DCT
4:19-cv-05784
Celgard LLC v. Shenzhen Senior Technology Material Co Ltd US Rese
Key Events
Complaint
I. Executive Summary and Procedural Information
- Parties & Counsel:
- Plaintiff: Celgard, LLC (Delaware)
- Defendant: Shenzhen Senior Technology Material Co. Ltd. (US) Research Institute, and Shenzhen Senior Technology Material Co. Ltd. (China)
- Plaintiff’s Counsel: Robins Kaplan LLP
- Case Identification: 5:19-cv-05784, N.D. Cal., 09/16/2019
- Venue Allegations: Venue is alleged to be proper because the foreign parent corporation may be sued in any judicial district and because a substantial part of the events giving rise to the claims allegedly occurred in the Northern District of California.
- Core Dispute: Plaintiff alleges that Defendant’s lithium-ion battery separators infringe patents related to ceramic-coated safety separators and manufacturing processes for separators, and further alleges that these products were developed through the misappropriation of trade secrets.
- Technical Context: The technology involves microporous separators, a critical component in lithium-ion batteries that prevents electrical shorting between the anode and cathode while allowing ion flow, directly impacting the safety and performance of batteries used in electric vehicles and consumer electronics.
- Key Procedural History: The complaint notes that the predecessor patent to one of the patents-in-suit survived three inter partes review challenges at the Patent Office, with the validity of the asserted claim being confirmed. Plaintiff also cites a history of successfully enforcing this patent family against other competitors in the battery separator market, including LG Chem and SK Innovation. The complaint alleges that Defendant was put on notice of infringement of one patent at least seven months prior to the suit's filing.
Case Timeline
| Date | Event |
|---|---|
| 2000-04-10 | U.S. Patent No. RE47,520 Priority Date |
| 2001-10-12 | U.S. Patent No. 6,692,867 Priority Date |
| 2002-08-13 | Issue Date of U.S. Patent No. 6,432,586 (predecessor to '520) |
| 2004-02-17 | U.S. Patent No. 6692867 Issue Date |
| 2016-10-01 | Key Celgard employee Dr. Zhang resigns (approx. date) |
| 2017-01-01 | Defendant Senior allegedly becomes a top producer |
| 2019-02-25 | Celgard sends notice letter to Defendant Senior |
| 2019-07-16 | U.S. Patent No. RE47520 Issue Date (Reissue) |
| 2019-09-16 | Complaint Filing Date |
II. Technology and Patent(s)-in-Suit Analysis
U.S. Reissued Patent No. RE47,520 E - "Separator for a High Energy Rechargeable Lithium Battery"
The Invention Explained
- Problem Addressed: The patent addresses safety problems in high-energy rechargeable lithium batteries, specifically the growth of lithium "dendrites." These needle-like structures can grow from an electrode during charging, penetrate the separator, and cause an internal electrical short, which can lead to overheating and "thermal runaway" (Compl. ¶34; ’520 Patent, col. 1:30-46).
- The Patented Solution: The invention is a multi-component separator. It combines a "ceramic composite layer" (a mixture of inorganic particles like silica or alumina within a polymer matrix) with a conventional "polymeric microporous layer" ('520 Patent, col. 2:63-67). The ceramic layer provides a physical barrier to block dendrite growth, while the microporous layer is designed to melt and close its pores at elevated temperatures, shutting down ion flow and preventing catastrophic failure in an overheating event ('520 Patent, col. 3:1-4).
- Technical Importance: This dual-function design enhanced battery safety, which was a critical barrier to the commercialization and widespread adoption of high-energy lithium batteries for demanding applications like electric vehicles (Compl. ¶¶35-36, 49).
Key Claims at a Glance
- The complaint asserts independent claim 12 (’520 Patent, col. 6:45-64).
- Essential elements of Claim 12:
- A separator for an energy storage system comprising:
- At least one ceramic composite layer or coating including a mixture of 20-95% by weight of specified inorganic particles and 5-80% by weight of a specified matrix material, with the layer being "adapted to at least block dendrite growth and to prevent electronic shorting"; and
- At least one polyolefinic microporous layer with specified porosity, pore size, and Gurley Number, with the layer being "adapted to block ionic flow between an anode and a cathode."
- The complaint reserves the right to assert other claims (Compl. ¶96, n.4).
U.S. Patent No. 6,692,867 B2 - "Battery Separator-Pin Removal"
The Invention Explained
- Problem Addressed: The patent targets a specific manufacturing problem. In the production of "jelly roll" style batteries, the separator and electrode materials are wound tightly around a metal pin or mandrel. If the separator material sticks to the pin when it is withdrawn, the entire battery assembly can deform ("telescope") and must be discarded, leading to increased manufacturing costs and reduced yield (’867 Patent, col. 1:10-24).
- The Patented Solution: The invention is a battery separator made with a polypropylene surface that includes a small amount (at least 50 parts per million) of a metallic stearate, such as calcium stearate, as an additive (’867 Patent, col. 2:33-36; Abstract). This additive acts as a lubricant or release agent, reducing the force required to remove the pin from the wound battery assembly and thereby preventing telescoping defects.
- Technical Importance: This solution addresses a practical and costly issue in the high-volume, automated manufacturing of batteries, improving production efficiency and reducing material waste (Compl. ¶39).
Key Claims at a Glance
- The complaint asserts independent claim 17 (’867 Patent, col. 6:17-20).
- Essential elements of Claim 17:
- A battery separator with improved pin removal properties comprising:
- a microporous membrane having a polypropylene surface portion
- including at least 50 ppm of a metallic stearate.
- The complaint reserves the right to assert other claims (Compl. ¶102, n.7).
III. The Accused Instrumentality
Product Identification
- The complaint identifies two categories of accused products sold by Defendant Senior: ceramic coated lithium-ion battery separators (including series SH, MCS, and MFS) and uncoated polypropylene lithium-ion battery separators (including series SD, SQ, ST, and SZ) (Compl. ¶¶87-88).
Functionality and Market Context
- The accused ceramic coated separators are described in marketing materials as having an "aluminum oxide ceramic coating to further enhance safety characteristics" (Compl. ¶93, 97). A photograph included in the complaint shows a representative of Defendant Senior, identified as former Celgard scientist Dr. Steven Zhang, at a meeting with Panasonic (Compl. ¶75).
- These products are marketed for advanced applications, including electric vehicles and energy storage systems, which directly compete with Celgard's target markets (Compl. ¶92).
- The complaint alleges that Defendant Senior rapidly gained significant global market share, matching Celgard's by 2017, through the use of Celgard's patented technology and misappropriated trade secrets (Compl. ¶¶10, 80).
IV. Analysis of Infringement Allegations
RE47,520 E Infringement Allegations
| Claim Element (from Independent Claim 12) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| at least one ceramic composite layer or coating, said layer including a mixture of 20-95% by weight of inorganic particles selected from the group consisting of SiO₂, Al₂O₃...and 5-80% by weight of a matrix material selected from the group consisting of polyethylene oxide, polyvinylidene fluoride... | The accused separators allegedly comprise a ceramic composite layer or coating, specifically an "aluminum oxide ceramic coating," with inorganic particles and matrix material of the nature and weight percentage set forth in the claim (Compl. ¶¶97-98). | ¶¶97-98 | col. 3:20-44 |
| said layer being adapted to at least block dendrite growth and to prevent electronic shorting | Marketing materials from Defendant's distributor allegedly state that the separators "must be able to withstand penetration and branching moss-like crystalline minerals in order to prevent the contamination of electrodes" (Compl. ¶99). | ¶99 | col. 2:65-67 |
| at least one polyolefinic microporous layer having a porosity in the range of 20-80%, an average pore size in the range of 0.02 to 2 microns, and a Gurley Number in the range of 15 to 150 sec... | The accused separators allegedly comprise a polyolefinic microporous layer with porosity, pore size, and Gurley Number measurements within the claimed ranges (Compl. ¶100). | ¶100 | col. 4:4-18 |
| said layer being adapted to block ionic flow between an anode and a cathode. | The accused separators allegedly possess a polyolefinic microporous layer that is adapted to perform this shutdown safety function (Compl. ¶101). | ¶101 | col. 3:1-4 |
- Identified Points of Contention:
- Scope Questions: A central issue may be whether the accused "aluminum oxide ceramic coating" meets the claim limitation of a "composite layer" that includes both inorganic particles and a specified "matrix material." The complaint alleges the presence of a matrix material but provides no specific evidence, which suggests this element may be a point of dispute (Compl. ¶98).
- Technical Questions: The infringement theory relies heavily on marketing statements from a distributor. A key factual question will be whether the physical products, when tested, actually possess the claimed structural and performance characteristics (e.g., weight percentages, porosity, Gurley number).
6,692,867 B2 Infringement Allegations
| Claim Element (from Independent Claim 17) | Alleged Infringing Functionality | Complaint Citation | Patent Citation |
|---|---|---|---|
| a microporous membrane having a polypropylene surface portion | At least certain of the accused separators are identified as "uncoated polypropylene lithium-ion battery separators" (Compl. ¶¶88, 102). | ¶¶88, 102 | col. 2:23-26 |
| including at least 50 ppm of a metallic stearate. | The complaint alleges that the accused separators' polypropylene surface portion includes at least 50 ppm of a metallic stearate (Compl. ¶103). | ¶103 | col. 2:33-36 |
- Identified Points of Contention:
- Technical Questions: The infringement allegation for the ’867 patent hinges entirely on the chemical composition of the accused separators. The complaint makes a conclusory allegation that the products contain "at least 50 ppm of a metallic stearate" but provides no supporting factual basis, such as chemical analysis results (Compl. ¶103). Therefore, the primary question for the court will be an evidentiary one: does discovery and testing reveal the presence of the claimed additive in the required concentration?
V. Key Claim Terms for Construction
The Term: "adapted to at least block dendrite growth" ('520 Patent, Claim 12)
- Context and Importance: This functional language is critical because it defines the required capability of the ceramic layer. Practitioners may focus on this term because the defendant could argue its product is not specifically designed or "adapted" for this purpose, even if its structure provides some incidental resistance to dendrite penetration. The outcome will likely depend on whether the term requires a specific design intent or is met simply by possessing the claimed structure that performs the function.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation: The patent's background broadly frames the problem as the "failure to control the dendrite growth," suggesting that any structure which achieves this functional goal could be covered (’520 Patent, col. 1:44-46).
- Evidence for a Narrower Interpretation: The detailed description links the function directly to the "ceramic composite layer" which "is, at least, adapted for...blocking dendrite growth," suggesting the structure itself embodies the adaptation (’520 Patent, col. 2:63-67).
The Term: "improved pin removal properties" ('867 Patent, Claim 17 Preamble)
- Context and Importance: This preamble term states the invention's purpose. Its construction is important because if it is found to be a limiting element of the claim, the plaintiff would need to prove not only that the accused product contains metallic stearate, but also that this results in "improved" performance relative to a baseline.
- Intrinsic Evidence for Interpretation:
- Evidence for a Broader Interpretation (Non-limiting): The patentee will likely argue the preamble is a non-limiting statement of purpose and that infringement is established by meeting the structural limitations in the body of the claim (i.e., the presence of at least 50 ppm of metallic stearate).
- Evidence for a Narrower Interpretation (Limiting): The specification provides a detailed test for quantifying "pin removal force" in grams (’867 Patent, col. 3:1-38). A defendant may argue this provides the standard by which "improved" must be judged, turning infringement into a question of comparative testing.
VI. Other Allegations
Indirect Infringement
- The complaint alleges both induced and contributory infringement for both patents. Inducement is based on Defendant allegedly providing instructions, datasheets, and technical support to customers on how to use the infringing separators (Compl. ¶¶110, 127). Contributory infringement is based on the allegation that the separators are a material part of the patented invention and have no substantial non-infringing uses (Compl. ¶¶114, 131).
Willful Infringement
- Willfulness for the ’520 patent is alleged based on Defendant’s knowledge of the patent since at least February 25, 2019, following a notice letter from Celgard (Compl. ¶117). For the ’867 patent, willfulness is alleged based on knowledge obtained "at least as of the filing of this Complaint" (Compl. ¶133).
VII. Analyst’s Conclusion: Key Questions for the Case
The resolution of this case appears to center on three primary questions for the court:
- A core issue will be one of compositional proof: can the plaintiff produce sufficient evidentiary support, likely through chemical analysis and product testing, to demonstrate that the accused separators literally contain the specific materials and concentrations required by the claims, most notably the "at least 50 ppm of a metallic stearate" in the ’867 patent?
- A second issue will be one of functional scope: how will the court construe the functional term "adapted to at least block dendrite growth"? Will demonstrating that the accused product’s structure inherently provides this benefit be sufficient for infringement, or must the plaintiff show a specific design choice by the defendant to achieve that function?
- A third, overarching question involves the interplay of patent and trade secret claims: to what extent can Celgard causally link the alleged misappropriation of trade secrets by a former employee to the development and composition of the accused products? Evidence of such a link could significantly influence the court's view on issues of intent, willfulness, and damages.