Role of Cationic Oxidation States to Enhance the Electroactive β‐Phase of Poly(vinylidene Fluoride) and its Energy Harvesting Performance

Abstract

Transparent, flexible and efficient ferroelectric composite films were fabricated by a simple ultrasonication approach followed by thermal treatment. The enhanced electroactive β‐phase and stabilization of the ferroelectric poly(vinylidene fluoride) (PVDF) polymer were analyzed by the substitution of various cations with different oxidation states (Li1+, Al3+) as fillers. The electroactive β‐phase was obtained due to the stretching of −CH2−/−CF2− molecular chains, stress‐induced effects during the sonication process and the interfacial interaction between the molecular chains and the surface charge of foreign elements. Further, a flexible ferroelectric nanogenerator was implemented and subjected to harness the waste biomechanical energy. The PVDF/Al3+ composite film‐based device gave the maximum amount of voltage and current of 189 V and 0.97 μA respectively at 2 N force. This high electrical output is caused by the electrostatic interaction between electronegative fluorine atoms and the surface active, positive charged ions of the fillers. The obtained maximum instantaneous power density of the FF‐CNG device at 20 MΩ load resistance is 1.92 mW/m2. The generated output is used to power up commercial light‐emitting diodes and display devices without using storage components. The proposed approach for enhancing the throughput of ferroelectric polymers can pave the way to develop new smart composite films for efficient energy conversion.

High-Performance Multifaceted Piezoelectric Composite Nanogenerators for Weight-Monitoring Sensors

“…The nature of the PS-CFs' P−E loop well matched with the many published reports on PVDF and its composite films. 21,30,31 The 0 wt % PS-CF exhibited a P r ≈ 10 nC/cm 2 (P−E loop area is low), which is increased with the substitution of Se-MRs in the PVDF matrix up to 4 wt % (P r ≈ 90 nC/cm 2 ). This is due to the improvement in the electrical conduction path between the PVDF molecular chains via the Se-MRs, and the developed pores between the grains may have acted as charge-trapping carriers.…”

“…The initial raw PVDF powder had a major α-phase (highly disordered) and minor β-(fully ordered) and γ-(partially ordered)-phases, 21 which were transformed during the ultrasonication process (DMF as a solvent) due to the rotation or orientation of −CH 2 −/−CF 2 − molecular chains in an aligned manner (parallel) to the polar axis and also by the stressinduced effects. A high amount of the electroactive β-phase (≈70.5%) was observed for the PS-CF with 0 wt % (i.e., pure PVDF film) as compared to the phases α ≈ 13.36%, and γ ≈ 16.14%.…”

“…The phase fractions F (β) and F (γ) were calculated by the following equations where Δ H β′ is the peak absorbance difference (height differences) between the peaks at 1275 and 1260 cm –1 (nearest valley point) and Δ H γ′ is the peak absorbance difference between the peaks at 1234 and 1225 cm –1 (nearest valley point). Furthermore, the relative phase fractions of the nonpolar α-phase were calculated by the following equation The initial raw PVDF powder had a major α-phase (highly disordered) and minor β- (fully ordered) and γ- (partially ordered)-phases, which were transformed during the ultrasonication process (DMF as a solvent) due to the rotation or orientation of −CH 2 –/–CF 2 – molecular chains in an aligned manner (parallel) to the polar axis and also by the stress-induced effects. A high amount of the electroactive β-phase (≈70.5%) was observed for the PS-CF with 0 wt % (i.e., pure PVDF film) as compared to the phases α ≈ 13.36%, and γ ≈ 16.14%.…”

“…Flexible polymer P-NGs made up of semicrystalline poly­(vinylidene fluoride) (PVDF) , and its copolymers and composites , have been studied. The piezoelectric coefficient in PVDF can be enhanced in many ways, such as using an external electrical poling process, piezoelectric (BaTiO 3 , ZnO, KNaNbO 3 , and PbZrTiO 3 )/nonpiezoelectric (Ce 3+ -graphene, cation salts, SnO 2 , rGO, and TiO 2 ) nanofiller substitution, and creation of self-poling , during fabrication. In these previous studies, it was found that the electrical output performances of polymer P-NGs mainly depend on the relative fraction of the electroactive phase (EAP) of PVDF, such as β- and γ-phases.…”

“…In these previous studies, it was found that the electrical output performances of polymer P-NGs mainly depend on the relative fraction of the electroactive phase (EAP) of PVDF, such as β- and γ-phases. Moreover, the functional properties of PVDF are altered by the substitution of various types of chemical compounds, such as binary, ,− ternary, ,, and many typical complex compounds. ,,, However, the investigation of the substitution of a pure chalcogen chemical element in PVDF and its functional properties is highly necessary, which will reduce the cost factor. Pure elemental filler compounds simplify the working mechanism and enhance (or stabilize) the output performances of films.…”