Methods and systems for detecting variations in minor total-impedance contributors in electrochemical cells

Abstract

Described herein are methods and systems for detecting variation in minor total-impedance contributors in sets of electrochemical cells. For example, a method comprises maintaining a substantially constant current through the set of electrochemical cells and obtaining multiple voltage readings of the cells while the substantially constant current is maintained. The method then proceeds with determining multiple differential capacity values from the multiple voltage readings, characterizing one or more peaks in the multiple differential capacity values, and determining the variation in the minor total-impedance contributor based on one or more peaks. More specifically, partial capacitance values can be assigned to different impedance channels based on these peaks or, more specifically, based on the separation of adjacent peaks. The variation in the minor total-impedance contributor can be attributed to one or more of a tap-weld quality, electrolyte wetting, tape damage, active material activation energy variations, and diffusion variation of the ion-conducting material.