Abstract
Triboelectric nanogenerators (TENGs) are flexible, efficient, and cost-effective energy harvesters. Here, we develop high-performance ferroelectric-assisted TENGs using electrospun fibrous surfaces based on P(VDF-TrFE) with dispersed BaTiO3 (BTO) nanofillers in either cubic (CBTO) or tetragonal (TBTO) form. TENGs with three types of tribo-negative surface (pristine P(VDF-TrFE), P(VDF-TrFE)/CBTO and P(VDF-TrFE)/TBTO) in contact with PET were investigated and output increased progressively from pristine (0.75 W/m2) to CBTO (2 W/m2) and to TBTO (2.75 W/m2). Accounting for contact pressure, the max output (Voc=315 V &Jsc=6.7 µA/cm2) is significantly higher than for TENGs having spin-coated P(VDF-TrFE)/BTO. It is hypothesized that electrospinning increases dipole alignment due to high applied voltages, but also aids the formation of a highly oriented crystalline β-phase via uniaxial stretching. Essentially, tribo-charge transfer is boosted due to increased surface potential owing to enhanced ferroelectric polarization. P(VDF-TrFE)/TBTO produced higher output than P(VDF-TrFE)/CBTO even though permittivity is nearly identical. Thus, it is shown that BTO fillers boost output, not just by increasing permittivity, but also by enhancing the crystallinity and amount of the β-phase (as TBTO produced a more crystalline β-phase present in greater amounts). Finally, the ferroelectric-assisted TENG was integrated with a flexible graphene electrode-based supercapacitor to produce a self-charging system capable of charging to 1.25 V in just 5 min. These results demonstrate that this technology can be valuable in wearable applications where higher power output, more efficient charging and flexibility are paramount.
Highlights
Energy autonomy of wearable electronic systems is a much-needed feature that has attracted considerable interest in recent years as re flected by the development of a wide variety of energy harvesters and storage devices [1,2,3]
Novel ferroelectric-assisted Triboelectric nanogenerators (TENGs) (Fe-TENGs) are fabricated whereby the tribo-negative surface is based on electrospun P
The approach uses electrospinning to significantly increase triboelectric output by boosting surface polarization
Summary
Energy autonomy of wearable electronic systems is a much-needed feature that has attracted considerable interest in recent years as re flected by the development of a wide variety of energy harvesters and storage devices [1,2,3]. TENGs have been explored in a wide range of applications, including self-powered wearable electro nics/sensors, powering of flexible electronics and even for harvesting ocean wave/wind energy Many of these applications place demands on TENG materials such as: high flexibility, ability to maximize electrical output and robustness in sustaining high mechanical stress/strain [4, 21,22,23,24]. Four key fac tors that help optimize this are maximizing: real contact area [27,28], difference in electron affinities of the interface pair [16], permittivity of the tribo-contact materials [29,30,31] and difference in residual surface potential between the interface surfaces [32,33] With these demands in mind, materials that have received particular attention are the ferro electric (FE) polymers polyvinylidene (PVDF) and copolymer poly (vinylidene fluoride-co-trifluoroethylene) (P(VDF-TrFE)) as these are flexible, and allow for permanent polarization of the tribo-contact surfaces and are piezoelectric.
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