Mechanical Analysis of Lithium-Ion Batteries Via Acoustic Impedance Spectroscopy

The mechanical properties of lithium-ion batteries (LIB) are closely related to their state-of-charge (SOC) and state-of-health (SOH). Here, we introduce an in-operando acoustic technique based on acoustic impedance spectroscopy (AIS) which probes the mechanical changes that occur in the LIB during operation. Using thin, inexpensive piezoelectric resonators and widely available impedance analyzers, we can identify the acoustic resonances of commercial LIBs by measuring the complex electrical impedance of the resonator. In-operando AIS shows that these resonances are dependent on the bulk mechanical properties of the LIB, which change reversibly as the cell is cycled. We show that this technique can provide substantial information on both the SOC and SOH of a commercial LIB.