In the case of dielectric energy storage devices, excessive pursuit of giant electric fields means greater exposure to high temperatures and insulation damage risk. Ferroelectric thin film devices offer opportunities for energy storage needs under finite electric fields due to their intrinsically large polarization and the advantage of small size. Herein, we designed the capacitor's dielectric layer by doping barium titanate Ba (1-x) Ce x TiO 3 (BCTO). The addition of highly charged ions Ce 3+ induce cell shrinkage thus further optimizing the ferroelectric polarization. Accordingly, the capacitor with Au/BCTO/Au structure integrated directly on silicon substrate showed excellent energy storage performance ( W rec ≈ 92.6 J/cm 3 and η ≈ 86.5%) under only 1961 kV/cm. In addition, we significantly increased the electrical breakdown strength from 1726 kV/cm to 3426 kV/cm by adjusting the Ba 0.95 Ce 0.05 TiO 3 film thickness, thus achieving ultra-high energy storage density (107.9 J/cm 3 ). The results expand the application prospects of silicon-based ferroelectric capacitors for energy storage at low electric field strength.