Background
SK nexilis, a South Korean manufacturer of electrolytic copper foil and a major supplier to the electric vehicle battery industry, sued competitor Solus Advanced Materials Co. and its four Volta Energy subsidiaries in the Eastern District of Texas in November 2023. SK nexilis alleged that Solus and Volta were manufacturing and selling copper foil products that infringed five of its U.S. patents: Nos. 9,457,541; 10,480,090; 10,811,689; 11,346,014; and 11,591,706.
The patents cover methods for producing electrolytic copper foil with specific handling and performance characteristics—properties that are critical for use as current collectors in lithium-ion batteries powering electric vehicles. The accused products include standard battery copper foil (BF-PLSP), high-elongation battery copper foil (SR-PLSP), and high-strength battery foil (HTS-PLSP), all produced by Solus and marketed through the Volta Energy brand.
The case sits at the intersection of two global trends: the rapid expansion of the EV battery supply chain and the fierce competition among Korean materials companies to supply that chain. SK nexilis and Solus are direct competitors in the global copper foil market, and this litigation is part of a broader IP strategy by SK nexilis that has also included filings at the Unified Patent Court in Europe.
The Court’s Holding
After trial, the jury returned a verdict finding that Solus and the Volta entities infringed all five asserted patents. Critically, the jury also found the infringement was willful—a finding that could allow the court to enhance damages up to three times under 35 U.S.C. § 284.
On the defense side, the jury rejected Volta’s invalidity challenges, concluding that the defendants failed to prove that any of the five patents were invalid. The jury awarded SK nexilis $3.3 million in compensatory damages.
While $3.3 million is modest by Eastern District of Texas patent verdict standards, the willfulness finding could significantly increase the final award if the court exercises its discretion to enhance damages. Post-trial motions on enhanced damages and attorneys’ fees are likely to follow.
Key Takeaways
- The verdict validates SK nexilis’ patent portfolio covering EV battery copper foil manufacturing, an increasingly valuable technology segment.
- The willfulness finding—indicating the jury believed the defendants knew about the patents and infringed anyway—opens the door to treble damages and attorneys’ fees.
- Solus’ failed invalidity defense means SK nexilis’ five patents emerge from trial strengthened, which may affect ongoing PTAB proceedings and the parallel UPC litigation in Europe.
- EV battery supply chain IP disputes are accelerating as the industry scales, and companies entering this space should expect aggressive patent enforcement from established players.
Why It Matters
The EV revolution depends on a complex supply chain of specialized materials, and copper foil is among the most critical. As current collectors in lithium-ion battery cells, copper foils must meet exacting specifications for thickness, tensile strength, and elongation. The companies that have developed proprietary manufacturing processes to produce these foils are increasingly turning to patent litigation to protect their competitive positions.
SK nexilis’ victory here—combined with its parallel enforcement campaign at the UPC—signals that EV battery materials IP will be a major battleground in the coming years. For companies sourcing copper foil for EV batteries, this verdict is a reminder that even commodity-seeming materials inputs can carry significant patent risk.