Micromachined electrolyte sheet, fuel cell devices utilizing such, and micromachining method for making fuel cell devices

Abstract

A sintered electrolyte sheet comprising: a body of no more than 45 μm thick and laser machined features with at least one edge surface having at least 10% ablation. A method of micromachining the electrolyte sheet includes the steps of: (i) supporting a sintered electrolyte sheet; (ii) micromachining said sheet with a laser, wherein said laser has a wavelength of less than 2 μm, fluence of less than 200 Joules / cm2, repetition rate (RR) of between 30 Hz and 1 MHz, and cutting speed of preferably over 30 mm / sec.

Description

BACKGROUND OF THE INVENTION[0001]1. Field of the Invention[0002]This invention relates in general to ceramic electrolytes and fuel cell devices utilizing them, and to the laser micromachining of electrolyte sheets and electrolyte supported multi-cell solid oxide fuel cell devices.[0003]2. Technical Background[0004]The present invention pertains to articles formed by laser processing of solid oxide fuel cell electrolyte sheets, as well as manufacture of electrolyte supported solid oxide fuel cells and fuel cell devices.[0005]Solid oxide fuel cell devices incorporating flexible ceramic electrolyte sheets are known. In such fuel cell devices, often one or more electrolyte sheets are supported within a housing, on a frame, or between a pair of mounting assemblies, which might be either a frame or a manifold. The electrolyte sheets may be utilized either in a multi-cell or single cell design.[0006]A common approach utilizes a fuel cell device that consists of a single cell design where t...

AI Technical Summary

Benefits of technology

[0017]One advantage of the present invention is that it advantageously allows fabrication of new fuel cell designs, and / or advantageously increases the fabrication yield and strength of the current fuel cell devices. More specifically, the speed, placement accuracy, and resulting quality of the electrolyte sheet edge(s) enable flexibility in device design, handling, and improved electrolyte sheet edge strength. Preferably, the surface roughness of the laser micromachined regions is less than 0.5 μm RMS, more preferably less than 0.4 μm RMS. Preferably this surface exhibits peak-to-valley roughness of less than 5.5 μm, or Ra surface roughness of less than 0.3 μm. Fuel Cell devices can also be drilled, cut, or micromachined at various times during the fabrication process resulting in fuel cell devices with unique attributes such as complex perimeter shapes or via hole patterns, electrodes or other layers existing up to the electrolyte edge, and thin electrolyte areas less than 5 μm thick. This micromachining process can be utilized at any desired time after the electrolyte sintering, enabling flexibility in device fabrication. The resulting method advantageously results in devices and electrolyte sheets that have surprising improvements to flatness and strength.

[0018]According to one embodiment of the present invention, laser machining of single and multi-cell devices may be performed after sealing or mounting of the fuel cell device(s) in a support or manifold structure, and results in improved: electrolyte sheet edge strength, device flatness, edge quality, fewer and smaller wrinkles, minimized electrolyte sheet edge curl, and process yield and throughput. According to another embodiment, the micromachining may also be performed to cut electrolyte sheets, where multiple fuel cell devices are patterned (e.g., printed) on a single electrolyte sheet and the electrolyte sheets are then optionally laser machined to produce multiple devices, thereby saving time and labor.

[0019]The laser micromachining method advantageously enables micromachining of the electrolyte in the sintered state, instead of before firing. This eliminates the need to accurately predict shrinkage during binder burn-out and sintering. It also eliminates the need for this shrinkage to be uniform across the entire electrolyte sheet.

Problems solved by technology

Mechanically punching and cutting of the un-fired electrolyte puts limitations on the fabrication speed, feature size, wrinkle, and edge quality produced.

Such prediction is very difficult to do with the desired accuracy and require actual devices to be sacrificed for testing.

Thin (less than 50 μm) zirconia based sintered electrolyte sheets are brittle when they are either cut or / and drilled by mechanical means, due to crack formation.

Applicants attempted to utilize CO2 laser in drilling thin zirconia ceramic electrolyte sheets, but were not successful due to a large number of cracks created by thermal effects.

U.S. Pat. No. 6,270,601 also provided no guidance on how to utilize excimer laser for successful cutting or drilling of the electrolyte sheets.

This application does not teach or suggest that it is possible to laser machine electrolyte sheets after sintering.

However, they also develop edge curl when sintered, and the edge curl can produce stress, and fracture the sheet when the curl is flattened.

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