Ultrahigh energy storage capacities in high-entropy relaxor ferroelectrics

Realizing ultrahigh recoverable energy-storage density (W_rec) alongside giant efficiency (η) remains a significant challenge for the advancement of dielectrics in next-generation pulse power energy-storage (ES) devices. In this study, we introduce an entropy engineering approach, manipulating local polar fluctuations and tailoring microstructure evolution through a high-entropy design strategy, to effectively regulate the ES performance of lead-free (Bi_0.5Na_0.5)TiO₃ (BNT)-based dielectrics. By intricately designing a high-entropy matrix, (Bi_0.375Na_0.3Sr_0.25K_0.075)TiO₃ (BNSKT), and enhancing configurational entropy with the Bi(Mg_0.5Sn_0.5)O₃ (BMS) end member, we developed multi-cation substituted BNT relaxor ceramics based on a viscous polymer process (VPP) method. Our findings reveal that modulating atomic configurational entropy yields favorable and stable microstructural characteristics, contributing to an improved breakdown electric field (E-field), reduced hysteresis and delayed polarization saturation. The VPP-synthesized high-entropy 0.85BNSKT-0.15BMS (BNT-H15_VPP) ceramics achieved a significant ES density W_rec of 11.24 J cm⁻³, η of 88.3%, and responsivity (ξ, defined as W_rec/E) of 184 J kV⁻¹ cm⁻² under 610 kV cm⁻¹. Additionally, pulse charging/discharging measurements indicated a large discharge energy density (W_dis) of 6.6 J cm⁻³, a short discharge time of 2.2 μs, and remarkable temperature stability over 20-120 °C. This work underscores the feasibility of the high-entropy strategy for designing robust dielectric ceramics, heralding promising advancements in advanced ES capacitors with comprehensive ES performance.