Characterization of non-aged and aged modern Prussian Blue pigments by Mössbauer spectroscopy, x-ray powder diffraction and x-ray absorption spectroscopy

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Aging Processes in Lithiated FeSn2 Based Negative Electrode for Li- Ion Batteries: A New Challenge for Tin Based Intermetallic Materials

Tin-based intermetallic compounds proposed as negative electrode materials for Li-ion batteries not only suffer from capacity fade during cycling due to volume variations but also from aging phenomena in lithiated states. By using FeSn2 as a model compound, we propose an analysis of this process by combining electrochemical potential measurements, 119Sn and 57Fe Mössbauer spectroscopies, magnetic measurements, and impedance spectroscopy. We show that the Fe/Li7Sn2 composite obtained at the end of the first discharge is progressively transformed during the aging process occurring within the electrochemical cell in open circuit condition. The Fe nanoparticles are stable while the Li7Sn2 nanoparticles are progressively delithiated with time leading to Sn-rich LixSn nanoalloys without observable back reaction with Fe. The deinserted lithium atoms react with the electrolyte and modify the surface electrode interphase (SEI) by increasing its thickness and/or decreasing its porosit

Structural and magnetic properties of Pr18Li8Fe5-xMxO39 (M = Ru, Mn, Co)

A polycrystalline sample of Pr18Li8Fe4RuO39 has been synthesized by a solid state method and characterized by neutron powder diffraction, magnetometry and Mössbauer spectroscopy; samples of Pr18Li8Fe5-xMnxO 39 and Pr18Li8Fe5-xCoxO 39 (x=1, 2) have been studied by magnetometry. All these compounds adopt a cubic structure (space group Pm over(3, -) n, a0∼11.97 Å) based on intersecting 〈111〉 chains made up of alternating octahedral and trigonal-prismatic coordination sites. These chains occupy channels within a Pr-O framework. The trigonal-prismatic site in Pr18Li8Fe4RuO39 is occupied by Li+ and high-spin Fe3+. The remaining transition-metal cations occupy the two crystallographically-distinct octahedral sites in a disordered manner. All five compositions adopt a spin-glass-like state at 7 K (Pr18Li8Fe4RuO39) or below. © 2009 Elsevier Inc. All rights reserved

Exploring the bottlenecks of anionic redox in Li-rich layered sulfides

Anionic redox chemistry has emerged as a new paradigm to design higher-energy lithium ion-battery cathode materials such as Li-rich layered oxides. However, they suffer from voltage fade, large hysteresis and sluggish kinetics, which originate intriguingly from the anionic redox activity itself. To fundamentally understand these issues, we decided to act on the ligand by designing new Li-rich layered sulfides Li1.33 – 2y/3Ti0.67 – y/3FeyS2, among which the y = 0.3 member shows sustained reversible capacities of ~245 mAh g−1 due to cumulated cationic (Fe2+/3+) and anionic (S2−/Sn−, n < 2) redox processes. Moreover, its negligible initial cycle irreversibility, mitigated voltage fade upon long cycling, low voltage hysteresis and fast kinetics compare positively with its Li-rich oxide analogues. Moving from the oxygen ligand to the sulfur ligand thus partially alleviates the practical bottlenecks affecting anionic redox, although it penalizes the redox potential and energy density. Overall, these sulfides provide chemical clues to improve the holistic performance of anionic redox electrodes, which may guide us to ultimately exploit the energy benefits of oxygen redox