Interface engineering to optimize polarization and electric breakdown strength of Ba2Bi3.97Pr0.03Ti5O18/BiFeO3 ferroelectric thin-film for high-performance capacitors

• High discharged energy density of 79.3 J/cm 3 and efficiency of 75% are achieved. • The (BBPT/BFO) 1 multilayer thin-film shows fatigue-free, favorable temperature and frequency stabilities. • The (BBPT/BFO) 1 multilayer thin-film exhibits ultrafast discharge time of 0.64 μs. Electrostatic capacitors based on dielectrics are ubiquitous components for applications in modern electronics and electric power systems. However, the relatively low energy density of electrostatic capacitors, which is one or two orders of magnitude lower than that of the batteries, has greatly hindered the implementation of its in energy storage devices. Here, we propose a strategy to overcome the tradeoff between high polarizability and breakdown electric field, and attain great enhancement energy storage density in the lead-free (Ba 2 Bi 3.97 Pr 0.03 Ti 5 O 18 /BiFeO 3 ) N (BBPT/BFO) N multilayer ferroelectric thin films with different BFO layers through interface engineering. The interface engineering could be utilized to concurrently modify both polarization and local electric field strength caused by the synergistic effect of multiple polar structures and electric field amplifying effect. Accordingly, the discharged energy density of the optimized (BBPT/BFO) 1 ferroelectric thin-film capacitors as high as ∼ 79.3 J/cm 3 with discharged efficiency exceeding ∼ 75 % are achieved. Combined with its fatigue-free, favorable temperature and frequency stabilities, the multilayer ferroelectric thin films of BBPT/BFO could be a promising dielectric material for practical energy storage applications.