JP2704689B2 - Manufacturing method of battery electrode - Google Patents

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. More specifically, the present invention relates to a battery electrode using, as an active material, a composite of an insoluble and infusible substance having semiconductor properties and a metal oxide.

[0002]

2. Description of the Related Art In recent years, portable and cordless home appliances and electronic devices have been rapidly advancing. Along with this, a small, lightweight and high-performance battery has been demanded as a power source. At present, so-called primary batteries such as dry batteries and secondary batteries such as Ni-Cd batteries and lead batteries are used as power supplies for the above devices. However, recently, a secondary battery that can be repeatedly charged for a primary battery that has a short life and needs to be replaced has been frequently used. Among them, Ni-Cd batteries are currently the mainstream as power supplies for small devices, but their performance improvement is approaching the limit for needs such as high capacity. In addition, global environmental issues have been debated in recent years, and public opinion on the harmfulness of Cd, an active material, has been increasing. Therefore, there is great expectation for the development of secondary batteries that have higher performance than Ni-Cd batteries, and that are more reliable and safer.

[0003] The present applicant has previously disclosed a secondary in which an insoluble and infusible substrate containing a polyacene skeleton structure, which is a kind of organic semiconductor, doped with an electron donating substance or an electron accepting substance is used as an electrode active material. A battery has been proposed (JP-A-60-170163). This battery is high performance and thin,
It is a promising secondary battery because it has the potential for weight reduction, has high oxidation stability of the electrode active material, and is easy to mold.

Further, the present applicant has proposed a secondary battery using a composite of a polyacene-based organic semiconductor and a metal oxide as an active material (JP-A-63-314759). However, the capacity of the battery was still insufficient. Further, a battery electrode in which the average particle size of the metal oxide is 1 μm or less and the ratio of pores of 0.1 μm or less in the electrode accounts for 70% or more has been proposed (November 28, 1991) Patent applied). A battery using this electrode is characterized by a large capacity per unit volume, but its quick chargeability is not yet satisfactory.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide an electrode for a battery having excellent quick charge characteristics.

Another object of the present invention is to provide a battery electrode which has a large capacity per unit volume, can be charged and discharged for a long period of time, is easy to manufacture, and is economical.

[0007]

Means for Solving the Problems The present inventors have made intensive studies in view of the above-mentioned problems, and made electrodes by various methods. As a result, the average particle size of the metal oxide and the pore volume of the electrodes were reduced. After controlling to a specific range, it was further found that when the electrode was a molded body of a composite obtained by simultaneously pulverizing the active material and the conductive material, the rapid chargeability of a battery using this electrode was improved.
The present invention has been reached. That is, the present invention provides (a) a heat-treated aromatic condensed polymer comprising carbon, hydrogen and oxygen, wherein the polyacene skeleton structure has a hydrogen atom / carbon atom number ratio of 0.05 to 0.5. And an insoluble and infusible substrate having a specific surface area of at least 600 m ² / g according to the BET method, (b) an active material that is a composite with a metal oxide, and (c) a battery containing at least a conductive material. In the method for manufacturing an electrode, (1) the average particle diameter of the metal oxide is 1 μm or less, and (2) the pore volume of the electrode having a pore diameter of 0.1 μm or less is based on the total pore volume. Occupies 70% or more (measured by a mercury intrusion method); (3) the electrode is a molded product of a composite powder obtained by simultaneously pulverizing and mixing (a), (b) and (c). And

The insoluble and infusible substrate having a polyacene-based skeleton structure (hereinafter sometimes referred to as PAS) used in the present invention is disclosed in Japanese Patent Application Laid-Open Nos. 60-152554 and 60-152554. No. 60-170163 and others. Here, the aromatic condensation polymer is a condensate of an aromatic hydrocarbon compound having a phenolic hydroxyl group with an aldehyde. Suitable aromatic hydrocarbon compounds include, but are not limited to, so-called phenols such as phenol, cresol, and xylenol.

For example, the following formula (Formula 1):

[0010]

Embedded image (Where x and y are each independently 0, 1, or 2)
Methylene bisphenols, or hydroxy-biphenyls and hydroxynaphthalenes. Of these, phenols, particularly phenol, are suitable for practical use.

As the aromatic condensation polymer in the present invention, one part of the above-mentioned aromatic hydrocarbon compound having a phenolic hydroxyl group is replaced with an aromatic hydrocarbon compound having no phenolic hydroxyl group, for example, xylene or toluene. , Modified aromatic polymers substituted with aniline and the like, for example, modified aromatic polymers which are condensates of phenol, xylene and formaldehyde, and modified aromatic polymers substituted with melamine and urea can also be used. Polymers can also be used. Furan resins are also suitable.

As the aldehyde, formaldehyde, acetaldehyde, furfural and the like can be used, and formaldehyde is preferred. The phenol-aldehyde condensate may be any of a novolak type, a resol type and a composite thereof. A spherical phenolic resin (sphere diameter of about 100 μm or less) commercially available as Bellpearl R (trade name, manufactured by Kanebo Co., Ltd.) can also be used. The PAS in the present invention is a heat-treated product of the aromatic compound as described above, and can be produced, for example, as follows.

An inorganic substance such as zinc chloride, sodium phosphate, sodium hydroxide, potassium hydroxide or potassium sulfide is mixed into the above-mentioned aromatic condensation polymer. As a mixing method, an aromatic condensation polymer may be dissolved in a solvent such as methanol, acetone, or water, and then the above-mentioned inorganic substance may be added and sufficiently mixed. Further, if the aromatic condensation polymer is a fusible one such as novolak, it may be mixed under heating. The mixing ratio of the aromatic condensed polymer and the above-mentioned inorganic substance varies depending on the type and shape of the polymer to be mixed and the inorganic substance.
0/1 to 1/7 are preferred.

Next, the mixture is cured into a film, plate, fiber, cloth, granule or a mixture thereof.

The cured product thus obtained is then heated in a non-acidic atmosphere at 350 to 800 ° C., preferably at 350 to 70 ° C.
It is heated to a temperature of 0 ° C, particularly preferably 400-600 ° C. The non-oxidizing atmosphere in which such heat treatment of the aromatic condensation polymer is performed is, for example, nitrogen, argon, helium, neon, carbon dioxide atmosphere, or vacuum,
Nitrogen is preferably used. Such a non-oxidizing atmosphere may be stationary or flowing.

By sufficiently washing the obtained heat-treated body with water or dilute hydrochloric acid, the inorganic salts contained in the heat-treated body can be removed, and thereafter, when this is dried, PAS having a large specific surface area can be obtained. it can.

The PAS used in the present invention has a hydrogen atom / carbon atom atomic ratio (hereinafter referred to as H / C ratio).
It has a polyacene skeleton structure of 0.05 to 0.5, preferably 0.1 to 0.35. According to X-ray diffraction (CuKα), the position of the main peak exists between 20.5 and 23.5 ° in terms of 2θ, and between 41 and 46 ° in addition to this main peak. There are other broad peaks.

That is, it is understood that the PAS is a polyacene-based benzene having a polycyclic structure uniformly and appropriately developed between polyacene-based molecules. When the H / C ratio exceeds 0.5, the charge efficiency of charging / discharging of a secondary battery using a composite of PAS and a metal oxide as an electrode deteriorates.
On the other hand, if this value is less than 0.05, the capacity of the battery will decrease.

The BET specific surface area of the PAS used in the present invention is at least 600 m ² / g. 600m ² /
If it is less than g, in the battery using the battery electrode of the present invention, it is necessary to increase the charging voltage, so that the energy efficiency is reduced and the electrolyte is deteriorated.

In the present invention, since PAS has a high specific surface area of 600 m ² / g or more as described above,
Regardless of the particle size, sufficient performance as an active material, that is, sufficient capacity of the PAS used can be sufficiently obtained. However, if the particle size of the PAS is too large,
Since it becomes difficult to disperse the metal oxide which is liable to secondary aggregation in the PAS matrix, that is, between the PAS particles, it is preferable that the final particle size be 1 μm or less.

As the metal oxide in the present invention, those capable of intercalating or deintercalating lithium ions can be used. Preferred are transition metal oxides, for example, oxides of metals such as vanadium, chromium, manganese, molybdenum, copper, bismuth, nickel and cobalt. Further, Li is previously added to the metal oxide, for example, LiCo.
O ₂ and LiMnO ₂ may be used. Stability of the battery to be manufactured, capacity, considering the voltage, etc., among which V ₂
Vanadium oxides such as O ₅ and V ₆ O ₁₃ are preferred.

The above-mentioned metal oxide may be in a crystalline state or in an amorphous state by heat treatment or the like.

In the electrode of the present invention, it is necessary that the average particle size of the above-mentioned metal oxide is 1 μm or less finally, that is, when the electrode is formed. This is because the above-mentioned PAS having a large surface area can sufficiently draw out its available capacity irrespective of the particle size, whereas in the case of metal oxides, if the particle size is too large, the available capacity can be sufficiently drawn out. Because it becomes difficult. Furthermore, since metal oxides have low conductivity, a large particle size is disadvantageous for quick charging. That is, when the particle size of the metal oxide is larger than 1 μm, the capacity is not sufficient and the quick chargeability is poor even if the pore distribution condition in the electrode described later is satisfied.

In the electrode of the present invention, the ratio of PAS / metal oxide can vary depending on the use of the electrode containing these, but is 90/10 to 30/70 (weight ratio), particularly 70/3.
It is preferably 0 to 30/70. In particular, when the amount of the metal oxide is too large, the rapid charge / discharge characteristic, which is a feature of the composite, tends to be lost.

Next, the conductive material used in the present invention includes, for example, carbon black such as acetylene black and Ketjen black, and preferably has as small a particle size as possible. The amount of conductive material in the electrode may vary depending on the application of the electrode, but may range from 2% to 40% by weight of the active material.
It is preferred that If the amount of the conductive material is too large, the amount of the active material becomes relatively small, so that the capacity of the battery becomes low.

The battery electrode of the present invention is characterized in that (a) PA
S, (b) a metal oxide and (c) a conductive material can be obtained by simultaneously pulverizing and mixing the three components. It is important to simultaneously grind and mix the three components, and the effect of the present invention cannot be obtained only by grinding and mixing the two components of PAS and metal oxide. For example, after simultaneously grinding and mixing (a) and (b)
When (c) is simply mixed to form an electrode, the metal oxide is homogeneously dispersed in the PAS, so that a battery with a large capacity can be obtained. However, the quick charging characteristics are not satisfactory.

The three forms of pulverization are lump, granular,
Any form that can be easily mixed, such as a plate, a powder, or a short fiber, may be used. When the powder of PAS and metal oxide is used, if the particle size before the pulverization is too small, the effect of the simultaneous pulverization is small, and it is difficult to obtain the advantages of the present invention.

The method of pulverization and mixing is not particularly limited, but it is preferable to use a fine pulverizer represented by a ball mill such as a pot mill and a vibration mill.

The pulverization time should be determined according to the pulverization method, the amount of pulverization, and the type of the substance to be pulverized, but is preferably 1 hour or more. preferable.

The battery electrode of the present invention can be obtained by molding a composite to which a binder and the like are added as required in addition to the above three components. The binder and the like are not specified in the present invention, and those generally used for battery electrodes are preferred.

The molding method is not particularly limited, and a conventional molding method used for powders, for example, a pressure molding method can be used.

The battery electrode of the present invention thus obtained is
It is necessary that the pore volume having a pore diameter of 0.1 μm or less accounts for 70% or more, preferably 75% or more of the total pore volume. Examples of the method for measuring the pore volume include a mercury intrusion method and a capillary condensation method. In the present invention, a mercury intrusion method having a wide measurement width (pore distribution of 0.006 μm to 100 μm) was used. Therefore, the total pore volume in the present invention is 0.006 per electrode unit weight.
It means the total volume of pores having a pore diameter of not less than μm and not more than 100 μm. Further, the pore volume having a pore diameter of 0.1 μm or less refers to the total volume of pores having a pore volume of 0.006 μm or more and 0.1 μm or less.

In the present invention, fine metal oxide particles of 1 μm or less are uniformly distributed between PAS particles.
The ratio of pores of 0.1 μm or less is large. Especially 0.1 μm
Metal oxide of about 0.2 to 0.6 μm
Those which are uniformly dispersed between S particles are preferred.

The shape of the electrode of the present invention is not particularly limited, and can take various shapes such as a plate shape, a film shape and a cylindrical shape.

The battery electrode of the present invention is used mainly as a positive electrode of a secondary battery using an organic solvent solution containing a lithium salt as an electrolyte. As the negative electrode of this secondary battery, lithium metal, an alloy containing lithium, or the like can be used, and PAS can also be used as the negative electrode.

[0036]

The battery electrode of the present invention is obtained by simultaneously pulverizing and mixing the three components of PAS, metal oxide and conductive material.
The finely divided metal oxide is immediately and uniformly dispersed in the PAS and the conductive material without secondary aggregation. Also,
Since the metal oxide is pulverized in the presence of the conductive material, the metal oxide having relatively low conductivity will be sufficiently entangled with the conductive material, and it is considered that the metal oxide can be sufficiently assisted by the conductive material. As a result, it seems that it is possible to sufficiently draw out the capacity that can be held even for quick charging, particularly for very quick charging such as 30 minutes.

Hereinafter, the present invention will be described in more detail with reference to examples.

[0038]

EXAMPLES In the examples, the following substances were used. A slurry obtained by mixing PAS water-soluble resol type phenol resin (about 60% concentration) / zinc chloride / water at a weight ratio of 10/25/5 is poured into a 10 cm × 10 cm × 1 cm mold, A glass plate is placed on top of the glass plate to prevent evaporation of water.
The composition was cured by heating at 0 ° C. for 1 hour. The cured product was placed in a siliconite electric furnace, heated at a rate of 40 ° C./hour and heated to 500 ° C. in a nitrogen stream to perform a heat treatment. Next, the heat-treated product is washed with dilute hydrochloric acid to remove zinc chloride, washed with water, and then dried to obtain a plate-shaped P.
AS was obtained. The specific surface area of this PAS by the BET method is 2
It was an extremely large value of 000 m ² / g. Elemental analysis revealed that the ratio of the number of hydrogen atoms to the number of carbon atoms was 0.23. The shape of the peak from X-ray diffraction is a pattern based on the polyacene-based skeletal structure.
A broad main peak was present around 0 to 22 °, and a small peak was found around 41 to 46 °.

The PAS thus obtained was divided into blocks of about 1 to 5 cm square, which were used in the following examples. Metal oxide Commercial V ₂ O ₅ was used. Example 1 60 parts by weight of PAS, 40 parts by weight of V ₂ O ₅ and 25 parts by weight of carbon black (trade name: Black Pearl, average particle size: 0.02 μm, manufactured by Cabot Corporation) as a conductive material were put into an alumina ball mill for 24 hours. (Example 1a) and pulverized and mixed for 48 hours (Example 1b). Observation of the obtained composite powder with an electron microscope revealed that the average particle diameter of the PAS was 0.5 μm and 0.3 μm, respectively.
However, V ₂ O ₅ particles are very small, and are homogeneously mixed with PAS particles and a conductive material particles, V ₂ O ₅ is an accurate measurement of the particle diameter has been difficult, for V ₂ O ₅ particles Did not find anything exceeding 0.1 μm.

With respect to 100 parts by weight of the obtained composite powder,
5 parts by weight of polytetrafluoroethylene was added as a binder, mixed and kneaded with a mortar, and then formed into a sheet with a roller to obtain an electrode sheet having a thickness of 750 μm. The pore distribution of this electrode sheet was measured with a mercury porosimeter (Poresizer, manufactured by Shimadzu Corporation), and was measured to be 0.006 μm or more and 0.1 μm.
Pore volume having a pore diameter of 1 μm or less) / (0.00
When the ratios of the pore volumes having a pore diameter of 6 μm or more and 100 μm or less were determined, 81% and 86% respectively were obtained.
Met.

This electrode sheet was punched out to a diameter of 15 mm to form a positive electrode, lithium as a negative electrode, and 1M Li as an electrolyte.
A battery as shown in FIG. 1 was assembled using a ClO ₄ propylene carbonate solution and a glass nonwoven fabric as a separator. The electromotive voltage was 3.44V. This battery is 4V
, And then discharged at a current of 2 mA to 2.5 V, and the initial capacity was measured. Subsequently, constant-voltage charging was performed at 4 V for 30 minutes, followed by discharging in the same manner as described above to measure the capacity, and the ratio of this value to the initial capacity was evaluated as the rapid charging characteristic. Table 1 shows the results. Comparative Example 1 The same PAS and V ₂ O ₅ used in Example 1 were
AS / V ₂ O ₅ = 60/40 (weight ratio), placed in an alumina ball mill for 24 hours (Comparative Example 1a) and 48
Time (Comparative Example 1b) was ground. PAS and V obtained
_When the composite of ₂ O ₅ was observed with an electron microscope, PAS
Were 0.5 μm and 0.4 μm, respectively. However, V ₂ O ₅ particles are very small and PA
The particles were homogeneously mixed with the S particles, and no particles exceeding 0.1 μm were found.

To 100 parts by weight of the obtained composite, 25 parts by weight of carbon black (trade name: Black Pearl, manufactured by Cabot Corporation) as a conductive agent and 5 parts by weight of polytetrafluoroethylene as a binder were added. After mixing, an electrode was manufactured in the same manner as in Example 1, and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 1 shows the results. Example 2 The same PAS used in Example 1 was pulverized with a nylon ball mill for 48 hours, and V ₂ O ₅ was further pulverized with an alumina ball mill for 48 hours. The average particle size of each of the obtained powders was 0.4 μm for PAS and 0.08 μm for V ₂ O ₅ . 60 parts by weight of the PAS powder thus obtained, V ₂
O ₅ powder 40 parts by weight of carbon black as a conductive material: the (manufactured by Cabot Corporation, trade black pearl) 25 parts by weight were co-milled mixture for 6 hours at a ball mill made of alumina. Observation of the obtained composite with an electron microscope revealed that P
The average particle size of AS was reduced to 0.3 μm. V ₂ O
Regarding the _five particles, a relatively large PAS has a small V ₂ O
_Since the particles of ₅ and the conductive material were mixed, it was impossible to identify the particle size.However, particles of 1 μm or more were not observed at all and were homogeneously dispersed, and no secondary aggregate was observed. .

Using this composite, an electrode was manufactured in the same manner as in Example 1, and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 1 shows the results. Comparative Example 2 The average particle diameter was 0.4 μm for PAS and 0.08 for V ₂ O _5.
Perform the same procedure as in Example 2 up to the point where
Next, a composite was produced in the same manner as in Example 2 except that the three materials were mixed in a mortar instead of adding the conductive material and simultaneously grinding the three materials with an alumina ball mill.

Using this composite, an electrode was manufactured in the same manner as in Example 1, and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 1 shows the results. Example 3 Acetylene black (manufactured by Denki Kagaku Kogyo Co., Ltd., trademark: Denka Black, average particle size 0.03 μm) as a conductive material
A composite powder was obtained in the same manner as in Example 1b except that 30 parts by weight was used. The average particle size of PAS was 0.3 μm. However, V ₂ O ₅ particles are very small and PAS
Particles and conductive material particles are homogeneously mixed,
Nothing exceeding μm was found at all.

Using this composite, an electrode was manufactured in the same manner as in Example 1, and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 1 shows the results.

[0046]

[Table 1] Table 1 ＰＡ PAS V ₂ O ₅ 0.1 μm or less Initial charge (30-minute charge capacity) / average particle size Percentage of pores with average particle size Pond capacity (initial capacity) (μm) (μm) (%) (at mA) × 100 (%) ─────── ───────────────────────────── Example 1a 0.5 <0.1 81 5.9 72 Example 1b 0.3 <0.1 85 6.0 74 Comparative Example 1a 0.5 <0.1 86 6.0 60 Comparative Example 1b 0.4 <0.1 84 5.9 58 Example 2 0.3 <0.1 76 5.8 70 Comparative Example 2 0.4 0.08 68 4.8 59 Example 3 0.3 <0.1 75 5.3 72 ─────────で は In the examples, the ratio of the capacity after charging for 30 minutes to the initial capacity is as high as 70% or more. . Also, the initial capacity of the battery is high. On the other hand, in Comparative Examples 1a and 1b, the initial capacity of the battery is high, but the quick charge characteristics are inferior. Example 4 The ratio of each component was PAS / V ₂ O ₅ / conductive material = 60/4
Example 1b except that PAS / V ₂ O ₅ / conductive material = 40/60/25 (weight ratio) instead of 0/25 (weight ratio)
A composite and an electrode were manufactured in the same manner as described above, and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 2 shows the results. Comparative Example 3 Instead of PAS / V ₂ O ₅ = 60/40 (weight ratio), P
A composite and an electrode were manufactured in the same manner as in Comparative Example 1b except that AS / V ₂ O ₅ = 40/60 (weight ratio), and then a battery was assembled. The electrodes of this battery were evaluated in the same manner as in Example 1. Table 2 shows the results.

[0047]

[Table 2] Table 2 ＰＡ PAS V ₂ O ₅ 0.1 μm or less Initial charge (30-minute charge capacity) / average particle size Percentage of pores with average particle size Pond capacity (initial capacity) (μm) (μm) (%) (at mA) × 100 (%) ─────── ───────────────────────────── Example 4 0.3 <0.1 83 8.9 70 Comparative Example 3 0.3 <0.1 86 8.8 45 ─── ─────────────────────────────────

[0048]

According to the present invention, it is possible to provide a battery electrode having excellent quick charge characteristics. The battery using the electrode of the present invention has a large capacity per unit volume, can be charged and discharged for a long time, and is easy and economical to manufacture.

[Brief description of the drawings]

FIG. 1 shows a basic configuration of a battery according to the present invention.

[Explanation of symbols]

1 is a positive electrode, 2 is a negative electrode, 3 is a current collector, 4 is an electrolytic solution,
Reference numeral 5 denotes a separator, 6 denotes a battery case, and 7, 7 ′ denote external terminals.

Continuation of the front page (72) Inventor Hajime Kinoshita 1-4-6-402, Tomobuchi-cho, Miyakojima-ku, Osaka-shi, Osaka

Claims (3)

(57) [Claims] 1. A heat-treated aromatic condensation polymer comprising (a) carbon, hydrogen and oxygen, wherein the polyacene skeleton structure has a hydrogen atom / carbon atom number ratio of 0.05 to 0.5. Having a specific surface area of 600 according to the BET method.
(b) an active material which is a composite of a metal oxide and an insoluble and infusible substrate having a m ² / g or more; and (c) a method for producing a battery electrode including at least a conductive material. (2) The pore volume of the electrode having a pore diameter of 0.1 μm or less accounts for 70% or more of the total pore volume (measured by a mercury intrusion method) (3) A method for producing an electrode for a battery, characterized in that the electrode is a composite powder compact obtained by simultaneously pulverizing and mixing (a), (b) and (c). 2. The method according to claim 1, wherein the metal oxide is a vanadium oxide. 3. The method for producing a battery electrode according to claim 1, wherein the insoluble infusible substrate comprises particles having an average particle size of 1 μm or less.