Examining different recycling processes for lithium-ion batteries

Electric vehicle lithium-ion battery recycling processes and policies should be aligned to minimize greenhouse gas emissions

Automakers are betting big on electric vehicles, with many companies joining Tesla in committing to all electric and hybrid-electric product lines in the coming years. Powering these vehicles will require gigawatt hours of energy storage, and today’s technology of choice is lithium-ion batteries. Managing the waste generated as battery packs from electric and hybrid electric vehicles also presents opportunities for recovering high-value materials and reducing greenhouse gas emissions from future battery manufacturing, but policies mandating electric vehicle battery recycling still haven’t been written.  

Most lithium-ion recycling policies and processes were designed with consumer electronic batteries in mind. While all lithium-ion batteries use lithium as the charge carrier, there are a variety of materials and formulations for the cathode, which stores the lithium ions as the battery is discharged. Batteries from consumer electronics are small, and the waste streams that feed into recycling processes contain a mixture of specific formulations. Processes like hydrometallurgical and pyrometallurgical recycling are suitable for these mixed streams because they reduce whole batteries to constituent metals, with particular focus on high-value metals like cobalt. But while small, consumer electronics batteries can be expensive because overall storage capacity is small (e.g. ~10 Wh per iPhone), batteries for electric vehicles must be extremely inexpensive, and formulations for the cathode materials aim to further reduce the amount of expensive materials.

EV battery packs are also much larger than batteries in consumer electronics, and automakers tend to utilize the same battery chemistry throughout their product lines, making it possible to deduce the battery chemistry formulation before battery recycling. Automakers are also interested in recycling as a potential source of low-cost material that can be remanufactured into new battery packs. In our paper, we wanted to examine how a direct cathode recycling process, which leaves cathode materials intact, would compare to other recycling processes, both in terms of greenhouse gas emissions and energy consumption. We also wanted to know whether the cathode material recovered would be economically competitive with traditional cathode manufacturing.

We focused our analysis on specific lithium-ion formulations that are most common in today’s electric vehicles, and found that for cathodes containing metals like nickel, manganese, and cobalt, direct cathode recycling can reduce the greenhouse gas emissions associated with manufacturing new batteries from the materials, and has the potential to be economically competitive with traditional cathode manufacturing. Other processes, like pyrometallurgical recycling, create too many emissions, and the lack of energy and emissions-intensive material in EV battery cathodes do not justify these processes. Other cathode chemistries made from materials that are easier to mine do not result in net greenhouse gas emissions reductions, regardless of how they are recycled. In order to maximize the greenhouse gas emissions benefits from battery recycling, policies should focus both encourage collection of automotive lithium-ion batteries (a hallmark of successfully-implemented lead-acid battery recycling policies) and should mandate that recycling processes offer net reductions in greenhouse gas emissions rather than focusing on the percentage of battery content that is recycled.

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