Effects of Ultrasonic Pretreatment on the Discharge for Better Recycling of Spent Lithium-Ion Batteries

Discharge treatment is a vital process in the pretreatment of spent lithium-ion batteries (LIBs). This paper focuses on the effects of ultrasonic pretreatment on the discharge of spent LIBs from the perspective of electrolyte concentration and ultrasonic power. By integrating characterizations such as pH measurement and X-ray fluorescence (XRF), the effect of ultrasonic pretreatment on the discharge of spent LIBs is evaluated. Experimental results show that sodium chloride (NaCl) solution and potassium chloride (KCl) solution have a more significant and better discharge efficiency (DE) under ultrasonic treatment, while organic electrolyte solutions which mainly contain formate and acetate generally show a less ideal DE. Under experimental conditions of using electrolyte discharge solutions with various electrolyte concentrations with the same ultrasonic power of 300 W, the DE generated from the experimental condition with KCl solution in 30 g/200 mL deionized water is the highest, 64.9%; under different ultrasonic powers in the same electrolyte solutions, the DE of 10 wt.% HCOONa solution is the highest at ultrasonic power of 500 W, at 4.7%. This work provides a reference for the efficient and cost-effective pretreatment of spent LIBs and the discharge mechanism in different electrolyte solutions with ultrasonic treatment is also explored to support the recycling of spent LIBs.