Acoustic emissions testing as a complementary tool to understand chemical and electrochemical changes in battery electrodes
Lukas Noll, Jana Mrowetz, Katja Kretschmer, Daniel Schröder
Abstract
The method of acoustic emissions (AE) testing provides real-time data on processes within an electrochemical system. It is a non-invasive and cost-effective operando method that allows for the analysis of distinct features such as gas evolution and particle cracking. For the first time, we apply unified and consistent AE testing to compare a set of very different electrode materials. Our study can be used to complement the electrochemical information by providing insights into the acoustic activity in coin cell batteries with NCM-graphite and LFP-graphite during cycling. NCM electrodes exhibit the highest acoustic emissions, especially during initial cycles, linked to surface layer processes and phase transitions. Graphite electrodes show moderate emissions, while LFP electrodes show minimal acoustic activity. Our results demonstrate that acoustic activity correlates with specific degradation processes, yet it is not consistently related to capacity fade. This finding suggests that some degradation mechanisms are acoustically active while others are not. Our study shows that AE is an effective method for gathering detailed insights into the characteristics and origin of degradation processes in real-time in running batteries and battery systems. Based on these findings, we propose the use of AE as an accessible and supplementary method in battery diagnostics. • All studied conventional battery electrodes emit distinct acoustic signals. • Absolute hit numbers during cycling show deviation; overall trends remain consistent. • Correlation between acoustics and cell aging varies by material type. • NCM showed the highest acoustic activity, followed by graphite; LFP had the least.