15 October 2013, Volume 44 Issue 19

    

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工艺 技术
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  Preparation of the Precursor FePO4 of LiFePO4 by Sulfuric Acid Assisted Circulation

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  . 2013, 44(19): 1-0.

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  In this essay, Based on iron powder for iron source, the precursor of LiFePO4 which is the cathode material of lithium ion battery were synthesized by sulfuric acid assisted circulation. The results show that: The excess sulfuric acid can make the reaction of iron powder and phosphate thorough, and it can be used circularly in the system, then the whole system did not produce any waste stream. The results of XRD and SEM indicate that the structure, morphology and size of FePO4 which were composed in the first time or cycle 30 times are the same. The LiFePO4/C composite cathode material was synthesized using self-regulating FePO4 under different cycle times as a precursor, glucose as a C source, and LiOH as a Li source, in a pipe furnace under an atmosphere of 5% H2–95% N2, followed by sintering in a pipe furnace at 350℃ for 5h, then at 750℃ for 15 h. LiFePO4/C displays good consistency and show excellent electrical performance: at a rate of 0.2C, 0.5C,1C, 5C ,the discharge capacities are 155.1mAhg?1,144.0mAhg?1, 134.4mAhg?1, 101.7mAhg?1, in addition, owns outstanding ratio and cycle performance.
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  Preparation and Supercapacitive Behaviors of Emission-Like OMS-2 Manganese Dioxide

  fen ran

  . 2013, 44(19): 2-0.

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  emission-like manganese dioxide was controlled synthesized by using the hydrothermal method in the different reaction time for supercapacitor electrode. The structures were characterized by XRD and SEM, and the supercapacitive behaviors were investigated with cyclic voltammetry (CV), charge–discharge tests, and ac impedance spectroscopy, respectively. The conclusion suggested that the as-prepared manganese dioxides indexed tetragonal cryptomelane phase and the morphology of which was emission-like nanoclusters. Crystallinity and structure dimension become larger and the nanostab structure of every single branch was changed into nanorod structure followed with the time. The specific capacitance values of manganese dioxide electrode was 448 F/g corresponding to the charge/discharge current densities of 5 mA/cm2. With the prolonging of reaction time, the specific capacitance tend to raise first and then declined.
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  Preparation of Nitrogen-doped Carbon Film as Counter Electrode for Dye-sensitized Solar Cells by Magnetron Sputtering

  . 2013, 44(19): 3-0.

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  The nitrogen-doped carbon film was prepared by bipolar pulsed magnetron sputtering as counter electrode in Dye-sensitized solar cells(DSSC). The structures and properties were investigated. The surface elemental of nitrogen-doped carbon film was analyzed by X-ray photoelectron spectroscopy. The sheet resistance of nitrogen-doped carbon film was detected by four point probe. The surface morphologies were observed by scanning electron microscopy. The performance of DSSC was tested by solar simulator after the cell built up. The results indicated that the surface morphology of nitrogen-doped carbon film was high density, when volume fraction of nitrogen was 30%, the nitrogen content in the film was15.21%, the sheet resistance was 9.4/□.The counter electrode exhibited a good photovoltaic performance, the efficiency reached 1.16 %.
研究 开发
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  Study and fabrication of lithium ion batteries using tris(methoxypolyethyleneglycol) aluminate esters as plasticizer for polymer electrolyte

  . 2013, 44(19): 4-0.

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  Abstract: A novel comb-like copolymer electrolyte was designed by co-polymerizing of two macro-monomers: methoxy-poly(ethylene glycol) methacrylate(MPEGM) and hexadecal-poly(ethylene glycol) methacrylate(HPEGM), tris(methoxypolyethyleneglycol) aluminate ester (MPEG–Al ester), Li-salt(LiClO4). Performances of the polymer electrolytes were studied by FT-IR, DSC and alternating current(AC) impedance and so on. The results showed that P(MPEGM-HPEGM) had been formed and the motion of PEO chains had been improved. The polymer electrolytes possessed excellent thermal stability and electrochemical stability. And when the weight ratio of MPEGM to HPEGM to MPEG7-Al ester was 4:1:5, the maximum ionic conductivity value reached 0.43×10-3 S.cm-1 with n(Li):n(EO)=1:20 at 30°C.
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  A novel redox-active gel polymer electrolyte application in supercapacitors

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  . 2013, 44(19): 5-0.

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  In this paper, a gel polymer electrolyte (GPE) polyvinyl alcohol-sulphuric acid-2-mercaptopyridine (PVA-H2SO4-PySH) was prepared by sol-gel method using PySH as a redox mediator and PVA as a polymer host. The effect of the added amount of PySH on the ionic conductivity of GPE was investigated. The electrochemical properties of the supercapacitor with the prepared gel polymer electrolyte and activated carbon electrodes were evaluated by cyclic voltammetry, galvanostatic charge-discharge, electrochemical impedance spectroscopy and self-discharge measurements. The results indicate that the ionic conductivity of GPE and the electrochemical properties of the supercapacitor were improved by introducting PySH. At the same current density, the electrode specific capacitance and energy density of the supercapacitor increase from 137 to 394 F?g?1 and 3.6 to 12.4 Wh×kg–1, respectively. In addition, the capacitive retention ratio of the supercapacitor still retains 89 % over 3000 charge-discharge cycles.
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  Preparation and performances of RuO2/CuO composite electrode materials

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  . 2013, 44(19): 6-0.

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  Amorphous hydrous ruthenium oxide and copper oxide powders respectively prepared by a sol-gel process and low heat solid-state reaction. The ruthenium oxide-copper oxide composite electrodes with different copper oxide contents were prepared .The morphology of the composite electrode was investigated by SEM. Based on the cyclic voltammetry, AC impedance spectroscopy and constant current charge-discharge techniques, the performances of the electrodes are investigated. The results show that the compositing of copper oxide and ruthenium oxide is beneficial to obtaining of fine particles and improving the impedance characteristic and conductivity. The results show that the composite electrode with 30 % (mass fraction) copper oxide is ideal, and its specific capacitance and inner resistance are 513 F/g and 0.361 Ω, respectively, measured at 5mV/s in 38% (mass fraction) H2SO4, After 400 cyclic-life, the specific capacitance of RuO2/CuO composite electrode is kept at 91.4%.
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  Synthesis and Electrochemical Properties of NaxCo2O4 as a Novel Electrode Material for Supercapacitors

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  . 2013, 44(19): 7-0.

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  NaxCo2O4（x=1.0,1.2,1.4,1.6,1.8,2.0）samples were prepared by sol-gel method, and applied to the supercapacitor as electrode materials for the first time. The synthesized NaxCo2O4 crystals were performed using XRD , SEM. Results indicated that they were all layered structure. The capacitance performance of NaxCo2O4 ( x=1.6 ) sample was the greatest and its specific discharge capacitance was 413F/g between 0.25 and 0.7V potential at 50mA/g current density in 6mol/L NaOH solution.
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  Fabrication and electrochemical performance of core-shell silicon/graphite composite anode material based on graphite matrix

  ;Xian-Hua HOU ;;;

  . 2013, 44(19): 8-0.

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  Silicon/graphite with core-shell structure composites were successfully synthetized by spray drying in combination with a following heat-treatment process. Structure and morphology of the composites were characterized by XRD/SEM measurements. Investigated by charge-discharge test（CC）, cyclic voltammetry (CV) and electrochemical impedance (EIS), the core-shell silicon/graphite composites coated by citric acid, phenolic resin and glucose have better electrochemical performance than that of the conventional graphite. And with the high initial coulombic efficiency and high capacity retention rate, the silicon/graphite composite coated by glucose has the best electrochemical performance.
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  Synthesis and Characterization of LiNi0.5Mn1.5O4 Cathode Materials for Lithium Ion Batteries by Solid State Method

  . 2013, 44(19): 9-0.

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  LiNi0.5Mn1.5O4 cathode materials were synthesized by solid state method using Ni(CH3COO)2?4H2O、Mn(CH3COO)2?4H2O as starting materials，then decomposed to get nickel manganese oxides at 400 ℃ and 500 ℃for 3h or 7h，Joined and mixed the source of lithium Li2CO3. The sample calcination in air at 800 ℃ for 12h and then annealed at 600 ℃ for 24h. XRD、SEM、EIS and charge-discharge performance tests showed that LiNi0.5Mn1.5O4 delivered the best electrochemical performance by used precursor made at 400 ℃ for 7h. Its initial specific discharge capacity Was 141.5mAh?g-1 when 0.1C charge-discharge at room temperature,and after 30 cycles the capacity retention is 98.59%；when charged-discharged at 1C initial capacity Was 120.34mAh?g-1，and after 30 cycles the capacity was 112.09 mAh?g-1.
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  The effect of La3+ and F- co-doping on high rate capability of LiMn2O4

  wang-wan ;;;

  . 2013, 44(19): 10-0.

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  Abstract: Co-doping with La and F lithium manganese oxide LiLaxMn2-xFxO4-x（x=0，0.01，0.02，0.05）materials were synthesized by segmented solid-state sintering method. The results showed that co-doping had unobvious effect on the discharge capacity at the current density below or equal to 1C. However, the rate performance from 2C to 10C was significantly improved. Besides, doping amount had great influence on the discharge property at 15C. Especially, when the doping amount was 0.02, the discharge capacity was increased from only 4％ to 56％. The results were supported by means of X-ray diffraction (XRD)，Cyclic voltammetry(CV) and Electrochemical impedance spectroscopy (EIS). When there was no second phase, the charge transfer resistance, the anodic and cathodic polarization decreased and the electrochemical reversibility enhanced gradually with the increase of doping amount. However，when the second phase appeared at x=0.05, the charge transfer resistance, anodic and cathodic polarization began to increase.
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  Hydrothermal synthesis and electrochemical performance of flower-like Li4Ti5O12 nanoplatelets

  Xinlu Li

  . 2013, 44(19): 11-0.

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  Flower-like Li4Ti5O12 nanoplatelets were synthesized by a hydrothermal method using Ti(OC4H9)4 and LiOH?H2O as the raw materials. The effect of different ratio of raw materials on the crystal structure was investigated. X-ray diffraction and scanning electron microscopy were used to analyze the crystal and morphology of Li4Ti5O12 na-noplatelets. The analysis show that the products are made up of Li4Ti5O12 nanoplatelets to form the flower-like microspheres with a spinel crystal structure. The constant charge-discharge experiments illustrate that the initial discharge capacity were up to 160mAh/g、141mAh/g、128mAh/g at the rate of 0.1 C、1C、2C, respectively.
工艺 技术
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  Electrically conductive graphene/polystyrene nanocomposites obtained by self-assembly based latex template technology

  Peng-Fei ZHAO ;;;

  . 2013, 44(19): 12-0.

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  Electrically conductive graphene nanosheets filled polystyrene (GNs/PS) nanocomposites were fabricated via electrostatic assembly integrated latex-template technology. Firstly, positive charged PS beads were synthesized with dispersed polymerization by using methacryloxyethyltrimethyl ammonium chloride as co-monomer, and then coassembled with graphene oxide. Eventually, GNs/PS nanocomposites with a honeycomb-like GNs framework were obtained after the follwoing in situ reduction and hot compression molding steps. Due to the well-constructed GNs network which elecrevealed by scanning electron microscope (SEM), the resulted GNs/PS nanocomposites show extremely low percolation threshold of 0.09vol.% and high saturated conductivity of 25.2 S/m. TGA analysis implied that the thermal stability of PS was improved by the addition of GNs. The mechanism of co-assembly and the formation of such microstructure were discussed.
综述 进展
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  Studies of vanadate compounds as anode materials for aqueous Li-ion battery

  . 2013, 44(19): 13-0.

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  Anode materials have become the key factor restricting the development of aqueous lithium-ion battery (ALIB). Due to their high specific capacities and suitable lithium insertion/extraction potentials, vanadate materials have been widely utilized as anode materials for ALIB. This paper reviewed the current research progress of ALIB on the basis of research results in our group and the emphasis was placed on their crystal structure, charge-discharge mechanism, synthesis methods and electrochemical properties. Meanwhile, improvement measures were put forward to further better the electrochemical properties of vanadate materials in ALIB.
研究 开发
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  Preparation of Polyaniline Nanotubes by Tubular Manganese Deoxide and its Super-capacitive Performance

  lei zhao;fen ran ;;;

  . 2013, 44(19): 14-0.

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  Abstract: Polyaniline nanotubes (PANI) were successfully prepared using tubular manganese dioxide as oxidant and template in acid water system. The structure was characterized by using scanning electron microscopy (SEM), transmission electron microscopy (TEM), and fourier transformation infrared spectroscope (FTIR), and the supercapacitive behaviors of these nanotubes were investigated with cyclic voltammetry (CV), charge–discharge tests, and electrochemical impedance spectroscopy (EIS), respectively. The effects of aniline (ANI) amount and electrolyte on the structure and electrochemical performance of prepared PANI were discussed in detail. The results indicate that the prepared PANI present nanotube morphology with inner diameters of about 90 nm, outer diameters of about 350 nm, and lengths of about 2 μm; When feed ratio of manganese dioxide (MnO2) to aniline (ANI) was changed from 9 to 25, a maximum specific capacitance (SC) of as-prepared PANI nanotubes of 473 F/g could be achieved in 1 M aqueous H2SO4.
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  Research on emulsion polymerization method and capacitive performance of doped PANI nanomaterial for supercapacitor

  Xin-Xian ZHONG ;;Youguo Huang ;;

  . 2013, 44(19): 15-0.

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  Abstract: In this paper, doped polyaniline (abbr. PANI) was prepared by using emulsion polymerization method and using MnO2 as the oxidant，adding surfactant (SDBS, SDS, T-X100) at ambient temperature. The morphology and structure of doped PANI (PANI-SDBS, PANI-SDS, PANI-T-X100) were characterized by scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray diffraction (XRD). Symmetric redox supercapacitor was assembled with the doped PANI as active electrode material and 1.0 mol/L H2SO4 aqueous solution as electrolyte. The electochemical performance of these supercapacitors was investigated by cyclic voltammetry (CV), electrochemical impedence (EIS) and galvanostatic charge-discharge. These results show that the specific capacitance of PANI-SDBS and PANI-T-X100 is about 393 F/g and 339 F/g at the current density of 5 mA/cm2, respectively, which is higher than that of PANI (228 F/g). After 1000 charge-discharge cycles the specific capacitance of PANI-SDBS is still higher than that of PANI. Among them PANI-SDBS fiber nanomaterial has higher specific capacitance and better cycle performance.
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  EIS Study on Different Status of Dye Adsorption of Dye-Sensitized Solar Cells

  Yu-Xun WANG;;

  . 2013, 44(19): 16-0.

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  Abstract：The energy conversion efficiency of dye-sensitized solar cells (DSC) with different status of dye adsorption on the TiO2 surface was investigated. The recombination of electrons in the DSC under different status of dye adsorption was characterized by electrochemical impedance spectra (EIS). The results showed a decline of electron recombination at interface under the condition of unsaturated dye adsorption through adjusting the dye loading amount on the TiO2 film, which increased the lifetime of electrons transport in the TiO2 film and enhanced the fill factor of the DSC.
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  In-situ carbonation synthesis of LiFePO4/C and its electrochemical properties with ferrous gluconate

  Li Ren

  . 2013, 44(19): 17-0.

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  LiFePO4/C composite materials were prepared by solid-state reaction with ferrous gluconate as carbon source and partial iron source. The structure and morphology of sample materials were characterizd by X-ray diffraction and scanning electromicro scopy. The electrochemical performances of composites were measured by Electrochemical Workstation and Charge-discharge Test System. The highest discharge capacity of LiFePO4/C composite with 4.75% carbon coating sintered at 650°C for 10h was 161.6, 147.2 and 123.3mAh/g at 0.1C, 0.2C and 1C rate, respectively. There is no fade of discharge capacity after being charge-discharge for 50 cycles at 1C rate. The results showed that due to the strong chemical bonds between gluconate and iron ions, a uniform layer of carbon film was formed on the surface of particles and some filamentous amorphous carbon was formed between the particles after sintering. The particle growth was inhibited during sintering and a complete conductive network was formed due to the effective carbon coating, hence the utilization of active materials was improved and the electrocemical properties were enhanced.
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  Preparation of LaNi0.6Fe0.4O3 Powders by Stearic Acid Gel Method

  Jian-Qiao HAN;;Jianfeng Zhu;

  . 2013, 44(19): 18-0.

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  LaNi0.6Fe0.4O3 cathode powders for solid oxide fuel cell was synthesized at 650℃ by stearic acid gel method using stearic acid, lanthanum oxide, nickel nitrate and ferric nitrate as raw materials. The direct calcination method was designed to efficiently avoid the formation of the impurities in the synthesis process. Differential scanning caborimetry analysis (DSC) and thermogravimetric analysis (TG) were used to characterize the process of calcining. The powder properties were characterized by XRD and SEM. The as-prepared LaNi0.6Fe0.4O3 powders showed a better degree of crystallization and a high degree of purity after calcined at 650℃ for 2h. The size of particles with pervoskite structure was in sub-micron and no large reunite in the powder.
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  Performance of MEMS microcapacitor based on polypyrrole/graphene oxide electrodes

  Ping ZHU ;;

  . 2013, 44(19): 19-0.

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  With the advantage of height capacity, higher energy storage density and resistance to high overload , microcapacitor has broad prospect of application in micro power systems, fuze system and things networking technology field. The MEMS microcapacitor with a three dimensional microstructure is designed. This microcapacitor is consists of current collectors with three dimensional structure, feature films as electrodes, gel electrolyte and BCB packaging. The three dimensional structure of current collectors is prepared by the deep reactive ion etching method. The feature films is deposited on the current collector surface by an electrochemical polymerization for polypyrrole/graphene oxide synthesis. The structural characterization of the electrode show that the polypyrrole has been doped graphene oxide fully and the microstructure of the feature films is structured.The electrochemical behaviors of microcapacitor was investigated by electrochemical tests. The microcapacitor presents 30 uF capacitance value, 7 mF/cm2 specific capacity at discharge current 3 mA, remained at 90% specific capacity after 4000 times charging and discharging cycle. The results indicate the microcapacitor has the stable capacitance performance and good cycle performance.
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  Preparation and discharge properties of amorphous Mg65-xNi21Pr14Agx alloy electrodes

  . 2013, 44(19): 20-0.

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  The amorphous alloys Mg65-xNi21Pr14Agx were prepared by copper-mold injection casting and the size of the alloy particles was decreased by ball-milling. The effects of different Ag contents to the charge/discharge behavior, the discharge capacity, cycle stability and high-rate dischargeability of the amorphous alloy electrodes were investigated respectively. The results showed that the charge/discharge properties of alloy electrodes were improved by Ag additive. The maximum discharge capacity and the cycle stability first increased and then decreased with the increase of Mg contents. The high rate discharge dischargeability of alloy electrodes was also improved. It indicated that the discharge property of the amorphous Mg-Ni-Pr-based alloys was significantly improved by the appropriate Ag content.
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  Preparation and properties of graphene for supercapacitor application

  Mei-Rong YUAN

  . 2013, 44(19): 21-0.

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  Graphene were prepared by simple redox method using graphite as raw materials. Supercapacitors were fabricated using the as-prepared graphene as electrode in organic electrolyte . The phase and morphology were characterized by XRD and SEM methods. The performance of supercapacitors were analyzed using galvanostatic charging and discharging testing, cyclic voltammetry and electrochemical impedance spectroscopy. The results showed that graphene-based supercapacitors had larger values of specific capacitance than that of the natural graphite-based ones. The specific capacitance was 45.5 F/g (rentention rate at 85.5%) after 888 charging and discharging cycles at the current density of 200 200 mA/g between the voltage from 1.25 V to 2.5 V. The graphene-based supercapacitors have a good charge-discharge cycle performance.
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  Investigation of structure and electrochemical properties of the V40Zr5Ti30Cr10Ni15Mox(x=0,2,4,6) alloys

  Yan-Wei TONG;Gao Jiao Cheng

  . 2013, 44(19): 22-0.

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  Effect of polyacrylic acid on the structure and properties of LiNi1/3Co1/3Mn1/3O2 cathode material for lithium ion battery

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  . 2013, 44(19): 23-0.

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  Nanocrystalline LiNi1/3Co1/3Mn1/3O2 cathode materials were synthesized by sol-gel method using polyacrylic acid (PAA) as a chelating agent. The effects of the molar ratio of PAA to total metal ions and calcination temperature on the structure and electrochemical performance of the LiNi1/3Co1/3Mn1/3O2 electrode materials were investigated. The results showed that the well-distributed LiNi1/3Co1/3Mn1/3O2 with lamellar structure was obtained at a calcination temperature of 700 oC. The crystal developed completely and the grain size of the LiNi1/3Co1/3Mn1/3O2 particle was about 80 nm. The initial discharge capacity of 169.2 mAhg-1 was obtained while the molar ratio of PAA to total metal ions 0.75, and the discharge capacity retention ratio was 89.3% after 30 cycles.
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  Use of LiPF6/LiBOB blend salt for improving cycling performances of LiFePO4/graphite battery at elevated temperature

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  . 2013, 44(19): 24-0.

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  LiPF6, LiBOB and LiPF6/LiBOB blend salt-based electrolytes were investigated for improving cycling performances of LiFePO4/graphite lithium-ion batteries at elevated temperature. It was demonstrated that dissolution of Fe from LiFePO4 was depressed in LiBOB based electrolyte, and columbic efficiency of LiFePO4/Li cell at elevated temperature was increased; LiBOB was reduced earlier on anode surface, forming compact SEI layer; and the capacity retention of LiFePO4/graphite cells at 55 ℃ increases with the LiBOB concentration due to protective depositions of LiBOB on cathode surface and the SEI layer on anode surface, while the impedance of the cell is increased. LiPF6/LiBOB blend salt-based electrolyte combines the advantages of the different salts and maximizes the performance of cells. When electrolytes with LiPF6/LiBOB blend salt was used, the LiFePO4/graphite cells have excellent capacity retention at 55℃, while the impedance was dramatically decreased.
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  Dielectric and surface potential study of NiO/ La2Mo2O9 composite

  Qin Li;Jin-Ling Wang;Chun Li;Guo-guang ZHANG

  . 2013, 44(19): 25-0.

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  The electron gain and loss capability and oxygen diffusion behavior of SOFC anode materials have effects on their catalytic property. In this paper，dielectric behavior and the capability of electron gain and loss for NiO/La2Mo2O9 composite with 20 % and 40% NiO in volume (abbreviated as N/L28and N/L46, respectively) were studied. According to the order from low to high temperature, the dielectric loss peaks associated with NiO phase and short distance diffusion of oxygen vacancies in La2Mo2O9 phase were observed respectively in both N/L28 and N/L46 samples. The stepwise change of dielectric loss at 833K in both N/L28 and N/L46 samples were attributed to the αLa2Mo2O9―βLa2Mo2O9 phase transition. For N/L46 sample, a broadened dielectric loss peak observed in 500K-813K can be fitted by one relaxation peak and two non-relaxation peaks. The results of surface potential measurement using Kelvin probe method indicate that the energy descending order for electron loss is La2Mo2O9> N/L28> N/L46>NiO
工艺 技术
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  Effects of annealing temperature on structure and electrochemical properties of Mm(NiCoMnAl)5/5wt% Mg2Ni hydrogen storage alloys

  xiao tian ;;;

  . 2013, 44(19): 26-0.

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  Mm(NiCoMnAl)5/5wt% Mg2Ni composite hydrogen storage alloys were prepared by two-step remelting and then annealed at 1023, 1123 and 1223K for 10h. The effect of annealing temperature on the microstructure and electrochemical properties of Mm(NiCoMnAl)5/5wt% Mg2Ni were investigated by means of X-ray diffraction (XRD), scanning electron microscope (SEM), and electrochemical measurements. The results showed that the as-cast composite alloy was composed of the LaNi5 phase and a small amount of the Mg2Ni phase. However, the annealed alloys consisted of the LaNi5 phase and a (La,Mg)Ni3 new phase. The maximum discharge capacity and high rate dischargeability of the alloys increased firstly and then decreased with increasing annealing temperature. The alloy annealed at 1023 K exhibited the best the maximum discharge capacity and high rate dischargeability. The capacity retention increased monotonically with the increase of annealing temperature, and the capacity retention of the alloy increased from 86.6 % (as-cast) to 92.4 % (annealed at 1223 K) after 60 charge-discharge cycles.
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  Influence of annealing temperature on the electrochemical hydrogen storage characters of the La0.8Mg0.2Ni3.3Co0.2Six (x=0, 0.1) alloys

  ;Yanghuan Zhang ;;;

  . 2013, 44(19): 27-0.

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  The La0.8Mg0.2Ni3.3Co0.2Six (x=0, 0.1) electrode alloys were prepared by using a vacuum induction furnace, immediately, a part of the as-cast alloys was annealed at 900, 950, 1000 and 1050℃ in vacuum for 8 hours. The phase structures of the as-cast and annealed alloys were checked out by XRD, what is more, the electrochemical hydrogen storage characteristics of the as-cast and annealed alloys were also examined. The results indicate that the as-cast and annealed alloys have a multiphase structure, involving two major phases of (La, Mg)2Ni7 and LaNi5 as well as a residual phase of LaNi3. There is not any change on the phase composition after annealing treatment, which is opposite to the content of the two major phases, changing a lot. Meanwhile, the lattice constants and cell volumes mount up with the growing of the annealing temperature. The as-cast and annealed alloys have a well activation properties, which reaches the maximum discharge capacity at the first cycle. The electrochemical cycle stability is markedly improved by annealing treatment, however, the discharge capacity first mounts up and then goes down with the annealing temperature rising. Which adjust well to the values of electrochemical kinetics by the tests of HRD, EIS and H-diffusion coefficient.
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  Nanometer MgO-templated Nitrogen-containing Porous Carbons for Capacitor Electrodes

  Yang YANG

  . 2013, 44(19): 28-0.

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  Abstract: Porous carbons containing nitrogen were prepared from polyacrylamide using the MgO template method which was produced by Magnesium chloride hexahydrate. Particle size range of nanometer MgO was 11-26nm. After carbons were heat-treated at different temperature in inert atmosphere, MgO formed in the carbonization products was dissolved out using a diluted acid. Carbons material were characterized by XRD, SEM, pore parameters test and electrochemical measurement. The results showed that porous carbons were layer structure, average pore size was 4.72nm. Specific surface area of the carbons obtained could be reached to 1873 m2·g-1 .The specific capacitance 176F/g was obtained at a current density 1A·g-1 in H2SO4.
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  Preparation and Electrochemical Capacitance Properties of NiO/P-CNT Composites by In Situ Precipitation–Calcination

  ; ;

  . 2013, 44(19): 29-0.

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  New NiO/P-CNT composite was synthesized by in-situ Precipitation –calcination method using PPy-derived carbon nanotube as the support. The samples were characterized and analysized by scanning electron microscopy (SEM), transmission electron microscopy (TEM) and X-ray diffraction (XRD) cyclic voltammetry and galvanostatic charge / discharge. The results indicated that whisker-like NiO was loaded uniformly on the PPy-derived carbon nanotube surfaces to generate a composite having three-dimensional network structure. Based on the New NiO/P-CNT composite was synthesized by in-situ precipitation–calcination method using PPy-derived carbon nanotubes as the support. The samples were characterized and analyzed by powder X-ray diffraction (XRD), thermogravimetric analysis (TG), energy dispersive spectrum (EDS), scanning electron microscopy (SEM), transmission electron microscopy (TEM), cyclic voltammetry and galvanostatic charge/discharge. The results indicated that whisker-like NiO was loaded uniformly on the PPy-derived carbon nanotube surfaces to generate a composite having three-dimensional network structure. Based on the advantages of this special structure, specific capacitances of the composite reached 382 F?g-1 at current densities of 2 A?g-1. NiO capacity contribution in the composite was 441 F g-1, whereas specific capacitance of NiO was 351 F g-1. A capacity retention of the composite was more than 90% after 400 charge/discharge cycles. which was 7.9% higher than that of pure NiO. Therefore, this composite had higher specific capacitance and better cycle performance than pure NiO.
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  Electrochemical hydrogen storage properties of ball milling La2Mg17 and Ni composite

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  . 2013, 44(19): 30-0.

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  The microstructure and electrochemical hydrogen storage properties of La2Mg17 and Ni powders prepared by mechanical grinding method have been studied. It is found that Ni powder induced the formation of amorphous/ nanocrystalline structure of La-Mg-Ni alloy. XRD and HRTEM results represent that when ball milling 80 hours, the alloy in the presence of metal Ni, and the intensity of XRD diffraction decreased and the peakbroad aggravation, forming to the amorphous structure. At the same time, transmission electron microscope and electron diffraction diagram (SAD) showing as the widen ring, which is further confirmed the amorphous structure. Electrochemical kinetics results indicated that the dynamic mechanism of electrochemical reaction is different with the different ball milling time. When ball milled 60 and 80 hours in the alloy not only exist amorphous La-Mg-Ni alloys, but also catalyst Ni, make the smaller alloy surface charge transfer reaction resistance and higher the diffusion coefficient D and limiting current density IL, ultimately lead to the discharge capacity for maximum at 948.3 mAh/g. However, when the alloy ball milling time increased to 100h and 120h, alloy powders were in nanosized, the charge transfer reaction resistance Rct with 100h is the largest, the electrochemical reaction of alloy surface is quite slow, and the limiting current density and the hydrogen diffusion coefficient D in the alloy bulk is minimum, which corresponding to charge transfer stage and the diffusion in alloy bulk combination controlling process. It is inevitably lead to the smaller discharge capacity.
研究 开发
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  Study on coal-tar pitch carbon coated microcrystalline graphite used as lithium ion batteries anode

  ; ;

  . 2013, 44(19): 31-0.

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  Abstract: To address the shortcomings, such as low tap density and low first cycle Coulombic efficiency of microcrystalline graphite when used as lithium ion battery anode, the paper investigated the liquid phase coating for microcrystalline graphite using vacuum impregnation method. The microscopic structure of the coated sample was tested with XRD, Raman spectrum. The surface feature was characterized by SEM and nitrogen adsorption-desorption. The performance of the sample was determined by Galvanostatic test and CV test. It shows that after the modification, the degree of graphitization is reduced slightly, the Raman R value increases from 0.63 to 0.85, the surface of the graphite particles become neater and smoother, the BET specific surface area decreases by 0.9m2/g, and the tap density increases from 0.95 g/m3 to 1.08 g/m3. The electrochemical performance of the modified graphite is significantly improved. and the irreversible capacity is reduced from 121mAh/g to 44mAh/g. The reversible capacity increases from 300mAh/g to 320mAh/g, the initial Coulombic efficiency increases from 71.2% to 87.4%.The cycle stability is improved significantly.
工艺 技术
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  Preparation and Characterization of xLi2MnO3?(1-x)Li(Ni1/3Co1/3Mn1/3)O2（x=0.2、0.4、0.6）Cathode Materials synthesized by hydroxide co-precipitation method

  ;Sheng-Ming XU ;;

  . 2013, 44(19): 32-0.

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  Spherical cathode materials xLi2MnO3?(1-x)Li(Ni1/3Co1/3Mn1/3)O2（x=0.2、0.4、0.6）, using ammonia as complexing agent, were synthesized by hydroxide co-precipitation method. Chemical component, structure, morphology and electrochemical performance of synthesized materials with diverse components were characterized by EDS, ICP, XRD, SEM and electrochemical performance measurement. Results show that chemical component of synthesized material is identical to its theoretical content. Increasing x value, particle size diminishes. Testing its charge-discharge performance under voltage ranging from 2.5 V to 4.6 V, first charge-discharge capacity increases as a function of x value and maximum discharge capacity at different ratios is reached when x=0.2. Key words: Lithium-ion battery; Hydroxide co-precipitation method; Cathode material; xLi2MnO3?(1-x)Li(Ni1/3Co1/3Mn1/3)O2
研究 开发
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  Impact of adding Si on the cycle stability of the La-Mg-Ni-based A2B7-type electrode alloy

  Yanghuan Zhang ;;;;

  . 2013, 44(19): 33-0.

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  In order to improve the cycle stability of the La-Mg-Ni-based A2B7- type electrode alloy, a small amount of Si has been added to the alloy. The compositions of La0.8Mg0.2Ni3.3Co0.2Six (x=0-0.2) alloys were prepared by using a vacuum induction furnace, and a part of the alloys was annealed at 900, 950, 1000 and 1050 ℃ in vacuum. The microstructure of the as-cast and annealed alloys was examined by XRD and SEM, what’s more, the electrochemical cycle stability of the as-cast and quenched alloys has been checked out. The results indicate that the as-cast and quenched alloys have a multiphase structure, including two major phases of (La, Mg)2Ni7 and LaNi5 as well as a residual phase of LaNi3. The additive Si leads to a increase in LaNi5 phase and a decrease in (La, Mg)2Ni7 phase. Additionally, with the increase of Si content from 0 to 0.2, the capacity retention rate (S100) of as-cast alloys enhances from 64.2% to 73.1%, meanwhile, the capacity remaining rate (S100) of the alloys quenched at 950 ℃ grows from 80.3% to 93.7%.