Antiferroelectric (AFE) materials are promising for the applications in advanced high-power electric and electronic devices. Among them, AgNbO₃ (AN)-based ceramics have gained considerable attention due to their excellent energy storage performance. Herein, multiscale synergistic modulation is proposed to improve the energy storage performance of AN-based materials, whereby the multilayer structure is employed to improve the breakdown strength (E_b), and Sm/Ta doping is utilized to enhance the AFE stability. As a result, ultrahigh recoverable energy storage density (W_rec) up to 15.0 J·cm⁻³ and energy efficiency of 82.8% are obtained at 1500 kV·cm⁻¹ in Sm/Ta co-doped AN multilayer ceramic capacitor (MLCC), which are superior to those of the state-of-the-art AN-based ceramic capacitor. Moreover, the discharge energy density (W_d) in direct-current charge–discharge performance reaches 9.1 J·cm⁻³, which is superior to that of the reported lead-free energy storage systems. The synergistic design of composition and multilayer structure provides an applicable method to optimize the energy storage performance in all dielectric energy storage systems.

Dielectric capacitors, serving as the indispensable components in advanced high-power energy storage devices, have attracted ever-increasing attention with the rapid development of science and technology. Among various dielectric capacitors, ceramic capacitors with perovskite structures show unique advantages in actual application, e.g., excellent adaptability in high-temperature environments. And the optimization of their energy storage performance has become a hot research topic recently. This review presents the basic principles of energy storage in dielectric ceramics and introduces multi-scale synergic optimization strategies according to the key factors for superior energy storage performance. By summarizing the common points in numerous works, several universal modification strategies are reviewed, and future research on fatigue fracture of ceramic capacitors under multi-field including but not limited to force, electric, and thermal coupling conditions is also anticipated.

Lead-free antiferroelectric ceramics with high energy storage performance show great potential in pulsed power capacitors. However, poor breakdown strength and antiferroelectric stability are the two main drawbacks that limit the energy storage performance of antiferroelectric ceramics. Herein, high-quality (Ag_1-xNa_x)(Nb_1-xTa_x)O₃ ceramics were prepared by the tape casting process. The breakdown strength was greatly improved as a result of the high density and fine grains, while the antiferroelectric stability was enhanced owning to the M₂ phase. Benefiting from the synergistic improvement in breakdown strength and antiferroelectric stability, (Ag_0.80Na_0.20)(Nb_0.80Ta_0.20)O₃ ceramic reveals a benign energy storage performance of W_rec = 5.8 J/cm³ and η = 61.7% with good temperature stability, frequency stability and cycling reliability. It is also found that the high applied electric field can promote the M₂-M₃ phase transition, which may provide ideas to improve the thermal stability of the energy storage performance in AgNbO₃-based ceramics.

AgNbO₃ is an antiferroelectric (AFE) material with double hysteresis loop. Both the antiferroelectricity and ferroelectricity can be enhanced by doping. Herein, the ferroelectricity of AgNbO₃ ceramics was enhanced via K-doping and the phase diagram of the (Ag_1-xK_x)NbO₃ ceramics was upgraded. In details, (Ag_1-xK_x)NbO₃ ceramics are ferrielectric (FIE) M₁ phase as x = 5.00–5.50 mol% and ferroelectric (FE) O phase as x = 5.75–6.00 mol% before poling, and FE O phase as x = 5.00–6.00 mol% after poling at room temperature. With increasing temperature, (Ag_1-xK_x)NbO₃ ceramics show the phase evolutions from FIE M₁, AFE M₂ to paraelectric (PE) T phase at x = 5.00–5.50 mol% and from FE O, FE T to PE T phase at x = 5.75–6.00 mol% before poling, and from FE O, FE T to PE T phase at x = 5.00–6.00 mol% after poling. High d₃₃ values of 180 pC/N and 285 pC/N are obtained at the FE O-FE T and FE T-PE T phase boundaries. This work sheds light on a novel and promising lead-free piezoelectric system.

The development of environmentally friendly ceramics for electrostatic energy storage has drawn growing interest due to the wide application in high power and/or pulsed power electronic systems. However, it is difficult to simultaneously achieve ultrahigh recoverable energy storage density (W_rec > 8 J/cm³) and high efficiency (η > 80 %), which restricts their application in the miniaturized, light weight and easy integrated electronic devices. Herein, the novel NaNbO₃-(Bi_0.8Sr_0.2)(Fe_0.9Nb_0.1)O₃ relaxor antiferroelectric ceramics, which integrates the merits of antiferroelectrics and relaxors, are demonstrated to exhibit stabilized antiferroelectric phase and enhanced dielectric relaxor behavior. Of particular importance is that the 0.88NN-0.12BSFN ceramic achieves giant electric breakdown strength E_b = 98.3 kV/mm, ultrahigh W_rec = 16.5 J/cm³ and high η = 83.3 %, as well as excellent frequency, cycling and thermal reliability simultaneously. The comprehensive energy storage performance of NN-BSFN not only outperforms state-of-the-art dielectric ceramics by comparison, but also displays outstanding potential for next-generation energy storage capacitors.