Stephane Levasseur

The insulator-metal transition upon lithium deintercalation from LiCoO2: electronic properties and 7Li NMR study

Samples of Li x CoO 2 (0.5≤x≤1) have been prepared by electrochemical deintercalation from high temperature LiCoO 2 and are characterized by X-ray diffraction, electrical measurements and 7 Li MAS NMR spectroscopy. X-Ray diffraction studies as a function of x are in good agreement with literature data and suggest that the two-phase domain for 0.75≤x≤0.94 is not due to structural reasons. Electrical conductivity and thermoelectronic power measurements evidence a gradual change in the electronic properties from localised to delocalised electrons upon lithium deintercalation. 7 Li MAS NMR suggests that the metal-non metal transition is the driving force for the existence of the biphasic domain.

The effects of moderate thermal treatments under air on LiFePO 4-based nano powders

The thermal behavior under air of LiFePO4-based powders was investigated through the combination of several techniques such as temperature-controlled X-ray diffraction, thermogravimetric analysis and Mossbauer and NMR spectroscopies. The reactivity with air at moderate temperatures depends on the particle size and leads to progressive displacement of Fe from the core structure yielding nano-size Fe2O3 and highly defective, oxidized LixFeyPO4 compositions whose unit-cell volume decreases dramatically when the temperature is raised between 400 and 600 K. The novel LiFePO4-like compositions display new electrochemical reactivity when used as positive electrodes in Li batteries. Several redox phenomena between 3.4 V and 2.7 V vs.Li were discovered and followed by in-situX-ray diffraction, which revealed two distinct solid solution domains associated with highly anisotropic variations of the unit-cell constants.

Preparation, structure and electrochemistry of LiFeBO3: a cathode material for Li-ion batteries

LiMBO3 (M = Fe, Co, Mn) has been identified as an interesting new cathode material for Li-ion batteries. It was shown to be difficult to synthesize the material as a pure phase and in a highly electrochemically active form. Here we report several methods for the successful preparation of LiFeBO3, including traditional ceramic and self-combustion reactions. By decreasing the particle size and introducing in situ carbon coating, conventionally ceramic-synthesized LiFeBO3/C yields a first discharge of 210 mA h g−1 within the 1.5–4.5 V voltage window at a C/20 rate, 55 °C. Using high-resolution synchrotron X-ray diffraction, neutron powder diffraction and single crystal X-ray diffraction in combination with 6Li NMR and 57Fe Mossbauer spectroscopies, we present a “1Fe 2Li” complex cation distribution model for LiFeBO3 powder.

Multiscale electronic transport mechanism and true conductivities in amorphous carbon–LiFePO4 nanocomposites

Composite and nanostructured materials have hierarchical architecture with different levels: (a) macroscopic (substructure of porous clusters); (b) mesostructural (particles constituting the clusters); and (c) microscopic and nanometric (coatings, bulk of the particles). The identification of the key parameters that affect the electronic transport across all observed size scales is required, but is not possible using conventional dc-conductivity measurements. In this paper, the powerful broadband dielectric spectroscopy (BDS) from low-frequencies (few Hz) to microwaves (few GHz) is applied to one of the most important composite materials for lithium batteries. LiFePO4 is wrapped in a carbon coating whose electrical properties, although critical for battery performance, have never been measured due to its nanometre-size and the powdery nature of the material. We provide a description of the electronic transport mechanism from the nanoscale (sp2 crystallites) up to the sample macroscopic scale for this material. Moreover, the true conductivities and their respective drop when going from one scale to another are given, for the very first time, in the case of a composite powdery material for lithium batteries.

Role of propane sultone as an additive to improve the performance of a lithium-rich cathode material at a high potential

This study presents the use of 1,3-propane sultone (PS) in the [EC–DMC + 1 mol L−1 LiPF6] electrolyte as a protective additive for the Li-rich-NMC xLi2MnO3–(1 − x)LiMO2 (x ≫ 1; M = Ni, Co, Mn) cathode–electrolyte interface during cathode material activation and cycling at a high potential (5 V vs. Li). The results showed that the presence of 1% PS (w/w) ensured complete and better electrode activation during the first cycle than EC–DMC + 1 mol L−1 LiPF6. Thus, Li//Li-rich-NMC half-cell and Gr//Li-rich-NMC full-cell provided capacities as high as C = 330 mA h g−1 during charge and C = 275 mA h g−1 during discharge with a higher cut-off voltage of 5 V. Measurements by cyclic voltammetry demonstrated that activating at such a voltage enhanced the redox activity from Li2MnO3 activation. At same time, the contribution of nickel and cobalt electroactivity is decreased at their regular voltage. This feature was attributed to structural modifications occurring on the surface to the bulk of the material. Long-cycling tests of Li//Li-rich-NMC half-cells with PS provided a higher reversible capacity and superior capacity retention (245 mA h g−1 after 240 cycles) with good coulombic efficiency (99 ± 1%) and better high-discharge rate capability (above 180 mA h g−1 at 1 C regime) than those obtained using conventional electrolytes without additive.

Probing Lithium and Vacancy Ordering in O3 Layered Li[sub x]CoO[sub 2] (x≈0.5)

X-ray and electron diffraction experiments were performed to understand lithium and vacancy ordering phenomenon and the monoclinic distortion in Li0.5CoO2. It was shown that the observed peak splitting, indicative of monoclinic distortion, was attributed primarily to the shearing of the rhombohedral oxygen lattice. Experimental electron diffraction studies of a monoclinic Li0.5CoO2 sample revealed additional reflections that were consistent with the in-plane ordering configuration of lithium and vacancy proposed previously by Reimers and Dahn [J. Electrochem. Soc., 139, 2091 (1992)]. Moreover, this study found that the electron diffraction patterns with appearances resembling those of the spinel structure could be explained fully by the formation of mazed microstructure and lithium ordering in Li0.5CoO2. Therefore, there was no evidence of the layered to spinel transformation in the LixCoO2 system, in agreement with the excellent cycling performance of Li/LixCoO2 batteries.X-ray and electron diffraction experiments were performed to understand lithium and vacancy ordering phenomenon and the monoclinic distortion in Li 0.5 CoO 2 . It was shown that the observed peak splitting, indicative of monoclinic distortion, was attributed primarily to the shearing of the rhombohedral oxygen lattice. Experimental electron diffraction studies of a monoclinic Li 0.5 CoO 2 sample revealed additional reflections that were consistent with the in-plane ordering configuration of lithium and vacancy proposed previously by Reimers and Dahn [J. Electrochem. Soc., 139, 2091 (1992)]. Moreover, this study found that the electron diffraction patterns with appearances resembling those of the spinel structure could be explained fully by the formation of mazed microstructure and lithium ordering in Li 0.5 CoO 2 . Therefore, there was no evidence of the layered to spinel transformation in the Li x CoO 2 system, in agreement with the excellent cycling performance of Li/Li x CoO 2 batteries.

Probing lithium and vacancy ordering in O3 layered LixCoO2 (x » 0.5)

X-ray and electron diffraction experiments were performed to understand lithium and vacancy ordering phenomenon and the monoclinic distortion in Li0.5CoO2. It was shown that the observed peak splitting, indicative of monoclinic distortion, was attributed primarily to the shearing of the rhombohedral oxygen lattice. Experimental electron diffraction studies of a monoclinic Li0.5CoO2 sample revealed additional reflections that were consistent with the in-plane ordering configuration of lithium and vacancy proposed previously by Reimers and Dahn [J. Electrochem. Soc., 139, 2091 (1992)]. Moreover, this study found that the electron diffraction patterns with appearances resembling those of the spinel structure could be explained fully by the formation of mazed microstructure and lithium ordering in Li0.5CoO2. Therefore, there was no evidence of the layered to spinel transformation in the LixCoO2 system, in agreement with the excellent cycling performance of Li/LixCoO2 batteries.X-ray and electron diffraction experiments were performed to understand lithium and vacancy ordering phenomenon and the monoclinic distortion in Li 0.5 CoO 2 . It was shown that the observed peak splitting, indicative of monoclinic distortion, was attributed primarily to the shearing of the rhombohedral oxygen lattice. Experimental electron diffraction studies of a monoclinic Li 0.5 CoO 2 sample revealed additional reflections that were consistent with the in-plane ordering configuration of lithium and vacancy proposed previously by Reimers and Dahn [J. Electrochem. Soc., 139, 2091 (1992)]. Moreover, this study found that the electron diffraction patterns with appearances resembling those of the spinel structure could be explained fully by the formation of mazed microstructure and lithium ordering in Li 0.5 CoO 2 . Therefore, there was no evidence of the layered to spinel transformation in the Li x CoO 2 system, in agreement with the excellent cycling performance of Li/Li x CoO 2 batteries.

Development of Novel Solid Materials for High Power Li Polymer Batteries (SOMABAT). Recyclability of Components

SOMABAT aims to develop more environmental friendly, safer and better performing high power Li polymer battery by the development of novel breakthrough recyclable solid materials to be used as anode, cathode and solid polymer electrolyte, new alternatives to recycle the different components of the battery and life cycle analysis. This challenge is being achieved by using new low-cost synthesis and processing methods in which it is possible to tailor the different properties of the materials. Development of different novel synthetic and recyclable materials based carbon based hybrid materials, novel LiFePO4 and LiFeMnPO4 based nanocomposite cathode with a conductive polymers or carbons, and highly conductive polymer electrolyte membranes based on fluorinated matrices with nanosized particles and others based on a series of polyphosphates and polyphosphonates polymers respond to the very ambitious challenge of adequate energy density, lifetime and safety. An assessment and test of the potential recyclability and revalorisation of the battery components developed and life-cycle assessment of the cell will allow the development of a more environmental friendly Li-polymer battery in which a 50 % weight of the battery will be recyclable and a reduction of the final cost of the battery up to 150 €/kWh is achievable. The consortium is made up of experts in the field and is complementary in terms of R&D expertise and geographic distribution.