Electronic band and core-shell structure engineering enables ultrahigh energy storage in high-entropy ceramics

Abstract Dielectric capacitors, characterized by their high power density and ultrafast charge/discharge capabilities, are pivotal components in modern pulsed power and renewable energy systems. However, the widespread adoption of ferroelectric ceramics is inherently hampered by the antagonistic relationship between polarization ( P ) and breakdown strength ( E b ), further compounded by significant polarization hysteresis and losses, which collectively obstruct the simultaneous realization of high recoverable energy density ( W rec ) and efficiency ( η ). Herein, we transcend this fundamental limitation via a novel high-entropy engineering strategy in (Bi, Na)TiO 3 -based ceramics. The designed materials achieve an exceptional W rec of 11.1 J/cm 3 and a remarkably high η of ~ 89.1%. This breakthrough is attributed to a synergistic interplay of mechanisms orchestrated by the high-entropy design: (i) a reduction in electronic band curvature that increases the charge carrier effective mass, thereby suppressing mobility and electrical conductivity; (ii) the emergence of self-assembled core-shell microstructures that effectively impede electrical treeing propagation through interfacial stress buffering and field homogenization; and (iii) the stabilization of nanoscale rhombohedral-orthorhombic-tetragonal-cubic (R-O-T-C) multiphase coexistence, which enhances dipole reorientability and disrupts long-range ferroelectric order. The confluence of these effects culminates in a significantly enhanced E b while maximizing the polarization disparity (Δ P = P max ​ - P r ). This study establishes high-entropy engineering as a transformative paradigm for designing advanced lead-free dielectric capacitors with superior energy storage performance.