Visualizing the growth process of sodium microstructures in sodium batteries by in-situ 23 Na MRI and NMR spectroscopy

• Published in: Nature nanotechnology Vol. 15; no. 10; p. 883
• Main Authors: Xiang, Yuxuan, Zheng, Guorui, Liang, Ziteng, Jin, Yanting, Liu, Xiangsi, Chen, Shijian, Zhou, Ke, Zhu, Jianping, Lin, Min, He, Huajin, Wan, Jiajia, Yu, Shenshui, Zhong, Guiming, Fu, Riqiang, Li, Yangxing, Yang, Yong
• Format: Journal Article
• Language: English
• Published: England 01.10.2020
• ISSN: 1748-3395

The growth of sodium dendrites and the associated solid electrolyte interface (SEI) layer is a critical and fundamental issue influencing the safety and cycling lifespan of sodium batteries. In this work, we use in-situ Na magnetic resonance imaging (MRI) and nuclear magnetic resonance (NMR) techniques, along with an innovative analytical approach, to provide space-resolved and quantitative insights into the formation and evolution of sodium metal microstructures (SMSs; that is, dendritic and mossy Na metal) during the deposition and stripping processes. Our results reveal that the growing SMSs give rise to a linear increase in the overpotential until a transition voltage of 0.15 V is reached, at which point violent electrochemical decomposition of the electrolyte is triggered, leading to the formation of mossy-type SMSs and rapid battery failure. In addition, we determined the existence of NaH in the SEI on sodium metal with ex-situ NMR results. The poor electronic conductivity of NaH is beneficial for the growth of a stable SEI on sodium metal.