Bi_0.5Na_0.5TiO₃-based energy storage ceramics with excellent comprehensive performance by constructing dynamic nanoscale domains and high intrinsic breakdown strength

Lead-free ceramic-based dielectric capacitors show huge potential in electrical energy storage in pulsed power systems due to their fast charge/discharge rate, ultrahigh power density and environmental friendliness. However, unsatisfied charge/discharge performance characterized by inferior recoverable energy storage density (W_rec generally <5 J/cm³) has become a key bottleneck to restrict their applications in cutting-edge energy storage devices. In this paper, we focus on simultaneously realizing ultrahigh W_rec and efficiency (ƞ) in eco-friendly Bi_0.5Na_0.5TiO₃ (BNT)-based dielectric ceramics via chemical doping. Interestingly, highly dynamic polar nanoregions (PNRs) and nanodomains are constructed by incorporating Sr_0.7Nd_0.2TiO₃ (SNT) into 0.94BNT-0.06BaTiO₃. Of great importance, the resulting relaxor ferroelectrics (RFEs) exhibit high bulk resistivity, submicron grain size and wide band gap due to high level of SNT doping accompanying with 1 at% Nb donor doping. Therefore, excellent energy storage properties with ultrahigh W_rec∼8.08 J/cm³ and ƞ∼92.1% are achieved due to coexistence of large polarization difference (ΔP=P_max−P_r) and giant dielectric breakdown electric field (E_b∼540 kV/cm). Furthermore, excellent temperature/frequency/cycling stability characterized by ΔW_rec < ±4% and Δη < ±2% ensure the energy storage applications of the studied dielectric ceramics over an enormous range of scales.