PTAB

IPR2021-00894

A123 Systems LLC v. Long Hua Technology Co Ltd

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Petition
petition

1. Case Identification

2. Patent Overview

  • Title: Lithium Ion Secondary Battery with High Rate Capability
  • Brief Description: The ’484 patent is directed to a lithium-ion secondary battery with high-rate discharge capability. The invention claims a positive electrode layer comprising LiFePO4 that has a ratio of its area to its thickness greater than 1.2×10⁶ mm, which purportedly results in a discharge capacity at a 10C rate that is greater than 80% of its capacity at a 1C rate.

3. Grounds for Unpatentability

Ground 1: Anticipation of Claims 1-19 under pre-AIA 35 U.S.C. §102(a)

  • Prior Art Relied Upon: Hisamitsu (Japanese Patent Pub. No. 2005-174691).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Hisamitsu discloses every limitation of the challenged claims. Specifically, Hisamitsu teaches a lithium-ion secondary battery and discloses LiFePO₄ as a suitable positive electrode material from a finite list of options. Hisamitsu’s Example 1 describes a positive electrode with a current collector area of 210 mm × 300 mm and an electrode layer thickness of 30 µm. Petitioner calculated this to be an area-to-thickness ratio of 2.1×10⁶ mm, which is greater than the claimed ratio of 1.2×10⁶ mm.
    • Key Aspects: The central argument for this ground rests on the assertion that the claimed high-rate discharge capability is an inherent property of the structure disclosed by Hisamitsu. Petitioner contended that the Patent Owner, during prosecution of the ’484 patent, repeatedly asserted that this "unique property" was "brought about by" the claimed area-to-thickness ratio. Therefore, because Hisamitsu discloses a structure meeting the ratio, it necessarily and inherently possesses the claimed discharge capability.

Ground 2: Obviousness of Claims 1-19 under pre-AIA 35 U.S.C. §103(a)

  • Prior Art Relied Upon: Hisamitsu in view of General Common Knowledge (GCK).
  • Core Argument for this Ground:
    • Prior Art Mapping: This ground was presented as an alternative to anticipation. Petitioner asserted that even if Hisamitsu’s disclosure of LiFePO₄ was considered insufficient for anticipation, a person of ordinary skill in the art (POSITA) would find it obvious to use LiFePO₄ in the battery structure of Hisamitsu's Example 1. Hisamitsu explicitly lists LiFePO₄ in a discrete list of suitable materials for forming a battery with "excellent output characteristics."
    • Motivation to Combine: A POSITA would be motivated to substitute the LiMn₂O₄ used in Hisamitsu's example with LiFePO₄ from the same reference to optimize battery performance, as both were known options for achieving good output.
    • Expectation of Success: A POSITA would have a reasonable expectation of success because Hisamitsu teaches that materials from its disclosed list are advantageous for achieving the desired battery characteristics. Further, GCK at the time, supported by references like Gozdz, confirmed that LiFePO₄-based batteries were known to exhibit high-rate discharge capabilities, making the claimed performance a predictable result of the combination.

Ground 3: Obviousness of Claims 1-19 under pre-AIA 35 U.S.C. §103(a)

  • Prior Art Relied Upon: Hisamitsu in view of Gozdz (Application # 2005/0233219).
  • Core Argument for this Ground:
    • Prior Art Mapping: Petitioner argued that Hisamitsu teaches the core battery structure with the high area-to-thickness ratio, while Gozdz provides explicit teachings and motivation for using LiFePO₄ to achieve high discharge rates. Gozdz discloses Li-ion cells with LiFePO₄ that demonstrate a 10C capacity of greater than 95% of nominal capacity.
    • Motivation to Combine: A POSITA would combine the references for at least two reasons. First, Gozdz teaches that using LiFePO₄ creates a low-impedance cell that avoids the undesirable plating of lithium, a known problem with conventional materials like the LiMn₂O₄ used in Hisamitsu’s example. Second, Hisamitsu provides a finite list of suitable electrode materials including LiFePO₄. A POSITA would therefore be motivated to substitute the material in Hisamitsu’s structural example with the superior LiFePO₄ taught by Gozdz to predictably achieve a low-impedance, high-rate battery that avoids known failure modes.
    • Expectation of Success: Success would be highly predictable, as both references are directed to improving the high-rate performance of lithium-ion batteries, and Gozdz explicitly demonstrates the superior results of using LiFePO₄ for this purpose.

4. Key Claim Construction Positions

  • Petitioner argued that the limitation recited in the independent claims, "wherein the lithium ion secondary battery has a ratio of its capacity at discharge rate of 10C to its capacity at discharge rate of 1C is greater than 80%," carries no patentable weight.
  • This argument was based on two primary theories:
    • Inherency: During prosecution, the Patent Owner overcame rejections by amending the claims to add this limitation, arguing it was a "unique property...brought about by" the claimed area-to-thickness ratio. Petitioner contended this is an admission of inherency, meaning any prior art disclosing the ratio necessarily possesses the property.
    • Intended Use / Result: Alternatively, Petitioner asserted the limitation describes the battery's performance (what it does) rather than its structure (what it is). As such, it is merely a non-limiting statement of intended use or result that cannot patentably distinguish the claims from prior art that discloses all structural elements.

5. Relief Requested

  • Petitioner requests institution of an inter partes review (IPR) and cancellation of claims 1-19 of the ’484 patent as unpatentable.