Preparation And Dielectric Energy Storage Properties Of Polystyrene-based Composite Dielectrics

In recent years,polymer composite dielectric energy storage thin film materials have gained increasing attention and applications in the context of the"double carbon"policy.Currently,polymer nanocomposites prepared by combining polymer matrix with high breakdown field strength and nano-fillers with high dielectric constants have shown great potential for modern electronic and power system applications.Among these materials,linear dielectric polymers are notable for their significant advantages in breakdown strength and efficiency.However,the practical application of linear dielectrics is usually severely hampered by their low energy density.In this paper,we use polystyrene-based linear dielectric polymer polystyrene methyl methacrylate（P（St-MMA）,or MS）as a substrate to improve the dielectric constant and breakdown strength of the composite dielectric films by microstructural modulation of polymer composite dielectric materials through multilayer structural design including ferroelectric/linear polymer dielectric composite and doping modification of various nano-fillers to achieve polymer composite The effective improvement of energy storage characteristics of the polymer composite dielectric,and its dielectric properties are characterized and studied.（1）The xwt%BT@P（St-MMA）composite dielectric films were prepared by the solution flow-delaying method using zero-dimensional material barium titanate nano powder（Ba Ti O₃,abbreviated as BT）ceramic powder as high dielectric ceramic filler compound P（St-MMA）.The results showed that the BT particles with high dielectric constant of zero-dimensional nanoparticles（50 nm）could be effectively dispersed in the P（St-MMA）matrix solution.The filling of the BT nanoparticles leads to effective improvement of the dielectric constant of the composite dielectric film material,and the corresponding polarization strength P_max of the composite dielectric film is significantly increased,while the composite material possesses a high level of effective energy storage efficiency because of the linear polymer material P（St-MMA）chosen as the matrix.In particular,when x=1,the xwt%BT@P（St-MMA）composite dielectric film shows the best performance with energy storage density W=15.47 J/cm3,effective energy storage density W_rec=14.31 J/cm3,and energy storage efficiency=92.48%at electric fields up to400 MV/m.It also exhibits high power density P_D=12.69 MW/cm³ and very short discharge time t_0.9=293 ns under 200 MV/m electric field.（2）The xwt%MXene@P（St-MMA）composite dielectric films were prepared by solution flow-delaying method using MXene,a two-dimensional conductive material,as a high dielectric inorganic filler composite P（St-MMA）.The results show that the high dielectric constant,high thermal and electrical conductivity of the two-dimensional morphology of MXene can be well dispersed in the P（St-MMA）matrix.the filling of MXene makes the dielectric constant of the composite dielectric film material gradually increase,corresponding to a significant increase in its saturation polarization strength Pmax,and can establish an effective conductive barrier in the nanocomposite to prevent the breakdown process of electrical dendrite growth and improve the breakdown strength of the composite dielectric film material.In addition,the high thermal conductivity of the 2D material can effectively dissipate Joule heat,which is beneficial to improve the high temperature performance of the dielectric.It can also reduce the thermal breakdown phenomenon caused by filler agglomeration,and then improve the energy storage density of the composite dielectric material.In particular,when x=1,xwt%MXene@P（St-MMA）composite dielectric film shows the best performance with energy storage density W=9.36 J/cm3,effective energy storage density W_rec=7.07 J/cm3,and energy storage efficiency=85.6%at electric fields up to 400 MV/m.（3）An all-polymer composite with an asymmetric three-layer structure design was used,consisting of a mixture of P（VDF-HFP）and P（St-MMA）as an intermediate layer sandwiched between a linear polymer P（St-MMA）dielectric layer and a nonlinear polymer P（VDF-HFP）dielectric layer.The P（VDF-HFP）-xvol%P（St-MMA）/P（VDF-HFP）-P（St-MMA）（abbreviated as P-xvol%M/P-M）three-layer asymmetric structure all-polymer composite dielectric films were prepared by the solution-by-layer flow-delay method.The results show that the three structures can be effectively fused tightly through the interlayer.Among them,the linear dielectric layer provides high energy efficiency,while the high energy density is provided by the nonlinear layer dielectric layer.In particular,the intermediate layer can effectively balance the electric field distribution,thus improving the breakdown strength and increasing the energy density.In particular,the P-xvol%M/P-M three-layer asymmetric structured all-polymer composite dielectric film exhibits the best performance at x=30,achieving both=94.14%efficiency and W_rec=14.86 J/cm³ effective energy storage density at electric fields up to 400 MV/m.At the same time,significant frequency stability（1～500 Hz）,power density P_D=4.69 MW/cm³,and short discharge time t_0.9=1.00μs were exhibited at an electric field of 200 MV/m.