title: Nanoscale Chemical Evolution of Silicon Negative Electrodes Characterized by Low-Loss STEM-EELS.
abstract: Continuous solid electrolyte interface (SEI) formation remains the limiting factor of the lifetime of silicon nanoparticles (SiNPs) based negative electrodes. Methods that could provide clear diagnosis of the electrode degradation are of utmost necessity to streamline further developments. We demonstrate that electron energy-loss spectroscopy (EELS) in a scanning transmission electron microscope (STEM can be used to quickly map SEI components and quantify LixSi alloys from single experiments with resolutions down to 5 nm. Exploiting the low-loss part of the EEL spectrum allowed us to circumvent the degradation phenomena that have so far crippled the application of this technique on such beam-sensitive compounds. Our results provide unprecedented insight into silicon aging mechanisms in full cell configuration. We observe the morphology of the SEI to be extremely heterogeneous at the particle scale but with clear chemical evolutions with extended cycling coming from both SEI accumulation and a transition from lithium-rich carbonate-like compounds to lithium-poor ones. Thanks to the retrieval of several results from a single data set we were able to correlate local discrepancies in lithiation to the initial crystallinity of silicon as well as to the local SEI chemistry and morphology. This study emphasizes how initial heterogeneities in the percolating electronic network and the porosity affect SiNPs aggregates along cycling. These findings pinpoint the crucial role of an optimized formulation in silicon-based thick electrodes.
authors.affiliation: Université Grenoble Alpes , F-38054 Grenoble, France.|CEA-INAC-MEM , F-38054 Grenoble, France.
authors.forename: Maxime
authors.initials: M
authors.lastname: Boniface
authors.affiliation: Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France.
authors.forename: Lucille
authors.initials: L
authors.lastname: Quazuguel
authors.affiliation: Université Grenoble Alpes , F-38054 Grenoble, France.|CEA-INAC-MEM , F-38054 Grenoble, France.
authors.forename: Julien
authors.initials: J
authors.lastname: Danet
authors.affiliation: Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France.
authors.forename: Dominique
authors.initials: D
authors.lastname: Guyomard
authors.affiliation: Institut des Matériaux Jean Rouxel (IMN), Université de Nantes, CNRS , 2 rue de la Houssinière, BP 32229, 44322 Nantes Cedex 3, France.
authors.forename: Philippe
authors.initials: P
authors.lastname: Moreau
authors.affiliation: Université Grenoble Alpes , F-38054 Grenoble, France.|CEA-INAC-MEM , F-38054 Grenoble, France.
authors.forename: Pascale
authors.initials: P
authors.lastname: Bayle-Guillemaud
keywords: Lithium ion battery; STEM-EELS; beam damage; chemical mapping; silicon anode; solid electrolyte interphase