Why Are Stainless Steel Pressure Plates Used For Solid-State Batteries? Achieve 2 Mpa Stability In Battery Cycling

Stainless steel pressure plates are critical structural components used to maintain the mechanical integrity of all-solid-state batteries. They provide a rigid constraint that applies a constant external pressure, specifically 2 MPa in this context, to counteract the physical volume changes that occur during the deposition and stripping of lithium metal. Without this external load, the internal stresses generated during charging and discharging would lead to component separation and failure.

Core Insight: Unlike liquid electrolytes, solid-state materials cannot flow to fill gaps created when electrodes expand or contract. A constant external pressure is required to mechanically force the battery layers together, preventing physical isolation and ensuring the ionic "highway" remains unbroken.

Managing Material Volume Changes

Compensating for Lithium Dynamics

During the charge and discharge process, lithium metal is deposited and stripped away. This movement causes significant volumetric fluctuations within the battery cell.

Preventing Layer Detachment

As the volume changes, stress fluctuations occur at the interfaces between layers. Without external pressure, these stresses would cause the layers to detach or separate.

The Function of Rigid Constraint

The stainless steel plates act as a non-deformable boundary. They ensure that as the internal volume attempts to shift, the components are held in tight compression to maintain their structural arrangement.

Critical Performance Benefits

Inhibiting Dendrite Growth

One of the primary dangers in solid-state batteries is the formation of lithium dendrites—needle-like projections that can short-circuit the cell. The 2 MPa mechanical load helps suppress the growth of these structures, contributing to safer operation.

Ensuring Stable Ion Conduction

For the battery to function, ions must move freely between the active materials and the solid electrolyte. The pressure plates ensure "intimate contact" is maintained, keeping these ion conduction channels open and stable.

Supporting High Current Densities

By stabilizing the interface against stress, the battery can handle higher current densities without degrading. This results in a more robust power delivery system.

Understanding the Trade-offs

Balancing Pressure and Integrity

While pressure is vital, it must be precise. The 2 MPa figure represents a specific balance; insufficient pressure leads to high interfacial impedance and contact failure, while excessive pressure could potentially damage brittle solid electrolyte materials.

System Weight and Complexity

The use of stainless steel plates adds weight and volume to the battery pack. While necessary for performance, this mechanical hardware reduces the overall gravimetric energy density of the final system compared to cells that do not require such heavy external fixturing.

Making the Right Choice for Your Goal

To apply this understanding to your battery design or testing protocols, consider the following:

If your primary focus is Cycle Life: Ensure your fixture maintains the pressure consistently over time to prevent the gradual increase of interfacial impedance and capacity loss.
If your primary focus is Safety: Prioritize the rigidity of the plates to prevent the interface fluctuations that allow lithium dendrites to nucleate and propagate.

External pressure is not merely a holding mechanism; it is an active variable essential for bridging the physical gap between solid-state components.

Summary Table:

Feature	Function in Solid-State Battery Research
Material	Rigid Stainless Steel (Non-deformable boundary)
Applied Pressure	2 MPa (Constant mechanical load)
Interface Management	Maintains intimate contact for stable ion conduction
Dendrite Control	Suppresses lithium needle growth to prevent shorts
Structural Goal	Counteracts volumetric changes during cycling

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References

Yang Zhang, Zhenxing Liang. Garnet‐Type Solid‐State Electrolyte with Tailored Lithium Compatibility for High Performance All‐Solid‐State Lithium Batteries. DOI: 10.1002/adma.202509828

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