Electroanalytical evaluation of temperature dependent electrolyte functions for lithium ion batteries: Investigation of selected mixed carbonate solvents using a lithium titanate electrode

摘要

Characterization of materials for advanced lithium ion batteries (LIBs) represents an essential area of the contemporary energy storage technologies. The present work illustrates an electroanalytical framework for quantitative testing of liquid electrolytes for LIBs. The measurements explore a temperature range from 40 °C to sub-zero regimes, with a special focus on the electrolyte functions for low temperature applications. The test electrolytes include different combinations of ethylene, dimethyl, diethyl and ethyl methyl carbonate (EC, DMC, DEC and EMC, respectively) solvents, with LiClO4, Li bis(trifluoromethane)sulfonimide (LiTFSI) and LIBF4salts. The experiments utilize the diagnostic features of electrochemical impedance spectroscopy (EIS), in combination with cyclic voltammetry (CV) and galvanostatic cycling. Temperature controlled measurements of two- and three-electrode EIS, coupled with CV, demonstrate how the electrolyte conductivity and electrochemical stability can be evaluated in a comprehensive approach. The compositions of the test electrolytes are optimized according to their temperature dependent ionic conductivities and their electrochemical windows. Two optimal electrolytes based on EC:EMC and EC:DMC:EMC mixtures are further examined for battery operations by galvanostatic cycling in a half-cell containing a Li4Ti5O12anode. Consistent with the findings of the conductivity and electrochemical window measurements, the EC:EMC system exhibits superior performance in these half-cell experiments.