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

Abstract

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□0.1TiO3–xNaNbO3 (x = 0, 0.05, and 0.15) system is designed with a room-temperature 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 (WRec, change rate: δ ≤ 14%) and efficiency (η = 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 (δ ≤ 85%, η = 0.08–0.88) and 0.05 (δ ≤ 36%, η = 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.