The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I). ##STR00001## In the formula, each of R.sup.1 and R.sup.2 independently represents a hydrogen atom, a —C(═O)—OR.sup.4 group, or the like, and R.sup.1 and R.sup.2 may be bonded to each other to form a ring structure. R.sup.3 represents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and R.sup.4 represent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O).sub.2— group, an —S(═O).sub.2—R.sup.5—S(═O).sub.2— group or a CR.sup.6R.sup.7 group, R.sup.5 represents an alkylene group having 1 to 4 carbon atoms, and each of R.sup.6 and R.sup.7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

The present invention provides a nonaqueous electrolytic solution capable of improving electrochemical characteristics in the case of using an energy storage device at a high temperature and at a high voltage and further capable of inhibiting the gas generation while maintaining a capacity retention rate after storage at a high temperature and at a high voltage and also provides an energy storage device using the same. Disclosed is a nonaqueous electrolytic solution having an electrolyte salt dissolved in a nonaqueous solvent, the nonaqueous electrolytic solution containing a carboxylic acid ester compound represented by the following general formula (I). ##STR00001## In the formula, each of R.sup.1 and R.sup.2 independently represents a hydrogen atom, a —C(═O)—OR.sup.4 group, or the like, and R.sup.1 and R.sup.2 may be bonded to each other to form a ring structure. R.sup.3 represents a hydrogen atom or the like, and n represents an integer of 1 to 3. When n is 1, then L and R.sup.4 represent an alkyl group having 1 to 6 carbon atoms or the like; and when n is 2 or 3, then L represents an n-valent connecting group, X represents a —C(═O)— group, an —S(═O)— group, an —S(═O).sub.2— group, an —S(═O).sub.2—R.sup.5—S(═O).sub.2— group or a CR.sup.6R.sup.7 group, R.sup.5 represents an alkylene group having 1 to 4 carbon atoms, and each of R.sup.6 and R.sup.7 represents a hydrogen atom or an alkyl group having 1 to 6 carbon atoms.

An additive for a non-aqueous electrolyte solution that can suppress the initial gas generation amount when used in a non-aqueous electrolyte solution battery. The additive for a non-aqueous electrolyte solution is represented by any one of formulae [1] to [4]: ##STR00001## wherein R.sup.1, R.sup.2, R.sup.3, R.sup.4, X.sup.1, X.sup.2 and Y are as defined in the specification.

An organic electrolytic solution includes a first lithium salt; an organic solvent; a bicyclic sulfate-based compound represented by Formula 1 below; and a nitrile group-containing compound, wherein the nitrile group-containing compound includes a plurality of nitrile groups:

##STR00001## in Formula 1, each of A.sub.1, A.sub.2, A.sub.3, and A.sub.4 is independently a covalent bond, a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group, a carbonyl group, or a sulfinyl group, wherein both A.sub.1 and A.sub.2 are not a covalent bond and both A.sub.3 and A.sub.4 are not a covalent bond.

An organic electrolytic solution includes a first lithium salt; an organic solvent; a bicyclic sulfate-based compound represented by Formula 1 below; and a nitrile group-containing compound, wherein the nitrile group-containing compound includes a plurality of nitrile groups:

##STR00001## in Formula 1, each of A.sub.1, A.sub.2, A.sub.3, and A.sub.4 is independently a covalent bond, a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group, a carbonyl group, or a sulfinyl group, wherein both A.sub.1 and A.sub.2 are not a covalent bond and both A.sub.3 and A.sub.4 are not a covalent bond.

An organic electrolytic solution includes a first lithium salt; an organic solvent; a bicyclic sulfate-based compound represented by Formula 1 below; and a monocyclic phosphate-based compound represented by Formula K1 below:

##STR00001## wherein in Formula 1, each of A.sub.1, A.sub.2, A.sub.3, and A.sub.4 is independently a covalent bond, a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group, a carbonyl group, or a sulfinyl group, wherein both A.sub.1 and A.sub.2 are not a covalent bond and both A.sub.3 and A.sub.4 are not a covalent bond, and in Formula K1, each of A.sub.5 and A.sub.6 is independently a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group.

An organic electrolytic solution includes a first lithium salt; an organic solvent; a bicyclic sulfate-based compound represented by Formula 1 below; and a monocyclic phosphate-based compound represented by Formula K1 below:

##STR00001## wherein in Formula 1, each of A.sub.1, A.sub.2, A.sub.3, and A.sub.4 is independently a covalent bond, a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group, a carbonyl group, or a sulfinyl group, wherein both A.sub.1 and A.sub.2 are not a covalent bond and both A.sub.3 and A.sub.4 are not a covalent bond, and in Formula K1, each of A.sub.5 and A.sub.6 is independently a substituted or unsubstituted C.sub.1-C.sub.5 alkylene group.

A lithium battery includes a cathode; an anode; and an organic electrolytic solution between the cathode and the anode, wherein the anode includes an anode current collector and an anode active material layer on the anode current collector, the anode active material layer includes carbonaceous and silicon-containing composite anode active materials, the anode active material layer includes first and second anode active material layers, and the first anode active material layer is between the anode current collector and the second anode active material layer, a content of silicon in the first anode active material layer is higher than the second anode active material layer, and the organic electrolytic solution includes a first lithium salt, an organic solvent, and a bicyclic sulfate-based compound represented by Formula 1 below:

##STR00001##

A lithium battery includes a cathode; an anode; and an organic electrolytic solution between the cathode and the anode, wherein the anode includes an anode current collector and an anode active material layer on the anode current collector, the anode active material layer includes carbonaceous and silicon-containing composite anode active materials, the anode active material layer includes first and second anode active material layers, and the first anode active material layer is between the anode current collector and the second anode active material layer, a content of silicon in the first anode active material layer is higher than the second anode active material layer, and the organic electrolytic solution includes a first lithium salt, an organic solvent, and a bicyclic sulfate-based compound represented by Formula 1 below:

##STR00001##

A lithium battery includes a cathode including a cathode active material; an anode including an anode active material; and an organic electrolytic solution between the cathode and the anode, wherein the cathode active material includes a first lithium transition metal oxide and a second lithium transition metal oxide, the first lithium transition metal oxide and the second lithium transition metal oxide have different particle diameters, the second lithium transition metal oxide includes primary particles having a particle diameter of about 1 μm or more, and the organic electrolytic solution includes a first lithium salt, an organic solvent, and a bicyclic sulfate-based compound represented by Formula 1 below:

##STR00001##