From pv magazine 06/2021
Manganese is making a comeback in the battery world. In March, Volkswagen said a significant portion of its popular vehicles will have high-manganese batteries. Chinese battery maker SVOLT is supplying carmaker Great Wall with a quarter-maganese cobalt-free cathode, and Tesla’s mid-range vehicle line-up is also set to rely on a cathode with a composition of one-third manganese. And, in a recent white paper, Roskill reported manganese-rich chemistries were the focus of most new battery research.
The shifts away from nickel and cobalt have long been expected, but the question about what would fill the gap has lingered. Manganese has the potential to bring both supply stability and chemical stability to the cell.
“It doesn’t surprise me that materials manufacturers want to go toward manganese, because it’s inexpensive, and the cathode makes a significant cost of the battery,” Jason Croy at Argonne National Laboratory, told pv magazine.
The heavy metal has a long history in battery science, but in the past decade it has been sidelined to the more sensational nickel- and cobalt-rich chemistries. Its prominence in batteries has shrunk alongside cobalt; from nickel-manganese-cobalt (NMC) 111 batteries to the more popular NMC 811 now. The numbers in the particular “recipes” indicate the relative ratios of nickel, cobalt and manganese cathode composition, respectively.
As the battery industry matures and manufacturers pay more attention to the supply issues of nickel and cobalt, some are increasingly seeing manganese as an “issue-free” option. A 2020 Nature paper deemed it more “environmentally benign” than cobalt and nickel. A report from think tank Hallgarten & Company calls it the “least problematic battery metal.” Compared to many other cathode options, manganese is more abundant, cheaper, and devoid of intense consumer scrutiny.
While EV makers are worried about material shortages and bottlenecks, manganese offers more stable supply, as well as more stable chemistry as other metals are abandoned. The IEA recently noted that manganese demand would increase eight times in fulfilling the most aggressive sustainable development scenarios, and three times in the stated policies scenario. More high-profile elements like lithium and cobalt would increase significantly more, but scientists think manganese could play a much larger role and reduce the pressures on other mineral supplies.
“In our opinion, one of the reasons we’re interested in manganese is that a market is not going to be sustainable if it’s dependent on one element like nickel. Every EV in the world is not going to be 90% nickel,” says Croy. “It only seems logical to broaden the portfolio of materials, even if you’re not going to have something that’s the highest energy density material that’s possible.”
Manganese has been a small part of the composition of EV batteries; there may be more manganese in the steel casing of a car frame than in a battery. However, evolving understandings of mineral supply chains and consumer choices may make manganese a core part of EVs.
The manganese market is already robust and large, providing vital components for the steel industry. But batteries require a form of manganese that hasn’t previously been in high demand. The manganese that has traditionally been used in steel and aluminum alloys comes from a smelting process. Batteries like NMC and lithium-manganese-oxide (LMO) require dioxides and sulphates, which complicate legacy producers’ ambitions to ride the wave of battery demand.
Batteries comprise a small portion of global manganese demand, but as EV makers begin to seek stability, batteries have the potential to dominate the market, says Xin Sun, a researcher at Tsinghua University who wrote on manganese supply for batteries last year.
“If LMO batteries become mainstream, demand for manganese could increase tenfold,” he says. “Battery demand will then be the most important part of manganese’s consumption mix.”
Manganese supply is concentrated in a few countries and processing is largely dominated by China, as with other battery metals. However, manganese is widely distributed around the world in places that are beginning to build up capacity to process manganese oxide, which can be used in battery manufacturing. As China’s industrial boom slows and environmental rules inch higher on the policy agenda, it may seek to shift manganese processing and sourcing offshore.
Not every company is building up manganese production in traditional ways. In Europe, Euro Manganese plans to provide half of the bloc’s predicted demand to 2025 by revisiting mine tailings. The Chvaletice project in the Czech Republic can produce battery-grade manganese from a former pyrite open-pit mine, and it plans to open in 2022.
South African companies stand to benefit from a manganese boost. A report this year from the think tank Trade & Industrial Policy Strategies found that South Africa is party to a quasi-monopoly on manganese ore production. The country hosts 80% of known resources, which it has turned into about one-third of global production. Most ore is sent outside the country for processing due to rising electricity costs and disruptions at home, but the only major refiner outside of China, Manganese Metal Co., is located in South Africa and has a reputation for high-purity products.
The same report found that the manganese market was much more resistant to price shocks than other battery metals, in addition to being one of the cheapest. As manganese consumes more and more of the market that was once held by nickel- and cobalt-rich batteries, supply may have trouble keeping up, in which case prices could rise.
“The supply of battery-grade manganese dioxide could become a bottleneck when the technological route changes. Its price may skyrocket, as lithium carbonate and cobalt sulfate did in 2017-18,” says Xin Sun. “The potential reason is that output of manganese dioxide may not be growing as fast as demand.”
Recycling has the potential to avoid this bottleneck, although most manganese recycling has so far targeted scrap from steel manufacturing. Manganese itself has not been a target of most recycling, but in theory, lithium-ion batteries could have 90% of their manganese recovered. Most battery recyclers don’t spend the money to recover manganese when prices are low, but if miners have trouble building projects, prices may rise and recyclers could play a bigger role.
“Recovery of manganese from steel slag is critical to improve manganese recycling,” says Xin Sun. Even in steel scrap, the proportions of manganese are often too low to worry about recycling, but they can be a large source of recycled materials.
With the absence of recycling options facing a predicted uptick in demand, companies are only just beginning to mobilize, but with caution. It’s not yet certain whether manganese will grow in importance as some anticipate.
This uncertainty hasn’t stopped proponents of deep-sea mining in the Clarion Clipperton Zone, which point out that the industry could produce several times the manganese required by even the most aggressive climate policies. However, seabed miners have not yet proven that they can reduce risks to ecosystems and people, as well as a valid business case that can fit within strict regulations. Opponents of the practice note that there are other ways to fulfill or shrink demand before it’s ever necessary to dredge unknown parts of the Earth. More likely, legacy players distributed around the world on land will build up manganese dioxide plants.
“Battery-grade manganese dioxide is likely to have the same price spike as lithium [and] cobalt if commercialization of the lithium-rich manganese base material is achieved,” says Xin Sun.
Stable cathode crystals
A few years ago, Croy and scientists at Argonne set themselves a goal: engineer a battery that was as energy-dense as the prominent NMC-622 battery, but with 50% manganese and no cobalt.
“A cathode like that we think has a place in this massive energy storage future, specifically in terms of sustainability and supply chains,” Croy says. More abundant and cheaper manganese could lighten the load on nickel and cobalt, as well as target specific market niches.
In a battery cell, manganese has played a largely “spectator” role, Croy says. It’s not directly involved in electro-chemical processes, but it provides a critical role in stabilizing the cathode as lithium is taken out and the cathode approaches high oxidation. Cathodes with these kinds of stabilizing metals, like lithium-iron-phosphate, regularly rank higher in safety.
Designing a manganese-rich cathode has thus come in conjunction with designing a lithium-rich cathode. With additional lithium, the battery has added capacity and the manganese ensures that the cathode structure doesn’t collapse. In essence, the manganese provides enough stability for more lithium to be used to store and release energy. These batteries, also invented by Argonne scientists, typically have 5-10% more lithium, one-third manganese, and more than half nickel. In some cases, they’ve been able to reduce the cobalt content down to 4% and still achieve performance that rivals NMC-622, which is 20% cobalt.
“It turns out for these lithium-rich materials, that manganese is one of the most attractive options. Not only is it abundant and cheap, but it tends to form these structures that we like when it comes to excess lithium,” Croy says. Stability, though, continues to be an issue. The trick to achieving high-manganese, cobalt-free, lithium-rich cathodes, he says, is designing the cathode on an atomic level.
“The problem is that the structure is not as stable over long-term cycles, like a layered oxide like [NMC-622],” says Croy. “So that’s pretty much where all the work is going right now, to engineer those local structures to make them behave like we need them to.”
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