Bi0.5Na0.5TiO3-based relaxor-ferroelectric ceramics for low-electric-field dielectric energy storage via bidirectional optimization strategy

•The present research offers a route for designing LEF dielectric energy storage ceramics.•An ultrahigh (Pmax − Pr) value of 48.7 μC/cm2 can be obtained at 200 kV/cm via bidirectional optimization strategy.•The REF ceramics can display a high Wrec of 3.6 J/cm3 at 200 kV/cm.