| The development of society is inseparable from electric energy.In the field of electric energy storage,organic film capacitors have been widely used due to their small size,high energy storage density and simple processing technology,and have become one of the indispensable power storage components.However,with the continuous development of society,traditional single organic dielectric materials have been unable to meet the growing needs of people.The upgrading of energy storage technology is imminent,and the design and development of dielectric materials with two-phase or multi-phase all-organic composites has become a research hotspot.We’re supposed to recombine multiphase organic polymers by means such as physical or chemical modification to achieve single-phase enhancement or multi-phase complementation,to improve storage density and energy storage technology.Therefore,in this paper,polyvinylidene fluoride(PVDF)was used as the research object,and polymethyl methacrylate(PMMA)or polyphenylthiourea(ArPTU)was used as the composite phase,which was prepared by using different modification methods.A series of PVDF-based all-organic composite materials with excellent performance,the specific research contents and related results are shown as follows:(1)A series of PVDF/PMMA composites were prepared by blending poly(methyl methacrylate)with polyvinylidene fluoride.The effects of PMMA addition on the PVDF performance of the matrix were studied,and the best blending of composites was determined at the ratio of 80/20.At this ratio,the breakdown field strength of the composite reached a maximum of 386.04 MV/m;the storage density can reach 0.825J/cm~3,which was 9.8%and 32%higher than that of pure PVDF,respectively.(2)The PVDF/PMMA composite material having a crosslinked structure was prepared by dissolving PVDF in a solvent of N,N-dimethylformamide under the optimal polymerization conditions of MMA.The experimental results showed that the composite material with cross-linked structure had better performance.Under the same conditions,the breakdown field strength and energy storage performance were improved by nearly 12%and 90%respectively compared with the matrix;For simple blended composites,the breakdown field strength increased by nearly 2%;the energy storage performance also increased by nearly 45%.(3)Polyphenylenethiourea was synthesized from 4,4’-diaminodiphenylmethane(MDA),thiourea as raw material,N,N-dimethylformamide(DMF)as solvent and p-toluene sulfonic acid(TsOH)as catalyst.(ArPTU).A series of PVDF/ArPTU composites were prepared by solution blending.The effects of different ArPTU contents on the properties of PVDF/ArPTU composites were investigated.When the addition amount of ArPTU was between 10%and 15%,the composite material had the best performance,and the maximum energy storage density can reach 2.76J/cm~3,which was nearly 50%higher than that of pure PVDF,but relatively poor in two-phase solubility.(4)Using dopamine(DA)as a modifier,the surface grafting modification of ArPTU can be carried out by reacting with amino or sulfur groups under alkaline conditions,and then the modified ArPTU was combined with the matrix to prepare a series of DA.The modified PVDF/ArPTU composites show that the modified two-phase interface had a significant improvement,and the maximum energy storage density can reach 3.0 J/cm~3,which was 63.3%higher than that of pure PVDF.The PVDF/ArPTU composites also increased by 8.7%.Moreover,the mechanical properties of the composites after dopamine modification also was greatly improved,and the maximum elongation at break reached 196.7%(5%),demonstrating the potential of flexible high breakdown energy storage materials. |
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