Polymorphic Superparaelectric Engineering Boosting Energy Storage Capacity in BaTiO ₃ ‐Based Ceramics

ABSTRACT Electrostatic energy storage using dielectrics plays a vital role in advanced electronics and high‐power electrical systems. While superparaelectric materials offer great potential for achieving high recoverable energy density ( W _rec ) and efficiency ( η ), their practical applications have been hindered by intrinsically low polarization. Herein, a polymorphic superparaelectric engineering approach that simultaneously enhances polarization and breakdown strength was introduced. By constructing coexisting cubic‐orthorhombic‐tetragonal (C‐O‐T) superparaelectric states in BaTiO ₃ ‐based ceramics, the energy barrier for polarization switching is effectively reduced, leading to improved macroscopic polarization and reinforced breakdown endurance. As a result, the optimized polymorphic superparaelectric ceramics achieve a high W _rec of 9.8 J cm ⁻³ and η of 88.5% under 820 kV cm ⁻¹ , along with exceptional stability‐frequency stability with W _rec variation within ±0.6% and η variation within ±3.3% from 1 to 400 Hz, and fatigue stability with both W _rec and η varying below ±0.3% over 10 ⁵ cycles. These results underscore the material's promise for high‐energy pulsed power applications and establish a new design strategy for next‐generation dielectric capacitors.