Opportunity for High Performance Lithium-Metal Batteries Enabled By in Situ Formation of Highly Stable Solid Electrolyte Interphase Layer

Abstract

Lithium(Li)-metal has been considered most promising candidates as anode to increase the energy density of Li-ion batteries because of its ultrahigh specific capacity (3,860 mAh g-1) and lowest redox potential (-3.040 V vs SHE).1 However, unstable dendritic electrodeposition, low Coulombic efficiency and infinite volume changes severely hinder its practical uses.2 To stabilize the Li metal anode , the electrolyte used in this study, consisting of ethyl methyl carbonate (EMC) and fluoroethylene carbonate (FEC), ensures a stable robust solid electrolyte interphase (SEI) layer on the anode surface. In a LMBs using a commercialized Ni-rich Li[Ni0.6Co0.2Mn0.2]O2 (NCM622) and 1M LiPF6 in EMC : FEC = 3 : 1 electrolyte exhibit a high initial capacity of 1.8 mAh cm-2 with superior cycling stability and high Coulombic efficiency above 99.8 % for 500 cycles while delivering a unprecedented energy density. The present work also highlights a significant improvement in scaled-up pouch-type Li/NCM622 cells. Moreover, the postmortem characterization of the cycled cathodes, separators and Li-metal anodes collected from the pouch-type Li/NCM622 cells helped identifying the improvement or degradation mechanisms behind the observed electrochemical cycling.3 References A. Varzi, R. Raccichini, S. Passerini, B. Scrosati, J. Mater. Chem. A 2016, 4, 17251-17259.W.-J. Kwak, S.-J. Park, H.-G. Jung, Y.-K. Sun, Adv. Energy, Mater. 2018, 8, 1702258.S.-J. Park, J.-Y. Hwang, C. S. Yoon, H.-G. Jung, Y.-K. Sun, ACS Appl. Mater. Interfaces 2018, 10, 17985-17993.