>>713964558Yes, 20-year-old lithium batteries are significantly more prone to pillowing due to cumulative degradation:
Anode Swelling: Aged anodes thicken irreversibly (>7% vs. ~3.4% in new batteries), deforming internal structure.
Material Fatigue: Electrolyte decomposition creates gas; separator brittleness increases pressure vulnerability.
Loss of Flexibility: Anodes stiffen by 15-20%, reducing stress absorption.
Extended Damage: Decades of overcharging, temperature swings, and inactivity accelerate gas buildup and internal shorts.
Newer batteries resist pillowing better through:
Thicker separators (โฅ24ยตm) and robust electrode coatings
Automated defect detection during manufacturing
Advanced battery management systems preventing overstress
Critical Risk: Bulging in old batteries often signals jellyroll stratification, increasing internal resistance by 200-300% and risking catastrophic failure. Replace immediately if casing deformation occurs.
Key Insight: Aging directly correlates with pillowing severityโstudies show 40-60% greater thickness expansion in aged vs. new batteries under identical conditions.