Energy storage properties of flexible dielectric composites containing Ba0.4Sr0.6TiO3/MnO2 heterostructures

Although flexible dielectric composites are attractive for high-power energy storage, their low energy storage density (Ue) and efficiency (eta) significantly restrict their practical applications. Ue is difficult to further improve due to the limitation of theoretical dielectric constant and polarization of the polymer matrix and filler. Herein, an effective strategy to enhance the Ue and eta of dielectric polymers by constructing Ba0.4Sr0.6TiO3/MnO2 (BST/ MnO2) heterostructure as filler in BST/MnO2/P(VDF-HFP)& PMMA composites is proposed. On one hand, the tightly attached MnO2 on BST particles can improve the local electric field intensity on the BST, enhancing the Ti4+ ionic displacement and contributing to the high polarization. On the other hand, semiconductive MnO2 with higher electron affinity can trap the injected and excited electrons, and the large trap energy level between MnO2 and the polymer that could inhibit the mobility of free charge carriers in the film. Thus, the leakage current density is suppressed and the breakdown strength is enhanced. Both of them improve the energy storage per-formance of film, resulting in the excellent Ue of 21.2 J cm-3 and high eta of 75.4 % at 667 kV mm-1. The proposed heterostructure strategy offers a new paradigm for improving the energy storage performance of composite capacitors.