IP Law Daily, PATENT—Fed. Cir.: Eveready’s design for lithium/iron disulfide battery was obvious over prior art, (May 31, 2016)

By Mark Engstrom, J.D.

The Patent Trial and Appeal Board did not err in finding that an Eveready patent on an improved design for a lithium/iron disulfide battery was obvious over prior art, the U.S. Court of Appeals for the Federal Circuit has ruled (Eveready Battery Company, Inc. v. Spectrum Brands, Inc., May 31, 2016, Bryson, W.). Significantly, a European patent (“Gan”) disclosed the balancing of a battery’s anode-to-cathode capacity to reduce the swelling of alkali metal electrochemical cells. According to the Federal Circuit, a skilled artisan would have applied that balancing concept to lithium/iron disulfide cells, as the patent in suit had. The circuit court affirmed the ruling of the Board, which upheld a trademark examining attorney’s obviousness findings in an inter partes reexamination (IPR) that was initiated by Spectrum Brands.

Spectrum Brands filed an IPR petition that challenged the validity of every claim of U.S. Patent No. 6,849,360, which was directed to a lithium/iron disulfide battery. The patent described the need for a lithium/iron disulfide cell with an “increased energy density and discharge efficiency” that accommodated the volume increase that reaction products generated while the cells were discharging.

During reexamination, Eveready canceled 9 claims and added 5 claims. Those changes eliminated all of the independent claims except for claim 1. The examiner found that the claims would have been obvious over different combinations of prior art references.

Eveready appealed the examiner’s findings to the PTAB and the Board affirmed the examiner’s determination that the independent claim was invalid for obviousness. Because the Board found that Eveready had not made a separate argument regarding any of the dependent claims, it affirmed those rejections without discussion.

Prior art. Eveready argued that a European patent application known as “Gan” was applicable to lithium/silver vanadium cells, but it was not applicable to cells that used other cathode materials, such as lithium/iron disulfide cells that were covered by the patent in suit.

Eveready did not argue that Gan was not directed to swelling in lithium cells. Nor did iot argued that swelling was not a key concern in designing a lithium/iron disulfide cell. In fact, Eveready acknowledged that the swelling issue in lithium/iron disulfide cells was greater than the swelling in lithium/silver vanadium cells.

Instead, Eveready argued that a skilled artisan would not have applied Gan to lithium/iron disulfide cells because of the chemistry differences in lithium/iron disulfide cells and lithium/silver vanadium cells.

The Board acknowledged that Gan described the lithium/silver vanadium cell as an “illustrated embodiment” of the invention. Nevertheless, it found that Gan generally disclosed that the invention involved the balancing of the anode-to-cathode (A/C) capacity ratio to improve cell swelling in alkali metal electrochemical cells.

In making its findings, the Board considered extensive record materials besides Gan, including competing expert declarations. Those declarations included explanations of why Gan would be applicable to lithium/iron disulfide cells.

In addition, the record contained statements by Eveready that: (1) Gan disclosed a lithium/iron disulfide cell and (2) a person of ordinary skill in the art would take the disclosure of Gan into account when creating an improved lithium/iron disulfide cell. In fact, in proceedings before the European Patent Office on essentially the same patent application, Eveready had stated that Gan appeared to be the closest prior art because it was “directed to the same technical problem(s).”

Finally, Eveready had admitted that a skilled artisan who was striving to solve the problem of maintaining or improving discharge capacity in a system that experienced swelling would have taken into account the disclosure of Gan.

In light of the facts and findings of record, the Board found that substantial evidence supported the Board’s finding that a person of ordinary skill in the art would have considered the teaching of Gan to be applicable to lithium/iron disulfide cells.

A/C input ratio. Eveready argued that Gan did not disclose an anode to cathode input ratio that was less than or equal to 1.0. The patent examiner construed the claim term “anode to cathode input ratio” to mean “the anode capacity divided by the cathode capacity, wherein the anode and cathode capacities are determined based on the interfacial area, i.e., the portions of the anode and cathode which overlap with each other.”

The examiner found that, to ensure optimal discharge rates and to avoid wasting material, a person of ordinary skill in the art would have found it obvious to prepare Gan’s electrochemical cell in a “jellyroll” configuration such that: (1) the cathode and anode were similar in size and (2) most of the electrodes were in interfacial relationship.

In that configuration, the examiner determined that Gan’s anode-to-cathode (A/C) ratio of about 0.68 to about 0.96 would be equivalent, or very close, to the interfacial A/C ratio, thus making the claimed A/C input ratio—i.e., less than or equal to 1.0—obvious. The Board agreed with the examiner that the total A/C ratio would be closely correlated to the interfacial A/C ratio in a jellyroll battery.

Eveready argued that Gan addressed the ratio of the “total” amount of anode to the “total” amount of cathode. In Eveready’s view, the “total” A/C ratio was unrelated to the interfacial A/C ratio because, in some situations, the total amounts of a cell’s anode and cathode material could be quite different from the amounts of anode and cathode material that were in an interfacial relationship. For that reason, the “interfacial ratio” portion of the limitation, as construed, was not taught by Gan, according to Eveready.

The Federal Circuit disagreed. According to the circuit court, the Board’s findings were supported by substantial evidence. Significantly, the record contained ample evidence that Gan disclosed a jellyroll cell, that the A/C input ratio of a jellyroll cell was closely correlated to the total A/C ratio in the cell, that Gan taught an A/C ratio that was less than or equal to 1.0, and that the principles of Gan applied to a lithium/iron disulfide cell. In light of that evidence, the circuit court affirmed the Board’s finding that the independent claim of the asserted patent would have been obvious in view of Gan.

The case is No. 2015-1824.

Attorneys: David Bogdan Cupar, Robert Baraona, and Matthew John Cavanagh (McDonald Hopkins LLC) for Eveready Battery Company, Inc. Deborah Ann Sterling, Robert Greene Sterne, and Nirav Desai (Sterne, Kessler, Goldstein & Fox, PLLC) for Spectrum Brands, Inc.

Companies: Eveready Battery Company, Inc.; Spectrum Brands, Inc.

Cases: Patent FedCirNews