JP2000100421A - Nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a nonaqueous electrolyte secondary battery having high initial charge and discharge efficiency and an excellent loading characteristic. SOLUTION: In this nonaqueous electrolyte secondary battery comprising positive electrodes 1, negative electrodes 2 and an electrolyte 4 of a nonaqueous solvent, graphite is used as an active material of the negative electrodes 2. The electrolyte 4 includes ester phosphate, and at least one of compounds having aliphatic unsaturated ether structural group or unsaturated ester structural group, then the content of the ester phosphate is set not less than 15% is volume ratio in the electrolyte 4. The compound having the aliphatic unsaturated ether structural group or unsaturated ester structural group can preferably be reduced on the negative electrodes 2 for metal Li at the volt of not less than 0.8 V, and the amount of the compound preferably is not less than 0.1 μL/cm2 per unit area.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a non-aqueous electrolyte secondary battery, and more particularly, to a non-aqueous electrolyte secondary battery having high initial charge / discharge efficiency and excellent load characteristics.

[0002]

2. Description of the Related Art Non-aqueous electrolyte secondary batteries represented by lithium secondary batteries have high capacity, high voltage and high energy density, and therefore, great expectations are placed on their development. .

In this non-aqueous electrolyte secondary battery, lithium or a lithium alloy has been used as a negative electrode active material. In the case of using such a negative electrode active material, a high capacity can be expected. The internal short circuit is likely to occur due to the growth, and therefore, there has been a problem that the battery performance is lowered or the safety is lacking.

Therefore, it has been proposed to use a carbon material capable of doping and undoping lithium ions as a negative electrode active material in place of lithium or a lithium alloy. Of these carbon materials, graphite is particularly preferred. It is highly active and can dope and undope a large amount of lithium ions, so that a high capacity can be achieved. -83609, JP-A-8-31582
0, JP-A-9-35752, JP-A-10-
No. 140425).

[0005]

However, in the above-mentioned non-aqueous electrolyte secondary battery, since an organic solvent is used as a constituent solvent of the electrolyte, it is required that there is no danger of ignition or ignition. To respond to such demands, measures such as protection circuits are provided to prevent overcharging and prevent internal short circuit from occurring, and a general internal short circuit only generates heat in the battery. Measures have been taken to prevent the problem from developing into safety.

However, if the capacity is increased by using an active material that can be expected to have a higher capacity, or depending on the specifications required by the user, intentional abnormal use may occur unless the structure of the battery is sufficiently devised. It was found that when a crush test or a nail piercing test, which is a safety confirmation test under severe conditions assuming the above, was performed, safety tended to decrease. Such a crush test or nail penetration test is based on the assumption that the battery is destroyed intentionally or by some accident, etc., and cannot occur under normal use conditions. It is desirable to have a high safety with no danger of ignition or ignition even during a crush test or a nail penetration test. In particular, graphite is suitable for high capacity because it can contain a large amount of lithium.However, when a short circuit occurs, an enormous current flows instantaneously, and its Joule heat causes rapid heat generation to reach a high temperature. There was a problem that the risk of ignition was high.

[0007] In order to solve the above problems, attempts have been made to make the electrolytic solution flame-retardant by using a flame-retardant solvent as a constituent solvent of the electrolytic solution. (Japanese Patent Laid-Open No. 4-184)
870, etc.).

However, in a non-aqueous electrolyte secondary battery using a combination of a negative electrode using graphite as a negative electrode active material and a phosphate-based electrolyte, a larger amount of gas is generated during formation or heating than in the conventional electrolyte. Therefore, there is a problem that the current cutoff mechanism may be operated during normal use, and the initial charge / discharge efficiency and load characteristics are reduced. Further, in order to improve the load characteristics, it has been proposed to use a cyclic carbonate or the like in combination. However, when a cyclic carbonate or the like is used, gas generation becomes more remarkable and impurities are generated in the electrolytic solution. There was also.

The present invention solves the problem of safety caused by abnormal use in the case of increasing the capacity as described above, and solves the problem when graphite, which can be expected to have a high capacity, is used as the negative electrode active material. Also eliminates the danger of ignition and ignition, has high capacity, high safety, and high initial charge / discharge efficiency.
It is another object of the present invention to provide a non-aqueous electrolyte secondary battery having excellent load characteristics.

[0010]

According to the present invention, there is provided a non-aqueous electrolyte secondary battery using graphite as a negative electrode active material, wherein a phosphate ester is used as a main constituent solvent of the electrolyte. To increase the safety of the battery by making the electrolyte solution flame-retardant, and to further include at least one compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group in the electrolyte solution. Thereby, it is possible to charge and discharge graphite even in an electrolytic solution containing a phosphate ester as a main constituent solvent, and to obtain a non-aqueous electrolyte secondary battery having high initial charge / discharge efficiency and excellent load characteristics. is there.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the present invention, as described above,
Even when graphite is used as the negative electrode active material and phosphate ester is used as the main constituent solvent of the electrolytic solution, by using a compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group, The reason why the generation of gas can be prevented, the initial charge / discharge efficiency can be improved, and the load characteristics can be improved is not always clear at present, but is considered as follows.

That is, when graphite is used as a negative electrode active material, which has been a problem in the past, and a phosphoric acid ester is contained in an electrolytic solution, a gas is generated during chemical formation or heating.
Prior to lithium ion doping graphite during charging,
It is considered that a decomposition reaction of the phosphate ester occurs on the graphite, and a gas is generated by the decomposition reaction. The decrease in the initial charge / discharge efficiency and load characteristics when graphite and phosphate are used is caused by the formation of a phosphorus (P) film on graphite due to the decomposition reaction, and the phosphorus film is transferred during charging. This is presumably because lithium ions are prevented from being doped into graphite. Further, the present inventors have examined in detail the conditions under which the decomposition reaction of the phosphate ester occurs, and as a result, it has been found that the conditions mainly occur during the first charge after the battery is assembled.

Therefore, based on the above findings, the present inventors have found that when a phosphate ester is contained in an electrolytic solution, it can be decomposed on graphite before the phosphate ester, and then the phosphorous ester can be decomposed. Even if the acid ester is in close proximity to graphite, it will hinder contact with graphite and suppress the decomposition reaction.Furthermore, intensive research has been conducted to find compounds that enable doping and undoping of lithium ions. It has been found that when a compound having an ether structure group or an unsaturated ester structure group is contained in an electrolytic solution together with a phosphate ester, it is possible to suppress a decrease in initial charge / discharge efficiency and load characteristics based on the phosphate ester. As the compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group, a compound that can be reduced at a potential of 0.8 V or more with respect to metal Li on a negative electrode is particularly preferable. .

Compounds having such an aliphatic unsaturated ether structure group or unsaturated ester structure group include:
For example, vinyl ethers, acrylic esters, vinyl esters and the like can be mentioned. Specifically, for example, compounds having an unsaturated ether structural group such as methoxybutadiene and butyl vinyl ether, and unsaturated compounds such as ethoxy acrylate, dimethyl fumarate and vinyl acetate In addition to the compound having an ester structure group, a compound having an aromatic ring, for example, vinyl benzoate can be used as long as it has an aliphatic unsaturated ether structure group or unsaturated ester structure group. Particularly, dimethyl fumarate in which a carbonyl group and an alkene group can be conjugated is preferable because it has a high affinity for the negative electrode and easily reacts on the negative electrode surface prior to the phosphate ester. These compounds may be used alone or in combination of two or more.

The amount of the compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group to be used is important in relation to the negative electrode from the viewpoint of forming a film based on the compound on graphite. . That is, according to the study of the present inventors, the compound having the aliphatic unsaturated ether structure group or unsaturated ester structure group is 0.1 μL / cm ² or more and 1.0 μL or more per unit area of the negative electrode.
L / cm ² or less is preferable, 0.3 [mu] L / cm ² or more 0.8μL / cm ² or less being more preferred. As described above, by using the amount of the compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group as described above, the decomposition of the phosphate ester is suppressed, the gas generation is reduced, and the first charge is performed. Discharge efficiency can be improved, and load characteristics can be improved. Note that the unit area of the negative electrode refers to a unit area of a portion where the negative electrode active material layer or the negative electrode mixture layer including the negative electrode active material is formed, such as an exposed portion of a negative electrode current collector and a lead body. Is not included. In addition, although L means liter, in this specification, in order to avoid erroneous recognition of the numeral "1", it is not represented by a lowercase letter but is represented by an uppercase "L".

In the present invention, the proportion of the phosphoric acid ester in the electrolytic solution is set to 15% or more by volume in the electrolytic solution in order to make the battery using a graphite having a high capacity as a negative electrode flame-retardant. It is necessary, and it is preferably at least 30%, more preferably at least 50%, more preferably at least 70%, further preferably at least 80%. The electrolyte is formed by dissolving the electrolyte in the electrolyte solvent, but the volume of the electrolyte when the electrolyte is dissolved is very small compared to the volume of the electrolyte solvent, so that the volume of the electrolyte is substantially the volume of the electrolyte solvent. It can be regarded as the same as the volume.

When the phosphate ester is used in a volume ratio of 70% or more in the electrolytic solution, the conductivity of the electrolytic solution is reduced, and the viscosity of the electrolytic solution is increased, so that the load characteristics may be reduced. is there. Therefore, the present inventors have further studied, and in such a case, by using a cyclic phosphate ester and a chain phosphate ester together, the conductivity of the electrolytic solution is improved, and the load characteristics are reduced. I found that it can be reduced. That is, by using a cyclic phosphate and a chain phosphate in combination as described above, it is possible to increase the induction rate while suppressing an increase in viscosity, thereby reducing the decrease in load characteristics. it can. The volume ratio of the cyclic phosphate to the chain phosphate is 1: 1 to 1:20, especially 1: 3 by volume.
１ ： 1: 10 is preferred.

Examples of the cyclic phosphate include ethylene methyl phosphate and ethylene ethyl phosphate, and examples of the linear phosphate include trimethyl phosphate and triethyl phosphate. Since the effect of the phosphoric acid ester on the flame retardancy is higher as the number of carbon atoms is smaller, it is preferable that 80% or more by volume of the phosphoric acid ester used in the present invention has 6 or less carbon atoms. 4
It is more preferable that:

In the present invention, in addition to the above, for example, 1,2-dimethoxyethane, 1,2-diethoxyethane, propylene carbonate, ethylene carbonate, γ-butyrolactone, tetrahydrofuran,
One or more organic solvents such as 1,3-dioxolane, dierucarbonate, dimethyl carbonate, ethyl methyl carbonate and the like can be used in combination. In addition to the phosphoric acid ester, a phosphazene derivative, a silane, a halide of an ether or an ester, and the like, which are expected to have an effect as a flame retardant solvent, can be used in combination.

As the electrolyte, for example, LiClO_Four,
LiPF₆, LiBF_Four, LiAsF₆, LiSb
F₆, LiCF_ThreeSO_Three, LiC_FourF₉SO_Three, LiC
F_ThreeCO _Two, Li_TwoC_TwoF_Four(SO_Three)_Two, LiN (C
F_ThreeSO_Two)_Two, LiC (CF_ThreeSO_Two)_Three, LiC_n
F_{2n + 1}SO_Three(N ≧ 2), LiN (RfO SO_Two)_Two
[Where Rf is a fluoroalkyl group] alone or
Can be used in combination of two or more, especially LiPF₆And LiC
_FourF₉SO_ThreeAre preferred. Electrolyte in electrolyte
Is not particularly limited, but the concentration is 1 m
ol / l or more make the safety even better
And more preferably 1.2 mol / l or more.
Also, when the content is 1.7 mol / l or less, the electric characteristics are improved.
And more preferably 1.5 mol / l or less.

In the present invention, the negative electrode active material only needs to be capable of doping and undoping lithium ions. From such a viewpoint, graphite is used as the negative electrode active material. The graphite may be either natural graphite or artificial graphite. It may be. Among them, the interplanar spacing (d ₀₀₂ ) of the (002) plane, which has a particularly large reaction area and can achieve high capacity, is 0.35 nm or less, and the crystallite size (Lc) in the c-axis direction is 35 nm or more. Are preferred. Graphite, which can be expected to have such a high capacity, has excellent properties, but has a drawback of easily decomposing the phosphate ester in the electrolytic solution, and in the past, it could not be fully utilized, According to the present invention, even when such a high capacity graphite is used,
When the present invention is applied to a case where graphite capable of preventing a decrease in load characteristics and expected to have such a high capacity is used, the effects of the present invention are remarkably exhibited.

The negative electrode is made of, for example, a conductive auxiliary such as flake graphite or carbon black, if necessary, polyvinylidene fluoride, polytetrafluoroethylene, ethylene propylene diene rubber, or polyacrylic. A binder such as an acid and carboxymethylcellulose is added and mixed to prepare a negative electrode mixture, which is dissolved or dispersed in water or a solvent to form a paste (the binder is dissolved in a solvent or the like beforehand, and then the negative electrode mixture is prepared). A negative electrode mixture paste may be applied to a current collector made of copper foil or the like, and dried to form a negative electrode mixture layer on at least one surface of the current collector. It is made by going through. However, the method for producing the negative electrode is not limited to the method exemplified above, and may be another method. The amount of the binder is not particularly limited, but is preferably 1 to 50% by weight, more preferably 2 to 20% by weight, based on the active material.

In the present invention, as the positive electrode active material, for example, lithium cobalt oxide such as LiCoO ₂ ;
lithium nickel oxide such as iNiO ₂ , LiMn ₂
Lithium manganese oxides such as O ₄ , lithium titanium oxides such as LiTiO ₂ , and metals such as Li (NiCo) O ₂ in which a part of Ni of LiNiO ₂ is replaced by Co, manganese dioxide, vanadium pentoxide, and chromium oxide Oxides or metal sulfides such as titanium disulfide and molybdenum disulfide are used. Among them, LiNiO ₂ , Li
The open circuit voltage during charging of NiO ₂ , LiMn ₂ O _4, etc. is L
A lithium composite oxide exhibiting 4 V or more on an i basis is preferable because a high energy density can be obtained. In particular, when the present invention is applied to a thermally unstable lithium nickel oxide such as LiNiO ₂ or a composite oxide containing nickel as the positive electrode active material, the effect is remarkably exhibited.

For the positive electrode, for example, a conductive additive such as flake graphite and a binder such as polyvinylidene fluoride are added to the above-mentioned positive electrode active material, if necessary, as in the case of the above-mentioned negative electrode. A paste is prepared by dissolving or dispersing the mixture in water or a solvent to form a paste (the binder may be dissolved in a solvent in advance and then mixed with the positive electrode active material). The current collector is applied to a current collector, dried and formed on at least one surface of the current collector to form a positive electrode mixture layer. However, the method for producing the positive electrode is not limited to the method described above, but may be another method.

As the current collector for the positive electrode and the negative electrode, for example, a metal foil such as aluminum, copper, nickel, and stainless steel, or a net formed of these metals is used. Aluminum foil is particularly suitable, and copper foil is particularly suitable as the negative electrode current collector.

The separator may be any one that has sufficient strength and can hold a large amount of electrolyte. From such a viewpoint, the separator has a thickness of 10 to 50 μm and a porosity of 30 to 70 μm.
% Of polyethylene, polypropylene, or a copolymer of ethylene and propylene.

The battery is, for example, a spirally wound electrode body or a laminated electrode body such as a spirally wound electrode body produced by spirally winding a separator between the positive electrode and the negative electrode produced as described above. Is inserted into a nickel-plated iron or stainless steel battery case and sealed. Further, the battery usually incorporates an explosion-proof mechanism for discharging the gas generated inside the battery to the outside of the battery when the pressure has risen to a certain pressure, thereby preventing the battery from bursting under high pressure.

[0028]

Next, the present invention will be described more specifically with reference to examples. However, the present invention is not limited to only these examples.

Example 1 Trimethyl phosphate, ethylene carbonate and dimethyl fumarate were mixed at a volume ratio of 84: 8: 8, and LiPF ₆ was dissolved in the mixture at a ratio of 1.0 mol / l to obtain a non-aqueous solvent system. Was prepared.

In addition, lithium cobalt oxide (LiCo
O ₂₎ 91 parts by weight were mixed by adding graphite 6 parts by weight and 3 parts by weight of polyvinylidene fluoride to prepare a positive electrode mixture, and a paste by dispersing it in N- methylpyrrolidone. This positive electrode mixture paste is uniformly applied to both sides of a 20 μm-thick aluminum foil as a positive electrode current collector, dried to form a positive electrode mixture layer, and then compression-molded by a roller press to form a lead body. Welding was performed to produce a belt-shaped positive electrode.

Separately from the above, 90 parts by weight of flaky graphite [plane spacing (d ₀₀₂ ) of (002) plane: 0.336 nm, crystallite size in the c-axis direction (Lc): 42 nm] and polyvinylidene fluoride The mixture was mixed with 10 parts by weight to prepare a negative electrode mixture, which was dispersed in N-methylpyrrolidone to form a paste. This negative electrode mixture paste is uniformly applied to both sides of a 18 μm-thick strip-shaped copper foil as a negative electrode current collector, dried to form a negative electrode mixture layer, and then compression-molded with a roller press to form a lead. The body was welded to produce a strip-shaped negative electrode. The area of the portion where the negative electrode mixture layer was formed was about 260 cm ² in total on both sides.

Next, the above-mentioned strip-shaped positive electrode was overlaid on the above-mentioned strip-shaped negative electrode via a separator made of a microporous polyethylene film having a thickness of 25 mm, spirally wound into a spiral electrode body, and then formed into an outer diameter of 14 mm. Was filled in the bottomed cylindrical battery case, and the positive electrode and the negative electrode lead bodies were welded. Then, 1.6 mL of the above-mentioned electrolytic solution was injected into the battery case. Then, close the opening of the battery case,
After aging, a cylindrical nonaqueous electrolyte secondary battery having the structure shown in FIG. 1 was produced. The amount of dimethyl fumarate per unit area of the negative electrode (however, the unit area of the portion where the negative electrode mixture layer was formed) was 0.48 μL / cm ² .

Referring to the battery shown in FIG. 1, 1 is the positive electrode and 2 is the negative electrode. In FIG. 1, in order to avoid complication, the current collector and the negative electrode used for producing the positive electrode 1 and the negative electrode 2 were used. A metal foil or the like as a base is not shown.
The positive electrode 1 and the negative electrode 2 are spirally wound with a separator 3 interposed therebetween, and are housed in a battery case 5 together with the electrolytic solution 4 as a spiral electrode body.

The battery case 5 is made of stainless steel, and an insulator 6 made of polypropylene is disposed at the bottom of the battery case 5 before the spiral electrode body is inserted. The sealing plate 7 is made of aluminum, has a disk shape, and has a thin portion 7 in the center.
In addition, a hole is provided around the thin portion 7a as a pressure introduction port 7b for applying the internal pressure of the battery to the explosion-proof valve 9. The projection 9a of the explosion-proof valve 9 is welded to the upper surface of the thin portion 7a to form a welded portion 11. In addition, the thin portion 7a provided on the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 are illustrated only in a cut plane so as to be easily understood in the drawings, and a contour line behind the cut plane is shown. Is not shown. Further, the welded portion 11 between the thin portion 7a of the sealing plate 7 and the protruding portion 9a of the explosion-proof valve 9 is shown in an exaggerated state rather than the actual one so as to be easily understood in the drawings.

The terminal plate 8 is made of rolled steel, nickel-plated on its surface, and has a hat-like shape with a brim-shaped peripheral portion. The terminal plate 8 is provided with a gas outlet 8a. . The explosion-proof valve 9 is made of aluminum and has a disk shape.
In the center thereof, a protruding portion 9a having a tip portion is provided on the power generation element side (the lower side in FIG. 1), and a thin portion 9b is provided, and the lower surface of the protruding portion 9a is, as described above, It is welded to the upper surface of the thin portion 7a of the sealing plate 7 to form a welded portion 11. The insulating packing 10 is made of polypropylene and has an annular shape. The insulating packing 10 is disposed above the peripheral portion of the sealing plate 7, and the explosion-proof valve 9 is disposed above the insulating packing 10. The insulating packing 10 insulates the sealing plate 7 from the explosion-proof valve 9. The gap between the two is sealed so that the electrolyte does not leak from between the two. The annular gasket 12 is made of polypropylene, and the lead body 13 is made of aluminum. The sealing plate 7 and the positive electrode 1 are connected to each other. An insulator 14 is disposed above the spiral electrode body. The bottom portion is connected by a lead body 15 made of nickel.

In this battery, the thin portion 7 of the sealing body 7
a and the explosion-proof valve 9a come into contact at the welded portion 11, and the explosion-proof valve 9a
And the peripheral edge of the terminal plate 8 are in contact with each other, and the positive electrode 1 and the sealing body 7 are connected by the lead 13 on the positive electrode side.
The positive electrode 1 and the terminal plate 8 are electrically connected to each other by the lead body 13, the sealing body 7, the explosion-proof valve 9, and the welded portion 11 thereof, and function normally as an electric circuit.

When an abnormal situation occurs in the battery and gas is generated inside the battery and the internal pressure of the battery rises, the internal pressure rises and the central part of the explosion-proof valve 9 moves in the direction of the internal pressure (FIG. 1).
Then, it is deformed in the upper direction)
The shearing force acts on the thin portion 7a integrated at 1 and the thin portion 7a is broken or the projection 9a of the explosion-proof valve 9 is formed.
And the thin portion 7a of the sealing plate 7 is peeled off, whereby the electrical connection between the positive electrode 1 and the terminal plate 8 is lost and the current is cut off. As a result, the battery reaction does not progress, so even during overcharging or short-circuiting, the battery temperature and internal pressure rise due to charging current and short-circuit current do not progress further, and it is designed to prevent battery rupture etc. Have been.

Example 2 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that vinyl benzoate was used instead of dimethyl fumarate.

Example 3 As an electrolyte, a mixture of trimethyl phosphate, ethylene methyl phosphate, ethylene carbonate and methoxybutadiene in a volume ratio of 74: 10: 8: 8 was added to L.
except that the iPF ₆ was used dissolved 1.0 mol / l was used to fabricate a non-aqueous electrolyte secondary battery in the same manner as in Example 1.

Example 4 A non-aqueous electrolyte secondary battery was produced in the same manner as in Example 1 except that butyl vinyl ether was used instead of dimethyl fumarate.

Comparative Example 1 The procedure of Example 1 was repeated except that a mixture of trimethyl phosphate and ethylene carbonate in a volume ratio of 90:10 in which LiPF ₆ was dissolved in an amount of 1.0 mol / l was used as the electrolytic solution. A non-aqueous electrolyte secondary battery was manufactured.

The batteries of Examples 1 to 4 and Comparative Example 1 were charged and discharged within a voltage range of 2.75 V to 4.0 V, and the initial charge / discharge efficiency [(discharge capacity / charge capacity) × 10 5
0] and the current density of the discharge capacity at a current density of 1 C of 0.1.
The ratio to the discharge capacity at C was examined. Table 1 shows the results.
Shown in In Table 1, the ratio of the discharge capacity at a current density of 1 C to the discharge capacity at a current density of 0.1 C is indicated as a percentage as a “discharge capacity ratio (1 C / 0.1 C)”.

[0043]

[Table 1]

As shown in Table 1, the batteries of Examples 1 to 4 had higher initial charge / discharge efficiency than the battery of Comparative Example 1, and
The ratio of the discharge capacity at a current density of 1 C to the discharge capacity at a current density of 0.1 C [discharge capacity ratio (1 C / 0.1
C)] and the load characteristics were excellent. In particular, the battery of Example 1 using dimethyl phthalate having an alkene group conjugated to a carbonyl group had high initial charge / discharge efficiency. The initial charge / discharge efficiency of the battery of Comparative Example 1 was poor.
In Comparative Example 1, the decomposition of the phosphate ester in the electrolytic solution occurs,
It is considered that this is because many irreversible parts occurred in the charging capacity. The poor load characteristics of the battery of Comparative Example 1 are considered to be due to the fact that the coating formed inhibited the electrode reaction in Comparative Example 1. However, the batteries of Examples 1 to 4 of the present invention did not. No reduction in initial charge / discharge efficiency or load characteristics was observed.

[0045]

As described above, according to the present invention, a non-aqueous electrolyte secondary battery having high initial charge / discharge efficiency and excellent load characteristics can be provided.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing one example of a non-aqueous electrolyte secondary battery according to the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Positive electrode 2 Negative electrode 3 Separator 4 Electrolyte

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 5H003 AA01 AA02 AA10 BB04 BB05 BB12 BD03 5H014 EE01 EE08 EE10 HH01 HH04 HH06 5H029 AJ02 AJ03 AJ12 AK03 AL07 AM03 AM04 AM05 AM07 BJ02 BJ14 H09H

Claims (6)

[Claims] 1. A non-aqueous electrolyte secondary battery comprising a positive electrode, a negative electrode and a non-aqueous solvent-based electrolyte, wherein the active material of the negative electrode comprises graphite, and the electrolyte comprises a phosphate ester and an aliphatic A non-aqueous electrolyte solution containing at least one compound having an unsaturated ether structure group or an unsaturated ester structure group, and wherein the phosphate ester is at least 15% by volume in the electrolyte solution. Rechargeable battery. 2. A method according to claim 1, wherein the compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group comprises a metal L on the negative electrode.
2. The non-aqueous electrolyte secondary battery according to claim 1, wherein the non-aqueous electrolyte secondary battery can be reduced at a potential of 0.8 V or more with respect to i. 3. The method according to claim 1, wherein the amount of the compound having an aliphatic unsaturated ether structure group or unsaturated ester structure group is 0.1 μL / cm ² or more per unit area of the negative electrode. The non-aqueous electrolyte secondary battery according to the above. 4. The phosphoric acid ester is at least 70% by volume in the electrolytic solution, and the phosphoric acid ester comprises a cyclic phosphoric acid ester and a chain phosphoric acid ester. The non-aqueous electrolyte secondary battery according to any one of the above. 5. An unsaturated structural group of a compound having an aliphatic unsaturated ether structural group or an unsaturated ester structural group,
The non-aqueous electrolyte secondary battery according to any one of claims 1 to 4, which is adjacent to an ether group or an ester group. 6. An unsaturated structural group of a compound having an aliphatic unsaturated ether structure group or an unsaturated ester structure group,
The nonaqueous electrolyte battery according to any one of claims 1 to 5, wherein the nonaqueous electrolyte battery is an acrylic group or a vinyl group.