DCT

2:23-cv-00539

SK nexilis Co Ltd v. Solus Advanced Materials Co Ltd

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Key Events
Amended Complaint

I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:23-cv-00539, E.D. Tex., 08/04/2025
  • Venue Allegations: Venue is asserted on the basis that all defendants are foreign corporations that do not reside in the United States and thus may be sued in any judicial district.
  • Core Dispute: Plaintiff alleges that Defendants’ battery copper foils infringe five U.S. patents related to the material properties and manufacturing of electrolytic copper foils used in lithium-ion batteries.
  • Technical Context: The technology concerns thin electrolytic copper foils, a critical component for anodes in high-capacity lithium-ion batteries for electric vehicles (EVs), a rapidly growing global market.
  • Key Procedural History: The complaint alleges that Plaintiff sent a notice letter to Defendant Solus on September 27, 2023, notifying it of infringement. This date may be used to establish a potential start date for willful infringement for patents other than U.S. Patent No. 9,457,541.

Case Timeline

Date Event
2010-07-15 U.S. Patent No. 9,457,541 Priority Date
2015-06-24 U.S. Patent No. 10,480,090 Priority Date
2016-10-04 U.S. Patent No. 9,457,541 Issues
2016-10-12 U.S. Patent No. 10,811,689 Priority Date
2017-09-01 U.S. Patent No. 11,346,014 Priority Date
2018-01-31 U.S. Patent No. 11,591,706 Priority Date
2019-10-01 Solus founded (approximate month)
2019-11-19 U.S. Patent No. 10,480,090 Issues
2020-01-01 Defendants begin commercial manufacturing (approximate year)
2020-10-20 U.S. Patent No. 10,811,689 Issues
2022-05-31 U.S. Patent No. 11,346,014 Issues
2023-02-28 U.S. Patent No. 11,591,706 Issues
2023-09-27 Plaintiff sends notice letter to Defendant Solus
2023-11-21 Original Complaint filed
2025-08-04 Second Amended Complaint filed

II. Technology and Patent(s)-in-Suit Analysis

U.S. Patent No. 10,480,090 - “Electrolytic copper foil, current collector comprising the same, electrode comprising the same, secondary battery comprising the same, and method for manufacturing the same,” Issued November 19, 2019

The Invention Explained

  • Problem Addressed: The patent’s background section states that while lithium secondary batteries require high charge/discharge capacity, repeated cycles can cause capacity to decrease rapidly. It notes that conventional approaches to improving adhesion between the copper foil and the active material by controlling surface roughness (e.g., ten-point mean roughness) were insufficient to guarantee high capacity maintenance (’090 Patent, col. 1:31-53; col. 5:6-18).
  • The Patented Solution: The invention proposes controlling a different surface property: the "peak count roughness (Rpc)." By ensuring the number of microscopic peaks on both surfaces of the foil falls within a specific range (10 to 100), the foil can better adhere to the active material layer without creating points of stress concentration that degrade battery performance over time (’090 Patent, Abstract; col. 5:19-55). This specific roughness profile is defined by a standardized measurement protocol (SEP 1940) which includes counting "effective peaks" that rise above a certain height and are separated by valleys of a certain depth (’090 Patent, col. 5:25-44; Fig. 2).
  • Technical Importance: This approach provided a new parameter for optimizing copper foils, enabling the production of more reliable high-capacity batteries needed for the growing EV market (Compl. ¶22, ¶25).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶80).
  • Claim 1 requires:
    • An electrolytic copper foil for a secondary battery
    • Comprising a first surface and a second surface
    • Wherein each surface has a peak count roughness Rpc of 10 to 100
    • Wherein the Rpc is an average of values from three points
    • Wherein the Rpc is defined as the number of effective peaks rising above an upper criteria line of 0.5 µm and having at least one valley deeper than a lower criteria line of -0.5 µm between adjacent peaks, measured per a 4 mm sampling length according to the SEP 1940 standard.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 10,811,689 - “Easily handleable electrolytic copper foil, electrode comprising the same, secondary battery comprising the same, and method for manufacturing the same,” Issued October 20, 2020

The Invention Explained

  • Problem Addressed: The patent identifies a manufacturing challenge: extremely thin copper foils (10 µm or less) are prone to curling and wrinkling, which makes them difficult to handle in production and can prevent the uniform application of the active material needed for a battery anode (’689 Patent, col. 1:63 - col. 2:2).
  • The Patented Solution: The invention is a copper foil defined by a specific combination of five distinct physical properties designed to enhance its "handleability" and durability. These properties are: (1) a coefficient of thermal expansion within a narrow range, (2) a specific tensile strength after heat treatment, (3) a low weight deviation, (4) a particular peak count on its surfaces, and (5) a low surface roughness (’689 Patent, Abstract; col. 2:35-51). This multi-factor solution ensures the foil is robust enough for manufacturing processes while still meeting the performance needs of a high-capacity battery.
  • Technical Importance: By defining a foil with superior mechanical stability, the invention sought to reduce manufacturing defects and improve the reliability of batteries made with ultra-thin foils, which are critical for increasing battery energy density (Compl. ¶25).

Key Claims at a Glance

  • The complaint asserts independent claim 1 (Compl. ¶94).
  • Claim 1 requires:
    • An electrolytic copper foil with a first and second surface
    • Comprising a copper layer (with matte and shiny surfaces) and protective layers
    • Wherein the foil has a coefficient of thermal expansion of 16 to 22 µm/(m·° C.) measured under specific heating conditions
    • Wherein the foil has a tensile strength of 21 to 36 kgf/mm² after a specific heat treatment
    • Wherein the foil has a weight deviation of 5% or less
    • Wherein each surface has a peak count (Pc) of 3 to 92
    • Wherein each surface has a surface roughness (Rz) of 3.5 µm or less.
  • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

U.S. Patent No. 11,346,014 - “Electrolytic copper foil, method for producing same, and high-capacity Li secondary battery negative electrode including same,” Issued May 31, 2022

  • Technology Synopsis: This patent addresses improving the adhesion between the copper foil and the battery’s active material. The solution is a foil with a specific "binding coefficient," which is calculated from a formula incorporating three factors: peak height (Rp), peak density, and the amount of chromium attached to the surface (Compl. ¶111; ’014 Patent, col. 2:14-20).
  • Asserted Claims: Independent claim 1 is asserted (Compl. ¶111).
  • Accused Features: The Accused Products are alleged to possess a binding coefficient between 1.5 and 9.4, as calculated by the formula defined in the patent (Compl. ¶115).

U.S. Patent No. 11,591,706 - “Electrolytic copper foil having excellent handling characteristics in postprocessing, and manufacturing method therefor,” Issued February 28, 2023

  • Technology Synopsis: This patent aims to improve the handling characteristics of copper foil to prevent curls and wrinkles during manufacturing. The solution involves controlling the foil’s crystalline structure to achieve a specific "texture coefficient" for the (220) crystal plane, and also controlling the difference in surface roughness ratios (Rz/Ra) and peak densities (PD) between the foil’s two surfaces to be below specified thresholds (Compl. ¶125; ’706 Patent, Abstract).
  • Asserted Claims: Independent claim 1 is asserted (Compl. ¶125).
  • Accused Features: The Accused Products are alleged to meet the claimed texture coefficient range (0.4 to 1.32) and the claimed maximum differences for Rz/Ra and peak density (Compl. ¶129-131).

U.S. Patent No. 9,457,541 - “Copper foil for current collector of lithium secondary battery with improved wrinkle characteristics,” Issued October 4, 2016

  • Technology Synopsis: This patent seeks to prevent the generation of wrinkles on the copper foil by controlling its crystalline structure. The invention is a copper foil defined by specific percentage ratios for the texture coefficients of its (111), (200), and (220) crystal surfaces relative to the total sum of those coefficients (’541 Patent, Abstract).
  • Asserted Claims: Independent claim 1 is asserted (Compl. ¶141).
  • Accused Features: The Accused Products, specifically the BF-PLSP and SR-PLSP types, are alleged to have crystalline structures that meet the four specific texture coefficient ratio ranges required by the claim (Compl. ¶144).

III. The Accused Instrumentality

Product Identification

  • The accused instrumentalities are Defendants’ battery copper foils, including standard battery copper foil (BF-PLSP), high-elongation battery copper foil (SR-PLSP), and high-strength battery foil (HTS-PLSP) (Compl. ¶9, ¶39).

Functionality and Market Context

  • The complaint alleges these products are thin electrolytic copper foils, with thicknesses ranging from 6 to 18µm, used as anode current collectors in lithium-ion batteries for electric vehicles (Compl. ¶21, ¶41). They are marketed for use in various battery types (cylindrical, prismatic, pouch) and are promoted as enhancing battery performance by enabling the loading of more active materials and minimizing deformation during charging and discharging (Compl. ¶42-43, ¶46). The complaint asserts that Defendants compete directly with Plaintiff in the market for supplying these foils to EV battery manufacturers and have entered into supply contracts with U.S. customers, including those in Texas (Compl. ¶10, ¶13-14).

IV. Analysis of Infringement Allegations

'090 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
An electrolytic copper foil for a secondary battery The Accused Products are electrolytic copper foils for use in secondary EV batteries. ¶82 col. 1:11-16
the electrolytic copper foil comprising: a first surface; and a second surface opposite to the first surface The Accused Products have two opposing surfaces, identified in marketing materials as a "drum side" and an "electrolyte side." A marketing image included as Figure 3 shows SEM photographs of these two distinct surfaces. ¶82-83 col. 5:21-27
wherein each of the first and second surfaces has a peak count roughness Rpc of 10 to 100 The complaint alleges that the first and second surfaces of the Accused Products have a peak count roughness (Rpc) between 10 and 100. ¶84 col. 5:45-47
wherein the peak count roughness Rpc...is the number of effective peaks which rise above an upper criteria line of 0.5 µm...and there is at least one valley deeper than a lower criteria line of -0.5 µm between adjacent ones of the effective peaks. The complaint alleges that when measured according to the standard, the Accused Products meet the claimed Rpc definition, including the criteria for effective peaks and valleys. ¶84 col. 5:29-44

'689 Patent Infringement Allegations

Claim Element (from Independent Claim 1) Alleged Infringing Functionality Complaint Citation Patent Citation
An electrolytic copper foil...comprising: a copper layer including a matte surface...and a shiny surface The Accused Products are electrolytic copper foils with two distinct surfaces, referred to as a "drum side" and an "electrolyte side." ¶96-97 col. 5:1-12
a coefficient of thermal expansion...ranges from 16 to 22 µm/(m·° C.) The complaint alleges that the Accused Products have a coefficient of thermal expansion within the claimed range when measured according to the specified protocol. ¶98 col. 5:32-38
a tensile strength...which is measured after a heat treatment at a temperature of 190° C. for 1 hour, ranges from 21 to 36 kgf/mm² The complaint alleges the Accused Products have a tensile strength within this range. The complaint references Figure 7, a marketing document, which states a "General purpose product" has a strength of "30~40 kgf/mm²." ¶99 col. 6:1-5
a weight deviation of the electrolytic copper foil is 5% or less The Accused Products are alleged to have a weight deviation of 5% or less. ¶100 col. 6:16-19
a peak count (Pc) of each of the first and second surfaces...ranges from 3 to 92 The Accused Products are alleged to have a peak count between 3 and 92 on each surface. ¶101 col. 7:51-64
each of the first and second surfaces has a surface roughness (Rz) of 3.5 µm or less The Accused Products are alleged to have a surface roughness of 3.5 µm or less on each surface. ¶101 col. 7:65-67
  • Identified Points of Contention:
    • Evidentiary Questions: A central point of contention will be factual and evidentiary. The complaint alleges that the Accused Products meet numerous, specific, numerically-defined parameters (e.g., peak count roughness, coefficient of thermal expansion, texture coefficients) that are defined by precise measurement protocols in the patents. However, the complaint does not appear to provide extrinsic test data or analysis to support these allegations, instead making conclusory statements (Compl. ¶84, ¶98, ¶100, ¶101). The allegation for tensile strength in the ’689 patent, for example, relies on a marketing graphic (Compl. ¶99; Fig. 7), raising the question of whether this marketing claim corresponds to the specific post-heat-treatment measurement required by the patent claim.
    • Scope Questions: The infringement theories depend on mapping the physical structure of the accused foils to the claim limitations. For example, the complaint maps the "drum side" and "electrolyte side" shown in product literature to the "first surface" and "second surface" recited in the claims (Compl. ¶83, ¶97). A potential dispute may arise over whether these commercially-identified surfaces correspond directly to the surfaces as defined and characterized in the patent specifications.

V. Key Claim Terms for Construction

  • For the ’090 Patent:

    • The Term: "peak count roughness Rpc"
    • Context and Importance: This term is the central technical limitation of claim 1 of the ’090 patent. The infringement analysis for this patent will hinge on whether the accused foils have a surface texture that falls within the claimed numeric range (10 to 100) as defined by the specific, multi-part measurement protocol recited in the claim itself. Practitioners may focus on whether this detailed definition constitutes an inescapable part of the claim scope.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: The claim preamble states the invention is "An electrolytic copper foil," suggesting the claim is directed to a product, not a method of measurement. A party might argue that any standard industry method that accurately measures peak count should suffice.
      • Evidence for a Narrower Interpretation: The claim body provides an explicit and detailed definition, referencing the "steel-iron test schedule (SEP 1940)" and defining "effective peaks" with specific upper (0.5 µm) and lower (-0.5 µm) criteria lines (’090 Patent, col. 10:11-28; Fig. 2). The specification elaborates on this, stating that if a valley between peaks is not deep enough, the lower peak is "excluded in determining the number of 'effective peaks'" (’090 Patent, col. 6:38-44). This language may support an argument that the claim scope is strictly limited to results obtained from this exact methodology.

  • For the ’689 Patent:

    • The Term: "...tensile strength...which is measured after a heat treatment at a temperature of 190° C. for 1 hour..."
    • Context and Importance: This limitation defines a property of the copper foil not in its as-sold state, but only after undergoing a specific laboratory heat treatment. Infringement depends on whether the accused foil would have the claimed property if it were subjected to this process. This raises questions about how to prove infringement for a product that is not used or sold in the post-heat-treatment condition.
    • Intrinsic Evidence for Interpretation:
      • Evidence for a Broader Interpretation: A party could argue this is a standard way to define an intrinsic material property, and that the protocol simply provides a clear, repeatable standard for testing. The specification describes this as a way to characterize the foil's durability under conditions mimicking battery operation (’689 Patent, col. 6:1-15).
      • Evidence for a Narrower Interpretation: A defendant may argue that this "product-by-process" style limitation improperly restricts the claim to foils made by a process that inherently imparts this characteristic. They may also contend that infringement can only be proven by physically performing the heat treatment on an accused product and measuring the result, raising the evidentiary bar for the plaintiff.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for all five asserted patents. The inducement theory is based on allegations that Defendants knowingly and intentionally encourage third-party customers and manufacturers to import and use the Accused Products in the U.S. in an infringing manner (e.g., Compl. ¶87, ¶104). Contributory infringement is alleged on the basis that the Accused Products are non-staple components specially made and adapted for infringing use with no substantial non-infringing uses (e.g., Compl. ¶89, ¶106).
  • Willful Infringement: Willfulness is alleged for the ’090, ’689, ’014, and ’706 patents based on Defendants' alleged knowledge since at least the receipt of Plaintiff's September 27, 2023 notice letter (Compl. ¶90, ¶107, ¶121, ¶137). For the ’541 patent, willfulness is alleged based on knowledge since the filing of the First Amended Complaint (Compl. ¶38).

VII. Analyst’s Conclusion: Key Questions for the Case

  • A core issue will be one of evidentiary proof: The complaint makes numerous allegations that the accused foils meet specific, numerically-defined physical property ranges (e.g., peak count, tensile strength, thermal expansion, texture coefficients) that are governed by detailed measurement protocols. A key question for the case will be whether discovery and expert testing can produce evidence that substantiates these conclusory allegations and confirms the accused foils fall within the claimed parameters when tested according to the patents' explicit instructions.
  • A second central issue will be one of claim scope and measurement methodology: The asserted claims incorporate highly specific testing protocols directly into the claim language. The case may turn on how strictly the court construes these limitations—for example, whether the definition of "peak count roughness Rpc" in the ’090 patent requires strict adherence to the SEP 1940 standard and the "effective peak" counting rule, or whether other industry-standard measurements could be deemed equivalent.