Preparation of β-Polyvinylidene Fluoride Film for Self-Charging Lithium-Ion Battery

Abstract

—In recent years development of sustainable energy sources is getting extensive research interest due to the ever-growing demand for energy. As an alternative energy source to power small electronic devices, ambient energy harvesting from vibration or human body motion is considered to be a potential candidate. Despite the enormous progress in the field of battery research in terms of safety, lifecycle, and energy density in about three decades, it has not reached the level to conveniently power wearable electronic devices such as smart watches, bands, hearing aids, etc. For this reason, the development of self-charging power units with excellent flexibility, and integrated energy harvesting and storage is crucial. Self-powering is a key idea that makes possible the system to operate sustainably, which is now getting more acceptance in many fields in the area of sensor networks, internet of things (IoT) and implantable in-vivo medical devices.For solving this energy harvesting issue, the self-powering nanogenerators (NGs) were proposed and proved their high effectiveness. Usually, sustainable power is delivered through energy harvesting and storage devices by connecting them to the power management circuit, as for energy storage, Li-ion battery (LIB) is one of the most effective technologies. Through the movement of Li ions under the driving of an externally applied voltage source, the electrochemical reactions generate the anode and cathode, storing the electrical energy as the chemical energy. In this paper, we present a simultaneous process of converting the mechanical energy into chemical energy in a way that NG and LIB are combined as an all-in-one power system.The electrospinning method was used as an initial step for the development of such a system with β-PVDF separator. The obtained film showed promising voltage output at different stress frequencies. X-Ray diffraction (XRD) and Fourier Transform Infrared Spectroscopy (FT-IR) analysis showed a high percentage of β phase of PVDF polymer material. Moreover, it was found that the addition of 1 wt.% of BTO (Barium Titanate) results in higher quality fibers. When comparing pure PVDF solution with 20 wt.% content and the one with BTO added the latter was more viscous. Hence, the sample was electrospun uniformly without any beads. Lastly, to test the electrical output of such film, a particular testing device has been developed. With this device, the force of a finger tap can be applied at different frequencies, so that voltage generation across the surfaces of the film is validated. Further, this piezoelectric PVDF film can be used as a separator for LIB. Acknowledgements This work was supported by the project 240919FD3914 “Self-Charging Rechargeable Lithium-ion Battery” from Nazarbayev University, Kazakhstan.