Fluorinated Carbamates as Suitable Solvents for LiTFSIbased Lithium-Ion Electrolytes: Physico-Chemical Properties and Electrochemical Characterization

Abstract

Herein, we present an extensive physico-chemical characterization of a series of fluorinated and non-fluorinated carbamates and their application as electrolyte solvents comprising lithium trifluoromethanesulfonyl imide (LiTFSI) as conducting salt. In a second step, these electrolyte compositions were characterized with respect to their ionic conductivity, salt dissociation, and electrochemical stability towards oxidation. In a third step, selected fluorinated electrolytes were studied concerning their ability to enable the utilization of LiTFSI as conducting salt in presence of an aluminum current collector by forming a protective aluminum fluoride surface layer, thus preventing the continuous anodic aluminum dissolution, i.e., aluminum corrosion. Finally, their electrochemical performance in combination with a state-of-the-art lithium-ion cathode material, Li(Ni1/3Mn1/3Co1/3)O2 (NMC), was investigated. It is shown that higher fluorinated carbamates reveal a very stable cycling performance of such cathodes due to their ability to form a sufficiently thick, i.e., protective aluminum fluoride layer on the surface of the aluminum current collector. These findings confirm their suitability as electrolyte solvents in combination with LiTFSI as conducting salt, enabling the successful replacement of toxic and unstable LiPF6 for the development of intrinsically safer lithium-ion batteries. 

IF: 4.8

DOI: 10.1021/acs.jpcc.5b07514