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

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 mu A 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.