The turning point was the oil crisis. Instead of relying on oil, the company set its sights on "sulfur components" as it sought new business ventures.

N.NAKAYA "After the oil crisis, activities were carried out at the research institute to create new businesses rather than relying solely on oil. During the oil refining process, sulfur compounds are produced. There was a discussion about whether it would be possible to add value to these compounds and provide them to the world.
Related to this, in the 1990s, it was discovered that using lithium sulfide as a raw material for a resin called polyphenylene sulfide (PPS) makes it easier to produce PPS. As a result, this technology was not adopted for the manufacture of PPS, but it led to the establishment of Idemitsu's own industrial manufacturing technology for high-purity lithium sulfide, so we decided to explore other applications. As we continued our investigation, we came across a certain academic research project, and heard that it was discovered that lithium sulfide could be used as an intermediate raw material for solid electrolytes."

-And that led to the current development of solid electrolytes-

N.NAKAYA "That's right. As we researched, we found that solid electrolytes are an important material that holds the key to the performance of all-solid lithium battery. From there, the target for “lithium sulfide” became “batteries. We had many options: should we become a raw material manufacturer, a materials manufacturer that provides solid electrolytes, or a manufacturer that makes all-solid lithium battery? I heard that among those options, we decided to become a materials manufacturer that could best utilize our mass production technology."

Y.WASHIDA"Regarding lithium sulfide, I heard that they first tested it using a small synthesis facility in a lab, and then built a small bench plant."

-What do you think of your predecessors who have been conducting research and development for 30 years?-

Y.WASHIDA"I think they had foresight, and I'm impressed by how they persevered and didn't give up. I think the seniors had a strong passion for the material, and a determination to get it out to the world."

N.NAKAYA"When we started working on solid electrolytes, the level of awareness was probably just, 'I've heard of all-solid lithium battery in the research field.' But I think my predecessors worked on it with the belief that 'this will provide new value to the world.' I've heard that it was sometimes difficult to get support for working on the development of inorganic materials at a company based on organic chemistry (petroleum). I really respect the fact that they have pushed forward with conviction for 30 years, including difficult times."

The International Rechargeable Battery Exhibition was a major turning point. The moment a bright light appeared

-Was there a time when you weren't understood?-

N.NAKAYA"all-solid lithium battery used to be called the dream battery. At a time when the performance of liquid lithium-ion batteries was improving rapidly, there was a headwind of 'all-solid lithium battery really be made? Are they worth it?'
One turning point was when we participated in an exhibition in 2009-2010 where we made our own prototype batteries to stimulate the market for all-solid lithium battery. There we highlighted the potential of all-solid lithium battery, such as their heat resistance and safety. As a result, I heard that we started receiving contact from automobile and related manufacturers."

Y.WASHIDA"I believe Idemitsu was able to contribute to creating an opportunity to discover the possibilities and feasibility of all-solid lithium battery."

N.NAKAYA "I heard that it was encouraging to hear from an automobile manufacturer. In fact, that was the catalyst that led to a full-scale collaboration with Toyota, so I think that was the biggest turning point."

Immediate decisions are required based on what happens on the day

In October 2024, Idemitsu Kosan will begin basic design work on a large-scale pilot device for "solid electrolytes," a material used in all-solid lithium battery.

Y.WASHIDA "The baton was passed to us after we had reached a milestone - the decision on the basic design of the large-scale pilot facility. I am currently involved in expanding the capacity of the small-scale demonstration facility, and this expansion is intended to verify mass production technology with the large-scale pilot facility in mind. As construction of the new equipment progresses steadily, I have been working behind the scenes to establish the mechanisms and logistics necessary for operation. Once these two are combined, we will finally be able to carry out actual trial operations. Our mission is to complete the expansion of capacity as planned and proceed with the verification of mass production technology, so we need to respond quickly to any issues that arise on the day and at the site. When we start up new equipment, something happens every day, but we quickly take the next step and set priorities as we move forward."

The difficulties of mass-producing powder that far exceed imagination

Y.WASHIDA "I'll explain mass production using the Imoni Festival in Yamagata as an example. At the Imoni Festival, a pot with a diameter of 5 to 6 meters is set on a large stove, and several excavators are used to stir the ingredients together to make the product."

N.NAKAYA "How to make Imoni (lol)"

Y.WASHIDA"At home, you cut the ingredients, put them in the pot, and mix with a spatula... but mass production requires a completely different size and thickness of pot. A household pot is only a few millimeters thick, but a mass-produced pot is only a few centimeters thick. If you apply heat from the outside, only the surface will heat up. If you don't mix evenly and do various other things, this part will be hot, but this part will always be cold. You may be able to calculate how heat is transferred, but when microscopic worlds overlap continuously, you don't know what will happen. That's the difficulty of mass production."

N.NAKAYA "And the difficult part is that it's a powder. Heating a liquid is completely different from heating a powder."

Y.WASHIDA"I really think so. Liquids flow. If you heat them up, convection will occur naturally."

N.NAKAYA "If you keep heating water in a kettle until it boils, it will always reach 100 degrees no matter where you measure it. But if you put flour in a pot and put it on the stove, the surface that's touching the pot may be over 100 degrees, but the inside isn't warm."

Someone has to make the final decision. That's why we need to discuss it.

-Generally, the design of the mass production plant begins after the material specifications and mass production method have been decided. This time, you said that you are working on both in parallel, but what are the difficulties?-

Y.WASHIDA "There is still room to explore the best process. People involved in equipment construction projects plan their processes with the goal of 'completing the equipment by this date.' Specifically, they evaluate profitability, draw up a basic plan for the equipment, proceed with the design, procure materials, construct, and test run it. However, as we proceed with mass production verification of 'solid electrolytes,' we sometimes find that a different process can produce more, or that it can be made more simply.
In such cases, it is necessary for the materials development side and the plant design side to negotiate and proceed with the study. If someone does not make the final decision, the product will not be able to be provided to the customer. The project leader is required to make some tough decisions."

-If the verification results are not satisfactory, do you ever consult with the material development team about changing the powder design?-

Y.WASHIDA"When things get difficult, we all get together and talk about it. However, the target performance of the material is more or less set, so we consider ways to change the operation or process as much as possible to match that."

N.NAKAYA "Tough people like Washida-san say, 'We have no choice but to do it to make it happen,' but we also sometimes consider whether there is any room for tweaking the material specifications, taking into account the technical difficulties of the manufacturing process."

Y.WASHIDA "Lithium Battery Material Department is compact, and there are many opportunities to talk, so decisions can be made very quickly. However, whereas a large organization would distribute the workload, a small organization can mean a higher workload per person. In a small organization, everyone needs to be an expert to a certain extent in order for things to function, so I think that's one of the difficulties."

N.NAKAYA"Unlike an established business, the things that need to be done change daily, so of course the scope of what you do also changes. When work gets dropped and the question arises of 'who will pick it up?' some people may take it as 'I didn't think it was my job, but now I have to pick it up.' Because things are changing so rapidly, sometimes some members can't keep up emotionally, but I feel that Washida-san provides solid support."

Learning how to blend in with colleagues during my time at the Nghi Nghi Son Refinery in Vietnam

Y.WASHIDA"How you speak and creating a good atmosphere are very important in an organization. It's okay to get angry, but I try to remember to switch gears and speak normally afterwards. If I remain angry for too long, everyone will get fed up, so I try to end it as quickly as possible."

-Was there any particular reason that triggered this?-

Y.WASHIDA"I have been involved in the launch of Nghi Son Refinery since 2015. I worked like a horse, dealing with changes in the plan and problems. I think I was able to overcome all of this because I was determined to launch Nghi Son Refinery.
At the time, I was young and sometimes spoke harshly to my Vietnamese colleagues or gave instructions without fully respecting their culture and way of thinking. Many Japanese had returned to their home countries, leaving only a small number of Japanese people, and I was tasked with taking on a major project. Most of Manager and the head of the operations department were foreigners, and I was just one of the staff. What I learned then was that it is important to convey your feelings, but you have to speak with respect for the other person. If you don't do that, people will never take action."

How did you feel when you decided to work on lithium battery materials?

-We have heard about the difficulties of developing and mass-producing something that does not exist in the world. What were your honest thoughts when you first became involved with lithium battery materials?-

Y.WASHIDA "I was grateful to have the opportunity to try new things. I joined the company as a production engineer, and when I was transferred to Technology & Engineering Center I became a staff engineer. I went from operating the equipment to making it. From the beginning I had the goal of trying new things and building my own equipment."

N.NAKAYA "When I joined this project, it was in the middle of rapid growth, so I was honored to be invited. It was a different field from what I had been involved in up until then, but I was happy to be invited to work in a field that will carry the future of Idemitsu."

In February 2025, Idemitsu Kosan announced its decision to build a lithium sulfide manufacturing facility, taking another step towards provide for society.