Li-Salt of AdipicAcid Incorporated Flexible Poly(vinylidenefluoride) Composite for Piezoelectric Energy Harvester with SuperiorEnergy Density Toward Self-Powered Traffic Monitoring System

The development of the composite material based on poly(vinylidene fluoride) (PVDF) incorporating lithium salt of adipic acid (Li-AA) presents a promising avenue for sustainable and renewable energy generation via piezoelectric nanogenerators. In this study, PVDF/Li-AA composites were prepared through melt-mixing, followed by the fabrication of thin films using compression molding and solution casting techniques, with Li-AA concentration ranging from 1% to 10% by weight. Analysis via Fourier transform infrared spectroscopy (FTIR) confirmed hydrogen bonding interactions between −CF₂ moieties of PVDF and the acid functional groups of Li-AA. Additionally, FTIR analysis revealed that the solution-cast PVDF/Li-AA composite containing 10 wt % Li-AA exhibited the highest polar phase amount (∼ 65%) among all the composites, with remnant polarization of ∼4.2 × 10^–3 μC/cm² (50 Hz and 500 V). Furthermore, the solution cast PVDF/Li-AA composite film containing 10 wt % Li-AA achieved the highest piezoelectric coefficient (<i>d</i>₃₃ value ∼ 42 pm/V), indicating superior piezoelectric response. Energy harvesting devices fabricated using compression molded and solution-cast films demonstrated an output voltage of ∼80 and ∼100 V, respectively, obtained from PVDF/Li-AA composite containing 10 wt % Li-AA. Furthermore, devices fabricated with compression molded and solution-cast composite films containing 10 wt % Li-AA exhibited higher power densities of ∼80 and ∼100 μW/cm², respectively. Finally, PVDF/Li-AA composite film based self-powered speed sensor was fabricated for speed detection of the vehicles.