Zhongbin Pan

Excellent energy density of polymer nanocomposites containing BaTiO3@Al2O3 nanofibers induced by moderate interfacial area

Inorganic/polymer nanocomposites, using one-dimensional (1D) core–shell structure BaTiO3@Al2O3 nanofibers (BT@Al2O3 nfs) as fillers and poly(vinylidene fluoride) (PVDF) as the polymer matrix, have been prepared. The core–shell structure BT@Al2O3 nfs have been synthesized via coaxial electrospinning. The breakdown strength (Eb) and discharged energy density of the nanocomposites can be significantly improved by creating an insulating Al2O3 shell layer with moderate dielectric constant on the surfaces of BT nanofibers to form a moderate interfacial area. The Al2O3 shell layer could effectively confine the mobility of charge carriers, which reduces energy loss by reducing the Maxwell–Wagner–Sillars (MWS) interfacial polarization and space charge polarization between the fillers and the polymer matrix. As a result, the nanocomposite films filled with 5 vol% BT@Al2O3 nfs exhibit a excellent discharge energy density of 12.18 J cm−3 at 400 MV m−1, which is ≈254% over bare PVDF (4.8 J cm−3 at 350 MV m−1) and ≈1015% greater than the biaxially oriented polypropylenes (BOPP) (≈1.2 J cm−3 at 640 MV m−1). The work here indicates that this promising state-of-the-art method of preparing high energy density nanocomposites can be used in the next generation of dielectric capacitors.

High-Energy-Density Polymer Nanocomposites Composed of Newly Structured One-Dimensional BaTiO3@Al2O3 Nanofibers

Flexible electrostatic capacitors are potentially applicable in modern electrical and electric power systems. In this study, flexible nanocomposites containing newly structured one-dimensional (1D) BaTiO3@Al2O3 nanofibers (BT@AO NFs) and the ferroelectric polymer poly(vinylidene fluoride) (PVDF) matrix were prepared and systematically studied. The 1D BT@AO NFs, where BaTiO3 nanoparticles (BT NPs) were embedded and homogeneously dispersed into the AO nanofibers, were successfully synthesized via an improved electrospinning technique. The additional AO layer, which has moderating dielectric constant, was introduced between BT NPs and PVDF matrixes. To improve the compatibility and distributional homogeneity of the nanofiller/matrix, dopamine was coated onto the nanofiller. The results show that the energy density due to high dielectric polarization is about 10.58 J cm-3 at 420 MV m-1 and the fast charge-discharge time is 0.126 μs of 3.6 vol % BT@AO-DA NFs/PVDF nanocomposite. A finite element simulation of the electric-field and electric current density distribution revealed that the novel-structured 1D BT@AO-DA NFs significantly improved the dielectric performance of the nanocomposites. The large extractable energy density and high dielectric breakdown strength suggest the potential applications of the BT@AO-DA NFs/PVDF nanocomposite films in electrostatic capacitors and embedded devices.

Multilayer hierarchical interfaces with high energy density in polymer nanocomposites composed of BaTiO3@TiO2@Al2O3 nanofibers

Polymer nanocomposites with high energy density have potential applications in advanced electronics and electric power systems. The inevitable electrical mismatch between nanofillers and the polymer matrix could compromise the energy storage capability and dielectric properties of the polymer nanocomposites. Herein, novel core–double-shell structured BaTiO3@TiO2@Al2O3 nanofibers (BT@TO@AO NFs) were prepared via a one step method, and were incorporated into poly(vinylidene fluoride) (PVDF). The novel design of gradually varying the multilayer hierarchical interface was advantageous to alleviating the local electric field and electric current density intensification in the filler/polymer system. As compared with the nanocomposites loaded with BT NFs and BT@TO NFs, the nanocomposites filled with BT@TO@AO NFs exhibit much decreased dielectric loss, enhanced breakdown strength, and suppressed leakage current densities. Simulations were carried out to verify that the new core–double-shell structure significantly enhances the breakdown strength and energy density. As a result, the nanocomposite films loaded with 3.6 vol% BT@TO@AO NFs show a maximum energy storage density (Ue) of 14.84 J cm−3 at 450 MV m−1, which is about twelve times greater than that of biaxially oriented polypropylene (BOPP) (≈1.2 J cm−3 at 640 MV m−1). Moreover, the nanocomposite exhibits a superior power density of 4.7 MW cm−3 and an ultra-fast discharge speed of 0.37 μs. This research opens up a convenient and effective way for designing high-performance dielectric polymer nanocomposites.

Ultrafast Discharge and Enhanced Energy Density of Polymer Nanocomposites Loaded with 0.5(Ba0.7Ca0.3)TiO3–0.5Ba(Zr0.2Ti0.8)O3 One-Dimensional Nanofibers

One-dimensional (1D) materials as fillers introduced into polymer matrixes have shown great potential in achieving high energy storage capacity because of their large dipole moments. In this article, 1D lead-free 0.5(Ba0.7Ca0.3)TiO3-0.5Ba(Zr0.2Ti0.8)O3 nanofibers (BCZT NFs) were prepared via electrospinning, and their formation mechanism was systematically studied. Polypropylene acyl tetraethylene pentamine (PATP) grafted into the surface of BCZT NFs was embedded in the polymer matrixes, which effectively improved the distribution and compatibility of the fillers via chemical bonding and confined the movement of the charge carriers in the interface filler-matrix. The energy density at a relatively low electric field 380 MV m-1 was increased to 8.23 J cm-3 by small loading of fillers, far more than that of biaxially oriented polypropylene (BOPP) (≈ 1.2 J cm-3 at 640 MV m-1). Moreover, the nanocomposite loaded with 2.1 vol % BCZT@PATP NFs exhibits a superior discharge speed of ≈0.189 μs, which indicates the potential application in practice. The finite element simulation of electric potential and electric current density distribution revealed that the PATP grafted into the BCZT NFs surface could significantly improve the dielectric performances. This work could provide a new design strategy for high-performance dielectric polymer nanocomposite capacitors.

Interfacial Coupling Effect in Organic/Inorganic Nanocomposites with High Energy Density

Organic/inorganic nanocomposites (OINs) can be potentially used as high-performance capacitors due to their rapid charge-discharge capability along with respectable power density. The coupling effect of the filler/matrix interface plays a prominent role in the dielectric and electric properties of OINs. Along with a review of contemporary theoretical models, recent advances in interfacial optimization to improve energy density through careful interface control and design are also presented. Possible mechanisms that may improve energy density and potential applications for high-energy-density capacitors are also highlighted.

High-performance capacitors based on NaNbO3 nanowires/poly(vinylidene fluoride) nanocomposites

Electrostatic capacitors with high power density have been demonstrated as efficient power sources in modern electrical and electronic devices. Nevertheless, the low energy density restricted the applications of electrostatic capacitors in the ever-developing electronic world. To improve energy density, herein, one-dimensional (1D) NaNbO3 (NN) nanowires with a high-aspect-ratio are prepared by a simple hydrothermal method and introduced into a poly(vinylidene fluoride) (PVDF) matrix. The NN@PDA nanowires/PVDF nanocomposite films show a high discharge energy density of 12.26 J cm−3 at 410 MV m−1, which is about 107% higher than that of pristine PVDF (5.87 J cm−3 at 350 MV m−1) and 510% higher than that of the best commercial biaxially-oriented-polypropylenes (BOPP) (2 J cm−3 at 640 MV m−1). Moreover, the composite films show a superior power density of 2.01 MW cm−3 and ultra-fast discharge speed of 146 ns. As verified by finite element simulations, 1D NN nanowires incorporation into the polymer matrix could significantly improve the local electric distribution and electric current density distribution in the nanocomposites. Ultimately, it is anticipated that this work will open a new design paradigm to boost the performance of polymer nanocomposites for compact and flexible electrical energy storage applications.

Largely enhanced energy storage capability of a polymer nanocomposite utilizing a core-satellite strategy

The development of new generation dielectric materials toward capacitive energy storage has been driven by the rise of high-power applications such as electric vehicles, aircraft, and pulsed power systems. Here we demonstrate remarkable improvements in the energy density and charge-discharge efficiency of poly(vinylidene fluoride) (PVDF) upon the incorporation of core-satellite structures, namely NaNbO3(NN)@polydopamine (PDA)@Ag nanowires. As compared to the NN NWs/PVDF and NN@PDA NWs/PVDF nanocomposites, the NN@PDA@Ag NWs/PVDF nanocomposites exhibit greatly enhanced energy density and significantly suppressed energy loss. As a result, the NN@PDA@Ag NWs/PVDF nanocomposite films with optimized filler content exhibit an excellent discharge energy density of 16.04 J cm-3 at 485 MV m-1, and maintain a high discharge efficiency of 62.8%. Moreover, the corresponding nanocomposite films exhibit a superior power density of 2.1 MW cm-3 and ultra-fast discharge speed of 153 ns. Ultimately, the excellent dielectric and capacitive properties of the polymer nanocomposites could pave the way for widespread applications in modern electronics and power modules.