Reductive roasting of cathode powder of spent ternary lithium-ion battery by pyrolysis of invasive plant Crofton weed

Recycling spent lithium-ion batteries has received wide attention because the spent batteries are hazardous and contain high-grade and catalytic active heavy metals. Reductive roasting is an effective pretreatment method to recover valuable metals from the used batteries. In this paper, Crofton weed, which has been defined as an invasive plant in China, was suggested as a biomass pyrolysis additive for the reducing pretreatment of spent lithium-ion batteries powder (LiNi0.6Co0.2Mn0.2O2). The process can reduce carbon consumption for the spent battery recycling industry. Meanwhile, the Ni, Co, and other metals in the cathode powder could catalyze biomass pyrolysis, reducing the reaction's activation energy. The effects of temperature, biomass ratio, heating rate, and roasting retention time on the reduction were studied. TG-DSC, XRD, and SEM were used to characterize the experimental results, and the pyrolysis reduction mechanism was analyzed. Under the optimum roasting conditions: temperature 800 °C, biomass ratio 30%, heating rate 5 °C/min, without retention time, Li in the powder is converted into Li2CO3, and the high valence Ni, Co, Mn are reduced to low valence and easily soluble Ni, Co, and MnO, respectively. This method provided an alternative technology solution for both spent lithium-ion battery treatment and controlling invasive plants in China, namely Crofton weed.