Green regeneration and recycling technology for spent graphite in lithium batteries: Biofilm coating-heat treatment repair process

With the explosive growth in graphite demand and the blowout retirement of lithium-ion batteries (LIBs), the recycling of spent graphite (SG) in anode materials has gradually become a hotspot due to its potential for achieving economic and environmental benefits, as well as contributing to the sustainable development of LIBs industry. An innovative green regeneration technology of SG based on bio-cycle leaching is proposed, and its repair and regeneration mechanism is discussed. The results show that bio-cycle leaching can effectively remove and enrich the metal impurities from SG while utilizing the extracellular polymeric substances secreted by strains to mediate and aggregate strong adhesion of strains on the surface, forming a biofilm to coat graphite and smooth its surface. Heat treatment can repair the crystal structure of SG while breaking down the biofilm into amorphous carbon to create a carbon core-shell structure. Under the optimal conditions, the regenerated graphite exhibits electrochemical properties similar to commercial graphite, with the initial charge capacity, initial coulomb efficiency, and cyclic capacity stability after 100 cycles at 0.1 C rate of 329.11 mAh/g, 92.9 %, and 96.4 %, respectively. This study represents a new thinking in SG recycling and contributes to realizing a complete closed-loop LIB recycling process.