Bai Yansong, Zhang Xiaoyan, Tang Ke, Yang Li, Liu Hong, Liu Lei, Zhao Qinglan, Wang Ying, Wang Xianyou
National Base for International Science & Technology Cooperation, National Local Joint Engineering Laboratory for Key Materials of New Energy Storage Battery, Hunan Province Key Laboratory of Electrochemical Energy Storage & Conversion, School of Chemistry , Xiangtan University , Hunan 411105 , China.
Department of Chemistry , The Chinese University of Hong Kong , Shatin , New Territories , Hong Kong.
ACS Appl Mater Interfaces. 2019 Sep 4;11(35):31980-31990. doi: 10.1021/acsami.9b10029. Epub 2019 Aug 22.
NaFeSiO, as one of the promising cathode materials in sodium-ion batteries, has attracted great interests. However, studies on the kinetic behaviors of Na ions insertion/extraction in NaFeSiO composite electrode have been barely considered, until now. Importantly, the specific capacity and rate capability of NaFeSiO cathode materials are greatly correlated with the kinetics of Na transfer in the host material. Herein, on the basis of the characterizations of microstructure and morphologies (i.e., Rietveld refinement, FESEM, HRTEM, etc.), the electrochemical kinetics of Na ions extraction in NaFeSiO/C electrode are first studied in detail via two electrochemical techniques (EIS and GITT), establishing the rate-controlling steps of Na transport in NaFeSiO/C, evaluating series of kinetic parameters, as well as calculating the Na diffusion coefficient at various state-of-desodiation. Changes of impedance response of NaFeSiO/C electrode depending on the different levels of desodiation show that a serial features of electrode process for Na ions migration have tremendous discrepancies, indicating that the kinetics of Na extraction from NaFeSiO/C electrode are largely influenced by different electrode reaction processes. These results provide useful insight into the inner properties of NaFeSiO/C electrode, and it is significant to optimize the electrochemical performance of NaFeSiO/C. Moreover, two models of equivalent circuits are also constructed to simulate the electrode processes and describe the behaviors of Na ions transfer in NaFeSiO/C.
NaFeSiO作为钠离子电池中一种很有前景的阴极材料，已引起了极大的关注。然而，迄今为止，关于NaFeSiO复合电极中Na离子嵌入/脱出的动力学行为的研究几乎未被考虑。重要的是，NaFeSiO阴极材料的比容量和倍率性能与主体材料中Na传输的动力学密切相关。在此，基于微观结构和形貌的表征（即Rietveld精修、场发射扫描电子显微镜、高分辨率透射电子显微镜等），首次通过两种电化学技术（电化学阻抗谱和恒电流间歇滴定技术）详细研究了NaFeSiO/C电极中Na离子脱出的电化学动力学，确定了NaFeSiO/C中Na传输的速率控制步骤，评估了一系列动力学参数，并计算了不同脱钠状态下的Na扩散系数。NaFeSiO/C电极的阻抗响应随脱钠程度的不同而变化，表明Na离子迁移的电极过程的一系列特征存在巨大差异，这表明从NaFeSiO/C电极中脱出Na的动力学在很大程度上受不同电极反应过程的影响。这些结果为深入了解NaFeSiO/C电极的内部性质提供了有用的见解，对优化NaFeSiO/C的电化学性能具有重要意义。此外，还构建了两种等效电路模型来模拟电极过程并描述NaFeSiO/C中Na离子的传输行为。
