Tape‐Casting Lead‐Free Dielectrics Permit Superior Capacitive Energy Storage Performance

Abstract Dielectric capacitors have garnered significant attention for their promising attributes in advanced pulse power systems of the future, owing to their rapid charge/discharge capabilities, high power density, and remarkable stability. Whereas environmentally friendly lead‐free ceramics are facing serious challenges of low breakdown strength, poor energy storage density, and/or conversion efficiency, which has been an obstacle to developing desirable dielectric capacitors. In this study, high‐quality ultrathin (<20 µm) lead‐free ceramic dielectrics are successfully produced via the tape‐casting method. The local structural characteristics of these ceramics are verified using piezoresponse force microscopy and aberration‐corrected scanning transmission electron microscopy. By introducing Ta 5+ ions into Bi 0.39 Na 0.36 Sr 0.25 TiO 3 ceramics, the polar clusters tend to decrease together while the maximum applied electric field tends to increase. This phenomenon can be attributed to the decreased grain size and complex polar structure characterized by extremely small polar clusters, enabling the simultaneous achievement of high applied electric field, large polarization, and minimized polarization hysteresis. Notably, the tape‐casted lead‐free ceramics exhibited exceptional comprehensive energy storage performance with a recoverable energy storage density of ≈10.06 J cm −3 and an efficiency of ≈93% under a high electric field of 915 kV cm −1 , surpassing the capabilities of most reported lead‐free ceramics. This work offers a viable solution for developing lead‐free ceramic dielectrics with outstanding energy storage capabilities.