Solvents in salt electrolyte: Benefits and possible use as electrolyte for lithium-ion battery

摘要

An EC/DEC [40:60% (v/v)] solvent mixture has been added in various amounts to the ionic liquid (IL) hexyltrimethylammonium bis(trifluoromethylsulfonyl)imide (Ni{sub}1116-NTf{sub}2) in the presence of NTf{sub}2 (lithium bis(trifluoromethylsulfonyl)imide) as lithium salt for possible use as electrolytes in lithium-ion batteries. These electrolytes exhibit a larger thermal stability than the reference electrolyte EC/DEC [40:60] + NTf{sub}2 1 M when the percentage of the IL exceeds 30% (v/v). All studied electrolytes are glass forming ones with an ideal glass transition temperature of ca. -85 ℃(±5 ℃), which has been determined by application of the VTF theory to conductivity and viscosity measurements and confirmed by DSC (T{sub}g = -90 ± 5 ℃). An electrochemical window of about 5 V versus Li/Li{sup}+ was measured at a glassy carbon electrode. The cycling ability of the optimized electrolyte Ni{sub}1116-NTf{sub}2/EC:DEC (40/60% (v/v))+1 M NTf{sub}2 has been investigated at a titanate oxide (Li{sub}4Ti{sub}5O{sub}12) and a cobalt oxide (Li{sub}xCoO{sub}2) electrodes. Cycling the positive and the negative electrodes was conducted successfully with a high capacity and without any significant fading.