Excellent temperature stability of energy storage performance by weak dipolar interaction strategy

High-performance dielectric materials are widely used in energy storage applications, and temperature stability at extreme conditions is rarely considered yet. In this work, the Bi0.5Na0.5TiO3-Sr0.7Bi0.2 square 0.1TiO3-xNaNbO3 (x = 0, 0.05, and 0.15) system is designed with a roomtemperature ergodic relaxor character to explore energy storage evolution with temperature. The addition of NaNbO3 increases tetragonal (P4bm) phase content and relaxor disorders and leads to a downshift of transition temperature, as verified by Rietveld refinement, dielectric analysis, and in situ Raman spectra. Superior temperature stability of recoverable energy storage density (W-Rec, change rate: delta <= 14%) and efficiency (eta = 0.79-0.98) is found in x = 0.15 composition in a wide temperature range of 243-373 K, in contrast to a significant variation for x = 0 (delta <= 85%, eta = 0.08-0.88) and 0.05 (delta <= 36%, eta = 0.60-0.96) compositions. The dielectric relaxation speed is faster in x = 0.15, as characterized by on-off-electric field dielectric curves. This work demonstrates that the weak-dipolar-interaction system retards dipolar coalescence under cryogenic temperature and, thus, maintains high energy storage efficiency, which predicts their suitability in energy storage applications at an extreme condition.

Automated summary

High-performing dielectric materials are commonly used in energy storage applications, but their temperature stability under extreme conditions is often overlooked. This study explores the energy storage evolution with temperature by designing a Bi0.5Na0.5TiO3-Sr0.7Bi0.2 square 0.1TiO3-xNaNbO3 system with room temperature ergodic relaxor character. It is found that the addition of NaNbO3 improves temperature stability of energy storage density and efficiency, particularly in the composition of x = 0.15.