Maxell, Ltd., a Japanese electronics and intellectual property licensing company and holder of US8691446B2, filed this appeal on August 9, 2023 at the Court of Appeals for the Federal Circuit (Case No. 23-2256), challenging a prior tribunal’s determination that the patent was unpatentable. The patent in question — US8691446B2, application number 11/976566 — covers a nonaqueous secondary battery and methods of using the same, a technology central to lithium-ion battery design and relevant across consumer electronics, electric vehicles, and energy storage sectors.

On January 23, 2025, the Federal Circuit issued its order affirming the unpatentability finding, bringing the case to a final close after 533 days. An affirmance at this level means the appellate panel found no reversible legal or factual error in the lower proceeding’s cancellation of the patent claims. For Maxell, this ruling extinguishes US8691446B2 as an enforceable asset. For Amperex Technology, Ltd., the decision provides definitive clearance from the specific claims at issue.

A 533-day appellate duration is consistent with — slightly above — the Federal Circuit’s typical resolution window, suggesting no extraordinary procedural complications, though the full briefing record is not public here. The affirmance on unpatentability grounds, rather than on procedural or standing bases, implies the panel engaged substantively with the patent’s claim validity. What remains unknown from the public record is whether specific prior art was dispositive, whether any claims survived, or whether Maxell has any further appellate avenue, such as en banc rehearing or certiorari petition.