Nanofiber-like polar configurations enable ultrahigh energy storage in relaxor ferroelectrics via high-entropy design

Dielectric capacitors are highly promising for advanced power electronics due to their superior power density. However, their widespread application has been limited by inadequate energy storage performance. In this work, we propose a distinct strategy, centered on creating a nanofiber-like polar configuration, to achieve ultrahigh energy storage performance in relaxor ferroelectrics. This is realized through a high-entropy composition design in NaNbO₃-based perovskites, where multiple cations with significant ferroelectric activity and ionic radius differences are introduced at both A- and B-sites. This approach effectively disrupts the long-range ferroelectric and antiferrodistortive orders simultaneously. The resulting nanofiber-like domain structure, which features several nanometers in length but only a few unit cells in width, exhibits a low-hysteresis and nearly linear polarization response to applied electric field (E). Consequently, an exceptional energy storage density (W_rec) of ~19.3 J cm^-3, a high efficiency (η) of ~95.2%, and an impressive W_rec/E coefficient of 208 J kV mm^-3 are simultaneously achieved in the NaNbO₃-(Bi_0.5Li_0.5)(Ti_0.8Zr_0.1Sn_0.1)O₃ multilayer ceramic capacitors. These results underscore the immense potential of the nanofiber-like polar configuration strategy for developing high-performance dielectric energy storage materials.