Introduction to the results
Hard carbon is a promising sodium/potassium ion battery negative electrode material, which has attracted much attention in the field of grid-scale energy storage. However, it is still affected by the slow electrochemical kinetics of the chaotic structure derived from carbon, resulting in poor magnification capacity. This article, Wuhan University of Science and Technology Li Xuanke, Zhang Qin and Yang Nianjun from the University of Siegen, Germany, published a paper titled "Edge-enriched and S-doped carbon nanorods to accelerate electron chemical kinetics of sodium/potassium storage" in the journal of the Carbon. study proposes to utilize a simple strategy to prepare edge-enriched and S-doped carbon nanorods (SCNs) with controlled diameter and highly oriented carbon layer arrangements.
The rich edges lead to shorter diffusion paths of ions and an enlarged layer spacing, which contribute to the rapid kinetics of ion insertion/detachment. This unique highly oriented structure allows the SCN anode to provide excellent magnification capacity and long-lasting cycle life for sodium and potassium ion storage. The results of density functional theory (DFT) show that the adsorption of Na+ ions near the sulfur-doped active site is enhanced and the ion diffusion barrier is reduced, confirming that the electrochemical kinetics of the SCN electrode are promoted. This work provides more ideas for the rational design of advanced electrodes and provides in-depth insights into the reaction kinetics of carbon anodes.
Picture and text introduction
Figure 1. (a) Schematic diagram of the synthesis process of SCPs and SCNs, (b) SEM images of polymerized and (c) carbonized SCPs, (d) SEM images of SCNs intermediates, (e-g) SEM images and diameter distributions (e) SCNs-850, (f) SCNs-950 and (g) SCNs-1050 (inset).
Figure 2. Sodium storage properties of three SCNs.
Figure 3. Potassium storage performance of SCNs-950
Figure 4. Na adsorption capacity of various S-doped sites, Na + ion diffusion coefficient of SCN electrodes, ion storage characteristics of traditional carbon (left) and SCNs electrodes (right)
Summary
In short, S-doped carbon nanorods with high-oriented carbon layers arranged perpendicularly along the axis are made by polymerizing thiophene in an atmosphere filled with sulfur steam. SCN provides rich active edge plane sites and short diffusion paths for Na/K ions, thereby enhancing the capacitance behavior. In addition, the large interlayer distance and reasonable adsorption energy caused by S doping reduce the ion diffusion barrier, thereby providing rapid reaction kinetics during the intercalation process. The unique structure allows SCNs to have large and stable specific capacity, as well as high-speed capacity and cycling durability for both SIBs and PIBs at different current densities. Therefore, the structural design concept for improving carbon anode dynamics is effective and forward-looking.
Literature:
https://doi.org/10.1016/j.carbon.2022.09.066
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