Environmental friendly multifunctional energy harvester and energy storage: A strain engineered perovskite oxide composite

Abstract

Piezoelectric energy harvesters are currently regarded as a promising solution to meet the escalating demand for power by harnessing abundant mechanical energy from the environment, thereby addressing the environmental challenges of fossil fuel usage. However, the efficient storage of this harvested energy remains a significant concern. In this context, the development of a self-charging, flexible piezoelectric supercapacitor represents a breakthrough as it not only converts mechanical energy into electrical energy but also stores it within a single unit. Our design involves a piezo nanogenerator utilizing NdMnO₃@PVDF films, which have demonstrated a substantial response with an open circuit voltage (V_OC) of approximately 50 V and a short circuit current (I_SC) of about 30 μA under periodic dynamic strain. These output characteristics ensure its practical application in Internet of Things (IoT) devices. The energy generated is stored effectively in commercially available capacitors, capable of powering multiple green and blue LEDs. Incorporating sol–gel-driven NdMnO₃ nanoparticles into PVDF has led to a significant formation of the β phase (∼89.71 %) and notably high V_OC. This observed piezoelectric effect is likely due to strain induced at the interface of NdMnO₃ nanoparticles embedded within the PVDF matrix, corroborated by XRD analysis. Using Universal Force Field (UFF) force field, energy optimization through molecular mechanics was also performed for NdMnO₃@PVDF composite which satisfactorily substantiates the distortion induced in NdMnO_3. Moreover, EDAX data indicating oxygen deficiency (NdMnO_3-δ) may suggest ferroelectric behaviour and consequently enhances the piezoelectric performance of NdMnO_3-δ. XPS analysis of the NdMnO₃@PVDF composite confirms the coexistence of Mn²⁺ and Mn³⁺, supporting the observed oxygen deficiency in NdMnO_3-δ. Exploration into the potential of a self-charging piezoelectric supercapacitor (SCPSC), using the same composite as a separator, demonstrates a significant capacitance of 41.37 mF cm⁻² and noteworthy capacitance retention of 99 % after 2000 cycles. This comprehensive study emphasizes the feasibility of fabricating self-powered piezoelectric wearable devices integrated with piezo-supercapacitors, thereby opening new avenues for energy-efficient technologies.