Solid-State Batteries: Hype vs. Reality

If you’ve been following battery tech for the past decade, you’ve heard the solid state battery story before. Toyota promised them by 2025. Samsung said they were just around the corner. QuantumScape’s stock soared on promises of revolutionary batteries. And yet here we are, still driving cars with the same lithium-ion tech. And if the sliding deadlines weren’t enough of a headache, the term “solid state battery” has become a marketing buzzword and is quickly losing meaning as a result.

But here’s the thing … 2025 might actually look different. Companies aren’t just filing patents anymore. They’re opening factories. They’re putting innovative new batteries in actual vehicles. Mercedes just drove 749 miles on a single charge with one. MG is taking pre-orders for a car with a semi-solid-state battery for under $15,000.

So is this finally it? Are solid-state batteries, or their close relatives at least, finally here? Or are we just being sold another round of hype?

The Definition Problem and What Actually Matters

Before we dive into who’s shipping what, we need to address a credibility crisis. Remember our investigation into Yoshino’s so-called solid state battery? When the company TechInsights cracked it open, they found liquid electrolyte in both the anode and cathode.¹ So was it not a solid state battery? Well, yes and no.

“Solid state battery” has become an umbrella term. What you’re probably picturing is an “all solid state battery” or ASSB: zero liquid.² However, there’s also semi-SSBs, where less than 10% of the electrolyte is liquid. Less than 5% means it’s a quasi-SSB.³ The catch? These definitions aren’t universally agreed upon. As QuantumScape’s Tim Holme told me, each company has their own thresholds. Some don’t even base it on liquid content, they base it on performance instead. Have you ever been in the middle of eating “ice cream” only to notice that its actually labeled as a “frozen dairy dessert”? It’s a lot like that, except we don’t have a USDA equivalent for solid state batteries.

Here’s my take: I’m not sure it matters that much. What matters is the user experience. Does it charge faster? Give you more range? Is it safer? If a battery charges to 80% in 10 minutes and won’t catch fire when punctured, I don’t care if it has 3% liquid electrolyte or zero. The terms are becoming meaningless, and combined with ever-sliding deadlines, we’ve got a real credibility crisis.

Even if this boom of prototypes and pilot factories is real, commercialization still lies beyond what experts call “development hell.”⁴ As Dr. James Edmondson, IDTechEX’s vice president for research, told Forbes, while progress is generally being made, he thinks real commercialization is still years away.⁵

“In terms of seeing them in larger production volume vehicles we wouldn’t expect that until the 2030s. Even by 2035, we are predicting just over 100 GWh of capacity for solid-state batteries, compared with our prediction for the overall EV car market at around 3,800GWH in the same year.”⁵

At this point, it’s a necessity to be skeptical about any and all SSB claims. So let’s look at what’s actually real, what’s close, and what’s still just promises.

Close to Shipping

Let’s start with what you can actually get your hands on, or at least pre-order right now … well, depending on the part of the world your in.

Chinese company SAIC Motor officially opened up pre-sales for the all-new MG4 model this past August.⁶ This makes it among the very first mass-produced vehicles to sport a semi-solid-state battery. And yes, it’s a semi-SSB with a reported 5% liquid electrolyte, not a full ASSB.

SAIC claims its battery successfully passed safety tests, including a three-direction needle penetration test without any smoke. But it’s not stated (at least not in English) if those are in-house or third-party tests. There’s not a lot of reporting about what the exact stats of this battery are. Based on information revealed during a July media event, the semi-solid-state battery will have a range of 537 kilometers or 333 miles and an energy density of 180 Wh/kg.⁷ That said, I haven’t heard a peep about how fast it charges.

The MG4 has a handful of versions, but it looks like only the most expensive option, the Anxin, will include the semi-solid-state battery. It’ll retail for the pretty reasonable 102,800 yuan (or about $14,290).⁸ I don’t want to overhype this, in part because that Anxin version hasn’t delivered yet, but it’s nice to see at least some kind of SSB tech based car making it to the commercialization finish line. In the case of this car, it sounds like it’s more about the safety benefits.

Then there’s Mercedes-Benz partnering with Factorial Energy. Factorial is a new face for the channel. In 2023, the company opened an SSB plant in Massachusetts.⁹ Its line-up includes the Fest quasi-SSB, and the Solstice ASSB. I can’t find anything stating if this plant will be producing the Fest, the Solstice, or both. Though, keep in mind that the plant predates the Solstice announcement.¹⁰

Mercedes just completed a long-distance test with its EQS model equipped with Factorial’s solid-state battery, and the result was impressive: 749 miles on a single charge.¹¹ That’s not a lab result under perfect conditions. That’s a real car, on real roads. Mercedes says the test EQS used Factorial’s Solstice ASSB technology.¹²

These aren’t vaporware: they’re functioning vehicles proving the technology works outside controlled lab environments. But they’re also not quite the revolutionary leap the hype machine promised us for the past decade.

Pilot Plants Opening

Now let’s look at who’s getting very close. Several major players have pilot production lines running, which means they’re past the lab stage but not yet at mass production. Pilot plants are the final gate before commercial production.

QuantumScape partnered with Volkswagen Group to put its QSE-5 SSBs in the new Ducati V21L electric racing motorcycle.¹³ The QSE-5 has an 844 Wh/L energy density, charges from 10% to 80% in around 12 minutes, and Volkswagen says its capable of “race-level power outputs.” The all-electric V21L had 150 horsepower and hit 170 miles per hour on the Mugello Circuit.¹⁴

The QSE-5s are being produced via the Cobra separator system we explored last year, which heat treats their batteries’ oxide separator 25 times faster.¹⁵ I can’t find independent info on what subspecies of SSB the QSE-5 is,¹⁶¹⁷ but what matters is whether performance and timelines match promises. QuantumScape initially aimed for commercial production in 2024. In 2025 they began shipping samples to launch customers, with field-testing starting in 2026.¹⁸ That’s progress, but field testing isn’t commercial production, and the timeline keeps sliding a little bit.

Next up: Solid Power and BMW working on an ASSB for a new BMW i7.¹⁹ Solid Power clearly states that its battery is an ASSB.²⁰ The company has worked with BMW since 2016, and this particular SSB is sulfide-based.

The big advantage? Sulfide SSBs can be produced with industry standard roll-to-roll manufacturing equipment.²¹ This could be critical because finding cost-effective ways to manufacture SSBs at scale remains an ongoing challenge. Solid Power claims it can manufacture SSBs 15-35% cheaper than competitors.²⁰

However, BMW and Solid Power’s own press releases note that “further development steps are required.”²² Not exactly confidence-inspiring, especially when Solid Power was saying in 2020 that they were hoping to sell batteries by 2021.²³ We’ve heard these optimistic timelines before.

While we’re on Solid Power, let’s talk about its partner SK On, one of South Korea’s powerful family-owned conglomerates known as chaebols. SK On has its own ASSB and claims it can mass produce it using “Warm Isostatic Press-free” (or WIP) technology.²⁴ This technique reduces porosity and increases density, suggesting SK On’s SSBs have a ceramic core, though that’s not clearly stated.²⁵

WIP applies uniform pressure to electrodes at elevated temperatures, improving energy density and performance while minimizing heat generation.²⁴ The result? An energy density of 800 Wh/L, twice what lithium-ion NMC batteries offer.²⁶

However, cell-sealing proved difficult to automate, so SK On tapped Solid Power for help. Things seem to be working out. They opened a 50,000 square foot pilot plant in Daejeon, South Korea in September, and moved their release date from 2030 to 2029.²⁷ Yeah, they actually moved it up. Surprising given the history of sliding deadlines, though 2029 is still four years away.

Then there’s Nissan, claiming it’ll have ASSB vehicles by 2028. The company is developing in-house batteries, but partnered with U.S.-based LICAP for “cathode electrode production process technology.”²⁸ The battery stats are unclear.²⁹ We can make some educated guesses, maybe, by looking at LICAP’s numbers, but that’s just a guess.²⁹

Nissan reached out to LICAP for its activated dry electrode technology, which manufactures electrodes without solvents. Ordinarily, solvents meld battery layers together for better charge flow. But manufacturers have to wait for electrodes to dry, then recapture the solvents for reuse. Both processes are time-consuming and expensive. Nissan figures skipping these steps will significantly reduce manufacturing costs. But the company only opened a pilot plant earlier this year,³⁰ so we’ll be waiting a while to see if that’s true.

Science Breakthroughs

SSB development isn’t all about pilot lines and test vehicles. There’s still formulas and developments being made in the lab.

Huawei recently filed a patent for a new kind of SSB. Allegedly optimized with the aid of AI, Huawei is doping sulfide electrolytes with nitrogen.³¹ Doping is the process of seeding little bits of one material into another. Think of it like adding a pinch of salt to chocolate chip cookie dough. That tiny addition changes the whole flavor profile…for the better. In batteries, these tiny impurities can dramatically alter the material’s chemical and electrical properties.

What properties do sulfides have? Their naturally high ionic conductivity allows for faster charging and discharging. Plus, they’re very energy dense and resistant to damaging dendrites, those gnarly spikes that can build up over time and eventually cause the battery to fail.³² However, the candle that burns bright also burns fast, and sulfides don’t last very long.³³ Doping the sulfide with nitrogen atoms helps create a more stable electrolyte lattice, essentially building express highways for the lithium ions to race down.³²

In theory, this makes for a battery with a 3,000 kilometer (or about 1,864 mile) range and an energy density between 400 and 500 Wh/kg.³⁴ Way ahead of standard NMC EV batteries. The real spice here, though, is the promise of a charge time of just five minutes. That is so far ahead of the others that, frankly, I’ll believe it when I see it. Experts have also warned that this would require charging infrastructure that does not currently exist.³² So, let’s not get too stoked just yet.

Another recent breakthrough comes from China’s Dalian Institute of Chemical Physics, or DICP. Researchers have created an ASSB prototype using sodium aluminum hydride, or NaAlH4, in place of lithium as a charge carrier.³⁵ But what’s a hydride? Think of it as hydrogen’s athletic younger sibling. It’s a negatively charged hydrogen atom that’s picked up some extra electrons. This makes it incredibly light, which translates to denser batteries. It’s also great at the electron shuffling that makes batteries work.³⁶ Redox, which is short for reduction and oxidation, is just the fancy chemistry term for gaining and losing electrons. That’s the fundamental dance that lets a battery charge and discharge. Another advantage? Hydrides just don’t form those nasty dendrites like lithium does.³⁵

Like the Tim Duncan era San Antonio Spurs, hydrides have great fundamentals, so what’s the issue? We’ve got a bit of a “triangle problem” going on. You can only pick two out of three benefits, because it’s very hard to find electrolytes that work well at room temperature, are thermally stable, and are compatible with the electrodes that hydrides require. Nail two of those, and the third falls apart.

DICP figured out how to break this triangle with a clever design its team calls a “core-shell composite hydride.”⁴ Picture an M&M. The cerium hydride core is like the chocolate center, super conductive and great at moving charge. The barium hydride shell is like the candy coating, tough and protective, making everything more thermally and chemically stable.

In testing, the hydride SSB started strong with 984 milliampere-hours per gram, but after 20 charge cycles, it settled down to 402 mAh/g.³⁷ Think of it this way: these researchers have built a battery that works, holds a decent charge, and doesn’t fall apart immediately. For a completely novel type of SSB, that’s a solid foundation to build on.

Reality Check

That’s a lot of different approaches to solid-state batteries coming down the pipeline. Surely, one of them is going to make it, right? Well, before any of us get too excited, let’s talk about what they’re not telling you…because there are serious manufacturing challenges at play here that could delay or even derail these timelines.

First off, temperature sensitivity. Some solid electrolytes only perform well at elevated temperatures or suffer when it’s humid, which isn’t ideal in the real world. In colder climates, this necessitates the need for heavy, energy-intense internal heating systems. These eat into the energy savings, making the car heavier, which harms your range and drives up overall costs.³⁸ This isn’t a minor inconvenience so much as a fundamental challenge: It affects where and how these batteries can be deployed.

Plus, as a paper from Clemson University’s Department of Electrical and Computer Engineering points out, lifecycle is still an issue. This is where dendrites come into the picture again, because they get bigger every time a battery is used. The buzz makes it sound like this is a solved problem. And as we’ve seen, there’s a lot of strategies for managing dendrites, but they’re still a concern.³⁹ They can pierce through solid electrolytes just like they do with liquid ones, causing internal short circuits. Different materials have their own way of handling this, but no approach has completely eliminated the problem.

Less dramatic, but no less important, is the solid-electrolyte interphase, or SEI, layer. This is a metallic layer that builds up around the electrodes with repeated use. It simultaneously eats away at the electrolyte to build itself, while making it harder for the lithium ions to pass from one electrode to the other. It usually drops the battery’s capacity and overall just harms its performance.³⁹ And much like the dendrites, there are ways to manage this, but none of them are easy or cheap.

There’s also the challenge of maintaining good contact between the solid electrolyte and the electrodes. Unlike liquid electrolytes that flow and maintain contact naturally, solid materials can separate or develop gaps during charging and discharging cycles. This increases resistance and reduces performance over time. Some companies are using various pressing techniques or composite materials to address this, but it adds complexity and cost to manufacturing.

And that’s all before we get into the difficulty of mass production. Even if we solve all of these challenges — and right now, that’s a big “if” — can we implement them efficiently and cost-effectively at scale? That remains to be seen. Manufacturing solid-state batteries requires different processes, different equipment, and different quality control measures than conventional lithium-ion production. The industry has decades of experience optimizing lithium-ion manufacturing. Solid-state is starting from scratch.

Each company we’ve discussed is forging its own path to viable SSBs. Some are betting on sulfides, others on oxides or polymers. Some are going for pure solid-state, others are accepting small amounts of liquid electrolyte as a pragmatic compromise. This diversity of approaches is both encouraging and concerning. It’s encouraging because it means lots of smart people are attacking the problem from different angles. It’s concerning because it suggests there isn’t a clear winner yet, and some of these bets won’t pay off.

Where We Actually Are

Where does this all leave solid state batteries? It’s challenging to separate the hype from facts. And how many of these solid state batteries will really, truly be all solid state when cracked open? As promising as these techniques and pilot plants can be, there’s still nothing solid to hang onto just yet.

The sheer variety of technologies under the umbrella of the term “SSB” means that it’s really difficult to give the technology a singular rating on NASA’s technological readiness, or TRL, scale. Some of these, like the new developments from Huawei and DICP, are still on the lab bench, putting them at 5 at best. The various auto manufacturers are plowing ahead, with tech that’s passed a real world demo or two. Others are so confident in their tech that they’re at the pilot plant stage. “Flight proven” systems like this would mean something like an 8 on the TRL.⁴⁰

I think by now it’s clear that deadlines like 2028 or 2030 are more aspirations than promises. It’s very possible that all these deadlines are just going to be pushed forward yet again as the commercialization process hits more road bumps. After all, a pilot plant is only a test, and sometimes you fail a test. It’s all part of the process. It’s normal.

And yet the challenges of mass producing a true SSB and a history of “the next year or two, we promise” leaves me more than a little skeptical. I really hope I’m wrong and the next few years do see the dawning of the SSB age. But I’m not holding my breath. Again, these commercialization road bumps are part of the process.

On the other hand, who cares if a battery is not, in fact, fully solid state, so long as it does what it says on the tin? If a battery really can charge to 80% in less than 12 minutes while maintaining a decent cycle life and energy density, then I’m not going to get hung up on whether or not it’s a true ASSB or a semi-SSB. The MG4 proves that solid-state adjacent technology can reach consumers at reasonable prices. The Mercedes test proves that range improvements are real and substantial. The pilot plants prove that major manufacturers are committed enough to invest serious money.

All that’s to say: you better believe we’ll be revisiting these companies in 2028 and 2030 to see if any of these promises materialize. For now, I’d say we’re in the “cautiously optimistic but maintaining healthy skepticism” zone. Not the revolution we were promised a decade ago, but meaningful progress toward better, safer batteries.