UES, Inc., Dayton, Ohio 45432, USA.
ACS Appl Mater Interfaces. 2013 Jun 26;5(12):5486-92. doi: 10.1021/am4005623. Epub 2013 May 2.
The ultimate energy storage performance of an electrostatic capacitor is determined by the dielectric characteristics of the material separating its conductive electrodes. Polymers are commonly employed due to their processability and high breakdown strength; however, demands for higher energy storage have encouraged investigations of ceramic-polymer composites. Maintaining dielectric strength, and thus minimizing flaw size and heterogeneities, has focused development toward nanocomposite (NC) films; but results lack consistency, potentially due to variations in polymer purity, nanoparticle surface treatments, nanoparticle size, and film morphology. To experimentally establish the dominant factors in broad structure-performance relationships, we compare the dielectric properties for four high-purity amorphous polymer films (polymethyl methacrylate, polystyrene, polyimide, and poly-4-vinylpyridine) incorporating uniformly dispersed silica colloids (up to 45% v/v). Factors known to contribute to premature breakdown-field exclusion and agglomeration-have been mitigated in this experiment to focus on what impact the polymer and polymer-nanoparticle interactions have on breakdown. Our findings indicate that adding colloidal silica to higher breakdown strength amorphous polymers (polymethyl methacrylate and polyimide) causes a reduction in dielectric strength as compared to the neat polymer. Alternatively, low breakdown strength amorphous polymers (poly-4-vinylpyridine and especially polystyrene) with comparable silica dispersion show similar or even improved breakdown strength for 7.5-15% v/v silica. At ∼15% v/v or greater silica content, all the polymer NC films exhibit breakdown at similar electric fields, implying that at these loadings failure becomes independent of polymer matrix and is dominated by silica.
静电电容器的最终储能性能取决于分隔其导电电极的材料的介电特性。由于其可加工性和高击穿强度，聚合物通常被使用；然而，对更高储能的需求鼓励了对陶瓷-聚合物复合材料的研究。为了保持介电强度，从而最小化缺陷尺寸和不均匀性，开发工作集中在纳米复合材料（NC）薄膜上；但是结果缺乏一致性，这可能是由于聚合物纯度、纳米颗粒表面处理、纳米颗粒尺寸和薄膜形态的变化。为了从实验上确定广泛的结构-性能关系中的主导因素，我们比较了四种高纯度无定形聚合物薄膜（聚甲基丙烯酸甲酯、聚苯乙烯、聚酰亚胺和聚 4-乙烯基吡啶）的介电性能，这些聚合物薄膜中均匀分散了二氧化硅胶体（高达 45%体积比）。在这个实验中，已经减轻了已知会导致提前击穿场排斥和团聚的因素，以便专注于聚合物和聚合物-纳米颗粒相互作用对击穿的影响。我们的研究结果表明，与纯聚合物相比，将胶体二氧化硅添加到具有较高击穿强度的无定形聚合物（聚甲基丙烯酸甲酯和聚酰亚胺）中会导致介电强度降低。相比之下，具有类似二氧化硅分散性的低击穿强度无定形聚合物（聚 4-乙烯基吡啶，尤其是聚苯乙烯）的击穿强度为 7.5-15%体积比的二氧化硅时，甚至会提高击穿强度。在约 15%体积比或更高的二氧化硅含量下，所有聚合物 NC 薄膜在相似的电场下都会发生击穿，这意味着在这些负载下，失效不再取决于聚合物基体，而是由二氧化硅主导。
