Three-phases Fe₃O₄@TiO₂-P(VDF-HFP) composite films with high energy storage density at low filler fraction under low operating electric field

Abstract

An enhanced energy storage ability, under a low operating electric field, was achieved in Fe3O4@TiO2-P(VDF-HFP) composite films. The low conductivity TiO2 layer was coated onto the high polarization Fe3O4 to construct Fe3O4@TiO2 core–shell fillers for decreasing filler fraction and alleviating conductivity contrast. For instance, the 2 vol.% Fe3O4@TiO2-P(VDF-HFP) film shows a discharged energy density and energy efficiency of 8.6 J cm−3 and 61.7%, respectively, under a low operating electric field of 261.9 kV mm−1. The coated TiO2 and modified –OH groups not only restrict the adverse effects (such as high conductivity, easy agglomeration, etc) caused by Fe3O4, but also contribute greatly to the improvement of polarization and breakdown strength, leading to a significantly improved energy storage performance. Additionally, the present work might possess great potential applications for energy storage owing to the low filler fraction, simple, and low electric filed operation.

Excellent Energy Storage Performance in Bilayer Composites Combining Aligned TiO2 Nanoarray and Random TiO2 Nanowires with Poly(vinylidene fluoride)

“…Moreover, the breakdown strength of ( x vol % TO NWs/TNA)–PVDF composites greatly improved in comparison with that of pure PVDF and TNA–PVDF composite (Figure S3), especially for the (5 vol % TO NWs/TNA)–PVDF composite, whose breakdown strength (513 MV/m) is nearly 1.5 times higher than that of the TNA–PVDF composite (330 MV/m). Similar results are further proved by the leakage current behavior of the ( x vol % TO NWs/TNA)–PVDF composites as shown in Figures d and S4. ,, The greatly improved breakdown strengths of ( x vol % TO NWs/TNA)–PVDF composites are contributed by the following reasons: (i) the uniform distribution of TO NWs in the upper layer acts as the scattering center of charges and obstacles in the process of electrical trees, leading to the increased tortuosity of the breakdown path and enhancement of breakdown strength. ,, It should be noted that the 5 vol % fraction is optimal in this study. Since 3 vol % is relatively low, it is less helpful to increase the curvature of breakdown path, resulting in lower breakdown strength, while for the (7 vol % TO NWs/TNA)–PVDF composite, the breakdown strength is greatly decreased owing to the aggregation of the TO NWs, which is in agreement with many previous reports. ,,, (ii) Due to the large dielectric contrast, the redistribution of the electric field that is mainly concentrated in the upper layer helps to protect the bottom layer from being premature breakdown at low electric field.…”

“…Similar results are further proved by the leakage current behavior of the (x vol % TO NWs/TNA)−PVDF composites as shown in Figures 4d and S4. 5,35,46 The greatly improved breakdown strengths of (x vol % TO NWs/TNA)−PVDF composites are contributed by the following reasons: (i) the uniform distribution of TO NWs in the upper layer acts as the scattering center of charges and obstacles in the process of electrical trees, leading to the increased tortuosity of the breakdown path and enhancement of breakdown strength. 13,25,47 It should be noted that the 5 vol % fraction is optimal in this study.…”

Effect of Nano-Clay Filler on the Thermal Breakdown Mechanism and Lifespan of Polypropylene Film Under AC Fields

“…In recent years, the application of polymer as dielectric materials in power grid has effectively improved the performance of power equipment, such as energy storage characteristics [1], [2], mechanical properties [3], electrical strength [4], [5] and so on. Many studies have shown that, on the basis of ensuring the original properties of the above polymeric dielectric materials, nano-fillers can further improve the properties of the materials through effective combination with the polymer matrix [6]- [8].…”

Influence of Hot‐Press Temperature on β‐Phase Formation and Electrical Properties of Solvent‐Casted PVDF‐HFP Co‐Polymer Films Prepared from Two Different Solvents: A Comparison Study

“…Reports are available with PVDF-HFP films being prepared by solvent casting method using either mixture of solvents or single solvent. Majority of the times, researchers have either utilized DMF alone [32][33][34][35] or combined DMF and Acetone mixture [36,31] to prepare PVDF-HFP film without a proper comparison of the results obtained from the two. Thus, suitability of the solvent is not found in the literature.…”