Robust, double-layered phase-changing microcapsules with superior solar-thermal conversion capability and extremely high energy storage density for efficient solar energy storage

Abstract

The encapsulation of phase change materials (PCMs) with typical core-shell structures is considered an effective and accessible technology to prevent liquid leakage and minimize the corrosion of PCMs. However, the poor solar-thermal conversion performance and significantly reduced energy storage density of microencapsulated PCMs seriously restrict their large-scale application. Herein, novel double-layered organic phase-changing microcapsules that contain n-eicosane as core material and polydopamine/poly(melamine-formaldehyde) resin (PDA@MF) as shell materials were designed and fabricated via a two-step polymerization. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD) and scanning electron microscopy (SEM) confirmed the successful fabrication of the PDA@MF/n-eicosane microencapsulated phase change materials (PMPCMs), which exhibited a regular, spherical shape. Differential scanning calorimetry (DSC) results showed that PMPCMs possessed extremely high phase change enthalpies (PMPCM-85, 199.4 J/g) and excellent thermal durability. Solar irradiation experiments showed that the introduction of PDA effectively improved the solar-thermal conversion efficiency of PMPCMs. Thermogravimetric analysis (TGA) and thermal reliability measurements demonstrated that the developed microcapsules exhibited good thermal reliability and stability. Furthermore, the introduction of PDA can significantly reduce the leakage rate of the microcapsules and strengthen the shell layer of the microcapsules. In conclusion, the double-layered PMPCMs expressed tremendous potential for efficient solar energy storage.