Ultrahigh Energy Efficiency and Large Discharge Energy Density in Flexible Dielectric Nanocomposites with Pb_0.97La_0.02(Zr_0.5Sn_<i>x</i>Ti_{0.5–<i>x</i>})O₃ Antiferroelectric Nanofillers

Abstract

Flexible dielectric capacitors have been widely studied recently on account of their fast charge-discharge speed, high power density, and superior wearable characteristics. Inorganic ferroelectric fillers/polymer matrix composites combining large maximum electric displacement (<i>D</i>_max) of ferroelectric materials with good flexibility and high electric breakdown strength (<i>E</i>_b) of the polymer are regarded as the most promising materials for preparing flexible dielectric capacitors with superior energy storage properties. However, simultaneously achieving large discharge energy density (<i>W</i>_d) and high energy efficiency (η) in these composites remains challenging on account of a large remnant electric displacement (<i>D</i>_r) and low <i>D</i>_max - <i>D</i>_r values of ferroelectric fillers. In contrast, antiferroelectrics (AFEs) exhibit near zero <i>D</i>_r and larger <i>D</i>_max - <i>D</i>_r values and are thus attractive composite fillers to simultaneously achieve large <i>W</i>_d and high η. On the basis of these factors, in this report, we design and prepare Pb_0.97La_0.02(Zr_0.5Sn_<i>x</i>Ti_0.5-<i>x</i>)O₃ (PLZST) AFE nanoparticles (NPs)/poly(vinylidene fluoride-<i>co</i>-hexafluoropropylene) (P(VDF-HFP)) nanocomposites and investigate the effects of the Sn and AFE NPs contents on the energy storage capacity of the nanocomposites. Through reasonable adjustment of the Sn content and the PLZST AFE fillers content, because of the large <i>D</i>_max - <i>D</i>_r value of 7.75 μC/cm² and small <i>D</i>_r value of 0.26 μC/cm² at the <i>E</i>_b as high as 3162 kV/cm, the Pb_0.97La_0.02(Zr_0.5Sn_0.38Ti_0.12)O₃ AFE NPs/P(VDF-HFP) polymer nanocomposite with 7 wt % fillers exhibits the most superior energy storage properties with an ultrahigh η of 93.4% and a large <i>W</i>_d of 12.5 J/cm³. These values are superior to those of the recently reported dielectric nanocomposites with a single-layer structure containing ferroelectric nanowires, nanofibers, nanobelts, nanotubes, and nanosheets or core-shell structure fillers, which are prepared via a very complicated method. This work not only shows that, in principle, the polarization characteristics of the composites depend mainly on those of the inorganic fillers but also demonstrates a convenient, effective, and scalable way to fabricate dielectric capacitors with superior flexibility and energy storage capacities.