Utilizing mechanochemistry: a universal method of lihium-ion battery recycling?

The production of #lithiumionbatteries (LIBs) is increasing due to the growing demand for LIBs. This means that ecological and efficient ways of recycling LIBs are needed in order to recover precious battery components that can be reused.

In 2021, around 80% of the lithium-ion battery waste came from small electronic devices such as laptops, mobile phones, tablets, and cameras. The other 20% of LIB waste came from large electronic devices, including electric vehicles and energy storage systems. With the continuously growing number of electric vehicles, LIB waste already sees a drastic increase and shift from electronic devices to electromobility. Whereas in 2020, the global LIB waste counted around 98,000 tons, it is estimated to reach 6,300,000 in 2030 and 120,000,000 in 2040 [1-4]. At the moment, there is no preferred concept for processing and #recycling #battery scrap, and this needs to change.

Unfortunately, currently used recycling techniques all have mostly negative connotations, not only because the processes consume a lot of energy, but they can also cause a risk to the environment as corrosive substances are added.

With 50% of the overall LIB production cost, the cathode, consisting of lithium and other transition metals, is the most expensive part of the battery. Researchers at the Institute for Applied Materials - Energy Storage Systems (IAM-ESS) at the Karlsruher Institut für Technologie (KIT) have found a highly efficient mechanochemically induced process to recycle lithium from cathode materials. ?

Current recycling of LIBs

As the volume of end-of-life batteries will continuously increase, more recycling facilities need to be developed with higher capacity. Although recycling of LIBs is happening, mainly nickel and cobalt (cathode materials), as well as copper and aluminum (collector materials), are recycled. Additionally, passive components of LIBs are also being recycled.

But what about lithium? With the currently available recycling processes, the cost of recycling lithium is very high, therefore, often not profitable, hence there is a need for huge development in the LIB recycling technology. Most of the present LIB recycling processes are based on #pyrometallurgy, #hydrometallurgy or #biohydrometallurgy, a process within the framework of hydrometallurgy.

Hoes does recycling of LIBs work?

First, the recycler looks at the type of battery. After the #sorting step, manual #disassembly follows – at this stage, copper conductors, synthetics, and metals are removed. As of now, each recycling company has different recycling processes: either burned in the blast furnace (pyrometallurgical recycling) or chemically dissolved in an acid bath (hydrometallurgical recycling).

In the blast furnace, the materials burn, melt or evaporate and are then separated from each other by physical-chemical processes. As a result, cobalt, copper, and nickel, for example, can be recovered to build new batteries later. In addition, a glass-like slag remains, which is suitable for use in road construction. This is also the material in which lithium is found. But there is another way to recycle batteries – the hydrometallurgical process. Here, the remaining powder is sieved after shredding. After that, the components are chemically dissolved via various filtering processes. For this purpose, the powder is placed in an acid bath to extract valuable raw materials from it.

LIB recycling using mechanochemistry

Researchers at the Institute for Applied Materials - Energy Storage Systems (IAM-ESS) at Karlsruhe Institute of Technology (KIT) have now developed two mechanochemically induced recycling processes to recycle lithium using a variety of commonly used cathode chemistries and their mixtures. By using aluminum (the material of the current collector of the cathode) as a reducing agent, extra external additives were not required during the recycling process. During the study, two recycling methods were investigated, both beginning with a mechanochemical treatment of the cathode with Al. This causes reduction reactions resulting in the formation of metallic composites that contain d-elements, aluminum oxide, and water-soluble lithium products.

The aqueous leaching step used in the first process causes the mixture of LACHH (a complex compound with the formula Li2Al4(CO3)(OH)12·3H2O) and Li2CO3 to form pure lithium carbonate. Al(OH)3 was discovered in the LiFePO4-Al system in this step. LACHH and Al(OH)3 decompose during the subsequent purification step, which involves heating, water solution, and filtration to produce pure Li2CO3. The loss of Li in the form of an insoluble component was the reason for the low Li yield in process 1 (29.8-39.6%).

Due to the introduction of a carbonatization step in process 2, the number of steps was decreased, and the Li yield significantly increased (55.6–75.9%). The developed method has a clear advantage over existing LIB recycling methods because it is straightforward and energy-efficient. The method can also be referred to as universal because it can be used with every cathode chemistry currently in use, both individually and in combination. Thus, when used, this technique can avoid the recycling plant's sorting process.

But why aren't all batteries actually recycled yet? Of course, the recovery of lithium, natural graphite, and electrolyte is desirable from a sustainability perspective. Sometimes it is technically problematic, but it is also problematic from an economic point of view. In addition, simply too few people still return their old batteries and store them at home instead of sending them for recycling. Meanwhile, more than 90% of the materials in a battery cell can be recycled, and experts believe that this figure will continue to rise. After all, battery recycling is enormously important to keep valuable materials in the cycle. Anyone can contribute and actively support battery recycling by simply returning old batteries. The demand for raw materials for battery production is high. Recycling and being able to reuse material won't ensure the security of supply, but it will definitely help.

[1]. M. Kaya, State-of-the-art lithium-ion battery recycling technologies, Circular Economy, 2022, 1, 100015.

[2]. Bae, et. al, Technologies of lithium recycling from waste lithium ion batteries: a review, Mater. Adv., 2021, 2, 3234.

[3]. IEA (2021), The Role of Critical Minerals in Clean Energy Transitions, IEA, Paris https://www.iea.org/reports/the-role-of-critical-minerals-in-clean-energy-transitions, License: CC BY 4.0.

[4]. A. Holland, Li-ion Battery Recycling: 2020-2040, IDTechEx Report.