Polymer-based Nanocomposites For Energy Storage Applications

Energy storage technology plays an important role for new energy industry and has been investigated widely as new energy industry is becoming a new engine of global economic growth.One of the strategy is to use dielectric materials for energy storage,which is characterized by fast charge-discharge speed,low cost and other advantages.The investigation of dielectric materials for energy storage applications is urgently needed with the miniaturization and integration of electron elements.So far,ceramics,polymers and polymer-based composites are most investigated for energy storage applications.Polymer-based composites is comprised of ceramic particles and polymer matrix,which exhibit excellent energy storage properties.This dissertation investigated polymer-based nanocomposites for energy storage applications.Polymer-based nanocomposites is comprised of ceramic nanoparticles and polymer matrix.This dissertation aimed to enhance the energy storage properties of polymer-based nanocomposites through the incorporation of ceramic nanoparticles into polymer matrix and promote their applications in energy storage fields.The main contents and relative theory background were introduced in chapter one.Polarization and electric breakdown properties of dielectric materials were described and dielectric displacement-electric field（D-E）loops of ferroelectric materials were also discussed.Then energy storage properties of dielectric materials were further introduced.Besides,the development of ceramics,polymers and polymer-based composites for energy storage applications were summarized.The structure,dielectric properties and energy storage properties of polymer-based nanocomposites were investigated systematically in chapter two.Firstly,the fabrication of polymer-based nanocomposite films was discussed,and instruments for the characterization of structure,dielectric properties and energy properties of polymer-based nanocomposites were also described.Secondly,nanocomposites comprising polyvinylidene fluoride（PVDF）polymer and Ba Ti O₃ nanoparticles were fabricated and further investigated.Influences of the incorporation of ceramic nanoparticles into polymer matrix were discussed emphatically.Thirdly,microwave properties of the nanocomposites were discussed.Fourthly,significant enhancement of electric breakdown strength of the nanocomposites caused by the incorporation of a small amount of ceramic nanoparticles were also investigated.At last,influences of particle size of nanoparticles on polymer-based nanocomposites were discussed.The results of chapter two indicated that the structure,dielectric properties and energy storage properties of polymer-based nanocomposites were influenced by the incorporation of ceramic nanoparticles.Effects of surface modification and core-shell coating of ceramic nanoparticles on dielectric properties and energy storage properties of polymer-based nanocomposites were investigated in chapter three.Polyvinylpyrrolidone（PVP）,tetrafluorophthalic acid and titanate coupling agent were used to modify the surface of Ba Ti O₃ nanoparticles,respectively,which contributed to the enhancement of energy density of the nanocomposites.Besides,Si O₂ shell were coated on the surface of Ba Ti O₃ nanoparticles,which contributed to the significant reduction of energy loss of the nanocomposites.The results of chapter three indicated that distribution of ceramic nanoparticles and homogeneity of the nanocomposites were improved,and interfaces in the nanocomposites were also influenced due to the surface modification and core-shell coating of ceramic nanoparticles.Effects of the introduction of a third phase material into the nanocomposites were further investigated in chapter four.Polyacrylate elastomers were introduced into nanocomposites comprising Ba Ti O₃ nanoparticles and PVDF polymer matrix,and as a result,the energy density of the nanocomposites was enhanced.Besides,silver nanoparticles were introduced into nanocomposites comprising Ba Ti O₃ nanoparticles and PVDF polymer matrix,and influences of percolation were investigated.The results of chapter four indicated that polarization and energy storage properties of polymer-based nanocomposites could be enhanced due to the introduction of a third phase material.Main research results of this dissertation were summarized in chapter five and further investigation of polymer-based nanocomposites for energy storage applications were also prospected.