Microthermal catalytic aerogenesis of renewable biomass waste using cathode materials from spent lithium-ion batteries towards reversed regulated conversion and recycling of valuable metals

Abstract

Sustainable recycling of metal resources from spent lithium-ion batteries (LIBs) with reduced environmental impacts is attracting increasing attention in the current recycling processes. However, over-reliance on energy and chemical input is one of the leading bottlenecks for the prevailing technologies. In this study, pyrolysis gases generated from renewable biomass waste by microthermal catalysis of the cathode material (LiNi_xCo_yMn_1−x−yO₂) in spent LIBs were innovatively used as reactants for the regulated reduction and conversion of different metals. Detailed experimental results suggest that different reaction pathways for metals can be controlled by the experimental conditions, especially reaction temperature. Li tends to be converted into Li₂CO₃, immune to the reaction temperature, while Co(III) and Mn(IV) can be just reduced into CoO and MnO in the lower roasting temperature range of 300 °C–500 °C, with further reduction into their metallic forms Co and Ni in the higher temperature range of 500 °C–700 °C, while MnO cannot be further reduced into metallic Mn, and the different converted products are recovered based on their forms with significantly reduced consumption of chemicals. Finally, tentative exploration of the reaction mechanism suggests that cathode materials are efficient catalysts to reduce the roasting temperature and promote the generation of H₂ from biomass wastes, changing the traditional solid–solid reaction of carbothermal metallurgy to the gas–solid reaction of hydrogen metallurgy with reduced input of chemical and energy.