(Invited) Laser-Assisted Exfoliation of Black Phosphorus with Thickness Control for Li-Ion Batteries

Abstract

Few-layer black phosphorus (BP) is an emerging two-dimensional (2D) material with exciting properties such as tunable bandgap and high charge carrier mobility, which make it a suitable candidate for energy storage applications. However, its preparation remains challenging. Currently, the exfoliation of bulk crystal to its few-layer form assisted by liquid-phase exfoliation (LPE) process using ultrasonic agitation is commonly adopted, which is time-consuming and suffers low efficiency and lack of morphologic control. In this study, we demonstrate a highly-efficient route for the scalable production few-layer BP nanosheets using a pulsed laser in low-boiling point solvents. By adjusting the laser irradiation time and solvent type, the morphology (layer number and lateral size) of the few-layer BP nanosheets is tuned with a narrow distribution (layer number from 3 to 13, lateral size from <2 µm to >5 µm). The laser-assisted exfoliation is understood by a plasma quenching mechanism and interlayer interaction weakened by the in situ generated vapor bubbles. The fine control of thickness and lateral size of the BP nanosheets enables us to study their impact on Li-ion battery performance when applied as anode material. We present herein the correlation of the layer number and larger lateral size of BP with the electronic conductivity, Li+ ion transfer rate and diffusivity, as well as long-term cyclability, revealing the morphology-dependent battery performance. Figure 1