# Effect of organic solvent additives on the enhancement of ultrasonic cavitation effects in water for lithium-ion battery electrode delamination

## TL;DR

Adding small amounts of organic solvents to water improves ultrasonic delamination of lithium-ion battery cathodes, but too much can reduce efficiency.

## Contribution

The study reveals how organic solvent additives affect cavitation and delamination efficiency in ultrasonic recycling of lithium-ion batteries.

## Key findings

- Adding 10–30 vol% ethylene glycol or glycerol improves delamination efficiency by altering thermophysical properties.
- Higher solvent fractions reduce efficiency due to increased viscosity dampening ultrasonic waves.
- Acoustic detection and sonochemiluminescence help identify optimal solvent compositions for cavitation.

## Abstract

Ultrasonic delamination is a low energy approach for direct recycling of spent lithium-ion batteries. The efficiency of the ultrasonic delamination relies both on the thermophysical properties (such as viscosity, surface tension, and vapour pressure) of the solvent in which the delamination process is carried out, and the properties of the ultrasound source as well as the geometry of the containment vessel. However, the effect of tailoring solutions to optimise cavitation and delamination of battery cathode coatings has not yet been sufficiently investigated. Acoustic detection, high-speed imaging, and sonochemiluminescence (SCL) are employed to study the cavitation processes in water-glycol systems and identify the effect of tailoring solvent composition on cavitation strength. The addition of small volume fractions of organic solvent (ca. 10–30 vol%), including ethylene glycol or glycerol, to the aqueous delamination solution were found to significantly improve the delamination efficiency of lithium-ion battery cathode coatings due to the alteration of these thermophysical properties. However, greater volume fractions of glycol decrease delamination efficiency due to the signal-dampening effect of viscosity on the ultrasonic waves. The findings of this study offer valuable insights for optimising ultrasonic bath solution composition to enhance film delamination processes.