Significant enhancement of comprehensive energy storage performance in BaTiO3-based ceramics through high-entropy design

Abstract

Relaxor ferroelectric oxides with the feature of polar nanoregions (PNRs) have attracted extensive attention due to their unique structure and physical properties, which can be realized by disrupting the long-range ferroelectric ordering through enhancing composition disorder. To overcome the limitations of traditional dielectric materials for energy storage, great efforts have been made to design new high-entropy compounds for high performance dielectric capacitors, typically through substitutional doping that introduces local chemical and structural disorder. In this work, high-entropy perovskite oxides (Bi_0.2Na_0.2Ba_0.2Ca_0.2Sr_0.2)TiO₃ (BNBSCT), (Bi_0.2K_0.2Ba_0.2Ca_0.2Sr_0.2)TiO₃ (BKBSCT) and (La_0.2Li_0.2Ba_0.2Ca_0.2Sr_0.2)TiO₃ (LLBSCT) ceramics are proposed to significantly improve the energy storage performance of BaTiO₃ ceramic by increasing the configurational entropy. The entropy-assisted synthesis approach, having A-site ions with different valence states and radii, can significantly increase the chemical disorder and lattice distortion of the high-entropy ceramics, resulting in strong local polar fluctuations which are found to influence the dielectric relaxor behavior, phase transitions and ferroelectric property. As a result, all the high-entropy ceramics exhibit higher maximum polarization (P_max) and smaller remnant polarization (P_r) values. Furthermore, it is found that a combination of relatively high P_max, low P_r and high dielectric breakdown strength (DBS) ensures that the LLBSCT high-entropy ceramic exhibits excellent recoverable energy density W_rec of 5.16 J/cm³, energy storage efficiency η of 88 %, and eminent charging-discharging capability (e.g., ultra-short discharge time t_0.9 ∼ 68 ns, current density C_D ∼ 716.51 A/cm² and power density P_D ∼ 85.98 MW/cm³ under an electric field of 240 kV/cm). Therefore, this work demonstrates that the high-entropy-assisted strategy provides a simple and effective approach for designing novel dielectric ceramic capacitors with superior energy-storage performance.