Nanofibrous-based composite materials for energy harvesting and storage applications

This study presents the development and characterization of advanced nanofibrous materials for energy harvesting and storage, with a focus on piezoelectric nanofibers and innovative separators for lithium-ion batteries (LIBs). Electrospun P(VDF-TrFE) nanofibrous mats were fabricated and subjected to various poling techniques to enhance their macroscale piezoelectric response through dipole alignment. Among the methods investigated, AC contact poling and corona poling were the most effective, yielding a β-phase content of 94% and piezoelectric strain coefficients (d33) of -27.2 ± 0.6 pC/N and -20.8 ± 1.7 pC/N, respectively—significantly surpassing conventional DC poling. These nanofibers were integrated into a piezoelectric energy harvesting system coupled with a pullulan-based ionic liquid micro-supercapacitor, achieving efficient energy conversion and storage under mechanical stimuli, with a maximum energy output of 211 mJ over 5 hours. This modular integration offers enhanced design flexibility and energy efficiency, indicating strong potential for wearable electronics. In parallel, novel electrospun PVDF-HFP separators for LIBs were developed and enhanced via plasma treatments and inorganic nanofillers. Plasma pre-treatment improved fiber uniformity, reducing average diameters from 557 ± 161 nm to 493 ± 71 nm, while post-treatment significantly boosted electrolyte uptake to 612%—a sixfold increase over commercial Celgard separators (110%). Incorporating nanofillers such as ZrO₂, SnO₂, and SiO₂ notably improved the mechanical and thermal performance of the separators. ZrO₂, for example, increased the elastic modulus from 141 ± 5 MPa to 237 ± 7 MPa and minimized thermal shrinkage. Electrochemical analyses revealed superior ionic conductivity and charge/discharge performance, with ZrO₂-based separators offering the best overall balance of mechanical, thermal, and electrochemical properties. These findings underscore the promise of piezoelectric nanofibers and nanocomposite LIB separators in next-generation energy systems, providing scalable, high-performance solutions for flexible and wearable electronics.