Operando Full‐Field Strain Reconstruction Reveals Geometry‐Driven Kinetic Desynchronization in LiFePO 4 Pouch Cells

ABSTRACT Fast‐charging operation in lithium‐ion batteries is influenced by internal mechanical heterogeneity, while its spatiotemporal evolution under high‐rate conditions remains poorly resolved. Existing diagnostic approaches provide only surface‐level information, leaving internal mechanical heterogeneity during fast charging inaccessible. Here, we employ operando distributed optical fiber sensing to reconstruct the strain evolution within LiFePO 4 pouch cells at millimeter‐scale resolution.