Structure, phonon, and energy storage density in Sr2+-substituted lead-free ferroelectric Ba1-xSrxTiO3 (BSTX) thin films (x = 0.1, 0.3, and 0.7) were prepared using RF sputtering technique, and investigated using x-ray diffraction, Raman, and ferroelectric polarization measurements as a function of temperature. The thin film is tetragonal for x = 0.1 with large c/a ratio. The tetragonal anisotropy (c/a ratio) decreases upon increasing x and that turns cubic for x = 0.7. All these structural and ferroelectric properties change due to change in the c/a ratio. Temperature dependent phonon spectra analyses (80-500 K) indicate decrease in tetragonal to cubic phase transition temperature upon x due to reduction in anisotropy. Overdamping of ~90 cm-1 E soft phonon mode along with a dramatic decrease of intensity of ~160 cm-1 A-phonon mode was observed around the tetragonal ferroelectric to cubic paraelectric phase (< 300 K). The energy storage densities of these thin film capacitors (metal-insulator-metal) were estimated from the measured polarization hysteresis loops and were compared. For x = 0.1, a larger energy storage density (Ure) of ~29 J/cm3 with efficiency of ~48 % was estimated at an applied voltage of 1.1 MV/cm. Nearly room temperature transition temperature Tc, larger dielectric constant and encouraging energy density values of our lead-free BSTX thin film capacitors suggest their possible application in high energy storage and pulse power technology. These results will be presented in detail in the ECS meetings.