Kinetics Study on CO2 Adsorption of Li4SiO4 Sorbents Prepared from Spent Lithium-Ion Batteries

With the advancement of global carbon reduction efforts and the rapid development of battery industries, the scale of spent lithium-ion batteries (LIBs) has increased dramatically. Extracting lithium from spent LIBs to synthesize Li4SiO4 sorbents not only addresses the challenge of battery recycling but also reduces the production cost of CO2 sorbents, making it a research hotspot. However, the CO2 adsorption behavior of these sorbents under the effect of impurities may differ from the traditional Li4SiO4, and there is a lack of systematic research on the adsorption kinetics. To address this issue, two Li4SiO4 sorbents are prepared from spent ternary LIBs, and their adsorption kinetics are comprehensively investigated using classical kinetic models. Results show that the reaction order of LSO and Na-LSO is 0.41 and 1.63, respectively, with activation energies of 72.93 kJ/mol and 99.23 kJ/mol in the initial kinetic-controlled stage, and 323.15 kJ/mol and 176.79 kJ/mol in the following diffusion-controlled stage. In the cyclic processes, loss-in-capacity is observed on LSO due to the simultaneous decrease in rate constants in both the kinetic and diffusion-controlled stages, while Na-LSO could almost maintain its capacity by having a much bigger rate constant during the kinetic-controlled stage. This study reveals the adsorption kinetics of Li4SiO4 prepared from spent LIBs and could provide theoretical support for the targeted design of efficient and low-cost CO2 sorbents.