Ultrahigh Capacitive Energy Storage Through Phase and Entropy Engineering

Abstract Dielectric energy storage capacitors play a pivotal role in advanced electronics and power devices due to their superb power density and fast charge‐discharge characteristics. A synergistic elevation of energy storage density and efficiency stands as an indispensable precondition for downsizing devices and expanding their functional versatility. In the present work, guided by the phase field simulation, the synergistic optimization of phase and entropy engineering is realized in (1‐ x ) (Ag 0.71 Bi 0.07 Sr 0.04 )(Nb 0.85 Ta 0.15 )O 3 ‐ x (0.85NaNbO 3 ‐0.15BiFeO 3 ) ceramics. With the greatly enhanced maximum displacement and breakdown strength, suppressed remnant displacement and hysteresis, an ultrahigh recoverable energy storage density of 13.5 J cm −3 with the efficiency of 81.7% is achieved, attaining the peak value of bulk AgNbO 3 ‐based ceramics. This strategy offers a reasonable and universal approach to enhance the energy storage performance in dielectrics featuring diverse phase structures.