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15 items found (0 items not approved), displaying 1 to 10.[First/Prev] 1, 2 [Next/Last]

Instruments / Technical Area	Publication Details	Published
I07-Surface & interface diffraction	Film before aggregates: an operando GISAXS study on electrochemically assisted surfactant assembly Gilles E. Moehl , Samuel D. Fitch , Katarina Cicvarić , Yisong Han , Ruomeng Huang , Jonathan Rawle , Li Shao , Richard Beanland , Philip N Bartlett , Guy Denuault , Andrew L. Hector Nanoscale DOI: 10.1039/D3NR05126A Diamond Proposal Number(s): [20593] Open Access Show Abstract ▼ Abstract: The process of electrochemically assisted surfactant assembly was followed in real time by grazing incidence small angle X-ray scattering with the aim to deconvolute the formation of mesoporous silica film and unwanted porous particles. The X-ray technique proved to be useful for the characterisation of this process, as it takes place at a very dynamic, solid/liquid interface. This paper shows the electrochemically driven onset and evolution of silica/surfactant structures. Additional control experiments indicate the formation of vertically aligned structures without the use of an electric field, although it seems to be beneficial increased pore ordering.	Feb 2024
I08-Scanning X-ray Microscopy beamline (SXM) I09-Surface and Interface Structural Analysis	Combined electrochemical, XPS, and STXM study of lithium nitride as a protective coating for lithium metal and lithium-sulfur batteries Samuel D. S. Fitch , Gilles E. Moehl , Nina Meddings , Sacha Fop , Samantha Soule , Tien-Lin Lee , Majid Kazemian , Nuria Garcia-Araez , Andrew L. Hector Acs Applied Materials & Interfaces DOI: 10.1021/acsami.3c04897 Diamond Proposal Number(s): [1860, 20639, 22619] Open Access Show Abstract ▼ Abstract: Li3N is an excellent protective coating material for lithium electrodes with very high lithium-ion conductivity and low electronic conductivity, but the formation of stable and homogeneous coatings is technically very difficult. Here, we show that protective Li3N coatings can be simply formed by the direct reaction of electrodeposited lithium electrodes with N2 gas, whereas using battery-grade lithium foil is problematic due to the presence of a native passivation layer that hampers that reaction. The protective Li3N coating is effective at preventing lithium dendrite formation, as found from unidirectional plating and plating–stripping measurements in Li–Li cells. The Li3N coating also efficiently suppresses the parasitic reactions of polysulfides and other electrolyte species with the lithium electrode, as demonstrated by scanning transmission X-ray microscopy, X-ray photoelectron spectroscopy, and optical microscopy. The protection of the lithium electrode against corrosion by polysulfides and other electrolyte species, as well as the promotion of smooth deposits without dendrites, makes the Li3N coating highly promising for applications in lithium metal batteries, such as lithium–sulfur batteries. The present findings show that the formation of Li3N can be achieved with lithium electrodes covered by a secondary electrolyte interface layer, which proves that the in situ formation of Li3N coatings inside the batteries is attainable.	Aug 2023
B18-Core EXAFS	High sodium-ion battery capacity in sulfur-deficient tin(II) sulfide thin films with a microrod morphology Zening Zhu , Geoffrey Hyett , Gillian Reid , Fred Robinson , Giannantonio Cibin , Andrew L. Hector Small Structures 7 DOI: 10.1002/sstr.202200396 Diamond Proposal Number(s): [14239] Open Access Show Abstract ▼ Abstract: Sulfur-deficient SnS thin films for sodium-ion battery anode application are prepared using aerosol-assisted chemical vapor deposition. Growth directly onto the metal foil current collector forms sulfur-deficient SnS microrod structures via a vapor–liquid–solid growth mechanism, with 92 nm average SnS crystallite size and an 800 nm film thickness. The sulfur deficiency is demonstrated with energy-dispersive X-ray analysis, powder X-ray diffraction, and X-ray absorption near-edge structure analyses. This sulfur-deficient SnS material demonstrates a very high capacity in sodium half cells. The first reduction scan at a specific current of 150 mA g−1 shows a capacity of 1084 mAh g−1. At the 50th cycle the specific capacity is 638 mAh g−1 for reduction and 593 mAh g−1 for oxidation. This capacity is demonstrated for tin sulfide itself without the need for a nanostructured carbon support, unlike previous high capacity SnS anodes in the literature. Both the capacity and ex situ characterization experiments indicate a conversion reaction producing tin, followed by alloying with sodium during reduction, and that both of these processes are reversible during oxidation.	Feb 2023
B18-Core EXAFS	Solvothermal synthesis of Sn3N4 as a high capacity sodium-ion anode: theoretical and experimental study of its storage mechanism Samuel D. S. Fitch , Giannantonio Cibin , Steven P. Hepplestone , Nuria Garcia-Araez , Andrew L. Hector Journal Of Materials Chemistry A 3 DOI: 10.1039/D0TA04034G Diamond Proposal Number(s): [14239] Open Access Show Abstract ▼ Abstract: A new simple and scalable method to synthesise spinel-structured Sn3N4 has been developed using SnCl4 and LiNH2 precursors under solvothermal conditions. Nanocrystalline Sn3N4 with a crystallite size < 10 nm was produced and tested as anode material in sodium half cells, demonstrating a very high reversible (de-sodiation) capacity of ∼850 mA h g−1 measured over 50 cycles, the highest reported reversible capacity for a sodium anode apart from sodium itself. Ex situ X-ray absorption spectroscopy and X-ray diffraction show that the electrochemical reactions are reversible and that Sn3N4 is recovered upon re-oxidation. X-ray diffraction shows that the peaks associated with Sn3N4 reflections become narrower during discharge (reduction), evidencing that the smaller Sn3N4 particles are primarily involved in the electrochemical reactions, and broadening of the peaks is reversibly recovered upon oxidation. The analysis of the near edge X-ray absorption data (XANES) shows that the Sn oxidation state decreases during reduction and nearly recovers the initial value during oxidation. DFT calculations suggest that the insertion of Na into the Sn3N4 surface followed by substitution of tetrahedral Sn by Na is energetically favourable, and evidence of the removal of tetrahedral Sn from the spinel Sn3N4 structure is obtained from the analysis of the extended X-ray absorption fine-structure (EXAFS) measurements of reduced electrodes, which also show the recovery of the pristine structure at the end of oxidation. DFT also shows that Sn substitution by Na is only favourable at the Sn3N4 surface (not for bulk Sn3N4), in agreement with the electrochemical characterisation that shows that controlling the nanoparticle size is crucial to achieve full utilisation of Sn3N4 (and thus high capacity).	Jul 2020
I15-Extreme Conditions	Covalency is frustrating: La2Sn2O7 and the nature of bonding in pyrochlores under high pressure-temperature conditions Christian Childs , Keith V. Lawler , Andrew L. Hector , Sylvain Petitgirard , Ori Noked , Jesse S. Smith , Dominik Daisenberger , Lucile Bezacier , Marek Jura , Chris J. Pickard , Ashkan Salamat Inorganic Chemistry DOI: 10.1021/acs.inorgchem.8b01419 Open Access Show Abstract ▼ Abstract: Natural specimens of the pyrochlore (A2B2O7) compounds have been found to retain foreign actinide impurities within their parent framework, undergoing metamictization to a fully amorphous state. The response to radionuclide decay identifies pyrochlore systems with having high radiation tolerance and tailored use in radioactive waste applications and radionuclide sequestration. High pressure is a powerful pathway to high density states and amorphization with parallels to radiation-induced processes. Here, La2Sn2O7 is evaluated under extreme conditions via the combination of laser heating in a diamond anvil cell with X-ray diffraction and Raman spectroscopy. The measurements are supported by ab initio random structure searching and molecular dynamics calculations. A new ground state at 70 GPa is revealed, and high temperature annealing is fundamental to access its crystalline ground state and fully determine the structure. This crystalline phase (P21/c) retains its structural integrity during decompression and is fully recoverable to ambient conditions. The final state of the system is shown to be highly pathway dependent due to the covalent nature of the Sn–O bonding. The Tc pyrochlore, La2Tc2O7, is analyzed for similarities in the bonding to determine the likelihood of an analogous pathway dependency to a final state.	Jul 2018
I07-Surface & interface diffraction	In situ phase behaviour of a high capacity LiCoPO 4 electrode during constant or pulsed charge of a lithium cell Michael G. Palmer , James T. Frith , Andrew L. Hector , Andrew W. Lodge , John R. Owen , Chris Nicklin , Jonathan Rawle Chemical Communications DOI: 10.1039/C6CC07756K Diamond Proposal Number(s): [11142] Open Access Show Abstract ▼ Abstract: The phase changes that occur during lithium extraction from LiCoPO4 in lithium half-cells were studied using synchrotron X-ray diffraction. The existence of two two-phase regions with an intermediate phase present was observed. Significant variations in the composition of the phases of nominal stoichiometry LiCoPO4, Li2/3CoPO4 and CoPO4 resulted in unit cell volume variations. On current pulsing, lattice parameter shifts and phase recovery were directly observed.	Nov 2016
I15-Extreme Conditions	Sol–gel preparation of low oxygen content, high surface area silicon nitride and imidonitride materials Kripasindhu Sardar , Richard Bounds , Marina Carravetta , Geoff Cutts , Justin Hargreaves , Andrew Hector , Joe Hriljac , William Levason , Felix Wilson Dalton Transactions 13 DOI: 10.1039/C5DT04961J Diamond Proposal Number(s): [9124] Open Access Show Abstract ▼ Abstract: Reactions of Si(NHMe)4 with ammonia are effectively catalysed by small ammonium triflate concentrations, and can be used to produce free-standing silicon imide gels. Firing at various temperatures produces amorphous or partially crystallised silicon imidonitride/nitride samples with high surface areas and low oxygen contents. The crystalline phase is entirely α-Si3N4 and structural similarities are observed between the amorphous and crystallised materials.	Feb 2016
I15-Extreme Conditions	Synthesis of U3Se5 and U3Te5 type polymorphs of Ta3N5 by combining high pressure-temperature pathways with a chemical precursor approach Ashkan Salamat , Katherine Woodhead , S. Imran U. Shah , Andrew Hector , Paul Mcmillan Chemical Communications DOI: 10.1039/C4CC05147E Diamond Proposal Number(s): [986] Show Abstract ▼ Abstract: Combining metastable precursors with high pressuretemperature treatment is a powerful tool to make nitrogen-rich metal nitrides. Two new dense polymorphs of Ta3N5 have previously been theoretically predicted, with U3Se5 (Pnma) and U3Te5 (Pnma) structure types, and are now shown to exist. Amorphous Ta3N5 from thermal ammonolysis of an amorphous polymeric precursor was laser heated at 22 GPa and examined using synchrotron X-ray diffraction to reveal the emergence of these two novel polymorphs.	Jul 2014
B18-Core EXAFS I15-Extreme Conditions	High pressure polymorphism of Beta-TaON K. Woodhead , S. Pascarelli , A. L. Hector , R. Briggs , N. Alderman , P. F. Mcmillan Dalton Transactions 43 (25), 7726-7733 DOI: 10.1039/c4dt00805g Show Abstract ▼ Abstract: The high pressure behavior of TaON was studied using a combination of Raman scattering, synchrotron X-ray diffraction, and X-ray absorption spectroscopy in diamond anvil cells to 70 GPa at ambient temperature. A Birch¨CMurnaghan equation of state fit for baddeleyite structured ¦Â-TaON indicates a high bulk modulus value Ko = 328 ¡À 4 GPa with K¡äo = 4.3. EXAFS analysis of the high pressure XAS data provides additional information on changes in the Ta¨C(O,N) and Ta¨CTa distances. Changes in the X-ray diffraction patterns and Raman spectra indicate onset of a pressure induced phase transition near 33 GPa. Our analysis indicates that the new phase has an orthorhombic cotunnite-type structure but that the phase transition may not be complete even by 70 GPa. Similar sluggish transformation kinetics are observed for the isostructural ZrO2 phase. Analysis of compressibility data for the new cotunnite-type TaON phase indicate a very high bulk modulus Ko 370 GPa, close to the theoretically predicted value.	May 2014
I07-Surface & interface diffraction	Direct observation of active material concentration gradients and crystallinity breakdown in LiFePO4 electrodes during charge/discharge cycling of lithium batteries Matthew R. Roberts , Alex Madsen , Chris Nicklin , Jonathan Rawle , Michael G. Palmer , John R. Owen , Andrew L. Hector The Journal Of Physical Chemistry C 118 (13) DOI: 10.1021/jp411152s PMID: 24790684 Diamond Proposal Number(s): [6799, 7698] Open Access Show Abstract ▼ Abstract: The phase changes that occur during discharge of an electrode comprised of LiFePO4, carbon, and PTFE binder have been studied in lithium half cells by using X-ray diffraction measurements in reflection geometry. Differences in the state of charge between the front and the back of LiFePO4 electrodes have been visualized. By modifying the X-ray incident angle the depth of penetration of the X-ray beam into the electrode was altered, allowing for the examination of any concentration gradients that were present within the electrode. At high rates of discharge the electrode side facing the current collector underwent limited lithium insertion while the electrode as a whole underwent greater than 50% of discharge. This behavior is consistent with depletion at high rate of the lithium content of the electrolyte contained in the electrode pores. Increases in the diffraction peak widths indicated a breakdown of crystallinity within the active material during cycling even during the relatively short duration of these experiments, which can also be linked to cycling at high rate.	Feb 2014

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