JP3449703B2 - Organic electrolyte secondary battery - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an organic electrolyte secondary battery, and more particularly to an organic electrolyte secondary battery having excellent safety.

[0002]

2. Description of the Related Art An organic electrolytic solution secondary battery is a secondary battery using an organic solvent as a solvent for the electrolytic solution. The organic electrolytic solution secondary battery has a large capacity, high voltage, high energy density and high capacity. Since it is an output, the demand tends to increase more and more.

As a solvent for the organic electrolytic solution of this battery (hereinafter, simply referred to as "electrolytic solution" except when the battery is used), a cyclic ester such as ethylene carbonate and dimethyl carbonate, diethyl carbonate or propion have been used so far. It has been used as a mixture with chain esters such as methyl acid.

[0004] However, while studying this organic electrolyte secondary battery with the aim of further improving safety,
If a chain ester is used as the main solvent for the electrolyte, or if the negative electrode has a large chargeable / dischargeable capacity, the battery structure must be carefully devised to prevent internal short circuits or nails. It was found that there is a tendency for the safety to be reduced when stabbed.

Usually, a protective circuit is used to prevent overcharging and prevent an internal short circuit. In a normal internal short circuit, the battery heats up and no abnormal situation occurs. Moreover, nail stabs are rare and rare unless they are intentionally performed by the user. It is possible that the battery may be partially crushed due to a shock accident or the like.

For this reason, a battery crush test is conducted, but it is usually safe. However, it cannot be said that it is safe enough to test dozens of them, and it is desirable to confirm the safety by conducting a test under a more dangerous condition.

On the other hand, in the nail piercing test, the battery is surely short-circuited in a smaller portion compared to the battery crushing test, so that the current is concentrated in the short-circuited portion and heat is generated more easily, and the battery is partially rapidly heated to a high temperature. It is easy to become. Therefore, the fuse (clogging due to melting) of the separator is likely to vary, and more heat is generated due to the reaction between the electrolytic solution and the negative electrode at the short-circuited portion, which further increases the heat generation of the battery. Therefore, the nail penetration test is effective as a severe safety test. Furthermore, when the nail penetration test is performed at a high temperature of 40 ° C. rather than at room temperature, the temperature of the battery rises to a higher temperature and the thermal runaway reaction of the battery is more likely to occur. Further, when the nail is stopped in the middle of the battery as in the case of ½ nail sticking, the short-circuited portion is reduced and the current is more concentrated and heat is easily generated. Therefore,
For higher safety, 1 /
2 It is desirable that it can withstand the nail penetration test to some extent.

[0008]

By the way, when a compound capable of deintercalating lithium such as carbon is used in the negative electrode, the reactivity with the electrolytic solution at a high temperature is much lower than that in the case of using metallic lithium. The safety of is improved. In order to improve the safety, the presence of a good-quality film formed by reacting with the electrolytic solution on the surface of the negative electrode using a compound capable of deintercalating lithium is essential.

Regarding the reaction with the electrolytic solution on the surface of the negative electrode, see D. Aurbach et al. Have reported that organic carbonate (ROCO ₂ Li), Li ₂ CO ₃ , alkoxide (ROLi), etc. are formed on carbon [J. Electrochemical Soc. , V
ol142 (No. 9), p2882 (1995)].
Further, in the same report, in a mixed solvent of cyclic ester ethylene carbonate and chain ester diethyl carbonate, the ratio of chain ester diethyl carbonate to cyclic ester ethylene carbonate was 1: 1.
Higher amounts are reported to adversely affect cycle performance. Further, also in the study by the present inventors, especially when the proportion of chain ester such as diethyl carbonate is large, especially when the proportion of chain ester having a methyl group is large, the safety in short circuit and nail sticking is lowered. It turns out that there is a tendency.

Therefore, an object of the present invention is to solve the problems relating to the safety of conventional organic electrolyte secondary batteries and to provide an organic electrolyte secondary battery with excellent safety.

[0011]

The present invention is directed to a positive electrode having at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide and lithium manganese oxide as an active material, and doping / dedoping with lithium ions.
In an organic electrolyte secondary battery having a negative electrode on which a film is formed by reacting part of a material capable of reacting with an electrolytic solution and an electrolytic solution containing a chain ester as a main solvent, a COO group is added to the electrolytic solution via a COO group. The number of carbon atoms bonded to the benzene ring is 4
The above problem is solved by containing a nonionic aromatic compound having one or more alkyl groups.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION Examples of the nonionic aromatic compound having an alkyl group having 4 or more carbon atoms which is bonded to the benzene ring through the COO group used in the present invention include: Trimellitic acid ester, tri-2-ethylhexyl trimellitate [(C ₆ H ₃ (COOC ₈ H ₁₇ ))
Derivatives of trimellitic acid esters such as _3], dibutyl phthalate _{[(C 6 H 4 (COOC 4} H 9) 2 ], and the like.

The alkyl group of the nonionic aromatic compound must have 4 or more carbon atoms , and preferably has 5 or more carbon atoms. Further, the alkyl group is bonded to the benzene ring via the COO group, which is a barrier effect on the surface of the negative electrode by suppressing the COO group (suppresses rapid reaction between the electrode and the electrolytic solution at high temperature). This is because the effect) becomes large. Here, the nonionic property of the nonionic aromatic compound means that the molecule does not have a cation part or an anion part.

In the present invention, the content of the nonionic aromatic compound having the specific alkyl group in the electrolytic solution is preferably 0.1 part by volume or more based on 100 parts by volume of the electrolytic solution solvent. , 0.2 parts by volume or more is more desirable, and 0.5 parts by volume or more is most desirable. When the nonionic aromatic compound having the specific alkyl group is a solid, a value converted into volume based on its density is used. Further, the content of the nonionic aromatic compound having the specific alkyl group in the electrolytic solution is preferably 10 parts by volume or less, more preferably 2 parts by volume or less, relative to 100 parts by volume of the electrolytic solution solvent. The capacity part or less is most desirable.

When the content of the nonionic aromatic compound having the above-mentioned specific alkyl group in the electrolytic solution is less than the above, safety may not be sufficiently improved, and the above-mentioned specific alkyl group may be used. If the content of the nonionic aromatic compound having a group in the electrolytic solution is higher than the above, the cycle characteristics and load characteristics of the battery may deteriorate.

The present inventors have examined in detail the effect of the addition of the aromatic compound to the electrolytic solution on the safety of the battery. Explaining this in detail, the present inventors first conducted a nail penetration test of a lithium-ion battery assuming an internal short circuit, etc., and although the risk is low with a normal commercially available lithium-ion battery, the energy of the battery is low. It was found that the danger increases as the density increases.

A compound such as a carbon material capable of deintercalating lithium is usually used for the negative electrode of these batteries.
About 1 if the negative electrode is overcharged and some lithium is electrodeposited
An exothermic reaction occurs between the electrolytic solution and the electrodeposited lithium or the carbon material in which lithium is inserted from around 00 ° C. Meanwhile, Richi
Um-cobalt oxide, lithium nickel oxide and lithium
At least one selected from the group consisting of titanium manganese oxide
In the positive electrode using one kind as the active material, the reaction start temperature with the electrolyte decreases due to the desorption of lithium, and when the temperature rises to the thermal runaway temperature of the positive electrode due to the reaction heat of the negative electrode, the battery heats abnormally. Will be caused.

Due to the exothermic phenomenon associated with such continuous reaction, when the chargeable / dischargeable capacity of the negative electrode of the battery under normal use conditions exceeds 85 mAh / cm ³ per unit volume of the battery, the battery is overheated. The safety when charged is reduced. That is, as the dischargeable capacity per unit volume of the negative electrode increases, the amount of heat generated per unit volume of the battery increases when heat is generated during overcharge, and the battery temperature is more likely to rise to the thermal runaway temperature of the positive electrode. It will be. Therefore, it is necessary to suppress the exothermic reaction between the negative electrode and the electrolytic solution as the battery has a larger negative electrode capacity per unit volume. Further, since the amount of heat generated is large even when the battery size is large, it is necessary to suppress the exothermic reaction between the negative electrode and the electrolytic solution, and the effect of incorporating the nonionic aromatic compound having a specific alkyl group of the present invention is Remarkably expressed. When the size of the unit cell is 10 cm ³ or more, particularly 15 cm ³ or more, the effect of the present invention is more remarkably exhibited.

In order to improve the safety of the battery, it is known to add an incombustible solvent, a polymer, or an aromatic compound to the electrolytic solution. By using an aromatic compound in a battery using a chain ester as a main solvent, the inventors have found a particularly excellent effect in improving safety. In the present invention, the reason why the safety can be improved by adding the above specific aromatic compound is considered as follows.

By preparing a negative electrode with a compound capable of deintercalating lithium such as a carbon material, the reactivity of the electrolytic solution and the negative electrode at high temperature is suppressed more than in the case of using lithium, but the charge of the negative electrode is reduced. The increase in the dischargeable capacity increases the reactivity with the electrolytic solution, the amount of heat generated when the battery generates heat and the reaction between the negative electrode and the electrolytic solution increases, and the temperature easily rises. However, when the aromatic compound is added to the electrolytic solution, the aromatic compound is adsorbed on the surface of the negative electrode and suppresses the direct contact between the surface of the negative electrode and the chain ester. It is believed that the reactivity is reduced and the temperature rise is limited. And
It was also found that the aromatic compound having a specific alkyl group is more effective. The details will be clarified in Examples described later.

The chain ester used as the main solvent of the electrolytic solution is, for example, an organic solvent having a chain COO-bond such as dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate and methyl propionate.
The main solvent means that the chain ester exceeds 50% by volume in the total electrolyte solvent containing these chain esters. If the chain ester exceeds 65% by volume, the safety of the battery in the nail penetration test tends to decrease, and the effect of adding the nonionic aromatic compound having a specific alkyl group increases. When the chain ester exceeds 70% by volume, the effect of adding the nonionic aromatic compound having a specific alkyl group is further increased, and the chain ester is 75%.
When it exceeds the volume%, the effect of adding the nonionic aromatic compound having an alkyl group is further increased. Further, when the chain ester has a methyl group, the safety of the battery is likely to be lowered, so that the effect of adding the nonionic aromatic compound having a specific alkyl group becomes more remarkable.

When the above chain ester is mixed with the following ester having a high dielectric constant (dielectric constant of 30 or more),
Since the cycle characteristics and the load characteristics of the battery are improved as compared with the case where only the chain ester is used, it is more desirable as a battery. Examples of such an ester having a high dielectric constant include propylene carbonate (PC), ethylene carbonate (EC), butylene carbonate (BC), gamma-butyrolactone (γ-BL), ethylene glycol sulfite (EGS), and the like. , Those having a cyclic structure are particularly preferable, and cyclic carbonates are particularly preferable, ethylene carbonate (EC)
Is most preferred.

The ester having a high dielectric constant is preferably less than 40% by volume in the total solvent of the electrolytic solution, more preferably 30% by volume.
It is at most volume%, more preferably at most 25 volume%.
The improvement in safety due to the ester having a high dielectric constant becomes remarkable when the ester having a high dielectric constant becomes 10% by volume or more in all the solvents of the electrolytic solution, and becomes more remarkable when it reaches 20% by volume. .

Examples of the solvent that can be used in combination with the chain ester other than the above-mentioned ester having a high dielectric constant include 1,2-dimethoxyethane (DME) and 1,3-dioxolane (D).
O), tetrahydrofuran (THF), 2-methyl-tetrahydrofuran (2Me-THF), diethyl ether (DEE) and the like. In addition, an amine imide-based organic solvent, a sulfur-containing or fluorine-containing organic solvent, or the like can be used.

The electrolyte of the electrolytic solution is, for example, LiC.
10_Four, LiPF₆, LiBF_Four, LiAsF₆, Li
SbF₆, LiCF₃SO₃, LiC_FourF₉SO₃, L
iCF₃CO₂, Li₂C₂F_Four(SO₃)₂, LiN
(CF₃SO₂)₂, LiC (CF₃SO₂)₃, Li
C_nF_{2n + 1}SO₃(N ≧ 2), LiN (Rf₃OS
O ₂)₂[Where Rf is a fluoroalkyl group]
Used alone or as a mixture of two or more, especially LiP
F₆And LiC_FourF₉SO₃Have good charge and discharge characteristics.
And desirable. The concentration of the electrolyte in the electrolyte is
The concentration is not limited to 1 mol / l or more
If it is set to 1, the safety is improved.
/ L or more is more desirable. In addition, the
Good electricity when the concentration of denaturation is 1.7 mol / l or less
It is desirable because the characteristics are maintained.
More preferably there is.

Examples of the positive electrode active material include LiCoO 2.
Lithium cobalt oxides such as _2, lithium manganese oxide such as LiMn ₂ O _4, lithium nickel oxides such as LiNiO ₂ is used.

For the positive electrode, for example, a mixture obtained by appropriately adding a conductive auxiliary agent, a binder such as polyvinylidene fluoride, or the like to the positive electrode active material is formed into a molded body using a current collecting material such as aluminum foil as a core material. The finished one is used.

In particular, LiNiO ₂ , LiCoO ₂ , LiM
When a lithium composite oxide having an open circuit voltage at the time of charging of 4 V or more based on Li such as n ₂ O ₄ is used as the positive electrode active material, high energy density can be obtained, which is desirable. Particularly, charged LiCoO ₂ and LiNiO ₂ have a reaction initiation temperature with an electrolytic solution lower than that of LiMn ₂ O ₄ , and are likely to reach the thermal runaway temperature of the positive electrode due to heat generation of the negative electrode, so that the effect of the present invention is more significantly exerted. .

Any material can be used for the negative electrode as long as it can be doped with lithium ions and dedoped, and examples thereof include graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, and mesomorphic compounds. Carbon material such as carbon micro beads, carbon fiber, activated carbon or S
An alloy of i, Sn, In, or the like and lithium, or an oxide of Si, Sn, In, or the like that can be charged and discharged at a low potential close to Li can be used.

When a carbon material is used for the negative electrode, the carbon material preferably has the following characteristics. That is, the interlayer distance d ₀₀₂ of the (002) plane is preferably 3.5 Å or less, more preferably 3.45 Å or less, and further preferably 3.4 Å or less. Further, the crystallite size Lc in the c-axis direction is preferably 30 Å or more, more preferably 80 Å or more, and further preferably 250 Å or more. And the average particle size is 8 to 15 μm, especially 10 to 10.
13 μm is desirable, and purity is desirably 99.9% or higher.

[0031]

EXAMPLES Next, the present invention will be described in more detail with reference to examples. However, the present invention is not limited to only those examples.

Example 1 Methyl ethyl carbonate and ethylene carbonate were mixed at a volume ratio of 76:24, and tri-2-ethylhexyl trimellitate [(C ₆ H ₃ (COOC ₈ H ₁₇ ) ₃ , below, "TOT
Abbreviated as “M”) and mixed to dissolve LiPF ₆ in 1.4 mol / l to obtain a composition of 1.4 mol / l.
LiPF ₆ / EC: MEC (24:76 volume ratio) +1
An electrolytic solution represented by% TOTM was prepared.

EC in the above electrolytic solution is an abbreviation for ethylene carbonate, and MEC is an abbreviation for methyl ethyl carbonate. Therefore, 1.4mo indicating the above electrolyte solution
l / l LiPF ₆ / EC: MEC (24:76 volume ratio) + 1% TOTM is methyl ethyl carbonate 76
It shows that 1.4 mol / l of LiPF ₆ was dissolved in a mixed solvent of vol% and 24% by volume of ethylene carbonate, and 1 part by volume of TOTM was dissolved in 100 parts by volume of the mixed solvent. .

Separately, LiC as a positive electrode active material is used.
Phosphorous graphite was added to oO ₂ as a conductive additive at a weight ratio of 100: 7.
And mixed with each other, and this mixture was mixed with a solution of polyvinylidene fluoride dissolved in N-methylpyrrolidone to form a slurry. The positive electrode mixture slurry was passed through a 70-mesh net to remove large ones, and then a thickness of 20
A positive electrode current collector made of an aluminum foil having a thickness of μm was evenly applied on both sides and dried, then compression molded by a roller press machine, cut, and then a lead body was welded to produce a strip-shaped positive electrode.

Next, a graphite-based carbon material (provided that the interlayer distance d ₀₀₂ = 3.37Å, the crystallite size in the c-axis direction Lc =
90 parts by weight of a graphite-based carbon material having characteristics of 950Å, average particle size of 10 μm, and purity of 99.9%) was mixed with a solution of 10 parts by weight of vinylidene fluoride dissolved in N-methylpyrrolidone to form a slurry. This negative electrode mixture slurry was passed through a 70-mesh net to remove large ones, and then uniformly coated on both sides of a negative electrode current collector made of a strip-shaped copper foil having a thickness of 10 μm and dried, and then a roller was used. After compression molding with a press and cutting, a lead body was welded to produce a strip-shaped negative electrode.

The band-shaped positive electrode was superposed on the band-shaped negative electrode via a microporous polyethylene film having a thickness of 25 μm and wound spirally to form a spiral electrode body, and then a cylindrical battery case with a bottom having an outer diameter of 18 mm. Then, the lead bodies of the positive electrode and the negative electrode were welded. Here, the positive electrode of the active material-containing mixture per unit volume of the positive electrode and the negative electrode facing each other /
The negative electrode weight ratio was 2.06. The charge and discharge capacity of the negative electrode is
Normal charging conditions for this battery (charged at 1400 mA, 4.
After reaching 1V, perform the operation of charging with a constant voltage of 4.1V.
It was 85 mAh / cm ³ for 30 minutes).

Next, the electrolytic solution is injected into the battery case, and after the electrolytic solution has sufficiently penetrated into the separator or the like, the electrolytic solution is sealed, precharged and aged, and the tubular organic electrolytic solution having the structure shown in FIG. A secondary battery was produced.

The battery shown in FIG. 1 will be briefly described. 1 is the positive electrode and 2 is the negative electrode. However, in FIG. 1, in order to avoid complication, the current collector and the like used in the production of the positive electrode 1 and the negative electrode 2 are not shown, and the positive electrode 1 and the negative electrode 2 are spirally formed with the separator 3 interposed therebetween. It is wound and used as a spiral electrode body together with the electrolytic solution.
It is housed in a battery case 4 made of stainless steel.

As described above, the above electrolytic solution contains TOTM (that is, tri-2-ethylhexyl trimellitate), the battery case 4 also serves as a negative electrode terminal, and the insulator 5 is provided on the bottom thereof. And the insulator 6 is also arranged on the spiral electrode body. Then, a sealing body 8 is arranged in the opening of the battery case 4 via an annular insulating packing 7, and the inside of the battery is sealed by tightening the opening end of the battery case 4 inward. However, the sealing body 8 incorporates a reversible vent mechanism for preventing the gas generated inside the battery from exploding to the outside of the battery when it rises to a certain constant pressure and preventing the battery from bursting under high pressure. Has been.

Example 2 Instead of TOTM, dibutyl phthalate [C ₆ H ₄ (CO
A cylindrical organic electrolyte secondary battery was produced in the same manner as in Example 1 except that OC ₄ H ₉ ) ₂ ] was used.

[0041]

Comparative Example 1 A cylindrical organic electrolyte secondary battery was prepared in the same manner as in Example 1 except that the electrolyte solution did not contain a nonionic aromatic compound having an alkyl group.

Comparative Example 2 A cylindrical organic electrolyte secondary battery was prepared in the same manner as Comparative Example 1 except that the volume ratio of ethylene carbonate (EC) to methyl ethyl carbonate (MEC) was 1: 2. It was made.

Comparative Example 3 A cylindrical organic electrolyte secondary battery was prepared in the same manner as in Comparative Example 1 except that the volume ratio of ethylene carbonate (EC) to methyl ethyl carbonate (MEC) was 1: 1. It was made.

Comparative Example 4 An electrode having a positive electrode / negative electrode weight ratio of the active material-containing mixture per unit volume of the positive electrode / negative electrode of the positive electrode and the negative electrode at the time of production of the electrode was 1.95 was produced. Total thickness,
A cylindrical organic electrolyte secondary battery was produced in the same manner as in Comparative Example 3 except that the spirally wound electrode body had the same winding diameter and the negative electrode had a charge / discharge capacity of 1300 mAh. The chargeable / dischargeable capacity of the negative electrode was 79 mAh / cm ³ .

Comparative Example 5 A cylindrical organic electrolyte secondary battery was prepared in the same manner as in Example 1 except that toluene was used instead of TOTM. Comparative Example 6 Instead of TOTM, dimethyl phthalate [C ₆ H ₄ (CO
OCH ₃ ) ₂ ] was used in the same manner as in Example 1.
A cylindrical organic electrolyte secondary battery was produced.

The batteries of Examples 1 and 2 and Comparative Examples 1 to 6 were discharged at 1400 mA to 2.75 V and then discharged to 140 V.
After being charged at 0 mA and reaching 4.18 V, charging was performed for 2 hours and 30 minutes under the condition that the constant voltage of 4.18 V was maintained. After that, the battery was placed in a constant temperature bath at 40 ° C., taken out after 2 hours, placed on a battery holder with a wooden groove, and a stainless steel nail with a shaft diameter of 3 mm was placed perpendicular to the center of the side surface of the battery. Immediately, the battery was pierced to a depth of 1/2 of the outer diameter of the battery and examined for abnormal heat generation. The results are shown in Table 1.

In this test, Examples 1 and 2 and Comparative Examples 1 to 6 were used.
For each battery, 20 batteries are used, and in Table 1, the number of batteries used in the test is shown in the denominator, and the number of batteries with abnormal heat generation is shown in the numerator to show the ratio of abnormal heat generation. 1 at 40 ℃ above
/ 2 nail penetration test is Ru test Der at very severe conditions as a test to confirm the safety.

[0049]

[Table 1]

As shown in Table 1, in Examples 1 and 2 , the chain ester was more than 50% by volume and constituted the main solvent of the electrolytic solution, but the nonionic aromatic compound was not contained. Oyo Comparative example 5 containing the nonionic aromatic compound having directly bonded to a methyl group in Comparative example 1 and the benzene rings
And the number of carbon atoms bonded to the benzene ring via the COO group
Contains a nonionic aromatic compound with one methyl group
As compared with the comparative example 6 obtained by abnormal ratio of heat generation is small, charcoal bound to the benzene ring via a COO group in the electrolyte
It can be seen that the safety in the nail penetration test is improved by including the nonionic aromatic compound having an alkyl group having a prime number of 4 or more . Further, as in Comparative Examples 2 to 3, when the amount of chain ester such as methyl ethyl carbonate is small, or when the chain ester has only an ethyl group, the safety is good, and the nonionic aromatic compound having an alkyl group is good. The effect of addition of is likely to decrease. Further, it can be seen that even when the charge and discharge capacity of the negative electrode is small as in Comparative Example 4, the safety is improved and the effect of adding the nonionic aromatic compound having an alkyl group is reduced.

[0051]

As described above, according to the present invention, a positive electrode having at least one selected from the group consisting of lithium cobalt oxide, lithium nickel oxide and lithium manganese oxide as an active material, and a lithium ion-doped electrode.
In an organic electrolytic solution secondary battery having a negative electrode on which a film is formed by reacting a part of a material that can be dedoped with an electrolytic solution and an electrolytic solution containing a chain ester as a main solvent, COO is added to the electrolytic solution. The stability of the battery could be improved by incorporating a nonionic aromatic compound having an alkyl group having 4 or more carbon atoms, which is bonded to the benzene ring via a group. In particular, when the chargeable / dischargeable capacity of the negative electrode exceeds 85 mAh / cm ³ per unit volume of the battery, the effect of improving safety is great.

[Brief description of drawings]

FIG. 1 is a partial cross-sectional perspective view schematically showing an example of an organic electrolyte secondary battery according to the present invention.

[Explanation of symbols]

1 positive electrode 2 Negative electrode 3 separator

─────────────────────────────────────────────────── ─── Continuation of front page (56) Reference JP-A-5-36439 (JP, A) (58) Fields investigated (Int.Cl. ⁷ , DB name) H01M 10/40 H01M 2/12 CA (STN )

Claims (5)

(57) [Claims] 1. A lithium cobalt oxide, at least one positive electrode of the active material selected from the group consisting of lithium nickel oxide and lithium manganese oxide, lithium
It is an organic electrolyte secondary battery that has a negative electrode on which a film is formed by reacting part of it with a material that can dope and de-dope the ions, and an organic electrolyte whose main solvent is a chain ester. And the above-mentioned organic electrolytic solution contains a nonionic aromatic compound having an alkyl group having 4 or more carbon atoms, which is bonded to a benzene ring through a COO group. Secondary battery. 2. The organic electrolyte secondary battery according to claim 1, wherein the alkyl group has 5 or more carbon atoms. 3. The content of the nonionic aromatic compound in the organic electrolytic solution is 10 per 100 parts by volume of the electrolytic solution solvent.
The organic electrolyte secondary battery according to claim 1 or 2, wherein the capacity is less than or equal to the capacity part. 4. A chain ester having a methyl group is used as a solvent for the organic electrolyte solution.
4. The organic electrolyte secondary battery according to any one of 3 to 3. 5. The organic electrolyte secondary battery according to any one of claims 1 to 4, wherein a vent mechanism for discharging gas generated inside the battery to the outside of the battery is incorporated.