JP2003068271A - Lithium secondary battery and manufacturing method of positive plate used for lithium secondary battery - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the decrease of the capacity of a battery by making the area of an active material plain part to which a positive lead is welded smaller, and to provide the battery having a superior high rate charge capability and a manufacturing method of a positive plate used for the battery. SOLUTION: A positive electrode active material layer formed on a current collector is pealed off using an ultrasonic horn, a heat plate, or a solvent-coating method, and the positive electrode active material is removed with a brush or a scraping board. The positive electrode lead 2 is welled to the positive active material plain part 11 narrower than the positive plate 1 to form the positive plate 1. The positive plate 1 and a negative plate 3 are wound around via a separator in such a way that the positive electrode lead 2 of the positive plate 1 is positioned in the active material area of the negative electrode 3, and the negative electrode lead 4 of the negative plate 3 is positioned outside of the positive electrode active material layer. The plate group of the battery is manufactured in the manner described above and the battery is manufactured using this plate group.

Description

Detailed Description of the Invention

The present invention relates to a lithium secondary battery and a method for manufacturing a positive electrode plate used in this battery, and more particularly to a lithium secondary battery having a uniform winding state of an electrode plate group and a high capacity, and a method for manufacturing a positive electrode plate used in this battery. .

[0001]

2. Description of the Related Art In recent years, the performance of mobile electronic devices such as mobile phones and personal digital assistants largely depends not only on the performance of semiconductor elements and electronic circuits, but also on the performance of rechargeable secondary batteries. It is desired to increase the capacity of the rechargeable battery to be mounted, and at the same time, realize weight reduction and compactness. As a secondary battery that meets these demands, a nickel-hydrogen storage battery having an energy density about twice that of a nickel-cadmium storage battery has been developed, and then a lithium secondary battery that exceeds this has been developed and is in the spotlight.

In this lithium secondary battery, a positive electrode and a negative electrode are arranged in a non-aqueous electrolyte solution, and each electrode plate has a positive electrode active material bound to the surface of the current collector or a negative electrode on the surface of the current collector. It has a structure in which an active material is bound. The battery electrode plate used in this battery generally collects a pasty mixture prepared by kneading and dispersing an active material (positive electrode active material or negative electrode active material), a conductive material, a binder (binder), etc. in a solvent. Apply to one or both sides of the body, dry, roll to a predetermined thickness,
It is made by cutting into a predetermined shape.

As shown in FIG. 8A, the positive electrode plate 1 of the conventional lithium secondary battery has the positive electrode lead 2 in the positive electrode active material uncoated portion 11 in which the positive electrode active material layer of the positive electrode plate 1 is partially removed. One end side is connected and the other end side is connected to the positive electrode terminal of the battery, and the negative electrode plate 3 is a negative electrode plate 3 as shown in FIG.
Negative electrode active material uncoated portion 1 in which the negative electrode active material layer of 1 is partially removed
One end side of the negative electrode lead 4 is connected to 2, and the other end side is connected to the negative electrode terminal of the battery. Insulating tapes 15 and 16 are attached to the positive electrode lead 2 and the negative electrode lead 4, respectively.

As a method of forming the positive electrode active material uncoated portion 11 and the negative electrode active material uncoated portion 12, a peeling method using an ultrasonic horn or a solvent is locally applied at a predetermined position on the active material to form the active material. A method of moistening to weaken the binding force with the current collector, and mechanically scraping this portion with a peeling tool (Japanese Patent Laid-Open No. 8-138655), heat raised to a temperature at which the binder softens A method of softening the active material layer by locally pressing the plate to release it from the metal foil and further removing the active material in the released portion using a peeling tool (JP-A-11-7939) is known. Proposed.

[0005]

However, since the active material uncoated portion for welding the leads does not contribute to the battery capacity, the area of the uncoated active material uncoated portion is formed to be small and the decrease in the battery capacity is suppressed. A battery excellent in high rate discharge is required because an active material layer is not blocked by the active material uncoated portion and a plate group having a uniform wound state can be obtained.

An object of the present invention is to provide a battery satisfying the above requirements and a method for manufacturing a positive electrode plate used therein.

[0007]

The first invention of the present application for achieving the above object is a negative electrode active material in which a positive electrode plate and a negative electrode plate are insulated via a separator, and the positions of positive electrode leads of the positive electrode plate are opposed to each other. In a lithium secondary battery in which a group of electrode plates arranged in a layer region is housed in a case, the positive electrode lead has a positive electrode active material non-coated portion without a positive electrode active material layer in a range narrower than the width of the positive electrode plate. It is characterized in that the electrode plate group is configured such that the negative electrode lead of the negative electrode plate is disposed outside the positive electrode active material layer region, and the positive electrode active material uncoated part is the positive electrode active material layer. It is desirable to form the positive electrode lead on the end side in the minimum area that enables stable welding.

According to the first invention of the present application, since the area peeled off as the uncoated portion becomes small, the positive electrode active material in the peeled portion is utilized, which contributes to the high capacity of the battery and the positive electrode plate. Since the positive electrode lead position is in the active material region of the negative electrode plate and the negative electrode lead position is outside the positive electrode active material layer, it is possible to prevent deformation of the group due to the negative electrode lead when winding the electrode plate group, A plate group with a uniform winding state is obtained, and by reducing the area of the positive electrode uncoated portion, the positive electrode active material layer is not blocked by the uncoated portion, and the electrode plate reaction area is expanded to increase the current density. Are dispersed, and as a result, they are excellent in high-rate discharge, and the manufacturing cost can be reduced by reducing the amount of leads and insulating tape used.

The second invention of the present application is a step of coating and drying a positive electrode active material on a hoop-shaped current collector, a step of rolling the coated positive electrode active material to form a hoop-shaped positive electrode plate, and a hoop. Stripping step of stripping the positive electrode active material at a predetermined interval in the width direction at predetermined intervals in the lengthwise direction with respect to the positive electrode plate, a removing step of removing the stripped active material to form a plain portion,
A method for manufacturing a positive electrode plate, which sequentially performs a step of welding a positive electrode lead to a plain portion and attaching an insulating tape, wherein the peeling step and the removing step have an area required in the width direction of the hoop-shaped positive electrode plate. The hoop-shaped positive electrode plate, which is doubled and has the uncoated portion, is slit at the center between the center of the uncoated portion and the adjacent uncoated portion to form a plurality of slits after the hoop positive electrode plate, and each slit is divided. The rear hoop positive electrode plate is wound up in parallel, the positive electrode lead is welded to the positive electrode active material uncoated portion formed on the edge of the rear hoop positive electrode plate after the slit, and then an insulating tape is attached onto the positive electrode lead. To do.

In the peeling step, an ultrasonic horn is pressed against a predetermined position of the hoop-shaped positive electrode plate at a predetermined pressure to separate the positive electrode active material layer from the current collector, or a coating nozzle with a solvent scattering prevention cover. A step of applying a solvent to a predetermined position of the hoop-shaped positive electrode plate by an apparatus to separate the positive electrode active material layer from the current collector, or pressing a hot plate heated to a predetermined temperature to a predetermined position of the hoop-shaped positive electrode plate with a predetermined pressure. A step of applying and peeling the positive electrode active material layer from the current collector can be applied.

[0011]

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

FIG. 1 is a plan view of a positive electrode plate according to the present invention. The positive electrode plate 1 includes a positive electrode active material and a binder, and if necessary, a conductive agent and a thickening agent on one or both sides of a current collector made of an aluminum foil or a foil having a thickness of 10 μm to 60 μm that has been lathed or etched. An active material layer is produced by applying a paste prepared by kneading and dispersing the agent in a solvent, drying and rolling.

The positive electrode active material is not particularly limited, but for example, a lithium-containing transition metal compound capable of accepting lithium ions as a guest is used. For example, cobalt, manganese, nickel, chromium,
Composite metal oxide of at least one metal selected from iron and vanadium and lithium, LiCoO ₂ , Li
MnO ₂ , LiNiO ₂ , LiCo _x Ni _(1-x) O ₂ (0 <
x <1), LiCrO ₂ , αLiFeO ₂ , LiVO _{2 and the} like are preferable.

The binder is not particularly limited as long as it can be kneaded and dispersed in a solvent. For example, a fluorine-based binder, acrylic rubber, modified acrylic rubber, styrene-butadiene rubber (SBR). , Acrylic polymers, vinyl polymers and the like can be used alone or as a mixture or copolymer of two or more kinds. Examples of the fluorine-based binder include polyvinylidene fluoride,
A copolymer of vinylidene fluoride and propylene hexafluoride or a dispersion of polytetrafluoroethylene resin is preferable.

If necessary, a conductive agent and a thickener can be added to the positive electrode active material and the binder. As the conductive agent, acetylene black, graphite, carbon fiber or the like is preferably used alone or in a mixture of two or more kinds. As the thickener, ethylene-vinyl alcohol copolymer, carboxymethyl cellulose, methyl cellulose and the like are preferable.

As the solvent, a solvent in which the binder is soluble is suitable, and in the case of an organic binder, N-methyl-2-
Organic solvents such as pyrrolidone, N, N-dimethylformamide, tetrahydrofuran, dimethylacetamide, dimethylsulfoxide, hexamethylsulfolamide, tetramethylurea, acetone and methylethylketone are preferably used alone or as a mixed solvent thereof, and an aqueous binder is used. In this case, water or warm water is preferable.

The method for preparing the paste mixture by kneading and dispersing the active material, the binder, and the conductive agent, which is added as necessary, in the present invention is not particularly limited. A Lee mixer, a homomixer, a pin mixer, a kneader, a homogenizer, etc. can be used. These may be used alone or in combination.

It is also possible to add various dispersants, surfactants, stabilizers, etc., if necessary, at the time of kneading and dispersing the above paste-like mixture.

The step of coating and drying on the current collector in the present invention is not particularly limited, and the paste mixture mixed and kneaded and dispersed as described above may be used, for example, in a slit die coater or a reverse roll coater. , Lip coater, blade coater, knife coater, gravure coater,
It can be easily applied by using a dip coater, and drying close to natural drying is preferable, but in consideration of productivity, drying at a temperature of 70 ° C. to 300 ° C. for 5 hours to 1 minute is preferable.

In the rolling process, a linear pressure of 1000 to 2000 kg / cm is applied by a roll press until a predetermined thickness is reached.
It is preferable to carry out rolling several times in (1) or to change the linear pressure.

In the step of peeling the active material layer in order to weld and join the positive electrode lead 2 to a predetermined position of the positive electrode plate 1, as shown in FIG. The provided ultrasonic horn 21a is arranged, or the small ultrasonic horns are arranged in parallel at the interval of the grounding portion so that the grounding portion or the small ultrasonic horns are arranged at a predetermined pressure in the hoop-shaped positive electrode plate
Means for pushing the active material layer from the current collector by pressing it against 0,
A heat plate 25 as shown in FIG. 6 is arranged at a predetermined position of the hoop-shaped positive electrode plate 20, and a means for pressing the active material layer at a predetermined pressure to separate the active material layer from the current collector, a solvent scattering prevention as shown in FIG. The coating nozzle device with a cover 28 may be arranged at a predetermined position on the hoop-shaped positive electrode plate 20, and a solvent coating may be performed to separate the active material layer from the current collector.

In the removing step, the active material separated by the metal or resin brush 22 or the scraping plate 26 is removed from the portion where the active material is separated by the above separating step.
Spark defects during lead welding can be eliminated.

Further, a stripping step and a stripping step are continuously performed at a predetermined pitch also in the length direction, and further, the active material layer is slit from the center of the hoop-shaped plain portion 24 stripped from the current collector. Then, the hoop electrode plates divided by the slits are wound in parallel so that the positive electrode lead 2
After the slit, the uncoated portion 32 for welding is positioned on the fixed side with respect to the winding direction.

A cylindrical lithium secondary battery using the positive electrode plate 1 thus manufactured will be described with reference to FIG.

In FIG. 2, the positive electrode plate 1 and the negative electrode plate 3 are placed in a bottomed battery case 8 having an open top, and a separator 5 is provided.
The other end of the positive electrode lead 2 connected to the positive electrode plate 1 accommodates the spirally wound electrode plate group in a state of being insulated via the gasket 9 through the opening of the battery case 8. The other end of the negative electrode lead 4 connected to the sealing plate for sealing and connected to the negative electrode plate is connected to the bottom of the battery case 8.

In order to manufacture an electrode plate group using an electrode plate hoop having a solid portion for welding the leads, first, the leads are welded and attached while maintaining a constant tension on the electrode plate hoop, and an insulating tape is attached. Then, the positive electrode plate 1 and the negative electrode plate 3
Must be insulated via the separator 5, and must be wound in a spiral manner so that the position of the positive electrode lead 2 of the positive electrode plate 1 is arranged in the negative electrode active material layer region of the opposing negative electrode plate 3.

The positive electrode plate 1 is attached by welding to a positive electrode active material uncoated portion 11 for welding the positive electrode lead 2. The dimension of the positive electrode active material uncoated portion 11 is 5 mm to 1 in the width direction.
It is preferable that the length is 5 mm and the dimension in the longitudinal direction is wider than the width of the positive electrode lead 1 by 1 mm to 2 mm from the viewpoints of weldability such as spot welding and resistance welding and suppression of battery capacity reduction.

The insulating tape 15 is used for the positive electrode plate 1.
By sticking so as not to cover the active material layer, it is possible to obtain an electrode plate group in which the wound state is uniform.

The negative electrode plate 3 is coated on one surface of the current collector with a negative electrode active material, a binder and, if necessary, a paste-like mixture in which a conductive additive is kneaded and dispersed in an organic solvent, and dried. It is prepared by coating the other surface of the current collector, drying and rolling.

The current collector of the negative electrode is made of copper foil, lath-processed foil, or etching-processed foil, and the thickness is preferably in the range of 10 μm to 50 μm.

The negative electrode active material is not particularly limited, but for example, a carbon material obtained by baking an organic polymer compound (phenol resin, polyacrylonitrile, cellulose, etc.), coke or pitch is baked. The carbon material thus obtained, artificial graphite, natural graphite, or the like can be used in the shape of a sphere, a scale, or a lump.

As the binder and the thickener that can be added if necessary, the same binder as used for the positive electrode plate can be used.

The separator 5 is preferably a microporous polyolefin resin such as polyethylene resin or polypropylene resin.

A negative electrode lead 4 is welded and attached to the negative electrode active material uncoated portion 12 of the negative electrode plate 3, and the negative electrode plate 4 is arranged so that the negative electrode lead 4 is disposed outside the positive electrode active material layer region. Since it is preferable to form a group, the negative electrode plate 3 is attached to the end portion in the longitudinal direction, the positive electrode plate 1 and the negative electrode plate 3 are simultaneously wound, and the negative electrode lead 4 is provided at the winding end portion of the electrode plate group.
The negative electrode plate 3 is started in advance, and the negative electrode lead 4 is arranged at the winding start portion of the electrode plate group. The negative electrode active material plain portion 12 is
Since it is outside the region of the positive electrode active material layer, the capacity does not decrease even if it is formed in the full width dimension, but from the viewpoint of reducing the manufacturing cost by reducing the usage amount of the leads and insulating tape, A range of 15 mm is preferred.
Insulating plates 6 and 7 are provided on the upper and lower portions of the electrode plate group, respectively.

Further, a non-aqueous electrolytic solution is injected into the battery case 8, and then a sealing plate 10 provided with a safety mechanism is put inward at the peripheral edge of the opening of the battery case 8 via an insulating packing 9. It is sealed by caulking.

The electrolytic solution is prepared by dissolving the electrolyte in a non-aqueous solvent. As the non-aqueous solvent,
For example, ethylene carbonate, propylene carbonate, butylene carbonate, dimethyl carbonate, diethyl carbonate, γ-butyrolactone, 1,2-dimethoxyethane, 1,2-dichloroethane, 1,3-dimethoxypropane, 4-methyl-2-pentanone, 1 ，
4-dioxane, acetonitrile, propionitrile,
Butyronitrile, valeronitrile, benzonitrile, sulfolane, 3-methyl-sulfolane, tetrahydrofuran, 2-methyltetrahydrofuran, dimethylformamide, dimethylsulfoxide, dimethylformamide,
Trimethyl phosphate, triethyl phosphate and the like can be used, and these non-aqueous solvents can be used alone or as a mixed solvent of two or more kinds.

As the electrolyte contained in the non-aqueous electrolyte, for example, a lithium salt having a strong electron-withdrawing property is used.
LiPF ₆ , LiBF ₄ , LiClO ₄ , LiAsF ₆ , L
_{iCF 3 SO 3, LiN (SO} 2 CF 3) 2, LiN (SO 2
_{C 2 F 5) 2, LiC} (SO 2 CF 3) 3 and the like. These electrolytes may be used alone or in combination of two or more. These electrolytes are preferably dissolved in the non-aqueous solvent at a concentration of 0.5 to 1.5M.

[0038]

EXAMPLES The present invention will be described in detail with reference to Examples and Comparative Examples, but these do not limit the present invention in any way.

(Example 1) A positive electrode active material uncoated portion 11 for welding a positive electrode lead 2 to a positive electrode plate 1 shown in FIG. 1 (a) was prepared as follows.

First, in the step of coating and drying the positive electrode active material on the current collector, lithium cobalt oxide is used as the positive electrode active material 10 times.
0 parts by weight, 3 parts by weight of acetylene black as a conductive agent, polytetrafluoroethylene (PTF as a binder)
E) 4 parts by weight of resin and 0.8 parts by weight of carboxymethyl cellulose were added, and the mixture was kneaded and dispersed with water as a solvent to prepare a paste. This paste is 20μ thick
When a current collector made of a strip-shaped aluminum foil of m was continuously intermittently coated and dried, and then heat-treated at 250 ° C. for 10 hours, the thickness was 290 μm. This is rolled to a predetermined thickness.

In the rolling process, a linear pressure of 1000 kg / cm was applied for 3
By performing rolling twice, the thickness was rolled to 180 μm.

In the step of peeling the active material in order to form the uncoated portion for welding the positive electrode lead 2, the peeling dimension is 5.0 m in the width direction with respect to the hoop-shaped electrode plate 20 as shown in FIG.
m, 6.0 mm in the longitudinal direction, SUS316-made concavo-convex processing ultrasonic horn 21a provided with a grounded portion and a non-grounded portion by performing concavo-convex processing at predetermined intervals.
Using the active material peeling device 21 having a pressure of 0.1 MPa, the active material layer is peeled off by pressing the hoop-shaped electrode plate 20.
The hoop-shaped peeling portion 23 was formed.

In the step of removing the peeled active material layer, the metal foil portion of the current collector is exposed by using the active material removing jig 22 composed of a brass rotating brush. As a result, the active material layer was peeled and removed from a plurality of positions in the width direction of the hoop-shaped electrode plate 20 to form the hoop-shaped plain portion 24.

The peeling process and the removing process are continuously performed in the longitudinal direction of the hoop-shaped electrode plate 20 at a pitch of 355 mm. By slitting the hoop-shaped electrode plate 20 from the center of the hoop-shaped plain part 24 and winding the cut slit hoop electrode plates 33, the post-slit plain part 32 is positioned on a certain side with respect to the winding direction. Was manufactured.

The negative electrode plate 3 shown in FIG. 1 (b) was manufactured as follows.

First, in the step of coating and drying the negative electrode active material on the current collector, 100 parts by weight of scaly graphite capable of absorbing and releasing lithium as the negative electrode active material, and styrene-butadiene rubber (SBR) as the binder. 4 parts by weight of the water-soluble dispersion as a solid content, 0.8 parts by weight of carboxymethyl cellulose as a thickening agent, and water as a solvent were added, kneaded and dispersed to prepare a paste mixture.

This paste was applied intermittently to a current collector made of a strip-shaped copper foil having a thickness of 14 μm at 110 ° C.
After drying for 30 minutes, the thickness was 300 μm.

In the rolling step, rolling was performed three times at a linear pressure of 110 Kg / cm to obtain a thickness of 196 μm.

In the step of peeling the active material to form the negative electrode active material uncoated portion 12 for welding the negative electrode lead 4, the peeling dimension is 10 in the width direction with respect to the hoop-shaped electrode plate 20 as shown in FIG. 0.0 mm, small ultrasonic horns are arranged in parallel at predetermined intervals so that they can be formed 5.0 mm in the longitudinal direction from the end in the longitudinal direction, and pressed against the hoop-shaped electrode plate 20 with a pressure of 0.2 MPa. The material layer was peeled off.

As in the case of the positive electrode plate 1, the peeled negative electrode active material is removed by using the active material removing jig 26 made of a brass rotating brush, and the longitudinal direction of the hoop-shaped electrode plate 20 is also increased. Direction is continuously performed at a pitch of 430 mm, slitting is further performed from the center of the hoop-shaped uncoated portion 24, and the slitted uncoated portion 32 is wound in parallel with the slit position 31 as a reference so that the slitted uncoated portion 32 is positioned on a certain side in the winding direction. Thus, the hoop electrode plate 33 after slitting was produced.

The procedure of welding the positive electrode lead 2 or the negative electrode lead 4 to the post-slit plain portion 32 immediately before forming the group while maintaining a constant tension in the post-slit hoop electrode plate 33 thus manufactured is excellent in mass productivity. Is preferable.

The positive electrode lead 2 is a hoop electrode plate 3 after slitting.
3 is 0.71 N / cm, while maintaining a constant tension, after slitting, the plain part 32 is made of aluminum and has a width of 4.5 m.
The positive electrode lead 2 having a length of m and a length of 14.0 mm is spot-welded and attached, and the positive electrode lead 2 is covered with an insulating tape 15 made of polypropylene resin and having a width of 6.0 mm and a length of 11.0 mm to prevent an internal short circuit. Affixed to. That is, the width dimension is 38 mm, the longitudinal dimension is 355 mm, and the width dimension of the positive electrode active material uncoated portion 11 for welding the positive electrode lead 2 is 5 m.
A positive electrode plate 1 having a length m and a longitudinal dimension of 6 mm was prepared as a positive electrode A.

The negative electrode lead 4 is the hoop electrode plate 3 after slitting.
3, while maintaining a constant tension of 0.95 N / cm, after spotting, the nickel-made negative electrode lead 4 having a width of 4.0 mm and a length of 30 mm is spot-welded and attached to the uncoated portion 32,
Further, an insulating tape made of polypropylene resin having a width of 5.0 mm and a length of 16.0 mm for preventing an internal short circuit was attached so as to cover the negative electrode lead 4. That is, the width dimension of the negative electrode plate 3 is 40 mm, the longitudinal dimension is 430 mm, and the negative electrode lead 4 is
The width of the plain part 12 of the negative electrode active material for welding is 30 mm,
A negative electrode plate 3 having a longitudinal dimension of 5.5 mm was produced.

Then, the positive electrode A and the negative electrode plate 3 are insulated via the separator 5, the position of the positive electrode lead 2 of the positive electrode A is disposed in the negative electrode active material layer region of the negative electrode 3 facing each other, and As shown in FIG. 2, the spirally wound electrode plate group is opened at the top so that the position of the negative electrode lead 4 is arranged outside the region of the positive electrode active material layer of the positive electrode A facing each other. The other end of the positive electrode lead 2 which is housed in the bottomed battery case 8 and connected to the positive electrode A is connected to the sealing plate 10, and the other end of the negative electrode lead 4 connected to the negative electrode 3 is connected to the battery case 8 Connected to the bottom of the.

An upper insulating plate 6 and a lower insulating plate 7 are arranged above and below the electrode plate group.

Further, a predetermined amount of an electrolytic solution prepared by dissolving 1.3 mol of lithium hexafluorophosphate (LiPF ₆ ) as an electrolyte in a mixed solvent of ethylene carbonate and ethyl methyl carbonate was poured, and then a gasket made of polypropylene resin was used. The battery case 8 is sealed with the sealing plate 10 through 9 and the battery capacity is 800 m with ICR17500 size.
A battery of Ah was prepared and designated as battery A.

The widthwise dimension of the uncoated portion 11 of the positive electrode A is 10
The positive electrode plates prepared in the same manner except that the thickness was 15 mm, 15 mm, 20 mm, and 30 mm were used as the positive electrodes B to D, and the batteries were used as the batteries B to D.

Example 2 A post-slit plain portion 32 for welding the positive electrode lead 2 to the positive electrode plate 1 shown in FIG. 3A was produced as follows.

The coating, drying and rolling were carried out in the same manner as in Example 1 to prepare a hoop-shaped electrode plate 20 having a thickness of 180 μm, and the peeling dimension from the hoop-shaped electrode plate 20 was 5. 0 mm, 6.0 mm in the longitudinal direction,
A hot plate 25 as shown in FIG. 6 is disposed at a predetermined position of the hoop-shaped electrode plate 20 and pressed against the hoop-shaped electrode plate 20 with a pressure of 0.3 MPa to peel the active material layer, and the hoop-shaped peeling portion 23. Was formed.

In the step of removing the peeled active material layer, the active material removing jig 26 made of a scraping plate made of urethane resin is used.
The metal foil portion of the current collector was exposed by using to remove the active material in the width direction of the hoop-shaped electrode plate 20 by peeling, and the hoop-shaped uncoated portion 24 for welding the positive electrode lead 2 was completed.

The lengthwise direction of the hoop-shaped electrode plate 20 is continuously performed at a pitch of 355 mm, which is the longitudinal dimension of the electrode plate, and the center of the hoop-shaped plain portion 24 is slit to form the slit position. A post-slit hoop electrode plate 33 was produced such that the post-slit plain portion 32 for welding the positive electrode lead 2 was positioned on a constant side with respect to the winding direction by winding in parallel with 31 as a reference.

Except for this, the positive electrode plate 1 manufactured in the same manner as in Example 1 was used as the positive electrode E, and the negative electrode plate 3 manufactured in the same manner as in Example 1 was insulated via the separator 5 to form the positive electrode E.
The positive electrode lead 2 is disposed inside the negative electrode active material layer region of the negative electrode 3 and the negative electrode lead 4 of the negative electrode plate 3 is disposed inside the positive electrode E outside the positive electrode active material layer region. As described above, the spirally wound electrode plate group is housed in a bottomed battery case 8 having an open top as shown in FIG. 2, and the positive electrode lead 2 connected to the positive electrode plate E is The other end was connected to the sealing plate 10, the other end of the negative electrode lead 4 connected to the negative electrode 3 was connected to the bottom of the battery case 8, and a battery produced in the same manner as in Example 1 was designated as a battery E. .

Example 3 An uncoated portion 11 for welding the positive electrode lead 2 to the positive electrode plate 1 shown in FIG. 3A was produced as follows.

As in Example 1, the positive electrode active material was applied to the current collector, dried, and rolled to form a hoop-shaped electrode plate 20 having a thickness of 180 μm, and the uncoated portion 11 for welding the positive electrode lead 2 was formed. In the step of peeling the active material to form the film, ethanol is formed at predetermined intervals so that the peeling dimension of the hoop-shaped electrode plate 20 as shown in FIG. 7 is 15.0 mm in the width direction and 6.0 mm in the longitudinal direction. The solvent consisting of was applied for 30 seconds using the coating nozzle device 27 with the solvent scattering prevention cover 28 to peel off the active material layer and form the hoop-shaped peeling portion 23.

Other than this, the positive electrode plate 1 manufactured in the same manner as in Example 1 was used as the positive electrode F, and the battery prepared using this was designated as the battery F.

(Comparative Example) The dimension of the plain portion 11 of the positive electrode plate 1 in the width direction is 38 mm, that is, the dimension in the longitudinal direction is 6 mm.
A positive electrode plate manufactured in the same manner as in Example 1 except that the entire width direction was a plain part was used as a positive electrode G, and a battery using this was used as a battery G.

Positive electrode plates A to G prepared in this manner
First, the relationship between the lead ground area provided on the plain portion 11 and the electric resistance was evaluated. As the evaluation method, as shown in FIG. 4, 20 sheets of each of the positive electrode plates A to G were prepared, and the active material layer at the lower end of the positive electrode plate 1 where the longest distance from the welding position of the positive electrode lead 2 was peeled off. The measurement point 11a is provided on the removed plain portion for measurement, and the result of the average value of the electrical resistance between both points measured by a digital milliohm meter is shown in Table 1.

[0068]

[Table 1] From the results of Table 1, it was feared that the electrical resistance would increase with the reduction of the lead grounding area provided in the uncoated portion 11, but the positive electrode plate G in which the uncoated portion 11 was formed over the entire width of the positive electrode plate 1 was used. No significant difference in electric resistance was observed between the positive electrode plate A to the positive electrode F in which the positive electrode lead 2 was provided on the uncoated portion 11 of the present invention.

Next, Table 1 shows the results of the average values of the prepared battery A to battery G prepared for 20 cells and evaluated for the discharge characteristics.

The test conditions are as follows:
Charging current 160mA (0.2C), constant current constant voltage charging with final voltage 4.2V, discharge current 160mA (0.2C),
800mAh (1.0C), 1600mA (2.0
C), and a constant current discharge with a final voltage of 3.0 V was used.

From the results of Table 1, as the size of the uncoated portion 11, that is, the area of the positive electrode active material facing the negative electrode increases as the area decreases, the battery capacity is improved by 0.2 C by the ratio of the increase. It was observed. Further, the discharge rate of 1.0 C (1.0 C / 0.2 C) has no correlation with the size of the active material uncoated portion, but the discharge rate of 2.0 C (2.0 C /
0.2C) has a significant difference between the battery G using the positive electrode G having the full width uncoated portion and the batteries A to F having no full width uncoated portion, and it is clear that the uncoated portion 11 is particularly preferably in the range of 5 mm to 15 mm. became. This is because the position of the positive electrode lead 2 of the positive electrode plate 1 is in the active material region of the negative electrode plate 3 and the position of the negative electrode lead 4 of the negative electrode plate 3 is outside the positive electrode active material layer. It is possible to prevent deformation of the group due to the leads 4,
An electrode plate group having a uniform winding state of the group is obtained, and by reducing the area of the uncoated portion 11, the positive electrode active material layer becomes the uncoated portion 11.
It is considered that the current density tends to be dispersed due to the expansion of the reaction area of the electrode plate without being blocked by, and as a result, it appears as an effect on the discharge rate of 2.0 C which is a high rate discharge. Be done.

In this example, a cylindrical ICR17500 size battery was used, but it is obvious that the same effect could be obtained with a rectangular battery. Also, in a battery system where the battery size is smaller and the electrode plate length is shorter,
The partially active material uncoated region of the present invention effectively acts to secure the battery capacity.

[0073]

As described above, according to the present invention, the positive electrode lead is welded to the uncoated portion of the positive electrode plate, which is narrower than the width of the positive electrode plate and does not have the positive electrode active material, and the positive electrode lead is disposed in the opposing negative electrode active material layer region. Since the lead is arranged outside the positive electrode active material layer region,
The area of the electrode plate contributing to the reaction is increased, the battery capacity is increased, and the high rate discharge performance is improved. Further, the amount of leads and insulating tape used is reduced, and the manufacturing cost can be reduced.

[Brief description of drawings]

FIG. 1A is a positive electrode plate according to an embodiment of the present invention,
(B) is a plan view of the negative electrode plate

FIG. 2 is a sectional view of a battery according to an embodiment of the present invention.

FIG. 3A is a positive electrode plate according to another embodiment of the present invention,
(B) is a plan view of the negative electrode plate

FIG. 4 is a plan view showing a method of measuring the electric resistance of the positive electrode plate.

FIG. 5 is a perspective view showing a method for manufacturing a positive electrode plate.

FIG. 6 is a perspective view showing another manufacturing method of the positive electrode plate.

FIG. 7 is a perspective view showing still another manufacturing method of the positive electrode plate.

8A is a plan view of a positive electrode plate and FIG. 8B is a plan view of a negative electrode plate according to a conventional example.

[Explanation of symbols]

1 Positive plate 2 Positive lead 3 Negative electrode plate 4 Negative electrode lead 5 separator 8 battery case 11 Solid part of positive electrode active material 12 Negative electrode active material plain area 15 Positive insulating tape 16 Negative insulating tape 20 hoop plate 21 Ultrasonic peeling device 21a Ultrasonic horn 22, 26, 29 Active material removal jig 23 Hoop-shaped peeling part 24 hoop-shaped plain area 25 hot plate 27 Solvent coating device 28 Solvent splash prevention cover 31 Slit position 32 Plain area after slitting 33 Slit back electrode plate

   ─────────────────────────────────────────────────── ─── Continued front page    F term (reference) 5H022 AA09 BB01 BB02 BB03 BB06                       BB11 BB22 BB25 BB28 CC02                       CC30                 5H029 AJ03 AJ14 AK03 AL06 AL07                       AL08 AM03 AM04 AM05 AM07                       BJ02 BJ14 CJ02 CJ03 CJ05                       CJ12 CJ22 CJ30 DJ02 DJ04                       DJ05 DJ07 HJ07 HJ15                 5H050 AA08 AA19 BA17 CA07 CA08                       CA09 CB07 CB08 CB09 DA04                       DA19 FA05 GA02 GA03 GA07                       GA09 GA12 GA22 GA30 HA07                       HA15

Claims (6)

[Claims] 1. A positive electrode plate and a negative electrode plate are insulated via a separator, and a positive electrode group disposed in a negative electrode active material layer region where the positions of the positive electrode leads of the positive electrode plate face each other is housed in a case. In the lithium secondary battery consisting of the above, the positive electrode lead is welded to a region of the positive electrode active material uncoated region where there is no positive electrode active material layer in a range narrower than the width of the positive electrode plate, and the negative electrode lead of the negative electrode plate is outside the positive electrode active material layer region. A lithium secondary battery, wherein the electrode plate group is configured so as to be disposed in. 2. The lithium secondary battery according to claim 1, wherein the uncoated portion of the positive electrode active material is formed in the minimum area where the positive electrode lead can be stably welded to the edge of the positive electrode plate. 3. A step of coating and drying a positive electrode active material on a hoop-shaped current collector, a step of rolling the coated positive electrode active material to form a hoop-shaped positive electrode plate, and a hoop-shaped positive electrode plate. A peeling step of peeling the positive electrode active material at a predetermined interval in the width direction at a predetermined feeding interval in the length direction, a removing step of removing the peeled active material to form a plain portion, and welding a positive electrode lead to the plain portion A method for manufacturing a positive electrode plate, which comprises sequentially performing a step of attaching an insulating tape, wherein the uncoated portion is formed to have a double area required in the width direction of the hoop-shaped positive electrode plate in the peeling step and the removing step. A hoop-shaped positive electrode plate with a plain part is slit in the middle of the plain part and the adjacent plain part to form a plurality of slit-post-hoop positive electrode plates, and each divided slit-post-hoop positive electrode plate is formed in parallel. Wind up and after this slit the hoop positive plate A method of manufacturing a positive electrode plate, comprising: welding a positive electrode lead to a non-coated portion of the positive electrode active material formed on the edge of the positive electrode lead, and then pasting an insulating tape on the positive electrode lead. 4. The positive electrode plate according to claim 3, wherein the peeling step is a step of pressing the ultrasonic horn against a predetermined position of the hoop-shaped positive electrode plate at a predetermined pressure to separate the positive electrode active material layer from the current collector. Manufacturing method. 5. The peeling step is a step of peeling the positive electrode active material layer from the current collector by applying a solvent to a predetermined position of the hoop-shaped positive electrode plate by a coating nozzle device with a solvent splash prevention cover. A method for producing the positive electrode plate described. 6. The peeling step is a step of pressing a hot plate heated to a predetermined temperature to a predetermined position of the hoop-shaped positive electrode plate at a predetermined pressure to separate the positive electrode active material layer from the current collector. Manufacturing method of the positive electrode plate.