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We have used operando 5D synchrotron total scattering computed tomography (TSCT) to understand the cycling and possible long term deactivation mechanisms of the lithium-ion battery anode bismuth vanadate. This anode material functions via a combined conversion/alloying mechanism in which nanocrystals of lithium–bismuth alloy are protected by an amorphous matrix of lithium vanadate. This composite is formed in situ during the first lithiation of the anode. The operando TSCT data were analyzed and mapped using both pair distribution function and Rietveld methods. We can follow the lithium–bismuth alloying reaction at all stages, gaining real structural insight including variations in nanoparticle sizes, lattice parameters and bond lengths, even when the material is completely amorphous. We also observe for the first time structural changes related to the cycling of lithium ions in the lithium vanadate matrix, which displays no interactions beyond the first shell of V–O bonds. The first 3D operando mapping of the distribution of different materials in an amorphous anode reveals a decline in coverage caused by either agglomeration or partial dissolution of the active material, hinting at the mechanism of long term deactivation. The observations from the operando experiment are backed up by post mortem transmission electron microscope (TEM) studies and theoretical calculations to provide a complete picture of an exceptionally complex cycling mechanism across a range of length scales. [ABSTRACT FROM AUTHOR]

Driven by the continuous search for improving performances, understanding the phenomena at the electrode/electrolyte interfaces has become an overriding factor for the success of sustainable and efficient battery technologies for mobile and stationary applications. Toward this goal, rapid advances have been made regarding simulations/modeling techniques and characterization approaches, including high‐throughput electrochemical measurements coupled with spectroscopies. Focusing on Li‐ion batteries, current developments are analyzed in the field as well as future challenges in order to gain a full description of interfacial processes across multiple length/timescales; from charge transfer to migration/diffusion properties and interphases formation, up to and including their stability over the entire battery lifetime. For such complex and interrelated phenomena, developing a unified workflow intimately combining the ensemble of these techniques will be critical to unlocking their full investigative potential. For this paradigm shift in battery design to become reality, it necessitates the implementation of research standards and protocols, underlining the importance of a concerted approach across the community. With this in mind, major collaborative initiatives gathering complementary strengths and skills will be fundamental if societal and environmental imperatives in this domain are to be met. [ABSTRACT FROM AUTHOR]

Bi2(MoO4)3 has been evaluated as an interesting anode material for application in lithium-ion batteries (LIBs). When cycled in the voltage window of 0.01–2.50 V a specific charge capacity of more than 800 mA h g−1 is retained after 50 cycles. According to operando synchrotron X-ray diffraction (XRD) the long-range order is lost during the initial lithiation. Direct insight into the electronic changes during cycling is obtained from operando Bi L3- and Mo K-edge X-ray absorption near edge spectroscopy (XANES) data collected during the first 1.5 cycles. A redox pair with anodic reactions at 0.97 V and cathodic reactions at 0.59 V is ascribed to alloying of bismuth: 3Li + Bi ↑ 2Li + LiBi ↑ Li3Bi. Likewise, reactions are ascribed to redox processes of Mo. Notably, the use of a cycling range limited to 2.00 V does not allow for a complete reoxidation of Mo, which in turn limits the reversibility of the Mo redox reactions. [ABSTRACT FROM AUTHOR]

Polycrystalline Sr2Fe1+xRe1−xO6 samples have been synthesized and structurally characterized by X-ray powder diffraction, transmission electron microscopy and X-ray absorption spectroscopy. Resistivity strongly increases with x, but a large and negative magnetoresistance persists up to x = 0.33. This is discussed considering the charge delocalization in iron and rhenium t2g orbitals. [ABSTRACT FROM AUTHOR]

BiVO4 undergoes a series of conversion and alloying reactions as an anode material in lithium ion batteries. The current work demonstrates a charge capacity of 485 mA h g−1 after 50 cycles in a voltage range of 0–2.00 V (graphite has a capacity of 372 mA h g−1 theoretically). An exceptionally high volumetric capacity makes BiVO4 suitable for compact applications (volumetric capacity of 3984 mA h cm−3 for BiVO4 in comparison to 756 mA h cm−3 for graphite theoretically). Reaction steps and electronic transformations have been identified by operando quasi simultaneous synchrotron X-ray diffraction and absorption spectroscopy studies. An irreversible reaction step occurs for the Bi3+/Bi0 redox pair, whereas reversible mechanisms are found for the V5+/V3+ and Bi0/Bi3− redox pairs. The proposed mechanisms are supported by density functional theory (DFT) calculations. [ABSTRACT FROM AUTHOR]

A new approach based on a combination of synchrotron radiation techniques, such as X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES), and powder X-ray diffraction (PXRD), has been applied to in situ study the processes of thermal decomposition of inorganic compounds and the formation of bimetallic nanoalloys. As an example, a double complex salt, [Pd(NH3)4][PtCl6], was selected because of (i) its sufficiently complicated structure and previous studies conducted via thermal analysis, ex situ PXRD and XPS, and (ii) its use as a prospective single-source precursor for the preparation of bimetallic (PdPt) nanoparticles or nanoalloys. The differences between the mechanisms based on ex situ and in situ data have been discussed for the first time. It has been found that the first step of thermal decomposition is related to the formation of crystalline [Pd(NH3)2Cl2][Pt(NH3)2Cl4]. Further decomposition results in the formation of {PdCl2}, {PtCl2}, and (NH4)2[PtCl6] in the second step. In the final step, the intermediates are completely reduced, and a bimetallic nanoalloy is formed. The different means of Pd and Pt reduction on the surface and in the bulk result in the formation of a disordered nanoalloy with possible monometallic inclusions. Further heating orders the nanoalloy that is accompanied by a decrease in the positive charge on Pt. [ABSTRACT FROM AUTHOR]

The GdFeO3-type perovskite NaFeF3 transforms to CaIrO3-type postperovskite at pressures as low as 9 GPa at room temperature. The details of such a transition were investigated by in situ synchrotron powder diffraction in a multianvil press. Fit of the p-V data showed that the perovskite phase is more compressible than related chemistries with a strongly anisotropic response of the lattice metrics to increasing pressure. The reduction in volume is accommodated by a rapid increase of the octahedral tilting angle, which reaches a critical value of 26° at the transition boundary. The postperovskite form, which is fully recoverable at ambient conditions, shows a regular geometry of the edge-sharing octahedra and its structural properties are comparable to those found in CaIrO3-type MgSiO3 at high pressure and temperature. Theoretical studies using density functional theory at the GGA + U level were also performed and describe a scenario where both perovskite and postperovskite phases can be considered Mott-Hubbard insulators with collinear magnetic G- and C-type antiferromagnetic structures, respectively. Magnetic measurements are in line with the theoretical predictions with both forms showing the typical behavior of canted antiferromagnets. [ABSTRACT FROM AUTHOR]

A new approach based on a combination of synchrotron radiation techniques, such as X-ray absorption fine structure (XAFS), X-ray photoelectron spectroscopy (XPS), hard X-ray photoelectron spectroscopy (HAXPES), and powder X-ray diffraction (PXRD), has been applied to in situ study the processes of thermal decomposition of inorganic compounds and the formation of bimetallic nanoalloys. As an example, a double complex salt, [Pd(NH3)4][PtCl6], was selected because of (i) its sufficiently complicated structure and previous studies conducted via thermal analysis, ex situ PXRD and XPS, and (ii) its use as a prospective single-source precursor for the preparation of bimetallic (PdPt) nanoparticles or nanoalloys. The differences between the mechanisms based on ex situ and in situ data have been discussed for the first time. It has been found that the first step of thermal decomposition is related to the formation of crystalline [Pd(NH3)2Cl2][Pt(NH3)2Cl4]. Further decomposition results in the formation of {PdCl2}, {PtCl2}, and (NH4)2[PtCl6] in the second step. In the final step, the intermediates are completely reduced, and a bimetallic nanoalloy is formed. The different means of Pd and Pt reduction on the surface and in the bulk result in the formation of a disordered nanoalloy with possible monometallic inclusions. Further heating orders the nanoalloy that is accompanied by a decrease in the positive charge on Pt. [ABSTRACT FROM AUTHOR]

Polycrystalline samples of perovskite-type NaFeF3 are prepared by solid state reaction of a 3:2:1 mixture of NaF, Fe, and FeF3 (Fe tube, 750 °C, 8 d). [ABSTRACT FROM AUTHOR]

Polycrystalline Sr2Fe1+xRe1-xO6 samples have been synthesized and structurally characterized by X-ray powder diffraction, transmission electron microscopy and X-ray absorption spectroscopy. Resistivity strongly increases with x, but a large and negative magnetoresistance persists up to x = 0.33. This is discussed considering the charge delocalization in iron and rhenium t2g orbitals.

BiVO4 undergoes a series of conversion and alloying reactions as an anode material in lithium ion batteries. The current work demonstrates a charge capacity of 485 mA h g-1 after 50 cycles in a voltage range of 0-2.00 V (graphite has a capacity of 372 mA h g-1 theoretically). An exceptionally high volumetric capacity makes BiVO4 suitable for compact applications (volumetric capacity of 3984 mA h cm-3 for BiVO4 in comparison to 756 mA h cm-3 for graphite theoretically). Reaction steps and electronic transformations have been identified by operando quasi simultaneous synchrotron X-ray diffraction and absorption spectroscopy studies. An irreversible reaction step occurs for the Bi3+/Bi0 redox pair, whereas reversible mechanisms are found for the V5+/V3+ and Bi0/Bi3- redox pairs. The proposed mechanisms are supported by density functional theory (DFT) calculations.