JP2002252032A - Manufacturing method of non-aqueous electrolyte secondary battery having polymer electrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a manufacturing method of an electrode for non-aqueous electrolyte secondary batteries having no micro short circuit, in which a polymer electrolyte is held to at least either of electrodes of a positive electrode or a negative electrode. SOLUTION: In the manufacturing method of the electrode for non-aqueous electrolyte secondary batteries, which has an impregnating process, an extracting process, and a drying process in order, the manufacturing method is constituted with preparing two or more above extraction tubs, making the above electrode sheet pass one by one through the inside of the two or more above extraction tubs, and preparing a solvent flow way between two or more above extraction tubs. While supplying a 2nd solvent to the extraction tub of the last stage, the 2nd solvent is poured in toward the extraction tub of a preceding stage from the extraction tub of a following stage, and a filtration means is prepared in the above solvent flow way.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a method for manufacturing a non-aqueous electrolyte secondary battery having a polymer electrolyte.

[0002]

2. Description of the Related Art A non-aqueous electrolyte secondary battery is widely used as a power source for small and portable electronic devices, taking advantage of its high energy density. In addition, application to electric vehicles is expected in the near future.

A nonaqueous electrolyte secondary battery uses a material capable of inserting and extracting lithium as a positive electrode active material and a negative electrode active material. Specifically, a composite oxide of a transition metal such as lithium cobalt oxide is used as a positive electrode active material, and a carbonaceous material such as lithium, a lithium alloy, and graphite is used as a negative electrode active material. In the reaction of a non-aqueous electrolyte secondary battery, during charging, lithium released from the positive electrode active material is occluded in the negative electrode active material,
In discharging, lithium occluded in the negative electrode active material is released and occluded in the positive electrode active material.

As an electrolyte for a non-aqueous electrolyte secondary battery, LiP is mixed with a mixed organic solvent containing various carbonates such as ethylene carbonate and ethyl methyl carbonate.
A non-aqueous electrolyte in which lithium salts such as F ₆ and LiBF ₄ are dissolved is used.

[0005] The shape of the power generating element of the non-aqueous electrolyte secondary battery is as follows.
A sheet-like positive electrode plate in which a positive electrode mixture containing a positive electrode active material is applied to a current collector, and a sheet-like negative electrode plate in which a negative electrode mixture containing a negative electrode active material is applied to a current collector are made of a polyolefin-based material such as polyethylene or polypropylene. A winding type wound through a separator having fine pores, a folding type in which a sheet-like positive electrode plate and a sheet-like negative electrode plate are folded through a separator and laminated together, a plate-like positive electrode plate and a plate-like negative electrode plate, Are stacked on each other with a separator interposed therebetween.

In such a non-aqueous electrolyte secondary battery, since the non-aqueous electrolyte is used as described above, in order to prevent decomposition of the electrolyte due to overcharging or internal short circuit,
Various protection circuits were required.

In non-aqueous electrolyte secondary batteries, attempts have been made to use polymer electrolytes instead of non-aqueous electrolytes in order to reduce the amount of free electrolyte and improve battery safety. As the polymer electrolyte, an all-solid electrolyte composed of a polymer and an electrolyte salt and a gel electrolyte obtained by swelling the polymer with a non-aqueous electrolyte have been studied. A porous polymer electrolyte which swells with a non-aqueous electrolyte solution in the pores and is held to be promising.

An example of a conventional method for manufacturing a non-aqueous electrolyte secondary battery having a porous polymer electrolyte is as follows. First, an electrode sheet is manufactured in which a mixture layer containing an active material, a conductive auxiliary agent and a binder is applied to both surfaces of a current collector made of a strip-shaped metal foil and dried.

Next, a polymer impregnation tank storing a polymer solution in which a polymer is dissolved in a first solvent is prepared, and the electrode sheet is passed through the polymer solution in the polymer impregnation tank, so that the mixture layer contains the polymer solution. (Impregnation step).

Next, the electrode sheet is immersed in a second solvent that is compatible with the first solvent and does not dissolve the polymer, and the first solvent in the polymer solution is extracted with the second solvent. (Extraction step), the first solvent is replaced with a second solvent. Thereafter, the electrode sheet is dried to remove the second solvent (drying step). Then, micropores are formed after the second solvent in the polymer solution has escaped, and an electrode sheet having a porous polymer in the mixture layer is obtained.

Therefore, by immersing the electrode sheet in a non-aqueous electrolyte, the non-aqueous electrolyte is held in the pores of the porous polymer, and at the same time, the polymer is swollen with the non-aqueous electrolyte. The electrode sheet provided with the conductive polymer electrolyte in the mixture layer is obtained (electrolyte impregnation step). Then, the electrode sheet is cut into a required length and width, and wound together with the electrode sheet of the counter electrode and the separator, thereby forming a battery.

Alternatively, an electrode sheet provided with a porous polymer in a mixture layer is cut into a required length and width, wound together with an electrode sheet of a counter electrode and a separator to form a power generating element, and stored in a battery case. Thereafter, by pouring the non-aqueous electrolyte, a battery having the porous polymer electrolyte in the electrode mixture layer is obtained.

[0013]

The conventional extraction process will be described in detail with reference to the drawings. FIG. 2 is a schematic longitudinal sectional view showing a conventional extraction step using one extraction tank. FIG.
, 31 is an electrode sheet, 32 is an extraction tank, 33 is a first turning roll, 34 is a guide roll, 35 is a second solvent for extraction, and 36 is a second turning roll.

An electrode sheet 31 impregnated with the polymer solution in the mixture layer through the impregnation step is supplied from the direction A, and after rotating around the first turning roll 33, a plurality of guide rolls provided in the extraction tank 32 are provided. And the solvent for extraction 35
In a meandering manner, during which the solvent (first solvent) in the polymer solution replaces the extraction solvent (second solvent). After that, the electrode sheet 31 travels through the second turning roll 36 to the drying process in the B direction.

In this extraction step, a small amount of the fine particles of the mixture comprising the active material and the conductive auxiliary agent are peeled off from the mixture layer of the electrode sheet 31 and fall off. Then, while the same extraction solvent is used for a long time, the particles of the dropped mixture accumulate in the second solvent for extraction, and the particles of the mixture adhere to the surface of the electrode sheet 31 and remain unchanged. Brought into the drying process,
An electrode sheet having fine particles of the mixture adhered to the surface was obtained.

When a power generating element of a battery is manufactured using such an electrode sheet, there has been a problem that the fine particles of the mixture present on the surface of the electrode sheet break through the separator and cause a short circuit between the positive electrode and the negative electrode.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to remove fine particles of a mixture that has accumulated in an extraction solution in an extraction step, so that the fine particles of the mixture on an electrode sheet surface are removed. It is an object of the present invention to provide a method for manufacturing a non-aqueous electrolyte secondary battery in which adhesion of water is suppressed, and to obtain a non-aqueous electrolyte secondary battery free from minute short circuits.

[0018]

The invention according to claim 1 is a method for manufacturing a non-aqueous electrolyte secondary battery in which a porous polymer electrolyte is held on at least one of a positive electrode and a negative electrode, An impregnating step of impregnating the polymer solution into the mixture layer of the electrode sheet by passing the strip-shaped electrode sheet through a polymer solution in which the polymer is dissolved in a first solvent; An extraction step of extracting the first solvent from the polymer solution by immersing the electrode sheet, and a drying step of drying the electrode sheet and then removing the second solvent are sequentially performed, and in the extraction step, A plurality of the extraction tanks are provided, the electrode sheet is sequentially passed through the plurality of the extraction tanks, a solvent flow path is provided between the plurality of the extraction tanks, and a second solvent is supplied to the last extraction tank. Do Both allowed flow into the second solvent toward the subsequent extraction tank upstream of the extraction vessel, wherein the solvent flow path, characterized in that a filtration means.

According to the first aspect of the present invention, in the extraction step, by removing the fine particles of the mixture that has accumulated in the extraction solution, the adhesion of the fine particles of the mixture to the surface of the electrode sheet is suppressed, and there is no minute short circuit. A non-aqueous electrolyte secondary battery can be obtained.

According to a second aspect of the present invention, in the method of manufacturing a non-aqueous electrolyte secondary battery, a bottom surface of the extraction tank is provided with an inclination, and the second solvent is discharged from the bottom of the extraction tank. After passing through a pump, it is circulated to the extraction tank.

According to the second aspect of the present invention, the fine particles of the mixture accumulated in the extraction solution can be more effectively removed, the adhesion of the fine particles of the mixture to the surface of the electrode sheet can be suppressed, and the short circuit of the minute short circuit can be prevented. No non-aqueous electrolyte secondary battery can be obtained.

[0022]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described with reference to the drawings based on an example applied to the manufacture of a lithium ion secondary battery. This lithium ion secondary battery includes a power generating element formed by winding a band-shaped positive electrode and a band-shaped negative electrode with, for example, a separator made of a polyolefin-based porous film interposed therebetween, and the negative electrode is, for example, a copper foil. A mixture layer containing graphite or the like as an active material is applied on both surfaces, and the positive electrode is formed by applying a mixture layer containing LiCoO ₂ or the like as an active material on both surfaces of an aluminum foil, for example. It is provided with a porous polymer electrolyte.

The non-aqueous electrolyte secondary battery according to the present invention is characterized in that a porous polymer is added to the mixture layer, which is produced through a step of manufacturing an electrode sheet having a mixture layer, an impregnation step, an extraction step, and a drying step. Use the provided electrode sheet.

According to the present invention, in the extraction step, a plurality of extraction tanks are provided, an electrode sheet is sequentially passed through the plurality of extraction tanks, and a solvent flow path is provided between the plurality of extraction tanks. And supplying the second solvent from the subsequent extraction tank to the previous extraction tank,
Further, a filtration means is provided in the solvent flow path.

The filtering means used here may pass through the second solvent, but may be any one capable of capturing fine particles contained in the second solvent, and may be a metal mesh having a desired mesh number (mesh / in). For example, filter paper or glass filter such as paper or cloth may be used.

Also, the bottom of the extraction tank is provided with a slope,
The second solvent is discharged from the bottom of the extraction tank, passed through a filter pump, and then circulated to the extraction tank. Filter pumps are used for quick filtration.
It is a device to make the filtrate side negative pressure, and uses an aspirator and a vacuum pump.

FIG. 1 shows a detailed longitudinal section of the extraction step according to the present invention, in which two extraction layers are used. The same extraction process is used for both the positive electrode and the negative electrode. In FIG. 1, 1 is an electrode sheet, 2 is a first extraction tank, 3 is a second extraction tank, 4 is a second solvent, 5 is a first turning roll, and 6 is a guide in the first extraction tank. Roll, 7 is the second turning roll, 8 is the guide roll in the second extraction tank, 9 is the third turning roll, 10 is the second solvent supply port, 11 is the solvent flow path, and 12 is the filtration Means, 13 is a drain, 14 is a pipe, 1
5 is a filter pump and 16 is an inlet. Note that a plurality of guide rolls 6 in the first extraction tank and a plurality of guide rolls 8 in the second extraction tank are provided.

As shown in FIG. 1, an electrode sheet 1 containing a polymer solution (a solution obtained by dissolving a polymer in a first solvent) in a mixture layer through an impregnation step is supplied from the A direction,
After turning around the deflecting roll 5, it turns around the guide roll 6 provided in the first extraction tank 2 and travels in a meandering manner in the second solvent 4 for extraction. The solvent therein (the first solvent) replaces the extraction solvent (the second solvent).

After that, the electrode sheet 1 is once pulled out of the first extraction tank 2 and circulates around the second turning roll 7.
After the direction is changed, the guide roller 8 is circulated around the guide roll 8 provided in the second extraction tank 3 and travels in a meandering manner in the second solvent 4 for extraction. Solvent (first
Solvent) replaces the extraction solvent (second solvent).

Thereafter, the electrode sheet 1 is pulled out above the second extraction tank, and travels through a third deflecting roll 9 to a drying step in the B direction.

The second solvent 4 for extraction is continuously supplied from the liquid supply port 10 to the second extraction tank 3 at the last stage, and the second solvent overflowed in the second extraction tank 3 is It flows into the first extraction tank 2 at the preceding stage through the solvent flow path 11. Then, the second solvent overflowed in the first extraction tank 2 flows out of the drain port 13 and is sent to a waste liquid treatment device (not shown).

In the extraction step of the present invention, the electrode sheet 1 impregnated with the polymer solution is first immersed in a second solvent 4 for extraction in a first extraction tank 2, where it runs in a meandering manner. Meanwhile, the first solvent in the polymer solution dissolves in the second solvent, and at the same time, the second solvent penetrates into the polymer, and the concentration of the first solvent in the first extraction tank 2 gradually decreases. To rise.

However, at that time, the electrode sheet 1 pulled out from the first extraction tank 2 is sent into the second extraction tank 3.
The electrode sheet 1 is also used in the second extraction tank 3 for the second extraction tank.
In the second extraction tank 3, since the second solvent is continuously supplied from the liquid supply port 10, the concentration of the first solvent excessively increases. Never
Since it is kept low, the first solvent, which is the polymer solution, is eluted from the electrode sheet 1 more quickly and is exchanged for the second solvent.

Second extraction tank 3 containing a small amount of first solvent
The second solvent for extraction inside flows through the solvent flow path 12 into the first extraction tank 2 at the preceding stage. Here, since the electrode sheet 1 containing a large amount of the first solvent passes through, even the second solvent for extraction containing a certain amount of the first solvent is impregnated in the electrode sheet 1. First in polymer solution
The concentration gradient with the solvent is large, and the first solvent is extracted at a sufficient speed. The shape of the solvent flow channel 11 is not particularly limited, and any shape such as a tube or a gutter through which a liquid flows can be used.

As described above, according to the present embodiment, the electrode sheet 1 is provided in the two-stage extraction tanks of the first and second extraction tanks 2 and 3.
Runs, the first solvent is efficiently extracted,
As a whole, the elution rate of the first solvent is higher than in the case of a single tank. Therefore, the total time for immersing the electrode sheet 1 in the second solvent for extraction can be reduced, and the size of the entire apparatus can be reduced. In the present embodiment, the second solvent for extraction is supplied to the second extraction tank 3 at the last stage, and the second solvent for extraction is poured into the first extraction tank 2 at the previous stage. As a result, a minimum amount of the second solvent for extraction can be used, and the amount of wastewater to be treated can be minimized.

The number of extraction tanks is not limited to two but may be three or more. In addition, it is not always necessary to supply the second solvent for extraction to the last-stage extraction tank, so that the second solvent is sequentially poured from the second-stage extraction tank to the first-stage extraction tank. All may be supplied with a second solvent.

When the electrode sheet 1 orbits the guide rolls 6 and 8, a force is applied to the mixture layer applied to the surface of the electrode sheet 1, and the fine particles of the mixture separate from the mixture layer and fall off.
It floats in the second solvent 4 for extraction.

Therefore, in the present invention, filtration means is provided in a solvent flow path provided between a plurality of extraction tanks. That is, in FIG. 1, a filtering means 12 is provided inside a solvent flow path 11 connecting the first extraction tank 2 and the second extraction tank,
When the solvent passes through the filtration means 12, the fine particles contained therein can be removed, and the adhesion of the fine particles to the surface of the electrode sheet 1 can be suppressed as much as possible.

In the case of an extraction apparatus having three or more extraction tanks, filtration means may be provided in all solvent flow paths connecting the extraction tanks, or filtration means may be provided in at least one solvent flow path. There may be a solvent flow path without a filtration means. The solvent flow path is preferably provided between the last extraction tank and the previous extraction tank.

Further, according to the present invention, as shown in FIG. 1, the bottom surfaces of the first extraction tank 2 and the second extraction tank 3 are provided with an inclination, and the second solvent 4 in each of the extraction tanks is extracted. Is circulated from the inlet 16 to the extraction tank after being discharged from the bottom of the filter, guided through the pipe 13 and passed through the filter pump 14. With this device, the fine particles contained in the second solvent 4 can be more effectively removed, and the second solvent 4
Can be reduced.

In FIG. 1, the pipes 14 from each extraction tank
And the filter pump is provided at one location. However, a filter pump may be provided for each pipe provided in each extraction tank, and the inlet 16 may be provided for each extraction tank.

The polymer used in the present invention is preferably a copolymer of vinylidene fluoride (VdF) and hexafluoropropylene (HFP), but is not limited thereto.
For example, other polymers such as polyacrylonitrile (PAN) and polymethyl methacrylate (PMMA), or a mixture or copolymer thereof may be used. The weight average molecular weight of these polymers is 100,000 to 10
100,000 is preferred. When the molecular weight is 1,000,000 or more, the viscosity of the electrolytic solution becomes high when dissolved in a solvent, it is difficult to impregnate the electrode, and when the molecular weight is 100,000 or less, the polymer is dissolved in the solvent and the network structure itself of the polymer is broken. Therefore, neither is preferable.

The first for dissolving or dispersing the above polymer
Examples of the solvent include N-methyl-2-pyrrolidone, dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran,
Organic solvents such as acetone, acetonitrile, dimethyl carbonate, ethyl acetate and butyl acetate can be used.

As the second solvent for extraction used in the extraction step, a solvent that is compatible with the first solvent and does not dissolve the polymer is used. Examples of the second solvent include water, alcohol or a mixed solvent of water and alcohol. As the water, deionized water having an electric conductivity of 5 μS / cm ² or less is preferable.

[0045] As the positive electrode active material, it is preferable that lithium ions using capable of absorbing and releasing oxides such as inorganic compounds, composition formula _Li x MO _2, or _Li y _{M 2}
O ₄ (where M is a transition metal, 0 ≦ x ≦ 1, 0 ≦ y ≦
Complex oxides, oxides having tunnel-like vacancies, and metal chalcogenides having a layered structure represented by 2) can be used. Specific examples include LiCoO ₂ , LiN
iO ₂ , LiMn ₂ O ₄ , Li ₂ Mn ₂ O ₄ , MnO ₂ , F
eOOH, FeO ₂ , V ₂ O ₅ , V ₆ O ₁₃ , TiO ₂ , T
iS ₂ , nickel oxyhydroxide and the like. Also,
Examples of the organic compound include a conductive organic polymer such as polyaniline. Furthermore, regardless of an inorganic compound or an organic compound, the above-mentioned various active materials may be mixed and used.

As the negative electrode active material, a carbon-based material,
A lithium metal, a lithium alloy, an oxide material, or the like is used. As the carbon-based material, for example, artificial or natural graphite, pyrolytic carbons, cokes, glassy carbons, fired bodies of organic polymer compounds, mesocarbon microbeads, activated carbon, graphite, carbon fibers, and the like are used. As the oxide, a compound mainly composed of tin oxide is used. These are used in a powder state.

In the battery of the present invention, the solvent of the nonaqueous electrolyte is ethylene carbonate (EC), propylene carbonate (PC), dimethyl carbonate (D
MC), diethyl carbonate (DEC), γ-butyrol cton, sulfolane, dimethyl sulfoxide, acetonitrile, dimethylformamide, dimethylacetamide, 1,2-dimethoxyethane, 1,2-diethoxyethane, tetrahydrofuran, 2-methyltetrahydrofuran, A polar solvent such as dioxolan, methyl acetate, or a mixture thereof may be used.

Further, the salts contained in the non-aqueous electrolyte include LiPF ₆ , LiBF ₄ , LiAsF ₆ , and LiClO.
₄ , LiSCN, LiI, LiCF ₃ SO ₃ , LiCl,
A lithium salt such as LiBr and LiCF ₃ CO ₂ or a mixture thereof may be used.

In the battery of the present invention, the separator is
Conventional polyolefin separators such as polyethylene and polypropylene having micropores can be used, or these separators may be used in combination with a solid polymer electrolyte. In some cases, only a polymer solid electrolyte containing an organic electrolyte may be used without using a polyolefin-based separator. As the polymer solid electrolyte containing the organic electrolyte, a gel polymer solid electrolyte, a porous polymer solid electrolyte, or the like can be used.

As the shape of the battery, batteries having any shape such as a square shape, a cylindrical shape, and a long cylindrical shape can be used.

[0051]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below using preferred embodiments.

The positive electrode sheet was prepared by mixing 80 wt% of lithium cobalt oxide (LiCoO ₂ ) as an active material, 8 wt% of acetylene black as a conductive additive, and 12 wt% of polyvinylidene fluoride (PVdF) as a binder.
-Methylpyrrolidone (NMP) was added to prepare a paste, which was 42 mm wide, 480 mm long and 20 μm thick
m of an aluminum foil current collector was applied to both sides, dried at 100 ° C., and NMP was evaporated to produce the same. The obtained positive electrode sheet has a thickness of 180 μm and has a mixture layer on both surfaces of the current collector.

First, in the impregnation step, the positive electrode sheet was passed through a polymer solution to impregnate the mixture layer with the polymer solution. Here, NMP (N-
Methyl-2-pyrrolidone) in which a polymer (copolymer of vinylidene fluoride and hexafluoropropylene) is dissolved (polymer concentration: 5 w
t%). The temperature of the polymer solution is 25 ° C.
And

The negative electrode sheet is prepared by mixing 92% by weight of graphite (graphite) as an active material and 8% by weight of polyvinylidene fluoride as a binder and mixing N-methylpyrrolidone (N
MP) to prepare a paste, which is then
m, a length of 480 mm and a thickness of 15 μm were applied to both sides of a copper foil, dried at 120 ° C. and evaporated to produce NMP.
The obtained negative electrode sheet had a thickness of 170 μm and provided a mixture layer on both sides of the current collector. The mixture layer was impregnated with the polymer solution also on the negative electrode sheet under the same conditions as the positive electrode sheet.

In the next extraction step, two extraction tanks were used, and the second solvent for extraction had an electric conductivity of 2 μS
/ Cm ² of deionized water was used. When the positive electrode sheet and the negative electrode sheet in which the mixture layer is impregnated with the polymer solution are passed through the deionized water 4 in the first extraction tank 2 and the second extraction tank 3, NMP (first Solvent) is extracted and deionized water instead penetrates into the micropores of the polymer.

In the next drying step, the positive electrode sheet and the negative electrode sheet are passed through a drying oven at 120 ° C. for about 10 minutes to remove deionized water in the fine pores of the polymer. An electrode sheet containing the porous polymer in the layer was obtained.

Here, in the extraction process, the same extraction device as that shown in FIG. 1 was used, and the positive electrode sheet and the negative electrode sheet obtained by using the extraction device provided with the filtering means 12 and the filter pump 14 were used. The battery using the positive electrode sheet and the negative electrode sheet obtained by using the battery A of Example 1 and the extraction device provided only with the filter pump 14 was used as the battery B of Example 2, and the extraction device provided only with the filtration means 12. A battery using the thus obtained positive electrode sheet and negative electrode sheet was referred to as a battery C of Example 3. A battery using a positive electrode sheet and a negative electrode sheet obtained by using a conventional extraction device having neither the filtration means 12 nor the filter pump 14 was used as a battery D of the comparative example.

Lead terminals were welded to the ends of the obtained positive electrode plate and negative electrode plate, respectively. 10 thickness for positive lead terminal
A 0 μm aluminum piece was used, and a 100 μm thick nickel piece was used for the negative electrode lead terminal. As the separator, a microporous polyethylene membrane having a width of 46 mm and a thickness of 25 μm was used.

Then, the positive electrode lead terminal and the negative electrode lead terminal are both formed as winding start portions, and the positive electrode plate, the separator, the negative electrode plate and the separator are alternately overlapped in this order, and a rectangular core of polyethylene is formed. Is wound around the power generation element in an elliptical spiral shape so that the long side is parallel to the winding center axis of the power generation element, to obtain a wound power generation element having a size of 46 × 35 × 4 mm.

The wound type power generating element was inserted into a stainless case 51 mm high, 38 mm wide and 6 mm thick to assemble a prismatic battery. Then, ethylene carbonate (EC) and diethyl carbonate (DEC) were mixed at a volume ratio of 1: 1 and an electrolytic solution to which 1 mol / l of LiPF ₆ was added was vacuum injected. After a certain period of time, the lid and the case of the battery were sealed and welded to produce 300 cells of 400 mAh nominal capacity.

These batteries were heated at 25 ° C. for 400 m
A: Charged at a constant current / constant voltage of 4.1 V for 3 hours, 400
Discharged to 2.75 V at mA. Two weeks later, at 25 ° C., the open circuit voltage (OCV) of each battery was measured. If the OCV was 3.0 V or more, the battery was determined to be a normal battery without a short circuit. Table 1 summarizes the results.

[0062]

[Table 1]

From the results shown in Table 1, it was found that the battery D of the comparative example using the electrode sheet manufactured using the conventional polymer impregnation tank was used.
Then, while the number of occurrences of the micro short-circuit was large, in the batteries A to C of Examples 1 to 3 using the electrode sheets manufactured using the extraction tank of the present invention, the batteries in which the micro short-circuit occurred were It was negligible, and the defect rate could be considerably reduced.

[0064]

According to the present invention, there is provided a method for producing a non-aqueous electrolyte secondary battery in which a polymer electrolyte is held on at least one of a positive electrode and a negative electrode. In this extraction step, a plurality of extraction tanks are provided, the electrode sheet is sequentially passed through the plurality of extraction tanks, a solvent flow path is provided between the plurality of extraction tanks, and the last extraction tank is provided in the last stage. While supplying the second solvent, the second solvent is poured from the latter extraction tank toward the former extraction tank, a filtration means is provided in the solvent flow path, and an inclination is provided on the bottom of the extraction tank, The extraction solvent is discharged from the bottom of the extraction tank, passed through a filter pump, and then circulated to the extraction tank.In the extraction process, the fine particles of the mixture contained in the extraction solvent are possible. Decrease as much as possible So, as a result, suppressing the adhesion of fine particles to the electrode sheet of the mixture layer, in which very small non-aqueous electrolyte battery of the micro short circuit can be obtained.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a detailed vertical section of an extraction step of the present invention.

FIG. 2 is a view showing a detailed vertical section of a conventional extraction step.

[Explanation of symbols]

 1, 31 Electrode sheet 2 First extraction tank 3 Second extraction tank 4, 35 Second solvent 5, 33 First turning roll 6 Guide roll in first extraction tank 7, 36 Second turning roll Reference Signs List 8 Guide roll in second extraction tank 9 Third turning roll 10 Second solvent supply port 11 Solvent flow path 12 Filtration means 13 Drainage port 14 Pipe 15 Filter pump 16 Inlet 32 Extraction tank 34 Guide roll

Continuation of the front page F term (reference) 5H029 AJ14 AK02 AK03 AK05 AK16 AK18 AL02 AL06 AL07 AL08 AL12 AM00 AM03 AM04 AM05 AM07 AM16 CJ02 CJ12 CJ23 CJ30

Claims (2)

[Claims] 1. A method for producing a non-aqueous electrolyte secondary battery in which a polymer electrolyte is held on at least one of a positive electrode and a negative electrode, wherein a polymer solution is prepared by dissolving a polymer in a first solvent. An impregnating step of impregnating the mixture layer of the electrode sheet with the polymer solution by passing through the electrode sheet, and immersing the electrode sheet in an extraction tank storing a second solvent to convert the polymer solution into the first solvent. Extraction step, and then a drying step of drying the electrode sheet to remove the second solvent is performed in order. In the extraction step, a plurality of extraction tanks are provided, and the electrode sheet is extracted by the plurality of extraction steps. Passing sequentially through the tanks, a solvent flow path is provided between the plurality of extraction tanks, and the second solvent is supplied to the last extraction tank, and from the latter extraction tank toward the former extraction tank. A second solvent is allowed to flow therein, and a filtration means is provided in the solvent flow path. 2. The extraction tank is provided with a slope on the bottom surface, the second solvent is discharged from the bottom of the extraction tank, passed through a filter pump, and then circulated to the extraction tank. A method for manufacturing a non-aqueous electrolyte secondary battery according to claim 1.