Recycling of used lithium-ion batteries

Newswise — Lithium-ion batteries (LIBs) power our portable devices like tablets and cellphones, and increasingly, cars. As the share of volatile renewables that require electricity storage increases, more and more LIBs are needed, lithium prices rise, resources are depleted, and the number of discharged batteries containing toxic substances increases. in the magazine Applied ChemistryResearchers have introduced a new approach to recover lithium from used LIBs.

Recycling LIBs is a difficult task. Recovering lithium to a high enough quality to be reused is difficult and expensive. Most recycling processes aim to extract the lithium from the cathodes (where most of the lithium in discharged batteries is located). However, it then accumulates with the other metals in the cathode and must be painfully removed. Removal from the anodes, which are mainly composed of graphite, is significantly more efficient and can be carried out without pre-charging the battery. However, due to their high reactivity, the risk of fire and explosion is high if the anodes are flushed with aqueous solutions, as is usually the case. These reactions release large amounts of energy and can produce hydrogen.

A team led by Yu-Guo Guo and Qinghai Meng at the Institute of Chemistry of the Chinese Academy of Sciences (ICCAS) and the University of the Chinese Academy of Sciences (UCAS) has now developed an alternative method that avoids these problems. Instead of water, they use aprotic organic solutions to recover lithium from anodes. Aprotic substances cannot release hydrogen ions, so hydrogen gas is not produced.

The solution consists of a polycyclic aromatic hydrocarbon (PAH) and an ether as a solvent. Some PAHs can accept a positively charged lithium ion along with one electron from the graphite anode. Under mild conditions, this redox reaction is controlled and very efficient. With PAH pyrene in tetraethylene glycol dimethyl ether, it was possible to almost completely dissolve the active lithium from the anodes.

An additional advantage is that the resulting lithium-PAH solutions can be used directly as reagents, for example, adding lithium to new anodes in pretreatment or in the regeneration of spent cathodes. The PAH/solvent system can be varied to optimize the material treated.

This recovery process is efficient and inexpensive, reduces safety risks, avoids waste and opens new perspectives for sustainable recycling of lithium-ion batteries.

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About the author

Dr. Yu-guo guo has been a full professor of chemistry at the Institute of Chemistry, Chinese Academy of Sciences (CAS) since 2007. He leads a research group with research interests focused on energy materials and electrochemical energy storage devices such as Li-ion, Li-metal, Na-ion batteries and solid-state batteries.