Preparation And Performance Optimization Of MnO₂/PVDF Composite Films

With the rapid development of electronic industry,the increasing need of high dielectric materials,high energy storage density materials have important effects on the development of electronic power system,especially in need of quick charge discharge areas such as wind,solar,tidal power,and these local energy storage has the highly decentralized,instability and intermittent,therefore the development of energy storage technology is imperative.Polyvinylidene fluoride(PVDF)has excellent ferroelectric properties,as well as good chemical corrosion resistance,high temperature resistance,piezoelectric property and small electromechanical coupling coefficient.It is often used as the matrix of composite materials to prepare dielectric composites by means of filler modification or blending modification.Since MnO₂has a small band gap,it has a good potential application value in the field of energy storage.However,there are few reports on the modification of PVDF by doping MnO₂.In this paper,a series of PVDF composite films with different filler contents were prepared by using polyvinylidene fluoride(PVDF)as the matrix and MnO₂as the main filler.The effects of KH570-GNs co-doping and C coating on the performance optimization of PVDF composite films were investigated.The MnO₂/PVDF composite films were tested and it was found that the introduction of MnO₂particles promoted the transformation of PVDF films from multinomial coexistence to?-phase with excellent ferroelectric properties.The dielectric constant of MnO₂/PVDF composite film with 15 wt%MnO₂doping is positively correlated with the content of filler.Under 100 Hz test condition,the dielectric constant of MnO₂/PVDF composite film with 15 wt%MnO₂doping is up to 27.The breakdown field strength of MnO₂/PVDF composite films with 10 wt%MnO₂doping is 100 k V/mm.When KH570-GNs and MnO₂are co-doped,MnO₂and KH570-GNs disperse well in the matrix at low addition amount,and agglomerate occurs with the continuous increase of KH570-GNs content.Under the test condition of 100 Hz,the dielectric constant of MnO₂10wt%KH570-GNs 7wt%composite film is the highest,which is 315.When the mass fraction of packing is MnO₂5wt%KH570-GNs 3 wt%,the maximum value is 10.58 k V/mm.MnO₂@C has a typical core-shell structure,and C is completely coated on the surface of MnO₂with a shell thickness of 5 nm.When MnO₂@C is used as filler,the nuclei and shells are uniformly dispersed in PVDF matrix.With the increase of MnO₂@C content,PVDF film can be promoted from multinomeric coexistence to?-phase with excellent ferroelectric properties.The dielectric constant of MnO₂/PVDF composite film with MnO₂@C doping amount of 15 wt%is up to 31 at 100 Hz.The breakdown field strength of MnO₂/PVDF composite films with 10 wt%MnO₂doping is 89.6k V/mm.