Tailoring the Electrical Energy Storage Capability of Dielectric Polymer Nanocomposites via Engineering of the Host–Guest Interface by Phosphonic Acids

Abstract

Polymer nanocomposites have attracted broad attention in the area of dielectric and energy storage. However, the electrical and chemical performance mismatch between inorganic nanoparticles and polymer leads to interfacial incompatibility. In this study, phosphonic acid molecules with different functional ligands were introduced to the surface of BaTiO3 (BT) nanoparticles to tune their surface properties and tailor the host–guest interaction between BT and poly(vinylideneflyoride-co-hexafluroro propylene) (P(VDF-HFP)). The dielectric properties and electrical energy storage capability of the nanocomposites were recorded by broadband dielectric spectroscopy and electric displacement measurements, respectively. The influence of the ligand length and polarity on the dielectric properties and electrical energy storage of the nanocomposites was documented. The nanocomposite with 5 vol% 2,3,4,5,6-pentafluorobenzyl phosphonic acid (PFBPA)-modified BT had the highest energy density of 12.8 J cm−3 at 400 MV m−1, i.e., a 187% enhancement in the electrical energy storage capability over the pure P(VDF-HFP). This enhancement can be attributed to the strong electron-withdrawing effect of the pentafluorobenzyl group of PFBPA, which changed the electronic nature of the polymer–particle interface. On the other hand, PFBPA improves the compatibility of the host–guest interface in the nanocomposites and decreases the electrical mismatch of the interface. These results provide new insights into the design and preparation of high-performance dielectric nanocomposites.

Synthesis and Characterization of Core–Double-Shell-Structured PVDF-grafted-BaTiO3/P(VDF-co-HFP) Nanocomposite Films

“…However, the actual weight concentrations of BT nanoparticles grafted using PVDF chains were 16% and 38%, respectively, after the removal of ungrafted and physisorbed chains by washing them with acetone, as determined in a previous work by our team [40]. The HR MAS NMR 19 F spectra of the two PVDF-g-BT nanocomposites employed are reported in Figures S2 and S3 of the Supporting Information [35]. TEM pictures of the BT particles grafted with PVDF chains were reported in Ref.…”

“…The following supporting information can be downloaded at: https:// www.mdpi.com/article/10.3390/polym15143126/s1, Figure S1: 19 F NMR spectrum of commercially available P(VDF-co-HFP) recorded in CDCl3; Scheme S1: Sketch illustrating the synthesis process of PVDF-g-BaTiO 3 nanocomposites via RAFT polymerization of VDF in the presence of xanthates (from the modification of BaTiO 3 nanoparticles), where TBPPi stands for tert-butyl peroxypivalate;…”

“…The process can be performed by modifying the surface and functionalizing the nanoparticles, thereby improving their compatibility with the polymer matrix. Various methods have been explored for surface modification, including hydroxylation [ 16 ], phosphonic acid treatment [ 17 , 18 , 19 ], dopamine coating [ 11 , 20 ], decoration with Ag nanocrystals [ 21 ], and the use of coupling agents [ 22 , 23 , 24 ]. In a different method known as “interfacial modifier engineering”, polymers are grafted onto the surface of BaTiO 3 nanoparticles to create core–shell nanostructures [ 25 , 26 , 27 , 28 ].…”

“…Expansion of the −64 to −120 ppm region of the19 F HRMAS spectrum recorded in d6-DMSO of PVDF-g-BaTiO 3 nanocomposite filled with 10 wt % of BaTiO3; FigureS3: Expansion of the −64 to −120 ppm region of the19 F HRMAS spectrum recorded in d6-DMSO of PVDF-g-BaTiO 3 nanocomposite filled with 20 wt % of BaTiO 3 ; Figure S4: Dielectric permittivity, ε , and loss tangent, tan δ, of 10-10, 10-20, and 20-10 nanocomposite films versus temperature at different frequencies; Figure S5: Selected representative isothermal spectra recorded for ε and tan δ of the 10-10, 10-20, and 20-10 nanocomposite films; Figure S6: Frequency dependence of the dielectric loss modulus (Modulus , or M ) of pristine P(VDF-co-HFP) and of its 10-10 nanocomposite film at different temperatures; Figure S7: Modulus M versus frequency at different temperatures of the 20-20 nanocomposite film. Author Contributions: Conceptualization, M.L.…”

MXene-Based Nanocomposites for Piezoelectric and Triboelectric Energy Harvesting Applications

“…Then, PVDF has high dielectric strength, meaning it can withstand high electrical fields without breaking down or becoming electrically conductive [ 199 ]. It has low dielectric loss, which loses only a small amount of electrical energy as heat during energy storage [ 200 ]. This leads to usefulness for energy storage applications, where it can be used as a dielectric material in capacitors [ 201 , 202 ].…”