# US 8,568,940 B2 · Joining bipolar plates using localized electrical nodes > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 8,568,940 B2 - Document ID: US8568940B2 - Status: Granted - Kind: B2 - Application number: 11/752,993 - Filed: 2007-05-24 - Published: 2008-11-27 - Granted: 2013-10-29 - Earliest claimed: 2007-05-24 - Assignees: GM Global Technology Operations LLC - Applicants: Keith E. Newman; Michael K. Budinski - Inventors: Keith E. Newman; Michael K. Budinski - Web page: https://patentgrep.com/patent/US8568940B2 ## CPC - H01M 8/0202: Collectors; Separators, e.g. bipolar separators; Interconnectors - H01M 8/0228: in the form of layered or coated products - H01M 8/0256: Vias, i.e. connectors passing through the separator material - H01M 8/0267: having heating or cooling means, e.g. heaters or coolant flow channels - H01M 8/04074: {Heat exchange unit structures specially adapted for fuel cell} - H01M 8/242: comprising framed electrodes or intermediary frame-like gaskets (H01M8/2425, H01M8/244 take precedence) - H01M 8/2483: characterised by internal manifolds - Y02E 60/50: Fuel cells - H01M: PROCESSES OR MEANS, e.g. BATTERIES, FOR THE DIRECT CONVERSION OF CHEMICAL ENERGY INTO ELECTRICAL ENERGY - Y02E: REDUCTION OF GREENHOUSE GAS [GHG] EMISSIONS, RELATED TO ENERGY GENERATION, TRANSMISSION OR DISTRIBUTION ## Abstract A bipolar plate assembly for a fuel cell is provided. The bipolar plate assembly includes a first unipolar plate disposed adjacent to a second unipolar plate. The first unipolar plate and the second unipolar plate are bonded by a plurality of localized electrically conductive nodes. A fuel cell stack including the bipolar plate assembly and a method for preparing the bipolar plate assembly are also described. ## Claims ### Claim 1 A bipolar plate assembly for a fuel cell, comprising: a first unipolar plate having a plurality of first lands disposed between a plurality of first flow channels; and a second unipolar plate having a plurality of second lands disposed between a plurality of second flow channels; wherein the first unipolar plate is disposed adjacent the second unipolar plate and at least one of the first lands is bonded to a corresponding one of the second lands by at least two localized electrically conductive nodes. ### Claim 2 (depends on 1) The bipolar plate assembly of claim 1, wherein the first flow channels of the first unipolar plate are first coolant channels formed in a first inner surface thereof and the second flow channels of the second unipolar plate are second coolant channels formed in a second inner surface thereof, wherein the first coolant channels and the second coolant channels cooperate to form a coolant flowfield in the bipolar plate assembly. ### Claim 3 (depends on 1) The bipolar plate assembly of claim 1, wherein a first perimeter flange of the first unipolar plate is joined with a second perimeter flange of the second unipolar plate to form a substantially hermetic seal therebetween. ### Claim 4 (depends on 3) The bipolar plate assembly of claim 3, wherein the seal is formed from one of a weld, a solder joint, a braze joint, and an adhesive. ### Claim 5 (depends on 1) The bipolar plate assembly of claim 1, wherein at least one of the first unipolar plate and the second unipolar plate have a hydrophilic coating deposited thereon. ### Claim 6 (depends on 1) The bipolar plate assembly of claim 1, wherein the nodes have an average diameter of less than about 0.3 mm. ### Claim 7 (depends on 6) The bipolar plate assembly of claim 6, wherein the nodes have an average diameter of about 0.1 mm. ### Claim 8 (depends on 1) The bipolar plate assembly of claim 1, wherein an average quantity of the nodes located on a square centimeter of a surface of at least one of the first unipolar plate and the second unipolar plate is between about 0.25 nodes/cm2 to about 4 nodes/cm2. ### Claim 9 (depends on 1) The bipolar plate assembly of claim 1, wherein a voltage drop between the first unipolar plate and the second unipolar plate is less than about 2 mV at a current density of 1 A/cm2. ### Claim 10 (depends on 1) The bipolar plate assembly of claim 1, wherein the nodes are formed from at least one of a weld, a solder joint, a braze joint, and an adhesive. ### Claim 11 (depends on 10) The bipolar plate assembly of claim 10, wherein the nodes are formed by a spot weld. ### Claim 12 (depends on 1) The bipolar plate assembly of claim 1, wherein at least one of the first unipolar plate and the second unipolar plate is formed from one of a metal, graphite, and a composite material. ### Claim 13 (depends on 1) The bipolar plate assembly of claim 1, wherein the first unipolar plate and the second unipolar plate are formed from stainless steel. ### Claim 14 A fuel cell stack comprising: a plurality of membrane electrode assemblies arranged in a stacked configuration, each of the plurality of membrane electrode assemblies having a cathode and an anode; and a bipolar plate assembly disposed between adjacent membrane electrode assemblies, the bipolar plate assembly including a first unipolar plate having a plurality of first lands disposed between a plurality of first flow channels and a second unipolar plate having having a plurality of second lands disposed between a plurality of second flow channels, wherein the first unipolar plate is disposed adjacent the second unipolar plate and at least one of the first lands is bonded to a corresponding one of the second lands by at least two localized electrically conductive nodes. ### Claim 15 A method for preparing a bipolar plate assembly for a fuel cell stack, comprising the steps of: providing a first unipolar plate having a first inner surface and a plurality of first lands disposed between a plurality of first flow channels; providing a second unipolar plate having a second inner surface and a plurality of second lands disposed between a plurality of second flow channels; positioning the first inner surface adjacent the second inner surface; and bonding at least one of the first lands to a corresponding one of the second lands by at least two localized electrically conductive nodes. ### Claim 16 (depends on 15) The method of claim 15, wherein the first unipolar plate and the second unipolar plate are positioned within a clamping fixture. ### Claim 17 (depends on 15) The method of claim 15, wherein the step of bonding the first unipolar late and the second unipolar plate includes spot welding. ### Claim 18 (depends on 15) The method of claim 15, further comprising the step of joining a first perimeter flange of the first unipolar plate with a second perimeter flange of the second unipolar plate, wherein a substantially hermetic seal is formed. ### Claim 19 (depends on 18) The method of claim 18, wherein the step of joining the first and second perimeter flanges includes laser welding. ### Claim 20 (depends on 1) The bipolar plate assembly of claim 1, wherein a distance a central point of each of the plurality of nodes is spaced apart from a central point of an adjacent node along at least one of a length and a width of the first and second unipolar plates is greater than a maximum diameter of each of the nodes.