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Internal Electrical Connections for Planar Fuel Cell Stacks

IP.com Disclosure Number: IPCOM000004816D
Original Publication Date: 2001-Jun-14
Included in the Prior Art Database: 2001-Jun-14
Document File: 5 page(s) / 1M

Publishing Venue

Motorola

Related People

Joseph Bostaph: AUTHOR [+2]

Abstract

Fuel Cells are electrochemical devices, which produce electricity from a fuel, such as hydrogen or methanol, and an oxidant, such as oxygen. Each fuel cell is capable of providing up to 1V. To obtain higher voltages, individual fuel cells are stacked in series, usually in a bipolar manor or one on top each other, to achieve higher voltages. Fuel cells assembled on a planar surface can not be stacked one on top another. Series connections of a planar stack can be made using Beryllium Copper (BeCu) contacts between the anode and cathodes of the fuel cells.

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Internal Electrical Connections for Planar Fuel Cell Stacks

Joseph Bostaph and Clarence Huntley

Abstract

Fuel Cells are electrochemical devices, which produce electricity from a fuel, such as hydrogen or methanol, and an oxidant, such as oxygen. Each fuel cell is capable of providing up to 1V. To obtain higher voltages, individual fuel cells are stacked in series, usually in a bipolar manor or one on top each other, to achieve higher voltages. Fuel cells assembled on a planar surface can not be stacked one on top another. Series connections of a planar stack can be made using Beryllium Copper (BeCu) contacts between the anode and cathodes of the fuel cells.

Description and operation

Currently, we are fabricating our planar fuel cell out of ceramic. The substrates are made using Motorola's low temperature co-fired ceramic process (LTCC). With the LTCC process, metal pastes are screen-printed on green tape prior to sintering. After firing, the metal pastes form electrical contacts for each individual membrane electrode assembly (MEA) of the fuel cell. A single fuel cell contains an anode current collector, gas-diffusion layer, anode electrode, proton exchange membrane, cathode electrode, gas diffusion layer, and cathode current collector. To achieve a two cell series connection, the cathode of the first cell is electrically connected to the anode of the next cell. External electrical connection is then made to the anode of the first cell and the cathode of the second cell. Hence, if each cell were operating at 0.4 volts, then the two-cell stack would have a voltage of 0.8 volts. Additional cells can be placed between the first and second cells in the example above to increase the voltage of the stack.

This electrical connection in a bi-polar stack is made by placing the anode collector plate of the second cell directly on top of the cathode collector plate of the first cell. End plates are placed at the anode of the first cell and the cathode of the second cell. Additional cells are added to increase the voltage in this sandwich type configuration.

In our ceramic planar design, the gold prints are patterned so that when assembled, the anode print of the first cell lines up underneath the cathode print of the second cell. When the anode and cathode ceramic pieces are assembled with the MEA and gaskets, a gap is created between the two ceramic pieces. A spring contact, such as BeCu, is placed between the two prints to bridge the gap created by the gaskets and MEA, and makes an internal electrical connection between the two electrodes (Figure 1.). Furthermore, a recessed area is designed into the cathode substrate to aid in the placement and retaining of the BeCu contact during assembly (Figure 2). Once fully assembled, the planar fuel cell stack has a single positive and negative electrical lead (Figures 3,4). Multiple fuel cells can be assembled and connected in such a manor to increase the voltage to the desired level.

BeCu was chosen for the electrical co...