Disclosed are an electrolyte for a lithium secondary battery and a lithium secondary battery comprising the same. The electrolyte for a lithium secondary battery, according to an embodiment, can comprise: a nonaqueous organic solvent; a lithium salt; a first additive comprising a compound represented by a specific chemical formula; and a second additive including at least one of lithium difluorophosphate (LiPO.sub.2F.sub.2), a cyclic carbonate including a fluorine atom, and a dinitrile compound.

There is provided a method for producing lithium difluorophosphate in which difluorophosphate ester reacts with a lithium salt compound in a nonaqueous organic solvent without using water as a raw material, a method for producing a difluoro phosphate ester including a step of allowing a dihalophosphate ester to react with a fluorinating agent having a concentration of contained hydrogen fluoride of 15 mol % or less in a nonaqueous organic solvent; lithium difluorophosphate in which a value of a relational expression (d90-d10)/MV represented by d90 which is a particle size at which a volume cumulative distribution is 90%, d10 which is a particle size at which a volume cumulative distribution is 10%, and MV which is a volume average particle size is 10 or less; and methods for producing a nonaqueous electrolytic solution and a nonaqueous secondary battery using the production method described above.

There is provided a method for producing lithium difluorophosphate in which difluorophosphate ester reacts with a lithium salt compound in a nonaqueous organic solvent without using water as a raw material, a method for producing a difluoro phosphate ester including a step of allowing a dihalophosphate ester to react with a fluorinating agent having a concentration of contained hydrogen fluoride of 15 mol % or less in a nonaqueous organic solvent; lithium difluorophosphate in which a value of a relational expression (d90-d10)/MV represented by d90 which is a particle size at which a volume cumulative distribution is 90%, d10 which is a particle size at which a volume cumulative distribution is 10%, and MV which is a volume average particle size is 10 or less; and methods for producing a nonaqueous electrolytic solution and a nonaqueous secondary battery using the production method described above.

An electrolyte for a lithium secondary battery according to exemplary embodiments of the present inventing includes an organic solvent, a lithium salt, a first additive represented by a predetermined chemical formula, and a second additive represented by a predetermined chemical formula. A protective film is formed by the additives to suppress an expansion of a lithium secondary battery and improve storage property at high temperature.

A 1,4-dioxane solvate of lithium difluoro bis(oxalato)phosphate, a method for preparing the same, and an electrolyte composition containing the same are disclosed. The 1,4-dioxane solvate of lithium difluorobis(oxalato)phosphate has excellent crystallinity and filterability, so that a compound with high purity can be obtained in high yield. Further, since it has excellent stability against moisture, its distribution and storage are easy and the stability of the composition containing 1,4-dioxane solvate of lithium difluoro bis(oxalato)phosphate can be greatly improved.

A 1,4-dioxane solvate of lithium difluoro bis(oxalato)phosphate, a method for preparing the same, and an electrolyte composition containing the same are disclosed. The 1,4-dioxane solvate of lithium difluorobis(oxalato)phosphate has excellent crystallinity and filterability, so that a compound with high purity can be obtained in high yield. Further, since it has excellent stability against moisture, its distribution and storage are easy and the stability of the composition containing 1,4-dioxane solvate of lithium difluoro bis(oxalato)phosphate can be greatly improved.

The present invention relates to a lithium secondary battery. The lithium secondary battery includes a positive electrode including a positive active material; a negative electrode including a negative active material; and an electrolyte including a non-aqueous organic solvent, a lithium salt, and an additive including a compound represented by Chemical Formula 1. The negative active material includes Si at about 0.1 wt % to about 32 wt % in amount based on a total weight of the negative active material. ##STR00001## wherein, in Chemical Formula 1, A is a substituted or unsubstituted aliphatic chain or (—C.sub.2H.sub.4—O—C.sub.2H.sub.4-)n, and n is an integer from 1 to 10.

Provided are an electrolyte for a secondary battery including a lithium salt, a nonaqueous organic solvent, and a difluorophosphite olefin compound, and a lithium secondary battery including the same.

Provided are an electrolyte for a secondary battery including a lithium salt, a nonaqueous organic solvent, and a difluorophosphite olefin compound, and a lithium secondary battery including the same.

An electrolyte for a lithium secondary battery according to exemplary embodiments of the present inventing includes an organic solvent, a lithium salt, a first additive represented by a predetermined chemical formula, and a second additive represented by a predetermined chemical formula. A protective film is formed by the additives to suppress an expansion of a lithium secondary battery and improve storage property at high temperature.