Stellantis lithium-sulfur EV batteries: cheaper, lighter, more range

In a potentially game-changing move for the EV industry, Stellantis and Zeta Energy Corp have teamed up to develop the next-generation EV battery with more range, more power, 50% faster charging, and at less than half the cost. Lithium-ion batteries have powered the electric vehicle (EV) revolution since 2008, when Tesla introduced the Roadster to the world, powered by 53 kWh of Li-ion goodness, with a range of around 245 miles (394 km). The iconic Roadster nearly doubled the 140-mile (225 km) range of General Motors’ 1999 EV1, which powered by an incredibly heavy, 26.4 kWh nickel-metal hydride (NiMH) battery pack. Despite lithium-sulfur (Li-S) batteries having been conceptualized in the 1960s, practical applications were limited due to issues like poor life cycles and capacity loss from something called “the polysulfide shuttle effect,” unique to Li-S batteries. As the battery discharges, sulfur at the cathode side reacts with the lithium, creating lithium polysulfides which diffuse through the electrolyte to the anode leaving deposits. While charging, some polysulfides would migrate back to the cathode, but not all, degrading the battery very quickly. Texas, USA-based Zeta, in partnership with global automotive giant, Stellantis, reckons it’s got that figured out. Recent advancements in material technology and the development of barriers and coatings trap these polysulfides, preventing them from “shuttling” between the electrodes, effectively fixing the pesky premature death effect. The collaboration could mean a leap in EV battery technology: Li-S is significantly lighter than their Li-ion counterparts. A Li-ion battery typically packs between 150-250 watt-hours per kilogram (Wh/kg) of energy in them. Li-S can achieve up to 400-600 Wh/kg. That’s a lot of juice. Li-S can provide same amount of power with a smaller package – meaning not only greater range in your EV because the batteries are going to weigh 30-50% less, but better handling and performance. The lighter, the better. The two companies also claim improvements in fast-charging speeds by as much as 50% over traditional lithium-ion battery packs. Li-S has a simpler chemistry and doesn’t rely on the slow diffusion of lithium ions into solid materials (like the graphite in Li-ion). Instead, reactions occur directly between the lithium and sulfur which is faster and more straightforward. They also operate at lower voltages, so they don’t have as much resistance during charging, making them absorb energy more quickly. The kicker: Li-S batteries are expected to cost less than half the price per kilowatt-hour than Li-ion. Sulfur is abundant and Zeta’s Li-S batteries use waste materials like methane and unrefined sulfur from various industries. They also ditch expensive, hard-to-source materials like cobalt, graphite, manganese or nickel; which Li-ion is also made from. Zeta’s approach can utilize locally sourced materials and use existing factories to assemble its batteries, slashing CO2 emissions compared to existing battery tech. They’re safer than Li-ion: Contrary to what you might think of “sulfur” being in the name, it’s not like what you find in gunpowder, matches or fireworks. The sulfur in Li-S is in a solid state. Li-S batteries don’t have flammable electrolytes like what you’d find in a typical Li-ion battery. It’s often the electrolyte that causes battery fires. They’re not without any flaws, however, as the the use of a lithium metal anode can pose risks like dendrite formation, which can lead to short circuits. But if you’ve ever seen an EV battery fire, you know it to be highly destructive. Fire departments often have to simply wait until the fire burns itself out when a lithium-ion battery “vents” or explodes. Punctures or thermal runaway (usually from over-charging) lead to chain reactions that create a lot of heat in lithium-ion batteries. Li-S batteries are less prone to this as the sulfur’s chemical reactions are less exothermic. And without ingredients like cobalt and nickel to fuel a fire, Li-S is considered to be safer than the batteries that power modern EVs, your laptop, your phone, et cetera. With Stellantis aiming to roll out Li-S-powered EVs by 2030, this partnership could redefine how we think about electric mobility.