An improved pretreatment method for recovering cathode materials from lithium-ion battery: ultrasonic-assisted NaOH-enhanced dissolving

It is always a challenge to separate cathode materials and aluminum foil collector efficiently in the pretreatment process of spent lithium-ion batteries (LIBs) recycling. In this work, the effects of NaOH concentration, liquid-solid ratio, dissolution temperature, and time on the traditional NaOH dissolving pretreatment process were systematically studied. Under the optimal conditions, the traditional dissolving process shows a limited aluminum dissolution rate of 83.59%. Through characterization and thermodynamic analysis, the fact that the traditional dissolving process results in the dissolution loss of lithium (5.5%) has been proved. The lost lithium may come from the free lithium ion and SEI layer on the cathode surface. Furthermore, a green and facile ultrasonic-assisted-enhanced dissolving pretreatment method was proposed. The dissolution rate of aluminum increases from 83.59% to 94.8% under the optimal conditions of NaOH concentration of 10 wt%, liquid-solid ratio of 10:1 ml/g, dissolution temperature of 30 degrees C, dissolution time of 60 min and ultrasonic power of 288 W. Due to the mechanical and cavitation effects of ultrasonic, the efficient separation of cathode materials and aluminum foil and the decomposition of binder PVDF are completed in one step, which reduces energy consumption and avoids HF gas emissions.