The COOL-Process—A Selective Approach for Recycling Lithium Batteries

Abstract

The global market of lithium-ion batteries (LIB) has been growing in recent years, mainly owed to electromobility. The global LIB market is forecasted to amount to $129.3 billion in 2027. Considering the global reserves needed to produce these batteries and their limited lifetime, efficient recycling processes for secondary sources are mandatory. A selective process for Li recycling from LIB black mass is described. Depending on the process parameters Li was recovered almost quantitatively by the COOL-Process making use of the selective leaching properties of supercritical CO2/water. Optimization of this direct carbonization process was carried out by a design of experiments (DOE) using a 33 Box-Behnken design. Optimal reaction conditions were 230 °C, 4 h, and a water:black mass ratio of 90 mL/g, yielding 98.6 ± 0.19 wt.% Li. Almost quantitative yield (99.05 ± 0.64 wt.%), yet at the expense of higher energy consumption, was obtained with 230 °C, 4 h, and a water:black mass ratio of 120 mL/g. Mainly Li and Al were mobilized, which allows for selectively precipitating Li2CO3 in battery grade-quality (>99.8 wt.%) without the need for further refining. Valuable metals, such as Co, Cu, Fe, Ni, and Mn, remained in the solid residue (97.7 wt.%), from where they are recovered by established processes. Housing materials were separated mechanically, thus recycling LIB without residues. This holistic zero waste-approach allows for recovering the critical raw material Li from both primary and secondary sources.

Recovery of Al, Co, Cu, Fe, Mn, and Ni from Spent LIBs after Li Selective Separation by the COOL‐Process. Part 1: Leaching of Solid Residue from COOL‐Process

“…The recycling process depicted in Fig. 1 had previously been developed and optimized for obtaining Li 2 CO 3 by the COOL‐process 2. In the present work, the starting material is the solid residue obtained after the COOL process, which is after leaching black mass with sc ‐CO 2 .…”

“…The solid residue obtained from the COOL‐process, which was carried out according to the optimized parameters described by Pavón et al. (230 °C for 4 h with a water/black mass ratio of 90 mL g −1 ) 2, was treated in a first digestion stage with different leaching reagents with a concentration of 2 N Sulfuric acid (95 %, Thermo Fischer Scientific, MA, USA), hydrochloric acid (37 %, VWR International, PA, USA), citric acid (99+ %, Alfa Aesar, MA, USA), and gluconic acid (50 %, Sigma‐Aldrich, MO, USA) as well as different concentrations of hydrogen peroxide (0–6 vol %; 30 %, Th. Geyer, Renningen, Germany) were tested.…”

“…Furthermore, the constant introduction of new technologies and shorter lifetime of electronic devises, increase the disposal number of spent LIBs. Moreover, it is expected, that the mandatory recycling rates of LIBs will be further increased (currently in the EU: 50 wt % of the hole LIB) 2. Thus, innovative recycling approaches, which allow for recovering valuable metals are required to contribute to a circular economy and to develop an economically viable zero‐waste solution.…”

“…Already the crude product has battery grade‐quality (> 99.8 wt %), i.e., there is no further refining needed. The other valuable metals Co, Cu, Mn, and Ni remain in the solid residue 2.…”

“…The aim of this work (Part 1) is the investigation of the solid residue digestion stage. Subsequent work (Part 2 23) comprises the selective separation of the valuable metals, which will be comprehensively investigated by using solvent extraction processes.…”