Under pressure:Mechanochemical effects on structure and ion conduction in the sodium-ion solid electrolyte Na₃PS₄

10.1021/jacs.0c06668Journal of the American Chemical Society1424318422-1843

Na7V3(P2O7)(4) as a high voltage electrode material for Na-ion batteries: crystal structure and mechanism of Na+ extraction/insertion by operando X-ray diffraction

International audienceThe crystal chemistry and the electrochemical properties of Na7V3(P2O7)(4) as a high voltage cathode material upon Na+ extraction/insertion were investigated. The crystal structure was solved and refined for the first time from single crystal X-ray diffraction data. Possible sodium migration pathways were determined using the bond valence energy landscape (BVEL) method based on the bond valence theory. The electrochemical behavior of the material in a wide voltage range demonstrates the activity of the V3+/V4+, V4+/V5+, and V3+/V2+ redox couples. The reversible capacity of the Na7V3(P2O7)(4) electrode is hence increased up to 118 mA h g(-1)vs. Na+/Na. Sodium extraction/insertion mechanisms are examined by operando X-ray diffraction, which provides direct information on the evolution of the material in nonequilibrium states upon electrochemical oxidation and reduction processes

(NH4)0.75Fe(H2O)2[BP2O8]·0.25H2O, a Fe3+/Fe2+ Mixed Valence Cathode Material for Na Battery Exhibiting a Helical Structure

International audienc

A High Voltage Cathode Material for Sodium Batteries: Na3V(PO4)(2)

International audienceA novel layered Na3V(PO4)(2) compound was synthesized and studied as a positive electrode material for Na-ion batteries for the first time. The as-prepared material exhibits two relatively high voltage plateaus at around 3.6 and 4.0 V vs Na+/Na. Operando X-ray diffraction investigation provides insight into the mechanisms of structural transformations upon cycling

LiMSO(4)F (M = Fe, Co and Ni): promising new positive electrode materials through the DFT microscope

A theoretical study of the lithium intercalated LiMSO(4)F and deintercalated MSO(4)F systems, where M = Fe, Co and Ni has been performed within the framework of density functional theory. Beyond predictions of structural evolution and average voltages versus a lithium electrode, we have applied partial density of states and Bader's topological analysis of the electron density to the study of lithium deintercalation. Upon lithium extraction, charge rearrangement occurs for nickel between different d-orbitals, but with little net positive charge gain, while cobalt and iron atoms end up with a clear oxidized state. The participation of oxygen ions in accepting the electron of the lithium is thus enhanced for LiNiSO(4)F. However, this effect does not affect the long-range electrostatic interactions a lot in the lithiated phase, since the valence of all transition metals is very close due to initial lower oxidized state for the Ni atom in the host. It is found that this is not essentially a long-range electrostatic interaction within the lithiated phase but within the host which explains, at least partly, the increase in voltage by passing from Fe to Ni. Our results also shed light upon the possibility of getting an approximate evaluation of the local strain associated with delithiation from the atomic volume evolutions, which are also likely to affect the electrochemical potential

Structural and electrochemical studies of novel Na7V3Al(P2O7)(4)(PO4) and Na7V2Al2(P2O7)(4)(PO4) high-voltage cathode materials for Na-ion batteries

International audienceA series of Na7V4-x3+Alx(P2O7)(4)(PO4) (x = 0, 1, 2, and 4) materials were synthesized by flux crystal growth. Novel Na7V4-xAlx(P2O7)(4)(PO4) (x = 1 and 2) compositions were structurally characterized by single crystal and powder X-ray diffraction analyses using laboratory and high-resolution synchrotron X-ray sources. The investigation of the electrochemical behavior of two new mixed V/Al phases as positive electrodes in Na-based batteries was performed using charge-discharge galvanostatic tests and operando X-ray diffraction experiments. It is demonstrated that the substitution of a part of vanadium with aluminum in Na7V4(P2O7)(4)(PO4) significantly increases the gravimetric capacity of these materials: from 70.9 mA h g(-1) to 113.1 mA h g(-1) and from 48.1 mA h g(-1) to 92.7 mA h g(-1) in Na7V3Al(P2O7)(4)(PO4) and Na(7)V(2)A(2)l(P2O7)(4)(PO4), respectively thanks to the activation of the V4+/V5+ redox couple. Different degrees of reversibility of the electrochemical reactions operating on the V3+/V4+ and V4+/V5+ redox couples in Na7V3Al(P2O7)(4)(PO4) are discussed from the analysis of operando X-ray diffraction

Hunting for Better Li-Based Electrode Materials via Low Temperature Inorganic Synthesis

International audienc

Design of new electrode materials for Li-ion and Na-ion batteries from the bloedite mineral Na2Mg(SO4)2*4H2O

International audienceMineralogy offers a large database to search for Li- or Na-based compounds having suitable structural features for acting as electrode materials, LiFePO4 being one example. Here we further explore this avenue and report on the electrochemical properties of the bloedite type compounds Na2M(SO4)2*4H2O (M = Mg, Fe, Co, Ni, Zn) and their dehydrated phases Na2M(SO4)2 (M = Fe, Co), whose structures have been solved via complementary synchrotron X-ray diffraction, neutron powder diffraction and transmission electron microscopy. Among these compounds, the hydrated and anhydrous iron-based phases show electrochemical activity with the reversible release/uptake of 1 Na+ or 1 Li+ at high voltages of [similar]3.3 V vs. Na+/Na0 and [similar]3.6 V vs. Li+/Li0, respectively. Although the reversible capacities remain lower than 100 mA h g−1, we hope this work will stress further the importance of mineralogy as a source of inspiration for designing eco-efficient electrode materials

2D-Layered Lithium Carboxylate Based on Biphenyl Core as Negative Electrode for Organic Lithium-Ion Batteries

International audienc