22 research outputs found
Operando SAXS/WAXS on the a-P/C as the Anode for Na-Ion Batteries
A complete chemical and morphological analysis of the evolution of battery electrode materials can be achieved combining different and complementary techniques. Operando small-angle X-ray scattering (SAXS) and wide-angle X-ray scattering (WAXS) were combined to investigate structural and electrochemical performances of an Na-ion battery, with amorphous red phosphorus in a carbon matrix (a-P/C) as the active anode material in a Swagelok-type cell. The charging process results in the formation of crystalline Na3P, while during discharging, the anode material returns to the initial a-P/C. From the analysis of the WAXS curves, the formation of crystalline phases appears only at the end of charging. However, SAXS data show that partial reorganization of the material during charging occurs at length scales nonaccessible with conventional X-ray diffraction, corresponding to a real space ordering distance of 4.6 nm. Furthermore, the analysis of the SAXS data shows that the electrode remains dense during charging, while it develops some porosity during the discharge phase. The presented results indicate that the combination of SAXS/WAXS adopted simultaneously, and nondestructively, on a working electrochemical cell can highlight new mechanisms of reactions otherwise undetected. This method can be applied for the study of any other solid electrode material for batteries
Structural and magnetic characterization of the elusive Jahn-Teller active NaCrF3
We report the structural and magnetic characterization of the elusive Jahn-
Teller active compound NaCrF3
5D total scattering computed tomography reveals the full reaction mechanism of a bismuth vanadate lithium ion battery anode
publishedVersio
In situ synchrotron study of ordered and disordered LiMn1.5Ni0.5O4 as lithium ion battery positive electrode
In situ powder synchrotron diffraction and X-ray absorption spectroscopy have been used to investigate cation ordered as well as disordered modifications of the LiMn1.5Ni0.5O4 spinel-type compound as a Li-ion battery (LIB) cathode during electrochemical cycling. The structural state depends on the adopted heat treatment conditions and is ascertained by Raman and neutron diffraction data. The degree of Mn-Ni ordering (none, partial, complete) is one parameter that influences the electrochemical behaviour. The in situ data reveal significant differences in behaviour with respect to structural phase transitions during electrochemical cycling. Ordered Li2Mn3NiO8 (P4332) undergoes two consecutive first order structural phase transitions between spinel type phases during charging - discharging. These are most probably connected with steps in oxidation state for the Ni-atoms as supported by XANES data. The disordered phases (Fd-3m) show a mixed âsolid solution - two phaseâ behaviour accompanied by a smooth decrease in the unit cell volume during charging over the two redox steps involved, Ni2+/Ni3+/Ni4+, however, also with volume jumps at first order transitions. This combined behaviour is explained for the first time for spinel type LiMn1.5Ni0.5O4 materials. It is not clear why ordered and disordered phases show different phase behaviors depending on the state of (dis)charge. This could be due to higher valent Mn taking part in the redox activity at higher voltages, however, future verification is required
An electrochemical cell for operando bench-top X-ray diffraction
International audienc
Playing with the Redox Potentials in Ludwigite Oxyborates: Fe 3 BO 5 and Cu 2 MBO 5 (M = Fe, Mn, and Cr)
International audienc
Understanding the (De)Sodiation Mechanisms in NaâBased Batteries through Operando XâRay Methods
Progress in the field of Naâbased batteries strongly relies on the development of new advanced materials. However, one of the main challenges of implementing new electrode materials is the understanding of their mechanisms (sodiation/desodiation) during electrochemical cycling. Operando studies provide extremely valuable insights into structural and chemical changes within different battery components during battery operation. The present review offers a critical summary of the operando Xâray based characterization techniques used to examine the structural and chemical transformations of the active materials in Naâion, Naâair and Naâsulfur batteries during (de)sodiation. These methods provide structural and electronic information through diffraction, scattering, absorption and imaging or through a combination of these Xârayâbased techniques. Challenges associated with cell design and data processing are also addressed herein. In addition, the present review provides a perspective on the future opportunities for these powerful techniques
Hyper-expanded interlayer separations in superconducting barium intercalates of FeSe
Intercalation of Ba in ÎČ-FeSe by ammonothermal synthesis results in the formation of different superconducting phases with interlayer distance ranging between 8.4 and 13.1 Ă
. The values of Tc are primarily dependent on Ba content, and are further modulated by the interlayer spacing through facile intercalation and deintercalation of ammonia
High temperature spin-driven multiferroicity in ludwigite chromocuprate Cu 2 CrBO 5
International audienceWe report spin-driven multiferroicity above 100 K in the ludwigite Cu(II) oxyborate Cu2CrBO5. Spontaneous polarization, which reaches 35 ”C.m-2 at 5 K, appears below 120 K, concomitantly with an incommensurate antiferromagnetic order and complex magnetodielectric effects. In magnetically induced ferroelectrics, multiferroicity usually appears at low temperature, because of the competing magnetic exchanges needed to stabilize a magnetic spiral : the remarkably high transition temperature observed in Cu2CrBO5 originates from the presence of strong Cu-O-Cu magnetic super-exchange interactions, which are not weakened by Cu/Cr cationic disorder. Our result provides an important contribution to the search for high temperature spindriven multiferroics amongst low-dimensional cuprates