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Key parameters governing lithium-ion mobility in an ionic liquid tethered on metal oxide nanoparticles as solvent-free hybrid electrolytes
No full textInternational audienceHere, we have synthesized and characterized a series of new hybrid materials based on ionic liquids grafted on metal oxides to assess the design of solvent-free solid-state electrolytes. The aim of this study is to determine the key parameters affecting the ionic conduction properties of the materials. Several aspects were modulated, such as the chemical composition of the metal oxide (SiO2, ZrO2 or Al2O3), anchoring bond (silane chemistry or coordinative bond) and length and nature of the spacer (propyl, undecyl, or polyethylene glycol). The ionic conductivity of the hybrid composite mixed with the lithium salt reaches 4 x 10-5 S cm-1 without the addition of any solvents or plasticizers. This study reveals that although lithium mobility is affected by the molecular structure of the ionic liquid and grafting function, it is more driven by the organization of the ILs on the surface of the nanomaterial
Formation dynamics of an ethylene carbonate-derived solid–electrolyte-interphase in commercial Li-ion batteries
No full textInternational audienceThe importance of the solid–electrolyte-interphase (SEI) is well-established in lithium-ion (Li-ion) batteries, but the technical story behind its formation remains incomplete. Current research has largely focused on the nature of the deposited layer, while the formation dynamics, particularly those occurring in the solution phase, remain elusive. Here, by employing operando infrared fiber evanescent wave spectroscopy (IR-FEWS) to conduct real-time monitoring of the chemical dynamics of ethylene carbonate-based electrolytes and graphite anodes, we reveal that the assembly of the SEI layer follows a classical heterogeneous nucleation and growth process under appropriate kinetic constraints. Our findings, supported by various other in situ/ex situ techniques, show that during charging, the newly generated species (e.g. lithium ethylene dicarbonate (LEDC) and Li2CO3), that are destined for the SEI, can also diffuse away from the graphite–electrolyte interface into the electrolyte. The deposition of the species occurs via a heterogeneous nucleation process with the low-solubility inorganic species (e.g. Li2CO3) preferentially nucleating on the graphite surface, followed by more-soluble organic species (e.g. LEDC). Limiting diffusion to promote the deposition is crucial for facilitating efficient SEI formation with competitive deposition kinetics depending not only on the charging rate and temperature, but also the electrolyte quantity. When the formation parameter-space is intentionally modified by employing a high current pulse during initial charging followed immediately by an ageing step, a more stable SEI with lower resistance is developed, leading to longer lifetimes for the Li-ion pouch cells prepared with this new protocol. Collectively, these findings deepen our mechanistic understanding of SEI formation from the “solution” phase perspective and offer an enriched framework for defining initial charging protocols for battery manufacturing
Wadsley-Roth FeNb11O29 as negative electrode material for lithium solid-state batteries
No full textInternational audienceFeNb 11 O 29 and Li 6 PS 5 Cl but revealed an interfacial degradation, with a resistive Li 2 S/oxide-rich interface, consistent with impedance growth. These findings highlight the critical role of microstructural and interfacial optimisation in the electrode composites and establish FeNb 11 O 29 as a promising candidate for high-rate solidstate batteries.</div
Understanding Degradation Mechanisms in Water‐In‐Salt Electrolyte: Part 1—In Depth Soaking Investigation by Means of Multiprobe Techniques of LiFePO 4 versus TiS 2
No full textInternational audienceWater‐based liquid electrolytes for Li‐ion batteries offer the promise of improved safety and lower cost, but the energy density remains too low due to the narrow electrochemical stability window of water. Switching to the water‐in‐salt electrolyte approach appears to be an ideal solution as the electrochemical stability window of water is extended, thereby increasing the overall energy density. To date, despite an increase in electrochemical stability window, hydrogen evolution reaction (HER) and oxygen evolution reaction still occur during cycling, resulting in poor electrochemical performance. Most articles report that this phenomenon is intrinsically related to the change in potential within the cell. In the present work, we carry out a complete surface‐to‐bulk investigation of two well‐known electroactive materials used in the water‐in‐salt system, LiFePO 4 and TiS 2 . The aim in this first part is to understand the role of soaking the composite electrode in the water‐in‐salt electrolyte and to see if degradation occurs prior to any electrochemical measurement. We show that LiFePO 4 is a robust material that develops a surface layer rich in LiF, whereas TiS 2 decomposes at the top surface into a mixture of TiO 2 /TiS 2 or oxysulfide byproduct
SIRT1 mediates brain metabolic and developmental consequences of methionine synthase deficiency in inborn errors of cobalamin metabolism
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Tailoring trap depth distributions in ZnGa2O4: Cr3+ nanoparticles for optimized persistent luminescence across various functional temperature ranges
No full textInternational audiencePersistent phosphors have attracted significant attention for their potential application in safety signage, road markings, data storage, anti-counterfeiting technologies, and biomedical fields. However, despite the significant advancements in room-temperature persistent phosphors and deep-trap materials for information storage, development of low-temperature persistent phosphors with strong afterglow emission remains a considerable challenge. In this study, we successfully modified the trap depth distribution in ZnGa2O4: Cr3+ nanoparticles (ZGO:Cr NPs) by carefully controlling the synthesis conditions in order to develop nanoscale persistent phosphors tailored for various temperature-dependent applications. ZnGa2O4: Cr3+ nanoparticles were synthesized via a rapid, facile, and environmentally friendly microwave-assisted hydrothermal method. A subsequent thermal treatment at temperatures of 500 and 700 ◦C was employed to further modify their structure and, consequently, their optical properties. Notably, the ZGO:Cr NPs without any subsequent calcination (ZGO MW) exhibit strong and long-lasting luminescence at cryogenic temperatures (15–200 K) and they show great potential for applications requiring continuous cooling at liquid nitrogen temperatures, such as the cryopreservation of biological agents, viruses, and tissues. In contrast, ZGO:Cr NPs calcined at 700 ◦C (ZGO 700) demonstrate stabili-zation of deeper traps, with activation energies near room temperature, which shows promise for conventional persistent luminescence applications requiring small particle sizes (<10 nm). Meanwhile, ZGO:Cr NPs calcined at 500 ◦C (ZGO 500) display a broad distribution of traps and a remarkably wide operational range (15–400 K), dueto the coexistence of multiple Cr3+ environments, making it highly suitable for applications requiring stable persistent luminescence behaviour at very wide range of temperatures
Overcoming sampling limitations using machine-learned interatomic potentials: the case of water-in-salt electrolytes
No full textMachine-learned interatomic potentials hold the promise to enable the modeling of highly concentrated liquids over meaningful timescales, far from reach for current ab initio electronic structure methods. Here we evaluate the performances of various MACE potentials in modeling a water-in-salt electrolyte based on lithium bis(trifluoromethanesulfonyl)imide. We test out-of-the-box foundation models, as well as both fine tuning and from scratch training strategies. Our simulations demonstrate that surrogate models allow to overcome sampling limitations of ab initio molecular dynamics, reaching an excellent agreement with experimental observables such as the structure factor. We also demonstrate the benefit of fine tuning a foundation model over training from scratch: in terms of data efficiency, but most importantly as a means to provide information regarding configurations hard to sample, such as short Li--Li distances. Finally, we show that depending on the reference exchange-correlation functional, empirical dispersion correction schemes can be detrimental. All in all, our work shows that machine-learned interatomic potentials are a good fit for the modeling of highly concentrated electrolytes over long timescales
Tailoring Electrode/Electrolyte Interfaces through Diazonium Chemistry in Aqueous Organic Redox Flow Batteries
No full textInternational audienceSurface engineering of carbon electrodes can play a critical role in mitigating interfacial polarization and improving charge-transfer kinetics in aqueous organic redox flow batteries (AORFBs), yet the mechanistic understanding of electrode/electrolyte interactions remains limited. We demonstrate a rational approach to tune the interfacial electrochemical reactivity of graphite felt electrodes through grafting of diazonium salts bearing negatively charged functional groups. The modified surfaces exhibit enhanced hydrophilicity and increased electrochemical capacitance. The impact of surface charge on electron-transfer behavior was systematically investigated using both negatively and positively charged redox probes, revealing a strong dependence of electrochemical activity on electrostatic interactions. While grafted layers partially hindered the ferro/ferricyanide couple, they maintained the reversibility of the [Ru(NH 3 ) 6 ] 3+ / 2+ system, confirming the charge-selective nature of the modified interfaces. When tested in neutral aqueous electrolytes containing nitroxide-based redox mediators, electrodes functionalized with sulfonate groups exhibited improved redox reversibility and reduced polarization. Flow battery tests using 4-OH-TEMPO electrolytes demonstrated up to 15% greater capacity and reduced polarization losses compared to pristine electrodes, particularly at high current densities. These findings establish diazonium chemistry as a versatile and controllable route to tailor electrode/electrolyte interactions in RFBs
Dual-Continuum Models of Lithium-Ion Batteries are Fast and Accurate Alternatives to the Doyle-Fuller-Newman Approach: II. Model Extensions
No full textInternational audienceIn Part I of this work, we derived and validated a dual-continuum model of a lithium-ion battery using the volume-averaging technique. Such models employ a fully macroscale description of the battery, thus avoiding the strong assumption made in the Doyle-Fuller-Newman (DFN) model that active material particles are isolated spheres. In all cases studied, our dual-continuum model predicted cell voltage more accurately than the DFN model, and required 70–80% less computation time. The physical insight offered by volume averaging gives rise to several interesting extensions of our derivation. Here in Part II, four of these are considered. Firstly, while Part I relied on a quasi-steady-state assumption for the closure problem, we now consider its transient behaviour to improve accuracy under changing battery loads. Secondly, we simulate electrodes with carbon additives and polymer binder, which can be explicitly modelled in the closure problem. Thirdly, we extend the dual-continuum theory to a multi-continuum model, which is particularly interesting for electrodes with a large particle size distribution. Finally, we reduce the dual-continuum theory to two single-continuum formulations, which are comparable with the well-known single-particle model—these maintain much of the accuracy of the dual-continuum approach whilst further reducing computation time
Fluorine-stabilized β-nickel hydroxides: composition, structural features, and electrochemical properties
No full text"ADC - Accord Couperin / American Chemical Society (2024-2026)"International audienceMost commercial Ni-based alkaline batteries use β-Ni(OH)2 as the cathode material. These batteries are particularly attractive due to the use of low-cost materials and nonflammable aqueous electrolytes, which enhance safety and recyclability. However, these electrodes suffer from structural instability during charge–discharge cycles caused by phase transitions between β-Ni(OH)2/β-NiOOH and α-Ni(OH)2/γ-NiOOH redox couples, leading to capacity fading over time. Therefore, stabilizing the β polymorph remains a significant challenge. In this study, nickel hydroxyfluorides (Ni(OH)2–xFx) were synthesized using microwave-assisted hydrothermal routes. It was possible to increase the fluorine content up to 0.48 while maintaining the β-Ni(OH)2 structural type. Powder X-ray diffraction and vibrational spectroscopy (FTIR, Raman) revealed substantial structural variations with fluorine incorporation. The highly electronegative fluorine plays a crucial role in enhancing both intraslab interactions, by increasing lattice rigidity, and interslab interactions, by affecting the level of the O–H bonds and H–H electrostatic repulsion. UV–vis–NIR spectroscopy confirmed the increased bond ionicity of the fluorinated samples, evidenced by an optical bandgap opening, a decrease of crystal field stabilization energy, and a slight increase of the Racah parameter. Thermogravimetric analysis showed a gradual increase in the decomposition temperature with higher fluorine content. Interestingly, the thermal decomposition of nickel hydroxyfluorides resulted in a novel synthesis method for nickel oxyfluorides (Ni1–(y/2) □y/2O1–yFy), stabilizing nickel vacancies. Galvanostatic cycling tests indicated a significant capacity decrease in the fluorine-containing samples. To further understand the mechanisms behind the reduced electrochemical performance, chemical oxidation tests were conducted. These tests demonstrated the inability of the fluorinated samples to be oxidized, suggesting that the high electronegativity of fluorine prevents nickel oxidation.</p