Scientists cook up a green recipe for recycling lithium-ion batteries using vegetable oil

University of Leicester scientists have developed a technique for sustainably extracting valuable metals from a waste product of used batteries with a mix of water and cooking oil.

The patent-pending technology allows lithium-ion battery black mass, a low-value mixture of anode and cathode and other materials, to be purified directly within minutes of operation at room temperature.

With billions of these batteries used worldwide in electronics and electric vehicles, it could enable a cheaper and more sustainable recycling method to support the switch to green technologies.

Research led by Professor Andy Abbott and Dr. Jake Yang at the University of Leicester working under the Faraday Institution’s ReLiB project found an innovative way of recovering valuable battery-grade metal oxides from crushed batteries by using nanoemulsions created from a trace of cooking oil in water. The study is published in the journal RSC Sustainability.

From everyday experience, we know oil and water do not mix unless we add soap, but research has shown that using ultrasound can create nano-droplets of oil that are stable for weeks. Crucially, oil nano-droplets are found to purify battery waste, commonly known as “black mass,” as it contains a mixture of carbon (graphite) and valuable lithium, nickel and cobalt metal oxides (NMC).

The oil nano-droplets stick to the surface of the carbon, acting as a “glue” to bind hydrophobic graphite particles together to form large oil-graphite conglomerates which float on water, leaving the valuable and hydrophilic lithium metal oxides untouched. The oil-graphite conglomerate can simply be skimmed off, leaving pure metal oxides.

Current recycling techniques use a combination of furnace heat treatment to burn off the undesired graphite, thereby increasing the CO₂ footprint of the EV value chain, as well as concentrated corrosive acids which take valuable battery-grade metal oxides all the way back to the lower-valued battery precursor materials from which the battery was first made.

The Leicester-developed emulsion technique allows short-loop recycling of lithium-ion batteries. The battery-grade crystalline structure of the recovered material is not destroyed in this process and allows the remanufacturing of the recovered material directly back into new battery cells, unlike pyro/hydrometallurgical methods. This could potentially make the battery supply chain more sustainable and cheaper.

Dr. Jake Yang from the University of Leicester School of Chemistry said, “This quick, simple and inexpensive method could revolutionize how batteries are recycled at scale. We now hope to work with a variety of stakeholders to scale up this technology and create a circular economy for lithium-ion batteries.”

The Electric Revolution comes with drawbacks—one being challenges around how we efficiently and sustainably recycle large volumes of batteries at the end of their working life.

The use of batteries for electric vehicles and energy storage is only a sustainable future if the recycling pathway is green and cost-efficient. Globally, there are an estimated 40 million electric vehicles (EVs), and there are approximately 10 billion active mobile phones, laptops and tablets worldwide, all powered by lithium-ion batteries. However, the lack of regulations means lithium-ion battery packs are not designed to be recycled.

The Universities of Leicester and Birmingham are also collaborating to bring together several technologies developed under ReLiB in an InnovateUK project, ReBlend. This is creating a pilot line capable of processing 10s of kg/h of black mass to demonstrate that this short loop reprocessing can function economically to provide battery grade material for new cells.

“The ReLiB project is one of the Faraday Institution’s flagship projects developing innovative technology to capture value and retain scarce resources in the circular economy of battery manufacture and recycling. This work offers a promising route for short-loop recycling of lithium-ion batteries at scale,” commented Professor Martin Freer, CEO of the Faraday Institution.