The element sulfur is cheap and plentiful. There‘s so much of it on Earth that big yellow piles of the stuff commonly sit outside of fossil fuel refineries after it’s been stripped of oil and natural gas.
But electrochemists — scientists who research how chemical reactions create electricity — have long seen sulfur as a tantalizing prospect for incredible energy storage. That’s because the combination of lithium and sulfur has the potential to make an extraordinary battery that could both store more energy and be made more cheaply than the lithium-ion batteries used today in laptops and electric vehicles.
A commercial lithium-sulfur battery could make "electrification something that is abundant," where "it’s easy to electrify everything," said Celina Mikolajczak, chief battery technology officer of startup Lyten, at the Bloomberg New Energy Finance Summit in San Francisco in January. Lyten is developing a lithium-sulfur battery.
Current lithium-ion batteries are hampered by the constrained supply of nickel. Cobalt, another key ingredient in today’s lithium-ion batteries, is largely mined in the Democratic Republic of Congo, where the cobalt mines are plagued with human rights issues. The idea is that sulfur’s abundance and low cost could make a lithium-sulfur battery far cheaper, and less dependent on problematic regions, than the current lithium-ion battery pack, which costs around $150 per kilowatt-hour.
At the same time, the use of sulfur in a battery could provide a theoretical super high energy density, or amount of energy that the battery can hold on a single charge. Today’s EVs can drive about 300 miles per charge, but a lithium-sulfur battery could potentially double that range — or create an EV that’s half the weight of the lithium-ion-powered equivalent.
At least these are the big hopes. Lithium-sulfur batteries are still confined to the research labs.
But as money flows into an emerging U.S. battery sector from the Inflation Reduction Act, companies and scientists are scrambling to crack the code to develop a breakthrough battery that could be next in line after lithium ion. At stake is technology that could potentially accelerate both EVs and storing clean energy.
A fussy battery
The big question is whether a company can develop and manufacture a lithium-sulfur battery to work as advertised when made in large volumes. While startups, researchers and big battery companies are working on the chemistry, no lithium-sulfur batteries are commercially manufactured at scale.
"Sulfur is unruly. Lithium is unruly. When you put these two elements together you get a chemistry that is really difficult to work with," said Mikolajczak at the BNEF summit. "There’s a reason this chemistry hasn’t been exploited for a long time."
One problem is that sulfur, used as the cathode of the lithium-sulfur battery, goes through a phase change as it’s charged and discharged. It moves from a solid to a liquid and back to a solid again. That makes it really "fussy," said Mikolajczak. "It’s painful to work with. It makes your head explode."
Early attempts at lithium-sulfur batteries saw the sulfur compound dissolve into the electrolyte, the medium (usually liquid) through which the ions charge and discharge.
Many attempts to develop lithium-sulfur batteries have ended up with low-functioning batteries that develop dendrites, tiny metallic structures that can form during the charging process. Dendrites cause short-circuiting and battery failure, and lithium-sulfur batteries have had trouble maintaining high charging cycles.
At stake is technology that could potentially accelerate both EVs and storing clean energy.
Mikolajczak’s company Lyten — an 8-year-old startup based in San Jose, California — can manufacture a crumpled form of graphene that it says is great at essentially holding the sulfur together in the battery while also acting as a conductor. The company says it’s seen promising results in its trials, and Mikolajczak told GreenBiz in an interview that she expects Lyten to be able to develop "a respectable battery cell" in about a year. It won’t be in high volumes, but early customers will be able to use it, she said. Lyten plans to sell the batteries to automakers and manufacturers of drones and flying vehicles.
Researchers at Argonne National Laboratory have also recently made some progress on the lithium-sulfur battery. Argonne scientists created a porous sulfur-containing layer within the battery that can help protect the materials from the dendrite destruction.
In the lab, Argonne’s lithium-sulfur battery was able to charge and discharge 700 times, which is competitive with today’s lithium-ion batteries. The Argonne scientist team was able to see the success of the layer within the lithium-sulfur cell by using a state-of-the-art X-ray diffraction machine in one of Argonne’s labs. It’s a billion-dollar cutting-edge tool.
Argonne scientist Guiliang Xu — one of the authors of a recent paper — told GreenBiz that Argonne plans to work with the private sector to commercialize the technology and build a prototype battery.
The U.S. of course isn’t the only place where researchers are trying to unlock the lithium-sulfur code. The European Union funded the LISA project, which just concluded, and looked at developing innovations around lithium-sulfur battery cell design.
Korean giant LG, through its energy arm LG Energy Solution, has said it plans to try to commercialize a lithium-sulfur battery in 2025. A German startup called Theion says on its website that it’s also trying to bring a lithium-sulfur battery to market soon.
Funding is flowing
With new funds available from the recently passed IRA, U.S. companies could be ready to capitalize on government support and the growing EV market.
Lyten’s Mikolajczak called the IRA "huge" for new battery development. "Battery-making is super capital-intensive. [The IRA subsidies] give everyone much more of a fighting chance," Mikolajczak said to GreenBiz.
At the same time, automakers are becoming more aggressive when it comes to investing in battery technology and battery supply chain. Companies such as GM, Daimler and Ford are partnering with promising battery startups and battery mineral suppliers. Other pure play EV companies such as Tesla and BYD have long invested heavily in their battery technology.
Climate tech startups have appeared to be relatively more immune to recession fears and layoffs than their IT startup counterparts. Private investors continue to fund climate tech startups, including battery-makers such as Lyten, which has raised over $200 million in funding to date.
Despite the recent innovations and funding, lithium-sulfur batteries still have a long road ahead. The current lithium-ion battery powering today’s EV revolution has benefited from 30 years of progress. Expect many years — if not decades — before a lithium-sulfur battery pack is used in a car as mainstream one of Tesla’s or GM’s.
The first lithium-sulfur batteries will likely end up in vehicles and devices that need to be super lightweight. Because the lithium-sulfur battery has double the energy density, it could power a vehicle with half the weight.
That light weight could help determine the first customers. When lithium-sulfur batteries finally break out of the lab, we shouldn’t expect the first ones to be powering cars on the roads. Instead it’ll likely be drones and small flying vehicles in the skies.