LG Chem Ltd v. Celgard LLC

1. Case Identification

• Case #: IPR2014-00692
• Patent #: 6,432,586
• Filed: April 25, 2014
• Petitioner(s): LG Chem, Ltd.
• Patent Owner(s): Celgard, LLC
• Challenged Claims: 1-12

2. Patent Overview

• Title: Separator for a High Energy Rechargeable Lithium Battery
• Brief Description: The ’586 patent discloses a two-layer separator for lithium batteries. The separator comprises a ceramic composite layer adapted to prevent dendrite growth and electronic shorting, and a polyolefinic microporous layer adapted to block ionic flow (i.e., shut down) during a thermal runaway event to enhance battery safety.

3. Grounds for Unpatentability

Ground 1: Anticipation and Obviousness over Tojo - Claims 1-12 are anticipated by or obvious over Tojo.

• Prior Art Relied Upon: Tojo (Japanese Application # Kokai 11-80395).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner argued that Tojo discloses every limitation of the challenged claims. Tojo teaches a two-layered separator with a "surface protection layer" and a "substrate membrane." The surface protection layer, a composite of inorganic microparticles and a resin binder, provides high mechanical strength, which Petitioner asserted meets the functional limitation of being "adapted to at least block dendrite growth and to prevent electronic shorting." The substrate membrane is a polyolefinic microporous layer explicitly taught to have a "shutdown (SD) function," where its pores close during excessive temperature increases to stop the cell reaction. Petitioner argued this directly maps to the claimed layer "adapted to block ionic flow...in the event of thermal runaway." For dependent claims reciting specific materials (e.g., claim 4) or properties (e.g., claim 7), Petitioner contended Tojo either directly anticipated the limitations or rendered them obvious, as Tojo’s disclosure of broad material classes (e.g., "various acrylic resins") would lead a POSITA to select well-known, conventional species from within those classes.
  • Motivation to Combine (for §103 grounds): For claim limitations not explicitly disclosed, Petitioner argued a POSITA would be motivated to select specific materials or properties from the predictable solutions disclosed by Tojo to optimize known battery performance, making the selection obvious to try.
  • Expectation of Success (for §103 grounds): Success was expected because the choices involved selecting from a finite number of identified, predictable solutions within the battery cell field.

Ground 2: Obviousness over Tobishima and Tojo - Claims 1-12 are obvious over Tobishima in view of Tojo.

• Prior Art Relied Upon: Tobishima (Japanese Application # H5-190208) and Tojo (Japanese Application # Kokai 11-80395).
• Core Argument for this Ground:
  • Prior Art Mapping: Petitioner asserted that Tobishima describes a two-layer separator having the same fundamental functions as the ’586 patent: (1) a porous polyolefin polymer film that melts to block electric current during thermal events, and (2) an electrolyte solution-impregnated polymer layer that prevents internal shorts from dendritic lithium deposition. Petitioner argued that to the extent Tobishima’s dendrite-blocking layer does not explicitly disclose a "mixture of inorganic particles," Tojo supplies this teaching. Tojo explicitly teaches adding inorganic microparticles to a resin to enhance the mechanical strength and durability of a separator, preventing penetration.
  • Motivation to Combine (for §103 grounds): A POSITA would combine these references because both address the same well-known problems of dendrite growth and thermal runaway in lithium batteries. Tobishima suggests the need to increase the mechanical strength of its separator. A POSITA would have been motivated to look to known strengthening techniques, such as the inorganic particle-resin mixture taught by Tojo, to improve the mechanical integrity and safety of Tobishima’s separator.
  • Expectation of Success: A POSITA would have a high expectation of success in combining the references, as it involved applying a known solution (inorganic particles for strength) to a known problem (separator durability) in an analogous device.

Ground 3: Obviousness over Yamashita and Kubota - Claims 1-6 and 11(1-6) are obvious over Yamashita in view of Kubota.

• Prior Art Relied Upon: Yamashita (Patent 6,287,720) and Kubota (Patent 5,270,137).

• Core Argument for this Ground:

  • Prior Art Mapping: Petitioner argued that Yamashita discloses a two-layer separator with a first layer containing inorganic insulating particles mixed with a binder and a second layer made of an organic insulating substance (e.g., polyethylene) that melts to shut off current during thermal runaway. Petitioner contended that while Yamashita’s first layer is porous, it lacks an explicit disclosure that this layer is adapted to block dendrite growth by being non-porous. Kubota was argued to supply this missing element by teaching that dendrites grow through the pores of a separator film and discloses filling those pores with a polymer to create a composite structure that prevents short-circuiting.
  • Motivation to Combine (for §103 grounds): A POSITA seeking to improve the safety of the Yamashita separator would be motivated to address dendrite penetration through the pores of its inorganic layer. Kubota directly addresses this exact problem by teaching the solution of filling separator pores. Therefore, a POSITA would combine Kubota’s pore-filling technique with Yamashita’s separator to improve dendrite resistance.
  • Expectation of Success: The combination was a straightforward application of a known solution to a known problem, and a POSITA would have expected it to successfully improve the safety and performance of the battery.

• Additional Grounds: Petitioner asserted additional obviousness challenges, including claims being obvious over Lundquist in view of Venugopal and Yamashita in view of Kubota and Venugopal. These grounds primarily relied on Venugopal to provide more specific teachings on separator properties such as porosity, pore size, and Gurley Number ranges. Petitioner also asserted an anticipation ground against claims 1-6 based on Lundquist.

4. Key Claim Construction Positions

• "adapted to block ionic flow between an anode and a cathode": Petitioner argued this phrase must be construed as "adapted to block ionic flow between an anode and a cathode in the event of thermal runaway." This construction was based on the patent's specification and the fundamental principle that a battery requires ionic flow to function during normal operation. A literal reading would render the battery inoperable.
• "membrane": Petitioner argued this term should be construed broadly as "a thin layer or sheet." This construction was proposed to prevent an artificial distinction between the terms "layer" and "membrane" as used in the claims, which Petitioner contended were used interchangeably in the art.

5. Key Technical Contentions (Beyond Claim Construction)

• Petitioner argued that the core technological concepts of the ’586 patent were not novel at the time of the invention. Specifically, the use of two-layered separator structures to provide both a thermal shutdown function (via a meltable polyolefin layer) and a physical barrier to dendrite growth was a common and well-known approach in the lithium battery field, as demonstrated by numerous prior art references.

6. Relief Requested

• Petitioner requests institution of an inter partes review (IPR) for claims 1-12 of the ’586 patent and cancellation of all challenged claims as unpatentable.