Lithium-ion battery technology has made impressive gains over the years. Today’s cells are cheaper than they’ve ever been, but lithium-ion still leaves a lot to be desired in terms of energy density compared to liquid hydrocarbon fuels. Which means that putting enough of them in a car to give it an acceptable range adds a lot of mass and volume. Which is where solid-state batteries come in.
In a traditional battery, a pair of electrodes are immersed in an electrolyte solution, and it’s this liquid electrolyte that allows ions to move from one electrode to the other. But liquid electrolytes can leak, and that’s not a great thing, whether the material is highly corrosive, as in a lead-acid battery, or highly flammable, as in a lithium-ion battery. So researchers around the world have been experimenting with batteries that use a solid electrolyte instead, with a particular eye on using them in electric vehicles.
And now, it seems it’s a technology that is ready to be deployed, as Mercedes-Benz just announced that its new eCitaro and eCitaro G city buses will be available with roof-mounted solid-state battery packs, developed in conjunction with the Canadian power company Hydro Quebec.
Although details are still rather limited right now, Mercedes-Benz says that the solid-state pack has a 25-percent higher energy density than even the most advanced lithium-ion chemistry. It also says that the solid-state battery has a much better service life than lithium-ion and is warrantying these batteries for 10 years or an energy throughput of 280MWh. When configured with a total of 441kWh onboard (composed of seven 63kWh packs), an eCitaro G has a range of up to 137 miles (220km) under favorable conditions, or 105 miles (170km) in the depth of winter with the bus’s heaters running.
However, these solid-state batteries aren’t perfect. In particular, they aren’t able to fast-charge at rates comparable to lithium-ion, which is why Mercedes-Benz is also offering the bus with an optional lithium-ion pack that can be charged at 150kW or even 300kW instead. This uses a nickel-manganese-cobalt chemistry and comes in assemblies of 33kWh that can be combined to give a bus up to 396kWh in total.
Listing image by Mercedes-Benz