Selective recycling of valuable metals from waste LiCoO2 cathode material of spent lithium-ion batteries through low-temperature thermochemistry

Efficient recycling of valuable metals from spent lithium-ion batteries (LIBs) with the minimized environmental footprint is prevailing among different recycling processes. However, the extensive energy consumption, associated with secondary contaminations, is one of the leading bottlenecks during thermochemical processing. Herein, low-temperature thermochemistry route was explored by thermal reduction using biomass wastes as reductants for selective recycling of valuable metals from spent LIBs based on their inherent conversion characteristics. It can be concluded from the experimental results that corn stalk exhibits better reducing capacity than saw dust and rice straw, and different metals in cathode materials (LiCoO2) of spent LIBs demonstrate different conversion pathways with the variation of reaction temperatures. Specifically, Li in waste LiCoO2 tends to be converted into Li2CO3 under reaction temperature range of 250–500 °C, while Co will mainly exist as CoO (400–600 °C) or Co (600–800 °C). Then, the converted product of Li2CO3 can be selectively extracted by water leaching, and CoO or Co will be subjected for mild acidic leaching or magnetic separation, respectively. Detailed characterizations and thermochemical mechanism suggest that the reduction reactions are mainly controlled by one-dimensional model and different products can be obtained through regulation of reaction temperature. This win–win tactics using biomass wastes with significantly reduced roasting temperature is expected to be high-efficiency, high-selectivity and pollutant-free process for spent LIBs recycling.