Normal-ferroelectric Pb(Zr0.52Ti0.48)O-3 (PZT) and relaxor-ferroelectric Pb0.9La0.1(Zr0.52Ti0.48 )O-3 (PLZT) thinfilms are deposited on SrRuO3-covered SrTiO3/Si substrates. An ultrahigh recoverable energy-storage density (U-reco) of 68.2 J/cm(3) and energy efficiency (eta) of 80.4% are achieved in the PLZT thin-films under a large breakdown strength (E-BD) of 3600 kV/cm. These values are much lower in the PZT thin-films (U-reco of 10.3 J/cm(3) and eta of 62.4% M E-BD of 1000 kV/cm). In addition, the remanent polarization (P-r) and dielectric-constant are also investigated to evaluate the breakdown strength in thin-films. Polar nano-regions (PNRs) are created in the PLZT thin-films to enable relaxor behavior and lead to slim polarization loops along with very small P-r. The excellent operating temperature of energy-storage performance and also the breakdown strength obtained in the PLZT thin-films are mainly ascribed to the presence of PNRs. Moreover, both PZT and PLZT thin-films exhibit superior performance up to 10(10) times of charge-discharge cycling.