Maxell, Ltd. v. Amperex Tech. Ltd

Authored by: Jeremy J. Gustrowsky

In a recent decision, the Federal Circuit provided important guidance on how patent claims should be interpreted when it comes to potentially conflicting language. The case involved Maxell, Ltd., which owns U.S. Patent No. 9,077,035, covering a rechargeable lithium-ion battery. Maxell accused Amperex Technology Limited of infringing this patent, but the district court initially ruled that the patent was invalid because the claim language was supposedly contradictory and therefore indefinite.

The dispute centered on two limitations in the patent claims about the battery’s transition metal component, labeled M1. One part of the claim said M1 could be cobalt, nickel, or manganese, while another part required that M1 contain cobalt at a concentration of 30% to 100% by mole. The district court thought this was a contradiction—if M1 could be any of the three metals, how could it also be required to have at least 30% cobalt? The court concluded that this made the claim indefinite and therefore invalid.

However, the Federal Circuit disagreed. The appellate court explained that there was no real contradiction because it is entirely possible for M1 to be cobalt, nickel, or manganese, as long as the cobalt content is at least 30%. In other words, the claim simply sets two requirements that must both be met, and there’s nothing inherently confusing or contradictory about that. The court also pointed out that it’s common for patent claims to include narrowing limitations, and that doesn’t make them indefinite or invalid.

This decision is a helpful reminder that patent claims should be read as a whole, and that multiple requirements can coexist without creating confusion, as long as they can logically be satisfied together. The case was sent back to the district court for further proceedings, giving Maxell another chance to enforce its patent.