Superior energy storage properties with prominent thermal stability in lead-free KNN-based ceramics through multi-component optimization strategy

The advancement of high energy storage properties and outstanding temperature stability ceramics plays a decisive role in the field of pulsed power systems. The multi-component optimization strategy is conducted by introducing Li+, Bi(Ni1/2Zr1/2)O3 and NaNbO3 into KNN-based ceramics. An excellent energy storage (W) of 7.82 J/cm3 along with a large efficiency (η) of 81.8 % is achieved at the breakdown strength (BDS) of 500 kV/cm for the ceramics. Simultaneously, the remarkable energy storage thermal stability (ΔWrec: ∼ 2.9 %, Δη: ∼ 3.9 %) is acquired in the range from 20 ℃ to 100 ℃. The splendid charging-discharging performances (discharge energy density Wd = 1.78 J/cm3, current density CD = 1376 A/cm2, power density PD = 124 MW/cm3) are also realized in the ceramics after doping. By investigating the evolution of crystal structure and domain structure, complex impedance and first-principle calculations, the internal mechanism of obtaining superior energy storage properties is analyzed. Thus, this research proves that the ceramics can effectively broaden the temperature range of the applications for the pulsed power systems while maintaining high energy storage properties, which offers a valuable approach for the improvement of dielectric capacitors.