Li4Ti5O12/TiN复合材料的制备及电化学性能

以尿素为氮源,采用高温热处理方法在Li4Ti5O12表面自生长一层纳米尺寸厚度的TiN导电包覆膜。利用DSC-TG、Raman、TEM、FT-IR、XRD及恒流充放电等测试手段,研究热处理工艺对材料结构、形貌及电化学性能的影响。结果表明:使用适中的尿素原料含量可以获得均匀连续、厚度适中的TiN导电膜,较高的热处理温度有利于促进TiN的生成,而较短的热处理时间可以保持材料物相的纯净和较高结晶度。在尿素含量10%(质量分数)、热处理温度800℃、热处理时间20 min的工艺条件下,所制备的复合材料的容量和倍率性能最优,0.2C和3C初始放电比容量分别达到162.4和130.2 mA.h/g。     

二步煅烧法合成Li4Ti5O12材料的性能

采用超声活化对原材料Li2CO3和TiO2进行预处理,并采用二步煅烧方法制备Li4Ti5O12材料。利用X射线衍射仪、扫描电镜和电池充放电测试仪研究二步煅烧条件对材料结构、形貌及电化学性能的影响,并得到二步煅烧的最佳工艺。结果表明:采用600℃预烧温度制备的材料具有较高的纯度和结晶度;800℃高温煅烧温度下制备的Li4Ti5O12材料具有均一分散的颗粒结构;超声活化制备Li4Ti5O12的最佳煅烧工艺是600℃预烧8 h后800℃高温煅烧10 h,制备的材料在0.1C倍率下首次放电容量达170.6 mA.h/g,0.2C倍率下20次循环后的放电比容量由152 mA.h/g降至150 mA.h/g,容量保持率为98.7%。     

Fe3+掺杂Li4Ti5O12的结构及电化学性能

采用高温固相法合成Li4FexTi5-xO12(x=0.025,0.1,0.2)负极材料。通过X射线衍射、扫描电镜、充放电性能测试等对掺杂Fe3+的Li4Ti5O12材料的组成、结构、形貌进行表征,并对其电化学性能进行研究。结果表明,所合成的材料具有良好的尖晶石结构,无杂相。适当Fe3+掺杂能细化材料,提高材料的电子导电性,使材料的循环性能得到改善。Li4Fe0.025Ti4.975O12的充电容量最佳,0.1C倍率下首次充电比容量达到162.5 mA.h/g,循环性能较好。     

溶胶-凝胶法制备球形Li_4Ti_5O_(12)及其电化学性能研究

为提高Li4Ti5O12材料的振实密度,以十六烷基三甲基溴化铵(CTAB)为结构导向剂,通过溶胶-凝胶法合成了球形Li4Ti5O12材料。利用TGA/DSC、XRD、SEM、CV和恒流充放电仪对材料的结构、形貌和电化学性能进行测试。结果表明,在800℃热处理12 h所得样品为单一的尖晶石晶体结构,结晶度较高,颗粒基本呈规则球形、流动性较好,粒径分布均匀,并表现出较好的电化学性能,振实密度达1.86 g/m L。在室温下以0.1 C充放电时,其首次放电比容量为173.19 m Ah/g,50次充放电循环后其放电比容量保持率为97.4%。     

水热法制备Li_4Ti_5O_（12）负极材料及其电化学性能

以钛酸四丁酯和乙酸锂为原料,水热法制备前驱体,再经过短时间的高温煅烧制备Li4Ti5O12负极材料。利用XRD、SEM和恒电流充放电方法分别测定材料的结构、形貌以及材料的电化学性能。结果表明：制备出的产物Li4Ti5O12颗粒具有尖晶石型结构,其中800°C、6h烧结出的样品具有约800nm的粒径,并表现出优良的电化学性能,0.1C和5C首次放电容量分别达到158.7（mA.h）/g和109.3（mA.h）/g,不同倍率下循环20次容量保持率较好。     

Li_4Ti_5O_(12)的溶胶-凝胶合成及其电化学性能

以乳酸(LA)为配位剂,Ti(OC4H9)4和LiAc.2H2O为原料,通过溶胶-凝胶法制备具有优良电化学性能的电极材料Li4Ti5O12。采用热重分析(TG)、X射线衍射(XRD)、扫描电镜(SEM)、恒流充放电以及循环伏安(CV)等方法对合成的材料进行结构表征和电化学性能测试。结果表明:在800℃烧结18 h制备的样品颗粒分布均匀、结晶度良好、电化学性能优良。0.5 C倍率的首次放电比容量为184.32 mA.h/g,50次循环后仍然保持在155.62mA.h/g。     

焙烧温度对Li2FeSiO4前驱体Li2SiO3性能的影响（英文）

以Li2CO3,HNO3,Si(OC2H5)4为原材料,采用溶胶-凝胶和高温焙烧法合成Li2SiO3;研究焙烧温度和回流系统对硅酸锂组分和性能的影响;利用TGA/DTA,XRD,SEM和粒径分析等手段对样品进行表征;采用Li2SiO3和Fe2C2O4.2H2O固相反应制备Li2FeSiO4。XRD结果表明,在溶胶-凝胶制备过程中使用回流系统能减少Li2SiO3样品中Li2SiO5和Li4SiO4杂质。焙烧结温度对Li2SiO3的性能有重要的作用,当温度为700℃时,Li2SiO3前驱体材料样品纯度为97%,并具有良好的形貌;它是由粒径为1～3μm的一次粒子组成,一次粒子束形成疏松、多孔的团聚体。     

水热法合成尖晶石型Li4Ti5O12及其电化学性能

以钛酸丁酯和乙酸锂为原料、三乙醇胺为结构导向剂,通过水热法合成前驱物,然后采用固相烧结制备Li4Ti5O12,探讨不同的钛锂比和煅烧温度对Li4Ti5O12结构和电化学性能的影响,并通过XRD、SEM、恒电流充放电和循环伏安测试对其进行表征.结果表明:当钛和锂的摩尔比为1:0.82、煅烧温度为800 ℃时,制备得到平均粒径为200 nm的纯相尖晶石型Li4Ti5O12,并具有良好的电化学性能;在0.1C倍率下,其首次放电比容量高达到181.7 mA-h/g,经过50次循环后放电比容量仍有151.5 mA-h/g,从第5次到第50次循环,平均每个循环放电比容量衰减量仅为6 μA-h/g;当电流倍率增大到2.0C时,其首次放电比容量仍然保持135 mA-h/g,从第5次到第50次循环,平均每个循环放电比容量衰减量为0.48 mA-h/g.     

锰掺杂对锂离子电池正极材料Li3V2（PO4）3/C性能的影响（英文）

采用溶胶-凝胶法合成Li3V2-2/3xMnx(PO4)3(0≤x≤0.12)。采用XRD、SEM、XPS、恒流充放电和电化学阻抗谱(EIS)研究Mn掺杂对Li3V2(PO4)3/C结构和电化学性能的影响。XRD研究表明:掺杂少量的Mn2+不会影响材料的结构,所有样品均具有单一相态的单斜结构(P21/n空间群)。XPS分析表明:在Li3V1.94Mn0.09(PO4)3/C中,V和Mn的化合价分别为+3和+2,原料中的柠檬酸在煅烧过程中分解成C而残留在Li3V1.94Mn0.09(PO4)3/C中。电化学测试表明:掺杂Mn改善了电极材料的循环性能和倍率性能,正极材料Li3V1.94Mn0.09(PO4)3/C表现出最好的循环稳定性和倍率性能。在40mA/g的放电电流密度下,循环100次后,Li3V1.94Mn0.09(PO4)3/C的放电容量从158.8mA·h/g衰减到120.5mA·h/g,容量保持率为75.9%,而未掺杂样品的放电容量从164.2mA·h/g衰减到72.6mA·h/g,容量保持率为44.2%。当放电电流密度增加到1C时,Li3V1.94Mn0.09(PO4)3/C的初始放电容量仍能达到146.4mA·h/g,循环100次后,放电容量保持为107.5mA·h/g。EIS测试表明,掺杂适量的Mn2+减小了电荷转移阻抗,这有利于Li+的脱嵌。     

浸渍提拉法合成Bi4Ti3O12基复合薄膜及其光催化性能

以TiO2、Bi4Ti3O12为原材料,采用浸渍-提拉法制备复合薄膜,研究了材料合成工艺对复合薄膜微观形貌、相结构及光催化性能的影响。XRD研究结果表明,合成的复合薄膜材料中含有正交相Bi4Ti3O12和锐钛矿TiO2两种晶相,Bi4Ti3O12沿垂直于玻璃基片的<001>方向取向生长。TiO2溶胶的浓度,Bi4Ti3O12的用量,以及表面活性剂的用量,拉膜次数对复合薄膜的成型有明显的影响,当TiO2溶胶的浓度为3mol/L、TiO2溶胶和Bi4Ti3O12质量比为10:1、表面活性剂的质量分数为3%、拉膜次数为3次的时候,合成的Bi4Ti3O12/TiO2复合薄膜较均匀且具有较优异的光催化性能。     

Heat treatment effect on electrochemical properties of spinel Li4Ti5O12

Anode material Li4Ti5O12 was prepared at 800℃ by a solid-state reaction, followed by heat-treatment at 600℃ for different times （0, 2, 8, and 12 h）. The effects of heat-treatment time on the particle morphology, rate-capability, and electrode kinetic process of the Li4Ti5O12 electrode, and on the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode were investigated. Proper heat treatment could smoothen the particle surface of Li4Ti5O12 particles and increase the rate-capability of the electrode. Overlong heat treatment might cause particle aggregation and hence result in a poor electrode kinetic process. A sample with 8 h of heat treatment showed the best rate-capability and the lowest electrode reaction resistance. Heat treatment for 2-8 h does not significantly change the lithium ion diffusion coefficient inside the Li4Ti5O12 electrode, whereas, 12-h treatment results in a lower lithium ion diffusion coefficient.     

锂离子占位情况对钛酸锂结构及性能的影响

Li₄Ti₅O₁₂在快速充放电条件下具有优异的结构稳定性和高安全性,使其受到新能源汽车和储能领域的青睐。大量的研究人员已经对钛酸锂的锂离子插层过程进行了研究,研究表明放电过程中外界和位于8a位的锂离子全部转移到16c位,钛酸锂的容量受限于参与其中晶格位点和可逆锂离子的数量。然而,钛酸锂晶胞结构表明可容纳锂离子的晶格位点不止于此。锂离子可能取代Ti原子占据八面体16d位点,位于四面体48f位点,重新占据相变后空出的四面体的8a位点。本文主要综述了在Li₄Ti₅O₁₂的制备过程或成品中,通过化学或电化学方法处理后,LTO中锂离子占位情况与传统认知发生的改变及其这种变化带来的影响。同时,本文对这种变化和影响之间的内在机理展开了讨论和分析。     

Synthesis and electrochemical properties of Li4Ti5O12

The spinel compound Li₄Ti₅O₁₂ was synthesized by a solid state method. In this synthesizing process, anatase TiO₂ and Li₂CO₃ were used as reactants. The influences of reaction temperature and calcination time on the properties of products were studied. When calcination temperature was 750 °C and calcination temperature was 24 h, the products exhibited good electrochemical properties. Its discharge capacity reached 160 mAh g⁻¹ and its capacity retention was 97% at the 50th cycle when the current rate was 1 C. When current rate increased to 10 C, its first discharge capacity could reach 136 mAh g⁻¹, and its capacity retention was 85% at the 50th cycle.     

Sol-gel synthesis and electrochemical performance of Li4Ti5O12/graphene composite anode for lithium-ion batteries

Li₄Ti₅O₁₂/graphene composite was prepared by a facile sol-gel method. The lattice structure and morphology of the composite were investigated by X-ray diffraction (XRD) and scanning electronic microscopy (SEM). The electrochemical performances of the electrodes have been investigated compared with the pristine Li₄Ti₅O₁₂ synthesized by a similar route. The Li₄Ti₅O₁₂/graphene composite presents a higher capacity and better cycling performance than Li₄Ti₅O₁₂ at the cutoff of 2.5-1.0 V, especially at high current rate. The excellent electrochemical performance of Li₄Ti₅O₁₂/graphene electrode could be attributed to the improvement of electronic conductivity from the graphene sheets. When discharged to 0 V, the Li₄Ti₅O₁₂/graphene composite exhibited a quite high capacity over 274 mAh g⁻¹ below 1.0 V, which was quite beneficial for not only the high energy density but also the safety characteristic of lithium-ion batteries.     

溶胶-凝胶法合成LiMnPO4/C锂离子电池复合材料（英文）

通过溶胶-凝胶法合成LiMnPO4/C锂离子电池复合材料,采用XRD、SEM和电化学性能测试对LiMnPO4/C进行性能表征。XRD研究表明,在500°C下能够合成得到纯的LiMnPO4;SEM研究表明,柠檬酸作为螯合剂和碳源能有效地抑制LiMnPO4/C颗粒的长大。在500°C下烧结10h合成的LiMnPO4/C样品的电化学性能最好,首次放电容量为122.6mA·h/g,以0.05C倍率循环30次后其容量为112.4mA·h/g。     

Porous Li4Ti5O12 anode material synthesized by one-step solid state method for electrochemical properties enhancement

A porous Li₄Ti₅O₁₂ anode material was successfully synthesized from mixture of LiCl and TiCl₄ with 70 wt% oxalic acid by a modified one-step solid state method. The anode material Li₄Ti₅O₁₂ exhibited a cubic spinel structure and only one voltage plateau occurred around 1.5 V. The initial capacity of porous Li₄Ti₅O₁₂ was 167 and 133 mAh g⁻¹ at 0.5 and 1C charge/discharge rate, respectively, and the capacity retention maintained above 98% after 200 cycles. The porous Li₄Ti₅O₁₂ structure showed promising rate performance with a capacity of 70 mAh g⁻¹ at charge/discharge 10C rate after 200 cycles. It was demonstrated that the porous structure could withstand 50C charge/discharge rate and exhibited excellent cycling stability.     

Characterization and electrochemical properties of carbon-coated Li4Ti5O12 prepared by a citric acid sol-gel method

Since carbon coating can effectively improve electrical wiring of Li₄Ti₅O₁₂ and thus enhance its high rate performance, a novel and simple citric acid sol-gel method for in situ carbon coating is employed in this study. The effects of the amount of the carbon source in the starting xerogel on the particle size, the resistance and the electrochemical performance of the synthesized Li₄Ti₅O₁₂ samples are systematically studied. The physical and electrochemical properties of the obtained samples have been characterized by XRD, TG-DSC, SEM, TEM, BET, A.C. impedance, galvanostatically charge-discharge and cyclic voltammetry tests. The results show that the initial amount of the carbon source in the starting xerogel is a critical factor which determines the content of the coated carbon and the pore volume, therefore governs the high rate performance of the Li₄Ti₅O₁₂/C composites. The Li₄Ti₅O₁₂/C composite with in situ carbon coating of 3.5 wt% exhibits the best electrochemical performance which delivers delithiation capacities of 143.6 and 133.5 mAh g⁻¹ with fairly stable cycling performance even after 50 cycles at 0.5C and 1C rate, respectively.     

Synthesis and electrochemical properties of LiNi0.4Mn1.5Cr0.1O4 and Li4Ti5O12

Spinel compound LiNi_0.4Mn_1.5Cr_0.1O₄ (LNMCO) and Li₄Ti₅O₁₂ (LTO) were synthesized by the sol-gel method and the solid-state method, respectively. The particle sizes of the products LiNi_0.4Mn_1.5Cr_0.1O₄ and Li₄Ti₅O₁₂ were 0.5 to 2 um and 0.5 to 0.8 um, respectively. All samples exhibited excellent electrochemical properties. A LiNi_0.4Mn_1.5Cr_0.1O₄/Li₄Ti₅O₁₂ (LNMCO/LTO) cell was fabricated and was demonstrated to exhibit good electrochemical properties at the high current rate of 1 C. When the specific capacity was determined based on the mass of the LNMCO cathode, the LNMCO/LTO cell delivered 125 mAh g⁻¹ at 1 C and 77 mAh g⁻¹ at 5 C. The capacity retentions after 30 cycles were 94.4 % and 83.1 %, respectively.     

锂离子电池正极材料LiCoO2-LiFePO4的性能

研究用LiCoO2-LiFePO4作正极的锂离子电池的电化学性能和安全性能。结果表明:电池在1、3和5C倍率的放电容量分别为347.7、327.2和322.5 mA.h,5C条件下的放电容量为1C放电容量的92.8%。在25℃、1C条件下循环150次的容量保持率为100%;在?10℃、1C条件下的放电容量为256.5 mA.h,是25℃、1C放电容量的74.8%。电池具有很好的耐过充性能,在3C、10 V条件下进行过充电,电池不漏液、起火或爆炸。短路时电池的表面温度低于LiCoO2电池的表面温度。     

锂离子电池极材料钽掺杂钛酸锂的制备及电化学性能

通过固相合成制备了钽掺杂材料Li4Ti4.95Ta0.05O12。通过XRD和SEM来表征Li4Ti4.95Ta0.05O12的结构和形貌。钽掺杂并没有改变本体材料的结构和形貌,而且显著提高了材料的循环性能和倍率性能。Li4Ti4.95Ta0.05O12在10C和30C倍率时的放电容量分别是116.1mA.h/g和91.0mA.h/g。Ta掺杂取代了Li4Ti5O12中的Ti的位置,产生了Ti4＋/Ti3＋混合价态,从而提高了钛酸锂的电导率。故具有优异的高倍率性能,是一种优异的锂离子电池负极材料。.