CO ₂ Adsorption by Low-Cost Li ₄ SiO ₄ from Spent Lithium-Ion Batteries via Biomass Direct Reduction

With the global boom in lithium-ion battery (LIB) deployment, the massive production of end-of-life LIBs has become a significant challenge for resource recycling and environmental risk mitigation. Concurrently, the advancement of carbon capture is driving an urgent demand for low-cost, high-performance CO 2 sorbents, among which Li 4 SiO 4 stands out as a promising candidate. A critical insight is that impurities such as K and Na, which are traditionally costly to remove during LIB recycling, act as effective dopants to enhance CO 2 adsorption of Li 4 SiO 4 . To address these dual needs, this work proposes an innovative strategy for the direct reduction of spent ternary cathode materials via biomass pyrolysis. By utilizing the synergistic effects of reductive gases and biochar generated in situ during pyrolysis, Li 2 CO 3 doped with Na and K is recovered and integrated into Li 4 SiO 4 sorbents. Systematic optimization identifies corn stover (20 wt % addition) as the optimal biomass feedstock, with pyrolysis-reduction at 650 °C for 60 min as the ideal condition. The resulting sorbent exhibits exceptional durability, retaining a high CO 2 capacity of 0.190 g/g after 80 consecutive adsorption-desorption cycles. More notably, its production cost is only 19% of that via conventional routes. This study provides a sustainable pathway for valorizing spent LIBs while enabling the scalable preparation of CO 2 sorbents, bridging the gap between LIBs’ recycling and CCUS advancement.