UNIST and Kookmin University Develop Self-Healing Ultra-High-Efficiency Thermoelectric Material

A material with ultra-high-efficiency thermoelectric performance that can self-heal wounds and stretch has been developed. It is also expected to be used for the commercialization of wearable technology, as it can be charged solely by the body's ‘heat’ without battery concerns.

The research team led by Professor Jang Sung-yeon from the Department of Energy and Chemical Engineering at UNIST, in collaboration with Professor Jeon Joo-won from the Department of Applied Chemistry at Kookmin University, developed a ‘high-performance ionic polymer thermoelectric material’ with self-healing capabilities for mechanical and electrical faults and issues.

The team utilized a ‘self-healing thermoelectric material’ that maintains mechanical properties and electrical performance by restoring itself when torn or cut, thanks to the strong intermolecular forces within the thermoelectric material.

They also precisely analyzed and optimized the variables determining the thermoelectric performance of ionic thermoelectric materials, which had not been addressed in previous studies. Based on this, they developed a material with ultra-high-efficiency thermoelectric conversion performance, excellent mechanical properties, and self-healing ability.

Most electronic devices use lithium-ion batteries with liquid electrolytes, but these batteries containing liquids have design limitations due to leakage risks and rely on external power sources for charging, which clearly limits their use.

In contrast, ionic polymer thermoelectric materials are highly anticipated as next-generation independent power sources because of their inherent flexibility and ability to self-generate power from surrounding thermal energy.

However, thermoelectric materials have lower thermal energy conversion performance compared to conventional lithium-ion batteries, requiring significant improvements for commercialization. Moreover, systematic scientific analysis for performance enhancement is still lacking.

Self-healing ability and elasticity of the developed ionic polymer thermoelectric material.

The research team thermodynamically analyzed the ionic thermoelectric effect inside the material for the first time in the world and optimized the thermal energy conversion performance. The ionic thermoelectric performance index of the developed material was 12.3, recording a performance more than 70% higher than the previous best record.

Along with self-healing ability, the material exhibits excellent physical properties, capable of stretching more than 10 times its original length and maintaining mechanical and electrical characteristics without performance loss even after more than 50 repeated durability tests.

Donghoo Kim, the first author and a researcher in the Department of Energy and Chemical Engineering, said, “We were able to break the record by maximizing the energy change of ions diffusing thermally inside the material,” adding, “Its excellent self-healing and elasticity suggest it can be applied to self-powering wearable electronic devices in the future.”

The research team manufactured ionic thermoelectric supercapacitor devices using the developed material and connected multiple devices in series to amplify the output, creating a module.

The fabricated module demonstrated a high voltage output (0.37 V/K), proving that the developed thermoelectric material can generate sufficient voltage to operate various electronic devices in everyday life.

Professor Jang Sung-yeon from the Department of Energy and Chemical Engineering said, “This study presented all necessary processes from material design considering mechanical and electrical properties to commercialization demonstration through modules,” and added, “It is an important study that will guide many researchers developing ionic thermoelectric materials in the future.”

This research was published in Nature Communications on June 5. The study was supported by the Ministry of Science and ICT and the National Research Foundation of Korea (NRF).

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