目的 开发兼具高介电常数、低介电损耗、高储能密度及高放电效率的柔性聚合物基介电复合材料。方法 采用水热合成法制备纳米SnO2,并通过多巴胺进行表面修饰改性;同时利用逐步加成聚合法合成芳香聚硫脲。将改性纳米SnO2与ArPTU及聚偏氟乙烯-三氟乙烯-三氟氯乙烯基体进行三元复合,系统考察多巴胺改性SnO2填充量对复合材料介电储能性能的调控规律。结果 表征分析表明,改性纳米SnO2表面均匀包覆约5 nm厚无定型层,在基体中实现均匀分散,无明显团聚现象。随填料含量增加,复合材料储能性能持续提升;当填充量（质量分数）为30%时,介电常数提高至74,为纯PVDF-TrFE-CTFE的1.9倍,且介电损耗与基体相当。低填充量下材料仍保持较高击穿场强;10%（质量分数）填充时,在600 MV/m电场下获得24.3 J/cm3的储能密度,放电效率维持在80%以上。结论 针对高电场下铁电相变滞后与漏导损耗导致的放电效率瓶颈,本研究提出“刚性非晶聚合物-多巴胺修饰无机填料”双重微观结构调控策略。ArPTU刚性链段有效破坏弛豫铁电基体的长程有序结构,显著抑制高电场下的铁电相变与偶极翻转滞后;多巴胺界面层有效消除半导体填料的局域漏导通道。两者协同作用使复合材料电滞回线显著收窄,在保持高介电常数与高Weibull击穿场强的同时,实现了低高场损耗与高放电效率的协同优化,为高性能柔性介电储能材料的设计提供了新思路。
Abstract
Polymer-based dielectric capacitors are indispensable in advanced pulsed power and electronic systems owing to their ultrafast charge-discharge capability and superior reliability. However, state-of-the-art relaxor ferroelectric polymers such as PVDF-TrFE-CTFE suffer from an inherent contradiction: achieving high polarization requires strong ferroelectric ordering, yet strong ordering inevitably produces large hysteresis loss under high electric fields, severely compromising charge-discharge efficiency. Conventional approaches have invariably failed to simultaneously satisfy the three critical requirements of high dielectric constant, high breakdown strength, and low high-field loss. In particular, incorporating high-permittivity inorganic fillers (e.g., BaTiO3, TiO2) into ferroelectric polymers typically introduces severe interfacial charge accumulation and increased conduction loss, degrading energy storage efficiency rather than improving it. The work aims to experimentally validate a structurally rational dual synergistic strategy that integrates rigid amorphous aromatic polythiourea (ArPTU) with dopamine-modified SnO2 nanoparticles (SnO2@DA) to synergistically regulate the microstructure, ferroelectric domain architecture, and interfacial charge transport of a PVDF-TrFE-CTFE matrix. The central innovation lies in recognizing that the two major loss mechanisms in polymer dielectrics—ferroelectric phase-transition hysteresis and interfacial conduction loss—require distinct material solutions: the former demands disruption of long-range crystalline ordering, while the latter necessitates elimination of charge leakage pathways at the filler-polymer interface. ArPTU, synthesized via step-addition polycondensation of 4,4’-diaminodiphenylmethane and p-phenylenediisothiocyanate, is a fully amorphous polymer with a rigid aromatic backbone and intrinsic low dielectric loss (~0.05). The SnO2 nanoparticles (~100 nm) were surface-modified through a dopamine coating process. This procedure yielded a uniform and continuous amorphous polydopamine shell with a precisely controlled thickness of approximately 5 nm, as confirmed by transmission electron microscopy (TEM). Ternary composites with SnO2@DA loadings of 5, 10, and 15wt.% (ArPTU fixed at 10wt.%) were fabricated via solution blending and hot pressing at 195 ℃ under 10 tons pressure. SnO2@DA nanoparticles were homogeneously distributed throughout the matrix without observable aggregation, even at 15wt.% loading, in contrast to unmodified SnO2, which exhibited severe agglomeration at the same loading. This homogeneous dispersion was attributed to the dopamine shell, which reduced the high surface energy of inorganic nanoparticles and established strong interfacial adhesion through hydrogen bonding with both PVDF-TrFE-CTFE. X-ray diffraction (XRD) combined with Scherrer analysis revealed that the addition of SnO2@DA progressively refined the crystalline domain size of the polymer matrix from 30.9 nm (pure polymer) to 28.6 nm (5wt.% SnO2@DA), fundamentally transforming the ferroelectric domain architecture from macroscopic domains into nanoscale polar regions with significantly reduced switching barriers. Dielectric spectroscopy measurements demonstrated that the dielectric constant of the ternary composites increased monotonically with SnO2@DA content, reaching a maximum value of 74. Remarkably, the dielectric loss tangent at low filler loading (≤10wt.%) was substantially lower than that of the pure polymer across the entire measured frequency range (102-107 Hz), a counterintuitive finding attributed to the synergistic dual mechanism: the dense interfacial polymer layer constrained by dopamine suppressed the β-relaxation loss dominant in PVDF-based ferroelectrets, while the amorphous ArPTU diluted the high-loss PVDF phase and disrupted long-range carrier migration pathways. Weibull statistical analysis of breakdown strength revealed a characteristic breakdown strength of 700.3, 620.3, and 553.9 MV/m at 5, 10, and 15wt.% SnO2@DA loading, respectively, all significantly exceeding the 530.3 MV/m of the pure polymer matrix. The ferroelectric hysteresis (D-E) loops provided the most compelling evidence for the dual synergistic effect: the ternary composites evolved from the characteristic relaxor ferroelectric shape of pure PVDF-TrFE-CTFE into nearly linear dielectric responses with dramatically narrowed loop widths. At a SnO2@DA loading of 10wt.%, the composite achieved a discharged energy density of 24.3 J/cm3 under 600 MV/m, while simultaneously maintaining a charge-discharge efficiency exceeding 80%.
关键词
多巴胺 /
二氧化锡 /
聚偏氟乙烯-三氟乙烯-三氟氯乙烯 /
芳香聚硫脲 /
表面改性 /
介电性能
Key words
dopamine /
tin dioxide /
poly(vinylidene fluoride-trifluoroethylene-chlorotrifluoroethylene) /
aromatic polythiourea /
surface modification /
dielectric properties
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