In the search for more powerful, faster-charging, longer-life batteries, researchers have set their sights on a technology known as solid-state, though conventional wisdom suggests this alternative to familiar lithium-ion batteries won’t make it to market until later this decade.
Apparently, somebody failed to tell Mercedes-Benz. The German manufacturer says it’s ready to launch the first production application of solid-state batteries in its new eCitaro G articulated bus. Eventually, the technology could wind up in Mercedes passenger vehicles, as well.
The new batteries aren’t a panacea. Though eventually expected to charge up almost as fast as you can fill a gas tank, Mercedes says these first-generation solid-state batteries will take longer than current technology. For customers who need more rapid charging, they still can order the eCitaro with a specially formulated lithium-ion pack.
Conventional batteries are filled with a slurry-like material. That creates a number of drawbacks, including limits to energy density, or the amount of power that can be stored, as well as power density, the speed at which power can be charged and discharged. These batteries also have the unfortunate potential to catch fire if punctured or shorted out, a problem that has plagued a number of EV manufacturers, notably Tesla.
As the name suggests, solid-state batteries replace that liquid slurry with a carbon-ceramic material that is nearly indestructible and non-flammable. The technology is expected to have a number of other advantages which appear to be playing out with the first-generation batteries Mercedes is bringing to market.
“They have a very high energy density which is around 25% greater than the coming generation of traditional lithium-ion batteries with liquid electrolyte,” Mercedes notes in a release. “The result is an impressive energy content of 441 kWh for the new eCitaro G. This battery technology is also free of the chemical element cobalt and therefore especially environmentally friendly in the manufacture of the components.”
Energy capacity translates, of course, into range,
The new batteries are expected to have a much longer life than the lithium-ion technology currently used in vehicles like the eCitaro, Mercedes guaranteeing each pack for 10 years or up to 280 megawatt-hours of energy usage. That would work out to about 635 complete charge cycles were the batteries to be fully drained, though in most cases, only some of the energy capacity will be drained on a daily basis.
The one surprise is that the new solid-state batteries will charge up more slowly than comparable lithium-ion technology. The automaker did not explain why, though manufacturers often err on the side of caution when charging new battery formulations to reduce the risk of cutting their life span. Eventually, proponents of solid-state technology claim they will actually be much faster, so much so that charging up a vehicle could take about the same time as it would to fill up a gas tank.
For those that need faster charging, the eCitaro G will be offered with an alternative known as NMC, a version of lithium technology particularly suited to bus applications, according to Mercedes. Even here, the automaker said it has boosted potential battery storage capacity from earlier versions of the bus – though still about 25% less than what the solid-state system can provide. The NMC batteries can be retrofitted into existing eCitaro buses to boost range.
The Mercedes announcement should give a big boost to solid-state proponents who had watched other development programs slip behind schedule and some, like the Sakti3 technology that Dyson had bought for its now-aborted EV program, abandoned entirely.
With Mercedes planning to roll out an array of plug-in vehicles, including both PHEVs and all-electric BEVs, it remains to be seen if and when solid-state will show up under the hood of one of those models.