Ultrahigh Energy Storage Density and Efficiency of Lead-Free Dielectrics with Sandwich Structure.

Lead-free dielectric capacitors have attracted significant research interest for high-power applications due to their environmental benefits and ability to meet the demanding performance requirements of electronic devices. However, the development of lead-free ceramic dielectrics with outstanding energy storage performance remains a challenge. In this study, environmentally friendly ceramic dielectrics with sandwich structures are designed and fabricated to improve energy storage performance via the synergistic effect of different dielectrics. The chemical compositions of the outer and middle layers of the sandwich structure are 0.35BiFeO 3 -0.65SrTiO 3 and Bi 0.39 Na 0.36 Sr 0.25 TiO 3 , respectively. The experimental and theoretical simulation results demonstrate that the breakdown strength is over 700 kV cm -1 for prepare sandwich structure ceramics. As a result, an ultrahigh recoverable energy storage density of 9.05 J cm -3 and a near-ideal energy storage efficiency of 97% are simultaneously achieved under 710 kV cm -1 . Furthermore, the energy storage efficiency maintains high values (≥ 96%) within 1-100 Hz and the power density as high as 188 MW cm -3 under 400 kV cm -1 . These results indicate that the designed lead-free ceramics with a sandwich structure possess superior comprehensive energy storage performance, making them promising lead-free candidates in the energy storage field.