Why Are Current Collector Surface Flatness And Pressing Precision Critical For Anode-Less All-Solid-State Batteries?

In anode-less all-solid-state battery structures, current collector surface flatness and pressing precision are the primary defenses against catastrophic failure. Because lithium metal deposits directly onto the collector during charging, any surface irregularity or pressure variance concentrates current density, triggering dendrite formation that can pierce the electrolyte.

Success in anode-less designs relies on maintaining a pristine, void-free interface between the current collector and the solid electrolyte. Without high-precision mechanical control, localized stress points create pathways for lithium dendrites, compromising both battery safety and longevity.

The Mechanics of the Anode-Less Interface

The Deposition Challenge

In an anode-less configuration, there is no pre-existing anode material to host ions. Lithium metal must plate directly onto the current collector’s surface every time the battery charges.

This process demands a perfectly uniform "canvas" to ensure the lithium layer grows evenly across the entire active area.

Why Flatness Dictates Safety

High-flatness current collectors are essential to prevent the "lightning rod" effect. If the surface is uneven, microscopic protrusions attract higher electrical current.

This excessive local current density accelerates lithium growth at specific points. This rapid, localized growth forms sharp dendrites capable of puncturing the solid-state electrolyte, leading to short circuits.

The Critical Role of Pressing Precision

Ensuring Uniform Current Distribution

High-precision pressing ensures that the physical contact between layers is identical across the entire cell.

If the pressing precision is insufficient, interface pressure becomes uneven. Areas of varying pressure disrupt the uniformity of the current, inducing the same dendrite-forming conditions caused by rough surfaces.

Eliminating Microscopic Voids

Beyond preventing dendrites, pressure is required to facilitate basic function. As high-precision presses apply forces up to 375 MPa, they eliminate microscopic voids between solid-solid interfaces.

Removing these voids is physically necessary to construct low-impedance interfaces. This ensures efficient ion transport between the electrolyte and electrode layers, which is impossible if gaps exist.

Common Pitfalls to Avoid

Overlooking Equipment Specifications

Standard pressing equipment often lacks the strict tolerance controls required for anode-less architectures.

Utilizing high-specification pressing equipment is a vital safeguard. Relying on lower-grade machinery is a direct path to failure modes caused by uneven interface pressure.

Ignoring the Surface-Current Link

Designers often focus heavily on chemical compatibility while underestimating mechanical topography.

Failing to prioritize surface flatness results in unpredictable cycle life. Even chemically perfect cells will fail if physical irregularities trigger random dendrite nucleation.

Making the Right Choice for Your Goal

Achieving a viable anode-less cell requires balancing mechanical precision with electrochemical needs.

If your primary focus is Safety: Prioritize current collector flatness to eliminate high-current density hot spots that generate dangerous dendrites.
If your primary focus is Performance: Ensure high-precision pressing to eliminate voids and minimize interfacial impedance for maximum ion transport efficiency.

Mastering the mechanical interface is the prerequisite for unlocking the high energy density potential of anode-less solid-state batteries.

Summary Table:

Critical Factor	Primary Function	Impact on Battery Performance
Surface Flatness	Prevents "lightning rod" effect	Eliminates localized current density & dendrite growth
Pressing Precision	Ensures uniform contact pressure	Minimizes interfacial impedance & removes microscopic voids
High Pressure (375 MPa)	Facilitates solid-solid contact	Enables efficient ion transport between electrolyte and electrodes
Interface Integrity	Maintains void-free canvas	Enhances cycle life and prevents catastrophic short circuits

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References

Julia H. Yang, Amanda Whai Shin Ooi. Buried No longer: recent computational advances in explicit interfacial modeling of lithium-based all-solid-state battery materials. DOI: 10.3389/fenrg.2025.1621807

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