Effective improved energy storage performances of Na0.5Bi0.5TiO3-based relaxor ferroelectrics ceramics by A/B-sites co-doping

•Excellent recoverable energy density (Wrec ~ 2.52 J/cm3) and efficiency (η ~ 89.3%) are achieved concomitantly in 0.55NBT-0.45SLTS ceramic.•Both Wrec and η of 0.55NBT-0.45SLTS ceramics display excellent temperature stability (20–140 °C), frequency stability (1–1000 Hz) and fatigue endurance (106 cycles).•The 0.55NBT-0.45SLTS ceramics ceramic shows large power density (50.53 MW/cm3) and ultrashort discharge time (<53 ns).