Innovative green approach for recovering Co2O3 nanoparticles and Li2CO3 from spent lithium-ion batteries

Abstract

Although previous studies have obtained promising results for recovering valuable metals from spent LIBs at low temperatures using organic acids combined with reducing agents, additional chemicals such as H2O2, huge amounts of organic acids, and environmental protection remain challenges. In this study, a subcritical water (SCW) assisted diluted formic acid process was proposed as a green approach for recovering Co2O3 nanoparticles and Li2CO3 from spent LiCoO2 cathode materials without using any reducing agents. The effects of leaching parameters such as (H2O: HCOOH) ratio (v/v), temperature, reaction time, and liquid-solid ratio on the extraction of Li and Co have been carefully evaluated. The findings revealed that SCW-assisted (DFA) successfully leaches Li and Co from the spent LiCoO2 cathode materials of Li-ion batteries without using any assistance from reducing reagents. The solid materials were characterized by XRD, XPS, FT-IR, and SEM-EDS analyses. Meanwhile, the leaching liquor was analyzed by ICP-OES. More than 99% of Li and Co were effectively recovered from the spent LiCoO2 powder at 220 °C for 25 min, H2O: HCOOH ratio (v/v,) of 78:12 and a liquid-solid ratio of 25 mL/g. Further, the activation energy for Li was 24.15 KJ/mol, while that for Co was 31 KJ/mol. Finally, Co2O3 and Li2CO3 were successfully recovered from the leaching liquor by the precipitation and calcination methods after the separation steps. The overall findings suggested that SCW-assisted (DFA) could be an alternative method due to its low energy consumption, dual function properties at mild temperatures, low chemical input, and environmentally friendly.