In-situ inducing hydroxyl radicals for the stripping of cathode materials from spent lithium iron phosphate battery

This study reports two green systems, i.e. electrolysis system and hydrogen peroxide system, for cathode materials recovery from spent lithium iron phosphate (LiFePO4, LFP) battery. Both systems avoided the usage of strong acid, strong alkali or organic solvent. Experiment results showed that in electrolytic system, cathode materials could be completely stripped within 15 min under the voltage of 10 V. Electron spin resonance spectrometer (ESR) and X-ray photoelectron spectroscopy (XPS) analysis showed that hydroxyl radicals were produced in electrolytic system. Therefore, hydrogen peroxide was added into the stripping system to improve the stripping efficiency. In H2O2 system, LFP cathode materials could be stripped completely with 0.2% H2O2 addition, and Al foil had a low dissolution rate (<0.4%). Morphology and crystal structure analysis indicated that the stripped cathode materials were complete and the Al foil was clean and free of corrosion traces. Mechanism analysis indicated that in both foregoing systems, hydroxyl radicals could oxidize polyvinylidene fluoride (PVDF), reducing the binding energy between PVDF and Al foil, thereby weakened the adhesion between Al foil and cathode materials. From economic analysis, it was found that hydrogen peroxide system was much more profitable and suitable for industrial application for post-consumer battery recycling.