Direct flotation separation of active materials from the black mass of lithium nickel cobalt manganese oxides-type spent lithium-ion batteries

Abstract

Batteries based on lithium nickel cobalt manganese oxides (NCM), which have not been extensively studied, were considered for this study. A black mass (BM) derived from a diverse mix of NCM-type batteries was pyrolyzed at three different temperatures before flotation. The optimum pyrolysis temperature was determined via X-ray spectrometry, contact angle measurements, thermogravimetry, X-ray diffraction, and X-ray photoelectron spectroscopy as 400 °C at which the active materials in the BM were successfully liberated without generating new phases on the material surfaces. This is crucial for recovering materials from the BM using flotation and their potential subsequent application in battery manufacturing, which requires high-purity materials. After optimal pretreatment, the flotation of the treated BM was conducted to separate active materials. At the laboratory scale, the optimal conditions were an impeller speed of 1600 rpm, a collector dosage of 150 g/t, a frother dosage of 150 g/t, and a pulp density of 20 g/L. Furthermore, the initial anode and cathode grades of 84 % and 92 % were further enhanced to 97 % and 95 %, respectively, by employing additional cleaning and scavenging stages. Therefore, this study offers a promising method for recovering high-purity active materials from the BM through systematic pyrolysis pretreatment and subsequent flotation.