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Li[B(OCH 2 CF 3 ) 4 ]: Synthesis, Characterization and Electrochemical Application as a Conducting Salt for LiSB Batteries
Author(s) -
Rohde Michael,
Eiden Philipp,
Leppert Verena,
Schmidt Michael,
Garsuch Arnd,
Semrau Guenter,
Krossing Ingo
Publication year - 2015
Publication title -
chemphyschem
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.016
H-Index - 140
eISSN - 1439-7641
pISSN - 1439-4235
DOI - 10.1002/cphc.201402680
Subject(s) - chemistry , lithium (medication) , raman spectroscopy , cyclic voltammetry , electrochemistry , dimethoxyethane , electrolyte , diglyme , inorganic chemistry , thermal stability , thermal decomposition , toluene , analytical chemistry (journal) , organic chemistry , electrode , solvent , medicine , physics , optics , endocrinology
A new Li salt with views to success in electrolytes is synthesized in excellent yields from lithium borohydride with excess 2,2,2‐trifluorethanol (HOTfe) in toluene and at least two equivalents of 1,2‐dimethoxyethane (DME). The salt Li[B(OTfe) 4 ] is obtained in multigram scale without impurities, as long as DME is present during the reaction. It is characterized by heteronuclear magnetic resonance and vibrational spectroscopy (IR and Raman), has high thermal stability ( T decomposition >271 °C, DSC) and shows long‐term stability in water. The concentration‐dependent electrical conductivity of Li[B(OTfe) 4 ] is measured in water, acetone, EC/DMC, EC/DMC/DME, ethyl acetate and THF at RT In DME (0.8 mol L −1 ) it is 3.9 mS cm −1 , which is satisfactory for the use in lithium‐sulfur batteries (LiSB). Cyclic voltammetry confirms the electrochemical stability of Li[B(OTfe) 4 ] in a potential range of 0 to 4.8 V vs. Li/Li + . The performance of Li[B(OTfe) 4 ] as conducting salt in a 0.2 mol L −1 solution in 1:1 wt % DME/DOL is investigated in LiSB test cells. After the 40th cycle, 86 % of the capacity remains, with a coulombic efficiency of around 97 % for each cycle. This indicates a considerable performance improvement for LiSB, if compared to the standard Li[NTf 2 ]/DOL/DME electrolyte system.