Enhanced energy storage performance of Mn-doped NBT-based flexible films by defect engineering

The rapid development of advanced flexible electronics leads to higher demands on the energy storage performance and spatial adaptability of capacitors. Here, Mn²⁺ is doped into 0.6(Na_0.5Bi_0.5)TiO₃-0.4Bi(Mg_0.5Zr_0.5)O₃ (0.6NBT-0.4BMZ), which effectively reduces the carrier content by forming defective complexes through the bonding of Mn²⁺ with oxygen vacancies, while maintaining a relatively high polarizability and enhancing the breakdown strength. The optimal storage performance is demonstrated by the 0.6NBT-0.4BMZ film with a Mn doping amount of 1 mol%. The observed breakdown strength, storage density, and storage efficiency are 2,900 kV/cm, 60.2 J/cm³, and 60.3%, respectively. Furthermore, the films exhibit excellent stability in various temperature ranges (25~205 ℃), frequencies (1~5 kHz), fatigue tests (at 10⁷ charge/discharge cycles), and bending resistance tests (20,000 cycles/radius R ≈ 2 mm). These results indicate that NBT-based film materials hold great promise for future flexible energy storage applications.