Parmar Rahul, Rezvani Javad, Amati Matteo, Gregoratti Luca, Neto Decio Batista de Freitas, Rosolen Jose Mauricio, Gunnella Roberto
Elettra-Sincrotrone Trieste, Strada Statale 14, AREA Science Park, 34149 Trieste, Italy.
Physics Division, School of Science and Technology, Università di Camerino, Via Madonna delle Carceri 9, 62032 Camerino, Italy.
Materials (Basel). 2023 Mar 2;16(5):2069. doi: 10.3390/ma16052069.
Improvements in sodium intercalation in sodium cathodes have been debated in recent years. In the present work, we delineate the significant effect of the carbon nanotubes (CNTs) and their weight percent in the intercalation capacity of the binder-free manganese vanadium oxide (MVO)-CNTs composite electrodes. The performance modification of the electrode is discussed taking into account the cathode electrolyte interphase (CEI) layer under optimal performance. We observe an intermittent distribution of the chemical phases on the CEI, formed on these electrodes after several cycles. The bulk and superficial structure of pristine and Na+ cycled electrodes were identified via micro-Raman scattering and Scanning X-ray Photoelectron Microscopy. We show that the inhomogeneous CEI layer distribution strongly depends on the CNTs weight percentage ratio in an electrode nano-composite. The capacity fading of MVO-CNTs appears to be associated with the dissolution of the Mn2O3 phase, leading to electrode deterioration. This effect is particularly observed in electrodes with low weight percentage of the CNTs in which the tubular topology of the CNTs are distorted due to the MVO decoration. These results can deepen the understanding of the CNTs role on the intercalation mechanism and capacity of the electrode, where there are variations in the mass ratio of CNTs and the active material.
近年来，关于钠阴极中钠嵌入的改进一直存在争议。在本工作中，我们阐述了碳纳米管（CNTs）及其重量百分比对无粘结剂锰钒氧化物（MVO）-碳纳米管复合电极嵌入容量的显著影响。在最佳性能下，考虑到阴极电解质界面（CEI）层，讨论了电极的性能改性。我们观察到在经过几个循环后，在这些电极上形成的CEI上化学相的间歇性分布。通过显微拉曼散射和扫描X射线光电子显微镜确定了原始电极和Na⁺循环电极的体相和表面结构。我们表明，不均匀的CEI层分布强烈依赖于电极纳米复合材料中碳纳米管的重量百分比。MVO-碳纳米管的容量衰减似乎与Mn₂O₃相的溶解有关，导致电极劣化。这种效应在碳纳米管重量百分比低的电极中尤为明显，其中碳纳米管的管状拓扑结构由于MVO修饰而变形。这些结果可以加深对碳纳米管在电极嵌入机制和容量方面作用的理解，其中碳纳米管与活性材料的质量比存在变化。
