Lithium-ion batteries are the primary power source for tablets, mobile phones, and automobiles. The demand for lithium-ion batteries is increasing as market demand for unstable renewable energy sources for electricity storage continues to grow. However, lithium metal resources are currently limited and expensive, and the number of spent batteries containing toxic substances is increasing.
According to foreign media reports, Chinese researchers have introduced a new method for recovering lithium from spent lithium-ion batteries in the German journal *Angewandte Chemie*.
Lithium-ion battery recycling is a challenging task; recovering high-quality lithium for reuse is a complex and expensive process. Most recycling processes aim to extract lithium from the cathode (where most of the lithium is located during battery discharge). However, this lithium precipitates out along with other metals in the cathode, making separation difficult.
Extracting lithium from the anode (primarily composed of graphite) is significantly more efficient and can be done without pre-discharging the battery. However, due to its high reactivity, leaching lithium from the anode with aqueous solutions as usual carries a high risk of fire and explosion. These reactions can release large amounts of energy and produce hydrogen gas.
A team led by Guo Yuguo and Meng Qinghai at the Institute of Chemistry, Chinese Academy of Sciences (ICCAS) and the University of Chinese Academy of Sciences (UCAS) has developed an alternative method to avoid these problems. The researchers used an aprotic organic solution instead of water to recover lithium from the anode. Aprotic substances cannot release any hydrogen ions and therefore cannot form hydrogen gas.
The solution consists of polycyclic aromatic hydrocarbons (PAHs) and an ether as a solvent. Some PAHs can absorb positively charged lithium ions and an electron from the graphite anode. Under mild conditions, this redox reaction is controllable and highly efficient. Using PAH pyrene in tetraethylene glycol dimethyl ether, the active lithium in the anode can be almost completely dissolved.
Another advantage is that the resulting lithium-PAH solution can be used directly as a reactant, for example, to add lithium to new anodes during pretreatment or regeneration of spent cathodes. The PAH/solvent system can be tuned to be optimized for the materials being processed.
This recycling process is efficient and low-cost, not only reducing safety risks but also helping to avoid waste, opening up new prospects for the sustainable recycling of lithium-ion batteries.
