Green and sustainable recycling of lithium-ion batteries via an ionic liquid-driven cathode reduction method

Abstract

The recycling of spent lithium-ion battery (LIB) cathodes is crucial to ensuring the sustainability of natural resources and environmental protection. The current pyrometallurgical and hydrometallurgical recycling strategies involve high energy processing and expensive reagent consumption, raising both environmental and economic concerns. Here we demonstrate a green and recyclable process using an ionic liquid (IL), 1-(2,3-dihydroxypropyl)-3-methylimidazolium chloride (imidazolium glycol). This IL induces the reduction and dissolution of transition metal ions from LIB cathodes. For a lithium cobalt oxide cathode, we demonstrate very high leaching efficiencies of 100% for Li and 99.62% for Co. X-ray diffraction and thermogravimetric-mass spectroscopy show that our imidazolium glycol preferentially dissolves lithium and induces lattice oxide anions (O²⁻) to reduce insoluble high-valent Co(III) to soluble Co(II) complexes. This imidazolium glycol-based process avoids noxious gas emissions and the imidazolium glycol is also easily recycled, which shows both economic and environmental advantages. Our process provides environmentally friendly and sustainable recycling of LIB cathodes and offers a suitable pathway for industrial-scale recycling.