Multilevel Structure Engineered Lead‐Free Piezoceramics Enabling Breakthrough in Energy Harvesting Performance for Bioelectronics

Abstract The prevalence of wearable/implantable medical electronics together with the rapid development of the Internet of Medicine Things call for the advancement of biocompatible, reliable, and high‐efficiency energy harvesters. However, most current harvesters are based on toxic lead‐based piezoelectric materials, raising biological safety concerns. What hinders the application of lead‐free piezoelectric energy harvesters (PEHs) is the low power output, where the key challenge lies in obtaining a high piezoelectric voltage constant ( g 33 ) and harvesting figure of merit ( d 33 × g 33 ). Here, micron pores are introduced into phased boundary engineered high‐performance (K, Na)NbO 3 ‐based ceramic matrix, resulting in the state‐of‐the‐art g 33 and the highest d 33 × g 33 values of 57.3 × 10 −3 Vm N −1 and 20887 × 10 −15 m 2 N −1 in lead‐free piezoceramics, respectively. Concomitantly, ultrahigh energy harvesting performances are obtained in porous ceramic PEHs, with output voltage and power density of 200 V and 11.6 mW cm −2 under instantaneous force impact and an average charging rate of 14.1 µW under high‐frequency (1 MHz) ultrasound excitation, far outperforming previously reported PEHs. Porous ceramic PEHs are further developed into wearable and bio‐implantable devices for human motion sensing and percutaneous ultrasound power transmission, opening avenues for the design of next‐generation eco‐friendly WIMEs.