Good Conductivity and Liquid Permablity Graphite Bipolar Plates

Graphite bipolar plates are made from high-purity graphite (typically ≥99.9% purity) as the base material, processed through molding, precision milling, and surface coating.

Graphite bipolar plates are a core component of flow batteries, primarily responsible for separating the positive and negative electrolytes, conducting current, and supporting the battery structure.

In a flow battery stack, the graphite bipolar plate acts as a current collector, connecting the positive and negative electrodes of a single cell and conducting current; simultaneously, it prevents self-discharge by isolating the positive and negative electrolytes, provides mechanical support for the electrodes, and maintains the stability of the stack. Its thickness is typically 0.6 mm, its conductivity can reach 400 S/cm, and its tensile strength meets usage requirements.

Graphite bipolar plates are core components in hydrogen fuel cells, PEM water electrolysis for hydrogen production, and flow batteries. Their manufacturing process directly affects the gas tightness, power output, and lifespan of the fuel cell stack. The following are the main production processes and technical characteristics of graphite bipolar plates:
1. Expanded Graphite Plate Process: Expanded graphite (flexible graphite) undergoes burnishing, molding, and material removal before entering processes such as resin impregnation, vulcanization, bonding, and sealing vulcanization. This process ensures the shape and dimensional accuracy of the plate and, due to the continuity of graphite, provides high electrical and thermal conductivity. Key parameters include molding pressure, resin ratio, and post-treatment of surface contact resistance.

2. Molding/Hot Pressing Process: Graphite powder is mixed with resin, followed by pre-molding treatment, molding, and vulcanization, and finally bonding and sealing curing. This process also meets the shape and dimensional requirements of the plate, but requires a collaborative approach of materials and processes to address the surface hydrophobicity issue. Modern intelligent molding equipment (such as servo hot presses) can control precision within ±0.03mm and flatness to 0.02mm.

3. Impregnation and Dispensing Processes
Impregnation: Graphite plates are impregnated with resin under vacuum and cured under pressure to form a dense structure.
Dispensing: Used for bipolar plate air circuit sealing, frame bonding, etc., requiring precise control of adhesive width and height. Water bonding often uses screen printing + epoxy adhesive.

4. Intelligent Production Line Technology
Modern intelligent production lines integrate high-precision servo hot pressing, full-process automation, and MES data traceability systems.
Flexible Graphite Plate Molding Line: Automatic feeding, pressing, appearance inspection, and unloading.
Fully Automatic Dispensing Line: Includes airtightness testing, laser marking, etc., achieving a yield rate of up to 99.8%.

Graphite bipolar plates are mainly used in electrochemical fields such as fuel cells, flow batteries, and energy storage devices. Specific applications include:
1. Fuel Cells In proton exchange membrane fuel cells, graphite bipolar plates are a core component, responsible for separating the reacting gases at the anode and cathode, providing current conduction paths, and optimizing flow channel design to achieve efficient gas distribution and heat management.

2. Flow Batteries As a key component of vanadium redox flow batteries, graphite bipolar plates ensure efficient and stable battery operation through functions such as conductivity and current collection, electrolyte separation, electrode structure support, and optimized fluid distribution. Their high conductivity and corrosion resistance make them perform excellently in acidic electrolyte environments.

3. Energy Storage Devices In novel energy storage batteries and water electrolysis devices, graphite bipolar plates serve as electrodes or conductive components, utilizing their excellent conductivity and chemical stability to improve device efficiency. Furthermore, their high thermal conductivity enables rapid heat conduction in heat dissipation components of electronic devices.

Graphite bipolar plates are a core component of flow batteries or fuel cells, combining conductivity, liquid resistance, support, and fluid distribution functions. Their performance directly affects battery efficiency, lifespan, and cost. The following are their key performance indicators and characteristics:

1. Conductivity: The surface conductivity of graphite bipolar plates is typically higher than 40 mΩ·cm (typical value 41.7 mΩ·cm), enabling efficient current conduction and reducing internal resistance.

2. Corrosion Resistance: They remain stable in strong acid environments such as 2-2.5 M HSO, suitable for acidic electrolyte scenarios.

3. Mechanical Strength: Bending strength needs to be greater than 25 MPa to withstand the pressure of stack assembly, but they are relatively brittle (thickness needs to be 4-6 mm to reduce the risk of breakage).

4. Airtightness: Permeability is less than 10 cm³/(cm²·s), effectively isolating the positive and negative electrolytes and preventing self-discharge.