Actively tunable infrared emissivity regulator based on electrochemical lithium intercalation in three-dimensional graphene foam

Abstract

Dynamic engineering of thermal infrared radiation offers significant potential for applications in thermal camouflage, radiative cooling, and solar energy harvesting. In this work, we demonstrate that three-dimensional (3D) graphene foam enables active thermal radiation control via electrochemical lithium intercalation. It exhibits a remarkable reduction in infrared absorptivity, from 0.50 at 25 µm and 0.64 at 2.5 µm to 0.20 across the wavelength range of 2.5–25 µm. At background temperatures of 30, 40, and 50 °C, the infrared apparent temperature decreases by ∼1.5, 2.5, and 4.5 °C, respectively, upon charging from 1 to 3.8 V. The infrared response time of the device at 50 °C is approximately 2.5 s and remains stable over 20 cycles. This optical change is achieved by introducing lithium-ion into graphene layers, causing a shift of Fermi energy (EF). Our findings indicate a significant decrease in broadband infrared absorptivity, which is suitable for infrared stealth applications.