Stellantis and Zeta Energy Corp have teamed up to change the game for the electric car industry. They aim to develop the next generation battery for electric vehicles with more autonomy, more power, 50% faster charging for less than half the cost: lithium-sulfur batteries.
Lithium-ion batteries have been key in the industry since 2008, when Tesla launched the Roadster, which represented a giant evolution. Since then there have been multiple attempts to overcome them, such as solid-state batteries or LFP batteries. Why could lithium-sulfur (Li-S) batteries, available since the 1960s, be a third way?
They have not been thought about until now because they had short life cycles. As the battery discharges, the sulfur on the cathode side reacts with the lithium, creating lithium polysulfides that diffuse through the electrolyte to the anode, leaving deposits. Since not all of these polysulfides returned to the cathode during charging, the battery degraded very quickly.
Well then. Zeta (based in Texas, USA), partners with Stellantis and believes it has solved the problem. They have advanced in materials that create a barrier to trap these polysulfides, preventing them from “moving” between the electrodes. This way the battery should not die prematurely.
Advantages of lithium-sulfur batteries
- Li-S batteries are lighter than lithium-ion batteries. If a lithium-ion battery usually contains between 150-250 Wh/kg) of energy, they go up to 400-600 Wh/kg. The batteries would weigh between 30 and 50% less, improving the behavior of the vehicles… and reducing consumption.
- Additionally, both companies claim to improve fast charging speeds by up to 50% compared to traditional lithium-ion battery packs. They also operate at lower voltages, so they absorb energy more quickly.
- Lithium-steel batteries have simpler chemistry and do not rely on the slow diffusion of lithium ions in solid materials
- Additionally, Li-S batteries are expected to cost less than half the price per kilowatt-hour of Li-ion ones. Sulfur is abundant and Zeta’s Li-S batteries use waste materials such as methane and unrefined sulfur from various industries. They also rule out expensive and difficult to obtain materials such as cobalt, graphite, manganese or nickel.
The idea is to use locally sourced materials and use existing factories to assemble its batteries, reducing CO2 emissions. Furthermore, although sulfur can be found in gunpowder, matches or fireworks, they are safe: the sulfur in Li-S batteries is in a solid state, they do not have flammable electrolytes like those in a conventional battery. And it is usually the electrolyte that causes fires in batteries.
Yes, having a lithium anode can form dendrites and from there short circuits and fires that are difficult to put out. Of course, lithium sulfur batteries are less prone since the chemical reactions of sulfur are less exothermic. Since they also have no cobalt or nickel to fuel a fire, they are considered safer than the batteries in modern electric cars or your mobile phone.
Of course, don’t expect to see them until at least 2030 in street cars… but Li-S batteries could redefine our way of thinking about electric mobility.
