Low-carbon recycling of spent lithium iron phosphate batteries via a hydro-oxygen repair route

Abstract

In this study, we proposed a sequential and scalable hydro-oxygen repair (HOR) route consisting of key steps involving cathode electrode separation, oxidative extraction of lithium (Li), and lithium iron phosphate (LiFePO₄) crystal restoration, to achieve closed-loop recycling of spent LiFePO₄ batteries. A hydro-oxygen environment (with a cathode electrode : H₂O₂ ratio of 30 g mL⁻¹) was first used to achieve nondestructive separation of the LiFePO₄ cathode material and aluminum foil within a short period of time (0.25 min). The selective and high-efficiency extraction of Li from exfoliated LiFePO₄ cathode materials was subsequently achieved by mechanochemically coupled oxidation potential regulation (conditions: 10 min, a rotational speed of 1000 rpm, and a LiFePO₄ cathode material : H₂O₂ ratio of 1 : 37.5 g mL⁻¹). The LiFePO₄ crystals were successfully restored via a solid phase sintering process using the extracted Li and residual iron phosphate framework, and the regenerated LiFePO₄ crystal exhibited a considerable specific electrochemical capacity (∼151.2 mA h g⁻¹, 1C), which is comparable to that of commercial cathode materials. A life cycle assessment demonstrated that the HOR route can significantly reduce carbon emissions by −0.38 kg CO₂ eq. and smog release by −0.17 kg O₃ eq. per kg of spent LiFePO₄ batteries, thus contributing to a circular economy and global decarbonization.