High-Energy Density Nancomposite Capacitor

Abstract

A composite film having a high dielectric permittivity engineered particles dispersed in a high breakdown strength polymer material to achieve high energy density.

Claims

1. A method for forming a composite film comprising: a. forming a plurality of particles of high dielectric permittivity ceramic filler, said high dielectric permittivity ceramic filler having a core-shell structure, a core of said core-shell structure having a different composition than a shell of said core-shell structure, said shell heated after being coated on said core; b. dispersing a plurality of said particles of said high dielectric permittivity ceramic filler having said one or more functional groups into a polymer material; and, c. solution casting said polymer material having said plurality of said coated particles of said high dielectric permittivity ceramic filler into a film to form said composite film.

2. The method as defined in claim 1, wherein said polymer material includes polar groups.

3. The method as defined in claim 1, wherein said shell is a dielectric material that has a breakdown strength that is at least three times that of said material used to form said core.

4. The method as defined in claim 1, wherein said particles of said high dielectric permittivity ceramic filler have a particle size of less than 1 micron.

5. The method as defined in claim 1, wherein said particles of said high dielectric permittivity ceramic filler have a particle size of about 10 nanometer to less than about 1 μm.

6. The method as defined in claim 1, wherein said particles of said high dielectric permittivity ceramic filler have a particle size of about 50-450 nanometers.

7. The method as defined in claim 1, wherein said particles of said high dielectric permittivity ceramic filler have a particle size of less than about 200 nanometers.

8. The method as defined in claim 1, wherein said shell has a coating thickness of at least about 10 Å and less than 1 μm.

9. The method as defined in claim 1, wherein said shell has a coating thickness of less than 20 nanometer.

10. The method as defined in claim 1, wherein said core of said high dielectric permittivity ceramic filler includes a high dielectric material, said shell includes a high breakdown strength material, said core is at least partially encapsulated by said shell.

11. The method as defined in claim 8, wherein said high dielectric material includes one or more materials selected from the group consisting of BaTiO.sub.3, (Pb(Zr.sub.xTi.sub.1-x)O.sub.3), Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3—PbTiO.sub.3, CaCu.sub.3Ti.sub.4O.sub.12, TiO.sub.2, BaSrTiO.sub.3, and Ba.sub.0.8Pb.sub.0.2(Zr.sub.0.12Ti.sub.0.88)O.sub.3.

12. The method as defined in claim 1, wherein said shell includes one or more materials selected from the group consisting of Al.sub.2O.sub.3, SiO.sub.2, Si.sub.3N.sub.4, MgO, aluminosilicates, mica, and diamond.

13. The method as defined in claim 1, wherein said high dielectric material includes doped BaTiO.sub.3 and said shell includes one or more compounds selected form the group consisting of Al.sub.2O.sub.3, MgO and SiO.sub.2.

14. The method as defined in claim 1, wherein said thickness of said shell is less than said particle size of said core.

15. The method as defined in claim 1, wherein said composite film has a greater dielectric constant than a dielectric constant of said polymer material and any polymer included in said polymer material that is used to form said composite film, said composite film has a greater breakdown strength than a breakdown strength of any of said high dielectric permittivity ceramic filler in said composite film.

16. The method as defined in claim 1, wherein said high dielectric permittivity ceramic filler in said composite film has one or more properties selected from the group consisting of a) a plurality of different particle sizes of said high dielectric permittivity ceramic filler, b) said high dielectric permittivity ceramic filler formed of particles that have been calcined at different temperatures, and/or c) said high dielectric permittivity ceramic filler formed of particles formed of different materials.

17. The method as defined in claim 1, wherein a dielectric performance, dielectric permeability, energy storage performance, and combinations thereof of said composite film is achieved by adjusting a crystal structure, a particle size, or combinations thereof of said high dielectric permittivity ceramic filler, said adjusting of said crystal structure, a particle size, or combinations thereof is achieved by a) calcining a plurality of said high dielectric permittivity ceramic filler at different temperatures for inclusion in said polymer material, b) incorporating different composition high dielectric permittivity ceramic filler in said polymer material, c) incorporating a plurality of different particle sizes of said high dielectric permittivity ceramic filler in said polymer material, and any combination of a), b), and c).

18. The method as defined in claim 1, wherein said polymer material includes one or more compounds selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF copolymers such as trifluoroethylene (P(VDF-TrFE)), hexafluoropropylene (P(VDF-HFP)) and chlorotrifluoroethylene (P(VDF-CTFE)) as well as terpolymers such as poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), polytetrafluoroethylene (PTFE), polyimide (PI), Teflon™, polyethylene naphthalate (PEN), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylenimine (PEI), and polyarylsulfones (PSU).

19. The method as defined in claim 1, including the step of applying one or more functional groups to an outer surface of said particles of said high dielectric permittivity ceramic filler, said one or more functional groups includes one or more compounds selected from the group consisting of an amine group, a hydroxyl group, a phosphonate group, a silyl group, and a carboxylic group.

20. The method as defined in claim 1, wherein one or more of said particles of said high dielectric permittivity ceramic filler in said polymer material has a greater relative permittivity than said polymer material.

21. The method as defined in claim 1, wherein all of said particles of said high dielectric permittivity ceramic filler in said polymer material has a greater relative permittivity than said polymer material.

22. The method as defined in claim 1, wherein said polymer material has a greater breakdown strength than one or more of said particles of said high dielectric permittivity ceramic filler in said polymer material.

23. The method as defined in claim 1, wherein said polymer material has a greater breakdown strength than any of said particles of said high dielectric permittivity ceramic filler in said polymer material.

24. The method as defined in claim 1, wherein said composite film has a dielectric constant of at least 150% a dielectric constant of any polymer in said polymer material.

25. The method as defined in claim 1, wherein said high dielectric permittivity ceramic filler comprises about 1 vol. % to 95 vol. % of said composite film.

26. The method as defined in claim 1, wherein said high dielectric permittivity ceramic filler comprises about 5-25 vol. % of said composite film.

27. The method as defined in claim 1, wherein said core of said high dielectric permittivity ceramic filler is calcined at a temperature of about 800° C. to about 1300° C. prior to applying said shell to said core.

28. The method as defined in claim 1, including the step of post-heat treating said calcined core, said step of post-heat treating includes one or more processes selected from the group consisting of quench in water, quench in ice water, quench in liquid nitrogen, and heat above melting point.

29. The method as defined in claim 1, wherein said step of post-heat treating said calcined core is used to improve breakdown strength of said high dielectric permittivity ceramic filler, achieve higher energy density of said high dielectric permittivity ceramic filler, or combinations thereof.

30. The method as defined in claim 1, including the step of stretching or aligning said composite film to achieve higher energy density of said composite film, said step of stretching or aligning includes one or more processes selected from the group consisting of uniaxial stretching, and biaxial stretching.

31. The method as defined in claim 1, wherein a thickness of said composite film is at least about 1 μm.

32. The method as defined in claim 1, wherein a thickness of said composite film is about 1 μm to 1 mm.

33. The method as defined in claim 1, wherein said composite film is included in a device or component selected from the group consisting of power pulse devices, energy storage devices, inverters, converters, motors, DC bus capacitors, and high-power lighting.

34. The method as defined in claim 1, wherein said composite film is included in a device or component selected from the group consisting of radar devices, lasers, rail guns, high-power microwave devices, defibrillators, and pacemakers.

35. A composite film formed by the method as defined in claim 1.

36. A power pulse device, an energy storage device, inverter, converter, motor, DC bus capacitor, or high-power lighting that includes a composite film formed by the method as defined in claim 1.

37. A composite film comprising a polymer material that includes a plurality of particles of high dielectric permittivity ceramic filler, said high dielectric permittivity ceramic filler having a core-shell structure, a core of said core-shell structure having a different composition than a shell of said core-shell structure.

38. A high-power density dielectric composite, said composite includes: a high dielectric strength polymer material which can include polar groups; a surface functionalized core-shell high dielectric permittivity ceramic filler having an average particle size between 10 nm and 500 nm, said high dielectric permittivity ceramic filler having a surface-functionalized core-shell structure, containing a core of said core-shell structure having a different composition than a shell of said core-shell structure, where said shell is formed of a dielectric material having a dielectric breakdown strength of at least three times a breakdown strength of said material forming said core; and wherein said high dielectric permittivity ceramic filler constitutes greater than 3 vol. % and less than 25 vol. % of said composite and a content of said high dielectric permittivity ceramic filler in said composite does not reach a percolation threshold in said composite film.

39. The high-power density composite as defined in claim 38, wherein said high dielectric permittivity ceramic filler has a dielectric constant in bulk form of greater than 10,000 over a temperature range of at least room temperature to 100° C.

40. The high-power density composite as defined in claim 38, wherein said high dielectric permittivity ceramic filler has a broad curie point range.

41. The high dielectric composite as in claim 38, wherein the dielectric filler has an average particle size between 30 and 80 nm.

42. The high-power density composite as defined in claim 38, wherein said composite film has a film energy storage density that is greater than 10 J/cc.

43. The high-power density composite as defined in claim 38, wherein said composite film has a film energy storage density that is greater than 20 J/cc.

44. The high-power density composite as defined in claim 38, wherein said high dielectric ceramic filler includes one or more materials selected from the group consisting of doped BaTiO.sub.3, (Pb(Zr.sub.xTi.sub.1-x)O.sub.3), Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3—PbTiO.sub.3, CaCu.sub.3Ti.sub.4O.sub.12, TiO.sub.2, BaSrTiO.sub.3, and Ba.sub.0.8Pb.sub.0.2(Zr.sub.0.12Ti.sub.0.88)O.sub.3, and wherein said material can be heat treated at a temperature to achieve optimum performance.

45. The high-power density composite as defined in claim 38, wherein said polymer material includes one or more compounds selected from the group consisting of polyvinylidene fluoride (PVDF), PVDF copolymers such as trifluoroethylene (P(VDF-TrFE)), hexafluoropropylene (P(VDF-HFP)) and chlorotrifluoroethylene (P(VDF-CTFE)) as well as terpolymers such as poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), polytetrafluoroethylene (PTFE), polyimide (PI), Teflon™, polyethylene naphthalate (PEN), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylenimine (PEI), and polyarylsulfones (PSU).

46. The high-power density composite as defined in claim 38, wherein said shell has a coating thickness of at least about 10 Å and less than 100 nm.

47. The high-power density composite as defined in claim 38, wherein said shell has an average coating thickness between 3 and 15 nanometers.

48. The high-power density composite as in claim 47, wherein the shell is produced using a process selected from chemical vapor deposition, atomic layer deposition, sol-gel coating, or solution coating.

49. The high-power density composite as defined in claim 38, wherein said high dielectric material includes one or more materials selected from the group consisting of doped BaTiO.sub.3, (Pb(Zr.sub.xTi.sub.1-x)O.sub.3), Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3—PbTiO.sub.3, CaCu.sub.3Ti.sub.4O.sub.12, TiO.sub.2, BaSrTiO.sub.3, and Ba.sub.0.8Pb.sub.0.2(Zr.sub.0.12Ti.sub.0.88)O.sub.3.

50. The high-power density composite as defined in claim 38, wherein said shell includes one or more materials selected from the group consisting of Al.sub.2O.sub.3, SiO.sub.2, Si.sub.3N.sub.4, MgO, aluminosilicates, mica, and diamond.

51. The high-power density composite as defined in claim 38, wherein a coating thickness of said coating on said outer surface of said high dielectric permittivity ceramic filler is about 3 Å to 80 nm.

52. The high-power density composite as defined in claim 38, wherein an said outer surface of said high dielectric permittivity ceramic filler includes one or more functional groups on said outer surface of said high dielectric permittivity ceramic filler, said functional groups include one or more groups selected from an amine group, a hydroxyl group, a phosphonate group, a silyl group, and a carboxylic group.

53. The high-power density composite as defined in claim 38, wherein said composite further includes an additional dielectric insulator particles, said additional dielectric insulator particles have a size of less than 150 nm, said additional dielectric insulator particles include one or more materials selected from the group consisting of MgO, Al.sub.2O.sub.3, SiO.sub.2 and other insulators.

54. The high-power density composite as defined in claim 53, wherein said additional dielectric insulator particles have a surface functionalization, which surface functionalization can primarily include an organosilane.

55. The high-power density composite as defined in claim 53, wherein said additional dielectric insulator particles have a particle size of less 50 nm, and typically less than 20 nm.

56. The high-power density composite as defined in claim 53, wherein said additional dielectric insulator particles constitute about have a 0.2 vol. % to 2 vol. % of said composite film.

57. The high-power density film composite as defined in claim 38, wherein said composite has a dielectric constant that is at least 150% of a value of a dielectric constant of said polymer material, and typically said composite has a dielectric constant that is at least 200% of a value of a dielectric constant of said polymer material.

58. The high-power density composite as defined in claim 38, wherein said composite has a breakdown strength that is at least 80% of the breakdown strength of said polymer material, and typically said composite breakdown strength that is at least 90% of the breakdown strength of said polymer material.

59. The high-power density composite as defined in claim 38, wherein a concentration of said high dielectric ceramic filler in said composite is different at an outer surface region of said composite than compared to an average concentration of said high dielectric ceramic filler in said composite.

60. The high-power density composite as defined in claim 38, wherein said concentration of said high dielectric ceramic filler in said composite is less at an outer surface region of said composite than compared to an average concentration of said high dielectric ceramic filler in said composite.

61. The high-power density composite as defined in claim 38, wherein said core is calcined at a temperature to optimize or tune a structure, a particle size, or combinations thereof of said core.

62. The high-power density composite as defined in claim 61, wherein said core is calcined in a controlled atmosphere such as in oxygen partial pressure.

63. The high-power density composite as defined in claim 38, wherein said composite is in the form of a film.

64. The high-power density film as defined in claim 61, wherein a thickness of said composite film is 2-200 microns, said thickness of said film being designed to allow operating at 30-60% of the effective film breakdown strength at a selected operating voltage.

65. The composite film as in claim 37 in the form of printed layers, such as those used for passive devices.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0033] FIG. 1 illustrates the XRD patterns of doped BaTiO.sub.3 calcined at different temperatures showing that the crystal structures vary with calcining temperature, wherein the top line is at the temperature 1200° C., the second line is at the temperature 1150° C., the third line is at the temperature 1000° C., and the fourth and bottom line is at the temperature 950° C.;

[0034] FIG. 2 illustrates the ability to control the dielectric constant of the nanocomposites by the incorporation of 7.5 vol % BaTiO.sub.3 particles, which are calcined at different temperatures;

[0035] FIG. 3 illustrates modified nanoparticles creating a gradient interface between a filler and a polymer material to achieve high-energy density nanocomposite;

[0036] FIG. 4 illustrates the hierarchical structure of (a) a TEM picture; and (b) a doped BaTiO.sub.3 nanoparticle developed for ultra-high-energy density nanocomposite capacitors;

[0037] FIG. 5 illustrates a Weibull distribution of the observed dielectric breakdown strength of a dielectric nanocomposite film including doped nanoparticles with gradient interface; and,

[0038] FIG. 6 illustrates the energy density (19.6 J/cc) calculated from typical D-E loop of nanocomposites dielectric nanocomposite film (a); and red arrows illustrating how the nanocomposite films failed under high electric field (b).

DETAILED DESCRIPTION OF INVENTION

[0039] The present invention relates in general to high-energy density nanocomposite capacitors that include nanoceramic filler in a polymer material. The invention also relates to a nanocomposite having a high dielectric permittivity nanoengineered particle dispersed into a high breakdown strength polymer material to achieve high-energy density. The invention also related to nanocomposite films and a method for making such films. The nanocomposite films are formed in the following process: 1) create high dielectric permittivity ceramic fillers with core-shell structure and 2) modify the surface with functional groups. The resulted engineered nanoparticles are dispersed into the polymer material; the mixture is then solution cast into the thin nanocomposite films.

[0040] The dielectric permittivity of the nanocomposite can be improved by incorporating high dielectric permittivity fillers into a polymer material. The invention is directed to a method to prepare doped nanoceramic fillers calcined at different temperatures to tune the dielectric properties of the nanocomposites. The novel fabrication method is generally comprised of the steps of 1) ball mill the powder, and 2) calcine the powder at different temperatures. In the present invention, high-energy density nanocomposite capacitor films can be based on the doped BaTiO.sub.3 particles ((Ba.sub.0.9575Nd.sub.0.0025Ca.sub.0.04)[Ti.sub.0.815Mn.sub.0.0025Y.sub.0.18].sub.0.997O.sub.3) that have a dielectric constant around 33,000 at room temperature which is about ten times higher than conventional BaTiO.sub.3 particles.

[0041] Doped barium titanate with the formula Ba.sub.0.9575Nd.sub.0.0025Ca.sub.0.04)[Ti.sub.0.815Mn.sub.0.0025Y.sub.0.18].sub.0.997O.sub.3 was produced by ball milling BaCO.sub.3, Nd.sub.2O.sub.3, CaCO.sub.3, TiO.sub.2, MnCO.sub.3, and Y.sub.2O.sub.3 for 24 hours. The mixed powder was then calcined at high temperature, such as 800° C. to 1300° C. (and all values therebetween). It is observed that different temperature calcining yields different crystal structure and particle size of doped materials. In this non-limiting composition, the nanocomposites with doped BaTiO.sub.3 nanoparticles calcined at 900° C. have the highest dielectric permittivity. Other similar compositions will have a different optimum calcining temperature.

[0042] While this non-limiting example was directed to BaTiO.sub.3, it is understood that other high dielectric materials can be chosen, doped, coated and activated for the same purpose. These materials include any selected ferroelectric materials such as lead zirconate titanate (Pb(Zr.sub.xTi.sub.1-x)O.sub.3), Pb(Mg.sub.1/3Nb.sub.2/3)O.sub.3—PbTiO.sub.3 (PMN-PT), BaTiO.sub.3 and so on, or any other high dielectric materials, for example, calcium copper titanate (CaCu.sub.3Ti.sub.4O.sub.12). As defined herein, a high dielectric material has a dielectric constant (i.e., relative permittivity) at the frequency of 1 kHz at room temperature (e.g., 70° F.) of at least 100, typically at least 300, and more typically at least 500 (e.g., 100-100,000 and all values and ranges therebetween).

[0043] Assuming there is no loss, the energy density of the capacitor can be expressed by the following equation: U=κE.sup.2/2, where U is energy density, κ is the dielectric permittivity and E is the dielectric breakdown strength. The energy density is a square relationship to the breakdown strength, while it is linear to the dielectric permittivity of the nanocomposite. However, while current nanocomposites improve the dielectric permittivity of the capacitor, the gains come at the expense of the breakdown strength, which limits the ultimate performance. One of the main reasons of this limitation is that these high dielectric permittivity fillers have low breakdown strength resulting in a low-energy density capacitor.

[0044] The invention is directed to improving the breakdown strength of the nanocomposite by creating gradient interfaces between the polymer material and the filler. First, the core-shell structure dielectric particle is designed. The shell materials typically have high dielectric permittivity, and the core materials are chosen from many that have exceptional high voltage breakdown (particularly in thin films) such as Al.sub.2O.sub.3, SiO.sub.2, mica, diamond and so on. This core-shell structure not only provides high dielectric permittivity, but also improves the breakdown strength of the shell. Also, the shell structure can improve the high charge storage capability at the dielectric-dielectric interfaces. The thickness of the shell can range from 10 Å to 500 nm, and in some cases from 5 Å to 1000 nm (and all values therebetween).

[0045] Following the encapsulation, hierarchical particles are functionalized with different terminated groups to create the gradient interface between the polymer material and the filler. The gradient functional group not only improves the compatibility of the filler with the polymer material, but also improves the breakdowns strength of the nanocomposite. The terminated group can be any group to create the bond between the polymer material and filler, such as, but not limited to, amine group, hydroxyl group or others selected from phosphonate group, a silyl group, or a carboxylic group and others. The process for coating the one or more functional groups on the outer surface of the shell is non-limiting. Generally the thickness of the coating or layer of the one or more functional groups on the outer surface of the shell is about 1 Å to 200 nm.

[0046] By incorporating these hierarchical particles into a polymer material, the invention provides a novel method to prepare a high-energy density nanocomposite capacitor. The polymers can be selected from many dielectric films including polyvinylidene fluoride (PVDF), PVDF copolymers such as trifluoroethylene (P(VDF-TrFE)), hexafluoropropylene (P(VDF-HFP)) and chlorotrifluoroethylene (P(VDF-CTFE)) as well as terpolymers such as poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene) (P(VDF-TrFE-CFE)), polytetrafluoroethylene (PTFE), polyimide (PI), Teflon™, polyethylene naphthalate (PEN), polypropylene (PP), polycarbonate (PC), polystyrene (PS), polyphenylene sulfide (PPS), polyether ether ketone (PEEK), polyethylenimine (PEI), polyarylsulfones (PSU), and others. The nanofillers can be dispersed into the polymer solution; the nanocomposite films can then be solution cast into films. It is understood by one skilled in the art that these films can be made by extrusion, blown film techniques, calendaring and other film preparation techniques. The films can then be heat treated to reach high breakdown strength and high dielectric permittivity to reach high-energy density.

[0047] The following example is directed to tape casting technology that provides a means for producing large quantities of thin film materials at a low cost. The system is easily scalable and ideal for processing material for capacitors, which require high-quantity, low-cost production.

Examples

[0048] Doped barium titanate with the formula Ba.sub.0.9575Nd.sub.0.0025Ca.sub.0.04)[Ti.sub.0.815Mn.sub.0.0025Y.sub.0.18].sub.0.997O.sub.3 was produced by ball milling BaCO.sub.3, Nd.sub.2O.sub.3, CaCO.sub.3, TiO.sub.2, MnCO.sub.3, and Y.sub.2O.sub.3 for 24 hours. Different calcining temperatures will yield different final structures of the powder, thereby leading to a change in the dielectric properties of the materials. FIG. 1 illustrates the XRD patterns of the samples calcined at different temperatures (900° C., 1000° C., 1050° C., and 1200° C.). As illustrated in FIG. 1, peaks corresponding to BaTiO.sub.3 as well as peaks corresponding to other doped ceramic phases are illustrated. The peaks around 25 and 63 degrees suggest that there was some phase change after 1050° C. during the calcining process. This phase change was likely brought on by doping with many differently sized elements (Ca, Mn, Y and Nd). As illustrated in FIG. 1, there is a slightly different final structure for doped BaTiO.sub.3 that was calcined at different temperatures.

[0049] The temperatures (950° C., 1000° C., 1150° C. and 1200° C.) were used to illustrate the effect of the BaTiO.sub.3 particles calcined at different temperatures on the dielectric and energy storage properties of the nanocomposites. FIG. 2 is a graph illustrating the dielectric constant of the nanocomposites with the incorporation of 7.5 vol % BaTiO.sub.3 ceramic fillers, which are calcined at different temperatures (950° C., 1000° C., 1150° C. and 1200° C.). It is showed that the dielectric constant of the nanocomposite is influenced by the filler nanoparticles, which are calcined at different temperatures. By adjusting the structure and particle of the ceramic fillers in the polymer material, the dielectric constant of the composites can be tuned.

[0050] FIG. 3 schematically illustrates the hierarchical structure of ceramic fillers in the polymer material to create a high-energy density nanocomposite capacitor. More specially, high dielectric permittivity ceramic filler is designed as a core-shell structure. The core has a high dielectric permittivity, while the shell materials have high breakdown strength. In a representative example, particle cores occupy at least about 50% (e.g., 50-99% vol. % and all values and ranges therebetween) of the total of the volume in core-shell ceramic fillers; however, this is not required. Representative materials that can be used to form the core-shell structure can be any high dielectric permittivity materials (e.g., barium titanate, lead zirconium titanate, CCTO, etc.). The shell is a thin film with high breakdown strength materials to protect the high dielectric core structure. Representative materials can be any high-breakdown strength materials (e.g., Al.sub.2O.sub.3, SiO.sub.2, mica, diamond and others). The particle cores can have a variety of shapes (e.g., spherical, elongated, or irregular), and a variety of sizes. The particle cores have a relatively small size, usually less than about 100 μm (e.g., 0.05-500 μm and all values and ranges therebetween), and the thickness of the film is generally between about 0.1 nm to 1 μm (and all values and ranges therebewteen).

[0051] FIG. 4 illustrates an example to create a gradient interface between the filler and polymer material, as well as a core-shell structure nanoparticle. The nano-engineered particle designed for the nano-laminated dielectric particle is illustrated in FIG. 4a. In this non-limiting example, high dielectric permittivity doped BaTiO.sub.3 nanoparticles with around 100 nm were chosen as core materials. The coating materials have exceptional high voltage breakdown (particularly in thin films), as well as providing for high-charge storage at the dielectric-dielectric interfaces. The sol-gel process uses an ultrasonic horn to disperse BaTiO.sub.3 in anhydrous ethanol, a solution of aluminum isopropoxide in anhydrous ethanol was then added to the BaTiO.sub.3 dispersion, and was again blended ultrasonically to fully disperse and coat the particles. This step was followed by the addition of deionized water to the mixture. The aluminum isopropoxide, which clings to the surface of the BaTiO.sub.3, undergoes a hydrolysis reaction and leaves aluminum oxide on the surface of the particles. The particles were then dried in air and calcined to densify the Al.sub.2O.sub.3 surface coating. This method successfully coated the doped barium titanate with 10 nm Al.sub.2O.sub.3 film observed in high-resolution transmission electron microscopy (HRTEM), as shown on the FIG. 4b.

[0052] In order to prepare high-energy nanocomposite films, these nanoparticles can be dispersed in the dimethylformamide (DMF)/polyvinylidene fluoride (PVDF) solution by high-power horn solicitation. The entire process developed by this invention (encapsulation, surface function, high-power horn dispersion) stabilizes the particles in the solution for about one week, and sometimes more. Nanocomposite films were cast by using a solution casting method. The breakdown strength was measured by using an electrostatic pull-down method with Weibull distribution analysis as shown in FIG. 5. Pull-down between the conductive substrate and a brass dome typically occurs at an electrical field of 10 MV/m and is maintained until breakdown occurs over the test area. The pull-down method was chosen over a point-contact method to avoid any mechanical force that might cause premature breakdown at the contact point. Breakdown testing was performed in silicon oil to avoid electric arcing and was performed using a high voltage supply by sweeping the applied voltage until sample failure, as evidenced by spurious current changes. Every sample was tested for at least 15 data points. Dielectric breakdown strength was then extracted from a fit using Weibull failure statistics across at least 15 tests per sample. Following the procedure developed in this invention, the dielectric strength of the nanocomposites can reach 442 MV/m. It should be noticed that the breakdown strength of the nanocomposites reported here is much higher than that of any composites reported in current literature.

[0053] Energy density is identified through the measurement of the discharge energy from the sample when subjected to a unipolar electric field. The electric displacement-electric field (D-E) loops of the capacitor were measured using a Sawyer-Tower circuit, which allowed for the direct computation of the energy density U=∫EdD (illustrated in FIG. 6a). The polarization loop was measured with increasing electric field until breakdown occurred and the maximum energy could be recorded. The graph on the left side of FIG. 6 shows the typical D-E loops of the nanocomposite films. From the graph, it can be calculated that the nanocomposite film can achieve an energy density 19.6 J/cc. FIG. 6b also demonstrates the self-healing ability of the metalized nanocomposite film. Under a high electric field, the current vaporizes the thin electrodes on the films in the immediate vicinity of the current flow (red arrow). This means that the local breakdown of the film nanocomposite will not influence the work status of the capacitor, and will help to greatly extend the life of the capacitor and the equipment in which it is installed.

[0054] It will thus be seen that the objects set forth above, among those made apparent from the preceding description, are efficiently attained, and since certain changes may be made in the constructions set forth without departing from the spirit and scope of the invention, it is intended that all matter contained in the above description and shown in the accompanying drawings shall be interpreted as illustrative and not in a limiting sense. The invention has been described with reference to preferred and alternate embodiments. Modifications and alterations will become apparent to those skilled in the art upon reading and understanding the detailed discussion of the invention provided herein. This invention is intended to include all such modifications and alterations insofar as they come within the scope of the present invention. It is also to be understood that the following claims are intended to cover all of the generic and specific features of the invention herein described and all statements of the scope of the invention, which, as a matter of language, might be said to fall there between. The invention has been described with reference to the preferred embodiments. These and other modifications of the preferred embodiments as well as other embodiments of the invention will be obvious from the disclosure herein, whereby the foregoing descriptive matter is to be interpreted merely as illustrative of the invention and not as a limitation. It is intended to include all such modifications and alterations insofar as they come within the scope of the appended claims.