Recovery of NixMnyCoz(OH)2 and Li2CO3 from spent Li-ionB cathode leachates using non-Na precipitant-based chemical precipitation for sustainable recycling

Abstract

The interest in recycling spent lithium-ion batteries (Li-ionB) has surged due to the rising demand for valuable metals (e.g., Co, Ni, Li and Mn) and concerns about environmental repercussions emanating from conventional battery waste disposal. Conventional precipitation-based hydrometallurgy recycling processes utilise Na-based or metal-based precipitants. The Na, from Na-based precipitants, is present in high concentrations in the process effluent since they are not recovered during the recycling process. The Na-rich effluent cannot be discarded since it doesn't meet environmental regulations as per the U.S. Environmental Protection Agency (EPA) (2023) therefore creating a storage and disposal problem. It is therefore imperative to utilise non-Na-based precipitants to eliminate the effluent disposal problem. This paper focuses on the recovery of NixCoyMnz(OH)2 and Li2CO3, main precursors for Li-ionB cathode production, from a typical spent Li-ionB cathode (NMC 532) using non-Na precipitant-based chemical precipitation. This study reports NixCoyMnz(OH)2 and Li2CO3 recovery from spent Li-ionBs for closed-loop Li-ionB cathode recycling through an integrated hydrometallurgy and chemical precipitation process. Through the utilisation of leachate solutions comprising 2 M H2SO4 + 6 vol.% H2O2, and a 75 g/L S/L ratio and conducting leaching for 120 min at a temperature of 60 °C and IS of 350 rpm, the recovery efficiency of 98.1 % for Li, 97.1 % for Co, 96.1 % for Ni, and 95.7 % for Mn. The pH of the NMC leachate was initially adjusted to 5 to precipitate Fe, Al and Cu impurities. Thereafter, active metal species (Ni, Mn and Co) were precipitated at a pH of 13 as Ni0.5Co0.2Mn0.3(OH)2 composite microparticles by adding LiOH precipitant. Thereafter, the Li-rich resultant liquor was further used to recover the Li by adding 3.4 mol of CO2 bubbled at 0.068 mol (CO2)/L.min and 40 °C for 45 min. The Li2CO3 precipitates were separated from the suspension through filtration followed by washing using deionised water and hot air drying. The reaction time is 45 mins, and the agitation speed is 150 rpm. Through this multi-stage precipitation process, >98 % of Ni, Co, Mn and > 91 % of Li can be recovered in the form of Ni0.5Mn0.3Co0.2OH2 and Li2CO3 respectively. The process exhibits great potential for recovery of valuable materials from spent Li-ionBs. The recovered Ni0.5Co0.2Mn0.3(OH)2 and Li2CO3 materials will be used as precursors in the anhydrous NMC cathode production process.