Simplifying and Optimizing Li4SiO4 Preparation from Spent LiFePO4 Batteries with Enhanced CO2 Adsorption

A large amount of spent lithium batteries, especially lithium iron phosphate (LiFePO4), is discarded due to their limited lifespan and poses a great threat to the environment. At the same time, the potential application of Li4SiO4, an efficient high-temperature CO2 sorbent, is largely limited by the high cost of lithium resources. Thus, the preparation of Li4SiO4 from spent LiFePO4 batteries has great potential for achieving waste recycling and reducing CO2 capture costs. However, the process of recycling spent LiFePO4 batteries to synthesize Li4SiO4 sorbents still needs to be well investigated. This work proposes to simplify the preparation scheme by combing precipitation, Na doping, and synthesis processes and further optimizing the key variables of pH, Na2CO3 ratio, and heating rate. An optimal condition is determined to be pH = 9, Na2CO3 ratio = 11 wt %, and heating rate = 5 °C/min, and the sorbent prepared shows a superior stable CO2 capacity of 0.24 g/g in 80 adsorption/desorption cycles. The work develops an effective Li4SiO4 preparation scheme from spent LiFePO4 batteries with largely enhanced CO2 adsorption performance and reduced cost and could achieve a win–win situation in waste recycling and CO2 mitigation.