On 23 October 2026, the Unified Patent Court (UPC) Mannheim Local Division dismissed SK nexilis’ copper foil patent action against three Volta Energy Solutions companies, valued by the court at EUR 15 million. The defendants are European subsidiaries of Solus Advanced Materials, and the case turned on how to count peaks on the surface of the foil.
Five months earlier, a Texas jury had found that Solus infringed five related SK nexilis patents in the US. The contrast shows how a single definition in a patent can produce a loss in one forum after a win in another.
What happened
EP 3 316 363 covers an electrolytic copper foil for secondary batteries. Claim 1 requires each surface to have a peak count roughness (Rpc) of 10 to 100. It defines Rpc as the number of effective peaks per “unit sampling length” of 4 mm.
SK nexilis argued that the industry normally expresses Rpc per 1 cm. It multiplied the 4 mm counts by 2.5, which put the accused foil above the lower limit of 10. Counted over 4 mm, as the claim states, the accused foil averaged 5.6 and 6.0 peaks on its two sides.
The panel accepted that Rpc is usually quoted per 1 cm. It held that the patent had deliberately chosen a different, binding definition and so acted as its own lexicon. It contrasted this with the next feature of claim 1, which simply refers to a Japanese Industrial Standard (JIS). The court added that the US claim construction orders did not call its reading into question.
The infringement action was dismissed. The conditional counterclaim for revocation was not decided, so the patent stands. SK nexilis must pay agreed costs of EUR 1.1 million, and it can appeal within two months of service.
In the US case, the jury in the Eastern District of Texas returned its verdict on 22 May 2026, according to SK nexilis’ parent company, SKC. The Mannheim decision records that the judgment entered on 2 June 2026 included a finding of wilful infringement.
Similar disputes over claim wording
The Federal Circuit faced a related gap in Actelion v. Mylan, decided on 13 May 2026. The claims required “a pH of 13 or higher” but did not say at what temperature pH was measured. The court read the term as pH at the standard temperature of 25 °C used in the field, drawing on the specification, the prosecution history and industry practice. It affirmed that Mylan did not literally infringe and held that the doctrine of equivalents was not available.
A second comparison involves one set of parties and patents in two European courts. On 18 November 2025, the UPC Hague Local Division held that two Advanced Cell Diagnostics patents were valid but not infringed by Molecular Instruments, reading “non-overlapping” probe regions strictly. The English High Court, on 23 April 2024, had read the term more broadly but revoked the UK patents as obvious.
The wider picture in claim interpretation and battery materials
The UPC Court of Appeal set out its method in NanoString v 10x Genomics on 26 February 2024. Under that order, the wording of the claim leads, but a court reads it alongside the description every time, weighing the patentee’s interests against those of competitors who need clear boundaries.
The European Patent Office (EPO) has taken a matching line. In G 1/24, issued on 18 June 2025, its Enlarged Board of Appeal confirmed that examiners and boards also look to the description when construing claims. A definition in the specification now carries weight at grant and in court.
The stakes are high in battery supply chains. LG Energy Solution and SK Innovation fought over electric vehicle battery trade secrets and patents in the US and Korea. They settled on 11 April 2021 for KRW 2 trillion in lump sums and running royalties.
What it means for battery materials and parameter patents
Applicants claiming materials by measured properties should state the method, reference length and unit in the claim. They should also check that these match how products are tested in practice. In this patent, the priority document referred to 10 mm and the application to 4 mm, and the court applied the 4 mm definition as granted. Careful patent drafting of parameter claims is a commercial decision, not a formality.
The decision suggests that implementers test products against the literal definition, not the trade convention, before relying on a non-infringement position.
Patent owners preparing claim charts for several forums should map each element to the patent’s own definition. A chart that converts units to suit one court may not survive another.
Synoptic IP’s view
Synoptic IP’s view is that the Mannheim decision is a sound application of settled UPC principles rather than a sign of hostility to patentees. The patent chose a 4 mm count, and the court found nothing in the prosecution file that contradicted that reading. Actelion shows that convention can fill silence in a claim; Mannheim adds that it does not overwrite an express definition. NanoString and G 1/24 both point to the specification as the dictionary, and here the dictionary was clear.
The practical lesson concerns forum strategy. Related patents in one family can fare differently across forums, so a US win may be a weak guide to a European outcome for parameter claims.
The strongest counter-argument is that a skilled person would read Rpc in its usual 1 cm form. On that view, the patentee loses on a drafting choice even though the accused foil may not differ in substance. The Court of Appeal may weigh this differently if SK nexilis appeals. The view holds for now because legal certainty for third parties is part of the UPC test, so competitors may rely on the definition the patentee wrote.
If you are drafting parameter claims or assessing risk under them, our freedom-to-operate search and drafting teams can help. We read the definitions in the description as closely as the claims.
This article is commentary and opinion based on public reports as of 4 November 2026 and is not legal advice.