Relaxor dielectric ceramic capacitors are very attractive for high-power energy storage. However, the low breakdown strength severely restricts improvements to the energy storage density and practical application. Here, a strategy of designing small grain sizes and abundant amorphous grain boundaries is proposed to improve the energy storage properties under the guidance of phase field theory. 0.925(K_0.5Na_0.5)NbO₃–0.075Bi(Zn_2/3(Ta_0.5Nb_0.5)_1/3)O₃ (KNN–BZTN) relaxor ferroelectric ceramic is taken as an example to verify our strategy. The grain sizes and grain boundaries of the KNN–BZTN ceramics are carefully controlled by the high-energy ball milling method and two–step sintering strategy. Impedance analysis and diffusion reflectance spectra demonstrate that KNN–BZTN ceramics with a small grain size and abundant amorphous grain boundary exhibit a lower charge carrier concentration and higher band gap. As a consequence, the breakdown electric field of KNN–BZTN ceramics increases from 222 kV/cm to 317 kV/cm when the grain size is decreased from 410 nm to 200 nm, accompanied by a slightly degraded maximum polarization. KNN–BZTN ceramics with an average grain size of ∼250 nm and abundant amorphous grain boundaries exhibit optimum energy storage properties with a high recoverable energy density of 4.02 J/cm³ and a high energy efficiency of 87.4%. This successful local structural design opens up a new paradigm to improve the energy storage performance of other dielectric ceramic capacitors for electrical energy storage.

弛张电介质陶瓷电容器对于高功率能量存储非常有吸引力。然而，低的击穿强度严重地限制了对能量存储密度和实际应用的改进。在此，在相场理论的指导下，提出了一种设计小晶粒尺寸和丰富的非晶态晶界的策略，以提高储能性能。0.925（K _0.5 Na _0.5）NbO ₃ –0.075Bi（Zn _2/3（Ta _0.5 Nb _0.5）_1/3）O ₃以（KNN–BZTN）弛豫铁电陶瓷为例来验证我们的策略。KNN-BZTN陶瓷的晶粒尺寸和晶界是通过高能球磨法和两步烧结策略来仔细控制的。阻抗分析和扩散反射光谱表明，具有小晶粒尺寸和丰富无定形晶界的KNN-BZTN陶瓷具有较低的载流子浓度和较高的带隙。结果，当晶粒尺寸从410 nm减小到200 nm时，KNN–BZTN陶瓷的击穿电场从222 kV / cm增加到317 kV / cm，同时最大极化强度稍有下降。³和87.4％的高能源效率。这种成功的局部结构设计开辟了新的范式，以改善其他用于电能存储的介电陶瓷电容器的能量存储性能。