Coupled long- and short-period dynamics in Bi3+-doped BCZT/cellulose nanogenerators for optimized output and high-temperature stability

Abstract

In response to the growing demand for sustainable energy solutions, piezoelectric nanogenerators (PENGs) have been extensively investigated for their ability to convert mechanical energy into electrical output. However, improving piezoelectric performance and thermal stability, particularly for wearable applications and high temperature environments, remains a significant challenge. In this study, a “doping-composite” strategy was employed to simultaneously improve the piezoelectric properties and high-temperature reliability of PENGs. Bi³⁺ ions were incorporated into a barium calcium zirconate titanate (BCZT) lattice, which was subsequently embedded in a cellulose/polyvinylidene fluoride (PVDF) composite matrix as a filler. Through Bi³⁺ doping, lattice distortion was induced, and a stabilized quasi-isotropic morphotropic phase boundary (MPB) was achieved. Furthermore, the ceramic–polymer interface was optimized via hydrogen bond network formation, thereby establishing the basis for multiscale polarization dynamics. Consequently, the devices exhibited a distinctive dual-period voltage output: a short-period component, which corresponds to the intrinsic operating frequency of the PENGs, and a long-period component, which is governed by interfacial charge accumulation and its delayed release. Among the compositions studied, the output performance of the PENGs increased with increasing Bi³⁺ concentration, reaching a maximum at a doping level of 0.025 mol, after which performance declined. At this optimal doping level, the PENGs exhibited an open-circuit voltage (V_OC) of 15.3 V, a short-circuit current (I_SC) of 16.85 µA, and a peak power density of 36.56 µW cm⁻² under an applied force of 10 N at 5 Hz. These findings demonstrate that Bi³⁺ doping provides an effective approach for the multiscale synergistic optimization of “doping-composite” systems, thereby laying both theoretical and experimental foundations for wearable electronics and energy harvesting devices capable of functioning under extreme environmental conditions.