Nuvoton Announces Joint Research with AIST “Battery Internal Temperature Estimation Technology to Enhance Safety of Lithium-Ion Batteries”

Kyoto, Japan, December 5, 2025 - Nuvoton Technology and the National Institute of Advanced Industrial Science and Technology (AIST), Research Institute of Electrochemical Energy jointly presented the results of their collaborative research on battery internal temperature estimation technology at the 66th Battery Symposium in Japan.

This research targets lithium-ion secondary batteries (LIBs) and utilizes electrochemical impedance spectroscopy (EIS) data obtained under various states of charge and temperature conditions. By fitting this data to an equivalent circuit model, the team constructed a temperature estimation algorithm and verified its accuracy in estimating internal battery temperatures. This technology is expected to improve the safety of LIBs.

Presentation Theme :
“Temperature-Correlated Battery Impedance Identification and Temperature Estimation Algorithm[1]”
Source :

[1] Presented at the 66th Battery Symposium 2MH06, in "Lithium-ion Battery (Safety and Evaluation)" session

LIBs are rapidly becoming foundational components in realizing a decarbonized society, with widespread adoption in electric vehicles and energy storage systems. However, incidents of battery fires are increasing due to the high energy density of LIBs, which makes them vulnerable to thermal runaway—a dangerous condition caused by overcharging or overdischarging, leading to rapid temperature rise.
To ensure safe usage, it is essential to monitor the internal temperature of LIBs in real time and with high precision, enabling early detection of anomalies and prevention of accidents.

In this joint research, NTCJ and AIST evaluated the correlation between model parameters and temperature by fitting EIS data obtained under different charge states and temperature conditions to an equivalent circuit model. Based on this correlation, they constructed a temperature estimation algorithm and verified its accuracy. This technology enables real-time, high-precision monitoring of internal temperatures even at the battery pack level, and is expected to contribute to the safe operation and broader deployment of electric vehicles and industrial energy storage systems through applications such as early detection of thermal runaway.

Last year, NTCJ and AIST presented a method for estimating the State of Health (SOH) of batteries using EIS data at the 91st Annual Meeting of the Electrochemical Society of Japan. The current presentation builds upon that initiative.
For details on last year’s presentation, please refer to the following press release:
[Press Release: Report on Joint Research Outcomes in Battery Diagnostic Technology with AIST]

Looking ahead, NTCJ will continue collaborative research with AIST on battery impedance and temperature estimation using electrochemical data, aiming to apply these technologies to next-generation battery monitoring ICs and contribute to the realization of a sustainable energy society.