Lithium-ion battery technology has made great strides over the years. Cells today are cheaper than they have ever been, but lithium-ion still leaves much to be desired in terms of energy density compared to liquid hydrocarbons. Which means putting enough of it in a car to give it an acceptable range adds a lot of mass and volume. And this is where solid state batteries come into play.
In a traditional battery, a pair of electrodes are immersed in an electrolyte solution, and it is this liquid electrolyte that allows ions to move from one electrode to another. But liquid electrolytes can leak, and that’s not a big deal, if the material is highly corrosive, like in a lead-acid battery, or highly flammable, like in a lithium-ion battery. So researchers around the world have experimented with batteries that use a solid electrolyte instead, with a particular eye on their use in electric vehicles.
And now, it looks like it’s ready-to-roll technology, as Mercedes-Benz has just announced that its new eCitaro and eCitaro G city buses will be available with roof-mounted solid-state battery packs, developed in collaboration with Canadian power company. Hydro Quebec.
While the details are still quite limited at this time, Mercedes-Benz says the solid-state package 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 lifespan than lithium-ion and guarantees these batteries for 10 years or an energy yield of 280 MWh. When configured with a total of 441 kWh on board (consisting of seven 63 kWh packs), an eCitaro G has a range of up to 137 miles (220 km) in favorable conditions, or 105 miles (170 km) in the dead of winter with bus heaters running.
However, these solid-state batteries aren’t perfect. Notably, they are unable to recharge quickly at speeds comparable to lithium-ion, which is why Mercedes-Benz also offers the bus with an optional lithium-ion pack that can be charged at 150kW or even 300kW. This uses nickel-manganese-cobalt chemistry and is available in 33kWh batches which can be combined to provide a bus of up to 396kWh in total.
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