Ultrahigh Energy Storage in Aurivillius‐Phase Dielectric Thin Films Through Multiscale Optimization Design

Abstract Electrostatic capacitors with the highest power densities, high‐voltage endurance, and a long lifetime are integral energy storage components for application in wind turbine generators, grid‐connected photovoltaics, and high‐frequency inverters. However, realizing ultrahigh recoverable energy storage density (W_rec > 100 J cm⁻³) combined with exceptional efficiency (η > 80%) is still a long‐standing challenge. Herein, a high‐performance Ba₂Bi₄Ti₅O₁₈ (BBPT) Aurivillius‐phase ferroelectric thin film achieved through multiscale optimization design is presented. The Pr³⁺ substitution in BBPT thin film effectively modulates lattice distortion, band‐gap E_g, and leakage current density, achieving optimal balance between polarization and breakdown strength. Accordingly, an ultrahigh discharged energy density (W_rec) of ≈142 J cm⁻³ is achieved, accompanied by a high efficiency of around 88.3%, representing a significant breakthrough in the comprehensive energy storage performance of lead‐free ferroelectric thin films. Especially, when the value of η >90% of their thin film, the high W_rec value of around 100 J cm⁻³ is still realized. The present research opens up a generalizable approach for designing ferroelectric thin films to develop next‐generation high‐performance energy storage devices applications.