Acoustic Interrogation of Batteries

Abstract

A novel method utilizing acoustic time-of-flight measurements is presented for monitoring state of charge and state of health of batteries. The method demonstrates potential as a non-invasive, in situ, and in operando tool capable of characterizing most any closed battery regardless of chemistry. A conceptual underpinning for this method is presented and is based on a fundamental principle regarding mechanical properties of batteries: any battery irrespective of chemistry changes its distribution of density and electrode bulk modulus in direct relation to of state of charge and state of health. These alterations impact speed and attenuation of acoustic waves traveling through a cell. Acoustic computational modeling and experimental results indeed indicate time-of-flight measurements correlate well with state of charge and state of health, and can describe the mechanical evolution of a cell. Initial application of singular value decomposition (SVD) to acoustic time-of-flight measurements in cycling systems is also presented. SVD demonstrates the ability to decouple complex acoustic data; it is capable of revealing internal cell structure from raw data, and exhibits potential to quantify state of charge and state of health.