Browsing by Author "Pramudita, JC"
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- ItemA comprehensive picture of the current rate dependence of the structural evolution of P2-Na2/3Fe2/3Mn1/3O2(Royal Society of Chemistry, 2015-09-02) Sharma, N; Han, MH; Pramudita, JC; Gonzalo, E; Brand, HEA; Rojo, TCathodes that feature a layered structure are attractive reversible sodium hosts for ambient temperature sodium-ion batteries which may meet the demands for large-scale energy storage devices. However, crystallographic data on these electrodes are limited to equilibrium or quasi-equilibrium information. Here we report the current-dependent structural evolution of the P2-Na2/3Fe2/3Mn1/3O2 electrode during charge/discharge at different current rates. The structural evolution is highly dependent on the current rate used, e.g., there is significant disorder in the layered structure near the charged state at slower rates and following the cessation of high-current rate cycling. At moderate and high rates this disordered structure does not appear. In addition, at the slower rates the disordered structure persists during subsequent discharge. In all rates examined, we show the presence of an additional two-phase region that has not been observed before, where both phases maintain P63/mmc symmetry but with varying sodium contents. Notably, most of the charge at each current rate is transferred via P2 (P63/mmc) phases with varying sodium contents. This illustrates that the high-rate performance of these electrodes is in part due to the preservation of the P2 structure and the disordered phases appear predominantly at lower rates. Such current-dependent structural information is critical to understand how electrodes function in batteries which can be used to develop optimised charge/discharge routines and better materials. © 2015 The Royal Society of Chemistry. This article is Open Access.
- ItemCorrelating 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, NEx 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.
- ItemGraphene and selected derivatives as negative electrodes in sodium- and lithium-ion batteries(John Wiley & Sons, Inc, 2015-05-02) Pramudita, JC; Pontiroli, D; Magnani, G; Gaboardi, M; Riccò, M; Milanese, C; Brand, HEA; Sharma, NThe performance of graphene, and a few selected derivatives, was investigated as a negative electrode material in sodium- and lithium-ion batteries. Hydrogenated graphene shows significant improvement in battery performance compared with as-prepared graphene, with reversible capacities of 488 mA h g−1 for lithium-ion batteries after 50 cycles and 491 mA h g−1 for sodium-ion batteries after 20 cycles. Notably, high rates of 1 A g−1 for graphene and 5 A g−1 for hydrogenated graphene indicate higher capacities in sodium-ion batteries than in lithium-ion batteries. Alternatively, nickel-nanoparticle-decorated graphene performed relatively poorly in lithium-ion batteries. However, in sodium-ion batteries they showed the highest reversible capacities of all studied batteries and graphene derivatives, with 826 mA h g−1 after 25 cycles with ≈97 % coulombic efficiency. Overall, minor modifications to graphene can dramatically improve electrochemical performance in both lithium-ion and sodium-ion batteries. © 2015 Wiley-VCH Verlag GmbH & Co.
- ItemMoisture exposed layered oxide electrodes as Na-ion battery cathodes(Royal Society of Chemistry, 2016-11-09) Han, MH; Sharma, N; Gonzalo, E; Pramudita, JC; Brand, HEA; López del Amo, JM; Rojo, TMn-rich layered oxides of P2 Na2/3Mn0.8Fe0.1Ti0.1O2 have been shown to exhibit a remarkably stable electrochemical performance even after exposure to moisture for extended periods of time. Here, a detailed investigation of the electrochemical performance of pristine, protonated, and hydrated electrodes is reported. Neutron powder diffraction and 23Na NMR are employed in order to correlate the overall electrochemical performance of each electrode with that of the as-synthesized crystal structure. The effects of proton and water (or OH) moieties on the Na+ layers are discussed based on the electrochemical performance of each phase. The complete structural evolution of the protonated and pristine P2 Na2/3Mn0.8Fe0.1Ti0.1O2 electrodes during charge/discharge is determined via in situ synchrotron X-ray diffraction. The protonated phase at the potential cut-offs (1.5-4.2 and 2-4 V) and the applied currents used shows a predominantly solid-solution reaction with little evidence of a secondary phase while the pristine phase shows the formation of secondary phases and typically better electrochemical capacities. Therefore, the formation of the secondary phase, in part, enhances capacity in this system. Thus moisture exposure (and subsequent treatment) of generally P2 electrodes can lead to significantly different structural evolution during charge/discharge reactions and hence observed capacities. © 2016 The Royal Society of Chemistry.
- ItemPotassium-ion intercalation in graphite within a potassium-ion battery examined using in situ x-ray diffraction(Cambridge University Press, 2017-09-04) Pramudita, JC; Peterson, VK; Kimpton, JA; Sharma, NGraphite has been widely used as a negative electrode material in lithium-ion batteries, and recently it has attracted attention for its use in potassium-ion batteries. In this study, the first in situ X-ray diffraction characterisation of a K/graphite electrochemical cell is performed. Various graphite intercalation compounds are found, including the stage three KC36 and stage one KC8 compounds, along with the disappearance of the graphite during the potassiation process. These results show new insights on the non-equilibrium states of potassium-ion intercalation into graphite in K/graphite electrochemical cells. © International Centre for Diffraction Data 2017
- ItemRate and composition dependence on the structural–electrochemical relationships in P2–Na2/3Fe1–yMnyO2 positive electrodes for sodium-ion batteries(American Chemical Society, 2018-10-02) Dose, WM; Sharma, N; Pramudita, JC; Avdeev, M; Gonzalo, E; Rojo, TStructural–electrochemical compositional evolution of attractive cathode candidates for sodium-ion batteries is illustrated. Varying the Fe/Mn ratio plays a significant role in phase evolution, which ranges from a simple solid solution or two-phase transitions to more complex combinations and sequences of phase transitions dependent on the Na concentration. Further complexity is added by the kinetic limitations placed on the compositions with applied current and associated material utilization. This work provides a standardized set of electrochemical and structural data for members of the Na2/3Fe1–yMnyO2 series, exploring the phase evolution at a selected rate of 15 mA g–1, comparing this with literature data at various current rates, and focusing on the evolution of the y = 0.9 at higher and lower current rates. The y = 0.8 composition shows the highest capacity, while y = 0.9 shows slightly better capacity retention at 15 mA g–1. Structurally, the y = 0.8 features a solid-solution evolution throughout the charge–discharge process, while the y = 0.9 shows a solid solution and two-phase evolution, yet shows better capacity retention. Such studies illustrate how chemical tuning and electrochemical current influences structural evolution with sodium insertion/extraction and how this in turn influences electrochemical performance. © 2018 American Chemical Society
- ItemSodium uptake in cell construction and subsequent in operando electrode behaviour of Prussian blue analogues, Fe[Fe(CN)6]1−x·yH2O and FeCo(CN)6(Royal Society of Chemistry, 2014-07-23) Pramudita, JC; Schmid, S; Godfrey, T; Whittle, T; Alam, AKMM; Hanley, TL; Brand, HEA; Sharma, NThe development of electrodes for ambient temperature sodium-ion batteries requires the study of new materials and the understanding of how crystal structure influences properties. In this study, we investigate where sodium locates in two Prussian blue analogues, Fe[Fe(CN)6]1-x·yH2O and FeCo(CN)6. The evolution of the sodium site occupancies, lattice and volume is shown during charge-discharge using in situ synchrotron X-ray powder diffraction data. Sodium insertion is found to occur in these electrodes during cell construction and therefore Fe[Fe(CN)6]1-x·yH2O and FeCo(CN)6 can be used as positive electrodes. NazFeFe(CN)6 electrodes feature higher reversible capacities relative to NazFeCo(CN)6 electrodes which can be associated with a combination of structural factors, for example, a major sodium-containing phase, ∼Na0.5FeFe(CN)6 with sodium locating either at the x = y = z = 0.25 or x = y = 0.25 and z = 0.227(11) sites and an electrochemically inactive sodium-free Fe[Fe(CN)6]1-x·yH2O phase. This study demonstrates that key questions about electrode performance and attributes in sodium-ion batteries can be addressed using time-resolved in situ synchrotron X-ray diffraction studies. © 2014 Royal Society of Chemistry Open Access CC Licence
- ItemStructure–electrochemical evolution of a Mn-rich P2 Na 2/3 Fe 0.2 Mn 0.8 O2 Na-ion battery cathode(American Chemical Society, 2017-08-04) Dose, WM; Sharma, N; Pramudita, JC; Brand, HEA; Gonzalo, E; Rojo, TThe structural evolution of electrode materials directly influences the performance of sodium-ion batteries. In this work, in situ synchrotron X-ray diffraction is used to investigate the evolution of the crystal structure of a Mn-rich P2-phase Na2/3Fe0.2Mn0.8O2 cathode. A single-phase reaction takes place for the majority of the discharge-charge cycle at ∼C/10, with only a short, subtle hexagonal P2 to hexagonal P2 two-phase region early in the first charge. Thus, a higher fraction of Mn compared to previous studies is demonstrated to stabilize the P2 structure at high and low potentials, with neither "Z"/OP4 phases in the charged state nor significant quantities of the P′2 phase in the discharged state between 1.5 and 4.2 V. Notably, sodium ions inserted during discharge are located on both available crystallographic sites, albeit with a preference for the site sharing edges with the MO6 octahedral unit. The composition Na∼0.70Fe0.2Mn0.8O2 prompts a reversible single-phase sodium redistribution between the two sites. Sodium ions vacate the site sharing faces (Naf), favoring the site sharing edges (Nae) to give a Nae/Naf site occupation of 4:1 in the discharged state. This site preference could be an intermediate state prior to the formation of the P′2 phase. Thus, this work shows how the Mn-rich Na2/3Fe0.2Mn0.8O2 composition and its sodium-ion distribution can minimize phase transitions during battery function, especially in the discharged state. © 2017 American Chemical Society.
- ItemThe unique structural evolution of the O3-phase Na2/3Fe2/3Mn1/3O2 during high rate charge/discharge: a sodium-centred perspective(John Wiley & Sons, Inc, 2015-08-17) Sharma, N; Gonzalo, E; Pramudita, JC; Han, MH; Brand, HEA; Hart, JN; Pang, WK; Guo, ZP; Rojo, TThe development of new insertion electrodes in sodium-ion batteries requires an in-depth understanding of the relationship between electrochemical performance and the structural evolution during cycling. To date in situ synchrotron X-ray and neutron diffraction methods appear to be the only probes of in situ electrode evolution at high rates, a critical condition for battery development. Here, the structural evolution of the recently synthesized O3-phase of Na2/3Fe2/3Mn1/3O2 is reported under relatively high current rates. The evolution of the phases, their lattice parameters, and phase fractions, and the sodium content in the crystal structure as a function of the charge/discharge process are shown. It is found that the O3-phase persists throughout the charge/discharge cycle but undergoes a series of two-phase and solid-solution transitions subtly modifying the sodium content and atomic positions but keeping the overall space-group symmetry (structural motif). In addition, for the first time, evidence of a structurally characterized region is shown that undergoes two-phase and solid-solution phase transitions simultaneously. The Mn/Fe-O bond lengths, c lattice parameter evolution, and the distance between the Mn/FeO6 layers are shown to concertedly change in a favorable manner for Na+ insertion/extraction. The exceptional electrochemical performance of this electrode can be related in part to the electrode maintaining the O3-phase throughout the charge/discharge process. © 2015 Wiley-VCH Verlag GmbH & Co.
- ItemUsing in situ synchrotron x-ray diffraction to study lithium- and sodium-ion batteries: a case study with an unconventional battery electrode (Gd2TiO5)(Cambridge University Press, 2014-11-04) Pramudita, JC; Aughterson, RD; Dose, WM; Donne, SW; Brand, HEA; Sharma, NDesigning materials for application as electrodes in sodium-ion batteries may require the use of unconventional materials to realize acceptable reversible sodium insertion/extraction capabilities. To design new materials simple electrochemical methods need to be coupled with other techniques such as in situ x-ray diffraction (XRD) to correlate the influence of electrochemical performance on a parameter that can be modified, e.g., the crystal structure of the material. Here we use in situ synchrotron XRD data on Gd2TiO5-containing cells to show the minor changes in reflection positions during discharge/charge that illustrates minimal volume expansion and contraction due to insertion/extraction reactions. These small changes correlate to the Gd2TiO5 anode material in both lithium- and sodium-ion batteries showing reversible capacities of ∼45 and ∼23 mA h/g after 20 cycles, respectively. Analysis of sodium location in the crystal structure shows a preference for sodium in the smaller channels along the c axis direction during the first discharge before moving to the larger channels at the charged state. Therefore, in this work, in situ studies highlight minimal structural changes with respect to volume expansion during electrochemical cycling and illustrate where sodium ions locate within the Gd2TiO5 structure. © 2014 Materials Research Society
- ItemUsing neutron-based techniques to investigate battery behaviour(Australian Institute of Nuclear Science and Engineering, 2016-11-29) Pramudita, JC; Goonetilleke, D; Peterson, VK; Sharma, NThe 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.