Patent Application
20250030032
This application claims the benefit of priority to Japanese Patent Application No. 2023-119116 filed on Jul. 21, 2023. The entire contents of this application are hereby incorporated by reference herein.
The present invention relates to a method for producing a wound electrode assembly, an apparatus for producing the wound electrode assembly, and a power storage device including the wound electrode assembly.
For example, Japanese Laid-Open Patent Publication No. 2001-302034 discloses a method for producing a lithium ion secondary battery including a band-like positive electrode sheet, a band-like negative electrode sheet and separator sheets that are wound while being laminated on each other. According to the method described in Japanese Laid-Open Patent Publication No. 2001-302034, a winding core is rotated in a state where each of the sheets are supplied with a tension by a tension roller, and as a result, the sheets are wound around the winding core. Japanese Laid-Open Patent Publication No. 2001-302034 describes that in a state where the sheets are tension-free, for example, after the sheets are cut or when the winding of the sheets is finished, the sheets may occasionally move freely and may not be wound in a satisfactory manner. For this reason, a winding device described in
Japanese Laid-Open Patent Publication No. 2001-302034 includes a support roller that keeps supplying a tensile force on the positive electrode sheet, which is the last sheet to be wound among the four sheets, until winding of an end portion thereof is finished.
At the time when a wound body of the sheets formed by winding the sheets around a winding shaft is molded by pressing, curved portions of the sheets are deformed. Therefore, at the time of pressing, a large stress is applied to the curved portions of the sheets. It is preferred that such a stress applied to the curved portions of the sheets is as small as possible.
A method for producing a wound electrode assembly disclosed herein includes winding a lamination sheet including a band-like positive electrode sheet, a band-like negative electrode sheet, a band-like first separator sheet and a band-like second separator sheet laminated in a predefined order around a winding shaft, the winding the lamination sheet including feeding the lamination sheet and rotating the winding shaft, and the winding shaft having an outer circumferential surface of an oval shape including a pair of flat surfaces facing each other and a pair of arcked surfaces connecting both of ends of the pair of flat surfaces to each other; and pressing the lamination sheet formed to have an oval shape by the winding, such that a pair of flat portions of the lamination sheet are pressed to each other. In the winding the lamination sheet, the lamination sheet is fed by, per rotation of the winding shaft, a length longer than an outer circumferential length corresponding to the number of winds of the lamination sheet wound around the winding shaft.
With the above-described method for producing the wound electrode assembly, in the winding the lamination sheet, the lamination sheet is fed by, per rotation of the winding shaft, outer a length longer than an circumferential length corresponding to the number of winds of the lamination sheet wound around the winding shaft. Therefore, each time the rotation shaft is rotated, a space is generated between an inner layer of the lamination sheet already wound around the winding shaft and an outer layer of the lamination sheet to be wound outer to the inner layer. In the pressing, the pressed portion of the lamination sheet may escape into the space. Therefore, the above-described method for producing the wound electrode assembly may alleviate the stress to be applied in the pressing to curved portions, of the lamination sheet, formed by the arcked surfaces of the winding shaft.
An apparatus for producing a wound electrode assembly disclosed herein is an apparatus for producing a wound electrode assembly including a lamination sheet in a wound state, the lamination sheet including a band-like positive electrode sheet, a band-like negative electrode sheet, a band-like first separator sheet and a band-like second separator sheet laminated in a predefined order. The apparatus includes a winding shaft having an outer circumferential surface of an oval shape including a pair of flat surfaces facing each other and a pair of arcked surfaces connecting both of ends of the pair of flat surfaces to each other, the winding shaft allowing the lamination sheet to be wound around the outer circumferential surface thereof; a winding shaft driving device rotating the winding shaft; a feeding device feeding the lamination sheet toward the winding shaft; and a controller controlling the winding shaft driving device to control the rotation of the winding shaft and controlling the feeding device to control a length of the lamination sheet to be fed. The controller controls the feeding device to feed the lamination sheet by, per rotation of the winding shaft, a length longer than an outer circumferential length corresponding to the number of winds of the lamination sheet wound around the winding shaft.
The above-described apparatus for producing a wound electrode assembly provides the same functions and effects as those of the above-described method for producing a wound electrode assembly.
A power storage device disclosed herein includes a wound electrode assembly including a lamination sheet in a state of being wound a plurality of times, the lamination sheet including a band-like positive electrode sheet, a band-like negative electrode sheet, a band-like first separator sheet and a band-like second separator sheet laminated in a predefined order. The wound electrode assembly is wound to have an oval shape including a pair of flat portions facing each other and a pair of arcked R portions connecting both of ends of the pair of flat portions to each other. The lamination sheet includes a plurality of curved portions forming the R portions, the plurality of curved portions being laminated on each other in a diametrical direction of the R portions. An inner circumferential length of one curved portion among the plurality of curved portions is longer than an outer circumferential length of another curved portion among the plurality of curved portions immediately inner to the one curved portion.
In the above-described power storage device, the inner circumferential length of one curved portion is longer than the outer circumferential length of another curved portion immediately inner to the one curved portion. Therefore, the stress applied to the curved portions of the wound electrode assembly is small for the above-described reason.
Hereinafter, a preferred embodiment of an apparatus for producing a wound electrode assembly of a power storage device will be described. The embodiment described herein is not intended to specifically limit the present invention, needless to say. The drawings show schematic views, and do not reflect any actual product embodying the present invention.
In this embodiment, the wound electrode assembly production apparatus 10 produces the wound electrode assembly 1, which is a power generation element of a lithium ion secondary battery 100 (see
The positive electrode sheet 3 includes a band-like current collecting foil having a predefined width and a predefined thickness (e.g., an aluminum foil) and a positive electrode active material layer containing a positive electrode active material formed on a surface thereof. In, for example, a lithium ion secondary battery, the positive electrode active material is a material capable of releasing lithium ions when being charged and absorbing lithium ions when being discharged, like a lithium transition metal composite material. The negative electrode sheet 4 includes a band-like current collecting foil having a predefined width and a predefined thickness (e.g., a copper foil) and a negative electrode active material layer containing a negative electrode active material formed on a surface thereof. In, for example, a lithium ion secondary battery, the negative electrode active material is a material capable of, when being charged, occluding lithium ions and, when being discharged, releasing lithium ions occluded when being charged, like natural graphite. Various materials other than those mentioned above have been proposed as the positive electrode active material and the negative electrode active material, and there is no specific limitation thereon.
The first separator sheet 5 and the second separator sheet 6 are each formed of, for example, a porous resin sheet that has a required level of heat resistance and may transmit an electrolyte. Various materials for the separators have been proposed, and there is no specific limitation thereon. In this embodiment, the wound electrode assembly 1 includes the lamination sheet 2, which includes the first separator sheet 5, the positive electrode sheet 3, the second separator sheet 6 and the negative electrode sheet 4 laminated in this order. The lamination sheet 2 of the wound electrode assembly 1 is wound such that the negative electrode sheet 4 is on an outermost side.
As shown in
The winding shaft 21 has an outer circumferential surface of an oval shape including a pair of flat surfaces 21a facing each other and a pair of arcked surfaces 21b connecting both of ends of the pair of flat surfaces 21a to each other. The winding shaft 21 has a flat shape with which a distance between the pair of arcked surfaces 21b is longer than a distance between the pair of flat surfaces 21a. The lamination sheet 2 is to be wound around the outer circumferential surface of the winding shaft 21. A depth direction with respect to the paper sheet of
The winding shaft 21 forms the lamination sheet 2 into an oval shape that is close to the shape of the wound electrode assembly 1 in a finished state. Hereinafter, the lamination sheet 2 formed to have an oval shape by being wound around the winding shaft 21 will be referred to also as a “wound body of the lamination sheet 2”. The lamination sheet 2 is formed to be the wound body having a shape corresponding to the shape of the outer circumferential surface of the winding shaft 21. As shown in
Hereinafter, flat portions and R portions of the post-press wound electrode assembly 1 will be referred to as a “pair of flat portions 1a” and a “pair of R portions 1b” (see
As shown in
The winding shaft moving device 23 moves the winding shaft 21 in accordance with the rotation of the winding shaft 21, such that a trailing end of a portion, of the lamination sheet 2, that is wound around the winding shaft 21 is kept just below the nip rollers 31. A specific movement of the winding shaft 21 will be described below with reference to
The winding shaft moving device 23 includes, for example, a slide guide (not shown) engaged with the rotation shaft 22a of the winding shaft 21 such that the rotation shaft 22a is slidable in a left-right direction in
The pair of nip rollers 31 of the feeding device 30 rotate while sandwiching the lamination sheet 2. The pair of nip rollers 31 feed the lamination sheet 2 toward the winding shaft 21. The pair of nip rollers 31 are respectively rotatable about axial lines 31a extending in the width direction of the lamination sheet 2. The pair of nip rollers 31 are provided above the winding shaft 21. The lamination sheet 2 fed by the pair of nip rollers 31 advances downward by the action of the gravitational force because no tensile force is applied to the lamination sheet 2. The nip roller driving device 32 rotates the pair of nip rollers 31. In this embodiment, the nip roller driving device 32 includes a driving motor 32a rotating one of the pair of nip rollers 31. The other nip roller 31 rotates subordinately in accordance with the rotation of the nip roller 31 driven by the driving motor 32a. It should be noted that the nip roller driving device 32 may drive both of the pair of nip rollers 31. Whether the driving motor 32a is to be driven, or to be stopped, the rotation speed thereof, and the rotation angle thereof are controlled by the controller 50.
The nip roller moving device 33 causes the pair of nip rollers 31 to be closer to each other such that the pair of nip rollers 31 sandwich the lamination sheet 2, or causes the pair of nip rollers 31 to be away from each other such that the pair of nip rollers 31 release the lamination sheet 2. In this embodiment, the nip roller moving device 33 moves the left nip roller 31. The left nip roller 31 moves between a position where the left nip roller 31 may sandwich the lamination sheet 2 together with the right nip roller 31 and a position that is to the left, in
The press roller 34 presses the lamination sheet 2 wound along each of the arcked surfaces 21b of the winding shaft 21 toward the arcked surface 21b. The lamination sheet 2 including the current collecting foil, which is formed of a metal material, is pressed by the press roller 34 and thus is plastically deformed. As a result, the lamination sheet 2 is shaped to be along the shape of the outer circumferential surface of the winding shaft 21. In this manner, the lamination sheet 2 may be shaped to be along the shape of the outer circumferential surface of the winding shaft 21 with no tensile force being applied to the lamination sheet 2.
The press roller driving device 35 rotates the press roller 34. The press roller driving device 35 rotates the press roller 34 about a rotation shaft 35a extending in the width direction of the lamination sheet 2. The press roller driving device 35 includes a driving motor 35b rotating the press roller 34. Whether the driving motor 35b is to be rotated, or to be stopped, the rotation speed thereof, and the rotation angle thereof are controlled by the controller 50. The press roller 34 is rotated by a driving force of the driving motor 35b in this manner. The press roller 34 is to cause the shape of the lamination sheet 2 to be along the shape of the outer circumferential surface of the winding shaft 21 and also to rotate to feed the lamination sheet 2 on each of the arcked surfaces 21b. It should be noted that a press member that causes the shape of the lamination sheet 2 to be along the shape of the outer circumferential surface of the winding shaft 21 does not need to be associated with the feeding of the lamination sheet 2. Such a press member may be, for example, a member that does not rotate and is warped following the movement of the arcked surfaces 21b.
The following device 36 moves the press roller 34 such that the press roller 34 moves along each of the arcked surfaces 21b of the winding shaft 21 in accordance with the movement of the arcked surface 21b. The following device 36 moves the press roller 34 and thus keeps the press roller 34 in contact with the arcked surface 21b, which is moved by the rotation of the winding shaft 21 and the driving of the winding shaft moving device 23. In this embodiment, the following device 36 keeps the press roller 34 in contact with the winding shaft 21 while the lamination sheet 2 is wound along about a half of the outer circumferential surface of the winding shaft 21. The timing at which the following device 36 puts the press roller 34 into contact with the winding shaft 21 will be described below.
The following device 36 includes, for example, a slide guide (not shown) engaged with the press roller 34 such that the press roller 34 is slidable in an up-down direction, a driving motor 36a moving the press roller 34 along the slide guide, and a ball screw mechanism (not shown) connected with the driving motor 36a. It should be noted that there is no specific limitation on the configuration of the following device 36. Whether the driving motor 36a is to be driven, or to be stopped, the rotation speed thereof, and the rotation angle thereof are controlled by the controller 50.
The press roller moving device 37 causes the press roller 34 to contact, or to separate from, each of the arcked surfaces 21b of the winding shaft 21. The press roller moving device 37 moves the press roller 34 between a position where the press roller 34 is capable of contacting the winding shaft 21 just below the nip rollers 31 and a position which is to the right, in
The controller 50 controls the winding shaft driving device 22 to control the rotation of the winding shaft 21, and also controls the feeding device 30 to control a length of the lamination sheet 2 to be fed. In more detail, the controller 50 controls the feeding device 30 to feed the lamination sheet 2 by, per rotation of the winding shaft 21, a length longer than an outer circumferential length corresponding to the number of winds of the lamination sheet 2 wound around the winding shaft 21. The lamination sheet 2 is fed in this manner, and as a result, an outer circumferential length of a portion of the lamination sheet 2 that is already wound around the winding shaft 21 (hereinafter, such a portion of the lamination sheet 2 will be referred to also as an “inner layer of the lamination sheet 2”) is shorter than an inner circumferential length of a portion of the lamination sheet 2 that is to be wound around the inner layer of the lamination sheet 2 (hereinafter, such a portion of the lamination sheet 2 will be referred to also as an “outer layer of the lamination sheet 2”). That is, the inner circumferential length of the outer layer of the lamination sheet 2 is longer than the outer circumferential length of the inner layer of the lamination sheet 2. As a result, each time the rotation shaft 21 is rotated, a space is generated between the inner layer of the lamination sheet 2 and the outer layer of the lamination sheet 2. An effect provided by the space will be described below.
The outer circumferential length of the lamination sheet 2 wound around the winding shaft 21 becomes longer as the number of winds increases. The controller 50 increases the length of the lamination sheet 2 to be fed by the feeding device 30 each time the number of winds of the lamination In this embodiment, the controller 50 sheet 2 increases. calculates a sum of the increase in the outer circumferential length caused by the increase in the number of winds, a predetermined additional length provided to generate a space, and the outer circumferential length of the inner layer of the lamination sheet 2, and thus sets the found sum as the length of the outer layer of the lamination sheet 2. In this preferred embodiment, the additional length provided to generate a space is fixed regardless of the number of winds. However, the additional length does not need to be fixed.
The above-described additional length is set to, for example, such a length as to generate spaces 1c each having a gap G1 between the plurality of curved portions 2d of the lamination sheet 2 (see
In this preferred embodiment, for at least a part of a time period in which the lamination sheet 2 is being wound along each of arcked surfaces 21b, the controller 50 controls the feeding device 30 to feed the lamination sheet 2 at a speed higher than the speed at which the lamination sheet 2 is wound along the arcked surface 21b. With such control, while being wound along each arcked surface 21b, the lamination sheet 2 is fed by a length longer than the outer circumferential length corresponding to the number of winds of the lamination sheet 2 wound along the arcked surface 21b. As a result, a space is easily formed by an excessive part of the lamination sheet 2 that has been fed, in each of the R portions 2b of the wound body of the lamination sheet 2. In this preferred embodiment, for the rest of the above-mentioned time period, the controller 50 feeds the lamination sheet 2 at a speed same as the speed at which the lamination sheet 2 is wound around the winding shaft 21. With such control, very little space is formed by an excessive part of the lamination sheet 2 that has been fed, in each of the flat portions 2a of the lamination sheet 2.
In more detail, for at least a part of the time period in which the lamination sheet 2 is being wound along each arcked surface 21b, the controller 50 controls the nip roller moving device 33 to cause the pair of nip rollers 31 to be away from each other. For the above-mentioned part of the time period, the controller 50 also controls the press roller moving device 37 and the press roller driving device 35 to rotate the press roller 34 in a state where the press roller 34 is in contact with the arcked surface 21b. In this state, the feeding speed of the lamination sheet 2 is controlled by the rotation speed of the press roller 34. The controller 50 controls such that the feeding speed of the lamination sheet 2 by the press roller 34 is higher than the speed at which the lamination sheet 2 is wound along the arcked surface 21b.
For the rest of the above-mentioned time period, the controller 50 controls the press roller moving device 37 to cause the press roller 34 to separate from the winding shaft 21. For the rest of the above-mentioned time period, the controller 50 also controls the nip roller moving device 33 and the nip roller driving device 32 to cause the pair of nip rollers 31 to sandwich and feed the lamination sheet 2. In this state, the feeding speed of the lamination sheet 2 is controlled by the rotation speed of the nip rollers 31. The controller 50 controls such that the feeding speed of the lamination sheet 2 by the pair of nip rollers 31 is the same as the speed at which the lamination sheet 2 is wound around the winding shaft 21.
The press device 40 presses the wound body of the lamination sheet 2 such that the pair of flat portions 2a are pressed to each other. As shown in
In this preferred embodiment, the wound body of the post-press lamination sheet 2 is further pressed by the final press device different from the press device 40, and thus is compressed to have a predetermined thickness. The final press device includes no leaf spring and presses the lamination sheet 2 by use of press members. It should be noted that the above-described final press may be performed also by the press device 40. The press device 40 may be a part of, or the entirety of, a press apparatus in a broad sense that presses the wound body of the lamination sheet 2 such that the pair of flat portions 2a are pressed to each other, and thus forms the wound electrode assembly 1 by molding.
First, the winding step S10 will be described in detail.
As shown in
In step S11, as shown in
In step S12, it is determined whether or not the winding shaft 21 has arrived at the 3 o'clock position. In the case where the winding shaft 21 has not arrived at the 3 o'clock position (NO in step S12), step S11 is continued.
In the case where the winding shaft 21 has arrived at the 3 o'clock position (YES in step S12), in step S13, the pair of nip rollers 31 are caused to be away from each other, and the lamination sheet 2 is released from the state of being sandwiched by the nip rollers 31 (see
In step S15, the winding shaft 21 is rotated, and the press roller 34 is also rotated. In step S15, formation of one of the R portions 2b by the corresponding arcked surface 21b is mainly performed. As shown in
In step S15, the press roller 34 is rotating and feeding the lamination sheet 2 downward. A portion of the lamination sheet 2 that is upstream with respect to the press roller 34 is supplied with a tensile force. By contrast, a portion of the lamination sheet 2 that is downstream with respect to the press roller 34 is supplied with no tensile force. In step S15, the press roller 34 rotates so as to feed the lamination sheet 2 at a speed higher than the speed at which the lamination sheet 2 is wound around the winding shaft 21. As a result, the lamination sheet 2 wound along the arcked surface 21b is slackened. Such control allows the lamination sheet 2 to be adjusted to be arc-shaped and allows a space to be formed between the curved portion 2d of the inner layer of the lamination sheet 2 and the curved portion 2d of the outer layer of the lamination sheet 2.
In step S16, it is determined whether or not the winding shaft 21 has arrived at the 6 o'clock position. In the case where the winding shaft 21 has not arrived at the 6 o'clock position (NO in step S16), step S15 is continued. In the case where the winding shaft 21 has arrived at the 6 o'clock position (YES in step S16), in step S17, the press roller 34 is separated from the winding shaft 21 (see
In the first press step S21, the pressing is started with a part of the pair of flat portions 2a of the lamination sheet 2 (in this embodiment, a central portion, in the longitudinal direction, of the wound body), and the pressing is performed such that the pressed region spreads toward the pair of R portions 2b of the lamination sheet 2 formed to have an oval shape.
In the first press step S21, the leaf springs 42 are each sandwiched between the corresponding press member 41 and the lamination sheet 2, and thus is gradually crushed outward from the apex of the protrusion. In this manner, the pressing is started with a part of the pair of flat portions 2a of the lamination sheet 2 (in this embodiment, a central portion), and the pressed region spreads toward the pair of R portions 2b of the lamination sheet 2. As a result, spaces that are also present between the plurality of layers in the flat portions 2a of the wound body of the lamination sheet 2 are The excessive parts of the lamination sheet 2 crushed. generated as a result of the spaces being crushed are absorbed by the plurality of curved portions 2d. As a result, the spaces between the plurality of curved portions 2d are expanded, and as shown in
In the second press step S22, the wound body of the lamination sheet 2 is further pressed until the wound body has a predefined thickness. As a result, the wound electrode assembly 1 is formed.
Hereinafter, functions and effects provided by the wound electrode assembly production apparatus 10 and the method for producing the wound electrode assembly 1 according to this preferred embodiment will be described.
The wound electrode assembly production apparatus 10 according to this preferred embodiment is an apparatus for producing the wound electrode assembly 1 including the lamination sheet 2 in a wound state. The lamination sheet 2 includes the band-like positive electrode sheet 3, the band-like negative electrode sheet 4, the band-like first separator sheet 5 and the band-like second separator sheet 6 laminated in a predefined order. The wound electrode assembly production apparatus 10 includes the winding shaft 21 having an outer circumferential surface of an oval shape including the pair of flat surfaces 21a facing each other and the pair of arcked surfaces 21b connecting both of the ends of the pair of flat surfaces 21a to each other, the winding shaft 21 allowing the lamination sheet 2 to be wound around the outer circumferential surface thereof; the winding shaft driving device 22 rotating the winding shaft 21; the feeding device 30 feeding the lamination sheet 2 toward the winding shaft 21; and the controller 50 controlling the winding shaft driving device 22 to control the rotation of the winding shaft 21 and controlling the feeding device 30 to control a length of the lamination sheet 2 to be fed. The controller 50 controls the feeding device 30 to feed the lamination sheet 2 by, per rotation of the winding shaft 21, a length longer than an outer circumferential length corresponding to the number of winds of the lamination sheet 2 wound around the winding shaft 21.
With the wound electrode assembly production apparatus 10 having such a configuration, the lamination sheet 2 is fed by, per rotation of the winding shaft 21, a length longer than an outer circumferential length corresponding to the number of winds of the lamination sheet 2 wound around the winding shaft 21. Therefore, each time the rotation shaft 21 is rotated, a space is generated between the inner layer of the lamination sheet 2 already wound around the winding shaft 21 and the outer layer of the lamination sheet 2 to be wound outer to the inner layer. In the press step S20, the pressed portion of the lamination sheet 2 may escape into the space. Therefore, the wound electrode assembly production apparatus 10 having such a configuration may alleviate the stress to be applied to the R portions 2b of the lamination sheet 2 in the press step S20.
In the case where the laminate sheet 2 is wound around the winding shaft 21 while a tensile force is applied to the lamination sheet 2, no space is generated between the inner layer of the lamination sheet 2 and the outer layer of the lamination sheet 2. Therefore, when the R portions 2b of the lamination sheet 2 are deformed in the press step S20, a large stress is applied to the R portions 2b of the lamination sheet 2. In addition, at the time of charge and discharge of the power storage device, the wound electrode assembly 1 is expanded and contracted. Such expansion and contraction of the wound electrode assembly 1 also applies a large stress to the R portions 2b of the lamination sheet 2. In the case where the number of winds of the lamination sheet 2 is increased in an attempt to increase the capacitance of the power storage device, the wound electrode assembly 1 is expanded and contracted to a higher degree. From the point of view of the durability and the reliability of the R portions 2b, it is preferred that the stress to be applied to the R portions 2b of the lamination sheet 2 is small. With the wound electrode assembly production apparatus 10 according to this preferred embodiment, a space is formed between the inner layer of the lamination sheet 2 and the outer layer of the lamination sheet 2, so that the stress to be applied to the R portions 2b of the lamination sheet 2 may be alleviated.
The wound electrode assembly production apparatus 10 according to this preferred embodiment includes the press roller 34 pressing the lamination sheet 2 wound along each of the arcked surfaces 21b of the winding shaft 21 toward the arcked surface 21b. With such a configuration, the press roller 34 presses the lamination sheet 2, so that the lamination sheet 2 may be shaped to be along the shape of the outer circumferential surface of the winding shaft 21 with no tensile force being applied to the lamination sheet 2.
In this preferred embodiment, for at least a part of a time period in which the lamination sheet 2 is being wound along each of the arcked surfaces 21b, the controller 50 controls the feeding device 30 to feed the lamination sheet 2 at a speed higher than a speed at which the lamination sheet 2 is wound along the arcked surface 21b. With such control, while being wound along the arcked surface 21b, the lamination sheet 2 may be fed by a length longer an outer circumferential length corresponding to the number of winds of the lamination sheet 2 wound along the arcked surface 21b. As a result, the lamination sheet 2 wound along the arcked surface 21b is slackened, and a space may be formed between the curved portion 2d of the inner layer and the curved portion 2d of the outer layer. In this embodiment, for a second half of the time period in which the lamination sheet 2 is being wound along the arcked surface 21b (time period shown in
In this preferred embodiment, the feeding device 30 includes the pair of nip rollers 31 rotating while sandwiching the lamination sheet 2 and feeding the lamination sheet 2 toward the winding shaft 21, the nip roller driving device 32 rotating the pair of nip rollers 31, the nip roller moving device 33 causing the pair of nip rollers 31 to be closer to each other such that the pair of nip rollers 31 sandwich the lamination sheet 2, or causing the pair of nip rollers 31 to be away from each other such that the pair of nip rollers 31 release the lamination sheet 2, the press roller 34 pressing the lamination sheet 2 wound along each of the arcked surfaces 21b of the winding shaft 21 toward the arcked surface 21b, the press roller driving device 35 rotating the press roller 34, and the press roller moving device 37 causing the press roller 34 to contact, or to separate from, each of the arcked surfaces 21b.
For at least a part of the time period in which the lamination sheet 2 is being wound along each of the arcked surfaces 21b, the controller 50 controls the nip roller moving device 33 to cause the pair of nip rollers 31 to be away from each other, and controls the press roller moving device 37 and the press roller driving device 35 to rotate the press roller 34 in a state where the press roller 34 is in contact with the arcked surface 21b. For the rest of the time period, the controller 50 controls the press roller moving device 37 to cause the press roller 34 to separate from the winding shaft 21, and controls the nip roller moving device 33 and the nip roller driving device 32 to cause the pair of nip rollers 31 to sandwich and feed the lamination sheet 2. The controller 50 causes the pair of nip rollers 31 to feed the lamination sheet 2 at a speed same as a speed at which the lamination sheet 2 is wound around the winding shaft 21. The controller 50 causes the press roller 34 to feed the lamination sheet 2 at a speed higher than the speed at which the lamination sheet 2 is wound along each of the arcked surfaces 21b.
With such a configuration, for at least a part of the time period in which the lamination sheet 2 is being wound along each of the arcked surfaces 21b, the feeding speed of the lamination sheet 2 is controlled by the rotation speed of the press roller 34. Therefore, the rotation speed of the press roller 34 is controlled for the above-described part of the time period, so that the feeding speed of the lamination sheet 2 may be made higher than the speed at which the lamination sheet 2 is wound along the arcked surface 21b.
The wound electrode assembly production apparatus 10 according to this preferred embodiment starts pressing the lamination sheet 2 from a part of the pair of flat portions 2a thereof and spreads a pressed region toward the pair of R portions 2b of the lamination sheet 2. With such a configuration, spaces that are also present between the plurality of layers in the flat portions 2a of the wound body of the lamination sheet 2 are crushed by the above-described step, and the spaces 1c each having a desired gap G1 are formed between the plurality of curved portions 2d. This may further alleviate the stress to be applied to the R portions 2b.
In more detail, the wound electrode assembly production apparatus 10 according to this preferred embodiment further includes the press device 40 pressing the wound body of the lamination sheet 2 such that the pair of flat portions 2a thereof are pressed to each other. The press device 40 includes the pair of press members 41 facing each other and respectively pressing the pair of flat portions 2a of the lamination sheet 2, and the pair of leaf springs 42 respectively provided for the pair of press members 41 and each curved to protrude toward the press member 41 facing the corresponding press member 41. With such a configuration, the press device 40 may start pressing the lamination sheet 2 from a part of the pair of flat portions 2a thereof and spread the pressed region toward the pair of R portions 2b of the lamination sheet 2.
In this preferred embodiment, a power storage device (in this embodiment, the lithium ion secondary battery 100) as follows may be provided. The lithium ion secondary battery 100 includes the wound electrode assembly 1 including the lamination sheet 2 in a state of being wound a plurality of times. The lamination sheet 2 includes the band-like positive electrode sheet 3, the band-like negative electrode sheet 4, the band-like first separator sheet 5 and the band-like second separator sheet 6 laminated in a predefined order. In the lithium ion secondary battery 100 according to this preferred embodiment, the wound electrode assembly 1 is wound to have an oval shape including the pair of flat portions 1a facing each other and the pair of arcked R portions 1b connecting both of ends of the pair of flat portions 1a to each other. The lamination sheet 2 includes the plurality of curved portions 2d forming the R portions 1b, the plurality of curved portions 2d being laminated on each other in a diametrical direction of the R portions 1b. An inner circumferential length of one curved portion 2d is longer than an outer circumferential length of another curved portion 2d immediately inner to the one curved portion 2d. With the lithium ion secondary battery 100 having such a configuration, the stress to be applied to the R portions 1b of the wound electrode assembly 1 may be alleviated for the above-described reason.
In the lithium ion secondary battery 100 according to this preferred embodiment, the space 1c is provided between one curved portion 2d and the another curved portion 2d immediately inner to the one curved portion 2d. With the lithium ion secondary battery 100 having such a configuration, the stress to be applied to the R portions 1b of the wound electrode assembly 1 may be alleviated for the above-described reason.
In the lithium ion secondary battery 100 according to this preferred embodiment, the lamination sheet 2 includes the plurality of straight portions 2c laminated on each other to form the flat portions 1a. The plurality of straight portions 2c have an identical length to each other. With such a configuration, even when the laminate sheet 2 is expanded and contracted by the charge and discharge of the lithium ion secondary battery 100, no difference is caused to the length of the plurality of straight portions 2c. Therefore, no space is easily formed between the plurality of straight portions 2c (the plurality of straight portions 2c are not easily peeled off from each other), and thus the lithium ion secondary battery 100 is not deteriorated easily.
A preferred embodiment of an apparatus for producing a wound electrode assembly proposed herein is described above.
The above-described embodiment is merely an example, and the present invention may be carried out in any of other embodiments. For example, in the above-described preferred embodiment, when the lamination sheet 2 is to be wound along each of the arcked surfaces 21b of the winding shaft 21, the feeding speed of the lamination sheet 2 is increased to feed the lamination sheet 2 by a length longer than the outer circumferential length corresponding to the number of winds of the lamination sheet 2. Alternatively, when the lamination sheet 2 is to be wound along each of the flat surfaces 21a of the winding shaft 21, the feeding speed of the lamination sheet 2 may be made higher than the speed at which the lamination sheet 2 is wound around the winding shaft 21. Still alternatively, the lamination sheet 2 may be fed in advance and slackened before being wound around the winding shaft 21.
In the above-described preferred embodiment, the feeding device 30 rotates the press roller 34 such that the lamination sheet 2 is fed also by the press roller 34. Alternatively, the feeding device 30 may be configured such that the lamination sheet 2 is fed only by the pair of nip rollers 31. The press roller 34 may merely rotate subordinately. In a configuration in which the press roller 34 is not needed to wind the lamination sheet 2 around the winding shaft 21, the press roller 34 may be omitted.
In the above-described preferred embodiment, the press device 40 includes the pair of leaf springs 42 to spread the slackened parts of the lamination sheet 2 outward from the center of the flat portions 2a. Alternatively, the press device 40 does not need to include an element, such as the leaf springs 42, to spread the slackened parts of the lamination sheet 2. In the case where the lamination sheet 2 is fed by a length longer than the outer circumferential length corresponding to the number of winds of the lamination sheet 2, the function and the effect of alleviating the stress to be applied to the R portions 2b may be provided to some extent even if the slacked parts of the lamination sheet 2 are not spread toward the R portions 2d.
The above-described embodiments do not limit the present invention in any way unless otherwise specified. The technology disclosed herein may be altered in any of various manners. The elements and the processes referred to herein may each be omitted where appropriate, or may be combined in an appropriate manner, unless any specific problem is caused.
This specification includes the following disclosure.
A method for producing a wound electrode assembly, comprising:
The method for producing the wound electrode assembly according to item 1, wherein in the winding the lamination sheet, while being wound along each of the arcked surfaces, the lamination sheet is fed by a length longer than the outer circumferential length corresponding to the number of winds of the lamination sheet wound along the each arcked surface.
The method for producing the wound electrode assembly according to item 1 or 2, wherein the pressing the lamination sheet includes a first pressing of starting pressing the lamination sheet from a part of the pair of flat portions thereof and spreading a pressed region toward a pair of arcked portions of the lamination sheet.
The method for producing the wound electrode assembly according to item 3, wherein the first pressing uses a press device including:
An apparatus for producing a wound electrode assembly including a lamination sheet in a wound state, the lamination sheet including a band-like positive electrode sheet, a band-like negative electrode sheet, a band-like first separator sheet and a band-like second separator sheet laminated in a predefined order, the apparatus comprising:
The apparatus for producing the wound electrode assembly according to item 5, further comprising a press roller pressing the lamination sheet wound along each of the arcked surfaces of the winding shaft toward the each arcked surface.
The apparatus for producing the wound electrode assembly according to item 5 or 6, wherein for at least a part of a time period in which the lamination sheet is being wound along each of the arcked surfaces, the controller controls the feeding device to feed the lamination sheet at a speed higher than a speed at which the lamination sheet is wound along the each arcked surface.
The apparatus for producing the wound electrode assembly according to item 7, wherein:
The apparatus for producing the wound electrode assembly according to any one of items 5 through 8, further comprising a press device pressing the lamination sheet, formed to have an oval shape by being wound around the winding shaft, such that a pair of flat portions of the lamination sheet are pressed to each other,
A power storage device, comprising:
The power storage device according to item 10, wherein a space is provided between the one curved portion and the another curved portion immediately inner to the one curved portion.
The power storage device according to item 10 or 11, wherein:
| Number | Date | Country | Kind |
|---|---|---|---|
| 2023-119116 | Jul 2023 | JP | national |
