<scp>PVDF</scp>‐based high‐energy‐storage dielectrics by introducing insulating layer on the surface of metal‐organic frameworks

Abstract In this paper, UiO‐66 nanoparticles were synthesized through the hydrothermal synthesis technique. Subsequently, a series of metal‐organic framework/polyvinylidene fluoride (MOF/PVDF) composite films were produced via a solution‐casting approach. The dielectric properties of UiO‐66/PVDF (U/P) composite are improved with the addition of UiO‐66. The dielectric constant ( ɛ r ) of 20 wt% U/P composite film at 10 2 Hz is 11.20, 1.44 times that of pure PVDF film ( ɛ r = 7.78). However, the breakdown strength ( E b ) was only 95 kV mm −1 . To solve the problem of sharp decline in E b , TiO 2 with a wide band gap was introduced to form an insulating layer on the surface of UiO‐66. This reduces the difference in electrical properties between the filler and PVDF, hinders the formation of the conductive path within the composite, reduces leakage current, and increases E b . Compared with the U/P composite, the ɛ r and E b of TiO 2 @UiO‐66/PVDF (T@U/P) composite film are increased, and the dielectric loss (tan δ ) and leakage current density ( J ) are decreased. The energy storage density ( U e ) of 10 wt% T@U/P composite film is 4.51 J cm −3 and the charge and discharge efficiency ( η ) is 84.61% at 150 kV mm −1 . These results indicate that the dielectric properties of UiO‐66 can be significantly enhanced by using titanium dioxide as an insulating layer. Highlights By introducing UiO‐66, the ɛ r of PVDF material is improved. Modifying UiO‐66 with TiO 2 can improve its breakdown strength significantly. The U e of the T@U/P‐10 composite modified with UiO‐66 is 4.51 J cm −3 .