Second-harmonic electron paramagnetic resonance spectroscopy and imaging reveal metallic lithium depositions in Li-ion batteries

We have investigated metallic lithium particle nucleation following lithiation and delithiation steps of the graphite electrode using X-band electron paramagnetic resonance (EPR). Metallic lithium aggregates like dendrites and/or filaments which are formed during electrochemical cycling on the graphite anode are complex structures which may lead to internal short-circuit and safety issues. Understanding and following, in real conditions, this nucleation process is necessary to improve the development of Li-ion batteries. The complexity to detect metallic lithium structures inside Li-ion batteries depends on the number of EPR lines and their linewidth. The presence of lithiated graphite phases affects the detection of micrometric Li-metal elements. Herein, we report a new approach using cw-EPR (continuous-wave EPR) spectroscopy and imaging, combining the first- and second-harmonic detection schemes to provide evidence for the metallic lithium aggregate nucleation in these negative electrodes. Although the first harmonic gives all the EPR signals present in the sample, it is found that the second-harmonic EPR signal is mainly sensitive to metallic lithium depositions.</p

Transferts électroniques à une microITIES : influence des potentiels rédox en phase aqueuse

Conférence du 03 au 06 juin 2003. Communication par affiche

Effect of amino acid mutations on the conformational dynamics of amyloidogenic immunoglobulin light-chains: A combined NMR and in silico study

The conformational dynamics of a pathogenic κ4 human immunoglobulin light-chain variable domain, SMA, associated with AL amyloidosis, were investigated by 15N relaxation dispersion NMR spectroscopy. Compared to a homologous light-chain, LEN, which differs from SMA at eight positions but is non-amyloidogenic in vivo, we find that multiple residues in SMA clustered around the N-terminus and CDR loops experience considerable conformational exchange broadening caused by millisecond timescale protein motions, consistent with a destabilized dimer interface. To evaluate the contribution of each amino acid substitution to shaping the dynamic conformational landscape of SMA, NMR studies were performed for each SMA-like point mutant of LEN followed by in silico analysis for a subset of these proteins. These studies show that a combination of only three mutations located within or directly adjacent to CDR3 loop at the dimer interface, which remarkably include both destabilizing (Q89H and Y96Q) and stabilizing (T94H) mutations, largely accounts for the differences in conformational flexibility between LEN and SMA. Collectively, our studies indicate that a correct combination of stabilizing and destabilizing mutations is key for immunoglobulin light-chains populating unfolded intermediates that result in amyloid formation, and underscore the complex nature of correlations between light-chain conformational flexibility, thermodynamic stability and amyloidogenicity

Electron transfer at the liquid-liquid interface between Lu(III) bisphtalocyanines in a solvent and Fe(III)/Fe(II) in water. Studies at a micro-interface and at solvent film electrodes

Conférence du 27 avril au 2 mai 2003. Communication orale

Electron transfer at the liquid-liquid interface between Lu(III) bisphtalocyanines in a solvent and Fe(III)/Fe(II) in water. Studies at a micro-interface and at solvent film electrodes

Conférence du 27 avril au 2 mai 2003. Communication orale

Characterization of polyalphaolefins using halogen anion attachment in atmospheric pressure photoionization coupled with ion mobility spectrometry-mass spectrometry

International audiencePolyalphaolefins (PAOs) are saturated alpha olefin oligomers used as a base stock oil for synthetic lubricants. The synthetic base stocks are manufactured from linear alpha olefins by catalytic oligomerization processes. The aim of this work was the characterization of different PAO grades, synthesized from different linear alpha olefins using two oligomerization processes, acid and metallocene catalyses. Negative ion atmospheric pressure photoionization (APPI) coupled with ion mobility spectrometry-mass spectrometry (IMS-MS) permitted the detection of intact PAO adducts with either chloride, bromide or iodide ions using halogenated solvents (e.g. dichloromethane, dibromomethane and diiodomethane) and toluene as the dopant. The best signal-to-noise ratio was obtained with dichloromethane. The APPI mass spectra displayed characteristic ion distributions for high viscosity PAO grades. The mass shift between two adjacent ions permitted the identification of repeating units and consequently the monomers of alpha olefins used to manufacture the PAO. For low PAO grades, the halide anion adducts were not detected as they are less stable. The IMS-MS data, as well as the correlated variables, i.e. the drift time and full width at half maximum (FWHM) of the IMS peaks, can be used to differentiate polyalphaolefins of the same grade but differently synthesized