PTAB

IPR2022-00026

A123 Systems LLC v. Long Hua Technology Co Ltd

Key Events

Petition

petition

Title: Lithium Ion Secondary Battery
Brief Description: The ’480 patent describes a lithium ion secondary battery with improved high-rate discharge capabilities. The invention focuses on a positive electrode containing LiFePO4 as the active material, where the electrode layer has a specific ratio of its area to its thickness (A/t ratio) to achieve a high discharge capacity (a "10C discharge capability").

Prior Art Relied Upon: Ito (Japanese Patent Publication No. 2002-117832).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner argued that Ito, a non-bipolar battery reference, disclosed all structural elements of the challenged claims. Specifically, Example 1 of Ito described a lithium ion secondary battery with a cathode compound layer having an area of 54mm × 450mm and a thickness of 20µm, which calculates to an A/t ratio of 1.215 × 10⁶ mm. This ratio is greater than the claimed ratio of "about 9.31×10⁵ mm". While Ito’s Example 1 used a different active material, Ito expressly identified LiFePO4 in a finite list of six suitable alternative cathode materials. Petitioner contended that a person of ordinary skill in the art (POSITA) would at once envisage using LiFePO4 with the disclosed structure.
- Key Aspects: The petition's central argument for this ground was that the final limitation of claim 1—the "high rate capability"—was an inherent property of the disclosed structure, not a separate structural element. Because Ito taught all the structural components, it would inherently possess this capability. Alternatively, Petitioner argued the limitation described an intended use or result and carried no patentable weight.

Prior Art Relied Upon: Ito (Japanese Patent Publication No. 2002-117832) and Gozdz (Application # 2005/0233219).
Core Argument for this Ground:
- Prior Art Mapping: To the extent Ito was not found to anticipate, Petitioner argued the combination with Gozdz rendered the claims obvious. Ito provided the foundational battery structure with the required A/t ratio. Gozdz taught using LiFePO4 as a major component in a positive electrode for a high-rate lithium ion battery and expressly disclosed a battery achieving a 10C discharge capacity greater than 90%.
- Motivation to Combine: A POSITA would combine Ito and Gozdz to improve the performance of lithium ion batteries. Gozdz provided the express motivation to select LiFePO4 from Ito’s finite list of materials to achieve the desirable high-rate capability that Gozdz taught was a benefit of using LiFePO4. Both references taught similar battery constructions, making the combination straightforward.
- Expectation of Success: A POSITA would have a reasonable expectation of success because combining Ito's structure with Gozdz's preferred material (LiFePO4) for high-rate performance was a predictable substitution of known elements to achieve a known, desirable result.

Prior Art Relied Upon: Hisamitsu (Japanese Patent Publication No. 2005-174691).
Core Argument for this Ground:
- Prior Art Mapping: Petitioner asserted that Hisamitsu, which described a bipolar battery, also taught all structural limitations of the claims. Hisamitsu disclosed a positive electrode layer on a collector with an area of 210mm × 300mm and a thickness of 30µm, yielding an A/t ratio of 2.1 × 10⁶ mm, which met the claimed threshold. Hisamitsu also expressly disclosed LiFePO4 as a suitable positive electrode material in a finite list of examples.
- Key Aspects: As with the Ito ground, Petitioner contended the "high rate capability" was an inherent property of the battery structure disclosed in Hisamitsu and that the broad claim language of "a lithium ion secondary battery" was not limited to non-bipolar types, thus encompassing Hisamitsu’s disclosure.
Additional Grounds: Petitioner asserted an additional obviousness challenge (Ground 4) against claims 1-19 based on Hisamitsu in view of Desilvestro (International Patent Publication No. 2005/018038), Gozdz, and Saito (Application # 2005/0132562). This ground argued that Desilvestro and Gozdz provided further motivation to select LiFePO4 from Hisamitsu's list and to incorporate the high-rate discharge capability.

Petitioner argued that the claim phrase "wherein the lithium ion secondary battery has a ratio of its capacity at discharge rate of 10 C to its capacity at discharge rate of 1 C is greater than 80%" should be construed as an in-use property or intended use, not a structural limitation.
This construction was central to the petition's arguments. Petitioner asserted that this "high rate capability" was a natural result that flowed from the claimed structural elements (such as the A/t ratio) and did not impart separate patentable weight. The capability could only be measured during operation and did not define what the battery is, but rather what it does.

Petitioner requested institution of an inter partes review and cancellation of claims 1-19 of the ’480 patent as unpatentable.