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 linearlike 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.

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