Energy-storage properties play a critical role in determining whether or not dielectric capacitors can be applied in high power pulse devices, but single improvements in electric field parameters or polarization severely limit the achievement of superior comprehensive performance. Herein, we propose a simple means of enhancing the energy-storage capability of antiferroelectric materials via optimization of property parameters. As a consequence, an ultrahigh recoverable energy density (W_rec) of 14.5 J cm⁻³, together with high energy conversion efficiency (η) of 87.7% under a high applied electric field of 54.5 kV mm⁻¹ is obtained in the (Pb_0.875La_0.05Sr_0.05)(Zr_0.995Ti_0.005)O₃ (PLSZT5) antiferroelectric ceramic, superior to most currently reported dielectric ceramics. It is revealed that Sr²⁺ doping enhances the interaction among ions and reduces oxygen vacancies, leading to a significantly enhanced antiferroelectricity and breakdown strength. Besides this, the enhanced diffuse phase transition leads to a small hysteresis width. In addition, an ultrahigh discharge energy density (W_dis) of 11.8 J cm⁻³ and a large power density (P_D) of 377 MW cm⁻³ are realized. The outstanding energy storage capabilities are also manifested in a broad frequency range (1–100 Hz) and temperature range (25–120 °C), along with strong fatigue endurance (1000 cycles). The above results reveal that the PLSZT5 ceramic is a highly promising dielectric material for high-energy-storage device applications.