The present disclosure provides a non-invasive and acoustic signal-based approach for examining a quality of SEI formation for any given battery cell and providing an objective assessment thereof. In one example, the objective assessment may be provided as a score that may be referred to as a Solid Electrolyte Interphase (SEI) score for a given battery cell. In one aspect, a method includes transmitting acoustic signals through a battery cell via one or more first transducers, receiving response signals in response to the acoustic signals at one or more second transducers, determining a score indicative of quality of SEI formation in the battery cell based on analyzing the response signals, and outputting the score.