External pressure plays a significant role in battery aging, particularly in the context of mechanical stress on cell components. The range of 5-1000 kPa encompasses operational conditions for various battery formats, influencing degradation mechanisms differently across lithium-ion, solid-state, and other advanced battery systems.

In solid-state batteries, stack pressure is critical for maintaining interfacial contact between the solid electrolyte and electrodes. Insufficient pressure leads to increased interfacial resistance due to poor contact, while excessive pressure may induce mechanical degradation of brittle solid electrolytes. Studies indicate optimal stack pressures typically fall between 50-300 kPa for sulfide-based solid electrolytes, while oxide-based systems often require higher pressures up to 500 kPa. Below 50 kPa, interfacial delamination accelerates, causing rapid capacity fade, whereas pressures exceeding 500 kPa risk fracture propagation in ceramic electrolytes.

Pouch cells exhibit distinct pressure sensitivity due to their flexible packaging. External pressure below 20 kPa can lead to delamination between electrode layers, increasing internal resistance. At pressures above 200 kPa, deformation of the aluminum laminate may occur, compromising seal integrity and promoting electrolyte evaporation. Cycling under variable pressure conditions between 10-100 kPa has been shown to accelerate delamination by up to 40% compared to constant-pressure conditions.

Cylindrical cells, constrained by rigid casings, demonstrate less sensitivity to external pressure variations within the 100-1000 kPa range. However, excessive pressure above 700 kPa can distort the jelly roll structure, leading to localized stress points that promote lithium plating. Prismatic cells, with semi-rigid designs, exhibit intermediate sensitivity, where pressures beyond 400 kPa may cause electrode stack compression, altering porosity and ion transport kinetics.

Pressure distribution uniformity is another critical factor. Non-uniform pressure across large-format cells creates stress gradients, exacerbating heterogeneous aging. In solid-state batteries, pressure gradients as low as 20 kPa/cm can induce uneven interfacial degradation, reducing cycle life by up to 30%. Pouch cells subjected to uneven pressure show preferential delamination at low-pressure zones, while cylindrical cells mitigate this effect through structural symmetry.

Temperature-pressure coupling further complicates aging dynamics. Elevated temperatures soften polymer components, making cells more susceptible to pressure-induced deformation. At 45°C, pouch cell delamination rates under 50 kPa pressure double compared to room temperature. Solid-state batteries experience accelerated interfacial degradation at high temperatures when pressure is insufficient to compensate for thermal expansion mismatches.

Mechanical fatigue from cyclic pressure loading is another concern. Repeated pressure fluctuations between 10-100 kPa, simulating real-world applications, cause progressive bond weakening in pouch cells, reducing adhesion strength by 15% after 500 cycles. Solid-state batteries subjected to pressure cycling between 100-300 kPa develop microcracks in the solid electrolyte after 200 cycles, increasing short-circuit risks.

Mitigation strategies include optimized cell design and pressure management systems. For solid-state batteries, compliant interlayers help maintain interfacial contact under variable pressure. Pouch cells benefit from internal spacers that distribute pressure evenly. Cylindrical and prismatic cells incorporate structural reinforcements to minimize deformation under external loads.

Understanding pressure effects requires standardized testing protocols. Current methods include constant-pressure aging, pressure cycling, and spatially resolved pressure application. Results vary significantly depending on test conditions, highlighting the need for industry-wide pressure testing standards.

In summary, external pressure between 5-1000 kPa significantly impacts battery aging through interfacial degradation, delamination, and mechanical fatigue. Solid-state batteries are highly sensitive to stack pressure, while pouch cells suffer from delamination under low or non-uniform pressure. Cylindrical and prismatic cells exhibit lower but non-negligible pressure sensitivity. Optimizing pressure conditions and cell designs can mitigate these effects, improving longevity and reliability across battery formats. Future research should focus on pressure-thermal coupling effects and standardized testing methodologies to better predict real-world performance.