In situ recycling of Al foil and cathode materials from spent lithium-ion batteries through exogenous advanced oxidation

Abstract

The efficient and sustainable recycling of spent lithium-ion batteries (LIBs), especially valuable metal enriched cathodes, is critical to achieve the goals of carbon peaking and carbon neutrality of new energy industry. However, current energy-intensive separation technologies to liberate cathode materials from current collector can hardly balance urgent requirements to sustainability and efficiency. Herein, an improved advanced oxidation technology based on ultrasonic assisted S2O82−-Fe2+-H+ system (USFH) was innovatively proposed to exfoliate the cathode materials from Al foil through the selective degradation of polyvinylidene difluoride binders (PVDF), with the emphasis on degradation mechanism. Experimental results illustrate that nearly all of coating materials were effectively separated from Al foil under the optimized conditions. Then, the density function theory (DFT) calculations and possible chemical reactions were conducted to reveal the detailed degradation mechanism for PVDF. It can be discovered that the functional groups in PVDF will be attacked by free radicals generated in USFH, leading to defluoridation with the formation of oxyorganics containing oxygen groups (e.g. C=O, O–H) and fracture of C–C skeleton to olefins, carboxylic acids, ketones and alkanes with shorter carbon chains, along with exfoliation of organic intermediates into solution. It may promise a green and efficient alternative by novel improved advanced oxidation technology with sound fundamental theory for in-situ recycling of spent LIBs.