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

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 BaTiO₃-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 10⁵ 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.