JP2018133146A - Non-aqueous secondary battery electrolyte, electrolytic solution using the same, and battery - Google Patents

Abstract

［ＭはＢ、Ａｌ、Ｇａ、Ｐ、Ａｓ又はＳｂ；０＜ｒ＜１；ｍは１又は２；ｎは１〜４の整数；ｑは０又は１；Ｒ^１はＣ_１〜Ｃ_１０のアルキレン、Ｃ_１〜Ｃ_１０のハロゲン化アルキレン、Ｃ_６〜Ｃ_２０のアリーレン又はＣ_６〜Ｃ_２０のハロゲン化アリーレン（前記アルキレン及びアリーレンは、その構造中に置換基、ヘテロ原子を持っていてもよい）；Ｒ^２はハロゲン；Ｘ^１及びＸ^２は夫々独立にＯ、Ｓ、Ｓｅ又はＮ］
【選択図】なしAn electrolyte for a non-aqueous secondary battery having excellent cycle characteristics, an electrolytic solution using the electrolyte, and a battery are provided. .
An electrolyte for a non-aqueous secondary battery represented by the formula (I).

[M is B, Al, Ga, P, As or Sb; 0 <r <1; m is 1 or 2; n is an integer of 1 to 4; q is 0 or 1; R ¹ is C _{1 to} C ₁₀ Alkylene, C ₁ -C ₁₀ halogenated alkylene, C ₆ -C ₂₀ arylene, or C ₆ -C ₂₀ halogenated arylene (the alkylene and arylene may have a substituent or a hetero atom in the structure thereof) R ² is halogen; X ¹ and X ² are each independently O, S, Se or N].
[Selection figure] None

Description

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

  Lithium ion secondary batteries are characterized by high energy density and electromotive force compared to lead-acid batteries and nickel metal hydride batteries, so they are widely used as power sources for mobile phones and laptop computers that require small size and light weight. ing. In these lithium ion secondary batteries, those using a nonaqueous electrolytic solution in which a lithium salt is dissolved in an organic solvent are used as an electrolyte.

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

In 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 to 2, n is 1 to 4, and q is 0 or Each represents 1 and R ¹ is a C _{1 to} C ₁₀ alkylene, a C _{1 to} C ₁₀ halogenated alkylene, a C _{6 to} C ₂₀ arylene, or a C _{6 to} C ₂₀ halogenated arylene (these alkylene and Arylene may have a substituent or a hetero atom in its structure, and m R ^{1 s} may be bonded to each other.), R ² is halogen, X ¹ , X ² is O Each is shown.

Japanese Patent No. 372285

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

  This invention is made | formed in view of the said situation, Comprising: Compared with the conventional electrolyte, it aims at the electrolyte for non-aqueous secondary batteries excellent in cycling characteristics, the electrolyte solution using the same, and a battery.

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 general formula (I), M represents B, Al, Ga, P, As, or Sb, r represents a number of 0 <r <1, m is 1 to 2, n is 1 to 4, q Represents an integer of 0 or 1, and R ¹ represents a C _{1 to} C ₁₀ alkylene, a C _{1 to} C ₁₀ halogenated alkylene, a C _{6 to} C ₂₀ arylene, or a C _{6 to} C ₂₀ halogenated arylene (these In the structure may have a substituent or a hetero atom, R ² represents halogen, and X ¹ and X ² represent 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 nonaqueous secondary batteries according to any one of [1] to [3], wherein the r satisfies the following formula (1).
2.0 × 10 ⁻⁶ ≦ r ≦ 1.0 × 10 ⁻² (1)
[5] An electrolytic solution containing the nonaqueous secondary battery electrolyte according to any one of [1] to [4] and a nonaqueous solvent.
[6] The electrolyte 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 electrolyte solution according to [5] or [6], further including LiPF ₆ .
[8] A battery comprising a positive electrode, a negative electrode, and the electrolytic solution according to any one of [5] to [7].

  ADVANTAGE OF THE INVENTION According to this invention, compared with the conventional electrolyte, the electrolyte for non-aqueous secondary batteries excellent in cycling characteristics, the electrolyte solution using the same, and a battery can be provided.

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

  Next, the part 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, an organic or inorganic part bonded 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 C _{1 to} C ₁₀ halogenated alkylene, or a C _{6 to} C ₂₀ arylene. And C ₆ -C ₂₀ halogenated arylene, these alkylene and arylene 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.
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-described structure or 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 is a five-membered ring, so that the chelate effect described later is most exerted and chemical stability is increased, which is preferable.

R ² in the general formula (I) represents halogen, and fluorine is particularly preferable. When R ² is fluorine, the ion conductivity is very high due to the effect of improving the dissociation of the electrolyte due to its strong electron-withdrawing property and improving the mobility due to the reduction in size.

X ¹ and X ² in the general formula (I) are each independently O, S, Se, or N, and the ligand is bonded to M through these heteroatoms. X ¹ and X ² are preferably O because of easy 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 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, and m is preferably 1 to 2, and n is preferably 1 to 4.

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

  r is the abundance ratio of sodium (Na / Li ratio in the solid electrolyte) when the total of the abundance ratios of lithium and sodium on a molar basis 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, in the electrolytic solution in which the electrolyte of the general formula (I) is dissolved in an organic solvent, lithium ions are much more present, and therefore (1-r) >> r.

r preferably satisfies the following formula (1).
2.0 × 10 ⁻⁶ ≦ r ≦ 1.0 × 10 ⁻² (1)
If r is equal to or higher than the lower limit, there is an advantage that a high capacity retention rate, a high capacity development rate, or both can be achieved, and if it is equal to or less than the upper limit value, a high capacity development rate is possible. There is an advantage of doing.

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 cation are easily dissociated.
There are countless salts called electrolytes, but most of them dissolve and dissociate in water to conduct ions. However, it often does not even dissolve in organic solvents other than water. Such an aqueous solution can also be used as an electrolytic solution, but there are many restrictions because the decomposition potential of water as a solvent is low and the compound is weak against oxidation and reduction. 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, organic solvents and polymers are more resistant to redox than water due to their structures, and are therefore used in devices that require high voltage, such as lithium batteries and electric double layer capacitors.

  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 as described above. For this reason, the solution with these organic solvents can be used as an excellent ionic conductor of a device such as a lithium battery. 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, hardly receives hydrolysis, etc., and has excellent hydrolysis resistance. In addition, those having fluorine in the chemical structure represented by the general formula (I) have improved ionic conductivity and chemical stability such as oxidation resistance due to their strong electron withdrawing effect, and more preferable.

  As described above, the electrolyte of the general formula (I) can be used as an electrolyte for electrochemical devices such as lithium ion batteries and electric double layer capacitors.

The method for synthesizing the electrolyte of the general formula (I) is not particularly limited. For example, in the case of the compound of the following chemical formula (II), LiBF ₄ and a trace amount of NaBF ₄ , 2 in a non-aqueous solvent After reacting a double mole of lithium alkoxide, oxalic acid is added, and the alkoxide bonded to boron is replaced 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 electrolyte solution.
The electrolytic solution of this embodiment contains the electrolyte of general formula (I) and a nonaqueous solvent.
The battery of this embodiment can have the same configuration as a 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 And so on.

As the ionic conductor, an electrolyte and a nonaqueous solvent or a mixture of polymers are 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 what is called a polymer solid electrolyte. The polymer solid electrolyte includes those containing a non-aqueous solvent as a plasticizer. As the electrolyte mentioned 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 electrolytes) not corresponding to the general formula (I) may be included. In this case, one type 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 of allowing the battery to have a high voltage and high energy density.

The electrolytic solution of this embodiment contains the electrolyte of general formula (I) and a nonaqueous solvent. The method for producing the electrolytic solution of the present embodiment is not particularly limited. For example, a predetermined amount of the electrolyte of the general formula (I) is weighed, mixed with a nonaqueous solvent such as ethylene carbonate, and stirred at an arbitrary temperature for an arbitrary time. By doing so, an electrolytic solution is 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 still more preferably 0.2 to 10,000 μM. When the sodium ion concentration in the electrolytic solution is within the above range, the cycle characteristics of the battery can be further 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 sometimes abbreviated as M), and 0.01 to 1. 5M is more preferable and 0.1-1M is further more preferable. If the concentration of the electrolyte of the general formula (I) is equal to or higher than the lower limit value, it is easy to improve the cycle characteristics of the battery and the storage stability of the electrolytic solution. If it is below the upper limit value, it is easy to suppress the generation of gas due to side reactions 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 electrolytes is preferably 0.01 to 2M, more preferably 0.05 to 1.5M, and further preferably 0.1 to 1M. If the density | concentration of another electric quality is more than the said lower limit, it will be easy to improve the energy density of a battery. If the concentration of the other electrolyte is less than or equal to the above upper limit value, it is easy to suppress generation of gas due to side reactions such as decomposition of the electrolyte on the electrode surface.

  When the electrolyte contains two or more kinds of electrolytes, the total concentration of the electrolyte of the general formula (I) and other electrolytes is preferably 0.015 to 3.5M, more preferably 0.06 to 3M. 0.2 to 2.5M is more preferable. When the total concentration of the electrolyte of the general formula (I) and other electrolytes is equal to or higher than the 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. If the total concentration of the electrolyte of the general formula (I) and other electrolytes is not more than the above upper limit value, it is easy to suppress the generation of gas due to side reactions such as decomposition of the electrolyte on the electrode surface.

  The non-aqueous solvent is not particularly limited as long as it is an aprotic solvent capable of dissolving the electrolyte of the general formula (I). For example, 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. 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.

  The polymer 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. 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. The electrolyte concentration of the general formula (I) in these ionic conductors is preferably 0.1 M or more and a saturation 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 equal to or higher than the lower limit value, the ionic conductivity is easily improved, and when it is equal to or lower than the upper limit value, the stability of the ionic conductor is likely to increase.

  In the battery of this embodiment, the material of the positive electrode is not particularly limited, but examples thereof include transition metal oxides such as lithium cobaltate, lithium nickelate, lithium manganate, and olivine-type lithium iron phosphate. It is preferable that it is one or more selected.

  In the battery of the present embodiment, the material of the negative electrode is not particularly limited, and examples thereof include metal lithium, lithium alloy, carbon-based material capable of inserting and extracting lithium, metal oxide, and the like, and are selected from the group consisting of these materials. One or more are preferred.

  In the battery of this embodiment, the material of the separator is not particularly limited, and examples thereof include a microporous polymer film, a nonwoven fabric, and glass fiber, and are preferably at least one selected from the group consisting of these materials. .

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

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

  EXAMPLES Next, although an Example demonstrates this invention further in detail, this invention is not limited at all by these examples.

[Production 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 200 g. When preparing the solution Y, 100 μL of a solution in which 13 mg of NaBF ₄ was dissolved in 200 g of acetonitrile was weighed, and a 1000-fold diluted solution of NaBF ₄ made up to 100 mL by using acetonitrile was used. Hereinafter, the same applies in the production example using the NaBF _4. 5.09 g of lithium hexafluoroisopropoxide (LiOCH (CF ₃ ) ₂ ) was slowly added to 10 g of the solution Y. Then, it was made to react by stirring at 60 degreeC for 3 hours. At this time, lithium fluoride was deposited. To the reaction solution thus obtained, 1.31 g of oxalic acid was added and stirred at 60 ° C. for 1 hour for reaction. Next, this reaction solution is filtered to separate lithium fluoride and sodium fluoride, and the solvent of the obtained filtrate is removed under reduced pressure conditions of 60 ° C. and 10 ⁻¹ Pa to obtain 1.90 g of a white solid. It was. This solid is dried at 100 ° C. under a reduced pressure of 10 ⁻¹ Pa for 24 hours, thereby being abbreviated as lithium sodium difluoro (oxalato) borate (hereinafter, Li · NaDFOB) represented by the chemical formula (II). The symbol of represents 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. It was 2 ppm when the abundance ratio r of the sodium of obtained electrolyte A-1 was measured with the cation chromatography (The product made by Dionex, brand name: ICS-1500). In addition, ppm in this specification represents the abundance ratio of sodium (Na / Li ratio in a solid electrolyte) when the total of the abundance ratios of lithium and sodium on a molar basis is 1.

[Production Example 2]
A mixed solvent of ethylene carbonate (EC) and diethyl carbonate (DEC) (EC / DEC = 3/7 (volume ratio)) was weighed into a sample bottle as a non-aqueous solvent, and the electrolyte A-1 obtained in Production Example 1 was used. In addition, the concentration of Li · NaDFOB was 0.1 M and 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.

[Production 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.

[Production Example 4]
A solution Z was prepared by dissolving 200.0 g of lithium hexafluorophosphate and 4.4 mg of sodium hexafluorophosphate in ethyl methyl carbonate to prepare 800 g, and 12.1 g of oxalic acid was charged into 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, and then the reactor was depressurized, 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 (oxalato) phosphate (hereinafter abbreviated as Li · NaTFOP. Chemical formula (III)). Let the obtained electrolyte be 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。

[Production Example 5]
A solution Z was prepared by dissolving 200.0 g of lithium hexafluorophosphate and 4.4 mg of sodium hexafluorophosphate in ethyl methyl carbonate to prepare 800 g, and 24.3 g of oxalic acid was charged into 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, and then the reactor was depressurized, 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 (oxalato) phosphate (hereinafter abbreviated as Li · NaDFOP. Chemical formula (IV)). Let the obtained electrolyte be C-1. When the sodium abundance ratio r of the obtained electrolyte C-1 was measured, it was 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.

[Production Example 6]
Electrolyte C-2 was obtained in the same manner as in Production Example 5 with the amount of sodium hexafluorophosphate added being 22 mg. When the abundance ratio (r) of sodium ion in the obtained electrolyte C-2 was measured, it was 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.

[Production 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 1M.

[Production Example 8]
Although 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, the mixture was stirred at 23 ° C. and stirred as in Production Example 2. The undissolved portion remained and the electrolyte was not uniform.

[Production Example 9]
6.0 g of oxalic acid was diluted with water to give a 200 ml solution, and 10.44 g of boric acid was diluted with water to give a 130 ml solution, and each solution was mixed. Thereto was slowly added 60 ml of a 2.8M aqueous sodium hydroxide solution. Then, it was made to react by stirring at 55 degreeC for 12 hours. The reaction solution thus obtained was cooled, and the precipitated solid was filtered to obtain sodium bis (oxalato) borate. The obtained sodium bis (oxalato) borate was recrystallized from acetonitrile to obtain purified sodium bis (oxalato) borate. Commercially available lithium bis (oxalato) borate was added to obtain lithium sodium bis (oxalato) borate (hereinafter abbreviated as Li · NaBOB. Chemical formula (V)). Let the obtained electrolyte be D-1. The sodium abundance ratio r of the obtained electrolyte D-1 was measured and found to be 20 ppm. An electrolyte 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 and the concentration of Li · NaBOB was 0.05M.

[Production Example 10]
Electrolyte A-3 was obtained in the same manner as in Production Example 1 with the amount of NaBF ₄ added being 0.0007 mg. When the abundance ratio r of sodium in the obtained electrolyte A-3 was measured, it was 0.1 ppm. An electrolytic 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.

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

  The production of lithium ion secondary batteries (sheet-type laminate batteries) in the following examples and comparative examples was all performed in a dry box or a vacuum desiccator.

[Example 1]
100 parts by mass of a solid component containing a positive electrode active material, 5 parts by mass of carbon black as a conductive additive, 5 parts by mass of polyvinylidene fluoride as a binder, and a slurry composed of NMP as a solvent are mixed, and 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 into a 40 mm square of electrode dimensions to produce a positive electrode.
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 a slurry made of an aqueous solvent are mixed, After adjusting the solid content to 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 into a 42 mm square of electrode dimensions to produce 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 laminate battery. When the battery was evaluated, the initial discharge capacity was 50 mAh.

[Examples 2-6, Comparative Examples 1-4]
A laminated battery was produced in the same manner as in Example 1 using each electrolytic solution described in Tables 1 and 2. In Comparative Example 1, an electrolyte solution could not be obtained, and thus a laminated battery could not be produced.

  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 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, symbols such as DFOB represent abbreviations of anionic species in the electrolyte of the general formula (I).

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

  According to the present invention, it has been found that an electrolyte for a non-aqueous secondary battery, an electrolytic solution using the same, and a battery excellent in cycle characteristics as compared with a conventional electrolyte can be provided.

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

Claims (8)

An electrolyte for a non-aqueous secondary battery represented by the general formula (I).

[In General Formula (I), M represents B, Al, Ga, P, As, or Sb, r represents a number of 0 <r <1, m is 1 to 2, n is 1 to 4, q represents an integer of 0 or 1, and R ¹ represents a C _{1 to} C ₁₀ alkylene, a C _{1 to} C ₁₀ halogenated alkylene, a C _{6 to} C ₂₀ arylene, or a C _{6 to} C ₂₀ halogenated arylene ( These alkylenes and arylenes may have a substituent or a hetero atom in the structure thereof), R ² represents a halogen, and X ¹ and X ² represent O, S, Se or N. Represent each. ]   The electrolyte for a non-aqueous secondary battery according to claim 1, wherein q is 0. The electrolyte for a non-aqueous secondary battery according to claim 1, wherein X ¹ and X ² are O. The electrolyte for a non-aqueous secondary battery according to any one of claims 1 to 3, wherein the r satisfies the following formula (1).
2.0 × 10 ⁻⁶ ≦ r ≦ 1.0 × 10 ⁻² (1)   The electrolyte solution containing the electrolyte for nonaqueous secondary batteries as described in any one of Claims 1-4, and a nonaqueous solvent.   The electrolyte solution according to claim 5, wherein the concentration of the electrolyte for a non-aqueous secondary battery is 0.005 to 1.5 mol / L. Further characterized in that it comprises LiPF _6, the electrolyte solution according to claim 5 or 6.   A battery comprising the positive electrode, the negative electrode, and the electrolytic solution according to claim 5.