Bipolar plate

© Chemnitz University of Technology
Bipolarplatte
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Bipolar plates (BPP) are considered a key component in hydrogen technologies. They are used in both fuel celland electrolysis stacks for hydrogen production. They have a significant impact on the efficiency and performance of hydrogen systems.

The three most important functions of bipolar plates in a stack are:

  1. Gas Supply
  2. Cooling
  3. Electrical Connection

Design and Manufacturing

A bipolar plate is a flat, rectangular plate made of conductive materials such as graphite, metal, or ceramic. The manufacture of bipolar plates is a complex process that requires a high degree of precision.

Proton Exchange Membrane Fuel Cell Bipolar Plate Analyses

Structure of a PEM fuel cell stack (© pengoodet.de)

Bipolar plates consist of two thin-walled stainless steel sheet halves, also known as half-plates. These plates, which are only a few tenths of a millimeter thick, contain a structure of flow fields, cooling channels, and openings. The three main manufacturing steps are pressing, milling, and electroplating:

  1. During the pressing process, the materials are shaped under high pressure and at high temperatures to achieve the desired structure and surface finish.
  2. During the milling process, the panels are precisely machined using CNC machines to create the channels and grooves.
  3. Electroplating is used to coat the surface of the plates with a thin layer of a conductive material in order to improve electrical conductivity. These coatings are currently produced by vapor deposition of, for example, gold. In this case, not only is the coating material itself very expensive, but so is the vapor deposition process, which uses Physical Vapor Deposition (PVD).

Bipolar plates in hydrogen systems

The name “bipolar” comes from the fact that the plate conducts electrical current between adjacent cells in both directions. This allows the plate to transmit both positive and negative charges. This is expected to improve the efficiency and performance of hydrogen systems.

In electrolysers, bipolar plates serve as structural components that separate the electrodes of the various cells from one another. At the same time, they conduct electrical current between them. In this way, the plates increase the efficiency of electrolysis by reducing electrical resistance and improving the system’s energy efficiency.

In fuel cells, bipolar plates also serve as structural connectors between the individual cells within a stack. The plate allows electrical current to flow in both directions between adjacent cells, which increases the fuel cell’s efficiency and performance. In addition, they serve as distributors for fuel and oxidant, as well as heat sinks to dissipate excess heat generated during operation.

Prospects and Economic Significance

The further development of bipolar plates is a key research focus in the hydrogen industry. Current efforts are centered on improving performance while reducing costs.
One promising approach is the development of novel coating methods that offer a more cost-effective alternative to the expensive vapor deposition of precious metals. In addition, researchers are working to optimize flow patterns to further increase efficiency. These innovations are of great economic importance, as bipolar plates account for a significant portion of the total cost of fuel cell and electrolysis systems: estimates suggest they can account for up to 50% of stack costs .
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