Today’s Cell Technology Roundup — CATL Proves Safety for a 350Wh/kg Aviation Cell, Factorial’s Cooling-Free 90°C Solid-State (2026.08.11)

What Is in Focus: At Which Layer Are Energy Density and Safety Secured Together?

The three cell-technology stories of the second week of August 2026 all share the thread of securing energy density and safety at the same time, but the layer at which each solution sits is different. CATL approaches the same problem through system design, Factorial Energy through electrolyte chemistry, and Verkor through the mass-production process. This article places the three cases side by side and sets out where each solution puts its weight, technically and in terms of rights.

Looking first at the industry situation, high-energy-density cells are expanding beyond EVs into new applications such as eVTOLs (electric vertical takeoff and landing aircraft) and space and aviation. As early as April 19, 2023, CATL announced a “condensed battery” of up to 500Wh/kg, pointing to electric passenger aircraft as a new electrification scenario, and said it was developing to aviation-grade safety and quality requirements. On August 9, 2026, it announced that a 350Wh/kg-class aviation battery had passed an adjacent-cell thermal-runaway propagation test.

The source of tension is that as energy density rises, the energy held by each cell grows, and so does the risk that a fault in one cell spreads through the entire pack. This article answers three questions: how is thermal propagation blocked, why does a solid electrolyte have an advantage at high temperature, and which rights layers should planning and IP staff track across these three cases?

Basic Principle: Keeping the Whole Row Standing When One Domino Falls

Thermal runaway is a phenomenon in which, once the internal temperature of a cell exceeds a certain level, exothermic reactions accelerate themselves and spiral out of control. Thermal propagation refers to thermal runaway that starts in one cell spreading to adjacent cells. If it is not blocked, a fire can spread through the entire pack, which is why it is an essential test item in applications such as aviation, where time for an emergency landing is needed.

By analogy, a pack is a tightly set row of dominoes. If it is hard to completely prevent one from falling, you need to put partitions between them and create a path to draw heat away so that the fallen domino cannot push its neighbor. The key point of CATL’s announcement is that it ran this test not by toppling one domino but by toppling two adjacent ones at the same time. According to reports, the usual industry practice is single-cell trigger verification, and CATL said that even when it drove two adjacent cells into thermal runaway simultaneously at different positions in the pack, such as the middle and the corners, there was no propagation to other cells.

The principle of a solid electrolyte is closer to changing the dominoes themselves to a material that does not topple easily. A liquid electrolyte carries a growing risk of decomposition and gas generation at high temperatures, whereas a sulfide-based solid electrolyte, which uses no liquid, is described as advantageous in terms of thermal stability. Factorial announced that Solstice maintains stability at operating temperatures above 90°C and that it aims thereby to reduce thermal-management and cooling requirements.

• System layer (CATL): Even if a cell goes into thermal runaway, it is prevented from spreading to its neighbors.
• Chemistry layer (Factorial): The electrolyte is changed so that the cell itself is less unstable at high temperature.
• Process layer (Verkor): The designed cell is mass-produced at consistent quality.

Comparison: Key Metrics of the Three Cases

The table below corrects the original comparison table using each company’s announcements and reports. All performance figures are company-announced values, not third-party-verified figures.

Category	CATL aviation battery	Factorial Solstice	Verkor Dunkirk plant
Solution layer	System (pack) design	Electrolyte chemistry	Mass-production process
Energy density (Wh/kg)	350 (prismatic cells)	Up to 450 (announced target)	No public data
Key metric	No propagation with 2 adjacent cells in simultaneous thermal runaway	Stability at operating temperatures above 90°C	Initial capacity 16GWh, 50GWh target by 2030
Verification / progress	Production, inspection, and testing witnessed by Civil Aviation Administration of China (CAAC) representatives	40Ah cell unveiled 2024-12-12; dry cathode coating	Start-up of 2nd line announced 2026-08-04
First application	AutoFlight passenger eVTOL	EVs and consumer electronics (target before 2030)	Renault Group, Alpine A390

What this table says: Both 350Wh/kg and 450Wh/kg are company-announced figures, but they differ in the nature of their verification. CATL’s figure is tied to a system safety test witnessed by the regulator, while Factorial’s figure is a target specification.

CATL said its aviation battery will first be used in AutoFlight’s passenger eVTOL and is ready for mass production. CATL became a strategic investor in AutoFlight in August 2024. When Factorial announced Solstice on September 10, 2024, it presented a sulfide-based all-solid-state electrolyte system, up to 450Wh/kg, up to 80% longer EV range, solvent-free dry cathode coating, and skipping of the formation process. On July 29, 2026, it signed a memorandum of understanding (MoU) with SK On to jointly evaluate whether Factorial’s FEST platform can be produced using SK On’s existing lithium-ion manufacturing infrastructure.

When Verkor opened its Bourbourg gigafactory in Dunkirk on December 11, 2025, it stated an initial capacity of 16GWh, a 50GWh target by 2030, and more than 3 billion euros in funding secured since 2020. On August 4, 2026, announcing the start-up of its second production line and the first deliveries of batteries made on site, it said that Chief Operating Officer Laurent Debrue would become CEO as of September 1 and that founder Benoit Lemaignan would move to Vice-Chairman of the Supervisory Board.

Patent Perspective: The Layer of the Solution Is the Layer of the Rights

CATL aviation battery: No patent corresponding directly to this announcement can be identified from published patent information. Judging from the announcement, however, the points where rights could form lie less in cell chemistry than in system design, such as inter-cell thermal barriers, heat and gas venting paths, and cell arrangement within the pack. The tracking point is whether applications published in CATL’s name for aviation battery packs pull test conditions such as “no propagation under simultaneous thermal runaway of multiple adjacent cells” into claim limitations.

Factorial: US12095034B2 (“Polymer solid electrolytes, methods of making, and electrochemical cells comprising the same”), a granted patent in Factorial’s name confirmed on Google Patents, has a priority date of November 7, 2018, a filing date of June 30, 2023, and a grant date of September 17, 2024; its legal status is Active, with an anticipated expiration of January 4, 2039. Its subject matter is a crosslinked polymer solid electrolyte with urea and carbamate functional groups. In other words, this patent covers the polymer family, not the sulfide-based Solstice.

Insight: FTO for a sulfide cell should start not from “the company’s flagship patent” but from “prior rights in the electrolyte family.” The fact that the confirmed Factorial granted patent is in the polymer family means that the scope of the company’s own rights over Solstice’s sulfide electrolyte composition cannot be seen from public data alone. A company seeking to source or co-develop a sulfide-based solid electrolyte can reduce the potential for infringement only by separately investigating third-party rights on the electrolyte composition itself, rather than looking only at the partner’s patent list.

Avoidance points: Because system-layer rights on thermal-propagation blocking are generally claimed as combinations of elements such as partition material, spacing, and venting paths, implementing one element of the combination differently may leave room to fall outside the literal scope. Conversely, in approaches like the SK On MoU that apply existing lithium-ion equipment to solid-state production, equipment modifications and process conditions themselves can become the subject of new rights, so it is important to settle ownership of improvement inventions by contract early in the joint-development stage.

Design-around scenario (counterargument): A design that changes only the partition material may look like a literal design-around, but if it achieves the same function (blocking heat transfer) in the same way, it may become subject to a doctrine-of-equivalents analysis. Also, if test conditions enter the claim limitations, the very fact that a product passes the test may be used as grounds that an element is satisfied. Ultimately, the avoidance potential must be judged after checking the wording of the claims actually published.

Limits and Outlook

What the three cases have in common is that a distance remains between the announcement stage and the mass-production and certification stage. CATL’s test was conducted in the presence of the regulator, but that does not mean full type certification of an aircraft. Factorial’s 450Wh/kg is a target specification, and Verkor is only now starting up its second line.

The optimistic outlook is that improvements in system design and electrolyte chemistry will mesh and high-energy-density cells will spread quickly into aviation and space applications. There is also a counter-scenario. Aviation certification involves long lists of test items and long timelines, so even when cell performance is ready, actual operational use may be delayed, tied to the certification schedule. In that case, early demand may remain in limited areas such as cargo and trial flights rather than passenger service.

A strategic alternative is to split technology tracking into three layers — chemistry, system, and process — and draw a separate rights map for each. Even for the same energy-density and safety goals, the counterparties with potential for infringement and the avoidance options differ depending on the layer at which the problem is solved.

Practical action: Staff planning cells or packs for eVTOL or aviation should require suppliers to state the thermal-propagation test conditions (number of trigger cells, trigger positions, witnessing body) in the specification, and should also check whether those conditions are being used as claim limitations in the supplier’s patents.

Items requiring verification

• The original article’s wording that Solstice operates at 90°C without dedicated active cooling, and whether it targets the space market (not confirmed in primary sources; public materials describe “stability at operating temperatures above 90°C” and reduced cooling requirements)
• The original article’s figure that Verkor reaches 16GWh in 2028 (official materials state an initial capacity of 16GWh)
• Whether Verkor cells go into next-generation electric commercial vehicles, and the target customers
• The cell chemistry of CATL’s aviation battery (whether condensed-battery technology is applied)
• The thermal-propagation blocking structure of CATL’s aviation battery and whether corresponding patent applications exist

Sources

1. CnEVPost, CATL aviation battery clears key safety test, paving way for use in eVTOLs (2026-08-09)
2. electrive.com, CATL tests 350 Wh/kg battery for eVTOLs (2026-08-10)
3. CATL press release, CATL launches condensed battery with an energy density of up to 500 Wh/kg (2023-04-19)
4. Factorial press release, Factorial Introduces Solstice, an All-Solid-State Battery with Mercedes-Benz as a Key Customer and Development Partner (2024-09-10)
5. Factorial press release, Factorial Unveils 40Ah All-Solid-State Battery Cells with Dry Coating Process (2024-12-12)
6. Factorial technology page, Factorial Electrolyte System Technology
7. Factorial press release, Factorial and SK On Sign MoU to Explore Solid-State Battery Manufacturing (2026-07-29)
8. The Elec, SK On, Factorial Energy Partner to Explore Solid-State Battery Manufacturing (2026-07-30)
9. Google Patents, US12095034B2 – Polymer solid electrolytes, methods of making, and electrochemical cells comprising the same (Factorial Inc)
10. Verkor press release, Verkor reaches a decisive milestone and opens its first gigafactory (2025-12-11)
11. Verkor press release, leadership change for the transition to large-scale industrial production (2026-08-04)

Related Reading — Cosmos Lab’s KRW 22 Billion Funding Round — A Look at the Patent Landscape for Zinc-Halogen Aqueous Batteries · All-Solid-State Is at 2027 Pilot Production, LFP Is Already at 63% · Winning ESS Volume Isn’t the End — Will It Extend Into an LFP Battery Ecosystem?