Preparation of λ-MnO_2 by Column Method and Its Ion-Sieve Property

1　Ｉｎｔｒｏｄｕｃｔｉｏｎλ ＭｎＯ2 ｉｓｆｏｃｕｓｅｄｏｎｂｅｃａｕｓｅｏｆｉｔｓｅｘｃｅｌｌｅｎｔｃｏｎ ｄｕｃｔｉｂｉｌｉｔｙｉｎｓｅｃｏｎｄａｒｙｌｉｔｈｉｕｍ ｉｏｎｂａｔｔｅｒｉｅｓａｎｄａｄｓｏｒｐ ｔｉｏｎｓｅｌｅｃｔｉｖｉｔｙｆｏｒｌｉｔｈｉｕｍｉｏｎｉｎａｑｕｅｏｕｓｐｈａｓｅ[1- 4] .λ ＭｎＯ2 ｗａｓｕｓｕａｌｌｙｐｒｅｐａｒｅｄｂｙｓｏｆｔ ｃｈｅｍｉｓｔｒｙｓｙｎ ｔｈｅｓｉｓ[5] .Ａｓａｐｒｅｃｕｒｓｏｒ ,ｎｏｒｍａｌｓｐｉｎｅｌＬｉＭｎ2 Ｏ4 ｗａｓｐｒｅ ｐａｒｅｄｆｉｒｓ…     

Sol—Gel Synthesis of Normal Spinel LiMn2O4 and Its Characteristics

Normal spinel LiMn2O4 was synthesized by sol-gel method using lithium nitrate,manganese nitrate,citric acid and ethylene glycol as raw materials.LiMn2O4 was characterized by XRD,TG-DTA,IR,SEMand AAS,The optimum conditions for the synthesis were explored.Citric and ethylene glycol were mixed with molar ratio of 0.25,and the mixtrue was esterified at 140℃ for 4 hours.Then lithium nitrate and manganese nitrate were added with molar ratio of 0.6,In the system,the total molar of cations was equal to that of citric acid.At last,reflux the system at 105℃ for 2 hours,Dried gel was fired at 600℃ for 8 hours.Particle diameters of raw product were about 100nm mainly.Further research shows that lithium ion of LiMn2O4 is easy to be extracted,and normal spinel λ-MnO2 can be obtained after lithium ion extraction.     

LixMnO2正极材料的合成及其电化学特性

综述了近年来LixMnO2正极材料的最新研究成果，归纳了合成层状结构的LixMnO2的主要方法，评述了该体系材料的电化学特征。     

Comparative study of LiNiO2,LiNi0.8Co0.2O2and LiNi0.75Al0.25O2 for lithium—ion batteries

The comparative study of LiNi0.8Co0.2O2 and LiNi0.75Al0.25O2 was carried out by X-ray diffraction(XRD) and electrochemical methods.The results show that Co and Al doping suppress the phase transition during charge-discharge.The experiments indicate that LiNi0.75Al0.25O2 has the better cycle-ability and over-charge resistance comparing with LiNi0.8Co0.2O2,The interfacial behavior was studied by use of electrochemical impedance spectroscopy(EIS).The results show that LiNi0.75Al0.25O2 has a slightly larger polarization character than LiNi0.8Co0.2O2.     

Preparation and Characterization of LiMn1.8Co0.2O3.95F0.05 by the Combustion-assisted Soft Route

LiMn1.8Co0.2O3.95F0.05 powder was prepared by heating the ignited LiMn1.8Co0.2O3.95F0.05 precursor gel using lithium acetate, magnesium acetate, cobalt acetate, lithium fluoride, citric acid and glycol as raw materials. The influence of the calcination temperature on the stractural and electrochemical properties of LiMn1. 8 Co0.2 O3.95 F0.05 was investigated by X-ray diffraction, scanning electron microscopy, and galvanostatic charge-discharge experiments. The powders prepared under different conditions are of good crystallinity. The discharge capacity of LiMn1. 8 Co0.2 O3.95 F0.05 powder inereased from 92 mAh/g to 105mAh/ g as the calcination temperature inereasedfrom 750 ℃ to 850 ℃ . The capacity of LiMn1. 8 Co0.2 O3.95 F0.05 heated at 750 ℃ , 800 ℃, 850 ℃ for 4 haurs remained at 95.2% , 97%, 94.2% , respectively, after being cycled 20 times, suggesting that the multiple substitution of Co and F for Mn and O results in a good cycling behavior.     

Effect of La Dopant on the Structure and Electrochemical Properties of LiCoO2

The cathode material LiCo1-xLaxO2（x=0,0.01,0.02,0.05）for Li-ion battery was prepared in solid phase,Effects of La dopant on the structure were analyzed by X-ray diffraction.and the morphology of the samples was observed by scanning electron microscopy.The results show that the structure of LiCoO2 becomes more and more non-perfect with the4 increasing comtent of La and some impurity peaks appear in the XRD pattern when the La content reaches 0.05.Meamchile,a high synthesis temperature is advantageous to the intact and unitary compound,The initial discharge capacity of doped material containing La（x=0.01）synthesized at 900℃ reaches 160 mAh/g by charge-discharge test.which prior to that of non-doped material synthesized under the same condition.However,the increasing La content deteriorates the cycling performance.Therefore,the appropriate content of La is 0.01 and the optimum synthesis temperature is 900℃.     

Characterization and Electrochemical Properties of LiMn2O4 Thin Films Prepared by Solution Deposition

1 IntroductionThin-filmlithium-ion batteries have attracted greatattention of researchfor possible use inimplantable medi-cal devices , CMOS-based integrated circuits ,radio fre-quency (RF) identification tags for inventory control andanti-theft protection[1],etc. Li Mn2O4thin films , aspromising cathode materials for thin-filmlithium-ion bat-teries, have been prepared by a few methods such aspulsedlaser deposition[2 ,3],electrospraying[4-9],RF mag-netron sputtering[10], laser ablation[11]…     

液相法制备LiMn2O4及掺杂研究

以LiNO3,Mn(NO3)2和弱有机酸为原料，将其按一定比例混合，先天低温蒸干水分，再在250℃加热1h，得到黑色前驱物粉末；将前驱物在650－800℃焙烧10－20h便可得到LiMn2O4晶体；此外，研究了生产LiMn2O4晶体过程中温度及添加Ni,Co,Al对LiMn2O4晶化程度和结晶结构的影响。研究结果表明：利用液相法可以使反应物充分反应，能够得到晶形完整、结晶度高的尖晶石型LiMn2O4；并通过该液相法能更均匀掺杂，得到晶粒粒径更小的掺杂Ni,Co,Al型LiMxMn2-xO4。     

Bactericidal and Photocatalytie Activity of Fe^3＋-TiO2 Thin Films Prepared by the Sol-gel Method

Pure TiO2 thin films and iron doped TiO2 thin films on glass substrate were prepared by sol-gel method, and characterized by X-ray diffractometer （XRD）, thermo-gravimetric analysis （TG-DSC）, high resolution transmission electron microscope （HRTEM）, scanning electron microscope （SEM） and UV-Vis spectroscopy, respectively. The experimental results show that the pure TiO2 thin films and iron doped TiO2 thin films can destroy most of the escherichia coli and bacillus subtillis under the irradiation of 365 nm UV-light. However, the iron doped TiO2 thin film is a better photocatalyst than pure TiO2 thin film. The ultrastructural studies provide direct evidences for understanding the bactericidal mechanism of the TiO2 photocatalyst.