Li Doping‐Mediated Ultrahigh Current Generation from Flexible 2D MoS2 Nanosheets‐Based Nanogenerators

Abstract

Engineering piezoelectric properties of 2D nanosheets is crucial to design high‐performance piezoelectric nanogenerator devices to scavenge mechanical energy. Herein, highly crystalline 2D Li‐doped MoS2 nanosheets are grown by the simple and cost‐effective hydrothermal method. High‐resolution transmission electron microscope and Raman analysis confirm the hexagonal crystal structure and formation of few‐layered MoS2 nanosheets with thickness of 3 nm and length of about 500 nm. Piezoelectric force microscopy study reveals the nanoscale high piezoelectric charge coefficient of 130 pm V−1 from few‐layered Li‐doped MoS2 nanosheets. Surprisingly, the piezoelectric flexible nanogenerator fabricated from Li‐doped MoS2 nanosheets exhibits very high output voltage of 13.5 V and ultrahigh current density of 30 μA cm−2 even under small compressive force. A very high dielectric constant of 28117 is observed from Li‐doped MoS2 nanosheets, which is almost 10 times higher than pristine MoS2 nanosheets (2320). The high output voltage and charge generation mechanism are also discussed in terms of the Li‐mediated defect passivation and formation of the nanodipole in the nanosheets.