Structure and electrochemical properties of La, F dual-doped LiLa0.01Mn1.99O3.99F0.01 cathode materials

The cathode materials LiMn2O4 and rare earth elements La-doped or La and F dual-doped spinel lithium manganese oxides were synthesized by the citric acid-assisted sol-gel method. The synthesized samples were investigated by differential thermal analysis (DTA) and thermogravimetry (TG) measurements, X-ray diffraction (XRD), scanning electronic microscope (SEM), cyclic voltammetry (CV), and charge-discharge test. XRD data shows that all the samples exhibit the same pure spinel phase, and the LiLa0.01Mn1.99O3.99F0.01 and LiLa0.01Mn1.99O4 samples have smaller lattice parameters and unit cell volume than LiMn2O4. SEM indicates that LiLa0.01Mn1.99O3.99F0.01 has a slightly smaller particle size and a more regular morphology structure with narrow size distribution. The charge-discharge test reveals that the initial capacities of LiMn2O4, LiLa0.01Mn1.99O4, and LiLa0.01Mn1.99O3.99F0.01 are 129.9, 122.8, and 126.4 mAh·g-1, and the capacity losses of the initial values after 50 cycles are 14.5%, 7.6%, and 8.0%, respectively. The CVs show that the La and F dual-doped spinel displays a better reversibility than LiMn2O4.     

Effects of Al, F dual substitutions on the structure and electrochemical properties of lithium manganese oxide

Spinel LiMn2O4 and F, Al-doped spinel LiAl0.05Mn1.95O3.98F0.02 have been synthesized by a soft chemistry method using adipic acid as the chelating agent. The synthesized spinel materials were characterized by differential thermal analysis (DTA) and thermogravimetery (TG), X-ray diffraction (XRD), scanning electron microscopy (SEM), cyclic voltammetry (CV), and charge-discharge testing. The results indicate that all the samples have high phase purity, and fluorine is important in controlling the morphology; the doped aluminum enhances the stability of spinel LiMn2O4. The charge-discharge tests indicate that LiAl0.05Mn1.95O4 has high capacity retention, which is 92.60% of the initial after 50 cycles. It is found that the novel compound LiAl0.05Mn1.95O3.98F0.02 with smaller particles can offer much higher capacity, whose initial discharge capacity is 126.5 mAh?g-1. The cyclic voltammetric experiments disclose the enhanced reversibility of the F, Al3 -modified spinel as compared with the undoped spinel.     

锂离子电池正极材料Li0.97Re0.01FePO4的合成及性能

采用固相反应法合成了锂离子电池正极材料Li0.97Re0.01FePO4(Re=Er,Y,Gd,Nd,La),采用X射线衍射、恒电流充放试验对掺杂试样的微观结构和电化学性能进行测试。试验结果表明:掺杂稀土金属离子对LiFePO4的晶体结构没有影响,与LiFePO4相比,掺杂Er3+,Y3+,Gd3+的试样具有优良的循环性能和倍率性能,而掺杂Nd3+,La3+的试样的循环性能和倍率性能较差。掺杂试样中,Li0.97Gd0.01FePO4的电化学性能最佳,在C/10和1C(1C=120 mA.g-1)倍率下放电容量均最大。     

Electrochemical properties of spinel LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1 synthesized by solid-state reaction

Two types of spinel cathode powders, LiMn2O4 and LiAl0.1Mn1.9O3.9F0.1, were synthesized by solid-state reaction. X-ray diffraction (XRD) patterns of the prepared samples were identified as the spinel structure with a space group of Fd 3 m. The cubic lattice parameter was determined from least-squares fitting of the XRD data. The LiAl0.1Mn1.9O3.9F0.1 sample showed a little lower initial capacity, but better cycling performance than the LiMn2O4 sample at both room temperature and an elevated temperature. The Vanderbilt method was used to test the electrochemical conductivity of the LiMn2O4 samples. The electrochemical impedance spec-troscopy (EIS) method was employed to investigate the electrochemical properties of these spinel LiMn2O4 samples.     

L i F e 1-yMg yP O4的制备及电化学性能研究

采用机械活化一步固相法, 在F e位掺杂 Mg 2+ 合成了结晶度较好的 L i F e 1-yMg yP O4。采用 XR D、S EM 等方法对L i F e 1-yMg yP O4的结构和形貌进行了表征, 利用恒电流充放电法研究了 Mg 2+ 掺杂对 L i F e 1-yMg yP O4电化学性能的影响。结果表明, 适量 Mg 2+掺杂不改变L i F e P O4的晶体结构, 同时可以细化颗粒粒径, 增强导电性和可逆性, 有效地提高L i F e P O4的倍率性能和循环稳定性。L i F e 0. 9 9Mg 0. 0 1P O4在0. 1C和1C倍率条件下首次放电比容量分别为1 5 8. 7mA h / g和1 4 1. 9mA h / g, 循环5 0次后放电比容量几乎没有衰减。     

尖晶石型锰酸锂的复合掺杂改性

以固相烧结法制备的尖晶石型锰酸锂为基础,对其结构中掺杂复合非金属元素B和F,合成了B、F掺杂的尖晶石。通过X射线衍射、扫描电镜、电化学分析方法对试样的晶体结构、表面形貌及电化学性能进行表征。结果表明,采用B、F包覆的锰酸锂与纯锰酸锂的X射线衍射结果相似,波峰尖锐且峰值高;随着B的掺入,尖晶石作为正极材料充放电的循环性能得到了提高,但是其初始容量较低,仅为102.3mA·h/g。随着加入复合非金属元素B和F,样品的初始容量提高到了110.9mA·h/g,50次循环后的容量保持率为83.14%。实验结果表明,复合掺杂有效提高了锰酸锂的电化学性能。     

锂离子电池负极材料Li_4Ti_(5-x)Co_xO_(12)的结构与电化学性能

主要采用溶胶凝胶法合成Li4Ti5-xCoxO12负极材料,通过XRD、SEM和电化学测试手段,系统的研究了尖晶石型Li4Ti5-xCoxO12的结构和电化学性能.结果表明:0.06≤x≤0.24的样品均为纯相尖晶石型结构,掺杂Co3+对晶粒的生长有抑制作用,但团聚现象明显;引入Co元素降低了样品的首次放电比容量,但是没有影响样品的循环稳定性.     

溶胶-凝胶法制备尖晶石结构镍锰氧化物型锂离子筛

采用溶胶-凝胶法,以乙酸锂、乙酸镍和乙酸锰为主要原料,通过正交试验得到制备镍锰氧化物型锂离子筛LiNixMn2-xO4的适宜条件:x=0.05,柠檬酸作螯合剂,焙烧温度700℃,焙烧时间8 h。用0.5 mol.L-1过硫酸铵作抽锂剂,Mn2+的溶出率较低,仅为0.31%。通过X射线衍射分析证明所合成的锂离子筛为尖晶石结构,每克离子筛对Li+的饱和交换容量达36.72 mg。     

Mg2+掺杂的LiFePO4材料的共沉淀合成与表征

提出了一种采用共沉淀法合成镁掺杂的锂离子正极材料LiFePO4的新方法,研究了合成条件,采用XRD,SEM,循环伏安测定,电化学阻抗谱分析,以及充放电测试对合成的材料作了表征分析．结果表明,采用共沉淀合成方法可以获得性能良好的LiFePO4;Mg^2＋掺杂对LiFePO4结构没有产生明显的影响,但掺杂量的大小对LiFePO4的放电性能有较大影响．     

纳米絮状Li_4Ti_5O_(12)的水热法合成及性能的研究

为解决高温烧结制备的锂离子电池负极材料Li4Ti5O12易团聚、形貌差的问题,采用水热低温烧结法,以钛酸丁酯、氢氧化锂分别为钛源和锂源,异丙醇为溶剂,制备纯相Li4Ti5O12。用X射线衍射仪(XRD)、扫描电子显微镜(SEM)和比表面测试仪对样品进行表征,采用恒流充放电法对钛酸锂进行电化学性能评价。结果表明,在400℃低温煅烧后可得到单一纯相尖晶石型Li4Ti5O12,所制备样品为具有大比表面积的纳米絮状粉体,表现出良好的电化学性能,在常温条件下,以0.1C倍率进行充放电,首次放电容量达到155.7mA·h/g,经50次循环后容量仍保持约143mA·h/g,容量保持率达到91.8%。     

锂离子电池正极材料LiCexNdxMn2-2xO4（x=0～0.018）的Pechini合成及表征

采用X射线衍射仪、电池测试系统等,研究了采用Pechini法合成的锂离子电池正极材料LiCexNdxMn2-2xO4（x=0、0.012、0.014、0.016、0.018）的组织结构、首次充放电性能、循环稳定性能等。结果表明：当稀土元素掺入量较少（x≤0.014）时,样品由尖晶石型LiMn2O4相组成,否则,样品中将出现微量的杂质相（CeO2、Nd2O3）;适量的稀土元素掺杂将使LiMn2O4样品的初始容量减小、循环稳定性能增加。LiCe0.014Nd0.014Mn1.972O4样品具有较好的循环稳定性能,其初始放电容量为124.8 mAh/g,经30次循环充放电后的容量保持在116.3 mAh/g,容量保持率为93.2%。     

高岭土掺杂NASICON固体电解质及全固态电池性能

针对LiTi2(PO4)3基固态电解质电导率低的问题,采用浙江三门高岭土矿作为主要原料,以高温固相法制备铝、镁、硅共掺杂钠超离子导体(NASICON)型快离子导体Li1+2x+2yAlxMgyTi2-x-ySixP3-xO12.研究掺杂比例、温度对固态电解质离子电导率的影响.结果表明,组成为Li1.8Al0.1Mg0.3Ti1.6Si0.1P2.9O12固体电解质在423 K时有最高离子电导率7.86×10-4 S·cm-1.以该组成固态电解质为基片,喷雾热解原位制备Al/ Li1+xV3O8/ Li1.8Al0.1Mg0.3Ti1.6Si0.1 P2.9O12 /C全固态电池并在1.8～3.9 V电压区间进行50次充放电测试.该电池具有较好的稳定性及循环容量保持能力.30次循环以后放电容量基本稳定在190～205 mAh·g-1之间,充放电效率大于90%.     

掺铌硅酸亚铁锂正极材料的电化学性能

采用固相烧结法,以LiOH、FeC2O4.2H2O、Nb2O5、正硅酸四乙酯和蔗糖为原料制备出单斜结构的Li2.05FexNb2(1-x)/3SiO4/C(x=1,0.99,0.98,0.96,0.94,0.92,0.90)系列样品.通过红外光谱、X射线衍射、扫描电镜、恒电流充放电测试、交流阻抗和循环伏安法等方法研究了制备样品的结构及电化学性能.实验结果表明,颗粒尺寸介于0.2～1.5μm之间的Li2.05Fe0.96Nb0.026 7SiO4/C的充放电性能最好,在0.3C倍率电流下,第1次循环的放电容量为116.6 mAh/g,第30循环的放电容量为78.3 mAh/g.掺铌减少了样品的电荷传递阻抗,提高了锂离子的扩散系数.     

锂离子电池正极材料Li0.97Re0.01FePO4的合成及性能

采用固相反应法合成了锂离子电池正极材料Li0.97Re0.01FePO4（Re=Er,Y,Gd,Nd,La）,采用X射线衍射、恒电流充放试验对掺杂试样的微观结构和电化学性能进行测试。试验结果表明：掺杂稀土金属离子对LiFePO4的晶体结构没有影响,与LiFePO4相比,掺杂Er^3＋,Y^3＋,Gd^3＋的试样具有优良的循环性能和倍率性能,而掺杂Nd^3＋,La^3＋的试样的循环性能和倍率性能较差。掺杂试样中,Li0.97Re0.01FePO4的电化学性能最佳,在C/10和1C（1C=120mA·g^-1）倍率下放电容量均最大。     

5V锂离子电池正极材料的制备和电化学性能研究

用液相法合成出用锂和镍取代的尖晶石锂锰氧化物正极材料.用XRD和FTIR对其进行了表征,并探讨了其在有机电解液的电化学性能.研究结果表明:在锂锰氧化物掺入适量的镍(锰∶镍的摩尔比为1.4∶0.6)可以改善尖晶石LiMn2O4的循环性能,提高放电平台,使其大部分容量往高电位方向移动,电池的放电电压提高,这样的材料适合做5V电池的正极材料.     

LaCoO3掺杂Ba和Fe催化分解NO的研究

采用柠檬酸溶胶-凝胶法合成了La(Ba)Co(Fe)O3钙钛矿型氧化物催化剂,通过XPS、XRD、H2-TPR、FT-IR、BET等表征手段考察了催化剂分解NO的催化活性.结果表明,LaCoO3的A位掺杂适量Ba可以提高催化剂表面的氧空位浓度,La0.8 Ba0.2CoO3的B位掺杂Fe,活化了Co-O键,产生协同作用,提高了分解NO的催化活性.     

Comparative experiment on layered Li（Ni1/3Co1/3Mn1/3）O2 as the alternative material for LiCoO2

This work was financially supported by the National Natural Science Foundation of China （No.50472093）.     

Enhanced photocatalytic activity of (La, N) co-doped TiO_2 by TiCl_4 sol-gel autoigniting synthesis

(La, N) co-doped TiO2 photocatalysts were synthesized using TiCl4 sol-gel autoigniting synthesis (SAS) starting from a complex compound system of TiCl4-La(NO3)3-citric acid-NH4NO3-NH3?H2O, in which the (La, N) co-doped process was accom- plished in the formation of TiO2 nanocrystals. The prepared samples were characterized by using X-ray diffraction (XRD), X-ray photoemission spectroscopy (XPS) and UV-vis diffuse reflectance spectra. The results indicated that nitrogen and lanthanum were incorporated into the lattice and interstices of titania nanocrystals, which resulted in narrowing the band gap and promoting the sepa- ration of photoexcited hole-electron pairs, respectively, and showing expected red-shifts and enhanced photocatalytic activity under visible light. The mechanism on nitrogen doping and enhancement in photocatalytic activity of (La, N) co-doped titania by SAS was discussed in detail.     

尖晶石型锰酸锂制备及其电化学性能

锰酸锂被认为是取代商品锂离子电池正极材料的LiCoO2候选材料.以二氧化锰、醋酸锰及氢氧化锂为原料,蒸馏水为分散剂,在空气气氛下进行分段烧结,控制烧结温度和时间,制备了锂离子电池正极材料锰酸锂.用X射线衍射仪,电子扫描电镜对产物的结构特征、微观表面形貌和恒流充放电性能进行了表征.结果表明:所制得正极材料为尖晶石型锰酸锂,结晶度高,无杂质相,材料颗粒的粒径均匀,首次放电比容量为117.3 mAh/g(0.5 mA/cm2,2.8~4.4 V,vs.Li+/Li);50次循环后,放电比容量为107.9 mAh/g,不可逆容量损失为9.4 mAh/g,比容量保持率为92.0%.得到了很好的综合电化学性能.     

微波合成LiMn2O4正极材料及其电化学性能的研究

本文以Li2CO3 、MnO2为原料,采用微波热处理合成锂离子电池正极材料LiMn2O4,研究了热处理温度,Li/Mn摩尔比对产物结构和电化学性能的影响,同时研究了微波热处理和传统热处理两种加热方式的差别.通过X射线衍射（XRD）、扫描电镜（SEM）、恒电流充放电测试分别对产物的结构、形貌及电化学性能进行表征,结果表明：采用微波法在750℃保温15 min,快速地制备出尖晶石型LiMn2O4,纯度高,尺寸分布均匀,约100-300 nm;于0.1C倍率下,以微波法制备的正极材料首次放电比容量可达112.38 mA·h/g,1C倍率充放电50次循环后,容量保持率为91.6％;以传统方法制备的正极材料0.1C倍率下首次放电比容量为94.07 mA·h/g,1C倍率充放电50次循环后,容量保持率为71.4％