Monitoring lithium-ion batteries (LIBs) degradation is essential for decarbonizing electricity generation and transportation.Key metrics include State of Charge (SOC) and State of Health (SOH).SOC measures the charge level, while SOH represents usable capacity.SOH is crucial in determining end-of-life.Even at 70-80% SOH, LIBs can still store energy, finding value as secondlife batteries (SLBs).However, conventional estimation methods for SOC/SOH are timeconsuming.Recent research suggests that degradation affects ultrasonic wave propagation in batteries.This study investigates quantitative ultrasound spectroscopy (QUS) to track SOC/SOH changes in cylindrical LIBs at three conditions: pristine, accelerated degraded, and SLBs.