Credit: American Manganese | In a battery-recycling pilot plant near Vancouver, British Columbia, American Manganese engineers examine shredded aluminum recovered from Li-ion battery cathodes.
Lithium-ion batteries have made portable electronics ubiquitous, and they are about to do the same for electric vehicles. That success story is setting the world on track to generate a multimillion-metric-ton heap of used Li-ion batteries that could end up in the trash. The batteries are valuable and recyclable, but because of technical, economic, and other factors, less than 5% are recycled today. The enormousness of the impending spent-battery situation is driving researchers to search for cost-effective, environmentally sustainable strategies for dealing with the vast stockpile of Li-ion batteries looming on the horizon.
As the popularity of electric vehicles starts to grow explosively, so does the pile of spent lithium-ion batteries that once powered those cars. Industry analysts predict that by 2020, China alone will generate some 500,000 metric tons of used Li-ion batteries and that by 2030, the worldwide number will hit 2 million metric tons per year.
If current trends for handling these spent batteries hold, most of those batteries may end up in landfills even though Li-ion batteries can be recycled. These popular power packs contain valuable metals and other materials that can be recovered, processed, and reused. But very little recycling goes on today. In Australia, for example, only 2–3% of Li-ion batteries are collected and sent offshore for recycling, according to Naomi J. Boxall, an environmental scientist at Australia’s Commonwealth Scientific and Industrial Research Organisation (CSIRO). The recycling rates in the European Union and the US—less than 5%—aren’t much higher.
“There are many reasons why Li-ion battery recycling is not yet a universally well-established practice,” says Linda L. Gaines of Argonne National Laboratory. A specialist in materials and life-cycle analysis, Gaines says the reasons include technical constraints, economic barriers, logistic issues, and regulatory gaps.
All those issues feed into a classic chicken-and-egg problem. Because the Li-ion battery industry lacks a clear path to large-scale economical recycling, battery researchers and manufacturers have traditionally not focused on improving recyclability. Instead, they have worked to lower costs and increase battery longevity and charge capacity. And because researchers have made only modest progress improving recyclability, relatively few Li-ion batteries end up being recycled.
Most of the batteries that do get recycled undergo a high-temperature melting-and-extraction, or smelting, process similar to ones used in the mining industry. Those operations, which are carried out in large commercial facilities—for example, in Asia, Europe, and Canada—are energy intensive. The plants are also costly to build and operate and require sophisticated equipment to treat harmful emissions generated by the smelting process. And despite the high costs, these plants don’t recover all valuable battery materials.
Until now, most of the effort to improve Li-ion battery recycling has been concentrated in a relatively small number of academic research groups, generally working independently. But things are starting to change. Driven by the enormous quantity of spent Li-ion batteries expected soon from aging electric vehicles and ubiquitous portable electronics, start-up companies are commercializing new battery-recycling technology. And more scientists have started to study the problem, expanding the pool of graduate students and postdocs newly trained in battery recycling. In addition, some battery, manufacturing, and recycling experts have begun forming large, multifaceted collaborations to tackle the impending problem.
In January, for example, US Department of Energy secretary Rick Perry announced the creation of the DOE’s first Li-ion battery recycling R&D center, the ReCell Center. According to Jeffrey S. Spangenberger, the program’s director, ReCell’s key goals include making Li-ion battery recycling competitive and profitable and using recycling to help reduce US dependence on foreign sources of cobalt and other battery materials. Launched with a $15 million investment and headquartered at Argonne National Laboratory, ReCell includes some 50 researchers based at six national laboratories and universities. The program also includes battery and automotive equipment manufacturers, materials suppliers, and other industry partners.
At the same time, the DOE also launched the $5.5 million Battery Recycling Prize. The program’s goal is to encourage entrepreneurs to find innovative solutions for collecting and storing discarded Li-ion batteries and transporting them to recycling centers, which are the first steps in turning old batteries into new ones.
And last year, researchers in the UK formed a large consortium dedicated to improving Li-ion battery recycling, specifically from electric vehicles. Led by the University of Birmingham, the Reuse and Recycling of Lithium Ion Batteries (ReLiB) project brings together some 50 scientists and engineers at eight academic institutions, and it includes 14 industry partners.
140 million: The number of electric vehicles predicted to be on the road worldwide by 2030
11 million: Metric tons of Li-ion batteries expected to reach the end of their service lives between now and 2030
30–40%: The percentage of a Li-ion battery’s weight that comes from valuable cathode material
<5%: The percentage of Li-ion batteries that are recycled currently
~100%: The percentage of the lead in common lead-acid car batteries that gets recycled into new batteries
~$70 billion: The value of the Li-ion battery market projected for 2022
Sources: International Energy Agency, US Department of Energy.
Battery specialists and environmentalists give a long list of reasons to recycle Li-ion batteries. The materials recovered could be used to make new batteries, lowering manufacturing costs. Currently, those materials account for more than half of a battery’s cost. The prices of two common cathode metals, cobalt and nickel, the most expensive components, have fluctuated substantially in recent years. Current market prices for cobalt and nickel stand at roughly $27,500 per metric ton and $12,600 per metric ton, respectively. In 2018, cobalt’s price exceeded $90,000 per metric ton.
In many types of Li-ion batteries, the concentrations of these metals, along with those of lithium and manganese, exceed the concentrations in natural ores, making spent batteries akin to highly enriched ore. If those metals can be recovered from used batteries at a large scale and more economically than from natural ore, the price of batteries and electric vehicles should drop.
In addition to potential economic benefits, recycling could reduce the quantity of material going into landfills. Cobalt, nickel, manganese, and other metals found in batteries can readily leak from the casing of buried batteries and contaminate soil and groundwater, threatening ecosystems and human health, says Zhi Sun, a specialist in pollution control at the Chinese Academy of Sciences. The same is true of the solution of lithium fluoride salts (LiPF6 is common) in organic solvents that are used in a battery’s electrolyte.
Batteries can have negative environmental effects not just at the end of their lives but also long before they are manufactured. As Argonne’s Gaines points out, more recycling means less mining of virgin material and less of the associated environmental harm. For example, mining for some battery metals requires processing metal-sulfide ore, which is energy intensive and emits SOx that can lead to acid rain.
Less reliance on mining for battery materials could also slow the depletion of these raw materials. Gaines and Argonne coworkers studied this issue using computational methods to model how growing battery production could affect the geological reserves of a number of metals through 2050. Acknowledging that these predictions are “complicated and uncertain,” the researchers found that world reserves of lithium and nickel are adequate to sustain rapid growth of battery production. But battery manufacturing could decrease global cobalt reserves by more than 10%.
There are also political costs and downsides that recycling Li-ion batteries could help address. According to a CSIRO report, 50% of the world’s production of cobalt comes from the Democratic Republic of the Congo and is tied to armed conflict, illegal mining, human rights abuses, and harmful environmental practices. Recycling batteries and formulating cathodes with a reduced concentration of cobalt could help lower the dependence on such problematic foreign sources and raise the security of the supply chain.
Just as economic factors can make the case for recycling batteries, they also make the case against it. Large fluctuations in the prices of raw battery materials, for example, cast uncertainty on the economics of recycling. In particular, the recent large drop in cobalt’s price raises questions about whether recycling Li-ion batteries or repurposing them is a good business choice compared with manufacturing new batteries with fresh materials. Basically, if the price of cobalt drops, recycled cobalt would struggle to compete with mined cobalt in terms of price, and manufacturers would choose mined material over recycled, forcing recyclers out of business. Another long-term financial concern for companies considering stepping into battery recycling is whether a different type of battery, such as Li air, or a different vehicle propulsion system, like hydrogen-powered fuel cells, will gain a major foothold on the electric-vehicle market in coming years, lowering the demand for recycling Li-ion batteries.
Battery chemistry also complicates recycling. Since the early 1990s when Sony commercialized Li-ion batteries, researchers have repeatedly tailored the cathode’s composition to reduce cost and to enhance charge capacity, longevity, recharge time, and other performance parameters.
Some Li-ion batteries use cathodes made of lithium cobalt oxide (LCO). Others use lithium nickel manganese cobalt oxide (NMC), lithium nickel cobalt aluminum oxide, lithium iron phosphate, or other materials. And the proportions of the components within one type of cathode—for example, NMC—can vary substantially among manufacturers. The upshot is that Li-ion batteries contain “a wide diversity of ever-evolving materials, which makes recycling challenging,” says Liang An, a battery-recycling specialist at Hong Kong Polytechnic University. Recyclers may need to sort and separate batteries by composition to meet the specifications of people buying the recycled materials, making the process more complicated and raising costs.
Battery structure further complicates recycling efforts. Li-ion batteries are compact, complex devices, come in a variety of sizes and shapes, and are not designed to be disassembled. Each cell contains a cathode, anode, separator, and electrolyte.
Cathodes generally consist of an electrochemically active powder (LCO, NMC, etc.) mixed with carbon black and glued to an aluminum-foil current collector with a polymeric compound such as poly(vinylidene fluoride) (PVDF). Anodes usually contain graphite, PVDF, and copper foil. Separators, which insulate the electrodes to prevent short circuiting, are thin, porous plastic films, often polyethylene or polypropylene. The electrolyte is typically a solution of LiPF6 dissolved in a mixture of ethylene carbonate and dimethyl carbonate. The components are tightly wound or stacked and packed securely in a plastic or aluminum case.
Large battery packs that power electric vehicles may contain several thousand cells grouped in modules. The packs also include sensors, safety devices, and circuitry that controls battery operation, all of which add yet another layer of complexity and additional costs to dismantling and recycling.
All these battery components and materials need to be dealt with by a recycler to get at the valuable metals and other materials. In stark contrast, lead-acid car batteries are easily disassembled, and the lead, which accounts for about 60% of a battery’s weight, can be separated quickly from the other components. As a result, nearly 100% of the lead in these batteries is recycled in the US, far surpassing recycling rates for glass, paper, and other materials.
Several large pyrometallurgy, or smelting, facilities recycle Li-ion batteries today. These units, which often run near 1,500 °C, recover cobalt, nickel, and copper but not lithium, aluminum, or any organic compounds, which get burned. The facilities are capital intensive, in part because of the need to treat the emission of toxic fluorine compounds released during smelting.
Hydrometallurgy processing, or chemical leaching, which is practiced commercially in China, for example, offers a less energy-intensive alternative and lower capital costs. These processes for extracting and separating cathode metals generally run below 100 °C and can recover lithium and copper in addition to the other transition metals. One downside of traditional leaching methods is the need for caustic reagents such as hydrochloric, nitric, and sulfuric acids and hydrogen peroxide.
Researchers running bench-scale studies have identified potential improvements to these recycling methods, but only a handful of companies run recycling tests on the methods at the pilot-plant scale. In the Vancouver, British Columbia, area, an American Manganese facility converts 1 kg/h of cathode scrap to a precursor that manufacturers can use to synthesize fresh cathode material. Scrap refers to off-spec cathode powder, trimmings, and other waste collected from battery manufacturing.
Zarko Meseldzija, the company’s chief technical officer, describes the scrap as “low-hanging fruit,” a convenient material to use for experiments before boosting the scale of operations and moving on to actual spent batteries. He explains that the company’s process relies on sulfur dioxide for leaching cathode metals and does not use hydrochloric acid or hydrogen peroxide.
Battery Resourcers in Worcester, Massachusetts, runs a pilot plant that processes Li-ion batteries at a rate of up to roughly 0.5 metric tons per day and is actively working to increase capacity by a factor of 10, according to CEO Eric Gratz. Many current recycling methods yield multiple single-metal compounds that must be combined to make new cathode material. Battery Resourcers’ process precipitates a mixture of nickel, manganese, and cobalt hydroxides. This mixed-metal cathode precursor simplifies battery preparation and could lower manufacturing costs.
Meanwhile, the DOE’s ReCell team is pursuing so-called direct recycling methods for recovering and reusing battery materials without costly processing. One approach calls for removing the electrolyte with supercritical carbon dioxide, then crushing the cell and separating the components physically—for example, on the basis of density differences.
In principle, nearly all the components can be reused after this simple processing. In particular, because the method does not use acids or other harsh reagents, the morphology and crystal structure of the cathode materials remain intact, and the materials retain the electrochemical properties that make them valuable. Gaines says more work is needed to implement this cost-saving approach.
At the University of Birmingham’s ReLiB project, principal investigator Paul Anderson says the team sees a clear opportunity to boost the economic efficiency of battery recycling through automation. To that end, the team is developing robotic procedures for sorting, disassembling, and recovering valuable materials from Li-ion batteries. Birmingham’s Allan Walton, a coinvestigator, adds that using robotic devices to disassemble batteries could eliminate human workers’ risk of electrical and chemical injury. Automation could also lead to enhanced separation of battery components, increasing their purity and value, he says.
Although most of these strategies remain at an early stage of development, the need for them is growing. Currently, the number of end-of-life electric-vehicle batteries is low, but it’s about to skyrocket. Numerous impediments stand in the way of large-scale recycling, but “opportunities always coexist with challenges,” says An of Hong Kong Polytechnic. It’s time to take the bull by the horns and get serious about recycling Li-ion batteries.