We have recently determined a correlation between the acoustic response, state of charge and state of health of closed system electrochemical energy storage systems. Because a closed cell is a mass redistribution reactor, and in a standard cell the volume is effectively fixed, the distribution of density within a battery must change as a function of state of charge and, along with density, the elastic moduli of the anode and cathode changes as well. Since
cs = sqrt(E/rho)
This basic relation establishes a link between acoustic behavior and battery state. In this presentation we will review the physical basis of our hypothesis and present progress in
- Correlating structural evolution and failure analysis with acoustic signal evolution
- Preliminary inverse models which describe the changes we see in the acoustic/state of charge response
- "Physics free” machine learning results to examine the uniqueness of an acoustic signal for a given battery in a given state of charge and health.