Lithium Secondary Sources

secondary sources

As demand for lithium is forecast to rise sharply in the short- to medium-term recycling and reuse will become an increasingly important part of the supply chain. However, some end-use applications of lithium, for example glass and ceramics, and lubricants are dispersive uses and hence recovery of lithium from these secondary sources is unlikely to be important in the future. Lithium-ion batteries are more promising for both reuse, remanufacturing and recycling, although currently, this is not happening at a large-scale.

Reuse

Reuse of Li-ion batteries typically takes two forms: (1) direct reuse where the battery remains intact, or (2) indirect reuse where some remanufacturing is required (e.g. only the cathode is reused). The reuse of Li-ion batteries can also be considered in terms of whether the battery is used in the same application (primary reuse) or in a different application (secondary or tertiary resuse). An example of direct secondary reuse would be using an end-of-use EV battery for domestic energy storage.

However, reuse has its limitations, with second-life batteries typcially needing to be used in less demanding applications (e.g. domestic energy storage), but also whether the battery design allows for reuse. For example, assembly methods that reply on glues and adhesives to bond cells, can make future repair or reuse impossible if a single cell fails in the battery pack, with the whole pack needing to be replaced. There are also concerns around the safe reuse of Li-ion batteries, where there are typically very few, or no codes or standards related to the regulation of second-life applications for Li-ion batteries. For example, there are currently no standards focused on the testing of second-life batteires (Harper et al., 2023).

Future direction

There are many opportunities for recycling of Li-ion batteries; however, a great deal of research is required to optimise processes for the recovery of lithium in a safe and cost effective manner. Similarly, there is scope for reuse of Li-ion batteries in secondary appliactions, although concerns around safety and regulation need to be addressed. In both cases academia, industry and governments will need to collaborate to realise these opportunities in the future.

Recycling

Processes for recycling Li-ion batteries exist, although the focus is largely on recovery of the higher value metals, such as Co, Mn and Ni. Recently, there has been a great deal of reserach interest in Li-ion battery recycling, with a particular focus on the recovery of lithium.

There are three principal routes for Li-ion battery recycling:

Pyrometallurgy
Hydrometallurgy
Mild recycling

Pyrometallurgy is fairly rapid process that is easy to scale-up, it also has the benefit of being able to accept a range of different battery chemistries. However, the high temperatures used during the process can generate signifncant emisisons (e.g. CO2, CO, SO2), which require treatment and therefore increase the operating costs. The energy consumption is also very high. The other drawback is that lithium is not easily recovered, as it usually ends up in the slag (Liu et al., 2019).

Hydrometallurgy is a complex process that relies heavily on the use of inorganic acids, organic acids and alkaline solutions. It can be a costly process, as set-up times can be long and there is a requirement to treat wastewater and spent reagents, which further adds to the cost. On the plus side, all metals, inlcuding lithium can be recovered using hydrometallurgical methods resulting in the precipitation of high purity compounds, although reported ltihium recoveries are not as high as for other metals (Liu et al., 2019).

Mild recycling methods, for example carbothermal reduction or sulfation roasting typically use less energy and have generally good recycling efficiencies. Lithium can also be recovered using these methods. However, like pyrometallurgy, these processes produce gaseous emissions that need to be treated (Liu et al., 2019).