Why Consistent Pressure Management Is Critical for ASSB Reliability

First, let us take a closer look at what ASSB technology is. In all-solid-state battery technology, the liquid electrolyte used in traditional lithium-ion (Li-ion) batteries is replaced with a solid electrolyte. This fundamental change brings several differences in design, performance, and safety.

• Safety: Using solid electrolytes offers enhanced thermal stability and a significantly lower risk of fire or leakage due to the absence of flammable liquid electrolytes—providing improved safety and a longer lifespan compared to conventional lithium-ion batteries.
• Lifetime: ASSB technology potentially delivers a longer lifespan due to reduced side reactions and better stability at high voltages.
• Performance: Increased energy density is perhaps the most important performance advantage ASSB technology provides. These higher energy densities are achieved through the use of metal anodes, which store more energy than graphite. Additionally, solid electrolytes can support higher current densities, enabling extremely fast charging rates.

As we can see, ASSBs promise lighter, safer, and more energy-dense batteries, making them ideal for electric vehicles and high-performance applications. However, they introduce new engineering challenges—particularly pressure management, thermal control, and manufacturing scalability.

Applying the correct pressure to EV battery cells is nothing new and has led to significant improvements in the safety, performance, and lifespan of Li-ion EV batteries. But given the different design, does this apply to ASSB technology as well?

The answer is: Yes. ASSBs rely on solid-solid interfaces for ionic transport. These interfaces must remain in close contact throughout the battery’s lifecycle. Consistent pressure ensures low interfacial resistance for efficient ion flow, stable mechanical integrity during charge/discharge cycles, and prevention of lithium dendrite formation, which can cause short circuits.

Therefore, without uniform pressure, microscopic gaps can form between layers, risking reduced conductivity and accelerated degradation. In short: the correct pressure in ASSB batteries isn’t optional; it’s essential.

We learned that applying the correct pressure in ASSB is important, but it is also far from straightforward. During operation, ASSBs experience volume changes throughout cycling due to expansion and contraction, as well as thermal expansion and temperature fluctuations. These factors, among others, make applying the correct pressure challenging, which could result in reduced cycle life, lower energy efficiency, increased safety risks caused by gaps that may trigger dendrite growth or the formation of thermal hotspots.

Innovative foam materials optimised for consistent pressure application during ASSB operation could be the solution. Let’s see how.

Pressure management in ASSBs is not a secondary design consideration; it is a core reliability factor. Unlike liquid-based systems, solid-state batteries rely on intimate contact between solid electrolyte layers and electrodes to maintain ionic conductivity. Any loss of contact increases interfacial resistance, reduces efficiency, and accelerates degradation.

There are various material strategies for pressure management and achieving uniform pressure across the stack, alongside mechanical resilience, thermal stability, and long-term reliability.

Compression Pads for Uniform Pressure Distribution 
Advanced compression pads with controlled elasticity and creep resistance help compensate for expansion and contraction, maintaining consistent pressure for improved stack integrity even under dynamic conditions. Key properties include:

• Elastic modulus tuning for predictable deformation under load.
• Long-term compression set resistance to prevent pressure loss over time.
• Custom geometries for integration into complex module designs.

Specialty Foams for Stress Absorption and Thermal Control 
High-performance foams serve a dual role by absorbing mechanical stress and managing heat during operation. Closed-cell structures provide cushioning while maintaining dimensional stability, and formulations can be tailored for thermal conductivity. Benefits include:

• Vibration damping to protect fragile interfaces during vehicle operation.
• Thermal insulation or heat spreading to mitigate hotspots during rapid charging.
• Lightweight design to support EV efficiency targets.

These advanced materials could be further optimised with adhesive properties and pre-cut foam components that simplify assembly, streamline production processes, reduce labour costs, and ensure repeatable quality.

ASSBs represent a significant advancement in EV technology, but their success relies on more than just chemistry. Mechanical design, particularly pressure management, is a crucial factor for reliability. By utilising the expertise and unique capabilities of Saint-Gobain® Tape Solutions, our experts can assist in creating advanced compression pads and foams to address challenges in solid-state battery development.