The present disclosure is directed towards electrochemical cells, and more particularly, to electrochemical cells with improved fluid flow design.

Electrochemical cells, usually classified as fuel cells or electrolysis cells, are devices used for generating current from chemical reactions, or inducing a chemical reaction using a flow of current. For example, a fuel cell converts the chemical energy of fuel (e.g., hydrogen, natural gas, methanol, gasoline, etc.) and an oxidant (air or oxygen) into electricity and waste products of heat and water. A basic fuel cell comprises a negatively charged anode, a positively charged cathode, and an ion-conducting material called an electrolyte.

Different fuel cell technologies utilize different electrolyte materials. A Proton Exchange Membrane (PEM) fuel cell, for example, utilizes a polymeric ion-conducting membrane as the electrolyte. In a hydrogen PEM fuel cell, hydrogen atoms are electrochemically split into electrons and protons (hydrogen ions) at the anode. The electrons then flow through the circuit to the cathode and generate electricity, while the protons diffuse through the electrolyte membrane to the cathode. At the cathode, hydrogen protons combine with electrons and oxygen (supplied to the cathode) to produce water and heat.

An electrolysis cell represents a fuel cell operated in reverse. A basic electrolysis cell functions as a hydrogen generator by decomposing water into hydrogen and oxygen gases when an external electric potential is applied. The basic technology of a hydrogen fuel cell or an electrolysis cell can be applied to electrochemical hydrogen manipulation, such as, electrochemical hydrogen compression, purification, or expansion. Electrochemical hydrogen manipulation has emerged as a viable alternative to the mechanical systems traditionally used for hydrogen management. Successful commercialization of hydrogen as an energy carrier and the long-term sustainability of a “hydrogen economy” depend largely on the efficiency and cost-effectiveness of fuel cells, electrolysis cells, and other hydrogen manipulation/management systems.

In operation, a single fuel cell can generally generate about 1 volt. To obtain the desired amount of electrical power, individual fuel cells are combined to form a fuel cell stack, wherein fuel cells are stacked together sequentially. Each fuel cell may include a cathode, an electrolyte membrane, and an anode. A cathode/membrane/anode assembly constitutes a “membrane electrode assembly,” or “MEA,” which is typically supported on both sides by bipolar plates. Reactant gases or fuel (e.g., hydrogen) and oxidant (e.g., air or oxygen) are supplied to the electrodes of the MEA through flow fields. In addition to providing mechanical support, the bipolar plates (also known as flow field plates or separator plates) physically separate individual cells in a stack while electrically connecting them. A typically fuel cell stack includes manifolds and inlet ports for directing the fuel and oxidant to the anode and cathode flow fields, respectively. A fuel cell stack also includes exhaust manifolds and outlet ports for expelling the excess fuel and oxidant. A fuel cell stack may also include manifolds for circulating coolant fluid to help expel heat generated by the fuel cell stack.

In fuel cells it is desirable to have full and even distribution of the fuel and oxidant throughout the flow fields in order to maximize the active area of the MEA utilized, which improves the overall performance. But, prior art fuel cell designs have struggled to achieve even and full distribution. Additionally, it is desirable not to create excessive pressure drop along the flow path of the fuel and the oxidant, which can otherwise consume some of the electrical energy generated by the fuel cell stack and decrease the overall efficiency of the fuel cells stack. As such, there is a continuing challenge to improve the flow design of fuel cells.

Another way to improve the overall performance and power density of a fuel cell stack can be to reduce the pitch (i.e., spacing) between adjacent cells of the fuel cell stack and/or thickness of the cells. Cell thickness can be reduced, for example, by reducing the thickness of the flow fields of each individual fuel cell. This, however, can be difficult to achieve without creating an excessive pressure drop along the fuel and oxidant flow path due to the reduction in the flow path caused by compression of the fuel cell stack, which can increase the load on the fuel cell stack.

In consideration of the aforementioned circumstances, the present disclosure is directed toward a fuel cell and fuel cell stack design having improved flow design and improved performance and power density.

In one aspect, the present disclosure is directed to an electrochemical cell stack having a plurality of electrochemical cells stacked along a longitudinal axis. The electrochemical cells may each include a membrane electrode assembly comprising a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer. The electrochemical cells may each further include an anode plate and a cathode plate with the membrane electrode assembly interposed therebetween, and the anode plate defines a plurality of channels that form an anode flow field facing the anode catalyst layer. The electrochemical cells may each also include a cathode flow field positioned between the cathode plate and the cathode catalyst layer, wherein the cathode flow field comprises a porous structure. The electrochemical cells may each further include: a first manifold section that includes an anode feed manifold and a second manifold section that includes an anode discharge manifold; a first anode distribution channel positioned between the first manifold section and the anode flow field configured to distribute fuel supplied from the anode feed manifold to the anode flow field; a second anode distribution channel positioned between the second manifold section and the anode flow field configured to collect fuel from the anode flow field and direct the fuel to the anode discharge manifold; an anode inlet port fluidly connecting first anode distribution channel with the anode feed manifold via an anode inlet passage; and an anode outlet port fluidly connecting second anode distribution channel with the anode discharge manifold via an anode outlet passage. In some embodiments, the anode inlet passage and anode outlet passage may be positioned between the anode plate and the cathode plate of adjacent electrochemical cells. In some embodiments, the anode inlet port may be formed in a side wall of a structural feature that extends from the surface of the anode plate into the first anode distribution channel toward the membrane electrode assembly. In some embodiments, the anode inlet port may be configured to direct the anode reactant flow into the first anode distribution channel in a direction generally parallel to the anode plate. In some embodiments, the structural feature may be a generally rounded rectangular shape. In some embodiments, the structural feature may include a plurality of anode inlet ports evenly distributed along a length of the side wall. In some embodiments, the anode outlet port may be formed in a side wall of a structural feature that extends from the surface of the anode plate into the first anode distribution channel toward the membrane electrode assembly. In some embodiments, the anode outlet port may be configured to receive the anode reactant flow from the second anode distribution channel in a direction generally parallel to the anode plate. In some embodiments, the structural feature may be a generally rounded rectangular shape. In some embodiments, the structural feature may include a plurality of anode inlet ports evenly distributed along a length of the side wall.

In another aspect, the present disclosure is directed to an electrochemical cell stacked along a longitudinal axis. The electrochemical cells may each include: a membrane electrode assembly comprising a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer; an anode plate and a cathode plate with the membrane electrode assembly interposed therebetween, and the anode plate defines a plurality of channels that form an anode flow field facing the anode catalyst layer; a cathode flow field positioned between the cathode plate and the cathode catalyst layer, wherein the cathode flow field comprises a porous structure; a first manifold section that includes a cathode discharge manifold and a second manifold section that includes a cathode feed manifold; a plurality of cathode inlet ports fluidly connecting the cathode flow field with the cathode feed manifold via a cathode inlet passage; and a plurality of cathode outlet ports fluidly connecting the cathode flow field with the cathode discharge manifold via a cathode outlet passage. In some embodiments, the cathode inlet passage and cathode outlet passage may be positioned between the anode plate and the cathode plate of adjacent fuel cells. In some embodiments, the plurality of cathode inlet ports and the plurality of cathode outlet ports may be rectangular shaped. In some embodiments, the plurality of cathode inlet ports may include at least two cathode inlet ports arranged perpendicular to one another and the plurality of cathode outlet ports may include at least two cathode outlet ports arranged perpendicular to one another. In some embodiments, the plurality of cathode inlet ports may include at least one cathode inlet port positioned at opposite ends of the cathode inlet passage and the plurality of cathode outlet ports may include at least one cathode outlet port positioned at opposite ends of the cathode inlet passage. In some embodiments, a total inlet area of the plurality of cathode inlet ports may be greater than a total outlet area of the cathode outlet ports. In some embodiments, the porous structure may include at least nickel and chromium. In some embodiments, the porous structure may include a nickel concentration of 60% to 80% by mass and a chromium concentration of 20% to 40% by mass and at least one surface of the porous structure includes a chromium concentration of about 3% to about 50% by mass. In some embodiments, the porous structure may include a chromium concentration of about 3% to about 6%, a tin concentration of about 10% to about 20%, and a nickel concentration of about 74% to about 87%. In some embodiments, a first surface of the porous structure may have a higher chromium concentration than an opposite second surface. In some embodiments, the first surface may have a chromium concentration ranging from about 3% to about 50% by mass and the second surface may have a chromium concentration less than about 3% by mass. In some embodiments, the first surface of the porous structure faces the membrane electrode assembly. In some embodiments, the cathode plate of each cell may be formed of uncoated stainless steel.

In another aspect, the present disclosure is directed to an electrochemical cell having a membrane electrode assembly comprising a cathode catalyst layer, an anode catalyst layer, and a polymer membrane interposed between the cathode catalyst layer and the anode catalyst layer. The electrochemical cell may also have an anode plate and a cathode plate with the membrane electrode assembly interposed therebetween, and the anode plate defines a plurality of channels that form an anode flow field facing the anode catalyst layer. The electrochemical cell may further include a cathode flow field positioned between the cathode plate and the cathode catalyst layer, wherein the cathode flow field comprises a porous structure.

It is to be understood that both the foregoing general description and the following detailed description are exemplary and explanatory only and are not restrictive of the disclosure, as claimed.

