JP2002008637A - Manufacturing method of nonaqueous electrolyte secondary battery using polyelectrolyte - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce lead welding insufficiency of an electrode sheet in a nonaqueous electrolyte secondary battery using polyelectrolyte. SOLUTION: In a manufacturing method of the nonaqueous electrolyte secondary battery wherein an electrode sheet 10 that is coated with a mixture while intermittently forming non-coating parts at a current collector is made to pass in a polymer solution, and after removal of a solvent an electrolytic solution is made to be retained by a polymer in the electrode sheet, a part corresponding to a non-coated part of the electrode sheet 10 that has been made to pass in a polymer solution is wiped out by nonwoven fabric sheet 75. By this, a polymer layer which has adhered to a current collector surface of the non-coated part is wiped out, which prevents obstruction at the time of welding of the lead.

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 In recent years, in non-aqueous electrolyte secondary batteries,
For the purpose of reducing the amount of free electrolyte and improving the safety of a battery, the use of a polymer electrolyte instead of a conventional liquid electrolyte is attracting attention. This polymer electrolyte has a structure in which an electrolyte salt having ionic conductivity or an electrolyte is compatible with and held by a polymer having a solid or gel network structure.

An example of a conventional method for manufacturing a non-aqueous electrolyte secondary battery having a polymer electrolyte is as follows. First, a mixture is applied to both sides of a current collector made of a strip-shaped metal foil, and a dried electrode sheet is continuously manufactured, and this is passed through a polymer solution obtained by dissolving a polymer in a solvent to form a mixture in the mixture layer. Impregnate the polymer solution. Note that the mixture contains an active material, a conductive assistant, and a binder. Thereafter, the electrode sheet is immersed in, for example, water, and the solvent in the polymer is eluted in water, whereby the solvent and water are exchanged and dried. Then, fine holes are formed after moisture in the polymer is released, and the polymer has a porous network structure.

The electrode sheet is coated with a mixture so that a non-coated portion is formed intermittently at a predetermined length, and the current collector is exposed in the non-coated portion. Therefore, if this electrode sheet is cut at the non-applied part, the lead is welded to this, then wound together with the electrode sheet and the separator of the counter electrode to form a battery, then housed in the case and injected with the electrolyte Then, the electrolyte penetrates into the network structure of the polymer, and the electrolyte is held in the mixture by the polymer.

[0005]

However, in the above-described method for manufacturing a non-aqueous electrolyte secondary battery, when the electrode sheet is cut and the lead is welded to the exposed portion of the current collector, defective lead attachment occurs. There was a problem that it was easy. The cause is considered to be that the electrode sheet is continuously immersed in the polymer solution, so that the polymer solution also adheres to the non-applied portion of the mixture, which causes poor lead welding.

Accordingly, an object of the present invention is to provide a method for manufacturing a non-aqueous electrolyte secondary battery having a polymer electrolyte, which can prevent lead welding failure to a current collector.

[0007]

According to a first aspect of the present invention, there is provided a method of manufacturing a non-aqueous electrolyte secondary battery in which at least one of a positive electrode and a negative electrode holds a polymer electrolyte. The electrode sheet coated with the mixture while intermittently forming a non-coated portion on the belt-shaped current collector is passed through a polymer solution in which a polymer is dissolved in a solvent to form a mixture layer of the electrode sheet. After the polymer solution is impregnated in the inside and the solvent is removed, the polymer in the electrode sheet is impregnated with the electrolytic solution. The present invention is characterized in that the polymer adhering to the current collector is removed by bringing the wiping member into contact with the portion to be cleaned.

According to a second aspect of the present invention, in the first aspect of the present invention, the wiping member is constituted by a nonwoven fabric sheet movably provided between pressing rolls movable in directions approaching and separating from each other, The nonwoven fabric sheet and the electrode sheet run in opposite directions to each other, and an optical sensor is provided near the electrode sheet to detect a non-coated portion of the electrode sheet. It is characterized in that the non-woven fabric sheet is brought into contact with the non-coated portion of the electrode sheet by moving a pressing roll.

[0009]

According to the first aspect of the present invention, the polymer solution is impregnated in the mixture layer of the electrode sheet by passing the electrode sheet through the polymer solution. At this time, the polymer solution also adheres to the uncoated portion where the mixture has not been applied, and a polymer layer is formed on the surface of the current collector in that portion. However, since the polymer layer is thereafter wiped by the wiping member, there is no obstacle to welding the lead. According to the invention of claim 2, the nonwoven fabric sheet can be addressed to the electrode sheet at an appropriate timing, and automation can be performed.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to the manufacture of a lithium ion secondary battery will be described below with reference to the drawings. Although not shown in detail, the lithium ion secondary battery has a well-known structure in which both a band-shaped positive electrode and a negative electrode are wound around a separator made of, for example, a polyolefin-based porous film. For example, graphite or the like is applied to both sides of a copper foil, and the positive electrode is made of, for example, LiCoO ₂ as an active material on both sides of an aluminum foil.
A mixture containing an electrolyte solution is impregnated in the mixture layer as described later.

FIG. 1 shows an overall structure of an apparatus for impregnating a positive electrode with a polymer. Here, the electrode sheet 10 for the positive electrode is supplied from the right side in the figure, and runs toward the left side. As shown in FIG. 2, the electrode sheet 10 is formed by applying the mixture 12 to a current collector 11 made of a band-shaped aluminum foil. A non-coating portion 13 where no mixture is applied is formed for each L, and the current collector 11 is exposed here. The electrode sheet 10 is continuously supplied to the apparatus and processed. However, in the final stage, the electrode sheet 10 is cut at the non-applied section, and a lead (not shown) is welded to the non-applied section 13 together with the negative electrode and the separator. It is wound, and this is accommodated in a case and an electrolyte is injected.

Now, the present apparatus comprises a polymer impregnation stage 2
0, solvent extraction stage 40, polymer wiping stage 60
And a drying stage 80 in order. The polymer impregnation stage 20 is provided with an impregnation tank 21 storing a polymer solution, and a polymer impregnation step is performed. An impregnating roll 22 is rotatably arranged in the impregnating tank 21, and the electrode sheet 10 guided by the guide roll 23 is placed in the impregnating tank 2.
1, the polymer solution stored in the impregnation tank 21 while being turned upward by the impregnation roll 22 adheres to the entire electrode sheet 10 and is impregnated in the mixture layer. The electrode sheet 10 turned upward from the impregnation roll 22 is guided to the solvent extraction stage 40 side after passing between the pair of squeezing rolls 24.

In this embodiment, a polymer solution is prepared by dissolving a polymer (copolymer of vinylidene fluoride and hexafluoropropylene) in NMP (N methyl 2-pyrrolidone) as a solvent (concentration: 2 to 10% by weight). ).

In the solvent extraction stage 40, two water tanks 4
The electrode sheets 10 run in a meandering manner in the water stored in the water tanks 41 and 42. As a result, the solvent of the polymer solution impregnated in the mixture layer of the electrode sheet 10 dissolves into water, and water permeates into the polymer network instead (solvent extraction step). Then, the electrode sheet 10 that has passed through the water tank 42 at the subsequent stage is drawn upward, and is sent to the next polymer wiping stage 60 via the turning rollers 44 and 45 and the outlet device 46.

In the polymer wiping stage 60, as will be described in detail later, excess polymer solution adhering to the front and back surfaces of the electrode sheet 10 is wiped (wiping step). Thereafter, the electrode sheet 10 is introduced into the drying stage 80. Drying oven 81
Drive inside. This completely removes water that has penetrated into the polymer network, and the polymer becomes a porous network. The polymer is not necessarily required to be porous. However, since the polymer layer can hold a large amount of electrolyte, the conductivity is increased, and a battery having excellent high-rate discharge characteristics is obtained. It is preferred that Although not shown, the electrode sheet 10 is thereafter wound up on a reel and sent to a battery winding device. In this winding device, the electrode sheet 10 is cut at every predetermined length L (see FIG. 2), and the current collector 1 of the non-application portion 13 of the mixture is cut.
A lead is welded to 1 and spirally wound together with an electrode sheet for a negative electrode and a separator. Then, this is accommodated in the case, and when the electrolytic solution is injected into the case, the electrolytic solution permeates into the network structure of the polymer impregnated in the mixture of the positive electrode to be held in the polymer. .

The feature of the present invention resides in the polymer wiping stage 60, which will be described in more detail. As shown in FIG. 1, first and second wiping devices 61 and 62 are provided on the polymer wiping stage 60 in the vertical direction. First, the first wiping device 61 will be described with reference to FIG. A pressing roll 64 is rotatably provided on the base frame 63, and the electrode sheet 10 is laid over the pressing roll 64 to turn the traveling direction downward. Press roll 6
A pair of reflection-type photoelectric sensors 65 is provided in the vicinity of 4 (the introduction side of the electrode sheet 10), and the electrode sheet 10 runs between the photoelectric sensors 65. As a result, the non-application portion 13 of the mixture in the electrode sheet 10 is detected by the photoelectric sensor 65.
Can be detected at the timing of contact with the pressing roll 64. A slide frame 66 is supported on the base frame 63 by a linear guide 66A so as to be slidable in the left-right direction, and can be driven left and right by an air cylinder 67 fixed to the base frame 63. The other pressing roll 68 is provided on the slide frame 66 so as to be rotatable along the left side of the pressing roll 64. Thus, by operating the air cylinder 67, the state can be switched between a state in which the pressing roll 68 is moved right and left and pressed against the pressing roll 64 and a state in which the pressing roll 68 is separated therefrom.

Further, the slide frame 66 includes
The sub frame 69 is provided so as to be movable left and right with respect to the slide frame 66 by being guided by the linear guide 69A, and can be driven left and right by an air cylinder 70 fixed to the slide frame 66. The sub-roll 71 is provided with a pressing roll 68 on the sub-frame 69.
The sub-roll 71 is moved left and right by operating the air cylinder 70 to switch between a state in which the sub-roll 71 is pressed to the pressing roll 68 and a state in which the sub-roll 71 is separated therefrom.

A plurality of guide rolls 72 are provided above the pressing roll 64 to guide the electrode sheet 10 upward, and to guide it to a take-up reel 73 provided on the base frame 63. On the right side of the take-up reel 73, a non-woven fabric reel 74 is rotatably provided.
Here, a nonwoven fabric sheet 75 corresponding to a wiping member is wound. The nonwoven fabric sheet 75 has a width substantially equal to the width of the electrode sheet 10, is guided downward by a guide roll 76, is guided so as to be wound around the pressing roll 68 and the sub roll 71, and is further guided by a group of guide rolls 72. The winding reel 73 is reached.
The take-up reel 73 is driven to rotate in the direction of the arrow by a motor (not shown), and the non-woven fabric sheet 75 and the electrode sheet 10 run in the opposite direction between the pressing rolls 64 and 68.

The material of the nonwoven fabric sheet 75 is as follows.
Polypropylene, polyethylene, a mixture of polypropylene and polyethylene, a mixture of polyethylene and polyethylene terephthalate, etc. are suitable, but the key is to use a material that can hold the polymer, is resistant to friction, and has high tensile strength. I just need.

Although the second wiping device 62 is shown in FIG. 4, it has the same configuration as that of the first wiping device 61, and the same functional portions are denoted by the same reference numerals, and redundant description will be omitted. . Here, the running direction of the electrode sheet 10 is configured to pass from the top to the left, and the nonwoven sheet 75
At the portion of the pressing roll 68 from below to above.

According to the above configuration, the electrode sheet 10 impregnated with the polymer solution in the polymer impregnation stage 20
Is sent to the solvent extraction stage 40. Here, the electrode sheet 10 sequentially passes through the first water tank 41 and the second water tank 42, during which time the solvent in the polymer solution dissolves into water.
When the solvent dissolves in the water, the water penetrates into the network of the polymer, and the solvent and the water are exchanged.

The electrode sheet 10 pulled out of the second water tank 42 is first sent to a first wiping device 61. In addition,
Here, in the first and second wiping devices 61 and 62, the nonwoven fabric sheet 75 is set in advance. This will be described with reference to FIG. 5. First, the air cylinder 70 is operated to separate the sub-roll 71 from the pressing roll 68 (FIG. 5).
(A)). In this state, the nonwoven fabric sheet 75 is laid,
By operating the air cylinder 70, the sub-roll 71 is moved to the pressing roll 68 side. Thereby, the nonwoven fabric sheet 75
Is sandwiched between the rolls 68 and 71 (FIG. 5).
(B)). In this state, since the pressing roll 68 is separated from the pressing roll 64, the electrode sheet 10 travels without contacting the nonwoven fabric sheet 75. Therefore, the electrode sheet 1
The mixture layer on the zero surface is not rubbed by the nonwoven fabric sheet 75.

However, when the electrode sheet 10 runs and the non-applied portion 13 of the mixture faces the photoelectric sensor 65, the current collector 11 is exposed at this portion and the light reflectance is different. This is detected by the photoelectric sensor 65. Then, the air cylinder 67 operates at a predetermined timing delay from the detection, and the pressing roll 68 is pressed against the pressing roll 64 side. As a result, the nonwoven fabric sheet 75 is pressed against the non-coating portion 13 of the surface of the electrode sheet 10, and the current collector 11 in that portion is rubbed by the nonwoven fabric sheet 75. As a result, the polymer solution attached to the surface of the current collector 11 of the non-applied portion 13 is wiped by the nonwoven fabric sheet 75, and the metal surface of the current collector 11 is exposed.
At the time of this wiping, the nonwoven fabric sheet 75 is
And run in the opposite direction.

When the polymer solution in the non-applied portion 13 is wiped by the first wiping device 61 on one surface of the electrode sheet 10 as described above, the second wiping device 6 is similarly operated.
By 2, the polymer solution in the non-coated portion 13 on the opposite surface is wiped, and the current collector 11 in the non-coated portion 13 is exposed on both the front and back surfaces of the electrode sheet 10.

Therefore, when the electrode sheet 10 is cut and the lead is welded to the current collector 11 of the non-coated portion 13 thereafter, it is ensured that the polymer on the surface of the current collector 11 inhibits the welding. Can be prevented. The welding of the lead can be applied by either ultrasonic welding or spot welding.

Incidentally, in the following table, the lead welding defect rate was measured for several examples in which the concentration of the polymer solution was varied in this embodiment and a comparative example in which the wiping step was omitted at the same concentration. The results are shown. From this measurement result, it is apparent that the lead welding defect rate is significantly reduced in the present embodiment including the wiping step.

Polymer solution concentration (%) Wiping step Lead welding defect rate (%) Example 12 Yes 0.01 Example 2 5 Yes 0.02 Example 3 10 Yes 0.03 Comparative Example 1 2 None 2.4 Comparative Example 2 5 None 4.7 Comparative Example 3 10 None 8.9

The present invention is not limited to the above-described embodiment. For example, the following embodiments also belong to the technical scope of the present invention. (1) Examples of the polymer components of the polymer electrolyte used in the present invention is a copolymer of vinylidene fluoride and (V d _F) and hexafluoropropylene (HFP) are preferred, the invention is not limited to this, for example, polyacrylonitrile (PAN ), Polymethyl methacrylate (PMMA), or a mixture or copolymer thereof.
The weight average molecular weight of these polymers is 100,000 to 1
One million 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.

(2) As the organic solvent for dissolving or dispersing the above polymer, besides N-methyl-2-pyrrolidone, for example, dimethylformamide, methyl ethyl ketone, methyl isobutyl ketone, toluene, xylene, tetrahydrofuran, acetone, acetonitrile, dimethyl Carbonate, ethyl acetate, butyl acetate and the like can be used.

(3) In the above embodiment, the polymer is impregnated in the positive electrode. However, the polymer may be impregnated in the negative electrode. As the positive electrode mixture, it is preferable to use an oxide or the like capable of storing and releasing lithium ions. Examples of such an oxide include a lithium cobalt oxide such as LiCoO _{2 and} a lithium manganese oxide such as LiMn ₂ O ₄ . , L
lithium nickel oxide such as iNiO _{2, LiV 2 O 4}
Such as lithium vanadium oxides, these composite oxides,
There are mixtures and the like. As the negative electrode mixture, 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 addition, as a separator, a nonwoven fabric, a porous film, etc. can be used, for example. Furthermore, the nonaqueous electrolyte battery of the present invention can be used in any of a cylindrical type, a square type, a sheet type, a stacked type, a coin type, a pin type, and the like, and the shape is not particularly limited.

(4) In the above embodiment, the wiping step is performed after the solvent extraction step. However, the present invention is not limited to this. Even if the wiping step is performed between the polymer impregnation step and the solvent extraction step or after the drying step. Of course, it may be performed at any stage after the polymer impregnation step and before the lead welding step.

(5) In the above embodiment, the electrode sheet 10
Although both sides are wiped, the lead is attached by ultrasonic welding, so that only the lead attachment surface side may be wiped.

[Brief description of the drawings]

FIG. 1 is a schematic side view of a manufacturing apparatus showing one embodiment of the present invention.

FIG. 2 is a partially broken enlarged perspective view showing the structure of an electrode sheet.

FIG. 3 is a side view showing the first wiping device.

FIG. 4 is a side view showing a second wiping device.

FIG. 5 is an enlarged side view showing the operation of the pressing roll.

[Explanation of symbols]

 Reference Signs List 11 current collector 12 mixture 13 non-applied part 20 polymer impregnating stage 40 solvent extraction stage 60 polymer wiping stage 61 first wiping device 62 second wiping device 64 … Pressing roll 65… Photoelectric sensor 68… Pressing roll 71… Sub-roll 75… Non-woven fabric sheet (wiping member) 80… Drying stage

 ──────────────────────────────────────────────────の Continuing from the front page (72) Inventor Yoshihiro Kuwahara 1st Kinoshoin Nishinosho Ino Babacho, Minami-ku, Kyoto Inside Nippon Battery Co., Ltd. No. 1, Nobabacho, Japan Battery Co., Ltd. (72) Naoto Matsueda, Inventor Naoto Matsueda, Kichijoin, Minato-ku, Kyoto 5 No.1, Nitta Ichidandan-cho, Japan Mercury Tech Co., Ltd. (72) Koichi Imai, Kichijoin, Minami-ku, Kyoto 5nd in Ichidandancho, Nitta, GS Melcotec Co., Ltd. (72) Inventor Kazuki Tagawa 5th in Ichidandan, Nitta, Kichijoin, Minami-ku, Kyoto F term in GS Mercotec Co., Ltd. 5H029 AJ14 AK03 AL02 AL06 AL07 AL08 AM00 AM16 BJ02 BJ03 BJ04 CJ22 CJ23 CJ30 5H050 AA19 BA16 BA17 CA07 CA08 CA09 CB02 CB07 CB08 CB09 CB12 DA13 EA24 EA28 GA22 GA23 GA29 GA3 0

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 non-coated portion is intermittently formed on a belt-shaped current collector. The electrode sheet coated with the mixture while forming,
The polymer is passed through a polymer solution dissolved in a solvent to impregnate the polymer solution in the mixture layer of the electrode sheet, and after removing the solvent, the polymer in the electrode sheet is impregnated with the electrolytic solution. In the above configuration, the polymer attached to the current collector is removed by bringing a wiping member into contact with a portion of the electrode sheet that has passed through the polymer solution, the portion corresponding to the non-application portion of the mixture. A method for producing a non-aqueous electrolyte secondary battery having a polymer electrolyte. 2. The wiping member is constituted by a nonwoven fabric sheet provided so as to be able to travel between pressing rolls movable in directions approaching and separating from each other, and the nonwoven fabric sheet and the electrode sheet are in opposite directions. An optical sensor is provided near the electrode sheet for detecting the non-applied portion of the electrode sheet, and the pressing roller is moved based on the detection timing of the non-applied portion by the optical sensor to move the electrode sheet. The method for producing a non-aqueous electrolyte secondary battery having a polymer electrolyte according to claim 1, wherein the non-woven fabric sheet is brought into contact with the non-coated portion of (1).