Nicolas Louvain

Surface fluorination is an effective strategy to stabilize high-voltage LiNi0.5Mn1.5O4 (LNMO) cathodes against interfacial degradation, yet the role of the fluorinating agent and its decomposition pathway in governing surface speciation remains poorly understood. Here, PTFE and CYTOP are investigated as solid fluoropolymer-derived fluorinating agents for LNMO surface modification via thermal decomposition under inert atmosphere, yielding comparable surface fluorine contents of approximately 0.08 mmol g–1 for both treatments. X-ray diffraction and Raman spectroscopy confirm that both treatments preserve the cubic spinel framework, indicating that fluorination is confined to the particle surface. XPS reveals the formation of LiF-like species, M–F bonds and manganese oxyfluoride-like environments, while EPR reveals modifications of the manganese electronic environment after treatment. Galvanostatic cycling over 100 cycles at C/10 demonstrates improved capacity retention for both fluorinated samples: all three electrodes deliver an initial discharge capacity close to 143 mAh g–1. After 100 cycles, LNMO–PTFE retains 95% of its initial discharge capacity (136 mAh g–1), compared to 91% for LNMO–CYTOP and 90% for pristine LNMO (∼128 mAh g–1). TGA-MS and in situ gas-phase FTIR identify the reactive species generated during decomposition: PTFE mainly releases :CF2, •CF, •C2F3 and •CF3 fragments, whereas CYTOP produces a broader distribution of fluorinated species over a wider temperature range. These differences in decomposition chemistry directly control the nature of the fluorinated interphase and the resulting electrochemical stabilization of LNMO. This work establishes mechanistic guidelines for designing scalable fluoropolymer-based surface treatments for high-voltage cathode materials, as an alternative to reactive fluorine sources such as F2 or XeF2.

A surge in the need for energy storage with high energy density is evident, especially given the rise of electric vehicles and hand-held electronic devices. This growing demand underscores the importance of innovating in battery technology. In this realm, lithium-ion batteries (LIBs) stand out for their impressive energy density. Notably, the spinel LiNi_0.5Mn_1.5O₄ (LNMO) material has caught the attention of LIBs due to its commendable electrochemical characteristics. This study focuses on the surface modification of disordered LNMO using the Atomic Layer Fluorination (ALF) method and investigates the influence of atomic fluorine on the interface between the LNMO and the electrolyte. Various characterization techniques, including X-ray Photoelectron Spectroscopy (XPS), Auger Electron Spectroscopy-Scanning Auger Microscopy (AES-SAM), Scanning Electron Microscopy (SEM), Nuclear Magnetic Resonance (NMR), and Electron Paramagnetic Resonance (EPR), are used to analyze the modified LNMO samples and understand the surface mechanism. Electrochemical tests reveal significant improvements in the cycling stability of fluorinated LNMO, while the rate capacity remains comparable to that of the pristine LNMO.

A Fe-thiolate MOF is capable of accommodating K ⁺ ions electrochemically, achieving low polarization, high capacity utilization and stable cycling performance thanks to Fe ³⁺ /Fe ²⁺ reversible redox processes and polyphasic transformations.

Solid electrolytes in Li-ion batteries offer enhanced safety and stability and contribute to improved energy density. In this study, a novel approach to synthesize a solid molecular ionic composite as an electrolyte for Li-ion batteries using 1-benzyl-3-methylimidazolium bis(trifluoromethanesulfonyl)imide [(Bn)mim][TFSI] ionic liquid as the principal component, a rigid polymer poly(2,2'-disulfonyl-4,4'-benzidine terephthalamide) (PBDT), and LiTFSI salt was explored. The composition of the membrane was systematically varied, with the percentage of polymer fixed at 10%, while the percentages of ionic liquid and LiTFSI salt were modified. The electrochemical performance of the resulting membranes was evaluated. Remarkably, the membrane containing 10% polymer, 10% LiTFSI salt, and 80% ionic liquid demonstrated exceptional electrochemical properties with a capacity of 150 mAh/g in LFP-Li half-cell, closing the theoretical capacity of LiFePO₄. This membrane exhibited high conductivity and excellent stability, making it a promising candidate for use as an electrolyte in Li-ion batteries. The findings of this study provide valuable insights into the design and optimization of polymer-based electrolyte membranes for advanced energy storage applications.

Atomic layer fluorination of Li(Ni _0.80 Co _0.15 Al _0.05 )O ₂ leads to improved charge/discharge cyclability in Li-ion cells and limited electrolyte decomposition.

Metal organic frameworks (MOFs) built up from metal–sulfur (M–S) bonds have shown great promise in the last decade thanks to their impressive electronic properties arising from the more covalent nature of the M–S bond when compared to M–O. In this study, we aim to expand the scope of available S-based MOFs to high oxidation state cations Mⁿ⁺ (n ≥ 3). Through the systematic exploration of the reactivity of the mixed thiolate-carboxylate ligand 2,5-disulfhydrylbenzene-1,4-dicarboxylic acid (H₄DSBDC) with Fe(III) salts, three new compounds were isolated. The structure of these materials consists of the same hybrid layers made of chains of edge-sharing FeS₄O₂ octahedra connected by fully deprotonated DSBDC⁴⁻, alternating with either organic (dimethyammonium, H₂N(CH₃)₂ ⁺) or inorganic (Na⁺ or K⁺) cations. The Fe–S connection leads to a strong absorption in the visible range, while the +III oxidation state of Fe, evidenced by Mössbauer spectroscopy, ensures a fairly good stability towards oxygen and water, higher than that typically observed with +II cations. Furthermore, Na{Fe(DSBDC)} exhibits an interesting reversible electrochemical activity when cycled both versus Li, Na and K in half-cells with good capacity retention, confirming the potential of this family of materials for applications involving electron transfer.

The properties of hybrid Sn-based artificial solid electrolyte interphase (SEI) layers in protecting Li-metal electrodes toward surface instabilities were investigated via a combined experimental and theoretical approach. The performance of coating layers can be coherently explained based on the nature of the coating species. Notably, when starting from a chloride precursor, the hybrid coating layer is formed by an intimate mixture of Li₇Sn₂ and LiCl: the first ensures a high bulk ionic conductivity, while the second forms an external layer allowing a fast surface diffusion of Li⁺ to avoid dendrite growth, a low surface tension to guarantee the thermodynamic stability of the protective layer, and a negative underneath plating energy (UPE) to promote lithium plating at the interface between the Li metal and the coating layer. The synergy between the two components and, in particular, the crucial role of LiCl in the promotion of such an underneath plating mechanism are shown to be the key properties to improve the performance of artificial SEI layers.

The Si surface coating by carbon is an appealing strategy to improve both the electronic conductivity and to stabilize the solid electrolyte interphase (SEI). In the present study, the electrochemical performance comparison of three nanocrystalline silicon‐based electrodes confirms the advantage brought by the carbon presence either as coating or in a composite, to improve their performance in Li‐ion batteries (LIBs). To rationalize this behavior, a full study of the electrode/electrolyte interface was achieved through the analysis of the cumulated relative irreversible capacity and the impedance and X‐ray photoelectron spectroscopies measurements. The study highlighted that the carbon coating leads to more efficient and less resistive SEI than that formed on silicon or on the native oxide surface. The pitch carbon matrix offers the same advantages and avoids moreover the isolation of particles. The control of the Si/electrolyte interface has a crucial role in the performance of Si‐based electrodes as negative electrodes for LIB.

The current revival of lithium metal batteries (LMB) has been driven by both the search for high energy‐density systems and the development of solid‐state batteries. Lithium electrode surface engineering is crucial to limit both the dendritic growth and the electrolyte reduction. Among the various strategies to obtain protecting layers, there has been a recent growing interest in metal coatings forming alloys with lithium. Here, various strategies to coat lithium and other metal electrodes (sodium, potassium and magnesium) are reviewed and discussed with respect to their efficiency, versatility, and their possible practical transfer to the battery industry.