Achieving high energy storage performance and ultrafast discharge speed in SrTiO3-based ceramics via a synergistic effect of chemical modification and defect chemistry

Environmentally friendly energy storage materials with high energy storage performance and excellent stability for applications in pulse power systems are urgently needed. SrTiO3-based ceramics have a relatively high dielectric constant and a high breakdown strength (BDS). However, a low polarization strength in this system often yields a low energy storage density. In this paper, high energy storage performance of SrTiO3-based ceramics with the composition of (Sr1-x-y-φNayBix□φ)TiO3 (abbreviated as zSNBT, where x = 0.2 + 0.3z, y = 0.5z, φ = 0.1–0.1z, and z = 0.8–0.1; □ represents Sr vacancies) was achieved using a synergistic effect of chemical modification and defect chemistry. With the decrease of z, the ferroelectric macro-domain of zSNBT ceramics vanishes due to the original effect of paraelectric SrTiO3, significantly improving the BDS and energy storage performance. When z = 0.2, the material exhibited a single cubic phase structure with a nearly hysteresis-free P-E loop. The maximum BDS reached 390 kV/cm, and under such electric field, a large recoverable energy storage density (Wrec) of 3.94 J/cm3 and ultrahigh energy efficiency (η) of 94.71% were achieved simultaneously. Meanwhile, the 0.2SNBT ceramic showed good thermal stability and satisfying cycling stability in the temperature range of 20–160 °C. In addition, the 0.3SNBT ceramic demonstrated outstanding thermal stability with an ultrafast discharge speed (t0.9 ≤ 26 ns) in the temperature range of 20–180 °C. Furthermore, a simulation model containing grains and grain boundaries was established to explain the enhanced BDS and the energy storage performance. Fine and uniform grains with many grain boundaries significantly hindered the propagation of breakdown cracks, yielding a higher BDS value. These results indicate that zSNBT ceramics are promising environmentally friendly materials for pulse power capacitor applications.