Batteries | Interview with the Author—Dr. Hiroyuki Ueda

Dr. Hiroyuki Ueda’ published paper:

“A Polymer-Binder-Free Approach to Creating Functional LiFePO4 Cathodes by Organic Ionic Plastic Crystal-Derived Ion-Conductive Binders”
by Daniela M. Josepetti, Maria Forsyth, Patrick C. Howlett and Hiroyuki Ueda
Batteries 2025, 11(1), 3; https://doi.org/10.3390/batteries11010003
Available online: https://www.mdpi.com/2313-0105/11/1/3

The following is a short interview with Dr. Hiroyuki Ueda:

1. Could you introduce yourself or your research group?
I am an Alfred Deakin Postdoctoral Research Fellow at Deakin University (Australia). I received my Ph.D. degree (Doctor of Engineering) from Kumamoto University (Japan) in 2016. After my graduation, I worked in the research and development divisions of three companies in the chemical and automotive industries, where I contributed to many projects on lithium-ion and solid-state batteries (SSBs). In 2020, I joined my current research group (Electromaterials, Institute for Frontier Materials, Deakin University) as an Associate Research Fellow and was fully committed to the Linkage Project (grant number: LP180100674) with Toyota Motor Corporation for the development of SSBs using an emerging class of solid electrolytes known as organic ionic plastic crystals (OIPCs). I was a lead CI on its subsequent industry project until March 2023, while helping with selecting and sourcing battery materials, tools, and pilot-scale manufacturing instruments for a newly built Australian unique battery-prototyping facility called Battery Research and Innovation Hub (https://batteryinnovationhub.com.au). Following this, I was awarded a research fellowship to be in my current position. Now I have been developing OIPC-containing solid-electrolyte membranes and electrodes for battery applications (mainly for SSBs).

The Electromaterials group at Deakin University is a diversified, multidisciplinary research team with >50 people, including professors, associate professors, research, technical, or administrative staff members, Ph.D. students, and research interns. We have been tackling many research questions in the energy sector by leveraging the group’s extensive expertise in material modelling, synthesis, and characterisation; battery implementation, testing, and demonstration from the laboratory to pilot scale; and metal recovery. The group was established in 2010 and was formerly led by Prof. Maria Forsyth, who has significantly contributed to research on energy materials, especially ionic materials, including ionic liquids, OIPCs, and solid polymer electrolytes. The group has continually reported groundbreaking findings for multiple battery formats, including lithium-ion, lithium-metal, sodium-ion, sodium-metal, zinc-air, and SSBs. Among them, my team has mainly focused on the development of SSBs to provide breakthrough energy-storage options.

2. Please share what inspired your research?
Our paper demonstrated the use of OIPC−Li salt binary mixtures (hereafter referred to as OIPC electrolytes) as binders in the electrode layer for the first time. This approach was inspired by my previous discovery in graphite−OIPC composite electrodes (Batter. Supercaps, 2022, 5(7), e202200057); containing OIPC electrolytes in the electrode composition minimised the changes in the state-of-charge-dependent resistances of the electrodes, which implies that OIPC electrolytes can stabilise particle−particle and particle−current-collector contacts. This would be the additional benefit of using OIPC electrolytes as their intended function is mainly ion conduction in SSBs. Therefore, I was motivated to investigate the binding properties of OIPC electrolytes in this paper. We deliberately removed the polymer binders from the electrode layer so that we could clarify this point by the achievable electrode parameters (i.e., theoretical areal capacity and electrode density) and battery performance (i.e., cyclability).

3. In your career of battery research, which mentor or predecessor has had the greatest influence on your scientific thinking? How does this influence reflect on the writing style of this paper or the choice of research path?
Since I came back to academia, Prof. Maria Forsyth and Prof. Patrick C. Howlett have served as mentors for me. I have been fortunate to receive countless pieces of invaluable advice from them throughout my research career. Prof. Forsyth’s everlasting passion towards scientific understanding and development has often reminded me of the importance of consistently advancing research activities with enthusiasm, even if I face the chains of unsuccessful experimental results. In addition, Prof. Howlett’s forward-thinking approach has helped me form novel research ideas and assisted in shaping pragmatic solutions for any difficulties in research activities. Both distinguished researchers in the battery field have significantly influenced my research philosophy. Owing to their support, I was able to believe in my research path, overcome many challenges associated with this paper, and succeed in demonstrating the idea of using OIPC electrolytes as ion-conductive binders in electrodes.

4. Why did you choose to publish with Batteries, and how was your experience?
This was because I had an invitation to submit a research paper to Batteries, and their editorial team was generous to consider options to accommodate the standard article processing charge after reviewing the previous pre-printing version of the paper (https://doi.org/10.20517/scierxiv202408.01.v1) and its potential impact if published. Batteries is one of the well-known journals in the energy sector. Their peer-review process was fast and accurate; I received many suggestions from reviewers and addressing them surely improved the quality of the paper. The proofreading process after peer review was also fast, ensuring the speedy dissemination of scientific findings. Moreover, the Editorial Office was happy to announce the publication of this paper on their social media and chose my research for the cover of their January 2025 issue (https://www.mdpi.com/2313-0105/11/1). Overall, I have been satisfied with the journal’s strong support for fast-paced publication with high-quality papers and assistance in forming its impact on the battery community.

5. What was the biggest challenge you faced while writing this paper, and how did you overcome it?
The electrode preparation for this paper was done before the establishment of the Battery Research and Innovation Hub in mid-2022 and, therefore, Daniela (+MESC master’s student at that time) and I had to develop a reliable method to generate homogeneous electrode slurries without using a planetary centrifugal mixer that is commonly used for this purpose. We did multiple trials using many small-scale instruments (including magnetic stirrers) and finally concluded that ball-milling with a few ZrO₂ balls allows us to prepare homogeneous electrode slurries (without unnecessarily crushing electrode materials). Although another preparation method would be beneficial in improving theoretical areal capacity for reference polymer-binder-containing electrodes, this approach enabled reliable comparisons in performance metrics between resulting polymer-binder-free LFP−OIPC electrodes with different compositions in this paper.

6. How did feedback during your research influence your direction?
Feedback from my research team and reviewers’ comments on earlier versions of the paper were important in refining the methodology of experiments as well as the way of presenting research findings. For instance, we successfully proved the structural stability of polymer-binder-free LFP−OIPC electrodes by showing their intactness in liquid electrolyte solutions; the concept of this experiment was mutually formed through multiple discussions within the team. On the other hand, we were able to explain many advantageous features of our polymer-binder-free approach (when compared to the conventional polymer-binder-containing composition) after revision. We did additional experiments to address reviewers’ comments, which effectively correlated the electrode’s processability with the physical state of OIPC electrolytes. Therefore, I feel that consistent teamwork and peer reviews greatly improved the significance and potential impact of the paper.

7. What are the current challenges in the battery research field, and how can they be addressed?
There are many ongoing challenges in battery research. For instance, there is a trade-off between the safety and energy density of batteries; the more active materials can store energy, the more risk these batteries inherently have (e.g., thermal runaway when shorted). Although many researchers have been studying metal anodes intending to exploit their exceptionally high theoretical capacity, a strong tendency of metal–dendrite formation hampers their widespread applications in real-world rechargeable batteries. “Anode-free” configurations partly improve battery safety, but their reversible operation relies on the plating/stripping of metal species and, therefore, safety issues associated with metal anodes have yet to be overcome intrinsically. In this respect, battery chemistries without plating/stripping might be highly sought after; these include intercalation/deintercalation reactions (e.g., well-known for graphite), alloying/dealloying reactions (e.g., for Si), and redox reactions in general. My research team has demonstrated the versatility of composite electrode formulations with non-flammable OIPC electrolytes across a wide range of active materials for SSBs, which not only includes conventional materials (e.g., LFP, LiNi_xMn_yCo_1−x−yO₂, graphite, and Li₄Ti₅O₁₂) but also high-capacity materials (e.g., Si, and conversion cathode material: Chem. Mater. 2024, 36(15), 7222–7231). Therefore, I believe one of the possible solutions to balance safety and energy density is employing the SSB format with thermally stable solid electrolytes (e.g., OIPC electrolytes) and high-capacity materials. I hope the ongoing research in my team will generate many fruitful findings to address this point.

8. What role did you play in your research team, and how did teamwork affect the paper's outcome?

This is my first last-corresponding-author paper where I contributed to most aspects of the paper preparation and handling from the beginning. I consistently helped Daniela with her experimental progress and assisted her with manuscript drafting through multiple discussions about possible story flow and key findings that we needed to write. Daniela successfully drafted the first version of the manuscript from scratch, and I took over further writing with some additions of new sections. Prof. Forsyth and Prof. Howlett joined some discussions within the team and advised us on further experimental investigations, which ensured that the paper’s narrative did not fully rely on assumptions and helped construct discussions based on actual data. I think our teamwork significantly enriched the paper’s quality, and I hope it provides useful insights into the development of OIPC-containing electrodes for battery applications.

9. What trends and technologies do you see shaping the future of battery technology?
Other than the safety and energy-density limitations mentioned earlier, I think the focus on developing battery technology has been gradually shifting towards more sustainable options. For instance, many researchers have started investigating electrode-preparation methods without using a harmful solvent (e.g., N-methyl-2-pyrrolidone), which includes water-based slurry preparation and electrode manufacturing without any solvents (i.e., dry process). These will potentially reduce the environmental impact of the current production steps. Another example is replacing synthetic polymers in batteries with bio-based ones. This makes resulting batteries more eco-friendly and potentially simplifies their recycling processes (e.g., by dissolving the polymer separators in water for separation, whereas polyethylene or polypropylene separators are relatively hard to separate). My research team has also been studying some sustainable approaches using OIPC electrolytes, and I hope I can disseminate relevant publications in the near future.

10. What impact do you hope your research will have, and what key innovation do you see in your paper?
Our paper clearly showed the three advantages of the polymer-binder-free approach over the conventional polymer-binder-containing electrode formulation: (1) A higher active-material loading without crack formation in the electrode layer, (2) a lower electrolyte amount in the electrode layer, and (3) a higher Coulombic efficiency during battery operation. Although I must admit that the cyclability of polymer-binder-free LFP−OIPC electrodes in this paper was not as good as that containing a polymer binder, this would potentially be solved when the electrodes are tested in SSBs. Through this study, we have demonstrated the dual functionalities of OIPC electrolytes as both ion conductors and binders, which lays a robust foundation for further development of OIPC-containing electrodes.

The paper was featured as the journal cover (https://www.mdpi.com/2313-0105/11/1) with an impressive scientific illustration for the top view of a polymer-binder-free LFP−OIPC electrode, which visually intensifies these two roles as the pre-built Li⁺-conduction pathways and intricate networks formed by the OIPC electrolyte. I would like to acknowledge Hibiki Asahori (https://www.hibikiasahori.com) for creating this cover illustration and The Fujikura Foundation for supporting this cost. I hope the journal cover will attract readers’ attention and encourage studies on innovative electrode formulations (e.g., composite electrodes with pre-filled electrolytes) for advanced rechargeable batteries.