Probing Degradation in Lithium Ion Batteries with On‐Chip Electrochemistry Mass Spectrometry**

Abstract

The rapid uptake of lithium ion batteries (LIBs) for large scale electric vehicle and energy storage applications requires a deeper understanding of the degradation mechanisms. Capacity fade is due to the complex interplay between phase transitions, electrolyte decomposition and transition metal dissolution; many of these poorly understood parasitic reactions evolve gases as a side product. Here we present an on‐chip electrochemistry mass spectrometry method that enables ultra‐sensitive, fully quantified and time resolved detection of volatile species evolving from an operating LIB. The technique's electrochemical performance and mass transport is described by a finite element model and then experimentally used to demonstrate the variety of new insights into LIB performance. We show the versatility of the technique, including (a) observation of oxygen evolving from a LiNiMnCoO2 cathode and (b) the solid electrolyte interphase formation reaction on graphite in a variety of electrolytes, enabling the deconvolution of lithium inventory loss (c) the first direct evidence, by virtue of the improved time resolution of our technique, that carbon dioxide reduction to ethylene takes place in a lithium ion battery. The emerging insight will guide and validate battery lifetime models, as well as inform the design of longer lasting batteries.

Elucidating Gas Evolution of Prussian White Cathodes for Sodium‐ion Battery Application: The Effect of Electrolyte and Moisture

“…This includes experiments in full cells and with a reference electrode, [72,136] experiments where a correct electrolyte-to-active material ratio limits the amount of conductive salt and electrolyte available for degradation reactions, i. e. measurements in larger cell formats, [137,138] and a reliable and precise quantification and separation of both HCN and (CN) 2 , which may be achieved by novel DEMS cell designs, such as onchip electrochemistry-mass spectrometry (EC-MS). [139] To better understand follow-up reactions, we envision that labeling the PW CAM with 13 CN may allow for the detection of gaseous products via DEMS/OEMS and electrolyte side products via 13 C nuclear magnetic resonance (NMR) spectroscopy. Overall, the findings highlight the importance of gas evolution measurements for an exhaustive characterization of battery materials, and the effect of coating, doping, additives, synthesis, and processing procedures on suppression of (CN) 2 evolution may become a new field of consideration in PBA/PW research.…”

Recent development and applications of differential electrochemical mass spectrometry in emerging energy conversion and storage solutions

“…The SEI can prevent further decomposition of electrolyte, suppressing additional outgassing. Thornton et al 341 found that substantially more CO and C 2 H 4 are evolved in the first cycle. The non-negligible amount of evolved gas in the following cycles suggests that the graphite surface is not entirely passivated after one cycle (see Fig.…”