Tang Yuxin, Zhang Yanyan, Malyi Oleksandr I, Bucher Nicolas, Xia Huarong, Xi Shibo, Zhu Zhiqiang, Lv Zhisheng, Li Wenlong, Wei Jiaqi, Srinivasan Madhavi, Borgna Armando, Antonietti Markus, Du Yonghua, Chen Xiaodong
Innovative Centre for Flexible Devices (iFLEX), School of Materials Science and Engineering, Nanyang Technological University, 50 Nanyang Avenue, Singapore, 639798, Singapore.
Centre for Materials Science and Nanotechnology, Department of Physics, University of Oslo, P.O. Box 1048 Blindern, NO-0316, Oslo, Norway.
Adv Mater. 2018 Jul 3:e1802200. doi: 10.1002/adma.201802200.
Fundamental insight into the surface charging mechanism of TiO (B) nanomaterials is limited due to the complicated nature of lithiation behavior, as well as the limitations of available characterization tools that can directly probe surface charging process. Here, an in situ approach is reported to monitor the dynamic valence state of TiO (B) nanotube electrodes, which utilizes in situ X-ray absorption spectroscopy (XAS) to identify the origin and contribution of surface storage. A real-time correlation is elucidated between the rate-dependent electrode performance and dynamic Ti valence-state change. A continuous Ti valence state change is directly observed through the whole charging/discharging process regardless of charging rates, which proves that along with the well-known non-faradaic reaction, the surface charging process also originates from a faradaic reaction. The quantification of these two surface storage contributions at different charging rates is further realized through in situ dynamic valence state monitoring combined with traditional cyclic voltammetry measurement. The methodology reported here can also be applied to other electrode materials for the real-time probing of valence state change during electrochemical reactions, the quantification of the faradaic and non-faradaic reactions, and the eventual elucidation of electrochemical surface charging mechanisms.
由于锂化行为的复杂性以及现有能够直接探测表面充电过程的表征工具的局限性，对TiO (B)纳米材料表面充电机制的基本认识有限。在此，报道了一种原位方法来监测TiO (B)纳米管电极的动态价态，该方法利用原位X射线吸收光谱(XAS)来确定表面存储的起源和贡献。阐明了速率依赖的电极性能与动态Ti价态变化之间的实时相关性。无论充电速率如何，在整个充电/放电过程中都直接观察到Ti价态的连续变化，这证明除了众所周知的非法拉第反应外，表面充电过程也源于法拉第反应。通过原位动态价态监测与传统循环伏安法测量相结合，进一步实现了不同充电速率下这两种表面存储贡献的量化。这里报道的方法也可以应用于其他电极材料，用于实时探测电化学反应过程中的价态变化、法拉第和非法拉第反应的量化以及最终阐明电化学表面充电机制。
