Electrolytic properties and application to lithium batteries of 3-propyl-4-methylsydnone-based binary solvent electrolytes

The electrolytic conductivity and charge-discharge characteristics of lithium electrodes were examined in three types of tetrahydrofurans (tetrahydrofuran, 2-methyl-tetrahydrofuran and 2,5-dimethyltetrahydrofuran)-3-propyl-4-methylsydnone (3-PMSD) binary solvent electrolytes. The order of decrease of the specific conductivities in the electrolytes except LiBPh4 is LiN(CF3SO2)(2) > LiPF6 > LiClO4 > LiBF4 > LiCF3SO3. The conductivity in the LiBPh4 electrolyte continued to gradually increase with the addition of the tetrahydrofurans. The energy density for a Li/V2O5 (2025) coin-type cell in LiN(CF3SO2)(2)/3-PMSD-tetrahydrofuran (THF) electrolyte at 0.9 mole fraction of THF was 380 Wh kg(-1), which is almost equal to that in an ethylene carbonate-1, 2-dimethoxyethane equimolar solvent electrolyte containing LiPF6. The LiBPh4/3-PMSD-2-methyltetrahydrofuran (2-MeTHF) equimolar solvent electrolyte showed a moderate cycling efficiency of more than 60% at a higher cycle number. The dendrite formation observed in the LiBPh4 electrolyte using atomic force microscopy (AFM) was minimal in spite of the increased cycle number. In addition, the film in the LiBPh4 electrolyte seems to be very thin, that is, the film thickness on the Ni electrode affects the charge-discharge process.