Atomic Layer Deposition of Aluminum Phosphorus Oxynitride and Its Application as a Passivation Layer on Aluminum Metal Anode

Why It Matters

By suppressing parasitic corrosion, AlPON enables durable, low‑cost aqueous aluminum batteries, accelerating their commercial viability.

Key Takeaways

• First PEALD AlPON coating for aluminum anodes
• Deposition temperature controls growth rate and composition
• AlPON reduces self‑corrosion in acidic Al electrolyte
• Improves electrochemical stability and cycle life
• Enables practical aqueous Al‑ion batteries

Pulse Analysis

Aqueous aluminum batteries promise high energy density, inexpensive raw materials, and a greener footprint than lithium‑based systems, yet their adoption has been stalled by aggressive corrosion at the metal‑electrolyte interface. Conventional protective layers either lack chemical compatibility with acidic electrolytes or add prohibitive processing steps, leaving a performance gap that researchers have struggled to close. The introduction of a thin, conformal AlPON film addresses this gap by providing a chemically inert barrier while preserving the metallic conductivity essential for fast charge transfer.

The AlPON layer is synthesized via plasma‑enhanced atomic layer deposition, a technique prized for its atomic‑scale thickness control and uniform coverage on complex geometries. Operating between 100 °C and 180 °C, the process leverages trimethylaluminum, water, tris(dimethylamino)phosphine, and oxygen plasma to embed phosphorus‑nitrogen bonds within an aluminum‑oxide matrix. X‑ray photoelectron spectroscopy reveals doubly and triply coordinated nitrogen environments, indicating a mixed oxynitride structure that can be tuned by temperature. This tunability translates into a predictable growth rate and compositional gradient, allowing engineers to optimize barrier thickness for specific electrolyte chemistries.

Electrochemical evaluation demonstrates that AlPON‑coated aluminum exhibits dramatically reduced corrosion currents in Tafel analyses and lower charge‑transfer resistance in impedance spectra, even in the aggressive 1 M Al(OTf)₃ acidic medium. The resulting stability extends cycle life and opens pathways for higher voltage aqueous chemistries that were previously untenable. For the battery industry, this breakthrough could lower material costs, simplify cell manufacturing, and accelerate the rollout of safe, recyclable energy storage solutions, positioning aqueous aluminum technology as a credible alternative to conventional lithium‑ion platforms.