NaNbO3‐(Bi0.5Li0.5)TiO3 Lead‐Free Relaxor Ferroelectric Capacitors with Superior Energy‐Storage Performances via Multiple Synergistic Design

Abstract Relaxor ferroelectric (FE) ceramic capacitors have attracted increasing attention for their excellent energy‐storage performance. However, it is extremely difficult to achieve desirable comprehensive energy‐storage features required for industrial applications. In this work, very high recoverable energy density W rec ≈ 8.73 J cm –3 , high efficiency η ≈ 80.1%, ultrafast discharge rate of <85 ns, and temperature‐insensitive high W rec and η ( W rec ≈ 5.73 ± 4% J cm –3 , η ≈ 75 ± 6%, 25–200 °C) are simultaneously obtained in 0.68NaNbO 3 ‐0.32(Bi 0.5 Li 0.5 )TiO 3 relaxor FE ceramics by introducing various polarization configurations in combination with microstructure modification. The structure mechanism for the excellent energy‐storage performance is disclosed by analyzing in situ structure evolution on multiple scales during loading/unloading by means of transmission electron microscopy and Raman spectroscopy. Both local regions consisting of different‐scale polar nanodomains and a nonpolar matrix, and local orthorhombic symmetry remaining with electric fields ensure a linear‐like polarization response within a wide field and temperature range owing to significantly delayed polarization saturation. The stabilization of orthorhombic FE phases rather than antiferroelectric orthorhombic phases in NaNbO 3 after adding (Bi 0.5 Li 0.5 )TiO 3 is also explored by means of X‐ray diffraction, dielectric properties, and selected area electron diffraction. In comparison with antiferroelectric ceramics, NaNbO 3 ‐based relaxor FE ceramics provide a new solution to successfully design next‐generation pulsed power capacitors.