Monodisperse Na2SO4·10H2O@SiO2 Microparticles against Supercooling and Phase Separation during Phase Change for Efficient Energy Storage

Uniform SiO2 microparticles containing controllable content of Na2SO4·10H2O against supercooling and phase separation are developed for efficient energy storage at mild temperatures. Na2SO4 solution with 3-aminopropyltriethoxysilane and silicone oil with tetraethylorthosilicate are emulsified into monodisperse water-in-oil (W/O) emulsions from microfluidics for template fabrication of the microparticles via hydrolysis and condensation. During the reaction process, Na2SO4 in the emulsion droplets crystallizes in the microparticles. Incorporation of sodium borate and sodium hexametaphosphate, combined with the confined distribution of Na2SO4·10H2O in the mesoporous microparticles, successfully avoids the phase separation of Na2SO4·10H2O and dramatically reduces its supercooling. This allows the microparticles to achieve repeatable energy storage/release property at mild temperatures for thermoregulation. Such a thermoregulating performance is demonstrated by incorporating the microparticles into a model hou...