Nonaqueous electrolytic solution and nonaqueous-electrolyte battery employing the same

Abstract

The present invention is to provide: a nonaqueous-electrolyte battery excellent in terms of safety during overcharge and high-temperature storability; and a nonaqueous electrolytic solution which gives the battery. The present invention relates to a nonaqueous electrolytic solution comprising an electrolyte and a nonaqueous solvent, wherein the nonaqueous electrolytic solution comprises at least one of specific compounds.

Claims

1. A nonaqueous electrolytic solution, comprising: an electrolyte; a nonaqueous solvent; and at least one of a compound represented by formula (I) and a compound represented by formula (II): ##STR00007## wherein, in formula (I), Ar represents a phenyl group, m represents an integer of 2 or larger, X represents an alkoxycarbonyloxy group, an organic sulfonate group, or a phosphoric acid ester group, and R.sup.1 and R.sup.2 each independently represent a hydrogen atom, a halogen atom, or an optionally substituted hydrocarbon group having 1-12 carbon atoms, and wherein, in formula (II), A represents an optionally substituted alkylidene groups or cycloalkylidene groups, R.sup.3 to R.sup.12 each independently represent a hydrogen atom, a halogen atom, an optionally substituted hydrocarbon group having 1-12 carbon atoms, an alkoxy group, an alkoxycarbonyloxy group, an organic sulfonate group, or a phosphoric acid ester group, and at least one of the R.sup.3 to R.sup.12 representing an alkoxycarbonyloxy group, an organic sulfonate group, or a phosphoric acid ester group.

2. The nonaqueous electrolytic solution according to claim 1, wherein R.sup.1 and R.sup.2 in formula (I) are each a hydrogen atom.

3. The nonaqueous electrolytic solution according to claim 1, wherein the total content of the compound represented by formula (I) and the compound represented by formula (II) in the nonaqueous electrolytic solution is 0.001-10% by mass.

4. The nonaqueous electrolytic solution according to claim 1, further comprising: at least one compound selected from the group consisting of cyclic carbonate compounds having a carbon-carbon unsaturated bond, cyclic carbonate compounds having a fluorine atom, monofluorophosphoric acid salts, and difluorophosphoric acid salts.

5. A nonaqueous-electrolyte battery comprising: a negative electrode and a positive electrode which are capable of occluding and releasing lithium ions; and a nonaqueous electrolytic solution, wherein the nonaqueous electrolytic solution is the nonaqueous electrolytic solution according to claim 1.

6. The nonaqueous electrolytic solution according to claim 1, comprising the compound of formula (I).

7. The nonaqueous electrolytic solution according to claim 1, comprising the compound of formula (II).

Description

EXAMPLES

(1) The invention will be explained below in more detail by reference to Examples and Comparative Examples. However, the invention should not be construed as being limited to the following Examples unless the invention departs from the spirit thereof.

(2) The batteries obtained in the following Examples and Comparative Examples were evaluated by the methods shown below.

(3) [Capacity Evaluation]

(4) Each sheet-form nonaqueous-electrolyte secondary battery was evaluated in the state of being sandwiched between glass plates in order to enhance contact between the electrodes. At 25° C., this battery was charged to 4.1 V at a constant current corresponding to 0.3 C and then discharged to 3 V at a constant current of 0.3 C. Five cycles of this charge/discharge were conducted to stabilize the battery. In the fourth cycle, the battery was charged to 4.1 V at a constant current of 0.3 C, subsequently charged at a constant voltage of 4.1 V until the current value became 0.05 C, and then discharged to 3 V at a constant current of 0.3 C to determine initial discharge capacity.

(5) Here, “1 C” means a current value at which the reference capacity of the battery is discharged over 1 hour. For example, “0.3 C” means the current value which is 0.3 times the current of 1 C.

(6) Incidentally, when the state of charge (SOC) of a battery is expressed, the SOC of the battery having a voltage of 3 V is regarded as 0% and that of the battery having a voltage of 4.1 V is regarded as 100%. Using the initial discharge capacity as a reference for 100%, the SOC (%) of the battery can be calculated from a quantity charged. For example, in the case where a battery of 4.1 V (SOC, 100%) is charged in the same quantity as the initial capacity, the state of charge of this battery is expressed as SOC 200%.

(7) [Output Evaluation]

(8) With respect to Examples B-1 to B-6, Comparative Examples B-1 to B-5, and Reference Example B-1, the batteries produced in the manners described above were charged at room temperature and at a constant current of 0.3 C from 3 V to one-half the reference capacity of the battery (50% of full charge), subsequently allowed to stand in a −30° C. thermostatic chamber for 2 hours or longer, and then examined for output.

(9) [Evaluation of Overcharge Characteristics]

(10) With respect to Examples A-1 and A-2 and Comparative Examples A-1 to A-10, the batteries which had undergone the capacity evaluation test were evaluated in the following manner. At 25° C., each battery was charged to 4.1 V at a constant current of 0.3 C, subsequently charged at a constant voltage of 4.1 V until the current value became 0.05 C, and then immersed in an ethanol bath to measure the volume thereof. Thereafter, at 45° C., a constant current of 1.0 C was applied to the battery and the current was cut off at the time when the voltage had reached 4.9 V. The open-circuit voltage (OCV) of this battery which had undergone the overcharge test was measured.

(11) With respect to Examples B-1 to B-6, Comparative Examples B-1 to B-5, and Reference Example B-1, the batteries which had undergone the output evaluation test were evaluated in the following manner. At 25° C., each battery was charged to 4.1 V at a constant current of 0.3 C, subsequently charged at a constant voltage of 4.1 V until the current value became 0.05 C, and then immersed in an ethanol bath to measure the volume thereof. Thereafter, at 45° C., a constant current of 0.5 C was applied to the battery and the current was cut off at the time when an SOC of 180% had been reached. The open-circuit voltage (OCV) of this battery which had undergone the overcharge test was measured.

(12) Each battery which had undergone the OCV measurement was immersed in an ethanol bath to measure the volume thereof. The amount of the gas which had been evolved was determined from the difference in volume between before and after the overcharge.

(13) The lower the OCV of a battery which has undergo the overcharge test, the lower the state of overcharge thereof and the higher the safety thereof during overcharge. Furthermore, the larger the amount of evolved gas after the overcharge, the more the battery is preferred in the case where this battery is of the type in which an abnormal increase in internal pressure due to an abnormality, e.g., overcharge, is sensed to make the safety value work. This is because the safety valve can operate in an early stage.

(14) Moreover, it is preferable that the difference between the amount of evolved gas after the overcharge and the amount of gas which is evolved during high-temperature storage or the like should be larger, because it is possible to prevent the safety valve from erroneously working during high-temperature storage or the like, while making the safety valve work in overcharge without fail.

(15) [Evaluation of High-Temperature Storability]

(16) At 25° C., each battery which had undergone the capacity evaluation test or the output evaluation test was charged to 4.1 V at a constant current of 0.3 C, subsequently charged at a constant voltage of 4.1 V until the current value became 0.05 C, and then immersed in an ethanol bath to measure the volume thereof. Thereafter, a high-temperature storage test was conducted at 75° C. for 72 hours (3 days).

(17) After the high-temperature storage test, the battery was cooled to 25° C. and then immersed in an ethanol bath to measure the volume thereof. The amount of the gas which had been evolved was determined from the difference in volume between before and after the high-temperature storage.

(18) After the determination of the amount of evolved gas, the battery was discharged to 3 V at a constant current of 0.3 C at 25° C. to measure the residual capacity remaining after the high-temperature storage test.

(19) Next, at 25° C., the battery was charged to 4.1 V at a constant current of 0.3 C, subsequently charged at a constant voltage of 4.1 V until the current value became 0.05 C, and then discharged to 3 V at a constant current of 0.3 C to measure the 0.3 C discharge capacity of the battery which had undergone the high-temperature storage test.

(20) Furthermore, with respect to Examples B-1 to B-6, Comparative Examples B-1 to B-5, and Reference Example B-1, the batteries charged to an SOC of 50% were examined for output in a −30° C. thermostatic chamber.

Example A-1

(21) [Production of Positive Electrode]

(22) In N-methylpyrrolidone solvent, 90% by mass lithium-cobalt-nickel-manganese oxide (LiNi.sub.1/3Co.sub.1/3Mn.sub.1/3O.sub.2) as a positive-electrode active material was mixed with 7% by mass acetylene black as a conductive material and 3% by mass poly(vinylidene fluoride) (PVdF) as a binder by means of a disperser. Thus, a slurry was obtained. This slurry was evenly applied to both surfaces of an aluminum foil and dried, and the resultant coated foil was pressed to obtain a positive electrode.

(23) [Production of Negative Electrode]

(24) Ninety-eight parts by mass of a graphite powder as a negative-electrode active material was mixed with 2 parts by mass of PVdF, and N-methylpyrrolidone was added thereto to obtain a slurry. This slurry was applied to one surface of a current collector made of copper, and the slurry applied was dried to obtain a negative electrode.

(25) [Production of Electrolytic Solution]

(26) In a dry argon atmosphere, a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio, 3:4:3) was mixed with 2% by mass methyl 3-phenylpropyl carbonate, in terms of content in the nonaqueous electrolytic solution, as shown in Table 1. Subsequently, sufficiently dried LiPF.sub.6 was dissolved therein so as to result in a proportion thereof of 1.0 mol/L. Thus, an electrolytic solution was obtained.

(27) [Production of Nonaqueous-Electrolyte Secondary Battery]

(28) The positive electrode and negative electrode described above and a separator made of polyethylene were stacked in the order of negative electrode/separator/positive electrode/separator/negative electrode to produce a battery element. This battery element was inserted into a bag constituted of a laminated film obtained by coating both surfaces of aluminum (thickness, 40 μm) with a resin layer, with the terminals of the positive and negative electrodes projecting outward. Thereafter, the electrolytic solution was injected into the bag, and this bag was vacuum-sealed to produce a sheet-form battery. This battery was evaluated for overcharge characteristics and high-temperature storability. The results of the evaluation are shown in Table 1.

Example A-2

(29) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that 0.5% by mass vinylene carbonate was further added in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-1

(30) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that the methyl 3-phenylpropyl carbonate was omitted in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-2

(31) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that cyclohexylbenzene was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-3

(32) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that methyl phenyl carbonate was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-4

(33) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that n-butylbenzene was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-5

(34) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that 3-phenylpropyl acetate was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-6

(35) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that phenethyl butyrate was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-7

(36) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that 0.5% by mass vinylene carbonate was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-8

(37) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that 2% by mass cyclohexylbenzene and 0.5% by mass vinylene carbonate were used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-9

(38) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that benzyl methyl carbonate was used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Comparative Example A-10

(39) A sheet-form battery was produced and evaluated for overcharge characteristics and high-temperature storability in the same manners as in Example A-1, except that 2% by mass benzyl methyl carbonate and 0.5% by mass vinylene carbonate were used in place of the methyl 3-phenylpropyl carbonate in preparing the electrolytic solution of Example A-1. The results of the evaluation are shown in Table 1.

Example B-1

(40) [Production of Electrolytic Solution]

(41) In a dry argon atmosphere, vinylene carbonate was added to a mixture of ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate (volume ratio, 3:4:3) in an amount of 0.5% by mass in terms of content in the nonaqueous electrolytic solution. Furthermore, 2,2-bis(p-methoxycarbonyloxyphenyl)propane was added in such an amount as to result in a content thereof of 2.2% by mass. Subsequently, sufficiently dried LiPF.sub.6 was dissolved therein so as to result in a proportion thereof of 1.0 mol/L. Thus, an electrolytic solution was obtained. For the evaluation of overcharge characteristics, however, a nonaqueous electrolytic solution prepared without adding vinylene carbonate was used. Incidentally, it is thought that whether vinylene carbonate is present or absent does not considerably affect the overcharge characteristics.

(42) A sheet-form battery was produced in the same manner as in Example A-1, except for the production of the electrolytic solution. This battery was evaluated for overcharge characteristics, output characteristics, and high-temperature storability. The results of the evaluation are shown in Table 2.

(43) Incidentally, the 2,2-bis(p-methoxycarbonyloxyphenyl)propane used was a synthesized product of Mitsubishi Chemical Corp.

Example B-2

(44) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 2,2-bis(p-methoxycarbonyloxyphenyl)propane was added in an amount of 1.1% by mass in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Example B-3

(45) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 1,1-bis(p-methoxycarbonyloxyphenyl)cyclohexane was added in an amount of 2.4% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

(46) Incidentally, the 1,1-bis(p-methoxycarbonyloxyphenyl)cyclohexane was synthesized by the following method.

(47) A dropping funnel was attached to a 2.0-L four-necked flask, and the atmosphere therein was replaced with a nitrogen atmosphere. Thereinto was introduced 100.0 g (372 mmol) of bisphenol A, followed by dichloromethane (400 mL) and triethylamine (190 mL; 1,363 mmol). The resultant mixture was stirred. While the mixture was being cooled with ice, 121.3 g (1,284 mmol) of methyl chloroformate was added dropwise thereto and this mixture was stirred for 30 minutes. Thereafter, water was added to terminate the reaction.

(48) The resultant liquid reaction mixture was extracted with dichloromethane three times, and the organic layers were mixed together. The mixed organic layer was washed successively with dilute hydrochloric acid, water, and an aqueous sodium chloride solution and dried with anhydrous sodium sulfate. The solvent was distilled off, and the residue obtained was dissolved in heated ethyl acetate. This solution was allowed to cool, and the solid which had precipitated was taken out by filtration. This recrystallization operation was repeated, and the solid obtained was dried under vacuum to obtain 120 g of 1,1-bis(p-methoxycarbonyloxyphenyl)cyclohexane as a white solid (yield, 84%).

(49) The compound synthesized was subjected to .sup.1H-NMR spectroscopy and .sup.13C-NMR spectroscopy (Avance 400, manufactured by Bruker GmbH: measurement conditions; 400 MHz, CDCl.sub.3, TMS) to identify the structure thereof. The results of the analysis are shown below.

(50) .sup.1H-NMR (400 MHz, CDCl.sub.3) δ 7.26 (2H, d, J=8.8 Hz), 7.43 ppm (2H, d, J=8.8 Hz), 3.88 (6H, s), 2.27-2.22 ppm (4H, m), 1.60-1.45 ppm (6H, m)

(51) .sup.13C-NMR (100 MHz, CDCl.sub.3) δ 154.27 ppm, 148.75 ppm, 145.98 ppm, 128.20 ppm, 120.57 ppm, 55.30 ppm, 45.69 ppm, 37.23 ppm, 26.17 ppm, 22.69 ppm

(52) From the results of the analysis by .sup.1H-NMR and .sup.13C-NMR spectroscopy, the compound obtained was ascertained to be 1,1-bis(p-methoxycarbonyloxyphenyl)cyclohexane.

Example B-4

(53) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 1,1-bis(p-methoxycarbonyloxyphenyl)cyclohexane was added in an amount of 1.2% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Comparative Example B-1

(54) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that the 2,2-bis(p-methoxycarbonyloxyphenyl)propane was omitted in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Comparative Example B-2

(55) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that cyclohexylbenzene was added in an amount of 2% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Comparative Example B-3

(56) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that cyclohexylbenzene was added in an amount of 1% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Example B-5

(57) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 1,1-bis(p-methoxysulfonyloxyphenyl)cyclohexane was added in an amount of 2.65% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Example B-6

(58) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 2,2-bis(p-methoxysulfonyloxyphenyl)propane was added in an amount of 2.4% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Comparative Example B-4

(59) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 2,2-diphenylpropane was added in an amount of 1.2% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Comparative Example B-5

(60) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 2,2-bis(p-acetoxyphenyl)propane was added in an amount of 2.0% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

Reference Example B-1

(61) A sheet-form battery was produced and evaluated for overcharge characteristics, output characteristics, and high-temperature storability in the same manners as in Example B-1, except that 1,1-diphenylcyclohexane was added in an amount of 1.5% by mass in place of the 2,2-bis(p-methoxycarbonyloxyphenyl)propane in preparing the electrolytic solution of Example B-1. The results of the evaluation are shown in Table 2.

(62) In Examples B-1 to B-6, Comparative Examples B-1 to B-5, and Reference Example B-1, the addition amount of each compound serving as an additive shown in Table 2 was determined on the basis of the number of phenyl groups present in the compound or of the number of moles of the compound in order that a specific structure within the compound be accurately evaluated as an object to be evaluated.

(63) TABLE-US-00001 TABLE 1 Residual capacity after Gas Addition Addition high- amount amount amount Initial temperature after Additive 1 wt % Additive 2 wt % capacity storage overcharge Example methyl 2.0 — — 0.99 0.99 6.0 A-1 3-phenylpropyl carbonate Comparative — — — — 1.00 1.00 1.0 Example A-1 Comparative cyclohexyl- 2.0 — — 0.98 0.97 6.6 Example benzene A-2 Comparative methyl phenyl 2.0 — — 0.97 0.97 2.9 Example carbonate A-3 Comparative n-butyl 2.0 — — 0.99 0.95 4.6 Example carbonate A-4 Comparative 3-phenylpropyl 2.0 — — 1.00 0.93 4.6 Example acetate A-5 Comparative phenethyl 2.0 — — 0.99 0.95 2.3 Example butyrate A-6 Example methyl 2.0 VC 0.5 1.01 1.00 8.6 A-2 3-phenylpropyl carbonate Comparative — — VC 0.5 1.00 1.01 1.4 Example A-7 Comparative cyclohexyl- 2.0 VC 0.5 0.99 0.98 8.6 Example benzene A-8 Comparative benzyl methyl 2.0 — — — — 2.1 Example carbonate A-9 Comparative benzyl methyl 2.0 VC 0.5 1.00 0.98 — Example carbonate A-10

(64) In Table 1, VC represents vinylene carbonate.

(65) In Table 1, the initial capacity, residual capacity after high-temperature storage, and gas amount after overcharge were shown as normalized values with respect to the values of Comparative Example A-1 which were taken as 1.0 or 1.00.

(66) As apparent from Table 1, the batteries of Comparative Examples A-1, A-7, and A-9 show too small an evolved-gas amount after overcharge and have low safety during overcharge, although excellent in terms of initial characteristics and characteristics after the high-temperature storage test. The batteries of Comparative Examples A-2 to A-6 and A-8 show a large evolved-gas amount after overcharge and have excellent safety, but have poor characteristics after the high-temperature storage test. Furthermore, Comparative Example A-10 has poor characteristics after the high-temperature storage test, although excellent in terms of initial characteristics.

(67) The batteries of Examples A-1 and A-2 show a large evolved-gas amount after overcharge to have high safety during overcharge, and have excellent characteristics after the high-temperature storage test. It can hence be seen that the batteries employing the nonaqueous electrolytic solutions according to the invention are highly safe during overcharge and have excellent high-temperature continuous-charge characteristics.

(68) Incidentally, a secondary battery is a battery which is used while being repeatedly charged and discharged, and in which only a slight difference in residual capacity exerts a considerable influence on the continuous-charge performance.

(69) For example, a battery which showed a residual capacity of 0.99 (99%) is compared with a battery which showed a residual capacity of 0.96 (96%). In cases when the two batteries are subjected to 100 cycles of charge/discharge, the resultant charge capacity of the former battery is 0.99.sup.100≈0.366=36.6%, whereas that of the latter is 0.96.sup.100≈0.0168≈1.7%. That is, the difference of 3% per cycle results in a difference of 20 times or more through 100 cycles.

(70) It is thus understood that a difference on the order of percent in the residual capacity after high-temperature storage seriously affects the continuous-charge characteristics.

(71) TABLE-US-00002 TABLE 2 After Overcharge Addition Initial storage characteristics amount Out- Residual Gas Additive mass % Capacity put capacity Output amount OCV/V Example 2,2-bis(p- 2.2 1.00 1.00 1.01 1.01 2.90 4.65 B-1 methoxycarbonyl- oxyphenyl)- propane Example 2,2-bis(p- 1.1 1.00 1.00 1.00 1.04 — — B-2 methoxycarbonyl- oxyphenyl)- propane Example 1,1-bis(p- 2.4 1.00 1.01 1.00 0.98 4.50 4.65 B-3 methoxycarbonyl- oxyphenyl)cyclo- hexane Example 1,1-bis(p- 1.2 1.00 1.00 1.00 0.99 — — B-4 methoxycarbonyl- oxyphenyl)cyclo- hexane Comparative none — 1.00 1.00 1.00 1.00 1.00 4.7  Example B-1 Comparative cyclohexylbenzene 2.0 0.99 0.87 0.96 0.86 3.30 4.65 Example B-2 Comparative cyclohexylbenzene 1.0 1.00 0.94 0.98 0.98 3.00 4.69 Example B-3 Example 1,1-bis(p- 2.65 1.00 0.95 1.01 0.96 3.63 4.62 B-5 methoxysulfonyl- oxyphenyl)cyclo- hexane Example 2,2-bis(p- 2.4 1.00 0.95 1.01 0.93 3.13 4.62 B-6 methoxysulfonyl- oxyphenyl)- propane Comparative 2,2-diphenyl- 1.2 1.00 0.95 1.00 0.95 1.44 4.68 Example propane B-4 Comparative 2,2-bis(p- 2.0 0.99 0.89 0.98 0.75 2.56 4.69 Example acetoxyphenyl)- B-5 propane Reference 1,1-diphenyl- 1.5 1.00 0.94 1.00 0.93 2.56 4.66 Example cyclohexane B-1

(72) In Table 2, the initial capacity, residual capacity after high-temperature storage, gas amount after overcharge, and output were shown as normalized values with respect to the values of Comparative Example B-1 which were taken as 1.00.

(73) As apparent from Table 2, the batteries of Comparative Examples B-2 and B-3 have a large amount of gas evolved during overcharge and a low OCV after overcharge as compared with the battery of Comparative Example B-1, to which no additive for overcharge has been added, and hence have excellent safety during overcharge. However, as the addition amount increased, not only the initial output of the batteries decreased but also the residual capacity after storage and the output also decreased considerably.

(74) The batteries of Examples B-1 and B-3 compare favorably with Comparative Examples B-2 and B-3 in evolved-gas amount after overcharge and show a low OCV after overcharge. Consequently, these batteries are considered to have high safety during overcharge.

(75) A comparison between Examples B-1 to B-4 and Comparative Examples B-2 and B-3 indicates that the batteries of the Examples have a high initial output and a high residual capacity after storage even when the addition amount is increased, and compare favorably with Comparative Example B-1, to which no additive for overcharge has been added. It can hence be seen that the batteries employing the nonaqueous electrolytic solutions according to the invention are highly safe during overcharge and have excellent high-temperature storability.

(76) Moreover, Comparative Example B-4 has a small amount of gas evolved during overcharge, and Comparative Example B-5 shows a low output. Meanwhile, Examples B-5 and B-6 show a large amount of gas evolved during overcharge and have a low OCV after overcharge. It can hence be seen that the batteries of the Examples are highly safe during overcharge and can retain both the capacity and the output.

(77) While the invention has been described in detail and with reference to specific embodiments thereof, it will be apparent to one skilled in the art that various changes and modifications can be made therein without departing from the spirit and scope thereof.

(78) This application is based on a Japanese patent application filed on Mar. 30, 2012 (Application No. 2012-82142) and a Japanese patent application filed on Oct. 26, 2012 (Application No. 2012-236679), the contents thereof being incorporated herein by reference.

INDUSTRIAL APPLICABILITY

(79) The nonaqueous-electrolyte battery employing the nonaqueous electrolytic solution of the invention has enhanced safety during overcharge and, despite this, has high capacity and excellent high-temperature continuous-charge characteristics. This battery can hence be used in various known applications.

(80) Specific examples thereof include notebook type personal computers, pen-input personal computers, mobile personal computers, electronic-book players, portable telephones, portable facsimile telegraphs, portable copiers, portable printers, headphone stereos, video movie cameras, liquid-crystal TVs, handy cleaners, portable CD players, mini-disk players, transceivers, electronic pocketbooks, electronic calculators, memory cards, portable tape recorders, radios, backup power sources, motors, motor vehicles, motor cycles, bicycles fitted with a motor, bicycles, illuminators, toys, game machines, clocks and watches, power tools, stroboscopes, cameras, power sources for load leveling, and power sources for storing natural energy. This battery can be used in all applications ranging from small-size applications to large-size applications.