Size-dependent characterization of toxic aerosol emissions from ignition of cryogenically processed black mass from fully charged lithium-ion batteries.

Lithium-ion (Li-ion) battery recycling facilities face escalating fire hazards from both black mass and manufacturing scrap. Although black mass fires generate hazardous airborne particulates, the physicochemical properties of these emissions remain poorly understood. This study examined particulate matter released during combustion of black mass cryogenically produced from charged Li-ion batteries, ignited by a droplet of deionized water. In a closed environment, bulk aerosol concentrations, including PM₂.₅ and PM₁₀, were quantified. Higher battery state of charge (SOC) produced substantially greater particulate emissions, while metallic contamination intensified ignition and further increased aerosol concentrations. Size-resolved, particle-by-particle characterization was performed using a gravimetric sampler with a 10-mm Dorr-Oliver cyclone to collect respirable (<10 µm) and inhalable (10-100 µm) fractions. Microscopy showed that the respirable fraction was dominated by ultrafine particles enriched in metal oxides and fluorinated species from electrolyte decomposition. The inhalable fraction consisted mainly of mixed metal oxides, graphite, and metal debris. These results have important implications for occupational exposure assessment, emergency response, and environmental risk management in battery recycling facilities.