Abstract. Full text available at https://doi.org/10.1021/acs.jpcc.0c07016The current work presents the designed series of compositions within pseudocubic regions based on (1–x)La0.03Na0.91NbO3–xBi(Li0.5Nb0.5)O3 ceramics abridged as (1–x)LNN–xBLN meant for energy storage applications. The addition of Bi(Li0.5Nb0.5)O3 (BLN) considerably disrupted the ferroelectric order of the La0.03Na0.91NbO3 (LNN) ceramics and favored the perfection of the energy storage density properties. Material properties like breakdown strength (BDS), charge–discharge efficiency (η), and dielectric loss of the system were enhanced via the incorporation of BLN into LNN. The external electric field supply into the system drastically enlarged the energy storage density, where the maximum recoverable energy density value of 2.02 J cm–3 at 300 kV cm–1 was achieved in 0.88LNN–0.12BLN ceramics. Besides this, the new system also demonstrates a strong ability to withstand stress (fatigue-free character) and sound temperature stability characteristics. The impressive storage density, temperature stability, cycle stability, and frequency stability credited to a steady relaxor pseudocubic phase covering a broad temperature range describes the newly designed system. The results demonstrate the potential for the (1–x)LNN–xBLN ceramics as the promising lead-free energy storage materials.