JP6845052B2 - How to manufacture a secondary battery - Google Patents

Description

The present invention relates to a method for manufacturing a secondary battery including an electrode body formed by winding a positive electrode, a negative electrode, and a separator formed in a band shape in a superposed state.

In a secondary battery provided with an electrode body formed by winding a positive electrode body, a negative electrode body, and a separator formed in a band shape in a superposed state, the electrode body is subjected to a difference in expansion ratio between the positive electrode body and the negative electrode body due to charging and discharging. It is known that deflection occurs inside. When such a deflection occurs inside the electrode body of the secondary battery, the thickness of the battery may be increased due to the deflection, and the battery characteristics may be deteriorated due to the deflection.

On the other hand, there is known a method for manufacturing a secondary battery capable of suppressing the occurrence of deflection inside the electrode body due to charging and discharging of the secondary battery. As a method for manufacturing such a secondary battery, for example, Patent Document 1 discloses a method in which the winding state of the electrode plate is slightly loosened by rotating the electrode body in the same direction as the winding direction.

Specifically, in the method for manufacturing a secondary battery provided with a flat spiral electrode body disclosed in Patent Document 1, first, a positive electrode plate, a negative electrode plate, and a separator interposed between both electrode bodies are formed by using a winding core. It is wound to produce a substantially cylindrical electrode body. Then, the electrode body is rotated in the same direction as the winding direction to loosen the winding state, and then the electrode body is pressed to obtain a flat spiral electrode body.

As a result, the winding state of the electrode plate can be slightly loosened in the entire electrode body. Moreover, after loosening the winding state of the electrode plate, the electrode body is pressed to form a flat shape, so that the looseness moves to the vicinity of the corner portion. Therefore, when the electrode plate expands, the electrode plate deforms in a direction to fill the looseness, so that the occurrence of deflection of the electrode body can be prevented.

Japanese Unexamined Patent Publication No. 2006-164956

By the way, as disclosed in Patent Document 1, when the electrode body is rotated in the same direction as the winding direction, the winding state of the electrode plate (positive electrode, negative electrode) is loosened in the entire electrode body. Then, the obtained electrode body becomes larger than the wound electrode body before loosening. Moreover, by loosening the winding of the electrode body as described above, the positions of the tabs (positive electrode connection terminal, negative electrode connection terminal) attached to the electrode body may change. It is preferable that the positive electrode connection terminal and the negative electrode connection terminal attached to the electrode body are positioned at predetermined positions of the electrode body in relation to the connection with the external device, wiring, etc. of the battery.

An object of the present invention is a secondary battery having an electrode body formed by winding a positive electrode, a negative electrode, and a separator formed in a band shape in a superposed state, inside the electrode body at the time of charging and discharging of the secondary battery. It is an object of the present invention to realize a manufacturing method capable of accurately positioning the positive electrode connection terminal and the negative electrode connection terminal attached to the electrode body while suppressing the occurrence of deflection and suppressing the enlargement of the electrode body.

The present inventors have investigated in detail the mechanism by which bending occurs inside the electrode body due to charging and discharging of the secondary battery. As a result, it was found that, in the bent portion of the electrode body, the outermost peripheral side rather than the inner peripheral side has a great influence on the deflection generated inside the electrode body. That is, since the deformation of the electrode body is greatly restricted by the outermost peripheral side of the electrode body, the inside of the electrode body is bent when the positive electrode and the negative electrode are deformed by charging and discharging the secondary battery. I noticed that.

Further, the present inventors suppress the increase in size of the electrode body by loosening only the outermost peripheral side of the electrode body, and shift the positions of the positive electrode connection terminal and the negative electrode connection terminal attached to the electrode body. I also noticed that it can be suppressed.

Based on these points, the present inventors diligently studied a method for manufacturing a secondary battery capable of loosening only the outermost peripheral side of the electrode body, and found the following method.

The method for manufacturing a secondary battery according to an embodiment of the present invention is a tubular shape extending in the winding axis direction by winding a positive electrode, a negative electrode, and a separator formed in a band shape in a state of being stacked in the thickness direction. A winding step of obtaining an electrode body, a flattening step of forming a flat electrode body by applying a predetermined force to a side surface (wide surface) of the tubular electrode body, and a flattening step of forming the flat electrode body, and the electrode body. It has a loosening processing step of loosening the outermost peripheral side of the electrode body by applying a loosening force in a direction opposite to the winding direction. The loosening processing step is performed at the same time as the flattening step or after the flattening step (first method).

As described above, by applying a force to the electrode body in the direction opposite to the winding direction, it is possible to loosen only the outermost peripheral side without loosening the inner peripheral side of the electrode body.

Moreover, by performing the loosening processing step of loosening the outermost peripheral side of the electrode body at the same time as the flattening step of forming the flat electrode body or after the flattening step, the entire electrode body is loosened. Can be further suppressed.

That is, in the flattening step, the positive electrode and the negative electrode are bent inside the electrode body. However, since the amount of bending deformation of the positive electrode and the negative electrode is smaller on the outermost peripheral side of the electrode body than on the inner peripheral side, only the outermost peripheral side can be loosened by the loosening processing step. Therefore, by performing the loosening processing step at the same time as or after the flattening step as described above, it is possible to loosen only the outermost peripheral side of the electrode body while suppressing the displacement inside the electrode body. become. As a result, it is possible to suppress the enlargement of the electrode body and prevent the positive electrode connection terminal and the negative electrode connection terminal attached to the electrode body from moving significantly.

Therefore, by the above-mentioned method, while suppressing the occurrence of internal deflection of the electrode body during charging and discharging of the secondary battery, the enlargement of the electrode body is suppressed, and the positive electrode connection terminal attached to the electrode body and the positive electrode body The negative electrode connection terminal can be positioned with high accuracy.

Here, the outermost peripheral side of the electrode body means an outer peripheral side portion of the electrode body that causes bending inside the electrode body when the secondary battery is charged and discharged. The outermost peripheral side includes, for example, a positive electrode, a negative electrode, and a separator located in the outermost layer of the electrode body and the second layer from the outermost layer among the positive electrode, the negative electrode, and the separator.

In the first method, in the method for manufacturing a secondary battery, the loosening of the electrode body on the outermost peripheral side due to the loosening process is detected by the amount of movement of the detected portion provided on the outermost peripheral side of the electrode body. It further has a loosening detection step (second method).

Thereby, the loosening on the outermost peripheral side of the electrode body due to the loosening process can be detected by the amount of movement of the detected portion. Therefore, it is possible to easily detect whether or not the electrode body has undergone the loosening process in the loosening detection step. Therefore, it is possible to efficiently manufacture a secondary battery in which the occurrence of deflection inside the electrode body is suppressed.

In the second method, the detected portion is a winding stop tape for fixing the winding end end portion of the electrode body (third method). As a result, it is possible to easily detect whether or not the electrode body has been loosened without adding a new component to the electrode body. Therefore, it is possible to easily manufacture a secondary battery in which the occurrence of deflection inside the electrode body is suppressed at low cost.

In the second method, the detected portion is a portion of the current collector exposed portion in the positive electrode or the negative electrode located on the outermost peripheral side of the electrode body, and the current collector is located in the winding axis direction. It is a film member provided so as to project outward from the exposed portion (fourth method).

For example, in the case of manufacturing a positive electrode, a positive electrode active material layer is formed at a predetermined interval on a part of a band-shaped positive electrode current collector, and then connection terminals are attached to an exposed portion. A part of the connection terminal and a part of the exposed portion are covered with a coating film protruding outward in the width direction (winding axis direction in the electrode body) of the exposed portion. Then, the exposed portion is cut together with the coating film at a predetermined position in the longitudinal direction to obtain a positive electrode. The exposed portion is separated into two exposed portions of the current collector by being cut off.

In the method for manufacturing a positive electrode as described above, in order to obtain a positive electrode by cutting a strip-shaped member, the exposed portion of the current collector to which a part of the coating film (film member) is attached after cutting is the other secondary battery. It is used as a part of the positive electrode. In the other secondary battery, the exposed portion of the current collector is positioned on the outermost peripheral side of the electrode body. Therefore, in the electrode body, the film member projects from the positive electrode to the outside of the current collector exposed portion in the winding axis direction on the outermost peripheral side of the electrode body.

By using the film member protruding outward of the current collector exposed portion in the winding axis direction as a detected portion for detecting looseness on the outermost peripheral side of the electrode body in the detection step, the electrode It is possible to easily detect whether or not the electrode body has undergone the loosening process without providing a new member on the body. Therefore, it is possible to easily manufacture a secondary battery in which the occurrence of deflection inside the electrode body is suppressed at low cost.

In any one of the second to fourth methods, the loosening processing step controls the loosening amount of the electrode body according to the moving amount of the detected portion in the loosening detecting step (the first). Method 5).

Thereby, the loosening amount of the electrode body in the loosening processing step can be adjusted with high accuracy. Therefore, it is possible to suppress variations in the amount of looseness of the electrode body in each secondary battery. Therefore, the quality of the secondary battery can be improved.

In any one of the first to fifth methods, in the winding step, the positive electrode connection terminal connected to the positive electrode and the negative electrode connection terminal connected to the negative electrode are included in the tubular electrode body. The positive electrode, the negative electrode, and the separator are wound so as to project from the circumferential side toward the outside of the winding shaft (sixth method).

As a result, the positive electrode connection terminal and the negative electrode connection terminal are located on the inner peripheral side of the electrode body. Therefore, by the above-mentioned first method, it is possible to prevent the positions of the positive electrode connection terminal and the negative electrode connection terminal from changing even when the outermost peripheral side of the electrode body is loosened. Therefore, the positive electrode connection terminal and the negative electrode connection terminal can be positioned with high accuracy.

In any one of the first to sixth methods, the method for manufacturing the secondary battery is an exterior forming step of covering the electrode body after the flattening step and the loosening processing step with a laminated film exterior body. (7th method).

As described above, the so-called laminated battery in which the electrode body is covered with the laminated film outer body is easily affected by the deformation of the electrode body during charging and discharging. Therefore, in this laminated battery, the deformation of the electrode body can be suppressed by loosening the outermost peripheral side of the electrode body by the above-mentioned first method. Thereby, the deformation of the laminated battery 1 can be suppressed.

According to the method for manufacturing a secondary battery according to an embodiment of the present invention, loosening is applied to the electrode body in a direction opposite to the winding direction to loosen the outermost peripheral side of the electrode body. The processing step is performed at the same time as the flattening step of forming the flat electrode body, or after the flattening step. As a result, only the outermost peripheral side of the electrode body can be loosened. Therefore, it is possible to suppress the occurrence of deflection inside the electrode body, suppress the increase in size of the electrode body, and suppress the deterioration of the positioning accuracy of the positive electrode connection terminal and the negative electrode connection terminal in the electrode body.

FIG. 1 is a perspective view showing a schematic configuration of a laminated battery according to an embodiment. FIG. 2 is a cross-sectional view taken along the line II-II of FIG. FIG. 3 is a perspective view showing a schematic configuration of the electrode body. FIG. 4 is a diagram schematically showing a state in which the positive electrode, the negative electrode, and the separator are stacked in the thickness direction. FIG. 5 is a diagram schematically showing how the positive electrode, the negative electrode, and the separator are wound in a state of being overlapped in the thickness direction. FIG. 6 is a diagram schematically showing how the tubular electrode body is crushed by the pressing device. FIG. 7 is a diagram schematically showing a state in which an electrode body is obtained by crushing a tubular electrode body with a pressing device. FIG. 8 is a diagram showing a state in which a positive electrode connection terminal and a coating film are provided on an exposed portion located between adjacent positive electrode active material layers on a metal foil. FIG. 9 is a diagram schematically showing a configuration in which the pressing device is driven according to the position of the winding stop tape of the tubular electrode body.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. The same or corresponding parts in the drawings are designated by the same reference numerals and the description thereof will not be repeated.

(overall structure)
FIG. 1 is a perspective view showing a schematic configuration of a laminated battery 1 (secondary battery) according to an embodiment of the present invention. FIG. 2 is a cross-sectional view showing a schematic configuration of the laminated battery 1. The laminated battery 1 is a secondary battery having a rectangular shape in a plan view in which an electrode body 10 functioning as a power generator is covered with a laminated film exterior body 20. In FIG. 2, a part of the electrode body 10 is not shown.

As shown in FIGS. 1 and 2, the laminated battery 1 includes an electrode body 10 and a laminated film exterior body 20 that covers the electrode body 10. Further, the laminated battery 1 includes a positive electrode connection terminal 41 and a negative electrode connection terminal 42 that are electrically connected to the positive electrode 11 and the negative electrode 12 of the electrode body 10, respectively. A non-aqueous electrolytic solution is also sealed inside the laminated battery 1.

The laminated film exterior body 20 is made of a material in which one side of an aluminum metal foil is covered with nylon and the other side is covered with polypropylene. That is, the laminated film exterior body 20 is made of a material obtained by laminating aluminum with nylon and polypropylene. As a result, the laminated film outer body 20 is welded by applying pressure while heating the laminated film outer bodies 20 in a state where they are overlapped with each other. The metal foil is not limited to aluminum, and may be formed of other metal materials such as stainless steel.

Further, the laminated film exterior body 20 is formed in a substantially rectangular shape. By welding the outer peripheral sides of the laminated film exterior 20 with the electrode body 10 sandwiched between the pair of laminated film exteriors 20, the bulging portion 1a and the sealing portion 1b as shown in FIGS. 1 and 2 are welded to each other. Is formed. That is, the bulging portion 1a is formed by covering the electrode body 10 with the laminated film outer body 20, and the laminated film outer bodies 20 are welded to each other around the bulging portion 1a to seal the bulging portion 1a. Part 1b is formed.

In the present embodiment, the electrode body 10 is a flat electrode body formed by crushing a cylindrical tubular electrode body 60 into a flat shape. That is, the electrode body 10 has a rectangular shape when viewed from the side. Therefore, as shown in FIG. 1, the bulging portion 1a has a rectangular shape in a plan view (hereinafter, also simply referred to as a plan view) of the laminated film exterior body 20. The seal portion 1b is formed around the bulging portion 1a so that the laminated battery 1 has a rectangular shape in a plan view.

Further, in the pair of laminated film exterior bodies 20, as shown in FIG. 2, the laminated battery 1 has a flat surface portion 1c on one side in the thickness direction of the electrode body 10 and the other side in the thickness direction of the electrode body 10. The outer peripheral sides of the laminated film outer body 20 are welded to each other with the electrode body 10 sandwiched so as to have the above-mentioned bulging portion 1a. That is, of the pair of laminated film exterior bodies 20, one of the laminated film exterior bodies 20 is arranged so as to follow the outer shape of the electrode body 10.

In the portion of the seal portion 1b located on the end side in the longitudinal direction of the laminated battery 1, the positive electrode connection terminal 41 and the negative electrode connection terminal 42, which will be described later, are sandwiched between the pair of laminated film exterior bodies 20. The laminated film exterior bodies 20 are fixed by welding to each other.

In the present embodiment, the outer peripheral sides of the pair of laminated film outer bodies 20 are welded to each other, but this is not limited to this, and one laminated film outer body is folded back so as to sandwich the electrode body 10 and welded. May be done. The direction in which the laminated film exterior body is folded back may be the stretching direction of the positive electrode connection terminal 41 and the negative electrode connection terminal 42 with respect to the electrode body 10, or may be the width direction.

(Electrode body)
In the following description, the winding axis direction of the electrode body 10 means a direction along the axis L shown in FIG. Further, the minor axis direction of the electrode body 10 means the direction in which the diameter of the electrode body 10 is the smallest when the electrode body 10 is viewed from the winding axis direction. The major axis direction of the electrode body 10 means the direction in which the diameter of the electrode body 10 is the largest when the electrode body 10 is viewed from the winding axis direction.

As shown in FIG. 3, the electrode body 10 is a flat wound electrode body formed in an ellipse when viewed from the winding axis direction. The electrode body 10 is wound by winding the positive electrode 11 and the negative electrode 12 formed in a band shape in a state of being overlapped between the two and under the positive electrode 11 so that the separator 13 is located, and then crushed. Is formed flat. The flat electrode body 10 is housed in the space formed by the laminated film exterior body 20.

The state of forming the electrode body 10 is schematically shown in FIGS. 4 to 7. As shown in FIG. 4, the positive electrode 11, the negative electrode 12, and the separator 13 are laminated in the order of the negative electrode 12, the separator 13, the positive electrode 11, and the separator 13 in the thickness direction from the top. In this state, the positive electrode 11, the negative electrode 12, and the separator 13 are wound by a winding core (not shown) in the direction of the white arrow in FIG. 4 to obtain a substantially cylindrical tubular electrode body 60. .. Therefore, the outermost circumference of the electrode body 10 of the present embodiment is the separator 13.

In FIG. 4, in order to illustrate the state in which the positive electrode 11, the negative electrode 12, and the separator 13 are overlapped with each other, the positions of the positive electrode 11, the negative electrode 12, and the separator 13 are moved from the actual arrangement and shown in a perspective view. Further, in FIG. 4, in order to distinguish the positive electrode 11, the negative electrode 12, and the separator 13, hatching is provided on the positive electrode active material layer 11b of the positive electrode 11 and the negative electrode active material layer 12b of the negative electrode 12, although it is not a cross section.

After obtaining the tubular electrode body 60 as described above, as shown in FIGS. 6 and 7, by crushing the tubular electrode body 60 in the radial direction, the flat electrode body 10 as shown in FIG. 3 is formed. can get. As will be described in detail later, when the tubular electrode body 60 is crushed in the radial direction to form a flat shape, the tubular electrode body 60 is given a force to loosen in the direction opposite to the winding direction to form a tubular shape. The positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side of the electrode body 60 are loosened. As a result, the flat electrode body 10 has a gap in the major axis direction on the outermost peripheral side.

When there is no such gap inside the electrode body 10, the difference in expansion coefficient between the positive electrode 11 and the negative electrode 12 causes deflection inside the electrode body 10 when the laminated battery 1 is charged and discharged. That is, the deformation of the electrode body 10 is limited by the outermost peripheral side of the electrode body 10. Therefore, when the positive electrode 11 and the negative electrode 12 expand due to the charging and discharging of the laminated battery 1, the inside of the electrode body 10 is bent due to the difference in the expansion coefficient between them.

On the other hand, by providing the gap on the outermost peripheral side of the electrode body 10 as described above, the inside of the electrode body 10 due to the difference in expansion coefficient between the positive electrode 11 and the negative electrode 12 when the laminated battery 1 is charged and discharged. The deformation of the above can be absorbed by the gap. Therefore, it is possible to suppress the occurrence of bending inside the electrode body 10 when the laminated battery 1 is charged and discharged.

The positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side are the positive electrode 11 located on the outermost peripheral layer and the second layer from the outermost peripheral layer among the positive electrode 11, the negative electrode 12, and the separator 13 of the electrode body 10. , Negative electrode 12 and separator 13. Further, the outermost peripheral side of the electrode body 10 means an outer peripheral side portion of the electrode body 10 that causes bending inside the electrode body 10 when the laminated battery 1 is charged and discharged.

Further, the winding direction means a direction in which the electrode body 10 extends from the winding start side to the winding end side when viewed from one end in the winding axis direction. The winding direction coincides with the rotation direction of the winding core when the positive electrode 11, the negative electrode 12, and the separator 13 are wound by the winding core. In the example shown in FIG. 6, the winding direction is clockwise.

As shown in FIG. 3, the electrode body 10 formed flat as described above has a pair of bent portions 10a in which the positive electrode 11, the negative electrode 12, and the separator 13 are bent so as to be folded back in the thickness direction. The pair of bent portions 10a are located at the end portions in the width direction when the electrode body 10 is viewed from the side.

Further, the positive electrode 11, the negative electrode 12, and the winding end end of the separator 13 of the electrode body 10 are fixed by the winding stop tape 50 (detected portion). The winding stop tape 50 has a length equivalent to that of the electrode body 10 in the axial direction of the electrode body 10. As a result, the winding end end of the electrode body 10 can be more reliably fixed by the winding stop tape 50. The winding stop tape 50 is made of, for example, PP (polypropylene) or the like.

In the present embodiment, as will be described later, the winding stop tape 50 is used to detect the presence or absence of looseness of the positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side of the electrode body 10.

The positive electrode 11 has a positive electrode current collector 11a made of a metal foil such as aluminum, and a positive electrode active material layer 11b containing a positive electrode active material and provided on both sides of the positive electrode current collector 11a. Specifically, the positive electrode 11 is coated with a positive electrode mixture containing a positive electrode active material, a conductive auxiliary agent, a binder, etc., which are lithium-containing oxides capable of storing and releasing lithium ions, on a positive electrode current collector made of aluminum foil or the like. It is formed by drying. As the lithium-containing oxide as the positive electrode active material, for example, _{a lithium cobalt oxide such as LiCoO 2} , a lithium manganese oxide such as LiMn ₂ O _4, and a lithium composite oxide such as a lithium nickel oxide such as _{LiNiO 2 are used.} Is preferable. As the positive electrode active material, only one kind of substance may be used, or two or more kinds of substances may be used. Further, the positive electrode active material is not limited to the above-mentioned substances.

As shown in FIG. 4, the positive electrode 11 has positive electrode current collector exposed portions 11c and 11d on both ends of the positive electrode current collector 11a in the longitudinal direction in which the positive electrode active material layers 11b are not provided on both sides. That is, the positive electrode current collector exposed portion 11c is located on one side of the positive electrode 11 in the longitudinal direction, and the positive electrode current collector exposed portion 11d is located on the other side of the positive electrode 1 in the longitudinal direction. In the electrode body 10 of the present embodiment, the positive electrode current collector exposed portion 11c is located on the winding start side (inside of the electrode body 10) of the electrode body 10, and the positive electrode current collector exposed portion 11d is the winding of the electrode body 10. It is located on the end side (the outermost peripheral side of the electrode body 10).

The negative electrode 12 has a negative electrode current collector 12a made of a metal foil such as copper, and a negative electrode active material layer 12b containing a negative electrode active material and provided on both sides of the negative electrode current collector 12a, respectively. Specifically, the negative electrode 12 is dried by applying a negative electrode mixture containing a negative electrode active material capable of occluding and releasing lithium ions, a conductive auxiliary agent, a binder, and the like onto a negative electrode current collector made of copper foil or the like. It is formed. As the negative electrode active material, for example, it is preferable to use a carbon material (graphites, pyrolytic carbons, cokes, glassy carbons, etc.) capable of occluding and releasing lithium ions. The negative electrode active material is not limited to the above-mentioned substances.

As shown in FIG. 4, similarly to the positive electrode 11, the negative electrode 12 also has negative electrode current collector exposed portions 12c and 12d on both ends of the negative electrode current collector 12a in the longitudinal direction in which the negative electrode active material layers 12b are not provided on both sides. Have. That is, the negative electrode current collector exposed portion 12c is located on one side of the negative electrode 12 in the longitudinal direction, and the negative electrode current collector exposed portion 12d is located on the other side of the negative electrode 12 in the longitudinal direction. In the electrode body 10 of the present embodiment, the negative electrode current collector exposed portion 12c is located on the winding start side (inside of the electrode body 10) of the electrode body 10, and the negative electrode current collector exposed portion 12d is the winding of the electrode body 10. It is located on the end side (the outermost peripheral side of the electrode body 10).

A positive electrode connection terminal 41 is connected to the positive electrode current collector exposed portion 11c located on the winding start side of the electrode body 10 in the positive electrode 11. The negative electrode connection terminal 42 is connected to the negative electrode current collector exposed portion 12c located on the winding start side of the electrode body 10 in the negative electrode 12. The positive electrode connection terminal 41 and the negative electrode connection terminal 42 are drawn out of the electrode body 10 and out of the laminate film outer body 20.

The positive electrode connection terminal 41 is made of an aluminum metal foil formed in a rectangular shape in a plan view. One side of the positive electrode connection terminal 41 in the longitudinal direction is connected to the exposed portion 11c of the positive electrode current collector of the positive electrode 11 by welding, and the other side in the longitudinal direction is located outside the laminated film exterior body 20 (FIG. 1). reference). That is, the positive electrode connection terminal 41 is sandwiched by the laminated film outer body 20, and extends from the inside to the outside of the laminated film outer body 20.

The negative electrode connection terminal 42 is made of a metal foil such as copper or nickel formed in a rectangular shape in a plan view. As shown in FIG. 2, one side of the negative electrode connection terminal 42 in the longitudinal direction is connected to the exposed portion 12c of the negative electrode current collector by welding, and the other side in the longitudinal direction is located outside the laminated film exterior body 20. There is. That is, the negative electrode connection terminal 42 is sandwiched by the laminated film exterior body 20 and extends from the inside to the outside of the laminated film exterior body 20.

By using the positive electrode connection terminal 41 and the negative electrode connection terminal 42 having the above-described configuration in the laminated battery 1, the impedance can be reduced as compared with the configuration in which the connection terminal is pulled out to the outside via other connection components. it can.

As shown in FIGS. 1 and 2, on the surfaces of the positive electrode connection terminal 41 and the negative electrode connection terminal 42, the positive electrode side resin portion 45 and the negative electrode side resin portion are located on the surfaces sandwiched by the laminated film exterior body 20, respectively. 46 is formed. That is, the positive electrode side resin portion 45 is located between the laminated film exterior body 20 and the positive electrode connection terminal 41, and the negative electrode side resin portion 46 is located between the laminated film exterior body 20 and the negative electrode connection terminal 42.

As a result, the adhesive strength between the laminated film outer body 20 and the positive electrode connection terminal 41 and the negative electrode connection terminal 42 sandwiched between the laminated film outer body 20 can be improved, and the positive electrode connection terminal 41 and the negative electrode connection terminal 42 It is possible to more reliably electrically insulate the laminated film exterior body 20 from the outer body 20.

The positive electrode side resin portion 45 and the negative electrode side resin portion 46 are each formed of a rectangular sheet in a plan view made of a resin material such as polypropylene (PP). The positive electrode connection terminal 41 and the negative electrode connection terminal 41 and the negative electrode connection terminal are arranged so that the sheet extends in a direction orthogonal to the positive electrode connection terminal 41 and the negative electrode connection terminal 42 and sandwiches the positive electrode connection terminal 41 and the negative electrode connection terminal 42, respectively. By depositing on each surface of 42, the positive electrode side resin portion 45 and the negative electrode side resin portion 46 are formed, respectively.

Protective films 55a are attached to both sides of the positive electrode current collector exposed portion 11c of the positive electrode 11 to which the positive electrode connection terminal 41 is connected. The protective film 55a projects outward from the positive electrode current collector exposed portion 11c in the lateral direction of the positive electrode 11. That is, the width of the protective film 55a in the lateral direction is larger than the width of the positive electrode current collector exposed portion 11c in the lateral direction. In the present embodiment, the protective film 55a covers from the positive electrode current collector exposed portion 11c side to the positive electrode side resin portion 45 in the positive electrode connection terminal 41. The protective film 55a is made of, for example, PP (polypropylene) or the like.

By attaching the protective film 55a to the positive electrode current collector exposed portion 11c in this way, a short circuit occurs between the positive electrode current collector exposed portion 11c of the positive electrode 11 and the negative electrode current collector exposed portion 12c of the negative electrode 12. Can be prevented.

At least one of the protective films 55a attached to both sides of the positive electrode current collector exposed portion 11c is colored (for example, blue). This makes it possible to easily confirm whether or not the protective film 55a is attached to the exposed portion 11c of the positive electrode current collector.

As will be described later, the positive electrode 11 is obtained by cutting a long metal foil 15 (see FIG. 8) to a predetermined length. As will be described in detail later, the positive electrode 11 can be obtained by cutting the long metal foil 15 on which the positive electrode active material layers 11b are formed at predetermined intervals at the exposed portion 15a to which the coating film 55 is attached. Since the coating film 55 is also cut by cutting the exposed portion 15a, the coating film 55 is separated into a protective film 55a and a film member 55b. At this time, of the cut exposed portions 15a, the portion to which the protective film 55a is attached becomes the positive electrode current collector exposed portion 11c of one positive electrode 11, and the remaining portion to which the film member 55b is attached. Is the positive electrode current collector exposed portion 11d of the other positive electrode 11.

Therefore, a film member 55b as a part of the coating film 55 is attached to the end portion of the positive electrode 11 in the longitudinal direction of the positive electrode current collector exposed portion 11c.

The separator 13 has a resin porous layer. As the separator 13, a microporous film made of polyolefin used in an electrochemical element such as a conventionally known lithium secondary battery can be used.

(Manufacturing method of laminated battery)
Next, a method of manufacturing the laminated battery 1 having the above-described configuration will be described with reference to FIGS. 4 to 8.

First, a method for manufacturing the positive electrode 11 will be described. As shown in FIG. 8, a plurality of positive electrode active material layers 11b are formed on the long aluminum metal foil 15 at predetermined intervals in the longitudinal direction thereof. The positive electrode active material layer 11b may be formed on the metal foil 15 according to the number of positive electrodes 11 to be manufactured.

The predetermined interval is the sum of the length of the positive electrode current collector exposed portion 11c in the positive electrode 11 in the longitudinal direction and the length of the positive electrode current collector exposed portion 11d in the longitudinal direction. That is, between the positive electrode active material layers 11b adjacent to each other on the metal foil 15 at a predetermined interval, the exposed portion 15a where the metal foil 15 is exposed.

Next, the positive electrode connection terminal 41 is connected to the exposed portion 15a of the metal foil 15 by welding or the like. The positive electrode connection terminal 41 is provided with a positive electrode side resin portion 45. After that, the coating film 55 is attached so as to sandwich a part of the exposed portion 15a and a part of the positive electrode connection terminal 41 in the thickness direction. Specifically, the coating film 55 is attached on the metal foil 15 so as to cover a part of the exposed portion 15a in the longitudinal direction of the metal foil 15 and project from the exposed portion 15a in the width direction of the metal foil 15. The coating film 55 covers the metal foil 15 side of the positive electrode connection terminal 41 with respect to the positive electrode side resin portion 45.

Subsequently, the exposed portion 15a of the metal foil 15 and the portion to which the coating film 55 is attached are cut by a cutting tool (not shown). FIG. 8 shows an example of the cut portion by a chain double-dashed line. By cutting the portion of the exposed portion 15a to which the coating film 55 is attached, the exposed portion 15a is separated into two positive electrode active material layers 11b formed on the metal foil 15 with the exposed portion 15a interposed therebetween. The positive electrode 11 including each positive electrode active material layer 11b is formed.

That is, the exposed portion 15a is separated into a positive electrode current collector exposed portion 11c of one positive electrode 11 and a positive electrode current collector exposed portion 11d of the other positive electrode 11. Further, by cutting the exposed portion 15a described above, the coating film 55 is formed by the protective film 55a covering the positive electrode current collector exposed portion 11c of the one positive electrode 11 and the positive electrode current collector exposed portion 11d of the other positive electrode 11. It covers a part of the film and is separated from the film member 55b that projects outward in the width direction of the positive electrode current collector exposed portion 11d.

Although not particularly shown, the negative electrode 12 also forms a plurality of negative electrode active material layers 12b on a long copper metal foil at regular intervals like the positive electrode 11, and exposes between adjacent negative electrode active material layers 12b. Obtained by cutting at the part. By cutting the metal foil at the exposed portion, the exposed portion is separated into the negative electrode current collector exposed portions 12c and 12d of the negative electrode 12.

As shown in FIG. 4, the positive electrode 11 and the negative electrode 12 obtained as described above are wound around the separator 13 in a state of being overlapped with each other in the thickness direction to obtain a cylindrical tubular electrode body 60. When winding the positive electrode 11, the negative electrode 12, and the separator 13, the positive electrode 11, the negative electrode 12, and the separator 13 are wound so as to be wound around a core (not shown) (see FIG. 5).

In the present embodiment, the positive electrode 11, the negative electrode 12, and the separator 13 are stacked in the order of the separator 13, the positive electrode 11, the separator 13, and the negative electrode 12 from the bottom. When winding the positive electrode 11, the negative electrode 12, and the separator 13, the positive electrode 11, the negative electrode 12, and the separator 13 are wound while applying a predetermined tension to them. Then, inside the electrode body 10, the distance between the positive electrode 11, the negative electrode 12, and the separator 13 on the innermost peripheral side is narrowed by tightening with the electrodes on the outer peripheral side.

The step of winding the positive electrode 11, the negative electrode 12, and the separator 13 corresponds to the winding step. In this winding step, the positive electrode 11, the negative electrode 12, and the separator 13 are wound so that the separator 13 is located on the outermost periphery of the electrode body 10. Further, in the winding step, the positive electrode connection terminal 41 connected to the positive electrode 11 and the negative electrode connection terminal 42 connected to the negative electrode 12 project from the inner peripheral side of the electrode body 10 toward the outside in the winding axis direction. , The positive electrode 11, the negative electrode 12, and the separator 13 are wound around.

The winding end end of the tubular electrode body 60 obtained by winding the positive electrode 11, the negative electrode 12, and the separator 13 as described above is fixed by the winding stop tape 50.

After that, as shown in FIGS. 6 and 7, the tubular electrode body 60 is sandwiched between the pair of pressing portions 101 and 102 of the pressing device 100 and formed into a flat shape. Although the detailed configuration of the pressing device 100 will be omitted, one of the pair of pressing portions 101 and 102 arranged so as to face each other, one pressing portion 101 moves in the vertical direction and the horizontal direction. The pressing device 100 can apply a load of about 80 N in the vertical direction and a load of about 60 N in the horizontal direction to the tubular electrode body 60.

The pressing device 100 differs depending on the electrode length of the tubular electrode body 60 (the length in the longitudinal direction of the positive electrode 11 and the negative electrode 12), but is 60 in the vertical direction with respect to the tubular electrode body 60, for example. A load of ~ 100N and a load of 40-80N in the left-right direction can be applied.

The tubular electrode body 60 is arranged so as to be sandwiched between the pair of pressing portions 101 and 102 of the pressing device 100. In that state, the one pressing portion 101 moves downward with respect to the other pressing portion 102, so that the tubular electrode body 60 is flattened by applying a predetermined force to the side surface. The step of forming the flat electrode body 10 by applying a predetermined force to the side surface of the tubular electrode body 60 corresponds to the flattening step.

At this time, one pressing portion 101 moves in the left-right direction with respect to the tubular electrode body 60 so as to give a loosening force to the tubular electrode body 60 in the direction opposite to the winding direction. Specifically, when the winding direction is clockwise, one pressing portion 101 is moved counterclockwise with respect to the other pressing portion 102. When the winding direction is counterclockwise, one pressing portion 101 is moved clockwise with respect to the other pressing portion 102.

In the examples of FIGS. 6 and 7, one of the pressing portions 101 moves diagonally downward with respect to the tubular electrode body 60, as shown by the white arrows. As a result, a diagonally downward load is input to the tubular electrode body 60 by one of the pressing portions 101. Therefore, a downward load that is crushed by one of the pressing portions 101 and a load that loosens the outermost peripheral side are simultaneously input to the tubular electrode body 60.

As a result, the tubular electrode body 60 is crushed into a flat electrode body 10, and gaps are formed in the positive electrode 11, the negative electrode 12, and the separator 13 on the outermost peripheral side of the electrode body 10. The gap is hardly formed on the inner peripheral side of the electrode body 10.

As described above, by forming a gap between the positive electrode 11, the negative electrode 12, and the separator 13 on the outermost peripheral side of the electrode body 10, the difference in expansion ratio between the positive electrode 11 and the negative electrode 12 during charging and discharging of the laminated battery 1 It is possible to suppress the occurrence of bending inside the electrode body 10.

Here, as described above, the step of applying a loosening force to the electrode body 10 in the direction opposite to the winding direction corresponds to the loosening processing step.

Whether or not the loosening process has been performed can be easily determined by the position of the winding stop tape 50 (detected portion) that fixes the winding end end portion of the electrode body 10. That is, the position of the winding stop tape 50 when the loosening process is performed is different from the position of the winding stop tape 50 when the loosening process is not performed. This is because the separator 13 and the like on the outermost peripheral side of the electrode body 10 move slightly loosely from the state immediately after winding due to the loosening process. Therefore, by detecting the amount of movement of the winding stop tape 50, it is possible to detect whether or not the outermost peripheral side of the electrode body 10 is loosened.

The position of the winding stop tape 50 may be determined, for example, by acquiring an image of the winding stop tape 50 and performing image processing on the image. Further, the position of the winding stop tape 50 may be detected electrically or magnetically. In this case, the winding stop tape 50 may be made of a material that can be detected electrically or magnetically, or the winding stop tape 50 may be provided with a member that can be detected electrically or magnetically.

Here, as described above, the step of detecting whether or not the electrode body 10 has been loosened according to the position of the winding stop tape 50, that is, the looseness generated on the outermost peripheral side of the electrode body 10 due to the loosening is detected. The process corresponds to the loosening detection process.

After that, with the electrode body 10 placed on the laminate film exterior body 20, another laminate film exterior body 20 is superposed, and two laminate film exterior bodies 20 are welded around the electrode body 10. As a result, as shown in FIG. 1, the seal portion 1b is formed so as to surround the electrode body 10. When forming the seal portion 1b, the positive electrode side resin portion 45 of the positive electrode connection terminal 41 connected to the electrode body 10 and the negative electrode side resin portion 46 of the negative electrode connection terminal 42 are also two laminated film exterior bodies 20. Welding while sandwiched between.

As described above, when the electrode body 10 is covered with the two laminated film outer bodies 20, the two laminated film outer bodies 20 are covered with the electrode body so that the flat surface portion 1c is formed by one of the laminated film outer bodies 20. Arrange for 10. That is, of the two laminated film exterior bodies 20, one of the laminated film exterior bodies 20 constitutes a flat surface portion 1c, and the other laminated film exterior body 20 constitutes a bulging portion 1a.

When the electrode body 10 is covered with one laminated film outer body, the laminated film outer body is folded back on the side opposite to the positive electrode connection terminal 41 and the negative electrode connection terminal 42 of the electrode body 10, and the electrode body is covered with the laminated film outer body. The outer peripheral sides of the laminated film outer body may be welded to each other with the 10 sandwiched between them. In this case, since the configuration is the same as described above except that the electrode body is covered with one laminated film outer body, detailed description thereof will be omitted.

Here, as described above, the step of covering the electrode body 10 with the laminated film exterior body 20 corresponds to the exterior forming step.

From the above, when the tubular electrode body 60 obtained by winding the positive electrode 11, the negative electrode 12 and the separator 13 in a state of being overlapped in the thickness direction is crushed into a flat shape, the tubular electrode body 60 is subjected to. Apply a loosening force in the direction opposite to the winding direction. As a result, a gap in the major axis direction can be formed between the positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side of the flat electrode body 10. Therefore, it is possible to prevent the laminated battery 1 from being deformed when the laminated battery 1 using the electrode body 10 is charged and discharged.

Moreover, by loosening only the outermost peripheral side of the electrode body 10 as described above, the positive electrode connection terminal 41 is suppressed from becoming larger than the case where the entire electrode body 10 is loosened. And the movement of the negative electrode connection terminal 42 can be suppressed.

Therefore, it is necessary to prevent the electrode body 10 from being bent due to charging and discharging of the laminated battery 1, suppress the increase in size of the electrode body 10, and accurately position the positive electrode connection terminal 41 and the negative electrode connection terminal 42. Can be done.

In the present embodiment, the positive electrode connection terminal 41 and the negative electrode connection terminal 42 are located on the inner peripheral side of the electrode body 10. Therefore, by loosening only the outermost peripheral side of the electrode body 10 as described above, the positive electrode connection terminal 41 And the negative electrode connection terminal 42 can be prevented from moving more reliably. Therefore, the positive electrode connection terminal 41 and the negative electrode connection terminal 42 can be positioned more accurately.

Further, it can be easily determined whether or not the electrode body 10 has been loosened as described above by the position of the winding stop tape 50 for fixing the winding end end portion of the electrode body 10. Therefore, the productivity of the laminated battery 1 can be improved. Moreover, since it is not necessary to provide the electrode body 10 with another member for detecting the presence or absence of the loosening process, an increase in manufacturing cost can be suppressed.

In the above configuration, the separator 13 is located on the outermost circumference of the electrode body 10. Therefore, when the positive electrode 11, the negative electrode 12, and the separator 13 are wound in a state of being overlapped in the thickness direction, it is necessary to apply a predetermined tension to them. As a result, inside the electrode body 10, the distance between the positive electrode 11, the negative electrode 12, and the separator 13 becomes tight. In the case of such an electrode body, the inside of the electrode body tends to be bent by charging and discharging the battery.

On the other hand, as in the present embodiment, when the tubular electrode body 60 is crushed, a force to loosen the tubular electrode body 60 in the direction opposite to the winding direction is applied to the outermost periphery of the electrode body 10. By forming the gap, it is possible to effectively prevent bending inside the electrode body 10 due to the difference in expansion ratio between the positive electrode 11 and the negative electrode 12 when the laminated battery 1 is charged and discharged. , The deformation of the battery can be suppressed.

Further, in the case of the laminated battery 1 in which the electrode body 10 is covered with the laminate film outer body 20 as in the present embodiment, when the electrode body 10 is deformed by charging / discharging, it is easily affected by the deformation. On the other hand, as described above, by suppressing the deformation of the electrode body 10, the deformation of the laminated battery 1 can be suppressed.

(Other embodiments)
Although the embodiments of the present invention have been described above, the above-described embodiments are merely examples for carrying out the present invention. Therefore, the embodiment is not limited to the above-described embodiment, and the above-described embodiment can be appropriately modified and implemented within a range that does not deviate from the gist thereof.

In the above embodiment, the loosening process for the tubular electrode body 60 is performed at the same time as the flattening step of crushing the tubular electrode body 60 to make it flat. However, the loosening process may be performed after the flattening step. Even after the electrode body is formed into a flat shape by the flattening process, the bent portion on the outermost outer peripheral side of the electrode body is not deformed much as compared with the inner peripheral side. In the above embodiment, the positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side of the tubular electrode body 60 are loosened in the direction opposite to the winding direction. Therefore, even if the electrode body is formed flat by the flattening step, gaps can be formed in the positive electrode, the negative electrode, and the separator located on the outermost peripheral side of the electrode body.

In the above embodiment, the presence or absence of loosening of the electrode body 10 is determined by the position of the winding stop tape 50 for fixing the winding end end portion of the electrode body 10. However, the presence or absence of loosening is determined by, for example, the position of another member provided on the outermost peripheral side of the electrode body 10, such as the position of the film member 55b attached to the positive electrode current collector exposed portion 11d of the positive electrode 11. , The position of a mark, a pattern, or the like provided on the outermost peripheral side may be used. Further, the presence or absence of the loosening process may be determined by the position of a member (resin or the like) for fixing the winding end end of the electrode body 10 instead of the winding stop tape 50.

In the above embodiment, the winding stop tape 50 is used to determine whether or not the electrode body 10 is loosened. However, the winding stop tape 50 may be used to detect the amount of loosening when the electrode body 10 is loosened. As described above, by using the winding stop tape 50 for detecting the loosening amount in the loosening process, it is possible to drive and control the pressing device 100 so that the loosening amount becomes an appropriate value in the loosening process. ..

For example, as shown in FIG. 9, the pressing device 100 may be driven so as to adjust the amount of deflection according to the position of the winding stop tape 50 of the electrode body 10.

Specifically, the control device 110 that controls the drive of the pressing device 100 includes a position detection unit 111 and a drive control unit 112.

The position detection unit 111 detects the position of the winding stop tape 50 of the electrode body 10. The position detection unit 111 may detect the position of the winding tape 50 by, for example, image processing, or may detect the position of the winding tape 50 by an electric or magnetic method.

The drive control unit 112 moves the one pressing unit 101 in the pressing device 100 in the left-right direction according to the position of the winding stop tape 50 detected by the position detecting unit 111, that is, according to the amount of movement of the winding stop tape 50. Control the amount of movement. In the drive control unit 112, a predetermined gap is formed in the positive electrode 11, the negative electrode 12, and the separator 13 located on the outermost peripheral side of the electrode body 10 so that the inside of the electrode body 10 does not bend during charging and discharging of the battery. As described above, the drive of one pressing portion 101 is controlled. Thereby, the loosening amount on the outermost peripheral side of the electrode body 10 can be controlled.

In the above embodiment, the protective film 55a and the film member 55b are attached to the positive electrode 11. However, the protective film 55a and the film member 55b may be attached to the negative electrode 12. Even in this case, the film member 55b is attached to the negative electrode current collector exposed portion 12d located on the outermost peripheral side of the electrode body 10.

In the above embodiment, the positive electrode 11 and the negative electrode 12 formed in a band shape are superposed on the separator 13 so that the separator 13 is located between the two and under the positive electrode 11, respectively. However, the order in which the positive electrode 11, the negative electrode 12, and the separator 13 are stacked may be any order as long as the secondary battery can be configured.

In the above embodiment, the laminated battery is formed in a rectangular shape in a plan view. However, the laminated battery may have other shapes such as a polygonal shape.

In the above embodiment, the electrode body 10 is covered with the laminate film outer body 20. However, the electrode body 10 may be enclosed in a space formed by a bottomed tubular outer can and a sealing can.

In the above embodiment, the laminated battery 1 is a lithium ion battery. However, the laminated battery 1 may be a battery other than the lithium ion battery.

The present invention can be used for a secondary battery having an electrode body formed in a flat shape after winding a positive electrode, a negative electrode and a separator.

1 Laminated battery (secondary battery)
10 Electrode body 11 Positive electrode 11a Positive electrode current collector 11b Positive electrode active material layer 11c Positive electrode current collector exposed part 11d Positive electrode current collector exposed part (current collector exposed part)
12 Negative electrode 12a Negative electrode current collector 12b Negative electrode active material layer 12c, 12d Negative electrode current collector exposed part 13 Separator 20 Laminate film exterior body 41 Positive electrode connection terminal 42 Negative electrode connection terminal 45 Positive electrode side resin part 46 Negative electrode side resin part 50 Winding tape (Detected part)
55 Covering film 55a Protective film 55b Film member (film member)
60 Cylindrical electrode body 100 Pressing device 101, 102 Pressing unit 110 Control device 111 Position detection unit 112 Drive control unit

Claims (7)

A winding step of obtaining a tubular electrode body extending in the winding axis direction by winding the positive electrode, the negative electrode, and the separator formed in a band shape in a state of being stacked in the thickness direction.
A flattening step of forming a flat electrode body by applying a predetermined force to the side surface of the tubular electrode body, and a flattening step.
A loosening processing step of loosening the outermost peripheral side of the electrode body by applying a loosening force to the electrode body in a direction opposite to the winding direction.
Have,
A method for manufacturing a secondary battery, wherein the loosening processing step is performed at the same time as the flattening step or after the flattening step to loosen only the outermost peripheral side of the electrode body. In the method for manufacturing a secondary battery according to claim 1,
The loosening detecting step further comprises a loosening detecting step of detecting the loosening of the electrode body on the outermost peripheral side due to the loosening process by the amount of movement of the detected portion provided on the outermost peripheral side of the electrode body.
, How to manufacture a secondary battery. In the method for manufacturing a secondary battery according to claim 2.
The detected portion is a winding stop tape for fixing the winding end end portion of the electrode body.
How to manufacture a secondary battery. In the method for manufacturing a secondary battery according to claim 2.
The detected portion projects outward from the current collector exposed portion in the winding axis direction at a portion of the current collector exposed portion in the positive electrode or the negative electrode located on the outermost peripheral side of the electrode body. A method for manufacturing a secondary battery, which is a film member provided so as to be used. In the method for manufacturing a secondary battery according to any one of claims 2 to 4.
The loosening processing step is a method for manufacturing a secondary battery, in which the loosening amount of the electrode body is controlled according to the moving amount of the detected portion in the loosening detection step. In the method for manufacturing a secondary battery according to any one of claims 1 to 5.
In the winding step, the positive electrode connection terminal connected to the positive electrode and the negative electrode connection terminal connected to the negative electrode project from the inner peripheral side of the tubular electrode body toward the outside in the winding axial direction. A method for manufacturing a secondary battery, which comprises winding the positive electrode, the negative electrode, and the separator. In the method for manufacturing a secondary battery according to any one of claims 1 to 6.
A method for manufacturing a secondary battery, further comprising an exterior forming step of covering the electrode body after the flattening step and the loosening processing step with a laminate film exterior body.