The background story of joint development

Yamada: I’ve been acquainted with Mr. Umemoto for ten years. Since that time, our company has worked on the development of many different batteries to replace lithium-ion batteries—not only all-solid-state batteries but also aqueous rechargeable batteries and batteries made from materials that are non-toxic to the body and the environment. However, there was an issue: even if we developed a new battery, customers would not accept a battery without optimized charging equipment.

Umemoto: A shared concern of our company and Maxell was that power supply ICs and batteries individually do not convey their advantage and they lack appeal in the market. And so, we started collaborating with the development of an aqueous rechargeable battery ten years ago, and now we have finally commercialized a power supply module kit for evaluation equipped with Maxell’s high-performance all-solid-state batteries and our power supply IC with high performance and low current consumption.

Nagasato: I was originally involved in the design of the IC mounted with our Nano Energy^TM ultra-low current consumption technology designed for batteries, but I also felt that it would be difficult to attract customers with just this unit. I heard about the all-solid-state battery project from Mr. Umemoto, and eventually we worked on it together. I think this was a great collaboration that enabled us to make the most of the characteristics of Nano Energy^TM.

Furukawa: I am mainly responsible for the design of the ceramic package type all-solid-state batteries, and I got involved in this project in the early product design stage, around four years ago.

The advantages and ingenuity of the power supply module kit for evaluation

Umemoto: When a customer considers equipping new batteries, they have to think of a design based on the specifications of that battery and order IC components, which can take several months and incur design cost. If a customer uses this evaluation module, they can immediately connect it to the device in which they are considering using all-solid-state batteries, and confirm its operation. They can clearly understand what will change and what won’t change with an all-solid-state battery (voltage, applicable temperature range, electricity consumption, etc.), and easily compare and evaluate it with existing batteries such as lithium-ion batteries.

Yamada: Conventional batteries are cylindrical-type or coin-type, but we have developed the world’s first ceramic package type battery, so it is not easy for customers to evaluate it if we hand it over as it is. This circuit board for evaluation mounted with an all-solid-state battery that we have created with ROHM enables easy external connection, so customers can now use it for development without any stress.

Nagasato: The ROHM power supply IC used for this collaboration incorporates ultra-low current consumption technology developed with the target of “over 10 years of operation with a coin battery.” We struggled to find an operating current with the best balance between low consumption and responsiveness to achieve low current consumption without compromising the key power supply characteristic of responsiveness. However, with the collaboration of Maxell’s engineers including Mr. Furukawa, we were able to fully bring out the discharge performance of all-solid-state batteries and maximize their battery life. In addition, this technology allows for the placement of a charge control IC and power supply system in the extremely small circuit board space, without compromising the advantageous characteristic of small size inherent in Maxell’s all-solid-state batteries.

Looking back on development and expectations for the future

Yamada: Until now, our company has engaged in business selling ready-made batteries, including dry cell batteries, and there was a lack of customer-oriented approach of providing product samples to facilitate further discussions. Collaborating with ROHM and providing product samples has significantly enhanced customer understanding and accelerated our business development—it was really helpful.

Umemoto: The semiconductor industry development cycle is typically two or three years, but being involved in the battery business with its long development span of 10 years has been an opportunity to broaden my perspective and my work. This has been a long, ongoing collaborative project in our company, and I hope it continues in the future. We anticipate further technology development from Maxell.

Furukawa: All-solid-state batteries are safe and reliable, so they have the potential to replace the batteries in a variety of products in the future. We are also now focusing on developing multi-cell series batteries (bipolar-type batteries). If lithium-ion batteries are connected in series inside a battery, the electrolyte does not react properly across the multiple cells. This issue does not occur in all-solid-state batteries, so it is possible to obtain high output from each battery, and we expect these to be used as the main power source for a variety of devices. Furthermore, we have cultivated markets where primary batteries have been used, and will also cultivate markets where batteries have not been used by engaging in development to further increase heat resistance.

Nagasato: To increase the effectiveness of all-solid-state batteries, we need solutions that can make use of microenergy from light or vibrations, similar to energy harvesting. We also developed a new module kit for evaluation in July 2023 by creating a solution that enables all-solid-state batteries to charge using electricity generated from the sun or indoor lights. I hope both companies continue our activities to expand the market for all-solid-state batteries.

Yamada: All-solid-state batteries can handle low power consumption, and have the characteristics of heat resistance, a wide temperature range, and long life. We will contribute to solutions to social issues through usage that makes the most of these characteristics. As the working population decreases, I hope we can work together to reduce maintenance work, with our focus on long-lasting batteries and ROHM’s focus on achieving longer life by low power consumption.