D.E. Molina, M. Shi, B. Adhikari, J. Klaehn, L. Diaz, T. Lister
Idaho National Laboratory,
United States
Keywords: lithium-ion battery, sustainable recycling, critical material recycling, leaching, electrochemistry
Summary:
As the world heads towards a decarbonized, electrified future, energy storage devices are key components enabling renewable energy sources to substitute traditional carbon-emitting sources. Lithium-ion batteries (LIBs) are the leading electrochemical storage device for electric vehicles, stationary storage banks and mobile consumer electronics. Despite recent improvements in battery lifetime, these batteries eventually degrade with use and need to be discarded, generating a large amount of waste. The International Energy Agency estimates that by 2040, there will be almost 15GWh worth of spent batteries coming from electric vehicles and storage. There is a huge incentive to recycle end-of-life batteries due to environmental concerns and to supply chain constraints of critical materials that are necessary to fabricate these batteries. Efficient and sustainable recycling technologies are needed to realize a sustainable circular economy for batteries. At the heart of the recycling process is the extraction of critical materials such as cobalt, nickel, lithium, manganese, and graphite. After these materials are extracted, they need to be separated and purified. Compared to high-temperature smelting processes, aqueous extraction processes are considered cleaner and less expensive, but they are still not very efficient, generate significant waste and consume large quantities of harsh chemicals such as sulfuric acid and hydrogen peroxide. Their carbon footprint also increases due to external heating needs. We have developed an electrochemical leaching (EC-Leach) process for the dissolution of metals from LIB black mass, for which we have won an R&D100 award. EC-Leach uses electricity that can come from renewable sources, as reagent to extract the critical materials in LIBs. It uses an electrochemical mediator (iron) already present in the LIB black mass at low concentrations. This reductant is constantly regenerated electrochemically to complete the leaching of metals of interest, while copper impurities are removed concurrently by electroplating, eliminating hydrogen peroxide and downstream copper removal steps. Part of the acid needed for this process is produced electrochemically at a bipolar membrane, reducing the addition of sulfuric acid. It also features low energy consumption due to no external heating and has remarkable life-cycle scores compared to the sulfuric acid/peroxide method. In this talk we present an innovative electrochemical cell we have developed, along with key results and life-cycle analysis metrics of our EC-leach technology.