Shengkui Zhong

Soochow University (PRC), Wu-hsien, Jiangsu Sheng, China

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Publications (18)13.63 Total impact

  • Shengkui ZHONG, You WANG, Jiequn LIU, Kang WAN, Fan LÜ
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    ABSTRACT: The layered material of Ce-doped LiNi1/3Mn1/3Co1/3O2 with α-NaFeO2 was synthesized by a co-precipitation method. X-ray diffraction (XRD) showed that Ce-doped LiNi1/3Mn1/3Co1/3O2 had the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. The scanning electron microscopy (SEM) images exhibited that the particle size of Ce-doped LiNi1/3Mn1/3Co1/3O2 was smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2. The Ce-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Ce was x=0.02 in the LiNi1/3–xMn1/3Co1/3CexO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Ce-doping. The improved electrochemical performances of the Ce-doped LiNi1/3Mn1/3Co1/3O2 cathode materials were attributed to the addition of Ce4+ ion by stabilizing the layer structure.
    Journal of Rare Earths - J RARE EARTH. 01/2011; 29(9):891-895.
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    ABSTRACT: The electron transport behaviors of oxygen and carbon monoxide complexes of Fe-porphyrin (FeP) are investigated by nonequilibrium Green's function techniques combined with Density Functional Theory calculations. The results show that the molecular current of FeP decreases dramatically after adsorptions of oxygen and carbon monoxide. The molecular current decreases with a order of FeP > FeP+O2 complex > FeP+CO complex. This change of the molecular current after adsorption of oxygen or carbon monoxide can be potentially used to design a molecular sensor or a molecular switch.
    Integrated Ferroelectrics 01/2011; 127(1):91-96. · 0.38 Impact Factor
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    ABSTRACT: The layered Li(Ni1/3Co1/3Mn1/3)1-xYxO2 cathode materials (x = 0, 0.03, 0.06, 0.09) were prepared by a co-precipitation method. The properties of the Y-doped LiNi1/3Mn1/3Co1/3O2 were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. XRD studies show that the Y-doped LiNi1/3Mn1/3Co1/3O2 has the same layered structure as the undoped LiNi1/3Mn1/3Co1/3O2. SEM images exhibit that the particle size of Y-doped LiNi1/3Mn1/3Co1/3O2 is smaller than that of the undoped LiNi1/3Mn1/3Co1/3O2 and the smallest particle size is only about 2μm. The Y-doped LiNi1/3Mn1/3Co1/3O2 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Y is that x = 0.06 in the Li(Ni1/3Co1/3Mn1/3)1-xYxO2 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through Y-doping. The improved electrochemical performances of the Y-doped LiNi1/3Mn1/3Co1/3O2 cathode materials are attributed to the addition of Y ion by stabilizing the layer structure.
    Integrated Ferroelectrics 01/2011; 127(1):150-156. · 0.38 Impact Factor
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    ABSTRACT: The effect of molecular orientation on the electron transport behavior of single porphyrin sandwiched between two gold (111) electrodes is investigated by density functional theory calculations combined with non-equilibrium Green’s function method. The results show that the porphyrin with parallel connection to gold (111) electrodes is more conductive than the porphyrin with diagonal connection to gold (111) electrodes. The mechanism of the difference of electron transport for these two molecular junctions is analyzed from the transmission spectra and the molecular projected self-consistent Hamiltonian states. It is found that the intrinsic nature of the molecule, such as the π-conjugated framework and the strength of molecule–electrode coupling, are the essential reason for generating this difference of electron transport for the two molecular systems.
    Current Applied Physics - CURR APPL PHYS. 01/2011; 11(6):1349-1353.
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    ABSTRACT: Li3V2(PO4)3/C samples were synthesized by two different synthesis methods. Their influence on electrochemical performances of Li3V2(PO4)3/C as cathode materials for lithium-ion batteries was investigated. The structure and morphology of Li3V2(PO4)3/C samples were characterized by X-ray diffraction and scanning electron microscopy. Electrochemical performance was characterized by charge/discharge, cyclic voltammetry, and alternating current (AC) impedance measurements. Li3V2(PO4)3/C with smaller grain size showed better performances in terms of the discharge capacity and cycle stability. The improved electrochemical properties of the Li3V2(PO4)3/C were attributed to the decreasing grain size and enhanced electrical conductivity produced via low temperature route. AC impedance measurements also showed that the Li3V2(PO4)3/C synthesized by low temperature route significantly decreased the charge-transfer resistance and shortened the migration distance of lithium ion.
    Ionics 01/2010; 16(2):117-121. · 1.67 Impact Factor
  • Chemistry Letters - CHEM LETT. 01/2009; 38(4):374-375.
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    ABSTRACT: Y-doped LiVPO4F cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped LiVPO4F samples were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies show that the Y-doped LiVPO4F samples have the same triclinic structure as the undoped LiVPO4F. The Li extraction/insertion performances of Y-doped LiVPO4F samples were investigated through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Y is x=0.04 in LiY x V1−x PO4F system. The Y-doped LiVPO4F samples show a better cyclic ability. The electrode reaction reversibility is enhanced, and the charge transfer resistance is decreased through the Y-doping. The improved electrochemical performances of the Y-doped LiVPO4F cathode materials are attributed to the addition of Y3+ ion by stabilizing the triclinic structure.
    Journal of Wuhan University of Technology-Mater Sci Ed 01/2009; 24(4):552-556. · 0.48 Impact Factor
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    ABSTRACT: Cr-doped Li3V2(PO4)3 cathode materials Li3V2−x Cr x (PO4)3 were prepared by a carbothermal reduction(CTR) process. The properties of the Cr-doped Li3V2(PO4)3 were investigated by X-ray diffraction (XRD), scanning electron microscopic (SEM), and electrochemical measurements. Results show that the Cr-doped Li3V2(PO4)3 has the same monoclinic structure as the undoped Li3V2(PO4)3, and the particle size of Cr-doped Li3V2(PO4)3 is smaller than that of the undoped Li3V2(PO4)3 and the smallest particle size is only about 1 μm. The Cr-doped Li3V2(PO4)3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra(EIS). The optimal doping content of Cr was that x=0.04 in the Li3V2−x Cr x (PO4)3 samples to achieve high discharge capacity and good cyclic stability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Cr-doping. The improved electrochemical performances of the Cr-doped Li3V2(PO4)3 cathode materials are attributed to the addition of Cr3+ ion by stabilizing the monoclinic structure.
    Journal of Wuhan University of Technology-Mater Sci Ed 01/2009; 24(3):343-346. · 0.48 Impact Factor
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    ABSTRACT: The effect of fluorine substitution on the electrochemical properties of Li3V 2(PO4)3 cathode materials was studied. Samples with stoichiometric proportions of Li3V 2(PO4)3−xFx (x=0,0.05,0.10,0.15) were prepared by adding LiF in the starting materials of Li3V 2(PO4)3. XRD studies showed that the F-substituted Li3V 2(PO4)3 had the same monoclinic structure as the un-substituted Li3V 2(PO4)3. SEM images showed that F-substitution Li3V 2(PO4)3 had a regular and uniform particles. The results of electrochemical measurement showed that F-substitution can improve the rate capability of these cathode materials. The Li3V 2(PO4)2.90F0.10 sample showed the best high rate performance. Its discharge capacity at 10 C rate was 117 mA h g−1 with 30th capacity retention of about 90.60%. The electrode reaction reversibility and electronic conductivity was enhanced, and the charge transfer resistance was decreased through F-substitution. The improved electrochemical performance of F-substitution Li3V 2(PO4)3 cathode materials were attributed to the above factors.
    Solid State Communications 01/2009; 149(39):1679-1683. · 1.53 Impact Factor
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    ABSTRACT: Y-doped Li3V2(PO4)3 cathode materials were prepared by a carbothermal reduction(CTR) process. The properties of the Y-doped Li3V2(PO4)3 were investigated by X-ray diffraction (XRD) and electrochemical measurements. XRD studies showed that the Y-doped Li3V2(PO4)3 had the same monoclinic structure as the undoped Li3V2(PO4)3. The Y-doped Li3V2(PO4)3 samples were investigated on the Li extraction/insertion performances through charge/discharge, cyclic voltammogram (CV), and electrochemical impedance spectra (EIS). The optimal doping content of Y was x=0.03 in Li3V2–xYx(PO4)3 system. The Y-doped Li3V2(PO4)3 samples showed a better cyclic ability. The electrode reaction reversibility was enhanced, and the charge transfer resistance was decreased through the Y-doping. The improved electrochemical performances of the Y-doped Li3V2(PO4)3 cathode materials were attributed to the addition of Y3+ ion by stabilizing the monoclinic structure.
    Journal of Rare Earths - J RARE EARTH. 01/2009; 27(1):134-137.
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    ABSTRACT: Triclinic LiVPO4F/C composite materials were prepared from a sucrose-containing precursor by one-step heat treatment. As-prepared composites were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), and electrochemical measurements. XRD studies showed that Li3PO4 impurity phase appeared in the sample synthesized at 600 °C and pure LiVPO4F samples could be obtained when the sintered temperature was higher than 650 °C. The sample synthesized at 650 °C presents the highest initial discharge capacity of 132 mAh g−1 at 0.2 C rate, and exhibited better cycling stability (124 mAh g−1 at 50th cycle at 0.2 C rate) and better rate capability (100 mAh g−1 at 50th cycle under 1 C rate) in the voltage range 3.0–4.4 V.
    Journal of Physics and Chemistry of Solids 01/2009; 70(7):1080-1082. · 1.53 Impact Factor
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    ABSTRACT: Theoretical investigations on the diblock molecular diode, thiophene–thiazole compound, have been carried out at the Hartree–Fock (HF) level by considering the interaction under the external bias. They demonstrate that the electronic structures of this kind of diode molecule are essentially different from those based on the Aviram and Ratner model, in which donor and acceptor π-conjugated segments are separated by an insulating σ-bonded segment, in terms of the energy levels of the frontier molecular orbitals as well as their spatial distributions. The introduction of the external bias modifies both the geometric and electronic structures. In particular, the spatial distributions of the frontier molecular orbitals are also shifted under the external bias. Moreover, all these features show a strong dependence on the polarity of the applied bias due to the build in intrinsic molecular asymmetric structures, which could be used to intuitively interpret the asymmetrical current–voltage behaviours of molecules.
    Molecular Simulation 01/2009; 35(4):301-307. · 1.06 Impact Factor
  • Shengkui Zhong, Ling Wu, Jiequn Liu
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    ABSTRACT: 9LiFePO4·Li3V2(PO4)3/C composite cathode material is prepared by a sol–gel method, using ferric citrate, V2O5, Li2CO3, NH4H2PO4 and citric acid as raw materials. The composite material is composed of the olivine LiFePO4 and monoclinic Li3V2(PO4)3 phases. XRD results indicate that most of the iron and vanadium in the raw materials tend to form the LiFePO4 and Li3V2(PO4)3 phases, and only small amounts of Fe and V as the dopants enter into the lattice of Li3V2(PO4)3 and LiFePO4, respectively. The electronic conductivity and Li+ diffusion coefficient of 9LiFePO4·Li3V2(PO4)3/C are 6.615 × 10−3 S cm−1 and ∼10−10 cm2 s−1, which are three orders of magnitude and one order of magnitude larger than those of the LiFePO4/C, respectively. The composite material shows a first discharge specific capacity of 131.3 mAh g−1 and capacity retention of 95.1% after 200 cycles at 10 C rate. Compared with the LiFePO4/C, its rate capability and cycle performance are both remarkably improved.
    Electrochimica Acta. 74:8–15.
  • Ling Wu, Shengkui Zhong, Jiajia Lu, Jiequn Liu, Fan Lv
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    ABSTRACT: LiMn1-x Crx PO4/C (x = 0, 0.01, 0.03, and 0.05) compounds are synthesized by a sol–gel combined ball milling method. The effects of Cr doping on the structure, morphology, and electrochemical performance of LiMnPO4 are investigated. XRD analysis results indicate that all the samples exhibit the single LiMnPO4 phase and Cr ions substitute on Mn site (x ≤ 0.03), with charge compensating vacancies on Li site. The vacancies are of benefit to improving the electronic conductivity of LiMnPO4. SEM studies reveal that Cr doping can effectively inhibit the aggregation of LiMnPO4 particles. Electrochemical tests show that the Cr-doped samples exhibit higher initial capacities and better cycling performance than the undoped one. LiMn0.97Cr0.03PO4/C exhibit the best electrochemical performance that the first specific discharge capacity is 132.4 mAh g−1 at 0.1 C rate, and the capacity retention is 94.8 % after 30 cycles.
    Ionics 19(7). · 1.67 Impact Factor
  • Ling Wu, Jiajia Lu, Shengkui Zhong
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    ABSTRACT: The xLiFePO4·yLi3V2(PO4)3/C cathode materials are synthesized by a sol spray drying method. X-ray diffraction results reveal that the xLiFePO4·yLi3V2(PO4)3/C (x,y ≠ 0) composites are composed of LiFePO4 and Li3V2(PO4)3 phases, and no impurities are detected. The samples show spherical particles with the size of 0.5–5 μm, and the tap densities of all the samples are higher than 1.5 g cm−3. Electrochemical tests show that the xLiFePO4·Li3V2(PO4)3/C (x,y ≠ 0) composites exhibit much better performance than the single LiFePO4/C or Li3V2(PO4)3/C. Among all the samples, 3LiFePO4·Li3V2(PO4)3/C possesses the best comprehensive performance in terms of the discharge capacity, average working voltage, and rate capability. At 1, 5, and 10 C rates, the sample shows first discharge capacities of 152.0, 134.3, and 116.8 mAh g−1 and capacity retentions of 99.2, 98.2, and 97.7 % after 100 cycles, respectively. The excellent electrochemical performance of micron-sized xLiFePO4·Li3V2(PO4)3/C (x,y ≠ 0) powders is owing to the homogeneous mixing of reactants at a molecular level by sol spray drying, the incorporation of fast ion conductor Li3V2(PO4)3, and the mutual doping in LiFePO4 and Li3V2(PO4)3.
    Journal of Solid State Electrochemistry 17(8). · 2.28 Impact Factor
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    ABSTRACT: LiMnPO4/C composites were synthesized via solid-state reaction with different carbon sources: sucrose, citric acid and oxalic acid. The samples were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and electrochemical performance test. The results of XRD reveal that carbon coating has no effect on the phase of LiMnPO4. The LiMnPO4/C synthesized at 600 °C with citric acid as carbon source shows an initial discharge capacity of 117.8 mAh·g−1 at 0.05 C rate. After 30 cycles, the capacity remains 98.2 mAh·g−1. The improved electrochemical properties of LiMnPO4/C is attributed to the decomposition of organic acid during the sintering process.
    Rare Metals 31(5). · 0.49 Impact Factor
  • Shengkui Zhong, Wei Chen, Ling Wu, Jiequn Liu
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    ABSTRACT: 5LiFePO4⋅Li3V2(PO4)3/C composite cathode material is synthesized by a polyethylene glycol (PEG)-assisted rheological phase method. As a surfactant and dispersing agent, PEG can effectively inhabit the aggregation of colloidal particles during the formation of the gel. Meanwhile, PEG will coat on the particles to play the role of carbon source during the sintering. The samples are characterized by X-ray diffraction (XRD), scanning electron microscopy, and electrochemical methods. XRD results indicate that the 5LiFePO4⋅Li3V2(PO4)3/C composites are well crystallized and contain olivine-type LiFePO4 and monoclinic Li3V2(PO4)3 phases. The composite synthesized at 650 °C exhibits the initial discharge capacities of 134.8 and 129.9 mAh g−1 and the capacity retentions of 96.2 and 97.1 % after 50 cycles at 1C and 2C rates, respectively.
    Ionics 18(5). · 1.67 Impact Factor
  • Shengkui Zhong, Ling Wu, Junchao Zheng, Jiequn Liu
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    ABSTRACT: The 9LiFePO4·Li3V2(PO4)3/C composite cathode material is synthesized by spray-drying and post-calcining method based on citrate. The composite is well crystallized, and contains olivine-type LiFePO4 and monoclinic Li3V2(PO4)3 phases. The composite material exhibits spherical particles in the size of 0.5–5 μm, and shows a high tap-density of 1.64 g cm− 3. The electrochemical performance of the material is excellent. At 5C and 10C rates, the sample exhibits the initial discharge capacities of 135.3 and 109.6 mAh g− 1 and capacity retentions of 96.2% and 93.7% after 100 cycles, respectively. The homogenous mixing of the LiFePO4 and fast ion conductor additive Li3V2(PO4)3, which is resulted from spray-drying, can be the reason why the composite has good rate capability.
    Powder Technology. 219:45–48.