Progress on the Microwave-Assisted Recycling of Spent Lithium Battery Graphite

Abstract

The robust development of electric vehicles has driven a surging decommission stream of lithium-ion batteries (LIBs) owing to their limited service life. The recycling of spent LIBs has become an urgent and essential task for the sustainable development of the LIB industry. However, the prevailing recycling methods focus only on recycling valuable metal, whilst the graphite anode materials are usually discarded or burned as fuels, leading to great waste of valuable carbon material. A facile strategy to obtain value-added products in an efficient manner is of great significance for the recycling of spent graphite. As graphite has excellent microwave absorption capability and electrical conductivity, microwave radiation on spent graphite can induce a Joule heat–discharge–plasma coupled effect, leading to a rapid heating process, especially when discharge occurs, exhibiting a thermal shock effect with the generation of a large number of high-energy electrons and active materials. This special feature facilitates microwave heating that is tailored for assisting the removal of impurities, structure repair, and graphite intercalation and exfoliation in an efficient manner. Therefore, different from the conventional graphite recycling route that is associated with energy/solution-intensive processes, this paper reviews the progress on microwave-assisted removal of impurities, repair of damaged graphite structure, and innovatively discusses the breakthroughs in microwave-assisted preparation of graphite intercalation compounds, expanded graphite, graphene and graphene-based materials, and porous graphene, with an aim to provide a scientific reference for the value-added resource utilization of spent graphite and preparation of new energy storage materials.