Browsing by Author "Singh, P"

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    Lithium extraction-insertion from/into LiCoPO4 in aqueous batteries
    (American Chemical Society, 2011-02-16) Minakshi, M; Singh, P; Sharma, N; Blackford, MG; Ionescu, M
    A novel 1 V battery composed of Sn−LiCoPO4 using aqueous lithium hydroxide electrolyte is described. Reversible extraction and insertion of lithium from and into the olivine-type LiCoPO4 is reported. The electrochemical behavior of the Sn−LiCoPO4 battery was analyzed using charge/discharge cycling and cyclic voltammetry. Sn−LiCoPO4 battery exhibited charge/discharge voltages of 1.3 V/0.8 V versus Sn with a reversible capacity of 80 mAh/g. The structural and morphological changes of LiCoPO4 particles before and after electrochemical measurements were investigated by X-ray diffraction (XRD) and transmission electron microscopy. XRD data showed that extraction of lithium proceeds via at least a two-phase mechanism with LiCoPO4 and CoPO4 phases. Upon lithium reinsertion crystalline LiCoPO4 was formed. The cell voltage indicated these batteries were not completely charged, forming single-phase CoPO4 material. Energy-dispersive X-ray analysis coupled with transmission electron microscopy confirmed the chemical quality of the charged and discharged LiCoPO4 in terms of crystallinity and elemental distribution. © 2011, American Chemical Society
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    Structural characteristics of olivine Li(Mg0.5Ni0.5)PO4 via TEM analysis
    (Springer Nature, 2012-01-13) Minakshi, M; Singh, P; Ralph, D; Appadoo, D; Blackford, MG; Ionescu, M
    The structural characteristics of olivine-type lithium orthophosphate Li(Mg0.5Ni0.5)PO4 synthesized via solid-state reaction have been studied using X-ray diffraction, ion beam technique, scanning electron microscopy, infrared spectroscopy, transmission electron microscopy and energy dispersive X-ray analysis. The parent LiNiPO4 compound can be synthesized in olivine structure without any evidence of secondary phases as impurities. The structural quality of the parent LiNiPO4 in the absence of secondary component phases resulted in the formation of hexagonal closed packed structure. The olivine analogue compound containing mixed M (M = Mg, Ni) cations, Li(Mg0.5Ni0.5)PO4 contained Li3PO4 as a second phase upon synthesis, however a carbothermal reduction method produced a single-phase compound. The redox behaviour of carbon-coated Li(Mg0.5Ni0.5)PO4 cathode in aqueous lithium hydroxide as the electrolyte showed reversible lithium intercalation. © 2020 Springer Nature Switzerland AG.
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    Study of lithium insertion into MnO2 containing TiS2 additive a battery material in aqueous LiOH solution
    (Elsevier, 2007-08-01) Minakshi, M; Singh, P; Mitchell, DRG; Issa, TB; Prince, KE
    The electrochemical behavior and surface characterization of manganese dioxide (MnO2) containing titanium disulphide (TiS2) as a cathode in aqueous lithium hydroxide (LiOH) electrolyte battery have been investigated. The electrode reaction of MnO2 in this electrolyte is shown to be lithium insertion rather than the usual protonation. MnO2 shows acceptable rechargeability as the battery cathode. The influence of TiS2 (1, 3 and 5 wt%) additive on the performance of MnO2 as a cathode has been determined. The products formed on reduction of the cathode material have been characterized by scanning electron microscopy (SEM), X-ray photoelectron spectroscopy (XPS), secondary ion mass spectrometry (SIMS), fourier transform infrared spectroscopy (IR) and transmission electron microscopy (TEM). It is found that the presence of TiS2 to <= 3 wt% improves the discharge capacity of MnO2. However, increasing the additive content above this amount causes a decrease in its discharge capacity. © 2007, Elsevier Ltd.
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    TEM characterization of MnO2 cathode in an aqueous lithium secondary battery
    (Australian Institute of Physics, 2006-12-05) Minakshi, M; Mitchell, DRG; Singh, P; Thurgate, S
    The discharge characteristics of manganese dioxide cathode in the presence of small amounts (1, 3 and 5 wt. %) of TiS2 additive has been investigated in an alkaline cell using aqueous lithium hydroxide as the electrolyte [1]. The incorporation of small amounts of TiS2 additives into MnO2 was found to improve the battery discharge capacity from 150 to 270 mAh/g. However, increasing the additive from 3 to 5 wt. % causes a decrease in the discharge capacity. Hence, the objective is to gain insight into the role of TiS2 in MnO2 and its lithiation mechanism. For this purpose, we have used transmission electron microscopy (TEM) and electron energy loss spectroscopy (EELS). The valence state determination of the discharged MnO2 was performed using EELS. The Mn L2,3 edge contains two white lines (strong peaks) at about 640 eV (L3) and 650 eV (L2). The relative intensities of these Mn L2,3 peaks varies as a function of valence state in the Mn oxides i.e. MnO, Mn2O3 and MnO2 [2]. As-received MnO2 has a valence state of 4, as expected. However, Li intercalated materials showed evidence for reduction, the extent of which depended on the amount of TiS2 additive. The valance state of Li intercalated MnO2 with 3 wt. % TiS2 additive was 3.1 while that for the equivalent material with 5wt. % TiS2 additive was 3.5. Reduction of Mn occurs as a result of Li intercalation, the extent being more marked for the 3 wt. % TiS2 loading. This result is in accordance with the discharge behavior, since the capacity of the 3 wt. % material (270 mAh/g) was significantly larger than that for the equivalent 5 wt. % material (75 mAh/g)). TEM imaging showed a presence of nano particulate Mn oxides, of about 50 nm diameter, in the 5 wt. % TiS2 material. This could inhibit the lithium intercalation resulting in a valence state of 3.5 and thereby low discharge capacity whereas this nano particulate material is not present in 1 and 5 wt. % TiS2 loaded material.