JPH1116578A - Battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To impart flame resistance to a battery, and enhance the energy density, ion conductivity and safety by using a gel electrolyte consisting of a polymer material containing polyacrylonitrile and an electrolytic salt mainly composite of a nonaqueous solvent having a specified composition and LiPF6 . SOLUTION: This battery has a gel electrolyte consisting of a polymer material containing polyacrylonitrile and a solubility parameter of 8-15 (cal/m<2> )<1/2> , and an electrolytic salt mainly composed of a nonaqueous solvent and LiPF6 . The nonaqueous solvent is a mixture of ethylene carbonate, propylene carbonate, and a third nonaqueous solvent, and as the third nonaqueous solvent, any one of dimethyl carbonate, methyl propionate, and ethyl propionate is used. In a battery using this gel electrolyte, the gel electrolyte has an ion conductivity of 1 ms/cm or more at about 25 deg.C or lower and shows a high ion conductivity of 0.4 ms/cm or more even at a low temperature of about -20 deg.C.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

TECHNICAL FIELD The present invention relates to a battery having a gel electrolyte.

[0002]

2. Description of the Related Art A lithium battery comprising a positive electrode and a negative electrode capable of inserting and extracting lithium, and a non-aqueous electrolyte,
Compared with aqueous secondary batteries such as lead batteries and nickel cadmium batteries, they have attracted attention in recent years because of their higher energy density and lower self-discharge rate.

[0003] In order to further improve the battery performance of such a lithium secondary battery, it is of course important to select an electrode material, but the characteristics of an electrolytic solution that plays a role in ionic conduction between the two electrodes greatly affect the battery characteristics. Come. For this reason, the electrolyte is required to have high ionic conductivity as much as possible and electrochemical stability that can withstand a high voltage, and many non-aqueous electrolytes have been proposed from such a point.

For example, as a non-aqueous solvent for an electrolytic solution, cyclic or chain ester organic molecules are often used. Specifically, propylene carbonate (PC), ethylene carbonate (EC), methyl ethyl carbonate (MEC),
Dimethyl carbonate (DMC), gamma-butyrolactone (GBL), 1,2-dimethoxyethane (DM
E), methyl propionate, butyl propionate and the like are typical.

As electrolyte salts, LiPF ₆ , L
iClO ₄ , LiBF ₄ , LiCF ₃ SO ₃ , LiAs
F ₆ , LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₂ SO ₂ ) ₃
Etc. are known. All of these electrolyte salts show high ionic conductivity of several mS / cm in an appropriate concentration range.

However, the above non-aqueous electrolyte composed of a non-aqueous solvent and an electrolyte salt has a relatively low flash point, so that if the battery is accidentally thrown into a fire, There is a danger that the non-aqueous solvent leaking from the inside will become gaseous and ignite.

Therefore, for example, Japanese Patent Application Laid-Open No. 4-184870 proposes to add a flame retardant such as a phosphoric acid ester to a non-aqueous electrolyte as a method for preventing such ignition. This flame retardant is known as a flame retardant for polymer materials, and its effect is proportional to the amount added.

As other flame retardants, halogen compounds are generally known.

[0009]

However, phosphate-based compounds and halogen-based compounds are not necessarily electrochemically stable substances, and are liable to undergo chemical transformation and decomposition in a high voltage region of 3 V or more. As a result, there is a concern that the battery performance may be degraded. In particular, when the added amount of the flame retardant is increased to obtain a large flame retardant effect, the battery performance is significantly impaired.

Therefore, the present invention has been proposed in view of such conventional circumstances, and has as its object to provide a battery having a high energy density, a high ionic conductivity, and excellent safety. And

[0011]

In order to achieve the above-mentioned object, a battery of the present invention comprises a positive electrode, a negative electrode, and a gel electrolyte.

This gel electrolyte contains polyacrylonitrile and has a solubility parameter of 8 to 15 (cal / cm 2).
² ) It comprises a ^1/2 polymer material and a gel electrolyte made of a non-aqueous solvent and an electrolyte salt mainly composed of LiPF ₆ .

The non-aqueous solvent includes (1) a mixed solvent of ethylene carbonate, propylene carbonate and a third non-aqueous solvent, and (2) a mixed solvent of ethylene carbonate, gamma-butyrolactone and a third non-aqueous solvent. A mixed solvent obtained by mixing a solvent, (3) ethylene carbonate, propylene carbonate, gamma-butyrolactone, and a fourth non-aqueous solvent is used. Here, the third non-aqueous solvent and the fourth non-aqueous solvent are at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate.

In a battery using such a gel electrolyte, the gel electrolyte exhibits a high ionic conductivity of 1 ms / cm or more at a temperature of 25 ° C. and 0.4 ms / cm or more at a low temperature of about −20 ° C. Therefore, good battery performance can be obtained not only under a normal temperature environment but also at a low temperature.

Further, since the gel electrolyte is excellent in flame retardancy, even if the battery is accidentally thrown into a fire, the risk of ignition is low. In addition, since the gel electrolyte itself has excellent flame retardancy, it is not necessary to include a general-purpose flame retardant having poor electrochemical stability. Therefore, deterioration of the battery performance due to the flame retardant can be avoided.

Further, since the non-aqueous electrolyte is fixed in the gel electrolyte, even if a load is applied to the battery, the non-aqueous electrolyte does not leak, and high safety can be obtained.

When the structure of the electrode is viewed, the positive electrode
Since the gel electrolyte is interposed between the negative electrodes and the gel electrolyte is adhered to both electrode surfaces, the distance between the electrodes is always constant. For this reason, for example, in a conventional flat battery using a liquid non-aqueous electrolyte as it is, a pressurizing means was necessary to maintain a stable positional relationship between the two electrodes, but such a pressurizing means became unnecessary. Structure is simplified.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, specific embodiments of the present invention will be described.

The battery of the present invention comprises a positive electrode, a negative electrode, and a gel electrolyte.

The gel electrolyte is composed of a polymer material, a non-aqueous solvent and an electrolyte salt, wherein the polymer material contains polyacrylonitrile and has a solubility parameter of 8-15.
(Cal / cm ² ) ^1/2 polymer material. This polymer material easily forms a carbonized film on the surface when heated, which is considered to contribute to the flame retardancy of the gel electrolyte.

The polymer material is a polymer containing acrylonitrile in the repeating unit structure. This repeating unit structure may be composed of only acrylonitrile, or may be a copolymer with another monomer. As monomers to be copolymerized, acrylic acid, methacrylic acid, vinyl acetate, itaconic acid, hydrogenated methyl acrylate, hydrogenated ethyl acrylate, acrylamide, vinyl chloride,
Vinylidene fluoride, vinylidene chloride and the like. Specific examples of the copolymer include acrylonitrile butadiene rubber, acrylonitrile butadiene styrene resin, acrylonitrile chloride polyethylene propylene diene styrene resin, acrylonitrile vinyl chloride resin, acrylonitrile methacrylate resin, acrylonitrile acrylate resin, and the like. What is necessary is just to select what is used.

The degree of gelation of the gel electrolyte has a close relationship with the molecular weight of the polymer material, and the number average molecular weight of the polymer material should be 5,000 to 500 to obtain an appropriate gelation degree.
It is desirable to be about 500,000.

The solubility parameter of the polymer material is preferably from 8 to 15 (c) from the viewpoint of obtaining a flame retardant effect and compatibility with other components.
al / cm ² ) ^1/2 . The solubility parameter was determined by POLYMER HAN.
D BOOK THIRD EDITION J. Br
andrup. and EH. IMMERGUT W
ILEY INTERSCIENCE. 1989 (P.
IV-340 to 341).

The amount of this polymer material in the gel electrolyte is preferably such that the number of repeating unit structures is 5 to 30 mol% from the viewpoint of flame retardancy and compatibility. Considering ease of handling after gel molding, 5-15
It is preferable to set the amount to be mol%. Note that the molar fraction referred to here is 10 times the sum of the number of repeating unit structures of the polymer material and the number of moles of the nonaqueous solvent and the electrolyte salt.
This is the value when 0 mol% is set.

The non-aqueous solvent includes (1) a mixed solvent obtained by mixing ethylene carbonate, propylene carbonate and a third non-aqueous solvent, (2) ethylene carbonate, gamma-
A mixed solvent obtained by mixing butyrolactone and a third nonaqueous solvent, and (3) a mixed solvent obtained by mixing ethylene carbonate, propylene carbonate, gamma-butyrolactone, and a fourth nonaqueous solvent are used. Here, the third non-aqueous solvent and the fourth non-aqueous solvent are at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate.

These non-aqueous solvents have a potential window in the range of -0.3 to 5.0 V with respect to the lithium potential, and are well compatible with the above-mentioned polymer material containing polyacrylonitrile.

As the electrolyte salt, LiPF ₆ is used here because it has a high effect of promoting carbonization of the polymer material when the gel comes into contact with a flame and imparting flame retardancy to the gel electrolyte. LiPF ₆ may be used alone or in combination with another electrolyte salt. As electrolyte salts to be mixed, LiN (CF ₃ SO ₂ ) ₂ , LiC (CF ₂ SO ₂ ) ₃ , L
iBF ₄ , LiAsF ₆ , LiCF ₃ SO ₃ , LiCl
O ₄ and NaClO ₄ can be used. Among them, LiN (CF
₃ SO ₂ ) ₂ is preferable because it has a high effect of imparting flame retardancy next to LiPF ₆ .

The amount of the electrolyte salt in the gel electrolyte is desirably selected so that the concentration of lithium ions is 3 to 9 mol%. If the concentration of lithium ions is less than 3 mol%, sufficient ion conductivity cannot be obtained, which may cause an increase in polarization during electrode reaction. When the concentration of lithium ions exceeds 9 mol%, it becomes difficult to dissolve the polymer material. Further, in consideration of the salt concentration dependence of the ionic conductivity, the lithium ion concentration is preferably in the range of 4 to 9 mol% in order to secure sufficient ionic conductivity.

The kind of the non-aqueous solvent and the electrolyte salt greatly affects the characteristics of the gel electrolyte as described above. Here, this kind is specified in terms of flame retardancy and ionic conductivity. Then, of course, high ionic conductivity can be obtained even at a low temperature of about −20 ° C.

In order to prepare a gel electrolyte, for example, a non-aqueous electrolyte is prepared by dissolving an electrolyte salt in a non-aqueous solvent, and the non-aqueous electrolyte is heated and a polymer material containing polyacrylonitrile is added. . Then, when the polymer material is completely dissolved, the solution is quickly spread on the substrate and allowed to cool to obtain a gel electrolyte.

As described above, this gel electrolyte does not require a special crosslinking operation, and can be easily prepared only by cooling after dissolution.

The battery of the present invention comprises such a gel electrolyte, a positive electrode and a negative electrode, and each form is appropriately selected according to the shape of the battery. For example, in a flat battery, a first gel electrolyte, a separator, and a second gel electrolyte are sandwiched between a plate-shaped positive electrode and a negative electrode, and this electrode element is housed in a predetermined battery exterior material. A battery is configured.

In a battery using such a gel electrolyte, since the gel electrolyte exhibits high ionic conductivity even at a temperature of 25 ° C. or a low temperature of about −20 ° C., good battery performance is obtained regardless of the temperature environment. can get.

Further, since the gel electrolyte is excellent in flame retardancy, even if the battery is accidentally thrown into a fire, the risk of ignition is low. In addition, since the gel electrolyte itself has excellent flame retardancy, it is not necessary to include a general-purpose flame retardant having poor electrochemical stability. Therefore, deterioration of the battery performance due to the flame retardant can be avoided.

Further, since the non-aqueous electrolyte is fixed in the gel electrolyte, even if a load is applied to the battery, no leakage of the non-aqueous electrolyte occurs and high safety is obtained.

When the structure of the electrode is viewed, the positive electrode
Since the gel electrolyte is interposed between the negative electrodes and the gel electrolyte is adhered to both electrode surfaces, the distance between the electrodes is always constant. For this reason, for example, in a conventional flat battery using a liquid non-aqueous electrolyte as it is, a pressurizing means was necessary to maintain a stable positional relationship between the two electrodes, but such a pressurizing means became unnecessary. Structure is simplified.

The battery may be of a primary battery type or a secondary battery type. For example, in the case of a secondary battery specification, the following positive electrode material and negative electrode material are used.

First, as a positive electrode material, a general formula Li _x M
O ₂ (where M is one or more transition metals, preferably M
At least one of n, Co, Ni, and Fe. Also,
0.05 ≦ x ≦ 1.10) is used.

As the negative electrode material, lithium metal,
A lithium alloy, and a material capable of inserting and extracting lithium, such as a carbonaceous material, a silicon compound, and a tin compound, are used. Of these, as carbonaceous materials,
Pyrolytic carbons, cokes (pitch coke, needle coke, petroleum coke, etc.), graphites, glassy carbons, carbons using organic polymer as precursor (furan resin, etc. fired at appropriate temperature, etc.) ), Carbon fiber, activated carbon and the like.

[0040]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described based on experimental results.

Example 1 A gel electrolyte was prepared as follows.

First, ethylene carbonate (EC), propylene carbonate (PC) and dimethyl carbonate (DMC) were added at 50 mol%: 30 mol%: 4 mol.
%, And ₇ mol% of LiPF ₆ was further added to prepare a non-aqueous electrolyte.

Then, the non-aqueous electrolyte was poured into a beaker and heated to 120 ° C. while stirring in a dry atmosphere having a dew point of −50 ° C. or less. Next, polyacrylonitrile (PAN, number average molecular weight:
A powder having a solubility of 150,000 and a solubility parameter of 12) was added so that the mole fraction of acrylonitrile was 9 mol%, and heating and stirring were further continued for 20 minutes to obtain a transparent and highly viscous solution. Thereafter, the heating was stopped, and this highly viscous solution was quickly spread on a flat chalet, and a glass test tube (inner diameter 12 mm × length 15 mm) was prepared.
0 mm), and the mixture was allowed to cool all day and night to produce a gel electrolyte.

Examples 2 to 8 A gel electrolyte was prepared in the same manner as in Example 1 except that the ratio between the nonaqueous solvent and polyacrylonitrile was changed as shown in Table 1.

Examples 9 to 16 Except that a mixed solvent of ethylene carbonate, propylene carbonate and ethyl methyl carbonate (EMC) was used as the non-aqueous solvent, and this ratio and the ratio of polyacrylonitrile were changed as shown in Table 2. In the same manner as in Example 1, a gel electrolyte was produced.

Examples 17 to 24 Except that a mixed solvent of ethylene carbonate, gamma-butyrolactone (GBL) and dimethyl carbonate was used as the non-aqueous solvent, and that the ratio of polyacrylonitrile was changed as shown in Table 3. In the same manner as in Example 1, a gel electrolyte was produced.

Examples 25 to 32 Except that a mixed solvent of ethylene carbonate, gamma-butyrolactone and ethyl methyl carbonate was used as the non-aqueous solvent, and that this ratio and the ratio of polyacrylonitrile were changed as shown in Table 4, A gel electrolyte was prepared in the same manner as in Example 1.

Examples 33 to 36 Except that a mixed solvent of ethylene carbonate, propylene carbonate, gamma-butyrolactone and dimethyl carbonate was used as the non-aqueous solvent, and this ratio and the ratio of polyacrylonitrile were changed as shown in Table 5. In the same manner as in Example 1, a gel electrolyte was produced.

Comparative Examples 1 to 4 In the same manner as in Example 1 except that a mixed solvent of ethylene carbonate and propylene carbonate was used as the non-aqueous solvent, and that the ratio of polyacrylonitrile was changed as shown in Table 6. Thus, a gel electrolyte was prepared.

Comparative Examples 5 to 8 The same as Example 1 except that a mixed solvent of ethylene carbonate and gamma-butyrolactone was used as the non-aqueous solvent, and the ratio of polyacrylonitrile was changed as shown in Table 7. Thus, a gel electrolyte was prepared.

Comparative Examples 9 to 20 A mixed solvent of ethylene carbonate and propylene carbonate or a mixed solvent of ethylene carbonate, propylene carbonate and dimethyl carbonate was used as the non-aqueous solvent, LiClO ₄ was used as the electrolyte salt, and this ratio was compared with polyacrylonitrile. A gel electrolyte was produced in the same manner as in Example 1 except that the ratio of was changed as shown in Table 8.

Comparative Examples 21 to 32 A mixed solvent of ethylene carbonate and gamma-butyrolactone or a mixed solvent of ethylene carbonate, gamma-butyrolactone and ethyl methyl carbonate was used as the nonaqueous solvent, and LiClO ₄ was used as the electrolyte salt. A gel electrolyte was prepared in the same manner as in Example 1 except that the ratio of polyacrylonitrile and polyacrylonitrile was changed as shown in Table 9.

The gel electrolyte prepared as described above was evaluated for ionic conductivity, temperature dependence of activation energy, and flame retardancy. In addition, these characteristics were measured as follows.

<Measurement of Temperature Dependence of Ionic Conductivity and Activation Energy> A gel electrolyte in a flat chalet was cut into a columnar shape having a diameter of 1.0 cm, and was cut between two platinum disk electrodes (1.0 cm in diameter). And ion conductivity was measured by a complex impedance method using an impedance analyzer (trade name: HP4192A). In addition, the measurement was performed at each of the temperature of 25 ° C and -20 ° C. The measurement conditions are as follows.

Applied voltage: 0.5 V Sweep frequency range: 5 to 13 MHz In addition, ion conductivity σ1 at a temperature of 25 ° C. and a temperature of −20
The activation energies of the ion conduction reaction were obtained from the ion conductivity σ2 at ° C based on the following equation, and the temperature dependence of the ion conduction reaction was examined by taking the difference.

Σ = Aexp (−E / RT) σ: ion conductivity A: frequency factor E: activation energy R: gas constant T: temperature <flame retardancy test> The flame retardancy test is shown in FIG. The device was assembled.

In this apparatus, two columns 2 are fixed on a base 1, and a wire mesh (made of stainless steel, mesh shape: 5 mm × 5 mm square) 3 is stretched between the two columns 2. Have been. A butane gas burner 4 is provided below the wire mesh 3. The butane gas burner 4 is oriented so that the gas outlet 5 is at an angle θ of 45 ° with respect to the horizontal plane, and at a height such that the blue flame ignited by the gas blows upward through the wire mesh 3. Adjusted. On the other hand, the measurement sample 6 is obtained by cutting the gel electrolyte in a test tube to have a length of 130 mm, and is placed on the wire mesh 3.

The flame retardancy was evaluated by causing the flame 7 from the butane gas burner 4 to strike a portion 6 mm from the end of the measurement sample 6, continuing the indirect flame for 30 seconds in this state, and moving the flame away. After that, the degree of combustion in this portion was observed. Here, the case where the combustion part of the gel electrolyte did not reach the mark line S of 25 mm from the end was determined as “non-flammable”, and the case where the combustion part exceeded the mark line S of 25 mm was determined as “flammability”. .

Tables 1 to 9 show the evaluation results of ionic conductivity, activation energy and flame retardancy at −20 ° C. measured as described above.

[0060]

[Table 1]

[0061]

[Table 2]

[0062]

[Table 3]

[0063]

[Table 4]

[0064]

[Table 5]

[0065]

[Table 6]

[0066]

[Table 7]

[0067]

[Table 8]

[0068]

[Table 9]

In Tables 1 to 9, EC is ethylene carbonate, PC is propylene carbonate, GB
L represents gamma-butyrolactone, DMC represents dimethyl carbonate, EMC represents ethyl methyl carbonate, and PAN represents polyacrylonitrile. The mole fraction of PAN is calculated based on the molecular weight of the repeating unit structure.

First, in the gel electrolytes of Comparative Examples 9 to 32 using LiClO ₄ as the electrolyte salt, flammability was observed in the flame retardancy test.

On the other hand, in Examples 1 to 36 and Comparative Examples 1 to 8 in which LiPF ₆ was used as the electrolyte salt, almost no combustion was observed and the composition had flame retardancy.

From this, it was found that LiPF ₆ is suitable as the electrolyte salt used for the gel electrolyte.

However, among the gel electrolytes having flame retardancy, the gel electrolytes of Comparative Examples 1 to 8 in which dimethyl carbonate and methyl ethyl carbonate were not mixed with the non-aqueous electrolyte were the same as those of Example 1. -The ion conductivity is lower than that of the gel electrolyte of Example 36, and the temperature dependence of the activation energy is large.

From the above, as the non-aqueous solvent used in the gel electrolyte, the third non-aqueous solvent such as dimethyl carbonate and ethyl methyl carbonate was used in place of ethylene carbonate and propylene carbonate as in Examples 1 to 16. , A mixed solvent of Examples 17 to 32
A mixed solvent obtained by mixing ethylene carbonate and gamma-butyrolactone with a third non-aqueous solvent such as dimethyl carbonate and ethyl methyl carbonate. Further, as in Examples 33 to 36, ethylene carbonate, propylene carbonate and gamma -It has been found that a mixed solvent obtained by mixing butyrolactone with a fourth non-aqueous solvent such as dimethyl carbonate or ethyl methyl carbonate is preferable.

In Examples 1 to 32, the ratio of polyacrylonitrile was the same, and the ratio of the third nonaqueous solvent or the fourth nonaqueous solvent (dimethyl carbonate, methyl ethyl carbonate) and the ion conductivity Looking at the relationship between the degrees, the larger the amount of these non-aqueous solvents, the higher the ionic conductivity and the smaller the temperature dependence.

This suggests that the addition of the third nonaqueous solvent and the fourth nonaqueous solvent is effective in increasing the ionic conductivity of the gel electrolyte and reducing the temperature dependence.

Next, a primary battery and a secondary battery were actually fabricated by incorporating the above-mentioned gel electrolyte, and the characteristics thereof were evaluated.

Manufacturing of Primary Battery The manufacturing process of the battery is shown in FIGS.

First, the positive electrode plate 8 shown in FIG. 2 was manufactured as follows.

Mixing 85% by weight of manganese dioxide, 10% by weight of graphite and 5% by weight of polyvinylidene fluoride,
Furthermore, dimethylformamide was added as a powder in substantially the same amount, and then kneaded to prepare a positive electrode mixture.

This positive electrode mixture was applied to a 2 cm × 2 cm area on a stainless steel mesh as a current collector, dried in a dryer at a temperature of 120 ° C., and roll-pressed. Then, the electrode plate was formed into a shape such that the band-shaped current collector 8b protruded from the application region 8a of the positive electrode mixture as shown in FIG.

Next, a lithium metal plate having a thickness of 30 μm was cut into a size of 2 cm × 2 cm, and pressed on a current collector having substantially the same planar shape as the above-mentioned positive electrode plate to produce a negative electrode plate 9.

Then, a gel electrolyte was applied to the positive electrode plate 8 and the negative electrode plate 9.

Subsequently, a nonwoven fabric made of polypropylene (150 μm in thickness) to be a diaphragm 10 as shown in FIG. 3 was prepared, and a gel electrolyte 11 was applied to the diaphragm 10 as shown in FIG. The gel electrolyte had the same composition as that of Example 3 described above.

Then, as shown in FIG. 5, the positive electrode plate 8, the diaphragm 10, and the negative electrode plate 9 were overlapped in this order and pressed to form an electrode element.

Then, the obtained electrode element was covered with a bag-shaped heat-fusible laminate film (manufactured by Dai Nippon Printing Co., Ltd.) as the battery exterior material 12 and, as shown in FIG. A flat primary battery was manufactured by vacuum packing 12a. In addition, this heat-fusible laminate film is
It consists of three layers, a polyethylene terephthalate film, an aluminum foil, and an unstretched polypropylene film. The polyethylene terephthalate film side is outside the battery.

The discharge characteristics of the primary battery manufactured as described above were examined. The discharge current density at the time of discharge is 1 mA / c
m ² , and the discharge was terminated when the closed circuit voltage reached 1.0 V. FIG. 7 shows the discharge characteristics.

As shown in FIG. 7, this primary battery has an average discharge voltage of 2.6 to 2.8 V and has a good flatness of a discharge curve. From this, it was found that this gel electrolyte exhibited sufficient performance as an electrolyte material for a primary battery.

Preparation of Secondary Battery 90% by weight of lithium nickelate, 8% by weight of graphite, and 2% by weight of polyvinylidene fluoride are mixed, and dimethylformamide is added in a substantially equal amount as a powder, followed by kneading to form a positive electrode. Materials were produced.

The positive electrode mixture was applied to a 2 cm × 2 cm area on a stainless steel mesh as a current collector, dried in a dryer at a temperature of 120 ° C., and roll-pressed. Then, this electrode plate was molded into a shape such that the band-shaped current collector protruded from the application region of the positive electrode mixture, to produce a positive electrode plate.

Next, 90% by weight of mesophase spheroidal carbon and 10% by weight of polyvinylidene fluoride were mixed, and dimethylformamide was added in a substantially equal amount of powder, followed by kneading to prepare a negative electrode mixture.

This negative electrode mixture was applied to a 2 cm × 2 cm area on a stainless steel mesh serving as a current collector, dried in a dryer at a temperature of 120 ° C., and roll-pressed. Then, this electrode plate was molded into a shape such that the band-shaped current collector protruded from the application region of the negative electrode mixture, and a negative electrode plate was produced.

A flat secondary battery was manufactured in the same steps as those shown in FIGS. 3 to 6 except that the positive electrode plate and the negative electrode plate manufactured as described above were used.

The charge / discharge characteristics of this secondary battery were examined.

The charging is performed by the constant current / constant voltage method which switches to the constant voltage method at 4.2 V, and the charging current is 312 μA / c.
m ² , and the charging time was set to 10 hours. Also, the discharge
The measurement was performed by the constant current method, and a continuous discharge was performed at 312 μA / cm ² until the closed circuit voltage became 2.5 V.

FIG. 8 shows the charge / discharge characteristics in the third cycle of charge / discharge. From FIG. 8, it was found that the average voltage of the battery was 3.61 V and the charge / discharge efficiency was 99%, indicating that the battery exhibited excellent reversibility. From this, it was found that this gel electrolyte exhibited sufficient performance as an electrolyte material for a secondary battery having a high energy density.

[0097]

As is clear from the above description, the battery of the present invention comprises a polymer material containing polyacrylonitrile, a nonaqueous solvent having a predetermined composition, and an electrolyte salt mainly composed of LiPF _6. Since a gel electrolyte is used,
Flame retardancy can be imparted to the battery without impairing the battery performance. Further, particularly when applied to a non-aqueous battery using an alkali metal ion as a reactive species, the safety can be greatly improved.

[Brief description of the drawings]

FIG. 1 is a schematic diagram showing a configuration of an apparatus used for measurement of a flame retardancy test.

FIG. 2 is a schematic view illustrating a positive electrode plate and a negative electrode plate, illustrating a method for manufacturing a battery in the order of steps.

FIG. 3 is a schematic view showing a diaphragm.

FIG. 4 is a schematic view showing a step of applying a gel electrolyte to a diaphragm.

FIG. 5 is a schematic view showing a process of storing a positive electrode plate, a diaphragm, and a negative electrode plate in a battery exterior material.

FIG. 6 is a schematic view showing a heat fusion step of a battery exterior material.

FIG. 7 is a characteristic diagram showing discharge characteristics of a primary battery to which a gel electrolyte is applied.

FIG. 8 is a characteristic diagram showing charge / discharge characteristics of a secondary battery to which a gel electrolyte is applied.

[Explanation of symbols]

8 positive electrode plate, 9 negative electrode plate, 10 diaphragm, 11 gel electrolyte, 12 battery exterior material

 ────────────────────────────────────────────────── ─── Continued on the front page (72) Inventor Kazuhiro Noda 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Inside Sony Corporation (72) Inventor Shinichiro Yamada 6-35, Kita-Shinagawa, Shinagawa-ku, Tokyo No. Sony Corporation (72) Inventor Toshikazu Yasuda 6-7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation (72) Inventor Koji World 7-35 Kita-Shinagawa, Shinagawa-ku, Tokyo Sony Corporation

Claims (9)

[Claims] 1. A positive electrode and a negative electrode, comprising polyacrylonitrile, having a solubility parameter of 8 to 10.
15 (cal / cm ² ) ^1/2 of a polymer material, a mixed solvent obtained by mixing ethylene carbonate, propylene carbonate and a third non-aqueous solvent, and a gel electrolyte composed of an electrolyte salt mainly composed of LiPF ₆ Wherein the third non-aqueous solvent is at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate. 2. The electrolyte salt is LiN (CF ₃ SO ₂ ) ₂ ,
LiC (CF ₂ SO ₂ ) ₃ , LiBF ₄ , LiAsF ₆ , L
iCF ₃ SO _3, LiClO _4, battery according to claim 1, wherein the a mixture of LiPF ₆ and at least one of NaClO _4. 3. The battery according to claim 1, wherein the polymer material of the gel electrolyte has a number average molecular weight of 5,000 to 500,000. 4. A cathode and an anode, comprising polyacrylonitrile, having a solubility parameter of 8 to 10.
15 (cal / cm ² ) ^1/2 of a polymer material, a mixed solvent obtained by mixing ethylene carbonate, gamma-butyrolactone and a third non-aqueous solvent, and a gel electrolyte made of an electrolyte salt mainly composed of LiPF _6. Wherein the third non-aqueous solvent is at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate. 5. The electrolyte salt is LiN (CF ₃ SO ₂ ) ₂ ,
LiC (CF ₂ SO ₂ ) ₃ , LiBF ₄ , LiAsF ₆ , L
5. The battery according to claim 4, wherein the battery is a mixture of at least one of iCF ₃ SO ₃ , LiClO ₄ , and NaClO ₄ with LiPF ₆ . 6. The battery according to claim 4, wherein the polymer material of the gel electrolyte has a number average molecular weight of 5,000 to 500,000. 7. A cathode and an anode, comprising polyacrylonitrile, having a solubility parameter of 8 to 10.
A mixed solvent obtained by mixing 15 (cal / cm ² ) ^1/2 of a polymer material, ethylene carbonate, propylene carbonate, gamma-butyrolactone, and a fourth non-aqueous solvent;
a gel electrolyte made of an electrolyte salt mainly composed of iPF ₆ , wherein the fourth non-aqueous solvent is at least one of dimethyl carbonate, ethyl methyl carbonate, methyl propionate, and ethyl propionate. Battery. 8. The electrolyte salt is LiN (CF ₃ SO ₂ ) ₂ ,
LiC (CF ₂ SO ₂ ) ₃ , LiBF ₄ , LiAsF ₆ , L
8. The battery according to claim 7, wherein the battery is a mixture of at least one of iCF ₃ SO ₃ , LiClO ₄ , and NaClO ₄ with LiPF ₆ . 9. The battery according to claim 7, wherein the polymer material of the gel electrolyte has a number average molecular weight of 5,000 to 500,000.