JP2003162991A - Manufacturing method of separator for battery, separator for battery, and battery using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a new separator for a battery, a new manufacturing method for the separator, a battery using the separator, and a manufacturing method for the battery. <P>SOLUTION: This manufacturing method for the battery includes a process for forming a film 16 consisting of a mixture comprising a foaming agent, an organic solvent, and two or more kinds of rubbers dissolved in a compatible state, and a process for forming a porous film separator by heating the film 16 so that the foaming agent is foamed and an organic solvent is vaporized. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a separator for a primary battery and a secondary battery, a method for manufacturing the same, a battery using the same, and a method for manufacturing the same.

[0002]

2. Description of the Related Art A general battery requires a separator to prevent physical contact between a positive electrode and a negative electrode. Most conventional lithium secondary batteries use a film made of a polyolefin material as a separator. However, it has been difficult to control the porosity of the conventional film, which requires time and effort for molding and has a great influence on the ion conductivity. In addition, the conventional film cannot sufficiently meet the demand for higher capacity and smaller battery size.

In recent years, as a new method of producing a separator, a method of forming a film having nanoscale porosity by heating a block polymer to cause spinodal decomposition has been attracting attention. This new film has a large surface area and is capable of more highly efficient ion conduction as compared with the conventional polyolefin film.

[0004]

However, the above-mentioned new techniques are limited in the block polymers that can be used, and the electrolyte resistance of the polymers is not always sufficient. For example, when an olefin block polymer is used, phase separation due to spinodal decomposition may not be sufficiently performed depending on the polarities of the block units constituting the polymer. In such cases,
The pores formed in the film become extremely non-uniform, and the domains generated during phase separation can be easily swollen or dissolved by the electrolytic solution. Therefore, in such a case, a sufficient function as a separator could not be obtained.

In view of the above situation, it is an object of the present invention to provide a new separator for a battery, a new method of manufacturing the separator, a battery using the same, and a method of manufacturing the same.

[0006]

In order to achieve the above object, the method for producing a battery separator of the present invention comprises: (i) forming a film made of a mixture containing a foaming agent, an organic solvent and two or more kinds of rubber. And (ii) forming a porous film by heating the film so that the foaming agent foams and the organic solvent evaporates.

In the above-mentioned manufacturing method, it is preferable that in the step (ii), heating is performed so that the mixture undergoes phase separation.

In the above manufacturing method, in the step (i), the film may be formed by applying the mixture on at least one electrode plate selected from a positive electrode and a negative electrode.

In the above manufacturing method, the rubber may include isobutylene rubber.

In the above manufacturing method, the rubber may contain a copolymer rubber having a styrene structure.

In the above manufacturing method, the soft segment in the rubber may be saturated hydrocarbon. According to this configuration, the hard segment and the soft segment each form a molecular assembly (domain), so that an effect of inducing a more microscopic phase-separated state can be obtained.

In the above manufacturing method, the copolymer rubber is styrene-butadiene-styrene copolymer rubber, styrene-
Isoprene-styrene copolymer rubber, styrene-ethylene-butadiene-styrene copolymer rubber, or styrene-
It may be any of ethylene-propylene-styrene copolymer rubber.

In the above manufacturing method, the styrene content in the copolymer rubber is preferably in the range of 10% to 30% in terms of composition ratio.

The battery separator of the present invention is manufactured by the method for manufacturing a battery separator of the present invention.

The battery of the present invention comprises a positive electrode, a negative electrode,
A battery including a separator disposed between the positive electrode and the negative electrode, wherein the separator is a battery separator manufactured by the method for manufacturing a battery separator of the present invention.

The method for producing a battery according to the present invention is a method for producing a battery including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, which is for the battery according to the present invention. It is characterized by including a step of manufacturing the separator by a method of manufacturing the separator.

[0017]

BEST MODE FOR CARRYING OUT THE INVENTION Embodiments of the present invention will be described below.

(Embodiment 1) In Embodiment 1, a method for producing a battery separator of the present invention and a separator obtained by the method will be described.

In the production method of the present invention, first, a film made of a mixture containing a foaming agent and two or more kinds of polymers (specifically, rubber) compatible with an organic solvent is formed (step (i)). The mixture is usually made by mixing the materials at temperatures on the order of room temperature. The film is formed, for example, by applying the mixture onto at least one electrode plate selected from a positive electrode and a negative electrode.

Thereafter, the porous film (separator) is formed by heating the film made of the mixture so that the foaming agent foams and the organic solvent evaporates (step (i
i)). At this time, heating is performed under the condition that the film made of the mixture causes phase separation.

In the above mixture, the rubbers are uniformly compatible (mixed) at the time of preparation, and microphase separation (microphase separation means a microscopic aggregate at the molecular level) at the time of heating in the step (ii). To form a mixture). Such a mixture can be prepared by selecting the type of rubber as a material and the mixing ratio. In this specification, "compatibility" means that two or more kinds of rubbers are dissolved / dispersed in a solution to the extent that they cause thermodynamic heat generation and mutual interpenetration of molecules.

During the heating in step (ii), phase separation of the mixture, foaming of the blowing agent and vaporization of the organic solvent occur. The phase-separated mixture has a function of maintaining the shape of fine pores formed by the foaming agent. In addition, the organic solvent is vaporized, so that the phase-separated rubber maintains the phase-separated state even when cooled. Therefore, in the step (ii), it is possible to form a porous membrane (separator) in which the fine pores formed by the foaming agent are maintained. By making the separator porous, the ionic conductivity of the separator and the ion concentration in the separator can be increased. As a result, the distance between the positive electrode and the negative electrode can be reduced, and the separator can be thinned.

It is necessary to blend a particular rubber to induce the microphase separation which is a feature of the present invention. That is, the mixture used in the present invention is made to have a lower critical solution temperature (LCST). It is believed that such a blend causes the mixture to undergo spinodal decomposition upon heating and phase separation. When the lower critical solution temperature of the mixture is lower than the foaming temperature of the foaming agent, phase separation can be caused by heating at a temperature equal to or higher than the foaming temperature of the foaming agent. The rubber contained in the mixture will be described below.

One of the rubbers contained in the mixture (hereinafter referred to as the first
(Sometimes referred to as rubber), polyisobutylene (isobutylene rubber) can be used. Isobutylene rubber has high stability against electrolytic solutions such as ethylene carbonate, propylene carbonate, γ-butyl lactone and dimethoxy ether used as electrolytic solutions for lithium batteries, etc. Also has a low degree of swelling. Therefore, by using isobutylene rubber, it is possible to manufacture a separator having high adhesion to the electrodes. The number average molecular weight of the isobutylene rubber is, for example, in the range of about 50,000 to about 120,000, preferably in the range of about 80,000 to about 100,000. By setting the molecular weight of the isobutylene rubber within this range, it is possible to manufacture a separator having high adhesion to electrodes and high electrolytic solution characteristics. Further, by setting the molecular weight to 50,000 or more, it is possible to prevent the isobutylene rubber from being dissolved in the electrolytic solution even when the highly polar electrolytic solution is used.
Moreover, when the molecular weight is 50,000 or more, sufficient microphase separation can be obtained when blended with a styrene-ethylene-butadiene-styrene copolymer rubber (SEBS) described later. Further, by setting the molecular weight to be 120,000 or less, it is possible to prevent the viscosity of the mixture from becoming too high and the handling property from being lowered. Furthermore, when the molecular weight is 120,000 or less, it can be easily made compatible (mixed) with SEBS described later at room temperature.

As another rubber (hereinafter sometimes referred to as a second rubber) contained in the mixture, a copolymer rubber made from styrene as a raw material (hereinafter sometimes referred to as styrene-containing rubber) can be mentioned. Specifically, as the second rubber, styrene-butadiene-styrene copolymer rubber (SBS),
Styrene-isoprene-styrene copolymer rubber (SI
S), styrene-ethylene-butadiene-styrene copolymer rubber (SEBS), or styrene-ethylene-propylene-styrene copolymer rubber (SEPS) can be used. In order to obtain a separator having good characteristics, the styrene content in the entire rubber contained in the mixture is particularly important. Specifically, the styrene content in the entire second rubber is preferably in the range of 10% to 30% in terms of composition ratio. Here, the composition ratio means the ratio of the numbers of the segments (for example, styrene and butadiene in SBS and butylene in isobutylene rubber) constituting each rubber. When the composition ratio of styrene is less than 10%, it may be difficult to achieve sufficient microphase separation. When the composition ratio of styrene is more than 30%, the compatibility (miscibility) with the isobutylene rubber at room temperature may decrease.

The number average molecular weight of the styrene-containing rubber is
For example, it is about 50,000 to about 100,000, preferably about 70,000 to about 80,000. When the number average molecular weight of the styrene-containing rubber is out of the range of 50,000 to 100,000, the compatibility with the isobutylene rubber decreases, and it may not be easy to cause phase separation.

Specific examples of the mixture used in the above step (i) include, for example, a mixture containing only isobutylene rubber and SBS as rubber, a mixture containing only isobutylene rubber and SIS as rubber, and isobutylene rubber and SEB.
A mixture containing only S as rubber, isobutylene rubber and S
A mixture containing only EPS as rubber can be mentioned. The molecular weight and mixing ratio of these are as described above. As long as the composition causes phase separation by heating, other rubber combinations may be used, and the mixture may be 3
It may contain more than one type of rubber. Further, the mixing ratio of the first rubber and the second rubber is preferably in the range of 10 to 100 parts by weight of the latter with respect to 100 parts by weight of the former.

The rubber contained in the mixture preferably contains a soft segment composed of a saturated hydrocarbon. Here, the soft segment is a high molecular weight substance (butadiene, ethylene) composed of C—H contained as a copolymerization unit of SBS or SEBS, and is considered to be an essential component controlling the above-mentioned spinodal decomposition. The present invention is characterized in that porosity is generated in the blend of the polyisobutylene and the rubber that is separated and mixed, and the separated state at that time is the phase of the styrene component in the copolymer and the polymer component itself composed of CH. Due to the solubility, styrene component and C-H
The molecular mobility of the polymer component consisting of controls the separation and mixing. In other words, separation / mixing depends on how easily each component in the copolymer moves.
It is also possible to adjust the state of separation / mixing by controlling the unit ratio of the styrene part, which is a unit (harder unit) that is harder than the polymer component consisting of.

As the foaming agent for imparting porosity, a general organic foaming agent mixed with a resin or the like can be used. For example, azodicarbonamide derivative, benzenesulfonylhydrazide derivative, dinitrosopentamethylenetetramine derivative, etc. Can be used. Unlike an inorganic foaming agent, an organic foaming agent is preferable because an ionic decomposition product does not remain in the separator. The amount of the foaming agent added is not particularly limited, but is, for example, 3% by mass or less, and preferably 1% by mass to 3% by mass of the mixture. By controlling the addition amount of the foaming agent to 3% by mass or less, it becomes easy to control the thickness of the coating film.

The heating temperature in step (ii) is a temperature above the temperature at which the foaming agent foams. The heating conditions (temperature and time) are selected such that the mixture causes phase separation and the organic solvent in the mixture almost evaporates.
The heating conditions vary depending on the materials used and the mixing ratio, but as an example, when the temperature at which the foaming agent foams is T (° C), the temperature is about T to T + 20 (° C) for 10 minutes to 30 minutes.
It may be heated for about a minute.

The organic solvent used in the mixture is not particularly limited as long as it can dissolve the rubber to be used, and can be arbitrarily selected from known solvents according to the kind of rubber. For example, toluene, xylene, ethylcyclohexane, methylcyclohexane, cyclohexanone or the like can be used as the organic solvent.

The amount of solid content when the rubber is dissolved is not particularly limited, and can be set arbitrarily according to the type of rubber used and the solvent. Usually, 5 to 5
It may be 30% by mass.

According to the manufacturing method of the first embodiment, a separator having a large capacitance and a high ionic conductivity in the electrolytic solution can be manufactured. The separator manufactured by the manufacturing method of Embodiment 1 is the separator of the present invention.
This separator contains the above-mentioned first and second rubbers and is porous.

(Embodiment 2) In Embodiment 2, a battery of the present invention and a manufacturing method thereof will be described. Embodiment 2
The battery of No. 1 includes a case, a positive electrode, a negative electrode, a separator and an electrolytic solution arranged in the case. The separator is arranged between the positive electrode and the negative electrode. The separator of the battery of Embodiment 2 is the separator of the present invention manufactured by the manufacturing method of Embodiment 1. The parts other than the separator are selected according to the type of battery. The present invention is
It can be applied to various primary batteries and secondary batteries as described in the examples. As an example of the battery of the second embodiment, a partially exploded perspective view of a cylindrical battery 10 is shown in FIG.

Referring to FIG. 1, the battery 10 includes a case 11
A positive electrode 12, a negative electrode 13, a separator 14 and an electrolytic solution (not shown) arranged in the case 11, and the case 11
And a sealing plate 15 for sealing. In the manufacturing method of the second embodiment, the separator is manufactured by the method described in the first embodiment. An example of a method of manufacturing the battery 10 will be described below with reference to FIG.
Will be described with reference to. The positive electrode 12 and the negative electrode 13
Includes a support and an active material layer, but FIG. 2 shows a simplified cross-sectional view.

First, as shown in FIG. 2A, the negative electrode 13
The mixture described in Embodiment 1 is applied to both surfaces of
6 is formed. Then, the rubber contained in the film 16 causes phase separation, the foaming agent foams, and the film 16 is heated so that the organic solvent evaporates. By this heating, as shown in FIG. 2B, the separator 14 which is a porous film is formed. After that, the positive electrode 12 is prepared, and the negative electrode 13 on which the separator 14 is formed and the positive electrode 12 are wound in a coil shape to produce an electrode plate group. And the battery 10 shown in FIG. 1 is produced using the obtained electrode plate group.

In FIG. 2, the separator 1 is placed on the negative electrode 13.
4 has been described, the separator 14 may be formed on the positive electrode 12. That is, in the battery manufacturing method of the present invention, the separator may be formed by heating the mixture after applying the mixture onto at least one electrode plate selected from the positive electrode and the negative electrode to form a film. An example of the electrode plate when the separator 14 is formed on the positive electrode 12 is shown in FIG. 3A, and an example of the electrode plate when the separator 14 is formed on the negative electrode 13 is shown in FIG. FIG. 3C shows an example of the electrode plate in the case where 13 and 13 are bound by the separator 14.

Although a cylindrical battery has been described with reference to FIGS. 1 and 2, the battery of the present invention may be a battery of any shape such as prismatic or card type.

[0039]

EXAMPLES The present invention will be described in more detail with reference to examples.

Example 1 In Example 1, an example of producing the separator of the present invention will be described. First, 8 parts by mass of isobutylene rubber (number average molecular weight: 100,000)
And 2 parts by mass of SEBS (number average molecular weight: 70,000)
And 1 part by mass of the foaming agent were dispersed and dissolved in 89 parts by mass of xylene at room temperature to prepare a mixed solution. As the foaming agent, 4,4′-oxybis (benzenesulfonylhydrazide) having a foaming temperature of 150 ° C. was used. The styrene content in all rubbers was 30%. The isobutylene rubber and SEBS were dissolved in xylene without phase separation.

Next, the above mixed solution was applied onto a glass plate to form a thin film. Then, the thin film formed on the glass plate was heated at 100 ° C. for 10 minutes. In this way, a porous film (separator) was formed. In addition, in Example 1, the compatibility of the mixed liquid after room temperature and after heating was visually evaluated (the same applies to the following Examples and Comparative Examples).

(Example 2) In Example 2, a porous membrane was prepared in the same manner as in Example 1 except that SBS (number average molecular weight: 100,000) was used instead of SEBS. The styrene content in all rubbers was 30%.

(Example 3) In Example 3, a porous membrane was prepared in the same manner as in Example 1 except that SEPS (number average molecular weight: 70,000) was used instead of SEBS. The styrene content in all rubbers was 30%.

Comparative Example 1 In Comparative Example 1, 8 parts by mass of isobutylene rubber (number average molecular weight: 10,000), 2 parts by mass of styrene-butadiene copolymer rubber (SBR, number average molecular weight: 80,000), and 1 Part by mass of the foaming agent was dispersed and dissolved in 89 parts by mass of xylene at room temperature to prepare a mixed solution. 4,4′-oxybis (benzenesulfonylhydrazide) was used as the foaming agent. The styrene content in all rubbers was 30%.

Next, the above mixed solution was applied onto a glass plate to form a thin film. Then, the thin film formed on the glass plate was heated at 100 ° C. for 10 minutes. In this way, a porous film was formed.

Comparative Example 2 In Comparative Example 2, 10 parts by mass of isobutylene rubber (number average molecular weight: 100,000),
1 part by mass of the foaming agent was dispersed and dissolved in 89 parts by mass of xylene at room temperature to prepare a mixed solution. The foaming agent
4,4'-oxybis (benzenesulfonyl hydrazide) was used.

Next, the above mixed solution was applied onto a glass plate to form a thin film. Then, the thin film formed on the glass plate was heated at 100 ° C. for 10 minutes. In this way, a porous film was formed. (Comparative Example 3) In Comparative Example 3, 10 parts by mass of SEBS (number average molecular weight: 70,000) and 1 part by mass of a foaming agent were used.
At room temperature, it was dispersed and dissolved in 89 parts by mass of xylene to prepare a mixed solution. 4,4′-oxybis (benzenesulfonylhydrazide) was used as the foaming agent.

Next, the above mixed solution was applied onto a glass plate to form a thin film. Then, the thin film formed on the glass plate was heated at 100 ° C. for 10 minutes. In this way, a porous film (separator) was formed.

The 6 kinds of porous membranes thus obtained were immersed in propylene carbonate at room temperature for 24 hours, and the change in mass before and after the immersion was measured. Table 1 shows the measurement results for each example and comparative example. In addition, the results of visually evaluating the compatibility of the mixed liquid before heating (room temperature) and during heating (100 ° C.) for each of the examples and comparative examples are also shown in Table 1.
Shown in.

[0050]

[Table 1] As shown in Table 1, in the samples of Examples 1 to 3 to which the styrene-containing rubber was added, microphase separation at high temperature suggesting spinodal decomposition was observed. As described above, in the production method of the present invention, phase separation of the separator material can be easily caused as compared with the conventional method. In addition, the films of Examples 1 to 3 have a porous structure due to pores at the molecular level and voids due to the foaming agent, but with respect to the electrolyte solution that will penetrate into the pores. No swelling or dissolution was observed, and it was found from the results of the immersion test in the electrolytic solution that the electrolytic solution had good resistance to the electrolytic solution. That is, it can be presumed that the film state can be maintained even when the film is in contact with the electrolytic solution when it is used as a separator, and the voids formed in the film can have a sufficient liquid retaining property.

In the above-mentioned embodiment, when the rubber to be used as the film material is selected, the mixed solution has a lower critical solution temperature (Lower Cr).
Two rubbers were chosen to have an itical Solution Temperature (LCST). That is, it is considered that the mixed liquids of Examples cause phase separation by heating for volatilizing the organic solvent, xylene, and can maintain the phase separated state after cooling. The reason for this is not clear, but at this point it can be considered as follows. In this example, by limiting the styrene content to be mixed with the isobutylene rubber, at room temperature, ethylene / butadiene (E / B portion) was compatible with the saturated hydrocarbon-based isobutylene rubber, and the styrene domain was apparently formed. It is believed to induce a non-forming state (ie, a state that is not a microphase-separated state). Then, the heating activates the molecular motion of the E / B portion and the blended rubber to increase the local concentration of styrene and increase the probability of forming a styrene domain. It is believed that the resulting phase separation preserves the shape of the voids formed by the blowing agent and forms a porous film.

On the other hand, as in Comparative Example 1, in the case where the rubber is not compatible at room temperature, the SBR is pseudo-crosslinked and the storage stability of the resin is greatly reduced. Furthermore, since the film of Comparative Example 1 does not have very good electrolytic solution characteristics, it is considered that long-term reliability as a battery material is not sufficient. Further, the film of Comparative Example 2 does not cause phase separation upon heating,
It is considered that the voids formed by the foaming agent could not be retained.

Example 4 In Example 4, an example of producing a lithium battery using the method of Example 1 will be described.

First, artificial graphite powder (average particle size: 10 μm)
m) and polyvinylidene fluoride (PV
DF) and n-methylpyrrolidone (NMP) are mixed to form a paste-like mixture (mass ratio of artificial graphite: PVDF =
100: 9.0) was prepared. Next, this mixture was applied on both sides of a copper foil (thickness: 10 μm) as a current collector to form an active material layer (thickness: about 40 μm). The sheet thus obtained was dried (140 ° C., 1 hour) with a drier to vaporize the solvent to obtain a negative electrode.

Next, a separator was formed on this negative electrode by the method described in Example 1. That is, the mixed solution described in Example 1 was applied to both surfaces of the negative electrode, and then heated at 100 ° C. for 10 minutes to form a porous film (separator) on both surfaces of the negative electrode.

On the other hand, lithium manganate (LiMn
₂ O ₄ ) and acetylene black (AB) as a conductive agent
Then, PVDF as a binder and an NMP solution were mixed to prepare an active material paste. At this time, each material was used in a mass ratio of LiMn ₂ O ₄ : AB: PVDF = 100: 2.5:
Mix so as to be 4.0. The obtained active material paste was applied to both sides of an aluminum foil (thickness: 20 μm) as a support. The sheet thus obtained was dried and rolled, and then cut into a predetermined size to obtain a positive electrode.

Next, the negative electrode on which the porous film was formed and the positive electrode were overlapped and spirally wound to prepare an electrode plate group. Next, insulating plates made of polypropylene were attached to the upper and lower parts of the electrode plate group and inserted into the battery case. A nickel-plated iron case was used as the battery case.

Next, an electrolytic solution was poured into the battery case and sealed with a sealing plate to obtain a lithium battery (hereinafter referred to as battery A). The electrolytic solution contains ethylene carbonate, dimethyl carbonate, and ethyl methyl carbonate at 30: 5.
1.0 mol / l was added to the solvent mixed in a volume ratio of 6:14.
A solution in which LiPF ₆ was dissolved at a concentration of was used.

(Example 5) In Example 5, a battery was produced in the same manner as in Example 4 except that the positive electrode was different.
In Example 5, lithium cobalt oxide (LiCoO ₂ ) 7
0 parts by mass, AB6 parts by mass, PVDF9 parts by mass, N
An active material paste was prepared by mixing 15 parts by mass of MP. Then, this active material paste was applied to both sides of an aluminum foil (thickness: 20 μm) as a support. The sheet thus obtained was dried at 150 ° C. for 1 hour to evaporate NMP, then rolled and cut into a predetermined size to obtain a positive electrode. Using this positive electrode, a lithium battery (hereinafter referred to as battery B) was produced in the same manner as in Example 4.

(Example 6) In Example 6, a battery was manufactured in the same manner as in Example 4 except that the positive electrode was different.
In Example 6, a commercially available lithium-nickel-cobalt composite oxide _{(Li 1. 0 Ni 0.8 Co 0.2} O 2) and 75 parts by weight,
20 parts by mass of AB and polytetrafluoroethylene (PT
FE) 5 parts by mass and NMP to obtain a viscosity that can be applied
And were mixed to prepare an active material paste. Then, this active material paste was applied to an aluminum foil (thickness: 20
μm) on both sides. The sheet thus obtained was dried at 150 ° C. for 1 hour to vaporize NMP, then rolled and cut into a predetermined size to obtain a positive electrode. Using this positive electrode, a lithium battery (hereinafter referred to as battery C) was produced in the same manner as in Example 4.

Comparative Example 4 In Comparative Example 4, a battery different from the battery A of Example 4 only in the separator was manufactured. In Comparative Example 4, a conventional microporous membrane made of polypropylene was used as the separator. Then, a separator was sandwiched between the same positive electrode and negative electrode as in the battery A of Example 4 and spirally wound to form an electrode plate group. After that, a lithium battery (hereinafter referred to as battery D) was manufactured in the same manner as in Example 4.

(Comparative Example 5) In Comparative Example 5, a battery different from the battery B of Example 5 only in the separator was prepared. In Comparative Example 5, a conventional microporous membrane made of polypropylene was used as the separator. Then, a separator was sandwiched between the same positive electrode and negative electrode as in the battery B of Example 5 and spirally wound to form an electrode plate group. After that, a lithium battery (hereinafter, referred to as battery E) was manufactured by the same method as in Example 4.

(Comparative Example 6) In Comparative Example 6, a battery different from the battery C of Example 6 only in the separator was prepared. In Comparative Example 6, a conventional microporous membrane made of polypropylene was used as the separator. Then, a separator was sandwiched between the same positive electrode and negative electrode as in the battery C of Example 6 and spirally wound to prepare an electrode plate group. After that, a lithium battery (hereinafter referred to as battery F) was manufactured in the same manner as in Example 4.

The initial discharge capacities of the six types of lithium batteries thus obtained were measured. The ratio of the initial capacities of the batteries of Examples and Comparative Examples in which only the separator is different,
For example, Table 2 shows the values of (initial capacity of battery A) / (initial capacity of battery D).

[0065]

[Table 2] Next, the discharge capacity after standing for 20 days at 60 ° C. was measured to evaluate the capacity retention rate (storage characteristic). Further, a charge / discharge cycle test was performed, the discharge capacity after 500 cycles was measured, and the capacity retention rate (%) = (capacity after 500 cycles) * 100 / (initial capacity) was calculated. Table 3 shows the capacity retention rate and the capacity retention rate of each battery.

[0066]

[Table 3] As shown in Table 2 and Table 3, the batteries A to C of the present invention are
The initial capacities, the capacity retention ratios when left at high temperature, and the capacity retention ratios after the charging / discharging cycle were higher than those of Comparative batteries B to F.

The separator of the present invention has a three-dimensional stitch structure and has a high porosity due to the pores formed by the foaming agent. Therefore, the separator of the present invention has a high electrolytic solution holding power and a high ionic conductivity. As a result, it is considered that the battery using the separator of the present invention has a higher capacity retention rate after standing and a capacity retention rate after the charge / discharge cycle. Further, it is considered that the battery using the separator of the present invention has a low ionic conductivity of the separator and thus the internal resistance of the battery is lowered, and the initial capacity is improved.

Example 7 In Example 7, an example of producing a Ni—Cd battery using the method of Example 1 will be described.

First, a negative electrode containing Cd and Cd (OH) ₂ was prepared. Then, a separator was formed on this negative electrode by the method described in Example 1. That is, after applying the mixed solution described in Example 1 on the negative electrode, 100
A porous film (separator) was formed on the negative electrode by heating at 0 ° C for 10 minutes. A Ni-Cd battery was manufactured using the negative electrode thus obtained.
A battery having a high capacity and high reliability as compared with the Cd battery was obtained.

(Example 8) In Example 8, a nickel-hydrogen storage battery was produced. First, MmN, a hydrogen storage alloy
A negative electrode was prepared using i ₅ (Mm: misch metal),
A separator was formed on this negative electrode by the method described in Example 1. When a nickel-hydrogen storage battery was manufactured using the negative electrode thus obtained, a battery having a high capacity and high reliability was obtained as compared with a conventional nickel-hydrogen storage battery.

(Example 9) In Example 9, a lead storage battery was manufactured. First, a Pb paste type negative electrode was prepared, and a separator was formed on this negative electrode by the method described in Example 1. When a lead storage battery was manufactured using the negative electrode thus obtained, the reliability could be improved as compared with the conventional lead storage battery. Further, the cost can be greatly reduced as compared with the conventional separator made of polypropylene having microporosity.

(Example 10) In Example 10, a nickel-zinc storage battery was produced. First, on the zinc surface of the negative electrode,
A separator was formed by the method described in Example 1. When a nickel-zinc storage battery was manufactured using the negative electrode thus obtained, the reliability could be greatly improved as compared with the case where a conventional separator made of polypropylene having microporosity was used. .

(Example 11) In Example 11, silver oxide
A zinc battery was produced. First, a separator was formed on the surface of zinc of the negative electrode by the method described in Example 1, and a silver oxide / zinc battery was produced using this negative electrode. As a result, it was possible to prevent the internal short circuit due to the dendrite precipitation of zinc and silver oxide, which was a conventional problem. In addition, storage characteristics and reliability could be improved as compared with conventional silver oxide / zinc batteries.

Although the embodiments of the present invention have been described above with reference to examples, the present invention is not limited to the above embodiments and can be applied to other embodiments based on the technical idea of the present invention. .

For example, although the separator is formed on the negative electrode in the embodiment, the same effect can be obtained by forming the separator on the positive electrode.

[0076]

As described above, according to the separator manufacturing method of the present invention, a novel battery separator can be manufactured. According to this manufacturing method, it is possible to manufacture a separator having a large capacitance and a high conductivity of ions in the electrolytic solution.

The battery using the separator manufactured by the manufacturing method of the present invention is a battery having good characteristics such as initial capacity, internal resistance, storage characteristics, and cycle characteristics. Moreover, in the battery manufacturing method of the present invention, since the separator is directly formed on the electrode plate, it is possible to prevent winding deviation of the separator and to manufacture the battery with high yield. Furthermore, according to the manufacturing method of the present invention, it is possible to manufacture a battery capable of preventing the separator from shifting and short-circuiting due to a vibration test or the like.

[Brief description of drawings]

FIG. 1 is a partially exploded perspective view showing an example of a battery of the present invention.

FIG. 2 is a process sectional view showing an example of a method for manufacturing a separator of the present invention.

FIG. 3 is a cross-sectional view showing an example of an electrode plate manufactured by the battery manufacturing method of the present invention.

[Explanation of symbols]

10 batteries 11 cases 12 Positive electrode 13 Negative electrode 14 Separator 15 Seal plate 16 membranes

Continued front page    (72) Inventor Katsuhiko Kishi             1456, Hamaoji-shi, Hamaoji-shi, Tokyo             In Rebond F term (reference) 5H021 AA06 BB01 BB13 EE03 EE15                       HH01                 5H028 AA05 BB05 BB06 BB18 EE01                       EE05 EE06 EE08                 5H029 AK03 AL07 AM03 AM05 AM07                       BJ02 BJ14 CJ02 CJ12 CJ22                       DJ04 EJ14

Claims (11)

[Claims] 1. (i) a step of forming a film made of a mixture containing a foaming agent and two or more kinds of rubbers compatible with an organic solvent, and (ii) such that the foaming agent foams and the organic solvent. And a step of forming a porous membrane by heating the membrane so as to evaporate. 2. The method for producing a battery separator according to claim 1, wherein in the step (ii), heating is performed so that the mixture undergoes phase separation. 3. The battery separator according to claim 1, wherein in the step (i), the film is formed by applying the mixture on at least one electrode plate selected from a positive electrode and a negative electrode. Production method. 4. The method for manufacturing a battery separator according to claim 1, wherein the rubber contains isobutylene rubber. 5. The method for producing a battery separator according to claim 1, wherein the rubber contains a copolymer rubber having a styrene structure. 6. The method for producing a battery separator according to claim 5, wherein the soft segment in the rubber is a saturated hydrocarbon. 7. The copolymer rubber is styrene-butadiene-styrene copolymer rubber, styrene-isoprene-styrene copolymer rubber, styrene-ethylene-butadiene-styrene copolymer rubber, or styrene-ethylene-propylene-styrene copolymer rubber. The method for manufacturing the battery separator according to claim 5, wherein the battery separator is one of rubber. 8. The method for producing a battery separator according to claim 5, wherein the styrene content in the copolymer rubber is in the range of 10% to 30% in terms of composition ratio. 9. A battery separator manufactured by the manufacturing method according to claim 1. 10. A battery including a positive electrode, a negative electrode, and a separator arranged between the positive electrode and the negative electrode, wherein the separator is manufactured by the manufacturing method according to any one of claims 1 to 8. A battery, which is a separated battery separator. 11. A method of manufacturing a battery including a positive electrode, a negative electrode, and a separator disposed between the positive electrode and the negative electrode, wherein the manufacturing method according to claim 1. A method for manufacturing a battery, including a step of manufacturing a separator.