Small dissymmetry, yet large effects on the transport propertiesof electrolytes based on imide salts: Consequences on performancein Li-ion batteries  

作　　者：Joseph Chidiac Laure Timperman Mérièm Anouti 

机构地区：[1]Laboratoire PCM2E,Universitéde Tours,Parc de Grandmont,37200 Tours,France

出　　处：《Journal of Energy Chemistry》2022年第2期352-366,共15页能源化学（英文版）

基　　金：“La Région Centre Val de Loire” for financial support。

摘　　要：To gain better insight into the influence of the anion size and symmetry on the transport properties and thermal stability of an electrolyte based on lithium(fluorosulfonyl)(trifluoromethanesulfonyl)-imide(FTFSI)salt,we performed the physical and electrochemical characterization of an electrolyte based on FTFSI incorporated in standard binary(3 EC/7 EMC)and ternary(EC/PC/3 DMC)alkylcarbonate mixtures.By applying the Jones-Dole-Kaminsky(JDK),Eyring and Arrhenius empirical models to the electrolyte viscosity we show that the activation enthalpy and entropy energy barriers(ΔH≠,ΔS≠)for viscous flow are between 12 and 15 kJ·mol^(-1).They are strongly dependent on the solvent nature and are significantly lower than their symmetric anions LiFSI and LiTFSI(19-20 kJ·mol^(-1))in the binary mixture.Furthermore,the hydrodynamic radius,rs,calculated by JDK,and the ionicity behavior illustrated by the Walden role,showed that the FTFSI anion is outside the solvation sphere(rs>0.6 nm)which is smaller in the case of an EC/EMC solvent base.In the 3 EC/7 EMC solvent mixture,LiFTFSI is less conductive than in the ternary mixture i.e.,σ_(max)=8.9 mS cm^(-1) at C_(max)=1.1 mol L^(-1) for 3 EC/7 EMC and,σ_(max)=10.5 mS cm^(-1) at max=0.7 mol L^(-1) for EC/PC/3 DMC,due to a strong solvation and a greater association of FTFSI ions in the binary solvent mixture.The thermal stability of FTFSI based electrolytes was determined by the shift of the evaporation temperature of the volatile solvents(DMC,EMC)in the presence of salt,towards the higher temperatures.This feature is visible on the thermograms obtained by DSC both with the liquid electrolyte and with charged LMO cathodes in presence of electrolytes.The consequences of these properties on the electrochemical behavior of a graphite(Gr)half-cell,a lithium metal(Li)anode and a manganese lithium oxide(LMO)cathode demonstrated on the one hand the formation of a thick solid electrolyte interphase(SEI)on graphite that consumed a significant amount of lithium i.e.,18%of total capacit

关 键 词：LiFTFSI ELECTROLYTE Viscosity Interface Li-ion battery 

分 类 号：TQ226.31[化学工程—有机化工] TM912[电气工程—电力电子与电力传动]