Browsing by Author "Goonetilleke, D"

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    Correlating cycling history with structural evolution in commercial 26650 batteries using in operando neutron powder diffraction
    (Elsevier, 2017-03-01) Goonetilleke, D; Pramudita, JC; Hagan, M; Al Bahri, OK; Pang, WK; Peterson, VK; Groot, J; Berg, H; Sharma, N
    Ex situ and time-resolved in operando neutron powder diffraction (NPD) has been used to study the structural evolution of the graphite negative electrode and LiFePO4 positive electrode within ANR26650M1A commercial batteries from A123 Systems, in what to our knowledge is the first reported NPD study investigating a 26650-type battery. Batteries with different and accurately-known electrochemical and storage histories were studied, enabling the tell-tale signs of battery degradation to be elucidated using NPD. The ex-situ NPD data revealed that the intensity of the graphite/lithiated graphite (LixC6 or LiyC) reflections was affected by battery history, with lower lithiated graphite (LiC12) reflection intensities typically corresponding to more abused batteries. This indicates that the lithiation of graphite is less progressed in more abused batteries, and hence these batteries have lower capacities. In operando NPD allows the rate of structural evolution in the battery electrode materials to be correlated to the applied current. Interestingly, the electrodes exhibit different responses to the applied current that depend on the battery cycling history, with this particularly evident for the negative electrode. Therefore, this work illustrates how NPD can be used to correlate a battery history with electrode structure. Crown Copyright ©2016 Published by Elsevier B.V.
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    Structural evidence for Mg-doped LiFePO4 electrode polarisation in commercial Li-ion batteries
    (Elsevier, 2018-08-01) Goonetilleke, D; Faulkner, T; Peterson, VK; Sharma, N
    The reaction evolution and kinetics of the LiFePO4 positive electrode material is dependent on the synthesis method and cycling conditions. In operando neutron powder diffraction is used investigate the structure-electrochemistry relationship of the electrode materials in a Valence Technology Inc. 18650 Energy cell (IFR18650EC) containing a graphite negative electrode and a Mg-doped LiFePO4 (Li(MgFe)PO4) positive electrode. Two cells were studied at ambient (298 K) and elevated (323 K) temperature, and higher temperatures were found to improve reaction kinetics and hence capacity. Rietveld refinement of structural models against the diffraction data revealed information about the nucleation of the lithiated and delithiated phases in the Li(MgFe)PO4 positive electrode material as a function of each cell's state of charge. Polarisation was indicated by a shift in the potential at which the lithiated and delithiated (MgFe)PO4 phases nucleate during cycling, the extent of which was found to be linearly proportional to the applied current. This work provides new evidence for polarisation of the positive electrode material in a Li-ion battery system. © 2018 Elsevier B.V.
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    Structural evolution and high-voltage structural stability of Li(NixMnyCoz)O2 electrodes
    (American Chemical Society, 2018-12-17) Goonetilleke, D; Sharma, N; Pang, WK; Peterson, VK; Petibon, R; Li, J; Dahn, JR
    Positive electrode materials remain a limiting factor for the energy density of lithium-ion batteries (LIBs). Improving the structural stability of these materials over a wider potential window presents an opportune path to higher energy density LIBs. Herein, operando neutron diffraction is used to elucidate the relationship between the structural evolution and electrochemical behavior for a series of Li-ion pouch cells containing Li(NixMnyCoz)O2 (x + y + z = 1) electrode chemistries. The structural stability of these electrodes during charge and discharge cycling across a wide potential window is found to be influenced by the ratio of transition-metal atoms in the material. Of the electrodes investigated in this study, the Li(Ni0.4Mn0.4Co0.2)O2 composition exhibits the smallest magnitude of structural expansion and contraction during cycling while also providing favorable structural stability at high voltage. Greater structural change was observed in electrodes with a higher Ni content, while decreasing inversely to the Ni and Co content in the positive electrode. The combination of structural and electrochemical characterization of a wide range of NMC compositions provides useful insight for the design and application of ideal electrode compositions for long-term cycling and structural stability during storage at the charged state. © 2018 American Chemical Society
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    Using neutron-based techniques to investigate battery behaviour
    (Australian Institute of Nuclear Science and Engineering, 2016-11-29) Pramudita, JC; Goonetilleke, D; Peterson, VK; Sharma, N
    The extensive use of portable electronic devices has given rise to increasing demand for reliable high energy density storage in the form of batteries. Today, lithium-ion batteries (LIBs) are the leading technology as they offer high energy density and relatively long lifetimes.[1] Despite their widespread adoption, Li-ion batteries still suffer from significant degradation in their performance over time.[1] The most obvious degradation in lithium-ion battery performance is capacity fade – where the capacity of the battery reduces after extended cycling. This talk will focus on how in situ time-resolved neutron powder diffraction (NPD) can be used to gain a better understanding of the structural changes which contribute to the observed capacity fade. The commercial batteries studied each feature different electrochemical and storage histories that are precisely known, allowing us to elucidate the tell-tale signs of battery degradation using NPD and relate these to battery history. Moreover, this talk will also showcase the diverse use of other neutron-based techniques such as neutron imaging to study electrolyte concentrations in lead-acid batteries, and the use of quasi-elastic neutron scattering to study Na-ion dynamics in sodium-ion batteries.