前驱体二水磷酸铁对磷酸铁锂电化学性能的影响

以钛白生产副产物七水硫酸亚铁为铁源,工业磷酸二氢铵为磷源,双氧水为氧化剂,采用共沉淀法合成了不同粒径和形貌的二水磷酸铁,并以此为前驱体,通过碳热还原法制备了粒径不同的LiFePO₄/C正极材料。经过对样品进行X射线衍射（XRD）、扫描电镜（SEM）以及恒电流充放电测试,研究了二水磷酸铁及LiFePO₄/C的结构、形貌以及电化学性能。结果表明,以较细的二水磷酸铁为铁源,制备得到的LiFePO₄/C颗粒较细,且具有更优异的电化学性能。0.1、0.5、1、2、5、10 C放电比容量分别为154、148、144、140、130、120 mA·h/g。     

Influence of synthesis parameters on the properties of LiFePO4/C cathode material☆

The influence of sintering temperature,carbon content and dispersive agent in ball-milling was investigated on the properties of Li Fe PO_4/C prepared using Fe_2O_3,NH_4H_2PO_4,Li_2CO_3 and glucose via solid state reaction.X-ray powder diffraction,scanning electron microscopy and charge–discharge test were applied to the characterization of the Li Fe PO_4/C samples synthesized under different conditions.Sintering temperature affects the crystallite/particle size and degree of crystallinity of LiF eP O_4,formation of Fe_2 P and maintenance of carbon in LiF e PO_4/C.Carbon maintenance is favored by low sintering temperature,and 700 °C is optimum for synthesis of LiF eP O_4/C with superior electrochemical performance.A higher carbon content in the range of 4.48%–11.03% results in a better rate capability for Li Fe PO_4/C.The dispersive agent used in ball-milling impacts the existent state of carbon in the final product which subsequently determines its charge–discharge behavior.The sample prepared at700 °C by using acetone as the dispersive agent in ball-milling exhibits an excellent rate capability and capacity retention without any fade at 0.1C,1C and 2C,with corresponding average discharge capacities of 153.8,128.3and 121.0 m A·h·g~(-1),respectively,in the first 50 cycles.     

High-rate properties of LiFePO4/carbon composites as cathode materials for lithium-ion batteries

Electrochemical properties of LiFePO₄/carbon composites were investigated to achieve a high-rate lithium electrode performance. LiFePO₄/carbon composites were synthesized by a hydrothermal reaction of a solution of FeSO₄·7H₂O, H₃PO₄, and LiOH·H₂O mixed with carbon powders under nitrogen atmosphere followed by annealing under 1% H₂–99% Ar atmosphere. Particle size of the obtained LiFePO₄/carbon composites observed by scanning electron microscopy was less than 100 nm. At a high current density of 1000 mA g⁻¹, the LiFePO₄/carbon composites showed a high discharge capacity of 113 mA h g⁻¹, and a flat discharge potential plateau was observed around 3.4 V. The discharge capacity at the high current density, 85% of that at a low current density of 30 mA g⁻¹, is a quite high value for LiFePO₄ cathodes. Homogeneous microstructure consisting of small particles contributed to the high-rate properties of the LiFePO₄/carbon composites.     

乙醇-水体系3D纳/微米球形磷酸铁的制备与表征

提出了一种在温和条件下制备高振实密度球形磷酸铁的简单方法。制备过程中无需引入碱性物质调节pH和添加其他模板剂,仅以九水合硝酸铁[Fe（NO₃）·9H₂O]和磷酸（H₃PO₄）为原料,在乙醇-水体系中即可制备3D纳/微米球形磷酸铁（记为FPE）。采用扫描电镜（SEM）、激光粒度仪、X射线衍射仪（XRD）、热重-差式扫描量热仪（TG-DSC）、比表面积测试仪（BET）等对制备的磷酸铁进行表征分析。结果显示,制备的磷酸铁具有3D纳/微米球形结构,平均一次粒径为27.2 nm,二次粒径D₅₀为3.75 μm。FPE的组成为二水合磷酸铁（FePO₄·2H₂O）,纯度较高,具有介孔结构,平均孔径为2.75 nm,比表面积为22.41 cm ²/g,同时具有较高的振实密度（1.34 g/cm ³）。3D纳/微米球形磷酸铁制备方法简单,性能优异,以其为前驱体制备的磷酸铁锂（LiFePO₄/C）具有较高的振实密度（1.46 g/cm ³）,在0.2C倍率下的放电比容量为157.9 mA·h/g。     

Long-term cyclability of nanostructured LiFePO4

Amorphous LiFePO₄ was obtained by lithiation of FePO₄ synthesized by spontaneous precipitation from equimolar aqueous solutions of Fe(NH₄)₂(SO₄)₂·6H₂O and NH₄H₂PO₄, using hydrogen peroxide as oxidizing agent. Nano-crystalline LiFePO₄ was obtained by heating amorphous nano-sized LiFePO₄ for different periods of time. The materials were characterized by TG, DTA, X-ray powder diffraction, scanning electron microscopy (SEM) and BET. All materials showed very good electrochemical performance in terms of energy and power density. Upon cycling, a capacity fading affected the materials, thus reducing the electrochemical performance. Nevertheless, the fading decreased upon cycling and after the 200th cycle the cell was able to cycle for more than 500 cycles without further fading.     

Synthesis of sub-micrometer lithium iron phosphate particles for lithium ion battery by using supercritical hydrothermal method简

A supercritical hydrothermal method was employed to prepare sub-micrometer LiFePO4 particles with high purity and crystallinity. The structure and morphology of LiFePO4 particles were characterized by X-ray diffraction and scanning electron microscope. The electrochemical tests were carried out to determine the reversible capacity, rate and cycling performance of the LiFePO4 particles as cathode material for lithium ion battery. Experimental results show that solvent and calcining time have significant effects on purity, size and morphology of LiFePO4 particles. Mixed solvent contained deionized water and ethanol is conducive to synthesize smaller and more uniform particles. The size of LiFePO4 particles as-prepared is about 100-300 nm. The specific discharge capacities of the LiFePO4 particles are 151.3 and 128.0 mA. h. g-1 after first cycle at the rates of 0.1 and 1.0 C, respectively. It retains 95.0% of the initial capacity after 100 cycles at 1.0 C.     

片状LiFePO4/C正极材料制备及其电化学性能研究

在温和的反应条件下，使用十二烷基苯磺酸钠(SDBS)成功合成了片状二水磷酸铁，并将其与氢氧化锂、柠檬酸球磨混合，采用碳热还原法制备了具有纳米厚度的片状LiFePO₄/C电极材料。研究了SDBS对磷酸铁形貌以及LiFePO₄/C电极材料电化学性能的影响。利用X-射线衍射、扫描电子显微镜和充放电测试等技术手段，对合成样品的物相、形貌和电化学性能进行了分析测试。电化学测试表明，在25℃，2.0～4.2 V电压范围条件下，使用片状二水磷酸铁为前驱体制备的LiFePO₄/C样品，在0.1 C下放电比容量高达166.4 mA·h·g^-1，且首次库仑效率达到99.6%，在1 C下循环500次容量保持率为99%，表现出了优异的电化学性能。     

Reaction Sintering of ZnO-AI2O3

The reaction sintering of equimolar mixtures of ZnO and A1₂O₃ powders was investigated as a function of primary processing parameters such as the temperature, heating rate, green density, and particle size. The powder mixtures were prepared by two different methods. In one method, the ZnO and A1₂O₃ powders were ball-milled. In the other method, the ZnO powder was chemically precipitated onto the A1₂O₃ particles dispersed in a solution of zinc chloride. The sintering characteristics of the compacted powders prepared by each method were compared with those for a prereacted, single-phase powder of zinc aluminate, ZnAl₂O₄. The chemical reaction between ZnO and A1₂O₃ occurred prior to densification of the powder compact and was accompanied by fairly large expansion. The mixing procedure had a significant effect on the densification rate during reaction sintering. The densification rate of the compact formed from the ball-milled powder was strongly inhibited compared to that for the single-phase ZnAl₂O₄ powder. However, the densification rate of the compact formed from the chemically precipitated mixture was almost identical to that for the ZnAl₂O₄ powder. The difference in sintering between the ball-milled mixture and the chemically precipitated mixture is interpreted in terms of differences in the microstructural uniformity of the initial powder compacts resulting from the different preparation procedures.     

响应面法优化碳热还原合成LiFePO4/C的工艺参数（英文）

A statistically based optimization strategy is used to optimize the carbothermal reduction technology for the synthesis of LiFePO4/C using LiOH,FePO4 and sucrose as raw materials.The experimental data for fitting the response are collected by the central composite rotatable design(CCD).A second order model for the discharge ca-pacity of LiFePO4/C is expressed as a function of sintering temperature,sintering time and carbon content.The ef-fects of individual variables and their interactions are studied by a statistical analysis(ANOVA).The results show that the linear effects and the quadratic effects of sintering temperature,carbon content and the interactions among these variables are statistically significant,while those effects of sintering time are insignificant.Response surface plots for spatial representation of the model illustrate that the discharge capacity depends on sintering temperature and carbon content more than sintering time.The model obtained gives the optimized reaction parameters of sinter-ing temperature at 652.0 ℃,carbon content of 34.33 g?mol-1 and 8.48 h sintering time,corresponding to a dis-charge capacity of 150.8 mA·h·g-1.The confirmatory test with these optimum parameters gives the discharge ca-pacity of 147.2 and 105.1 mA·h·g-1 at 0.5 and 5 C,respectively.     

镁离子掺杂磷酸铁锂的制备及其电化学性能

通过简单水热反应制备磷酸铁锂前驱体,并结合后期热处理过程制备了镁离子掺杂碳包覆的磷酸铁锂正极材料。利用X射线衍射（XRD）、扫描电镜（SEM）和透射电镜（TEM）等表征了镁离子掺杂磷酸铁锂的成分、形貌和结构。元素分布结果证明镁离子均匀掺杂在磷酸铁锂材料中。通过恒流充放电和循环伏安、交流阻抗等方法对材料的电化学性能进行测试。结果表明,镁离子掺杂后的磷酸铁锂材料具有较高的放电比容量（0.1C放电比容量为 160.1 mA·h/g）和优越的倍率性能（20C放电比容量为77.2 mA·h/g）,同时减小了极化和电荷迁移电阻。这条合成路线是提高水热法制备磷酸铁锂正极材料电化学性能的有效方法。     

水热法一步合成磷酸铁锂及其性能研究

为优化液相法一步制备磷酸铁锂（LiFePO₄）技术,以七水合硫酸亚铁、磷酸二氢铵、一水合氢氧化锂为原料,通过添加十二烷基苯磺酸钠（SDBS）作为表面活性剂,采用液相水热法合成技术,一步合成了LiFePO₄正极材料。研究了水热法一步合成技术对LiFePO₄材料的组成、结构、形貌、粒度等的影响,通过电感耦合等离子体发射光谱仪（ICP-OES）、X射线衍射仪（XRD）、扫描电镜（SEM）、粒度分析仪等对材料进行了表征分析,并测试了材料的电化学性能。研究结果表明,合成得到的LiFePO₄材料为微米级球形颗粒形貌的正交晶系非化学计量比的Li_1.02Fe_0.994PO₄材料。电化学性能测试结果表明,在0.1C倍率下首次充、放电比容量分别为162.0、159.9 mA·h/g,库伦效率达到98.7%、倍率性能（以1C/0.1C保持率计）为92.3%,0.1C倍率循环100次容量保持率为96.4%,展现出良好的电化学性能。     

核桃壳炭的制备及其对氨氮废水的吸附性能研究

为解决当前氨氮废水污染问题,以自制核桃壳炭为吸附剂,以NH4+为模型吸附分子,考察了核桃壳预处理方式、焙烧温度、焙烧时间和铵根离子初始浓度等对氨氮废水吸附的影响,并采用多种手段对核桃壳炭进行表征.研究结果表明:经H3PO4预处理后于700 ℃焙烧2h制备的核桃壳炭对低浓度的NH4+具有优异的吸附能力;当铵根离子初始质量...     

球形LiMnPO4/C正极材料的喷雾干燥法制备及性能研究

以氢氧化锂、乙酸锰、磷酸二氢铵和聚乙二醇为原料,采用一次喷雾干燥法制备了球形LiMnPO₄/C正极材料,并研究了煅烧温度对球形LiMnPO₄/C样品形貌、结构和电化学性能的影响。通过X射线衍射（XRD）和场发射扫描电镜（SEM）对其进行了结构和形貌的表征。结果表明,经700 ℃焙烧的LiMnPO₄/C为橄榄石型结构,在SEM下呈规则的球形,由粒径约为50 nm的一维纳米颗粒堆积而成。该样品在室温0.1C倍率下首次放电比容量可达148 mA·h/g,循环80圈后的放电比容量依然在140 mA·h/g左右,容量保持率为94.6%。     

Enhancement of Densification and Thermal Conductivity in AlN Ceramics by Addition of Nano-Sized Particles

The effect of addition of nano-sized particles on densification and thermal conductivity of AlN ceramics was investigated. The commercially available AlN powder (∼0.9 μm) was mixed with 1.89 mass% nano-sized AlN particles (<0.1 μm), 3.53 mass% Y₂O₃, and 2.0 mass% CaO as sintering aid. The mixture was fired at 1500° and 1600°C in a tungsten resistance furnace under flowing N₂ atmosphere. The results showed that a fully densified specimen was obtained at the lower temperature of 1600°C by addition of nano-sized particles. The thermal conductivity of the resulting product was 133 W/m°C. The value is much higher than the 52 W/m°C for the sample prepared without adding the nano-sized AlN powder. This study indicates a strong potential for the use of nano-sized particles as additives in the densification of AlN ceramics.     

A PVB-based rheological phase approach to nano-LiFePO4/C composite cathodes

Nano-LiFePO₄/C cathode materials were synthesized by a PVB-based rheological phase method, followed by calcination at 550 °C for 10 h in argon. Simultaneous thermogravimetric-differential scanning calorimetry analysis indicates that the crystallization temperature of LiFePO₄ is about 436 °C. In the process of heat treatment, the decomposition of polyvinylbutyral coats carbon on the synthesized LiFePO₄ particles in situ. The resulting LiFePO₄ powders with fine particle sizes and homogeneous carbon network connection were observed by using scanning electron microscopy and transmission electron microscopy. Electrochemical measurements show that the LiFePO₄/C composite cathode delivers a large discharge capacity of 162.3 mAh·g^− 1 at the 0.1 C rate, and exhibits a favorable capacity cycling maintenance at lower charge and discharge rate such as 0.5 C rate.     

Influence of chemical composition on corrosion of alumina in acids and caustic solutions

The corrosion behaviour of pure alumina, doped with different amounts of MgO, Y₂O₃, ZrO₂, Cr₂O₃, Co₃O₄ and BaO, was investigated. Corrosion media were concentrated HCl, HNO₃, HF, H₂SO₄/H₃PO₄ (1:1 mixture), HCl (1%) and NaOH (10%). The reaction conditions were 180°C (autoclave) for 168 h. The corroded specimens were investigated by SEM, the leaching solutions were analysed with ICP-OES (optical emission spectroscopy with inductively coupled plasma). The corrosion resistance was found to depend mainly on the microstructure and the composition of the grain boundary phase. Both parameters are influenced by the type and concentration of the additive, the method by which the sintering aid was added and the sintering conditions.     

高电压磷酸钴锂正极材料性能调控研究

高性能、高安全储能电池的迫切需求加速了橄榄石型高电压正极材料的研究步伐。为了改善高电压磷酸钴锂(LiCoPO₄)的综合电化学性能,采用溶剂热法研究了溶剂比、过渡元素(Fe、Mn)单掺杂和双掺杂(掺杂元素总量占10%)对正极材料形貌、尺寸、反位缺陷和电化学性能的影响。结果表明,当溶剂比为2.3时,未掺杂LiCoPO₄在0.1C下表现出163.1 mAh·g^-1的最高理论比容量;双掺杂LiCo_0.9Mn_0.05Fe_0.05PO₄正极材料具有突出的循环性能,在0.5C电流密度下,循环100圈后的容量保持率为78.9%,循环稳定性得到明显改善。     

磷酸二氢钙对玉米秆灰熔融烧结特性的影响研究

农业秸秆通常含有较高的碱金属,在燃烧过程中易造成锅炉高温熔融烧结问题,影响锅炉正常运行。使用灰熔点测试仪并结合灰样烧结度测试研究磷酸二氢钙添加剂对玉米秆灰熔融烧结特性的影响规律。此外,使用固定床管式炉研究了磷酸二氢钙与两种不同钾盐之间的反应特性。结果表明燃烧温度和磷酸二氢钙与钾盐混合比例对反应产物影响显著。在碱金属盐过量时,磷酸二氢钙与碱金属盐在温度高于300℃时开始反应,300～600℃产物以Ca₂P₂O₇、Ca(PO₃)₂、KCa(PO₃)₃为主,700～900℃反应产物主要为K₂CaP₂O₇。当磷酸二氢钙过量时,除磷酸二氢钙与钾盐的反应外同时存在磷酸二氢钙的高温分解反应以及反应产物间的二次反应。此外,研究发现磷酸二氢钙与K₂CO₃的反应活性显著高于KCl。在玉米秆中添加磷酸二氢钙后可在灰分中形成高熔点的Ca_9<...     

Preparation of carbon-supported nano-sized LaMnO3 using reverse micelle method for energy-saving oxygen reduction cathode

Two ways of reverse micelle (RM) method were investigated to prepare carbon-supported nano-sized LaMnO₃ with high oxygen reduction activity. Hydrolysis precipitation in reverse micelle (HP-RM) method could give nano-sized particles of LaMnO₃ easily because the particles size decreased with decreasing R_w (=[H₂O]/[surfactant]) value as well as nitrate concentration. The electrode prepared by the resulting particles showed high oxygen reduction activity as compared with that prepared by mechanical mixing-method. Furthermore, it was found that new RM method (ROP-RM) using KMnO₄ as an oxidizer gave higher oxygen reduction activity than the HP-RM method, although particle size of LaMnO₃ obtained by the ROP-RM method was almost same as that by RM-HP method.     

具有多级孔道结构的高比表面多孔炭活化策略及VOCs吸附性能

以废弃榛壳为前体,采用不同活化策略制备多孔炭,探究活化策略和活化温度对多孔炭挥发性有机化合物（VOCs）吸附性能的影响,以及多孔炭的结构、表面性质与VOCs吸附性能的构效关系。结果表明,H₃PO₄法制备的多孔炭介孔体积大,且炭结构缺陷较少,吸附位点较少; KOH法获得的微孔体积较大,孔径集中在0.5~0.7nm的微孔,不利于VOCs分子吸附位点的有效利用。H₃PO₄-KOH分步法在850℃下制备具有高比表面积,孔径集中在0.5~1nm的宽微介孔分布,且炭结构高度无序并含有丰富缺陷位的多孔炭,为VOCs吸附提供了充足的吸附位点并提高了吸附位点了利用率,相比于H₃PO₄与KOH活化法制备的多孔炭的VOCs饱和吸附量显著提升,特别是对于弱极性VOCs。另外,H₃PO₄-KOH分步法制备的多孔炭表面官能团含量较低,极性较低,对非极性VOCs的吸附量远大于极性VOCs。因此,H₃PO₄-KOH分步活化策略是制备具有高比表面积、高VOCs吸附性能多孔炭的最优策略与方案。