Engineering liquid crystal elastomer unlocks high thermopower for fiber-shaped ionic thermoelectric capacitors

Area of Science:

• Materials Science
• Energy Harvesting
• Thermoelectrics

Background:

• Ionic thermoelectric (i-TE) materials are promising for low-grade thermal energy harvesting.
• Development of n-type i-TE materials lags behind p-type, hindering applications.
• Liquid crystal elastomers (LCEs) offer tunable properties for advanced materials.

Purpose of the Study:

• To engineer novel n-type and p-type i-TE materials for improved thermal energy harvesting.
• To overcome the limitations of existing i-TE materials, particularly n-type counterparts.
• To demonstrate the integration of these materials into functional thermoelectric devices.

Main Methods:

• Engineered LCEs from side-chain to main-chain structures.
• Swelled LCEs with LiBF4 or EMIM TFSI electrolytes.
• Fabricated fiber-shaped i-TE capacitors using p/n pairs.

Main Results:

• Achieved the largest adjustable p-n Seebeck coefficient span (-27.4 to 28.8 mV K⁻¹) for homologous materials below 30% RH.
• Integrated a homogeneous π-type fiber-shaped i-TE capacitor with three p/n pairs.
• Generated an output voltage of 402.5 mV with a 2.5 K temperature difference.
• Attained an areal energy density of 8.1 mJ m⁻² per n-type fiber.
• Demonstrated excellent material stability under cyclic stretching, long-term testing, and thermal cycling.

Conclusions:

• Engineered LCE-based i-TE materials exhibit superior n-type and p-type performance.
• The developed materials enable efficient thermal-charge energy storage in flexible devices.
• These findings highlight the potential for LCE-based i-TE materials in wearables and flexible electronics.