用β-环糊精制备LiFePO4/C锂离子电池正极材料

采用高温固相法制备了β-环糊精为碳源前驱体、具有橄榄石结构的LiFePO4/C复合正极材料.与采用相同工艺制备的LiFePO4和以碳黑作为碳源制备的LiFePO4/C产物比较,该复合材料粉体粒度小,电化学性能优良,体现在:占体积分数为26.88%的产物粒度小于1 μm;0.1C放电比容量可达到147 mA·h·g-1,相对纯净LiFePO4提高66 mA·h·g-1.此外,初步分析了β-环糊精在制备过程中细化颗粒的机理.     

固相法合成LiFePO4/C正极材料的电化学性能

以廉价原材料FeSO4·7H2O为铁源,以蔗糖为碳源,采用固相法合成了锂离子电池正极材料--LiFePO4/C复合材料.用X射线衍射(XRD)、扫描电镜(SEM)和电化学测试技术对不同铁源合成的LiFePO4/C复合材料的结构、形貌和电化学性能进行研究.结果表明:合成的样品具有均一的橄榄石型结构,以FeSO4·7H2O为铁源合成的LiFePO4/C复合材料的循环性能和高倍率放电性能均优于以FeC2O4·2H2O为铁源合成的LiFePO4/C复合材料的;由FeSO4·7H2O合成的LiFePO4/C复合材料的5C倍率放电比容量为105.9 mA-h/g,经循环30次后,容量仍高达105.2 mA-h/g.     

钇掺杂LiFePO4锂离子电池正极材料的制备与性能

用固相法合成LiFe1-xYxPO4 (x=0, 0.01, 0.02, 0.03, 0.04)锂离子电池正极材料,采用X射线衍射仪、扫描电子显微镜、粉末比电阻法和充放电性能测试表征材料的晶体结构、微观形貌、电子电导率和电化学性能。结果表明,少量的钇掺杂并未改变材料的晶体结构,但改善了材料的微观结构,提高其电子电导率,改善可逆容量和电化学性能。在10 mA/g的电流密度下,LiFe0.97Y0.03PO4首次放电容量可达146.54 mAh/g。     

锂离子电池正极材料LiFePO4掺碳纳米管的性能研究

以Li2CO3、FeSO4·7H2O、(NH4)2HPO4和Na2EDTA为原料,掺杂碳纳米管采用水热法合成了锂离子电池正极材料LiFePO4.研究了表面活性剂和碳纳米管对产物形貌和电化学性能的影响.结果表明:LiFePO4/MWCNTs样品属于橄榄石结构,在0.1C、3.0～4.3V条件下的首次放电比容量为145 mAh·g--,第20次循环的比容量为144.3 mAh·g-1.     

分步碳包覆合成高密度LiFePO4/C复合材料

采用分步碳包覆法合成LiFePO4/C复合材料。首先,将原料Fe2O3、NH4H2PO4和葡萄糖经过固相反应合成Fe2P2O7/C复合材料,再将Fe2P2O7/C与前驱体Li2CO3、葡萄糖混合,通过二次碳包覆工艺合成LiFePO4/C复合材料,并考察合成温度对LiFePO4/C复合材料电化学性能的影响。采用X射线衍射、扫描电镜、差热-热重分析、电化学阻抗谱(EIS)和充放电测试对材料的性能进行表征。结果表明:以制取的Fe2P2O7/C为前驱体合成的LiFePO4/C复合材料具有较好的物理和电化学性能,材料的振实密度达1.26 g/m3,0.1C放电容量为158.3 mA.h/g,1C初次放电比容量达到140 mA.h/g。     

共沉淀法制备正极材料LiFePO4的研究

以氢氧化锂、硫酸亚铁铵和磷酸氢二铵为原料，研究了液相共沉淀法制备LiFePO4正极材料和掺杂Co^2＋的LiFePO4改性正极材料，并对其进行XRD、SEM分析和电化学性能测试。结果表明掺杂Co^2＋对正极材料的初始充电比容量为156．7mAh·g^-1，且循环60次后，容量仍有138．7mAh·g^-1，容量衰减率仅为11．4％。     

LiFePO4/C锂离子电池正极材料的电化学性能

以碳凝胶作为碳添加剂,采用固相法制备了复合型LiFePO4/C锂离子电池正极材料.研究了不同掺碳量对样品性能的影响.利用X射线衍射仪、扫描电镜和碳硫(质量分数)分析方法对所得样品的晶体结构、表面形貌、含碳量进行分析研究.结果表明:样品中的碳含量(质量分数)分别为0%、5%、10%、22%,所得样品均为单一的橄榄石型晶体结构,碳的加入使LiFePO4颗粒粒径减小.另外,碳分散于晶体颗粒之间,增强了颗粒之间的导电性.合成样品的电化学性能测试结果表明,掺碳后的LiFePO4放电比容量和循环性能都得到显著改善.其中,含碳量为22%的LiFePO4/C在0.1 C倍率下放电,首次放电容量达143.4 mA·h/g,充放电循环6次后电容量为142.7 mA·h/g,容量仅衰减0.7%.     

Synthesis and characterization of LiFePO4／C composite used as lithium storage electrodes

LiFePO4/C composites with good rate capability and high energy density were prepared by adding sugar to the synthetic precursor, A significant improvement in electrode performance was achieved. The resulting carbon contents in the sample 1 and sample 2 are 3.06% and 4.95% (mass fraction), respectively. It is believed that the synthesis of LiFePO4 with sugar added before heating is a good method because the synthesized particles having uniform small size are covered by carbon. The performance of the cathodes was evaluated using coin cells. The samples were characterized by X-ray diffraction and scanning electron microscope observation. The addition of carbon limits the particles size growth and enables high electron conductivity. The LiFePO4/C composites show very good electrochemical performance delivering about 142 mAh/g specific capacity when being cycled at the C/10 rate. The capacity fade upon cycling is very small.     

锂离子电池正极材料LiFePO4改性研究

介绍了LiFePO4正极材料的结构特点和反应机理,详细讨论了金属离子掺杂、碳包覆和控制活性材料的尺寸等改性研究对LiFePO4材料的电化学性能的影响.从而进一步优化高性能锂离子电池正极材料的改性过程,促进锂离子电池性能的改善.     

锂离子电池正极材料LiVPO4F的合成及分析

通过2步高温固相反应来合成LiVPOF正极材料.第一步是将五氧化二钒、磷酸二氢铵和乙炔黑在N2的保护下合成中间体VPO4(即为α);第二步是VPO4和LiF进一步反应生成单相LiVPO4F.考察了乙炔黑不同的过量百分比(过量25％时,合成的LiVPO4F为β1,过量50％时,合成的LiVPO4F为β2)对产物组成和电化学性能的影响.结果表明:β1的产物组成和电化学性能优于β2.XRD测试表明:所合成的LiVPO4F属于三斜晶系,其晶胞参数:a=0.5173im、b=0.5309 nm、c=0.7250 nm;红外测试表明:LiVPO4F的吸收峰主要是由V=O、O-V-O和PO4基团引起;SEM测试表明:样品β1颗粒均匀度优于样品β2,平均粒径为2μm左右.电化学测试表明:β1和β2在第一个循环的充电比容量分别为82.2、99.2 mAh/g,放电比容量分别为71.7、58.5 mAh/g,19周后,其充电比容量分别为64.7、58.8 mAh/g,放电比容量分别为在62.4、52.0 mAh/g.LiVPO4F的平均脱锂电位在4.3V以上,平均嵌锂电位在4.15V左右.这说明,样品β1具有更好的电化学性能.以上综合表明,LiVPOF作为一种锂离子电池正极材料具有良好的稳定性和可逆性.     

Preparation and electrochemical properties of LiFePO4/C composite with network structure for lithium ion batteries

The bare LiFePO4 and LiFePO4/C composites with network structure were prepared by solid-state reaction. The crystalline structures, morphologies and specific surface areas of the materials were investigated by X-ray diffractometry（XRD）, scanning electron microscopy（SEM） and multi-point brunauer emmett and teller（BET） method. The results show that the LiFePO4/C composite with the best network structure is obtained by adding 10% phenolic resin carbon. Its electronic conductivity increases to 2.86 × 10^-2 S/cm. It possesses the highest specific surface area of 115.65 m^2/g, which exhibits the highest discharge specific capacity of 164.33 mA.h/g at C/IO rate and 149.12 mA.h/g at 1 C rate. The discharge capacity is completely recovered when C/10 rate is applied again.     

Synthesis and electrochemical performances of spherical LiFePO4 cathode materials for Li-ion batteries

Spherical LiFePO4 and LiFePO4/C composite powders for lithium ion batteries were synthesized by a novel processing route of co-precipitation and subsequent calcinations in a nitrogen and hydrogen atmosphere. The precursors of LiFePO4, LiFePO4/C composite and the resultant products were characterized by X-ray diffraction (XRD), scanning electron microscope (SEM), and the electrochemical performances were investigated by galvanostatic charge and discharge tests. The precursors composed of amorphous Fe3(PO4)2·xH2O and crystalline Li3PO4 obtained in the co-precipitation processing have a sphere-like morphology. The spherical LiFePO4 derived from the calcinations of the precursor at 700 ℃ for 10 h in a reduction atmosphere shows a discharge capacity of 119 mAh·g -1 at the C/10 rate, while the LiFePO4/C composite with 10wt.% carbon addition exhibits a discharge capacity of 140 mAh·g -1.The electrochemical performances indicate that the LiFePO4/C composite has a higher specific capacity and a more stable cycling performance than the bare olivine LiFePO4 due to the carbon addition enhancing the electronic conductivity.     

Influence of Ti^4＋ doping on electrochemical properties of LiFePO4/C cathode material for lithium-ion batteries

To improve the performance of LiFePO4, single phase Li1-4xTixFePO4/C (x=0, 0.005, 0.010, 0.015) cathodes were synthesized by solid-state method. A certain content of glucose was used as carbon precursor and content of carbon in every final product was about 3.5%. The samples were characterized by X-ray diffraction(XRD), scanning electron microscopy observations(SEM), charge/discharge test, carbon analysis and electrochemical impedance spectroscopy(EIS). The results indicate that the prepared samples have ordered olivine structure and doping of the low concentration Ti~(4+) does not affect the structure of the samples. The electrochemical capabilities evaluated by charge-discharge test show that the sample with 1% Ti~(4+) (molar fraction) has good electrochemical performance delivering about an initial specific capacity of 146.7 mA·h/g at 0.3C rate. Electrochemical impedance spectroscopy measurement results show that the charge transfer resistance of the sample could be decreased greatly by doping an appropriate amount Ti~(4+).     

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。     

Preparation and characteristics of Li2FeSiO4/C composite for cathode of lithium ion batteries

A Li2FeSiO4/C composite cathode for lithium ion batteries was synthesized at 650 ℃ by solid-state reaction. The effects of carbon sources and carbon content on the properties of the Li2FeSiO4/C composites were investigated. The crystalline structure, morphology, carbon content and charge/discharge performance of Li2FeSiO4/C composites were determined by X-ray diffraction(XRD), scanning electron microscopy(SEM), carbon/sulfur analyzer and electrochemical measurements. As carbon content increases in the range of 5%-20%, the amount of Fe3O4 impurity phase decreases. The SEM micrographs show that the addition of the carbon is favorable for reducing the Li2FeSiO4 grain size. Using sucrose as carbon source, the Li2FeSiO4/C composite with 14.5% carbon synthesized at 650 ℃ shows good electrochemical performance with an initial discharge capacity of 144.8 mA-h/g and a capacity retention ratio of 94.27% after 13 cycles.     

球形磷酸铁锂正极材料制备中试研究

用湿法球磨-喷雾干燥法制备LiFe0.98Mg0.02PO4/C复合正极材料;用激光粒度分析仪、X射线衍射仪、扫描电镜和恒流充放电等对前驱体和磷酸铁锂样品进行表征;考察不同球磨工艺对磷酸铁锂颗粒形貌、粒度分布、振实密度和电化学性能的影响。结果表明:用湿法球磨-喷雾干燥法可以制得球形颗粒、高振实密度且电化学性能优良的磷酸铁锂正极材料,原料经粗磨后再超细球磨制得的材料性能更佳,振实密度达1.67 g/cm3,在0.1 C、0.5 C和1.0 C倍率下的首次放电比容量分别为151、143和132 mA·h/g。     

锂离子电池用LiVPO4F/C基正极材料的制备和性能（英文）

将H2C2O4·2H2O,NH4H2PO4,NH4VO3和LiF通过球磨反应、烧结,合成了LiVPO4F/C基正极材料。在这个过程中,草酸起还原剂和碳源的作用,利用热重、X射线衍射、扫描电镜、透射电镜和碳-硫分析等手段对合成的前驱体和材料进行检测和分析。XRD分析表明,球磨反应后所得到的前驱体为无定形态,而烧结后的材料中除了LiVPO4F的衍射峰外,还存在Li3V2(PO4)3和V2O3衍射峰。材料颗粒均匀,尺寸约2μm。透射电镜分析表明,合成的材料颗粒表面包裹着一层约2nm厚的无定形碳。在截止电压3.0～4.4V时,合成的材料在0.1C和10C倍率下的放电比容量分别为151.3和102.5mA·h/g。在10C倍率下循环50次后容量保持率为90.4%。在LiVPO4F和Li3V2(PO4)3的循环伏安曲线中可以明显看到V3+/V4+的氧化还原峰。     

利用新颖的三层电极提高LiFePO4／C正极材料的电化学性能

对常用的两层电极（活性材料层｜集电极）进行改进,提出一种新颖的夹心状三层电极（导电材料层｜活性材料层｜集电极）以提高 LiFePO4/C 的电化学性能。充放电测试表明：相比两层电极,三层电极中 LiFePO4/C 表现出更优的倍率性能。循环伏安和电化学阻抗测试表明：相比两层电极,三层电极中LiFePO4/C材料中的Fe3＋/Fe2＋氧化还原电对表现出更快的氧化还原速度。更好的可逆性能以及更低的电荷转移阻抗。在三层电极中,活性材料层表层中与LiFePO4/C颗粒尺寸相当的孔洞被粒径小得多的乙炔黑微粒填充,形成LiFePO4/C颗粒间的导电连接,为暴露在电解液主体LiFePO4/C颗粒中的LiFePO4晶体提供更多运输电子到达或离开的路径。