Orientation-Controlled Electrostatic Energy Storage in BaTiO ₃ -Based Lead-Free Nanocomposite Films with a Simple Composition

Relaxor ferroelectric (RFE) films are highly desirable for modern electronic devices and power systems due to their ability to store and recycle electrostatic energy. However, achieving both the high energy density U e and efficiency η simultaneously remains a significant challenge. Herein, lead-free 0.7BaTiO 3 –0.3CeO 2 (BT–C) RFE films with a simple chemical composition (containing only four elements of Ba, Ti, O, and Ce) were developed to modulate energy storage performance via tailoring polarization behavior. The (110)-oriented BT–C films show a high energy storage density U e of 42.7 J/cm 3, with an ultrahigh efficiency η of 93.1% at room temperature, which can be attributed to the improved polarization response and suppressed hysteresis. Moreover, these BT–C films exhibit exceptional frequency stability (2 Hz to 5 kHz) and thermal stability (25–120 °C), along with reliable operation endurance (>10 6 cycles) without performance degradation. The orientation control strategy, combined with polymorphic nanodomains, offers a promising approach for developing high-performance lead-free energy storage materials, indicating their great potential for practical power-storage applications.