Recovery of graphite from industrial lithium-ion battery black mass†

Abstract

The escalating production of commercial lithium-ion batteries (LIBs) is anticipated to result in a substantial accumulation of waste upon end-of-life disposal of LIBs, which however also represents a secondary source of raw materials. Among the components of LIBs, graphite anode is a critical material and its production via high-temperature carbonisation is highly energy- and cost-intensive. One of the major challenges regarding recycling of graphite materials from spent LIBs is the presence of residual metal and organic species that are difficult to eliminate, preventing direct reuse as anodes. Here, we propose a recycling workflow to eliminate the various impurities and regenerate the graphite materials from industrially sourced black mass, composed of mixed cathode materials, anode materials, aluminium and copper current collectors, Li salts, and polyvinylidene fluoride binders. After selective extraction of high-value transition metal ions, such as Li, Ni, and Co, from the black mass, the proposed workflow for graphite recovery involves a second step of acid leaching for the removal of Al, Cu, and other residual metal species, and mild-temperature pyrolysis for the removal of polyvinylidene fluoride (PVDF). The regenerated graphite (AG-2.0M-800) demonstrates an initial specific charge capacity of 387.44 mA h g⁻¹ at 0.1C (35 mA g⁻¹) in lithium half cells, on par with commercial battery-grade graphite. This workflow provides a promising approach to the recycling of spent graphite that could be integrated with existing cathode materials' recycling processes developed in the industry.