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Oct 28, 2024

From trash to treasure: How Princeton is turning dead EV batteries into gold

150 million batteries are expected to come to end of lifespan by 2035. A scalable approach to recycling them is urgently required. Ameya Paleja Spent batteries are problem to contend with already.

150 million batteries are expected to come to end of lifespan by 2035. A scalable approach to recycling them is urgently required.

Ameya Paleja

Spent batteries are problem to contend with already.

Victor Golmer/iStock

The era of electric vehicles (EVs) is just getting started, but the problem of waste from batteries is already becoming too hard to ignore.

Battery recycling technology has existed for decades, but it is time- and energy-intensive and difficult to scale. Princeton NuEnergy, a spinoff from Princeton University, has devised a solution that could help.

According to a BBC report, 550,000 electric vehicle (EV) batteries reached their end of life in 2020. The life cycle of these batteries began when EV adoption was yet to take off. By 2035, this number is expected to reach a whopping 150 million.

The Environmental Protection Agency (EPA) classifies lithium-ion batteries as hazardous waste. When disposed of at the end of their life cycle, they are more likely to explode or catch fire if not handled properly.

If untreated, batteries also end up in landfills, where they can leak toxic chemicals that contaminate groundwater and soil, posing a health risk to nearby communities. The EPA recommends recovering chemicals from spent batteries since they can be reused.

For instance, sourcing one ton of lithium from natural resources requires 250 tons of ore and generates 750 tons of brine. In sharp contrast, only 28 tons of used lithium-ion batteries can generate the one ton of high-grade lithium that can be used again in batteries.

A common approach to recycling is shredding, where part or all of the battery is shredded after being completely discharged. This generates streams of different materials such as plastics, electrolytes, steel, copper, aluminum, and black mass—granular material that contains shredded cathodes and anodes and is then used to make cathodes and anodes for new batteries.

Two methods can be used to recover materials from the black mass: pyrometallurgy, where heat is used to smelt metals out of the mass, and hydrometallurgy, where liquid is used to leach out metals.

However, these approaches have issues of low selectivity and emissions of toxic gases like nitrous oxide and sulfur dioxide. Pyrometallurgy reactions occur at temperatures as high as 2,912 degrees Fahrenheit (1,600 degrees Celsius), requiring the use of fossil fuels. Hydrometallurgy may not require higher temperatures but still suffers from incomplete metal recovery and excess mineral usage to facilitate recovery.

With only five percent of batteries recycled currently, there is a need to ramp up recycling efforts as battery wastage is expected to increase in the coming decade. However, the recycling processes need to be more efficient if large-scale recycling is to be effective.

The US Department of Energy has been keen to explore newer technologies for battery recycling beyond heat and liquid-based approaches. This is where Princeton New Energy’s plasma-based recycling technology can help.

The approach follows the same separating and shredding steps as conventional battery recycling but uses a low-temperature plasma-assisted separation (LPAS) instead of energy-consuming steps.

Before deploying the LPAS step, battery components such as copper, aluminum, plastic, cathode, and anode are separated. Only the cathode and anode enter the LPAS step, where they can be rejuvenated after removing surface impurities.

“Unlike hydro/pyro processes that turn aged cathode materials into chemicals by acid leaching, LPAS uses low-temperature plasma to create highly reactive species (electrons, ions, atoms) that remove surface impurities and activate the materials for later rejuvenation,” explained Xiaofang Yang, co-founder and Chief Technology Officer at Princeton New Energy, in an email to Interesting Engineering.

While plasma is usually associated with high temperature, PNE’s plasma is low temperature, achieved by keeping the molecular temperature low but the electron temperature high. “This is achieved by controlling discharge power, pressure, and the design of the plasma reactor, not by burning fossil fuels,” added Yang.

The patented technology delivers battery-grade rejuvenated cathode and anode materials that are at par with those sourced from natural resources and meet quality standards set by original equipment manufacturers (OEMs).

Crucial to delivering high-quality materials from the recycling process is the relithiation of the electrode materials. PNE achieves this through a process it refers to as Micro-Molten Shell-Assisted Lithiation or MSAL.

“MSAL repairs the structure, composition, and function of aged cathode materials, which often have less lithium and poor electrochemical performance after long-time cycling,” explained Yang.

“The rejuvenation step involves fine control of lithiation environments where a micro-shell of lithium forms on the material’s surface, leading to uniform and complete relithiation.”

The recovery rate achieved using this approach is as high as 95 percent, but it also improves cost and environmental outcomes. According to the company, LPAS offers a 73 percent reduction in energy consumption and a 69 percent reduction in carbon dioxide emissions compared to conventional mining while also using 69 percent less water.

“Our direct recycling method aims to be cost-competitive by reducing energy and chemical consumption compared to traditional methods. It generally offers a 38% reduction in production costs compared to virgin Cathode Active Material (CAM) production,” asserted Yang.

“We reduce costs by not using acid leaching, needing less lithium in our recycling process, and less energy consumption, carbon emissions and waste handling which reduce our operating cost.”

“The cost savings from eliminating disposal expenses should be factored into the overall return on investment (ROI),” explained Jon M Williams, CEO of Viridi, a US-based energy storage solution provider. “By recycling instead of disposing, companies can avoid the growing costs of handling hazardous waste, which adds an important financial incentive to the equation.”

While conventional techniques like hydrometallurgy struggle against the changing composition of electrodes as battery technology matures, LPAS has been demonstrated to work across battery technologies such as nickel, cobalt, and manganese (NCM) and nickel, cobalt, and aluminum oxide (NCA) used largely in electric vehicles.

The technology has been demonstrated to work effectively for lithium iron phosphate (LFP) batteries currently deployed in EVs and lithium cobalt oxide (LCO) batteries used in consumer electronics.

Under test conditions, the recycling technology delivered a discharge capacity retention of 83.66% from LCO batteries, and 88.9% from NCM batteries, after over 1,000 deep cycles. This is at par with performance of Li-ion batteries made with virgin materials.

After responding to the DOE’s call for innovative battery recycling technologies in 2017, Princeton researchers explored the use of low-temperature plasma, decided to commercialize the technology, and founded PNE.

As part of its commercialization efforts, the team built a prototype facility at Princeton’s Chemical and Biological Engineering facility. After demonstrating significant potential, the PNE is setting up the US’s first commercial-scale lithium-ion battery direct recycling facility in South Carolina.

The facility, expected to come online by Q3 of 2028, is designed to produce 10,000 tons of battery-grade CAM every year, equivalent to producing batteries for more than 100,000 electric vehicles yearly.

“We have agreements with multiple companies to supply recycled batteries, ensuring a steady feedstock for our recycling,” added Yang in the email to IE.

The need for battery recycling has been identified, and multiple research groups have worked to solve this problem. Interesting Engineering regularly reports on new approaches to how recycling could be sped up or made more efficient.

However, the challenge is scaling up the technology. UK-based company Altilium also announced plans to produce batteries from spent EV batteries, showing signs that the technology is now mature enough to be scaled and rolled out.

The next level is demonstrating that recycling also works out economically.

“When you also factor in the elimination of disposal costs, recycling offers a powerful ROI opportunity that could significantly improve the economics of lithium-ion cell recovery,” explained Williams to IE.

“Ultimately, for any of these technologies to succeed, they must scale effectively and generate more value from the recovered materials than the total costs of the plant, equipment, and operations.”

Even upon inquiry, PNE did not divulge the cost aspects of its large-scale project or when it was likely to break even. “Our mission is to be equal to or better than OEM-grade cathode materials at a lower cost than the original battery materials,” added Yang. He maintained that the cost of recycling batteries was confidential information.

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Ameya Paleja Ameya is a science writer based in Hyderabad, India. A Molecular Biologist at heart, he traded the micropipette to write about science during the pandemic and does not want to go back. He likes to write about genetics, microbes, technology, and public policy.

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