Comparative Analysis on Carbon Mitigation by High-Temperature Lithium Adsorption Systems

High-temperature adsorption is a promising technology for carbon mitigation, and it can be applied in direct carbon capture and the integration with utilization. Lithium-based adsorbents, known for their high CO2 uptake and rapid kinetics, have garnered significant interest. However, adsorption performance, cycling stability, and degradation behavior of this type of adsorbent are rarely reported and compared under comparable conditions. In this work, nine lithium-based adsorbents were synthesized and characterized for their physicochemical properties. Dynamic and isothermal thermogravimetric analysis were conducted to determine adsorption/desorption equilibrium temperatures, evaluate CO2 adsorption characteristics under varying thermal conditions, and assess cycling stability over 20 adsorption–desorption cycles. The results reveal exceptional initial CO2 capacities for α-Li5AlO4, Li5GaO4, Li5FeO4, and Li6ZnO4; however, these values decline to 30.2 wt.%, 24.3 wt.%, 41.6 wt.%, and 44.2 wt.% after cycling. In contrast, Li2CuO2 and Li4SiO4 exhibit lower initial capacities but possess superior cycling stability with final values of 21 wt.% and 21.6 wt.%. Phase composition and microstructural analysis identify lithium carbonate and metal oxides as primary products, and microstructural sintering was observed during cycling. This study could provide insights into the trade-offs between the initial capacity and cycling stability of lithium-based adsorbents, offering guidelines for adsorbent optimization through doping or pore engineering to advance high-temperature CO2 capture technologies.