Atomic layer deposition for next-generation batteries

Adriana Creatore (Eindhoven University of Technology) and Auke Kronemeijer (TNO/Holst Centre) opened the workshop Atomic Layer Deposition for Next-Generation Batteries, organized under the NWA ORC BatteryNL project in collaboration with the National Growth Fund NXTGEN Hightech and High Tech NL.

The event brought together participants from academic research groups working on ALD, battery materials and testing, representing the collaborative effort of companies, knowledge institutes, organizations building knowledge and competencies in battery technology.

In their introduction, Adriana and Auke reflected on the motivation for the workshop. While the Netherlands is a recognized hub for research and manufacturing of deposition technologies, the application of these techniques in the battery field still faces obstacles.

The concerns raised from these experiences resonated within the BatteryNL community and were shared during a meeting with colleagues and stakeholders. With support from NXTGEN Hightech and High Tech NL, these conversations evolved into a lunch session during Battery Day in September 2024, where ideas for a dedicated workshop began to take shape.

The vision was clear: to create an inclusive and safe platform that could spark open dialogue, identify strategic opportunities for high-throughput ALD in batteries, weigh costs against benefits and highlight both scientific and technological challenges. Several online meetings followed during the preparation phase, leading to the final program presented to participants in September.

Workshop morning session

The morning session featured perspective talks on ALD in battery engineering, SEI engineering and formation cycles in lithium-ion batteries and nanocoatings on powder cathodes and anodes, presented by Mahmoud Ameen (TechMatter BV), Marnix Wagemaker (TUD) and Sébastien Moitzheim (Powall).

Mahmoud opened his talk with the statement that controlling interfaces in batteries is key to cost reduction, improved performance and enhanced safety, while also noting that new interface challenges emerge as battery generations evolve. After reviewing key literature results on SEI and CEI, along with examples of conformal ALD layers, Mahmoud shared his perspective on why the adoption of ALD in batteries has been slow. Among the main reasons he highlighted were: unclear return of investment models, lack of standardized KPI’s, expectations of free samples, difficulties in achieving self-limiting reactions, absence of clear assessment protocols and references and challenges in detecting the presence of ALD layers both before and after electrochemical testing.

The morning session continued with scientific insights from Marnix Wagemaker, who opened his contribution with the “99.99% Coulombic efficiency challenge”, how crucial it is for the ratio of the total charge extracted during discharge to the total charge put in during charge, to reach 99.99%, which would then guarantee that, after 1000 cycles, 90% of the capacity of the battery is withheld.

The session ended with the contribution from Sébastien Moitzheim, who confirmed Mahmoud’s forecast that the next major application of ALD will be in batteries. At the same time, Sébastien reflected on the challenges faced by ALD equipment and processing, particularly the extremely high throughput required when shifting from the chip to the battery manufacturing industry, given the roughly 100,000-fold increase in surface area to be coated in batteries compared to the flat surfaces in chips.

Workshop afternoon session

Paul Poodt (SparkNano & TU/e) and Adriana Creatore (TU/e) introduced the topics of discussion to the audience. Participants were then invited to join a group discussion and summarize the outcomes. Milou Arts (High Tech NL) interviewed the moderators on the outcome of the discussions.

Three key, major projects at national level

Moderated by Auke Kronemeijer (TNO/Holst Centre): NWA ORC BatteryNL, Growth Fund NextGen Equipment for Batteries and Battery Materials and Growth Fund SMART CBAT.

The Dutch battery ecosystem is concentrated, which should encourage more collaborations. However, collaboration within ongoing projects is often hampered by gaps and diverging objectives between academia and R&D, limited access to high-end characterization on a small number of samples and delayed feedback. Focusing on a shared case study could help in aligning efforts around a common challenge. Basic steps, such as sourcing the same unprocessed cathode material and adopting standardized protocols, would further support this approach.

It is also recommended that future calls focus on acquiring additional infrastructure for characterization, as well as technical staff. Ongoing and near-future projects could additionally benefit from transversal events, such as workshops and lectures on topics like “how to take it from lab to fab” and “battery manufacturing.”

Energy impact and LCA of ALD in battery manufacturing

Moderated by Felipe Blanco Rocha (TNO): Energy consumption in high throughput ALD vs. added value in terms of battery performance and CO₂ footprint reduction (ultra-thin layers).

Sustainability analyses of emerging technologies are often narrow in scope and not well documented. This is certainly true for calculations concerning the adoption and impact of ALD processing in batteries. Beyond the tendency to quickly conclude that an ALD process is inherently greener than a wet chemistry process, it remains unclear how much of the CO₂ footprint of the raw materials is included in such calculations.

Often only the energy consumption and basic process steps are considered, while analysis of by-products, precursor consumption efficiency and the use or recycling of carrier gases is neglected. Therefore, LCA studies should be broadened in scope and applied toward developing a concerted message that clearly highlights the benefits of ALD in battery applications. Finally, rather than being treated as a separate, parallel study, LCA should actively guide the implementation of an ALD process or tool in future battery manufacturing lines.

Business case(s) for ALD

Moderated by Mahmoud Ameen (TechMatter BV): What is the added value of sALD for battery performance in comparison with the needed additional investment into an sALD tool / potential CO2 footprint decrease?

The added value of ALD must be clearly defined first, with the aim of generating savings in battery manufacturing costs that outweigh the additional investment. A business case is not something to simply find, it is something to build, based on identifying the added value of an ALD processing step in a battery manufacturing line.

Developing this business case requires consideration of several key steps: recognizing a challenge (which could range from simplifying part of the manufacturing line, increasing uptime, improving safety or targeting energy-materials independence) and identifying the primary customer Whether it is the electrode supplier or the cell manufacturer who will cover the ALD CapEx. ALD will likely play a role on the anode side first.

For graphite anodes, the primary customer will likely be the cell manufacturer, as ALD can impact formation time. Similarly, for lithium-metal anodes, the cell manufacturer is expected to be the primary customer, due to the reactivity of lithium metal. For cathodes, it is more difficult to predict where ALD applications could create a business case, so close monitoring of cathode development roadmaps is necessary.

High throughput, efficient ALD processing

Moderated by Paul Poodt (SparkNano & TU/e): Emerging/promising tools for inline detection in (high throughput) ALD.

One of the main challenges when transferring an ALD recipe from a 2D flat substrate to a 3D, high-surface-area or porous substrate is the lack of appropriate in situ diagnostics to detect film growth and assess its conformality and uniformity. Currently, most studies apply sufficiently thick ALD layers on electrodes so that they can be detected using techniques such as SEM/EDX (for morphology and elemental analysis). Alternative methods, such as XRF (for elemental detection) and QCM (for mass change), can also be used, although their sensitivity varies depending on the chemical elements.

Closely related to this challenge is the need to develop suitable ALD processes for 3D/high-surface-area substrates while ensuring efficient use of precursors and co-reactants, taking into account throughput and CoO/LCA considerations. Process optimization typically requires feedback loops for the precursor/co-reactant supply and evaporation system, for example by monitoring precursor/co-reactant concentrations before and after chemisorption on the substrate surface.

Solving these challenges is essential to establish an ALD process that is reproducible in terms of layer properties for a given substrate or electrode, while also being versatile in terms of process parameters depending on substrate/electrode characteristics.

Beyond controlling ALD process development for a specific substrate, the next challenge is verifying its impact at the device level. Electrochemical characterization is key, but it is not readily available and is certainly not a routine method for assessing the influence of specific ALD process parameters on device performance.

Written by: Adriana Creatore