Enhanced energy storage performance of layered polymer composites with an ultralow loading rate of TNSs@PDA

Polymer-based dielectric nanocomposites have attracted much attention since they have advantages such as high power density and stability. The introduction of inorganic fillers is one of the strategies to enhance the discharge energy density (U_d) of polymer composite dielectrics. However, the negative coupling effect of relative dielectric permittivity (ε_r) and breakdown strength (E_b) is the key reason for the difficulty in achieving high energy storage density. In this work, polydopamine-modified titania nanosheet (TNSs@PDA) was fabricated, which has been used as fillers for monolayer TNSs@PDA/P(VDF-HFP) composites. The monolayer TNSs@PDA/P(VDF-HFP) composite with 0.2 wt% TNSs@PDA (0.2 wt% 1 L) has a low dielectric loss of 0.038 and its ε_r increased to 11.94 at 10 kHz, which corresponded to 129 % of that of P(VDF-HFP) (∼ 9.25). Additionally, the monolayer 0.2 wt% 1 L composite film was hot pressed with PEI and P(VDF-HFP) films to form a sandwich structure, which has a high E_b of 599.3 kV/mm, a high U_d of 9.97 J/cm³, a low dielectric loss of 0.025, and an energy storage efficiency of 82 %. This study provides an effective approach for designing polymer composites that combine high U_d with high energy storage efficiency.