JP2000182669A - Battery electrolyte and nonaqueous electrolyte secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve energy and output densities by including a cyclic carbonate compound, at least one kind of an alkylmonocarbonate compound and an alkylenebiscarbonate compound, and a phosphorus-containing organic compound in an organic solvent. SOLUTION: This battery electrolyte includes an alkylmonocarbonate compound in an organic solvent is indicated by formula I. In formula I, R1 and R2 are each the same or different alkyl group, with the carbon number of at least one of them >=3. An alkylenebiscarbonate compound is indicated by formula II. In formula II, R1 and R2 are each the same or different 1-4C alkyl group, and R3 is a linear or branched 1-3C alkylene group. The electrolyte contains both two kinds of compounds and its content is preferably 5 to 50 vol.% when the total mass of the organic solvent is 100 vol.%.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a battery electrolyte which can be used as a battery electrolyte, and a non-aqueous electrolyte secondary battery which can be used as a battery for electric vehicles and portable electronic devices.

[0002]

2. Description of the Related Art In the background of energy problems and environmental problems,
There is a need for technology that makes more efficient use of electric power. For that purpose, an electric storage means capable of storing a large amount of electricity and efficiently taking out the stored electricity is required. As such an electricity storage means, a secondary battery having a large discharge capacity and a high discharge voltage and capable of repeatedly performing charging and discharging is optimal.

In such a secondary battery, a lithium secondary battery generates a charging reaction in which lithium ions are released from a positive electrode and occluded in a negative electrode during charging, and a discharging reaction is released from a negative electrode and occluded in a positive electrode during discharging. There is a battery. Since a lithium secondary battery has a high energy density and a high output density, a large discharge capacity and a high discharge voltage can be obtained. In particular, a lithium ion secondary battery in which a negative electrode active material made of a carbon material is used for the negative electrode has a long service life and high safety, and is considered to be practically excellent in batteries such as portable electronic devices and electric vehicles. It is expected to be used for such purposes.

In a lithium ion secondary battery, an electrolyte obtained by dissolving a supporting salt in an organic solvent is used as an electrolyte. In such non-aqueous electrolyte secondary battery electrolytes,
There is one in which a supporting salt such as lithium hexafluorophosphate (LiPF ₆ ) is dissolved in an organic solvent of a cyclic carbonate compound such as ethylene carbonate or propylene carbonate. Since the cyclic carbonate compound has a high dielectric constant, the energy density and the power density of the battery can be extremely high.

However, the cyclic carbonate compound has a high viscosity, so that the mobility of lithium ions is low. Therefore, organic solvents in which a low-viscosity chain carbonate compound such as dimethyl carbonate or diethyl carbonate is mixed with these cyclic carbonate compounds are widely used. However, these chain carbonate compounds have a drawback that they are easily volatilized because they are low molecular compounds.

Therefore, as described in JP-A-7-262849, it is possible to reduce the volatility and to improve the storage stability and cycle characteristics by incorporating an alkylenebiscarbonate compound in the electrolytic solution. It has been done. However, it is difficult to sufficiently increase the flame retardancy of the electrolytic solution simply by containing the alkylene biscarbonate compound. Therefore, although this electrolyte has the necessary safety, the safety has not been sufficiently satisfied.

On the other hand, as disclosed in JP-A-4-184870 and JP-A-8-111238, organic solvents such as phosphoric esters such as chain alkyl phosphates and cyclic phosphates and halogen compounds are disclosed. The safety has been improved by using.

However, when a phosphate ester is used as a main solvent, a side reaction occurs at the negative electrode interface during charging, and lithium ions cannot be efficiently absorbed. As a result, battery performance such as energy density, charge / discharge efficiency, and cycle characteristics may be significantly reduced.

On the other hand, in the electrolyte using ethylene carbonate as a main solvent and adding a small amount of a phosphoric acid ester, the battery performance is not affected, but within the required safety range, the safety is reduced. There was a problem of doing it.

[0010] Further, none of those using a phosphate ester, a halogen compound or the like as a main solvent can provide excellent battery performance even in a temperature range other than room temperature.

[0011]

DISCLOSURE OF THE INVENTION The present invention has been made in view of the above-mentioned circumstances, and it is possible to improve the battery performance such as energy density and output density. Provided is a battery electrolyte which can be kept high even in a temperature range and is extremely excellent in flame retardancy.

A non-aqueous electrolyte which is excellent in battery performance such as energy density, output density, charge / discharge efficiency, cycle characteristics and the like, is maintained at a high level even in an environment other than room temperature, and is extremely excellent in safety. Provide a secondary battery.

[0013]

Means for Solving the Problems The battery electrolyte of the present invention for solving the above problems is a battery electrolyte obtained by dissolving a supporting salt in an organic solvent, wherein the organic solvent comprises a cyclic carbonate compound. And at least one of an alkyl monocarbonate compound represented by Chemical Formula 1 and an alkylene biscarbonate compound represented by Chemical Formula 2, and a phosphorus-containing organic compound.

The cyclic carbonate compound can increase the dielectric constant and the like of the electrolytic solution. Therefore, the battery characteristics can be improved, for example, the energy density of the battery can be increased.

The alkyl monocarbonate compound represented by Formula 1 can lower the viscosity of the electrolyte.
Therefore, battery characteristics such as energy density and output density can be improved, for example, the mobility of electrolyte ions can be increased. In particular, the performance of the electrolyte at low temperatures can be improved, such as maintaining a high energy density of the battery even at low temperatures.

The alkylene biscarbonate compound represented by Chemical Formula 2 can improve the storage characteristics of the electrolytic solution. This alkylene biscarbonate compound can improve the performance of the electrolytic solution at high temperatures, for example, it can have excellent storage characteristics especially at high temperatures.

The phosphorus-containing organic compound can increase the flame retardancy of the electrolyte. Therefore, the safety of the electrolytic solution can be enhanced.

Each of the above compounds can exhibit its own function efficiently without inhibiting the functions of other compounds. Therefore, the battery electrolyte of the present invention can have excellent battery performance such as energy density and output density, and can maintain the battery performance high even in a temperature range other than room temperature. Extremely flame retardant. In particular, the battery electrolyte containing the alkylene biscarbonate compound represented by Chemical Formula 2 has excellent volatility and storage characteristics.

Therefore, according to the battery electrolyte of the present invention,
It is possible to obtain a battery that has excellent battery performance, is maintained at a high level even in a temperature range other than room temperature, and is extremely safe.

Further, a non-aqueous electrolyte secondary battery according to the present invention that solves the above-mentioned problems has a positive electrode and a negative electrode capable of releasing and occluding lithium ions, a positive electrode and a negative electrode interposed between the positive electrode and the negative electrode, and A non-aqueous electrolyte secondary battery comprising an electrolytic solution obtained by dissolving a supporting salt, wherein the organic solvent is
It is characterized by containing a cyclic carbonate compound, at least one of an alkyl monocarbonate compound represented by the chemical formula 1 and an alkylene biscarbonate compound represented by the chemical formula 2, and a phosphorus-containing organic compound.

In the nonaqueous electrolyte secondary battery of the present invention, since the electrolyte used has a high dielectric constant, the battery performance such as energy density, output density, charge / discharge efficiency, and cycle characteristics is extremely excellent. In addition, the electrolytic solution, the electrolytic solution performance is maintained high even in a temperature range other than room temperature, so that even if the battery is used in a temperature environment other than room temperature, the battery performance can be maintained high. Since the flame retardancy is extremely excellent, the safety of the battery can be made extremely excellent.

Therefore, the non-aqueous electrolyte secondary battery of the present invention is excellent in battery performance such as energy density, output density, charge / discharge efficiency, cycle characteristics, and the like. It can be maintained at a high level even in an environment with extremely high safety.
In particular, a non-aqueous electrolyte secondary battery in which an electrolytic solution containing an alkylene biscarbonate compound represented by Chemical Formula 2 is used, since the electrolytic solution has excellent volatility and storage characteristics, even when used for a long period of time. Battery performance can be maintained high.

Therefore, according to the non-aqueous electrolyte secondary battery of the present invention, a portable electronic device, a car, and the like can be driven with a high function, and can be used safely regardless of the environmental temperature. And the reliability of the battery becomes extremely high.

[0024]

BEST MODE FOR CARRYING OUT THE INVENTION (Electrolyte for Battery) The electrolyte for a battery of the present invention is not particularly limited by the type of battery used, and can be used for known types of batteries. Further, the battery may be a primary battery or a secondary battery.

In the electrolytic solution for a battery of the present invention, the type of the cyclic carbonate compound is not particularly limited, but ethylene carbonate, propylene carbonate, or the like can be used.

The type of the alkyl monocarbonate compound is not particularly limited either, but may be ethyl-n-butyl carbonate, methyl-t-butyl carbonate, di-
i-Propyl carbonate, t-butyl-i-propyl carbonate and the like can be used alone or in combination of two or more.

Although the kind of the alkylene biscarbonate compound is not particularly limited, 1,2-bis (methoxycarbonyloxy) ethane, 1,2-bis (ethoxycarbonyloxy) ethane, 1,2-bis ( Ethoxycarbonyloxy) propane or the like can be used alone or in combination of two or more.

The type of the phosphorus-containing organic compound is not particularly limited, either, and linear or cyclic phosphates such as trimethyl phosphate, triethyl phosphate, tricresyl phosphate, ethylene methyl phosphate and ethylene ethyl phosphate may be used alone. Or 2
More than one kind can be used in combination.

The battery electrolyte of the present invention preferably contains both an alkyl monocarbonate compound and an alkylene biscarbonate compound. This battery electrolyte can maintain excellent battery performance not only at room temperature but also at low and high temperature ranges. As a result, the temperature range in which excellent battery performance can be obtained is widened, and the battery can be made practical.

In the electrolyte solution for a battery of the present invention, the content of at least one of the alkyl monocarbonate compound represented by the chemical formula 1 and the alkylene biscarbonate compound represented by the chemical formula 2 is not particularly limited. Assuming that the total amount of the organic solvent is 100% by volume, the content is preferably 5 to 50% by volume, more preferably 30 to 50% by volume.

The battery electrolyte can further improve the battery performance, can maintain the battery performance even higher in a temperature range other than room temperature, and is extremely flame-retardant. Excellent. The reason is that the content of at least one of the alkyl monocarbonate compound represented by the chemical formula 1 and the alkylene biscarbonate compound represented by the chemical formula 2 is appropriate for the content of the cyclic carbonate compound and the phosphorus-containing organic compound. It is conceivable that a good balance can be achieved and the function can be exhibited efficiently.

The type and content of the phosphorus-containing organic compound are not particularly limited, but may be at least one of chain and cyclic phosphate compounds, and the total amount of the organic solvent may be 100% by volume. Then, preferably 5 to 35% by volume, more preferably 25 to 35% by volume
It is preferably contained.

This battery electrolyte solution can further improve the battery performance, can maintain the battery performance even higher in a temperature range other than room temperature, and can be extremely flame-retardant. Excellent. The reason is that the content of the phosphorus-containing organic compound of that type is reduced to the content of at least one of the cyclic carbonate compound, and the alkyl monocarbonate compound represented by the chemical formula 1 and the alkylene biscarbonate compound represented by the chemical formula 2. It is conceivable that an appropriate balance can be obtained for the function and that the function can be exhibited efficiently.

Further, the kind of the supporting salt is not particularly limited, but an inorganic salt selected from LiPF ₆ , LiBF ₄ , LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ ) ₂ and L
It is preferably at least one kind of an organic salt selected from iN (SO ₃ CF ₃ ) ₃ and a derivative of the organic salt.

This battery electrolyte can further improve the battery performance, can maintain the battery performance even higher in a temperature range other than room temperature, and can be extremely flame-retardant. Excellent.

The concentration of the supporting salt is not particularly limited, either, and it is preferable to appropriately select the concentration in consideration of the type of the supporting salt and the organic solvent depending on the application. (Non-Aqueous Electrolyte Secondary Battery) The non-aqueous electrolyte secondary battery of the present invention is not particularly limited in its shape, and can be used as batteries of various shapes such as a coin shape, a cylindrical shape, and a square shape. FIG.
Fig. 2 shows an example of a coin type non-aqueous electrolyte secondary battery of the present invention, and Fig. 2 shows an example of a cylindrical type non-aqueous electrolyte secondary battery of the present invention.

For the positive electrode, if lithium ions can be released during charging and occluded during discharging,
The material configuration is not particularly limited, and a known material configuration can be used. In particular, it is preferable to use a mixture obtained by applying a mixture obtained by mixing a positive electrode active material, a conductive material and a binder to a current collector.

The type of the active material is not particularly limited as the positive electrode active material, and a known active material can be used. Among them, LiCoO ₂ , LiNiO ₂ , LiM
Composite oxides of lithium and transition metals such as n ₂ O ₄
Excellent performance of active materials such as excellent diffusion performance of electrons and lithium ions. Therefore, when such a composite oxide of lithium and transition metal is used for the positive electrode active material, high charge / discharge efficiency and good cycle characteristics can be obtained. In particular, Li
If Mn ₂ O ₄ is used, the cost can be reduced because the manganese resources are abundant.

The material of the negative electrode is not particularly limited as long as it can occlude lithium ions during charging and release lithium ions during discharging, and can use a material having a known material configuration. In particular, it is preferable to use a mixture obtained by applying a mixture obtained by mixing a negative electrode active material, a conductive material and a binder to a current collector.

The negative electrode active material is not particularly limited by the type of the active material, and a known negative electrode active material can be used. Above all, carbon materials such as natural graphite and artificial graphite having high crystallinity are excellent in active material performance such as excellent in lithium ion occlusion performance and diffusion performance. for that reason,
If such a carbon material is used for the negative electrode active material, high charge / discharge efficiency and good cycle characteristics can be obtained.

As the electrolytic solution, the same type of electrolytic solution as the battery electrolytic solution of the present invention can be used.

[0042]

The present invention will be described below in detail with reference to examples. (Example 1) First, an organic solvent was prepared by mixing ethylene carbonate, diisopropyl carbonate, and triethyl phosphate at the same volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Example 2 First, an organic solvent was prepared by mixing ethylene carbonate, ethyl-n-butyl carbonate, and triethyl phosphate at an equal volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. (Example 3) First, an organic solvent was prepared by mixing ethylene carbonate, 1,2-bis (ethoxycarbonyloxy) ethane, and triethyl phosphate at an equal volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Example 4 First, an organic solvent was prepared by mixing ethylene carbonate, 1,2-bis (methoxycarbonyloxy) propane, and triethyl phosphate at the same volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 1 First, an organic solvent was prepared by mixing ethylene carbonate and diethyl carbonate at an equal volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 2 First, an organic solvent was prepared by mixing ethylene carbonate and diisopropyl carbonate at an equal volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 3 First, an organic solvent was prepared by mixing ethylene carbonate and 1,2-bis (ethoxycarbonyloxy) ethane at an equal volume ratio. In this organic solvent,
LiPF ₆ was dissolved at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 4 First, an organic solvent was prepared by mixing ethylene carbonate and triethyl phosphate at an equal volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 5 First, ethylene carbonate, diisopropyl carbonate, and 1,2-bis (ethoxycarbonyloxy) ethane were mixed at an equal volume ratio to prepare an organic solvent. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Comparative Example 6 An organic solvent was prepared by mixing diisopropyl carbonate, 1,2-bis (ethoxycarbonyloxy) ethane, and triethyl phosphate at the same volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. (Example 5) First, ethylene carbonate was 33% by volume, diisopropyl carbonate was 17% by volume,
An organic solvent was prepared by mixing -bis (ethoxycarbonyloxy) ethane at a volume ratio of 17% by volume and triethyl phosphate at 33% by volume. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. Example 6 First, 30% by volume of ethylene carbonate, 20% by volume of diisopropyl carbonate,
An organic solvent was prepared by mixing -bis (ethoxycarbonyloxy) ethane at a volume ratio of 20% by volume and triethyl phosphate at 30% by volume. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain an electrolytic solution. Example 7 First, an organic solvent was prepared by mixing ethylene carbonate, diisopropyl carbonate, 1,2-bis (ethoxycarbonyloxy) ethane, and triethyl phosphate at the same volume ratio. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. (Example 8) First, ethylene carbonate was 33% by volume, ethyl-n-butyl carbonate was 17% by volume,
An organic solvent was prepared by mixing 1,2-bis (methoxycarbonyloxy) propane at a volume ratio of 17% by volume and triethyl phosphate at 33% by volume. LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte. (Example 9) First, 33% by volume of ethylene carbonate, 17% by volume of ethyl-n-butyl carbonate,
17% by volume of 1,2-bis (methoxycarbonyloxy) propane, 33% by volume of ethylene ethyl phosphate
The organic solvents were prepared by mixing at the following volume ratios.
LiPF ₆ was dissolved in this organic solvent at a concentration of 1 mol / liter to obtain a battery electrolyte.

Table 1 summarizes the composition of the organic solvent in each of the battery electrolyte solutions obtained as described above.

[0044]

[Table 1]

[Evaluation Method of Flame Retardancy of Electrolyte Solution] In order to examine the flame retardancy of each battery electrolyte solution obtained in the above Examples and Comparative Examples, the following burning rate test was carried out.

First, a 0.04 mm-thick separator manila paper cut into a 15 mm width and a 320 mm length was immersed in each battery electrolyte solution, and the electrolyte solution was impregnated in the manila paper. Thereafter, the manila paper was pulled up from each of the electrolytes, suspended vertically in the atmosphere for 3 minutes, and extra battery electrolyte attached to the manila paper was dropped and removed.

Next, a sample table having a supporting needle and capable of piercing and arranging manila paper was prepared, and each of the manila paper impregnated with the battery electrolyte was pierced into the supporting needle of the sample table at 25 mm intervals. And fixed horizontally. This sample table is 25
Put it in a metal box of 0mm x 250mm x 500mm,
One end was lit with a lighter.

At this time, the speed at which the combustion moves in the longitudinal direction of the manila paper (hereinafter simply referred to as the burning speed).
Was measured, and the flame retardancy of the battery electrolyte was evaluated. [Method for Evaluating Viscosity] At 20 ° C., the viscosities of the respective battery electrolytes were measured with a rotational viscometer. [Evaluation Method of Storage Characteristics at High Temperature] A lithium metal body was immersed in each battery electrolyte and kept at 60 ° C. for 50 hours. A change in the color of the electrolyte solution before and after the high-temperature holding test was observed. [Preparation of Non-Aqueous Electrolyte Secondary Battery] Next, coin-type non-aqueous electrolyte secondary batteries schematically shown in FIG. 1 were prepared using the respective battery electrolytes obtained as described above.
This nonaqueous electrolyte secondary battery includes a positive electrode 1 and a negative electrode 2 capable of releasing and occluding lithium ions, and an electrolytic solution 3 interposed between the positive electrode 1 and the negative electrode 2.

In this battery, the cathode 1, the anode 2, and the electrolyte 3 are made of stainless steel in the cathode case 4 and the anode case 5, respectively.
6 are sealed. A separator 7 made of a polyethylene film is interposed between the positive electrode 1 and the negative electrode 2. This battery was manufactured as follows.

The positive electrode 1 was formed as follows.

N-methyl-2-pyrrolidone (NMP) was added to a mixture of 90 parts by weight of LiMn ₂ O ₄ and 10 parts by weight of polyvinylidene fluoride and kneaded to obtain a slurry.
This slurry was applied to a positive electrode current collector 1a made of aluminum, dried, and further subjected to press molding to obtain a positive electrode 1.

The negative electrode 2 was formed as follows.

NMP was added to a mixture of 90 parts by weight of carbon powder and 10 parts by weight of polyvinylidene fluoride and kneaded,
A slurry was obtained. This slurry was applied to a negative electrode current collector 2a made of copper, dried, and further subjected to press molding to obtain a negative electrode 2.

The positive electrode 1 and the negative electrode 2 obtained as described above were welded to the positive electrode case 4 and the negative electrode case 5, respectively, and were overlapped with a separator 7 interposed between these welded bodies. Subsequently, after injecting the electrolyte 3 into a predetermined place,
The non-aqueous electrolyte secondary battery shown in FIG. 1 was completed by sealing with gaskets 6 and 6.

It should be noted that the battery of the present invention is not limited to the coin type battery used in the embodiment, and similar results can be obtained with, for example, a cylindrical battery shown in FIG.

FIG. 2 is a conceptual diagram of a cylindrical type of the non-aqueous electrolyte secondary battery of the present invention. FIG. 2A is a schematic perspective sectional view of the battery, and FIG. 2B is an explanatory schematic diagram showing an electrode portion. .

The cylindrical nonaqueous electrolyte secondary battery 10 is formed by laminating the same positive electrode and negative electrode as those manufactured in a coin shape into a sheet shape, laminating them through a separator, and winding them in a spiral shape many times. It is housed in a predetermined cylindrical case as a rotator.

That is, as shown in FIG. 2B, the structure of the electrodes is such that the negative electrode mixture 11 formed on the negative electrode current collector 12 and the positive electrode mixture 13 formed on the positive electrode current collector 14 have a mixed surface. They are arranged so as to face each other, and are wound with a separator 16 and an electrolyte solution 15 interposed therebetween to form a wound body and housed in a battery can shown in FIG. 2A via an insulating plate.

A negative electrode lead 12 ′ is welded to the end of the negative electrode current collector 12 of the wound body, and a nickel negative electrode terminal 1 is connected to the end.
8 is welded to the case 21 via the current interrupting thin plate 22. On the other hand, a positive electrode terminal 17 made of aluminum is attached to an end of the positive electrode lead 14 ′ welded to the positive electrode current collector 14, and is fixed as a battery lid via a current interrupting thin plate 22. As a result, the bottom part of the case 21 becomes the negative terminal part 18 and the lid part of the case becomes the positive terminal part 17. The above-mentioned non-aqueous electrolyte 15 is injected into the wound body accommodated in the case 21, sealed with a gasket 23, and
4, a cylindrical non-aqueous electrolyte secondary battery having a diameter of 18 mm and a height of 65 mm can be formed.

The method for producing a cylindrical battery is the same as described above, except that a positive electrode, a negative electrode, and an electrolytic solution are produced and a thickness of 25 μm is obtained.
m is used as a separator, and the above-described positive electrode and negative electrode are sequentially laminated, and then spirally wound many times to form a wound body. Next, an insulator was inserted into the bottom of the battery can, and the wound body was stored. And
The negative electrode and the positive electrode terminal are connected to the bottom and the lid of the battery can, and the above-described non-aqueous electrolyte is injected into the battery can prepared as described above, and sealed to form a cylindrical non-aqueous electrolyte secondary battery. Can be made.

In this example, evaluation was performed using a coin-shaped secondary battery. [Measurement of Discharge Capacity of Nonaqueous Electrolyte Secondary Battery] Examples 1 to 9
Each of the nonaqueous electrolyte secondary batteries using the battery electrolytes of Comparative Examples 1 to 6 was charged and discharged 50 times at 20 ° C. and 60 ° C. under the following charge and discharge conditions. The discharge capacity was measured at the beginning of the charge / discharge cycle and after the end of the 50th cycle. Then, a capacity retention ratio after 50 cycles of charge / discharge with respect to the initial discharge capacity was calculated. Further, in the test at 20 ° C., the internal resistance of each battery was measured before and after 50 cycles of charge and discharge.

At 0 ° C., a charge / discharge test was performed under the same charge / discharge conditions, and the discharge capacity was measured at the beginning of the charge / discharge cycle.

Charge / discharge conditions: The current density per unit area of the positive electrode 1 was set to a constant current of 1.1 mA / cm ² and 4.2 V
After charging at the final voltage of (CC), 1.1 mA / cm ²
The discharge was performed at a constant voltage of 3.0 V and a final voltage of 3.0 V (CC). [Results] Table 2 shows the results of each test described above.

[0064]

[Table 2]

[Evaluation of Each Electrolyte Solution for Battery and Evaluation of Each Nonaqueous Electrolyte Secondary Battery] In each of the battery electrolyte solutions of Examples 1 to 9, the combustion speed was 0.1 m / s or less. Never burned Manila paper. Therefore, it can be seen that the electrolyte solutions of these examples are extremely excellent in flame retardancy and high in safety.

In the battery electrolytes of Examples 3 to 9, no color change was observed even after the high temperature holding test.
Further, its volatilization amount was small. Therefore, it can be seen that the electrolytes of these examples are excellent in volatility and storage characteristics at high temperatures.

On the other hand, it was found that each of the non-aqueous electrolyte secondary batteries using the battery electrolytes of Examples 1 to 9 had a high discharge capacity at 20 ° C. Also, 5
The capacity retention rate after 0 cycles was also high. Therefore, it can be seen that batteries using the electrolytes of these examples have high battery performance at room temperature.

In each of the nonaqueous electrolyte secondary batteries using the battery electrolytes of Examples 3 to 9, there was little decrease in the 50-cycle capacity retention rate at high temperatures.

Examples 1, 2, and 5 to 9
It can be seen that each of the nonaqueous electrolyte secondary batteries using each of the battery electrolyte solutions maintains a high discharge capacity at 0 ° C. Therefore, it can be seen that batteries using the electrolytes of these examples can maintain high battery performance even at low temperatures.

On the other hand, it was found that the burning rates of the electrolyte solutions of Comparative Examples 1 to 3 and Comparative Example 5 were all 2.0 mm / s or more. Their flame retardancy is within the safety tolerance, but not necessarily high. It is considered that such a result was obtained because none of diethyl carbonate, diisopropyl carbonate, and 1,2-bis (methoxycarbonyloxy) ethane had the effect of increasing the flame retardancy.

In contrast to these comparative examples, Comparative Example 4
Also, it can be seen that the electrolyte solution of Comparative Example 6 has excellent flame retardancy of 0 mm / s and 0.3 mm / s, and high safety.

However, in the non-aqueous electrolyte secondary battery using the battery electrolyte solution of Comparative Example 4 (a system containing neither the alkyl monocarbonate compound nor the alkylene biscarbonate compound), the discharge capacity and the capacity retention were so high. It can be seen that no value was obtained. In addition, the internal resistance after 50 cycles has increased significantly as compared with the initial value.
The reason why such a result was obtained is considered that triethyl phosphate selectively solvates lithium ions because triethyl phosphate has a higher number of donors than ethylene carbonate. for that reason,
It is conceivable that a side reaction easily occurs at the negative electrode interface, and consumption of lithium ions increases.

It can also be seen that the nonaqueous electrolyte secondary battery using the battery electrolyte of Comparative Example 6 (a system containing no cyclic carbonate compound) did not have a very high discharge capacity. The reason for obtaining such a result is that the conductivity of the electrolytic solution is low.

Further, in Comparative Examples 1 and 2, since no alkylene biscarbonate compound was contained, the electrolytic solution was discolored in the high temperature holding test. In Comparative Example 3, the viscosity was high and the internal resistance was high because no alkyl monocarbonate compound was contained.

Therefore, it can be seen that the battery electrolyte of this comparative example cannot achieve both excellent discharge capacity and extremely high safety.

From the above results, all of the battery electrolytes of the present embodiment can have excellent battery performance and can maintain the battery performance high even in a temperature range other than room temperature. In addition, it can be seen that extremely excellent safety can be obtained.

In the electrolytes for batteries of Examples 1 to 4,
Assuming that the total amount of the organic solvent is 100% by volume, either one of the alkyl monocarbonate compound represented by the chemical formula 1 and the alkylene biscarbonate compound represented by the chemical formula 2 is contained in an amount of 30 to 50% by volume. ing. In the battery electrolytes of Examples 5 to 9,
In each case, the alkyl monocarbonate compound represented by Chemical Formula 1 and the alkylene biscarbonate compound represented by Chemical Formula 2 are both contained in an amount of 30 to 50% by volume.

Further, in each of the electrolyte solutions for batteries of Examples 1 to 9, the phosphorus-containing organic compound is at least one of chain and cyclic phosphate compounds and is contained in an amount of 25 to 35% by volume. ing. Further, LiPF ₆ is used as a supporting salt in each of the electrolyte solutions.

The electrolytes for the batteries of Examples 1 to 9 also overlap with each other, so that the battery performance can be extremely excellent in any case, and the battery performance can be extremely improved even in a temperature range other than room temperature. It is thought that it is possible to maintain high and to obtain extremely excellent safety.

Among them, the electrolytes for batteries of Examples 5 to 9 were:
Excellent battery performance can be maintained high in both low and high temperature ranges. The reason that such a result was obtained is that any of the electrolyte solutions contains both the alkyl monocarbonate compound having the chemical formula represented by Chemical Formula 1 and the alkylene biscarbonate compound represented by Chemical Formula 2. Can be considered.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a battery schematically showing a non-aqueous electrolyte secondary battery of the present embodiment.

FIG. 2 is an explanatory view of a cylindrical battery schematically showing a non-aqueous electrolyte secondary battery of the present embodiment, 2a is a cross-sectional perspective view of a cylindrical battery, and 2b is an explanatory schematic diagram illustrating an electrode portion. is there.

[Explanation of symbols]

1: positive electrode 2: negative electrode 3: non-aqueous electrolyte 4: positive electrode case 5: negative electrode case 6: gasket 7: separator 10: cylindrical battery, 11: negative electrode mixture, 12: negative electrode current collector, 12 ': negative electrode lead , 13: positive electrode mixture, 14: positive electrode current collector, 14 ': positive electrode lead, 15: electrolytic solution, 16: separator, 17: positive electrode terminal, 18: negative electrode terminal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Naohiro Kubota 7-35, Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kako Kogyo Co., Ltd. (72) Tomoyuki Oikawa 7-35, Higashiogu, Arakawa-ku, Tokyo Asahi Denka Kogyo Co., Ltd.

Claims (6)

[Claims] An electrolyte for a battery comprising a supporting salt dissolved in an organic solvent, wherein the organic solvent comprises a cyclic carbonate compound,
A battery electrolyte comprising: at least one of an alkyl monocarbonate compound represented by the formula (1) and an alkylene biscarbonate compound represented by the chemical formula (2); and a phosphorus-containing organic compound. Embedded image Embedded image 2. The organic solvent contains a cyclic carbonate compound, the alkyl monocarbonate compound, the alkylene biscarbonate compound, and a phosphorus-containing organic compound, wherein the alkyl monocarbonate compound, the alkylene biscarbonate compound, and the phosphorus The battery electrolyte according to claim 1, wherein at least one kind of the contained organic compound is contained. 3. The method according to claim 1, wherein at least one of the alkyl monocarbonate compound and the alkylene biscarbonate compound is contained in an amount of 5 to 50% by volume when the total amount of the organic solvent is 100% by volume. Battery electrolyte. 4. The phosphorus-containing organic compound is at least one of a chain and cyclic phosphate compound, and when the total amount of the organic solvent is 100% by volume, 5-35.
3. The battery electrolyte according to claim 1, wherein the battery electrolyte is contained by volume%. 4. 5. The supporting salt is LiPF ₆ , LiBF ₄ ,
Inorganic salt selected from LiClO ₄ and LiAsF ₆ , a derivative of the inorganic salt, LiSO ₃ CF ₃ , LiC (SO ₃ CF ₃ )
_2. An organic salt selected from ₂ and LiN (SO ₃ CF ₃ ) ₃ , and at least one kind of a derivative of the organic salt.
5. The electrolytic solution for a battery according to any one of items 1 to 4. 6. A non-aqueous electrolyte comprising a positive electrode and a negative electrode capable of releasing and occluding lithium ions, and an electrolytic solution interposed between the positive electrode and the negative electrode and having a supporting salt dissolved in an organic solvent. A secondary battery, wherein the organic solvent comprises: a cyclic carbonate compound;
An alkyl monocarbonate compound represented by the following formula:
Wherein the alkyl monocarbonate compound, the alkylene biscarbonate compound, and the phosphorus-containing organic compound each contain at least one kind. Non-aqueous electrolyte secondary battery.