To realize the ultrahigh W rec , it is essential to improve the above factors simultaneously.Recently, numerous studies have shown that linear dielectrics, ferroelectrics, and antiferroelectrics are difficult to achieve breakthroughs in energy-storage performance owing to the lack of high-polarization genes, poor efficiency caused by high P r , unstable antiferroelectric phase and antiferroelectric-ferroelectric phase transition, respectively. [2] To further enhance the W rec , transforming ferroelectrics and antiferroelectrics into relaxors is a simple but effective method, leading to the decreased domain size and P r . Interestingly, the strategies for the formation of relaxors are diverse. For relaxor antiferroelectrics, ultrahigh W rec of 12.2 and 18.5 J cm −3 can be achieved in NaNbO 3 (NN)-based ceramics using nanodomain engineering, causing a diffuse antiferroelectric to ferroelectric phase transition behavior to reduce the possibility of breakdown by reducing large transient currents and volume changes. [3] However, relatively low efficiency (η < 80%) limits their actual applications. The strategy of constructing phase boundary was designed to obtain excellent comprehensive energy-storage properties in AgNbO 3 (AN)-based ceramics. [4] For relaxor ferroelectrics, many strategies, such as composition adjustment, [5] domain/nanodomain engineering, [6] high-entropy design [7] were proposed to improve the energy-storage performance. Unfortunately, in addition to high-entropy strategy, there is no effective design to realize ultrahigh energy storage density (W rec ≥ 10 J cm −3 ) in relaxor ferroelectrics, making them comparable to relaxor antiferroelectric energy storage ceramics in competitiveness and development potential. [3,8] The control of polarization, domain or polar nanoregions (PNRs) configuration is an amusing approach to design new dielectric materials with enhanced energy-storage performance. Unmatched temperature range, [9] nanoscale polarization mismatch and reconstruction, [10] and crossover region [11] were adopted to form different domain configurations such as coexisting Ti-rich and Bi-rich PNRs, and coexisting nanodomain and PNRs. However, low W rec (<4 J cm −3 ) and medium η (≈80%) were obtained in relaxors due to the insufficient E b , fast polarization saturation and the existence of large size nanodomains. It is common that enhanced relaxation can result in a decreased polarization, and some methods should be used Lead-free dielectric ceramics with ultrahigh energy-storage performance are the core components used in next-generation advanced pulse power capacitors. However, the low energy storage density largely hinders their development towards miniaturization, lightweight, and integration. Here, an effective strategy of constructing local diverse polarization is designed in superparaelectrics to realize an ultrahigh energy storage density of ≈10.59 J cm −3 as well as a large efficiency of ≈87.6%. The excellent comprehensive energy-storage performance is mainly attributed to the desi...

Advanced lead-free energy storage ceramics play an indispensable role in next-generation pulse power capacitors market. Here, an ultrahigh energy storage density of ~ 13.8 J cm−3 and a large efficiency of ~ 82.4% are achieved in high-entropy lead-free relaxor ferroelectrics by increasing configuration entropy, named high-entropy strategy, realizing nearly ten times growth of energy storage density compared with low-entropy material. Evolution of energy storage performance and domain structure with increasing configuration entropy is systematically revealed for the first time. The achievement of excellent energy storage properties should be attributed to the enhanced random field, decreased nanodomain size, strong multiple local distortions, and improved breakdown field. Furthermore, the excellent frequency and fatigue stability as well as charge/discharge properties with superior thermal stability are also realized. The significantly enhanced comprehensive energy storage performance by increasing configuration entropy demonstrates that high entropy is an effective but convenient strategy to design new high-performance dielectrics, promoting the development of advanced capacitors "Image missing".

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Lead‐free dielectric ceramics with excellent energy‐storage performance are crucial to the development of the next‐generation advanced pulse power capacitors. However, low energy‐storage density limits the evolution of capacitors toward lightweight, miniaturization, and integration. Here, an effective strategy of constructing highly dynamic polarization heterogeneous nanoregions is proposed in lead‐free relaxors to realize an ultrahigh energy‐storage density of ≈8.0 J cm−3, making almost ten times the growth of energy‐storage density compared with pure Bi0.5Na0.5TiO3 ceramic, accompanied by a higher energy efficiency of ≈80% as well as an ultrafast discharge rate of ≈20 ns. Ultrasmall polarization heterogeneous nanoregions with different orientations and ultrahigh flexibility, and significantly decreased grain size to submicron lead to reduced heat loss, improved breakdown electric field and polarization, enhanced relaxation, and delayed polarization saturation behaviors, contributing to the remarkable energy‐storage performance. Moreover, the breakdown path distribution or electrical tree evolution behaviors are systematically studied to reveal the origin of ultrahigh breakdown electric field through phase field simulations. This work demonstrates that constructing highly dynamic polarization heterogeneous nanoregions is a powerful approach to develop new lead‐free dielectric materials with high energy‐storage performance.

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