# Research Progress and Applications of 2D Antimonene
## 3 Practical Applications
### Energy Storage  
Antimonene, with a theoretical capacity of up to 660 mAh g\({}^{-1}\) and a large surface area of active material, is an excellent choice as a cathode material for batteries. Based on the results of X-ray diffraction (XRD), selected area electron diffraction (SAED) and density functional theory (DFT), the superior sodium storage properties of the few layers of antimonene were determined and the mechanism of sodium conversion/removal of the few layers of antimonene was elucidated [64]. Several layers of antimonene underwent reversible crystal phase evolution (Sb) \(\Longrightarrow\) NaSb \(\Longrightarrow\) Na3 Sb) and Na ion alloy reaction along the a/b axis, resulting in in-plane anisotropic lattice expansion, while due to unconstrained in-plane expansion along the a/b axis, few-layer antimonene can realize sodium ion storage with high structural stability. Meanwhile, it is determined that the Na+ diffusion potential of antimonene is only 0.14 eV, which is lower than that of other two-dimensional materials. In this study, antimonene was used as the working electrode and sodium as the counter electrode. Due to the large surface area of electrolyte/electrode in the first cycle process, the excess side reactions resulted in irreversible effects. The low-layer antimonene anode  
Figure 12: (**a**) Schematic diagram of the sensor system; (**b**) The flexible sensing system includes a supercapacitor placed on the surface of the coating and a sensor attached to the skin, as well as a schematic diagram of the complete circuit. Reprinted with permission from Ref. [11]. Copyright 2022, Elsevier. provides a capacity of 642 mAh g\({}^{-1}\) at 0.1 C. When the current density increases to 5 C, the capacity is only 429 mAh g\({}^{-1}\). When the current density returns to 0.1 C after 36 cycles, the capacity also returns to 642 mAh g\({}^{-1}\), which shows that it has good reversibility. The long-term cycle of antimony and antimonene was measured as shown in Figure 13a at a current density of 0.5 C, and the stable capacity of 620 mAh g\({}^{-1}\) was obtained at 0.5 C. For antimony, the capacity of bulk Sb rapidly decays due to significant volume changes during sodium conversion and removal, resulting in severe pulverization. However, the Sb atom content of antimonene is 93.9% after 150 cycles, and the Coulombic efficiency is close to 100%, as shown in Figure 13b. They are the highest capacity and Sb utilization reported so far. Layered two-dimensional (2D) materials are ideal materials for high-performance lithium-ion battery electrodes due to their high surface-volume ratio, which can alleviate the strain caused by volume changes during lithium absorption and release. However, the van der Waals force limits the motion of lithium atoms and thus reduces the efficiency of the battery. To solve this problem, charge transport has been improved by creating ordered holes in two-dimensional sheets. However, the complexity of the process limits the practical application, and single-layer antimonene allows the movement of lithium atoms without structural engineering conditions. [PERSON] et al. [65] proved the theory through the first-principle study, and found that lithium atoms have an ultra-low diffusion barrier (0.36 eV) on antimonene, which is consistent with the movement of lithium atoms in the horizontal plane. The results show that antimonene is a two-dimensional material with rapid outward diffusion of lithium, which may be unique in the design of a new generation of lithium-ion battery materials and solid ion conductors. [PERSON] et al. [66] applied antimonene quantum dots as photoactive materials in solar cells. Based on the application of antimonene quantum dots as sensitizers in solar cells, the photoelectric conversion efficiency of antimonene quantum dots remains above 90% of the initial value after 1000 h. Meanwhile, antimonene quantum dots showed excellent photostability against oxidation and degradation, indicating that antimonene is indeed a promising optical material for solid solar cells.