Polar Chaos Unleashes Outstanding Energy Storage in Lead‐Free Multilayer Ceramic Capacitors

ABSTRACT Multilayer ceramic capacitors with excellent energy storage performance are urgently demanded as the vital core component for next‐generation pulse power systems, yet a persistent trade‐off between density ( W rec ) and efficiency ( η ) under high electric fields remains a major challenge. Herein, we constructed a polar chaos state with significant local polar heterogeneity via multiple ferroelectric‐active A‐/B‐ sites cations co‐substituting. Atomic‐scale structural analysis reveals that this state is characterized by unit‐cell polar vectors lacking any long‐range spatial correlation with completely random orientation, and displaying substantial local fluctuations in magnitude. These features collectively suppress long‐range dipole ordering and domain formation, yielding a macroscopically negligible remanent polarization while retaining a high average polar amplitude. Consequently, the polar chaos state endows the material with greatly enhanced high‐field polarizability, delayed polarization saturation, and significantly reduced hysteresis. Thus, an ultrahigh W rec of 19.3 J cm −3 and ideal η of 94.3% are achieved in the designed (Na, K)NbO 3 ‐based multilayer ceramic capacitors, together with excellent thermal, frequency, and cyclic stability. These results demonstrate a practical route to reconciling the W rec ‐ η trade‑off in high‑field dielectric capacitors, an approach that can be extended to other energy‐storage dielectric systems.