Dynamic tunability of phase-change material transition temperatures using ions for thermal energy storage

Abstract

Thermal energy storage (TES) based on phase-change materials (PCMs) has many current and potential applications, such as climate control in buildings, thermal management for batteries and electronics, thermal textiles, and transportation of pharmaceuticals. Despite its promise, the adoption of TES has been limited, in part due to limited tunability of the transition temperature, which hinders TES performance for varying use temperatures. Transition temperature tuning of a material using an external stimulus, such as pressure or an electric field, typically requires very large stimuli. To circumvent this problem, here, we report on the dynamic transition temperature tunability of a PCM using ions. We achieve a transition temperature tunability up to 6°C in polyethylene glycol (PEG) by using the salt lithium oxalatodifluoroborate at a low voltage of 2.5 V, which may enable simpler and safer devices/system designs. We also explain the thermal properties of the salt/PCM solution using the Flory-Huggins theory. Dynamically tunable T m (15°C–21°C) of phase change materials with 2.5 V perturbation A dual-ion battery approach using ions to modulate T m of the phase-change materials Combination of thermal energy storage with electrical energy storage in one device Demonstration of higher thermal utilization of the dynamically tunable PCM Lau et al. develop a dynamic tunable phase-change material (PCM) that uses ions to tune the T m , based on the dual-ion battery concept. With static T m PCM, utilization at ambient temperature is limited, whereas for tunable PCM, where T m closely aligns with ambient temperature, higher energy storage is possible.