Phase transition driven tough hydrogel ionic thermoelectric cell with giant thermopower

The application of quasi-solid ionic thermoelectric (i-TE) cells holds great potential for powering ubiquitous wearable electronics without the need for cables or batteries. However, their practical application is restricted by low thermopower. Herein, a temperature-responsive supramolecular hydrogel, P(N-acryloylsemicarbazide-co-acrylic acid) (PNA), has been developed as a i-TE cell that integrates good mechanical and electrochemical properties. The volume phase transition (VPT) of PNA i-TE cell can generate a substantial ion entropy difference, thereby enhancing both the redox reaction efficiency and ionic thermodiffusion rate. A single PNA i-TE cell can generate a thermopower of 2.04 volts with a temperature difference of 50 K. The Seebeck coefficient (S_e), specific output power density ( <mml:math xmlns:mml="http://www.w3.org/1998/Math/MathML"> <mml:msub><mml:mrow><mml:mi>P</mml:mi></mml:mrow> <mml:mrow><mml:mi>max</mml:mi></mml:mrow> </mml:msub> <mml:mo>/</mml:mo> <mml:msup> <mml:mrow><mml:mrow><mml:mo>(</mml:mo> <mml:mrow><mml:mi>Δ</mml:mi> <mml:mi>T</mml:mi></mml:mrow> <mml:mo>)</mml:mo></mml:mrow> </mml:mrow> <mml:mrow><mml:mn>2</mml:mn></mml:mrow> </mml:msup> </mml:math> ) and figure of merit (ZT) of PNA i-TE cell can reach up to 40.9 mV K^-1, 35.2 mW m^-2 K^-2 and 1.33 respectively. This ionic hydrogel is promising for the design of high performance polymer based i-TE cells in an environmentally friendly and cost-effective manner.