Utilizing waste carbon residue from spent lithium-ion batteries as an adsorbent for CO₂ capture: A recycling perspective

Recycling and reusing the carbon-residues (i.e., graphite), as well as recovering valuable metals by leaching from spent lithium-ion batteries, is environmentally and economically significant. In particular, since a large amount of spent lithium-ion batteries (LIBs) will be generated along with the rapid growth of electric vehicles (EVs), research on recycling carbon-residues from LIB anodes is urgently needed. Herein, the battery powder (BP) was obtained from spent lithium-ion batteries (LIBs) through physical-pyrolysis and sieving. Chemical composition analysis confirmed that the battery used in this work was composed of NCM cathode with high-nickel content and graphite anode material. The average particle size of the obtained BP was 87 μm. In order to obtain the residue having high concentration of carbon, the metal extraction was applied using an HCl solution. As a result, metals (Li, Ni, Co, Mn, Al, Cu, and Fe) in the final remnant were found to be less than 2%, and carbon was found to have a purity of 97% or more. The obtained BP was tested as both the adsorbent and support for indoor CO₂ capture. Various activation treatments were examined to enhance the textural properties of BP. BP-K (K₂CO₂ impregnated BP) adsorbents were prepared, and their CO₂ adsorption performances were evaluated with CO₂ adsorption isotherms, thermogravimetric analysis (TGA), and 0.1m³ chamber (CO₂ IR analyzer) at low CO₂ level (1000–2000 ppm). Through XRD and FT-IR analyses, the adsorption mechanism between K₂CO₃ and CO₂ under moisture-containing indoor air conditions was confirmed to depend on chemisorption in the following reaction pathway: R1–R3(K₂CO₃(s) + H₂O (g) + CO₂ (g) ⇋ 2KHCO₃(s) (R1), K₂CO₃(s) + 1·.5H₂O(g) ⇋ K₂CO₃·1·.5H₂O(s) (R2), K₂CO₃·1·.5H₂O(s) + CO₂(g) ⇋ 2KHCO₃(s) + 0·.5H₂O(g)(R3)). The adsorption working capacities of the recycled BP-K adsorbents were remained relatively constant during four consecutive cycles.