in-situ-neutron-powder-diffraction-using-custom-made-lithium-ion

<em>In Situ</em> Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries

Li-ion batteries are widely used in portable electronic devices and are considered as promising candidates for higher-energy applications such as electric ...

Australian Synchrotron

This paper reports the results of time-resolved synchrotron powder diffraction experiments where jarosites with different K/H(3)O, K/Na and Na/H(3)O ratios were synthesized in situ at temperatures of 353, 368 and 393 K in order to observe the effect on kinetics and species produced. The Na/H(3)O sample formed monoclinic jarosite at all three temperatures, whereas the K/H(3)O and K/Na samples formed as rhombohedral jarosites at 353 K, and as mixtures of rhombohedral and monoclinic jarosites at the higher temperatures. The relative amount of the monoclinic phase increased with increase in temperature. Unit-cell parameter changes with reaction time could be explained by changes in iron stoichiometry (samples become more stoichiometric with time) together with changes in K/H(3)O and Na/H(3)O ratios. The reaction kinetics have been fitted using a two-stage Avrami model, with two different Avrami exponents corresponding to initial two-dimensional growth followed by one-dimensional diffusion-controlled growth. Activation energies for the initial growth stage were calculated to be in the range 90-126 kJ mol(-1).

In situ synchrotron diffraction studies on the formation kinetics of jarosites.

This paper reports the results of time-resolved synchrotron small-angle scattering and powder diffraction experiments where natrojarosites were synthesized in situ in order to observe the species produced at the earliest stages of nucleation. The sample temperatures were 333, 353 and 368 K. These compounds were synthesized by co-precipitation from solution on the Small and Wide Angle Scattering and Powder Diffraction beamlines at the Australian Synchrotron. Scattering data were collected continuously throughout the syntheses. The results presented here show that the first particles to form in solution appear to be amorphous and nucleate on the walls of the reaction vessel. Crucially, there is a single nucleation event which forms particles with an elliptical disc morphology which then grow uniformly before natrojarosite crystallization is observed in complementary powder diffraction data. This nucleation event may represent the key to controlling the growth of jarosites in industrial and environmental settings.

In situ SAXS studies of the formation of sodium jarosite.

The nuclear and magnetic structures and properties of Sr0.65Pr0.35-xCexMnO3 (0.00 ≤ x ≤ 0.35) were investigated using a combination of synchrotron x-ray and neutron powder diffraction, along with magnetic and x-ray absorption near edge structure measurements. At room temperature, doping with Ce results in a transition from a tetragonal structure in I4/mcm to an orthorhombic one in Imma associated with the loss of long range orbital ordering. At low temperatures, we observe the formation of an orthorhombic Fmmm phase. XANES measurements demonstrate that the Ce exists as a mixture of Ce(3+) and Ce(4+).

Structural and magnetic studies of the electron doped manganites Sr0.65Pr0.35-xCexMnO3 (0.00 ≤ x ≤ 0.35).

The 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.

Helen E. A. Brand

Australian Synchrotron

In Situ Neutron Powder Diffraction Using Custom-made Lithium-ion Batteries