Fig. 3

Energy storage performance. a Discharged energy density and b efficiency of the BFSTO films as a function of the applied electric field. c Comparisons of energy density and efficiency between BFSTO and representative dielectric systems10,11,12,28,29,30,31,32,33, showing that the BFSTO films possess the most outstanding energy storage performance. d Energy density and efficiency for x = 0.60 and 0.75 at an electric field of 2.5 MV cm−1 over 1 × 107 charging-discharging cycles. e Temperature-dependent energy storage performance for x = 0.60 and 0.75 at an electric field of 1.5 MV cm−1