JPH10112320A - Electrode for battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To decrease falling frequency during charge and discharge and improve charge and discharge cycle life characteristic, by binding powder elements composing mix for electrode using polyolefine fluorine. SOLUTION: The surface 1a of a powder element 1 such as that of nickel hydroxide is uniformly coated with polyolefine fluorine film 2 whose thickness is 1/100-1/10 of the grain diameter of the powder element 1, and mix paste is created. Then, by filling or painting the paste to a current collector, drying it, and spreading polyolefine fluorine to the film through rolling process, the surface of composition agent for electrode is coated with a thin film of fluororesin. Thus, producing mix for electrode reduces falling of the mix from the current collector during charge and discharge cycle and improves charge and discharge cycle life characteristic.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrode for a battery incorporated in an alkaline secondary battery such as a nickel-cadmium battery, a lithium-ion battery, and a nickel-metal hydride battery. At the same time, the powder component constituting the electrode mixture, which is supported in a layered state on the surface of the current collector and is supported in a state of being formed, has excellent mutual binding properties, and is charged and discharged. The present invention relates to a battery electrode which is capable of preventing the electrode mixture from falling off in (1) and filling the current collector with the electrode mixture at high density, thereby exhibiting excellent battery characteristics.

[0002]

2. Description of the Related Art For example, a nickel-hydrogen secondary battery, which is being rapidly commercialized as a high-capacity battery, is a battery that operates using hydrogen as a negative electrode active material, and a powder of nickel hydroxide as a positive electrode active material. And a positive electrode, and a negative electrode is a hydrogen storage alloy electrode obtained by supporting a hydrogen storage alloy powder for electrochemically storing and releasing hydrogen on a current collector. And the negative electrode are housed in an outer can together with a predetermined alkaline electrolyte, and the battery is entirely sealed.

[0003] As the above-mentioned nickel electrode, a sintered nickel electrode and a non-sintered nickel electrode are manufactured. The latter can increase the packing density of the active material and provide a high capacity electrode. It is advantageous in that it is possible to reduce the manufacturing cost. This non-sintered nickel electrode is generally manufactured as follows.

That is, first, usually, the particle size is 1 to 200 μm.
Nickel hydroxide powder, a thickener, and if necessary, a conductive material powder having a particle size of 1 to 20 μm, a binder, and distilled water or deionized water containing no harmful components for battery reaction. Are kneaded at a predetermined ratio to prepare a mixture paste. Here, the thickener functions as a surfactant for realizing uniform dispersion thereof by coating the surface of the powder component in the mixture paste by dissolving in water, for example, carboxymethylcellulose, methylcellulose, hydroxyethylcellulose, Cellulose polymers such as ethyl cellulose and synthetic polymers such as ethylene glycol, polyethylene glycol, propylene glycol, polyvinyl alcohol, and sodium polyacrylate are widely used.

The conductive material powder enhances the current collecting ability of the manufactured nickel electrode. For example, nickel powder, carbonyl nickel powder, cobalt powder, cobalt oxide powder, cobalt hydroxide powder and the like are widely used. ing. The binder is a component for supporting the powder components such as the above-described nickel hydroxide powder and the conductive material powder on a current collector by binding them to each other.
Polytetrafluoroethylene (PTFE) powder, tetrafluoroethylene / hexafluoropropylene copolymer (FEP) powder, tetrafluoroethylene / perfluoroalkylvinyl ether copolymer (PFA) powder, polychlorotrifluoroethylene (PCTFE) powder, Fluororesin powders such as polyvinylidene fluoride (PVDF) powder, polyvinyl fluoride powder, ethylene / tetrafluoroethylene copolymer (ETFE) powder, ethylene / chlorotrifluoroethylene copolymer (ECTFE) powder, and fluorine-based rubber Powders such as chloroprene rubber, nitrile rubber and styrene rubber, and powders such as polystyrene and nylon polyamide are widely used.

[0006] Of these binders, the above-mentioned fluororesin powder is generally used in the form of a dispersion prepared to a predetermined concentration. In particular, dispersions having a PTFE powder concentration of 30 to 60% by weight are frequently used. The prepared mixture paste is then filled into the voids of a current collector made of a conductive material and having a three-dimensional network structure, for example, a nickel foam, and is simultaneously adhered in layers to the surface. Thereafter, the mixture paste is dried, and further roll-rolled.

[0007] In this process, the water component of the mixture paste is removed, and a dry mixture mainly composed of nickel hydroxide powder (hereinafter, referred to as an electrode mixture) is left in the voids and the surface of the current collector. Remaining, and the binder powder is spread at the time of roll rolling, thereby binding the nickel hydroxide powder and the conductive material powder, which are powder components in the electrode mixture, to each other. It is carried on the voids and the surface of the current collector.

[0008] If necessary, the entire mixture is heated to a desired temperature to melt the binder, whereby the electrode mixture is firmly supported on the current collector. On the other hand, in the case of the above-mentioned hydrogen storage alloy electrode, usually, a hydrogen storage alloy powder having a predetermined particle size, a thickener aqueous solution obtained by dissolving the above-mentioned thickener in water, and a conductive material if necessary. A powder mixture is prepared at a predetermined ratio to prepare a mixture paste, and the mixture paste is applied to a current collector such as a punched nickel sheet, and the mixture paste is layered on both surfaces of the sheet. After being adhered, drying and rolling are sequentially performed to mechanically bind the hydrogen storage alloy powder and the conductive material powder, and to collect the electrode mixture of these powder components due to the tackiness of the remaining thickener. It is carried on an electric body.

[0009]

By the way, in the case of the above-mentioned nickel electrode, in the process of repeated charging and discharging, γ-oxyhydroxide, which is an irreversible reaction product to nickel hydroxide as a positive electrode active material, is used. Nickel accumulates. And
Since the crystal grains of this γ-nickel oxyhydroxide are larger than nickel hydroxide, the mixture carried on the current collector swells and deforms over time.

As a result, in the course of the progress of the charge / discharge cycle, a situation may occur in which nickel hydroxide, which is an active material, falls off, or the whole or a part of the mixture falls off from the current collector. When such a situation occurs, not only does the capacity of the nickel electrode itself decrease, but also if the amount of the nickel electrode drops, the nickel hydroxide powder causes a short circuit between the positive electrode and the negative electrode (hydrogen storage alloy electrode). The cycle life of the battery is shortened.

In the case of the above-mentioned hydrogen storage alloy electrode,
Since the powder components such as the hydrogen storage alloy powder constituting the electrode mixture are only supported on the current collector in a state of being mutually bound by the thickener, the binding force is not so strong. Is not good. Then, in the course of the battery charge / discharge cycle, the hydrogen storage alloy powder carried on the current collector repeatedly absorbs and releases hydrogen. The alloy powder is pulverized.

As a result, the finely divided hydrogen-absorbing alloy powder falls off from the mixture, and therefore, the layered body of the mixture tends to peel off from the surface of the current collector as a whole. In particular, at the time of quick charging, this tendency becomes noticeable. When such a situation occurs, as in the case of the nickel electrode described above, the capacity of the hydrogen storage alloy electrode itself is reduced, and at the same time, a short circuit between the positive electrode and the negative electrode is caused, thereby deteriorating the cycle life characteristics of the battery. Resulting in.

Therefore, in these positive electrodes and negative electrodes, the mutual binding properties of the respective powder components constituting the electrode mixture carried on the current collector are enhanced, and at the same time, the entirety of the mixture and the current collector are improved. Enhancing the binding property with respect to the electrode has begun to become a very important issue from the viewpoint of securing the capacity of the electrode itself and from the viewpoint of improving the cycle life characteristics of the battery.

In order to solve such a problem, for example, in the case of a nickel electrode, it is considered that the amount of the binder powder or the dispersion thereof to be mixed at the time of preparing the mixture paste should be increased. For example, Japanese Patent Application Laid-Open No. 4-248265 discloses a method based on the above-described technical idea.
However, although increasing the amount of the binder certainly increases the binding property between the powder components, on the other hand, the relative abundance of the active material powder, which governs the quality of the electrode reaction, in the electrode mixture is increased. Is to decrease. Therefore, even if the amount of the electrode mixture supported on the current collector is a specified amount, the amount of the active material actually supported, that is, the packing density of the active material into the current collector is reduced. Thus, the capacity of the obtained electrode is reduced.

In addition, when PTFE or a dispersion thereof is used as a binder and is blended for a nickel electrode, the PTFE is subjected to a shearing force during the kneading process during the preparation of the mixture paste, and is converted into fibers. It is difficult to fill the current collector with the obtained mixture paste, and similarly, there is a problem that the packing density of the active material is reduced.

In addition, the fluororesin powder typified by PTFE powder, which is generally commercially available, covers the surface of the powder component constituting the electrode mixture considerably thickly in the process of spreading during the above-mentioned roll rolling. As a result, there is a strong tendency to reduce the functions of these powder components. Therefore, in the case of an electrode in which an electrode mixture formed by kneading a fluororesin as a binder with another powder component is supported on a current collector,
It is necessary to solve the above problems.

On the other hand, with respect to the problem of preventing the electrode mixture from falling off, for example, in JP-A-60-131766, a mixture paste is prepared using spherical nickel hydroxide powder, and the mixture paste is prepared. The paste is filled in a current collector, and drying and rolling are sequentially performed so that the electrode mixture is supported on the current collector. Then, a dispersion of a fluororesin is applied to the surface of the electrode mixture, followed by drying and drying. A method for performing a rolling process is disclosed.

According to this prior art, the occurrence of the phenomenon of the powder components constituting the electrode mixture falling off is considerably suppressed. However, it cannot be said that the application of the active material powder on the surface of the electrode mixture alone can not sufficiently suppress the falling off of the active material powder. The surface of the electrode mixture will be coated with a thick fluororesin, and since the fluororesin exhibits strong water repellency, the surface of the electrode mixture will have an appropriate gas-solid-liquid 3 necessary for the battery reaction. A problem arises in that a phase interface is hardly formed, and the electrode reaction is suppressed.

The present invention solves the above-mentioned problems, and the powder components constituting the electrode mixture are firmly bound to each other.
During the charge / discharge cycle, the electrode mixture is prevented from falling off from the current collector, and the packing density of the powder components that define the battery reaction, such as active material powder and hydrogen storage alloy powder, into the current collector is high, which is excellent. It is an object of the present invention to provide a battery electrode capable of manufacturing a battery exhibiting improved cycle life characteristics.

[0020]

In order to achieve the above-mentioned object, the present invention relates to a battery electrode in which an electrode mixture formed by binding powder components to each other is supported on a current collector. In addition, there is provided a battery electrode, wherein the powder components are mutually bound by a fluorinated polyolefin, and the surface of the electrode mixture is coated with a fluororesin.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The electrode of the present invention has the same structure as the conventional electrode in that an electrode mixture composed of each powder component as described above is supported on a current collector. Are characterized by being mutually bound by a fluorinated polyolefin, and the surface of the electrode mixture is covered with a thin film of a fluororesin.

That is, two kinds of binders are used in the electrode of the present invention in order to prevent the powder components from falling off. That is, the former fluorinated polyolefin is used to bind each powder component to each other in the process from preparation of the mixture paste to supporting of the electrode mixture on the current collector, and the latter fluororesin is It is used for coating the surface of the electrode mixture carried on the current collector in a dry state.

In producing the battery electrode of the present invention, first, a powder component such as an active material powder or a conductive material to be blended as required, a thickener aqueous solution, and a fluorinated polyolefin described below are prepared. To prepare a mixture paste. Here, the fluorinated polyolefin is a thermoplastic resin in which only a part of hydrogen atoms of a polyolefin such as polyethylene, polypropylene, polybutylene, polypentylene, and polyhexylene is substituted with a fluorine atom, and has an average molecular weight of usually 10 ⁴ to 10. ⁶ , having an average molecular weight of about 1/10 ⁴ to 1/10 as compared with a fluororesin represented by PTFE having an average molecular weight of 10 ⁷ to 10 ^8. Also exhibits water repellency like resin.

The fluorinated polyolefin is
Physical properties such as hardness, heat resistance temperature, heat deformation temperature, strength characteristics, volume resistivity, and water repellency vary depending on the type of polyolefin employed as the base material and the degree of fluorination.
And even if it receives a shearing force at the time of kneading, it does not fibrillate even if it is kneaded as in the case where the PTFE powder is blended in the mixture paste.

The use of this fluorinated polyolefin is preferred because its dispersion can realize a uniform kneading state with other powder components. If the amount of the fluorinated polyolefin used is too large, it is effective in binding each powder component and suppressing its falling off, but on the other hand, the conductivity of the supported electrode mixture is poor. As a result, the current-collecting ability deteriorates and the active material surface becomes deactivated, and the amount of the active material actually carried on the current collector, that is, the packing density of the active material in the current collector decreases. However, eventually, the battery capacity is reduced. On the other hand, if the amount is too small, the powder components cannot be sufficiently bound, and there is a problem in that the powder components are prevented from falling off.

From the above, it is preferable that the blending amount of the fluorinated polyolefin is set to 0.1 to 2 parts by weight based on 100 parts by weight of the active material powder as the main component. When a dispersion of fluorinated polyolefin is used, it is preferable that the dispersion concentration of the fluorinated polyolefin in the dispersion is 10 to 50% by weight. This is because the kneading operation can proceed smoothly.

In the process of kneading during the preparation of the above-mentioned mixture paste, the fluorinated polyolefin is uniformly attached to the surface of the powder component such as the active material and the conductive material without surrounding the fiber, without being fiberized. FIG. 1 shows this state as a conceptual diagram. That is, for example, the surface 1a of the powder component 1 such as the nickel hydroxide powder is uniformly formed by the fluorinated polyolefin film 2 having a thickness of 1/100 to 1/10 of the particle size of the powder component 1. Each powder component 1 is dispersed in the paste in this state. On the other hand, as in the conventional case, for example, P
When TFE is used, the surface 1a of each powder component has a larger thickness than a fluorinated polyolefin.
It is covered with a film of FE, and in this state, each powder component is dispersed in the paste.

Therefore, when a fluorinated polyolefin is used as a binder as in the present invention, the amount required for binding other powder components is smaller than that of the prior art by the thinner film thickness. You will need less. Conversely, powder components such as active material powder can be bound with a smaller amount of binder than before, so when preparing a certain amount of mixture paste, a larger amount than before is required. An active material powder can be blended.

The prepared mixture paste is then filled or applied to a current collector. The current collector is not particularly limited. For example, when the purpose is to produce a nickel electrode, a nickel foam having a three-dimensional network structure having a large porosity is preferable. This is because the porosity of the nickel foam is usually 90 to 97%, and the mixture paste can be filled in a large amount.

Next, the water in the mixture paste is removed by performing a drying treatment on the whole. Therefore, next, roll rolling is performed. Due to the external force applied at the time of the roll rolling, the voids inside the current collector formed by the removal of moisture were eliminated, and the adhesion between the active materials was increased, and the powder was adhered to the surface of each powder component in a powder state. The fluorinated polyolefin is spread and further thinned, and through this thin film, the respective powder components 1 are bound to each other as shown in FIG.

Since this thin film is formed by extending the fluorinated polyolefin shown in FIG. 1, its thickness is very small. Therefore, the volume ratio of the fluorinated polyolefin to the total amount of the supported electrode mixture is much smaller than that of a conventional fluororesin such as PTFE. Conversely, when the electrode mixture of the same volume is compared, in the present invention, the existence ratio of the active material powder is large. That is, the packing density of the active material is high.

Next, on the surface of the electrode mixture supported on the current collector while the respective powder components are bound to each other,
A dispersion of a fluororesin is applied, and drying and rolling are sequentially performed. Specifically, at the time of coating, it is preferable to adopt a method in which the whole is immersed in a fluororesin dispersion and taken out. This is because the operation is simple. Of course, a method such as brushing or spraying the dispersion may be used.

By the rolling treatment, the fluororesin powder is spread and thinned, and the surface of the electrode mixture is covered with the fluororesin thin film. As a result, the exfoliation phenomenon of each powder component constituting the electrode mixture is suppressed. The fluororesin is not particularly limited, and may be any as long as it has been conventionally used as a binder. Specifically, PTFE, FEP, PFA, PCTFE, PVD
Suitable examples include F, ETFE, ECTFE, FEVE, PVF and the like.

Here, since the thin film of the fluorinated polyolefin is much thinner than the thin film of the fluororesin,
The fluorinated polyolefin is not included in the fluororesin for the thin film formed on the surface of the electrode mixture. In the dispersion used, if the suspension concentration of the fluororesin is too high, the thin film covering the surface of the electrode mixture becomes too thick and hinders the electrode reaction, and conversely if the suspension concentration is too low It is preferable to use a dispersion having a suspension concentration of 20 to 70% by weight, since the effect of suppressing the powder component peeling phenomenon by the thin film becomes insufficient.

[0035]

【Example】

Examples 1 to 6, Comparative Examples 1 and 2 (1) Production of Nickel Electrode Particle size was determined based on 100 parts by weight of spherical nickel hydroxide powder having a solid solution of zinc of 7% by weight and a particle size of 5 to 50 μm. But
0.5 to 30 μm of cobalt oxide powder (5 parts by weight) was mixed,
Here, 50 parts by weight of a 2% by weight aqueous solution of carboxymethylcellulose (corresponding to 1 part by weight of carboxymethylcellulose) and a dispersion of fluorinated polyethylene having a suspension concentration of 30% by weight are added in the indicated amounts, and the whole is kneaded. Then, various mixture pastes having different blending amounts of the fluorinated polyethylene were prepared.

These mixture pastes were filled in a sponge-like nickel plate having a porosity of 95%. The filling operation was able to proceed smoothly. Then, after performing a drying treatment at a temperature of 150 ° C. for 20 minutes, roll rolling was performed at a pressure of 4 ton / cm ² . Thereafter, the obtained plate material was immersed in a PTFE dispersion having a suspension concentration of 60% by weight, taken out, dried at a temperature of 120 ° C. for 20 minutes, and further roll-rolled at a pressure of 6 ton / cm ² to a thickness of 0. It was a 7 mm nickel electrode.
On the surface of each nickel electrode, a 50-100 nm thick PTF
It was confirmed that the E thin film was formed.

On the other hand, a mixture paste was prepared using 6 parts by weight of the above-mentioned PTFE dispersion (3 parts by weight of PTFE) instead of the above-mentioned fluorinated polyethylene dispersion. A nickel electrode was manufactured in the same manner as in Example except that a thin film of PTFE was not formed on the surface of the mixture. This is referred to as a comparative example nickel electrode 1.

(2) Production of hydrogen storage alloy electrode Composition formula: MmNi _3.2 Co _1.0 Al _0.2 Mn _0.4 (However,
A hydrogen storage alloy represented by Mm (mish metal) was pulverized into an alloy powder having a particle size of 20 to 60 μm. 10 parts by weight of nickel powder having a particle size of 10 to 5 μm and 5 parts by weight of fluorinated polyethylene are mixed with 100% by weight of the alloy powder, and 50 parts by weight of deionized water is added thereto, and the whole is kneaded. A mixture paste for a negative electrode was prepared.

This mixture paste was applied to both surfaces of a punched nickel plate (opening diameter 1.5 mm, opening ratio 38%, thickness 0.07 mm). Then, after drying at a temperature of 80 ° C. for 60 minutes, it was roll-rolled at a pressure of 3 ton / cm ² . afterwards,
The obtained plate was converted to PTFE having a suspension concentration of 60% by weight.
Take out after immersion in dispersion, temperature 100
The resultant was dried at 20 ° C. for 20 minutes and roll-rolled at a pressure of 4 ton / cm ² to form a 0.35 mm thick hydrogen storage alloy electrode. It was confirmed that a PTFE thin film having a thickness of 30 to 80 nm was formed on the surface of the hydrogen storage alloy electrode.

On the other hand, a mixture paste was prepared by using 3 parts by weight of PTFE powder instead of the above-mentioned fluorinated polyethylene, and PTF was added to the surface of the carried electrode mixture.
A hydrogen storage alloy electrode was manufactured in the same manner as in Example except that the thin film of E was not formed. This is designated as a hydrogen storage alloy electrode 1 of a comparative example. (3) Battery assembly FT-310 (trade name, polyolefin-based nonwoven fabric manufactured by Japan Vilene Co., Ltd.) was washed with water to remove the nonionic surfactant attached to the surface, and then dried. The surface was sulphonated by immersing it in 95% hot concentrated sulfuric acid (temperature: 100 ° C.) for 30 minutes. The treated nonwoven fabric was sufficiently washed with running water, dried at a temperature of 80 ° C. for 1 hour, immersed in a 1% aqueous sodium hydroxide solution for 5 minutes, and further washed with water.

FT-773 (trade name, nonwoven fabric of polyamide resin manufactured by Japan Vilene Co., Ltd.) was washed with water,
The treated product of FT-310 is superimposed on both sides of this nonwoven fabric, and the temperature is 80 ° C. while applying a pressure of 3 kg / m ^{2 to} the whole.
Was subjected to a heat and pressure treatment for 1 hour to be integrated to obtain a separator. Between the nickel electrode and each hydrogen storage alloy, the separator is interposed to form an electrode plate group, which is accommodated in a stainless steel can that has been subjected to nickel plating. An electrolytic solution consisting of NaOH, 1N LiOH and 7N KOH was injected and sealed, and a square nickel-hydrogen secondary battery having a rated capacity of 1200 mAh was assembled.

A nickel-metal hydride secondary battery was assembled in the same manner as in each of the examples except that the above-mentioned nickel electrode of the comparative example and the hydrogen storage alloy electrode of the comparative example were used. (4) Investigation of battery characteristics For the assembled battery, 1200mAh at 10 ° C
A cycle life test was performed in which the battery was charged for 1.5 hours, discharged at 1.25 mAh and the battery voltage was set to a complete discharge state of 0 V, and discharged for 1.25 hours and 0.25 hours of rest as one cycle. The discharge capacity was measured at the beginning of the cycle test and after the 500 cycle test, and the value was divided by the initial capacity to calculate the capacity retention (%). The results are shown in Table 1.

In the above cycle life test, 5
At the end of the 00 cycle, the battery was disassembled, the nickel electrode and the hydrogen storage alloy electrode were taken out, and the respective weights were measured to determine the total shedding amount of the nickel hydroxide powder and the hydrogen storage alloy powder from the weight before being incorporated into the battery. Table 1 shows the relative amounts of the total dropout of the nickel electrode and the hydrogen storage alloy electrode when the total dropout of the nickel electrode and the hydrogen storage alloy electrode of each comparative example was set to 1.

[0044]

[Table 1]

As is apparent from Table 1, the batteries incorporating the nickel electrode and the hydrogen storage alloy electrode manufactured according to the present invention were all comparative examples in which the powder component of the mixture was bound with PTFE. Of the powder component from each electrode is 3/10 even after 500 cycles of charging and discharging.
~ 3/5, very little. Therefore, the capacity retention also shows a high value.

However, as is clear from the comparison between the embodiments,
When the amount of the fluorinated polyethylene to be blended during the preparation of the mixture paste is small, the amount of falling off increases and the tendency to decrease the capacity retention rate of the battery appears, and conversely, when the amount of the fluorinated polyethylene increases, the amount of falling off increases. Although the number decreases, the rated capacity tends to decrease in the first place. For this reason, the blending amount of the fluorinated polyethylene depends on the active material powder 10
It is preferable to set the range of 0.1 to 2 parts by weight with respect to 0 parts by weight.

Examples 7 to 12 Nickel electrodes were manufactured in the same manner as in Examples 1 to 6, except that fluorinated polypropylene was used instead of fluorinated polyethylene during the manufacture of the nickel electrode. These nickel electrodes were used as positive electrodes, and the hydrogen storage alloy electrodes used in Examples 1 to 6 were used as negative electrodes.
A hydrogen secondary battery was assembled. Table 2 shows the characteristics of these batteries.

[0048]

[Table 2]

When fluorinated polypropylene is used as the binder, the same effects as in Examples 1 to 6 can be obtained. Examples 13 and 14 The nickel electrode used in the battery of Example 5 was selected as the positive electrode.
A nickel-hydrogen secondary battery was assembled in the same manner as in Examples 1 to 6, except that the hydrogen storage alloy electrode of the comparative example was used as the negative electrode. This is referred to as Example Battery 1
3 is assumed.

A nickel-hydrogen secondary battery was manufactured in the same manner as in Examples 1 to 6, except that the above-described comparative nickel electrode was used as the positive electrode and the hydrogen storage alloy electrode of the above-described example was used as the negative electrode. The battery was assembled. This is designated as Example Battery 14. Table 3 shows the characteristics of these batteries.

[0051]

[Table 3]

As is evident from Table 3, the battery in which the electrode manufactured according to the present invention was incorporated as either the positive electrode or the negative electrode was slightly inferior in the battery characteristics as compared with the result in which both electrodes were incorporated. It shows better characteristics than the example battery.

[0053]

As is evident from the above description, the battery electrode of the present invention has less dropout of the electrode mixture carried on the current collector during charge / discharge than the conventional electrode. Therefore, the battery incorporating this electrode has excellent charge / discharge cycle life characteristics.

This is an effect obtained by binding the powder components constituting the mixture with the fluorinated polyolefin and covering the surface of the electrode mixture carried with a thin film of fluororesin. And in the case of the battery electrode of the present invention, it is possible to increase the relative compounding amount of the active material powder at the time of preparing the mixture paste, and as a result, to increase the packing density of the active material in the current collector. Therefore, the electrode has a high capacity.

[Brief description of the drawings]

FIG. 1 is a conceptual diagram showing a binding state of powder components of a mixture in the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Powder component 1a Surface of powder component 1 2 Thin film of fluorinated polyolefin

Continued on the front page (72) Inventor Manabu Manabu 23-6 Tsukuwaku, Jobanshita Funao-cho, Iwaki-shi, Fukushima Furukawa Battery Co., Ltd. Iwaki Works

Claims (2)

[Claims] Claims: 1. An electrode for a battery in which an electrode mixture formed by binding powder components to each other is supported on a current collector, wherein the powder components are bound to each other by a fluorinated polyolefin,
A battery electrode, wherein the surface of the electrode mixture is coated with a fluororesin. 2. The battery electrode according to claim 1, wherein the fluorinated polyolefin is fluorinated polyethylene and / or fluorinated polypropylene.