JP2019061828A - Nonaqueous electrolyte for lithium ion secondary battery and lithium ion secondary battery using the same - Google Patents

Abstract

To provide a nonaqueous electrolyte for a lithium ion secondary battery and a lithium ion secondary battery using the same capable of improving cycle characteristics.SOLUTION: In a nonaqueous electrolyte for a lithium ion secondary battery containing carboxylic acid ester and group 5 element, the carboxylic acid ester is propionic acid ester or acetic acid ester, and the group 5 element is vanadium, and the electrolyte contains 1.0×10to 3.0×10mol/L, and the positive electrode contains LiVOPO4 as a lithium vanadium compound.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a non-aqueous electrolyte for a lithium ion secondary battery and a lithium ion secondary battery using the same.

  2. Description of the Related Art In recent years, the miniaturization and cordlessization of electronic devices such as mobile phones and personal computers are rapidly advancing, and the demand for secondary batteries having small size, light weight and high energy density as power sources for driving them is increasing. Under such circumstances, a lithium ion secondary battery having a large charge / discharge capacity and a high energy density has attracted attention.

  The electrolyte solution for lithium ion secondary batteries is comprised from the lithium salt which is electrolyte, and the non-aqueous organic solvent. The non-aqueous organic solvent is required to have a high dielectric constant to dissociate the lithium salt, to exhibit high ionic conductivity in a wide temperature range, and to be stable in the battery. Since it is difficult to achieve these requirements with one solvent, it is usually used by combining a high dielectric constant solvent typified by propylene carbonate, ethylene carbonate, etc. with a low viscosity solvent such as dimethyl carbonate, diethyl carbonate, etc. It is common to do.

  It is very useful to lower the viscosity of the electrolytic solution in increasing the output of a lithium ion secondary battery. For example, there is a solvent called carboxylic acid ester as one of low viscosity solvents, and when it is used, a technique for improving the output characteristics particularly at low temperatures has been reported. (Patent Document 1)

JP, 2009-129719, A

  However, the carboxylic acid esters mentioned in the prior art have a problem that the reduction resistance is particularly bad and the cycle characteristics are deteriorated.

  The present invention has been made in view of the problems of the prior art, and provides a non-aqueous electrolytic solution for lithium ion secondary battery capable of improving cycle characteristics, and a lithium ion secondary battery using the same. The purpose is

  In order to solve the above problems, the non-aqueous electrolyte for a lithium ion secondary battery according to the present invention is characterized by containing a carboxylic acid ester and a group 5 element.

  According to this, the carboxylic acid ester having chelate coordination ability and the Group 5 element capable of taking various bond values are incorporated into the solid electrolyte membrane (SEI) of the negative electrode, thereby three-dimensionally. A strong SEI with a network can be formed. This makes it possible to suppress excessive reductive decomposition even when using a carboxylic acid ester having a low resistance to reduction, thereby improving cycle characteristics.

  In the non-aqueous electrolyte for a lithium ion secondary battery according to the present invention, preferably, the above-mentioned group 5 element is vanadium.

  According to this, it is suitable as a Group 5 element, and the cycle characteristics are further improved.

In the non-aqueous electrolyte for a lithium ion secondary battery according to the present invention, the group V element is further contained in the electrolyte in an amount of 1.0 × 10 ^{−6 to} 3.0 × 10 ⁻³ mol / L. preferable.

  According to this, it is suitable as the content of the Group 5 element, and the cycle characteristics are further improved.

In the non-aqueous electrolyte for a lithium ion secondary battery according to the present invention, preferably, the carboxylic acid ester is represented by the following chemical formula (1).
(Here, R ₁ and R _{2 each} represent a linear or branched alkyl group having 1 to 4 carbon atoms or a substituted alkyl group, and the total number of carbon atoms of R ₁ and R ₂ is 5 or less.)

  According to this, it is suitable as a carboxylic acid ester, and the cycle characteristics are further improved.

  In the nonaqueous electrolyte for a lithium ion secondary battery according to the present invention, preferably, the carboxylic acid ester is propionic acid ester or acetic acid ester.

  According to this, it is suitable as a carboxylic acid ester, and the cycle characteristics are further improved.

  A lithium ion secondary battery according to the present invention is characterized by comprising a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and the non-aqueous electrolyte for the lithium ion secondary battery.

  In the lithium ion secondary battery according to the present invention, preferably, the positive electrode contains a lithium vanadium compound.

Lithium-ion secondary battery according to the present invention further, it is preferable that the lithium vanadium compound is LiVOPO _4.

  According to the present invention, a non-aqueous electrolyte for a lithium ion secondary battery capable of improving cycle characteristics and a lithium ion secondary battery using the same are provided.

It is a schematic cross section of the lithium ion secondary battery of this embodiment.

  Hereinafter, preferred embodiments according to the present invention will be described with reference to the drawings. The present invention is not limited to the following embodiments. Further, the components described below include those which can be easily conceived by those skilled in the art and those substantially the same. Furthermore, the components described below can be combined as appropriate.

<Lithium ion secondary battery>
As shown in FIG. 1, the lithium ion secondary battery 100 according to this embodiment is disposed adjacent to each other between the plate-like negative electrode 20 and the plate-like positive electrode 10 facing each other, and between the negative electrode 20 and the positive electrode 10. And an electrolytic solution containing lithium ions, a case 50 for accommodating these in a sealed state, and one end of the negative electrode 20 are electrically connected. It has a lead 62 whose other end protrudes outside the case, and a lead 60 whose one end is electrically connected to the positive electrode 10 and whose other end protrudes outside the case.

  The positive electrode 10 has a positive electrode current collector 12 and a positive electrode active material layer 14 formed on the positive electrode current collector 12. Further, the negative electrode 20 has a negative electrode current collector 22 and a negative electrode active material layer 24 formed on the negative electrode current collector 22. The separator 18 is located between the negative electrode active material layer 24 and the positive electrode active material layer 14.

<Positive electrode>
(Positive current collector)
The positive electrode current collector 12 may be any conductive plate material, and for example, aluminum or an alloy thereof, or a thin metal plate (metal foil) such as stainless steel can be used.

(Positive electrode active material layer)
The positive electrode active material layer 14 is mainly composed of a positive electrode active material, a positive electrode binder, and a positive electrode conductive aid.

(Positive electrode active material)
As a positive electrode active material, absorption and release of lithium ion, desorption and insertion (intercalation) of lithium ion, or doping and dedoping of counter anion (for example, PF ₆ ⁻ ) of the lithium ion are reversible It is not particularly limited as long as it can be advanced, and known electrode active materials can be used. For example, lithium cobaltate (LiCoO ₂ ), lithium nickelate (LiNiO ₂ ), lithium manganese spinel (LiMn ₂ O ₄ ), and chemical formula: LiNi _x Co _y Mn _z MaO ₂ (x + y + z + a = 1, 0 ≦ x ≦ 1 , 0 ≦ y ≦ 1, 0 ≦ z ≦ 1, 0 ≦ a ≦ 1, M is a composite metal oxide represented by one or more elements selected from Al, Mg, Nb, Ti, Cu, Zn and Cr) Lithium vanadium compound Li _a (M) _b (PO ₄ ) _c (where M = VO or V, and 0.9 ≦ a ≦ 3.3, 0.9 ≦ b ≦ 2.2, 0.9 ≦ c ≦ 3.3), olivine type LiMPO ₄ (wherein M represents one or more elements or VO selected from Co, Ni, Mn, Fe, Mg, Nb, Ti, Al, and Zr), titanium Lithium (Li ₄ Ti) _{5 O 12), LiNi x Co} y Al z O 2 ( composite metal oxide such as 0.9 <x + y + z < 1.1) can be mentioned.

When a lithium vanadium compound is used among the above-mentioned positive electrode active materials, when combined with the negative electrode and the electrolytic solution according to the present embodiment, the effect of improving the cycle characteristics is strongly obtained. Among lithium vanadium compounds, in particular LiVOPO ₄ , the effect of improving cycle characteristics can be obtained more strongly. Although the exact mechanism of the above action is still unknown, complex compounds of carboxylic acid ester and Group 5 element form a film with low interface resistance and high affinity on the positive electrode containing lithium vanadium containing the homologous element It is guessed as one of the factors.

(Binder for positive electrode)
The positive electrode binder bonds the positive electrode active materials to one another, and also bonds the positive electrode active material layer 14 and the positive electrode current collector 12. The binder may be any one as long as the above-mentioned bonding is possible, for example, a fluorine resin such as polyvinylidene fluoride (PVDF) or polytetrafluoroethylene (PTFE), cellulose, styrene butadiene rubber, ethylene / propylene rubber, polyimide Resin, polyamide imide resin, etc. may be used. In addition, an electron conductive conductive polymer or an ion conductive conductive polymer may be used as the binder. Examples of the electron conductive conductive polymer include polyacetylene, polythiophene, polyaniline and the like. As the ion conductive conductive polymer, for example, those obtained by combining a polyether type polymer compound such as polyethylene oxide or polypropylene oxide with a lithium salt such as LiClO ₄ , LiBF ₄ or LiPF ₆ are listed. Be

  Although content of the binder in the positive electrode active material layer 14 is not specifically limited, When adding, it is preferable that it is 0.5-5 mass parts with respect to the mass of a positive electrode active material.

(Conductive agent for positive electrode)
The conductive aid for the positive electrode is not particularly limited as long as it can improve the conductivity of the positive electrode active material layer 14, and a known conductive aid can be used. Examples thereof include carbon-based materials such as graphite and carbon black, fine powders of metals such as copper, nickel, stainless steel and iron, and conductive oxides such as ITO.

<Negative electrode>
(Negative current collector)
The negative electrode current collector 22 may be any conductive plate material, and for example, a thin metal plate such as copper (metal foil) can be used.

(Anode active material layer)
The negative electrode active material layer 24 is mainly composed of a negative electrode active material, a binder for a negative electrode, and a conductive additive for a negative electrode.

(Anode active material)
The negative electrode active material is not particularly limited as long as it can reversibly advance absorption and release of lithium ions and desorption and insertion (intercalation) of lithium ions, and known electrode active materials can be used. . For example, carbon-based materials such as graphite and hard carbon, silicon-based materials such as silicon oxide (SiO _x ) metal silicon (Si), metal oxides such as lithium titanate (LTO), and metal materials such as lithium, tin and zinc Can be mentioned.

(Binder for negative electrode)
The negative electrode binder is not particularly limited, and the same positive electrode binder as described above can be used.

(Conductive additive for negative electrode)
There is no limitation in particular as a conductive support agent for negative electrodes, The thing similar to the conductive support agent for positive electrodes described above can be used.

<Electrolyte solution>
The electrolytic solution according to the present embodiment contains a carboxylic acid ester and a group 5 element.

  According to this, the carboxylic acid ester having chelate coordination ability and the Group 5 element capable of taking various bond values are incorporated into the solid electrolyte membrane (SEI) of the negative electrode, thereby three-dimensionally. A strong SEI with a network can be formed. This makes it possible to suppress excessive reductive decomposition even when using a carboxylic acid ester having a low resistance to reduction, thereby improving cycle characteristics.

  In the electrolytic solution according to the present embodiment, it is preferable that the group 5 element be vanadium.

  According to this, it is suitable as a Group 5 element, and the cycle characteristics are further improved.

In the electrolytic solution according to the present embodiment, it is preferable that the group 5 element be further contained in the electrolytic solution in an amount of 1.0 × 10 ^{−6 to} 3.0 × 10 ⁻³ mol / L.

  According to this, it is suitable as the content of the Group 5 element, and the cycle characteristics are further improved.

The Group 5 element is not particularly limited, and halides such as VF ₅ , NbF ₅ , TaF ₅ , VCl ₃ , NbBr ₅ , NbI ₅ , oxides such as VO, V ₂ O ₅ , and phosphorus such as VPO ₄ Acid vanadium etc. can be used.

  Further, in the electrolytic solution according to the present embodiment, the carboxylic acid ester is preferably represented by a chemical formula (1), and more preferably a propionic acid ester or an acetic acid ester.

  According to this, it is suitable as a carboxylic acid ester, and the cycle characteristics are further improved.

  In the electrolytic solution according to the present embodiment, the carboxylic acid ester is preferably contained in the electrolytic solution in an amount of 50% by volume or more and 90% by volume or less.

  According to this, it is suitable as a ratio of carboxylic acid ester, and cycle characteristics are further improved.

(Other solvents)
The electrolyte solution which concerns on this embodiment can use the solvent generally used for the lithium ion secondary battery other than the said carboxylic ester. The solvent is not particularly limited, and examples thereof include cyclic carbonate compounds such as ethylene carbonate (EC) and propylene carbonate (PC), linear carbonate compounds such as diethyl carbonate (DEC) and ethyl methyl carbonate (EMC), and the like. It can be mixed and used in the ratio of

(Electrolytes)
The electrolyte is not particularly limited as long as it is a lithium salt used as an electrolyte of a lithium ion secondary battery, and examples thereof include inorganic acid anion salts such as LiPF ₆ , LiBF ₄ and lithium bis oxalate borate, LiCF ₃ SO ₃ , Organic acid anionic salts such as (CF ₃ SO ₂ ) ₂ NLi and (FSO ₂ ) ₂ NLi can be used.

  As mentioned above, although the suitable embodiment concerning the present invention was described, the present invention is not limited to the above-mentioned embodiment.

  Hereinafter, the present invention will be more specifically described based on examples and comparative examples, but the present invention is not limited to the following examples.

Example 1
(Production of positive electrode)
50 parts by mass of LiVOPO ₄ as a lithium vanadium compound, 35 parts by mass of Li (Ni _0.80 Co _0.15 Al _0.05 ) O ₂ as a lithium nickel compound, 5 parts by mass of carbon black, 10 parts by mass of PVDF N-methyl-2 -It disperse | distributed to pyrrolidone (NMP) and prepared the slurry for positive electrode active material layer formation. The slurry was applied to one surface of a 20 μm thick aluminum metal foil so that the coating amount of the positive electrode active material was 9.0 mg / cm ^2, and dried at 100 ° C. to form a positive electrode active material layer. Then, it pressure-molded by the roller press, and produced the positive electrode.

(Fabrication of negative electrode)
90 parts by mass of natural graphite, 5 parts by mass of carbon black and 5 parts by mass of PVDF were dispersed in N-methyl-2-pyrrolidone (NMP) to prepare a slurry for forming a negative electrode active material layer. The slurry was applied to one surface of a 20 μm thick copper foil so that the coating amount of the negative electrode active material was 6.0 mg / cm ^2, and dried at 100 ° C. to form a negative electrode active material layer. Then, it pressure-molded by the roller press, and produced the negative electrode.

(Preparation of electrolyte)
Using ethyl propionate as a carboxylic acid ester, adjust the composition ratio of EC: ethyl propionate = 30: 70 in volume ratio, and dissolve LiPF ₆ in this to a concentration of 1.0 mol / L. The The VF ₅ as a fifth group element compound to the above solution was added to a 1.0 × ¹⁰ -6 mol / L, to prepare an electrolyte solution.

(Preparation of lithium ion secondary battery for evaluation)
The positive electrode and the negative electrode produced above and a separator made of a polyethylene microporous film were interposed between them and placed in an aluminum laminate pack. The electrolytic solution prepared above was injected into the aluminum laminate pack, and vacuum sealing was performed to prepare a lithium ion secondary battery for evaluation.

(Measurement of capacity retention rate after 300 cycles)
For the lithium ion secondary battery for evaluation prepared above, using a secondary battery charge and discharge test device (manufactured by Hokuto Denko Corporation), charging rate 1.0 C (constant current charging at 25 ° C.) takes 1 hour The battery was charged until the battery voltage reached 4.2 V by constant current charging (the current value at which the charging is completed), and was discharged until the battery voltage reached 2.8 V by constant current discharging at a discharge rate of 1.0C. The charge / discharge cycle was defined as one cycle, followed by 300 cycles of charge / discharge, and after 300 cycles, the capacity retention ratio (300th cycle discharge capacity / 1st cycle discharge capacity × 100) was determined. The higher the value, the better the cycle characteristics. The obtained results are shown in Table 1.

Example 2
A lithium ion secondary battery for evaluation of Example 2 was produced in the same manner as Example 1 except that the amount of addition of the Group 5 element compound used in production of the electrolytic solution was changed as shown in Table 1.

[Example 3]
A lithium ion secondary battery for evaluation of Example 3 was produced in the same manner as Example 1 except that the amount of addition of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

Example 4
A lithium ion secondary battery for evaluation of Example 4 was produced in the same manner as Example 1 except that the addition amount of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 5]
A lithium ion secondary battery for evaluation of Example 5 was produced in the same manner as Example 1 except that the amount of addition of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 6]
A lithium ion secondary battery for evaluation of Example 6 was produced in the same manner as in Example 1 except that the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 7]
A lithium ion secondary battery for evaluation of Example 7 was produced in the same manner as in Example 6 except that the amount of addition of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 8]
A lithium ion secondary battery for evaluation of Example 8 was produced in the same manner as Example 6, except that the amount of addition of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 9]
A lithium ion secondary battery for evaluation of Example 9 was produced in the same manner as in Example 1 except that the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 10]
A lithium ion secondary battery for evaluation of Example 10 was produced in the same manner as Example 9, except that the amount of addition of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 11]
A lithium ion secondary battery for evaluation of Example 11 was produced as in Example 9 except that the addition amount of the Group 5 element compound used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 12]
A lithium ion secondary battery for evaluation of Example 12 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 13]
A lithium ion secondary battery for evaluation of Example 13 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in producing the electrolytic solution was changed as shown in Table 1.

Example 14
A lithium ion secondary battery for evaluation of Example 14 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in producing the electrolytic solution was changed as shown in Table 1.

[Example 15]
A lithium ion secondary battery for evaluation of Example 15 was produced in the same manner as Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 16]
A lithium ion secondary battery for evaluation of Example 16 was produced as in Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 17]
A lithium ion secondary battery for evaluation of Example 17 was produced in the same manner as in Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 18]
A lithium ion secondary battery for evaluation of Example 18 was produced as in Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 19]
A lithium ion secondary battery for evaluation of Example 19 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 20]
A lithium ion secondary battery for evaluation of Example 20 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 21]
A lithium ion secondary battery for evaluation of Example 21 was produced in the same manner as in Example 2 except that the carboxylic acid ester used for producing the electrolytic solution was changed as shown in Table 1.

Example 22
A lithium ion secondary battery for evaluation of Example 22 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in production of the electrolytic solution was changed as shown in Table 1.

[Example 23]
A lithium ion secondary battery for evaluation of Example 23 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 24]
A lithium ion secondary battery for evaluation of Example 24 was produced in the same manner as in Example 20 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 25]
A lithium ion secondary battery for evaluation of Example 25 was produced as in Example 20 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 26]
A lithium ion secondary battery for evaluation of Example 26 was produced in the same manner as Example 20 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 27]
A lithium ion secondary battery for evaluation of Example 27 was produced in the same manner as in Example 20 except that the composition ratio of the electrolytic solution was changed as shown in Table 1.

[Example 28]
A lithium ion secondary battery for evaluation of Example 28 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in producing the electrolytic solution was changed as shown in Table 1.

[Example 29]
A lithium ion secondary battery for evaluation of Example 29 was prepared in the same manner as Example 2 except that the carboxylic acid ester used in preparation of the electrolytic solution was changed as shown in Table 1.

[Example 30]
A lithium ion secondary battery for evaluation of Example 30 was produced in the same manner as in Example 2 except that the carboxylic acid ester used in the production of the electrolytic solution was changed as shown in Table 1.

[Example 31]
A lithium ion secondary battery for evaluation of Example 31 was produced in the same manner as in Example 2 except that the lithium vanadium compound used in the production of the positive electrode was changed as shown in Table 1.

[Example 32]
A lithium ion secondary battery for evaluation of Example 32 was produced in the same manner as in Example 2 except that the lithium vanadium compound used in the production of the positive electrode was changed as shown in Table 1.

Comparative Example 1
A lithium ion secondary battery for evaluation of Comparative Example 1 was produced in the same manner as in Example 1 except that the Group 5 element compound was not added in the production of the electrolytic solution.

Comparative Example 2
A lithium ion secondary battery for evaluation of Comparative Example 2 was produced as in Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1 without using a carboxylic acid ester.

Comparative Example 3
A lithium ion secondary battery for evaluation of Comparative Example 3 was produced as in Example 2 except that the composition ratio of the electrolytic solution was changed as shown in Table 1 without using a carboxylic acid ester.

Comparative Example 4
A lithium ion secondary battery for evaluation of Comparative Example 4 was produced in the same manner as in Example 31 except that the Group 5 element compound was not added in the production of the electrolytic solution.

Comparative Example 5
A lithium ion secondary battery for evaluation of Comparative Example 5 was produced as in Example 32 except that the Group 5 element compound was not added in the production of the electrolytic solution.

  About the lithium ion secondary battery for evaluation produced in Examples 2-32 and Comparative Examples 1-5, the measurement of the capacity retention after 300 cycles was performed in the same manner as in Example 1. The results are shown in Table 1.

  All of Examples 1 to 32 were confirmed to improve the capacity retention rate after 300 cycles as compared to Comparative Example 1 in which the Group 5 element compound was not added.

  From the results of Examples 1 to 5, it is confirmed that the capacity retention rate after 300 cycles is further improved by optimizing the addition amount of the Group 5 element compound.

  From the results of Examples 6 to 11, it was confirmed that the capacity retention after 300 cycles is further improved when vanadium is used as the group 5 element.

  From the results of Examples 12 to 14 and 19 to 23, it was confirmed that the capacity retention rate after 300 cycles is further improved by setting the total carbon number of the carboxylic acid to 5 or less.

  From the results of Examples 15 to 18 and Examples 24 to 27, it was confirmed that the capacity retention after 300 cycles was further improved by optimizing the composition of the electrolytic solution.

  From the results of Examples 28 to 30, it is confirmed that the use of propionic acid ester or acetic acid ester as a carboxylic acid ester has an effect of further improving the capacity retention after 300 cycles.

From the results of Examples 31-32 and Comparative Examples 4-5, the use of LiVOPO ₄ as lithium vanadium compounds, it was confirmed that after 300 cycles the capacity retention rate is more improved.

  The present invention provides a non-aqueous electrolyte for a lithium ion secondary battery capable of improving cycle characteristics, and a lithium ion secondary battery using the same.

  DESCRIPTION OF SYMBOLS 10 ... Positive electrode, 12 ... Positive electrode collector, 14 ... Positive electrode active material layer, 18 ... Separator, 20 ... Negative electrode, 22 ... Negative electrode collector, 24 ... Negative electrode active material layer, 30 ... Laminate, 50 ... Case, 60 , 62 ... lead, 100 ... lithium ion secondary battery.

Claims (8)

  A non-aqueous electrolytic solution for a lithium ion secondary battery, comprising a carboxylic acid ester and a group 5 element.   The non-aqueous electrolytic solution for a lithium ion secondary battery according to claim 1, wherein the group 5 element is vanadium. The lithium ion secondary battery according to claim 1 or 2, wherein the group 5 element is contained in the electrolyte solution in an amount of 1.0 × 10 ^{-6 to} 3.0 × 10 ^-3 mol / L. Nonaqueous electrolyte. The non-aqueous electrolytic solution for a lithium ion secondary battery according to any one of claims 1 to 3, wherein the carboxylic acid ester is represented by the following chemical formula (1).
(Here, R ₁ and R _{2 each} represent a linear or branched alkyl group having 1 to 4 carbon atoms or a substituted alkyl group, and the total number of carbon atoms of R ₁ and R ₂ is 5 or less.)

  The non-aqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 4, wherein the carboxylic acid ester is propionic acid ester or acetic acid ester.   A lithium ion secondary battery comprising a positive electrode, a negative electrode, a separator positioned between the positive electrode and the negative electrode, and the non-aqueous electrolyte for a lithium ion secondary battery according to any one of claims 1 to 5. .   The lithium ion secondary battery according to claim 6, wherein the positive electrode contains a lithium vanadium compound. The lithium ion secondary battery of claim 7, wherein the lithium vanadium compound characterized in that it is a LiVOPO _4.

Images