Battery age monitoring: Ultrasonic monitoring of ageing and degradation in lithium-ion batteries

Lithium-ion batteries, widely used in modern technology, degrade with use, leading to reduced capacity and power output. Monitoring and diagnosing this degradation is essential, and ultrasound has emerged as a potential tool because of its low cost and non-destructive nature. Studies have noted changes in ultrasound behaviour with battery degradation, making it potentially valuable for tracking battery health. However, the behaviour of ultrasound as a battery degrades has been an issue within studies. This paper explores the relationship between state-of-health (SOH) loss and permanent ultrasonic signal changes over 100 charge cycles. A strong correlation was found between SOH reduction, observed to be caused by the loss of lithium inventory (LLI), and shifts in ultrasound signal responses. The analysis of individual peaks within a single acoustic signal showed consistent shifts in time-of-flight (TOF), often trending towards shorter TOFs. In particular, the rate of degradation was not entirely linear, with fluctuations observed across the cycles. These findings suggest that ultrasound can effectively monitor the rate of lithium-ion battery degradation. Future work could expand on these results by inducing varied degradation conditions and cathode chemistries to determine specific TOF shifts, enhancing detection methods for different degradation mechanisms in lithium-ion batteries.