锂离子电池负极活性材料Li4Ti5O12的研究进展

描述了Li4Ti5O12的晶体结构、性能、合成方法以及掺杂改性的研究现状。Li4Ti5O12作为锂离子电池的负极材料，在Li嵌入和脱出的过程中，其晶型不发生改变，体积变化小于1％，被称之为“零应变材料”。目前主要合成方法为固相反应法和溶胶-凝胶法。     

Chemically driven synthesis of Ti3+ self-doped Li4Ti5O12 spinel in molten salt

Surface doping of Li₄Ti₅O₁₂ (LTO) with Ti³⁺ ions is an effective way to enhance its electrochemical properties for lithium ion batteries (LIBs). Herein, a molten salt approach was reported to synthesize Ti³⁺ self-doped LTO powder. The reaction mechanism and the role of molten salt for the synthesis have been systemically discussed. Finally, electrochemical performance of the LTO powder was preliminarily evaluated as anode material of LIBs. The molten salt accelerated the mass transportation for the formation of LTO by transferring a solid diffusion to the diffusion of ions in a liquid media. Self-doping of Ti³⁺ ions on the surface of LTO particles was achieved by controlling equilibriums of chemical reactions in the reactor. Electrochemical performance of the LTO powders was effectively promoted by doping Ti³⁺ ions on the surface. The discharge capacity of the Ti³⁺ self-doped LTO powder prepared at 850°C was 171 mAhg⁻¹, and the capacity dacayed 9.9% after 200 cycles at a rate of 0.5 C.     

无定形TiO2合成尖晶石Li4Ti5O12的性能

用无定形TiO2与Li2CO3高温固相反应合成了性能良好的"零应变"电极材料Li4Ti5O12. XRD, SEM和激光粒度分析表明,产物结晶度好,无杂质相,为纯立方尖晶石相,Li4Ti5O12颗粒呈砾石状形貌,有团聚现象,平均粒度约2.66 μm. Li4Ti5O12电极具有较宽的充放电平台,循环性能稳定. 以0.1 C电流比率恒电流充放电,首次放电容量和循环容量分别达180和150 mA·h/g. 交流阻抗谱研究发现,Li4Ti5O12不同嵌锂程度下的电导率对其电极的电化学阻抗具有较大影响,电极的Warburg阻抗曲线斜率与其荷电状态相关.     

二次锂离子电池负极材料Li4Ti5O12的研究进展

Li4Ti5O12由于其长的循环寿命及高的安全性能,成为二次锂离子电池,特别是动力电池的优秀候选材料.本文综述了负极材料Li4Ti5O12的结构、合成方法、物理特性和电化学性能,着重介绍了各种元素的掺杂对Li4Ti5O12循环容量、充放电电压平台及高倍率性能的影响.     

Li4Ti5O12/Fe3O4复合材料的制备及其电化学性能

以醋酸锂和钛酸四正丁酯为原料,制备了纯相Li_4Ti_5O_(12),再用简单的水热法合成Li_4Ti_5O_(12)/Fe_3O_4复合材料作为锂离子电池的负极材料,通过XRD、SEM以及电池测试系统对纯相Li_4Ti_5O_(12)和Li_4Ti_5O_(12)/Fe_3O_4复合材料进行了结构、形貌及电化学性能测试。结果表明,制得的复合物具有较好的球形结构且粒径较小(200～300 nm),综合电化学性能较好。由于复合的Fe_3O_4有较高的理论容量,该Li_4Ti_5O_(12)/Fe_3O_4复合材料表现出比纯相Li_4Ti_5O_(12)大的容量,在1.0 C下循环100圈后,Li_4Ti_5O_(12)/Fe_3O_4的放电比容量仍能达到470.2 m A·h/g,同时也表现出比纯相Li_4Ti_5O_(12)更优的倍率性能。     

共沉淀法制多孔类球型钛酸锂及电性能研究

用NH4HCO3为起泡剂共沉淀法成功的合成出一种多孔类球形钛酸锂,并对它的结构及电化学性能进行了研究。经测试表明合成出的Li4Ti5O12振实密度达到1.68 g/cm3,采用XRD粉末衍射测试表明产物为纯相尖晶石型Li4Ti5O12,扫描电镜表明产物为平均尺寸为2~5μmd的多孔的类球体结构。在1.0~3.0 V下充放电0.1 C、1 C、1.5 C、2 C、3 C倍率下首次放电容量分别为176.4、151.6、143.8、138.5 mAh/g。     

提高钛酸锂负极材料倍率性能的研究进展

锂离子动力电池目前存在的主要问题为快速充电和安全性能较差。与石墨负极相比,钛酸锂负极能够明显提高锂离子动力电池的快速充电和安全性能,具有较大的应用前景。介绍了钛酸锂的嵌脱锂机制,分析了提高钛酸锂倍率充放电性能的主要方法,发现钛酸锂与金属和碳基材料复合,能够显著提高材料的电化学性能;通过控制钛酸锂形貌,也可得到倍率性能良好的钛酸锂,但是材料的振实密度较低;制备由纳米级一次粒子组成的微米级二次粒子,材料兼具纳米级一次粒子优越的电化学性能和微米级粒子较高的振实密度。总体而言,高性能钛酸锂材料的设计和制备已经取得了重大进展,然而目前钛酸锂电池面临的主要问题是其胀气行为,所以未来的研究重点将是揭示和研究钛酸锂电池的胀气机理和解决机制。     

Bi@Bi4Ti3O12/TiO2 films on glass with photocatalytic and self-cleaning performance

A stable and translucent Bi@Bi₄Ti₃O₁₂/TiO₂ film was fabricated on conventional glass substrates for the first time. The film exhibited a good photocatalytic performance and efficient self-cleaning capability against organic dyes under full spectral irradiation and visible light irradiation. Bi₄Ti₃O₁₂/TiO₂ film was first prepared on a glass substrate with colloidal silica as a high temperature binder, followed by implantation of nanoscale Bi in it by an in-situ partially reduction of Bi₄Ti₃O₁₂ to generate Bi@Bi₄Ti₃O₁₂/TiO₂ films. The improved photocatalytic ability is probably attributed to the surface plasmon resonance of Bi atom as well as the enhanced electron transfer efficiency and synergistic effect of Bi₄Ti₃O₁₂ and TiO₂. According to trapping experiments, hydroxyl radicals (OH) were active species in the photocatalytic degradation of dyes under full spectral light irradiation and possible photocatalytic mechanism was proposed. The film prepared in this work may well have potential practical applications in many aspects, such as cleansing treatments for high building external decorative panels and also systematic characterization of the film suggests that the in-situ reduction is an effective and simple way to produce nanoscale Bi@Bi₄Ti₃O₁₂.     

锂离子电池负极材料Li4Ti5O12的研究进展

Li4Ti5O12作为锂离子电池的负极材料, 在Li 嵌入和脱出的过程中,其晶型不发生改变,被称之为“零应变材料”。因而具有优良的循环性能和平稳的放电电压,能够避免电解液分解现象或保护膜的生成,安全性和可靠性得以大大改善。详细描述了Li4Ti5O12的结构和电化学性能,介绍了Li4Ti5O12的两种合成方法以及掺杂改性研究的现状。     

Tuning fermi level and band gap in Li4Ti5O12 by doping and vacancy for ultrafast Li+ insertion/extraction

Li₄T_i5O₁₂ (LTO) attracts great interest due to the “zero strain” during cycles but the poor electronic and ionic conductivity critically impede the practical application. Herein, we report a synergy strategy of tuning localized electrons to shift Fermi level and band gap by Mg/Zr co-doping and oxygen vacancy incorporation, which significantly improves Li⁺ and electronic transport. More importantly, the intrinsic synergistic mechanism has been revealed by neutron diffraction, X-ray absorption spectra, and first-principles calculations. The “elastic effect” of lattice induced by Mg/Zr co-doping allows LTO to accommodate more oxygen vacancies to a certain degree without a severe lattice distortion, which largely improves the electronic conductivity. Mg/Zr co-doping and oxygen vacancy incorporation effectively enhanced the dynamic characteristics of LTO electrode, achieving the excellent rate performance (90 mAh/g at 20C) and cycle stability (96.9% after 500 cycles at 10C). First-principles calculations confirm Fermi level shifts to the conduction band, and the band gap becomes narrowed due to the synergistic modulation, and the intrinsic mechanism of the enhanced electronic and Li-ion conductivity is clarified. This study offers some insights into achieving the fast Li⁺ insertion/extraction by tuning the crystal and electronic structure with lattice doping and oxygen vacancy engineering.     

制备方法对尖晶石Li4Ti5O12负极材料的性质影响

采用高温固相法、热聚合法和改良溶胶-凝胶法制备锂离子电池负极材料Li4Ti5O12。通过X-射线衍射、扫描电镜、恒电流充放电及电化学阻抗等技术和手段表征合成产物的结构、形貌及电化学性能。结果表明：溶胶-凝胶法合成的粉末为纯相Li4Ti5O12,而高温固相法和聚合法合成的Li4Ti5O12则存在TiO2杂相。高温固相法合成的Li4Ti5O12粉末晶粒最大,溶胶-凝胶法合成的粉末晶粒最小,分布最为均匀,晶粒尺寸约为80nm。高温固相法、热聚合法和溶胶-凝胶法制备的Li4Ti5O12粉末首次放电容量分别为161.6mAh/g、165.9mAh/g和171.5mAh/g,循环25次后的容量保持率分别为84.7%、87.7%和94.3%,溶胶-凝胶法合成的Li4Ti5O12粉末电化学性能最好。     

尖晶石型Li4Ti5O12锂离子电池负极材料研究现状

尖晶石型Li4Ti5O12因其在循环过程中具有良好的稳定性和安全性以及优良的快速充电性能,成为锂离子二次电池负极材料研究的热点。较完备的介绍了锂离子电池负极材料尖晶石型Li4Ti5O12的国内外研究制备方法,通过比较,详细描述了各方法存在问题及优缺点,给出了相应问题的解决方案,同时对尖晶石型Li4Ti5O12作为锂离子动力电池负极材料的发展趋势进行了展望,使用Li4Ti5O12负极材料的电池最有可能作为HEV动力电池率先得到应用。     

负极材料Li_4Ti_5O_(12)合成中优化原料组成的研究

以不同的钛源(锐钛矿型TiO2、金红石型TiO2和无定形TiO2)和不同的锂源(Li2CO3和LiOH.H2O),采用高温固相合成法合成Li4Ti5O12,并对Li4Ti5O12的合成工艺进行了优化。经试验发现,在900℃下以锐钛矿型TiO2和Li2CO3为原料合成的Li4Ti5O12具有良好的电化学性能,Li4Ti5O12材料在Li+嵌入和脱出的过程中,其晶型不发生变化。     

锂离子电池负极材料Li4Ti5O12/C的制备与表征

针对Li₄Ti₅O₁₂导电性和倍率性能差的缺陷,以PEG为碳源采用溶胶-凝胶法制备出电池负极材料Li₄Ti₅O₁₂/C,考察不同分子量聚乙二醇PEG(400、600、1000)做碳源制备的Li₄Ti₅O₁₂/C复合材料电化学性能的优劣,采用热重分析仪(TG)、X射线衍射仪(XRD)、扫描电镜(SEM)、透射电镜(TEM)、恒流充放电、倍率放电、交流阻抗(EIS)等方法对材料进行了结构表征和电化学性能测试。结果表明:以PEG1000为碳源时得到的Li₄Ti₅O₁₂/C,0.1C下首次放电比容量为143.5 mA·h·g^-1,2C的倍率下仍然保持了105 mA·h·g^-1的比容量,容量保持率达到73.17%,并且此材料有最小的电阻,在大电流条件下有良好的电化学性能。     

水热法制备钛酸铋粉体的研究

以TiCl4乙醇溶液和Bi（NO3）3·5H2O为原料．NaOH为矿化剂，其摩尔配比的关系为TiCl：Bi（NO3）3·5H2O：NaOH=0．1：0．75：1．5．用水热法合成钙钛矿结构的钛酸铋粉体。讨论了水热合成条件（前驱物和粉体处理、晶化时间、填充率）对钛酸铋粉体结构和形貌的影响。XRD、SEM分析表明，在240℃，晶化时间16h，填充比为60％的条件下，可制备平均晶粒粒径为9～12nm，团聚较轻，颗粒边界明显．球形的钛酸铋粉体。     

片状Bi4Ti3O12的合成及表征

采用熔盐法制备了Bi4Ti3O12粉体,研究了煅烧温度和盐的加入量对粉体显微形貌的影响.结果表明:Bi4Ti3O12晶粒呈较规则的薄片状四边形;烧温度的升高,晶粒尺寸显著增大,a-b面取向生长明显;盐与反应原料的质量比为1:1时,晶粒尺寸分布均匀,为6～8μm;晶粒生长遵循Ostwald熟化机理.     

LiNO3-TiO2-尿素体系燃烧合成锂离子电池负极材料Li4Ti5O12及电化学性能

以纳米TiO2和LiNO3为原料,尿素为燃料,燃烧法合成了锂离子电池负极材料Li4Ti5O12. 利用XRD、SEM和恒电流充放电、循环伏安和交流阻抗对其进行表征. 结果表明,预设炉温850℃,尿素与锂摩尔比1,焙烧8 h,制备得到平均粒径小于500 nm、粒度分布均匀的纯相尖晶石型结构Li4Ti5O12,并具有良好的电化学性能,具有1.5 V充放电平台,在0.1 C倍率下(1 C=170 mA·h/g),其首次充放电容量达到168 mA·h/g,经过100次循环后放电比容量仍有162 mA·h/g,容量保持率96.4%.     

钛酸铋陶瓷靶材的热压烧结

纯相、高致密度、结晶良好的陶瓷靶材是物理气相沉积薄膜的前提.采用热压烧结方法制备钛酸铋(Bi4Ti3O12)陶瓷靶材,重点研究了制备工艺对靶材的物相、微观结构和致密度的影响.以Bi2O3和TiO2微粉为原料,采用固相反应法,在800℃合成出纯相的Bi4Ti3O12粉体;加入过量3wt%的Bi2O3,可以有效防止烧结过程中因Bi挥发所产生的杂相,得到纯相的Bi4Ti3O12陶瓷;采用热压烧结方法,进一步实现了Bi4Ti3O12粉体的致密烧结,确定了适宜的制备条件为850℃,30MPa,2b,在该条件下制备的Bi4Ti3O12陶瓷致密度达到99%,晶粒呈片层状,大小约2-4μm,可满足靶材制备薄膜的需求.     

Fabrication,microstructure, and optical properties of Yb:Y3ScAl4O12 transparent ceramics with different doping levels

Transparent Yb:Y₃ScAl₄O₁₂ (Yb:YSAG) ceramics with different ytterbium doping concentrations such as 5, 10, 15, 20 at.% have been successfully fabricated by solid-state reactive sintering. All the obtained ceramics are in dense and homogeneous structure after sintering at 1820°C for 30 hours and with a posttreatment by hot isostatic pressing at 1750°C for 3 hours with 200 MPa pressure. We systematically analyzed the influence of Yb³⁺ doping concentration on the microstructure and optical properties of the ceramics. The 10 at.% Yb:Y₃ScAl₄O₁₂ ceramics with a thickness of 3.2 mm show the best transparency as high as 80.9% at 1100 nm. The laser emission of the 10 at.% Yb:YSAG ceramics was tested, resulting in a maximum slope efficiency of 67.6% and a maximum output power of 11.3 W under quasi-continuous wave pump conditions. The tuning range spanned from 990 to 1071 nm.     

硅基铌掺杂Bi_4Ti_3O_(12)薄膜溶胶-凝胶工艺的制备及铁电性改善研究

采用溶胶-凝胶(Sol-Gel)法制备了铌元素(Nb)取代Ti元素的Bi4Ti3O12(BTN)铁电薄膜,研究不同掺杂浓度,不同退火温度等工艺对BTN薄膜的微观特性及剩余极化强度、矫顽场等电性能的影响。研究表明,650℃进行退火的BTN薄膜生长形态,晶粒开始呈棒状生长;当温度高于850℃时,薄膜的c轴生长取向增长趋势不再明显。铁电性方面,对Ti进行2%掺杂取代的BTN薄膜的铁电性能最佳。从而获得了BTN薄膜制备的合理工艺参数。