[Document Name] Specification [Title of the Invention] NONAQUEOUS ELECTROLYTE SOLUTION AND LITHIUM SECONDARY BATTERY USING SAME [Technical Field] [0001] The present invention relates to a nonaqueous electrolytic solution which can provide a lithium secondary battery having excellent battery characteristics such as battery cycle property, electrical capacity and storage characteristics, and to a lithium secondary battery using the same. [Background Art] [0002] In recent years, lithium secondary batteries have been widely used as power supplies for driving small electronic devices and the like. Lithium secondary batteries are mainly constituted of a positive electrode, a nonaqueous electrolytic solution and a negative electrode. In particular, lithium secondary batteries constituted of a positive electrode comprised of a lithium compound oxide such as LiCo02 and a negative electrode comprised of a carbon material or a lithium metal are used. As the nonaqueous electrolytic solution for such lithium secondary batteries, a carbonate such as ethylene carbonate (EC) or propylene carbonate (PC) is used. However, secondary batteries having better battery characteristics, i.e., battery cycle properties, electrical capacities and the like, are required. [0003] In a lithium secondary battery using, for example, LiCo02, LiMn204, or LiNi02 as the positive electrode, part of a solvent in a nonaqueous electrolyte locally decomposes oxidatively during charging, and the decomposition products inhibit a desirable electrochemical reaction of the battery, thereby lowering the battery performance. This is thought to result from the electrochemical oxidation of the solvent at the interface between the positive electrode material and nonaqueous electrolytic solution. Moreover, in a lithium secondary battery using, for example, natural graphite, artificial graphite and like highly crystallized carbon materials as the negative electrode, a solvent in a nonaqueous electrolytic solution reductively decomposes on the surface of the negative electrode during charging. Therefore, part of ethylene carbonate (EC) which is generally and widely used as a nonaqueous electrolytic solution solvent is reductively decomposed through repeated charging and discharging, thereby lowering the battery performance. Especially, propylene carbonate (PC) having a low melting point and a high dielectric constant, which is preferably used as a nonaqueous solvent since it has a high electric conductivity at low temperatures, cannot be used as a lithium secondary battery because of its very high level of decomposition. [0004] Various suggestions have been made to improve the battery characteristics of this lithium secondary battery. For example, Patent Document 1 discloses an electrolytic solution containing the first solvent such as propylene carbonate, the second solvent such as dimethyl carbonate, and vinylene carbonate in an amount of 0.01 to 10% by weight of a solvent mixture. Moreover, Patent Document 2 discloses an electrolytic solution containing 0.1 to 5% by weight of vinylene carbonate and asymmetrical linear carbonate. Patent Document 3 suggests a nonaqueous solvent containing a cyclic carbonate and a linear carbonate as main ingredients and 1,3-propane sultone added thereto, and discloses the improvement of cycle property by adding 1,3-propane sultone. Patent Document 4 discloses a nonaqueous electrolytic solution containing diketones such as ethyl levulinate and acetonylacetone. Patent Document 5 discloses a nonaqueous electrolytic solution containing diketones such as acetylacetone. Moreover, Patent Document 6 discloses a lithium secondary battery having the density of the layer of a positive electrode mixture of 3.3 to 3.7 g/cm3 and the density of the layer of a negative electrode mixture of 1.4 to 1.8 g/cm3. As mentioned above, in known lithium secondary batteries having relatively low capacities, battery characteristics such as cycle properties are somewhat improved by adding vinylene carbonate, 1,3-propane sultone and other substances. However, the techniques of Patent Documents 1 to 6 cannot provide satisfactory battery characteristics required for high-capacity lithium secondary batteries of these days, especially lithium secondary batteries with high-density layers of the positive electrode mixture and negative electrode mixture- An electrolytic solution having an even higher long-term cycle property is thus required. [0005] [Patent Document 1] Japanese Unexamined Patent Publication No. H08-45545 [Patent Document 2] Japanese Unexamined Patent Publication No. H11-185806 [Patent Document 3] Japanese Unexamined Patent Publication No. 2000-3724 [Patent Document 4] Japanese Unexamined Patent Publication No. 2001-176551 [Patent Document 5] Japanese Unexamined Patent Publication No. 2001-185212 [Patent Document 6] Japanese Unexamined Patent Publication No. 2003-142075 [Disclosure of the Invention] [0006] An object of the present invention is to solve the above-mentioned problems, and to provide a nonaqueous electrolytic solution which can constitute a lithium secondary battery having excellent battery cycle property, and further excellent electrical capacity, storage characteristic during charging and other battery characteristics, and to provide a lithium secondary battery using the same. The inventors of the present invention conducted a research to achieve the above objects. As a result, they found that the above objects can be achieved by adding a specific dicarbonyl compound to a nonaqueous electrolytic solution as an additive. Thus, the present invention provides the following items (1) to (3): (1) A nonaqueous electrolytic solution for lithium secondary batteries in which an electrolyte salt is dissolved in a nonaqueous solvent, comprising a dicarbonyl compound represented by the following general formula (I) in the nonaqueous electrolytic solution. [0007] [Chemical formula 1] (wherein R1 represents a hydrogen atom, a Ci to C12 alkyl group, a C3 to C& cycloalkyl group, a C2 to C12 alkenyl group, a C2 to C12 alkynyl group or an unsubstituted or substituted phenyl group; and X represents a hydrogen atom, an R2 group or an OR2 group. R2 represents a Ci to C12 alkyl group, a C3 to C8 cycloalkyl group, a C2 to Ci2 alkenyl group, a C2 to Ci2 alkynyl group or an unsubstituted or substituted phenyl group.) (2) A nonaqueous electrolytic solution for lithium secondary batteries in which an electrolyte salt is dissolved in a nonaqueous solvent, comprising 0.01 to 10% by weight of a dicarbonyl compound represented by the following general formula (II) and at least one member selected from vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate,. 1,3-propane sultone and glycol sulfite . [0008] [Chemical formula 2] (wherein R1and X are the same as above, each of Y and Z independently represents a hydrogen atom, an R2 group, an OR2 group, a COR2 group or a CH2COR2 group (R2 is the same as above) . n represents an integer from 1 to 6; when n is 2 or more, Y and Z bonding to different carbons are independent from each other. R1, X, Y and Z may bond to each other to form a ring.) (3) A lithium secondary battery comprising a positive electrode, a negative electrode and the nonaqueous electrolytic solution of (1) or (2) above. [0009] According to the present invention, a lithium secondary battery having excellent battery cycle property, electrical capacity, storage characteristic and other battery characteristics can be provided. In particular, in the present invention, a nonaqueous electrolytic solution containing (i) a specific dicarbonyl compound, or (ii) a specific dicarbonyl compound and vinylene carbonate (VC) or the like in combination as an additive is used, whereby the cycle property is improved particularly for a long period of time in a lithium secondary battery with an increased density of the layer of a positive electrode mixture and the layer of a negative electrode mixture. Moreover, the nonaqueous electrolytic solution of the present invention can be also used suitably as a nonaqueous electrolytic solution for known lithium secondary batteries having relatively low capacities. [Best Mode for Carrying out the Invention] [0010] The nonaqueous electrolytic solution for lithium secondary batteries of the present invention is a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent, comprising (i) a dicarbonyl compound represented by the following general formula (I), or (ii) a dicarbonyl compound represented by the following general formula (II) and at least one member selected from vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS) and glycol sulfite (GS). [0011] [Chemical formula 3] [0013] In the present invention, it was found that when the nonaqueous electrolytic solution obtained by adding the dicarbonyl compound mentioned above to the nonaqueous electrolytic solution is used for a high-capacity lithium secondary battery, the cycle property, which has been an object to be improved, is excellent. Although its mechanism is unknown, it is presumably because a strong coating is formed on the negative electrode by using the dicarbonyl compound mentioned above. Specific embodiments of the present invention will be described below. [0014] R1and R2 of X of the dicarbonyl compound represented by the general formula (I) is a hydrogen atom; a Ci to C12, preferably C1 to C8, especially preferably C1 to C4 alkyl group which may be branched; a C3 to C8, preferably C3 to C6, especially preferably C5 to C6 cycloalkyl group; a C2 to C12, preferably C2 to C8, especially preferably C2 to C8 alkenyl group which may be branched; a C2 to C12, preferably C2 to C8, especially preferably C2 to C6 alkynyl group which may be branched; or an unsubstituted or a substituted phenyl group. [0015] (i) Specific examples when X in the general formula (I) is an hydrogen atom When R1 is a hydrogen atom, Examples include 2-oxoethanal. When R1 is an alkyl group examples include 2-oxopropanal, 2-oxobutanal, 3-methyl-2-oxobutanal, 3,3-dimethyl-2-oxobutanal and the like. When R1 is a cycloalkyl group, examples include 2-cyclopentyl-2-oxoethanal, 2-cyclohexyl-2-oxoethanal and the like. When R1 is an alkenyl group, examples include 2-oxo-3-butenal, 2-oxo-4-pentenal, (1'-cyclohexenyl)-2-oxoethanal, (2'-cyclohexenyl)-2-oxoethanal and the like. When R1 is an alkynyl group, examples include 2-oxo-3-butynal or the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 2-oxo-2-phenylethanal, 2-tolyl-2-oxoethanal, 2-(4'-isopropylphenyl)-2-oxoethanal, 2-(4'-t-butylphenyl)-2-oxoethanal and the like. Among the aldehyde compounds mentioned above, 2-oxopropanal, 2-oxobutanal, 3-methyI-2-oxobutanal, 3,3-dimethyl-2-oxobutanal, 2-oxo-3-butenal are preferable. [0016] (ii) Specific examples when X in the general formula (I) is R2 = alkyl group When R1 is an alkyl group, examples include diacetyl, 2,3-pentanedione, 4-methyl-2,3-pentanedione, 4,4-dimethyl-2,3-pentanedione, 1-cyclohexyl-1,2-propanedione or the like. When R1 is an alkenyl group, examples include 4-pentene-2,3-dione, 5-hexene-2,3-dione, 1-(1'-cyclohexenyl)-1,2-propanedione, 1-(2'-cyclohexenyl)-1,2-propanedione and the like. When R1 is an alkynyl group, examples include 4-pentyne-2,3-dione, 5-hexyne-2,3-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-1,2-propanedione, 1-tolyl-1,2-propanedione, 1-(4,-isopropylphenyl)-1,2-propanedione, 1-(4,«t«butylphenyl)-1l2-propanedione or the like. When R1and X bond to each other to form a ring, examples include 1,2-cyclobutanedione, 1,2-cyclopentanedione, 1,2-cyclohexanedione and the like. Among the saturated diketone compounds mentioned above, diacetyl, 2,3-pentanedione, 4-methyl-2,3-pentanedione, 4,4-dimethyl-2,3-pentanedione, 4-pentene-2,3-dione, 5-hexene-2,3-dione, 4-pentyne-2,3-dione, 5-hexyne-2,3-dione, 1,2-cyclobutanedione, 1,2-cyclopentanedione and 1,2-cyclohexanedione are preferable. [0017] (iii) Specific examples when X in the general formula (I) is R2=cycloalkyl group When R1 is a cycloalkyl group, examples include 1,2-dicyclohexyl-1,2-dione and the like. When R1 is an alkenyl group, examples include 1-cyclohexyl-2-hexadiene-1,2-ethanedione and the like. When R1 is an alkynyl group, examples include 1-cyclohexyl-2-hexadiyne-1,2-ethanedione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-cyclohexyl-2-phenyl-1,2-ethanedione and the like. [0018] (iv) Specific examples when X in the general formula (I) is R2=alkenyl group When R1 is an alkenyl group, examples include 1,5-hexadiene-3,4-dione, 1,6-heptadiene-3,4-dione, 1,7-octadiene-4,5-dione, 1-(1'-cyclohexenyl)-3-butene-1,2-dione, 1-(1,-cyclohexenyl)-4-pentene-1,2-dione and the like. When R1 is an alkynyl group, examples include 5-hexene-1-yne-3,4-dione, 1-heptene-6-yne-3,4-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-3-butene-1,2-dione and the like. Among the diketone compound having a carbon-carbon double bond mentioned above, 1,5-hexadiene-3,4-dione, 5-hexene-1-yne-3,4-dione and 1-phenyl-3-butene-1,2-dione are preferable. [0019] (v) Specific examples when X in the general formula (I) is R2=alkynyl group When R1 is an alkynyl group, examples include 1,5-hexadiyne-3,4-dione, 1,6-heptadiyne-3,4-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-3-butyne-1,2-dione, 1-phenyl-4-pentyne-1,2-dione and the like. Among the diketone compounds having a carbon-carbon triple bond mentioned above, 1,5-hexadiyne-3,4-dione and 1,6-heptadiyne-3,4-dione are preferable. [0020] (vi) Specific examples when X in the general formula (I) is R2=an unsubstituted or a substituted phenyl group When R1 is an unsubstituted or a substituted phenyl group, examples include 1,2-diphenyl-1,2-ethanedione, 1-phenyl-2-tolyl-1,2-ethanedione and the like. [0021] (vii) Specific examples when X in the general formula (I) is an OR2 group When R1 is an alkyl group, examples include methyl pyruvate, ethyl pyruvate, propyl pyruvate, isopropyl pyruvate, butyl pyruvate, t-butyl pyruvate, vinyl pyruvate, allyl pyruvate, ethynyl pyruvate, 2-propynyl pyruvate and the like. When R1 is a cycloalkyl group, examples include cyclohexyl pyruvate and the like. When R1 is an alkenyl group, examples include hexadiene pyruvate and the like. When R1 is an alkynyl group, examples include methyl 2-oxo-but-3-ynoate, methyl 2-oxo-pent-4-ynoate and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include methyl 2-oxo-2-phenylethanoate and the like. When R1 and X bond to each other to form a ring, examples include oxetane-2,3-dione, dihydrofuran-2,3-dione, dihydropyran-2,3-dione, methyl cyclobutanone-2-carboxylate, methyl cyclopentanone-2-carboxylate, ethyl cyclohexanone-2-carboxylate and the like. Among the keto ester compounds mentioned above, methyl pyruvate, ethyl pyruvate, propyl pyruvate, isopropyl pyruvate, butyl pyruvate, t-butyl pyruvate, vinyl pyruvate, allyl pyruvate, ethynyl pyruvate, 2-propynyl pyruvate, oxetane-2,3-dione, dihydrofuran-2,3-dione, dihydropyran-2,3-dione, methyl cyclopentanone-2-carboxylate and ethyl cyclohexanone-2-carboxylate are preferable. [0022] Among the dicarbonyl compounds represented by the general formula (I), diacetyl, 1,2-cyclohexanedione, methyl pyruvate, ethyl pyruvate, propyl pyruvate, butyl pyruvate, ethynyl pyruvate and 2-propynyl pyruvate are particularly preferable. [0023] R1 and R2 of X, Y and Z of the dicarbonyl compound represented by the general formula (II) are each a hydrogen atom; a Ci to C12, preferably Ci to C8, especially preferably Ci to C4 alkyl group which may be branched; a C3 to C8, preferably C3 to C6, especially preferably C5 to C6 cycloalkyl group; a C2 to Ci2, preferably C2 to C8, especially preferably C2 to C8 alkenyl group which may be branched; a C2 to C12, preferably C2 to C8, especially preferably C2 to C6 alkynyl group which may be branched; or an unsubstituted or a substituted phenyl group. R1 and X, R1 and Y, R1 and Z, X and Y, X and Z, and Y and Z may bond to each other to form a ring. [0024] (viii) Specific example when X in the general formula (II) is a hydrogen atom When R1 is a hydrogen atom, examples include malonaldehyde, succinic aldehyde and the like. When R1 is an alkyl group, examples include 3-oxobutanal, 4-oxopentanal, 4-oxohexanal, 5-methyl-4-oxohexanal, 5,5-dimethyl-4-oxohexanal, 4-cyclohexyl-4-oxobutanal, 5-oxohexanal, 6-oxoheptanal, 7-oxooctanal, 8-oxononanal and the like. When R1 is an alkenyl group, examples include 4-oxo-5-hexenal, 4~oxo-6-heptenal and the like. When R1 is an alkynyl group, examples include 4-oxo-5-hexynal, 4-oxo-6-heptynal and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 4-oxo-4-phenyl butanal, 2-tolyl-4-oxobutanal, 4- (4,-isopropylphenyl) -4-oxobutanal, 4- (4'-t-butylphenyl) -4-oxobutanal and the like. When R1, Y and Z bond to each other to form a ring, examples include 2-oxocyclobutanecarboxaldehyde, 3-oxocyclobutanecarboxaldehyde, 2-oxocyclopentanecarboxaldehyde, 3-oxocyclopentanecarboxaldehyde, 2-oxocyclohexanecarboxaldehyde, 3-oxocyclohexanecarboxaldehyde, 4-oxocyclohexanecarboxaldehyde and the like. [0025] (ix) Specific examples when X of the general formula (II) is R2 = alkyl group When R1 is an alkyl group, examples include saturated diketone compounds such as acetylacetone, acetonylacetone, 2,5-heptanedione, 6-methyl-2,5-heptanedione, 6,6-dimethyl-2,5-heptanedione, 1-cyclohexyl-1,4-pentanedione, 2,6-heptanedione, 2,7-octanedione, 2,8-nonanedione, 2,9-decanedione and the like. When R1 is an alkenyl group, examples include 6-heptene-2,5-dione, 7-octene-2,5-dione, 1- (1'-cyclohexenyl) -1,4-pentenedione, 1- (2,-cyclohexenyl) -1,4-pentene dione and the like. When R1 is an alkynyl group, examples include 6-heptyne-2,5-dione, 7-octyne-2,5-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-1,4-pentanedione, 1-tolyl-1,4-pentanedione, 1- (4,-isopropylphenyl) -1,4-pentanedione,1- (4'-t-butylphenyl) -1,4-pentanedione and the like. When R1, Y and Z bond to each other to form a ring, examples include 1,3-cyclobutanedione, 1,3-cyclopentanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, 2-acetylcyclobutanone, 3-acetylcyclobutanone, 2-acetylcyclopentanone, 3-acetylcycIopentanone, 2-acetylcyclohexanone, 3-acetylcyclohexanone, 4-acetylcyclohexanone and the like. [0026] (x) Specific examples when X of the general formula (II) is R2 = alkenyl group When R1 is an alkenyl group, examples include 1,7-octadiene-3,6-dione, 1,8-nonadiene-3,6-dione, 1,9-decadiene-4,7-dione, 1- (V-cyclohexenyl) -5-hexene-1,4-dione, 1- (V-cyclohexenyl) -6-heptene-1,4-dione and the like. When R1 is an alkynyl group, examples include 7-octene-1-yne-3,6-dione, 1-nonene-8-yne-3,6-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-5-hexene-1,4-dione and the like. When R1, Y and Z bond to each other to form a ring, examples include 5-acetyl-2-cyclopentenone, 6-acetyI-2-cyclohexenone, 2-(T-oxo^'-propenyl) cyclopentanone and the like. [0027] (xi) Specific examples when X of the general formula (II) is R2 = alkynyl group When R1 is an alkynyl group, examples include 1,7«octadiyne-4,5-dione, 1,7-octadiyne-3,6-dione, 1,8-nonadiyne-3,6-dione, 1,9-decadiyne-4,7-dione and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 1-phenyl-5-hexyne-1,4-dione, 1-phenyl-6-heptyne-1,4-dione and the like. When R\ Y and Z bond to each other to form a ring, examples include 2-(1,-oxo-2,-propynyl)cyclopentanone, 2-(1,-oxo-3,-butynyl)cyclopentanone and the like. (xii) Specific examples when X of the general formula (II) is R2 = an unsubstituted or a substituted phenyl group When R1 is an unsubstituted or a substituted phenyl group, examples include 1,4-diphenyl-1,4-butanedione and the like. [0029] (xiii) Specific examples when X of the general formula (II) is an OR2 group When R1 is an alkyl group, examples include keto ester compounds such as methyl acetoacetate, methyl diacetoacetate, ethyl diacetoacetate, methyl levulinate, ethyl levulinate, propyl levulinate, isopropyi levulinate, butyl levulinate, t-butyl levulinate, vinyl levulinate, allyl levulinate, ethynyl levulinate, 2-propynyl levulinate, methyl 5-oxohexanoate, methyl 6-oxoheptanoate, methyl 7-oxooctanoate, methyl 8-oxononanoate and the like. When R1 is an alkenyl group, examples include 2-oxo-3-methyl butenoate, 2-oxo-4-methyl pentenoate, 4-oxo-5-methyl hexenoate, 4-oxo-6-methyl heptenoate and the like. When R1 is an alkynyl group, examples include 4-oxo-5-methyl hexynoate, 4-oxo-6-methyl heptynoate and the like. When R1 is an unsubstituted or a substituted phenyl group, examples include 4-oxo-4-methyl phenylbutanoate and the like. When R1, Y and Z bond to each other to form a ring, examples include 2-formylcyclopropaneethyl carboxylate, dihydrofuran-2,4-dione, dihydropyran-2,4-dione, dihydropyran-2,5-dione, methyl cyclobutanone-3-carboxylate, ethyl cyclopentanone-2-carboxylate, methyl cyclopentanone-3-carboxylate, methyl cyclohexanone-2-carboxvlate, methyl cyclohexanone-3-carboxylate, methyl cvclohexanone-4-carboxvlate. ethyl cyclohexanone-4-carboxylate, 2-acetyl-y-butyrolactone, 3-acetyl-y-butyrolactone, 4-acetyl-y-butyrolactone, 2-acetonyl-y-butyrolactone, 3-acetonyl-y-butyrolactone, 4-acetonyl-y-butyrolactone, 2-(3'-oxobutyl)-y-butyrolactone, 3-(3'-oxobutyl)-y-butyrolactone, 4-(3'-oxobutyl)-y-butyrolactone, 2-acetyl-5-valerolactone, 3-acetyl-5-valerolactone, 4-acetyl-5-valerolactone, 5-acetyl-8-valerolactone, 2-acetonyl-5-valerolactone, 3-acetonyl-8-valerolactone, 4-acetonyl-5-valerolactone, 5-acetonyl-8-valerolactone, 2-(3'-oxobutyl)-8-valerolactone, 3-(3'-oxobutyl)-8-valerolactone, 4-(3'-oxobutyl)-5-valerolactone, 5-(3'-oxobutyl)-8-valerolactone and the like. [0030] (xiv) Specific examples when X of the general formula (II) is a COR2 group Examples include 2,3,5-hexanetrione, 1,4-dicarboethoxycyclopentane-2,3-dione, ethyl 2,3,5-trioxo-1-cyclopentane glyoxylate and the like. (xv) Specific examples when X of the general formula (II) is CH2COR2 group Examples include 2,4,6-heptatrione, 3,5-diacetyltetrahydropyran-2,4,6-trioneJ hexamethylcyclohexane-1,3,5-trione, 1,5-diphenyl-1,3,5-pentanetrione and the like. [0031] Among the dicarbonyl compounds represented by the general formula (II), compounds which are reductively decomposed at a potential higher than vinylene carbonate are preferable. Among these, compounds in which n in the general formula (II) is 1 to 4 are preferable, and compounds in which n is 1 to 2 are particularly preferable. Moreover, compounds in which X in the general formula (II) is an R2 group or OR2 group are preferable. In these compounds, substituents for the R2 group and OR2 are more preferably a Ci to C-i2, even more preferably Ci to C8, especially preferably Ci to C4 alkyl group which may be branched; a C3 to Cs, even more preferably C3 to C6, especially preferably C5 to C6 cycloalkyl group; a C2 to Ci2l even more preferably C2 to C8, especially preferably C2 to C4 alkenyl group which may be branched; or a C2 to Ci2, even more preferably C2 to Ce, especially preferably C2 to C6 alkynyl group which may be branched. [0032] Especially preferable dicarbonyl compounds represented by the general formula (II) include acetylacetone, acetonylacetone, 1,3-cyclopentanedione, 1,3-cyclohexanedione, 1,4-cyclohexanedione, 2-acetylcyclopentanone, 3-acetylcyclopentanone, 2-acetylcyclohexanone, methyl diacetoacetate, ethyl diacetoacetate, methyl levulinate, ethyl levulinate, 2-propynyl levulinate, dihydrofuran-2,4-dione, ethyl cyclopentanone-2-carboxylate, methyl cyclopentanone-3-carboxylate, ethyl cyclohexanone-2-carboxylate, methyl cyclohexanone-3-carboxylate, ethyl cyclohexanone-4-carboxylate and 2-acetyl-y-butyrolactone and succinic aldehyde. Examples of most preferable compounds include methyl levulinate, ethyl levulinate and 2-propynyl levulinate which are compounds in which the value of n is 2, cyclic diketone compounds such as 1,3-cyclopentanedione, 1,3-cyclohexanedione and 1,4-cyclohexanedione (n=2), cyclic ketone compounds which have an exocyclic carbonyl substituent, such as 2-acetylcyclopentanone, 2-acetylcyclohexanone, cyclopentanone-2-ethyl carboxylate, cyclopentanone-3-methyl carboxylate (n=2), cyclohexanone-2-ethyl carboxylate, cyclohexanone-3-methyl carboxylate (n=2), cyclohexanone-4-ethyl carboxylate, lactone compounds which have a cyclic ketone group such as 2-acetyl-y-butyrolactone and other cyclic diketone compounds. [0033] The effects of dicarbonyl compounds represented by the general formula (I) and (II) are unknown, but it is assumed that a strong coating is formed on the negative electrode (i) by using a dicarbonyl compound represented by the general formula (I), or (ii) by using a specific amount of a dicarbonyl compound represented by the general formula (II) and a specific amount of at least one member selected from vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS), and glycol sulfite (GS) in combination. [0034] If the contained amount of a dicarbonyl compound represented by the general formulae (I) and (II) is too high, the electric conductivity and other properties of the electrolytic solution are changed and thus the battery performance may be lowered. Therefore, the amount of the dicarbonyl compound is preferably not higher than 10% by weight, particularly preferably not higher than 5% by weight, and most preferably not higher than 3% by weight based on the weight of the nonaqueous electrolytic solution. Moreover, if the amount is too low, sufficient coating is not formed, and desired battery characteristics cannot be obtained. Therefore, the amount of the dicarbonyl compound is preferably not lower than 0.01% by weight, particularly preferably not lower than 0.05% by weight, and most preferably not lower than 0.1% by weight based on the weight of the nonaqueous electrolytic solution. Moreover, if the contained amount of vinylene carbonate (VC), vinylethylene carbonate (VEC), fluoroethylene carbonate (FEC), 1,3-propane sultone (PS) or glycol sulfite (GS) which can be contained in the nonaqueous electrolytic solution in combination with the dicarbonyl compound is too high, the electric conductivity and other properties of the electrolytic solution are changed and thus the battery performance may be lowered. Therefore, the amount is preferably not higher than 10% by volume based on the volume of the nonaqueous solvent, particularly preferably not higher than 5% by volume, and most preferably not higher than 3% by volume. Moreover, if the amount is too low, a sufficient coating is not formed and desired battery characteristics cannot be obtained. Therefore, the amount is preferably not lower than 0.01% by volume, particularly preferably not lower than 0.1% by volume, and most preferably not lower than 0.5 % by volume based on the volume of the nonaqueous solvent. These additives can be used singly or in combination of two or more kinds. [0035] [Nonaqueous solvent] Examples of nonaqueous solvents used for the nonaqueous electrolytic solution of the present invention include cyclic carbonates, linear carbonates, linear esters, ethers, amides, phosphates, sulfones, lactones, nitriles, compounds containing S=0 and the like. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate, dimethylvinylene carbonate, vinylethylene carbonate and the like. Particularly, a cyclic carbonate containing EC having a high dielectric constant is the most preferable. Examples of linear carbonates include asymmetrical linear carbonates such as methyl ethyl carbonate (MEC), methyl propyl carbonate, methyl butyl carbonate, ethyl propyl carbonate, and symmetrical linear carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, dibutyl carbonate and the like. Moreover, examples of linear esters include methyl propionate, methyl pivalate, butyl pivalate, hexyl pivalate, octyl pivalate, dimethyl oxalate, ethyl methyl oxalate, diethyl oxalate and the like. Examples of ethers include tetrahydrofuran, 2-methyltetrahydrofuran, 1,4-dioxane, 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dibutoxyethane and the like. Examples of amides include dimethyl formamide and the like. Examples of phosphates include trimethyl phosphate, tributyl phosphate, trioctyl phosphate and the like. Examples of sulfones include divinyl sulfone and the like. Examples of lactones include y-butyrolactone, 5-valerolactone, oc-angelicalactone and the like, Examples of nitriles include acetonitrile, adiponitrile and the like. [0037] Examples of S=0-containing compounds include sulfate ester compounds such as 1,4-propanesultone, 1,4-butanediol dimethane sulfonate, propylene sulfite, glycol sulfate, propylene sulfate, dipropargyl sulfite, methyl propargyl sulfite and ethyl propargyl sulfite, and divinyl sulfone and the like. Among the S=0-containing compounds, sulfate ester compounds such as 1,4-butanediol dimethane sulfonate, propylene sulfite, glycol sulfate and propylene sulfate, and divinyl sulfone are preferably used in combination. [0038] The above-mentioned nonaqueous solvents are normally used as mixtures to achieve appropriate properties. Examples of combinations of the solvents include the combinations of a cyclic carbonate and a linear carbonate, combinations of a cyclic carbonate and a lactone, combinations of a lactone and a linear ester, combinations of a cyclic carbonate, a lactone and a linear ester, combinations of a cyclic carbonate, a linear carbonate and a lactone, combinations of a cyclic carbonate and an ether, combinations of a cyclic carbonate, a linear carbonate and an ether, combinations of a cyclic carbonate, a linear carbonate and a linear ester and various other combinations. In these combinations, the ratio of the solvents mixed is not particularly limited. In the case of combinations including lactones, lactones are preferably used in the combinations in an amount higher than any other components by volume. [0039] Among these, combinations of a cyclic carbonate and a linear carbonate are preferable. More specifically, combinations of a cyclic carbonate such as EC and PC and a linear carbonate such as methyl ethyl carbonate (MEC), dimethyl carbonate (DMC) and diethyl carbonate (DEC) are particularly preferable. The ratio of a cyclic carbonate to a linear carbonate is preferably the cyclic carbonate: linear carbonate (volume ratio) =20:80 to 40:60, and particularly preferably 25:75 to 35:65. Moreover, among the linear carbonates, asymmetrical carbonates such as MEC, methyl propyl carbonate and methyl butyl carbonate are preferably used. Particularly, it is preferable to use MEC which is liquid at low temperatures and thus has low evaporation because of its relatively high boiling point. Furthermore, the ratio by volume of MEC, which is an asymmetrical linear carbonate, to DMC and/or DEC, which are symmetrical linear carbonates is preferably 100/0 to 51/49, and more preferably 100/0 to 70/30. [0040] [electrolyte salt] Examples of electrolyte salts for use in the present invention include lithium salts containing a linear alkyl group such as LiPF6, UBF4, UCI04, LiN(S02CF3) 2, LiN(S02C2F5) 2, UCF3SO3, UC (S02CF3) 3, LiPF4 (CF3) 2, UPF3(C2F5)3, LiPF3(CF3) 3, LiPF3(iso-C3F7)3, LiPF5(iso-C3F7), and lithium salts containing a cyclic alkylene group such as (CF2)2(S02)2NLi, (CF2)3(S02)2NLi and the like. Among these, particularly preferable electrolyte salts are LiPF6, UBF4 and LiN(S02CF3)2, and the most preferable electrolyte salt is LiPF6. These electrolyte salts can be used singly or in combination of two or more kinds. [0041] Electrolyte salts can be mixed at any ratio. Examples of suitable combinations include the combination of LiPF6 and LiBF4) the combination of LiPF6 and UN(S02CF3)2, the combination of LiBF4 and LiN(S02CF3)2 and the like. The combination of LiPF6 and UBF4 is particularly preferable. A preferable ratio is LiPF6:LiBF4 (volume ratio) =80:20 to 99:1, and a particularly preferable ratio is 90:10 to 98:2. Moreover, when one of LiPF6, LiBF4 and UN(S02CF3)2 is selected as a first electrolyte salt and another electrolyte salt is used in combination as a second electrolyte salt, the amount of the second electrolyte salt based on the entire electrolyte salts is preferably 0.01 mol% or more, more preferably 0.03% or more, and most preferably 0.05% or more. The upper limit of the amount is preferably 45% or less, more preferably 20% or less, even more preferably 10% or less, and most preferably 5% or less. The concentration of these electrolyte salts dissolved and used is normally 0.3 M or more, more preferably 0.5 M or more, and most preferably 0.7 M or more based on the nonaqueous solvent. The upper limit of the concentration is preferably 3 M or less, more preferably 2.5 M or less, and most preferably 2 M or less. [0042] Examples of the most preferable combinations of the nonaqueous solvent and electrolyte salt include an electrolytic solution containing LiPF6 and/or LiBF4 as an electrolyte salt combined with a solvent mixture comprising (i) EC and/or PC, (ii) at least one member selected from VC, VEC, FEC, PS and GS, and (iii) at least one member selected from MEC, DMC and DEC. More specifically, it is preferable to combine a solvent mixture having the ratio by volume of the (i) : (ii) : (iii) =10:0.2:89.8 to 40:10:50, preferably 20:0.5:79.5 to 35:5:60, more preferably 25:1:74 to 32:3:65 and an electrolyte salt having the ratio of LiPF6:LiBF4 (molar ratio) =100:0 to 55:45, preferably 99.8:0.2 to 75:25, even more preferably 99.5:0.5 to 85:15, and most preferably 99:1 to 90:10. [0043] [Preparation of nonaqueous electrolytic solution] The nonaqueous electrolytic solution of the present invention can be obtained, for example, by mixing nonaqueous solvents such as EC, PC, MEC and DMC mentioned above, dissolving the above-mentioned electrolyte salts in the mixture, and dissolving (i) the dicarbonyl compound represented by the general formula (I), or (ii) the dicarbonyl compound represented by the general formula (II) and at least one member selected from VC, VEC, FEC, PS and GS in the solution. At this time, it is preferable that the used nonaqueous solvents, dicarbonyl compounds represented by the general formula (I) or (II), VC, VEC, FEC, PS or GS and other additives are purified in advance to reduce impurities therein as much as possible within the range the productivity is not significantly lowered. [0044] Gas generation due to decomposition of the electrolytic solution can be inhibited and long-term cycle property, charge storage characteristic and other battery characteristics can be improved by incorporating, for example, air and carbon dioxide to the nonaqueous electrolytic solution of the present invention. As the method for incorporating (dissolving) carbon dioxide or air in the nonaqueous electrolytic solution, there may be used (1) a method in which the nonaqueous electrolytic solution is previously contacted with air or a carbon dioxide-containing gas before the solution is poured in the battery; or (2) a method in which after the solution has been poured in the battery, air or a carbon dioxide-containing gas is charged in the battery before or after sealing the battery. It is preferred that the moisture content of the air or carbon dioxide-containing gas is as low as possible and that the air or carbon dioxide-containing gas have a dew point of -40°C or lower, particularly preferably -50°C or lower. In the present invention, from the perspective of improving charge and discharge characteristics at high temperatures, using an electrolytic solution containing carbon dioxide dissolved in the nonaqueous electrolytic solution is particularly preferable. The amount of carbon dioxide dissolved is preferably 0.001% by weight or more, more preferably 0.05% by weight or more, and even more preferably 0.2% by weight or more based on the weight of the nonaqueous electrolytic solution, and most preferably carbon dioxide is dissolved in the nonaqueous electrolytic solution until it is saturated. [0045] [Lithium secondary battery] The lithium secondary battery of the present invention comprises a positive electrode, a negative electrode and a nonaqueous electrolytic solution in which an electrolyte salt is dissolved in a nonaqueous solvent. The positive electrode, negative electrode and other components than the nonaqueous electrolytic solution are not particularly limited, and various known components can be used. [0046] For example, as a positive electrode active material, lithium compound metal oxides containing cobalt, manganese or nickel may be used. These positive electrode active material can be used singly or in combination of two or more kinds. Examples of such compound metal oxides include LiCo02f LiMn204, LiNi02, LiCOi-xNixOa (0.01