Highly Fluorinated Interphases Enable High-Voltage Li-Metal Batteries

By Fan, Xiulin; Chen, Long; Ji, Xiao; Deng, Tao; Hou, Singyuk; Chen, Ji; Zheng, Jing; Wang, Fei; Jiang, Jianjun; Xu, Kang; Wang, Chunsheng
Published in Chem 2018

Abstract

Summary We were able to demonstrate excellent cycling performance of Li-metal anodes in carbonate electrolytes by increasing the Li bis(fluorosulfonyl)imide (LiFSI) concentration to ?10 M. The high concentration (10 M) of FSI anion enabled interphases of high F content on both Li-metal anode and Ni-rich NMC (nickel-manganese-cobalt) cathode surfaces. Such F-rich interphases effectively suppressed Li dendrite formation, as demonstrated by a high Li plating/stripping Coulombic efficiency of ?99.3%, and stabilized the carbonate molecules against oxidation at high cutoff voltages of 4.6 V on the surface of LiNi0.6Mn0.2Co0.2O2 (NMC622). The combination of unique stabilization on both Li-metal anode and NMC622 cathodes enabled high-energy Li-metal batteries constructed on the aggressive chemistry. Under the harsh conditions of a high charge voltage of 4.6 V and high loading of 2.5 mAh/cm2, the NMC622||Li cells retained ?86% of their original capacity after 100 cycles. The electrolyte strategy presented here offers unique guidelines for further optimizing beyond Li-ion chemistries.

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