Marin Lagacé

New Lithium metal polymer solid state battery for an ultra-high energy: Nano C-LiFePO4 versus Nano Li1.2V3O8

Novel lithium metal polymer solid state batteries with nano C-LiFePO4 and nano Li1.2V3O8 counter-electrodes (average particle size 200 nm) were studied for the first time by in situ SEM and impedance during cycling. The kinetics of Li-motion during cycling is analyzed self-consistently together with the electrochemical properties. We show that the cycling life of the nano Li1.2V3O8 is limited by the dissolution of the vanadium in the electrolyte, which explains the choice of nano C-LiFePO4 (1300 cycles at 100% DOD): with this olivine, no dissolution is observed. In combination with lithium metal, at high loading and with a stable SEI an ultrahigh energy density battery was thus newly developed in our laboratory.

An Open-Source Engine for the Processing of Electron Backscatter Patterns: EBSD-Image

An open source software package dedicated to processing stored electron backscatter patterns is presented. The package gives users full control over the type and order of operations that are performed on electron backscatter diffraction (EBSD) patterns as well as the results obtained. The current version of EBSD-Image (www.ebsd-image.org) offers a flexible and structured interface to calculate various quality metrics over large datasets. It includes unique features such as practical file formats for storing diffraction patterns and analysis results, stitching of mappings with automatic reorganization of their diffraction patterns, and routines for processing data on a distributed computer grid. Implementations of the algorithms used in the software are described and benchmarked using simulated diffraction patterns. Using those simulated EBSD patterns, the detection of Kikuchi bands in EBSD-Image was found to be comparable to commercially available EBSD systems. In addition, 24 quality metrics were evaluated based on the ability to assess the level of deformation in two samples (copper and iron) deformed using 220 grit SiC grinding paper. Fourteen metrics were able to properly measure the deformation gradient of the samples.

Towards A More Quantitative Measurement of the Deformation During Metallographic Specimen Preparation Using EBSD and FIB

Surface deformation during metallographic preparation have been previously studied using light optical microscopy (LOM) and transmission electron microscopy (TEM) [1]. With its submicron resolution, electron backscattered diffraction (EBSD) can provide quantitative deformation analysis at a smaller length scale than LOM while provide higher statistics than TEM. This work aims to determine the level of deformation produced during different metallographic preparation steps of common materials. As a first iteration, the deformation profile induced by 80, 240 and 600 ANSI grit SiC papers on commercially pure iron (BCC), copper (FCC) and titanium (HCP) was measured.

Development of Tools to Increase the Spatial Resolution of EBSD Maps

APPARENT RESOLUTION • At a tilt of 70◦, the volume of interaction of electrons is asymmetric, elliptical in the direction perpendicular to the tilt axis. • Backscattered electrons forming the Kikuchi patterns are however coming from a much smaller generation volume. [1] • The lateral resolution is therefore smaller than the longitudinal resolution (approximately 3 times smaller). [2,3] EFFECTIVE RESOLUTION • Convolution of two patterns can be seen as a linear combination of two patterns: P = xPA + (1− x)PB • Depending on the pattern quality and if there is a significant difference in intensity, an indexing algorithm could identify the pattern with the highest intensity. [4] • The effective resolution is therefore smaller than the apparent resolution. [1,4–7]

Direct and Indirect Observation of Lithium in a Scanning Electron Microscope; Not Only on Pure Li!

Battery is one of the most used technologies in everyday life (cellular, electric vehicle or hybrid cars). Improvement in the specific capacity (energy by weight or volume) and charging rate has a potential to even significantly improve their used. Hence, the research in battery materials is very important, well founded and will have a direct economical and social impact. Most of the actual battery technology is based on the displacement of Lithium ion (Li) from two active materials (i.e., graphite for the anode and LiFePO4 for the cathode). It is thus essential to determine the distribution and the amount of Li with a good spatial resolution (<< 1 μm) In terms of microstructural characterization Li is very difficult to analysed using conventional detector because it is a very light element and emits low energy x-rays (52 eV). Optical Emission spectrometry and XPS can easily detect Li but without any no good lateral resolution. In counterpart, Li has a relatively high sputtered yield and low backscattered coefficient. Mass spectra have been used in dedicated secondary ion mass microscope (SIMS), either static or Time of Flight (TOF) but with, again, with a limited lateral resolution.

On the Precision of EDS Analysis with Sample Tilted at 70

Simultaneous collection of electron backscattered diffraction (EBSD) pattern and X-Ray spectrum using energy dispersive spectrometer (EDS) promise to greatly improve upon the phase differentiation by combining chemical and crystallographic information[1-2]. To achieve the promised level of indexation accuracy, quantitative X-Ray analysis must be performed with noisy spectra of highly tilted samples (usually 70°). The accuracy of X-ray quantification using EDS was demonstrated for spectra acquired from specimens normal to the beam and with sufficient statistics to give at least 10k counts on the lowest intensity peaks. This scenario is far from the one that prevailed for the spectra acquired during an EBSD automatic run.

Quantitative Film Thickness Measurement Using Scintillator/Photomultiplier Backscattered Electron Detectors. Possible or Not?

Scintillator/photomultiplicator backscattered electron detectors (BSE) are now commonly used in scanning electron microscopy (SEM) since they have sufficient sensitivity to detect low energy backscattered electrons at high scan rates (i.e. TV rate). These detectors are often the main source of imaging in SEMs under variable pressure operating mode. Two scintillating materials are mainly used to convert electron signal to light: high-Z powders and plastic scintillators [1]. The most commonly used are high-Z powders coated on a conductive layer (Al or other) to remove charging. However, those detectors have very rough surfaces. These rough surfaces combined with the high-Z material can produce a large amount of type III BSEs. In addition, the number of BSEs hitting the high-Z scintillating material depends on the angular distribution of the BSEs emitted from the sample. Taking this into consideration along with the fact that the samples being analyzed may have high surface roughness, we have evaluated the possibility of obtaining quantitative information from the BSE signal.