A pivotal obstacle of obtaining dielectric ceramics with large recoverable energy density (W_rec) and ultrahigh energy efficiency (η) desperately needs to be overcome for the development of advanced energy storage devices for high pulsed power systems, especially via an environment-friendly lead-free method. Here we report a series of lead-free dielectric bulk ceramics for high-temperature energy storage capacitors with near-zero energy loss. Confirmed by aberration-corrected scanning transmission electron microscopy and phase-field simulation, a judiciously designed heterostructure in which rhombohedral and tetragonal polar nanoregions are embedded in a cubic paraelectric matrix was constructed. The combination of the increased breakdown strength and the minimized polarization hysteresis, respectively, based on the heterostructure design and repeated rolling process, contributes to a large W_rec of 10.28 J cm⁻³ and a record-high η of 97.11%, superior to the reported lead-free bulk ceramics. Based on such structure-induced advantages, the wide-temperature stability (25–200 °C) and high performance (W_rec ∼ 6.35 ± 9.1% J cm⁻³, η ∼ 94.82% ± 3.4%) of the dielectric ceramics broaden their application in high temperature energy storage systems. This work conspicuously contributes to the development of the next generation high-temperature capacitors and suggests a new paradigm that may stimulate the development of higher-performance energy storage dielectrics.

The immense potential of lead-free dielectric capacitors in advanced electronic components and cutting-edge pulsed power systems has driven enormous investigations and evolutions heretofore. One of the significant challenges in lead-free dielectric ceramics for energy-storage applications is to optimize their comprehensive characteristics synergistically. Herein, guided by phase-field simulations along with rational composition-structure design, we conceive and fabricate lead-free Bi_0.5Na_0.5TiO₃-Bi_0.5K_0.5TiO₃-Sr(Sc_0.5Nb_0.5)O₃ ternary solid-solution ceramics to establish an equitable system considering energy-storage performance, working temperature performance, and structural evolution. A giant W_rec of 9.22 J cm⁻³ and an ultra-high ƞ ~ 96.3% are realized in the BNKT-20SSN ceramic by the adopted repeated rolling processing method. The state-of-the-art temperature (W_rec ≈ 8.46 ± 0.35 J cm⁻³, ƞ ≈ 96.4 ± 1.4%, 25–160 °C) and frequency stability performances at 500 kV cm⁻¹ are simultaneously achieved. This work demonstrates remarkable advances in the overall energy storage performance of lead-free bulk ceramics and inspires further attempts to achieve high-temperature energy storage properties.

Multilayer ceramic capacitor as a vital core-component for various applications is always in the spotlight. Next-generation electrical and electronic systems elaborate further requirements of multilayer ceramic capacitors in terms of higher energy storage capabilities, better stabilities, environmental-friendly lead-free, etc., where these major obstacles may restrict each other. An effective strategy for energy storage performance global optimization is put up here by constructing local polymorphic polarization configuration integrated with prototype device manufacturing. A large energy density of 20.0 J·cm⁻³ along with a high efficiency of 86.5%, and remarkable high-temperature stability, are achieved in lead-free multilayer ceramic capacitors. The strategy provides a feasible routine from nano, micro to macro regions in manipulating local polarizations, domain-switching barriers and breakdown strength, illustrating its great potential to be generally applicable in the design of high-performance energy storage multilayer ceramic capacitors.

Multilayer ceramic capacitors with ultra-high-power densities are widely used in electronic power systems. However, achieving a balance between high energy density and efficiency remains a substantial challenge that limits the practical application of advanced technologies. Here, guided by a phase-field simulation method, we propose a directional slush-like polar structure design with nanodomains embedded in polar orthorhombic matrix in NaNbO₃-based lead-free multilayer ceramic capacitors. This strategy can effectively reduce the hysteresis loss by lowering domain size and improve the breakdown electric field by grain refining, which leads to a high energy storage density of 14.1 J▪cm⁻³ and an ultrahigh energy storage efficiency of 96.8% in multilayer ceramic capacitors. The proposed strategy can be utilized to design high-performance energy storage dielectrics and other related functionalities.

Due to their responsiveness to modulation by external direct current fields, dielectric tunable materials are extensively utilized in integrated components, such as ferroelectric phase shifters. Barium strontium titanate ceramics have been considered the most potential tunable materials for a long time. However, the significant dielectric loss and high voltage drive have limited their further applications. Recently, Bi₆Ti₅WO₂₂ ceramic has regained attention for its high dielectric tunability with low loss. In this study, we judiciously introduce Nb⁵⁺ with a larger ionic radius, replacing Ti⁴⁺ and W⁶⁺. This successful substitution enables the modulation of the phase transition temperature of Bi₆Ti₅WO₂₂ ceramics to room temperature, resulting in superior tunable properties. Specifically, the 0.7Bi₆Ti₅WO₂₂−0.3Bi₆Ti₄Nb₂O₂₂ ceramics exhibit giant tunability (~75.6%) with ultralow loss (<0.002) under a low electric field (1.5 kV/mm). This tunability is twice that of barium strontium titanate ceramics with a similar dielectric constant and only one-tenth of the loss. Neutron powder diffraction and transmission-electron-microscopy illustrate the nanodomains and micro-strains influenced by ion substitution. Density functional theory simulation calculations reveal the contribution of ion substitution to polarization. The research provides an ideal substitute for tunable material and a general strategy for adjusting phase transition temperature to improve dielectric properties.