Recycling lithium-ion batteries cuts emissions and strengthens supply chain

Recycling lithium-ion batteries to recover their critical metals has significantly lower environmental impacts than mining virgin metals, according to a new Stanford University lifecycle analysis published in Nature Communications. On a large scale, recycling could also help relieve the long-term supply insecurity – physically and geopolitically – of critical battery minerals.

Lithium-ion battery recyclers source materials from two main streams: defective scrap material from battery manufacturers, and so-called “dead” batteries, mostly collected from workplaces. The recycling process extracts lithium, nickel, cobalt, copper, manganese, and aluminum from these sources. 

The study quantified the environmental footprint of this recycling process, and found it emits less than half the greenhouse gases (GHGs) of conventional mining and refinement of these metals and uses about one-fourth of the water and energy of mining new metals. The environmental benefits are even greater for the scrap stream, which comprised about 90% of the recycled supply studied, coming in at: 19% of the GHG emissions of mining and processing, 12% of the water use, and 11% of the energy use.  While it was not specifically measured, reduced energy use also correlates with less air pollutants like soot and sulfur.

“This study tells us that we can design the future of battery recycling to optimize the environmental benefits. We can write the script,” said William Tarpeh (BS ’12), assistant professor of chemical engineering in the School of Engineering and the study’s senior author.

Location, location

Battery recycling’s environmental impacts depend heavily on the processing facility’s location and electricity source. 

“A battery recycling plant in regions that rely heavily on electricity generated by burning coal would see a diminished climate advantage,” said Samantha Bunke, a PhD student at Stanford and one of the study’s three lead investigators.

“On the other hand, fresh-water shortages in regions with cleaner electricity are a great concern,” added Bunke.

Most of the study’s data for battery recycling came from Redwood Materials in Nevada — North America’s largest industrial-scale lithium-ion battery recycling facility — which benefits from the western U.S.’s cleaner energy mix, which includes hydropower, geothermal, and solar. 

Transportation is also a crucial factor. In the mining and processing of cobalt, for example, 80% of the global supply is mined in the Democratic Republic of the Congo. Then, 75% of the cobalt supply for batteries travels by road, rail, and sea to China for refining. Meanwhile, most of the global supply of lithium is mined in Australia and Chile. Most of that supply also makes its way to China. The equivalent process for battery recycling is collecting used batteries and scrap, which must then be transported to the recycler. 

“We determined that the total transport distance for conventional mining and refining of just the active metals in a battery averages about 35,000 miles (57,000 kilometers). That’s like going around the world one and a half times,” said Michael Machala, PhD ’17, also a lead author of the study.

“Our estimated total transport of used batteries from your cell phone or an EV to a hypothetical refinement facility in California was around 140 miles (225 kilometers),” added Machala, who was a postdoctoral scholar at Stanford’s Precourt Institute for Energy at the time of research and is now a staff scientist for the Toyota Research Institute. This distance was based on presumed optimal locations for future refining facilities amid ample U.S. recyclable batteries.

Patent advantage

Redwood’s environmental outcomes do not represent the nascent battery recycling industry’s overall environmental performance for recycling used batteries. Conventional pyrometallurgy, a key refining step, is very energy intensive, usually requiring temperatures of more than 2,550 degrees Fahrenheit (1,400 degrees Celsius).

Redwood, however, has patented a process called “reductive calcination,” which requires considerably lower temperatures, does not use fossil fuels, and yields more lithium than conventional methods.

“Other pyrometallurgical processes similar to Redwood’s are emerging in labs that also operate at moderate temperatures and don’t burn fossil fuels,” said the third lead author, Xi Chen, a postdoctoral scholar at Stanford during the time of research and now an assistant professor at City University of Hong Kong.

“Every time we spoke about our research, companies would ask us questions and incorporate what we were finding into more efficient practices,” added Chen. “This study can inform the scale-up of battery recycling companies, like the importance of picking good locations for new facilities. California doesn’t have a monopoly on aging lithium-ion batteries from cell phones and EVs.”

Looking ahead

Industrial-scale battery recycling is growing, but not quickly enough, according to senior author Tarpeh.

“We’re forecast to run out of new cobalt, nickel, and lithium in the next decade. We’ll probably just mine lower-grade minerals for a while, but 2050 and the goals we have for that year are not far away,” he said.

While the U.S. now recycles about 50% of available lithium-ion batteries, it has successfully recycled 99% of lead acid batteries for decades. Given that used lithium-ion batteries contain materials with up to 10 times higher economic value, the opportunity is significant, Tarpeh said.

“For a future with a greatly increased supply of used batteries, we need to design and prepare a recycling system today from collection to processing back into new batteries with minimal environmental impact,” he added. “Hopefully, battery manufacturers will consider recyclability more in their future designs, too.”