Bifunctional nanoencapsulated eutectic phase change material core with SiO 2 /SnO 2 nanosphere shell for thermal and electrical energy storage

Abstract A novel bifunctional nanoencapsulated phase change materials (NEPCMs) were synthesized based on oleic acid (OA) - polyethylene glycol (PEG) core with SiO 2 /SnO 2 shell via in situ emulsion interfacial hydrolysis and polycondensation followed by successive ionic layer adsorption and reaction method. Microscopic analysis reveals the uniform formation of SnO 2 as mild-flower like structure on the surface of SiO 2 nanocapsules. The chemical functional groups of NEPCMs were deduced by fourier transform infrared spectroscopy. The crystalline nature and structure of NEPCMs were analyzed using x-ray diffraction analysis. Thermal property (heat transfer rate of 0.7053 Wm −1  K −1 ), electrical property (electrical conductivity of 1.08 × 10 −7  S/cm) and electrochemical performance (specific capacitance of 59.2 F/g) were analyzed. Melting/solidification at 3.11, 2.57 °C with a latent heat of 58.79, 55.49 J/g and an encapsulation ratio of 52.12% were observed for OA-PEG/SiO 2 /SnO 2 NEPCMs by differential scanning calorimetry. Thermogravimetric analysis recorded the enhanced thermal stability of NEPCMs. The yield load and hardness was determined as 89.65 ± 3 μN, 4.7 ± 0.3 GPa using a nanoindenter. Based on all results, the bifunctional NEPCMs can be used as shape-stabilized phase change materials for cold thermal energy storage (CTES), and in cooling functions for electronic chips as well as promising electrode materials for electrochemical energy storage.