Ascorbic-acid-assisted recovery of cobalt and lithium from spent Li-ion batteries

► We report an ultrasonic-assisted hydrometallurgical technique. ► Ascorbic acid is chosen as both leaching reagent and reducing agent. ► This technique avoids use of the traditional reducing agent H2O2. ► Leaching efficiencies are as high as 94.8% for Co and 98.5%. ► The acid leaching reaction mechanism has been preliminarily studied.