Novel lead-free KNN-based ceramic with giant energy storage density, ultra-high efficiency and excellent thermal stability via relaxor strategy

Dielectric capacitors with high energy storage performance are highly desired for advanced power electronic devices and systems. Even though strenuous efforts have been dedicated to closing the gap of energy storage density between the dielectric capacitors and the electrochemical capacitors/batteries, a single-minded pursuit of high energy density without a near-zero energy loss for ultrahigh energy efficiency as the grantee is in vain. Herein, for the purpose of decoupling the inherent conflicts between high polarization and low electric hysteresis (loss), and achieving high energy storage density and efficiency simultaneously in multilayer ceramic capacitors (MLCCs), we propose an interlaminar strain engineering strategy to modulate the domain structure and manipulate the polarization behavior of the dielectric mediums. With a heterogeneous layered structure consisting of different antiferroelectric ceramics [(Pb0.9Ba0.04La0.04)(Zr0.65Sn0.3Ti0.05)O3/(Pb0.95Ba0.02La0.02)(Zr0.6Sn0.4)O3/(Pb0.92Ca0.06La0.02)(Zr0.6Sn0.4)0.995O3], our MLCC exhibits a giant recoverable energy density of 22.0 J cm−3 with an ultrahigh energy efficiency of 96.1%. Combined with the favorable temperature and frequency stabilities and the high antifatigue property, this work provides a strain engineering paradigm for designing MLCCs for high-power energy storage and conversion systems.

Giant energy storage density, high efficiency and excellent stability achieved in lead-free KNN-based ceramic via a composition optimization strategy

Next-generation advanced high/pulsed power capacitors rely heavily on dielectric ceramics with high energy storage performance. However, thus far, the huge challenge of realizing ultrahigh recoverable energy storage density (Wrec) accompanied by ultrahigh efficiency (η) still existed and has become a key bottleneck restricting the development of dielectric materials in cutting-edge energy storage applications. Here, we propose a high-entropy strategy to design “local polymorphic distortion” including rhombohedral-orthorhombic-tetragonal-cubic multiphase nanoclusters and random oxygen octahedral tilt, resulting in ultrasmall polar nanoregions, an enhanced breakdown electric field, and delayed polarization saturation. A giant Wrec ~10.06 J cm−3 is realized in lead-free relaxor ferroelectrics, especially with an ultrahigh η ~90.8%, showing breakthrough progress in the comprehensive energy storage performance for lead-free bulk ceramics. This work opens up an effective avenue to design dielectric materials with ultrahigh comprehensive energy storage performance to meet the demanding requirements of advanced energy storage applications.

Although extensive studies have been done on lead-free dielectric ceramics to achieve excellent dielectric behaviors and good energy storage performance, the major problem of low energy density has not been solved so far. Here, we report on designing the crossover relaxor ferroelectrics (CRFE), a crossover region between the normal ferroelectrics and relaxor ferroelectrics, as a solution to overcome the low energy density. CRFE exhibits smaller free energy and lower defect density in the modified Landau theory, which helps to obtain ultrahigh energy density and efficiency. The (1-x)Ba0.65Sr0.35TiO3-xBi(Mg2/3Nb1/3)O3 ((1-x)BST-xBMN) (x = 0, 0.08, 0.1, 0.18, 0.2) ceramic was synthesized by a solid-state reaction method. The solid solutions exhibit dielectric frequency dispersion, which suggests typical relaxor characteristics with the increasing BMN content. The crossover ferroelectrics of 0.9BST-0.1BMN ceramic possesses a high energy storage efficiency (η) of 85.71%, a high energy storage density (W) of 3.90 J/cm3, and an ultrahigh recoverable energy storage density (Wrec) of 3.34 J/cm3 under a dielectric breakdown strength of 400 kV/cm and is superior to other lead-free BaTiO3 (BT)-based energy storage ceramics. It also exhibits strong thermal stability in the temperature range from 25 to 150 °C under an electric field of 300 kV/cm, with the fluctuations below 3% and with the energy storage density and energy efficiency at about 2.8 J/cm3 and 82.93%, respectively. The enhanced recoverable energy density and breakdown strength of BT-based materials with significantly high energy efficiency make it a promising candidate to meet the wide requirements for high power applications.

Advanced energy storage properties and multi-scale regulation mechanism in (1-x)(Bi0.5Na0.5)0.7Sr0.3TiO3-xCa(Nb0.5Al0.5)O3 relaxor ferroelectric ceramics

A critical challenge for the application of lead-free antiferroelectrics in energy storage systems is their poor thermal stability and low efficiency when the superior energy storage density is attained, primarily due to the inherent first-order nature and narrow temperature window of antiferroelectric-to-ferroelectric transitions. Here, we elucidate a unique percolating interaction between antipolar regions in antiferroelectrics and engineered defect pairs using density functional theory and phase field calculations. Strategic distribution of the strongly coupled Li-Ta pairs in AgNbO3 fosters a percolating interaction that facilitates antipolar rotations, enabling a pronounced polarization change with minimal hysteresis. Guided by theoretical calculations, a large recoverable energy storage density of 12.8 J/cm3, with a high efficiency of 90%, is achieved at room temperature in Ag0.95Li0.05Nb0.35Ta0.65O3 ceramics. Moreover, the superior energy storage performance can remain stable within a wide temperature range from -70 to 170 °C, which paves the way for application in advanced energy capacitors.

Enhanced energy storage properties and stability in (Pb0.895La0.07)(ZrxTi1-x)O3 antiferroelectric ceramics

In this work, a high energy storage density in transparent capacitors, based on linear dielectric ZrO2 thin films, with thickness scaled up to hundreds of nanometers, is reported. Linear dielectric ZrO2 films with a thickness of several hundred nanometers are grown on Sn-doped In2O3 (ITO) electrode layers grown on transparent glass substrates at room temperature. The fabricated ITO/ZrO2/ITO capacitors show excellent dielectric energy storage performance, including a large dielectric constant, low loss and leakage current, and large breakdown strength. Consequently, these capacitors present high energy density and efficiency, as well as robust device endurance. In particular, ultra-high recoverable energy storage density (Wrec ∼ 75.4 J/cm3) and efficiency (η ∼ 88%) are achieved simultaneously in ZrO2 film-based (470 nm thick) capacitors, rivaling those of other lead-free ferroelectric-like and other linear dielectric film capacitors. Moreover, the capacitors show good transparency in the visible range, indicating the potential energy-storage applications in transparent electronics.

Enhanced energy storage properties of BaTiO3 ceramics: Effect of doping Bi(Mg0.25Zn0.25Ti0.5)O3 on microstructure, dielectric and ferroelectric properties

Driven by the information industry, advanced electronic devices require dielectric materials which combine both excellent energy storage properties and high temperature stability. These requirements hold the most promise for ceramic capacitors. Among these, the modulated Bi0.5 Na0.5 TiO3 (BNT)-based ceramics can demonstrate favorable energy storage properties with antiferroelectric-like properties, simultaneously, attaching superior temperature stability resulted from the high Curie temperature. Inspired by the above properties, a strategy is proposed to modulate antiferroelectric-like properties via introducing Ca0.7 La0.2 TiO3 (CLT) into Bi0.395 Na0.325 Sr0.245 TiO3 (BNST) ((1-x)BNST-xCLT, x = 0.10, 0.15, 0.20, 0.25). Combining both orthorhombic phase and defect dipole designs successfully achieve antiferroelectric-like properties in BNST-CLT ceramics. The results illustrate that 0.8BNST-0.2CLT presents superior recoverable energy storage density ≈8.3 J cm-3 with the ideal η ≈ 80% at 660kV cm-1 . Structural characterizations demonstrate that there is the intermediate modulated phase with the coexistence of the antiferroelectric and ferroelectric phases. In addition, in situ temperature measurements prove that BNST-CLT ceramics exhibit favorable temperature stability over a wide temperature range. The present work illustrates that BNT-based ceramics with antiferroelectric-like properties can effectively enhance the energy storage performance, which provides novel perspectives for the subsequent development of advanced pulsed capacitors.

Simultaneously realizing ultrahigh energy storage density and efficiency in BaTiO3-based dielectric ceramics by creating highly dynamic polar nanoregions and intrinsic conduction

Achieving ultrahigh energy storage density and efficiency above 90% via reducing defect concentrations for AgNbO3-based multilayer capacitors

Temperature-stable MgO-doped BCZT lead-free ceramics with ultra-high energy storage efficiency

Achieving high energy storage performance and ultrafast discharge speed in SrTiO3-based ceramics via a synergistic effect of chemical modification and defect chemistry

Ni-modified BaTiO3 film prepared by sol-gel with high energy storage performance