High-performance solid-state electrochemical thermal switches with earth-abundant cerium oxide
Ahrong Jeong, Mitsuki Yoshimura, Hyeonjun Kong, Zhiping Bian, Jason Tam, Bin Feng, Yuichi Ikuhara, Takashi Endo, Yasutaka Matsuo, Hiromichi Ohta
Abstract
Thermal switches, which electrically turn heat flow on and off, have attracted attention as thermal management devices. Electrochemical reduction/oxidation switches the thermal conductivity (κ) of active metal oxide films. The performance of the previously proposed electrochemical thermal switches is low; the on/off κ-ratio is mostly less than 5, and the κ-switching width is less than 5 watts per meter kelvin. We used a CeO 2 thin film as the active layer deposited on a solid electrolyte YSZ substrate. When the CeO 2 thin film was reduced once (off-state) and then oxidized (on-state), κ was about 2.2 watts per meter kelvin in the most reduced state, and κ increased with oxidation to 12.5 watts per meter kelvin (on-state). This reduction (off-state)/oxidation (on-state) cycle was repeated 100 times, and the on/off κ-ratio was 5.8, and the κ-switching width was 10.3 watts per meter kelvin. The CeO 2 -based solid-state electrochemical thermal switches would be potential devices for thermal shutters and thermal displays.