Coupling liquid electrochemical TEM and mass-spectrometry to investigate electrochemical reactions occurring in a Na-ion battery anode

Kevyn Gallegos Moncayo; Nicolas Folastre; Milan Toledo; Hélène Tonnoir; François Rabuel; Grégory Gachot; Da Huo; Arnaud Demortière

arXiv · 2308.04981

Coupling liquid electrochemical TEM and mass-spectrometry to investigate electrochemical reactions occurring in a Na-ion battery anode

Kevyn Gallegos Moncayo·Nicolas Folastre·Milan Toledo·Hélène Tonnoir·François Rabuel·Grégory Gachot·Da Huo·Arnaud Demortière

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Abstract

In this study, we propose a novel approach for investigating the formation of solid electrolyte interphase (SEI) in Na-ion batteries (NIB) through the coupling of in situ liquid electrochemical transmission electron microscopy (ec-TEM) and gas-chromatography mass-spectrometry (GC/MS). To optimize this coupling, we conducted experiments on the sodiation of hard carbon materials (HC) using two different setups: in situ ec-TEM holder (operating in an "anode free" configuration, referred to as $μ$-battery) and ex-situ setup (Swagelok battery configuration). In the in situ TEM experiments, we intentionally degraded the electrolyte (NP30) using cyclic voltammetry (CV) and analyzed the recovered liquid product using GC/MS, while the solid product ($μ$-chip) was analyzed using TEM techniques in a post-mortem analysis. The ex-situ experiments served as a reference to observe and detect the insertion of Na+ ions in the HC, SEI size (389 nm), SEI composition (P, Na, F, and O), and Na plating. Furthermore, the TEM analysis revealed a cyclability limitation in our in situ TEM system. This issue appears to be caused by the deposition of Na in the form of a "foam" structure, resulting from the gas release during the reaction of Na with DMC/EC electrolyte. The foam structure, subsequently transforms into a second SEI, is electrochemically inactive and reduce the cyclability of the battery. Overall, our results demonstrate the powerful synergy achieved by coupling in situ ec-TEM and GC/MS techniques, which provides a deeper understanding of the dynamics and behavior of SEI. Consequently, this knowledge contributes to the advancement of the new generation of NIB.

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Kevyn Gallegos Moncayo, Nicolas Folastre, Milan Toledo, Hélène Tonnoir, François Rabuel, Grégory Gachot, Da Huo, Arnaud Demortière. 2023-08-09. Coupling liquid electrochemical TEM and mass-spectrometry to investigate electrochemical reactions occurring in a Na-ion battery anode. https://arxiv.org/abs/2308.04981

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