Electrolytic Recovery of Lithium from Used Li-Ion Battery Material Leachate through a CO2-Negative Process

Abstract

Lithium materials are attracting attention from industrial and research institutes in recent decades.[1-3] The demand of lithium battery materials is growing due to applications in Li-ion batteries for portable devices, electric-vehicles, and energy storage. In 2016, around 78,000 metric tons of lithium carbonate (equivalent) was consumed, much higher than that in 2010 at 29,000 metric tons, and the statistics forecasted a global demand reaching 509,000 metric tons by the year 2025.[4] Though the increasing consumption of Li2CO3 opens a big market, the producers were still limited, mostly due to high manufacture cost for high purity lithium carbonate. In recent studies, researchers focused on electrolytic extraction of lithium from salt-lake brines and seawater [5, 6], and solvent extraction using organic solvents such as DEHPA/kerosene [7]. These methods were applicable in producing lithium species, but the drawbacks included large amounts of chemical additions and waste generations.In our study, lithium has been electrochemically recovered in a form of Li2CO3, as the last step in separating critical metals from shredded battery materials. This work is part of a larger effort to recover critical elements from Li ion batteries. Other efforts in the project include shredding of used batteries, leaching critical metals from shredded battery materials, and separating Ni and Co from the leachate. The elution from Ni and Co extraction will be used as the anolyte in the electrolytic cell, containing primarily Li and Mn.Aiming at recovering lithium from the elution in a green pathway, we introduced an electrochemical process consuming only the produced Li-rich elution and CO2. In the recovery process, the anolyte was the elution, and the catholyte was a CO2-captured solution. Electrolytic studies were carried out through chronoamperometry and chronopotentiometry measurements. Li2CO3 could be collected as a precipitate product with a 100% purity analyzed with atomic adsorption spectroscopy and X-ray diffraction. After each experiment, the catholyte could be simply recovered by bubbling CO2, and the recovered catholyte has been proved to be effective for multiple uses.The electrochemical method used in this study has been proved to be feasible for the purpose of separating and recovering lithium as a Li ion battery material. In this lithium recovery process, CO2 is captured and solidified. As the only reagent consumed in the process, CO2 can be sourced from air and waste emissions from burning of fossil fuels. Instead of adding additional chemicals such as LiCl [8] and Na2CO3 [9] to catholyte to accelerate lithium extraction and precipitation in literatures, Li ions are directly converted into ultrahigh purity Li2CO3 precipitates in this work.