Behind the Paper

Interface Matters: Rethinking Current Collector Stability in Sulfide-Based Solid-State Batteries

Sulfide electrolytes enable high ionic conductivity in solid-state batteries; however, their chemical stability with current collectors is often overlooked. This study reveals corrosion trends across various metals, providing valuable insights for industrial design and battery material selection.
Artur Tron Oct 20, 2025

Solid-state batteries (SSBs) are widely hailed as the next leap in energy storage offering higher safety, greater energy density, and longer cycle life compared to conventional lithium-ion batteries. Among the many contenders for solid electrolytes, sulfide-based materials like Li6PS5Cl (an argyrodite compound) stand out for their exceptional ionic conductivity and favorable mechanical properties [1]. However, as research advances on cathode compatibility and lithium metal interfaces [2], one critical component has remained in the shadows: the current collector.

In this study, Dr. Artur Tron and colleagues shine a spotlight on the overlooked interface between sulfide electrolytes and current collectors, revealing how subtle chemical instabilities can undermine battery performance and scalability. Their findings offer a roadmap for industrial designers and researchers seeking to build robust, corrosion-resistant solid-state cells [1].

Why Argyrodite Electrolytes?

Argyrodite-type sulfide electrolytes Li6PS5X, where X = Cl, Br, or I, have emerged as leading candidates for SSBs due to their high lithium-ion conductivity (often >10-3 S cm-1), low processing temperatures, and relatively soft mechanical behavior [3]. These properties make them ideal for forming intimate contact with electrodes, reducing interfacial resistance, and enabling high-rate performance.

However, sulfide electrolytes are chemically reactive. They can degrade in the presence of moisture, oxygen, and certain metals, especially under low-pressure conditions typical of coin or pouch cells. While cathode and anode interfaces have been extensively studied [4], the interaction between sulfide electrolytes and current collectors has received far less attention.

Current collectors, typically thin metal foils, are essential for transporting electrons in and out of the cell. In conventional lithium-ion batteries, copper (Cu) and aluminum (Al) are standard choices due to their conductivity and apparent inertness. But in sulfide-based systems, these assumptions may not hold.

Experimental Design: Testing Real-World Interfaces

To address this gap, the research team conducted a systematic study of six current collector materials:

  • Copper (Cu)
  • Nickel (Ni)
  • Stainless Steel (SS)
  • Aluminum (Al)
  • Aluminum coated with carbon (Al/C)
  • Lithium-coated copper (Cu/Li)

Each metal was paired with Li6PS5Cl in a coin cell format, simulating realistic industrial conditions with a mechanical pressure of ~0.2 MPa, far lower than the 10 MPa often used in lab-scale press devices. This choice was deliberate: low-pressure formats are more representative of commercial battery designs and more likely to reveal subtle corrosion phenomena.

The team employed a suite of physicochemical and electrochemical techniques, including:

  • X-ray Photoelectron Spectroscopy (XPS) to probe surface chemistry
  • Scanning Electron Microscopy (SEM) to visualize corrosion products
  • Electrochemical Impedance Spectroscopy (EIS) to measure interfacial resistance
  • Cyclic Voltammetry (CV) to assess electrochemical stability

To illustrate the comparative behavior of current collectors in contact with Li6PS5Cl, Figure 1 presents an overview of their composition, observed corrosion phenomena, and resulting impact on electrochemical performance.

Figure 1. Composition of current collectors, observed corrosion behavior, and impact on electrochemical performance.

This visual summary highlights the stark contrast between stable interfaces such as those formed with stainless steel, nickel, and aluminum, and the pronounced degradation seen with copper and lithium-coated copper. The formation of side reactions of Cu2S, Li2S, Li3P, and MexSy (Cu, Al, Ni, Fe, Li) at reactive interfaces increases impedance and compromises long-term stability [1]:

Cu: Li6PS5Cl+Cu→Li3P+Li2S+Cu2S+LiCl;                                        (1)

SS: Li6PS5Cl+Fe→Li3P+Li2S+FeS+LiCl;                                             (2)

Ni: Li6PS5Cl+Ni→Li3P+Li2S+NiS+LiCl;                                              (3)

Al: Li6PS5Cl+Al→Li3P+Li2S+Al2S3+LiCl;                                          (4)

Al/C: Li6PS5Cl+Al/C→Li3P+Li2S+Al2S3+LiCl+C;                       (5)

Li and/or bi-layer Cu/Li: Li6PS5Cl+Li→Li3P+Li2S+LiCl.     (6)

Key Findings: Stability Isn’t Universal

The results were striking. While some metals maintained stable interfaces with Li6PS5Cl, others showed significant degradation:

  • Stable Interfaces: SS, Ni, Al, and Al/C exhibited minimal chemical reactivity. Their surfaces remained largely intact, and impedance measurements confirmed low and stable interfacial resistance.
  • Reactive Interfaces: Cu, Cu/Li, and pure Li underwent substantial corrosion. XPS revealed the formation of compounds like Cu2S, Li2S, Li3P, and MexSy (Cu, Al, Ni, Fe, Li) , which disrupted the interface and increased resistance.

These findings challenge the assumption that copper is universally safe as a current collector. In sulfide-based systems, its susceptibility to corrosion can lead to poor cycling performance, reduced capacity, and shortened battery life [5].

Industrial Implications: Designing for Durability

From an industrial perspective, the choice of current collectors is not just about conductivity or cost, it directly affects the chemical integrity of the cell. The study suggests:

  • Nickel and stainless steel are promising alternatives for anode-side collectors in sulfide-based SSBs.
  • Aluminum and Al/C are suitable for cathode-side applications, especially when paired with protective coatings or buffer layers.
  • Copper and lithium should be used with caution, particularly in wet-chemistry processes where prolonged contact with sulfide electrolytes is unavoidable.

This is especially relevant for manufacturers exploring scalable fabrication routes. Wet-chemistry methods such as slurry casting and solvent-based processing expose materials to longer reaction times and ambient conditions. Selecting chemically compatible current collectors can mitigate degradation and improve yield [1].

Bridging Lab and Industry

One of the most important contributions of this study is its focus on realistic cell formats. Many previous investigations used high-pressure setups that may suppress or mask corrosion effects. By working with coin cells at industrially relevant pressures, the authors provide actionable data for engineers and materials scientists.

Their work underscores the importance of holistic design where every component, from electrolyte to collector, must be chemically and mechanically aligned. It also highlights the need for interface-focused research to bridge the gap between promising lab-scale materials and commercial viability [2].

Future Directions

This study opens several avenues for further exploration:

  1. Protective Coatings: Investigating thin-film barriers or surface treatments that can shield reactive metals from sulfide electrolytes.
  2. Interface Modeling: Using computational methods to predict reaction pathways and guide material selection.
  3. Long-Term Cycling Studies: Evaluating how interfacial degradation evolves over hundreds of cycles in full-cell configurations.
  4. AI-Guided Discovery: Leveraging machine learning to correlate material properties with stability outcomes, accelerating innovation [4].

Toward Sustainable Solid-State Batteries

Beyond performance, the findings have implications for sustainability. Corrosion not only reduces battery lifespan, but it can also lead to toxic byproducts and complicate recycling. By identifying stable, recyclable current collectors, this research supports the development of greener energy storage systems.

Moreover, the study aligns with broader efforts to industrialize solid-state batteries for electric vehicles, grid storage, and portable electronics. As the field advances, mastering interfacial chemistry will be crucial to unlocking the full potential of sulfide-based technologies [3].

Final Thoughts

Dr. Artur Tron and his team have delivered a timely and technically rigorous investigation into a critical but often neglected aspect of solid-state battery design. Their work reveals that not all current collectors are created equal, and that chemical compatibility with sulfide electrolytes must be carefully considered.

By combining surface science, electrochemistry, and industrial insight, this study provides a foundation for safer, more durable, and scalable solid-state batteries. It’s a reminder that in advanced materials research, the smallest interfaces can have the biggest impact.

To learn more about the interfacial stability between current collectors and sulfide-based solid electrolytes developed by researchers at the AIT Austrian Institute of Technology, we invite you to read our recent publication in Communications Chemistry: “Probing the chemical stability between current collectors and argyrodite Li6PS5Cl sulfide electrolyte” https://doi.org/10.1038/s42004-025-01609-9.

References

  1. Tron, A., Beutl, A., Mohammad, I. Paolella, A. Probing the Chemical Stability between Current Collectors and Argyrodite Li6PS5Cl Sulfide Electrolyte. Communications Chemistry 8, 212 (2025).
  2. Zhang, W. Weber, A.D., Weigand, H., Arit, T., Manke, I., Schroder, D., Koerver, R., Leichtweiss, T., Hartmann, Pascal., Zeier, G.W., Janek, J. Interfacial Processes and Influence of Composite Cathode Microstructure Controlling the Performance of All-Solid-State Lithium Batteries. ACS Applied Materials & Interfaces, 9, 21, 17835-17845 (2017).
  3. Asano, T. Sakai, A., Ouchi, S., Sakaida, M., Miyazaki, A., Hasegawa, S. Solid Halide Electrolytes with High Lithium-Ion Conductivity for Application in 4 V Class Bulk-type All-Solid-State Batteries. Advanced Materials 30, 1803075 (2018).
  4. Banerjee, A., Wang, X., Fang, C., Wu, A.E., Meng, Y.S. Interfaces and Interphases in All-Solid-State Batteries with Inorganic Solid Electrolytes. Chemical Reviews 120, 14, 6878-6933 (2020).
  5. Kato, Y., Hori, S., Saito, T., Suzuki, K., Hirayama, M., Mitsui, A., Yonemura, M., Iba, H., Kanno, R. High-Power All-Solid-State Batteries using Sulfide Superionic Conductors. Nature Energy 1, 16030 (2016).