Progress towards industrial recycling of end-of-life graphite for demanding applications

Graphite is a critical anode material for lithium-ion batteries, but its supply is constrained by limited natural sources and the energy costs of synthetic production. Recycling graphite from spent Li-ion batteries offers an alternative feedstock for cell manufacturing; however, graphite recovered from black mass processing contains impurities and non-ideal surface chemistry for use in a Li-ion battery designed for demanding applications. In this research, recycled graphite, called “re-claimed graphite” was processed with an acid treatment, annealing process, and coated with pitch for full cell testing with nickel manganese cobalt (NMC) and lithium iron phosphate (LFP) as the cathode. The performance of the graphite coated with 10% pitch performed as well as or better than pristine graphite in tests up to 1000 cycles and at C-rates up to 2C. Cycling data indicate that capacity loss in the recycled graphite samples was due to loss of Li inventory mechanisms similar to those observed in pristine graphite. Complementary characterization techniques revealed removal of impurities in the best performing samples, as well as changes in the graphitic structure over the course of the treatment steps. This treatment process shows promise for enabling graphite performance comparable to pristine graphite demonstrated at an industrially relevant scale.