Browsing by Author "Nallathamby, K"

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    Electrochemical characterization of an aqueous lithium rechargeable battery: the effect of CeO2 additions to the MnO2 cathode
    (Elsevier, 2009-06-24) Minakshi, M; Nallathamby, K; Mitchell, DRG
    The effect of CeO2 additions on an aqueous rechargeable lithium battery has been investigated. The CeO2 additions (0, 2, and 5 wt.%) were made to the manganese dioxide (MnO2) cathode of a cell comprising zinc as an anode and an aqueous saturated lithium hydroxide solution as the electrolyte. The CeO2 enhances the performance of the cell in terms of capacity and resistance to capacity fade with cycling. This effect is only evident after the first charge cycle. The mechanism by which this occurs may be due to suppression of the oxygen evolution reaction during charging. This results in full reversion of the products of discharge (principally LixMnO2) to MnO2 during charging, and suppresses the formation of non-rechargeable oxyhydroxides. CeO2 additions of 2 wt.% were found to be most effective, since additions at the 5 wt.% level caused a decrease in capacity during long-term cycling. This could be due to a synchronizing effect. The effect of additions of a rare earth oxide (CeO2) and an alkaline earth oxide (CaO) on the electrochemical behavior of the cell is also compared and discussed. © 2009, Elsevier Ltd.
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    Microstructural and spectroscopic investigations into the effect of CeO2 additions on the performance of a MnO2 aqueous rechargeable battery
    (Elsevier, 2009-04-30) Minakshi, M; Mitchell, DRG; Carter, ML; Appadoo, D; Nallathamby, K
    The influence of CeO2 additions on the electrochemical behaviour of the MnO2 cathode in a Zn–MnO2 battery using lithium hydroxide (LiOH) as an electrolyte is investigated using microscopy and spectroscopic techniques. The results showed that such additions greatly improve the discharge capacity of the battery (from 155 to 190 mAh g−1) but only from the second discharge cycle onwards. Capacity fade with subsequent cycling is also greatly reduced. With an aim to understand the role of CeO2 on the discharge–charge characteristics of MnO2 and its mechanism, we have used a range of microscopy, spectroscopy and diffraction-based techniques to study the process. The CeO2 is not modified by multiple discharged and charged cycles. The CeO2 may enhance the discharge–charge performance of the battery by raising the oxygen evolution potential during charging but does not take part directly in the redox reaction. © 2009, Elsevier Ltd.
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    Synthesis and characterization of Li(Co0.5Ni0.5)PO4 cathode for li-ion aqueous battery applications
    (The Electrochemical Society, 2011-03-17) Minakshi, M; Sharma, N; Ralph, D; Appadoo, D; Nallathamby, K
    Olivine-type lithium orthophosphate Li(Co0.5Ni0.5)PO4 was synthesized in a solid state reaction at 800 degrees C in air. Infra-red spectroscopy, x-ray and neutron powder diffraction were used to characterize the as-prepared compound and its electro-oxidized analogue. Rietveld analysis was used to illustrate that the synthesized compound is isostructural with LiNiPO4 and LiCoPO4 with lattice parameters larger than the former and smaller than the latter. The Rietveld-refined Ni:Co ratio was found to be 0.498(4):0.502(4) and no evidence for long-range Ni: Co ordering or mixed Li/Ni/Co cation sites was found. The electro-oxidised electrode showed a mixture of two phases i.e. parent Li(Co0.5Ni0.5)PO4 and lithium extracted Li1-x(Co0.5Ni0.5)PO4 suggesting a delithiation process in aqueous electrolytes. Reversible Li transfer between a Li(Co0.5Ni0.5)PO4 electrode and an aqueous LiOH electrolyte was demonstrated. (C) 2011 The Electrochemical Society. [doi:10.1149/1.3561764]