Advanced Dielectric Materials for Electrostatic Capacitors
Capacitors are passive electrical components that store energy in an electric field. Applications include electric power conditioning, signal processing, motor starting, and energy storage. The maximum charge a capacitor can hold largely depends on the dielectric material inside. That material is the enabler for the performance. Ongoing development in fields such as high-power electronics, renewable energy, hybrid electric vehicles and electric aircraft, is posing an urgent need for more advanced electrostatic capacitor technology. This book for researchers in industry and academia provides an overview of key dielectric materials for capacitor technology. It covers preparation and characterization of state-of-the art dielectric materials including ceramics, polymers and polymer nanocomposites, for the most popular applications including energy storage, microwave communication and multi-layer ceramic capacitors. The book begins with an introduction to electrostatic capacitor technology, then goes on to cover the following topics: techniques for capacitor dielectrics characterization; dielectric polymers and dielectric metamaterials for high energy capacitors; polymer/nanofiller composites; high-temperature polymer-based dielectrics for electrostatic energy storage; design and simulations of capacitor dielectrics by phase-field computations; rational design on polymer dielectrics; inorganic dielectrics for high-energy-density capacitors; ceramic dielectrics for microwave communication; ceramic dielectrics for MLCCs; and finally two chapters on future prospects for polymers and ceramics.
Inspec keywords: dielectric materials; electrostatic devices; capacitors; polymers
Other keywords: high-temperature polymer-based dielectrics; microwave communication; high-energy-density capacitors; electrostatic energy storage; dielectric metamaterials; ceramic dielectrics; high-energy capacitors; dielectric polymers; MLCCs; electrostatic capacitors; phase-field computations; polymer-nanofiller composites; inorganic dielectrics; dielectric materials
Subjects: Capacitors; General electrical engineering topics; Dielectric materials and properties; Polymers and plastics (engineering materials science); Electrostatic devices
- Book DOI: 10.1049/PBPO158E
- Chapter DOI: 10.1049/PBPO158E
- ISBN: 9781785619885
- e-ISBN: 9781785619892
- Page count: 446
- Format: PDF
-
Front Matter
- + Show details - Hide details
-
p.
(1)
-
1 Introduction to electrostatic capacitor technology
- + Show details - Hide details
-
p.
1
–32
(32)
A capacitor is a device that stores electric energy between a pair of electrodes on which electric charges (Q in Coulomb) accumulate. Historically, capacitors have taken the form of a pair of thin metal plates, which are either flat or tightly wound up in a cylinder having capacitance (C). This is a measure of the potential difference or voltage (V), which appears across the plates for a given amount of energy stored on each plate (Q/V in a unit of Farad). A traditional parallel-plate capacitor stores the amount of energy that is proportional to the surface area (A) of the conducting plate and inversely proportional to the distance (d) between the plates. It is also proportional to the permittivity of the dielectric substance that separates the plates, whether vacuum, air, or electrically insulating materials chosen for their special dielectric characteristics.
-
2 Techniques for capacitor dielectrics characterization
- + Show details - Hide details
-
p.
33
–69
(37)
Electrostatic capacitors are indispensable components in high voltage pulsed power systems and power electronics. They are widely employed in applications such as pulse-forming networks, switched-mode power supplies, medical defibrillators, and power electronics in hybrid electric vehicles (HEY), grid-tied wind turbine generators, high-speed trains, photovoltaics, etc. They perform the conversion of prime electric energy to energize large loads, and regulate electrical inputs into stable outputs over a wide range of load conditions. In most applications, the electrostatic capacitors are not the primary energy storage device; rather, their function is more likely conditioning primary electrical energy to certain pulse form, AC/DC, frequency, or voltage level to drive the final electrical load.
-
3 Dielectric polymers and dielectric metamaterials for high-energy capacitors
- + Show details - Hide details
-
p.
71
–107
(37)
In this pursuit, we have developed a class of high T g amorphous polymers, containing high density dipoles possessing high dipole moment p, i.e., urea and thiourea, which have p of 4.56 and 4.89 Debye, respectively [35-38]. It has been shown that by increasing the dipole moment and the dipole density, the dielectric constant in this series of polymers increases from 4.1 to 5.7. The high dipole moments in these amorphous polymers provide strong polar -scattering centers and traps, which significantly reduce the conduction loss at high electric fields.The results of dielectric nanocomposites in which a very low volume loading of nanofillers generate remarkable changes in the dielectric performance of polymers presented in this chapter demonstrate that such a dielectric metamaterial strategy can also be explored at low frequencies for controlling and storing charges and electric energy in dielectric composites. Hence, we refer to this class of dielectric nanocomposites presented in this chapter as dielectric metamaterials.
-
4 Polymer/nanofiller composites
- + Show details - Hide details
-
p.
109
–155
(47)
This chapter firstly summarized the recent utilization of different kinds of nanofillers with various functionalities and morphologies and their surface modification methods in dielectric composites. Besides using fillers to increase k of polymer composites, a new design concept, in which the introduction of nano filler with a moderate k and a wide bandgap to inhibit the leakage current and reduce energy loss, is highlighted. Second, the recent progress on the polymer/ nanofiller composite films with heterogeneous and electrically topologic structures beyond simple 0-3 composites is described and discussed. The design paradigm aims to currently improve k value and breakdown strength of the resulting polymer/ nanofiller composites through the elegant combination of different polymers and/or fillers with complementary functionalities. The control of the organic -inorganic interface properties allows tailoring of the physical and chemical compatibility of the filler and polymer phases. The architecture of topologically arranged nanofillers induces anisotropic dielectric responses and electric field distributions in the polymer/nanofiller composites.
-
5 High-temperature polymer-based dielectrics for electrostatic energy storage
- + Show details - Hide details
-
p.
157
–199
(43)
Dielectric materials are the core elements of dielectric capacitors that are one of the most important passive components in advanced electrical and electronic systems. dielectric performance deteriorates significantly under elevated temperature and the maximum operating temperature of BOPP is only 105 °C which cannot meet the urgent demands for film capacitors operating under harsh environment. For example, the ambient temperature of power inverters near the engines in hybrid electric vehicles (HEVs) exceeds 140 °C. To maintain the regular work of DC/AC inverters, a secondary cooling system is introduced into present HEVs, bringing extra volume and weight. The development of wide-bandgap semiconductors, such as silicon carbide (SiC) and gallium nitride (GaN), is expected to bring about the revolution of electronic devices, enabling higher operating temperature of over 150 °C. The dielectric performance of these polymers can be further improved by modifying the molecular structures. In addition, combination of polymer and inorganic nanomaterials to form the nanocomposites may overcome some common limitations of polymer dielectrics and obtain favorable features for high-temperature applications. The fundamental theories on the relationship between the chemical structures and thermal stability or dielectric performance of polymers, which are essential to the rational design of high-T g polymer dielectrics, are largely unexplored
-
6 Design and simulations of capacitor dielectrics by phase-field computations
- + Show details - Hide details
-
p.
201
–235
(35)
In this chapter, we will give a comprehensive introduction on the theory of phase -field simulation, and summarize its recent applications on interpreting dielectric behaviors observed in experiment, and instructing experimental efforts toward advanced dielectrics.
-
7 Rational design on polymer dielectrics
- + Show details - Hide details
-
p.
237
–252
(16)
In this chapter, the polymer dielectric for the energy storage polymer capacitor applications is mainly discussed. The structure of a polymer capacitor is a stack of polarizable dielectric materials between two conductive metal plates. It can store energy and has the advantage of fast response, compared with lithium batteries, which can quickly release stored energy.
-
8 Inorganic dielectrics for high-energy-density capacitors
- + Show details - Hide details
-
p.
253
–276
(24)
The dielectric materials are the heart of the energy storage capacitors, playing a determining role in the performance of the dielectric energy storage devices.The dielectrics with high energy density and efficiency are essential for the high -power energy system
-
9 Ceramic dielectrics for microwave communication
- + Show details - Hide details
-
p.
277
–320
(44)
Ceramic microwave dielectrics shows that large progress has been made in the past more than 50 years. A series of ceramic dielectric materials have been developed and commercialized. Some new concepts like ULTCC material and cold sintering process have been developed. These new materials and new process make it possible to promote the application of ceramic dielectrics in more emerging fields. While, although large amount of materials with different element compositions, phase compositions, forms and microstructures have been explored, to develop dielectric materials with low dielectric loss and near -zero temperature coefficient for higher frequency applications is still the main theme of ceramic microwave dielectric study. It is still difficult to establish the composition - structure -property relationship to guide new material design due to the complicity of the impact factors of dielectric performance. But, the huge experimental and theoretical data on microwave dielectric ceramics make it possible for researchers to use the emerging technology like machine learning to explore high-performance new microwave dielectric materials.
-
10 Ceramic dielectrics for MLCCs
- + Show details - Hide details
-
p.
321
–393
(73)
Multilayer ceramic capacitors (MLCCs), characterized by their high capacitance and compactness, are in high demand due to the rapid development of modern electronics. Section 10.2 of this chapter begins with a discussion of the size effect for grain sizes down to 5 nm . In Section 10.3 of this chapter, the chemical coating method for the preparation of core-shell structured dielectric ceramics is reviewed. In Section 10.4 of this chapter, the most recently reported MLCCs with greatly improved energy-storage densities are reviewed. Finally, some conclusions and considerations for the prospects for MLCCs were drawn.
-
11 Future prospects: polymer part
- + Show details - Hide details
-
p.
395
–402
(8)
Driven by an urgent need for the development of high-power energy storage devices, both scientists and engineers pay increasing attention to the electrostatic capacitor, which possesses the highest power density among various types of energy storage technologies [1-5]. As the passive electronic component, electrostatic capacitor stores and releases electrical energy through rapid electric field induced polarization and depolarization. In its simplest form, electrostatic capacitor consists of two electrically conductive plates and a dielectric layer. Among various types of electrostatic capacitors, the film capacitor using an insulating polymeric film as the dielectric layer is highly desirable in the electric power systems due to the high electrical breakdown strength (Eb) of the polymeric film. However, the miniaturization of the power system and the realization of compact energy storage technologies are severely hindered by the low volumetric energy density and operating temperature of the polymeric film. For example, the energy density of biaxially oriented polypropylenes (BOPP), the best commercially available film with a market share of 50%, is merely 1-2 J/cm 3 , which is at least one order of magnitude lower than those of electrochemical supercapacitors and batteries. Additionally, the highest operating temperature for BOPP film is limited to 105 °C due to the low melting temperature of PP resin. As a result, an extra cooling system is required to decrease the environmental temperature so that the BOPP film capacitor can be operated at a safe temperature, accordingly leading to the dramatic increases in the weight, volume and cost of the power system. Therefore, improvements in the energy density and operating temperature of the polymeric film have become essential for the development of advanced film capacitors.
-
12 Future prospects: ceramic part
- + Show details - Hide details
-
p.
403
–416
(14)
Dielectric capacitors, featured in high charge -discharge rate, low cost and long cyclic lifetime, play an important role in electrical and electronic applications. Among various dielectrics, ceramics and polymers are mainstream materials dominating the dielectric capacitors. Many modern applications including hybrid vehicles and power converters require the capacitors to work under high temperature, which poses challenges for polymer capacitors with low melting/ glass -transition temperature [1], while ceramic capacitors can be operated at much higher temperature than polymer capacitors due to the inorganic nature of ceramics. Although the ceramic capacitors are suitable for high -temperature energy storage applications, there are still a lot of challenges such as low energy density, which will be discussed in details in Section 12.2. The perspectives and future development trends for dielectric capacitors are proposed.
-
Back Matter
- + Show details - Hide details
-
p.
(1)