Current lithium-ion [Li-ion] batteries, while more energy-dense than their nickel-cadmium [NiCad] and nickel-metal hydride [NiMH] predecessors, are still limited to 200 watt-hours per kilogram [Wh/kg]. While Li-ion technology is fine for laptops and mobile devices, the inherent density limitation of Li-ion batteries has made the adoption of electric vehicles [EV] difficult.
Aside from the density limitations, an Li-ion EV battery is also extremely expensive, up to $10,000 in the case of the Tesla Model S 80kWh battery, which offers industry-leading range at nearly 300 miles. That being said, however, the Tesla Model S is also a luxury car, out of reach of the average consumer.
For years, researchers have theorized that a lithium sulfur [LS] EV battery might be three to five times more dense than Li-ion batteries. An LS battery would use pure lithium and sulfur electrodes, but wouldn’t last long because pure lithium tends to short circuit over time.
To fix this, a new material, lithium-sulfide [Li2S] can be used to replace the sulfur electrode, becoming the lithium source. The lithium electrode, no longer needed, can be replaced with cheaper graphite. The only thing left is to fix the insulating properties of Li2S. Carbon combinations help, but until now weren’t efficient.
Yuegang Zhang, a staff scientist at Lawrence Berkeley National Laboratory [BL], developed a new way to mix carbon with lithium-sulfide to produce a cathode with up to 67.5% Li2S. The new material Li2SC has all the right properties of lithium and sulfur with the conductivity of carbon. The new Li2SC battery could have a density between 300 and 600 Wh/kg.
Still, the lab and simulation results have to be tested in the real world, but it looks promising. If EV battery manufacturers can increase density and reduce price, EVs just might make it mainstream.