JP6871008B2 - Electrolytes for lithium-ion secondary batteries, electrolytes for lithium-ion secondary batteries using them, and lithium-ion secondary batteries - Google Patents

Description

The present invention relates to an electrolyte for a non-aqueous secondary battery, an electrolyte solution using the same, and a battery.

Lithium-ion secondary batteries are characterized by higher energy density and electromotive force than lead-acid batteries and nickel-metal hydride batteries, and are therefore widely used as power sources for mobile phones and laptop computers that require smaller size and lighter weight. ing. Most of these lithium ion secondary batteries use a non-aqueous electrolyte solution in which a lithium salt is dissolved in an organic solvent as an electrolyte.

Although many studies have been conducted on various compounds using such a lithium salt as an electrolyte, lithium hexafluorophosphate (LiPF ₆ ), which has been put into practical use as an electrolyte for lithium batteries, has heat resistance and hydrolysis resistance. It has a problem of being inferior in sex. Therefore, Patent Document 1 proposes an electrolyte for an electrochemical device having a chemical structural formula represented by the following general formula (X).

In the general formula (X), M is B or P, A ^{a +} is Li ion, a is 1, b is 1, p is 1, m is 1-2, n is 1-4, q is 0 or represents 1 respectively, ^{R 1} _is, C 1 _-C alkylene _10, C 1 _-C halogenated _{10 alkylene,} C 6 _{-C 20} arylene or _C 6 _{-C 20} arylene halide (and their alkylene, arylene substituent group in its structure, may have a hetero atom, and R ¹ to m number present may be linked respectively.), R ² is halogen, X ^1, X ² is a O Each is shown.

Japanese Patent No. 3722685

The electrolyte of Patent Document 1 has improved heat resistance and hydrolysis resistance as compared with the conventional electrolyte, and enables a battery using the electrolyte.
However, in a lithium ion secondary battery, it is required to improve the number of cycles (cycle characteristics) that can be repeatedly charged and discharged.

The present invention has been made in view of the above circumstances, and an object of the present invention is an electrolyte for a non-aqueous secondary battery, an electrolyte solution using the same, and a battery, which are superior in cycle characteristics to conventional electrolytes.

In order to solve the above problems, the present invention has the following aspects.
[1] An electrolyte for a non-aqueous secondary battery represented by the general formula (I).

In the general formula (I), M represents B, Al, Ga, P, As or Sb, r represents the number 0 <r <1, m is 1-2, n is 1-4, q. represents an integer of 0 or 1, ^{R 1} _is, C 1 _-C alkylene _10, C 1 _-C halogenated _{10 alkylene,} C 6 _{-C 20} arylene or _C 6 _{-C 20} arylene halide (such The alkylene and arylene of the above may have a substituent or a heteroatom in the structure), R ² represents a halogen, and X ¹ , X ² represents O, S, Se or N, respectively. Represent.

[2] The electrolyte for a non-aqueous secondary battery according to [1], wherein q is 0.
[3] The electrolyte for a non-aqueous secondary battery according to [1] or [2], ^{wherein X 1} and X ^{2 are O.}
[4] The electrolyte for a non-aqueous secondary battery according to any one of [1] to [3], wherein r satisfies the following formula (1).
2.0 × ^10-6 ≦ r ≦ 1.0 × 10 ^-2 ... (1)
[5] An electrolytic solution containing the electrolyte for a non-aqueous secondary battery according to any one of [1] to [4] and a non-aqueous solvent.
[6] The electrolytic solution according to [5], wherein the concentration of the electrolyte for a non-aqueous secondary battery is 0.005 to 1.5 mol / L.
[7] The electrolytic solution according to [5] or [6], _{further comprising LiPF 6.}
[8] A battery having a positive electrode, a negative electrode, and the electrolytic solution according to any one of [5] to [7].

According to the present invention, it is possible to provide an electrolyte for a non-aqueous secondary battery, an electrolyte solution using the same, and a battery, which are superior in cycle characteristics to conventional electrolytes.

The electrolyte for a non-aqueous secondary battery of the present embodiment (hereinafter, also referred to as “electrolyte of the general formula (I)”) has an ionic metal complex structure, and M at the center thereof is a transition metal and a period. It is selected from the 13th or 15th group elements of the periodic table. It is preferably any of Al, B, Ga, P, As or Sb, and more preferably B (boron) or P (phosphorus). It is possible to use various elements as the central M, but in the case of Al, B, Ga, P, As, or Sb, synthesis is relatively easy, and in the case of B or P, synthesis is possible. In addition to its ease of use, it has excellent properties in all aspects such as low toxicity, stability, and cost.

Next, the portion of the ligand that is characteristic of the ionic metal complex in the electrolyte of the general formula (I) will be described. Hereinafter, in the present specification, the organic or inorganic portion bound to M is referred to as a ligand.

^{R 1} in the general formula (I) is an alkylene having 1 to 10 carbon atoms (hereinafter _{abbreviated as C 1 to} C ₁₀ ), a halogenated alkylene having _{C 1 to} C ₁₀ , and an arylene having _{C 6 to} C _20. And _{selected from C 6 to} C ₂₀ halogenated arylene, these alkylene and arylene may have substituents, heteroatoms in their 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. , Ami groups, hydroxyl groups, and structures in which nitrogen, sulfur, and oxygen are introduced instead of carbon on alkylene and arylene can be mentioned.
The ^{constant q attached to R 1} represents an integer of 0 or 1. ^{When q is 1, R 1} in the general formula (I) has the above-mentioned structure and the like, but when q is 0, it has a structure in which two carbonyl carbons are directly bonded (for example, chemical formula (II)). Compound). When q is 0, the cyclic structure containing M becomes a five-membered ring, so that the chelating effect described later is most strongly exerted and the chemical stability is increased, which is preferable.

^{R 2} in the general formula (I) represents a halogen, and fluorine is particularly preferable. When R ² is fluorine, the ionic conductivity becomes very high due to the effect of improving the dissociation degree of the electrolyte due to its strong electron attraction and improving the mobility due to the decrease in size.

^{X 1} , X ² in the general formula (I) are independently O, S, Se or N, respectively, and the ligand is bonded to M via these heteroatoms. X ¹ and X ² are preferably O because they are easy to synthesize. Since the characteristic of this compound is the ^{bond of M by X 1} and X ² in the same ligand, these ligands form a chelate structure with M. Due to the effect of forming this chelate structure (chelate effect), the heat resistance, chemical stability, and hydrolysis resistance of this compound are improved.

The integers m and n related to the number of ligands described so far are determined by the type of M at the center, but m is preferably 1 to 2, and n is preferably 1 to 4.

The electrolyte of the general formula (I) contains both lithium and sodium as cation species. By containing sodium in addition to lithium in the cation species of the electrolyte of the general formula (I), it is possible to improve the cycle characteristics when the battery is used.

r is the sodium abundance ratio (Na / Li ratio in the solid electrolyte) when the sum of the molar abundance ratios of lithium and sodium is 1. Since the electrolyte of the general formula (I) contains both lithium and sodium as cation species, r is greater than 0 and less than 1 (0 <r <1). Usually, lithium ions are much more abundant in the electrolytic solution obtained by dissolving the electrolyte of the general formula (I) in an organic solvent, so that (1-r) >> r.

r preferably satisfies the following formula (1).
2.0 × ^10-6 ≦ r ≦ 1.0 × 10 ^-2 ... (1)
When r is at least the lower limit value, there is an advantage that a high capacity retention rate, a high capacity expression rate, or both can be enabled, and when r is below the upper limit value, a high volume expression rate is possible. There is an advantage to do.

The compound represented by the general formula (I) of the present invention has a strong electron-withdrawing carbonyl group (C = O group), so that the anion is stabilized and the charge of the anion and the cation can be easily separated. Become. That is, the anion and the cation are easily dissociated.
There are innumerable salts called electrolytes, but most of them dissolve and dissociate in water to conduct ionic conduction. However, in many cases, it does not even dissolve in an organic solvent other than water. Although such an aqueous solution can be used as an electrolytic solution, there are many restrictions because the decomposition potential of water as a solvent is low and it is vulnerable to redox. For example, in a lithium battery or the like, since the potential difference between the electrodes of the device is 3 V or more, water is electrolyzed into hydrogen and oxygen. On the other hand, many organic solvents and polymers are more resistant to redox than water due to their structure, and are therefore used in devices that require high voltage, such as lithium batteries and electric double layer capacitors.

As described above, the electrolyte of the general formula (I) is very easily dissolved in an organic solvent and easily dissociated due to the effect of the C = O group and the effect of increasing the anion size as compared with the conventional electrolyte. Therefore, the solution with these organic solvents can be used as an excellent ionic conductor for devices such as lithium batteries. In general, organic and metal complexes are susceptible to hydrolysis and are often chemically unstable. On the other hand, since the electrolyte of the general formula (I) has a chelate structure, it is very stable, is not easily hydrolyzed, and has excellent hydrolysis resistance. In addition, those having fluorine in the chemical structure represented by the general formula (I) have improved ionic conductivity due to their strong electron attraction effect, and further increased chemical stability such as oxidation resistance. preferable.

As described above, the electrolyte of the general formula (I) can be used as an electrolyte for an electrochemical device such as a lithium ion battery or an electric double layer capacitor.

The method for synthesizing the electrolyte of the general formula (I) is not particularly limited, but for example, in the case of the compound of the chemical formula (II) shown below, LiBF ₄ and a trace amount of NaBF ₄ , 2 in a non-aqueous solvent It can be synthesized by reacting a double molar lithium alkoxide and then adding oxalic acid to replace the alkoxide bonded to boron with oxalic acid.
The abundance ratio r of sodium in the electrolyte is adjusted by, for example, the amount of _{NaBF 4} added when the electrolyte of the general formula (I) is synthesized by the method described above.
As the sodium source, an electrolyte containing sodium as a sodium source can be used. For example, in addition to the above NaBF ₄ , (COO) ₂ Na ₂ , NaClO _{4 and the} like can be mentioned.

The battery of this embodiment is a battery having a positive electrode, a negative electrode, and an electrolytic solution.
The electrolytic solution of the present embodiment contains the electrolyte of the general formula (I) and a non-aqueous solvent.
The battery of the present embodiment can have the same configuration as the conventional lithium ion secondary battery except that the electrolyte of the general formula (I) is used. For example, an ion conductor, a positive electrode, a negative electrode, a separator and a container. Etc. are provided.

As the ionic conductor, a mixture of an electrolyte and a non-aqueous solvent or a 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. Polymer solid electrolytes also include those containing a non-aqueous solvent as a plasticizer. As the electrolytes listed here, the electrolyte of the general formula (I) is used in one kind or a mixture of two or more kinds. When two or more kinds of electrolytes are mixed, an electrolyte (other electrolyte) that does not correspond to the general formula (I) may be contained. In this case, one kind always contains the electrolyte of the general formula (I). As other electrolytes, general lithium salts such as LiClO ₄ , LiPF ₆ , LiBF ₄ , LiCF ₃ SO ₃ , LiN (CF ₃ SO ₂ ) ₂ and LiSbF ₆ can also be used. _{LiPF 6} is preferable from the viewpoint that the battery can have a high voltage and a high energy density.

The electrolytic solution of the present embodiment contains the electrolyte of the general formula (I) and a non-aqueous solvent. The method for producing the electrolytic solution of the present embodiment is not particularly limited. For example, the electrolyte of the general formula (I) is weighed in a predetermined amount, mixed with a non-aqueous solvent such as ethylene carbonate, and stirred at an arbitrary temperature for an arbitrary time. By doing so, an electrolytic solution can be obtained.
According to this method, it is not necessary to separately add sodium ions to the electrolytic solution, and an electrolytic solution having an appropriate sodium ion concentration can be easily prepared.
The sodium ion concentration in the electrolytic solution is preferably 0.01 to 15000 μM, more preferably 0.02 to 15000 μM, and even more preferably 0.2 to 10000 μM. When the sodium ion concentration in the electrolytic solution is within the above range, the cycle characteristics of the battery can be more easily improved.

When the ionic conductor is an electrolytic solution, the concentration of the electrolyte of the general formula (I) is preferably 0.005 to 1.5 mol / L (hereinafter, may be abbreviated as M), and 0.01 to 1. 5M is more preferable, and 0.1 to 1M is even more preferable. When the concentration of the electrolyte of the general formula (I) is at least the above lower limit value, it is easy to improve the cycle characteristics of the battery and the storage stability of the electrolytic solution. When it is not more than the upper limit value, it is easy to suppress the generation of gas due to a side reaction such as decomposition of the electrolyte on the electrode surface.

When two or more kinds of electrolytes are contained in the electrolytic solution, the concentration of the other electrolyte is preferably 0.01 to 2M, more preferably 0.05 to 1.5M, still more preferably 0.1 to 1M. When the concentration of other electric field qualities is at least the above lower limit value, the energy density of the battery can be easily improved. When the concentration of the other electrolyte is not more than the upper limit value, it is easy to suppress the generation of gas due to a side reaction such as decomposition of the electrolyte on the electrode surface.

When two or more kinds of electrolytes are contained in the electrolytic solution, the total concentration of the electrolyte of the general formula (I) and the concentration of other electrolytes is preferably 0.015 to 3.5M, more preferably 0.06 to 3M. , 0.2-2.5M is more preferable. When the sum of the concentration of the electrolyte of the general formula (I) and the concentration of other electrolytes is at least the above lower limit value, it is easy to improve the cycle characteristics of the battery, the storage stability of the electrolytic solution, and the energy density of the battery. When the total concentration of the electrolyte of the general formula (I) and the concentration of other electrolytes is not more than the upper limit value, it is easy to suppress the generation of gas due to a side reaction such as decomposition of the electrolyte on the electrode surface.

The non-aqueous solvent is not particularly limited as long as it is an aprotonic solvent capable of dissolving the electrolyte of the general formula (I), and for example, carbonates, esters, ethers, lactones, nitriles, and amides. Classes, sulfones, etc. can be used. Moreover, not only a single solvent but also two or more kinds of mixed solvents may be used. 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, and dimethyl sulfoxide. , Sulfolane, γ-butyrolactone and the like.

The polymer to be mixed with the electrolyte is not particularly limited as long as it is an aprotic polymer in which the electrolyte of the general formula (I) is dispersed. For example, polymers having a polyethylene oxide in the main chain or side chains, homopolymers or copolymers of polyvinylidene fluoride, methacrylic acid ester polymers, polyacrylonitrile and the like can be mentioned. When adding a plasticizer to these polymers, the above-mentioned aprotic non-aqueous solvent can be used. The electrolyte concentration of the general formula (I) in these ionic conductors is preferably 0.1 M or more and a saturated concentration or less, and more preferably 0.5 M or more and 1.5 M or less. When the electrolyte concentration of the general formula (I) is at least the lower limit value, the ionic conductivity is likely to be improved, and when it is at least the upper limit value, the stability of the ionic conductor is likely to increase.

In the battery of the present embodiment, the material of the positive electrode is not particularly limited, but transition metal oxides such as lithium cobalt oxide, lithium nickel oxide, lithium manganate, and olivine-type lithium iron phosphate can be exemplified, and the group consisting of these materials can be exemplified. It is preferably one or more selected.

In the battery of the present embodiment, the material of the negative electrode is not particularly limited, but metallic lithium, a lithium alloy, a carbon-based material capable of occluding and releasing lithium, a metal oxide, and the like can be exemplified and selected from the group consisting of these materials. It is preferably one or more.

In the battery of the present embodiment, the material of the separator is not particularly limited, but a microporous polymer film, a non-woven fabric, a glass fiber and the like can be exemplified, and it is preferable that the material is one or more selected from the group consisting of these materials. ..

The shape of the battery of the present embodiment is not particularly limited, and can be adjusted to various shapes such as a cylindrical type, a square type, a coin type, and a sheet type.

The battery of the present embodiment may be manufactured according to a known method, for example, in a glove box or in a dry air atmosphere using the electrolyte of the general formula (I), the electrolytic solution and the electrodes.

Next, the present invention will be described in more detail by way of examples, but the present invention is not limited to these examples.

[Manufacturing Example 1]
Solution Y was prepared by dissolving 27.4 g of lithium tetrafluoroborate (LiBF ₄ ) and 0.013 mg of sodium tetrafluoroborate (NaBF ₄ ) in acetonitrile at room temperature to make 200 g. When adjusting the solution _Y, NaBF 4 100μL weighed the solution was dissolved in acetonitrile 200 g 13 mg, with NaBF ₄ 1000-fold diluted solution was 100mL acetonitrile was added. Hereinafter, the same applies to the production example using _{NaBF 4.} 5.09 g of lithium hexafluoroisopropoxide (LiOCH (CF ₃ ) ₂ ) was slowly added to 10 g of the solution Y. Then, the reaction was carried out by stirring at 60 ° C. for 3 hours. At this time, lithium fluoride was precipitated. To the reaction solution thus obtained, 1.31 g of oxalic acid was added, and the mixture was stirred at 60 ° C. for 1 hour for reaction. Next, this reaction solution was filtered to separate lithium fluoride and sodium fluoride, and the solvent of the obtained filtrate ^{was removed under reduced pressure conditions of 60 ° C. and 10 -1} Pa to obtain 1.90 g of a white solid. Was done. By drying this solid at 100 ° C. under ^{a reduced pressure condition of 10 -1} Pa for 24 hours, lithium sodium difluoro (oxalate) borate represented by the chemical formula (II) (hereinafter, abbreviated as Li · NaDFOB). The symbol of 1 indicates that lithium and sodium coexist in the molecule.) 1.90 g (yield: 91%) was obtained. The electrolyte obtained in this production example is designated as A-1. The sodium abundance ratio r of the obtained electrolyte A-1 was measured by cation chromatography (manufactured by Dionex, trade name: ICS-1500) and found to be 2 ppm. In addition, ppm in this specification represents the abundance ratio of sodium (Na / Li ratio in a solid electrolyte) when the sum of the abundance ratios of lithium and sodium on a molar basis is 1.

[Manufacturing Example 2]
A mixed solvent (EC / DEC = 3/7 (volume ratio)) of ethylene carbonate (EC) and diethyl carbonate (DEC) as a non-aqueous solvent was weighed into a sample bottle, and the electrolyte A-1 obtained in Production Example 1 was obtained. In addition, the concentration of Li / NaDFOB was 0.1 M, _{the concentration of LiPF 6} was 1 M, and the mixture was mixed at 23 ° C. and stirred to obtain an electrolytic solution E-1.

[Manufacturing Example 3]
The amount of NaBF _{4 to be} added was 0.13 mg, and an electrolyte A-2 was obtained in the same manner as in Production Example 1. The sodium abundance ratio r of the obtained electrolyte A-2 was measured and found to be 20 ppm. An electrolytic solution E-2 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte A-2.

[Manufacturing Example 4]
200.0 g of lithium hexafluorophosphate and 4.4 mg of sodium hexafluorophosphate were dissolved in ethyl methyl carbonate to prepare a solution Z of 800 g, and 12.1 g of oxalic acid was added to 80 g of the solution Z and stirred. Next, 10.9 g of silicon tetrachloride was introduced over 1 hour. After completion of the introduction, stirring was continued for 1 hour, the pressure was reduced, 15 g of the solvent was distilled off, and dissolved hydrogen chloride and silicon tetrafluoride were removed. The obtained solid was purified with ethyl methyl carbonate / hexane to obtain lithium sodium tetrafluoro (oxalate) phosphate (hereinafter abbreviated as Li · NaTFOP. Chemical formula (III)). The obtained electrolyte is designated as B-1. The sodium abundance ratio r of the obtained electrolyte B-1 was measured and found to be 20 ppm. An electrolytic solution F-1 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte B-1.

［製造例５］
ヘキサフルオロリン酸リチウム２００．０ｇ、ヘキサフルオロリン酸ナトリウム４．４ｍｇをエチルメチルカーボネートに溶解して８００ｇとした溶液Ｚを作成し、溶液Ｚ８０ｇに、シュウ酸を２４．３ｇ仕込み、攪拌した。次に四塩化ケイ素２２．４ｇを１時間かけて導入した。導入終了後、１時間攪拌を継続したのち、反応器を減圧にし、溶媒を１５ｇ留去し、溶存する塩化水素、四フッ化ケイ素を除去した。得られた固体をエチルメチルカーボネート／ヘキサンで精製し、ジフルオロビス（オキサラト）リン酸リチウムナトリウム（以下、Ｌｉ・ＮａＤＦＯＰと略記する。化学式（ＩＶ）。）を得た。得られた電解質をＣ−１とする。得られた電解質Ｃ−１のナトリウムの存在比率ｒを測定したところ、２０ｐｐｍであった。添加する電解質を電解質Ｃ−１に変更した以外は、製造例２と同様にして電解液Ｇ−１を得た。

[Manufacturing Example 5]
200.0 g of lithium hexafluorophosphate and 4.4 mg of sodium hexafluorophosphate were dissolved in ethyl methyl carbonate to prepare a solution Z of 800 g, and 24.3 g of oxalic acid was added to 80 g of the solution Z and stirred. Next, 22.4 g of silicon tetrachloride was introduced over 1 hour. After completion of the introduction, stirring was continued for 1 hour, the pressure was reduced, 15 g of the solvent was distilled off, and dissolved hydrogen chloride and silicon tetrafluoride were removed. The obtained solid was purified with ethyl methyl carbonate / hexane to obtain lithium sodium difluorobis (oxalate) phosphate (hereinafter abbreviated as Li · NaDFOP; chemical formula (IV)). The obtained electrolyte is designated as C-1. The sodium abundance ratio r of the obtained electrolyte C-1 was measured and found to be 20 ppm. An electrolytic solution G-1 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte C-1.

[Manufacturing Example 6]
The amount of sodium hexafluorophosphate to be added was 22 mg, and the electrolyte C-2 was obtained in the same manner as in Production Example 5. The sodium ion abundance ratio (r) of the obtained electrolyte C-2 was measured and found to be 100 ppm. An electrolytic solution G-2 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte C-2.

[Manufacturing Example 7]
An electrolytic solution E-3 was obtained in the same manner as in Production Example 3 except that the concentration of Li / NaDFOB was adjusted to 1 M.

[Manufacturing Example 8]
The electrolyte A-2 obtained in Production Example 3 was added so that the concentration of Li / NaDFOB was 2M and the concentration of _{LiPF 6 was 1M.} , Undissolved component remained, and the electrolytic solution was not uniform.

[Manufacturing Example 9]
6.0 g of oxalic acid was diluted with water to make a 200 ml solution, and 10.44 g of boric acid was diluted with water to make a 130 ml solution, and the respective solutions were mixed. 60 ml of a 2.8 M aqueous sodium hydroxide solution was slowly added thereto. Then, the reaction was carried out by stirring at 55 ° C. for 12 hours. The reaction solution thus obtained was cooled, and the precipitated solid was filtered to obtain sodium bis (oxalate) borate. The obtained sodium bis (oxalate) borate was recrystallized from acetonitrile to obtain purified sodium bis (oxalate) borate. Commercially available lithium bis (oxalate) oxalate was added thereto to obtain sodium bis (oxalate) oxalate (hereinafter abbreviated as Li · NaBOB. Chemical formula (V)). The obtained electrolyte is designated as D-1. The sodium abundance ratio r of the obtained electrolyte D-1 was measured and found to be 20 ppm. An electrolyte solution H-1 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte D-1 so that the concentration of Li / NaBOB was 0.05 M.

[Manufacturing Example 10]
The amount of NaBF _{4 to be} added was 0.0007 mg, and the electrolyte A-3 was obtained in the same manner as in Production Example 1. The sodium abundance ratio r of the obtained electrolyte A-3 was measured and found to be 0.1 ppm. An electrolyte solution E-4 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to the electrolyte A-3.

[Manufacturing Example 11]
The amount of NaBF _{4 to be} added was 0.007 mg, and an electrolyte A-4 was obtained in the same manner as in Production Example 1. The sodium abundance ratio r of the obtained electrolyte A-4 was measured and found to be 1 ppm. Electrolyte E-5 was obtained in the same manner as in Production Example 2 except that the electrolyte to be added was changed to electrolyte A-4.

The lithium ion secondary batteries (sheet-type laminated batteries) in the examples and comparative examples shown below were all manufactured in a dry box or a vacuum desiccator.

[Example 1]
A slurry consisting of 100 parts by mass of a solid component containing a positive electrode active material, 5 parts by mass of carbon black as a conductive auxiliary agent, 5 parts by mass of polyvinylidene fluoride as a binder, and NMP as a solvent are mixed to form a solid content of 45. After adjusting to%, it was applied to an aluminum foil, pre-dried, and then vacuum dried at 120 ° C. The electrode was pressure-pressed at 4 kN and further punched to a 40 mm square of the electrode size to prepare a positive electrode.
A slurry consisting of 100 parts by mass of a solid component containing a negative electrode active material, 1.5 parts by mass of styrene-butadiene rubber as a binder, 1.5 parts by mass of sodium carboxymethyl cellulose as a thickener, and an aqueous solvent was mixed. After adjusting to a solid content of 50%, the slurry was applied to a copper foil and dried at 100 ° C. The electrode was pressure-pressed at 2 kN and further punched to a 42 mm square electrode size to prepare a negative electrode.
A positive electrode, a negative electrode, and a separator were laminated, and the electrolytic solution E-1 obtained in Production Example 2 was injected and sealed to prepare a sheet-type laminated battery. When the battery was evaluated, the initial discharge capacity was 50 mAh.

[Examples 2 to 6, Comparative Examples 1 to 4]
A laminated battery was produced in the same manner as in Example 1 using each of the electrolytic solutions shown in Tables 1 and 2. In Comparative Example 1, a laminated battery could not be produced because an electrolytic solution could not be obtained.

The laminated batteries of the above Examples and Comparative Examples were charged to 4.2 V at a current value of 1 C at 25 ° C., and then discharged to 2.7 V at a current value of 1 C. This charge / discharge cycle was repeated, and the capacity retention rate (%) after repeating 1000 cycles and the capacity expression rate (%) at rate 2C were measured, and the cycle characteristics and rate characteristics were evaluated. The results are shown in Tables 1-2. In the table, reference numerals such as DFOB represent abbreviations for anion species in the electrolyte of the general formula (I).

As shown in Tables 1 and 2, the cycle characteristics of Examples 1 to 6 to which the present invention was applied were 75% or more. Further, in Examples 1 to 6, the rate characteristics were all 85% or more.
On the other hand, in Comparative Example 2 in which an electrolyte containing no halogen as the anion of the general formula (I) was used, the cycle characteristics were as low as 66% and the rate characteristics were as low as 70%.
In Comparative Examples 3 to 4 in which the sodium abundance ratio r was less than 2 ppm, the cycle characteristics were 71% or less.

According to the present invention, it has been found that it is possible to provide an electrolyte for a non-aqueous secondary battery, an electrolyte solution using the same, and a battery, which are superior in cycle characteristics to conventional electrolytes.

The present invention can be used in the field of lithium ion secondary batteries.

Claims (6)

An electrolyte for a lithium ion secondary battery represented by the general formula (I), wherein the following r satisfies the following formula (1).

[In the general formula (I), M represents B, Al, Ga, P, As or Sb, r represents a number of 0 <r <1, m represents 1-2, n represents 1-4, q represents an integer of 0 or 1, ^{R 1} _is, C 1 _-C alkylene _10, C 1 _-C halogenated _{10 alkylene,} arylene halide arylene or _C 6 _{-C 20} in C 6 _{-C 20} ( These alkylene and arylene may have a substituent or a heteroatom in the structure), R ² represents halogen, and X ¹ , X ² represents O, S, Se or N. Represent each. ]
2.0 × ^10-6 ≦ r ≦ 1.0 × 10 ^-2 ... (1) The electrolyte for a lithium ion secondary battery according to claim 1, wherein q is 0. The electrolyte for a lithium ion secondary battery according to claim 1 or 2, wherein X ¹ and X ^{2 are O.} The electrolyte for a lithium ion secondary battery according to any one of claims 1 to 3 and a non-aqueous solvent are contained.
An electrolytic solution for a lithium ion secondary battery, characterized in that the concentration of the electrolyte for the lithium ion secondary battery is 0.005 to 1.5 mol / L. The electrolytic solution for a lithium ion secondary battery according to claim 4 _{, further comprising LiPF 6.} The positive electrode, the lithium ion secondary battery characterized by having a negative electrode and claim 4 or a lithium ion secondary battery electrolyte according to 5.