Ultrahigh Energy Storage Performances Induced by Weaker La–O Orbital Hybridization in (Na0.85K0.15)0.5Bi4.5 – xLaxTi4O15Relaxor Ferroelectric Films

Dielectric capacitors have caused wide concern due to their high power density and quick charge and discharge characters. However, improving their energy densities and efficiency at the same time has been a long-standing obstacle to the development of ideal dielectric materials. Herein, we report (Na 0.85 K 0.15 ) 0.5 Bi 4.5 – x La x Ti 4 O 15 ferroelectric films with both ultrahigh energy densities and efficiency by introducing a weaker La–O orbital hybridization. Electrical hysteresis is minimized, while high polarization is maintained, which induces a giant energy storage density W re of 111 J/cm 3 and a high storage efficiency η of 83% in (Na 0.85 K 0.15 ) 0.5 Bi 3.2 La 1.3 Ti 4 O 15 films. The outstanding energy storage performances are attributed to the weakened dipole–dipole interaction and the increased band gap derived from the substitution of the weaker La–O orbital hybridization for the strong orbital hybridization between the Bi–O bond. This work obtains ultrahigh energy storage density and efficiency after introducing ions with the same radius and valence state, which provides a concise approach for the design of next-generation pulsed power capacitors.