Ultrasonically carbon coated Si nanoparticles for lithium ion batteries

A new and simple method for making nano-sized silicon/carbon composite materials was developed. The composite powders were prepared by dispersing HF-etched SiNPs in CHCl3, followed by bath sonication. Transmission Electron Microscopy (TEM) was used to identify the carbon layer outside the silicon particle. Impedance spectroscopy and cyclic voltammetry confirmed the improved electrode conductivity due to the carbon layer and the subsequent increased involvement of the silicon in the lithiation/delithiation process. The optimal composition of the composite, 20 wt.% SiNP/C, and 20 wt.% graphite, exhibited excellent cyclability after ten cycles with a reversible discharging capacity near 465 mAhg(-1) which is 1.5 times larger than that of the graphite and SiNPs electrode without ultrasonic process.     

石墨烯桥联碳-聚乙二醇包覆的Si纳米颗粒Li离子电池复合负极材料

Si是一种很有前途的Li离子电池负极材料。为解决其巨大体积形变导致的容量衰退快、循环寿命短等问题,采用简单的搅拌和热还原,利用聚乙二醇衍生的薄碳修饰Si纳米颗粒(C-PEG@Si NPs),并通过石墨烯的桥联来制备具有多级包覆结构的石墨烯桥联C-PEG包覆的Si纳米颗粒(graphene@C-PEG@Si NPs)复合材料。利用SEM、 TEM、 X射线衍射、恒流充放电测试等一系列表征测试方法对材料结构、物相和电化学性能进行分析。C-PEG与石墨烯涂层可有效地减小Li离子储存过程中Si对电解质的暴露面积并缓解其体积膨胀。研究结果表明,相比纯Si, graphene@C-PEG@Si NPs复合材料表现出优异的电化学性能,在210 mA/g的电流密度下,经过100次循环可逆比容量仍高达1 032 mA·h/g,电极在4 200 mA/g的大电流密度下循环100次,其比容量仍保持在430 mA·h/g以上。     

锂离子电池碳纳米管负极材料储锂性能研究

将碳纳米管用于锂离子电池负极材料,用循环伏安及充放电实验研究了电极的性能.结果表明,碳纳米管用作锂离子电池负极,具有较高的储锂容量,首次放电容量达560mAh/g,但首次不可逆容量损失也大,高达430mAh/g.经过第1次充放电的容量损失后,随后各次的容量损失很小,碳纳米管的循环性能趋于稳定.     

3DOM SnO2-SiO2锂离子电池负极材料的制备及电化学性能

针对SnO2锂离子电池负极材料长循环性能差的缺点,把非晶SiO2引入SnO2材料中,形成SnO2-SiO2纳米复合材料。采用聚苯乙烯(PS)胶晶作为模板,制备出三维有序大孔SnO2-SiO2纳米复合材料。研究结果表明,3DOM SnO2材料晶体结构和3DOM SnO2-SiO2材料相似,但是加入SiO2以后,3DOM SnO2-SiO2材料的长循环性能得到显著提高。在500 mAh/g的电流密度下循环100次,此时加0%Si的3DOM SnO2-SiO2材料的充电比容量急剧衰减为147 mAh/g,加5%Si的3DOM SnO2-SiO2材料的充电比容量达654 mAh/g,此外500次循环后加5%Si的3DOM SnO2-SiO2材料充电比容量增至728 mAh/g。这些结果表明SiO2能够改善3DOM SnO2材料长循环稳定性。     

硅/天然石墨/沥青炭复合材料的合成及其电化学性能

以纳米硅(Si)、天然石墨(NG)和高软化点沥青为前驱体,通过球磨和裂解制备了具有壳核结构的硅/天然石墨/沥青炭( Si-NG/PC)复合材料.考察了球磨时间、球磨速率和物料比等因素对制备材料的组成、结构及其作为锂离子电池阳极电化学性能的影响.结果表明:最佳球磨速率为300 r/min,最适宜的球磨时间为21h.所制Si-NG/PC复合材料的循环性能随PC含量的增加而提高,但其比容量却随PC含量的增加迅速降低,PC的最佳质量分数为30％.同时,Si-NG/PC复合材料的比容量随Si含量的增加而增大,为获得好的循环性能,纳米Si质量分数应低于35％.在优化条件下制备的Si-NG/PC复合材料在50个循环中表现出高的比容量和优异的循环性能.     

Fabrication of superhydrophobic surfaces by a Pt nanowire array on Ti/Si substrates

Superhydrophobic surfaces were prepared on Ti/Si substrates via the fabrication of a platinum (Pt) nanowire array. The Pt nanowire array was obtained by dc electrodeposition of Pt into the pores of an anodic aluminium oxide (AAO) template on the substrate followed by the removal of the template. Transmission electron microscopy (TEM) examination demonstrated that all the nanowires have uniform diameter of about 30?nm. Field emission scanning electron microscopy (FE-SEM) showed that the structures at both the micrometre scale and nanometre scale bestowed the prerequisite roughness on the surfaces. The chemical surface modification made the Pt nanowire array superhydrophobic. The surface modified Pt nanowire array exhibited superhydrophobicity even in corrosive solutions over a wide pH range, such as acidic or basic solutions. The results demonstrated that the Pt nanowire array will have good potential applications in the preparation of superhydrophobic surfaces.     

Fabrication of nanopore array electrodes by focused ion beam milling

Single nanopore electrodes and nanopore electrode arrays have been fabricated using a focused ion beam (FIB) method. High aspect ratio pores (approximately 150-400-nm diameter and 500-nm depth) were fabricated using direct-write local ion milling of a silicon nitride layer over a buried platinum electrode. This local milling results in formation of a recessed platinum electrode at the base of each nanopore. The electrochemical properties of these nanopore metal electrodes have been characterized by voltammetry. Steady-state voltammograms were obtained for a range of array sizes as well as for single nanopore electrodes. High-resolution scanning electron microscopy imaging of the arrays showed that the pores had truncated cone, rather than cylindrical, conformations. A mathematical model describing diffusion to an electrode located at the base of a truncated conical pore was developed and applied to the analysis of the electrode geometries. The results imply that diffusion to the pore mouth is the dominant mass transport process rather than diffusion to the electrode surface at the base of the truncated cone. FIB milling thus represents a simple and convenient method for fabrication of prototype nanopore electrode arrays, with scope for applications in sensing and fundamental electrochemical studies.     

Rheological behavior of concentrated slurry and wet granules for lithium ion battery electrodes

Dynamic rheological behaviors of concentrated slurry and wet granules made of graphite, carboxymethyl cellulose, and water have been investigated, because there are few studies on wet granules despite the importance of controlling them. The internal structure and the rheological behaviors of the wet granules were compared with those of the concentrated slurry through the X-ray computed tomography (CT) observation and large amplitude oscillatory shear (LAOS) measurement. At small strain (1%), the concentrated slurry showed larger storage modulus G′ than loss modulus G″, that is, tanδ (=G″/G′) less than 1.0. In contrast, the wet granules indicated larger G″ than G′, that is, tanδ more than 1.0. This rheological behavior of wet granules seems to be attributed to the voids that was suggested to exist in the granular layer. On the other hand, at large strain (100%), the tanδ values of the wet granules were extremely higher than those of the slurry. It appears that this behavior of wet granules is due to the collapse of the granular layer indicated by the high second-harmonic intensities observed in the LAOS measurement. These results elucidated the change of rheological behavior from slurry to wet granules with increasing solid content.     

锂离子电池隔膜材料EVOLi-OMMT的制备与性能

以聚(乙烯-乙烯醇)(EVOH),锂基蒙脱土(Li-OMMT)为主要原料,先合成了一种离子型树脂,后与锂基蒙脱土复合以制备一种全新的有机-无机杂化材料EVOLi-OMMT.采用高压静电纺丝法,将其制成锂离子电池用无纺布隔膜.先用红外表征了杂化材料的键接结构,又用SEM表征了隔膜的微观结构,后将合成的两种复合隔膜与Cel...     

Fabrication of a porous polyimide membrane using a silicon nanowire array as a template

We demonstrate that a porous polyimide membrane can be fabricated by curing liquid polyimide on a vertically oriented silicon nanowire array and selectively etching away the nanowire-array-template using xenon difluoride (XeF₂). Pore size and density using the described technique are controllable. The former is dependent on nanowire diameter and the duration of etching, whereas pore density is determined by silicon nanowire density. We believe that the described porous membrane fabrication method can be applied to various polymer and nanowire systems.     

Silicon nanowire array films as advanced anode materials for lithium-ion batteries

Silicon nanowire array films were prepared by metal catalytic etching method and applied as anode materials for rechargeable lithium-ion batteries. The films completely consisted of silicon nanowires that were single crystals. Aluminum films were plated on the backs of the silicon nanowire films and then annealed in an argon atmosphere to improve electronic contact and conduction. In addition to easy preparation and low cost, the silicon nanowire film electrodes exhibited large lithium storage capacity and good cycling performance. The first discharge and charge capacities were 3653 mAh g⁻¹ and 2409 mAh g⁻¹, respectively, at a rate of 150 mA g⁻¹ between 2 and 0.02 V. A stable reversible capacity of about 1000 mAh g⁻¹ was maintained after 30 cycles. The good properties were ascribed to the silicon nanowires which better accommodated the large volume change during lithium-ion intercalation and de-intercalation.     

Electrochemical performance of the chalcopyrite CuFeS2 as cathode for lithium ion battery

Chalcopyrite CuFeS₂ was synthesized by solvothermal process. It was used as active species to prepare cathode of lithium ion batteries together with some conducting materials. Electrochemical performance of the assembled Li/CuFeS₂ batteries was characterized by cyclic voltammetry and discharging test. Our results proved that CuFeS₂ as a new cathode material showed room-temperature specific discharging capacity of 1100 mAh g⁻¹ at a current density of 14 mA g⁻¹, and that its specific discharging capacity was higher than 500 mAh g⁻¹ at a current density of 350 mA g⁻¹. Different from what reported by Eda et al., the discharging curves presented two apparent plateaus, which were related to different cathode reactions, in the whole measured temperature range.     

射频磁控溅射制备Sn薄膜及其电化学性能研究

采用射频磁控溅射方法在铜基片上制备了锡薄膜,把在两种溅射功率(200和350W)下制备的Sn薄膜制成锂离子电池电极。用X射线衍射、电子探针、扫描电镜及充放电实验研究比较了二电极的性能。结果表明,在350W的溅射功率下制备的Sn薄膜,与基底生成了锡铜合金;锡铜合金的生成提高了Sn薄膜与铜基片的结合力,因而具有更高的循环性能,其首次嵌锂比容量为707mAh/g,30次循环后,仍保持有643mAh/g的嵌锂比容量。     

三维网络结构氧化铜纳米线锂离子电池负极材料的制备和性能研究

通过阳极氧化法和后退火处理在铜箔上合成了三维网络结构氧化铜纳米线,将其作为负极材料制备了无需添加粘结剂的锂离子电池。研究了恒压氧化时间对材料形貌和电化学性能的影响。在1C的倍率下,氧化1000 s制备的CuO纳米线表现出最高的1172 mAh/g首圈放电比容量和594 mAh/g的可逆比容量,500圈循环可逆比容量为607.6 mAh/g,可逆容量保留率为102.3%。交联的三维网络结构CuO纳米线相互支撑,提供稳定的结构,有效缓解了CuO纳米线作为锂离子电池负极材料中的体积膨胀问题,表现出了优异的倍率性能和循环寿命。     

Electrospray deposition of silver nanowire films for transparent electrodes

Silver nanowire (AgNWs) films were fabricated as transparent electrodes by electrostatic spray deposition (ESD) at atmospheric pressure and room temperature. The effects of solution concentration, spray flow rate, applied high voltage, and annealing temperature were characterized to obtain uniform films. AgNWs thin film was produced with ca. 20 Ω/[square] sheet resistance and 83% transparency in the visible range. Morphologies, optical and electrical properties, and stabilities of the films were investigated in this work. A maximum ratio of DC to optical conductivity of 288 was achieved in a 120 nm thick AgNW thin film. Chemical stability was evaluated in various solvents and we found that solvents had little effect on conductivity.     

锂离子电池正极材料LiMnBO3的研究现状

简要概括了硼酸盐类正极材料LiMBO3的国内外研究现状。对LiMnBO3的结构、性能、改性及合成方法以及LiMnBO3在上述各方面存在的不足进行了归纳总结。     

一种用于锂离子电池的无机复合隔膜

为了替代传统的聚烯烃微孔膜,对用于锂离子电池的Al₂O₃/SiO₂/PAN (聚丙烯腈)复合隔膜进行了研究。复合膜具有高度多孔性和良好液体电解液湿润性。由于高的毛细吸附作用,通过吸附液态电解液,膜极易传导锂离子。膜中Al₂O₃/SiO₂的两性特征,将电解液中的酸性HF(氟化氢)消耗掉,而HF作为现在锂离子电池所用电解液中的杂质是不可避免的。复合膜作为隔膜制备的碳/正极材料锂离子电池不仅具有优良的容量保持性、高温安全性,也显示出良好的倍率放电性和耐过充电保护性能。