Nanocomposites containing high dielectric permittivity ceramics embedded in high breakdown strength polymers are currently of considerable interest as a solution for the development of high energy density capacitors. However, the improvement of dielectric permittivity comes at expense of the breakdown strength leading to limit the final energy density. Here, an ultra-high energy density nanocomposite was fabricated based on high aspect ratio barium strontium titanate nanowires. The pyroelectric phase Ba0.2Sr0.8TiO3 was chosen for the nanowires combined with quenched PVDF to fabricate high energy density nanocomposite. The energy density with 7.5% Ba0.2Sr0.8TiO3 nanowires reached 14.86 J/cc at 450 MV/m, which represented a 42.9% increase in comparison to the PVDF with an energy density of 10.4 J/cc at the same electric field. The capacitors have 1138% greater than higher energy density than commercial biaxial oriented polypropylene capacitors (1.2 J/cc at 640). These results demonstrate that the high aspect ratio nanowires can be used to produce nanocomposite capacitors with greater performance than the neat polymers thus providing a novel process for the development of future pulsed-power capacitors.
High energy density capacitors are critically important in advanced electronic devices and electric power systems due to
their reduced weight, size and cost to meet desired applications. Nanocomposites hold strong potential for increased
performance, however, the energy density of most nanocomposites is still low compared to commercial capacitors and
neat polymers. Here, high energy density nanocomposite capacitors are fabricated using surface-functionalized high
aspect ratio barium titanate (BaTiO3) nanowires (NWs) in a poly(vinylidene fluoride-trifluoroethylene-chlorofluoroethylene)
(P(VDF-TrFE-CFE)) matrix. These nanocomposites have 63.5% higher dielectric permittivity
compared to previous nanocomposites with BaTiO3 nanoparticles and also have high breakdown strength. At a 17.5%
volume fraction, the nanocomposites show more than 145.3% increase in energy density above that of the pure P(VDF-TrFE-
CFE) polymer (10.48 J/cm3 compared to 7.21 J/cm3). This value is significant and exceeds those reported for the
conventional polymer-ceramic composites; it is also more than two times larger than high performance commercial
materials. The findings of this research could lead to broad interest due to the potential for fabricating next generation
energy storage devices.
The use of piezoelectric materials has become more popular for a wide range of applications, including structural health
monitoring, power harvesting, vibration sensing and actuation. However, piezoceramic materials are often prone to
breakage and are difficult to apply to curved surfaces when in their monolithic form. One approach to alleviate these
issues is to embed the fragile piezoceramic inclusion into a polymer matrix. The flexible nature of the polymer matrix
protects the ceramic from breaking under mechanical loading and makes the resulting compoistes easier to apply onto
curved structure. However, most developed active ceramic composites have relatively low electroelastic coupling
compared to bulk piezoceramics. There are two main methods to improve the eletroelastic properties of piezoceramic
composites, namely using higher aspect ratio active inclusions and alignment of inclusions in the electric field direction.
In this paper, the dielectric and energy storage property of nanowire composites is significantly enhanced by aligning the
nanowires in the direction of the applied electrical field. PZT nanowires are hydrothermally synthesized and solutioncast
into a polymer matrix, and then aligned using a shear flow based stretching method. The alignment was evaluated
by scanning electron microscopy images and it is shown that the nanowires can be successfully aligned in the PVDF.
The dielectric constant and energy density of the nanocomposites were tested using Agilent E4980A LCR meter and
Sawyer-Tower circuit. This testing result shows that the dielectric constant and energy density of the composites can be
increased by as much as 35.7% and 49.3% by aligning the nanowires in the electric field direction. Piezoceramic
composites with enhanced energy storage property could lead to broader applications when using this type of materials
for polymer based capacitive energy storage.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.