The ever-growing global energy demand has driven a surge of research interest in the field of energy harvesting and conversion. Among them, high-power force-electric energy conversion devices based on charge storage via the polarization effect of ferroelectric (FE) materials have attracted tremendous interest for specialized applications, owing to their superiorities of long shelf life, ultrafast response, and high current/voltage output. Nevertheless, the prevailing bottleneck hindering the development and practical deployment of such energy storage systems lies in the low remanent polarization (P_r) and insufficient thermal stability of most state-of-the-art lead-free ferroelectric materials. In this work, a synergistic optimization strategy of composition-driven structural distortions and defect-induced pinning effects via silver niobate (AN) and MnCO₃ doping is applied to bismuth sodium titanate (BNT)-based ferroelectric ceramics. The optimized 0.98Bi_0.5Na_0.5TiO₃-0.02AgNbO₃-0.20 wt.% MnCO₃ lead-free ferroelectric ceramics exhibit a significantly enhanced P_r and thermal stability, achieving an ultrahigh P_r of 52.21 μC/cm² and excellent stability up to 160 °C. The practical benefits of this synergistic strategy are exhibited in force-electric energy conversion application. The multilayer ceramic capacitors (MLCCs-BNT) release a record-breaking peak pulse current of 90 A via pressure-induced phase transition from ferroelectric R3c phase to nonpolar Pnma phase. The proposed strategy provides a highly feasible approach for enhancing the ferroelectricity and thermal stability of lead-free ferroelectric materials, thereby establishing a solid material foundation for the high-power force-electric energy conversion application.