JPH09161845A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve capacity and repetition stability, by using an electrolyte solution, wherein a lithium compound is dissolved in a specific organic solvent. SOLUTION: A lithium compound is dissolved in an organic solvent, obtained by mixing high and low active solvents having the numbers of donars of 14-20 and 10 or less respectively, so that a mol ratio (S/Li<+> ), between the high active solvent (S) and a lithium ion (Li<+> ), can be 3 or less, to obtain an electrolyte solution. A laminated electrode body, wherein a positive electrode 1, and a negative electrode 2 thereto negative active material composed of material, for absorbing and releasing a lithium ion at the time of charging and discharging respectively, is coated, are spirally wound many times; is housed in a battery vessel 6. The electrolyte solution is injected in the battery vessel 6, to fittedly engage an opening part 6a and a sealing plate 7 via a packing 8, to spot-weld a negative electrode lead terminal 4 to the inner bottom part of the battery vessel 6, thereby connecting a positive electrode lead terminal 3 to the sealing plate 7.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a non-aqueous electrolyte secondary battery having a high capacity and excellent in repeated stability (a secondary battery using a solution prepared by dissolving an electrolyte in an organic solvent as an electrolyte solution (electrolyte solution)). ), And more particularly to improvement of the non-aqueous electrolyte.

[0002]

2. Description of the Related Art In recent years, non-aqueous electrolyte secondary batteries such as lithium ion secondary batteries have attracted attention because of their high energy density. Conventionally, in this type of battery, as a solvent constituting the non-aqueous electrolyte, propylene carbonate,
One or a mixture of two or more of ethylene carbonate, γ-butyrolactone, 1,2-dimethoxyethane, dimethyl carbonate, diethyl carbonate, ethylmethyl carbonate, tetrahydrofuran, 1,3-dioxolane and the like is used.

Electrolysis used by dissolving in the above solvent
As for quality, LiBF_Four, LiPF ₆, CF_ThreeSO_ThreeL
i, (CF_ThreeSO_Two)_TwoFluorine-containing lithium such as NLi
Salts are used alone or as a mixture. Also, the negative electrode
As a material, a carbon material capable of inserting and extracting lithium
Is mainly used.

[0004]

By the way, in a secondary battery having a solution of such a solute dissolved in the above-mentioned non-aqueous solvent as an electrolytic solution, decomposition of the electrolytic solution gradually occurs due to repeated charging and discharging, Capacity tends to decrease. This tendency is generally observed when a carbon material is used for the negative electrode, and the tendency becomes even stronger when graphite is used.

For example, in a battery in which graphite is used as the negative electrode and propylene carbonate alone is used as the solvent of the electrolytic solution, propylene carbonate is easily decomposed on the graphite negative electrode so that charging is difficult and the battery has an extremely low capacity. There has been a problem that the capacity is largely reduced due to repeated charging and discharging, resulting in poor performance as a secondary battery.

The present invention aims to solve the above-mentioned problems of the prior art, and provides a non-aqueous electrolyte secondary battery having a high capacity and excellent repeated stability.

[0007]

In order to solve the above problems, the inventors of the present invention have diligently studied the relationship between the repetitive stability of a lithium secondary battery and the non-aqueous electrolyte, and as a result, the decomposition of the electrolyte was The present invention has been completed by finding that when the number of donors of the solvent is large, it is caused by free solvent molecules that are not solvated with the solute lithium ion.

That is, in the non-aqueous electrolyte secondary battery of the present invention, the negative electrode active material occludes lithium ions during charging,
And in the non-aqueous electrolyte secondary battery, which is a material that releases lithium ions during discharge, and the electrolyte solution is a solution in which a lithium compound is dissolved in an organic solvent, the organic solvent is
Highly active solvent with 14 to 20 donors and 10 donors
The electrolyte solution is a mixed solvent of the following low activity solvent, and the electrolyte solution contains the high activity solvent (S) and lithium ion (Li ⁺ ).
The molar ratio (S / Li) of is 3.0 or less.

As the negative electrode active material, various forms of carbonaceous materials such as graphite, coke, hard carbon, soft carbon, conductive polymers, lithium metal, and lithium alloy are used. It is preferable that the negative electrode active material is a carbon material having a surface spacing (d ₀₀₂ ) determined by X-ray diffraction of 0.3365 nm or more.

Here, the surface spacing (d ₀₀₂ ) is CuK.
It is a value obtained by the Gakushin method from X-ray diffraction using α rays. In addition, the number of solvent donors (hereinafter abbreviated as “DN”) refers to V.N. It is a parameter reported by Prof. Gutmann that represents the coordination force of the solvent to the metal ion.

A solvent having a large number of donors (active solvent: S)
Lithium ions (Li⁺)
If the difference in the number of donors is 3 or more,
A solvent with a large number is preferentially coordinated. And Richiu
Active solvent S is less than "3.0" for muion "1"
So that the lithium compound is dissolved in the mixed solvent.
Then, the molar ratio (S / Li) becomes 3.0 or less, for example, L
iS_Three ⁺, LiS_2.5 ⁺, LiS_Two ⁺Solvated complexes such as
Is generated. Generally, the solvent is 3 for lithium ions.
It is known to coordinate more than a molecule.

Therefore, like the electrolyte solution of the present invention, if the molar ratio (S / Li) of the highly active solvent (S) and the lithium ion (Li ⁺ ) is 3.0 or less, a free solvent that does not solvate. Molecules are virtually eliminated, and this highly active solvent S
Is difficult to disassemble. Further, when a carbon material having a surface spacing (d ₀₀₂ ) of 0.3365 nm or more is used as the negative electrode active material, decomposition of the highly active solvent is further suppressed, and the decrease in capacity due to repeated charge and discharge is reduced.

V. The number of donors reported by Prof. Gutmann is the heat generated by the reaction between the solvent and antimony pentachloride in Kcal / mol. This method is highly hygroscopic to antimony pentachloride and is very difficult to measure. Difficult to do. Therefore, the donor number is known for only a small part of the solvent used as the electrolyte solution solvent. Therefore, the number of donors in the present invention is K. Tabata et al. Ana. Sci., 1
0, p383 (1994), K.Sone et al. "Inorganic Thermochromism" Sp
The values are obtained as follows using the spectrophotometric method shown in Ringer, New York, p98 (1987). That is,
Acetylacetone VO complex (VO (a
cac) ₂ ) was dissolved at a concentration of 10 ^-4 mol / l, the absorption spectrum was measured, and the central wavelengths λI (long wavelength side) and λII (short wavelength side) of the two absorption peaks appearing in the visible region were measured. The number of donors D is calculated by substituting in the following equation (A).

D = 1.19 × 10 ⁵ [(1 / λII) − (1 / λI)] (A) V. When the donor number D was determined by the above method for a solvent whose donor number DN by Professor Gutman is known, the obtained donor number D and V. Number of donors D by Professor Gutman
Since it has a linear relationship with N, it can be used to convert D value to D
The value obtained by converting the N value was used as the number of donors.

As the highly active solvent S of the present invention, any solvent can be used as long as it has a donor number of 14 to 20, and in particular, cyclic carbonic acid ester, cyclic ester, chain ester, cyclic ether, chain ether. Good results are obtained when nitriles are used. The cyclic ester carbonate referred to herein is represented by the following general formula (1),

[0016]

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(Wherein n is 2 or 3 or 4 and R ₁
And R ₂ is hydrogen or any alkyl group,
Both may be the same or different, and may form a ring with a C—C bond. ) Specific examples thereof include ethylene carbonate, propylene carbonate, trans-2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, 1,3-dioxa-2-cyclohexanone, and 4-methyl-. 1,3-dioxa-2-cyclohexanone, 4-isopropyl-5,5-dimethyl-1,
Examples thereof include 3-dioxa-2-cyclohexanone and cyclohexyl carbonate.

The cyclic ester is represented by the following general formula (2):

[0019]

Embedded image

(Where n is an integer from 2 to 5 and R ₁
And R ₂ is hydrogen or any alkyl group,
Both may be the same or different. ) Specific examples thereof include β-butyrolactone, γ-butyrolactone, 2-methyl-γ-butyrolactone, γ-valerolactone, and δ-valerolactone.

The chain ester is represented by the following general formula (3):

[0022]

Embedded image

(In the formula, R ₁ is hydrogen or any alkyl group, and R ₂ is any alkyl group.) Specific examples thereof include methyl formate, ethyl formate, propyl formate, methyl acetate, ethyl acetate. , Propyl acetate, pentyl acetate, methyl propionate, ethyl propionate,
Examples thereof include butyl propionate, methyl butyrate, ethyl butyrate and the like.

Examples of cyclic ethers include cyclic ethers such as tetrahydrofuran and 2-methyltetrahydrofuran, and cyclic diethers such as 1,3-dioxolane, 1,4-dioxane, 2-methyldioxolane and 4-methyldioxolane. Is mentioned. As the chain ether, for example, ethers such as ethyl ether, propyl ether, butyl ether, pentyl ether, hexyl ether, phenyl ether,
Diethers such as 1,2-dimethoxyethane, 1,2-diethoxyethane, 1,2-dimethoxypropane, 1,2-diethoxypropane, diethylene glycol dimethyl ether, diethylene glycol diethyl ether, and diethylene glycol dibutyl ether may be mentioned.

Examples of the nitriles include acetonitrile, propionitrile, malononitrile, succinonitrile, glutaronitrile, adiponitrile, pimelonitrile and 1,5-dicyanopentane. Further, sulfur-containing compounds such as sulfolane and 2-methylsulfolane can also be favorably used.

These highly active solvents may be used alone or in combination of two or more. As the low activity solvent of the present invention, any solvent can be used as long as the number of donors is 10 or less, and specifically, dimethyl carbonate, ethyl methyl carbonate, diethyl carbonate, methyl propyl carbonate, dipropyl carbonate, ethyl. Propyl carbonate, methyl isopropyl carbonate, ethyl isopropyl carbonate, diisopropyl carbonate, methyl butyl carbonate, ethyl butyl carbonate,
Examples thereof include dibutyl carbonate.

Even if only one of these low activity solvents is used,
Or, two or more kinds may be mixed and used. Book
The concentration of the electrolyte solution in the invention is 0.5 to 2.0 mo.
l / dm^ThreeIt is preferred that Non-aqueous electrolyte of the present invention
Specific examples of the electrolyte (lithium compound) that constitutes
Is LiPF₆, LiBF_Four, LiAsF₆, LiCl
O_Four, LiSbF₆, LiI, LiBr, LiCl, L
iAlCl_Four, LiHF_Two, LiSCN, CF_ThreeSO _Three
Li, C_FourF₉SO_ThreeLi, (CF_ThreeSO_Two)_TwoNL
i, (C_FourF₉SO_Two) _TwoBy using NLi etc.
Wear.

The material used for the positive electrode of the secondary battery of the present invention is not particularly limited and can be appropriately selected and used according to its purpose. As a specific example, Ti
S ₂ , TiS ₃ , MoS ₂ , MoS ₃ , FeS, FeS
₂ , metal sulfides such as CuCoS ₄ , V ₂ O ₅ , V ₆ O
₁₃ , MoO ₃ , MnO ₂ , CuO, Cu ₅ V ₂ O ₁₀ , C
Metal oxides such as r ₂ O ₃ and TiO ₂ , NbSe ₃ , V
Metal selenides such as Se ₂ , LiVO ₂ , LiCrO
₂ , LiFeO ₂ , LiNiO ₂ , LiCoO ₂ , Li
MnO ₂ , LiCo _x Sn _y O ₂ , LiCo _x Ni _y O
₂ , and alkali metal-containing composite oxides such as LiCo _x Fe _y O ₂ .

[0029]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described in detail below with reference to specific examples. [Example 1] 0.05 part by weight of polyvinylidene fluoride as a binder was added to 1 part by weight of powder of commercially available scaly graphite (manufactured by Chuetsu Graphite Co., Ltd., BF-20A, d ₀₀₂ = 0.3354 nm). In addition, a paste prepared by using dimethylformamide was applied to one surface of a copper foil having a thickness of 10 μm so that the dry film thickness would be 95 μm, thereby producing a negative electrode. A single cell was formed by bringing this negative electrode and a positive electrode made of a lithium foil having a thickness of 50 μm into close contact with each other with a separator made of a polyethylene microporous film interposed therebetween.

Further, propylene carbonate (DN = 1
5.1) 20% by volume and methyl butyl carbonate (DN
= 8.4) In a mixed solvent with 80% by volume, LiPF₆1
mol / dm^ThreeBy dissolving to the concentration of
An electrolytic solution was prepared. The propylene carbonate of this electrolyte
(PC) and LiPF₆Molar ratio of (PC / LiP
F ₆) That is, (S / Li) is 2.3.

The single cell was immersed in this electrolyte under a nitrogen atmosphere, and a metallic lithium plate was further provided as a reference electrode for measuring the potential of the negative electrode, and the charge / discharge characteristics were examined by cyclic voltammetry. As shown in the graph of FIG. 1, which shows the charge and discharge characteristics of this system, when lithium ions are inserted into the graphite of the negative electrode by passing a current at a current density of 0.4 mA / cm ² in this system in this system. First, the potential of the negative electrode, which was initially 1.5 V, gradually decreased, lithium ions were inserted into graphite at a potential of 0.2 V or less, and the first insertion amount was 330 mAh.
/ G. Then, the polarity was changed and a current was passed at the same current density to desorb the lithium ions inserted in the graphite. Its total capacity is 255mAh / g
Met. After that, the charge and discharge cycle could be repeated with the same capacity. [Comparative Example 1] LiP was added to a mixed solvent of propylene carbonate 50% by volume and methyl butyl carbonate 50% by volume.
An electrolytic solution was prepared by dissolving F ₆ to a concentration of 1 mol / dm ³ . The molar ratio of propylene carbonate (PC) and LiPF ₆ (PC / LiP
F ₆ ) or (S / Li) is 5.5. The same experiment as in Example 1 was conducted using this electrolytic solution. As can be seen from the graph of FIG. 2 showing the charge / discharge characteristics in this system, propylene carbonate was decomposed at 0.7 to 0.8 V, and lithium ions were not inserted in the graphite of the negative electrode. Example 2 A cylindrical non-aqueous electrolyte battery as shown in FIG. 3 was produced as follows.

First, LiCoO ₂ was pulverized with a ball mill to an average particle size of 3 μm, and then 0.025 parts by weight of graphite and 0.02 parts of acetylene black per 1 part by weight of this powder.
5 parts by weight, polyvinylidene fluoride 0.02 as a binder
A positive electrode 1 was prepared by adding parts by weight and applying a paste using dimethylformamide so as to have a dry film thickness of 100 μm on one surface of an aluminum foil having a thickness of 15 μm.

On the other hand, commercially available petroleum-based needle coke (KOA-SJ Coke, manufactured by Koa Oil Co., Ltd., d ₀₀₂ = 0.3)
(44 nm) was pulverized with a ball mill to an average particle size of 10 μm, and 0.05 part by weight of polyvinylidene fluoride as a binder was added to 1 part by weight of this powder, and the mixture was made into a paste using dimethylformamide. Negative electrode 2 was prepared by applying a 10 μm copper foil on one surface so that the dry film thickness was 130 μm. The positive electrode 1 and the negative electrode 2
A positive electrode lead terminal 3 made of aluminum and a negative electrode lead terminal 4 made of copper for collecting current were welded to each.

Then, the positive electrode 1 and the negative electrode 2 are spirally wound many times while being superposed with a separator 5 made of a polyethylene microporous film interposed therebetween and being spirally wound many times. An electrode body was produced. The laminated electrode body was housed in a battery container 6 made of a stainless steel cylinder. Further, the negative electrode lead terminal 4 was connected to the inner bottom portion of the battery container 6 by spot welding, and the positive electrode lead terminal 3 was similarly connected to the battery sealing plate 7.

On the other hand, ethylene carbonate (EC) (D
N = 16.4) and ethyl methyl carbonate (EMC)
(DN = 6.5) was mixed with each solvent in a volume ratio shown in Table 1 below to dissolve LiPF ₆ at a concentration of 1 mol / dm ³ to prepare an electrolytic solution for each sample. did. In addition, the ethylene carbonate (E
The molar ratio of C) to LiPF ₆ (EC / LiPF ₆ ), that is, (S / Li) is also shown in Table 1 below.

[0036]

[Table 1]

Next, for each sample, after injecting the above-mentioned respective electrolytic solutions into the battery container 6 accommodating the above-mentioned laminated electrode body, the opening 6a of the battery container 6 and the battery sealing plate 7 are opened. A polypropylene non-electrolyte secondary battery 10 having an outer diameter of 20 mm and a length of 50 mm was produced by fitting through a polypropylene packing 8 and caulking and sealing. Reference numeral 9 in FIG. 3 is an insulating plate.

The charging / discharging cycle characteristics of the batteries A to G prepared in the above-mentioned manner and different only in the electrolytic solution were examined. The test conditions were a charge / discharge current of 1 A and a charge end voltage of 4.2.
V, discharge end voltage 2.7V, charge and discharge at 20 ℃ 30
Repeated 0 cycles, 1 of discharge capacity at 300th cycle
The ratio to the discharge capacity at the cycle was calculated as the discharge capacity retention rate. The discharge capacity retention rates at the 300th cycle of the batteries A to F are shown in Table 2 below.

[0039]

[Table 2]

As can be seen from the results of Table 2, when the molar ratio of ethylene carbonate (EC) and LiPF ₆ is 3.0 or less, the discharge capacity retention rate is 80% or more, and the charge-discharge cycle characteristics are excellent. There is. Further, the battery G is DN
Does not contain a highly active solvent of 14 to 20, and only EMC, which is a low active solvent having a DN of 10 or less, is used as a solvent for the electrolyte, so that the discharge capacity at the first cycle is low,
It was also inferior in charge / discharge cycle characteristics. [Example 3] γ-butyrolactone (DN
= 15.9) 18% by volume and dimethyl carbonate (DN
= 8.7) In a mixed solvent of 82% by volume, 1 m of LiBF ₄ was added.
A battery was produced in the same manner as in Example 2 except that the melted product was used so as to have a concentration of ol / dm ³ . The molar ratio (BL / LiBF ₄ ) of γ-butyrolactone (BL) and LiBF ₄ in this electrolytic solution, that is, (S / Li), is 2.4.
It is.

When the charge-discharge cycle characteristics of this battery were examined in the same manner as in Example 2, the discharge capacity at the first cycle was 1115 mAh and the capacity retention rate at the 300th cycle was 83%, which were all good values. there were. [Comparative Example 2] As an electrolytic solution, a mixed solvent of 30% by volume of tributyl phosphate (DN = 23.7) and 370% by volume of dimethyl carbonate (DN = 8.7) was added to LiBF.
_A battery was produced in the same manner as in Example 2 except that 4 was dissolved to have a concentration of 1 mol / dm ³ . The molar ratio of tributyl phosphate (TBP) to LiBF ₄ (TBP / LiBF ₄ ), that is (S / Li), of this electrolytic solution is 1.1.

When the charge and discharge cycle characteristics of this battery were examined in the same manner as in Example 2, the discharge capacity at the first cycle was as low as 112 mAh, and the discharge capacity was 0 mAh after 10 cycles. [Comparative Example 3] LiPF ₆ was used as an electrolytic solution in a mixed solvent of 17% by volume of dimethyl sulfoxide (DN = 29.8) and 83% by volume of dimethyl carbonate (DN = 8.7).
A battery was produced in the same manner as in Example 2 except that the above was used so as to have a concentration of 1 mol / dm ³ .
This electrolyte contains dimethyl sulfoxide (DMS) and L
iPF ₆ molar ratio (DMS / LiBF ₄ ) or (S
/ Li) is 2.4.

This battery was charged in the same manner as in Example 2.
When the discharge cycle characteristics were examined, the first cycle discharge
The capacity is as low as 572 mAh, and the discharge capacity after 100 cycles
The amount became 0 mAh. [Example 4] 1,2-dimethoxyethane was used as the electrolytic solution.
(DN = 20.0) 25% by volume and methyl propyl carbo
Nate (DN = 7.4) in a mixed solvent of 75% by volume, Li
PF ₆1 mol / dm^ThreeUse the one dissolved at the concentration of
A battery was produced in the same manner as in Example 2 except that the above was performed. This
Dissolved 1,2-dimethoxyethane (DME) and LiPF
₆Molar ratio of (DME / LiBF_Four) That is (S / L
i) is 2.4.

The charge-discharge cycle characteristics of this battery were examined in the same manner as in Example 2. The discharge capacity at the first cycle was 1128 mAh, and the capacity retention rate at the 300th cycle was 85%. there were. [Example 5] As the electrolytic solution, propionitrile (DN =
16.1) in a mixed solvent of 17.8 volume% and methyl isopropyl carbonate (DN = 7.4) 82.2 volume%,
LiPF ₆ dissolved in a concentration of 1 mol / dm ³ was used, and spherical carbon (Kawasaki Steel Co., Ltd., ASK-2, d was used as a negative electrode active material instead of needle coke.
_A battery was produced in the same manner as in Example 2 except that ( ₀₀₂ = 0.3367 nm) was used. The molar ratio of propionitrile (PN) to LiPF ₆ in this electrolyte (PN / LiB
F ₄ ) or (S / Li) is 2.5.

This battery was charged in the same manner as in Example 2.
When the discharge cycle characteristics were examined, the first cycle discharge
Capacity is 1132mAh, capacity retention rate at 300th cycle
Was 87%, which were all good values. Example 6 As an electrolytic solution, glutaronitrile (DN =
14) 19% by volume and dimethyl carbonate (DN = 8.
7) Add 81% by volume of mixed solvent to LiPF₆1 mol /
dm ^ThreeOther than using the one that is dissolved so that the concentration becomes
A battery was manufactured in the same manner as in Example 5. This electrolyte
Glutaronitrile (GN) and LiPF₆Molar ratio of (G
N / LiBF_Four) That is, (S / Li) is 2.0
You.

This battery was charged in the same manner as in Example 2.
When the discharge cycle characteristics were examined, the first cycle discharge
Capacity is 1124 mAh, capacity retention rate at 300th cycle
Was 89%, which were all good values. [Example 7] Sulfolane (DN = 1) was used as the electrolytic solution.
4.8) 22% by volume and diethyl carbonate (DN =
9.2) Add 78% by volume of LiPF₆1mo
l / dm ^ThreeIf you use a solution that has been dissolved to give the
A battery was produced in the same manner as in Example 5 except for the above. This electrolysis
Liquid sulfolane (SF) and LiPF₆Molar ratio of (SF
/ LiBF_Four) That is, (S / Li) is 2.3.

When the charge and discharge cycle characteristics of this battery were examined in the same manner as in Example 2, the discharge capacity at the first cycle was 1111 mAh, and the capacity retention rate at the 300th cycle was 83%. there were. [Example 8] As an electrolytic solution, 1,4-dioxane (DN
= 19) 20% by volume and ethyl methyl carbonate (DN
= 6.5) 1 mL of LiPF ₆ in 80% by volume of mixed solvent
A battery was produced in the same manner as in Example 5, except that the melted product was used so that the concentration was ol / dm ³ . The molar ratio (DO / LiBF ₄ ) of 1,4-dioxane (DO) and LiPF ₆ in this electrolytic solution, that is, (S / Li), is 2.2.
It is.

When the charge and discharge cycle characteristics of this battery were examined in the same manner as in Example 2, the discharge capacity at the first cycle was 1121 mAh, and the capacity retention rate at the 300th cycle was 87%, which were all good values. there were. [Comparative Example 4] As a negative electrode active material, instead of needle coke, scaly graphite (manufactured by Chuetsu Graphite Co., Ltd., BF-
20 A, d ₀₀₂ = 0.3354 nm)
A battery was made in the same manner as the battery E of Example 2.

When the charge and discharge cycle characteristics of this battery were examined in the same manner as in Example 2, the discharge capacity at the first cycle was high at 1280 mAh, but the capacity retention rate at the 300th cycle was low at 62%. As can be seen from the above results, Examples 1, 2 (A to E only), 3 in which the electrolytic solution is within the scope of the present invention and the negative electrode active material is within the scope of Claim 2.
In Nos. 8 to 8, good results were obtained for both the discharge capacity at the first cycle and the capacity retention rate at the 300th cycle, and batteries having high capacity and excellent repeated stability were obtained.

On the other hand, the highly active solvent has a DN of 14 to
In Comparative Examples 2 and 3 out of the range of 20 and the battery G of Example 2 not containing the highly active solvent, the battery was low in capacity and inferior in repeated stability. Further, the negative electrode active material is claim 2.
Of Comparative Example 4 and the molar ratio of the electrolytic solution (S
/ Li) was out of the range of the present invention, the discharge capacity at the first cycle was high in the battery F of Example 2, but in terms of repeated stability, AE of Examples 1 and 2 and Examples Three
It was inferior to ~ 8.

[0051]

As described above, according to the present invention,
By specifying the non-aqueous electrolyte to be used in terms of the number of donors of the solvent and the molar ratio (S / Li) of the highly active solvent and the lithium ion, it is possible to obtain a secondary battery having high capacity and excellent repeated stability. it can. In addition to this, in claim 2,
By specifying the negative electrode active material, there is an effect that the charge / discharge repeating characteristics are further improved.

[Brief description of the drawings]

FIG. 1 is a graph showing charge / discharge characteristics obtained in Example 1.

2 is a graph showing charge / discharge characteristics obtained in Comparative Example 1. FIG.

FIG. 3 is a vertical cross-sectional view showing an embodiment of a non-aqueous electrolyte secondary battery in the present invention.

[Explanation of symbols]

 1 positive electrode 2 negative electrode 10 non-aqueous electrolyte secondary battery

Claims (2)

[Claims] 1. A non-aqueous electrolyte solution 2 in which the negative electrode active material is a material that occludes lithium ions during charging and releases lithium ions during discharging, and the electrolyte solution is a solution in which a lithium compound is dissolved in an organic solvent. In the next battery, the organic solvent is a mixed solvent of a high activity solvent having a donor number of 14 to 20 and a low activity solvent having a donor number of 10 or less, and the electrolyte solution is the high activity solvent (S). A non-aqueous electrolyte secondary battery having a lithium ion (Li ⁺ ) molar ratio (S / Li) of 3.0 or less. 2. The non-aqueous electrolyte secondary according to claim 1, wherein the negative electrode active material is a carbon material having an interplanar spacing (d _{00 2} ) determined by X-ray diffraction of 0.3365 nm or more. battery.