What Is The Purpose Of Using A High-Precision Uniaxial Pressure Device? Optimize All-Solid-State Battery Testing

The primary purpose of a high-precision uniaxial pressure device in all-solid-state battery (ASSB) testing is to apply and maintain a constant, specific stack pressure (e.g., 13 MPa or 120 MPa) throughout the testing duration.

This mechanical constraint is required to compensate for the "breathing effect"—the natural volume expansion and contraction of electrode materials during charge and discharge cycles. By enforcing this pressure, the device ensures continuous physical contact between the solid layers, preventing the sudden capacity drops and premature failure caused by interfacial separation.

Core Insight:
In solid-state batteries, the electrolyte cannot flow to fill physical gaps like a liquid can. A high-precision pressure device acts as a mechanical stabilizer, actively forcing the solid components together to counteract volume changes. This prevents internal voids from forming and ensures the ionic pathways remain intact for reliable long-term cycling.

The Challenge: The "Breathing" Electrode

Accommodating Volume Expansion

During the electrochemical process, cathode and anode materials physically change size as lithium ions are inserted and extracted.

This phenomenon, known as the "breathing effect," causes significant volume expansion and contraction. Without external constraint, these fluctuations lead to physical shifting within the cell stack.

The Problem of Solid Interfaces

Unlike liquid electrolytes, solid-state electrolytes lack fluidity. They cannot self-repair or redistribute to fill gaps created by electrode movement.

If the contact between the electrode and electrolyte is lost even microscopically, ions cannot pass through. This leads to interfacial separation or delamination, rendering parts of the battery inactive.

Why Constant Pressure is Critical

Preserving Physical Integrity

The device applies a constant load to maintain tight physical contact between the anode, solid electrolyte, and cathode.

This effectively negates the breathing effect. By compressing the layers, the device prevents the physical detachment of interfaces that leads to a rapid rise in impedance and performance decay.

Suppressing Void Formation

On the anode side, particularly with lithium metal, stripping lithium during discharge can create vacancies or voids.

High-precision pressure helps collapse these voids as they form. This ensures intimate solid-solid contact is maintained, preventing "dead spots" where the reaction can no longer occur.

Controlling Dendrite Growth

Appropriate stack pressure influences how lithium deposits.

References indicate that precise pressure control can guide lithium dendrite growth into a lateral expansion mode rather than vertical penetration. This suppresses short circuits and extends the safety and life of the cell.

The Role in Data Reliability

Ensuring Reproducibility

In a laboratory setting, consistent data is impossible without consistent physical conditions.

A hydraulic press or pressure frame ensures that the interfacial contact area remains constant from one test cell to another. This minimizes variations in resistance that are due to assembly technique rather than material properties.

Simulating Operational Environments

These devices simulate the mechanical constraints a battery would face in a commercial pack.

By mimicking these conditions (e.g., 15–120 MPa), researchers obtain reliable data regarding cycle life and rate performance that is actually applicable to real-world scenarios.

Understanding the Trade-offs

The Risk of "Over-Pressurization"

While pressure is necessary, applying too much can be detrimental.

Excessive pressure may mechanically damage soft separator materials or cause internal short circuits by forcing particles through the electrolyte layer. The pressure must be optimized for the specific materials being tested.

Mechanical Complexity

Introducing uniaxial pressure devices adds significant complexity to the testing setup compared to standard coin cells.

It requires bulky equipment (pressure frames or hydraulic presses) inside gloveboxes or test chambers, limiting the number of channels that can be tested simultaneously.

Making the Right Choice for Your Goal

When designing your experiment, align the pressure parameters with your specific objective:

If your primary focus is Cycle Life: Prioritize higher, constant pressures (e.g., >15 MPa) to aggressively suppress void formation and delamination during long-term cycling.
If your primary focus is Material Screening: Use a standardized, moderate pressure across all samples to ensure that differences in performance are due to material chemistry, not contact variation.
If your primary focus is Safety analysis: Focus on pressure ranges that influence lithium deposition to study the suppression of vertical dendrite growth.

Ultimately, the high-precision pressure device is not just a holder; it is an active component of the test that substitutes for the lack of fluidity in solid electrolytes.

Summary Table:

Feature	Impact on All-Solid-State Batteries
Pressure Control	Compresses solid layers to maintain continuous physical contact.
Breathing Effect	Counteracts volume expansion/contraction during cycling.
Interfacial Stability	Prevents delamination and rising impedance due to gaps.
Void Suppression	Collapses vacancies during lithium stripping to prevent 'dead spots'.
Dendrite Control	Guides lateral lithium growth to prevent internal short circuits.
Reproducibility	Ensures consistent interfacial resistance across laboratory tests.

Maximize Your Battery Research Precision with KINTEK

Maintaining consistent stack pressure is critical for reliable all-solid-state battery data. KINTEK specializes in comprehensive laboratory pressing solutions tailored for high-precision battery research. Whether you need manual, automatic, heated, multifunctional, or glovebox-compatible models, our equipment ensures your cells remain stabilized against the 'breathing effect.'

From cold and warm isostatic presses to specialized uniaxial frames, we provide the mechanical integrity your experiments demand. Contact KINTEK today to find the perfect pressing solution for your lab and accelerate your breakthrough in energy storage!

References

Chanhyun Park, Sung‐Kyun Jung. Interfacial chemistry-driven reaction dynamics and resultant microstructural evolution in lithium-based all-solid-state batteries. DOI: 10.1038/s41467-025-63959-1

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