JPS5848360A - Battery - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to metal oxides such as copper oxide, manganese dioxide, bismuth oxide, lead oxide, nickel oxide, or composite oxides made of these, and nickel chloride.

Metal halides such as copper chloride, lead chloride, nickel fluoride, copper fluoride, lead fluoride, cadmium fluoride, iron sulfide,
Metal sulfides such as nickel sulfide, or fluorocarbons (
(CF)n, (02F)n) are used as positive electrode active materials, and alkali metals such as lithium, sodium, and potassium, alkaline earth metals such as magnesium and calcium, and aluminum
Negative electrode active materials include light metals such as aluminum, or alloys mainly composed of them, propylene carbonate, γ-butyrolactone, 1.2-dimethoxyethane, and 1.3-dioxolane.

Organic solvents such as tetrahydrofuran contain lithium perchlorate, lithium fluoroborate, etc. in their mixed solvents.
This paper relates to improvements in organic electrolyte batteries using electrolytes containing dissolved solutes such as aluminum chloride.

In general, a binder for forming electrodes is one of the major elements in battery construction. Binders are usually made of organic resins and are difficult to react with or dissolve in water. Therefore, in the case of a battery using an aqueous solution, there is a great deal of freedom in selecting the binder. In contrast, in the case of batteries that use organic electrolytes, binders that are resistant to organic solvents must be used.
This method has the disadvantage that the degree of freedom in selecting a binder is extremely small.

In organic electrolyte batteries, fluororesins such as polytetrafluoroethylene, copolymers of tetrafluoroethylene and hexafluoropropylene 37□, polyvinylidene fluoride, or polyethylene have been used mainly because they are stable in organic solvents. However, when the above-mentioned two-node resin is used as a binder, it has strong water repellency and oil repellency, so it has poor compatibility with the electrode and electrolyte, and also in terms of quantity, e.g. When fluorocarbon, which has a very low specific gravity of 2.0 to 3.0, is used as an active material, if polytetrafluoroethylene is used as a binder, the total weight ratio is 16 to 20.
%, which results in a decrease in the filling amount of the active material in the battery and a significant deterioration in the battery characteristics.

Also, even when manganese dioxide, which has a relatively large specific gravity of 5.0, is used as the active material, the polytetrafluoroethylene binder is required to account for 10 to 16% of the total weight, and the filling amount of the active material in the battery is As the temperature decreases, the compatibility between the electrode and the electrolyte also deteriorates.
Battery characteristics also deteriorate.

On the other hand, when polyethylene is used as a binder, unlike fluororesin binders, it has low water and oil repellency and is superior in terms of compatibility between electrodes and electrolyte, but the amount of binder In order to have the same strength as the adhesive, a larger amount is required, and when using a fluorocarbon active material, the total weight ratio is ~26%, and when using a manganese dioxide active material, the weight ratio is approximately 26%. 16 to 20% of the total amount is required, which not only reduces the amount of active material filled in the battery but also reduces the reactivity.

As a way to compensate for this drawback, polytetrafluoroethylene is bound with a binder and molded into the required size with a mixture of approximately 10% by weight for fluorocarbon active materials and approximately 8% by weight for manganese dioxide active materials. If heat treatment is performed, an electrode with sufficient strength can be obtained even with a relatively small amount of binder.

However, in this case, the heat treatment causes the fluororesin to cover the surface of the active material, so the reactivity of the electrode is extremely reduced, making it impossible to exhibit the characteristics as a battery.

On the other hand, in Japanese Patent Application Laid-open No. 53-74242, a styrene-free) rubber (SBR>t$*m) using an activator dispersed in water was used as a binder. According to the above-mentioned publication, 7) When carbon dioxide is used as an active material, the amount of binder mixed in is 8% by weight. According to
It is said that sufficient strength and strength can be obtained, and since SBR particles of an appropriate size are interposed between the active material particles and do not cover the surface of the active material, the battery characteristics will not be deteriorated. It is true that the stele abutadiene rubber binder can be said to be a significantly superior binder compared to conventional fluororesin binders or polyethylene binders.

When this stereo/butadiene comb binder is used as an active material with a high specific gravity, for example, when the active material is manganese dioxide with a specific gravity of 5.0 or copper oxide with a specific gravity of 6.3, the required amount is about 6% by weight, which is very small compared to the 10 to 15% of polytetrafluoroethylene binders, and the amount of active material loaded is large, but because the hardness of styrene and butadiene rubber is large, their specific gravity is large. In the case of an active material with high hardness, the hardness of the electrode itself will also be high, resulting in poor electrolyte absorption properties and reduced properties.

This high hardness means that if it is used as a binder, the electrode hardness will be high and elasticity will be poor. Therefore, when used in so-called flat electrodes, some active materials may have insufficient properties. However, in coiled electrodes that require flexibility, the active material may fall off and the electrodes may crack, reducing the battery's characteristics. For example, when using an active material with relatively low specific gravity such as fluorocarbon, it is possible to form a spiral electrode by increasing the amount of butadiene in SBR, but manganese dioxide If a material with a high specific gravity such as copper oxide is used as an active material, even if datadiene is added, cracking or falling off will occur as an electrode, making it impossible to obtain a sufficient electrode. The brittle nature is thought to be due to the properties of its raw material, stenine, that is, polystyrene itself.

The basic properties of polystyrene are that at room temperature,
, - It shows a large amount of deformation and tenacious properties in the compression test, but it shows hard and brittle properties in the tensile test.

Therefore, it is thought that this property is the reason that when styrene-butadiene rubber is used as a binder, it is not sufficiently suitable for applications that require tensile strength, such as spirally wound electrodes. .

The present inventors focused on this point, and polyacrylonitrile has high toughness, extensibility, and high elasticity, and polyacrylonitrile itself is γ-buty-V lactone, which is used as an electrolyte in organic electrolyte batteries.

Although it is known to be soluble in dimethyl sulfoxide and cannot be used in organic electrolyte battery systems, nitrile-butadiene rubber (NBR), a copolymer of acrylonitrile and butadiene, is insoluble in organic solvents such as It was discovered that this material can be used in organic electrolyte batteries. Compared to styrene-butadiene rubber, nitrile-butadiene rubber has better adhesion, solvent resistance, and film flexibility; it requires less binder than styrene-butadiene rubber; *As the body becomes larger, the battery characteristics will inevitably improve as the amount is smaller. Furthermore, since it has excellent flexibility, it is possible to form a spiral electrode even with active materials having a relatively large specific gravity such as copper oxide and manganese dioxide.

The method for mixing nitrile-butadiene rubber into the positive electrode mixture is as follows:
In order to mix uniformly, nitrile-butadiene rubber with particles of an appropriate size is used in the form of dispersing it in water using a surfactant, as shown in JP-A-53-74242 for styrene-butadiene rubber. is the best, and if you want it to be better than a flat plate-shaped molded electrode, you can mix an aqueous dispersion of nitrile-butadiene rubber and mold it after completely volatilizing the water. When obtained, it may be rolled in the presence of appropriate moisture and then dried. Furthermore, in order to completely increase the filling degree, it is sufficient to further roll the material after drying.

9Penitrile-butadiene rubbers are manufactured with various blending ratios of acrylonitrile and butadiene, but generally the strength increases as the amount of acrylonitrile increases. Therefore, when this is used as a binder, the strength of the electrode itself increases in proportion to the amount of acrylonitrile.

When using a molded electrode, the greater the electrode strength, the better the ease of handling, but in this case, the absorbability of the electrolyte is poor and the utilization rate of the active material is reduced. On the other hand, if a flexible spiral electrode is to be obtained, tensile strength and flexibility are required rather than strength, and it is desirable to have a small amount of acrylonitrile. However, if the amount of acrylonitrile blended is too small, the electrolyte will be absorbed too well and the electrode will swell, which is not desirable in terms of battery production. Therefore, in order to satisfy these conditions, it is desirable that the molar ratio of acrylonitrile is in the range of 20 to 46%.

Fluorinated carbon powder, acetylene 10-black as a conductive agent, and an aqueous dispersion of nitrile-butadiene rubber (resin content 60%) with a molar ratio of 30% acrylonitrile as a binder, by weight. 100:1
Mix at a ratio of 2:15 and dry.

After drying and volatilizing the water, 1 q of it is sized 20 x 2.
A positive electrode is obtained by pressure molding into a titanium net current collector of 0 ml.

The negative electrode was constructed by pressing 0.19 liters of lithium onto a nickel net current collector with a size of 20×20 arms. These two negative electrodes are stacked on both sides of the positive electrode wrapped in seven pallets made of polypropylene nonwoven fabric, and sealed together with an electrolyte in a polypropylene container to prepare a test battery. The electrolytic solution used was a mixture of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1:1, in which lithium fluoroborate was dissolved at a concentration of 1 mol/l. The above battery is A
Then, an aqueous dispersion of styrene-butadiene rubber (resin content: 50%) with a styrene content of 30% as a binder, fluorocarbon and 7-terene plaque was mixed in a weight ratio of 1.
A battery using a positive electrode mixed at a ratio of 00:12:20 and pressure-molded on a dry net Togun body is designated as B.

Next, fluorocarbon, acetylene brazil, and a water-based nice version of polyteterninated ethylene (60% sebum content) as a binder are mixed in a weight ratio of 100:12:4o, dried, and water is removed. C is a battery using a positive electrode which is evaporated and then 1 q of it is taken and pressure-molded onto a titanium net current collector.

The theoretical filling capacity of the positive electrode of each of the batteries C, B, and C is 7 for A.
20mAH, B is 700mAH, and C is 650mAH.

Figure 1 shows the characteristics when the above battery was discharged at 20° C. with a current of 16 mA.

As is clear from FIG. 1, A is the best in both discharge voltage and discharge duration, followed by S and C.

That is, the smaller the amount of binder, the better the release characteristics, and the smaller the amount of binder, the higher the amount of active material filled.

Next, using the same binders as above, we first mixed manganese dioxide powder, acetylene black as a conductive agent, and nitrile-butadiene rubber as a binder. After mixing with an aqueous dispersion at a weight ratio of 100:8 and drying it to volatilize the water, 2q of it was mixed into a 20x20m+
A positive electrode is obtained by pressure molding onto a titanium net current collector of n. Thereafter, a battery A' is obtained in the same manner as the battery A above. However, the electrolytic solution used was a mixture of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1:1, in which lithium perchlorate was dissolved at 1 mol/l. Aqueous dispersion of manquan dioxide powder, acetylene black and styrene butadiene rubber in a weight ratio of 100:1
A battery B' was obtained in the same manner as battery A' using a positive electrode obtained by mixing the mixture at a ratio of 0 and evaporating the water and press-molding it on a titanium net current collector. do.

Also, manganese dioxide powder, acetylene black and 13,-
: A positive electrode obtained by mixing an aqueous dispersion of polytetrafluoroethylene at a weight ratio of 100:24, evaporating the water, and then taking 2 q of the mixture and press-molding it into a titanium net current collector. A battery obtained using the same method as batteries A/ and B/ is designated as C'.

A', BL, C/Theoretical filling capacity of the positive electrode of each battery is 560 mAH for A', 540 tnAH for B', C'
is 510mAH.

FIG. 2 shows the characteristics when the above battery was discharged at a constant current of 20 U and 16 mA.

As is clear from Figure 2, battery A' exhibits excellent characteristics in terms of discharge voltage and discharge duration, but battery B' has poor elasticity in the styrene-phtadiene rubber used as a binder for the positive electrode. The hardness of the electrode is large, and the specific gravity of the active material manganese dioxide is large. Inferior. In battery C', the binder, polytetrafluoroethylene, has excellent flexibility and liquid absorption properties, but the fluorine side fat treats the surface of the active material, resulting in a low discharge voltage.

Next, we investigated the effect of binders on spiral electrodes that require flexibility.

That is, a band-shaped titanium aggregate with a width of 35 m is placed between two rollers, and while the rollers are rotated at an appropriate speed,
A positive electrode was prepared by press-fitting a positive electrode mixture into both sides of a current collector.

After the positive electrode was sufficiently dried, it was cut into a piece with a width of 35+ m and a length of 250 m. The thickness at that time was 0.6 mm.

The positive electrode is wrapped with a polypropylene separator, and the width is 3
5 cabinets, a lithium plate with a length of 280 mm and a thickness of 0.4 wm is stacked with a negative electrode made of a nickel net current collector crimped and wound in a spiral shape, with a diameter of 26 II made of nickel plated iron.
II11, and the negative terminal is welded to the container, and the positive terminal is welded to a titanium sealing plate with a polypropylene gasket If. The height was f 50 mm. Obtain a so-called AA battery.

With the above configuration, the electrolytic solution used was a mixture of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1:1, in which lithium fluoroborate was dissolved at a ratio of 1 mol/l. A fluorocarbon active material as the positive electrode mixture, acetylene black as a conductive agent, an aqueous dispersion of the nitrile-butadiene rubber, and carboxymethyl cellulose as a thickener in a weight ratio of 100:12:30:2.
Mix fluorocarbon, acetylene black, the aqueous dispersion of styrene-butadiene rubber, and carboxymethyl cellulose in a weight ratio of 1oO:12:40:2. The resulting mixture was used as a positive electrode mixture, and the battery obtained from it was made into an E.
Aqueous dispersion of carbon monofluoride, acetylene black and the above polytetrafluoroethylene '1100:12:4
A positive electrode mixture is prepared by mixing the mixture at a ratio of 0, and a battery obtained from this mixture is designated as F.

Regardless of which binder is used, in order to obtain a flexible positive electrode, a larger amount of the binder is required than in the case of obtaining a molded positive electrode. However, since the aqueous polytetrafluoroethylene dispersion itself has excellent elasticity and elongation, the increase in the amount of binder was smaller than in the case of molded electrodes. On the other hand, when using an aqueous dispersion of styrene-butadiene rubber, phlegm itself
Because of the high hardness and poor elasticity, the amount of binder increased significantly compared to the molded electrode.

The theoretical filling capacity of the positive electrode of the above battery is 6.0AH,
Battery E was s, 5A)i, and battery F was 6.8AH. FIG. 3 shows the characteristics when these batteries were discharged at a constant current of 20 μ and 300 mA.

As is clear from Figure 3, battery glue with less binder is
Compared to batteries E and F, it has better voltage characteristics, has a larger amount of active material, and has better discharge characteristics, so the discharge duration is longer.

Next, we investigated the AA core ρ discharge characteristics when manganese dioxide, which has a higher specific gravity than fluorocarbon, was used as the active material.

In this case, the electrolyte is a mixture of propylene carbonate and 1,2-dimethoxyethane in a volume ratio of 1:1, and the positive electrode mixture is mankan dioxide as an active material, acetylene black as a conductive agent, The water t'4-r version of the above nitrile-butadiene rubber as a binder and carboxymethyl cellulose as a thickener were mixed in a weight ratio of 10.
D
', a positive electrode mixture consisting of a mixture of manganese dioxide, acetylene black, the aqueous dispersion of the above styrene-furidiene rubber, and carboxymethyl cellulose at a weight ratio of 100=7=3o:2, and a battery using the positive electrode obtained from the mixture. E′, an aqueous dispersion of manganese dioxide, acetylene black, and the above polytetrafluoroethylene were mixed at a ratio of 100:7:30 in terms of M ratio, and this was used as a repolarization mixture, and the positive electrode obtained from the mixture was used. Let the battery be F'.

The positive electrode uses styrene-butadiene rubber t- as a binder.
Because the active material, manganese dioxide, has a high hardness and the binder itself has low elasticity, the positive and negative electrodes peeled off.

The theoretical filling capacity of the positive electrode of these batteries is D = 6. OAH,
E and F were 4.8AH.

FIG. 4 shows the results of discharging these batteries at a constant current of 2,010 mA and 100 mA.

As is clear from Figure 4, battery F' using an aqueous dispersion of polytetrafluoroethylene as the positive electrode binder exhibits some discharge characteristics, but because the fluororesin covers the surface of the active material, the discharge voltage is low.

Also, styrene-butadiene rubber itself has high hardness.
Because of its poor elasticity, when used as a binder for active materials with high specific gravity and high hardness, such as manganese dioxide, the electrodes do not stretch well and have high hardness.

It lacks flexibility. As a result, when the electrode is spirally wound, cracks and peeling occur, resulting in a decrease in the discharge voltage and discharge utilization rate of the battery E'.

On the other hand, nitrile-butadiene rubber, which has excellent elasticity and hardness, is used as a binder, and shows good flexibility even with live wire materials such as manganese dioxide, which has a high specific gravity and hardness. It shows discharge characteristics 19, ---.

As shown below, nitrile-butadiene rubber exhibits good properties as a binder for the positive electrode of organic electrolyte batteries.Similar effects have also been observed for other metal oxides, halogenides, sulfides, etc. It was done.

It is also very effective when manufacturing spiral electrodes that require flexibility, and is particularly effective when used with active materials such as manganese dioxide which have a relatively high specific gravity and high hardness.

[Brief explanation of the drawing]

Figure 1 shows the constant current discharge characteristics at 16 mA of a battery in an example of the present invention, and Figure 2 shows the constant current discharge characteristics at 16 mA of a battery in an example of the present invention in which the positive electrode active material was changed. Figure 1. - Fig. 3 is a diagram showing the discharge characteristics of a battery of the present invention equipped with a spiral diagonal electrode, and Fig. 4 is a diagram showing constant resistance discharge characteristics of a battery of the present invention with a different positive electrode active material. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure C first class shield l vice η) Figure 2 Iron helmet special release (kashu)

Claims (1)

[Claims] a positive electrode containing one selected from the group of metal oxides, metal halogenides, metal sulfides, and fluorocarbons as an active material and nitrile rubber made of a copolymer of acrylonitrile and butadiene as a binder; a negative electrode made of a light metal;
Batteries with organic electrolytes 0