Optimization of high-temperature thermal pretreatment conditions for maximum enrichment of lithium and cobalt from spent lithium-ion polymer batteries

Abstract

Due to their increasingly high demand, lithium-ion batteries (LIBs) will encounter a scarcity of essential resources if recycling is not prioritized. The current pretreatment methods for spent LIBs used in industrial production are inefficient, costly, and hazardous. The study aimed to maximize the yield of lithium and cobalt from the black mass of spent Lithium-ion batteries through an optimized high-temperature thermal pretreatment process, which combined mechanical (direct crushing) and thermal treatments to facilitate the subsequent recovery of these valuable metals. Sieve analysis showed that direct crushing for 2 min resulted in 40.81 % of the anode material in the 4750 + 2500 μm size range, while 5 min of crushing led to a more even distribution, with 28.57 % in the smallest size range (−75 μm). Heat treatment followed by 2 min of crushing concentrated 52.38 % of the anode material in the 4750 + 2500 μm range. For the cathode material, 2 min of direct crushing distributed 24.49 % in the −2500 + 1250 μm range, while 5 min of crushing accumulated 38.80 % in the −75 μm range. Heat treatment and 2 min of crushing resulted in 56.05 % of the cathode material in the −75 μm range, indicating improved liberation. The combination of heat treatment and mechanical treatment effectively liberates and reduces the size of the active materials, resulting in a higher cumulative mass fraction of finer particles (≤630 μm). Heat treatment at 600 °C for 15 min, followed by 2 min of crushing, dissociated current collectors (Al) from the cathode material, minimized the harmful gas emissions and produced fine particles (630 μm) with minimal Al content (0.8 wt%). The optimal heat treatment condition of 600 °C for 35 min achieved complete decomposition of PVDF and enriched 73.49 wt% cobalt and 5.41 wt% lithium in the black mass, superior to previous studies.