PTAB

IPR2015-01511

Ube Maxell Co Ltd v. Celgard LLC

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1. Case Identification

2. Patent Overview

  • Title: Separator for High Energy Rechargeable Lithium Battery
  • Brief Description: The ’586 patent discloses a battery separator for lithium batteries comprising at least two layers: a ceramic composite layer containing inorganic particles in a matrix material, and a polyolefinic microporous layer. The separator is designed to prevent electronic shorting from dendrite growth while allowing ionic flow.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1-3, 5, 6, and 11 under 35 U.S.C. §102 by Tojo

  • Prior Art Relied Upon: Tojo (Japanese Patent Publication No. H11-80395).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Tojo discloses every element of the challenged claims. Tojo describes a two-layered separator for a lithium battery comprising a substrate and an air-permeable surface protection layer. Petitioner mapped Tojo’s polyolefin substrate to the claimed "polyolefinic microporous layer" and Tojo’s surface protection layer—comprising inorganic microparticles (e.g., alumina) in a resin binder—to the claimed "ceramic composite layer." Petitioner contended that the functional limitation of being "adapted to at least block dendrite growth" is inherently disclosed by Tojo. The petition asserted that Tojo’s layer, by having high mechanical strength and surface hardness to prevent penetration by conductive microparticles, would necessarily also block the penetration of lithium dendrites, which is a known cause of internal shorting.
    • Key Aspects: The core of this ground rested on the argument of inherency, stating that the structural and material properties explicitly taught by Tojo for preventing one type of shorting (from conductive particles) would inherently prevent another type (from dendrites).

Ground 2: Obviousness of Claims 1-3, 5, 6, and 11 under 35 U.S.C. §103 over Tojo in view of Tsukamoto

  • Prior Art Relied Upon: Tojo (Japanese Patent Publication No. H11-80395) and Tsukamoto (Japanese Patent Publication No. H10-284039).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground leveraged the same base teachings from Tojo as Ground 1. Tsukamoto was introduced for its explicit teaching of a ceramic separator designed specifically to "prevent damage due to the dendrite deposits" in lithium secondary batteries. Petitioner argued that while Tojo’s primary stated purpose was preventing shorts from conductive particles, Tsukamoto directly addressed preventing shorts from dendrites using a similar ceramic-based material. The combination of Tojo’s structure with Tsukamoto’s explicit purpose and teachings on dendrite prevention rendered the claims obvious.
    • Motivation to Combine: A POSITA would combine Tojo and Tsukamoto because both references were in the same field of endeavor (lithium battery separators) and addressed the same fundamental problem of internal short-circuiting. Petitioner argued a POSITA would be motivated to apply Tsukamoto's teachings on dendrite prevention to Tojo's separator to create a more robust product that guards against multiple known failure modes. Improving battery safety was a well-known goal in the art, providing a strong motivation for the combination.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because both references teach using a layer of inorganic particles in a binder to improve mechanical strength and prevent penetration. Substituting or modifying Tojo's surface protection layer with Tsukamoto's ceramic-based separator would involve applying known principles to achieve the predictable result of blocking both dendrites and other conductive particles.

Ground 3: Obviousness of Claims 1-6 and 11 under 35 U.S.C. §103 over Tobishima in view of Ishida

  • Prior Art Relied Upon: Tobishima (Japanese Patent Publication No. H5-190208) and Ishida (Japanese Patent Publication No. H9-306543).

  • Core Argument for this Ground:

    • Prior Art Mapping: Petitioner asserted that Tobishima teaches a two-layer separator with a microporous polyolefin layer for shutdown safety and a thicker polymer film (e.g., polyacrylonitrile) explicitly designed to prevent internal shorts caused by "dendritic lithium deposition." However, Tobishima's polymer film did not include inorganic particles. Ishida was introduced because it taught solving the problem of dendrite-induced shorting by dispersing ceramic particles (e.g., Al2O3) into a gel polymer electrolyte. Ishida demonstrated that this dispersion suppressed dendrite growth, prevented shorting, and extended battery cycle life without decreasing ionic conductivity.
    • Motivation to Combine: A POSITA would be motivated to modify Tobishima’s dendrite-blocking polymer film by incorporating the ceramic particles taught by Ishida. The motivation was to further improve the dendrite suppression capabilities and overall performance (i.e., cycle life) of Tobishima's separator. Ishida's teaching that adding ceramic particles actually improves ionic conductivity would have overcome any potential hesitation a POSITA might have about adding inert fillers to an electrolyte-containing polymer layer.
    • Expectation of Success: The combination was presented as the predictable application of an improvement (Ishida's ceramic particles) to a known base structure (Tobishima's polymer separator). A POSITA would expect that adding particles known to suppress dendrites to a layer already intended to suppress dendrites would predictably enhance that function and extend the battery’s cycle life, as demonstrated in Ishida.

  • Additional Grounds: Petitioner asserted an additional anticipation challenge (Ground 4) based on Lundquist (Patent 4,731,304), arguing its two-ply separator with a filler-containing second ply met all claim limitations.

4. Key Claim Construction Positions

  • "being adapted to at least block dendrite growth and to prevent electronic shorting": Petitioner argued this functional language should be given its broadest reasonable interpretation to encompass any layer capable of blocking dendrite growth with any degree of effectiveness. This construction was critical to the inherency argument in Ground 1, as it did not require the prior art to disclose a specific level of performance or state that dendrite blocking was its primary purpose.
  • "matrix material": Petitioner proposed this term be construed broadly as any material capable of holding inorganic particles that is also suitable for use in lithium batteries. This supported mapping the term to various binders and polymers disclosed in the prior art.
  • Preamble of Claim 1: Petitioner argued the preamble, "A separator for a high energy rechargeable lithium battery," was a non-limiting statement of intended use and should be given no patentable weight.

5. Relief Requested

  • Petitioner requested institution of an inter partes review and cancellation of claims 1-6 and 11 of the ’586 patent as unpatentable.