School of Materials Science and Engineering , Nanyang Technological University , 50 Nanyang Avenue , 639798 , Singapore.
Energy Research Institute @ NTU (ERI@N) , Nanyang Technological University , ResearchTechno Plaza, 50 Nanyang Drive , 637553 , Singapore.
ACS Appl Mater Interfaces. 2018 May 2;10(17):14727-14734. doi: 10.1021/acsami.8b01876. Epub 2018 Apr 17.
VS anode materials with controllable morphologies from hierarchical microflower, octopus-like structure, seagrass-like structure to urchin-like structure have been successfully synthesized by a facile solvothermal synthesis approach using different alcohols as solvents. Their structures and electrochemical properties with various morphologies are systematically investigated, and the structure-property relationship is established. Experimental results reveal that Li ion storage behavior in VS significantly depends on physical features such as the morphology, crystallite size, and specific surface area. According to this study, electrochemical performance degrades on the order of urchin-like VS > octopus-like VS > seagrass-like VS > flower-like VS. Among them, urchin-like VS demonstrates the best electrochemical performance benefiting from its peculiar structure which possesses large surface area that accommodates the volume change to a certain extent, and single-crystal thorns that provide fast electron transportation. Kinetic parameters derived from EIS spectra and sweep-rate-dependent CV curves, such as charge-transfer resistances, Li ion apparent diffusion coefficients and stored charge ratio of capacitive and intercalation contributions, both support this claim well. In addition, the EIS measurement was conducted during the first discharge/charge process to study the solid electrolyte interface (SEI) formation on urchin-like VS and kinetics behavior of Li ion diffusion. A better fundamental understanding on Li storage behavior in VS is promoted, which is applicable to other vanadium-based materials as well. This study also provides invaluable guidance for morphology-controlled synthesis tailored for optimal electrochemical performance.
通过使用不同醇类作为溶剂的简便溶剂热合成方法，成功合成了具有可控形态的 VS 阳极材料，包括分级微花、章鱼状、海草状和刺猬状结构。系统地研究了它们的结构和电化学性能与各种形态的关系，并建立了结构-性能关系。实验结果表明，VS 中的锂离子存储行为显著取决于物理特征，如形态、晶粒尺寸和比表面积。根据这项研究，电化学性能的降解顺序为刺猬状 VS > 章鱼状 VS > 海草状 VS > 花状 VS。其中，刺猬状 VS 表现出最佳的电化学性能，这得益于其独特的结构，具有较大的表面积，可以在一定程度上容纳体积变化，并且单晶刺提供了快速的电子传输。从 EIS 谱和扫描速率相关 CV 曲线得出的动力学参数，如电荷转移电阻、Li 离子表观扩散系数以及电容和嵌入贡献的存储电荷比，都很好地支持了这一说法。此外，在第一次放电/充电过程中进行了 EIS 测量，以研究刺猬状 VS 上的固体电解质界面（SEI）形成和 Li 离子扩散的动力学行为。这促进了对 VS 中 Li 存储行为的更好理解，这也适用于其他基于钒的材料。这项研究还为针对最佳电化学性能的形貌控制合成提供了宝贵的指导。
