By Kyle Proffitt
September 4, 2025 | The annual Solid-State & Sodium-Ion Battery Summit was held August 12-13 in Chicago, IL, with the solid-state and sodium-ion discussions split into two separate tracks. Although they overlap, sodium-ion is primarily looking to beat LFP as a low cost and plentiful alternative, whereas solid-state promises to supplant some of the currently-best technology. OEM auto manufacturers, startup battery companies, academics, and government representatives all joined to discuss the state of affairs, predict the future, and dispense advice.
Solid-state batteries are billed as the future for several reasons. They offer high energy density by enabling some cathode and anode solutions otherwise difficult to implement, they promise inherent safety by removing flammable electrolyte, and they might improve charging speeds if some issues of ion conductivity and interfacial resistance can be solved.
But how soon will they be mainstream?
Halle Cheeseman of ARPA-E kicked off the solid-state section by providing his view of progress. In short, he sees an “inevitable” future for solid-state batterys in EVs and elsewhere, but he cautions that the road is not direct or imminent. Any new battery chemistry needs to really do something that today’s lithium-ion battery cannot, not just match demand. “If your solid-state architecture is trying to sell 400 Wh/kg… that’s no longer competitive,” he said. Cost must also continue to drop to reach a mainstream EV market, and in the meantime, he advised that beachhead markets are necessary to prove technology and grow revenue. He suggested eVTOLs, drones, robots, stationary energy storage, and space applications as potential markets.
Cheeseman chided that “there has not been a successful U.S. battery start-up in the last 25 years.” Asia is beating us with their large, established companies. He showed the example of CATL, which employs 20,000 people in R&D and spends $2.5 billion per year. In contrast, he said in all of the U.S., there are about 20,000 people signed up for the Volta foundation, but they are working on a host of different specific projects. To bridge this gap, he suggested that collaboration is key and that we must find ways to speed processes, to learn fast and fail faster so time is not wasted, and to leverage AI in chemical process development.
Simon Buderath of P3 Group explained that solid-state is so attractive to EVs because it can potentially solve obstacles around vehicle range and charging. That’s largely because solid-state can improve and/or enable the utilization of silicon and lithium metal anodes, which promise up to 10-fold increases in energy storage capacity within the anode. Cost is a big issue though, because the price also shoots up, such that the cost per unit of energy storage at least doubles when moving from graphite to lithium metal anode. However, the anode is not the full picture, so for the complete battery pack, Buderath showed a calculation of $110/kWh with a current battery vs. $129/kWh in an all-solid-state formulation. With price remaining a major hindrance to EV adoption, this is not yet a formula for mainstream solid-state adoption. Conceivably, economies of scale and process efficiencies will minimize cost differences, gains will be made with lighter and smaller packs composed of higher energy density materials, and mainstream adoption can occur.
According to Buderath, China has a 3-step formula, as they lead the solid-state battery race. With this approach, step 1 maintains status quo, 200-300 Wh/kg, using NMC cathode and silicon-carbon anode, but introduces a sulfide-based solid electrolyte. This is starting now with a pilot line from BYD; pilot line announcements also came from Hyundai and Honda this year. Stage 2 will involve ramping to 400 Wh/kg from 2027-2030 using more silicon, and stage 3 will finally target 500 Wh/g from 2030-2035 using lithium metal anode. The staging approach should allow processes and scaling to be worked out while solid-state safety and longevity are established; then the major gains can come.
On the whole, Buderath predicted that we are still a few years out. “Announcements now are getting a little bit clearer in terms of timing to mass production, and that’s 2027-2030 as an outlook,” he said.
Given this background, Battery Power Online saw a few technologies to watch.
Veteran Player, Updated Chemistry
Blue Solutions is a veteran of solid-state, and Head of Business Development Adrian Tylim rehearsed their history, having had solid-state cells operating in commercial buses for 10 years and having completed production of more than 3 million cells. Those cells primarily used LFP cathode, a solid polymer electrolyte, and lithium metal foil anode. They aren’t terribly high density, but they fit the purpose for commercial urban buses. Blue Solutions is currently working on Gen 4, which retains the lithium metal foil, now squeezed to less than 20 µm (“going from 60 microns to 20 microns is extremely difficult,” Tylim said), and solid polymer electrolyte, but is cathode-agnostic, supporting LFP, LMFP, and NMC variants with promised energy density of 315, 350, and 450 Wh/kg, respectively. This approach allows them to serve markets “from the Fiat to the Ferrari,” according to Tylim. Their approach also dispenses with copper as the anode current collector; the lithium metal foil does this job.
Blue Solutions is banking on polymer electrolyte to win the solid-state race. “We choose a polymer electrolyte because of the integration and the manufacturability at scale,” Tylim said. “It has sort of a sticky surface that conforms very well to both the cathode and the anode side.” This adhesion allows them to operate under ~2 atm of pressure, and Tylim showed postmortem analyses of cells that had cycled 1000 times with no evidence of dendrites or mossy lithium deposits. Although they are targeting >3C charging, 2C was the fastest charge rate for which data were shown.
They have joint development agreements in place with 7 companies, including BMW and four more “top-tier automotive manufacturers”, and they are currently producing A samples for these companies. Electrolyte optimization is apparent, as previous generations required high temperature (80 °C) operation to offset low ionic conductivity, a commonly cited problem with solid polymer electrolytes. Now, 1 Ah LMFP-based Gen 4 A sample cells operating at 40 °C were independently shown to last more than 500 cycles.
Glass Batteries
Steven Visco shared some of the key innovations PolyPlus has made, starting with the protected lithium electrode (PLE), which they use to create exceptional (1600 Wh/kg) primary (non-rechargeable) water-activated lithium metal batteries and lithium metal sulfur batteries that use water as electrolyte. Their PLE enables the use of aqueous electrolyte, in which Li2S is highly soluble; the Li2S crashes out of all other non-aqueous electrolytes they tested. In this case, the water with Li2S dissolved in water is actually the lithiated cathode, and this allows a LiS battery to be manufactured in the discharged state for the first time, according to Visco. Adding in a lithium aluminum titanium phosphate (LATP) ceramic layer, they prepared batteries with either lithium metal or graphite anodes. Visco showed the lithium metal variant cycling about 300 times. Using graphite anode, they’ve only completed 25 cycles but accomplished 99.5% coulombic efficiency. Ultimately, Visco projects these batteries reaching 300-500 Wh/kg, lasting thousands of cycles, and significantly undercutting LFP in cost. Because they use water for electrolyte, they are not flammable.
For the solid-state enthusiasts, Visco gave an update on lithium metal batteries using a sulfide-containing glass separator. An anodeless cell created with a P2S5-based-glass-embedded NMC622 cathode and argyrodite ceramic electrolyte was shown cycling 250 times, albeit at a low discharge capacity of 0.2 mAh/cm2. Visco said that the cooling of the glass compresses the cathode material, obviating external pressure. He acknowledged that work remains, that they are clearly not there yet because of the low rate and density of charge transfer. They can also create the cathode as a composite containing the P2S5-based glass, skipping the argyrodite, and cycle effectively, but they remain limited in charge/discharge rate and discharge capacity.
Sulfide Supplier
Solid Power CTO Josh Buettner-Garrett presented an update on their place in helping bring solid-state batteries to the mass market. He says their core business is sulfide electrolyte. “We are stubbornly committed to sulfide all solid-state; we do nothing else,” he said. As an electrolyte supplier, though, Buettner-Garrett says they only win if everyone wins; they’re rooting for everyone in the building.
They’re also making cells, up to 60 Ah pouch versions, even though they aren’t trying to be a direct cell provider. And some of these hit the road this year. “In May of this year, BMW announced the beginning of road testing of an i7 electric demo car on the streets of Munich,” Buettner-Garrett said. Those vehicles are outfitted with the 60-Ah Solid Power batteries.
“We believe sulfides offer the best balance of performance and mass production attributes for ASSB cells,” Buettner-Garrett explained. These are argyrodites, and their latest generation (Gen 3) has improved Li ion conductivity to > 5.0 mS/cm. For reference, typical liquid electrolytes operate around 10 mS/cm at room temperature.
Because Li2S is a principal component of argyrodite manufacture, the price of this material is a major factor for Solid Power, and Buettner-Garrett dedicated time to discussing options. He said we are nearing an inflection point for Li2S supply capacity, but Solid Power is exploring alternative synthesis reactions to hedge their bets. He also discussed the use of machine learning interatomic potentials (MLIPs) to identify improved electrolytes. His slide made the point by stating that for every electrolyte composition that has been synthesized, there are more than 10,000 possible substitution combinations. Manas Likhit Holekevi Chandrappa also spoke extensively about how Nissan is using this approach to consider novel solid electrolytes. In that case, scandium-containing halospinel halide electrolytes are being explored, because they have good ionic conductivity (10 mS/cm) and stability at high voltages, but the scandium is very expensive. If the scandium could be replaced with cheaper materials while retaining the material characteristics, a winning electrolyte might be identified. The MLIPs essentially use machine learning to decrease the computational cost of detailed molecular dynamics simulations, fitting models instead of completely performing the extensive calculations necessary.
Solid-State Battery Manufacturer Leaning on Sulfides
Another player driving solid-state is Factorial. Vice President of Business Development Raimund Koerver discussed how their product offerings are progressing. Factorial has both quasi-solid-state polymer electrolyte and true solid-state sulfide electrolyte-based variants. Unlike Solid Power, Koerver says Factorial is not a materials company; their focus is on cell development, design, and manufacturing.
They have partnerships with Mercedes, Stellantis, Hyundai, and Kia and have shipped thousands of 70-100 Ah cells to automotive OEMs. They also started road testing in Mercedes vehicles this year in February using quasi-solid state 390 Wh/kg B samples, promising up to 1000 km range. Stellantis plans to road test their batteries in a Dodge Daytona fleet next year.
Koerver reported that their all-solid-state variant, Solstice, has been successfully scaled to 40 Ah cells. Solstice uses a proprietary high-capacity anode, sulfide separator, and a nickel-rich cathode material that also includes sulfide. Koerver used much of his presentation to highlight their dry cathode process, which he said eliminates toxic solvents and the energy needed to remove them while improving particle contact for the sulfides. He said the dry coating process is a very elegant way to avoid exposing the sulfides to materials with which they can react, such as solvent, moisture, or binders. The result, he says, is a less degraded cathode with lower resistance. Their approach enables a solution that works well with less than 1 MPa (~10 atm) external pressure.
Their generation B 0.15 Ah cells prepared this way cycled more than 3,000 times before dropping to 80% capacity (C/3 charge/discharge, 45 °C). He also showed data with 17 Ah cells cycling 1200 times under < 1 MPa pressure. Koerver highlighted data from slightly smaller 7 Ah cells in which swelling was only about 1% after more than 1000 cycles.
Collaboration is Key; Integrated Cell Heating
Ampcera is yet another company working with sulfide electrolyte. Eongyu Yi, Director of Battery Technology, was on hand to discuss how collaboration will help commercialize solid-state batteries. He echoed some of the concerns that ARPA-E’s Cheeseman introduced about the difficulties—and sometimes unrealistic expectations—around scaling and the refrain that solid-state is always “about two years away.”
“A typical conversation we have with a precursor manufacturer is that we ask them, ‘when will you lower the cost?’ And they ask back to us, ‘When will you scale up?’” Yi said. The answer to this impasse is actually quite simple, Yi says. “We need to make a solid-state battery that is at least on par or similar to lithium-ion battery but also outperforms in at least one performance metric.” Ultimately, he indicated that collaboration is crucial to leverage others’ expertise in the minutiae of good solid-state battery design.
One notable example was shown. Ampcera has developed what Yi referred to as their Gen 1 chemistry, using NMC811 cathode, a 10-30 µm sulfide separator, and a thin 40-100% silicon anode, with which they expect to get to 400 Wh/kg by end of year. They are working to reduce stack pressures, and results were shown with as little as 2 MPa (~20 atm) pressure. Additionally, up to 4.8 Ah cells were prepared, and 1000 cycles were shown for some samples. The key collaboration comes with FastLion Energy, who has developed a resistive thin film that can be incorporated within batteries and use their energy to provide rapid heating. In this way, within about 2 minutes, the battery can be heated from an ambient 28 °C to 60 °C, improving transfer kinetics such that 4C charging becomes possible. Integrating this technology and using a variable protocol of C/3 charging with 4C charging every 4th cycle, Ampcera has accomplished 250 successful cycles thus far (still cycling). “This technology enables us to make ambient temperature irrelevant to the cell’s operant temperature so that we can get both out of the solid-electrolyte thermal stability and also maximized cell performance,” Yi said, indicating that the technology would be very useful for subzero operation.
The Oxide Option
In contrast, Ion Storage is using an oxide electrolyte (LLZO) in their solid-state cells, prepared in an initially anode-free setup. Greg Hitz reported that they do backfill a liquid catholyte, but their technology is amenable to many cathode options, providing benefits for options such as LiS, LMFP, and even lithium-air. He says they are heavily focused on the consumer electronics space right now, highlighting that their cells operate with no pressure and do not swell. He expressed surprise upon being told by a major consumer electronics company that Ion is the only solid-state company sending them samples. The fact that their cells do not swell gives them a real opportunity to succeed in consumer electronics, where things keep getting lighter and thinner. Hitz also shared that automotive companies are telling him that the best path is to start with consumer electronics, even if you do have the absolute best anode solution. You’d like to know how the battery performs through thousands of iPhone drops before it experiences its first vehicle crash, he said. Compared with last year’s presentation, the main updates for Ion Storage this year included further engagement with consumer electronics and scaling their R&D cells to a pilot line—which came with lots of optimization to retain the same performance. Those cells are currently at 400 cycles with greater than 90% capacity retention. He showed 5C discharge performance, retaining 70% of original energy, after which they could return to C/5 and regain 100% energy. They’ve also scaled to 0.5 Ah cells, which Hitz says are useful in dozens of electronic products. They’re sitting at about 250 Wh/kg currently, but they have plans in two future generations to scale to 600 Wh/kg.
Moonshot Technology: Lithium-Air
Finally, looking into the future for the holy grail of lithium battery chemistry, Mohammad Asadi, from the Illinois Institute of Technology, was on hand to discuss his progress with lithium-air batteries. These batteries use lithium metal in the anode paired with a conversion cathode containing oxygen (O2), which reacts with lithium to form LiO2 (lithium superoxide, one-electron reduction), Li2O2 (lithium peroxide, two-electron reduction), or Li2O (lithium oxide, four-electron reduction). Most of the chemistry available today, Asadi said, stops at Li2O2, but the theoretical energy density of complete reduction to Li2O rivals that of gasoline, and batteries with >1000 Wh/kg are feasible. For his setup, Asadi uses a lithium metal anode, a composite electrolyte including sulfide ceramic nanoparticles embedded in a polymer matrix, and a cathode of conductive carbon and Mo3P nanoparticles, which act as catalysts of oxygen reduction and evolution. The oxygen just comes from the ambient air. They’ve previously cycled a cell like this 1000 times. Asadi reported that with various optimizations, they have now accomplished an energy density of 1000 Wh/kg at 4.5 mAh/cm2, although it’s kind of an academic exercise for now, as this variant only cycles five times. Work is ongoing.
