Liqun Zhou

Wuhan University, Wuhan, Hubei, China

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Publications (6)12.94 Total impact

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    ABSTRACT: Spherical LiVMoO6 nanocrystals as cathode for lithium ion batteries were synthesized using a solvothermal reaction method. Powder XRD data indicate that a single phase LiVMoO6 with brannerite-type structure is obtained at 550°C by the thermal treatment of the precursor for 6h. SEM image shows that the particles are composed of loosely stacked spheres with a uniform particle size about 40nm. The electrode properties of LiVMoO6 have also been studied by galvanostatic cycling and ac impedance spectroscopy. LiVMoO6 nanospheres delivered 172mAhg−1 capacity in the initial discharge process with a reversible capacity retention of 94.4% after 100 cycles in the range of 3.6–1.80V versus metallic Li at a current density of 100mAg−1. The microstructure developed in the electrodes give evidence that the particle size and morphological properties play an important role in the much improved capacity and cycling stability at large currents than ordinary samples.
    Journal of Alloys and Compounds 01/2008; 457(1):389-393. · 2.73 Impact Factor
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    ABSTRACT: Rod-like CaMoO4 nanocrystals were synthesized via a template-based rheological phase reaction route as a novel method. The physical characterization was carried out by thermogravimetric/differential thermal analysis (TG/DTA), X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), and elected-area electron diffraction (SAED). A structure-directed role of hexamethylene tetramine (HMTA) was observed during the formation of CaMoO4 nanocrystals. The electrochemical performance of CaMoO4 as anode for lithium ion batteries has also been investigated by galvanostatic cycling and AC impedance spectroscopy. CaMoO4/Li cell can deliver superior capacity than theoretical value in the initial cycle, and the much improved capacity was attributed to the contribution of oxygen besides the reduction of molybdenum during lithium insertion. Furthermore, a charge capacity of 276 and 438 mAh/g was retained after 50 cycles in the range of 0.01–2.50 V vs Li at a current density of 100 and 200 mA/g, respectively. The particle size and morphological properties were found to play an important role in fast lithium insertion/extraction performance and cycling stability at high rate.
    Journal of Solid State Electrochemistry 01/2007; 11(8):1127-1131. · 2.28 Impact Factor
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    ABSTRACT: LiNi1−xCoxO2 (x=0, 0.1, 0.2) cathode materials were successfully synthesized by a rheological phase reaction method with calcination time of 0.5h at 800°C. All obtained powders are pure phase with α-NaFeO2 structure (R-3m space group). The samples deliver an initial discharge capacity of 182, 199 and 189mAhg−1 (25mAg−1, 4.35–3.0V), respectively. The reaction mechanism was also discussed, which consists of a series of defect reactions. As a result of these defect reactions, the reaction of forming LiNi1−xCoxO2 takes place in high speed.
    Electrochimica Acta - ELECTROCHIM ACTA. 01/2007; 52(9):3022-3027.
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    ABSTRACT: This paper reports a newly developed method for the shape and size control of transition metal composite oxides, such as LiVMoO6, to obtain significantly enhanced electrode properties for lithium-ion batteries. Rod-like LiVMoO6 nanocrystals were synthesized through a designed route of partial reduction, self-assembly and re-oxidation. V5+ and Mo6+ ions were used with low-grade starting materials to get a mixed valence of V and Mo. It is believed that ion pairs of V5+/V4+ or Mo6+/Mo5+ in the resultant mixture play an important role in the formation of a template precursor by self-assembly during a rheological phase reaction, although further explanation is required. The electrochemical performance of the LiVMoO6 obtained has been much improved due to the increased crystallinity and reduced particle size of this material. 176 mA h g-1 and 166 mA h g-1 capacity was delivered in the initial discharge with a reversible capacity retention of 94.8% and 95.3% after 100 cycles in the range of 3.6-1.80 V versus metallic Li at 1 and 3 C current rate, respectively.
    Nanotechnology 01/2007; 18(13). · 3.84 Impact Factor
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    ABSTRACT: LiNi0.8Co0.2O2 and Ca-doped LiNi0.8Co0.2O2 cathode materials were synthesized via a rheological phase reaction method. It is found that the Ca doping significantly improves reversible capacity, cycling performance, thermal stability and rate capability. The Ca-doped LiNi0.8Co0.2O2 cathode material maintains nearly its initial discharge capacity up to 100 cycles at room temperature. It also delivers an initial discharge capacity of 183 mA h g− 1 and still keeps 131 mA h g− 1 even after 120 cycles at 60 °C. These results, together with the X-ray diffraction and electrochemical impedance spectroscopy analysis, reveal that Ca2+ ions occupy Li+ ion sites to form CaLi defects and lithium vacancies (VLi′), which reduce the resistance and increases conductivity of LiNi0.8Co0.2O2.
    Solid State Ionics 04/2006; 177(s 11–12):1027–1031. · 2.05 Impact Factor
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    ABSTRACT: Different morphological MoO2 nano-sized particles were synthesized by a low temperature hydrothermal reaction as a novel method. The physical characterizations were carried out by IR, TG/DTA, XRD, XPS, SEM, TEM and SAED. XRD and XPS data indicate the as-prepared samples present at pure phase MoO2 with monocline symmetry. Spherical, sheet-like and bar-shaped nano-particles are observed by SEM, respectively. The lithium-intercalation properties of spherical MoO2 powders were investigated by XRD, TEM and SAED in the light of bulk MoO2. The results showed an irreversible phase transition after the initial discharge process, which is obviously different from the bulk sample.
    Solid State Ionics 01/2006; 177(5):501-505. · 2.05 Impact Factor