JP4226844B2 - Method for inhibiting corrosion of electrochemical device member and battery - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a method and a battery for inhibiting corrosion of non-aqueous electrolyte electrochemical device members such as lithium batteries, lithium ion batteries, and electric double layer capacitors using LiPF ₆ as an electrolyte.
[0002]
[Prior art]
With the development of portable devices in recent years, the development of electrochemical devices using electrochemical phenomena such as batteries and capacitors as a power source has become active. Further, as an electrochemical device other than the power source, an electrochromic display (ECD) in which a color change is caused by an electrochemical reaction can be given.
[0003]
These electrochemical devices are generally composed of a pair of electrodes and an ionic conductor filling them. As the ionic conductor, a solution in which a salt (AB) composed of a cation (A ⁺ ) and an anion (B ⁻ ) called an electrolyte is dissolved in a solvent, a polymer, or a mixture thereof is used. When this electrolyte is dissolved, it dissociates into a cation and an anion to conduct ions. In order to obtain the ionic conductivity necessary for the device, it is necessary that this electrolyte is dissolved in a sufficient amount in a solvent or a polymer. Actually, a solvent other than water is often used as a solvent, and there are currently only a few types of electrolytes having sufficient solubility in such organic solvents and polymers. For example, as an electrolyte for a lithium battery, LiClO ₄ , LiPF ₆ , LiBF ₄ , LiAsF ₆ , LiN (SO ₂ CF ₃ ) ₂ , LiN (SO ₂ C ₂ F ₅ ) ₂ , LiN (SO ₂ CF ₃ ) (SO ₂ C ₄ F ₉ ), and LiCF ₃ SO ₃ only. The cation portion is often determined by the device, such as the lithium ion of a lithium battery, but the anion portion can be used if the condition that the solubility is high is satisfied. At present, those having PF ₆ as an anion portion are widely put into practical use, but have a problem that they are hydrolyzed by water mixed in a trace amount in the system to generate hydrogen fluoride. Recently, many metal parts and aluminum laminates are used for the exterior of the device, but corrosion is caused by the hydrogen fluoride generated here, and particularly, the one with the aluminum laminate is easily led to an accident such as leakage. Therefore, measures are taken by applying a surface treatment for corrosion prevention to the aluminum laminate sheet, but the effect is not sufficient in long-term use.
[0004]
[Means for solving problems]
As a result of intensive studies in view of the problems of the prior art, the present inventors have found a method for preventing corrosion by adding a specific additive, and have reached the present invention.
[0005]
That is, the present invention is an electrolyte or a gel electrolyte using LiPF ₆ as an electrolyte, a positive electrode, and a negative electrode, and, in the battery using the aluminum laminate film to the battery exterior, of 0.001-10 mol% for the LiPF ₆ In the method for inhibiting corrosion of an aluminum laminate film, which is an exterior of the battery, comprising adding at least one of compounds having the chemical structural formula represented by the general formula (1) in a range,
[0006]
[Chemical formula 2]
[0007]
Where M is B or P , A ^{a +} is lithium ion, a is 1 , b is 1 , p is b / a, m is 1 or 2 when M is B, and M is P , 1, 2 or 3 , n is 0 when M is B and m is 2, when M is B and m is 1, 2, when M is P and when m is 3, 0 and M are when the P, m is 2, 2, M is when the P, m is 1, 4, q represents 0, respectively, ^{R 2} is fluorine, ^X 1, ^{X 2} represents O, respectively, also By providing these methods, the present invention provides a battery in which corrosion of the aluminum laminate film that is the exterior of the battery is suppressed.
[0009]
Hereinafter, the present invention will be described in more detail.
[0010]
Here, first, specific examples of the compound represented by the general formula (1) used in the present invention are shown below.
[0011]
[Chemical 3]
[0012]
[Formula 4]
[0015]
Here, lithium ions are listed as A ^{a +} .
[0016]
Lithium ions are preferred when considering the use of a battery comprising an electrolyte solution or gel electrolyte using LiPF ₆ as an electrolyte, a positive electrode, a negative electrode, and using an aluminum laminate film for the battery exterior. The valence ^a of the cation of A ^{a +} is preferably 1 . Similarly, the valence b of the anion is preferably 1 . The constant p representing the ratio of cation to anion is inevitably determined by the valence ratio b / a of both.
[0017]
Compounds of general formula (1) used in the present invention, adopts an ionic metal complex structure, M serving as its center is selected from B or P. Although various elements can be used as the central M , in the case of B and P , synthesis is relatively easy, and in addition to the ease of synthesis, all aspects of low toxicity, stability, and cost It has excellent characteristics.
[0018]
Next, the part of the ligand that is a feature of the compound (ionic metal complex) used in the present invention will be described. Hereinafter, the organic or inorganic part bonded to M is referred to as a ligand.
[0019]
R ¹ in the general formula (1) is selected from C _{1 to} C ₁₀ alkylene, C _{1 to} C ₁₀ halogenated alkylene, C _{4 to} C ₂₀ arylene, or C _{4 to} C ₂₀ halogenated arylene. These alkylenes and arylenes may have a substituent or a hetero atom in the structure. Specifically, instead of hydrogen on alkylene and arylene, halogen, chain or cyclic alkyl group, aryl group, alkenyl group, alkoxy group, aryloxy group, sulfonyl group, amino group, cyano group, carbonyl group, acyl group , An amide group, a hydroxyl group, and a structure in which nitrogen, sulfur, or oxygen is introduced in place of carbon on alkylene and arylene. Furthermore, plural R ^{1 s} may be bonded to each other, and examples thereof include a ligand such as ethylenediaminetetraacetic acid.
[0020]
R ² is preferably good electron-withdrawing groups, particularly good fluorine. When R ² is fluorine, the solubility is improved.
[0021]
X ¹ and X ² are each independently O, and the ligand is bonded to M through these heteroatoms. Here, it is not impossible to combine other than O , but it becomes very complicated in synthesis. Since this compound has a bond of M by X ¹ and X ² in the same ligand, these ligands constitute a chelate structure with M. Due to the effect of this chelate, the heat resistance, chemical stability, and hydrolysis resistance of this compound are improved. The constant q in this ligand is 0 , but in particular, 0 is preferable because this chelate ring becomes a five-membered ring, so that the chelate effect is exerted most strongly and the stability is increased.
[0023]
The constants m and n related to the number of ligands described so far are determined by the type of M at the center, and m is 1 or 2 when M is B, and M is In the case of P, 1, 2 or 3, n is 0 when M is B and m is 2, 0 when M is B and m is 1, 0 when M is P and m is 3, When M is P and m is 2, 2, when M is P and m is 1, it is 4 .
[0024]
Corrosion inhibition of the aluminum laminate film which is the exterior of the battery is suppressed by a method in which the compound represented by the general formula (1) is mixed with LiPF ₆ . LiPF ₆ corrodes the metal or aluminum laminate used for the exterior of the device by generating hydrogen fluoride due to hydrolysis of anions by the entry of a very small amount of moisture into the battery . In addition, this hydrogen fluoride deteriorates the performance and life of the device by reaction with the electrode active material. In the present invention, it is possible to trap the generated hydrogen fluoride by using a mixture of LiPF ₆ and the compound of the general formula (1), and suppress corrosion, performance and deterioration of life. Although the details of the principle are not clear, it is presumed that the compound of the general formula (1) and hydrogen fluoride reacted rapidly and made harmless.
[0025]
The usage ratio of these electrolytes and compounds consists of an electrolyte solution or gel electrolyte using LiPF ₆ as an electrolyte, a positive electrode, a negative electrode, and considering the characteristics and corrosion prevention effect of a battery using an aluminum laminate film for the battery exterior . The concentration of the additive is in the range of 0.001 to 10 mol%, preferably 0.01 to 1 mol% with respect to the electrolyte. When the amount of the compound added is less than 0.001 mol%, the absorption capability of hydrogen fluoride is small, so that the corrosion inhibition effect is small and the cycle characteristics and storage stability are deteriorated. On the other hand, when the amount is more than 10 mol%, gas generation or the like occurs due to side reactions such as decomposition of the compound on the electrode surface.
[0026]
The basic components of an electrochemical device to which the compound of the present invention is applied include an ion conductor, a negative electrode, a positive electrode, a current collector, a separator, and an aluminum laminate film container.
[0027]
As the ionic conductor, a mixture of an electrolyte and a non-aqueous solvent or polymer is used. If a non-aqueous solvent is used, this ionic conductor is generally called an electrolytic solution, and if a polymer is used, it becomes a polymer solid electrolyte. A polymer solid electrolyte containing a non-aqueous solvent as a plasticizer is called a gel electrolyte.
[0028]
The non-aqueous solvent is not particularly limited as long as it is an aprotic solvent capable of dissolving the compound and electrolyte used in the present invention, and examples thereof include carbonates, esters, ethers, lactones, nitriles, amides. And sulfones can be used. Moreover, not only a single solvent but 2 or more types of mixed solvents may be sufficient. A mixed solvent composed of an aprotic solvent having a dielectric constant of 20 or more and an aprotic solvent having a dielectric constant of 10 or less is preferable. Specific examples include propylene carbonate, ethylene carbonate, diethyl carbonate, dimethyl carbonate, methyl ethyl carbonate, dimethoxyethane, acetonitrile, propionitrile, tetrahydrofuran, 2-methyltetrahydrofuran, dioxane, nitromethane, N, N-dimethylformamide, dimethyl sulfoxide. , Sulfolane, and γ-butyrolactone.
[0029]
The polymer mixed with the electrolyte is not particularly limited as long as it is an aprotic polymer capable of dissolving the compound. Examples thereof include polymers having polyethylene oxide in the main chain or side chain, homopolymers or copolymers of polyvinylidene fluoride, methacrylic acid ester polymers, polyacrylonitrile and the like. When a plasticizer is added to these polymers, the above-mentioned aprotic non-aqueous solvent can be used. Electrolyte concentration in these ion conductors in the, 0.1 mol / dm ³ or more, the saturation concentration or less, preferably, 0.5 mol / dm ³ or more and 2.5 mol / dm ³ or less. When the concentration is lower than 0.1 mol / dm ³ , the ionic conductivity is low, which is not preferable.
[0030]
Although it does not specifically limit as a negative electrode material, In the case of a lithium battery, the alloy of lithium metal and lithium and another metal is used. In the case of a lithium ion battery, a material that uses a phenomenon called intercalation such as carbon, natural graphite, or metal oxide obtained by firing a polymer, an organic material, pitch, or the like is used. In the case of an electric double layer capacitor, activated carbon, porous metal oxide, porous metal, conductive polymer, or the like is used.
[0031]
As the cathode material is not particularly limited, a lithium battery and a lithium ion battery, for _{example, LiCoO 2, LiNiO 2, LiMnO} 2, lithium-containing oxides such as _{LiMn 2 O 4, TiO 2,} V 2 O 5, MoO Oxides such as ₃ , sulfides such as TiS ₂ and FeS, or conductive polymers such as polyacetylene, polyparaphenylene, polyaniline, and polypyrrole are used. In the case of an electric double layer capacitor, activated carbon, porous metal oxide, porous metal, conductive polymer, or the like is used.
[0032]
【Example】
EXAMPLES Hereinafter, although an Example demonstrates this invention concretely, this invention is not limited by this Example.
[0033]
Example 1
A solution was prepared by dissolving LiPF ₆ at a concentration of 1.0 mol / l in a mixed solvent of ethylene carbonate 50 vol% and dimethyl carbonate 50 vol%. In this solution,
[0034]
[Chemical 7]
[0035]
An electrolyte solution was prepared by adding a lithium borate derivative having the structure of 0.01 mol / l.
[0036]
Using this electrolytic solution, the corrosion test of the aluminum laminate was performed as in the following procedure. First, 10 ml of the electrolytic solution and a 1 cm square aluminum laminate test piece were put in a fluororesin bottle and sealed. This was left still in a 60 degreeC high temperature tank, and the state of the aluminum laminate was observed. As a result, no change was observed in the aluminum laminate even after 2 weeks, and no corrosion was observed.
[0037]
Next, using this electrolytic solution, a cell was prepared using LiCoO ₂ as a positive electrode material and natural graphite as a negative electrode material, and a battery charge / discharge test was actually performed. The test cell was produced as follows.
[0038]
To 90 parts by weight of LiCoO ₂ powder, 5 parts by weight of polyvinylidene fluoride (PVDF) as a binder and 5 parts by weight of acetylene black as a conductive material were mixed, and N, N-dimethylformamide was further added to form a paste. The paste was applied on an aluminum foil and dried to obtain a test positive electrode body. Further, 90 parts by weight of natural graphite powder was mixed with 10 parts by weight of polyvinylidene fluoride (PVDF) as a binder, and N, N-dimethylformamide was further added to form a slurry. This slurry was applied on a copper foil and dried at 150 ° C. for 12 hours to obtain a test negative electrode body. Then, the electrolyte was immersed in a polyethylene separator to assemble the cell.
[0039]
The constant current charge / discharge test was conducted under the following conditions. Both charging and discharging were performed at a current density of 0.35 mA / cm ² , charging was performed at 4.2 V, discharging was performed at 3.0 V, and a test temperature was 70 ° C. As a result, charging / discharging was repeated 500 times, but the capacity at the 500th time was 80% of the first time.
[0040]
Example 2
A solution was prepared by dissolving LiPF ₆ at a concentration of 1.0 mol / l in a mixed solvent of ethylene carbonate 50 vol% and diethyl carbonate 50 vol%. An electrolytic solution was prepared by adding a lithium borate derivative having the same structure as in Example 1 to this solution so as to be 0.00001 mol / l.
[0041]
The corrosion test of the aluminum laminate similar to Example 1 was implemented using this electrolyte solution. As a result, no change was observed in the aluminum laminate even after 2 weeks, and no corrosion was observed.
[0042]
Example 3
A solution was prepared by dissolving LiPF ₆ at a concentration of 1.0 mol / l in a mixed solvent of ethylene carbonate 50 vol% and ethyl methyl carbonate 50 vol%. In this solution,
[0043]
[Chemical 8]
[0044]
The electrolyte solution which added the lithium phosphate derivative which has the structure of 0.01 mol / l was prepared.
[0045]
The corrosion test of the aluminum laminate similar to Example 1 was implemented using this electrolyte solution. As a result, no change was observed in the aluminum laminate even after 2 weeks, and no corrosion was observed.
[0046]
Comparative Example 1
An electrolytic solution in which 1.0 mol / l of LiPF ₆ was dissolved in a mixed solvent of 50% by volume of ethylene carbonate and 50% by volume of dimethyl carbonate was prepared.
[0047]
The corrosion test of the aluminum laminate similar to Example 1 was implemented using this electrolyte solution. As a result, the aluminum layer part and the resin layer part of the aluminum laminate were peeled after one day.
[0048]
【The invention's effect】
According to the corrosion inhibiting method of the present invention, corrosion of electrochemical devices such as lithium batteries, lithium ion batteries, electric double layer capacitors and the like can be easily suppressed by simply mixing the compound in the electrolytic solution.

Claims (2)

In a battery comprising an electrolytic solution or gel electrolyte using LiPF ₆ as an electrolyte, a positive electrode, a negative electrode, and using an aluminum laminate film for the battery exterior, a general formula (within a range of 0.001 to 10 mol% relative to LiPF ₆ ) A method for inhibiting corrosion of an aluminum laminate film, which is an exterior of the battery, comprising adding at least one of compounds having the chemical structural formula represented by 1).
Where M is B or P ,
A ^{a +} is lithium ion,
a is 1 ,
b is 1 ,
p is b / a,
m is 1 or 2 when M is B, 1, 2 or 3 when M is P ;
n is 0 when M is B and m is 2, when M is B and m is 2, 2 when M is P and m is 3, 0 when M is P and m is 2, , When M is P and m is 1, 4 ,
q represents 0 ,
R ² is fluorine,
X ^1, X ² represents O, respectively.   A battery using the corrosion inhibiting method according to claim 1.