Enhanced Energy Storage Performance in Mn-Doped BaTiO3-Based Epitaxial Thin Films

Lead-free dielectric films are ideal candidates for pulse power capacitors due to their rapid charge–discharge capability, but their energy storage performance still needs further improvement to meet the requirements of high-performance applications. In this work, 0.84BaTiO3-0.16Bi(Mg0.2Ni0.2Zn0.2Zr0.2Nb0.2)O3-xMn (0.84BT-0.16BMNZZN-xMn)/LaNiO3 (LNO) heteroepitaxial films were successfully fabricated on SrTiO3 (STO) (001) substrates via chemical solution deposition (CSD) technology, and the regulation effects of Mn doping on the films’ microstructure, electrical properties, and energy storage characteristics were systematically investigated. The results show that the introduction of Mn ions effectively refines the grain size, improves the leakage behavior of the films, and thus significantly enhances the breakdown strength. When the Mn doping content x = 0.01, the film exhibits optimal energy storage performance: the recoverable energy density (Wrec) reaches 72.3 J·cm–3, the efficiency (η) is 72.6%, and the breakdown strength (Eb) is as high as 5604 kV·cm–1. Meanwhile, the sample demonstrates excellent temperature stability over the wide temperature range of −120 to 120 °C (Wrec = 48.1 J·cm–3 with a fluctuation of less than 2%, @3500 kV·cm–1), and the Wrec changes by less than 2% after 109 cycles, indicating outstanding long-cycle reliability. These results confirm that the 0.84BT-0.16BMNZZN-0.01Mn epitaxial film has broad application prospects in high-power energy storage fields and is a promising candidate material.