Sustainable electrochemical process improves lithium-ion battery recycling

Worldwide consumption of electronic devices has led to a sharp increase in waste batteries. Spent lithium-ion batteries (LIBs) contain critical elements, such as lithium (5-8 per cent); cobalt (5–20 per cent); nickel (5–10 per cent), and manganese (10–15 per cent). Nickel–metal hydride batteries also possess a high content of nickel (36–42 per cent) and cobalt (3–5 per cent).

Future demand for such critical elements, especially cobalt and nickel, has been predicted to exceed identified reserves and there are increasing geographical, environmental and political pressures related to primary mining operations. This means there is urgent pressure to develop sustainable strategies to recover critical elements from the potentially valuable secondary resources.

However, it is difficult to separate the valuable metals inside spent lithium-ion batteries from each other for recycling purposes and current methods used for their separation have environmental and efficiency drawbacks.

A new technology uses electrochemistry to efficiently separate and recover the metals, making spent batteries a highly sustainable secondary source of cobalt and nickel and easing the pressure on their dwindling natural reserves.

The study, led by Xiao Su, a chemical and biomolecular engineering professor at the University of Illinois Urbana-Champaign in the USA, proposes using selective electrodeposition to recover valuable metals from commercially sourced lithium nickel manganese cobalt oxide (NMC) battery electrodes. The method produces final product purities of approximately 96.4 per cent and 94.1 per cent for cobalt and nickel, respectively, from spent NMC electrode wastes.

Cobalt and nickel have similar electrochemical properties – or standard reduction potentials – making it challenging for chemists to recover pure forms of each metal from battery electrodes.

“There are a variety of methods available for the recovery of cobalt and nickel from battery electrodes, but they have drawbacks,” Su said. “Most require energy-intensive high-temperature processes or strong solvents that present disposal challenges. The industry demands methods that will not cause additional problems like high energy consumption or toxic waste.”

The unique aspect of the study was the team’s development of a tunable liquid electrolyte and polymer coating on the electrodes. In the lab, the researchers combined the electrolyte-polymer method with dismantled, leached and liquefied components of fully discharged NMC battery electrodes.

By adjusting the salt concentrations of the electrolyte and the thickness of the polymer coating, researchers noted that distinct deposits of cobalt and nickel accumulated on the electrode surfaces through sequential electrodeposition. By the end of the process, the electrode had collected high-purity coatings of cobalt and nickel.

An economic analysis of the new approach showed that it was competitive with current Li-battery recycling methods, once material revenue, material cost and energy consumption were all considered, the study reported.

“There’s further engineering optimisation of the process that will be needed going forward, but this first proof-of-concept study confirms that low-temperature cobalt and nickel electrochemical recovery is possible,” Su said. “We’re very excited because the study shows a great example of sustainable electrically driven separations being used to recycle electrochemical batteries.”

The research paper - 'Selective cobalt and nickel electrodeposition for lithium-ion battery recycling through integrated electrolyte and interface control' - has been published in the journal Nature Communications.