JPH09161806A - Secondary battery electrode or secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve electrode strength while restraining the capacity lowering of an electrode, by joining the metallic base of two-dimensional structure to a multi-void metallic later, to form an current collector to fill a void in the multi-void metallic later with a mixture including battery active material. SOLUTION: In this secondary battery electrode, a current collector, to which the metallic base 1 of two-dimensional structure is joined, is quipped on a multi- void metallic layer 2 or 2 and 4; and voids in the metallic layers 2 and 4 are filled with mixtures including battery active material. The void ratio of the metallic layers 2 and 4 are preferably 85% or more. The base 1 is formed of metallic foil, and a metallic plate or a metallic boring plate. The metallic layers 2 and 4 or the base 1 is formed of stainless steel, nickel, aluminum, copper, or titanium. The elongation percentage of the electrode before and after press molding the electrode is 10% or less.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a rechargeable power source or an apparatus using a secondary battery, which is composed of an electrode for a secondary battery such as a lithium secondary battery, a secondary battery, and an assembled battery thereof.

[0002]

2. Description of the Related Art A lithium secondary battery, which is a typical example of a non-aqueous electrolyte secondary battery, has already been put to practical use as a lithium ion battery and used in portable electric equipment such as video cameras and mobile phones. . Most of these batteries are of a cylindrical type, and a film electrode in which a mixture containing a battery active material is pressure-bonded to a lithium plate on a current collector made of a perforated metal plate or a film electrode applied to the surface of a metal foil is used. ing. By winding the electrode and the separator, a large electrode area is obtained and high rate charge / discharge is enabled. Since the winding of the film electrode is relatively easy, there are many known examples of the structure of the wound cylindrical battery (Japanese Patent Laid-Open No. 60-109173).
JP-A-1-72049 or JP-A-5-74488).

On the other hand, the prismatic battery can be arranged with less wasted space than the cylindrical battery, which is advantageous for a power source using an assembled battery. Also in the case of the prismatic battery, in addition to the wound-type electrode group structure using the film-shaped electrode (JP-A-5-135780), a laminated electrode structure of strip-shaped electrodes (JP-A-6-150974) is considered. Has been. In particular, the latter is advantageous in that the filling rate of the electrode group with respect to the volume inside the battery is high.

As the capacity of a stacked prismatic battery increases, a technology for stacking a large number of positive electrodes and negative electrodes in a precise alignment becomes essential. The film-like electrode is advantageous for a wound battery, but is not suitable for a laminated battery because the electrode is not strong. When the mixture coating layer on the current collector is thickened, the electrode strength is improved, but problems such as the battery active material easily falling off during charging / discharging and the capacity of the battery active material falling are caused.
Therefore, an electrode having a positive electrode active material held on a porous sheet made of aluminum fibers and having a large number of voids (Japanese Patent Laid-Open No. 6-196170) and an electrode having a nickel metal porous body holding a negative electrode active material (Japanese Patent Laid-Open No. H7-78170) No. 22021), there is proposed a method of manufacturing a battery with a small number of layers by thickening electrodes.

[0005]

As described above in the description of the conventional example, when the number of laminated electrodes is reduced, it becomes easy to laminate a large number of electrodes. For that purpose, it is effective to use a current collector having a porous or multi-void metal layer structure so that good electric conductivity can be obtained even if the mixture portion containing the battery active material becomes thick. By the way, in order to retain a large amount of battery active material in the multi-void metal layer, the porosity of the multi-void metal layer is 90%.
With the above, the wire diameter of the metal fiber or the like forming the multi-void structure tends to be small, and the strength of the metal layer in the plane direction tends to be weak. As a result, when the electrode holding the battery active material on the multi-void metal layer is pressed, extension of the electrode occurs,
The desired electrode density may not be obtained. That is, when the electrodes extend, the following problems occur. Due to the pressure molding, the network structure of the multi-void metal layer is destroyed, that is, the metal fibers are cut, and the mixture is also broken and the cracked portions are scattered, increasing the resistance value of the current collector. To do. Furthermore, as the electrode extension rate increases, the pore diameter of the porous metal layer also increases, and the battery active material retained in the pores falls off from the current collector and ceases to function.

An object of the present invention is to provide an electrode for a secondary battery, a secondary battery, and an assembled battery thereof which can increase the thickness of the electrode by improving the electrode strength while suppressing the decrease in the capacity of the electrode. Another object of the present invention is to provide a rechargeable power source or a device using a secondary battery.

[0007]

As a result of addressing the above technical problems, the present inventors have found that a multi-void (porous) metal layer having a fibrous structure or a mesh structure is provided with a metal foil, a metal plate, and metal perforations. A current collector in which a metallic substrate having a two-dimensional structure such as a plate is joined has been developed, and the extension of the electrode can be suppressed by the metallic substrate at the time of pressure molding, and the above problems can be solved.

That is, the present invention has a current collector in which a metal substrate having a two-dimensional structure is bonded to a multi-void metal layer, and holds a mixture containing a battery active material in the void in the multi-void metal layer. It is a secondary battery electrode.

Further, the present invention of the present application and the like further provides a multi-void metal layer,
A mixture containing a current collector to which a metal substrate that prevents or reduces the elongation of the multi-void metal layer when pressure-molded is bonded, and a mixture containing a battery active material in the void in the multi-void metal layer is formed. It is a secondary battery electrode to be held.

Further, the present invention of the present application is the electrode for a secondary battery according to each of the above-mentioned inventions, wherein the multi-void metal layer is bonded to both surfaces of the metallic substrate.

Further, the present invention of the present application is the electrode for a secondary battery in each of the above inventions, wherein the porosity of the multi-void metal layer is 85% or more.

Further, in the present invention of the present application and the like, in each of the above-mentioned inventions, the metallic substrate is made of a metal foil, a metal plate or a metal perforated plate, and when the metal substrate is a metal perforated plate, the mixture is also present in the hole. It is an electrode for a secondary battery.

Further, the present invention of the present application is the electrode for a secondary battery in each of the above inventions, wherein the bulk density of the mixture is 70% or more of the true density of the mixture.

Further, in the present invention of the present application and the like, in each of the above-mentioned inventions, the extension rate of the electrode before and after the pressure molding of the electrode is 1
It is an electrode for a secondary battery whose content is 0% or less.

Further, the present invention of the present application is the electrode for a secondary battery in each of the above inventions, wherein the multi-void metal layer or the metallic substrate is made of stainless steel, nickel, aluminum, copper or titanium.

The present invention of the present application is the electrode for a secondary battery according to each of the above-mentioned inventions, wherein the thickness of the multi-void metal layer is 5 mm or less and the thickness of the metallic substrate is 0.5 mm or less.

The present invention of the present application and others is a secondary battery having a positive electrode, a negative electrode and an electrolyte, wherein at least one of the positive electrode and the negative electrode is any one of the above electrodes.

Further, the present invention according to another aspect of the present invention is the positive electrode in the secondary battery, which holds a mixture containing at least one kind of oxide of lithium cobalt oxide, lithium nickel oxide, lithium iron oxide or spinel type manganese oxide. And natural graphite capable of electrochemically inserting and releasing lithium, mesophase carbon, amorphous graphite, expanded graphite, the above-mentioned graphite having a metal or an alloy capable of alloying with lithium, or a metal capable of alloying with lithium Or at least one of the alloys
It is characterized in that it is composed of a negative electrode holding a mixture containing various kinds, and an electrolyte containing lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoroacetate or lithium perchlorate.

Further, the present invention according to the present invention is characterized in that each of the secondary batteries is a prismatic battery container in which a positive electrode, a negative electrode and an electrolyte are housed.

Another aspect of the present invention is a rechargeable power source comprising a plurality of the secondary batteries and an assembled battery in which the secondary batteries are connected in series or in parallel.

Further, the present invention according to another aspect of the present invention is an apparatus using a secondary battery including any one of the above secondary batteries or the power source.

Here, the multi-void metal layer is not limited in type and manufacturing method as long as the internal structure is fibrous or mesh-like and the external appearance is sheet-like. Hereinafter, a method for producing multi-void metal layers having different structures will be described.

The multi-void metal layer having a fibrous structure is obtained by depositing metal fibers produced by an injection method or a vapor growth method and press-molding. The porosity of the multi-pore metal layer is 85 in order to hold the battery active material as much as or more than the film electrode in the electrode.
% Is desirable. In order to obtain a multi-void metal layer having a porosity of 85% or more, for example, ultrafine fibers having a wire diameter of 20 μm or less may be used and the pressure during molding may be adjusted. Examples of metals that can be used for the multi-void metal layer of the lithium secondary battery include corrosion-resistant metals such as nickel, aluminum, and stainless steel for the positive electrode, and copper, nickel, and stainless steel that do not alloy with lithium for the negative electrode. .

On the other hand, the multi-void metal layer having a mesh structure is
It can be manufactured by the method exemplified below. The metals that can be used for the lithium secondary battery are the same as described above. Metal particles or fibrous metal powder produced by liquid phase reduction method of metal salt, vapor phase reduction method, pulverization method of bulk metal, etc. are pressure-molded with coarsely pulverized polymer particles, and only polymer particles are thermally decomposed. Or by melting, a multi-void metal layer having a network structure is obtained. Alternatively, a metal may be deposited on the surface of the polymer particles by vapor phase pyrolysis, electroless plating, or the like, and only the polymer powder may be pyrolyzed. In order to set the porosity (porosity) of the multi-void metal layer to 85% or more, polymer particles having a particle size of 0.1 to 1 mm may be used and the compounding ratio of the polymer particles and the molding pressure may be adjusted. Examples of the decomposable polymer or the low melting point polymer include polyethylene, polypropylene, urethane resin, and butadiene rubber.
Although the heat treatment temperature depends on the material, it is preferably as low as possible below the metal melting temperature, and it is generally preferable to select a temperature in the range of 300 to 800 ° C. In addition, the gas atmosphere during sintering is preferably a vacuum or an inert gas atmosphere in order to avoid metal oxidation.

The multi-void metal layer produced by the above method is brought into contact with the metal foil, and an electric current is applied between the metal layer and the metal foil to weld them. Other joining methods include ultrasonic welding, brazing,
There is heat welding. A metal plate or a metal perforated plate obtained by perforating the metal plate can be used as the two-dimensionally-structured metal substrate to be bonded to the metal layer. The thickness of the multi-pore metal layer is 5 m
m or less, the thickness of the two-dimensionally structured metal substrate is 20 to 500
When the thickness is in the range of μm, when the electrode using the current collector in which both are joined is pressure-molded, the extension of the electrode can be reduced to 10% or less, and the desired mixture density was obtained. In addition, a thin substrate is used for the two-dimensional substrate if it can be joined to the multi-void metal layer,
It is preferable to use a current collector having a multi-void metal layer bonded to both surfaces thereof. The reason is to reduce the volume of the two-dimensional substrate and increase the battery capacity. The material of the two-dimensional metallic substrate that can be used for the positive electrode is aluminum, stainless steel, or the like. Further, copper, nickel, stainless steel, titanium, etc. can be used for the negative electrode.

The positive electrode active materials for lithium secondary batteries studied in the present invention are lithium cobalt oxide, lithium nickel oxide,
Lithium iron oxide and spinel type manganese oxide. Graphite, mesophase carbon, amorphous carbon, conductive carbon such as acetylene black, a binder, and an organic solvent are mixed to form a positive electrode mixture, which is then formed by a doctor blade method, a dipping method, or the like. The positive electrode mixture is applied to the inside of the multi-pore metal layer of the current collector, and the mixture is dried.

On the other hand, in the negative electrode active material, carbon capable of electrochemically inserting and removing lithium ions, for example, graphite,
Mesophase carbon, amorphous carbon, expanded graphite and the like can be used. In addition, a metal or alloy capable of alloying with lithium, or a material in which a metal is supported on the surface of carbon particles is used. As with the positive electrode above, a binder is added to the negative electrode active material.
And an organic solvent are mixed to form a mixture slurry, and this negative electrode mixture is applied to the inside of the multi-pore metal layer of the current collector and dried.

The positive electrode and the negative electrode thus produced are pressure-molded and used as an electrode for a secondary battery. Since the metal substrate having a two-dimensional structure does not easily extend even when pressure-molded, the current collector of the present invention can suppress the planar extension of the porous body during pressure-molding. When the extension of the electrode is suppressed to 10% or less, the bulk density of the mixture held by the electrode after pressurization can be increased to 70% or more of the true density of the mixture. Further, the present invention is applicable to other than the above-mentioned battery active material, and a lithium metal sheet may be used for the negative electrode.

After press-molding the positive electrode and the negative electrode of the present invention, they are cut into strips, and a separator made of polypropylene or polyethylene is sandwiched between both electrodes and laminated. The laminated electrode group is housed in a rectangular battery can, the battery lid is attached after injecting the electrolytic solution, and the can and the lid are welded to complete the battery. Electrolytes that can be used are ethylene carbonate,
Solution prepared by dissolving lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoroacetate, lithium perchlorate, etc. in an organic solvent such as propylene carbonate, dimethyl carbonate, dimethoxyethane. Can be used.

According to the present invention, it is possible to easily increase the thickness of the electrode and stack the electrode group, and reduce the volume of the separator and the current collector in the battery, so that the capacity of the battery is increased. The present invention is particularly effective for a prismatic battery for the following reasons. In the electrode of the present invention, the battery active material is surrounded by the three-dimensional structure of the current collector, so that the drop of the battery active material is suppressed. Therefore, the pressure for tightening the electrode group can be reduced, so that the wall thickness of the battery container can be reduced and the weight of the battery can be reduced. Furthermore, when a plurality of prismatic lithium secondary batteries of the present invention are connected in series or in parallel and housed in a limited volume, the wasted space can be made as small as possible compared to a cylindrical battery. Therefore, the present invention increases the energy density of an assembled battery power source composed of a prismatic battery, and therefore a device system such as a personal computer or a word processor, which has a high demand for a prismatic battery, or an industrial power source. It is possible to reduce the weight of power supplies for electric vehicles and electric vehicles.

By using the electrode of the present invention as described above, the extension of the electrode can be effectively suppressed. Moreover, since the electrodes can be made thicker, it is possible to increase the capacity of the battery and simplify the electrode stacking. Therefore, the electrode of the present invention is very effective for a prismatic battery.

[0032]

BEST MODE FOR CARRYING OUT THE INVENTION

[Embodiment 1] Porous aluminum as a multi-pore metal layer is obtained by sufficiently mixing fine aluminum powder having an average particle size of 10 µm and polyethylene particles having an average particle size of 1 mm and pressure-molding using a roll press machine. A sheet having a thickness of 1 mm was produced. This was heated in nitrogen at 600 ° C. to sinter the fine aluminum powder. Further, the copper porous body as the multi-void metal layer was produced by an electroless plating method. The urethane resin was dipped in an alkaline copper nitrate solution, formaldehyde was added, and metallic copper was deposited on the resin surface. This is pressure-molded to form a sheet with a thickness of 1 mm, and the sheet is placed in nitrogen to 600
The copper plating was sintered by heating at ℃. The porosities of the aluminum and copper porous bodies produced above were both 90%.

FIG. 1 is an external view of an electrode used in the present embodiment, and FIG. 1A on the left is a metal base 1 having a two-dimensional structure.
Current collector with multi-void metal layer 2 bonded to one surface of the
(B) shows a current collector in which the multi-void metal layers 2 and 4 are bonded to both surfaces of a two-dimensionally structured metal substrate 1. In the case of (A), the positive electrode current collector has a thickness of 50 μm, a width of 45 mm, and a width of 30 mm.
2 dimensional structured metal substrate 1, namely aluminum foil 1
A multi-void metal layer 2 having a thickness of 1 mm, a vertical width of 40 mm and a horizontal width of 30 mm, that is, porous aluminum 2 was electro-welded on one surface of the above. Aluminum foil exposed on top 1
It was cut off from the end with a width of 10 mm and used for the electrode and the terminal weld 3 of the battery lid. Similarly, on both sides of the aluminum foil 1 having a thickness of 50 μm, a vertical width of 45 mm, and a horizontal width of 30 mm,
Porous aluminum 2 and 4 having a thickness of 1 mm, a vertical width of 40 mm, and a horizontal width of 30 mm were electrically welded, and a terminal welded portion was processed with the same dimensions.

A mixture of a slurry prepared by mixing lithium cobalt oxide, natural graphite and polyvinylidene fluoride with 1-methyl-2-pyrrolidone was applied to the multi-void metal layers of these two kinds of current collectors and dried. . After sufficiently drying 1-methyl-2-pyrrolidone, the positive electrode weight is measured,
The weight of the mixture filled in the current collector was calculated from the difference between the value and the weight of the current collector.

The positive electrode was passed through a roll press and pressure-molded. The volume of the mixture alone was estimated by subtracting the volume of aluminum before pressing from the apparent volume of the positive electrode. The mixture weight obtained previously was divided by the mixture volume, and the mixture density after pressure molding was calculated. The bulk density of the battery active material held on the positive electrode was controlled by adjusting the roll interval of the press.

A negative electrode having the same shape as that of FIG. 1 was prepared in the same manner as the above-mentioned two types of positive electrodes. The negative electrode current collector has a thickness of 30μ
m, vertical width 45 mm, horizontal width 30 mm, two-dimensional structure metal base, that is, copper foil on both sides, thickness 1 mm, vertical width 40 m
It was produced by electrically welding a multi-void metal layer having a width of m and a width of 30 mm, that is, porous copper. The terminal welded portion was processed into the shape shown in FIG. A mixture made of a slurry in which natural graphite and polyvinylidene fluoride were mixed with 1-methyl-2-pyrrolidone was applied to the multi-void metal layer of this current collector and dried. After the 1-methyl-2-pyrrolidone was sufficiently dried, the weight of the negative electrode was measured, and the weight of the mixture filled in the current collector was determined from the difference between the value and the weight of the current collector. Pass the negative electrode through a roll press machine,
It was molded under pressure. The volume of the mixture alone was estimated by subtracting the volume of copper before pressing from the apparent volume of the negative electrode. The mixture weight obtained previously was divided by the mixture volume, and the mixture density after pressure molding was calculated.

FIG. 2 shows the relationship between the roll gap of the roll press and the filling ratio of the positive electrode and the negative electrode. However, the result is the result of bonding a porous body, that is, a multi-void metal layer to both surfaces of the two-dimensional metal substrate. The filling rate is the bulk density relative to the true density of the mixture. In the positive electrode of the present invention, the filling rate was 70% or more at a roll interval of 0.4 mm or less, regardless of the number of bonded aluminum porous bodies. Also in the case of the negative electrode, the filling rate was 70% or more when the roll interval was 0.4 mm or less.
The maximum mixture bulk density of the positive electrode and the negative electrode is 3.2 g / c, respectively.
m ^3, was 1.6g / cm ^3.

Comparative Example 1 In this comparative example, the first embodiment
The porous aluminum of the same specifications used in 1. was used without being joined to the aluminum foil. The porous aluminum was cut into a thickness of 1 mm, a length of 45 mm, and a width of 30 mm, and the upper portion 5 mm was pressed. 10mm width from the end of the pressure part
Then, the entire upper part was cut off and used for the electrode and the terminal welded portion of the battery lid. The external shape of this current collector is the same as in FIG. The aluminum porous body used was manufactured by the same manufacturing method as that of the first embodiment, and its porosity was 90%. A slurry prepared by mixing lithium cobalt oxide, natural graphite and polyvinylidene fluoride with 1-methyl-2-pyrrolidone was applied to this current collector and dried. Enough 1-methyl-2-
After drying the pyrrolidone, the weight of the positive electrode was measured, and the weight of the mixture filled in the current collector was determined from the difference between the value and the weight of the current collector. The method for calculating the mixture density before and after pressure molding is the same as that in the first embodiment. The bulk density of the battery active material held on the positive electrode was controlled by adjusting the roll interval of the press.

A negative electrode was prepared in the same manner as the positive electrode described above. The thickness used in the first embodiment is 1 mm, the vertical width is 45 mm, and the horizontal width is 3.
The top 5 mm of 0 mm porous copper was pressure molded. Similar to the above positive electrode current collector, it was cut off from the end of the pressed part leaving a width of 10 mm and used for the terminal welded part of the electrode and the battery lid.
The used copper porous body is made by the same manufacturing method as in the first embodiment,
Its porosity is 90%. A slurry in which natural graphite and polyvinylidene fluoride were mixed with 1-methyl-2-pyrrolidone was applied to this current collector and dried. After the 1-methyl-2-pyrrolidone was sufficiently dried, the weight of the negative electrode was measured, and the weight of the mixture filled in the current collector was determined from the difference between the value and the weight of the current collector. The method for calculating the mixture density before and after pressure molding is the same as that in the first embodiment.

FIG. 2 also shows the relationship between the roll spacing of the roll press and the filling rate of the positive electrode and the negative electrode produced in Comparative Example 1.
In the electrode of Comparative Example 1, the filling rate did not increase beyond the range of 50 to 60% when the roll interval was 0.6 mm or less. The maximum mixture bulk density of the positive electrode and the negative electrode is 2.0 g / c, respectively.
It was m ³ and 1.0 g / cm ³ . Therefore, it was found that the electrode of Embodiment 1 is more advantageous than Comparative Example 1 for high-density filling of the battery active material.

[Second Embodiment] Instead of the aluminum foil 1 used in the first embodiment, the thickness is 20 μm and the vertical width is 45 m.
m, a width of 30 mm, a stainless steel plate 1, and two kinds of two-dimensional substrates of a stainless steel perforated plate 1 in which perforations having a diameter of 2 mm are opened at 5 mm intervals in a stainless steel plate of the same size,
An aluminum porous body having the same specifications as those of the first embodiment was joined to both sides of each. At the upper part of these two types of current collectors, a width of 10 mm was cut off from the ends and used for the terminal welding part 3 of the electrode and the battery lid. A positive electrode slurry having the same specifications as in Embodiment 1 was applied to this current collector and dried. After sufficiently drying 1-methyl-2-pyrrolidone, the positive electrode was passed through a roll press and pressure-molded. In the case of the electrode of the present embodiment, since stainless steel is less likely to extend than aluminum, the thickness of the two-dimensional substrate can be reduced, the roll interval is 0.3 mm or less, the filling ratio of the positive electrode mixture is 70% or more, and the maximum of the positive electrode is The mixture bulk density was 3.2 g / cm ³ .

[Embodiment 3] Porous aluminum having the same specifications as those of Embodiment 1 is used, with a thickness of 50 μm and a vertical width of 45 m.
m, width 30 mm aluminum foil, or thickness 50
Electric welding was performed on both sides of a perforated aluminum foil having a thickness of 45 μm, a width of 45 mm, a width of 30 mm, and a perforation diameter of 1 mm. FIG.
As in (B), it was cut off from the end of the aluminum foil exposed at the upper part, leaving a width of 10 mm, and used for the terminal welding portion of the electrode and the battery lid. Lithium cobalt oxide, natural graphite, and polyvinylidene fluoride were added to this current collector with 1-methyl-2.
Smeared the slurry mixed with pyrrolidone and dried. After the 1-methyl-2-pyrrolidone was sufficiently dried, the weight of the positive electrode was measured, and the weight of the mixture filled in the current collector was determined from the difference between the value and the weight of the current collector. The positive electrode was passed through a roll press and pressure-molded. The volume of the mixture alone was estimated by subtracting the volume of aluminum before pressing from the apparent volume of the positive electrode. The mixture weight obtained previously was divided by the mixture volume, and the mixture density after pressure molding was calculated. The bulk density of the battery active material held on the positive electrode was controlled by adjusting the roll interval of the press.

When the positive electrode was pressure-molded by a roll press, the positive electrode was observed to extend in the direction of roll rotation. FIG.
Shows the relationship between the roll interval of the roll press and the extension rate of the positive electrode. The elongation ratio is the ratio of the positive electrode length along the roll rotation direction before and after molding. In the positive electrode of the present invention, the elongation rate was 10% or less even when the roll interval was 0.2 mm or less.

The negative electrode of the present invention prepared under the same conditions and the same specifications as those of the first embodiment has a smaller elongation than the positive electrode of the present invention. This is probably because the strength of copper used for the negative electrode is stronger than that of aluminum.

Comparative Example 2 The positive electrode prepared in Comparative Example 1 was
Pressure molding was performed in the same manner as in the third embodiment, and the elongation rate of the positive electrode was measured. The results are shown in Fig. 3. It was found that the positive electrode of Comparative Example 2 was more than twice as easy to stretch than the positive electrode of the third embodiment. Further, the negative electrode of Comparative Example 2 also had a higher elongation rate than the negative electrode of Embodiment 2. From the above results, the electrode of the present invention was able to effectively reduce the elongation during pressure molding.

[Fourth Embodiment] Similar to the first embodiment,
On both sides of a two-dimensional substrate of aluminum and copper, using a current collector in which porous aluminum or copper is electrically welded,
A positive electrode and a negative electrode of the present invention were produced. The mixture composition of the positive electrode and the negative electrode is the same as that used in the first embodiment. These electrodes were pressure-molded with a roll press. The mixture densities of the manufactured positive electrode and negative electrode were 2.7 g / cm ³ and 1.
It was 3 g / cm ³ . 25 μm thick between the positive and negative electrodes
The polyethylene microporous film of
An electrode group consisting of one sheet and 10 sheets of negative electrode was prepared. Each of the positive and negative terminal welds is welded to the terminal attached below the battery lid, and the electrode group and lid are 50 mm high and 35 m wide.
It was stored in a stainless steel battery can 9 having a thickness of 10 mm and a thickness of 10 mm. Laser welding of the joint between the battery lid 8 and the can 9
The prismatic lithium secondary battery shown in was completed. Outside the battery, there are a positive electrode terminal 6, a negative electrode terminal 7, and a safety valve 5. The output voltage and design capacity of this battery are 3.6V and 14V, respectively.
60mAh, 300Wh / l, 140Wh / kg
The energy density of was obtained.

The upper and lower cutoff voltages are set to 4.2, respectively.
A charging / discharging test was conducted at a constant current of 500 mA with V and 2.5 V. The relationship between the number of cycles and the discharge capacity is shown in FIG. The battery using the electrode of the present invention had a stable cycle life and retained the capacity of 95% or more of the initial capacity even after 400 cycles.

[Comparative Example 3] A positive electrode and a negative electrode of Comparative Example 3 were produced using a current collector having the same specifications as in Comparative Example 1. The mixture density of each electrode is 2.0 g / cm ³ and 1.0 g / c, respectively.
It was m ^3. A 25 μm-thick polyethylene porous sheet was sandwiched between the positive electrode and the negative electrode to form an electrode group consisting of 8 positive electrodes and 9 negative electrodes. Each of the positive electrode and negative electrode terminal welds is welded to the terminal attached below the battery lid, and the electrode group and the lid are 50 mm in height, 35 mm in width, and 1 in thickness.
It was stored in a 0 mm stainless steel battery can. The joint between the battery lid and the can was laser-welded to complete the battery shown in FIG.

The upper and lower end voltages are set to 4.2, respectively.
A charging / discharging test was conducted at a constant current of 500 mA with V and 2.5 V. The relationship between the number of cycles and the discharge capacity is shown in FIG. Since the mixture density of the electrode of Comparative Example 1 could not be increased to the mixture density of the electrode used in the fourth embodiment, the initial battery capacity of the battery was smaller than that of the fourth embodiment. Further, the battery capacity of Comparative Example 3 also decreased with the number of cycles due to the deterioration of the current collecting property between the battery active materials due to the low electrode density. The capacity value after 400 cycles was 86% of the initial capacity. Therefore, it was revealed that the use of the electrode of the present invention can significantly reduce the decrease in battery capacity.

[Embodiment 5] FIG. 6 shows an assembled battery pack including four prismatic lithium secondary batteries. Four prismatic batteries 9 having the same specifications as those of the fourth embodiment were produced, and these batteries were housed in an assembled battery pack container 10. Each battery was connected to a wiring board 11 having an IC circuit, and a 4-series 2-parallel assembled battery was assembled. The output from the battery pack is obtained from the external positive electrode terminal 12 and the external negative electrode terminal 14 attached to the bottom surface of the container 10. The external terminal 13 is a common terminal. The output voltage and capacity of this battery pack are 14.4 V and 2.9, respectively.
Ah, and energy densities of 205 Wh / l and 100 Wh / kg were obtained. Compared to the case where a cylindrical battery having the same capacity and the same energy density as the rectangular battery used in the present embodiment is used, the volume energy density is about 1.5 times that of the cylindrical battery, and the weight energy density is cylindrical. I was able to improve the battery by about 1.2 times.

[Sixth Embodiment] FIG. 7 shows an example in which the power supply 15 of the battery pack of the fifth embodiment is incorporated in the bottom surface of the keyboard portion 16 of a personal computer or a word processor. The power supply 15 allows the display 17 of a personal computer or a word processor to be displayed.
Can be used to display and drive the floppy disk drive 15. The personal computer or word processor of the present invention is 1 / 1.5 to 1/1 / thicker than the conventional nickel-cadmium prismatic battery and cylindrical lithium secondary battery.
Up to 2 size and weight were reduced.

[0052]

When the electrode of the present invention is used, the bulk density of the electrode mixture can be increased and the extension of the electrode can be reduced. for that reason,
It is possible to increase the capacity and extend the life of the battery. Further, since the number of electrodes can be reduced, stacking of batteries becomes easy.

[Brief description of the drawings]

FIG. 1 is a perspective view showing an electrode for a secondary battery according to the present invention, in which (A) and (B) show different embodiments.

FIG. 2 is a diagram showing a relationship between a roll interval of a roll press machine and a bulk density with respect to a true density of the electrode mixture of Embodiment 1 and Comparative Example 1.

FIG. 3 is a diagram showing a relationship between a roll interval of a roll press machine and an electrode extension ratio in the second embodiment and the second comparative example.

FIG. 4 is a perspective view of a prismatic lithium secondary battery according to the present invention.

5 is a diagram showing the relationship between the number of charge / discharge cycles and the battery capacity of the prismatic lithium secondary battery of the present invention and the prismatic lithium secondary battery of Comparative Example 3. FIG.

FIG. 6 is a perspective view showing an assembled battery pack in which the rectangular lithium secondary batteries of the present invention are connected in 4 series and 2 parallel.

FIG. 7 is a perspective view showing a personal computer or a word processor equipped with the battery pack of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Two-dimensional base 2 Multi-void metal layer 3 Electrode terminal welding part 4 Multi-void metal layer 5 Safety valve 6 Positive external terminal 7 Negative external terminal 8 Battery lid 9 Battery container 10 Assembly battery pack container 11 IC control panel 12 External positive electrode terminal 13 Common Terminal 14 External negative electrode terminal 15 Battery pack 16 Keyboard section 17 Display

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI Technical indication location H01M 4/80 H01M 4/80 C 10/40 10/40 Z (72) Inventor Toshio Takeuchi Ibaraki Hitachi 1-1, Omika-cho, Hitachi, Ltd. Inside Hitachi Research Laboratory, Hitachi, Ltd. (72) Inventor Ren Muranaka 7-1-1, Omika-cho, Hitachi, Hitachi, Ibaraki Inside Hitachi Research Laboratory, Hitachi (72) Inventor Tatsuo HORIBA 7-1-1 Omika-cho, Hitachi-shi, Ibaraki Hitachi Ltd. Hitachi Research Laboratory

Claims (14)

[Claims] 1. A secondary battery having a current collector in which a metal substrate having a two-dimensional structure is bonded to a multi-void metal layer, and holding a mixture containing a battery active material in the void in the multi-void metal layer. Electrodes. 2. A multi-void metal layer having a current collector to which a metal substrate that prevents or reduces the elongation of the multi-void metal layer when pressure-molded is bonded, An electrode for a secondary battery, which holds a mixture containing a battery active material in the void. 3. The electrode for a secondary battery according to claim 1, wherein the multi-void metal layer is bonded to both surfaces of the metallic substrate. 4. The electrode for a secondary battery according to claim 1, wherein the porosity of the multi-void metal layer is 85% or more. 5. The metallic substrate according to claim 1, wherein the metallic substrate is a metal foil, a metal plate or a metal perforated plate, and when the metal substrate is a metal perforated plate, the mixture also exists in the holes thereof. Battery electrode. 6. The electrode for a secondary battery according to claim 1, wherein the bulk density of the mixture is 70% or more of the true density of the mixture. 7. The electrode for a secondary battery according to claim 1, wherein the extension rate of the electrode before and after pressure molding is 10% or less. 8. The multi-void metal layer or the metallic substrate according to any one of claims 1 to 7,
A secondary battery electrode made of aluminum, copper or titanium. 9. The electrode for a secondary battery according to claim 1, wherein the multi-void metal layer has a thickness of 5 mm or less and the metallic substrate has a thickness of 0.5 mm or less. 10. A secondary battery having a positive electrode, a negative electrode and an electrolyte, wherein at least one of the positive electrode and the negative electrode is defined by claim 1.
A secondary battery, which is the electrode according to any one of items 1 to 9. 11. The positive electrode according to claim 10, which holds a mixture containing at least one oxide selected from lithium cobalt oxide, lithium nickel oxide, lithium iron oxide, and spinel-type manganese oxide, and lithium electrochemically. At least one of natural graphite, mesophase carbon, amorphous graphite, expanded graphite, a metal or alloy capable of alloying with lithium, or a metal or alloy capable of alloying with lithium. A secondary battery comprising: a negative electrode that holds a mixture containing: and an electrolyte containing lithium hexafluorophosphate, lithium hexafluoroarsenate, lithium trifluoroacetate, or lithium perchlorate. 12. The secondary battery according to claim 10, wherein the positive electrode, the negative electrode, and the electrolyte are housed in a rectangular battery container. 13. A rechargeable power source comprising a plurality of secondary batteries according to claim 10 or 11 and comprising an assembled battery in which the secondary batteries are connected in series or in parallel. 14. A secondary battery utilizing device comprising the secondary battery according to claim 10, 11 or 12, or the power source according to claim 13.