| Energy-storage dielectrics are considered as key materials that can be used in devices for electrical energy-storage applications due to the high-power density,fast responsibilty,and low cost.Among various energy-storage dielectrics,polymer-ceramic nanocomposites have received extensive attention and research due to their good flexibility,low processing temperature,etc.As energy-storage dielectrics,the properties of polymer-ceramic nanocomposites are normally evaluated by two parameters:energy-storage density and energy-storage efficiency.The former is determined by the dielectric constant and breakdown strength;while the latter is determined by the charging-discharging performance.Besides the properties of the constituents,the dielectric properties and energy-storage performances of a polymer-ceramic nanocomposite is highly related to the interfaces between the ceramic filler and the polymer matrix and the fabrication processes.In this work,ferroelectric polymer P(VDF-HFP)and non-ferroelectric polar polymer PMMA were selected as matrices.and BaTiO3(BT)and Ba0.5Sr0.5TiO3(BST)nanoparticles were selected as fillers.Two groups of polymer-ceramic nanocomposite films,i.e.P(VDF-HFP)-BT and PMMA-BST,were fabricated and investigated.It is experimentally found that the dielectric constant of the polymer-ceramic nanocomposites increases with increasing content of ceramic fillers,and the temperature and frequency dependences of dielectric properties are mainly determined by the temperature and frequency dependences of dielectric properties of the polymer matrix,which is related to the relaxation processes of the polymer chains of the matrix and affected by the ceramic fillers.In contrast to that for dielectric constant,the breakdown strength decreases with inceseasing content of ceramic fillers.The energy-storge density of those nanocomposites are determined by the balance between dielectric constant and breakdown strength with different content of ceramic filler.The energy-storage efficiency of polymer-ceramic nanocomposites is mainly determined by the polymer matrix.The nanocomposites using ferroelectric polymers as matrix normally show a low energy-storage efficiency,which is caused by the high loss originating from the ferroelectricity of the matrix.The nanocomposites using non-ferroelectric polar polymers as matrix can show an ultrahigh energy-storage efficiency(?100%),which is due to the fact that the non-ferroelectric polar polymers are linear dielectricsThe results reported here indicate that the dielectric properties and energy-storage performances of polymer-ceramic nanocomposites are extensively determined by the polymer matrix.It is highly possible that fabrication of nanocomposites using non-ferroelectric polar polymers as matrix and ceramic nanoparticles with low dielectric loss is a promising approach and also opens a new avenue for the development of high-performance ceramic-polymer nanocomposites for energy-storage applications. |
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