The development of a high-precision pressure control system has demonstrated that maintaining an optimal and constant stack pressure doubled the cycle life of lithium-ion pouch cells. The findings show that both low and high stack pressures accelerate different degradation pathways, making pressure optimization a practical way to extend battery life without altering battery chemistry. These findings were published in Nature Energy.
Study: The interplay between stack pressure, mechanical expansion and degradation pathways in lithium-ion batteries. Image Credit: Black_Kira/Shutterstock.com
Role of Stack Pressure in Battery Aging
Extending the lifetime of lithium-ion batteries is essential for advancing electric vehicles and renewable energy storage. In this light, researchers have made significant progress in understanding the electrochemical processes that drive battery degradation.
However, they have paid less attention to the mechanical forces that develop inside batteries during operation.
Stack pressure plays an important role in maintaining stable battery operation, keeping electrode particles in close contact, reducing internal resistance, and limiting structural damage.
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Conventional battery-testing systems cannot maintain a constant stack pressure as batteries swell and shrink during cycling. As a result, researchers have struggled to determine how stack pressure influences long-term battery degradation.
In this study, the researchers have developed a high-precision, pressure-controlled dilatometry system that maintains a constant and uniform stack pressure throughout battery operation.
This platform evaluates commercially relevant graphite?single-crystal NMC811 pouch cells under different pressure conditions over hundreds of charge-discharge cycles. The results show that battery lifetime depends not only on electrochemistry but also on careful management of mechanical forces inside the cell.
Measuring Battery Expansion Under Controlled Pressure
The researchers developed a custom operando dilatometry system capable of maintaining a constant and uniform pressure throughout battery cycling. The system uses compliant pneumatic bellows and a highly sensitive displacement sensor to compensate for electrode expansion and contraction.
The new setup maintained pressure variations below 0.8%, which allowed the researchers to study the effects of stack pressure without interference from changes in cell thickness.
The team tested commercially relevant graphite?single-crystal NMC811 pouch cells under five stack-pressure conditions ranging from 1.5 to 37.5 bar. Their analysis focused primarily on low (3 bar), optimal (12.5 bar), and high (37.5 bar) pressures. During repeated charge-discharge cycles, the system continuously tracked both reversible and irreversible changes in battery thickness.
The researchers carried out various measurements with several advanced analytical techniques to identify the underlying degradation mechanisms. They examined changes in electrode structure, surface chemistry, lithium (Li) distribution, and transition metal dissolution using microscopy, spectroscopy, X-ray imaging, and electrochemical analysis.
These analyses linked stack pressure to the mechanical and electrochemical processes that govern long-term battery degradation.
Pressure Optimization Delivers Longer Battery Life
Optimizing stack pressure significantly improved battery performance. Cells operated at an optimal pressure of 12.5 bar retained 80% of their original capacity for more than 375 charge-discharge cycles.
In comparison, batteries cycled under either low (3 bar) or high (37.5 bar) pressure reached the same level of capacity loss after only 160–170 cycles. Making a simple mechanical adjustment nearly doubled battery lifetime without altering the battery's chemistry or materials.
The researchers also identified a strong relationship between irreversible battery expansion and degradation. Cells operated at the optimal pressure remained dimensionally stable throughout cycling.
In contrast, low-pressure cells gradually swelled over time, while high-pressure cells initially compacted before undergoing rapid expansion as degradation accelerated.
Further analyses showed that low and high stack pressures promote different degradation mechanisms. Under low pressure, weak particle contact increased mechanical stress within the cathode, causing extensive particle cracking.
These cracks exposed fresh electrode surfaces, accelerated transition metal dissolution, promoted electrolyte decomposition, and destabilized the solid electrolyte interphase (SEI) on the graphite anode.
High stack pressure produced a different set of challenges. Excessive compression reduced electrode porosity and restricted lithium-ion transport, increasing local overpotentials and eventually causing lithium plating on the graphite anode. The researchers confirmed these deposits using multiple imaging and spectroscopic techniques.
Overall, the results show that maintaining an intermediate stack pressure balances mechanical stability with efficient ion transport. This minimizes both cathode cracking and lithium plating, demonstrating that mechanical design plays a critical role alongside electrochemistry in determining battery lifetime.
Toward More Durable and Sustainable Batteries
Optimizing stack pressure offers a simple and practical way to extend the lifetime of lithium-ion batteries. Manufacturers can improve battery durability by better controlling the mechanical forces within the cell during assembly and operation.
The results are particularly relevant for high-energy graphite?NMC811 batteries used in electric vehicles and stationary energy-storage systems. Longer-lasting batteries can reduce replacement costs, improve resource efficiency, and lower the environmental impact associated with battery production.
Since pressure optimization does not require changes to existing battery chemistry, manufacturers may be able to integrate this approach into current production processes with minimal disruption.
The newly developed pressure-control system also gives researchers a powerful tool to investigate how mechanical behavior influences electrochemical degradation. The team demonstrated that the approach works across multiple battery systems, including polycrystalline NMC811 and lithium iron phosphate (LFP) cells, highlighting its potential for wider industrial adoption.
Future research will focus on scaling the technology to larger battery formats and incorporating pressure optimization into commercial battery packs. Overall, the findings emphasize that optimizing battery performance requires more than advances in chemistry alone.
Careful mechanical design can also play a critical role in developing longer-lasting, safer, and more sustainable energy storage systems.
Journal Reference
Wang, H., Wang, R. et al. (2026). The interplay between stack pressure, mechanical expansion and degradation pathways in lithium-ion batteries. Nature Energy. https://www.nature.com/articles/s41560-026-02087-6.
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