Toward Sustainable Li-Ion Battery Recycling: Green Metal–Organic Framework as a Molecular Sieve for the Selective Separation of Cobalt and Nickel

Jędrzej Piątek,Aleksander Jaworski,Erik Svensson Grape,Robin Gueret,Tetyana M Budnyak,Adam Slabon,Giovanni Barcaro,A Ken Inge,Susanna Monti,Bruno V M Rodrigues

doi:10.1021/acssuschemeng.1c02146

Abstract

The growing demand for Li-ion batteries (LIBs) has made their postconsumer recycling an imperative need toward the recovery of valuable metals, such as cobalt and nickel. Nevertheless, their recovery and separation from active cathode materials in LIBs, via an efficient and environmentally friendly process, have remained a challenge. In this work, we approach a simple and green method for the selective separation of nickel ions from mixed cobalt–nickel aqueous solutions under mild conditions. We discovered that the bioinspired microporous metal−organic framework (MOF) SU-101 is a selective sorbent toward Ni2+ ions at pH 5–7 but does not adsorb Co2+ ions. According to the Freundlich isotherm, the adsorption capacity toward Ni2+ reached 100.9 mg·g–1, while a near-zero adsorption capacity was found for Co2+ ions. Ni2+ removal from aqueous solutions was performed under mild conditions (22 °C and pH 5), with a high yield up to 96%. The presence of Ni2+ ions adsorbed on the surface of the material has been proven by solid-state 1H nuclear magnetic resonance spectroscopy. Finally, the separation of Ni2+ from Co2+ from binary solutions was obtained with approximately 30% yield for Ni2+, with a near-zero adsorption of Co2+, which has been demonstrated by UV–vis spectroscopy. The ion adsorption process of Ni2+ and Co2+ ions was additionally studied by means of classical molecular dynamics calculations (force fields), which showed that the Ni2+ ions were more prone to enter the MOF canals by replacing some of their coordinated water molecules. These results offer a green pathway toward the recycling and separation of valuable metals from cobalt-containing LIBs while providing a sustainable route for waste valorization in a circular economy.

Highlights

Cobalt and nickel are one of the most common components of cathode materials in lithium-ion batteries (LIBs) in the form of lithium−metal oxides
The ion adsorption process of Ni2+ and Co2+ ions was studied by means of classical molecular dynamics calculations, which showed that the Ni2+ ions were more prone to enter the metal−organic framework (MOF) canals by replacing some of their coordinated water molecules
The main characterizations of this material have been reported in a previous work, and it has been found that SU-101 is chemically stable in a pH range from 2 to 14.41 We have performed the synthesis of SU-101 using a much cheaper bismuth source

Summary

Introduction

Cobalt and nickel are one of the most common components of cathode materials in lithium-ion batteries (LIBs) in the form of lithium−metal oxides. These metals are found together in lithium nickel manganese cobalt oxide (NMC) or lithium nickel cobalt aluminum oxide (NCA) cathodes.[1,2] The European Commission predicts that the demand for cobalt supply related to LIBs production will increase 5 times in 2030 and 15 times in 2050, compared to the current supply to EU countries. Cobalt has already been classified as a critical raw material, while nickel is under observation due to the increasing requisition of LIBs for energy storage and electric vehicle batteries.[3] Depletion of natural deposits of cobalt and nickel may result in a global shortage for future prospects. The majority of electronic wastes containing many precious elements is, not recycled, while the permeation of toxic elements may have direct consequences for the natural environment.[4,5] due to the fact that the battery market is still expanding and new types of batteries have been developed, for example, Al-based batteries, recycling has become even more crucial.[6,7]

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