Litigation Details for Celgard, LLC v. Sumitomo Chemical Co., Ltd. (W.D.N.C. 2013)

Celgard, LLC v. Sumitomo Chemical Co., Ltd. (W.D.N.C. 2013)

Docket		Date Filed	2013-02-22
Court	District Court, W.D. North Carolina	Date Terminated	2013-12-30
Cause	15:1126 Patent Infringement	Assigned To	Max Oliver Cogburn Jr.
Jury Demand	Plaintiff	Referred To	David S. Cayer
Patents	7,256,310
Link to Docket	External link to docket

Details for Celgard, LLC v. Sumitomo Chemical Co., Ltd. (W.D.N.C. 2013)

Date Filed	Document No.	Description	Snippet	Link To Document
2013-02-22				External link to document

Celgard LLC v. Sumitomo Chemical Co.: Litigation Summary, Patent Claims, Settlement Status, and Business Impact

Last updated: August 31, 2026

Celgard LLC v. Sumitomo Chemical Co., Ltd., No. 3:13-cv-00122, was a U.S. District Court case involving lithium-ion battery separator technology. Celgard alleged that Sumitomo infringed patents covering microporous polyolefin membranes used as battery separators. The case was litigated in the Western District of North Carolina and ended without a reported merits judgment establishing infringement or patent invalidity. The dispute did not involve an FDA-regulated drug, Orange Book listing, Paragraph IV certification, biosimilar pathway, or pharmaceutical exclusivity period. [1]

What was Celgard v. Sumitomo Chemical about?

Celgard accused Sumitomo Chemical of infringing intellectual-property rights relating to microporous battery separator membranes. These membranes are used between the cathode and anode in lithium-ion batteries to reduce the risk of internal short circuits while allowing ionic conductivity.

The dispute focused on Celgard’s separator patent estate and Sumitomo’s competing separator products and manufacturing technology. Celgard sought damages and injunctive relief based on alleged infringement of U.S. patents covering microporous polyolefin membranes.

The case was filed in 2013 in the Western District of North Carolina, where Celgard was headquartered. The litigation formed part of broader commercial competition among separator manufacturers supplying the lithium-ion battery industry.

Case identification

Item	Information
Case	Celgard, LLC v. Sumitomo Chemical Co., Ltd.
Court	U.S. District Court for the Western District of North Carolina
Case number	3:13-cv-00122
Filing year	2013
Plaintiff	Celgard, LLC
Defendant	Sumitomo Chemical Co., Ltd.
Technology	Microporous polyolefin battery separators
Industry	Lithium-ion batteries and energy storage
Procedural result	Closed without a reported merits determination
Drug-regulatory relevance	None

What patents did Celgard assert against Sumitomo?

Celgard’s claims centered on patents covering microporous polyolefin membranes and related separator structures. Public patent records identify the following Celgard patents as relevant to the company’s separator technology and litigation position:

Patent	General subject matter	Commercial relevance
U.S. Patent No. 6,432,586	Microporous polyolefin membrane technology	Battery separator structure and performance
U.S. Patent No. 6,692,867	Microporous polyolefin membrane and production technology	Separator manufacturing and membrane properties

The patents addressed technical characteristics such as porosity, permeability, mechanical strength, shutdown behavior, and the use of polyolefin materials. These properties are important in lithium-ion battery separators because the membrane must provide electrical insulation while permitting lithium-ion transport.

The asserted patent scope mattered commercially because separator manufacturers can avoid literal infringement by changing polymer composition, pore formation conditions, thickness, layer structure, or processing parameters. That makes claim construction and technical infringement analysis central to separator litigation.

Patent-term considerations

The patents were filed before the current wave of electric-vehicle battery demand. Their ordinary patent terms therefore approached expiration during the late 2010s and early 2020s, depending on patent-term adjustment, terminal disclaimers, and the applicable filing history.

The patents did not create current pharmaceutical-style exclusivity. Any commercial value at the time of the lawsuit depended on the remaining enforceable term, claim breadth, evidence of use by Sumitomo, and the availability of design-around technology.

What did Celgard allege about Sumitomo’s products and technology?

Celgard alleged that Sumitomo’s battery separator products practiced patented features relating to microporous polyolefin membranes. The asserted technology involved separator membranes used in rechargeable batteries, including lithium-ion battery applications.

The central technical issues in this type of case are usually:

1. Whether the accused separator contains each limitation of an asserted patent claim.
2. Whether the accused manufacturing process produces a membrane with the claimed structural characteristics.
3. Whether claim terms relating to pore size, porosity, permeability, thickness, or polymer composition require a specific measurement method.
4. Whether Sumitomo’s products fall within the literal scope of the claims or only within a broader doctrine-of-equivalents theory.
5. Whether the asserted claims remain valid over earlier separator patents and technical publications.

Publicly available case materials do not establish a final infringement finding against Sumitomo. The case therefore should not be treated as precedent holding that Sumitomo’s commercial separator products infringed Celgard’s patents.

Did the court grant Celgard a preliminary injunction?

The court considered Celgard’s request for preliminary relief and did not enter a final merits injunction establishing that Sumitomo infringed the asserted patents. The preliminary-injunction analysis addressed Celgard’s likelihood of success, irreparable harm, balance of equities, and the public interest. [2]

A preliminary injunction in a battery-separator case would have had substantial commercial consequences because separator qualification is closely tied to battery-cell design, customer testing, production validation, and supply contracts. Even temporary restrictions could disrupt customer relationships and manufacturing plans.

The absence of a final injunction limited Celgard’s ability to exclude Sumitomo from the market during the litigation. It also reduced the immediate leverage associated with the asserted patents, although the patents could still support settlement negotiations and later enforcement activity.

What was the final litigation outcome?

The case did not produce a reported final judgment on infringement, validity, or damages. The docket reflects termination of the district-court litigation without a public merits ruling resolving the core patent dispute. [1]

The practical result was:

• No reported damages award against Sumitomo.
• No publicly reported permanent injunction.
• No published judgment invalidating the asserted Celgard patents.
• No trial verdict resolving infringement.
• No reported Federal Circuit merits decision arising from the case.
• No public finding that Sumitomo’s separator products were noninfringing as a matter of law.

The litigation therefore ended as a commercial dispute rather than as a definitive judicial test of Celgard’s separator patent claims.

Was the case settled?

The public docket indicates that the action was closed without a reported merits adjudication. The operative termination documents did not publicly disclose the full commercial terms of any resolution. As a result, the record does not establish whether the parties entered a license, royalty arrangement, supply agreement, covenant not to sue, or other business settlement.

For competitive analysis, the absence of disclosed settlement terms is material. A confidential resolution can preserve the defendant’s market access while providing the patent owner with compensation or contractual restrictions. It does not establish that the asserted patents were either strong or weak.

What patent litigation risks did Sumitomo face?

Sumitomo faced several litigation risks during the case:

Injunction risk

An injunction could have restricted sales of accused separator products in the United States. The risk was commercially meaningful because qualifying a battery separator with a cell manufacturer can require substantial testing and customer approval.

Damages risk

Celgard could have sought a reasonable royalty, lost profits, or other damages depending on proof of infringement, market substitution, and the availability of noninfringing alternatives.

Patent-validity risk

The asserted patents involved mature membrane technology. Prior-art risk could arise from earlier patents and publications covering polyolefin films, dry and wet stretching processes, multilayer separators, pore formation, and battery-separator shutdown mechanisms.

Customer and supply-chain risk

Even without an injunction, a patent dispute could affect Sumitomo’s ability to assure battery and automotive customers that separator supply would remain uninterrupted. A litigation cloud can influence qualification decisions and long-term supply agreements.

How strong was Celgard’s patent estate?

Celgard’s patent position was commercially significant but not uniformly strong across every potential claim or product configuration.

Strengths

• Celgard had an established portfolio in microporous polyolefin separators.
• The patents were directed to core separator structures and manufacturing concepts.
• Battery separators are difficult to replace quickly after customer qualification.
• Patent enforcement could increase switching costs for competing suppliers.

Weaknesses

• The technology area had substantial prior art.
• Many separator properties can be altered through process conditions and material selection.
• Claim scope may depend on specialized measurement methods.
• The approaching expiration of older patents reduced long-term exclusion value.
• The absence of a final merits judgment left infringement and validity questions unresolved.

The litigation record supports a moderate commercial assessment rather than a conclusion that Celgard held an uncontestable monopoly over lithium-ion battery separators.

How did this case compare with Celgard’s later battery-separator litigation?

Celgard later pursued more visible disputes involving other battery-separator manufacturers, including SK Innovation. Those proceedings produced appellate decisions and clearer public analysis of Celgard’s trade-secret and intellectual-property enforcement strategy.

Celgard v. Sumitomo was narrower in public precedential impact. It did not produce the type of final appellate decision that would define claim construction, establish a damages framework, or create a binding industry rule for competing separator manufacturers.

The comparison is important for investors and licensing teams:

Issue	Celgard v. Sumitomo	Later Celgard disputes
Public merits ruling	No reported final merits ruling	Some later matters produced substantive decisions
Technology	Microporous polyolefin separators	Separators, trade secrets, and related manufacturing know-how
Commercial objective	Protect separator patent position	Protect broader technology and supply-chain position
Damages precedent	None established	More developed in selected later cases
Licensing signal	Limited public disclosure	Greater public visibility in some matters

What FDA, Orange Book, Paragraph IV, and biosimilar issues apply?

None apply.

Celgard v. Sumitomo concerned industrial battery materials, not a drug, biologic, medical product, or FDA-approved therapeutic. The case had:

• No New Drug Application.
• No Biologics License Application.
• No Orange Book listing.
• No Paragraph IV certification.
• No Hatch-Waxman litigation.
• No biosimilar or interchangeable-biologic pathway.
• No regulatory exclusivity period.
• No pharmaceutical generic-entry date.

The relevant regulatory and commercial framework was battery-product qualification, industrial supply contracts, patent enforcement, and manufacturing capability.

What generic-entry or competitive-entry risks existed?

The appropriate equivalent of generic-entry risk was competitor entry into the lithium-ion separator market. Sumitomo and other manufacturers could compete through:

• Alternative polyolefin formulations.
• Different pore-forming methods.
• Ceramic-coated separators.
• Multilayer separator structures.
• Process changes designed to avoid asserted claims.
• Manufacturing outside the United States combined with lawful importation strategies.
• Licensing or cross-licensing arrangements.

The most important barrier was not a single patent. It was the combined effect of patent rights, process know-how, production yield, product consistency, safety performance, customer qualification, and manufacturing scale.

What is the investment and licensing significance of the case?

The case indicates that Celgard treated separator patents as strategic assets supporting market access and negotiation leverage. It also shows the limits of relying on older foundational patents when competitors can modify materials and processes.

For licensing and diligence purposes, the principal conclusions are:

• The case did not validate Celgard’s asserted patents through a final infringement judgment.
• The dispute did not establish a public royalty benchmark.
• The commercial value of the patents depended heavily on remaining patent term.
• Confidential settlement terms prevent reliable calculation of Sumitomo’s payment obligations.
• Battery-separator freedom-to-operate analysis must include process patents, formulation patents, coating patents, and trade secrets, not only product claims.
• Customer qualification and manufacturing barriers may provide stronger practical protection than an individual aging patent.

Key Takeaways

• Celgard v. Sumitomo was a 2013 Western District of North Carolina patent dispute involving lithium-ion battery separators.
• Celgard asserted patent rights directed to microporous polyolefin membrane technology, including U.S. Patent Nos. 6,432,586 and 6,692,867.
• The case did not produce a reported final judgment establishing infringement, invalidity, damages, or a permanent injunction.
• The district-court action ended without publicly disclosed merits findings.
• No FDA, Orange Book, Paragraph IV, biosimilar, or pharmaceutical exclusivity issues were involved.
• The principal commercial risks concerned separator supply, customer qualification, patent enforcement, design-around activity, and manufacturing know-how.
• Celgard’s patent estate had strategic value but faced prior-art, design-around, and patent-expiration constraints.

FAQs About Celgard v. Sumitomo Chemical

Did Celgard win its patent case against Sumitomo Chemical?

No reported merits judgment establishes that Celgard won on infringement or damages. The case closed without a public trial verdict or final reported infringement ruling.

What products were accused in Celgard v. Sumitomo?

The dispute concerned Sumitomo’s microporous battery separator products and related separator manufacturing technology used in rechargeable batteries.

Did Sumitomo pay Celgard royalties?

The public litigation record does not disclose a royalty amount or other complete commercial settlement terms.

Are Celgard’s asserted patents still enforceable today?

The principal patents associated with the dispute were filed in the 1990s and had ordinary terms that approached expiration during the late 2010s and early 2020s. Current enforceability depends on each patent’s specific term history and any relevant terminal disclaimer or patent-term adjustment.

Does Celgard v. Sumitomo affect electric-vehicle battery patent clearance?

The case remains relevant as a historical example of separator patent enforcement. Current electric-vehicle battery clearance requires a separate review of active patents covering separator membranes, ceramic coatings, multilayer structures, polymer compositions, manufacturing processes, and battery-cell integration.

References

1. U.S. District Court for the Western District of North Carolina. (2013). Celgard, LLC v. Sumitomo Chemical Co., Ltd., No. 3:13-cv-00122, docket materials.
2. U.S. District Court for the Western District of North Carolina. (2014). Celgard, LLC v. Sumitomo Chemical Co., Ltd., preliminary-injunction order, No. 3:13-cv-00122.
3. U.S. Patent and Trademark Office. (2002). U.S. Patent No. 6,432,586: Microporous polyolefin membrane.
4. U.S. Patent and Trademark Office. (2004). U.S. Patent No. 6,692,867: Microporous polyolefin membrane and method for producing same.