JP2014035876A - Electrode manufacturing method and battery manufacturing method - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrode manufacturing method with a small strain amount.SOLUTION: According to an embodiment, an electrode manufacturing method including a compression-molding step, and a tension providing step is provided. In the compression-molding step, an active material containing layer of a belt-like electrode plate 25 is compression-molded. The belt-like electrode plate 25 comprises: a belt-like collector; a collector exposure section that is formed on at least one long side of the belt-like collector and on both face of which the active material containing layer does not exist; and an active material containing layer formed on at least one part other than the collector exposure section of the belt-like collector. In the tension providing step, the belt-like electrode plate 25 is arranged on a roller having a step portion projecting from a circumferential face and a recess adjacent to the step portion, so that the collector exposure section is positioned at the step portion and the active material containing layer is positioned at the recess, so as to apply tension in a long side direction of the belt-like electrode plate 25. A level difference of the step portion satisfies a formula (1); 750<H. In the formula, H is a magnitude (%) of the level difference when thickness of the active material containing layer of an electrode per single face of the belt-like collector is 100%.

Description

  Embodiments described herein relate generally to an electrode manufacturing method and a battery manufacturing method.

  In recent years, batteries have been used for power supply applications of hybrid electric vehicles in addition to conventional applications of small electronic devices. Accordingly, there is a demand for a battery having high capacity, long cycle life, quick chargeability, and the like. In order to fill a limited battery with as much active material as possible, the electrodes are also compressed to a higher density.

  In the manufacture of the electrode, for example, the active material-containing slurry is applied to a current collector made of a metal foil, dried, and then the application portion is compressed by a roll press device or the like. The ground current collector of the compressed coated portion also expands due to plastic deformation, but the uncoated portion where the active material-containing slurry is not coated does not apply press pressure to the current collector, and therefore does not stretch as much as the ground current collector. As a result, the residual stress acts on the boundary between the coated portion and the uncoated portion due to the difference in elongation of the current collector, and the electrode is distorted and warped.

  When laminating such electrodes on a separator and winding them, the electrodes may be damaged due to distortion or warpage, or the electrodes may be damaged or cracked when correcting the displacement. Waking up occurs. In addition, the distortion and warpage of the electrodes are a factor that deteriorates quality and yield and hinders high-speed production line operation. The cause of the distortion and warping of the electrode is the difference in elongation of the base current collector between the slurry-applied portion after compression and the uncoated portion. As a solution, for example, a method of forming a groove in a press roll and compressing and extending an uncoated portion current collector simultaneously with the coated portion, and a method of extending the current collector by plastic deformation by tensile stress are proposed. ing.

  However, since it is assumed that the method of forming grooves on the press roll requires that the roll surface, which is scraped by pressing the current collector, be re-polished at a relatively high frequency, the groove shape of the press roll Managing is not technically or economically efficient. Further, when the uncoated portion current collector is removed from the groove formed by, for example, meandering of the electrode, there is a problem that uneven compression density of the electrode or electrode breakage occurs.

On the other hand, as a method of extending the current collector by plastic deformation by tensile stress, there is an application of tension annealing generally used in rolling and processing of steel materials. By applying a tensile stress to the workpiece while heating, there is an effect of reducing the stress required for elastic deformation. For example, when an aluminum foil is used for the current collector, the standard of stress required for plastic deformation is 100 N / mm ² or more, although it depends on the thickness and purity of the aluminum. By heating the current collector, the stress required for plastic deformation can be greatly reduced. However, when the active material-containing layer of the electrode contains materials / components that may be deteriorated at a high temperature and deteriorate the battery performance, the heating temperature must be limited. As a result, the tensile stress cannot be significantly reduced within the application range of the heating temperature, and several times the stress necessary for winding up the electrode is required. There is concern about a decline.

JP 2001-297553 A JP 2009-104850 A

  An object of the present invention is to provide a method for manufacturing an electrode with a small amount of distortion and a method for manufacturing a battery using this method.

  According to the embodiment, an electrode manufacturing method including a compression molding step and a tension applying step is provided. In the compression molding step, the active material-containing layer of the strip electrode plate is subjected to compression molding. The strip-shaped electrode plate is formed on at least one long side of the strip-shaped current collector and the strip-shaped current collector, and the current collector exposed portion where the active material-containing layer does not exist on both sides, and the current collector exposure of the strip-shaped current collector And an active material-containing layer formed on at least a part other than the part. In the tension applying step, the belt-like electrode plate is disposed on the roller having the step portion protruding from the circumferential surface and the concave portion adjacent to the step portion, the current collector exposed portion is located at the step portion, and the active material containing layer Are arranged so as to be positioned in the recesses, and tension is applied in the long side direction of the strip-shaped electrode plate. The step of the step satisfies the following formula (1).

750 <H (1)
However, H is the size (%) of the step when the thickness of the active material-containing layer of the electrode per side of the belt-like current collector is 100%.

  In addition, according to the embodiment, a method for manufacturing a battery including a positive electrode, a negative electrode, and a nonaqueous electrolyte is provided. At least one of the positive electrode and the negative electrode is manufactured by the electrode manufacturing method according to the embodiment.

FIG. 1 is a schematic diagram showing one step of the method according to the first embodiment. FIG. 2 is a schematic diagram showing the positional relationship between the guide roller and the strip electrode plate in FIG. FIG. 3 is a cross-sectional view showing the positional relationship between the guide roller and the strip electrode plate used in the first embodiment. FIG. 4 is a cross-sectional view showing the positional relationship between the guide roller and the strip electrode plate used in the first embodiment. FIG. 5 is an exploded perspective view of a battery manufactured by the method according to the second embodiment. 6 is a partially developed perspective view of an electrode group used in the battery shown in FIG. FIG. 7 is a schematic diagram illustrating a method of measuring the amount of strain of the electrode of the example.

  Hereinafter, embodiments will be described with reference to the drawings.

(First embodiment)
FIG. 1 is a schematic diagram showing a press device, a guide roller device, and a winding device used for manufacturing an electrode. FIG. 2 is a schematic diagram showing the positional relationship between the guide roller and the strip electrode plate in the curvature correction process. FIG. 2A is a plan view of the strip electrode plate running on the guide roller as viewed from the guide roller side, and FIG. 2B is obtained by cutting the guide roller parallel to the rotation axis. It is sectional drawing obtained. 3A is a cross-sectional view obtained when a guide roller having a taper formed at the corner of the step portion is cut in parallel to the rotation axis. FIG. 3B is a cross-sectional view of FIG. It is sectional drawing which shows the state which has arrange | positioned the strip | belt-shaped electrode plate to the guide roller shown in FIG. 4A is a plan view of the strip electrode plate running on the guide roller as viewed from the guide roller side, and FIG. 4B is a view of cutting the guide roller parallel to the rotation axis. It is sectional drawing obtained.

As shown in FIG. 1, a pressing device 21, a guide roller device 22, and a winding device 23 are arranged from the front side to the rear side of the manufacturing process. The press device 21 has a pair of press rolls 21a and 21b. The press rolls 21a and 21b are compression-molded by rotating a belt-like electrode plate 25 inserted between the press rolls 21a and 21 by being rotated in the direction of the arrow shown in FIG. The winding device 23 is configured such that the belt-like electrode plate 25 is wound in a hoop shape by rotating a rotating shaft 23a in the direction of the arrow shown in FIG. 1 by a drive unit (not shown). The guide roller device 22 is for conveying the belt-like electrode plate 25 from the press device 21 to the winding device 23, and has a plurality of metal guide rollers 24 _{1 to} 24 ₅ (driven rollers). Tension (winding tension) is applied in the longitudinal direction to the strip-shaped electrode plate 25 conveyed from the press rolls 21a and 21b to the winding device 23. The guide rollers 24 _{1 to} 24 ₅ are alternately arranged on the upper and lower surfaces of the strip electrode plate 25 so that the tension applied to the strip electrode plate 25 falls within a desired range suitable for winding. Guide rollers 24 ₃ also serves as a bending straightening device. Guide roller 24 _3, as shown in FIG. 2 (b), it has a stepped portion 26 protruding from the circumferential surface on one end of the rotation axis direction. In the guide roller 24 ₃ , the remaining portion adjacent to the step portion 26 is a recess 27.

  Hereinafter, an electrode manufacturing method using the apparatus shown in FIG. 1 will be described. First, the strip electrode plate 25 is produced. As shown in FIG. 2A and FIG. 3B, the strip electrode plate 25 is formed on one long side of the strip current collector and the strip current collector. It includes a current collector exposed portion 25a that does not exist, and an active material-containing layer 25b that is formed on both sides of the strip-shaped current collector other than the current collector exposed portion 25a. The active material-containing layer 25b is continuously formed in the long side direction of the strip-shaped current collector. The width in the short side direction of the active material containing layer 25b is wider than that of the current collector exposed portion 25a. The strip electrode plate 25 is obtained, for example, by applying an active material-containing slurry to a strip collector on both sides except for one long side, and drying. Or after apply | coating an active material containing slurry partially on both surfaces of a collector, and drying, it cuts so that the uncoated part used as a collector exposed part may be located in a long side, and can form the strip | belt-shaped electrode plate 25. obtain.

  The active material-containing slurry is prepared, for example, by adding a conductive agent and a binder to the active material as necessary, and kneading them in the presence of a solvent. As the active material, either a positive electrode or a negative electrode may be used.

The active material of the positive electrode is not particularly limited, and various oxides such as lithium-containing cobalt oxide (for example, LiCoO ₂ ), manganese dioxide, lithium manganese composite oxide (for example, LiMn ₂ O ₄ , LiMnO) ₂ ), lithium-containing nickel oxide (eg, LiNiO ₂ ), lithium-containing nickel cobalt oxide (eg, LiNi _0.8 Co _0.2 O ₂ ), lithium-containing iron oxide, lithium-containing vanadium oxide, titanium disulfide, Examples include chalcogen compounds such as molybdenum disulfide.

  The active material of the negative electrode is not particularly limited, and for example, a graphite material or a carbonaceous material (for example, graphite, coke, carbon fiber, spherical carbon, pyrolytic vapor carbonaceous material, resin fired body, etc.), chalcogen Compound (eg, titanium disulfide, molybdenum disulfide, niobium selenide, etc.), light metal (eg, aluminum, aluminum alloy, magnesium alloy, lithium, lithium alloy, etc.), lithium titanium oxide (eg, spinel type lithium titanate) And the like.

  The conductive agent is not particularly limited, and examples thereof include graphite, carbonaceous material, acetylene black, and carbon black. The binder is not particularly limited, and for example, polytetrafluoroethylene (PTFE), polyvinylidene fluoride (PVdF), or fluorine-based rubber can be used.

  A metal foil can be used for the strip-shaped current collector. Examples of the metal foil include an aluminum foil, an aluminum alloy foil, and a copper foil. The thickness of the strip-shaped current collector can be 50 μm or less.

  Next, the obtained strip-shaped electrode plate 25 is inserted between press rolls 21a and 21b rotating in the direction of the arrow shown in FIG. 1 and subjected to compression molding. Since the insertion direction of the strip electrode plate 25 is parallel to the longitudinal direction of the strip electrode plate 25, the pressing pressure is mainly applied to the active material-containing layer 25b, and the active material-containing layer 25b is compression-molded to increase the density. Since almost no pressing pressure is applied to the current collector exposed portion 25a, the elongation is smaller than that of the base current collector of the active material-containing layer 25b. As a result, the belt-like electrode plate 25 is distorted or warped.

The strip electrode plate 25 that has passed between the press rolls 21a and 21b is conveyed to the winding device 23 via the guide rollers 24 _{1 to} 24 ₅ . In the guide roller 24 _3, which also serves as a bending straightening device, as shown in FIGS. 2 and 3, the boundary X between the stepped portion 26 and the recess 27, the boundary between the current collector exposed portion 25a and the active material-containing layer 25b Only the current collector exposed portion 25 a is located on the stepped portion 26. The active material containing layer 25 b is disposed in the recess 27. Thereby, the winding tension applied in the conveying direction (longitudinal direction) of the strip electrode plate 25 can be concentrated on the current collector exposed portion 25a. As a result, the current collector exposed portion 25a can be sufficiently extended by the winding tension, so that the distortion and warpage generated in the strip electrode plate 25 can be corrected. The strip electrode plate 25 that has passed through the guide roller 24 ₃ is wound around the winding device 23 via the guide rollers 24 ₄ , 24 ₅ . Subsequently, the electrode is obtained by cutting the hoop-shaped strip electrode plate 25 into a desired size as necessary. The strip electrode plate 25 can be used as an electrode as it is.

In the strip-shaped electrode plate 25 before compression molding, the entire strip-shaped current collector is not stretched. Therefore, when the strip-shaped electrode plate 25 before compression molding is brought into contact with the guide roller 24 ₃ , the current collector exposed portion 25a on the step portion 26 is obtained. In addition, the winding tension (stress) is dispersed in the active material-containing layer 25b. After compression molding, the base current collector of the active material-containing layer 25b is stretched and loosened, so that the winding current (stress) is hardly applied to the base current collector of the active material-containing layer 25b and is not stretched. The winding tension can be concentrated on the exposed portion 25a. At this time, the amount of distortion of the electrode can be reduced by about 10% after the electrode is wound around the winding device 23 with the same tension as the winding tension at the time of compression.

However, when the guide roller 24 _third step section 26 the active material-containing layer 25b on are arranged, the winding tension is to distribute to the active material-containing layer 25b, the winding tension of the collector-exposed portion 25a Concentration becomes insufficient, and the base current collector of the active material-containing layer 25b that has already been stretched may be further extended, so that the distortion and warping of the electrode are not corrected.

Guide rollers 24 step H of the step portion 26 provided in the ₃ (%) is below the thickness per one side strip collector of the active material-containing layer upon 100% (1) satisfies the formula. Here, the thickness per side of the strip-shaped current collector of the active material-containing layer is the thickness per side of the strip-shaped current collector of the active material-containing layer in the manufactured electrode.

750 <H (1)
For example, even when the step H is 750% or less, it is possible to correct the distortion and warping of the electrode. However, since the current collector is plastically deformed and sufficiently stretched to obtain a sufficient correction effect, a certain time is required, so that the processing speed is limited. By making the step H larger than 750%, it becomes possible to obtain a sufficient effect in an extremely short processing time, to realize a high-speed operation of the production line, and to improve the production capacity in the correction process. In addition, when the thickness of the belt-shaped current collector is 50 μm or less and the step H exceeds 2000%, there is a risk of causing cracks or breaks.

Corner of the stepped portion 26 provided on the guide roller 24 _3, it may be a right angle or substantially a right angle as illustrated in FIG. 2 (b), may be provided a taper. As shown in FIGS. 3A and 3B, the taper is desirably formed at a portion where the boundary X between the step portion 26 and the recess 27 intersects with the upper surface of the step portion 26. The taper R (mm) is preferably R ≦ 15. By setting the taper R to 15 mm or less, the stress can be sufficiently concentrated and extended on the current collector exposed portion. The smaller the taper R is, the larger the effect of extending the exposed portion of the current collector is. However, there is a possibility that the electrode breaks when the electrode meanders. Therefore, the range of 0.5 ≦ R ≦ 7 is more preferable.

  The taper R is calculated by coordinate plotting several points on the R surface of the R portion of the step portion 26 with a three-dimensional measuring instrument. As the three-dimensional measuring instrument, for example, a three-dimensional measuring machine (model: WMM550) manufactured by Carl Zeiss Co., Ltd. can be used.

At least in the curvature correcting step, it is preferable that the tensile stress F (N / mm ² ) in the cross section parallel to the short side direction of the strip-shaped electrode plate 25 is in the range of 20 ≦ F ≦ 100. By setting the tensile stress F to 20 (N / mm ² ) or more, the current collector exposed portion can be sufficiently extended while satisfying the stress necessary for winding the electrode with high accuracy. By setting the tensile stress F to 100 (N / mm ² ) or less, the current collector exposed portion can be sufficiently extended without causing problems of electrode breakage and winding accuracy reduction. Therefore, by setting the tensile stress F (N / mm ² ) in the range of 20 ≦ F ≦ 100, the current collector exposed portion can be sufficiently extended without breaking the electrode and accurately winding the electrode. Can do. Although depending on the conditions of the step H and the taper R described above, the range of 20 ≦ F ≦ 40 is more preferable in order to enhance the effect of preventing the electrode from breaking and winding accuracy.

  It is desirable to correct the curvature of the strip electrode while performing a heat treatment at a temperature of 60 ° C. or higher and 150 ° C. or lower. By setting the heat treatment temperature T to 60 ° C. or more, the effect of reducing the stress required for plastic deformation can be enhanced. Further, when the stress applied to the strip electrode plate is the same, the effect of correcting the distortion and warpage of the electrode can be enhanced by heating. These effects are more easily obtained when the heat treatment temperature T is higher, but the heat treatment temperature T is preferably in the range of 60 ° C. or higher and 150 ° C. or lower in order to avoid alteration of the active material-containing layer due to heat.

  In FIG. 1, a press roll is used as the press device 21, but any press material that can increase the density of the active material-containing layer can be used instead of the press roll. For example, a flat plate press can be used instead of the press roll. The pressing process may be performed by changing the pressing pressure in multiple stages.

In FIG. 1, one guide roller among the plurality of guide rollers is used as the curvature correcting device, but the number of guide rollers used as the curvature correcting device is not limited to one, and a plurality of all or all of the guide rollers are used. be able to. Further, the position of the guide roller used as the curvature correcting device is not limited to the _third guide roller 243 from the front stage side, and a guide roller at an arbitrary position can be used.

In FIG. 2, the step portion 26 protruding from the circumferential surface is provided at one end portion in the rotation axis direction of the guide roller 24 ₃ , but the method of forming the step portion is not limited to this, and the current collector exposed portion is Any material can be used as long as the effect of stretching can be obtained. For example, as illustrated in FIG. 4, an annular step portion 26 protruding from the circumferential surface can be provided near the center in the rotation axis direction, and the circumferential surfaces on both sides adjacent to the step portion 26 can be formed as the recesses 27. .

  In FIGS. 2 to 4, the current collector exposed portion is provided only on one long side of the strip electrode plate, but the current collector exposed portion may be provided on both long sides of the strip electrode plate. Providing current collector exposed portions on both long sides of the strip electrode plate can further enhance the effect of preventing warping and distortion of the electrode. On the other hand, when the current collector exposed portion is provided only on the long side of one side of the strip electrode plate as shown in FIG. 2, a high battery capacity and energy density can be obtained.

  In FIGS. 2 to 4, the active material-containing layer is provided on both surfaces of the strip-shaped electrode plate.

  2 to 4, the active material-containing layer is continuously formed in the long-side direction of the strip-shaped current collector. However, the active material-containing layer is intermittently formed in the long-side direction of the strip-shaped current collector. You may provide an active material content layer non-formation part between content layers.

  According to the first embodiment described above, the strip-shaped electrode plate subjected to compression molding is arranged such that the current collector exposed portion is located in the stepped portion of the roller and the active material-containing layer is located in the recessed portion of the roller. Since the tension is applied in the long side direction of the belt-like electrode plate, the tension can be concentrated on the current collector exposed portion, and the current collector exposed portion can be sufficiently stretched by plastic deformation. In addition, by making the step H of the step portion larger than 750%, it becomes possible to obtain a sufficient effect in an extremely short processing time, to realize a high-speed operation of the production line, and thus to improve the production capacity. . Therefore, the distortion and the curvature which arose in the electrode by compression molding can be corrected in a short time. In addition, the electrode can be prevented from being broken when the electrode group is manufactured. As a result, an electrode with excellent quality can be manufactured with high production efficiency.

(Second Embodiment)
According to 2nd Embodiment, the manufacturing method of a battery provided with a positive electrode, a negative electrode, and a nonaqueous electrolyte is provided. At least one of the positive electrode and the negative electrode is manufactured by the method according to the first embodiment. FIG. 5 is an exploded perspective view of a nonaqueous electrolyte battery manufactured by the method according to the second embodiment. 6 is a partially developed perspective view of an electrode group used in the battery shown in FIG.

  The battery shown in FIG. 5 is a sealed prismatic non-aqueous electrolyte secondary battery. The nonaqueous electrolyte secondary battery includes an outer can 1, a lid 2, a positive electrode output terminal 3, a negative electrode output terminal 4, and an electrode group 5. As shown in FIG. 5, the outer can 1 has a bottomed rectangular tube shape, and is formed of a metal such as aluminum, an aluminum alloy, iron, or stainless steel, for example.

  As shown in FIG. 6, the flat electrode group 5 has a positive electrode 6 and a negative electrode 7 wound in a flat shape with a separator 8 therebetween. The positive electrode 6 is a positive electrode current collector except for a strip-shaped positive electrode current collector made of, for example, a metal foil, a positive electrode current collector tab 6a formed of a current collector exposed portion of the positive electrode current collector, and at least a portion of the positive electrode current collector tab 6a. A positive electrode active material layer 6b formed on the body. On the other hand, the negative electrode 7 is a negative electrode except for a strip-shaped negative electrode current collector made of, for example, a metal foil, a negative electrode current collector tab 7a formed of a current collector exposed portion of the negative electrode current collector, and at least a portion of the negative electrode current collector tab 7a. And a negative electrode active material layer 7b formed on the current collector.

  In the positive electrode 6, the separator 8, and the negative electrode 7, the positive electrode current collecting tab 6 a protrudes from the separator 8 in the winding axis direction of the electrode group, and the negative electrode current collecting tab 7 a protrudes from the separator 8 in the opposite direction. Thus, the positive electrode 6 and the negative electrode 7 are wound while being shifted in position. As a result of such winding, as shown in FIG. 6, the electrode group 5 has the positive electrode current collecting tab 6a wound spirally from one end face and is wound spirally from the other end face. The negative electrode current collection tab 7a protrudes.

  An electrolytic solution (not shown) is impregnated in the electrode group 5. The rectangular plate-like lid 2 is seam welded to the opening of the outer can 1 by, for example, a laser. The lid 2 is made of a metal such as aluminum, aluminum alloy, iron or stainless steel, for example. The lid 2 and the outer can 1 are preferably formed from the same type of metal.

  As shown in FIG. 5, a safety valve 9 is provided near the center of the outer surface of the lid 2. The safety valve 9 has a rectangular recess 9a provided on the outer surface of the lid 2 and an X-shaped groove 9b provided in the recess 9a. The groove 9b is formed, for example, by press-molding the lid 2 in the plate thickness direction. The liquid injection port 10 is opened in the lid 2 and sealed after the electrolytic solution is injected.

  On the outer surface of the lid 2, positive and negative output terminals 3, 4 are fixed by caulking via insulating gaskets (not shown) on both sides of the safety valve 9. In the case of a lithium ion secondary battery using a carbon-based material for the negative electrode active material, for example, aluminum or an aluminum alloy is used for the positive electrode output terminal 3, and for example, copper, nickel, nickel plating is used for the negative electrode output terminal 4. Used metals such as iron are used. When lithium titanate is used as the negative electrode active material, in addition to the above, aluminum or an aluminum alloy may be used for the negative electrode output terminal 4.

  One end of the positive electrode lead 11 is electrically connected to the positive electrode output terminal 3 by caulking or welding, and the other end is electrically connected to the positive electrode current collecting tab 6a. One end of the negative electrode lead 12 is electrically connected to the negative electrode output terminal 4 by caulking or welding, and the other end is electrically connected to the negative electrode current collecting tab 7a. A method of electrically connecting the positive and negative electrode leads 11 and 12 to the positive and negative electrode current collecting tabs 6a and 7a is not particularly limited, and examples thereof include welding such as ultrasonic welding and laser welding.

  In this way, the positive electrode output terminal 3 and the positive electrode current collecting tab 6 a are electrically connected via the positive electrode lead 11, and the negative electrode output terminal 4 and the negative electrode current collecting tab 7 a are electrically connected via the negative electrode lead 12. As a result, current can be taken out from the positive and negative output terminals 3 and 4.

  The material of the positive and negative electrode leads 11 and 12 is not particularly specified, but is preferably the same material as that of the positive and negative electrode output terminals 3 and 4. For example, when the material of the output terminal is aluminum or an aluminum alloy, it is preferable that the material of the lead is aluminum or an aluminum alloy. Further, when the output terminal is copper, it is desirable that the material of the lead is copper.

  Here, the separator and the non-aqueous electrolyte will be described.

  The separator is not particularly limited, and for example, a microporous film, a woven fabric, a non-woven fabric, a laminate of the same material or different materials among these can be used. Examples of the material for forming the separator include polyethylene, polypropylene, ethylene-propylene copolymer, ethylene-butene copolymer, and cellulose.

As the non-aqueous electrolyte, a non-aqueous electrolyte solution in which an electrolyte (for example, a lithium salt) is dissolved in a non-aqueous solvent can be used. Nonaqueous solvents include, for example, ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), dimethyl carbonate (DMC), diethyl carbonate (DEC), ethyl methyl carbonate (EMC), γ-butyrolactone (γ- BL), sulfolane, acetonitrile, 1,2-dimethoxyethane, 1,3-dimethoxypropane, dimethyl ether, tetrahydrofuran (THF), 2-methyltetrahydrofuran and the like. Nonaqueous solvents may be used alone or in combination of two or more. Examples of the electrolyte include lithium perchlorate (LiClO ₄ ), lithium hexafluorophosphate (LiPF ₆ ), lithium tetrafluoroborate (LiBF ₄ ), lithium hexafluoroarsenate (LiAsF ₆ ), and trifluoromethanesulfonic acid. A lithium salt such as lithium (LiCF ₃ SO ₃ ) can be given. The electrolyte may be used alone or in combination of two or more. The amount of electrolyte dissolved in the non-aqueous solvent is desirably 0.2 mol / L to 3 mol / L. If the electrolyte concentration is too low, sufficient ionic conductivity may not be obtained. On the other hand, if it is too high, it may not be completely dissolved in the electrolyte.

  According to the second embodiment described above, the strip-shaped electrode plate that has been subjected to compression molding is arranged such that the current collector exposed portion is located at the stepped portion of the roller and the active material-containing layer is located at the recessed portion of the roller. Since the tension is applied in the long side direction of the belt-like electrode plate, the tension can be concentrated on the current collector exposed portion, and the current collector exposed portion can be sufficiently stretched by plastic deformation. Also, by making the step H of the step portion larger than 750%, it becomes possible to obtain a sufficient effect in an extremely short processing time, realizing a high-speed operation of the production line, and thus improving the production capacity in the correction process. I can do it. Therefore, the distortion and the curvature which arose in the electrode by compression molding can be corrected in a short time. In addition, it is possible to eliminate problems such as electrode breakage, winding misalignment, wrinkles, cracks, etc. that have occurred in the process of producing a wound electrode group, so that it is possible to manufacture electrodes with excellent quality and production efficiency. Can do.

  Examples will be described below, but the embodiments are not limited to the examples listed below unless they exceed the gist of the embodiments.

Example 1
Examples of positive and negative electrodes for lithium ion secondary batteries are shown below.

LiCoO ₂ as a positive electrode active material, graphite powder as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were mixed and dispersed in an organic solvent to prepare a slurry. The obtained slurry was applied to a strip-shaped aluminum foil as a current collector except for both sides of the long side, and then dried to prepare a strip-shaped positive electrode plate.

Li ₄ Ti ₅ O ₁₂ as a negative electrode active material, carbon powder as a conductive agent, and polyvinylidene fluoride (PVdF) as a binder were mixed and dispersed in an organic solvent to prepare a slurry. The obtained slurry was applied to a strip-shaped aluminum foil as a current collector, excluding both sides of the long side, and then dried to prepare a strip-shaped negative electrode plate.

Each of the belt-like positive electrode plate and the belt-like negative electrode plate was compressed into a hoop shape by the winding device 23 via the guide roller device 22 after compressing the active material-containing layer with the press device 21 shown in FIG. In the guide roller 24 _3, which also serves as a bending straightening device, the boundary X between the stepped portion 26 and the recess 27, to position the boundary between the current collector exposed portion 25a and the active material-containing layer 25b, and collector-exposed portion 25a The active material-containing layer 25 b was disposed in the recess 27 on the stepped portion 26. Table 1 shows a step H and a taper R of the step portion 26. In addition, a tensile tension (winding tension) was applied in the longitudinal direction of each of the belt-like positive electrode plate and the belt-like negative electrode plate from the compression molding step by the press device 21 to the winding device 23 winding the hoop shape. Table 1 shows the tensile stress F in the cross section parallel to the short side direction of each of the belt-like positive electrode plate and the belt-like negative electrode plate. In each of the belt-like positive electrode plate and the belt-like negative electrode plate, the heat treatment was not performed in the curvature correction step, and the curvature correction was performed in a room temperature (RT) atmosphere.

Each of the positive electrode plate and the negative electrode plate wound in a hoop shape by the winding device 23 was cut into a length of 1 m, and the amount of distortion was measured. In the case of the positive electrode 6, the amount of strain is the shortest distance Y ₁ between a point parallel to the length L (1 m) of the positive electrode 6 and the most curved portion of the positive electrode 6, as shown in FIG. In the case of the negative electrode 7, the shortest distance Y ₂ between a point parallel to the length L (1 m) of the negative electrode 7 and the most curved portion of the negative electrode 7 is defined as the strain amount. Table 1 shows the measurement results of the strain amount.

  After measuring the amount of strain, a separator is disposed between the positive electrode and the negative electrode, and a positive electrode current collecting tab made of a current collector exposed portion is protruded from the separator in the winding axis direction of the electrode group, and a current collector exposed portion is formed. The negative electrode current collection tab was protruded from the separator in the opposite direction, and wound into a flat shape to produce the electrode group shown in FIG.

(Examples 2 to 13 and Comparative Examples 1 and 2)
Similar to Example 1, except that the step H of the step provided on the guide roller, the taper R, the tensile stress F of the strip-like positive and negative plates, and the heating temperature T of the electrode are as shown in Table 1. did. In Comparative Example 1, the guide roller was not provided with a step portion, and no electrode distortion or warpage was corrected. In addition, when the heating temperature T is displayed as “RT”, the curvature was corrected in a room temperature (RT) atmosphere. In Example 13, in which the heating temperature T is 140 ° C., the straightening was performed while heating the positive and negative electrode plates at 140 ° C.

  About the Example and the comparative example, the production capacity (tact time required for the machining) of the straightening process was measured, and the result is shown in Table 2 as Comparative Example 2 being 1. Also, the rate of occurrence of defects (electrode misalignment) caused by electrodes in the winding process during electrode group production, and the production capacity (takt time required for the winding process) in the winding process during electrode group production These results are shown in Table 2 with Comparative Example 2 as 1.

Furthermore, the presence or absence of wrinkles, cracks and electrode breaks during the winding process in electrode group production was measured, and the results are shown in Table 2.

  As can be seen from Tables 1 and 2, according to Examples 1 to 13, both the positive electrode strain amount and the negative electrode strain amount are smaller than those of Comparative Example 1. Moreover, according to Examples 1-13, the electrode fracture at the time of electrode preparation, the wrinkles and crack which arise in an electrode are none, and the defect rate at the time of electrode group preparation resulting from an electrode is small compared with the comparative example 1. On the other hand, in Comparative Example 2, since the level difference of the step portion was 750%, the production capacity of both the straightening process and the winding process was inferior to that of Example 1.

  From the comparison of Examples 1 to 4, the larger the difference in level H, the smaller the distortion of the positive and negative electrodes, the higher the production capacity of both the correction process and the winding process, and the lower the defect rate during electrode group production. It can be seen that

  In addition, although the example applied to the wound electrode group has been described in the above-described embodiments, the present invention is also applicable to a so-called stacked electrode group in which the positive electrode and the negative electrode are alternately stacked with a separator interposed therebetween. Can do. According to the embodiment, the distortion and warpage generated in the electrode by compression molding can be corrected with high production efficiency. Therefore, the stacked electrode group is formed by alternately stacking the positive electrode and the negative electrode with a separator interposed therebetween. When the is manufactured, no flaws, cracks or breaks occur in the positive electrode and the negative electrode, and the defect rate in the electrode group manufacturing can be reduced.

  According to at least one embodiment and example described above, a belt-shaped electrode plate using a roller having a step H of more than 750% and a compression molding is used, and a current collector exposed portion is a step portion of the roller. And the active material containing layer is positioned so as to be located in the concave portion of the roller, and tension is applied in the long side direction of the strip electrode plate, so that the tension can be concentrated on the current collector exposed portion. The body-exposed portion can be plastically deformed and sufficiently extended in a short time. Thereby, the distortion and the curvature which arose in the electrode by compression molding can be corrected with high production efficiency, without increasing the tension | tensile_strength added to a strip | belt-shaped electrode plate significantly. In addition, it is possible to prevent electrode breakage during the production of the electrode group.

  Although the embodiments and examples have been described above, the present invention is not limited to those described. For example, depending on the thickness and weight of the active material-containing paste applied, the ratio between the coated part and the uncoated part, the compression density of the electrode plate, or the influence of the second process, The same effect can be obtained by appropriately changing the shape, tensile stress, and the like. Furthermore, the active material paste can be applied continuously or intermittently, and the same effect can be obtained. The current collecting base material of the electrode is not limited to the aluminum foil, and its material, thickness, tension, etc. The same effect can also be obtained by appropriately changing the height and shape of the step, the tensile stress, etc. according to the strength and hardness.

  Although several embodiments of the present invention have been described, these embodiments are presented by way of example and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other forms, and various omissions, replacements, and changes can be made without departing from the scope of the invention. These embodiments and modifications thereof are included in the scope and gist of the invention, and are included in the invention described in the claims and the equivalents thereof.

DESCRIPTION OF SYMBOLS 1 ... Exterior can, 2 ... Cover, 3 ... Positive electrode output terminal, 4 ... Negative electrode output terminal, 5 ... Electrode group, 6 ... Positive electrode, 6a ... Positive electrode current collection tab, 6b ... Positive electrode active material containing layer, 7 ... Negative electrode, 7a DESCRIPTION OF SYMBOLS ... Negative electrode current collection tab, 7b ... Negative electrode active material containing layer, 8 ... Separator, 9 ... Safety valve, 9a ... Recessed part, 9b ... Groove part, 10 ... Injection hole, 11 ... Positive electrode lead, 12 ... Negative electrode lead, 21 ... Press apparatus 21a, 21b ... press roll, 22 ... guide roller device, 23 ... winding device, 24 _{1 to} 24 ₅ ... guide roller, 25 ... band electrode, 25a ... current collector exposed portion, 25b ... active material containing layer, 26: Stepped portion, 27: Recessed portion.

Claims (7)

Other than the current collector exposed portion of the belt-shaped current collector, the current collector exposed portion formed on at least one long side of the belt-shaped current collector and having no active material-containing layer on both sides, and the current collector exposed portion of the belt-shaped current collector A step of compression-molding the active material-containing layer of the strip electrode plate including an active material-containing layer formed on at least a part of
On the roller having a step protruding from the circumferential surface and a recess adjacent to the step, the strip electrode plate, the current collector exposed portion is located at the step, and the active material-containing layer Is disposed so as to be located in the concave portion, and includes a step of applying tension in the long side direction of the strip electrode plate,
The step of the step portion satisfies the following formula (1).
750 <H (1)
However, H is the size (%) of the step when the thickness of the active material-containing layer of the electrode per side of the strip-shaped current collector is 100%.   2. The electrode manufacturing method according to claim 1, wherein a taper R (mm) of the stepped portion is set to R ≦ 15. The electrode manufacturing method according to claim 2, wherein a tensile stress F (N / mm ² ) of the strip electrode plate in the step of applying the tension satisfies 20 ≦ F ≦ 100.   3. The method for manufacturing an electrode according to claim 2, wherein in the step of applying the tension, the belt-shaped electrode plate is subjected to a heat treatment at a temperature of 60 ° C. or higher and 150 ° C. or lower.   5. The electrode manufacturing method according to claim 3, wherein the active material-containing layer is formed continuously or intermittently in a longitudinal direction of the strip-shaped current collector.   5. The electrode manufacturing method according to claim 3, wherein the strip-shaped current collector is an aluminum foil, an aluminum alloy foil, or a copper foil. 6. A method for producing a battery comprising a positive electrode, a negative electrode, and a non-aqueous electrolyte,
A battery manufacturing method, wherein at least one of the positive electrode and the negative electrode is manufactured by the method according to claim 1.

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