Aging Mechanism Analysis for Series‐Connected Battery Pack Based on Open‐Circuit Voltage Reconstruction under Low Temperature

This study investigates aging mechanisms of series‐connected batteries at low temperatures through multiscale analysis. A novel open‐circuit voltage (OCV) reconstruction method—which tracks voltage evolution during battery degradation—quantifies three distinct degradation modes: loss of lithium inventory (LLI), cathode active material (LAM PE ), and anode active material (LAM NE ). The method establishes direct correlations between electrochemical behavior and electrode morphology using 3D structural parameters. Results demonstrate that LLI dominates performance decay throughout battery life. LAM PE peaks during early cycles then stabilizes, while LAM NE accelerates in late‐stage aging. Strong linear relationships emerge between degradation patterns and morphological features, providing mechanistic insights into low‐temperature deterioration. Microscopic analyses (XRD, SEM, and EDS) confirm that cold conditions intensify the growth of the solid–electrolyte interphase and lithium plating, accelerating battery failure. This OCV‐based approach offers a nondestructive method for understanding degradation mechanisms in battery packs, advancing knowledge for cold‐climate battery applications.