DCT

2:23-cv-00539

SK nexilis Co Ltd v. Solus Advanced Materials Co Ltd

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I. Executive Summary and Procedural Information

  • Parties & Counsel:
  • Case Identification: 2:23-cv-00539, E.D. Tex., 05/15/2024
  • Venue Allegations: Plaintiff alleges venue is proper because Defendants are foreign corporations that may be sued in any judicial district and have purposefully availed themselves of the U.S. market, including by offering for sale and selling products to customers in Texas.
  • Core Dispute: Plaintiff alleges that Defendants’ battery copper foil products, used in electric vehicle batteries, infringe five U.S. patents related to the physical, chemical, and microstructural properties of electrolytic copper foils.
  • Technical Context: The technology concerns electrolytic copper foil, a critical component for anodes in lithium-ion batteries, the demand for which has grown significantly with the expansion of the electric vehicle market.
  • Key Procedural History: The complaint alleges that Plaintiff sent a notice letter to Defendant Solus on September 27, 2023, identifying infringing products. The original complaint was filed on November 21, 2023. These events are cited to establish Defendants' knowledge of the asserted patents for the purposes of willful infringement.

Case Timeline

Date Event
2010-07-15 Earliest Priority Date for ’541 Patent
2015-06-24 Earliest Priority Date for ’090 Patent
2016-10-04 ’541 Patent Issued
2016-10-12 Earliest Priority Date for ’689 Patent
2017-09-01 Earliest Priority Date for ’014 Patent
2018-01-31 Earliest Priority Date for ’706 Patent
2019-10-01 Defendant Solus Founded
2019-11-19 ’090 Patent Issued
2020-01-01 Defendants allegedly began commercial manufacturing
2020-10-20 ’689 Patent Issued
2022-05-31 ’014 Patent Issued
2023-02-28 ’706 Patent Issued
2023-09-27 Plaintiff sent pre-suit notice letter to Defendant
2023-11-21 Original Complaint Filed
2024-05-15 First 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 Nov. 19, 2019)

  • The Invention Explained:
    • Problem Addressed: The patent describes the problem of rapidly decreasing charge/discharge capacity in secondary batteries over repeated cycles, which leads to short lifespan, user inconvenience, and energy waste (’090 Patent, col. 4:45-51).
    • The Patented Solution: The invention is an electrolytic copper foil for a battery current collector with specifically controlled surface topography on both its shiny and matte sides. The key feature is a "peak count roughness (Rpc)" within a narrow range of 10 to 100, which is a patent-specific metric for the number of microscopic peaks on the foil's surface (’090 Patent, Abstract; col. 4:18-32). This controlled roughness is intended to provide stable capacity maintenance, particularly when the battery uses high-capacity active materials like silicon that are prone to expansion and contraction (’090 Patent, col. 6:12-24).
    • Technical Importance: The invention claims to provide a solution for maintaining battery capacity that goes beyond simply minimizing surface roughness, addressing issues that arise with next-generation, high-capacity battery chemistries (’090 Patent, col. 6:12-24).
  • Key Claims at a Glance:
    • The complaint asserts independent claim 1 (Compl. ¶51).
    • Essential elements of claim 1 include:
      • An electrolytic copper foil for a secondary battery.
      • Comprising a first surface and a second surface opposite the first surface.
      • Wherein each of the first and second surfaces has a peak count roughness Rpc of 10 to 100.
      • Wherein the Rpc is defined as an average of values from three randomly-selected points.
      • Wherein the Rpc at each point is measured as the number of "effective peaks" rising above 0.5 µm per 4 mm sampling length, according to the steel-iron test schedule (SEP 1940).
      • Wherein there is at least one valley deeper than -0.5 µm between adjacent effective peaks.
    • 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 Oct. 20, 2020)

  • The Invention Explained:
    • Problem Addressed: The patent notes that as copper foils become thinner to increase battery capacity, they become more vulnerable to "curling or wrinkling." This makes the foil difficult to handle during manufacturing and can prevent the uniform coating of active material, compromising battery quality and performance (’689 Patent, col. 4:63-67).
    • The Patented Solution: The invention is an electrolytic copper foil defined by a combination of specific, interrelated physical properties designed to ensure it is "easily handleable." These properties include a controlled coefficient of thermal expansion (CTE), a specific range of tensile strength after heat treatment, low weight deviation across the foil, and defined limits on surface peak count and roughness (’689 Patent, Abstract). This multi-factor approach aims to produce a thin foil that is robust enough to withstand the stresses of battery manufacturing and operation (’689 Patent, col. 5:16-54).
    • Technical Importance: This technology addresses a key manufacturing bottleneck—the difficulty of handling ultra-thin materials—enabling the production of higher-capacity batteries without sacrificing manufacturing yield or product reliability (’689 Patent, col. 13:20-27).
  • Key Claims at a Glance:
    • The complaint asserts independent claim 1 (Compl. ¶65).
    • Essential elements of claim 1 include:
      • An electrolytic copper foil comprising a copper layer (with matte and shiny surfaces) and first and second protective layers.
      • A coefficient of thermal expansion between 16 and 22 µm/(m·° C.).
      • A tensile strength between 21 and 36 kgf/mm², measured after a specific heat treatment (190° C. for 1 hour).
      • A weight deviation of 5% or less.
      • A peak count (Pc) for each surface between 3 and 92.
      • A surface roughness (Rz) for each surface of 3.5 µm or less.
    • The complaint does not explicitly reserve the right to assert dependent claims for this patent.

Multi-Patent Capsule: U.S. Patent No. 11,346,014 (the '014 Patent)

  • Patent Identification: 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 the adhesion of negative electrode material to the copper foil. It defines a novel "binding coefficient" calculated from a combination of physical roughness (peak height Rp, peak density) and a chemical property (the amount of chromium attachment on the surface), claiming a foil with a coefficient in a specific range improves adhesion and lowers electrical resistance ('014 Patent, Abstract).
  • Asserted Claims: Independent claim 1 (Compl. ¶82).
  • Accused Features: The complaint alleges that the Accused Products possess the claimed combination of surface roughness, peak density, and chromium attachment that results in a binding coefficient within the patented range (Compl. ¶86).

Multi-Patent Capsule: U.S. Patent No. 11,591,706 (the '706 Patent)

  • Patent Identification: Electrolytic copper foil having excellent handling characteristics in postprocessing, and manufacturing method therefor (Issued Feb. 28, 2023).
  • Technology Synopsis: This patent aims to improve the handling of copper foil and prevent defects like curling and wrinkling. The solution involves controlling the foil's crystallographic orientation by specifying a texture coefficient for the (220) crystal plane, while also minimizing the difference in surface profile (specifically, the Rz/Ra ratio and peak density) between the foil's two sides ('706 Patent, Abstract).
  • Asserted Claims: Independent claim 1 (Compl. ¶96).
  • Accused Features: The complaint alleges the Accused Products have a crystallographic texture and surface property differential that fall within the ranges claimed by the patent (Compl. ¶¶100-102).

Multi-Patent Capsule: U.S. Patent No. 9,457,541 (the '541 Patent)

  • Patent Identification: Copper foil for current collector of lithium secondary battery with improved wrinkle characteristics (Issued Oct. 4, 2016).
  • Technology Synopsis: This patent seeks to prevent the formation of wrinkles on the copper foil by controlling its fundamental crystalline structure. It claims specific ratios between the texture coefficients of the (111), (200), and (220) crystal planes, in combination with defined tensile strength and weight deviation properties, to create a foil with improved wrinkle characteristics ('541 Patent, Abstract).
  • Asserted Claims: Independent claim 1 (Compl. ¶112).
  • Accused Features: The complaint accuses the BF-PLSP and SR-PLSP products of having a crystalline structure, tensile strength, and weight deviation that meet the limitations of the patent (Compl. ¶¶113, 115, 117).

III. The Accused Instrumentality

  • Product Identification: The accused instrumentalities are Defendants' battery copper foil products, including standard battery copper foil (BF-PLSP), high-elongation battery copper foil (SR-PLSP), and high-strength battery foil (HTS-PLSP) (Compl. ¶39).
  • Functionality and Market Context: These products are thin electrolytic copper foils that function as the anode current collector in lithium-ion batteries, primarily for electric vehicles (EVs) (Compl. ¶¶21, 39). The complaint alleges that Defendants manufacture these foils in various thicknesses (e.g., 6-18µm) for different battery types (cylindrical, prismatic, pouch) (Compl. ¶¶41-43). The complaint asserts that Defendants compete directly with SKn and supply these foils to "global-tier battery manufacturer[s]" and "global OEM company," including for use by EV manufacturers in the United States (Compl. ¶¶10, 13, 48). Figure 3 of the complaint provides scanning electron microscope images distinguishing the "drum side" and "electrolyte side" of the three accused product types (Compl. p. 15, Fig. 3).

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 foil products for use in secondary batteries, such as EV batteries. ¶53 col. 4:18-21
...the electrolytic copper foil comprising: a first surface; and a second surface opposite to the first surface, The Accused Products have a first surface ("drum side") and a second surface ("electrolyte side"). This is shown in a provided image of the accused products. ¶54; p. 15, Fig. 3 col. 5:22-27
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. ¶55 col. 6:45-56
wherein the peak count roughness Rpc of each of the first and second surfaces is an average of peak count roughness Rpc values measured at randomly-selected three points, The complaint alleges that measuring the Rpc values at three points and averaging them results in a value between 10 and 100. ¶55 col. 4:24-27
the peak count roughness Rpc of each point is the number of effective peaks which rise above an upper criteria line of 0.5 µm per unit sampling length of 4 mm in a surface roughness profile obtained according to steel-iron test schedule (SEP 1940), 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 the Accused Products meet the specific measurement methodology defined in the claim, including the SEP 1940 standard and the peak/valley criteria. ¶55 col. 4:27-32; col. 6:33-44
  • Identified Points of Contention:
    • Evidentiary Question: The complaint's allegation of infringement rests on a conclusory statement that the Accused Products meet the specific "peak count roughness Rpc" range (Compl. ¶55). A key point of contention will be whether Plaintiff can produce factual evidence, such as test results from the Accused Products, demonstrating that the foils meet the numerically-defined Rpc metric when measured according to the precise, multi-step methodology required by the claim (i.e., the SEP 1940 standard, the 0.5 µm peak height, and the -0.5 µm valley depth).

'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... a first protective layer on the matte surface... and a second protective layer on the shiny surface... The complaint alleges the Accused Products have a "drum side" and "electrolyte side," and consist of a copper layer with corresponding protective layers. ¶68; p. 20, Fig. 6 col. 5:1-7
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. ¶69 col. 5:31-35
a tensile strength... 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, referencing a marketing graphic. The graphic states a "General purpose product" has a strength of "30-40 kgf/mm²." ¶70; p. 21, Fig. 7 col. 6:1-6
a weight deviation of the electrolytic copper foil is 5% or less, The complaint alleges the weight deviation of the Accused Products is 5% or less. ¶71 col. 6:15-18
a peak count (Pc) of each of the first and second surfaces... ranges from 3 to 92, and each of the first and second surfaces has a surface roughness (Rz) of 3.5 µm or less. The complaint alleges that the Accused Products have a peak count and surface roughness that meet the claimed ranges. ¶72 col. 4:45-48
  • Identified Points of Contention:
    • Technical Question: The claim requires a specific tensile strength (21-36 kgf/mm²) measured after a specific heat treatment (190° C. for 1 hour). The complaint's evidence is a marketing graphic (Fig. 7) that shows a "General purpose product" having a strength of "30-40 kgf/mm²" (Compl. ¶70). This raises the question of whether the data in the marketing material was obtained under the claim's required testing conditions and whether the "General purpose product" corresponds to a specific Accused Product that also meets every other limitation of the claim.
    • Scope Question: Infringement requires that an accused product meet every one of the five distinct numerical limitations recited in the claim (CTE, tensile strength, weight deviation, peak count, and roughness). The analysis will question whether any single Accused Product simultaneously possesses all of these specific properties.

V. Key Claim Terms for Construction

Term from the '090 Patent: "peak count roughness Rpc"

  • The Term: "peak count roughness Rpc"
  • Context and Importance: This term is the central feature of the '090 patent's asserted claim. It is not a standard industry metric but is instead defined within the patent itself by reference to a specific testing standard (SEP 1940), a peak height criterion, and a valley depth criterion. The outcome of the infringement analysis for the '090 patent will depend entirely on the construction of this term and the methodology used to measure it.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party could argue that the definition provided in claim 1 is exhaustive and should be applied precisely as written, without importing limitations from the specification's embodiments or examples.
    • Evidence for a Narrower Interpretation: A party may argue that the term's meaning is informed by the specification's focus on solving problems associated with high-capacity active materials containing silicon ('090 Patent, col. 6:12-24). They might also point to the specific measurement conditions and results in the patent's examples as context for how the term should be understood and applied ('090 Patent, col. 8, Table 1).

Term from the '689 Patent: "tensile strength... measured after a heat treatment at a temperature of 190° C. for 1 hour"

  • The Term: "a tensile strength... measured after a heat treatment at a temperature of 190° C. for 1 hour, ranges from 21 to 36 kgf/mm²"
  • Context and Importance: This limitation defines a property of the foil not in its as-sold state, but after a specific conditioning process. Practitioners may focus on this term because infringement depends on the results of a physical test that must be performed according to the claim's instructions. The complaint's reliance on a marketing graphic (Compl. ¶70, Fig. 7) creates an immediate question about whether that graphic reflects the specific post-treatment conditions required by the claim.
  • Intrinsic Evidence for Interpretation:
    • Evidence for a Broader Interpretation: A party may contend that the heat treatment specified in the claim mimics standard processing steps in battery manufacturing, and therefore any product intended for such use that has a strength in the required range would necessarily infringe.
    • Evidence for a Narrower Interpretation: A party could argue that the claim requires strict adherence to the specified testing protocol. They may argue that marketing materials, which are not technical data sheets, cannot prove the tensile strength under these exact conditions and that the foil's properties could change in ways not reflected in such materials.

VI. Other Allegations

  • Indirect Infringement: The complaint alleges both induced and contributory infringement for all asserted patents. Inducement is based on allegations that Defendants actively encourage customers and manufacturers to import and use the Accused Products in the U.S. (e.g., Compl. ¶¶58, 75). Contributory infringement is based on allegations that the Accused Products are non-staple articles of commerce, are specially designed to infringe, and have no substantial non-infringing uses (e.g., Compl. ¶¶60, 77).
  • Willful Infringement: The complaint alleges willful infringement based on Defendants' knowledge of the patents. It alleges knowledge of the '541, '090, '689, '014, and '706 patents from at least the receipt of a notice letter on September 27, 2023, and subsequent filings (Compl. ¶¶37, 61, 78, 92, 108, 123). The complaint alleges that Defendants' infringement has continued despite this knowledge.

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

  • A central issue will be one of evidentiary proof: The asserted patents claim foils defined by very specific, quantitative metrics (e.g., "peak count roughness Rpc," "binding coefficient," texture coefficient ratios, and multiple physical properties) that must be measured by precise methods. A key question will be whether Plaintiff can produce sufficient testing data from the Accused Products to demonstrate that they meet every required numerical limitation of a given claim, moving beyond the complaint's reliance on marketing materials and conclusory allegations.
  • A second core issue will be one of claim construction: The patents introduce novel, multi-part definitions for terms like "peak count roughness Rpc" ('090 patent) and "binding coefficient" ('014 patent). The construction of these patent-specific metrics, and the precise methodology for their measurement, will be a critical battleground that will define the scope of the claims and may ultimately determine the outcome of the infringement analysis.