Solid-state batteries sometimes sound a bit like the missing link that would punt electric vehicles soundly into mainstream acceptance.

The list of potential virtues for solid-state tech, which would replace the polymer/gel electrolyte commonly used in lithium-ion cells with a solid one, is impressive: a longer driving range; smaller packaging; reduced chances of fire; easier cooling and conditioning; faster charging; and a longer service life.

Any automaker that can capitalize on solid-state tech before the others will probably enjoy an advantage on the market. But it might not be the day/night game-changer that some giddy futurists had anticipated earlier this decade. Automakers are splashing some cold water on what are perhaps some overheated expectations for what the technology can deliver and how soon it will arrive.

Volkswagen credited its anticipated rapid evolution of lithium-ion cells for its impressive energy-to-weight numbers in the next-generation battery packs it recently detailed for its MEB vehicles set to debut in a U.S. vehicle beginning in 2020. VW estimates that cell energy density—both by volume and weight—will increase nearly a quarter from 2018 to 2025, thanks to higher nickel content and, eventually, a higher-voltage electrolyte.

CHECK OUT: Battery tech may be getting a big solid-state boost soon

By then it sees lithium-ion (non-solid) cells offering 0.8 kwh per liter. Jumping to solid-state around then or later, it anticipates at an early stage it could pack another 25 percent more energy in the same space but offer no additional weight advantage.

VW’s own internal expectations might show a reality check versus what had been suggested at the time of VW’s $100 million investment in QuantumScape—a potential energy-density improvement of as great as 2.5 times that of current batteries.

Energy density (by volume and weight) had been increasing at a rate of about 30 percent every two to three years. That rate is due to slow; Bloomberg New Energy Finance anticipates energy density to improve 5-7 percent per year from 2018 into the 2020s.

DON'T MISS: Battery legend Goodenough not done yet: new solid-state chemistry introduced

“The use of solid-state batteries may result in another breakthrough in the second half of the next decade,” said Thomas Ulbrich, the member of the Volkswagen Group board of management for e-mobility, last month. Ulbrich noted that a limited test fleet of vehicles with solid-state batteries—possibly from its joint-venture development efforts with QuantumScape, could hit the road as soon as 2023.

That corresponds with what the technical development chief of fellow VW Group brand Audi, Ulrich Widmann, said last month—that it’s expecting solid-state batteries to arrive in 2025 to some extent. “Inside the VW Group we have really good connections to all this development,” he said. “We are partners in that development.

Widmann pointed out that there are definitely obstacles remaining. “We don’t know whether they can solve all of these things, but we have to prepare future architectures,” he said, so that they can take advantage of it if and when it arrives.

READ THIS: Fisker still aims at solid-state electric-car batteries, as patents attest

BMW is also anticipating that solid-state may first appear in one of its production vehicles around 2025. But there are a few outliers. Toyota, based on reports, could be aiming to make the jump in high-sales-volume vehicles before then.

Don't look for solid-state batteries to go into tens of thousands of vehicles anytime soon. VW may be planning for the possibility of solid-state batteries in some vehicles, but it doesn’t anticipate them becoming common in its EV lineup until 2030 or so—at which time it's hoping it will have made 10 million EVs globally. The attitude about the tech is similar in remarks made by BMW and Audi executives—and even Tesla’s Elon Musk and JB Straubel.

Perhaps the big players are being too conservative, and the longer timeline is unnecessary. Only time will tell, as some fledgling automakers such as Dyson and Fisker Inc. embark on the development of EVs that skip right to solid-state tech.

Sign up to get the latest green car and environmental news, delivered to your inbox daily!

I agree to receive emails from Green Car Reports. I understand that I can unsubscribe at any time. Privacy Policy.

The Leaf-compatible Fermata Energy charger will be the first bidirectional system in an EV able to supply power to the grid, Nissan claims.

Which automaker announced a big shift to cylindrical cells and a battery strategy sounding like that of Tesla? Which boxy production-bound Jeep EV is in “brotherhood” with the Wrangler? This is our look back at the Week In Reverse—right here at Green Car Reports—for the week...

BMW’s shift to cylindrical cells is official. Bollinger B1 and B2 electric trucks are back on, thanks to Mullen investment. Harbinger bows in the commercial-EV space with claims it can cost less. And we drive the Lexus RX 450h+. This and more, here at Green Car Reports. In a brief drive...

BMW is reversing course and embracing a type of cell it previously rejected, with huge goals to cut costs, boost efficiency, and perhaps speed up EV adoption.

EV startup says scalable powertrains can make electric commercial vehicles more competitive.

The Bollinger B1 and B2 were bound to be rugged cult-favorite heavy-duty EVs, and now with Mullen Automotive's majority stake in Bollinger they might once again be a possibility.

The RX 450h+ will cost more and weigh more than hybrid versions of the popular Lexus crossover—without remarkable performance or electric range.

Jeep rolls out its first three fully electric models. Rivian and Mercedes partner for electric vans. StoreDot sends its five-minute-charging battery tech out for testing. And Chevy confirms that the upcoming Equinox won’t be a niche model. This and more, here at Green Car Reports. Chevrolet...

The two companies aim to share costs around manufacturing electric vans, with plans for a factory in Europe.

If StoreDot's cells prove ready for production, they could enable EVs with charge rates to approach those of gas-station refueling.

GM sees the Equinox EV as leading the charge beyond early adopters—and a $30,000 starting price point is an important part of that.

Avenger, Wagoneer S, and Recon are among the EVs on the way by the end of 2025, plus a full portfolio of 4xe plug-in hybrids.