Prismatic Cell Enclosure Mechanical Stress Distribution under Solid-State Anode Expansion
Prismatic solid-state cell enclosures demand module preloads between 2 and 8 MPa with flexible interlayers to control wall deflection and dendrites.
Solid Electrolyte Contact Pressure
Meaning
Compressive loads maintain the physical connection between the active electrode particles and the solid ion conductor. Solid electrolyte contact pressure is necessary because these materials do not flow like liquids to wet the surfaces. Consistent force prevents the formation of voids that would otherwise increase the internal resistance of the cell.
Maintaining Contact
Constant pressure throughout the discharge cycle requires a dynamic spring system or an active clamping mechanism. As the anode expands and contracts, the solid electrolyte contact pressure must remain within a narrow range to prevent cracking. If the force drops below the threshold, the ionic pathway is severed and the capacity of the cell decreases.
High pressure also helps to suppress the growth of lithium dendrites by closing micro-cracks in the ceramic layer.
Interface Resistance
Impedance at the boundary is inversely proportional to the applied load. Increasing the solid electrolyte contact pressure reduces the energy needed for ions to cross the interface between materials.
Stack Design
Housing requirements for solid-state batteries are more demanding than those for liquid-filled cells. The assembly must accommodate the solid electrolyte contact pressure without adding excessive mass to the overall pack. Lightweight titanium or carbon fiber plates are often used to provide the necessary rigidity for the clamping system.