Synthesis of high-performance Li4SiO4 sorbent for CO2 capture using Li2CO3 extracted from spent lithium batteries

Among high-temperature sorbents, the remarkable stability, low regeneration temperature, and high cyclic sorption capacity of Li4SiO4 sorbent have attracted considerable attention. However, the high cost of lithium sources during the synthesis of Li4SiO4 has restricted its practical application. Meanwhile, the extensive utilization of lithium-ion batteries (LIBs) in renewable energy development has sparked concerns regarding the proper management of numerous discarded LIBs. The successful combination of the recycling of spent LIBs with carbon capture technology using Li4SiO4 sorbent can not only alleviate the waste problem of a large number of LIBs, but also effectively reduce the cost of materials required to capture CO2. Herein, LIBs were utilized to synthesize low-cost Li4SiO4 sorbents for CO2 capture, and the CO2 sorption/desorption performance was evaluated. The optimal regeneration temperatures of Li4SiO4 sorbents from LIBs are generally lower than the traditional regeneration temperature (>700 ℃) because of the existence of Li2SiO3 in fresh Li4SiO4 sorbents from LIBs, thereby reducing the energy consumption of CO2 capture. The results showed that the extraction rate of Li2CO3 increased by 69.92 % and 77.28 % respectively when graphitic carbon (GC) and banana peel activated carbon (BAC) were introduced during the extraction process compared to the absence of reductant. However, Li4SiO4 modified with graphitic carbon (Li4SiO4-GC) shows better cyclic CO2 capture performance than that modified with activated carbon from banana peels (Li4SiO4-BAC). It is found that Li4SiO4-GC could maintain a high sorption of 0.23 g/g after 50 cycles under the conditions of sorption temperature of 525 ℃, desorption temperature of 650 ℃, and 15 vol%CO2, owing to its more diverse variety of crystal phase substances, particularly Li3NaSiO4 crystal phase that plays a positive promoting role in the cyclic sorption/desorption. In addition, Li4SiO4-GC has more developed pore structure after cyclic reactions that other sorbents, which provides more channels for the diffusion of lithium ions, oxygen ions, and sodium ions, making it easier to adsorb more CO2 and increasing the overall reaction rate.