by When Chrysler unveiled its Halcyon Concept electric sedan on Tuesday, it noted that the vehicle incorporates an “800-volt lithium-sulfur battery,” which it said has an estimated carbon footprint of 60 percent less than the best batteries. Today.
The Lyten cells he “sees” do not include nickel, cobalt, or manganese among their metals. Instead, they use sulphur, which is lower on the atomic table than metals used in today’s lithium-ion cells – which means the cells are more energy dense, ie they weigh less for a given energy capacity . Sulfur is also the fifth most common element on earth, found in volcanic regions and near hot springs around the globe, which can reduce its raw material cost.
Last May, the release says, “Stellentis Ventures, Stellantis’ corporate venture fund, announced an investment in Lyten to accelerate the commercialization of Lyten 3D Graphene applications for the mobility industry.” In other words, Stellantis invested in a company making a major component of lithium-sulfur cells. So it makes sense that they would appear in a pure concept EV that seems far from production ready.
Unfortunately, when Car and driver contacted Stellantis for more details, the company declined to discuss the new cells. “Thank you for reaching out, but at this time we are not providing additional details on this future battery technology as planned for the Halcyon concept,” a Chrysler/Dodge spokesperson responded.
Cell of the Future?
Lithium-sulfur cells exchange sulfur for the various mixtures of nickel, manganese, cobalt, and aluminum (collectively known as NMCA) found in most of today’s EV cells. In theory, this results in a higher energy density than current cells, which translates to greater EV range in less volume – and less mass. But, to this day, it’s not just a road vehicle that’s driven by technology.
However, efforts to reduce the use of rare and expensive metals have increased as EV makers look beyond today’s NMCA and the lower-cost but less energy-intensive iron phosphate (LFP) chemistries. The goal is to use other elements – especially abundant ones – that have the right transport properties.
To assess where lithium-sulfur cells stand for electric vehicles, Car and driver she contacted Haresh Kamath, director of energy storage at the Electric Power Research Institute, known as EPRI.
We asked Kamath if lithium-sulfur batteries were a credible alternative to today’s lithium-ion cells. They are, he said, “and they have been recognized as such for 30 years—but, it will probably take years of steady work on the technology to [create] successful products, scalable manufacturing, and commercialization.”
Even with all these challenges to overcome, however, “there is no guarantee that commercial lithium-sulfur products will be cost-competitive with lithium-ion,” Kamath warned. “Mass commercialization will again require us to address the major issues of fire and explosion hazard in a new technology with important safety differences from lithium-ion.”
He continued: “Taking any battery technology from the lab to the field is no joke: it requires a lot of capital investment and the way cells can be designed, built, qualified and continuously scaled up, then batteries, then systems,” Kamath continued. “This takes years. Even mature, experienced, well-capitalized companies rarely hit their timelines.”
That said, “companies developing batteries today are massive operations backed by massive investment and the willingness to spend the time it takes to get there,” Kamath said. “As a result of these types of scaling efforts by Sony and Panasonic in the 1980s, the commercialization of the lithium-ion battery was successful. These efforts are now being applied to solid-state batteries, silicon anodes, and others.”
But, warns Kamath, lithium-sulfur is not a drop-in replacement for lithium-ion. He highlighted four important points that he believes developers must pay close attention to:
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The cell voltage is half that of a normal lithium-ion cell at full charge (2.1V/cell vs. 4.2 V/cell). This requires more cells per battery, which can reduce energy density.
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The cycle life for lithium-sulfur is very poor, in multiple cases. Many researchers say they have addressed these issues, but we have yet to see data showing that these cells perform as well as lithium-ion.
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Unlike lithium-ion, lithium-sulfur exhibits side reactions that create inefficiencies during charging, reducing charging efficiency and generating heat that must be handled carefully to maximize battery life.
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Lithium-sulfur lithium is metallic, so it requires a different safety approach from lithium-ion cells of all chemistries.
Not quite ready
In short, lithium-sulfur battery chemistry is still in development. Like solid-state lithium-ion cells, the chemistry shows theoretical promise – but has not yet progressed to the point where it will soon be scaled up for mass production and use in electric vehicles. As Kamath notes, battery development takes a very long time.
That means Chrysler EVs from the late 2020s, whatever they are, are more likely to be powered by some variant of today’s lithium-ion cells than by lithium-sulfur cells.
The author wrote occasional analyzes of the electric car world for the Electric Power Research Institute (EPRI), which is how he got in touch with its director of energy storage, Haresh Kamath, mentioned in the piece above.
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