Browsing by Author "Chowdari, BVR"

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    Preparation of Li(1.03)Mn(1.97)O(4) and Li(1.06)Mn(1.94)O(4) by the polymer precursor method and x-ray, neutron diffraction and electrochemical studies
    (The Electrochemical Society, 2011-01-01) Reddy, MV; Raju, MJS; Sharma, N; Quan, PY; Nowshad, SH; Emmanuel, HEC; Peterson, VK; Chowdari, BVR
    The compounds, Li(1.03)Mn(1.97)O(4) and Li(1.06)Mn(1.94)O(4) were prepared by the polymer precursor method followed by heat treatment at 650 degrees C for 6 hours in air. X-ray and neutron diffraction, scanning electron microscopy, and the Brunauer-Emmett-Teller surface area and density determination techniques were used to characterise the compounds. The lattice parameters obtained using neutron diffraction data of Li(1.03)Mn(1.97)O(4) and Li(1.06)Mn(1.94)O(4) are smaller than the parent LiMn(2)O(4) at a = 8.20717(17) and 8.22899(13) A degrees, respectively. Cyclic voltammetry studies were carried out in the potential range of 3.5-4.4V at scan rate of 0.058 mV/sec. Li-doped LiMn(2)O(4) showed the main cathodic and anodic redox peaks at similar to 3.9/4.0 and similar to 4.1/4.15V, respectively. The reversible charge capacities of Li(1.03)Mn(1.97)O(4) with an applied current rate of 360 mA g(-1) at the end of 2(nd) and 230(th) cycle are 88 and 83 (+/- 3) mAh g(-1), respectively. At a current rate of 600 mA g(-1) these charge capacities are 67 and 61 (+/- 3) mAh g(-1), respectively. Li(1.06)Mn(1.94)O(4) shows a capacity of 64 and 62 (+/- 3) mAh g(-1) at the end of 2(nd) and 100(th) cycles, respectively, at a current rate of 360 mA g(-1). (C) 2011 The Electrochemical Society.
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    Time-dependent in-situ neutron diffraction investigation of a Li(Co0.16Mn1.84)O4 cathode
    (American Chemical Society, 2011-11-03) Sharma, N; Reddy, MV; Du, GD; Adams, S; Chowdari, BVR; Guo, ZP; Peterson, VK
    Real-time in-situ neutron diffraction data reveal for the first time that the Li(Co0.16Mn1.84)O4 cathode undergoes current-free discharge. We find that current-free discharge occurs in a partially charged Li(Co0.16Mn1.84)O4 cathode during its first charge cycle over a period of 11 h resulting in a 44(2)% expansion of the crystal lattice. The rate of change in the lattice parameter during the current-free discharge process is half the rate and more linear than for an applied-current discharge of ?0.5 mA. The origins of current-free discharge are discussed along with the implications of nonequilibrium relaxation processes in in-situ neutron and X-ray diffraction studies. We show that the lattice does not return to the predischarge values after either current-applied or current-free discharge, indicating a limited ability for Li reinsertion (capacity loss) in partially charged Li(Co0.16Mn1.84)O4 batteries. © 2011, American Chemical Society
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    TiO2 nanoparticles synthesized by the molten salt method as a dual functional material for dye-sensitized solar cells
    (Royal Society of Chemistry, 2012-01-01) Zhu, PN; Wu, YZ; Reddy, MV; Nair, AS; Peng, S; Sharma, N; Peterson, VK; Chowdari, BVR; Ramakrishna, S
    We report the simple and versatile molten salt fabrication of mesoporous anatase TiO(2) nanoparticles with a high surface area of similar to 200m(2) g(-1), which show an impressive efficiency of similar to 7.5% in dye-sensitized solar cells. © 2012, Royal Society of Chemistry.