A Hybrid Material Approach Toward Solution‐Processable Dielectrics Exhibiting Enhanced Breakdown Strength and High Energy Density

Abstract

3505wileyonlinelibrary.com dielectric capacitors possess higher power density, faster charge-discharge capability, and longer lifetime, [ 3,4 ] but bear energy densities that are one order of magnitude lower than those of batteries. [ 5 ] As the energy density of capacitors is governed by the dielectric materials that separate the opposite static charges between two electrodes, the development of dielectric materials with greatly improved energy density is thus becoming one of the major enabling technologies. [ 6 ] In general, the energy density ( U e ) of linear dielectric materials is given by U e = ½ ε r ε 0 E 2 , where ε r is the effective permittivity, ε 0 is the vacuum permittivity, and E is the applied fi eld. Inorganic dielectric materials, while enjoying high dielectric permittivities, are limited by low breakdown strength ( E b ), i.e., typically in the scale of kV m ), and graceful failure mechanism, although their permittivities are orders of magnitude smaller than those of their inorganic counterparts. [ 7,8 ] To integrate the complementary advantages of inorganic and organic dielectric materials, polymer nanocomposites composed of inorganic ceramic fi llers with high dielectric constant ( k ) have been prepared by using a variety of methods, including mechanical blending, [ 9,10 ] solution mixing, [11][12][13][14][15] and surface-initiated polymerization. [ 16,17 ] As expected, k values of the polymer nanocomposites have indeed been improved, but there exist serious drawbacks in the nanocomposite approach. (1) The presence of a large contrast in k values between two phases augments the local electric fi eld distortions and results in a highly inhomogeneous fi eld distribution, and consequently, decreases E b . [ 4 ] As U e of dielectrics scales as the second power of the applied electric fi eld, a reduced E b would diminish any substantial improvement in energy storage capability even though k is increased. (2) The structural imperfections at the fi ller/ matrix interface such as fl aws and voids caused by the poor fi ller distribution and incompatibility between the inorganic and organic phases not only are detrimental to E b , but also give rise to large conduction loss. This, in turn, reduces the discharged energy density and shortens the lifetime of devices because of Joule heating. A Hybrid Material Approach Toward Solution-Processable Dielectrics Exhibiting Enhanced Breakdown Strength and High Energy DensityKuo Han , Qi Li , Chalathorn Chanthad , Matthew R. Gadinski , Guangzu Zhang , and Qing Wang * The ever-increasing demand for compact electronics and electrical power systems cannot be met with conventional dielectric materials with limited energy densities. Numerous efforts have been made to improve the energy densities of dielectrics by incorporating ceramic additives into polymer matrix. In spite of increased permittivities, thus-fabricated polymer nanocomposites typically suffer from signifi cantly decreased breakdown strengths, which preclude a substantial gain in energy density. Here...

Polymer Nanocomposites with Interpenetrating Gradient Structure Exhibiting Ultrahigh Discharge Efficiency and Energy Density

“…is the cumulative probability of electric failure, E is experimental breakdown strength, scale parameter E b is the field strength for which there is a 63.2% probability for the sample to breakdown and is also regarded as the characteristic breakdown strength, and shape parameter β is the Weibull modulus that shows the dispersion of E. [29] The results of Weibull statistical analysis for the gradient-structured PBPNs are presented in Figure 4a and the characteristic E b of the R-BZT_nfs nanocomposites with various BZT_nfs loadings are summarized in Table S1 in the Supporting Information. For the R-BZT_nfs nanocomposites, E b increases from ≈587.9 MV m −1 to ≈605.3 MV m −1 as the content of BZT_nfs increases from 0 to 3 vol%.…”

Ferroelectric Polymers and Their Energy‐Related Applications

“…On the other hand, it is noteworthy that the discovery of synergistic effects of ferroelectric polymers with their inorganic counterparts has recently yielded new ferroelectric material approaches such as composites and hybrids (Figure ). These approaches have shown immense potential for the improvement of material performance that are of great value for practical applications in energy storage and conversion . All these exciting aspects together may represent the trend of next‐stage ferroelectric polymer research.…”

High breakdown strength and low loss binary polymer blends of poly(vinylidene fluoride‐trifluoroethylene‐chlorofluoroethylene) and poly(methyl methacrylate)

“…The energy density of dielectric materials can be described as: where E is electric field and D is electric displacement. For linear dielectrics, where K is relative dielectric constant and ε 0 is vacuum dielectric constant . In particular, U is quadratically dependent on E .…”