanocomposite was characterized by X-ray diffraction, filed emission scanning electron microscope and transmission electron microscope, which revealed that tiny SnO₂ nanoparticles could be homogeneously distributed on the graphene matrix. The electrochemical performance of the SnO₂/graphene nanocomposite as anode material was measured by galvanostatic charge/discharge cycling. The SnO₂/graphene nanocomposite showed a reversible capacity of 665 mAh/g after 50 cycles and an excellent cycling performance for lithium ion battery, which was ascribed to the three-dimensional architecture of SnO₂/graphene nanocomposite. These results suggest that SnO₂/graphene nanocomposite would be a promising anode material for lithium ion battery.     

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.     

An investigation of super-hydrophilic properties of TiO2/SnO2 nano composite thin films

A sol-gel dip coating technique was used to fabricate TiO₂/SnO₂ nano composite thin films on soda-lime glass. The solutions of SnO₂ and TiO₂ were mixed with different molar ratios of SnO₂:TiO₂ as 0, 3, 4, 6, 8, 9, 10.5, 13, 15, 19.5, 25 and 28 mol.% then the films were prepared by dip coating of the glasses. The effects of SnO₂ concentration, number of coating cycles and annealing temperature on the hydrophilicity of films were studied using contact angle measurement. The films were characterized by means of scanning electron microscopy, X-ray diffraction and atomic force microscopy measurements. The nano composite thin films fabricated with 8 mol.% of SnO₂, four dip coating cycles and annealing temperature of 500 °C showed super-hydrophilicity.     

One-pot synthesis of intestine-like SnO2/TiO2 hollow nanostructures

In the present study the intestine-like binary SnO₂/TiO₂ hollow nanostructures are one-pot synthesized in aqueous phase at room temperature via a colloid seeded deposition process in which the intestine-like hollow SnO₂ spheres and Ti(SO₄)₂ are used as colloid seeds and Ti-source, respectively. The novel core (SnO₂ hollow sphere)-shell (TiO₂) nanostructures possess a large surface area of 122 m²/g (calcined at 350 °C) and a high exposure of TiO₂ surface. The structural change of TiO₂ shell at different temperatures was investigated by means of X-ray diffraction and Raman spectroscopy. It was observed that the rutile TiO₂ could form even at room temperature due to the presence of SnO₂ core and the unique core-shell interaction.     

Photocatalytic performance of very thin TiO2/SnO2 stacked-film prepared by magnetron sputtering

TiO₂/SnO₂ stacked-layers are synthesized by reactive sputter deposition on the glass substrate. Very thin TiO₂/SnO₂ bilayer-photocatalysts exhibited a very high photocatalytic activity for a degradation of gaseous acetaldehyde. Both the control of an electronic structure of TiO₂ overlayer in the near-surface region and the interfacial separation of photogenerated electrons/holes in the TiO₂/SnO₂ stacked-layer are keys to improve the photocatalytic performance.     

In-situ preparation of TiO2/SnO2 nanocrystalline sol for photocatalysis

A novel preparation method to synthesize TiO₂/SnO₂ nanocrystalline sol under mild conditions was presented. Ti(OC₄H₉)₄ used as a precursor was hydrolyzed in the rutile SnO₂ nanocrystalline sol, and in-situ formed TiO₂/SnO₂ nanocrystalline sol. The crystal structure, morphology and photocatalysis performance of samples were investigated. The results show that the additional rutile SnO₂ nano grains serve as heterogeneous crystal nucleus and exhibite the inducing effect on TiO₂ grains growth, thus leading to the changes in crystalline phase and particle morphology. In addition, the photoluminescence (PL) spectra analysis indicates that TiO₂/SnO₂ composite structure induces a better charge separation, and thus the photocatalytic activity of TiO₂/SnO₂ sol is increased significantly compared with TiO₂ sol.     

Influence of aqueous hexamethylenetetramine on the morphology of self-assembled SnO2 nanocrystals

The present report details the effects of synthesis time, concentrations of hexamethylenetetramine (HMTA) and precursor tin (II) chloride solutions on the self-assembly of SnO₂ nanocrystals. High-resolution electron microscopy images revealed that the structures were made of randomly attached SnO₂ nanocrystals with sizes in between ∼2 and 5 nm. X-ray photoelectron spectroscopy (XPS) showed that the Sn3d region was characterized by the spin-orbit splitting of the Sn3d_5/2 ground state at ∼487.6 eV and by the Sn3d_3/2 excited state at ∼496.1 eV, which was attributed to the Sn⁺⁴ oxidation state of the SnO₂ samples. We also found that the self-assembly could be achieved only with aqueous tin (II) chloride solution, and not with aqueous stannic (IV) chloride solution. A plausible growth mechanism is proposed in order to analyze the distinctive self-assembly of SnO₂ nanocrystals in the presence of aqueous HMTA solution.     

Effects of MoS2 doping on the electrochemical performance of FeF3 cathode materials for lithium-ion batteries

Orthorhombic structure FeF₃ was synthesized by a liquid-phase method. The FeF₃/MoS₂ for the application of cathode material of lithium-ion battery was prepared through mechanical milling with molybdenum bisulfide. The structure and morphology of the FeF₃/MoS₂ were characterized by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The electrochemical behavior of FeF₃/MoS₂ was studied by charge/discharge, cyclic voltammetry and electrochemical impedance spectra measurements. The results show that the prepared FeF₃/MoS₂ was typical orthorhombic structure, uniform surface morphology, better particle-size distribution and excellent electrochemical performances. The initial discharge capacity of FeF₃/MoS₂ was 169.6 mAh·g^− 1 in the voltage range of 2.0-4.5 V, at room temperature and 0.1 C charge-discharge rate. After 30 cycles, the capacity retention is still 83.1%.