The bipolar plate is the most geometrically complex and volumetrically dominant component in a PEM or SOFC fuel cell stack. A graphite bipolar plate manufacturer must combine ultra-low porosity graphite grades with precise flow-field machining and tight dimensional control — properties that Expo Advanced Materials delivers from our ISO 9001:2015 certified facility in New Delhi.
Why Graphite for Bipolar Plates?
- Chemical inertness — Graphite is stable in the acidic (pH 2–3) PEM fuel cell environment, unlike metals that corrode and contaminate the membrane.
- Electrical conductivity — Through-plane resistivity below 10 mΩ·cm² minimises internal stack resistance losses.
- Machinability — Fine-grain isostatic graphite machines to complex flow-field channel geometries with wall widths as narrow as 0.5 mm.
- Thermal conductivity — 80–150 W/m·K assists heat rejection and temperature uniformity across the active area.
Graphite Grades for Bipolar Plates
| Grade | Grain Size (μm) | Density (g/cm³) | Open Porosity |
|---|---|---|---|
| EDM-3 (fine-grain) | 5–8 | 1.82–1.86 | <3% |
| Isostatic HP fine-grain | 3–5 | 1.85–1.90 | <2% |
| Resin-impregnated | 5–10 | 1.90–1.95 | <0.5% |
For research and prototype stacks, standard fine-grain grades typically suffice. For production fuel cell systems requiring gas impermeability, we recommend resin-impregnated plates where leak rate under 0.5 bar differential is specified.
Flow Field Machining Capabilities
- Channel profiles: Parallel, serpentine, interdigitated, and custom pin-fin designs
- Minimum channel width: 0.5 mm; typical 0.8–1.5 mm
- Channel depth accuracy: ±0.02 mm
- Plate area: Up to 400 × 300 mm active area
- Manifold ports: Inlet/outlet bores CNC-drilled and reamed to ±0.05 mm
- Surface finish Ra: 0.8–1.6 μm on channel floors
Typical Applications
- PEM hydrogen fuel cell stacks (H₂/air and H₂/O₂)
- Redox flow battery electrode frames
- Electrolyser cell plates for green hydrogen production
- Research and lab-scale SOFC testing rigs
How to Order
Share your bipolar plate drawing (DXF, STEP, or PDF), required graphite grade, quantity, and any porosity or conductivity specifications. We can also machine from customer-supplied graphite blanks. Prototype quantities from 5 pieces. Contact us for pricing within 24 hours.