JP4496445B2 - Method for forming flat wound electrode body and flat wound electrode body - Google Patents

Description

【００６７】
つぎに、得られた扁平形状巻回型電極体の巻回軸長方向の中央部の位置で巻回軸方向に交差する断面が現れるまで削り落とし、扁平形状巻回型電極体の内周面側の電極板の状態を観察した。この観察結果を表１に示した。ここで、観察結果における○は、活物質層に割れが見られなかったことを示し、×は内周面近傍の湾曲部で活物質層に割れが見られたことを示す。
【００６８】
表１より、圧縮成形の前後における電極板の最内周面の距離が４ｍｍ以下の範囲においては、電極板の湾曲部近傍において活物質層の割れは見られなかった。しかし、電極板の最内周面の距離が５ｍｍの場合においては、最内周近傍の電極板に電極活物質層の割れが観察された。また、このとき、最内周近傍の電極板の湾曲部において隣接する電極板間に空隙が見られ、電極板の密着度が低下している状態が観察された。
【００６９】
このことから、第二圧縮行程前の電極体の電極板の最内周面の電極板間の距離が大きくなりすぎると、最内周面での隣接する電極板間の距離が大きくなりすぎると最内周面の湾曲部での隣接する電極板間の密着力が低下し、最内周面の電極板に過剰に応力がかかるようになり、電極板の破損を招くことがわかる。
【００７０】
【発明の効果】
本発明の扁平形状巻回型電極体の成形方法は、電極板の巻回体を圧縮して扁平化させるときに、圧縮時にかけられる圧力と直角な方向に巻回体を押圧することで、巻回体を扁平化させるときの圧力を低減することができる効果を示す。
【図面の簡単な説明】
【図１】 実施例１において、巻回型電極体の内周面側に一対のガイドを配置したときの図である。
【図２】 実施例１において、一対のガイドを用いて巻回型電極体を扁平化させるときの図である。
【図３】 実施例１において作製された扁平形状巻回型電極体の図である。
【図４】 実施例２のスペーサを有する扁平形状巻回型電極体の図である。
【図５】 実施例２のスペーサを示した図である。
【図６】 実施例２において、扁平形状電極板巻回体に挿入されるときの一対のスペーサを示す図である。
【符号の説明】
１…巻回型電極体 １１…負極板 １１１…集電体
１１２…負極活物質 １２…正極板 １２１…集電体
１２２…正極活物質 １３…セパレータ
２…スペーサ ２１…上底 ２２…下底
２３…一方の斜辺 ２４…傾斜した斜辺
３…ガイド ４…扁平形状巻回型電極体[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a flat wound electrode body used for a rectangular battery or the like.
[0002]
[Prior art]
In recent years, mounting of lithium ion secondary batteries is becoming mainstream as a power source for electric devices such as mobile phones and portable video cameras. Furthermore, this lithium ion secondary battery has attracted attention as a battery for automobiles. That is, the lithium ion secondary battery has a higher weight energy density than that of the nickel metal hydride battery, and is considered to be optimal for an automobile battery.
[0003]
In automobile batteries, there is always a demand for higher performance and higher grades. For example, it is possible to improve space efficiency such as downsizing and weight reduction of an automobile battery due to a reduction in an installation space of the automobile battery. As an automobile battery that satisfies such requirements, a rectangular battery with high mounting efficiency has attracted attention. As a prismatic battery, a battery having a laminated electrode body having a structure in which electrode bodies are laminated in several layers is widely used.
[0004]
Further, it is important that a large current can be generated in an automobile battery. In consideration of higher output and improved heavy load characteristics, the electrode body should be made thinner and denser, and wound into a spiral shape to use a wound electrode body having a flat cross section for an automobile battery. Is being considered. Moreover, it is known that this wound electrode body is also useful in productivity.
[0005]
The wound electrode body is composed of a sheet-like positive electrode plate, a negative electrode plate, and a separator. The positive electrode plate and the negative electrode plate are laminated via a separator, and the laminate is wound. The wound electrode body is usually formed in a circular shape or a circular shape close to it.
[0006]
In order to use the wound electrode body for a rectangular battery, it is required that the wound electrode body is flattened. In other words, storing a round or nearly circular wound electrode body in a square battery case as it is can reduce the adhesion of each electrode plate or loss of space inside the battery container. This is because.
[0007]
As a battery having such a flat wound electrode body, for example, a battery having a flat wound electrode body in which an electrode plate is wound around an elliptical core in JP-A-58-218768. However, in Japanese Patent Application Laid-Open No. 60-25164, a winding flattened by a method of pressing in a predetermined direction in a state where a core body is disposed in a central through hole portion of a perfect circular wound electrode body Japanese Patent Application Laid-Open No. 6-203870 discloses a battery having a flat wound electrode body that is compression-molded in a state where an electrode plate is wound around a hollow metal pipe as a winding core. Yes.
[0008]
Furthermore, there is a flat-shaped wound electrode body that is formed into a flat shape by compressing a wound-shaped electrode body formed in a perfect circle shape in the radial direction. This flat-shaped wound electrode body has a problem that the central through-hole portion of the spiral electrode body formed by winding the electrode plate exhibits distorted deformation. That is, when the central through-hole portion of the spiral electrode body is deformed into irregular shapes, non-uniformity occurs in the closeness of the electrode plates and the distance between the electrode plates in the vicinity of the inner peripheral surface of the electrode body, thereby reducing the performance of the electrode body. Because. In addition, this flat wound electrode body has a problem that the electrode plate in the vicinity of the innermost circumference of the wound electrode is bent at the minimum R (curvature radius), and the electrode active material is peeled off or slipped off at this portion. It was. That is, when the electrode active material is peeled off or slipped, the electrode active material breaks the separator and causes an internal short circuit.
[0009]
As a result, there was a big problem in the discharge performance and cycle characteristics of the battery using the flat wound electrode body formed by compression in such a radial direction.
[0010]
Further, the flat wound electrode body described in Japanese Patent Application Laid-Open No. 58-218768 has a sheet-like electrode wound around an elliptical core at the time of production. There was a problem that the body fluttered.
[0011]
Further, the flat wound electrode body manufacturing method described in JP-A-60-25164 is a manufacturing method for securing spot holes, and after flattening the wound electrode body, It had to be inserted into the can and the core removed. Therefore, as a result, there is a problem that the tightness of the wound electrode body is not ensured.
[0012]
Furthermore, since the manufacturing method described in JP-A-6-203870 has a hollow metal pipe in the central through hole portion of the electrode body, the pressing force for pressing in a predetermined direction for flattening is large. When the applied load increases, the electrode active material of the electrode plate is likely to be cracked or cracked. Furthermore, since a large pressing force is applied, the internal short circuit of the electrode body may be promoted.
[0013]
[Problems to be solved by the invention]
The present invention has been made in view of the above-described actual circumstances, and has a small pressing force for compressing the wound electrode body, and is caused by peeling, slipping, and cracking of the electrode active material in the obtained flat wound electrode body. It is an object of the present invention to provide a method for forming a flat wound electrode body and a flat wound electrode body in which deterioration of battery performance or the like caused by internal short circuit or non-uniformity in adhesion between electrodes is prevented.
[0014]
[Means for Solving the Problems]
(Formation method of flat wound electrode body)
In order to solve the above problems, the present inventors have invented the following molding method.
[0015]
The method for forming a flat wound electrode body of the present invention includes a sheet-like positive electrode plate, a negative electrode plate, and a separator, and the positive electrode plate and the negative electrode plate are laminated and wound through the separator to obtain a wound body. Later, a method of forming a flat wound electrode body in which the wound body is compressed into a flat shape, the opposite surface of the wound electrode body being on the inner peripheral surface side of the wound body. After arranging a pair of pressing members made of rod-shaped members formed so as to be parallel to the central axis, the winding body is pressed against a pair of axial portions opposite to the inner peripheral surface of the winding body. The wound body is formed into a flat shape by compressing the wound body in a direction perpendicular to the pressing direction of the pressing member while pressing the member outward in the radial direction. The pressing member has a substantially U-shaped outer peripheral shape with a thickness of 4.0 mm or less and a radius of curvature of a contact portion with the axial portion of 2.0 mm or less. It is characterized by that. Here, the pair of axial portions are portions that are symmetrical to the central axis of the wound body and are parallel to the central axis on the inner peripheral surface of the wound body. Further, the radial direction and the vertical direction to which compression molding is performed indicate a direction perpendicular to a plane formed by a pair of axial portions.
[0016]
That is, in the molding method of the present invention, a wound body obtained by winding a laminated body of sheet-like electrode plates is pressed radially outward from the inner peripheral surface side while being perpendicular to the pressing direction. This is a molding method in which the wound body is flattened by compressing in the direction.
[0017]
In the molding method of the present invention, when the wound body of the electrode plate is compressed and flattened, the wound body is flattened by pressing the wound body in a direction perpendicular to the pressure applied during compression. Can be reduced.
[0018]
The wound body used in the molding method of the present invention is manufactured by laminating a sheet-like positive electrode plate and a sheet-like negative electrode plate via a sheet-like separator and winding the laminate. Here, the sheet-like positive electrode plate, the negative electrode plate, and the separator can be a sheet-like member used in a conventional wound electrode body.
[0019]
The sheet-like electrode plate and separator are preferably formed in a substantially band shape. Moreover, the winding method which winds these laminated bodies can also be manufactured with the manufacturing method of the conventional winding type electrode body. When the electrode plate is wound using a winding core, the winding core is removed.
[0020]
It is preferable to arrange a pair of pressing members on the inner peripheral surface side of the wound body and press the inner peripheral surface of the wound body with the pressing members. Here, the inner peripheral surface side of the wound body indicates a shaft portion of the wound body that is partitioned by the innermost peripheral surface of the laminated body of electrode plates. That is, a pair of pressing members are arranged on the inner peripheral surface side of the wound body, and the inner peripheral surface of the wound body is pressed radially outward by moving the pressing members in directions opposite to each other. By pressing the inner peripheral surface of the wound body with this pressing member, it is possible to reduce the pressure when the wound body is flattened.
[0021]
The pair of pressing members has a thickness that prevents the electrode plate on the inner peripheral surface side of the wound body from being bent more than a predetermined amount when the wound body is compressed, and does not cause defects such as cracking or peeling of the electrode active material It is preferable to have a thickness.
[0022]
It is preferable to have a second compression molding step of further compressing the wound body in a direction compressed in the compression molding in a state where the pair of pressing members are removed after the compression molding. The shape change due to the residual stress of the wound body can be suppressed by further compression molding the wound body with the pair of pressing members removed. That is, even if the wound body is compressed while being pressed by the pressing member, the wound body is deformed radially outward because the stress in the reverse direction remains in the wound body. For this reason, after removing a press member, by applying compression molding further, residual stress can be removed and generation | occurrence | production of a deformation | transformation of a flat shaped winding body can be suppressed.
[0023]
The distance between the electrode plates on the inner peripheral surface of the wound body before being compressed in the second compression molding step is preferably 4 mm or less. Here, the distance between the electrode plates on the inner peripheral surface of the wound body before compression molding is the largest of the distances between the inner peripheral surfaces facing each other in the direction perpendicular to the direction pressed by the pressing member. A wide portion is shown, and this distance can be the thickness of the pressing member.
[0024]
By setting the distance between the electrode plates to 4 mm or less, breakage of the electrode plates forming the wound body can be suppressed. That is, when the distance between the electrode plates exceeds 4 mm, in the wound body before the second compression molding, in the portion near the curved portion on the inner peripheral surface of the wound body among the electrode plates forming the wound body, Adhesion between adjacent electrode plates is reduced. When the adhesion of the electrode plate is reduced, the electrode plate bends inward in the radial direction of the wound body. The portion where the electrode plate is bent is because the electrode plate is bent with a minimum curvature during compression molding, and the active material layer is cracked or peeled off.
[0025]
The pressing member preferably has a substantially U-shaped outer peripheral portion in contact with the axial portion. That is, since the contact portion with the axial portion of the pressing member is formed in a substantially U shape, the pressing force is not concentrated on the electrode plate when pressing the axial portion, and at the axial portion, Since the deformation amount of the electrode plate is restricted, the electrode plate can be prevented from being damaged. As a result, problems such as peeling of the electrode active material are less likely to occur.
[0026]
(Flat shape wound electrode body)
The flat-shaped wound electrode body of the present invention is a flat-shaped wound mold in which a wound body in which a sheet-like electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator is wound is formed into a flat shape. In the electrode body, the bent portion of the inner peripheral surface of the flat wound electrode body is bent. A substantially U-shaped curved shape portion that holds the curved shape in contact with Has holding member The holding member also serves as the pressing member according to any one of claims 1 to 3. It is characterized by that.
[0027]
That is, by pressing a flattened flat wound electrode body radially outward from the inner circumferential surface along the flat shape, pressure can be applied to the electrode plates, and each electrode plate in the radial direction can be The distance can be close. In addition, when the battery is actually used as a battery, if charging and discharging are performed, the electrode reaction causes variations in the distance between the electrode plates. By applying pressure to the electrode plates, this variation can be suppressed. it can.
[0028]
The flat wound electrode body of the present invention is preferably densified. By increasing the density of the flat wound electrode body, the energy density of the flat wound electrode body is improved. Here, the densified flat shape wound electrode body is densified by pressing the positive electrode plate and the negative electrode plate constituting the electrode body, and is wound around the densified electrode plate. The flattened electrode body is shown.
[0029]
The holding member is preferably composed of a pair of wedge-shaped members, and the wedge-shaped members are in contact with each other at the oblique sides and can move along the contact surface. That is, by pressing the pair of wedge-shaped members arranged on the inner peripheral surface of the flat wound electrode body in the axial direction of the flat wound electrode body, The distance of the contact portion with the curved portion of the flat wound electrode body can be adjusted. The inner peripheral surface of the flat wound electrode body is pressed by adjusting the distance between the back surfaces.
[0030]
Here, the wedge shape of the holding member is preferably a trapezoidal shape in which one oblique side is provided so as to form a right angle with the upper base and the lower base. The wedge-shaped member having such a trapezoidal shape is a flat winding type in which one oblique side faces away from the other, the other inclined oblique sides are in contact with each other, and the pair of upper and lower bases are on the same end face side. It arrange | positions at the inner peripheral surface side of an electrode body.
[0031]
In the present invention, a trapezoidal shape is preferable as the wedge-shaped holding member, but other shapes having a portion that presses the curved portion of the flat-shaped wound electrode body and inclined oblique sides that face each other are excluded. Not what you want.
[0032]
It is preferable that the holding member has a thickness in the compressed direction of the wound body. That is, since the holding member has a thickness, it is possible to prevent the electrode plate constituting the flat wound electrode body from being bent more than a predetermined amount, thereby preventing problems such as cracking and peeling of the electrode active material.
[0033]
Further, the holding member preferably has a substantially U-shaped outer peripheral portion in contact with the axial portion. Since the contact portion with the axial portion of the pressing member is formed in a substantially U shape, the pressing force does not concentrate on the electrode plate when the axial portion is pressed, and the electrode at the axial portion Since the deformation amount of the plate is restricted, the electrode plate can be prevented from being damaged. As a result, problems such as peeling of the electrode active material are less likely to occur.
[0034]
DETAILED DESCRIPTION OF THE INVENTION
The embodiments of the method for forming a flat wound electrode body of the present invention will be described clearly and sufficiently in the following examples so as to obtain a practicable understanding for those skilled in the art.
[0035]
Example 1
As an example of the method for forming a flat wound electrode body of the present invention, a flat wound electrode body used for a lithium secondary battery was produced. The production of this flat wound electrode body is shown in FIGS.
[0036]
In this embodiment, first, a wound electrode body 1 having a substantially circular cross section is manufactured, and a pair of guides 3 are arranged on the inner peripheral surface of the wound body of the wound electrode body 1. The electrode body 1 was compressed to a predetermined thickness while being pressed radially outward by 3 and then flattened with the guide 3 removed.
[0037]
First, a wound electrode body 1 was produced. This wound electrode body is composed of a positive electrode plate, a negative electrode plate, and two separators formed in a substantially strip shape. After the positive electrode plate, the separator, the negative electrode plate, and the separator are laminated in this order, the laminate is wound. It is formed by letting.
[0038]
Here, the wound electrode body 1 was wound using a normal winding electrode body winding method. Specifically, first, a cylindrical or oval core is used, and a positive electrode plate, a negative electrode plate, and a separator are wound around the outer peripheral surface of the core. Then, an electrode body is manufactured by removing the winding core. The wound electrode body 1 is formed in a pipe shape having an outer diameter of 63 mm, an axial length of 124 mm, and an inner diameter of 58 mm.
[0039]
The positive electrode plate is composed of a current collector formed of aluminum foil and a positive electrode active material layer made of lithium manganese oxide or the like formed on both surfaces of the current collector. This positive electrode plate was coated with a paste having lithium manganese oxide on both sides of an aluminum foil having a thickness of 15 μm, dried, and then compressed with a roll press machine with a linear pressure of 19.6 kN / cm. manufactured.
[0040]
The negative electrode plate includes a current collector formed of copper foil and a negative electrode active material layer made of carbon or the like formed on both surfaces of the current collector. This negative electrode plate was manufactured by applying a carbon-containing paste on both sides of a 10 μm thick copper foil and drying it, and then compressing it using a roll press machine with a linear pressure of 29.4 kN / cm.
[0041]
The separator is made of a sheet made of polyethylene or polypropylene. Specifically, it was a microporous polyethylene film having a thickness of 25 μm.
[0042]
Subsequently, a pair of guides 3 are arranged on the inner peripheral surface side which is the central shaft portion of the pipe-shaped wound electrode body 1. The guide 3 is a rod-shaped member formed such that the mutually opposing surfaces are parallel to the central axis of the wound electrode body 1, and the thickness of the wound electrode body 1 in the direction in which it is compressed. 3 mm, and the cross section of the back surface is formed in a substantially U-shaped outer peripheral shape with a radius of curvature of 1.5 mm. The pair of guides 3 are made of a rigid metal or resin. Furthermore, the axial length of the guide 3 is longer than the axial length of the wound electrode body 1.
[0043]
Thereafter, the wound electrode body 1 is pressed in a direction facing away from each other, which is a direction formed in a substantially U shape of the pair of guides 3, and the wound electrode body 1 is pressed by the pair of guides 3. Compressed in the direction perpendicular to the direction.
[0044]
This pair of guides 3 is performed until the limit until the pair of guides 3 can be pulled out, that is, until the thickness of the hollow portion of the inner peripheral surface of the wound electrode body 1 becomes 3 mm of the thickness of the guide 3. After that, the guide 3 was extracted from the wound electrode body 1. Thereafter, in a state where the guide 3 was pulled out, it was further compressed and flattened until the hollow portion on the inner peripheral surface of the wound electrode body 1 became 0.5 mm. The obtained flat wound electrode body is shown in FIG.
[0045]
In this flat-shaped wound electrode body 4, the electrode plate forming the flat-shaped wound electrode body 4 is in close contact with each other in the radial direction. The electrode plate on the innermost peripheral surface side is in close contact with the radial direction.
[0046]
The flat wound electrode body 4 produced according to the present embodiment is formed in a direction in which the wound electrode body 1 is flattened and extended when the wound electrode body 1 formed in a pipe shape is compressed. Since the electrode plate forming the wound electrode body 1 is pressed radially outward from the peripheral surface, abnormal stress is not applied to the flat wound electrode body 4 in which the electrode plate is closely adhered. Obtained. Furthermore, it was possible to reduce the pressure applied during the production of a flat wound electrode body by conventional compression.
[0047]
(Example 2)
This example is a flat wound electrode body having a holding member shown in FIG.
[0048]
In the flat wound electrode body of this example, the positive electrode plate 12, the negative electrode plate 11, and the two separators 13 were stacked in this order after the separator 13, the negative electrode plate 11, the separator 13, and the positive electrode plate 12. The body is wound and flattened, and a pair of trapezoidal spacers 2 are arranged on the inner peripheral surface side.
[0049]
The positive electrode plate 12, the negative electrode plate 11 and the two separators 13 were made of the same material and size as those used in Example 1.
[0050]
The positive electrode plate 12 includes a current collector 121 made of aluminum foil, and a positive electrode active material layer 122 made of lithium manganese oxide or the like formed on both surfaces of the current collector 121. The negative electrode plate 11 includes a current collector 111 made of copper foil, and a negative electrode active material layer 112 made of carbon or the like formed on both surfaces of the current collector 111. The separator 13 is made of a sheet made of polyethylene or polypropylene.
[0051]
The pair of trapezoidal spacers 2 have a trapezoidal shape in which the upper base 21 is 22.9 mm, the lower base 22 is 36.8 mm, and one oblique side 23 is formed perpendicular to the upper base 21 and the lower base 22, and has a thickness of 3 mm. It consists of a plate-shaped member. Furthermore, the spacer 2 is rounded so that the cross-sectional shape of one oblique side 23 has a curvature radius of 1.5 mm. This spacer 2 is shown in FIG.
[0052]
In the flat-shaped wound electrode body of the present embodiment, the electrode plate of the wound electrode body 1 is tightly pressed by pressing the wound electrode body 1 in the flat direction by the spacer 2 from the inner peripheral surface side. I keep it.
[0053]
(Production of flat wound electrode body)
The flat wound electrode body of this example was produced by the following method.
[0054]
First, a pipe-shaped wound electrode body 1 is manufactured, a pair of guides are arranged on the inner peripheral surface of the wound electrode body 1, and the electrode body is compressed while being pressed radially outward by the guides. And flattened.
[0055]
The pipe-shaped wound electrode body 1 was produced using the same material and winding method as in Example 1.
[0056]
Subsequently, a pair of guides are arranged on the inner peripheral surface side of the pipe-shaped wound electrode body 1. This guide is a rod-like member formed such that the mutually opposing surfaces are parallel to the central axis of the wound electrode body, and the thickness of the wound electrode body 1 in the direction of compression is 3 mm. The cross section of the back surface is formed into a shape having a substantially U-shaped outer peripheral surface with a radius of curvature of 1.5 mm. Further, the pair of guides are formed of a rigid metal or resin. Furthermore, the axial length of the guide is longer than the axial length of the wound electrode body.
[0057]
Thereafter, the wound electrode body 1 is compressed by compressing the outer peripheral surface of the wound electrode body 1 in a direction perpendicular to the direction in which the wound electrode body 1 is pressed. Almost U-shaped It was made to move in the direction opposite to each other. The movement of the pair of guides was performed until the limit until the pair of guides could be removed, that is, until the hollow portion of the inner peripheral surface of the wound body coincided with the thickness of the guide.
[0058]
The obtained flat electrode plate wound body 1 has a flattened pipe shape, and a flat space having the thickness of the guide is formed on the inner peripheral surface side. The flat electrode plate wound body 1 is flattened to have an axial length of 124 mm and a thickness of 13.9 mm, and a space on the inner peripheral surface side is formed to be 59 mm in the longitudinal direction and 3 mm in the thickness direction. It was.
[0059]
Subsequently, a pair of trapezoidal spacers 2 were inserted into the space on the inner peripheral surface side. The state at this time is shown in FIG.
[0060]
One oblique side 23 of the pair of spacers 2 was inserted along the curved portion side having an R shape on the inner peripheral surface of the flat electrode plate winding body 1 so that the upper bottom 21 side was in the distal direction. Further, the spacer 2 was inserted from both end face sides in the axial direction of the flat electrode plate roll 1.
[0061]
The pair of spacers 2 inserted in the space on the inner peripheral surface side are in contact with the hypotenuses 24 that are provided in an inclined manner in the space on the inner peripheral surface side. When the pair of spacers 2 are pressed in the inserted direction in this state, one of the oblique sides 23 of the spacer 2 presses the inner peripheral surface of the flat wound electrode body 1 due to the action of the oblique sides 24 of each other. Adhesion of the electrode plates forming the shape wound electrode body is maintained.
[0062]
Note that the end of the spacer that presses the inner circumferential surface of the flat wound electrode body is rounded so that the cross-sectional shape has a sufficient radius of curvature. Since the electrode plate on the peripheral surface side is held along this cross section, cracking and peeling of the electrode active material in this vicinity are suppressed.
[0063]
In the flat-shaped wound electrode body of the present example, in the electrode body with a high density, a spacer for holding the flat shape is disposed on the inner peripheral surface side, so that the diameter from the inner peripheral surface side of the electrode body is increased. The pressing force can be applied in the outer circumferential direction, and the flat wound electrode body can be brought into close contact. Further, since the contact portion of the spacer with the flat wound electrode body has a radius of curvature, the active material peeling or cracking caused by bending the electrode plate pressed against the contact portion is suppressed. It is done.
[0064]
(Example 3)
Example 3 is a flat wound electrode body formed by changing the thickness of the guide in the method for forming a flat wound electrode body of Example 1. Specifically, the third embodiment uses a guide in which the radius of curvature of the pressing portion of the guide is changed by changing the thickness to 1.0, 2.0, 3.0, 4.0, 5.0 mm. It is a manufactured flat wound electrode body.
[0065]
Specifically, two guides each having a thickness and a cross-sectional radius of curvature shown in Table 1 were produced to form a pair of guides. Using this pair of guides, flattening was performed in the same manner as in Example 1 to produce the flat wound electrode body of Example 3. Each flat-shaped wound electrode body has a distance of 0.5 mm at the maximum in the thickness direction of the flat-shaped wound electrode body after the guide is pulled out, It is compression-molded and flattened. The ratio of the distance between the electrode plates on the innermost peripheral surface of the electrode body before and after compression molding in the state where the guide was extracted is shown in Table 1 as the compression ratio.
[0066]
[Table 1]

[0067]
Next, scraping until the cross section intersecting the winding axis direction appears at the position of the central portion of the obtained flat-shaped wound electrode body in the winding axis length direction, and the inner peripheral surface of the flat-shaped wound electrode body The state of the side electrode plate was observed. The observation results are shown in Table 1. Here, ◯ in the observation result indicates that no crack was observed in the active material layer, and × indicates that the active material layer was cracked in the curved portion near the inner peripheral surface.
[0068]
From Table 1, the active material layer was not cracked in the vicinity of the curved portion of the electrode plate when the distance between the innermost peripheral surfaces of the electrode plate before and after compression molding was 4 mm or less. However, when the distance of the innermost peripheral surface of the electrode plate was 5 mm, cracking of the electrode active material layer was observed on the electrode plate near the innermost periphery. Moreover, the space | gap was seen between the adjacent electrode plates in the curved part of the electrode plate near the innermost periphery at this time, and the state where the adhesion degree of the electrode plate was observed was observed.
[0069]
From this, if the distance between the electrode plates on the innermost peripheral surface of the electrode plate of the electrode body before the second compression process becomes too large, the distance between adjacent electrode plates on the innermost peripheral surface becomes too large. It can be seen that the adhesion force between the adjacent electrode plates at the curved portion of the innermost peripheral surface is reduced, excessive stress is applied to the electrode plate of the innermost peripheral surface, and the electrode plate is damaged.
[0070]
【The invention's effect】
The method of forming the flat wound electrode body of the present invention is to press the wound body in a direction perpendicular to the pressure applied during compression when compressing and flattening the wound body of the electrode plate, The effect which can reduce the pressure when flattening a wound body is shown.
[Brief description of the drawings]
FIG. 1 is a view when a pair of guides are arranged on the inner peripheral surface side of a wound electrode body in Example 1. FIG.
2 is a diagram when flattening a wound electrode body using a pair of guides in Embodiment 1. FIG.
3 is a diagram of a flat wound electrode body produced in Example 1. FIG.
4 is a view of a flat wound electrode body having a spacer of Example 2. FIG.
5 is a view showing a spacer of Example 2. FIG.
6 is a view showing a pair of spacers when inserted into a flat electrode plate roll in Example 2. FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 ... Winding type electrode body 11 ... Negative electrode plate 111 ... Current collector
112 ... Negative electrode active material 12 ... Positive electrode plate 121 ... Current collector
122 ... Positive electrode active material 13 ... Separator
2 ... Spacer 21 ... Upper bottom 22 ... Lower bottom
23 ... One hypotenuse 24 ... Inclined hypotenuse
3 ... Guide 4 ... Flat shape wound electrode body

Claims (5)

A sheet-like positive electrode plate, a negative electrode plate, and a separator, and the positive electrode plate and the negative electrode plate are laminated and wound through the separator to form a wound body, and then the wound body is compressed to be flat A method of forming a flat wound electrode body formed into
After arranging a pair of pressing members made of rod-shaped members formed so that opposite surfaces are parallel to the central axis of the wound electrode body on the inner peripheral surface side of the wound body,
A direction perpendicular to the direction in which the pressing member is pressed while pressing the pair of axially opposite portions of the inner peripheral surface of the wound body radially outward with the pair of pressing members. By compressing and molding the wound body, the wound body is formed into a flat shape ,
The pressing member has a substantially U-shaped outer peripheral shape having a thickness of 4.0 mm or less and a radius of curvature of a contact portion with the axial direction portion of 2.0 mm or less. A method for forming an electrode body.   The flat-shaped winding of Claim 1 which has a 2nd compression molding process which further compresses the said winding body in the direction compressed in the said compression molding in the state where the pair of said press member was removed after the said compression molding. A method for forming a rotary electrode body. The method for forming a flat wound electrode body according to claim 2, wherein the distance between the electrode plates on the inner peripheral surface of the wound body before being compressed in the second compression molding step is 4 mm or less. In a flat wound electrode body in which a wound body in which a sheet-like electrode body in which a positive electrode plate and a negative electrode plate are laminated via a separator is wound is formed into a flat shape,
該扁and have a holding member having a curved shape of the substantially U-shaped to hold the flat shape wound electrode body in contact with a curved shape to the curved portion which is bent with the inner circumferential surface of
The flat-shaped wound electrode body , wherein the holding member also serves as the pressing member according to any one of claims 1 to 3 .   The holding member is composed of a pair of wedge-shaped members arranged in a state in which the contact portion with the curved portion is parallel to the axial direction of the flat-shaped wound electrode body and the oblique sides are in contact with each other. The flat wound electrode body according to claim 4, wherein the wedge-shaped member is movable along the contact surface.

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