The successful operation of many beyond-lithium-ion battery chemistries depends on efficient formation of the solid electrolyte interphase (SEI). During the first cycles, electrolyte is reduced at the anode surface and insoluble degradation products form a passivating layer, allowing ion transport while preventing additional electrolyte degradation. Sodium electrolyte degradation products are more soluble compared to lithium, resulting in lower columbic efficiency, faster capacity fade, and higher resistance. Addressing this limitation requires improved understanding of degradation product solubility, including methods to measure the relative concentration of dissolved electrolyte products. In-situ detection of soluble degradation products can allow increased understanding of SEI dynamics and enable real time evaluation of the efficiency of SEI formation. Interdigitated electrode arrays make use of small diffusion lengths between electrodes to allow for a collector-generator arrangement. The small diffusion lengths of these devices result in overlapping diffusion layers, causing a redox cycling effect, which is preferential for detection of sensitive products but is not desirable for accurate prediction of SEI formation efficiency. Here, we fabricate novel IDAs with a high aspect ratio of Wgen to Wcol(10:1 to 40:1) using photolithographic techniques. We are able to achieve a low feedback (1-1.1 X) while maintaining relatively high collection efficiency (25-40%). Through this work we demonstrate electrochemical monitoring of soluble products by chronoamperometric detection at the collector during SEI formation at the generator. Utilizing this technique, it is possible to observe the proportion of electroactive soluble degradation products formed as a function of potential and monitor changes in the system with time.

Electrochemical detection of electrolyte degradation products with patterned electrode arrays

Macromolecular Chemistry: The Second Century

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ACS Spring 2020 National Meeting & Expo

The official archive and repository for all ACS Meetings & Expositions abstracts and select posters or presentations.