Although dielectric ceramic capacitors possess attractive properties for high-power energy storage, their pronounced electrostriction effect and high brittleness are conducive to easy initiation and propagation of cracks that significantly deteriorate electrical reliability and lifetime of capacitors in practical applications. Herein, a new strategy for designing relaxor ferroelectric ceramics with K_0.5Na_0.5NbO₃-core/SiO₂-shell structured grains was proposed to simultaneously reduce the electric-field-induced strain and enhance the mechanical strength of the ceramics. The simulation and experiment declared that the bending strength and compression strength of the core-shell structured ceramic were shown to increase by more than 50% over those of the uncoated sample. Meanwhile, the electric-field-induced strain was reduced by almost half after adding the SiO₂ coating. The suppressed electrical deformation and enhanced mechanical strength could alleviate the probability of generation of cracks and prevent their propagation, thus remarkably improving breakdown strength and fatigue endurance of the ceramics. As a result, an ultra-high breakdown strength of 425 kV cm⁻¹ and excellent recoverable energy storage density (Wrec ∼ 4.64 J cm^-3) were achieved in the core-shell structured sample. More importantly, the unique structure could enhance the cycling stability of the ceramic (W_rec variation < ±2% after 105 cycles). Thus, mechanical performance optimization via grain structure engineering offers a new paradigm for improving electrical breakdown strength and fatigue endurance of dielectric ceramic capacitors.

尽管介电陶瓷电容器在大功率储能方面具有吸引人的特性，但其显着的电致伸缩效应和高脆性有利于裂纹的萌生和扩展，从而在实际应用中显着降低电容器的电气可靠性和使用寿命。在此，一种设计具有K _0.5 Na _0.5 NbO ₃核/SiO _{2的弛豫铁电陶瓷的新策略}提出了-壳结构晶粒以同时降低电场引起的应变并提高陶瓷的机械强度。模拟和实验表明，核壳结构陶瓷的抗弯强度和抗压强度比未涂层样品提高了 50% 以上。_{同时，添加SiO 2}涂层后，电场引起的应变几乎减少了一半。抑制电变形和提高机械强度可以减轻裂纹产生的可能性并防止裂纹扩展，从而显着提高陶瓷的击穿强度和疲劳耐久性。^{结果，425 kV cm -1}的超高击穿强度在核壳结构样品中实现了优异的可恢复储能密度（Wrec∼4.64 J cm ^{-3 ）。}更重要的是，独特的结构可以提高陶瓷的循环稳定性（ 105 次循环后W _rec变化 < ±2%）。因此，通过晶粒结构工程优化机械性能为提高介电陶瓷电容器的电击穿强度和疲劳耐久性提供了新的范例。