Tailoring Interfacial Electron Transfer in ZIF-8@SiO2 Catalysts: Boosting Contact-Electro-Catalytic Leaching of Critical Metals from Spent Ternary Cathodes

Abstract

Contact-electro-catalysis (CEC) holds significant potential for recycling spent lithium-ion batteries (LIBs) but faces notable challenges in the precise modulation and optimization of electron transfer efficiency. Herein, ZIF-8@SiO2 microspheres were successfully synthesized to overcome these challenges by synergistically adjusting electronegativity and specific surface area. Through systematically adjusting the synthesis process, the optimized ZIF-8@SiO2 microsphere possessed uniform dodecahedral microstructures and a BET surface area of 1298.33 m2/g, representing a ∼6.4-fold increase over original SiO2 microspheres (203.06 m2/g). Moreover, during the contact and separation of ZIF-8@SiO2 microspheres with water, the formation and disruption of the interfacial electric field between ZIF-8 and SiO2 effectively extended the charge carrier lifetime and further promoted the formation of hydroxyl and superoxide radicals. Consequently, nearly 100% metal leaching efficiency from spent ternary cathodes was achieved in the CEC process using ZIF-8@SiO2 microspheres as the catalyst. Furthermore, these microspheres could be directly recycled after simple sedimentation and rinsing, exhibiting remarkable reusability across five leaching cycles. The in situ H2O2 production substantially reduced material consumption, lowering both costs and greenhouse gas (GHG) emissions compared to traditional pyrometallurgy and hydrometallurgy. This work will significantly advance the development of CEC catalysts, addressing global resource and environmental challenges for sustainable LIB production.