Browsing by Author "Yusoff, RY"

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    Investigation of cell parameters, microstructures and electrochemical behaviour of LiMn2O4 normal and nano powders
    (Elsevier, 2009-03-01) Kamarulzaman, N; Yusoff, RY; Kamarudin, N; Shaari, NH; Aziz, NAA; Bustam, MA; Blagojevic, N; Elcombe, MM; Blackford, MG; Avdeev, M; Arof, AK
    Nano materials are usually difficult to prepare. This work presents a simple way of preparing LiMn2O4 nano powders using the high-energy ball milling method. This method has the advantage of producing pure, single-phase and crystalline nano powders. The milling method is carefully controlled to avoid unwanted chemical reactions that may change the stoichiometry of the material. Nano powders of between 30 and 50 nm are obtained. Structural studies of the nano powders, as well as the more-conventional micron-sized LiMn2O4, are made using X-ray diffraction and neutron diffraction methods. Electrochemical evaluation of the materials is undertaken with a three-probe cyclic voltammetry technique and galvanostatic charge-discharge measurements. Structural studies reveal that not only are the crystallites of the nano powders much reduced in size from the normal powders, but their cell parameters are also smaller. The performance characteristics of the nano material show an improvement over that of the micron-sized material by about 17% in the 1st cycle and 70.6% in the 5th cycle, at which the capacity is 132 mAh g(-1). The normal material suffers from severe capacity fading but the nano material shows much improved capacity retention. © 2008, Elsevier Ltd.
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    Neutron and X-ray diffraction studies of LiMn2O4 nano material and its electrochemical performance
    (Malaysian Nuclear Agency, 2009-06-29) Kamarulzaman, N; Yusoff, RY; Abdul Aziz, NA; Blagojevic, N; Elcombe, MM; Blackford, MG; Avdeev, M
    Nano materials are rather difficult to study due to their tiny particle size. This work presents a simple way of preparing LiMn2O4 nano powders using the high energy ball milling method. The preparation uses highly crystalline LiMn2O4 which has been earlier synthesized and optimized using the sol-gel method. The milling method is carefully controlled to avoid unwanted chemical reactions that may change the stoichiometry of the material. Nano powders of between 30 to 50 nm are obtained. Structural studies of the nano powders as well as the more conventional micron sized LiMn2O4 are made using X-ray, neutron and selected area electron diffraction methods. Electrochemical characterization of the materials are done using a three probe cyclic voltammetry technique and galvanostatic charge-discharge measurements. It is found that the performance characteristics of the nano material show an improvement over that of the micron sized material by about 17% in the first cycle and 70.6% in the fifth cycle.
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    Structural changes in a commercial lithium-ion battery during electrochemical cycling: an in situ neutron diffraction study
    (Elsevier, 2010-12-15) Sharma, N; Peterson, VK; Elcombe, MM; Avdeev, M; Studer, AJ; Blagojevic, N; Yusoff, RY; Kamarulzaman, N
    The structural response to electrochemical cycling of the components within a commercial Li-ion battery (LiCoO2 cathode, graphite anode) is shown through in situ neutron diffraction. Lithuim insertion and extraction is observed in both the cathode and anode. In particular, reversible Li incorporation into both layered and spinel-type LiCoO2 phases that comprise the cathode is shown and each of these components features several phase transitions attributed to Li content and correlated with the state-of-charge of the battery. At the anode, a constant cell voltage correlates with a stable lithiated graphite phase. Transformation to de-lithiated graphite at the discharged state is characterised by a sharp decrease in both structural cell parameters and cell voltage. In the charged state, a two-phase region exists and is composed of the lithiated graphite phase and about 64% LiC6. It is postulated that trapping Li in the solid|electrolyte interface layer results in minimal structural changes to the lithiated graphite anode across the constant cell voltage regions of the electrochemical cycle. © 2010, Elsevier Ltd.
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    X-ray and neutron diffraction studies of LiMn2O4 cathode materials
    (X-Ray Applications Malaysia Society, 2008-07) Kamarulzaman, N; Subban, RYH; Yusoff, RY; Shaari, NH; Aziz, NAA; Bustam, MA; Blagojevic, N; Elcombe, MM; Blackford, MG; Avdeev, M; Klooster, WT; Fun, HK
    No abstract available.