Infringement and Invalidity in Lithium-Ion Battery Patents: The Importance of Weight or Volume Claim Terms


Central to the infringement and invalidity of lithium-ion battery (LIB) patents are weight/volume claim terms. In this article, I first explore how this common claim term in lithium-ion patents is construed. I then offer some practical patent drafting tips on how to strengthen a specification to support the construction of this claim term or conversely how to attack one from the perspective of a patent litigation defendant.

Numerical Weight/Volume Claim Terms Are Critical to Infringement and Invalidity

Numerical weights or volumes expressed as a range are critical in lithium-ion patents because infringement and invalidity turn on them. In the patent prosecution context, just witness how many patent office rejections are centered on “XX, YY, and ZZ chemical components are disclosed in ABC reference” followed by the applicant's rebuttal that “The ABC reference fails to disclose XX, YY, and ZZ component where AA is 10 to 70% by weight, BB is 30 to 90% by weight, and ZZ is 0.1 to 4% by weight,” after which the patent issues. More often than not in the chemical arts (here the electro-chemical arts), chemical composition that can promote certain characteristic have been theoretically disclosed in the prior art before. What makes a claim novel or non-obvious is the specific quantity of a chemical component vis-a-vis other components. Quantifying chemical components using weight/volume claim terms are therefore critical to showing novelty.

Naturally, numerical weight/volume claim terms are also the linchpin for infringement in litigation and thus heavily disputed during claim construction. But how should they be construed? Generally speaking, numerical weight or volume as a range should be construed as they are understood by a person of ordinary skill in the art in the context of the particular claim in which the disputed term appears, but also in the context of the entire patent, including the specification. See Phillips v. AWH Corp., 415 F.3d 1303, 1313 (Fed. Cir. 2005). But what exactly does that mean when applied to LIB patents? A claim construction dispute over numerical weight/volume claim terms in a LIB electrolyte patent between Ube and Samsung sheds light on the importance of examples in the specification for construing weight/volume claim terms. See Advanced Electrolyte Techs. LLC v. Samsung SDI Co., Ltd, No. A:17-CV-0030-LY, 2018 WL 2770648 (W.D. Tex. June 8, 2018).

For those who are interested, you can read an article I shared earlier about the Ube v. Samsung dispute and the broader Ube electrolyte patent enforcement and licensing campaign here.

The Importance of Numerical Examples in Construing Weight/Volume Claim Terms

In their lawsuit, Ube and Samsung disputed the construction of the claim terms “0.1 to 4% by weight, based upon the total weight of the non-aqueous solvent, of a sultone derivative” and “30 to 50 percent volume percent of a cyclic carbonate, based on a total volume of the non-aqueous solvent.” Samsung argued that both terms were invalid for indefiniteness because the patent specification failed to inform which compounds are considered to be part of the solvent, rather than some other portion of the solution for purposes of determining “the total weight of the non-aqueous solvent” and the proportion of “sultone derivative.” Ube countered that the terms were not indefinite in light of the patent specification and more specifically in light of examples in the specification. The court agreed with Ube.

The court found that examples in the patent specification supported Ube's arguments that the weight/volume terms were not indefinite. As to the weight term, the court found that an example in the specification showing PS (1,3-propane sultone), PC (propylene carbonate), EC (ethyl carbonate), and DMC (dimethyl carbonate) in a weighted ratio of 1/20/19/60 provides enough certainty to a person of skill in the art that the PS is 1% by weight and is part of the total weight of the solvent. As to the volume term, the court found that another example in the patent specification showing EC (ethylene carbonate), VC (vinylene carbonate), and MEC (methyl ethyl carbonate) in a volume ratio of 28:2:70 provided sufficient certainty to a person of skill in the art that the cyclic carbonate is based on the total volume of solvent where EC and VC are cyclic carbonates that sum to 30% of the total volume.

The claim construction process in the Ube v. Samsung dispute illustrates the importance of numerical examples in construing weight/volume claim terms and determining infringement. Even though the focus of Samsung's defense was ostensibly about the indefiniteness of the weight/volume claim terms, the dispute was ultimately about infringement since Samsung's accused infringing electrolyte formulations likely already fell within the claimed weight and volume ranges.

Practice Tips on Drafting and Attacking Numerical Examples in LIB Patent Specifications

Given the importance of numerical examples, both patent owners and patent litigation defendants need to pay careful heed to how they are drafted. Here are some practical tips: First, the math must be correct. Inventor engineers and chemists should carefully perform the mathematical calculations in each example. Calculations should be double-checked after the specification is drafted. Second, the chemical components that constitute a numeric example should be clear and not create doubt. Third, when translating from a numerical expression to an expression in the English language, do not assume that the translation is universally understood; provide additional definition where necessary to eliminate uncertainty. Fourth, explain mathematical calculations in plain language if necessary. Unexplained results that leave out the mathematical steps will only force the court and others to guess.

Finally, where patent owners fail to apply these tips to numerical examples, patent litigation defendants must learn to exploit them. Defendants should run the mathematical calculations in examples themselves; never assume that they are correct. Checking each and every example and discovering inconsistencies can be the difference between victory and defeat in litigation.