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 (K_0.4425Na_0.52Li_0.0375)(Nb_0.8825Sb_0.07Ta_0.0475)O₃ (KNLNST) piezoelectric ceramics are synthesized by the conventional solid-state reaction method. The sintering temperature and poling temperature dependence of ceramic properties are investigated. Previous studies have shown that variation of sintering temperature can cause phase transition, similar to the morphotropic phase boundary (MPB) behavior induced by composition changes in Pb(Zr,Ti)O₃ (PZT). And the best piezoelectric performance can be obtained near the phase-transition sintering temperature. In this research, phase transition induced by sintering temperature cannot be detected and excellent piezoelectric properties can still be obtained. The sintering temperature of the largest piezoelectric coefficient of such composition is lower than that of the highest density, which is considered in composition segregation as a result of intensified volatilization of alkali metal oxides. Combined with the effect of poling temperature, the peak values of the piezoelectric properties are d₃₃ = 313 pC/N, k_p = 47%, ε_r = 1825, tanδ = 0.024, T_o–t = 88 ℃, and T_C = 274 ℃.