JP2003317800A - Manufacturing method of nonaqueous electrolyte battery and nonaqueous electrolyte battery provided by method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a manufacturing method of a nonaqueous electrolyte battery suppressing a negative effect of an additive, and thereby provide a manufacturing method of a nonaqueous electrolyte battery with a superior discharge characteristic and service life characteristics and little gas generation at a high temperature. <P>SOLUTION: The nonaqueous electrolyte battery includes, as components, at least a negative electrode using either one or a mixture of lithium metal, lithium alloy and a material capable of storing and releasing lithium as a negative electrode active material, a positive electrode, and a nonaqueous electrolytic solution comprising a nonaqueous solvent and an electrolyte. The manufacturing method of the nonaqueous electrolyte battery is characterized in that it has a process of manufacturing the nonaqueous electrolyte battery by using a first nonaqueous solution comprising at least electrolytic lithium salt and a nonaqueous solvent containing a compound having a carbon and carbon multiple bond, a process of carrying out one or more charge and discharge operations to the battery, and a process of adding a second nonaqueous solution containing an additive not contained in the first nonaqueous solution after the charge and discharge operations. <P>COPYRIGHT: (C)2004,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery which is excellent in discharge characteristics and life characteristics and generates little gas at high temperatures,
The present invention relates to a non-aqueous electrolyte secondary battery having excellent discharge characteristics and life characteristics and excellent safety, and a method for manufacturing the same.

[0002]

BACKGROUND OF THE INVENTION Batteries using non-aqueous electrolytes are widely used as power sources for consumer electronic devices because they have high voltage and high energy density and high reliability such as storability. Has been.

As such a battery, there is a non-aqueous electrolyte secondary battery, and a lithium battery and a lithium ion secondary battery can be mentioned. This battery is composed of a lithium metal or a negative electrode made of an active material capable of inserting and extracting lithium, a transition metal oxide, fluorinated graphite, a positive electrode made of a composite oxide of lithium and a transition metal, an electrolytic solution, and the like. There is.

A carbon material capable of inserting and extracting lithium is often used as a negative electrode active material of a lithium ion secondary battery. In particular, highly crystalline carbon such as graphite has the characteristics that the discharge potential is flat, the true density is high, and the filling property is good, and most negative electrodes of lithium ion secondary batteries currently on the market It is used as an active material.

The electrolyte solution of the lithium ion secondary battery includes an aprotic organic solvent, LiBF ₄ , LiPF ₆ , and LiClO.
₄ , LiAsF ₆ , LiCF ₃ SO ₃ , Li ₂ SiF ₆ , LiN
A non-aqueous solution in which a lithium salt of an electrolyte such as (SO ₂ CF ₃ ) ₂ or LiN (SO ₂ CF ₂ CF ₃ ) ₂ is mixed is used (Jean-Paul Gabano, "Lithium Battery", ACADEMIC).
PRESS (1983)). Carbonates are known as typical aprotic organic solvents, and the use of various carbonate compounds such as ethylene carbonate, propylene carbonate, and dimethyl carbonate has been proposed (JP-A-4-184872, JP-A-10-1872-). 2762
No. 5). In addition, a large number of sulfur-based solvents have been proposed as aprotic solvents that can be used. For example, cyclic sulfone (JP-A-57-187878, JP-A-6-67)
1-16478), chain sulfone (JP-A-3-15)
2879, JP-A-8-241732), sulfoxides (JP-A-57-141878, JP-A-61-1).
6478) and sultones (Japanese Patent Laid-Open No. 63-10217).
3), sulfites (JP-A-61-64080)
And the like. Further, use of esters (JP-A-4-14769, JP-A-4-284374), aromatic compounds (JP-A-4-249870), and the like have also been proposed.

Although the basic constitution of the electrolytic solution of the lithium ion secondary battery is as described above, it has been proposed to add a small amount of compound in order to improve the characteristics of the battery (hereinafter referred to as the electrolytic solution). Compounds added in small amounts to improve properties are called additives.)

For example, it is known that the reductive decomposition reaction of a small amount of electrolytic solution continues on the surface of the negative electrode (J. El.
ectrochem.Soc., 147 (10) 3628-3632 (2000), J. Electroch
em.Soc., 146 (11) 4014-4018 (1999), J. Power Sources, 81
-82 (1999) 8-12), which may cause problems such as a decrease in battery capacity, an increase in battery internal resistance, and a change in battery appearance due to gas generated by decomposition of the electrolyte. is assumed. As a method for preventing these problems, vinylene carbonate (Japanese Patent Application Laid-Open No. 5-13088, Japanese Patent Application Laid-Open No. 6-
No. 52887, JP-A-7-122296, JP-A-9-347778, Abstract No.286 of 10th International Conference on Lithium Battery, JP-A-11-339851) and addition of ethylene sulfate (J. Electrochem). .Soc., 146
(2) 470-472 (1999), 10th International Conference on Lithium Batteries No.289, JP-A-11-73990) and SO ₃ (JE
lectrochem.Soc., 143, L195 (1996)), sultone (Jour
nalof Power Sources, 43-44 (1993) 65-74, JP-A-11-
162511, JP-A-11-339850, JP2000-3724, JP2000-3725,
JP-A-2000-123868, JP-A-2000-77
098, Japanese Patent Application No. 2001-151863, sulfonic acid esters (JP-A-9-245834, JP-A-1).
Nos. 0-189041 and JP-A-2000-133304) have been proposed to improve the storage characteristics and cycle characteristics of batteries.

Further, as an attempt to make the electrolyte flame-retardant to make the battery safe, an attempt to add a phosphoric acid ester to the electrolyte solution has been disclosed (JP-A-8-22839).

As described above, various additives have been proposed,
Has achieved certain results in improving battery characteristics. However,
Additives often do not have any negative effect and can improve the battery characteristics, and depending on the characteristic items, the characteristics of the battery may be deteriorated. For example, according to the study by the present inventors, the addition of boric acid esters can suppress gas generation during high temperature storage, but electrolysis of the electrolytic solution at the negative electrode is likely to occur, which may reduce the capacity of the battery. . In addition, if too much 1,3-propene sultone or phosphoric acid ester is added, the resistance of the negative electrode may increase and the load characteristics of the battery may deteriorate.

From the above, an additive satisfying all aspects has not yet been obtained, and it is important at the same time to improve the battery characteristics by the additive so that the negative effect of the additive is less likely to appear.

[0011]

SUMMARY OF THE INVENTION In view of the above problems when using an additive, an object of the present invention is to provide a method for producing a non-aqueous electrolyte secondary battery in which the negative effect of the additive is less likely to appear. To provide. More specifically, it makes it difficult for the negative effects of borate esters, 1,3-propene sultones, and phosphoric acid esters to appear,
To provide a non-aqueous electrolyte secondary battery which has excellent discharge characteristics and life characteristics and generates less gas at high temperatures, and a method of manufacturing a non-aqueous electrolyte secondary battery which has excellent discharge characteristics and life characteristics and excellent safety. It is in.

[0012]

Means for Solving the Problems The inventors of the present invention have conducted extensive studies to solve the above problems and found that a first non-aqueous solution prepared by adding a compound having a carbon-carbon multiple bond to an electrolytic solution was used. A battery is produced by performing the charging / discharging operation of the battery at least once or more, and thereafter, an additive not included in the first non-aqueous solution (hereinafter, sometimes referred to as a second additive) is contained. It has been found that when the battery is manufactured by the method of adding the second non-aqueous solution, the negative effect of the second additive on the battery characteristics is hardly exhibited. As a result, for example, a non-aqueous electrolyte secondary battery containing a borate ester and 1,3-propene sultones, which generates less gas at high temperature and has excellent discharge characteristics and life characteristics, and a phosphoric acid ester are contained. Therefore, they have found that a non-aqueous electrolyte secondary battery having excellent safety and excellent discharge characteristics and life characteristics can be obtained, and the present invention has been completed.

That is, the present invention includes the following aspects. (1) A negative electrode using any one of a lithium metal, a lithium alloy, a material capable of inserting and extracting lithium, or a mixture thereof as a negative electrode active material, a positive electrode, and a non-aqueous electrolytic solution containing a non-aqueous solvent and an electrolyte. In the production of a non-aqueous electrolyte secondary battery containing at least a constituent element, a non-aqueous solution containing at least a lithium salt of an electrolyte and a non-aqueous solvent containing a compound having a carbon-carbon multiple bond is used. A step of producing an electrolyte secondary battery, a step of performing a charge / discharge operation on the battery once or more, and a second non-aqueous solution containing an additive that is not included in the first non-aqueous solution after the charge / discharge operation. And a step of adding the non-aqueous electrolyte secondary battery.

(2) The second non-aqueous electrolyte solution according to the above (1), wherein the second non-aqueous solution contains at least borate ester as an additive not included in the first non-aqueous solution. Next battery manufacturing method.

(3) The non-aqueous solution according to (1) above, wherein the second non-aqueous solution contains at least 1,3-propene sultone as an additive not contained in the first non-aqueous solution. Method for manufacturing electrolyte secondary battery.

(4) The second non-aqueous electrolyte solution according to (3) above, wherein the second non-aqueous solution contains at least phosphoric acid ester as an additive that is not included in the first non-aqueous solution. Next battery manufacturing method.

(5) The non-aqueous electrolyte secondary battery according to any one of (1) to (4) above, wherein the compound having carbon-carbon multiple bonds is vinylene carbonate and / or its derivative. Production method.

(6) The non-aqueous electrolyte secondary battery according to any one of (1) to (5) above, wherein the negative electrode active material is a carbon material capable of being doped / dedoped with lithium ions. Production method.

(7) A non-aqueous electrolyte secondary battery manufactured by the method according to any one of (1) to (6) above.

[0020]

DETAILED DESCRIPTION OF THE INVENTION Next, the method for producing a non-aqueous electrolyte secondary battery according to the present invention and the non-aqueous electrolyte secondary battery obtained therefrom will be specifically described.

The method for producing a non-aqueous electrolyte secondary battery according to the present invention uses a first non-aqueous solution comprising at least a lithium salt of an electrolyte and a non-aqueous solvent containing a compound having a carbon-carbon multiple bond. First to make non-aqueous electrolyte secondary battery
And the second step in which the battery is charged and discharged at least once.
And a third step of adding a second non-aqueous solution containing an additive that is not included in the first non-aqueous solution after the charge / discharge operation.

By the first and second steps, a non-conductive film having excellent ionic conductivity and sufficiently suppressing reductive decomposition of the electrolytic solution is formed on the negative electrode, and the subsequent deterioration of battery characteristics is significantly suppressed. Thus, even if a new non-aqueous solution containing the second additive is added in the third step, the deterioration of the battery characteristics due to the second additive is significantly suppressed.

[First Step] In this step, any one of lithium metal, a lithium alloy, a material capable of inserting and extracting lithium, or a mixture thereof is used as an anode active material, an anode, a cathode, and a nonaqueous solvent. A non-aqueous electrolyte secondary battery containing at least a non-aqueous electrolyte containing an electrolyte as a constituent element is manufactured. In the present invention, the non-aqueous electrolyte used in this step is called the first non-aqueous solution.

First, the first non-aqueous solution will be described. The basic composition of the first non-aqueous solution used here is the same as the composition of the non-aqueous electrolytic solution usually used for a lithium battery or a lithium ion battery, and consists of a non-aqueous solvent and a lithium salt of an electrolyte. A compound having a carbon-carbon multiple bond is contained in a non-aqueous solvent.

Examples of the compound having carbon-carbon multiple bonds include vinylene carbonate and its derivatives, vinylethylene carbonate, divinylethylene carbonate,
Ethylene carbonate derivatives having carbon-carbon multiple bonds such as acryloxymethylethylene carbonate, and carboxylic acids having carbon-carbon multiple bonds such as maleic anhydride, norbornene dicarboxylic acid anhydride, ethynyl phthalic anhydride, and vinyl phthalic anhydride. Anhydrides are exemplified. Of these compounds, vinylene carbonate and its derivatives are most desirable. Specific examples of the vinylene carbonate derivative include methylvinylene carbonate, ethylvinylene carbonate, propylethylene carbonate, dimethylvinylene carbonate, diethylvinylene carbonate and dipropylvinylene carbonate. These compounds having carbon-carbon multiple bonds may be used alone or in combination. Of these, vinylene carbonate is the most desirable.

The addition amount of the compound having carbon-carbon multiple bond is 0.1 to 10% by weight based on the total amount of the non-aqueous electrolyte solution after the production of the secondary battery for the product which has completed the second and third steps described later.
Is desirable, and further 0.2 to 5% by weight is desirable,
0.5 to 3% by weight is the most desirable.

The non-aqueous solvent is preferably a cyclic aprotic solvent and / or a chain aprotic solvent.
As the cyclic aprotic solvent, a cyclic carbonate such as ethylene carbonate, a cyclic ester such as γ-butyrolactone, a cyclic sulfone such as sulfolane,
Cyclic ethers such as dioxolane are exemplified, and chain aprotic solvents include chain carbonates such as dimethyl carbonate, chain carboxylic acid esters such as methyl propionate, and chain ethers such as dimethoxyethane. It is illustrated.

When the load characteristics and low temperature characteristics of the battery are intended to be improved, it is desirable that the non-aqueous solvent is a combination of a cyclic aprotic solvent and a chain aprotic solvent. Further, in view of the electrochemical stability of the electrolytic solution, it is most desirable to apply the cyclic carbonate to the cyclic aprotic solvent and the chain carbonate to the chain aprotic solvent.

Specific examples of the cyclic carbonate include ethylene carbonate, propylene carbonate and 1,2-
Examples thereof include butylene carbonate, 2,3-butylene carbonate, 1,2-pentylene carbonate, and 2,3-pentylene carbonate. In particular, ethylene carbonate and propylene carbonate having a high dielectric constant are desirable. In the case of a battery using graphite as the negative electrode active material, it is particularly preferable to contain ethylene carbonate. Moreover, you may use these cyclic carbonates in mixture of 2 or more types.

Specific examples of the chain carbonate include dimethyl carbonate, methyl ethyl carbonate, diethyl carbonate, methyl propyl carbonate, methyl isopropyl carbonate, dipropyl carbonate,
Methyl butyl carbonate, dibutyl carbonate, ethyl propyl carbonate, methyl trifluoroethyl carbonate, etc. are mentioned. Particularly, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, which have low viscosity, are desirable. You may use these chain carbonates in mixture of 2 or more types.

Specific examples of the combination of cyclic carbonate and chain carbonate include ethylene carbonate and dimethyl carbonate, ethylene carbonate and methyl ethyl carbonate, ethylene carbonate and diethyl carbonate, propylene carbonate and dimethyl carbonate, propylene carbonate and methyl ethyl carbonate, propylene. Carbonate and diethyl carbonate,
Ethylene carbonate and propylene carbonate and dimethyl carbonate, ethylene carbonate and propylene carbonate and methyl ethyl carbonate, ethylene carbonate and propylene carbonate and diethyl carbonate, ethylene carbonate and dimethyl carbonate and methyl ethyl carbonate, ethylene carbonate and dimethyl carbonate and diethyl carbonate, and ethylene carbonate. Methyl ethyl carbonate and diethyl carbonate, ethylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate and methyl ethyl carbonate,
Examples thereof include ethylene carbonate, propylene carbonate, dimethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, methyl ethyl carbonate and diethyl carbonate, ethylene carbonate, propylene carbonate, dimethyl carbonate, methyl ethyl carbonate and diethyl carbonate.

A preferable mixing ratio of the cyclic carbonate and the chain carbonate is expressed in a weight ratio in the non-aqueous electrolytic solution after the product secondary battery is manufactured, and the cyclic carbonate: chain carbonate is 5:95 to 80:20. More preferably, it is 10:90 to 70:30, and particularly preferably 15:85.
It is 55:45. With such a ratio, the increase in the viscosity of the electrolytic solution can be suppressed, and the dissociation degree of the electrolyte can be increased, so that the conductivity of the electrolytic solution related to the charge / discharge characteristics of the battery can be increased, and The solubility of can be further increased. Therefore, the electrolytic solution having excellent electrical conductivity at room temperature or low temperature can be obtained, and thus the load characteristics of the battery at room temperature to low temperature can be improved.

In order to improve the flash point of the solvent in order to improve the safety of the battery, a cyclic aprotic solvent may be used alone as the non-aqueous solvent, or a chain aprotic solvent may be used. It is desirable to limit the mixing amount of the organic solvent to less than 20% by weight with respect to the total amount of the non-aqueous solvent after the product secondary battery is manufactured.

As the cyclic aprotic solvent in this case, it is particularly preferable to mix one kind selected from ethylene carbonate, propylene carbonate, sulfolane, γ-butyrolactone, methyl oxazolinone or a mixture thereof. As a specific combination of solvents, ethylene carbonate and propylene carbonate,
Examples include ethylene carbonate and sulfolane, ethylene carbonate and γ-butyrolactone, ethylene carbonate and propylene carbonate and γ-butyrolactone, and the like.

The amount of the chain-like aprotic solvent mixed was 20% by weight based on the total weight of the non-aqueous solvent after the secondary battery was manufactured.
When mixed below, as a chain aprotic solvent,
Chain carbonate, chain carboxylic acid ester is desirable, especially dimethyl carbonate, diethyl carbonate, dipropyl carbonate, dibutyl carbonate,
Diheptyl carbonate, methyl ethyl carbonate,
Chain carbonates such as methyl propyl carbonate, methyl butyl carbonate, methyl heptyl carbonate and methyl octyl carbonate are preferred.

As the lithium salt of the electrolyte, LiPF₆,
LiBF_Four, LiClO_Four, LiAsF₆, Li₂SiF₆, LiO
SO₂C_kF_{(2k + 1)} (K = 1 to 8), LiN (SO
₂C _kF_{(2k + 1)})₂ (K = 1 integer of 8), LiPF
_n(C_kF_{(2k + 1)})_(6-n) (N = 1-5, k = 1-8
Number) and lithium salts. Also, the following general formula
A lithium salt represented by can also be used. LiC
(SO₂R⁷) (SO₂R⁸) (SO₂R⁹), LiN (SO₂
OR^Ten) (SO₂OR¹¹), LiN (SO₂R¹²) (SO₂
OR¹³) (Where R⁷~ R¹³Are identical to each other
May be different, and may be a perfluoroalkyl group having 1 to 8 carbon atoms.
Rukiru group). These lithium salts used alone
Alternatively, two or more kinds may be mixed and used.

Of these, LiPF ₆ , LiBF ₄ , Li
OSO ₂ C _k F _{(2k + 1)} (k = 1 to an integer of 8), LiCl
O ₄ , LiAsF ₆ , LiN (SO ₂ C _k F _{(2k + 1)} ) ₂ (k =
1-8), LiPF _n (C _k F _{(2k + 1)} ) _(6-n) (n
= 1 to 5 and k = 1 to 8) are preferable, and LiPF ₆ , LiBF _4, and LiN (SO ₂ C _k F _{(2k + 1)} ) ₂ (k = 1 to 8)
Is the most desirable.

The lithium salt of such an electrolyte is 0.1
It is desirable to be contained in the non-aqueous electrolyte after the production of the product secondary battery at a concentration of ˜3 mol / liter, preferably 0.5˜2 mol / liter.

Next, the structure of the non-aqueous electrolyte secondary battery will be described. The non-aqueous electrolyte secondary battery is composed of a negative electrode using a lithium metal, a lithium alloy, a material capable of inserting and extracting lithium or a mixture thereof as a negative electrode active material, a positive electrode, a non-aqueous solvent and an electrolyte. It is basically configured to include a non-aqueous electrolytic solution, and usually a separator is provided between the negative electrode and the positive electrode.

In the present invention, the negative electrode has a structure in which the negative electrode active material is formed on a collector metal such as a copper foil, an expanded metal, or a mandrel. A resin adhesive such as polyvinylidene fluoride or latex for improving the adhesion of the negative electrode active material to the current collecting metal, and carbon black for improving the electron conductivity in the negative electrode may be contained. Examples of the negative electrode active material include lithium metal, lithium alloys, materials capable of occluding and releasing lithium, and examples of materials capable of occluding and releasing lithium include germanium, silicon, germanium alloy, and silicon alloy that can be alloyed with lithium. , Tin, tin alloys; tin oxide and silicon oxide capable of doping / dedoping lithium ions; transition metal oxides capable of doping / dedoping lithium ions such as LiTiO ₂ ; doping / dedoping of lithium ions possible Examples of such transition metal nitrides include carbon materials capable of doping and dedoping lithium ions. Of these, silicon that can be alloyed with lithium, silicon alloys, tin, tin alloys, germanium, germanium alloys, lead, lead alloys, and carbon materials capable of doping / dedoping lithium ions are desirable, especially lithium ions. The carbon material that can be doped / undoped is used for charging / discharging efficiency and charging / discharging capacity,
It is desirable because it is excellent in reversibility of cycle charge and discharge.

The carbon material may be a graphite material or amorphous carbon, and may have any of fibrous, spherical, potato-like and flake-like forms. Specific examples of the amorphous carbon include hard carbon, coke, mesocarbon microbeads (MCMB) fired at 1500 ° C. or lower, mesophase pitch carbon fiber (MCF), and the like. Examples of the graphite material include natural graphite and graphite. MCM
Artificial graphite such as B or MCF is used. As the graphite material, a material containing boron can be used, and a material coated with a metal such as gold, platinum, silver, copper or Sn, or a material coated with amorphous carbon can also be used. it can. As a carbon material, it was measured by X-ray analysis (00
2) A carbon material having an interplanar spacing (d ₀₀₂ ) of 0.340 nm or less is preferable, and graphite having a true density of 1.70 g / cm ³ or more or a highly crystalline carbon material having a property close to that is preferable. When such a carbon material is used, the energy density of the battery can be increased. In the present invention,
These negative electrode active materials may be used alone or in combination of two or more.

In the present invention, the positive electrode has a structure in which the positive electrode active material is formed on a collector metal such as aluminum, titanium or stainless steel foil, expanded metal or mandrel. Contains a resin adhesive such as polyvinylidene fluoride or latex to improve the adhesion of the positive electrode active material to the collector metal, and carbon black, amorphous whiskers, graphite, etc. to improve the electron conductivity in the positive electrode. May be. Examples of positive electrode active materials include FeS ₂ and Mo.
Transition metal oxides or transition metal sulfides such as S ₂ , TiS ₂ , MnO ₂ and V ₂ O ₅ , LiCoO ₂ , LiMnO ₂ and LiMn ₂
O ₄ , LiNiO ₂ , LiNi _x Co _(1-x) O ₂ , LiNi _x C
_{o y Mn (1-xy)} O 2, LiNi x Co y Al (1- xy) composite oxide comprising lithium such as O ₂ and a transition metal, polyaniline, polythiophene, polypyrrole, polyacetylene, polyacene, dimercaptothiadiazole / Conductive polymer materials such as polyaniline composites, fluorinated carbon,
Examples include carbon materials such as activated carbon. Among these, a composite oxide composed of lithium and a transition metal is particularly preferable because it is excellent in charge / discharge efficiency, charge / discharge capacity, and cycle charge / discharge reversibility. Only one type of positive electrode active material may be used,
You may use it in mixture of 2 or more types.

The separator is a partition wall that electrically insulates the positive electrode and the negative electrode and allows lithium ions to pass therethrough, and examples thereof include a porous membrane and a polymer electrolyte. A microporous polymer film is preferably used as the porous film, and examples of the material include polyolefin, polyimide, polyvinylidene fluoride, polyester and the like. In particular, a porous polyolefin film is preferable, and specific examples thereof include a porous polyethylene film, a porous polypropylene film, and a multilayer film of a porous polyethylene film and polypropylene. The porous polyolefin film may be coated with another resin having excellent thermal stability. Examples of the polymer electrolyte include a polymer in which a lithium salt is dissolved and a polymer swollen with an electrolytic solution.

The first step of the present invention is the first non-aqueous solution comprising the lithium salt of the electrolyte described above and the non-aqueous solvent containing the compound having carbon-carbon multiple bonds, the negative electrode,
The battery is assembled using the positive electrode and, if necessary, the separator. As an example, the structures of a cylindrical type battery and a coin type battery will be described, but the non-aqueous electrolyte secondary battery can be formed in other shapes such as a prismatic type, a film type and the like. However, the basic structure of the battery is the same regardless of the shape, and the negative electrode active material, the positive electrode active material and the separator constituting each battery are the same as those described above.

The cylindrical non-aqueous electrolyte secondary battery is composed of a negative electrode formed by pressure bonding a carbon material such as natural graphite with polyvinylidene fluoride as an adhesive to a negative electrode current collector such as a copper foil, and a positive electrode collector such as an Al foil. A positive electrode obtained by pressure-bonding LiCoO ₂ using an adhesive agent of polyvinylidene fluoride and carbon black as a conductive auxiliary agent is wound around a separator, and a cylindrical shape with insulating plates placed above and below the wound body. It is obtained by a process in which a lead wire pulled out from the end of the current collector is welded and attached to the battery can, and an electrolytic solution (also referred to as a first non-aqueous solution in the present invention) is injected. In the coin-type battery, a disc-shaped negative electrode, a separator, a disc-shaped positive electrode, and, if necessary, a spacer plate made of aluminum or the like are stacked in this order and housed in a coin-type battery can. (Also referred to as one non-aqueous solution).

At this time, the injection amount of the first non-aqueous solution is preferably 0.05 g to 2 g per 100 mAh of battery capacity. Since the second non-aqueous solution is re-injected in the third step, it is necessary that a space for that is left in the battery.

[Second Step] In the present invention, the second step is the first step.
The battery manufactured in the step (1) is charged and discharged at least once, and is performed for the purpose of forming a non-conductive film on the negative electrode, which has excellent lithium ion conductivity and can significantly suppress reductive decomposition of the electrolytic solution.

The charging method may be any of constant voltage method, constant current constant voltage method, pulse constant current constant voltage method and the like. The charging voltage is preferably a voltage at which the potential of the negative electrode becomes 0.4 V or less, more preferably 0.2 V or less, and more preferably 0.1 V or less, with respect to the potential of metallic lithium. The formation of the non-conductive film on the negative electrode is insufficient at a voltage of 0.5 V or higher, and the reduction reaction on the negative electrode by the second additive in the second non-aqueous solution added in the third step is suppressed. I can't. The charging current is preferably 0.01 C or more and 2 C or more, assuming that the rated value of the battery can be used for 1 hour is 1 C current. If the current is too small, the charging time will be too long to be practical, and if it is too large, the current distribution in the electrode will be non-uniform and the non-conductive film on the negative electrode may not be formed uniformly. The amount of charged electricity needs to be supplied only when the negative electrode is exposed to the above-mentioned potential for a sufficient time, and as a guideline, the potential of the negative electrode is preferably relative to the potential of metallic lithium even after charging is completed. 0.4V
It is desirable to keep the voltage below, more preferably 0.2 V or less, and even more preferably 0.1 V or less.

The amount of charge electricity to be obtained in this way cannot be unconditionally discussed because it depends on the kind of the negative electrode active material. For example, when carbon is used as the active material, 30 mAh or more, and further 100 mAh or more per 1 g of carbon, especially Two
A quantity of electricity of 00 mAh or more is desirable. If it is less than 30 mAh, the formation of the non-conductive film may be insufficient. The number of times of charging may be such that the above-mentioned operation is performed at least once, but if the battery is once discharged and then repeatedly charged and discharged, the non-conductive film of the negative electrode is sufficiently completed, which is desirable. The number of times of charge and discharge is preferably 1 to 50 times, more preferably 1 to 1 times.
0 times, especially 1 to 5 times is desirable. If the number of times is too large, it takes a long time, which is not practical for battery production.

By the above second step, the non-conductive film which suppresses the decomposition of the electrolytic solution and has excellent lithium ion conductivity is formed on the negative electrode. As shown in the first step,
The electrolytic solution used in the first step (also referred to as the first non-aqueous solution in the present invention) needs to be an electrolytic solution containing a compound containing carbon-carbon multiple bonds. When the electrolytic solution containing no carbon-carbon multiple bond is used, the non-conductive film on the negative electrode does not sufficiently suppress the reductive decomposition of the electrolytic solution on the negative electrode, and the non-aqueous solution added in the third step is used. The suppression of the reductive decomposition of the second additive of No. 2 on the negative electrode becomes insufficient.

[Third Step] In the present invention, the third step is to add a second non-aqueous solution to the battery subjected to the above-mentioned second step. This second non-aqueous solution promotes the reductive decomposition reaction of the electrolytic solution on the negative electrode and deteriorates the lithium ion conductivity on the negative electrode surface when it is contained in the electrolytic solution from the initial stage of battery preparation. It contains an additive (also referred to as a second additive) that may deteriorate some of the characteristics.
In the present invention, by the second step, since the non-conducting film excellent in lithium-ion conductivity is formed on the negative electrode by sufficiently suppressing the decomposition of the electrolytic solution, the deterioration due to the second additive is significantly increased. Suppressed.

The second non-aqueous solution contains, in addition to the second additive,
It may also contain an aprotic solvent, a lithium salt, a compound containing a carbon-carbon multiple bond, and the like. The second additive, when contained in the electrolytic solution, improves some characteristics such as cycle characteristics, storage characteristics, safety, suppression of gas generation during storage, and discharge characteristics. It is an additive that may deteriorate some properties due to the reductive decomposition of.

Specific examples of such a potential compound include boric acid esters, sulfones such as sulfolane and dimethyl sulfone, 1,3-propane sultone and 1,3.
Sultones such as 4-butane sultone, 1,3-propene sultones, phosphoric acid esters, lactones such as γ-butyrolactone, biphenyls such as biphenyl and fluorobiphenyl, fluoroethers such as methoxytrifluoroethoxyethane, and tris Examples thereof include fluorocarbons such as fluoromethylethylene carbonate and di (trifluoroethyl) carbonate.
Of these, boric acid esters, 1,3-propene sultones, and phosphoric acid esters are preferable.

Specific examples of the borate ester include trimethyl borate, triethyl borate, tripropyl borate,
Tributyl borate, trioctyl borate, trimethoxyboroxine, triethoxyboroxine, boratran, tris (trimethylene) borate, tripropargyl borate, triallyl borate, trivinyl borate, pentaerythritol borate, triborate (tri Fluoroethyl), tri (methoxyethyl) borate, polyethylene glycol borate ester, tri (trifluoroethoxyethyl) borate and the like are exemplified.

As the 1,3-propene sultones,
1,3-prop-1-ene sultone, 1,3-propan
2-entultone, 1-methyl-1,3-prop-1-
Ensultone, 1-ethyl-1,3-prop-1-ene sultone, 1-fluoro-1,3-prop-1-ene sultone, 2-methyl-1,3-prop-1-ene sultone, 2-ethyl-1, 3-prop-1-enthultone,
2-fluoro-1,3-prop-1-ene sultone, 3
-Methyl-1,3-prop-1-ene sultone, 3-ethyl-1,3-prop-1-ene sultone, 3-fluoro-1,3-prop-1-ene sultone, 1,1-dimethyl-1,3 -Prop-1-ene sultone, 1,2-dimethyl-1,3-prop-1-ene sultone, 1,3-
Dimethyl-1,3-prop-1-ene sultone, 2,3
-Dimethyl-1,3-prop-1-ene sultone, 1,
2-difluoro-1,3-prop-1-ene sultone and the like are exemplified.

Examples of the phosphoric acid ester include trimethyl phosphate, triethyl phosphate, tripropyl phosphate, tributyl phosphate, trioctyl phosphate, tris (trifluoroethyl) phosphate, methyl di (trifluoroethyl) phosphate, and phosphoric acid. Examples include dimethyl (trifluoroethyl), tri (methoxyethyl) phosphate, tri (trifluoroethoxyethyl) phosphate, and the like.

As the aprotic solvent, lithium salt, and compound containing carbon-carbon multiple bond, the same compounds as those exemplified in the first step are exemplified, and preferable examples are also the same.

The content of the second additive in the second non-aqueous solution is not particularly limited, but it is preferably liquid because it is necessary to be injected into the battery, and in the case of an additive which is solid at room temperature, it is aprotic. It needs to be dissolved in a solvent. The composition of the second non-aqueous solution excluding the second additive is the same as the composition of the first non-aqueous solution exemplified in the first step, and the aprotic solvent is a cyclic carbonate and / or a chain carbonate. Preferably, the lithium salt is LiPF ₆ , LiBF ₄ and LiN (S
O ₂ C _k F _{(2k + 1)} ) ₂ (k = 1 to 8) is preferable.
However, the second non-aqueous solution does not necessarily need to contain a lithium salt. The injection amount of the second non-aqueous solution into the battery is
It is desirable that the amount of the second additive be 0.1 to 50 parts by weight based on 100 parts by weight of the first non-aqueous solution.
When the second additive is a borate ester or 1,3-propene sultone, it is preferably 0.1 to 5 parts by weight, and more preferably 0.2 to 100 parts by weight of the first non-aqueous solution.
The injection amount is preferably about 3 parts by weight. When the second additive is a phosphoric acid ester, 10% of the first non-aqueous solution is used.
The injection amount is preferably 1 to 40 parts by weight, more preferably 5 to 20 parts by weight with respect to 0 parts by weight.

After injecting the second non-aqueous solution as described above, the battery is sealed and completed (the battery in this state is also referred to as a product secondary battery). Examples of the encapsulation method include a method of caulking the open portion, a method of welding and sealing with a laser, a method of attaching a stopper, a method of fusion bonding with a resin, and the like.

[Non-Aqueous Electrolyte Secondary Battery] The non-aqueous electrolyte secondary battery of the present invention is a battery manufactured according to the above-mentioned steps.
In the first and second steps, the second addition added to the battery in the third step is performed because the non-conductive film excellent in lithium ion conductivity is formed by sufficiently suppressing the decomposition of the electrolytic solution on the negative electrode. The deterioration of the battery characteristics caused by the reductive decomposition of the agent at the negative electrode is significantly suppressed.

For example, a battery prepared by using an electrolytic solution containing a borate ester from the beginning gives a battery with a small amount of gas generated during storage, but the borate ester causes reductive decomposition of the electrolytic solution at the negative electrode. The reaction is promoted, resulting in a battery with a large reduction in capacity during storage and cycle use. However, by producing the second additive as a borate ester by the method of the present invention, the reductive decomposition reaction at the negative electrode of the electrolytic solution is significantly suppressed, the amount of gas generated during storage is small, and It is possible to obtain a battery with a small decrease in capacity during cycle use.

A battery produced from the beginning by using an electrolytic solution containing 1,3-propene sultones has a small amount of gas generated during storage and a small decrease in capacity. -If the added amount of propene sultones is too large, the lithium ion conductivity on the negative electrode decreases,
The battery has a slightly poor load characteristic. However, by producing the second additive as a 1,3-propene sultone by the method of the present invention, the lithium ion conductivity of the non-conductive film at the negative electrode is significantly improved, and the amount of gas generated during storage is increased. It is possible to obtain a battery that has a small amount and has a very small decrease in capacity during storage or cycle use.

A battery prepared by using an electrolyte solution containing phosphoric acid ester from the beginning gives a battery excellent in safety because the electrolyte solution is flame-retarded, but the amount of phosphoric acid ester is added. When the amount is high, the lithium ion conductivity on the negative electrode is lowered, and in the case of the graphite negative electrode, the negative electrode is broken, resulting in a battery having a slightly poor load characteristic and capacity. However, by producing the second additive as a phosphoric acid ester by the method of the present invention, the lithium ion conductivity of the non-conductive film at the negative electrode is significantly improved, and the reductive decomposition reaction is significantly suppressed. Therefore, it is possible to obtain a battery in which the electrolyte is flame-retardant and safe, and the capacity of which is not significantly reduced during storage or cycle use.

[0064]

[Example] 1. Preparation of battery [Preparation of first non-aqueous solution] Ethylene carbonate (EC)
And methyl ethyl carbonate (MEC), EC: ME
C = 4: 6 (weight ratio) is mixed, then LiPF ₆ which is a lithium salt of the electrolyte is dissolved in a non-aqueous solvent to prepare a non-aqueous solution so that the electrolyte concentration becomes 1.0 mol / liter. (This is used as a blank electrolyte). Further, 1 part by weight of vinylene carbonate (VC) was added to 100 parts by weight of this non-aqueous solution to prepare a first non-aqueous solution.

[Preparation of Second Non-Aqueous Solution] Ethylene Carbonate (EC) and Methyl Ethyl Carbonate (MEC)
Are mixed in a ratio of EC: MEC = 4: 6 (weight ratio),
Next, LiPF ₆ was dissolved in a non-aqueous solvent, and the electrolyte concentration was 1.
A non-aqueous solution was prepared so as to be 0 mol / liter (this is used as a blank electrolyte solution). Next, this non-aqueous solution 100
Three kinds of second non-aqueous solutions were prepared by mixing the second additive shown in Table 1 with respect to parts by weight.

[0066]

[Table 1]

[Production of Negative Electrode] 75 parts by weight of MCMB10-28 (manufactured by Osaka Gas) and natural graphite (LF-18 manufactured by Chuetsu Graphite)
A) 19 parts by weight of polyvinylidene fluoride (PV) as a binder
6 parts by weight of DF) were mixed and dispersed in N-methylpyrrolidinone as a solvent to prepare a negative electrode mixture slurry. Next, this negative electrode mixture slurry was applied to a negative electrode current collector made of a strip-shaped copper foil having a thickness of 18 μm, dried, and then compression-molded, and this was punched into a disc shape having a diameter of 14 mm to obtain a coin-shaped negative electrode. Got This negative electrode mixture has a thickness of 90 μm and a weight of 14 m.
It was 20 mg in a circle of m.

[Production of Positive Electrode] 82 parts by weight of LiCoO ₂ (HLC-22 manufactured by Honjo FMC Energy Systems Co., Ltd.), 7 parts by weight of graphite as a conductive agent, 3 parts by weight of acetylene black and 8 parts of polyvinylidene fluoride as a binder. Parts by weight are mixed and dispersed in N-methylpyrrolidone as a solvent, and LiCo
An O ₂ mixture slurry was prepared. This LiCoO ₂ mixture slurry was applied to an aluminum foil having a thickness of 20 μm, dried, compression-molded, and punched out to a diameter of 13 mm to prepare a positive electrode. The thickness of this LiCoO ₂ mixture was 90 μm, and the weight was 40 mg in a circle having a diameter of 13 mm.

[Production of coin-type battery] First step: negative electrode having a diameter of 14 mm, positive electrode having a diameter of 13 mm, thickness: 25 μ
A separator made of a microporous polypropylene film having a diameter of 16 mm and a diameter of 16 mm was laminated in the order of a negative electrode, a separator, and a positive electrode in a 2032 size stainless steel battery can. Then, the first non-aqueous solution 0.04m on the separator
1 was injected, and an aluminum plate (thickness 1.2 mm, diameter 16 mm) and a spring were stored. Finally, by crimping the battery can lid through a polypropylene gasket, the airtightness inside the battery is maintained, and the diameter is 20 mm.
A coin type battery having a height of 3.2 mm was produced.

Second step The battery prepared in the first step was set to 0.1 mA up to 3.0V.
, And then 0.3mA to 4.2V,
The voltage value shifts from 4.2 V to constant voltage charging, and the current value at this time is 0.
Charging was terminated when the current reached 05 mA. Next, 1mA
Discharge to 3.0V. By the same method, charging / discharging between 3.0 V and 4.2 V was repeated 3 times. Finally, 4.
It was charged to 1V. The potential of the negative electrode when charged to 4.2V was about 0.1V.

Third step The battery subjected to the second step is disassembled in an argon glove box, 0.04 ml of the second non-aqueous solution is added to the separator, and then the coin-type battery is the same as in the first step. Was produced.

[Preparation of Laminated Battery] First Step Using the same electrode as the coin type battery described above, the dimension is 55 m.
A m × 90 mm negative electrode and a size of 50 mm × 80 mm positive electrode were cut out and made to face each other through a separator made of a microporous polypropylene film to form an electrode group. This electrode group was housed in a cylindrical bag made of an aluminum laminate film (manufactured by Showa Laminate) so that both the positive and negative electrode lead wires could be pulled out from one of the open parts.
The side from which the lead wire was pulled out was heat-sealed and closed. next,
After injecting and impregnating 1.5 ml of the first non-aqueous solution into the electrode group, the remaining open portion is heat-sealed to seal the electrode group in the bag,
A laminated battery was obtained.

Second step The battery produced in the first step was 4.2 at a constant current of 10 mA.
The battery was charged to V, and the battery was charged from 4.2 V to constant voltage charging, and the charging was terminated when the current value at this time reached 0.2 mA.
Next, it was discharged to 3.0 V at 10 mA. By the same method, charging / discharging from 3.0 to 4.2V was repeated twice, and finally charging to 4.2V was performed.

Third Step A part of the laminated battery subjected to the second step is unsealed, 1.5 ml of the second non-aqueous solution is added, and then the open portion is heat-sealed to close the laminated battery. Got

2. Evaluation of battery characteristics [Storage test] The battery manufactured by the method of the present invention was aged (charged to 4.1 V and then stored at 45 ° C. for 7 days), and then stored at high temperature (charged to 4.2 V and then at 85 ° C. for 3 days). Stored for days). The discharge characteristics after aging and after high temperature storage were measured with a coin cell and the discharge characteristics were investigated, and the change in the battery volume before and after high temperature storage was measured with the laminated battery to investigate the amount of gas generated during high temperature storage.

[Evaluation of Discharge Characteristics] A coin battery was charged and discharged under the conditions shown in Table 2, and after aging and storage at high temperature,
The capacity and load characteristics were evaluated.

[0077]

[Table 2] Here, the discharge capacities of the first cycle, the second cycle, and the third cycle were defined as the low load capacity, the middle load capacity, and the high load capacity of the battery, respectively. Next, the charge / discharge characteristics and the storage characteristics were compared using the following indexes.

Recovery capacity ratio after high temperature storage = 100 × low load capacity after high temperature storage / low load capacity after aging Medium load capacity ratio after aging = 100 × medium load capacity after aging ÷ low load capacity after aging Medium load capacity ratio after high temperature storage = 100 x Medium load capacity after high temperature storage / Low load capacity after aging High load capacity ratio after aging = 100 x High load capacity after aging / Low load capacity after aging High temperature storage High load capacity ratio after = 100 x high load capacity after high temperature storage / low load capacity after aging

[Evaluation of Gas Generation during High Temperature Storage] The volume of the laminated battery was measured before and after the high temperature storage test, and the difference was defined as the gas generation during high temperature storage.

[Results] The experiments described above were evaluated using the batteries prepared by the method shown in Table 3 to verify the effects of the present invention.

[Table 3]

[Comparison of Battery Characteristics in Coin Type Battery] The results are shown in Table 4.

[Table 4]

As can be seen by comparing Example 1 and Comparative Example 1, a battery prepared by a usual method from the beginning using an electrolytic solution containing VC and a second additive (Comparative Example 1).
In comparison, the battery manufactured by applying the manufacturing method of the present invention (Example 1) was found to have significantly improved battery characteristics both after aging and after high temperature storage.

The characteristics of the second non-aqueous solution are the same as those of the second non-aqueous solution.
It was found that the same battery characteristics were exhibited as compared with the batteries (Comparative Examples 2 and 3) in which the additive of No. 2 was not added, and the deterioration of the battery characteristics due to the second additive was almost eliminated.

As can be seen by comparing Example 1 and Comparative Example 4, vinylene carbonate (VC) was added to the first electrolytic solution.
It was found that the addition of the compound (1) could not suppress the deterioration due to TBB, and that it was necessary to add a compound containing a carbon-carbon multiple bond to the first non-aqueous solution.

[Comparison of Gas Generation Amount in Laminated Battery] The results are shown in Table 5.

[Table 5]

From the above results, a battery to which the production method of the present invention was applied, in which boric acid esters (TBB in this example) and 1,3-propene sultones (PES in this example) were used as the second additives. In comparison with the blank electrolytic solution or the electrolytic solution containing only VC, it was found that the generation of gas during high temperature storage was suppressed.

[Evaluation of Flame Retardancy of Electrolyte Solution] The coin-type battery after aging was disassembled, the inside was ignited, and the subsequent state was observed. The results are shown in Table 6.

[Table 6]

From the above results, trimethyl phosphate was added to the second
The battery to which the manufacturing method of the present invention is applied as the additive of is compared with the blank electrolytic solution or the electrolytic solution containing VC,
It was found that it has excellent flame retardancy and high safety.

[0089]

By applying the manufacturing method of the present invention, it is possible to obtain a non-aqueous electrolyte secondary battery having excellent battery characteristics and a small amount of gas generated during high temperature storage. Further, it is possible to obtain a non-aqueous electrolyte secondary battery having excellent battery characteristics, an electrolyte that is flame-retardant, and safety.

Continued front page    F-term (reference) 5H029 AJ02 AJ05 AJ07 AJ14 AK02                       AK03 AK04 AK05 AK08 AK16                       AK18 AL02 AL06 AL07 AL11                       AL12 AL18 AM03 AM04 AM05                       AM07 CJ08 CJ16

Claims (7)

[Claims] 1. A non-aqueous electrolytic solution comprising a negative electrode containing any one of a lithium metal, a lithium alloy, a material capable of inserting and extracting lithium, or a mixture thereof as a negative electrode active material, a positive electrode, a non-aqueous solvent and an electrolyte. In the production of a non-aqueous electrolyte secondary battery containing at least as a constituent, a first non-aqueous solution comprising at least a lithium salt of an electrolyte and a non-aqueous solvent containing a compound having a carbon-carbon multiple bond is used. A step of producing a non-aqueous electrolyte secondary battery, a step of performing a charge / discharge operation on the battery once or more, and a second non-aqueous electrolyte containing additive that is not included in the first non-aqueous solution after the charge / discharge operation. A method of manufacturing a non-aqueous electrolyte secondary battery, comprising the step of adding an aqueous solution. 2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the second non-aqueous solution contains at least borate ester as an additive that is not included in the first non-aqueous solution. Manufacturing method. 3. The non-aqueous electrolytic solution according to claim 1, wherein the second non-aqueous solution contains at least 1,3-propene sultone as an additive which is not included in the first non-aqueous solution. Manufacturing method of secondary battery. 4. The non-aqueous electrolyte secondary battery according to claim 3, wherein the second non-aqueous solution contains at least phosphoric acid ester as an additive that is not included in the first non-aqueous solution. Manufacturing method. 5. The method for producing a non-aqueous electrolyte secondary battery according to claim 1, wherein the compound having a carbon-carbon multiple bond is vinylene carbonate and / or its derivative. 6. The negative electrode active material is doped with lithium ions.
It is a carbon material which can be dedoped, The manufacturing method of the non-aqueous electrolyte secondary battery in any one of Claim 1 to 5 characterized by the above-mentioned. 7. A non-aqueous electrolyte secondary battery manufactured by the method according to claim 1.