Ionic liquid, electrolyte for secondary battery including ionic liquid, and secondary battery including electrolyte
Provided is an ionic liquid including a cationic compound represented by Formula (1), where R represents an N-containing heterocyclic cation, and an anionic compound, an electrolyte including the ionic liquid, and a secondary battery.
1 . An ionic liquid comprising:
a cationic compound represented by Formulas (1), (3), or (4) below:
wherein R is pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium, pyrazolium, thiazolium, oxazolium, or triazolium; and
an anionic compound.
2 . The ionic liquid of claim 1 , wherein the anionic compound includes trifluoromethyl sulfonylimide (TFSI), bis (fluorosulfonyl) imide (FSI), chloride (Cl), dicyanamide (DCA), trifluoromethanesulfonate (Otf), acetate (Ac), hydrate (OH), diethylphosphate (DEP), thiocyanate (SCN), or methylsulfate (MeSO4).
3 . The ionic liquid of claim 1 , wherein the ionic liquid comprises a cationic compound and an anionic compound selected from the group represented by Formulas (6) and (7) below:
4 . An electrolyte for a secondary battery comprising:
an ionic liquid comprising:
a cationic compound represented by Formulas (1), (3), or (4) below:
wherein R is pyridinium, pyridazinium, pyrimidinium, pyrazinium, imidazolium. pyrazolium, thiazolium, oxazolium, or triazolium;
an anionic compound;
a lithium salt; and
a solvent.
5 . The electrolyte of claim 4 , wherein an amount of the ionic liquid is 3 to 10 wt % based on the total weight of the electrolyte.
6 . The electrolyte of claim 4 , wherein the anionic compound includes at least one selected from trifluoromethyl sulfonylimide (TFSI), bis (fluorosulfonyl) imide (FSI), chloride (Cl), dicyanamide (DCA), trifluoromethanesulfonate (Otf), acetate (Ac), hydrate (OH), diethylphosphate (DEP), thiocyanate (SCN), or methyl sulfate (MeSO4).
7 . The electrolyte of claim 4 , wherein the ionic liquid comprises a cationic compound and an anionic compound selected from the group represented by Formulas (6) and (7) below:
8 . The electrolyte of claim 4 , further comprising:
a negative electrode protective film former.
9 . The electrolyte of claim 8 , wherein the negative electrode protective film former comprises at least one selected from lithium bisoxalato borate (LiBOB) lithium difluoro (oxalato) borate (LiFOB), maleic anhydride, or lithium difluorobis-(oxalate) phosphate (W2).
10 . The electrolyte of claim 8 , wherein an amount of the negative electrode protective film former is 0.2 to 2 wt % based on the total weight of the electrolyte.
11 . A secondary battery comprising:
the electrolyte of claim 4 ;
a positive electrode;
a negative electrode; and
a separator interposed between the positive electrode and the negative electrode.
12 . The secondary battery of claim 11 , wherein the electrolyte comprises 3 to 10 wt % of an ionic liquid based on the total weight of the electrolyte.
13 . The secondary battery of claim 11 , wherein the anionic compound includes at least one of trifluoromethyl sulfonylimide (TFSI), bis (fluorosulfonyl) imide (FSI), chloride (Cl), dicyanamide (DCA), trifluoromethanesulfonate (Otf), acetate (Ac), hydrate (OH), diethylphosphate (DEP), thiocyanate (SCN), or methyl sulfate (MeSO4).
14 . The secondary battery of claim 11 , wherein the ionic liquid comprises a cationic compound and an anionic compound selected from a group represented by Formulas (6) and (7) below:
15 . The secondary battery of claim 11 , wherein the electrolyte further comprises a negative electrode protective film former.
16 . The secondary battery of claim 15 , wherein the negative electrode protective film former comprises at least one of lithium bisoxalato borate (LiBOB) lithium difluoro (oxalato) borate (LiFOB), maleic anhydride, or lithium difluoro bis-(oxalate) phosphate.