Looking beyond the practical application - The frontline and challenges of all-solid-state batteries

INTERVIEW 18

Professor Shigeo Mori
Department of Materials Science
Graduate School of Engineering, Osaka Metropolitan University

All-solid-state batteries are expected to become the next-generation batteries for electric vehicles, yet many challenges remain before full-scale commercialization can be achieved. At the All-Solid-State Battery Research Center of Osaka Metropolitan University, multiple research groups are tackling these technological issues while also promoting industry collaboration and human resource exchange through the "Consortium for Practical Application of All-Solid-State Batteries."
Where exactly do the difficulties of all-solid-state batteries lie, and how does the university aim to engage with industry? We spoke with Professor Shigeo Mori to learn more.

Advancing All-Solid-State Battery Development Through Industry-Academia Collaboration

There is a list known as the "Top 2% of the World's Most Influential Scientists"^*1, which ranks researchers by the number of citations in each field. In the 2025 edition, five researchers from the All-Solid-State Battery Research Center at Osaka Metropolitan University were included.

*1 "Science-wide author databases of standardized citation indicators"- created and published by Stanford University (USA) and Elsevier (Netherlands).

"Inability to return to the original state"

The basic structure of the all-solid-state batteries consists of a cathode active material (*2), an anode active material (*3), and a solid electrolyte between them. During charging and discharging, lithium ions migrate through the solid electrolyte. In addition, electrolytes and active materials are basically produced from powders. The All-Solid-State Battery Research Center conducts research of many types of materials, and they place an emphasis, in particular, on lithium ion rechargeable batteries with sulfide-based electrolytes.

*2 In case of the lithium ion rechargeable battery, material that releases lithium ions during charging and takes them in during discharging

*3 In case of the lithium ion rechargeable battery, material that takes in lithium ions coming from active materials and releases them during discharging.

Since the structure itself appears simple, there may not be any complex challenges.
The real challenge lies in "what kind of contact state these powders form and what kind of interfaces they create," says Professor Mori.

Interface matters - A typical example is the expansion and contraction of active materials by repeating charging and discharging. This worsens the contact between the active material and the electrolyte, increasing resistance and, in some cases, causing delamination that can lead to conditions close to insulation.

Also, "there are cases where applying voltage causes ions to move, altering the structure or triggering chemical reactions that make the battery unable to return to its original state," explains Professor Mori.

Charge carrier (lithium ions) are not the only mobile ions. There have been proposals for introducing halogens (*4) that are greater than lithium such as chlorine(Cl) or bromine(Br) in a sulfide-based solid electrolyte as the framework to facilitate lithium ions to move. However, these halogens become anions and may migrate to the active material interface during cycling or alter the composition near interface.

*4 Argyrodite-type sulfide solid electrolyte

Problem solving requiring diverse instruments

Naturally, a wide range of analytical instruments are required for analyzing problems. For observing powders, observation instruments of µm-scale would do, but analyzing compositional and structural changes requires instruments capable of a nanoscale elemental distribution and a chemical state. Light elements like lithium require different measurement techniques and instruments compared to heavier elements.

A variety of specifications that have been introduced lately

The center's diverse analytical needs are reflected in the specifications of the instruments introduced in FY2025 under the "J-PEAKS" program of the Ministry of Education, Culture, Sports, Science and Technology. Four instruments as below from JEOL were installed.

• Scanning Electron Microscope: JSM-IT810
• Gas Chromatograph Time-of-Flight Mass Spectrometer: JMS-T2000GC
• Electron Diffractometer: XtaLAB Synergy-ED
• Energy-filter SEM

The first one, JSM-IT810 has more functions than the usual scanning electron microscope (SEM).
There are several attachments around the chamber (specimen chamber). One is the EDS (energy Dispersive X-ray Spectrometer). This allows for qualitative and quantitative analyses, and elemental mapping of the element observed by SEM.
Another attachment is the SXES: Soft X-ray Emission Spectrometer. SXES enables a high sensitivity analysis of lithium, a light element which is difficult to analyze with EDS, with a high sensitivity, as well as information related to chemical and bonding states.

JSM-IT810 Schottky Field Emission Scanning Electron Microscope

Its capability for operando analysis is one of the features of JSM-IT810.
Operando analysis is direct observation of the process of the sample in motion.
Concretely, it equips an optional charging and discharging holder, enabling measurement of the current value during charging and discharging, and the micro change of the sample condition at the same time. By using such a function, "we also hope to work on the in-situ observation to capture the interface change while simulating charging and discharging cycles through the electrode contact". (Prof. Mori.)

The second instrument, JMS-T200GC is a "Gas Chromatograph Time-of-Flight Mass Spectrometer". However, it is equipped with more ionization methods than conventional ones, with the feature of enabling the detection of chemical substances that were difficult to ionize.
In addition, it is equipped with automatic qualitative analysis software using AI, it provides a candidate molecular formula of the chemical substance with high accuracy.

Osaka Metropolitan University refers to it as the "Unknown Substance Analysis System".
When unexpected chemical substances are produced by repeated charging and discharging, this system will surely demonstrate its power by revealing the true nature of the substances."

The fourth instrument, Energy Filter SEM is a completely new type of electron spectrometry instrument proposed by JEOL.
It can separate and acquire information from different energy bands, such as secondary electrons(below several tens of eV), Auger electrons(from several tens of EV to several keV), and backscattered electrons (ranging from high energies close to the incident electron energy down to the low energy band close to the secondary electrons) almost in real time, and then make analysis "later to look into the composition of this specific location later". By selecting energy bands afterward, researchers can perform the elemental analysis of the sample surface (Auger spectroscopy), chemical-state analysis, and electronic state analysis from a single measurement.
As the same sample can be analyzed multifacetedly from a single measurement, it is "expected to be a powerful tool in problem-solving" (Prof. Mori).

Former president looking beyond practical application

The All-Solid-State Battery Research Center was established in August 2020 under President Masahiro Tatsumisago of Osaka Prefecture University (*5), himself a solid-state battery researcher. Since the center was established with the expectation from industries, the center aimed at social implementation (practical application) from the beginning.
In April 2021--less than a year after its founding--the Consortium for Practical Application of All-Solid-State Batteries was launched mainly by the members of the center, to promote collaboration with industries and exchange researchers, as a natural flow.

(*5) In April 2022, he became the first president of Osaka Metropolitan University following the university merger. He concurrently served as president of Osaka City University (Apr. 2022-Mar. 2025) and Osaka Prefecture University (Apr. 2023-Mar. 2025) for united operation of both universities as long as students were enrolled.

The Kansai region hosts major battery-related companies such as the Panasonic Energy Co., Ltd. and GS Yuasa International Ltd. Along Osaka Bay, numerous lithium-ion battery factories, component manufacturers, and R&D institutions are concentrated--earning the nickname "Kansai Battery Bay."
With strong expectations from industries, the consortium has grown to over 100 participating companies as of April 2026.

"Professor Tatsumisago often says, "fundamental research becomes even more important after commercialization". Universities tend to stick to fundamental research and stop their research once a practical application is achieved. But that does not support Japan's industry. Understanding what happens after commercialization and continuing to improve performance is essential. I think that is what he means." (Professor Mori.)

Industry seeks breakthroughs for commercialization, but a university that continues fundamental research afterward and helps enhance product performance must be invaluable for industries.

Products