Fabrication of carbon microcapsules containing silicon nanoparticles-carbon nanotubes nanocomposite by sol-gel method for anode in lithium ion battery

Carbon microcapsules containing silicon nanoparticles (Si NPs)-carbon nanotubes (CNTs) nanocomposite (Si-CNT@C) have been fabricated by a surfactant mediated sol-gel method followed by a carbonization process. Silicon nanoparticles-carbon nanotubes (Si-CNT) nanohybrids were produced by a wet-type beadsmill method. To obtain Si-CNT nanocomposites with spherical morphologies, a silica precursor (tetraethylorthosilicate, TEOS) and polymer (PMMA) mixture was employed as a structure-directing medium. Thus the Si-CNT/Silica-Polymer microspheres were prepared by an acid catalyzed sol-gel method. Then a carbon precursor such as polypyrrole (PPy) was incorporated onto the surfaces of pre-existing Si-CNT/silica-polymer to generate Si-CNT/Silica-Polymer@PPy microspheres. Subsequent thermal treatment of the precursor followed by wet etching of silica produced Si-CNT@C microcapsules. The intermediate silica/polymer must disappear during the carbonization and etching process resulting in the formation of an internal free space. The carbon precursor polymer should transform to carbon shell to encapsulate remaining Si-CNT nanocomposites. Therefore, hollow carbon microcapsules containing Si-CNT nanocomposites could be obtained (Si-CNT@C). The successful fabrication was confirmed by scanning electron microscopy (SEM) and X-ray diffraction (XRD). These final materials were employed for anode performance improvement in lithium ion battery. The cyclic performances of these Si-CNT@C microcapsules were measured with a lithium battery half cell tests.     

Preparation of Li_4Ti_5O_(12) submicrospheres and their application as anode materials of rechargeable lithium-ion batteries

We report on the preparation of spinel Li4Ti5O12 submicrospheres and their application as anode materials of rechargeable lithium-ion batteries. The spinel Li4Ti5O12 submicrospheres are synthesized with three steps of the hydrolysis of TiCl4 to form rutile TiO2, the hydrothermal treatment of rutile TiO2 with LiOH to prepare an intermediate phase of LiTi2O4+δ, and the calcinations of LiTi2O4+δ to obtain spinel Li4Ti5O12. The as-prepared products are investigated by X-ray powder diffraction (XRD), scanning el...     

TiO2纳米管阵列制备及其电化学嵌锂性能研究

本文研究了TiO2纳米管阵列制备及其嵌锂电化学性能.采用阳极氧化法制备了TiO2纳米管阵列.利用XRD、SEM、恒电流充放电、CV、EIS等手段.对所制备TiO2纳米管阵列的结构、形貌进行了分析表征及电化学性能测试.实验结果表明,制备出的TiO2纳米管阵列薄膜具有很好的循环性能.首次嵌锂容量达73.3 μAh·cm-2...     

Double perovskite oxides Sr_2Mg_(1-x)Fe_xMoO(6-δ) for catalytic oxidation of methane

The double perovskite oxides Sr2Mg1-xF exMoO6-δ were investigated as catalysts for the methane oxidation.The structural properties of catalysts were characterized in detail by X-ray diffraction,X-ray photoelectron spectroscopy and X-ray absorption spectroscopy.The catalytic property was strongly influenced by the Fe substitution.The relation between catalytic performance and the degree of Fe substitution was examined with regard to the structure and surface characteristics of the mixed oxides.The Fe-containing catalysts exhibited higher activity attributable to the possible(Fe2+,Mo6+) and (Fe3+,Mo5+)valency pairs,and the highest activity was observed for Sr2Mg0.2Fe0.8MoO6-δ.The enhancement of the catalytic activity may be correlated with the Fe-relating surface lattice oxygen species and was discussed in view of the presence of oxygen vacancies.     

Beyond the Polysulfide Shuttle and Lithium Dendrite Formation: Addressing the Sluggish Sulfur Redox Kinetics for Practical High-Energy Li-S Batteries

Electrolyte modulation simultaneously suppresses polysulfide the shuttle effect and lithium dendrite formation of lithium–sulfur (Li-S) batteries. However, the sluggish S redox kinetics, especially under high S loading and lean electrolyte operation, has been ignored, which dramatically limits the cycle life and energy density of practical Li-S pouch cells. Herein, we demonstrate that a rational combination of selenium doping, core–shell hollow host structure, and fluorinated ether electrolytes enables ultrastable Li stripping/plating and essentially no polysulfide shuttle as well as fast redox kinetics. Thus, high areal capacity (>4 mAh cm⁻²) with excellent cycle stability and Coulombic efficiency were both demonstrated in Li metal anode and thick S cathode (4.5 mg cm⁻²) with a low electrolyte/sulfur ratio (10 μL mg⁻¹). This research further demonstrates a durable Li-Se/S pouch cell with high specific capacity, validating the potential practical applications.     

电沉积制备MnO2催化剂及其在微生物燃料电池中的应用

通过电沉积的方法获得了一种具有均匀孔隙结构的海绵状二氧化锰催化剂,结合扫描电子显微镜(SEM)、X射线衍射(XRD)、X射线光电子能谱(XPS)等手段表征了所制备材料的表面形貌、结构及元素构成和赋存价态,采用线性伏安扫描(LSV)法对电沉积材料的电化学性能进行分析,考察其催化氧还原反应的活性,最后以合成的材料为阴极催化剂,构建微生物燃料电池系统,考察其在微生物燃料电池中的应用效果。结果表明,以电沉积二氧化锰为阴极催化剂的微生物燃料电池最大功率密度为975.6 mW/m~2,是以商业二氧化锰为阴极催化剂的电池的1.7倍;这表明作为一种经济、高效、环境友好的阴极氧还原催化剂,电沉积法制备的二氧化锰为实现阴极催化剂的低成本制备以及微生物燃料电池放大化推进提供了新的研究途径。     

多孔金属有机框架材料作为锂金属负极保护层助力长寿命锂氧气电池

在众多能源储存系统中,锂氧气电池以其高达3500 Wh·kg^-1的理论能量密度有望在性能上超越商用锂离子电池.然而,在电池充放电过程中,金属锂不可控的枝晶生长和严重的腐蚀问题极大地阻碍了锂氧气电池的发展.为了解决以上问题,制备了一种具有高比表面积、丰富孔道结构的金属有机框架材料（MOF-801）,并将其设计成金属锂负极的保护层应用在锂氧气电池中.在本工作中,成功合成了具有高达762.9 m²·g^-1比表面积,边长约为800 nm的立方体状纯净MOF-801材料.并且这种材料表现出对于有机电解液体系（四乙二醇二甲醚1 mol·L^-1三氟甲基磺酸锂）和强还原性的金属锂都具有很好的稳定性.得益于该材料丰富的孔道结构以及高比表面积,锂离子得以更均匀地分布在电极表面促进金属锂均匀沉积,有效避免了由于枝晶刺破隔膜而导致的短路甚至火灾事故.此外,MOF-801保护层本身的阻隔作用和材料捕捉水的特性可以帮助减少污染物质（水、氧气、强氧化性物质等）的穿梭效应带来的副反应,缓解锂氧气电池中金属锂负极的腐蚀情况.因此,将经过保护的金属锂组装成的对称电池进行测试,循环寿命长达800 h,同时充/放电过电势仅为0.023 V（未经保护的电池寿命仅为254 h,最终充/放电过电势高达5 V）,且循环阻抗大大降低,证明了这种策略有效地稳定了金属锂/电解液界面.将经过MOF材料保护的电极实际应用在锂氧气电池中,在限容量1000 mAh·g^-1,限电流500 mA·g^-1条件下,可以实现长达170圈的稳定长寿命的循环（是未经保护的电池寿命的2.88倍）.使用MOF-801保护层的锂氧气电池还表现出了高达8935 mAh·g^-1的高比容量.因此,本工作所报道的保护层策略为未来的碱金属空气电池负极保护领域提供了新颖的视角.     

二次包覆法制备煤沥青基硅/碳复合物及其锂离子电池性能

本文采用市售纳米硅为硅源,以软化点低、得碳率高、价格便宜的煤沥青作为碳源,通过两步包覆法制备了煤沥青基硅/碳(Si/C/C)复合物,并研究其作为锂离子电池负极材料的电化学性能。 结果表明,所得复合物的粒径在300~350 nm间,Si纳米粒子被C包覆并相互连结成C-Si-C网络结构,其中Si含量为27%的硅/碳复合物(Si/C/C-27%)作为锂电池电极材料表现了良好的储锂性能。 在0.1 A/g的小电流密度下,Si/C/C-27%的放电比容量为1281 mA·h/g;在3 A/g的大电流密度下,其放电比容量仍能保持在582 mA·h/g,表现了良好的倍率性能。Si/C/C-27%在2 A/g的电流密度下经过100次的循环后其比容量保持率为76.61%,表现了良好的循环稳定性。 相比于煤沥青基碳的一次包覆所得的硅/碳复合材料(Si/C),Si/C/C有效提高了Si纳米粒子的导电性并抑制了其在嵌锂和脱锂过程中的体积膨胀。 本文提出的二次包覆的新方法为制备具有优异电化学性能的锂离子电池负极材料提供了新的研究思路。     

多孔硅纳米材料的制备及在高能锂电池中的应用

多孔硅纳米材料具有巨大的比表面积,可调控的物理化学性质,在药物治疗、传感、能源储存与转化等领域拥有巨大的应用前景。尤其在高能量密度锂离子电池领域,多孔硅由于其丰富的孔道结构能有效释放充放电过程中硅体积变化带来的巨大应力以及大大地缩短锂离子传输距离,而引起了人们的广泛研究兴趣。但是,开发简便快速的方法来合成结构可调变的多孔硅纳米材料仍是当前研究的挑战。近年来,一些用来合成多孔硅纳米材料的方法已有报道。我们基于本课题组最近的研究进展和近年来相关文献,比较详细综述了近年来多孔硅纳米材料的制备方法以及重点关注其在高能锂电池领域的应用。最后,对多孔硅纳米材料的未来发展方向做了进一步的展望。     

简便的两步直接固相反应法制备N、Se共掺杂碳限域的NiSe纳米晶及其储钠性能

通过简便的两步直接固相反应,即在室温下的固相自组装反应制备Ni席夫碱配合物前驱体,然后通过高温固相热解碳化和硒化反应,原位制备了N,Se共掺杂碳限域的NiSe纳米晶复合物。采用X射线衍射(XRD)、扫描电镜(SEM)、透射电镜(TEM)、X射线光电子能谱(XPS)和热重分析(TGA)等表征技术分别对其物相、形貌结构、组分和含量等进行分析,并通过循环伏安、恒电流充放电和电化学阻抗谱等方法测试其电化学储钠性能。研究结果表明,复合物中NiSe粒子的平均尺寸为100 nm,被均匀限域在N,Se共掺杂的碳基体中;得益于该结构的优势,复合物作为钠离子电池负极材料时,在0.1 A·g~(-1)的电流密度下充放电循环100次后仍保持291 mAh·g~(-1)的可逆充电比容量,保持了首圈充电比容量的88%。同时,在5 A·g~(-1)的电流密度下,可逆充电比容量为197 mAh·g~(-1)。