Effect of Long-Range and Local Order of Exfoliated and Proton-Beam-irradiated WSe2 Nanosheets for Sodium Ion Battery Application

WSe2 nanosheets were synthesized by mechanical exfoliation via sonication of bulk WSe2 in organic solvent. The exfoliated WSe2 nanosheets were separated into two different particle size ranges, and were then irradiated by a proton beam for modification of their local structure, along with the original bulk sample. According to X-ray diffraction (XRD) and X-ray absorption spectroscopy (XAS) analyses of the samples, the mechanical exfoliation reaction mainly affected the long-range order of the WSe2 samples, whereas proton beam irradiation influenced the local structure of the two-dimensional WSe2. To examine the structural dependence of exfoliated and proton-beam irradiated WSe2 in sodium ion battery (NIB) applications, charge/discharge experiments were carried out, which showed that proton beam irradiation could effectively enhance both the discharge capacity and cycling performance of the WSe2 samples. This synthetic procedure via proton beam irradiation is expected to be used for the development of new anode materials with increased energy density in NIBs.