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Claire Villevieille1

1, Paul Scherrer Institute – Electrochemistry Laboratory, Villigen, , Switzerland

The Li-ion chemistry is thus far the most advanced chemistry employed in battery technology. To date, Li-ion batteries dominate the market of the electronics and portables devices. However, in the field of electric and hybrid vehicles further improvements are required in terms of performance, safety, and cost. The same set of criteria concerns other systems based on alternative chemistries such as Na-ion and Lithium–Sulfur (Li–S) batteries. Advanced Li-ion batteries and the pre-cited novel systems utilize less understood electroactive materials and thus show new reaction mechanisms during electrochemical cycling, the understanding of which requires new characterization tools and techniques.
Development of a reliable electrochemical cells is thus of a prime importance when studying battery materials in in situ or operando mode during cycling. This is never an easy task, since the design of such cells has to be adequate to the technique of a choice and meet all necessary requirements (i.e. the use of a Be window for operando X-ray diffraction measurement to ensure “transparency” to the X-ray beam). However, once a proper design is found, the surface, the bulk, the interfaces, and finally the combination of those can be studied and lead to the elucidation of the reaction mechanisms, thus further improving the battery technology.
Unfortunately, in most cases the electrochemical cells used for operando measurement are not ideal and suffer from low internal pressure (i.e. poor contact between the electrodes). It shorts the lifespan of the cell and as a consequence most of the studies presented in the literature focus on the first/second cycle. Herein we present different cell designs developed in our laboratory and used for operando/in situ studies. Having overcome earlier mentioned obstacle our operando/in situ cells are able to sustain more than 100 cycles and simultaneously to perform structural studies such as X-ray and neutron diffraction. For the latter one, we also developed a new set-up called stroboscopic mode. It allows operando study of the batteries that are cycling at very high rates (e.g. 10C) with a neutron patterns collected each 1 s along 200 cycles and more.
All these efforts lead us closer to understand the aging phenomena occurring during cycling and to gain the insights into the failure of more academic systems like Na-ion, all solid state batteries and Li-S batteries.
Examples based on different operando/in situ techniques such as X-ray diffraction, neutron diffraction, neutron imaging, and X-ray tomography used to characterize solid-state Li-ion, Na-ion, and Li-S batteries will be presented during the talk.

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