Wen Xiaoyu, Yu Zhou, Zhao Yifan, Zhang Jian, Qiao Rui, Cheng Lei, Ban Chunmei, Guo Juchen
Department of Chemical and Environmental Engineering, University of California, Riverside, California 92521, United States.
Joint Center for Energy Storage Research, Argonne National Laboratory, Lemont, Illinois 60439, United States.
ACS Appl Mater Interfaces. 2021 Nov 10;13(44):52461-52468. doi: 10.1021/acsami.1c10446. Epub 2021 Nov 1.
A new deposition mechanism is presented in this study to achieve highly reversible plating and stripping of magnesium (Mg) anodes for Mg-ion batteries. It is known that the reduction of electrolyte anions such as bis(trifluoromethanesulfonyl)imide (TFSI) causes Mg surface passivation, resulting in poor electrochemical performance for Mg-ion batteries. We reveal that the addition of sodium cations (Na) in Mg-ion electrolytes can fundamentally alter the interfacial chemistry and structure at the Mg anode surface. The molecular dynamics simulation suggests that Na cations contribute to a significant population in the interfacial double layer so that TFSI anions are excluded from the immediate interface adjacent to the Mg anode. As a result, the TFSI decomposition is largely suppressed so does the formation of passivation layers at the Mg surface. This mechanism is supported by our electrochemical, microscopic, and spectroscopic analyses. The resultant Mg deposition demonstrates smooth surface morphology and lowered overpotential compared to the pure Mg(TFSI) electrolyte.
本研究提出了一种新的沉积机制，以实现镁离子电池中镁（Mg）阳极的高度可逆镀覆和剥离。众所周知，电解质阴离子如双（三氟甲磺酰）亚胺（TFSI）的还原会导致镁表面钝化，从而导致镁离子电池的电化学性能不佳。我们发现，在镁离子电解质中添加钠离子（Na）可以从根本上改变镁阳极表面的界面化学和结构。分子动力学模拟表明，Na阳离子在界面双层中占很大比例，从而使TFSI阴离子被排除在与镁阳极相邻的直接界面之外。结果，TFSI分解被大大抑制，镁表面钝化层的形成也被抑制。我们的电化学、显微镜和光谱分析支持了这一机制。与纯Mg（TFSI）电解质相比，所得的镁沉积表现出光滑的表面形态和更低的过电位。
