Biological separation of metals from lithium-ion batteries leachates 

From the 2030s, large improvements will be required in the scale, economics and environmental footprint of recycling processes to cope effectively with the expected volumes of lithium-ion batteries reaching end-of-life.

ReLiB project researchers at the University of Edinburgh have developed a biological process that uses two different types of bacteria to selectively separate the critical and valuable metals contained in the leachates generated during lithium-ion battery recycling. By selectively breeding strains of bacteria and controlling conditions (e.g., pH) the bacteria can selectively remove one metal from the leachate by precipitating nanoparticles of that metal. These biological reactions occur at room temperature, in aqueous solutions and without the need for harsh chemicals, thus falling within the principles of green chemistry.

To date, the metal bioseparation process has been successfully tested across different battery chemistries and leaching processes/solvents. Manganese, if present, is the first element separated biologically from the leachate as a carbonate salt, leaving cobalt, nickel and lithium in the dissolved fraction. Co and Ni are precipitated via a second bacterial process, while lithium remains in the leachate with a Li content similar to natural Li-brines.

The scale-up of manganese separation has been successfully achieved to a 30-litre capacity. The focus is now on optimisation of the Co and Ni separation process, which is currently undertaken in 5 litre bioreactors. A sustainability assessment of the process is underway, alongside the optimisation of the recycling yields. The properties of the biorecovered materials are being determined to assess their suitability for use in future battery production.

Image: Virginia Echavarri-Bravo and Louise Horsfall (centre) with Yuta Era and Nick Pantidos at the labs at the University of Edinburgh.

Case study published December 2024.