UPC Mannheim Rejects SK nexilis Copper Foil Claim, Splitting From a Texas Jury

By Haedar

Photo: byrev / Pixabay

Two Korean makers of battery copper foil now hold opposite results from courts on two continents. On 23 October 2026, the Mannheim Local Division of the Unified Patent Court dismissed SK nexilis's infringement action against three Volta Energy Solutions companies, the European arm of Solus Advanced Materials (case UPC_CFI_706/2025), according to the court's decision listing. Earlier this year, a jury in the Eastern District of Texas had found that Solus and Volta infringed SK nexilis patents, including a US member of the same family.

What the patent covers

The European patent, EP 3316363, protects copper foil for lithium battery anodes defined by surface parameters. As The Elec notes, thinner and stronger foil can raise energy density and cut battery weight, which makes it a key material for electric vehicle cells.

The fight came down to one number. Claim 1 requires a peak count roughness (Rpc) between 10 and 100, and the claim defines Rpc as the count of effective peaks over a 4 mm sampling length. According to The Elec and MoneyToday, SK nexilis argued that the count should be converted to a 1 cm basis, in line with industry practice. A published summary of the decision says this meant multiplying by 2.5, which would put Volta's foil at around 14 to 15. Volta argued that the claim meant what it said, and on the literal 4 mm count its values (about 5.6 and 6.0, according to the same summary) fell below the floor of 10.

The court went with the claim's own words

The Mannheim panel agreed with Volta. According to the summary, the court accepted that Rpc is commonly expressed per centimetre in the field, but held that this patent deliberately chose its own binding definition, so it acts as its own lexicon. Industry habit could not pull products back inside a claim that excluded them. The court found no infringement and, according to The Elec and MoneyToday, ordered SK nexilis to bear litigation costs of about EUR 1.1 million.

According to the same summary, Tesla had applied to intervene in support of the defendants and was turned down in September. A second UPC action between the parties, over EP 3309881, is pending before the Munich Local Division. An official at SKC, SK nexilis's parent, told The Elec that the company would review the ruling before deciding on next steps, including a possible appeal.

Why the Texas result differs

The US jury in the Eastern District of Texas found infringement of five SK nexilis patents, including wilful infringement, and awarded USD 3.3 million in damages, according to The Elec. The Elec reports that the US court accepted that a 4 mm measurement could be converted to the 1 cm basis, but did not decide whether converted values should be used to assess infringement. The summary of the Mannheim decision says that gap is why the panel did not find the US rulings persuasive.

Takeaways for applicants in Indonesia and Asia

Parameter claims are common in battery, steel and materials patents filed across Asia. The lesson from Mannheim is practical: if a claim fixes its own measurement method, it may be read that way, even against standard practice. Drafters should state units and methods clearly and check that the numbers line up with how competitors' products will actually be tested. We are not aware of an Indonesian court decision addressing this specific measurement question.

Sources

• Unified Patent Court, Decision UPC_CFI_706/2025, SK nexilis v. Volta Energy Solutions (23 October 2026)
• The Elec, "US, European Courts Split on SK Nexilis-Solus Copper Foil Patent Dispute" (26 October 2026)
• MoneyToday, "Solus Advanced Materials wins European battery foil patent lawsuit against SK Nexilis" (26 October 2026)
• Michael MA, "UPC Mannheim Says Industry Practice Cannot Expand Claims Under the Patent's 'Own Lexicon'" (25 October 2026)