JP2003123837A - Electrolyte and battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrolyte capable of improving stability and a battery equipped with the electrolyte. SOLUTION: A secondary battery is fabricated by housing a wound electrode structure 20 obtained by winding strip positive electrode 21 and negative electrode 22 through a separator 23 impregnated with an electrolyte, and the like in a cell can 11. An antioxidant soluble in a non-aqueous solvent, such as 4, 4'-thiobis (2-tert-butyl-5-methylphenol), is contained in the electrolyte. Since good storage stability and charging-discharging cycle characteristics are surely retained in a high-temperature environment (for example, 60 deg.C), the stability of the secondary battery is improved.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to an electrolyte and a battery provided with a positive electrode and a negative electrode together with the electrolyte.

[0002]

2. Description of the Related Art In recent years, with the progress of electronic technology, small portable electronic devices typified by a camera-integrated VTR (video tape recorder), a mobile phone, a laptop computer and the like have been developed. Therefore, a lithium ion secondary battery, which is small and lightweight and can obtain high energy density, has been attracting attention as a driving power source.

Conventionally, as an electrolyte used in a lithium-ion secondary battery, for example, from the viewpoint of relatively high conductivity and stable potential, carbonic acid ester-based non-aqueous compounds such as propylene carbonate and diethyl carbonate. A solution obtained by dissolving LiPF ₆ as an electrolyte salt in a solvent is widely used.

[0004]

However, the LiP
Although F ₆ exhibits excellent characteristics in terms of conductivity, etc., it has a problem that the storage characteristics and charge / discharge cycle characteristics of the battery deteriorate because the thermal stability is insufficient and thermal decomposition easily occurs in a high temperature environment. was there.

As the electrolyte salt, the above-mentioned LiP is used.
Other than F ₆ , for example, LiBF ₄ , LiCF ₃ SO ₃ , L
Although iClO ₄ , LiAsF _{6 and the} like have been conventionally used, these series of electrolyte salts have the following problems, for example. That is, LiBF ₄ has good thermal stability and oxidative stability, but has poor conductivity characteristics. Li
Although CF ₃ SO ₃ has good thermal stability, it is inferior in oxidative stability and conductivity, and cannot be discharged sufficiently when it is charged at a high voltage of about 4 V or higher. LiClO ₄ and LiAsF
No. ₆ has good conductivity characteristics, but does not have sufficient charge / discharge cycle characteristics.

In recent years, LiN (C ₂ F ₅ S
O ₂ ) ₂ and LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ )
Attempts have been made to utilize the above as an electrolyte salt, and their usefulness is expected, but these electrolyte salts have good electrical conductivity and thermal stability, but are inferior in oxidative stability to LiCF ₃ S.
Similar to O ₃ , sufficient discharge characteristics cannot be obtained.

The present invention has been made in view of such problems, and an object thereof is to provide an electrolyte capable of improving stability and a battery provided with the electrolyte.

[0008]

The electrolyte of the present invention contains an antioxidant.

The battery according to the first aspect of the present invention is provided with an electrolyte containing an antioxidant together with the positive electrode and the negative electrode.

A battery according to a second aspect of the present invention comprises a positive electrode, a negative electrode and an electrolyte, the negative electrode contains a material capable of inserting and extracting light metal, and the electrolyte contains a rust preventive agent. It was done like this.

Since the electrolyte of the present invention contains the antioxidant, the stability is improved.

In the battery according to the first aspect of the present invention, the stability is improved because the electrolyte contains the antioxidant.

In the battery according to the second aspect of the present invention, the stability is improved because the electrolyte contains a rust preventive agent.

[0014]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below in detail with reference to the drawings.

[First Embodiment] First, the first embodiment of the present invention will be described.
The battery according to the embodiment will be described. Since the electrolyte of the present invention constitutes one component of the battery according to this embodiment, it will be described below together.

FIG. 1 shows a sectional structure of a battery according to a first embodiment of the present invention, for example, a secondary battery. This secondary battery is a so-called cylindrical type,
A strip-shaped positive electrode 21 is provided inside the battery can 11 having a substantially hollow cylindrical shape.
And the negative electrode 22 have a wound electrode body 20 wound around a separator 23. The battery can 11 is made of, for example, iron (Fe) plated with nickel (Ni), and has one end closed and the other end open. Inside the battery can 11, a pair of insulating plates 12 and 13 is arranged so as to sandwich the spirally wound electrode body 20 perpendicularly to the spirally wound peripheral surface.

A battery lid 14 is provided at the open end of the battery can 11.
And a safety valve mechanism 15 provided inside the battery lid 14.
And PTC (Positive Temperature Coefficie)
nt (PTC) element 16 is attached by being caulked via a gasket 17,
The inside of 1 is sealed. The battery lid 14 is made of, for example, the same material as the battery can 11. The safety valve mechanism 15 is electrically connected to the battery lid 14 via the PTC element 16, and the disk plate 15a is inverted when the internal pressure of the battery exceeds a certain level due to an internal short circuit or heating from the outside. Then, the electrical connection between the battery lid 14 and the spirally wound electrode body 20 is cut off. The PTC element 16 limits the current due to an increase in the resistance value when the temperature rises, and prevents a large current from flowing due to an external short circuit or the like to cause the battery to abnormally generate heat. It is composed of barium-based semiconductor ceramics. The gasket 17 is made of, for example, an insulating material, and its surface is coated with asphalt.

The wound electrode body 20 is, for example, the center pin 2
It is wound around 4. Positive electrode 21 of wound electrode body 20
Is a positive electrode lead 25 made of aluminum (Al) or the like.
And a negative electrode lead 26 made of nickel or the like is connected to the negative electrode 22. The positive electrode lead 25 is electrically connected to the battery lid 14 by being welded to the safety valve mechanism 15, and the negative electrode lead 26 is welded and electrically connected to the battery can 11.

The positive electrode 21 is composed of, for example, a positive electrode mixture layer and a positive electrode current collector layer, and has a structure in which the positive electrode mixture layer is provided on both or one side of the positive electrode current collector layer. . The positive electrode current collector layer is made of, for example, a metal foil such as an aluminum foil, a nickel foil, or a stainless foil. The positive electrode mixture layer is configured to include, for example, a positive electrode active material, a conductive agent such as carbon black or graphite, and a binder such as polyvinylidene fluoride.

The positive electrode active material has a general formula of Li _x M, for example.
It is configured to include a lithium composite oxide represented by O ₂ (x is an arbitrary value). M in the formula is, for example, cobalt (Co), nickel (Ni), manganese (Mn).
Transition metals and the like, a mixture of these transition metals (e.g., _{Li x Ni y Co 1-y} O 2). x varies depending on the charging / discharging state of the battery, and is, for example, a value within the range of 0.05 ≦ x ≦ 1.10. The positive electrode active material is composed of, for example, a metal oxide containing no lithium, a metal sulfide, a polymer material, or a material containing two or more of these various materials, in addition to the lithium composite oxide described above. In some cases. Examples of the metal oxide include vanadium oxide (V ₂
O ₅ ) and the like. Examples of the metal sulfide include titanium sulfide (TiS ₂ ), molybdenum sulfide (MoS ₂ ),
Examples include niobium selenide (NbSe ₂ ). As the positive electrode active material, it is particularly preferable to use a lithium composite oxide from the viewpoint of being able to generate a high voltage and ensuring an excellent energy density.

The negative electrode 22 is, for example, similar to the positive electrode 21,
It is composed of a negative electrode mixture layer and a negative electrode current collector layer, and has a structure in which the negative electrode mixture layer is provided on both surfaces or one surface of the negative electrode current collector layer. The negative electrode current collector layer is, for example, a copper foil,
It is made of metal foil such as nickel foil or stainless foil. The negative electrode mixture layer includes a negative electrode material made of lithium metal or a material capable of inserting and extracting lithium, and a binder such as polyvinylidene fluoride. As the negative electrode mixture layer, it is particularly preferable to use a material capable of inserting and extracting lithium from the viewpoint of ensuring excellent charge-discharge cycle characteristics.

Examples of the negative electrode material capable of occluding / releasing lithium include a metal or semiconductor capable of forming an alloy or compound with lithium, or an alloy or compound thereof. Such metal or semiconductor,
Or as these alloys or compounds, for example,
Magnesium (Mg), boron (B), aluminum (Al), gallium (Ga), indium (In), silicon (Si), germanium (Ge), tin (Sn),
Lead (Pb), arsenic (As), antimony (Sb), bismuth (Bi), cadmium (Cd), silver (Ag), zinc (Zn), hafnium (Hf), zirconium (Zr).
Alternatively, yttrium (Y), or an alloy or compound thereof may be used. Specific examples of these alloys or compounds are LiAl and LiAlM.
III (provided that MIII is at least one of 2A, 3B, and 4B metal elements and semiconductor elements), AlS
b or CuMgSb.

Among them, 4B is a metal element or a semiconductor element capable of forming an alloy or a compound with lithium.
A metal element or semiconductor element of the group is preferable, silicon or tin is particularly preferable, and silicon is most preferable. These alloys or compounds are also preferable, specifically, SiB ₄ , SiB ₆ , Mg ₂ Si, Mg ₂ S.
n, Ni ₂ Si, TiSi ₂ , MoSi ₂ , CoS
i ₂ , NiSi ₂ , CaSi ₂ , CrSi ₂ , Cu ₅ S
i, FeSi ₂ , MnSi ₂ , NbSi ₂ , TaS
Examples thereof include i ₂ , VSi ₂ , WSi _{2 and} ZnSi ₂ . The series of silicon compounds described above may have a stoichiometric composition or a non-stoichiometric composition.

Examples of the material capable of inserting and extracting lithium include carbon materials, metal oxides and polymer materials.

Examples of the carbon material include pyrolytic carbons, cokes, graphites, glassy carbons, organic polymer compound fired bodies, carbon fibers and activated carbon. Among these, the cokes include, for example, pitch coke, needle coke, petroleum coke, and the like, and the glassy carbons include, for example, a non-graphitizable carbon material having a (002) plane spacing of 0.37 nm or more. Etc. are included.
The organic polymer compound fired body is obtained by firing a polymer material such as phenol resin or furan resin at an appropriate temperature to carbonize it.

Examples of the metal oxide include tin oxide (SnO ₂ ) and the like, and examples of the polymer material include polyacetylene and polypyrrole.

The separator 23 is composed of, for example, a porous film made of a polyolefin material such as polypropylene or polyethylene, or a porous film made of an inorganic material such as a ceramic non-woven fabric. It may have a structure in which quality films are laminated.

The separator 23 is impregnated with a liquid electrolyte, for example. This electrolyte is composed of, for example, a non-aqueous solvent, a lithium salt as an electrolyte salt, and a non-aqueous solvent-soluble antioxidant shown in Chemical formula 1. Specific examples of the antioxidant include, for example, 4,4′-thiobis (2-tert-butyl-5-methylp) shown in Chemical formula 2.
henol) and so on. By including an antioxidant in the electrolyte, the storage stability and charge / discharge cycle characteristics in a high temperature environment are stabilized. The concentration of the antioxidant is preferably, for example, in the range of 0.01% by weight or more and less than 5.0% by weight of the whole electrolyte. This is because proper and practical storage characteristics and charge / discharge cycle characteristics are ensured within such a range.

[0029]

[Chemical 2]

Examples of the non-aqueous solvent include cyclic carbonic acid esters such as propylene carbonate, ethylene carbonate and butylene carbonate, chain esters such as diethyl carbonate, carboxylic acid esters such as propionic acid ester and butyric acid ester, and ethers such as dimethoxyethane. , Γ-butyl lactone or 2-
Any one kind or a mixture of two or more kinds of methyltetrahydrofuran and the like is used. As the non-aqueous solvent, it is particularly preferable to include a carbonic acid ester from the viewpoint of ensuring good oxidative stability.

Examples of the lithium salt include LiP
F ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , Li
_{CF 3 SO 3, LiB (C} 6 H 5) 4, LiCl, Li
Br, CH ₃ SO ₃ Li, CF ₃ SO ₃ Li, LiN
(C ₂ F ₅ SO ₂ ) ₂ , LiN (CF ₃ SO ₂ ) ₂ or LiN (C ₄ F ₉ SO ₂ ) (CF ₃ SO ₂ ) and the like, and any one or more of them may be used. Are mixed and used. The lithium salt concentration in the electrolyte is, for example, in the range of about 0.5 mol / l to 2.0 mol / l (or about 0.5 mol / kg to 2.0 mol / kg). The lithium salt may be, for example, LiP from the viewpoint of storage characteristics, charge / discharge cycle characteristics, or material cost.
At least one selected from the group consisting of F ₆ , LiBF ₄ , and LiN (CF ₃ SO ₂ ) ₂ , preferably LiPF ₆ , L
iBF ₄ , LiN (CF ₃ SO ₂ ) ₂ , a mixture of LiPF ₆ and LiBF ₄ , or LiPF ₆ and LiN
It is preferred to include a mixture of (CF ₃ SO ₂ ) ₂ .

The secondary battery can be manufactured, for example, as follows.

First, for example, a positive electrode active material, a conductive agent, and a binder are mixed to prepare a positive electrode mixture.
It is dispersed in a solvent such as methyl-2-pyrrolidone to obtain a paste-like positive electrode mixture slurry. Subsequently, the positive electrode mixture slurry is applied to the positive electrode current collector layer, the solvent is dried, and then compression molding is performed with a roller press or the like to form the positive electrode mixture layer, whereby the positive electrode 21 is manufactured.

Then, for example, a negative electrode material and a binder are mixed to prepare a negative electrode mixture, and this negative electrode mixture is mixed with N-methyl-
Dispersed in a solvent such as 2-pyrrolidone to obtain a paste-like negative electrode mixture slurry. Subsequently, the negative electrode mixture slurry is applied to the negative electrode current collector layer, the solvent is dried, and then compression molding is performed by a roller press or the like to form the negative electrode mixture layer, whereby the negative electrode 22 is manufactured.

Subsequently, the positive electrode lead 25 is attached to the positive electrode current collector layer by welding and the negative electrode lead 26 is attached to the negative electrode current collector layer by welding. Subsequently, the positive electrode 21 and the negative electrode 22 are wound via the separator 23, the tip of the positive electrode lead 25 is welded to the safety valve mechanism 15, and the end of the negative electrode lead 26 is welded to the battery can 11 and wound. The positive electrode 21 and the negative electrode 22 are connected to the pair of insulating plates 12, 1
It is sandwiched by 3 and stored in the battery can 11. Then, for example, in a mixed solvent of propylene carbonate and diethyl carbonate, LiPF ₆ as an electrolyte salt and 4,4′-thiobis (2-tert-butyl-5-methylphene as an antioxidant are used.
The electrolyte is prepared by dissolving ol). Subsequently, the positive electrode 21 and the negative electrode 22 are housed inside the battery can 11, and then an electrolyte is injected into the battery can 11 to impregnate the separator 23. Then, at the open end of the battery can 11, the battery lid 14, the safety valve mechanism 15, and the PTC device 16 are provided.
Is fixed by caulking through the gasket 17. As a result, the secondary battery shown in FIG. 1 is formed.

This secondary battery operates as follows.

In this secondary battery, when charged, for example, lithium ions are desorbed from the positive electrode 21 and are occluded in the negative electrode 22 through the electrolyte impregnated in the separator 23. On the other hand, when discharged, for example, lithium ions are desorbed from the negative electrode 22 and are occluded in the positive electrode 21 via the electrolyte impregnated in the separator 23. Here, 4,4'-thiobis (2-tert-butyl-5-meth) is used as an antioxidant.
ylphenol) is contained in the electrolyte, a decrease in discharge capacity when charging and discharging are repeated in a high temperature environment (for example, 60 ° C.) is suppressed, and a high capacity retention rate is exhibited.

As described above, according to the secondary battery of the present embodiment, since the antioxidant contains the antioxidant represented by Chemical formula 1, it is excellent in a high temperature environment (for example, 60 ° C.). Storage characteristics and charge / discharge cycle characteristics can be obtained.

[0039]

EXAMPLES Further, specific examples of the present invention will be described in detail.

(Examples 1 to 6) As Examples 1 to 6, the so-called cylindrical type secondary battery shown in FIG. 1 was prepared as described below, and the storage characteristics and charge / discharge cycle characteristics in a high temperature environment were prepared. I checked.

First, the positive electrode 21 was manufactured by the following procedure. That is, first, lithium carbonate (Li ₂ CO
₃ ) Powder and cobalt carbonate (Co ₂ CO ₃ ) powder were mixed at a molar ratio of lithium carbonate: cobalt carbonate = 1: 2, mixed using a mortar, and then the mixture was heated to about 900 ° C. in normal pressure air. Then, the positive electrode active material (LiCoO ₂ ) composed of a powdery oxide of lithium and cobalt was synthesized by firing at about 5 hours.

Subsequently, 91 parts by weight of LiCoO ₂ powder,
6 parts by weight of graphite as a conductive agent and 3 parts by weight of polyvinylidene fluoride as a binder were mixed to obtain a positive electrode mixture. Then, the positive electrode mixture was used as a solvent N-methyl-2-
A paste-like positive electrode mixture slurry was prepared by dispersing it in pyrrolidone. Subsequently, the positive electrode mixture slurry is uniformly applied to both surfaces of the positive electrode current collector layer made of an aluminum foil having a thickness of about 20 μm and dried, and then the positive electrode mixture is compression-molded together with the positive electrode current collector layer to form the positive electrode 21. Was produced.

Next, the negative electrode 22 was produced by the following procedure. That is, first, about 10 functional groups containing oxygen are added.
% To 20% to crosslink the petroleum pitch as a starting material with oxygen and then calcining the petroleum pitch in an inert gas stream at about 1000 ° C. to obtain a non-graphitizable carbon having properties similar to glassy carbon. Got the material. Structural analysis of this non-graphitizable carbon material by X-ray diffraction measurement revealed that the (002) plane spacing was 0.376 nm,
It was confirmed that the true specific gravity was 1.58 g / cm ³ .

Subsequently, the non-graphitizable carbon material was crushed to obtain a carbon material powder having an average particle size of 10 μm, and 90 parts by weight of the carbon material powder and 10 parts by weight of polyvinylidene fluoride as a binder were mixed. A negative electrode mixture was obtained. Subsequently, the negative electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to obtain a paste-like positive electrode mixture slurry.
Subsequently, the negative electrode mixture slurry was uniformly applied to both surfaces of a copper foil having a thickness of about 10 μm, and dried, and then the negative electrode mixture was compression-molded together with the negative electrode current collector layer to prepare the negative electrode 22.

Next, lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte salt was dissolved at a concentration of 1 mol / L in a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate, and then oxidized. 4,4'-th as an inhibitor
An electrolyte was prepared by adding iobis (2-tert-butyl-5-methylphenol). At that time, in Examples 1 to 6,
4,4'-thiobis (2-tert-but for the whole electrolyte
The concentration of yl-5-methylphenol) was changed as shown in Table 1.

[0046]

[Table 1]

Next, the secondary battery shown in FIG. 1 was manufactured by using the positive electrode 21, the negative electrode 22, and the electrolyte together with the separator made of the polypropylene porous film. The size of the battery was 18 mm in diameter and 65 mm in thickness.

As Comparative Example 1 with respect to Examples 1 to 6, except that no antioxidant is contained in the electrolyte,
A secondary battery was made in the same manner as in Examples 1 to 6 except for the above.

Each of the secondary batteries thus obtained in Examples 1 to 6 and Comparative Example 1 was subjected to a storage characteristic test and a charge / discharge cycle characteristic test in a high temperature environment.

In the storage characteristic test, first, the battery was charged in a 20 ° C. environment with a constant current of 1 A until the battery voltage reached 4.2 V, and then with a constant current of 500 mA, the battery voltage was 2.5.
The discharge capacity when discharged to V was determined as the initial discharge capacity of each battery. After that, each battery was stored in an environment of 60 ° C. for 1 week, and then charged and discharged under the same conditions as above for 3 cycles, and the maximum value of the discharge capacity obtained in each cycle was discharged after storage of each battery. Calculated as capacity. Then, the discharge capacity retention rate (%) of each battery was determined as the ratio (percentage) of the discharge capacity after storage to the discharge capacity before storage. The test results are shown in Table 1. The initial discharge capacity is the same for each battery.

In the charge / discharge cycle characteristic test, 100 cycles of charging / discharging under the same conditions as in the storage characteristic test were performed in an environment of 60 ° C., and the discharge capacity retention ratio was obtained as the discharge capacity at the 100th cycle with respect to the initial discharge capacity. It was The test results are shown in Table 1.

As can be seen from the results shown in Table 1, the discharge capacity retention rates of Examples 1 to 6 relating to the storage characteristics are equal to or higher than the discharge capacity retention rate of Comparative Example 1, and in particular, antioxidation When the concentration of the agent was in the range of 0.01% by weight or more and less than 5.0% by weight of the electrolyte, a good discharge capacity retention rate was obtained.

Example 1 relating to charge / discharge cycle characteristics
The discharge capacity retention rate for Nos. 6 to 6 is equal to or higher than the discharge capacity retention rate for Comparative Example 1, and particularly, the concentration of the antioxidant is within the range of 0.01 wt% to less than 5.0 wt% of the electrolyte. In this case, a good discharge capacity retention rate was obtained.

From the above, by setting the concentration of the antioxidant within the range of 0.01% by weight to less than 5.0% by weight of the electrolyte, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics can be improved. The property has improved.

(Examples 7 and 8) Instead of LiPF ₆ , Li
A secondary battery was made in the same manner as in Example 1 except that BF ₄ was used as the electrolyte salt. At that time, in Examples 7 and 8, an antioxidant (4,
4'-thiobis (2-tert-butyl-5-methylpheno
The concentration of l)) was changed as shown in Table 2. Also,
As Comparative Example 2 with respect to Examples 7 and 8, a secondary battery was produced in the same manner as in Examples 7 and 8 except that the electrolyte did not contain an antioxidant.

[0056]

[Table 2]

With respect to the secondary batteries of Examples 7 and 8 and Comparative Example 2, a storage characteristic test and a charge / discharge cycle characteristic test were conducted in the same manner as in Example 1 to determine the discharge capacity retention rate of each battery. The test results are shown in Table 2.

As can be seen from the results shown in Table 2, the discharge capacity retention rates of Examples 7 and 8 relating to the storage characteristics and the charge / discharge cycle characteristics were higher than the discharge capacity maintenance rate of Comparative Example 2. . That is, also in the cases of Examples 7 and 8, the inclusion of the antioxidant in the electrolyte improved the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics.

(Examples 9 and 10) 1.0 mol of LiP
0.1 mol of F ₆ is LiN (CF ₃ SO ₂ ) ₂
A secondary battery was made in the same manner as in Example 1 except that the electrolyte salt substituted for was used. At that time, in Examples 9 and 10, an antioxidant (4,4′-thiobis (2-tert-butyl-5-methylphph) against the whole electrolyte was used.
The enol)) concentration was varied as shown in Table 3. Also, as Comparative Example 3 with respect to Examples 9 and 10, except that the electrolyte does not contain an antioxidant,
A secondary battery was produced in the same manner as in 10.

[0060]

[Table 3]

With respect to the secondary batteries of Examples 9 and 10 and Comparative Example 3, a storage characteristic test and a charge / discharge cycle characteristic test were conducted in the same manner as in Example 1 to determine the discharge capacity retention rate of each battery. The test results are shown in Table 3.

As can be seen from the results shown in Table 3, the discharge capacity retention ratios of Examples 9 and 10 relating to the storage characteristics and charge / discharge cycle characteristics were higher than the discharge capacity maintenance ratio of Comparative Example 3. . That is, Examples 9 and 10
Also in the above, by including an antioxidant in the electrolyte, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics was improved.

In this embodiment, 4,4'-thiobis (2-tert-butyl-5-methylph) is used as an antioxidant.
The case of using an enol) has been described, but the invention is not limited to this, and the antioxidant to be used can be freely selected as long as it has the basic structure shown in Chemical formula 1.
Furthermore, the antioxidant is not limited to the one having the basic structure shown in Chemical formula 1, and other antioxidants can be used.

[Second Embodiment] Next, the second embodiment of the present invention will be described.
The battery according to the embodiment will be described.

In the secondary battery as the battery according to the second embodiment of the present invention, instead of the antioxidant used in the first embodiment, a rust preventive agent is contained in the electrolyte. It is a thing. This rust preventive agent is, for example, soluble in a non-aqueous solvent and contains benzotriazole or its derivative having the basic structure represented by Chemical formula 3. Specific examples of the rust preventive agent include, for example, 1,2,3-benzotriazole shown in Chemical formula 4, 4-methyl 1H-benzotriazole shown in Chemical formula 5, and 4-methyl 1K-benzotriazole shown in Chemical formula 6. Alternatively, 5-methyl 1H-benzotriazole shown in Chemical formula 7 may be used. In addition, in the secondary battery according to the present embodiment, the configuration other than that the electrolyte contains a rust preventive agent, the manufacturing method, the action during charging and discharging, and the like are the same as those in the first embodiment. It is the same.

[0066]

[Chemical 3] In the formula, R5 represents hydrogen or a methyl group, and A represents a hydrogen atom or a potassium atom.

[Chemical 4]

[Chemical 5]

[Chemical 6]

[Chemical 7]

In this embodiment, since the electrolyte contains the rust preventive represented by Chemical formula 3, it is used in a high temperature environment (for example, 6
The capacity does not decrease even after repeated charge and discharge at 0 ° C.
It shows a high capacity retention rate. Therefore, excellent storage characteristics and charge / discharge cycle characteristics can be obtained in a high temperature environment.

[0068]

Examples (Examples 1 to 6) In Examples 1 to 6, lithium hexafluorophosphate (LiPF ₆ ) was used as an electrolyte salt in a mixed solvent of 50% by volume of propylene carbonate and 50% by volume of diethyl carbonate. After dissolving at a concentration of 1 mol / L, 1,2,3-benzotriazole shown in Chemical formula 4 was added as a rust preventive agent to prepare an electrolyte. At that time, in Examples 1 to 6, the concentration of 1,2,3-benzotriazole with respect to the entire electrolyte was changed as shown in Table 4. Then, a secondary battery was manufactured by the same procedure as in the case of the first embodiment, and a storage characteristic test and a charge / discharge cycle characteristic test in a high temperature environment (60 ° C.) were performed. The test results are shown in Table 4.

[0069]

[Table 4]

As Comparative Example 1 with respect to Examples 1 to 6, secondary batteries were produced in the same manner as in Examples 1 to 6 except that the electrolyte did not contain 1,2,3-benzotriazole. did.

As can be seen from the results shown in Table 4, the discharge capacity retention rates of Examples 1 to 6 relating to the storage characteristics were equal to or higher than the discharge capacity retention rate of Comparative Example 1, and in particular, rust prevention. When the concentration of the agent was in the range of 0.01% by weight or more and less than 5.0% by weight, a good discharge capacity retention rate was obtained.

Example 1 relating to charge / discharge cycle characteristics
The discharge capacity retention rate for Nos. 6 to 6 is equal to or higher than the discharge capacity maintenance rate for Comparative Example 1, and particularly when the concentration of the rust preventive agent is in the range of 0.01% by weight to less than 5.0% by weight. A good discharge capacity retention rate was obtained.

From the above, the concentration of the rust preventive agent should be 0.0
By setting the content within the range of 1% by weight or more and less than 5.0% by weight, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics was improved.

(Examples 7 and 8) LiPF ₆ was replaced with Li
A secondary battery was made in the same manner as in Example 1 except that BF ₄ was used as the electrolyte salt. At that time, in Examples 7 and 8, rust preventives (1, 2,
The concentration of 3-benzotriazole) was changed as shown in Table 5. In addition, as Comparative Example 2 with respect to Examples 7 and 8, a secondary battery was manufactured in the same manner as in Examples 7 and 8 except that the electrolyte did not contain a rust preventive agent. Table 5 shows the results of the storage characteristic test and the charge / discharge cycle characteristic test performed on the secondary batteries of Examples 7 and 8 and Comparative Example 2.

[0075]

[Table 5]

As can be seen from the results shown in Table 5, the discharge capacity retention rates of Examples 7 and 8 relating to the storage characteristics and the charge / discharge cycle characteristics were higher than the discharge capacity maintenance rate of Comparative Example 2. . That is, also in Examples 7 and 8, the stability of the secondary battery relating to the storage characteristics and the charge / discharge cycle characteristics was improved by including the rust preventive agent in the electrolyte.

(Examples 9 and 10) 1.0 mol of LiP
F₆0.1 mol of LiN (C₂F_FiveS0₂)
₂Other than using the electrolyte salt replaced by
A secondary battery was produced in the same manner as in Example 1. At that time, the example
In 9 and 10, rust preventive agent (1,
The concentration of 2,3-benzotriazole) is shown in Table 6.
I changed it. In addition, a comparative example with respect to Examples 9 and 10
3, except that the electrolyte contains no antioxidant
A secondary battery was prepared in the same manner as in Examples 9 and 10 except for the above.
It was Secondary batteries of Examples 9 and 10 and Comparative Example 3
About storage characteristic test and charge / discharge cycle characteristic test
The results obtained are shown in Table 6.

[0078]

[Table 6]

As can be seen from the results shown in Table 6, the discharge capacity retention ratios of Examples 9 and 10 relating to the storage characteristics and charge / discharge cycle characteristics were higher than the discharge capacity maintenance ratio of Comparative Example 3. . That is, Examples 9 and 10
Also in the above, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics was improved by including an anticorrosive agent in the electrolyte.

(Examples 11 and 12) In place of 1,2,3-benzotriazole, 4-methyl 1H- shown in Chemical formula 5 was used.
Except for using benzotriazole as a rust inhibitor
A secondary battery was produced in the same manner as in Example 1 except for the above. At that time, in Examples 11 and 12, the concentration of the rust preventive agent (4-methyl 1H-benzotriazole) with respect to the entire electrolyte was changed as shown in Table 7. Examples 7 and 8
Table 7 shows the results of the storage characteristic test and the charge / discharge cycle characteristic test of the secondary battery of No.

[0081]

[Table 7]

As can be seen from the results shown in Table 7, the discharge capacity retention ratios of Examples 11 and 12 were higher than the discharge capacity retention ratio of Comparative Example 3 due to the storage characteristics and the charge / discharge cycle characteristics. . That is, Examples 11 and 1
Also in No. 2, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics was improved by including an anticorrosive agent in the electrolyte.

(Examples 13 and 14) In place of 1,2,3-benzotriazole, 4-methyl 1K- shown in Chemical formula 6 was used.
Benzotriazole and 5-methyl 1K shown in Chemical formula 7
A secondary battery was made in the same manner as in Example 1 except that benzotriazole was used as the rust preventive agent. At that time, in Examples 13 and 14, the concentration of the rust preventive agent with respect to the entire electrolyte was changed as shown in Table 8. Table 8 shows the results of the storage characteristic test and the charge / discharge cycle characteristic test performed on the secondary batteries of Examples 13 and 14.

[0084]

[Table 8]

As can be seen from the results shown in Table 8, the discharge capacity retention ratios of Examples 13 and 14 relating to the storage characteristics and charge / discharge cycle characteristics were higher than the discharge capacity maintenance ratio of Comparative Example 1. . That is, Example 13,
Also in No. 14, the stability of the secondary battery relating to storage characteristics and charge / discharge cycle characteristics was improved by including an anticorrosive agent in the electrolyte.

Although the present invention has been described with reference to some embodiments and examples, the present invention is not limited to the above-described embodiments and examples, and various modifications can be made. For example, in each of the above-described embodiments and examples, the case where the electrolyte containing the antioxidant or the rust preventive is applied to the secondary battery has been described, but the same can be applied to the primary battery. In such a case, as the positive electrode active material, for example, TiS ₂ , MnO ₂ , graphite, FeS ₂ or the like can be used.

Further, in each of the above-described embodiments and examples, the case where the present invention is applied to the cylindrical type secondary battery and the coin type secondary battery having the winding structure has been described. The present invention is also applicable to secondary batteries having other shapes such as a cylindrical shape, a button shape, and a square shape.

Further, in each of the above-mentioned embodiments and examples, the secondary battery using the liquid electrolyte has been described. However, a gel electrolyte in which a polymer compound holds an electrolyte salt, and a high ion conductivity. A solid electrolyte in which an electrolyte salt is dispersed in a molecular compound or another electrolyte such as an inorganic electrolyte salt may be used.

In each of the above-described embodiments and examples, the secondary battery using lithium ion as the electrode reactive species has been described. However, the present invention is not limited to sodium (Na),
It can also be applied to a secondary battery using ions of other light metals such as potassium (K), magnesium (Mg), calcium (Ca) or aluminum (Al) as an electrode reactive species. In that case, the positive electrode active material and the electrode salt are selected according to the purpose.

[0090]

As described above, since the electrolyte according to any one of claims 1 to 9 contains the antioxidant, the stability in a high temperature environment is improved. be able to.

Particularly, according to the electrolyte of the third aspect, since the concentration of the antioxidant is set to be in the range of 0.01% by weight or more and less than 5.0% by weight of the whole, it is stable in a high temperature environment. It is possible to further improve the sex.

Further, according to the battery of the tenth aspect, since the electrolyte containing the antioxidant is provided, the stability relating to the storage characteristics and the charge / discharge cycle characteristics in a high temperature environment can be improved.

According to the battery of any one of claims 11 to 19, since the electrolyte contains a rust preventive agent, it is possible to improve the storage characteristics and the charge / discharge cycle characteristics in a high temperature environment. The stability can be improved.

In particular, according to the battery of the thirteenth aspect, since the concentration of the rust preventive agent is set in the range of 0.01% by weight or more and less than 5.0% by weight, the stability of the secondary battery is improved. It can be further improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a sectional configuration of a secondary battery according to a first embodiment of the present invention.

[Explanation of symbols]

11 ... Battery can, 12, 13 ... Insulation plate, 14 ... Battery lid, 1
5 ... Safety valve mechanism, 15a ... Disk plate, 16 ... PTC element, 17 ... Gasket, 20 ... Winding electrode body, 21 ... Positive electrode, 22 ... Negative electrode, 23 ... Separator, 24 ... Center pin, 25 ... Positive electrode lead, 26 ... Negative electrode lead.

Claims (19)

[Claims] 1. An electrolyte comprising an antioxidant. 2. The electrolyte according to claim 1, wherein the antioxidant contains a compound represented by the following chemical formula 1. [Chemical 1] (In the formula, R1, R2, R3, R4, R5 and R6 represent a hydrogen atom or an alkyl group having 1 to 5 carbon atoms.) 3. The total concentration of the antioxidant is 0.0
The electrolyte according to claim 1, which is in a range of 1% by weight or more and less than 5.0% by weight. 4. An electrolyte salt is further included, and the electrolyte salt is LiPF ₆ , LiBF ₄ and LiN.
The electrolyte according to claim 1, which contains at least one member selected from the group consisting of (CF ₃ SO ₂ ) ₂ . 5. The electrolyte according to claim 1, further comprising an electrolyte salt made of LiPF ₆ . 6. The electrolyte according to claim 1, further comprising an electrolyte salt of LiBF ₄ . 7. The electrolyte according to claim 1, further comprising an electrolyte salt made of LiN (CF ₃ SO ₂ ) ₂ . 8. The electrolyte according to claim 1, further comprising an electrolyte salt composed of LiPF ₆ and LiBF ₄ . 9. LiPF ₆ and LiN (CF)
_The electrolyte according to claim 1, which contains an electrolyte salt of ₃ SO ₂ ) ₂ . 10. A battery comprising an electrolyte containing an antioxidant together with a positive electrode and a negative electrode. 11. A battery provided with an electrolyte together with a positive electrode and a negative electrode, wherein the negative electrode contains a material capable of inserting and extracting a light metal, and the electrolyte contains a rust preventive agent. . 12. The battery according to claim 11, wherein the rust preventive agent contains benzotriazole or a derivative thereof. 13. The battery according to claim 11, wherein the concentration of the rust preventive agent is within a range of 0.01% by weight or more and less than 5.0% by weight of the electrolyte. 14. The electrolyte further comprises an electrolyte salt, wherein the electrolyte salt comprises LiPF ₆ , LiBF ₄ and LiN.
The battery according to claim 11, which contains at least one member selected from the group consisting of (CF ₃ SO ₂ ) ₂ . 15. The battery according to claim 11, wherein the electrolyte further contains an electrolyte salt of LiPF ₆ . 16. The battery according to claim 11, wherein the electrolyte further contains an electrolyte salt of LiBF ₄ . 17. The electrolyte further comprises LiN (CF
The battery according to claim 11, further comprising an electrolyte salt composed of ₃ SO ₂ ) ₂ . 18. The battery according to claim 11, wherein the electrolyte further contains an electrolyte salt of LiPF ₆ and LiBF ₄ . 19. The battery according to claim 11, wherein the electrolyte further contains an electrolyte salt of LiPF ₆ and LiN (CF ₃ SO ₂ ) ₂ .