JPH11167934A - Nonaqueous electrolyte secondary battery and its manufacture - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a stacked type nonaqueous electrolyte secondary battery with high characteristics and high manufacturing efficiency of an electrode element. SOLUTION: A negative electrode 3 is formed by interposing a negative current collector 2 between two negative electrode sintered bodies formed by sintering a negative active material. A positive electrode 6 is formed by interposing a positive current collector between two positive electrode molded bodies formed by molding a positive active material. Thereafter, the positive electrode 6 is wrapped with a microporous film 7 except for an electrode taking-out portion, then the positive electrode 6 is sealed by welding. Next, the negative electrode 3 and the positive electrode 6 are stacked alternately, reinforcing plates 9 are arranged on both sides of the stack to interpose the stack between them, and they are wound with an adhesive tape 10 to constitute an electrode element 11. The microporous film 7 serves as a separator 5 which separates the negative electrode 3 and the positive electrode 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-aqueous electrolyte secondary battery and a method for producing the same, and more particularly, to a stacked non-aqueous electrolyte secondary battery having excellent productivity of electrode elements and a large battery capacity. About.

[0002]

2. Description of the Related Art In recent years, with the advance of electronic technology, electronic devices have become smaller, more sophisticated, and more portable, and accordingly, the demand for batteries having a high energy density suitable for use of these portable electronic devices has increased. Is coming. Conventionally, secondary batteries used in these electronic devices include nickel-cadmium batteries and lead batteries using an aqueous electrolyte, but these batteries have low discharge potential,
The reality is that the demand for batteries having a large battery volume and a high energy density has not been sufficiently satisfied.

Under these circumstances, as a battery satisfying these requirements, a non-aqueous electrolyte secondary battery using a light metal such as lithium or aluminum as a negative electrode has recently attracted attention and has been actively studied. Among them, lithium ion secondary batteries using a composite oxide of lithium and a transition metal as a positive electrode active material and a carbonaceous material doped with lithium ions and undoped as a negative electrode active material have a high energy density. And a battery exhibiting good cycle characteristics.

By the way, as a method for preparing the above-mentioned electrode of the non-aqueous electrolyte secondary battery, an active material is dispersed in a solvent in which a binder is dissolved to form a slurry, and the slurry is applied to both surfaces of a current collector. A method of drying a solvent has been used. However, when the electrode is thick, it is difficult to completely dry the solvent, and the solvent remaining on the electrode exudes into the electrolytic solution, possibly deteriorating the battery characteristics.

As a countermeasure, a method has been devised in which an active material is granulated and dried, a current collector is sandwiched between the active materials at the center, and compression molding is performed to form an electrode. However, this method is technically difficult when a foil is used for the current collector, such that the active material and the current collector hardly adhere to each other even when compression-molded.
Further, a method of using a mesh for the current collector has been proposed to ensure this adhesion, but in this case, the contact area between the active material and the current collector is reduced, and the mesh is used as a lead as it is. It was necessary to secure strength. Therefore, it is necessary to use a current collector having a larger volume than in the case of using a foil.For this reason, in a battery of a predetermined size, the amount of the active material contained therein must be reduced, and the battery capacity decreases. There was a problem.

[0006]

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a non-aqueous electrolyte secondary battery having excellent battery characteristics and improved production efficiency of an electrode assembly element in a laminated non-aqueous electrolyte secondary battery. And a method of manufacturing the same.

[0007]

Means for Solving the Problems The present invention has been made in view of the above problems, and an invention according to claim 1 is an electrode element having a structure in which a microporous film is laminated between a positive electrode and a negative electrode. In the method for manufacturing a non-aqueous electrolyte secondary battery, in which the electrode element is housed in a battery can and a non-aqueous electrolyte is injected into the battery can, two sheets formed in a thin plate are provided. A step of forming a positive electrode with a current collector made of a conductor between the positive electrode active materials, and a subsequent step of wrapping the positive electrode with a microporous film except for an electrode extraction site,
A step of forming a negative electrode by sandwiching a current collector made of a conductor between two negative electrode active materials formed in a thin plate, and a step of alternately stacking the positive electrode and the negative electrode wrapped by the microporous film And a production method comprising:

Further, the invention according to claim 2 has an electrode element having a structure in which a microporous film is laminated between a positive electrode and a negative electrode, and the electrode element is housed in a battery can.
In a non-aqueous electrolyte secondary battery in which a non-aqueous electrolyte is injected into the battery can, the above-mentioned problem is solved by a configuration in which the positive electrode is wrapped by a microporous film except for an electrode take-out site.

According to the method for manufacturing a non-aqueous electrolyte secondary battery according to the first aspect and the non-aqueous electrolyte secondary battery according to the second aspect, the battery capacity is increased by using a metal foil for the current collector. It is possible to provide a non-aqueous electrolyte secondary battery which can secure the electrode element and is excellent in productivity of the electrode assembly element, and a method of manufacturing the same.

[0010]

BEST MODE FOR CARRYING OUT THE INVENTION As a result of intensive studies, the present inventors formed a positive electrode active material and a negative electrode active material in the form of a plate, formed an electrode with a metal foil in between, and further formed a positive electrode. The inventors have found that it is possible to solve the above-mentioned problems by wrapping a porous film except for an electrode take-out site and alternately stacking the positive electrode and the negative electrode to form an electrode element.

The present invention has been made based on such knowledge, and is composed of Li _X MO ₂ (where M represents one or more transition metals and 0.05 ≦ X ≦ 1.10.) A non-aqueous electrolyte secondary battery in which a positive electrode and a lithium-doped, negative electrode made of a carbonaceous material that can be doped and de-doped is stacked, and then housed in a battery can and then injected with a non-aqueous electrolyte. Is done.

FIGS. 1 to 5 show an embodiment of the present invention.
This will be described with reference to FIG. Here, FIG. 1 is a view showing a method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention. FIG. 2 is a perspective view showing the configuration of a negative electrode [FIG. 2 (a)] and a positive electrode [FIG. 2 (b)] of a non-aqueous electrolyte secondary battery according to the present invention, and FIG. It is a perspective view which shows the structure of a body element. FIG. 4 is a sectional view of a non-aqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention.
FIG. 2 is a cross-sectional view of a conventional non-aqueous electrolyte secondary battery manufactured for comparison.

First, as the negative electrode active material, a carbon material capable of doping / dedoping lithium is used, and a conductive polymer such as polyacetylene or polypyrrole, or coke, polymer charcoal, carbon fiber, etc. Pyrolytic carbons, cokes (petroleum coke, pitch coke, coal coke, etc.), carbon black (acetylene black, etc.)
Glassy carbon, a fired body of an organic polymer material (an organic polymer material fired at an appropriate temperature of 500 ° C. or higher in an inert gas stream or in a vacuum), and carbon fibers are preferable.

On the other hand, as the positive electrode active material, Li _X MO ₂
(Where M is one or more transition metals, preferably Co, Ni,
Represents at least one kind of Mn, and 0.05 ≦ X ≦
1.10), a composite metal oxide composed of lithium and a transition metal or an intercalation compound containing lithium is used.

Further, as the electrolytic solution, propylene carbonate, ethylene carbonate, butylene carbonate,
γ-butyrolactone, 1,2-dimethoxyethane, 1,
2-diethoxymethane, 1,2-dimethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran,
1,3-dioxolan, 4-methyl-1,3-dioxolan, diglymes, triglymes, sulfolane, dimethyl carbonate, diethyl carbonate, dipropyl carbonate and the like alone;
Alternatively, two or more kinds are mixed and used as a solvent.

Next, a method for manufacturing a non-aqueous electrolyte secondary battery according to the present invention will be described. The present manufacturing method has a feature regarding the formation of the electrode element, and the manufacturing steps of the other portions are the same as those in the related art.

As shown in FIG. 1, a negative electrode 3 is formed by sandwiching a negative electrode current collector 2 between two negative electrode sintered bodies 1 obtained by firing the above-described negative electrode active material. The positive electrode 6 is formed by sandwiching the positive electrode current collector 5 between the two positive electrode molded bodies 4 formed by molding the positive electrode active material described above. Thereafter, the positive electrode 6 is wrapped with a microporous film 7 except for the electrode take-out site, and the positive electrode 6 is sealed by welding. Next, the negative electrode 3 and the positive electrode 6 are alternately laminated, reinforcing plates 9 are provided on both sides of the laminate, these are sandwiched, and finally an adhesive tape 10 is wound to form the electrode element element 11.
At this time, the microporous film 7 becomes a separator 8 for separating the negative electrode 3 and the positive electrode 6.

FIGS. 2 and 3 show the configuration of the negative electrode 3 and the positive electrode 6 and the electrode element 11 formed by these components.
Note that the number of the negative electrode 3 and the positive electrode 6 to be laminated is not limited to the number shown in the figure, and it is natural that any number may be laminated. Further, the battery manufacturing process after manufacturing the electrode element element 11 is the same as the conventional one, and will be described in a later example.

Example First, a negative electrode sintered body 1 was produced as follows. The low-expansion mesophase carbon powder 250 mesh under product was treated in an oxidizing atmosphere to obtain a powder having an average particle diameter of 20 μm (this is referred to as carbonaceous powder A). Further, one part of the obtained carbonaceous powder A was calcined in an inert gas at 900 ° C. for 3 hours to form a coke, which was then pulverized to obtain a powder having an average particle diameter of 20 μm (this To carbonaceous powder B
And).

Next, the carbonaceous powder A and the carbonaceous powder B were mixed, polyvinyl alcohol (molecular weight: 500) was added as a binder, and kneaded using water as a solvent. Thereafter, granulation was performed using a mesh of 250 μm or less and 150 μm or more, and the particle size was adjusted.

This granulated product is formed into a square shape, and this is treated in an inert gas at 1000 ° C. for 3 hours to obtain a vertical 41.5%.
mm, a negative electrode sintered body 1 having a width of 32.3 mm was obtained. The volume density of the carbonaceous portion is 1.25 g / ml, and the true specific gravity is 1.
75. The thickness of the outermost two electrodes of the electrode element element 11 is 0.3 mm, and the thickness of the other two is 0.6 mm.
mm.

Next, a positive electrode molded body 4 was produced as follows. A conductive agent and a binder were added to LiCoO ₂ , which is a lithium composite oxide, and mixed, and dimethylformamide was added as a dispersant to prepare a slurry. This was granulated using a spray drier for organic solvent, and the granulated product was molded into a square shape, 39.5 mm long and 31.0 m wide.
m of the positive electrode molded body 4 was obtained. The pressing pressure at the time of molding was set to 200 kg / cm ² which can sufficiently increase the density of the electrode.

The negative electrode sintered body 1 described above has a thickness of 10 μm.
Is sandwiched from both sides to form the negative electrode 3. Also, the positive electrode molded body 4 sandwiches the aluminum foil having a thickness of 20 μm from both sides to form the positive electrode 6.
And furthermore, the microporous film 7 having a thickness of 35 μm
And the periphery was welded by heat except for the electrode take-out site to form a bag. The positive electrode 6 and the negative electrode 3 were alternately stacked. At this time, the microporous film 7 forms the separator 8. Thereafter, reinforcing plates 9 were added to both sides of the laminate, and an adhesive tape 10 was vertically wound to form an electrode element 11.

As shown in FIG. 4, the electrode element 11 thus prepared is housed in a nickel-plated iron rectangular battery can 21 and insulating plates 22 are provided on both upper and lower surfaces of the electrode element 11. Was placed. The negative electrode lead 23 of the negative electrode 3 was welded to the reinforcing plate 9, and the reinforcing plate 9 was further welded to the battery can 21,
On the other hand, the positive electrode lead 24 of the positive electrode 6 is attached to the battery lid 26 by the insulator 2.
Laser welding is carried out to the positive electrode terminal 25 provided via.
Although not shown, the battery lid 26 is provided with a cleavage valve as a safety device.

Next, in a battery can 21, a mixed solvent of 5% by volume of ethyl carbonate, 15% by volume of propylene carbonate, 40% by volume of dimethyl carbonate, and 40% by volume of methyl carbonate was mixed with 1.5 parts by weight of LiPF ₆ . The molten electrolytic solution was injected, and then the battery lid 26 was welded to the battery can 21 with a laser to produce a battery having a thickness of 14 mm, a height of 48 mm, and a width of 34 mm.

Comparative Example As a comparative example, a non-aqueous electrolyte secondary battery using a conventional spiral electrode body was manufactured as follows. FIG. 5 is a cross-sectional view of a battery manufactured by this method.

First, the negative electrode 31 was manufactured as follows. A petroleum pitch was used as a starting material, which was crosslinked with oxygen, and then fired in an inert gas stream to obtain a soft graphitized carbon material. This soft graphitized carbon material was pulverized into a carbon material powder having an average particle diameter (average volume diameter) of 10 μm. This carbon material powder is mixed with a binder to prepare a negative electrode mixture,
This negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry to prepare a negative electrode slurry. The negative electrode slurry thus obtained is uniformly applied to both sides of a 10 μm-thick strip-shaped copper foil serving as a negative electrode current collector, dried, and then compression-molded by a roll press to obtain a strip-shaped negative electrode 3.
1 was produced.

Next, the positive electrode 32 was manufactured as follows. 0.5 mol of lithium carbonate and cobalt carbonate: 1.0
Mole ratio and calcine the mixture in air to give Li
CoO ₂ was obtained. This LiCoO ₂ was mixed with a conductive material and a binder to prepare a positive electrode mixture, and this positive electrode mixture was dispersed in N-methyl-2-pyrrolidone as a solvent to form a slurry, thereby preparing a positive electrode slurry.

The positive electrode slurry thus obtained is uniformly coated on both sides of a 20 μm-thick strip-shaped aluminum foil serving as a positive electrode current collector, dried, and then compression-molded by a roll press to form a strip-shaped aluminum foil. A positive electrode 32 was produced.

The negative electrode 31, the positive electrode 32, and the separator 8 made of a microporous polypropylene film as described above were combined with the negative electrode 31, the separator 8, and the positive electrode 3.
2, the separator 8 was laminated in this order, and this was wound many times to produce a spiral electrode body element 33.

The electrode element element 33 thus produced
Was housed in a nickel-plated iron square battery can 21, and insulating plates 22 were arranged on both upper and lower surfaces of the electrode element element 33. The negative electrode lead 23 of the negative electrode 31 was welded to the battery can 21, while the positive electrode lead 24 of the positive electrode 32 was laser-welded to a positive electrode terminal 25 provided on a battery lid 26 via an insulator 27. Although not shown, the battery lid 26 is provided with a cleavage valve as a safety device.

Next, in a battery can 21, a mixed solvent of 5% by volume of ethyl carbonate, 15% by volume of propylene carbonate, 40% by volume of dimethyl carbonate, and 40% by volume of methyl carbonate was mixed with 1.5% of LiPF ₆ . The molten electrolytic solution was injected, and then the battery lid 26 was welded to the battery can 21 with a laser to produce a battery having a thickness of 14 mm, a height of 48 mm, and a width of 34 mm.

The charging current of the non-aqueous electrolyte secondary batteries of Examples and Comparative Examples produced as described above was 1000 m
A, charging was performed under the conditions of a final voltage of 4.2 V, and then 300 mA, 600 mA, and 750 m until a final voltage of 2.75 V.
The battery was discharged at each constant current of A, and the battery capacity was measured. Table 1 shows the results.

[0034]

[Table 1]

From this measurement result, it can be seen that the capacity of the nonaqueous electrolyte secondary battery according to the configuration of the present invention is increased at each load current as compared with the battery of the conventional configuration.

The negative electrode material, the positive electrode material, the electrolytic solution and the like are not limited to those described in the examples, and all commonly used materials can be applied to the present invention. Also, the number of layers of the negative electrode and the positive electrode, the thickness of the current collector, and the thickness of the negative electrode and the positive electrode are not limited to those described in the examples.

[0037]

As is apparent from the above description, according to the present invention, the non-aqueous electrolysis method in which the manufacturing process is simplified and the manufacturing efficiency is improved, the volume efficiency of the electrode element element is improved, and the battery capacity is increased. It becomes possible to provide a liquid secondary battery.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for manufacturing a nonaqueous electrolyte secondary battery according to the present invention.

FIG. 2 is a perspective view showing the configuration of a negative electrode [FIG. 2 (a)] and a positive electrode [FIG. 2 (b)] of a non-aqueous electrolyte secondary battery according to the present invention.

FIG. 3 is a perspective view showing a configuration of an electrode element of the nonaqueous electrolyte secondary battery according to the present invention.

FIG. 4 is a sectional view of a non-aqueous electrolyte secondary battery manufactured by the manufacturing method of the present invention.

FIG. 5 is a cross-sectional view of a conventional non-aqueous electrolyte secondary battery.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Negative electrode sintered body, 2 ... Negative electrode current collector, 3, 31 ... Negative electrode, 4
... Positive electrode molded body, 5 ... Positive electrode current collector, 6,32 ... Positive electrode, 7 ...
Microporous film, 8: separator, 9: reinforcing plate, 10
... Adhesive tape, 11, 33 ... Electrode element, 21 ... Battery can, 22 ... Insulating plate, 23 ... Negative electrode lead, 24 ... Positive electrode lead, 25 ... Positive electrode terminal, 26 ... Battery cover, 27 ... Insulator

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[Procedure amendment]

[Submission date] April 6, 1998

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

As shown in FIG. 1, a negative electrode 3 is formed by sandwiching a negative electrode current collector 2 between two negative electrode sintered bodies 1 obtained by firing the above-described negative electrode active material. The positive electrode 6 is formed by sandwiching the positive electrode current collector 5 between the two positive electrode molded bodies 4 formed by molding the positive electrode active material described above. Thereafter, the positive electrode 6 is wrapped with a microporous film 7 except for the electrode take-out site, and the positive electrode 6 is sealed by welding. Next, the negative electrode 3 and the positive electrode 6 are alternately laminated, reinforcing plates 9 are provided on both sides of the laminate, these are sandwiched, and finally an adhesive tape 10 is wound to form the electrode element element 11.
At this time, the microporous film 7 becomes a separator 8 for separating the negative electrode 3 and the positive electrode 6. In addition, the stacked electrodes
The negative electrode 3 at both ends is a negative electrode sintered body only on the side facing the positive electrode 6.
Having.

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0027

[Correction method] Change

[Correction contents]

First, the negative electrode 31 was manufactured as follows. Using petroleum pitch as a starting material, after which the oxygen bridge, and fired in an inert gas stream, to obtain a non-graphitizable carbon material. The graphitizable carbon material was pulverized, and the average particle size (average volume diameter) was the carbon material powder 10 [mu] m. This carbon material powder is mixed with a binder to prepare a negative electrode mixture,
This negative electrode mixture was dispersed in N-methyl-2-pyrrolidone to form a slurry to prepare a negative electrode slurry. The negative electrode slurry thus obtained is uniformly applied to both sides of a 10 μm-thick strip-shaped copper foil serving as a negative electrode current collector, dried, and then compression-molded by a roll press to obtain a strip-shaped negative electrode 3.
1 was produced.

[Procedure amendment 3]

[Document name to be amended] Drawing

[Correction target item name] Fig. 1

[Correction method] Change

[Correction contents]

FIG.

[Procedure amendment 4]

[Document name to be amended] Drawing

[Correction target item name] Figure 2

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FIG. 2

[Procedure amendment 5]

[Document name to be amended] Drawing

[Correction target item name] Figure 3

[Correction method] Change

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[Procedure amendment 6]

[Document name to be amended] Drawing

[Correction target item name] Fig. 4

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Claims (2)

[Claims] An electrode device having a structure in which a microporous film is laminated between a positive electrode and a negative electrode, the electrode device is housed in a battery can, and a non-aqueous electrolyte is contained in the battery can. In a method for producing a non-aqueous electrolyte secondary battery, a step of forming a positive electrode by sandwiching a current collector made of a conductor between two positive electrode active materials formed in a thin plate, A step of wrapping the positive electrode with a microporous film except for an electrode take-out site; a step of forming a negative electrode with a current collector made of a conductor between two negative electrode active materials formed in a thin plate; A process of alternately stacking the positive electrode and the negative electrode wrapped by a porous film, the method comprising the steps of: 2. An electrode device having a structure in which a microporous film is laminated between a positive electrode and a negative electrode, wherein the electrode device is housed in a battery can, and a non-aqueous electrolyte is contained in the battery can. A non-aqueous electrolyte secondary battery characterized in that the positive electrode is wrapped by a microporous film except for an electrode take-out site.