Hi All - Any rumors out there about when MB is hoping to switch to solid state batteries instead of the current Lithium Ion? These batteries promise double the range and much faster charge times, and so whenever they're introduced they will destroy the resale value of any old style EV. I'm headed in the electric direction, but sure would be tempted to wait for this new battery type if it's close.

 

So, on this topic, disclaimer, I'm not a battery chemist, instead I'm a professor of Computer Science & Engineering, but I do have more than a passing familiarity with lithium ion battery systems. Take my words with whatever grain or pinch of salt you feel necessary.

First off, there's a timeline issue. As you'll notice, many manufacturers are either posting a 5-year window on solid-state batteries, or have current "hybrid solid state" models in existence. The current models are not really competitive with non-solid-state batteries. Not saying they won't be, but they were hailed as a huge breakthrough, rather, they are hybrid solid-state batteries, not true solid-state batteries. All other batteries in this category have been "five years away" for the past 20. Not saying we can't get there, but presently, there are major challenges in current output, reliability, and general performance. "Double range" is deceptive in this case because the technology does not exist to reliably allow for this. It's been a while since I've read the numerous articles on the challenges of true solid-state batteries, but at present, there are significant durability concerns, for sure. While they *can* charge faster, they don't work well outside of strict laboratory conditions. Can "5 years" do it? Quite possibly. But we have quite a way to find out in this case, and I'm quite convinced those targets are aspirational instead of driven by engineering thinking.

Secondly, there's energy density. We all know that lithium-based batteries have a far lower energy density than say, gasoline or diesel. Currently, Li-Ion gives us around 0.5-0.8 MJ/kg, while gasoline and diesel are in the mid 40s. Of course, combustion engines run at 25-35% thermal efficiencies (yes, I know there are up to 50% cases in large transport and theoretical engines, but not in passenger vehicles), so the majority of the fuel potential is wasted in terms of kinetic energy. Still, if we doubled the energy density of a lithium battery, we enter into much more dangerous thermal runaway domains. It's something that could possibly be solved, but is a major factor when considering a higher energy density. The safety of the cell has to be paramount, and I haven't seen a whole lot of convincing work (not to say it doesn't exist, I just haven't seen it) on how the increased energy density will be managed in terms of thermal runaway potential. Higher energy density means more potential for fires, simply put.

Lastly, we have to consider that there are *many* technological changes that will be leading to the next big things. Energy density has changed marginally in Lithium Ion cells over the past 30 years. But other technologies have stepped in as well. From novel charging, to battery management, to perhaps even wireless charging (I'm skeptical on this one for now), the next big change in BEV technology will always be around some corner, and many of them will come to be. Solid-state has and always will sound fantastic. But currently, it's not much beyond marketing hype. Consider QuantumScape, or the many other Wallstreet darlings for solid-state battery tech that had huge IPOs and incredible press. Where are they? Unable to scale. Not saying they can't, but even their executives are fully admitting that they have a long ways to go before they get out of prototype stages in the lab.

So, in summary, if you like the EQE, don't worry about solid state batteries - just go for it! It's a fantastic car. Yes, eventually other technologies will come around. But people still bought early combustion vehicles in the 20th century even though changes were revolutionary, not evolutionary at the time. For now, it's a super solid car, and still a good investment. They did a great job with it.

 

Headlines I found from recent years:

• 2023: "Toyota to roll out solid-state-battery EVs as soon as 2027"
• 2020: "Toyota's Quick-Charging Solid-State Battery Coming in 2025"
• 2017: "Toyota’s new solid-state battery could make its way to cars by 2020"
• 2014: "Toyota to Offer High Performance Solid-State Batteries in 2020"

You see a common scheme? Lol. And media just keeps eating these predictions and don't even seem to honestly question them.

 

Thank you bytemaster. As a retired engineer, I really appreciate the depth and thoroughness of your reply.

 

The delay at least "by 2020" might have to do with what was going on in the world, we won't know and I guess they predicted 2025 and realized it is not realistic as the material shortage is still an issue and mass production will be difficult at least for now.