Standardizing Acceptance Quality Limit Metrics for Prismatic Cell Procurement
Standardizing prismatic cell procurement requires defining critical AQL thresholds, dynamic sampling plans, and precise metrology for lot acceptance.
Cell Swelling Metrology
Meaning
Dimensional variation tracking measures the physical volume increase of electrochemical cells caused by gas generation and lithium insertion. In energy storage engineering, cell swelling metrology quantifies both reversible breathing during charge cycles and irreversible expansion over lifetime cycling. High precision displacement sensors record dimensional shifts under controlled environmental temperatures.
Expansion Measurement
Tactile dial indicators, laser displacement sensors, and contact probes capture thickness changes across the face of a cell. Implementing cell swelling metrology requires constant fixture temperature to isolate electrochemical expansion from thermal expansion of mechanical components. Optical profilometry provides non-contact surface mapping across high-pressure containment plates.
Pressure Compensation
Mechanical restraint fixtures apply constant pre-loads to simulate pack-level clamping forces during laboratory testing. In pouch cell characterization, cell swelling metrology establishes load-versus-displacement curves across varied states of charge. Pneumatic or spring-loaded plates adjust to maintain targeted surface compression without exceeding structural limits of the casing.
Pack Clearance
Volumetric growth limits determine the physical gap required between adjacent cells inside a battery module. When battery cell thickness increases beyond designed tolerance, localized mechanical stress damages internal separator membranes and accelerates separator puncture risks. Cell swelling metrology supplies critical empirical data for mechanical housing design, module cooling plate spacing, and structural safety margins.
Contractual specifications require verified swelling profiles before cell selection is finalized for automotive production.