高振实密度球形LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2粉末的合成及性能

以共沉淀法制备的球形Ni_(0.5)Co_(0.3)Mn_(0.2)CO_3粉末为前驱体,按一定的比例将碳酸锂与前驱体混合,然后采用高温固相法合成高振实密度球形LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2正极材料.该材料的振实密度达到2.60 g/cm~3,与商品化LiCoO_2的密度相当.SEM分析表明, LiNi_(0.5)Co_(0.3)Mn_(0.2)O_2正极材料与前驱体形貌有良好的继承性,均为理想的球形.XRD物相分析表明,在不同合成温度下的Li Ni_(0.5)Co_(0.3) Mn_(0.2)O_2产物均为具有α-NaFeO_2层状结构的纯相物质,在较高合成温度下所得材料的结晶度较高.电化学性能研究表明,在2.7～4.3 V的电压范围内,电池的放电比容量在0.2C倍率下为168.1 mA-h/g,在1C倍率下为157.6 mA-h/g;经50次循环后,两种放电条件下的电池容量保持率分别为95.1%和97.2%,显示出良好的电化学性能.     

薄壁金刚石钻头的研制和在电熔锆刚玉耐火材料中的应用

电熔锆刚玉砖具有高硬度、耐高温、耐磨损、抗腐蚀等特点,因而成为玻璃熔窑的关键筑炉材料。文章通过复合电镀方法研制和生产薄壁金刚石钻头。在研制过程中,对金刚石钻头的胎体配方进行了优化,确定了电镀工艺参数,分析了金刚石参数等对钻进过程的影响,采用混目金刚石扩大了钻头的适用范围,提高了钻头的自锐性。研制的电镀薄壁金刚石钻头用于钻进锆刚玉砖耐火材料,其平均使用寿命达到6m,钻进时效为1.5m。使用结果表明:胎体配方、工艺流程和电镀参数是合理的,电镀金刚石薄壁钻头是最适合钻进电熔锆刚玉砖的金刚石工具,加工后的锆刚玉砖具有精确的几何形状和高光洁度的表面。     

Al2O3包覆改善P2型Na2/3Fe1/2Mn1/2O2正极材料的存储性能

采用超声喷雾热解与高温固相烧结相结合的方法合成P2型Na_2/3Fe_1/2Mn_1/2O₂材料。通过X射线衍射仪、扫描电子显微镜和电化学充放电设备对材料的结构、形貌和电化学性能进行全面的表征。此外,在Na_2/3Fe_1/2Mn_1/2O₂表面包覆Al₂O₃薄层,该包覆层可以抑制Na₂CO₃·H₂O的形成,提高Na_2/3Fe_1/2Mn_1/2O₂材料的存储性能,从而改善其电化学性能。这种简单的表面改性方法为合成高性能钠离子电池正极材料提供了新思路。     

制备过程pH值对FePO4·xH2O及LiFePO4性能的影响

以FeSO4·7H2O,H3PO4,H2O2和NH3·H2O为原料合成FePO4·xH2O前驱体,考察制备过程溶液pH值对合成FePO4·xH2O前驱体性能的影响;将Li2CO3,FePO4·xH2O和乙炔黑球磨混合,通过低温固相反应合成LiFePO4.用X射线衍射和扫描电镜对FePO4·xH2O和LiFePO4进行结构和表面形貌表征,研究不同pH值条件下合成的FePO4·xH2O前驱体为原料对制备的LiFePO4电化学性能的影响.结果表明溶液pH值1.5时制备的FePO4·xH2O中含有少量Fe(PO4)2(OH)2杂质.当pH分别为2、3、4和5时,合成的FePO4·xH2O均为纯相.pH值为2左右合成的FePO4·xH2O前驱体制备出的LiFePO4具有良好的电化学性能;其振实密度达1.11 g/cm3.     

LiFePO4包覆LiCoO2的结构及性能

采用固相法在锂离子电池正极材料LiCoO2表面包覆一层LiFePO4;研究了LiFePO4包覆量对材料性能的影响;采用X射线衍射仪和扫描电镜分析样品的晶体结构和表面形貌.研究结果表明:样品具备LiCoO2的α-NaFeO2型层状结构,但随着包覆量的增加,XRD衍射谱显示样品存在多种杂相;合成的样品电化学性能良好,当LiFePO4的包覆量为1%时,在室温下以0.1C倍率充放电,首次放电比容量达145.9 mA·h/g,纯相LiCoO2放电比容量为146.2 mA·h/g.样品采用1C倍率放电时,首次放电比容量达138.9 mA·h/g,循环性能较好,经过20次循环放电比容量仅衰减4.97%.     

Synthesis and electrochemical performance of Co3O4/C composite anode for lithium ion batteries

The Co3O4/acetylene black composite anodes were successfully prepared by combination of oxalate precipitation and pyrolysis of the precipitate. The composite and its precursor were characterized by thermo-gravimetric analysis(TGA), differential thermal analysis(DTA), X-ray diffractometry(XRD), scanning electronic microscopy(SEM) and electrochemical measurements. The effects of carbon content and calcination temperature on properties of the composite were investigated in detail. The cycling performance of the Co3O4 anode is improved remarkably by the addition of carbon. As the calcination temperature rises in the range of 300-450 ℃, the crystallinity of the composites increases, but their reversible capacity and cycling stability decrease. Being charged/discharged at a current density of 0.1C rate, the optimized Co3O4/C composite anode shows a large initial reversible capacity of 757 mA-h/g, and a capacity of 743 mA-h/g is observed after 10 cycles.     

Electrochemical properties of high-power lithium ion batteries made from modified spinel LiMn2O4

A prismatic 204056-type high power lithium-ion battery was developed. Modified LiMn₂O₄ and carbonaceous mesophase sphere (CMS) were adopted as the cathode and anode, respectively. The effects of proportion of conductive carbon black in cathode and the rest time after discharge on the electrochemical properties of batteries were investigated. The electrochemical tests show that the proportion of conductive carbon black in cathodes affects the high rate capability and discharge voltage plateau distinctly. The battery with 3.0% of conductive carbon black in cathode shows excellent electrochemical performances when being charged/discharged within 2.5?4.2 V at room temperature. The discharge capacity at 20C rate is 94.4% of that at 1C rate, and the capacity retention ratio charged at 1C and discharged at 5C is 86.6% after 390 cycles at room temperature. The test result of impulse discharge at 50C for 5 s shows that the battery has outstanding high rate discharge performance when the battery is in the depth of charge of 90%, 75%, 60%, 45%, 30% and 15%. The battery also shows good charge performance. When the battery is charged at 0.5C, 1C, 2C and 4C, the ratios of capacity for constant current charge are 98.4%, 96.4%, 91.0% and 72.9% of the whole charge capacity, respectively. In addition, the rest time after discharge affects the cycle performance distinctly when the battery is discharged at high rate.     

烹饪技术刀工技能的训练方法与运用分析

刀工技能是一名优秀厨师的专业基础技能.要想提高个人烹饪技术水平,就需要从刀工技能开始学习.刀工技能对于一盘菜肴的外观有着重要作用,可以体现出一名烹饪厨师的专业能力.为此,一名厨师在接受烹饪技术刀工技能训练的过程中,通过烹饪教师的引导,可以促使个人刀工技能得到全面提升,并在实际烹饪过程中熟练运用刀工技能,以此确保所烹饪出...     

Synthesis of Y2O3：Eu^3＋ phosphors by surface diffusion and their photoluminescence properties

Y2O3:Eu3+ phosphors were synthesized by the surface diffusion method (SDM). X-ray diffractometry (XRD), scanning electron microscopy (SEM), and energy dispersive spectrometry (EDS) were used to characterize the structure, morphology and component of Y2O3:Eu3+ phosphors. The photoluminescent (PL) properties were also investigated. The results reveal that the PL intensity of Y2O3:Eu3+ phosphors prepared by the surface diffusion method (SDM) is much higher than that prepared by homogeneous co-precipitation. Th...     

基准修正法开发设计异形MH/Ni电池

基准修正法是以设计合理、经过生产检验已成型的某种规格的MH/Ni电池为参照基准 ,进行缩放 ,并综合考虑电池尺寸特点、用电设备的具体使用要求 ,按照一定的规律进行修正 ,从而对电池极片尺寸、活性物质用量、电解液用量、隔膜尺寸及电池结构等进行优化设计。本研究采用基准修正法成功地开发设计了一系列具有高容量、长寿命 (标准寿命 >80 0次 ,1C5快速充放寿命 >5 0 0次 )、优良的负载特性和高倍率充放电能力、安全可靠、无污染的封口化成MH/Ni电池