Electrolyte and lithium metal secondary battery comprising same
An electrolyte for a lithium metal secondary battery is provided. The electrolyte comprises a lithium salt and a non-aqueous solvent and provides improved lifespan characteristics and high rate charging performance when applied to a secondary battery including a lithium metal as a negative electrode active material due to fewer side reactions and excellent stability of the electrolyte.
1 . A lithium metal secondary battery comprising:
a positive electrode;
a lithium metal negative electrode;
a separator between the positive electrode and the negative electrode; and
an electrolyte comprising a lithium salt and a non-aqueous solvent, wherein a concentration of the lithium salt is more than 2.2 M to 2.4 M or less, and
wherein the lithium salt consists of lithium bis(fluorosulfonyl)imide,
wherein the non-aqueous solvent consists of 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether (OTE); a cyclic fluorinated carbonate; and one or more chain solvents selected from the group consisting of chain carbonate and chain ester, and
wherein the 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether is included in an amount of 19% by volume to 21% by volume with respect to a total volume of the non-aqueous solvent,
wherein the cyclic fluorinated carbonate comprises fluoroethylene carbonate (FEC) and is included in an amount of 15% to 17% by volume with respect to the total volume of the non-aqueous solvent,
wherein the chain carbonate comprises dimethyl carbonate (DMC) and is included in an amount of 59% to 61% by volume with respect to the total volume of the non-aqueous solvent,
wherein the electrolyte does not include any solvent other than 1H,1H,5H-octafluoropentyl-1,1,2,2-tetrafluoroethyl ether, the cyclic fluorinated carbonate-based solvent and the chain solvents.
2 . The lithium metal secondary battery of claim 1 , wherein the cyclic fluorinated carbonate further comprises one or more selected from the group consisting of difluoroethylene carbonate, and trifluoromethylethylene carbonate.
3 . The lithium metal secondary battery of claim 1 , wherein the chain carbonate further comprises one or more selected from the group consisting of diethyl carbonate, dipropyl carbonate, ethylmethyl carbonate, methylpropyl carbonate, and ethylpropyl carbonate.
4 . The lithium metal secondary battery of claim 1 , wherein the chain ester further comprises one or more selected from the group consisting of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, and propyl propionate.
5 . The lithium metal secondary battery of claim 1 , wherein lithium bis(fluorosulfonyl)imide is included in an amount of 20% to 50% by weight with respect to the total weight of the electrolyte.