What Is The Purpose Of Using A Dedicated Stainless Steel Forming Press? Achieve Optimal Density In Solid-State Cells

The primary purpose of using a dedicated stainless steel forming press is to bypass the mechanical limitations of PEEK (polyetheretherketone) battery housings during the high-pressure densification phase.

Because PEEK material has specific tensile strength limits, it cannot withstand the ultra-high pressures (such as 400 MPa) required to form dense electrode sheets and electrolytes. By performing this "heavy lifting" externally in a robust stainless steel mold, you can ensure the components achieve the necessary density and interfacial contact before transferring them into the PEEK unit for testing.

Core Takeaway In-situ battery testing hardware often lacks the structural integrity required for the extreme pressures of component formation. Pre-pressing in stainless steel decouples the formation pressure (high intensity) from the testing pressure (moderate intensity), allowing for ideal material density without destroying the test cell.

Overcoming Hardware Limitations

The Tensile Strength Gap

In-situ battery cells are frequently made of PEEK to facilitate specific testing conditions, but this material is mechanically limited. PEEK cannot sustain the ultra-high-pressure operations necessary to compact powders into solid layers.

Externalizing Mechanical Stress

To solve this, researchers use a dedicated stainless steel press to apply extreme forces, such as 400 MPa, outside of the final battery assembly. This effectively creates a high-performance "pre-fab" component that is structurally sound before it ever touches the delicate PEEK housing.

Ensuring Component Density

High-pressure cold pressing (ranging from 240 MPa to 320 MPa or higher) is critical for reducing gaps between particles in electrolyte powders. This process significantly increases the density of the base layers, which is impossible to achieve safely within a PEEK cell.

Critical Impact on Battery Performance

Optimizing Interfacial Contact

Pre-pressing ensures atomic-level physical contact between the active materials, the electrolyte, and the anode (such as Lithium-Indium alloy). This tightness is vital for lowering interfacial impedance, which dictates how easily energy flows through the cell.

Enhancing Ion Transport Kinetics

By eliminating voids and ensuring a dense, well-contacted structure, the pre-pressing treatment facilitates better lithium-ion transport. This ensures that the battery performs ideally during testing, even though the working pressure inside the PEEK cell will be lower than the initial formation pressure.

Understanding the Trade-offs

The Risk of Transfer Damage

While pre-pressing creates a superior individual component, moving that dense pellet from the stainless steel mold to the PEEK cell introduces a risk of fracture or misalignment. The transition requires precise handling to maintain the integrity of the interface created under high pressure.

Pressure Relaxation Effects

You must account for the fact that the "working pressure" inside the PEEK cell will be significantly lower than the "formation pressure" applied by the stainless steel press. If the material relies solely on active pressure to maintain contact, performance may degrade once the ultra-high pressure is removed.

Making the Right Choice for Your Goal

To maximize the effectiveness of your solid-state battery assembly, consider these strategic priorities:

If your primary focus is Electrode Density: Use the stainless steel press to apply maximum pressure (up to 400 MPa) to eliminate particle gaps before assembly.
If your primary focus is Interface Stability: Ensure the pre-pressed components are transferred immediately and carefully to the PEEK cell to preserve the atomic-level contact generated during forming.

Success in solid-state battery testing relies on separating the brutal force of formation from the delicate precision of in-situ analysis.

Summary Table:

Feature	Dedicated Stainless Steel Press	PEEK In-situ Battery Cell
Primary Function	High-pressure component densification	In-situ electrochemical testing
Pressure Capacity	Ultra-high (up to 400 MPa+)	Moderate (limited by tensile strength)
Material Durability	Extremely high (robust steel)	Moderate (specialized polymer)
Key Benefit	Eliminates particle gaps & voids	Facilitates precise data collection
Primary Role	Formation Stage	Testing & Analysis Stage

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References

Jean‐Marc von Mentlen, Christian Prehal. Operando Scanning SAXS/WAXS Cell Design for Multiscale Analysis of All‐Solid‐State Battery Systems. DOI: 10.1002/batt.202500428

This article is also based on technical information from Kintek Press Knowledge Base .