An innovative strategy was designed to improve the energy storage properties of Bi_0.5Na_0.5TiO₃–SrTiO₃ (BNT–ST)-based relaxor ferroelectric ceramics, in which the bismuth layer-structured relaxor BaBi₂Nb₂O₉ (BBN) was adopted as the modifier.

In this study, novel lead-free Sr_1.75Ca_0.25NaNb₅O₁₅ tungsten bronze ceramics were designed for potential energy storage applications. A remarkable energy storage density (∼3.23 J cm⁻³) along with a high energy storage efficiency (∼88.2%) was obtained simultaneously at an applied electric field of 290 kV cm⁻¹. Moreover, the ceramic also showed exceptional discharging performance including a fast discharge rate (τ_0.9 < 70 ns), an ultrahigh discharge current density (1104 A cm⁻²) and a high power density (82.8 MW cm⁻³). The achieved capacitive performance in this work indicates the great potential of the designed novel tungsten bronze ceramic for energy storage applications.