Flexible multilayer lead-free film capacitor with high energy storage performances via heterostructure engineering

The immense potential of flexible energy storage materials applied in wearable electronic devices has stimulated a lot of science researches on manufacturing technology and performance optimization. Herein, an all-inorganic flexible ferroelectric film with multilayer heterostructure is prepared based on Mn doped Bi0.5Na0.5TiO3BiNi0.5Zr0.5O3 (Mn:BNT-BNZ) and Bi0.5Na0.5TiO3BiZn0.5Zr0.5O3 (BNT-BZZ) relaxor ferroelectrics. A win-win situation of breakdown strength and polarization is achieved in the Mn:BNT-BNZ/BNT-BZZ multilayer film with the stacking period N = 3, of which energy density and efficiency reach 80.4 J/cm3 and 62.0% respectively. It is proposed that the excellent energy storage performances are attributed to the synergistic effect of the electric field amplification effect, interface blocking effect and the polarization coupling effect based on the multilayer heterostructure. Moreover, the flexible ferroelectric film exhibits outstanding temperature (25–205 °C), frequency (0.5–5 kHz) stability and antifatigue property (1 × 108 cycles), and can well maintain stable performance at different tensile/compressive bending radii (10–5 mm) and even after 104 bending cycles with a fixed bending radius of 3 mm. This work opens up a promising route to the development of flexible energy storage materials.