Manufacturing method of battery and battery

Abstract

To suppress damage of a separator which is provided in contact with an electrode sheet in an innermost periphery of a wound body.SOLUTION: A manufacturing method of a lithium ion secondary battery is a manufacturing method of a battery comprising a wound body 30 in which a cathode sheet 50 as an electrode sheet, an anode sheet 40 as an electrode sheet and a separator 60 are wound while being laminated and which is configured by alternately forming a plane part 30B and an R part 30A. The manufacturing method includes a drying step of heating and drying the wound body 30 at a predetermined drying temperature in a state where at least a portion of an end of the separator 60 in a width direction is fixed by imparting a predetermined constraint load in a thickness direction of the separator 60 at a position corresponding to the plane part 30B which is formed at an outermost periphery side of the wound body 30. The end of the separator 60 in the width direction includes an end protruding from the anode sheet 40 disposed at an innermost periphery side of the wound body 30.SELECTED DRAWING: Figure 9

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a battery and a battery. [Background technology]

[0002] Patent Document 1 describes that in the manufacturing process of a stacked battery, when sheets such as positive electrode foil, negative electrode foil, and separator are transported and placed in the specified stacking position in sequence using a specified transport device, the vicinity of the corners of each sheet is pressed from above with a pressing member to prevent the sheet from shifting position.

[0003] Furthermore, Patent Document 2 describes that in a laminated lithium ion polymer battery, an electrode laminate in which a positive electrode and a negative electrode are laminated with a separator interposed between them is surrounded and fixed by an insulating porous sheet and housed in a laminate exterior, thereby making it difficult for the electrode laminate to shift position and improving workability when housing the electrode laminate in the exterior.

[0004] Furthermore, Patent Document 3 describes that in a secondary battery having an electrode group in which a positive electrode and a negative electrode are wound around a shaft core with a separator therebetween, by fixing the winding start end of the separator to the shaft core using a fixing member such as an adhesive tape, the separator can be reliably fixed to the shaft core without shifting its position during winding. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] JP 2016-195092 A [Patent Document 2] JP 2007-141714 A [Patent Document 3] JP 2018-107055 A Summary of the Invention [Problem to be solved by the invention]

[0006] In a battery having a wound body in which a positive electrode sheet, a negative electrode sheet, and a separator are wound in a stacked state, the separator shrinks due to heating during a drying process of the wound body. At this time, there is a risk that an end of the innermost electrode sheet and an end of the separator provided in contact with the electrode sheet will interfere with each other, causing damage to the separator.

[0007] In consideration of the above, an object of the present invention is to suppress damage to a separator provided in contact with an innermost electrode sheet of a wound body. [Means for solving the problem]

[0008] A first aspect of the present invention relates to a method for manufacturing a battery having a wound body in which a positive electrode sheet as an electrode sheet, a negative electrode sheet as the electrode sheet, and a separator are stacked and wound together, so that flat portions and R portions are alternately formed. The method includes a drying step of applying a predetermined restraining load along the thickness direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the wound body, thereby fixing at least a part of the width direction end portion of the separator, and heating the wound body at a predetermined drying temperature to dry it, and the width direction end portion of the separator includes an end portion protruding from the electrode sheet arranged on the innermost peripheral side of the wound body.

[0009] A second aspect of the present invention relates to a method for manufacturing a battery, and in the method for manufacturing the battery according to the first aspect, the widthwise end of the separator is an end that protrudes from the electrode sheet that is arranged on the innermost side of the wound body, and includes an end that overlaps with the R portion of the separator that is arranged on the innermost side of the wound body.

[0010] A battery manufacturing method of a third aspect of the present invention is the method of the first or second aspect, further comprising an activation step of initially charging a secondary battery including the wound body, heating it at a predetermined environmental temperature, and storing it for a predetermined time, wherein in the activation step, a predetermined restraining load is applied along the thickness direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the wound body, thereby fixing at least a part of the widthwise end portion of the separator, and the widthwise end portion of the separator includes an end portion located at the boundary with the R portion formed on the outermost peripheral side of the wound body.

[0011] A battery according to a fourth aspect of the present invention has a wound body in which a positive electrode sheet as an electrode sheet, a negative electrode sheet as the electrode sheet, and a separator are stacked and wound together, so that flat portions and R portions are alternately formed, and a concave fixing portion that is formed on at least a part of an end portion in a width direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the wound body and is depressed in a thickness direction of the separator by pressing, and the end portion in the width direction of the separator includes an end portion protruding from the electrode sheet arranged on the innermost peripheral side of the wound body. Effect of the Invention

[0012] In the battery manufacturing method according to the first aspect of the present invention, a predetermined restraining load is applied in the thickness direction of the separator at a position corresponding to the flat portion formed on the outermost periphery of the wound body, whereby the wound body can be dried while at least a part of the end portion in the width direction of the separator is fixed.

[0013] Here, the end of the separator in the width direction that is fixed includes an end protruding from the electrode sheet arranged on the innermost periphery of the wound body. This prevents the end of the separator provided in contact with the innermost electrode sheet of the wound body from shrinking due to heating in the drying process. As a result, it is possible to reduce interference between the end of the innermost electrode sheet and the end of the separator provided in contact with the electrode sheet, and to prevent damage to the separator.

[0014] In the battery manufacturing method according to the second aspect of the present invention, the wound body can be dried while the end of the separator protruding from the electrode sheet arranged on the innermost periphery of the wound body and located at the R part arranged on the innermost periphery of the wound body is fixed. This makes it possible to suppress contraction of the separator end at the R part of the separator that contacts the sharp part of the electrode sheet arranged on the innermost periphery, thereby suppressing damage to the easily damaged part of the separator.

[0015] Incidentally, in the activation process of a secondary battery including a wound body, the wound body may be heated at a predetermined environmental temperature. At this time, the electrode sheet of the wound body may be buckled due to the contraction of the separator, which may lead to a deterioration in performance.

[0016] In the battery manufacturing method according to the third aspect of the present invention, a predetermined restraining load is applied in the thickness direction of the separator at a position corresponding to the flat portion formed on the outermost periphery of the wound body in the activation process of the secondary battery including the wound body, whereby the wound body can be heated at a predetermined environmental temperature and stored for a predetermined time while at least a part of the end portion in the width direction of the separator is fixed.

[0017] Here, the end of the separator in the width direction that is fixed includes the end located at the boundary with the R portion formed on the outermost peripheral side of the wound body. Therefore, at the outermost peripheral side where the temperature rise during heating is large and the separator is likely to shrink, the end of the separator located at the boundary with the R portion is fixed. Since the R portion has a large curvature of the electrode sheet, it is a position that is difficult to absorb stress due to the shrinkage of the separator. Therefore, by fixing the end of the separator located at the boundary with the R portion and suppressing the shrinkage, the buckling of the electrode sheet can be effectively suppressed.

[0018] In the battery according to the fourth aspect of the present invention, a recessed fixing portion is formed on at least a part of the widthwise end of the separator at a position corresponding to the flat portion formed on the outermost periphery of the wound body, thereby making it possible to fix at least a part of the widthwise end of the separator to the wound body.

[0019] Here, the end of the separator in the width direction that is fixed includes an end that protrudes from the electrode sheet arranged on the innermost periphery of the wound body. This suppresses shrinkage of the end of the separator that is provided in contact with the innermost electrode sheet of the wound body due to heating in the manufacturing process such as the drying process. As a result, it is possible to reduce interference between the end of the innermost electrode sheet and the end of the separator that is provided in contact with the electrode sheet, and to suppress damage to the separator. [Brief description of the drawings]

[0020] [Figure 1] FIG. 1 is an exploded perspective view showing a lithium-ion secondary battery according to an embodiment. [Diagram 2] 2 is a schematic diagram showing a partial cross section of the wound body according to the embodiment, showing the cross section taken along the line AA in FIG. [Diagram 3] 3 is a cross-sectional view showing a schematic planar portion of a wound body according to the embodiment, showing the cross section BB of FIG. 2. [Figure 4] 3 is a cross-sectional view showing a schematic view of an R portion of the wound body according to the embodiment, as viewed from the direction of an arrow C in FIG. 2. [Diagram 5] FIG. 2 is a perspective view showing the innermost circumference of a wound body according to the embodiment; [Figure 6] FIG. 2 is an explanatory diagram illustrating the function of a battery, where (A) is a diagram illustrating the stress acting on a separator in a drying process, and (B) is a diagram illustrating a state in which the separator is torn. [Figure 7] FIG. 2 is an explanatory diagram for explaining the function of the battery, and is a cross-sectional view of the secondary battery showing a state in which the separator has shrunk and buckling has occurred in the electrode sheet during the activation process. [Figure 8] FIG. 2 is a flow diagram showing a method for manufacturing a battery according to an embodiment. [Figure 9] 1A and 1B are schematic diagrams showing an example of a fixing position of a separator in a drying process according to an embodiment, and 1C is a cross-sectional view showing the state cut along the DD cross section of 1A and 1B. [Figure 10]FIG. 2A is a schematic diagram showing an example of a fixing position of a separator in an activation step according to an embodiment, and FIG. 2B is a cross-sectional view showing a state cut along the E-E cross section. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0021] Hereinafter, the battery according to the embodiment will be described with reference to the drawings, with reference to Figs. 1 to 10. The battery according to the embodiment will be described as a lithium ion secondary battery constituting a battery module used as an on-board power source for electric vehicles, hybrid vehicles, etc. In the following description, for convenience of explanation, the front-back, up-down, left-right arrows appropriately shown in each figure are defined as the up-down direction, left-right direction, and front-back direction of the lithium ion secondary battery 10, respectively. In the following description, unless otherwise specified, the directions of up, down, left, right, front and rear refer to the directions of the lithium ion secondary battery 10. The left-right direction of the lithium-ion secondary battery 10 coincides with the width direction of the wound body 30, and the front-rear direction of the lithium-ion secondary battery 10 coincides with the thickness direction of the wound body 30. In the lithium-ion secondary battery 10, one side in the width direction of the wound body 30 is a positive electrode, and the other side in the width direction of the wound body is a negative electrode.

[0022] [Configuration of lithium-ion secondary battery 10] As shown in FIG. 1, the lithium ion secondary battery 10 includes a lid assembly 20, a wound body 30, and a battery case 70.

[0023] (battery case 70) The battery case 70 is made of aluminum, for example, and is formed in the shape of a rectangular box that is long in the left-right direction and has an open top.

[0024] (Lid Assembly 20) The lid assembly 20 includes a lid member 21, a negative electrode current collector terminal 22 as a current collector terminal, a positive electrode current collector terminal 23 as a current collector terminal, a negative electrode external terminal 24 as an external terminal, and a positive electrode external terminal 25 as an external terminal.

[0025] <Cover member 21> The lid member 21 is made of, for example, aluminum, and is formed in a rectangular plate shape extending in the longitudinal direction D. The lid member 21 is provided with a safety valve 21A and a cap 26 that closes the injection port 21B.

[0026] The safety valve 21A opens when the internal pressure of the battery case 70 reaches a predetermined pressure, and discharges gas generated inside the battery case 70.

[0027] Inlet 21B is formed as a through hole penetrating in the plate thickness direction of lid member 21. Inlet 21B is used when injecting an electrolyte into battery case 70. Cap 26 is attached to inlet 21B, for example, by laser welding, and is hermetically sealed.

[0028] With the wound body 30, the negative electrode current collector terminal 22, and the positive electrode current collector terminal 23 housed inside the battery case 70, the lid member 21 is attached, for example, by laser welding, so as to close the opening of the battery case 70. In the lithium-ion secondary battery 10 according to the embodiment, the wound body 30 is press-fitted into the battery case 70, so that the outer periphery of the wound body 30 is constrained (constrained to a fixed size) by the battery case 70.

[0029] <Negative electrode current collector terminal 22 and negative electrode external terminal 24> The negative electrode current collector terminal 22 and the negative electrode external terminal 24 are made of copper, and are disposed at the other end side in the longitudinal direction of the battery case 70 (the left end side in the left-right direction in FIG. 1 ). The negative electrode current collector terminal 22 is formed in a rectangular plate shape with the plate thickness direction being the front-rear direction. The negative electrode current collector terminal 22 is joined to the negative electrode current collector part 32 of the wound body 30 by, for example, ultrasonic welding. The negative electrode external terminal 24 is electrically connected to the negative electrode current collector terminal 22, and is exposed to the outside of the lid member 21.

[0030] <Positive electrode current collector terminal 23 and positive electrode external terminal 25> The positive current collector terminal 23 is made of aluminum, for example, and is disposed at one end side in the longitudinal direction of the battery case 70 (the right end side in the left-right direction in FIG. 1 ). The positive current collector terminal 23 is formed in a rectangular plate shape with the plate thickness direction being the front-rear direction. The positive current collector terminal 23 is joined to the positive current collector part 33 of the wound body 30 by, for example, resistance welding. The positive external terminal 25 is electrically connected to the positive current collector terminal 23, and is exposed to the outside of the lid member 21.

[0031] (Wound body 30) As shown in FIG. 1, the wound body 30 has a power generating body 31 , a negative electrode current collecting portion 32 , and a positive electrode current collecting portion 33 .

[0032] 2, the wound body 30 is formed into a flat shape by winding a negative electrode sheet 40 as an electrode sheet, a positive electrode sheet 50 as an electrode sheet, and two separators 60 in a stacked state. In other words, the wound body 30 is formed into a flat shape by winding the planar parts 30B and the curved R parts 30A alternately.

[0033] The power generating body 31 is formed by stacking a region of the positive electrode sheet 50 coated with a positive electrode active material, a region of the negative electrode sheet 40 coated with a negative electrode active material, and a separator 60. The power generating body 31 has a function of storing electric energy of the lithium ion secondary battery 10.

[0034] The negative electrode current collecting part 32 is not coated with an active material, and is formed by winding a negative electrode sheet 40. The positive electrode current collecting part 33 is not coated with an active material, and is formed by winding a positive electrode sheet 50.

[0035] <Negative electrode sheet 40> 3 is a schematic cross-sectional view of the flat portion 30B of the wound body 30. As shown in this figure, the negative electrode sheet 40 has a long strip-shaped negative electrode body 41 coated on both sides with a negative electrode active material 42. The negative electrode active material 42 has an outer periphery-side negative electrode active material 42A arranged on the outer periphery side and an inner periphery-side negative electrode active material 42B arranged on the inner periphery side.

[0036] The negative electrode sheet 40 has the other end in the width direction (the left end in the left-right direction in FIG. 3) not coated with the negative electrode active material 42, and the negative electrode body 41 is exposed.

[0037] <Positive electrode sheet 50> The positive electrode sheet 50 is formed by applying a positive electrode active material 52 to both sides of a long strip-shaped positive electrode body 51. The positive electrode active material 52 has an outer periphery-side positive electrode active material 52A arranged on the outer periphery side, and an inner periphery-side positive electrode active material 52B arranged on the inner periphery side.

[0038] The positive electrode sheet 50 has one end in the width direction (the right end in the left-right direction in FIG. 3) that is not coated with the positive electrode active material 52, and the positive electrode body 51 is exposed.

[0039] <Separator 60> The separator 60 is formed of an insulating material such as polypropylene, polyethylene, etc. The separator 60 is disposed between the positive electrode sheet 50 and the negative electrode sheet 40, and insulates the positive electrode sheet 50 from the negative electrode sheet 40.

[0040] The separator 60 is provided so as to protrude from one side (right side) in the width direction relative to the negative electrode sheet 40. The separator 60 is provided so as to protrude from the other side (left side) in the width direction relative to the positive electrode sheet 50. In Fig. 3, the position 40A of the end in the width direction of the negative electrode sheet 40, the position 50A of the end in the width direction of the positive electrode sheet 50, and the position 60A of the end in the width direction of the separator 60 are shown. In addition, the end of the separator 60 protruding in the width direction relative to the positive and negative electrode sheets 40, 50 is designated as 60B.

[0041] 4 is a schematic cross-sectional view of the R portion 30A of the wound body 30 as viewed from the direction of the arrow C in FIG. 2. As shown in this figure, the separator 60 arranged on the innermost periphery covers the end of the winding start of the negative electrode sheet 40 arranged on the inner periphery. The separator 60 arranged on the outermost periphery covers from the outside the R portion of the positive electrode sheet 50 arranged on the inner periphery. FIG. 4 also shows the position 60C1 of the apex of the R portion of the separator 60 arranged on the innermost periphery and the position 60C2 of the apex of the R portion of the separator 60 arranged on the outermost periphery.

[0042] Here, the negative electrode sheet 40 is disposed on the innermost periphery of the wound body 30, and an end 60B of the separator 60 protrudes to one side in the width direction (the right side in the left-right direction in FIG. 3) relative to the negative electrode sheet 40. This end 60B is hereinafter referred to as a separator protrusion 60B. As shown in FIG. 3 and FIG. 5, the difference between the position of one end 40A in the width direction of the negative electrode sheet 40 disposed on the innermost periphery of the wound body 30 among the electrode sheets and the position of one end 60A in the width direction of the separator 60 protruding from the negative electrode sheet 40 to one side in the width direction (the right side) is defined as a protrusion amount S of the separator protrusion 60B.

[0043] [Operation of lithium-ion secondary battery 10] In the lithium ion secondary battery 10 configured as described above, the output of the wound body 30 is taken from the negative electrode external terminal 24 and the positive electrode external terminal 25, and is used as a power source for electric vehicles, hybrid vehicles, and the like.

[0044] [Separator damage] When the wound body 30 is constrained to a fixed size in the battery case 70 as in the lithium ion secondary battery 10 of this embodiment, the wound body 30 needs to have spring properties against the constraint load applied from the battery case 70. On the other hand, when a constraint load is applied to the wound body 30 from the battery case 70 or the like in a manufacturing process in which heat is applied, such as a drying process of the wound body 30, creep progresses in the wound body 30, and the spring properties are significantly reduced. For this reason, in order to establish a spring constant corresponding to the spring property requirement in the wound body 30, it is desirable to apply as little pressure (constraint load) to the wound body 30 as possible in the manufacturing process in which heat is applied. However, when the pressure to the wound body 30 is suppressed in the manufacturing process in which heat is applied, the separator 60 undergoes thermal contraction.

[0045] 6(A), when thermal shrinkage occurs in the separator 60, a uniformly distributed load of the cantilever acts on the separator protruding portion 60B. The separator protruding portion 60B is then deformed so as to bend toward the inner periphery of the wound body 30. The amount of displacement of the widthwise end portion 60A of the separator 60 in this case along the radial direction of the wound body 30 (corresponding to the lamination direction of the electrode sheets) is defined as the amount of shrinkage H.

[0046] The bending moment M acting on the separator protrusion 60B is expressed by the following formula. M=wL 2 / 2 M: Bending moment w: Equally distributed load L: Beam span (length of separator protrusion 60B)

[0047] As shown in FIG. 6(B), a bending moment M acting on the base end of the separator protrusion 60B causes the end of the electrode sheet (negative electrode sheet 40) to interfere with the base end of the separator protrusion 60B, resulting in a tear G, which is an example of damage, at the base end of the separator protrusion 60B.

[0048] [Buckling of electrode sheet] The above-mentioned thermal shrinkage of the separator 60 also occurs when the lithium-ion secondary battery 10 is heated at a predetermined environmental temperature in the activation process. At this time, as shown in Fig. 7, the electrode sheets 40, 50 of the wound body 30 are buckled due to the shrinkage of the separator, which causes an increase in internal resistance and a deterioration in resistance to lithium precipitation, resulting in a decrease in performance.

[0049] For this reason, in the manufacture of the lithium ion secondary battery 10 according to this embodiment, the constraint of the wound body 30 is optimized in the manufacturing process in which heat is applied, thereby ensuring the springiness and suppressing the contraction of the separator 60. This makes it possible to meet the requirement for springiness of the wound body 30 while suppressing breakage of the separator 60 and buckling of the electrode sheets 40, 50.

[0050] [Method of manufacturing lithium ion secondary battery 10] The lithium ion secondary battery 10 is manufactured through a source process, a winding process, a drying process, a case insertion / sealing process, a liquid injection process, an activation process, and an inspection process.

[0051] (source process) As shown in FIG. 8, in the source process, the negative electrode sheet 40, the positive electrode sheet 50, and the separator 60 that constitute the battery element of the lithium ion secondary battery 10 are formed (step S1).

[0052] (winding process) In the winding step, the negative electrode sheet 40, the positive electrode sheet 50, and two separators 60 are wound in a laminated state into a substantially cylindrical shape to form the wound body 30 (step S2). The wound body 30 formed into a substantially cylindrical shape may be formed into a flat shape by pressing. In the winding step, a position difference measuring step is performed.

[0053] (drying process) In the drying process, the wound body 30 before being enclosed in the battery case 70 is vacuum-dried to remove moisture contained in the wound body 30 (step S3). Specifically, in the drying process, the end of the separator 60 of the wound body 30 is fixed with a jig 80 (see FIG. 9(C)) or the like, and the wound body 30 is dried in a drying chamber set to a predetermined drying temperature.

[0054] Here, Fig. 9(A) and Fig. 9(B) show an example of a fixing region F1 of a separator 60 fixed using a jig 80. Fig. 9(A) and Fig. 9(B) are schematic diagrams of the wound body 30 seen from the front-rear direction shown in Fig. 1. Fig. 9(A) and Fig. 9(B) also show a boundary L1 between a flat portion and an R portion of the separator 60 arranged on the innermost periphery side.

[0055] 9(A) and 9(B), the jig 80 is set at a position corresponding to the flat portion 30B of the wound body 30, and is configured to apply a predetermined restraining load from the outside of the separator 60 arranged on the outermost side along the thickness direction of the separator 60 (the front-rear direction in FIG. 1). Note that the "thickness direction of the separator 60" here can also be rephrased as the "stacking direction" of the electrode sheet and the separator 60.

[0056] The fixed region F1 by the jig 80 includes at least a part of a position corresponding to the end of the outermost separator 60 in the width direction (the left-right direction in FIG. 1). From the viewpoint of suppressing the tear G of the separator 60, it is more effective to suppress the contraction of the separator protrusion 60B on which the uniformly distributed load of the cantilever acts. Therefore, it is desirable that the separator protrusion 60B protruding from the negative electrode sheet 40 arranged on the innermost periphery of the wound body 30 is fixed by the restraining load input from the jig 80 to the separator 60 on the outermost periphery side.

[0057] From the viewpoint of suppressing the tear G of the separator 60, it is more effective to suppress the contraction of the separator protrusion 60B at the R portion of the separator 60 that contacts a sharp portion (for example, a corner portion at the start of winding of the negative electrode sheet 40) of the negative electrode sheet 40 arranged on the innermost periphery side. Therefore, it is desirable that the separator protrusion 60B is fixed at a position corresponding to the R portion of the separator 60 arranged on the innermost periphery side of the wound body 30 by the restraining load input to the separator 60 on the outermost periphery side.

[0058] In the example shown in FIG. 9(A), the fixing region F1 of the jig 80 is set at a position overlapping the separator protrusion 60B of the separator 60 arranged on the innermost periphery side of the wound body 30 when viewed from the thickness direction of the separator 60. The fixing region F1 is set as a strip-shaped region extending from the top 60C1 of the R part of one (upper end side) of the separator 60 arranged on the innermost periphery side to the top 60C1 (lower end side) of the R part of the other separator 60. The fixing region F1 is set in a pair at both ends in the width direction of the separator 60. The longitudinal ends of the fixing region F1 overlap the R part of the separator 60 arranged on the innermost periphery side of the wound body 30 when viewed from the thickness direction of the separator 60.

[0059] The example shown in Fig. 9(B) is an optimization of the fixing region F1 shown in Fig. 9(A). In Fig. 9(B), the fixing region F2 by the jig 80 is distributed to four locations corresponding to the four corners of the flat portion 30B of the separator 60 on the outermost side. That is, the fixing region F2 is set at the upper end and lower end of the flat portion 30B on one end side and the other end side in the width direction of the separator 60. Each fixed region F2 is set at a position overlapping with a separator protruding portion 60B of the separator 60 arranged on the innermost side of the wound body 30 when viewed in the thickness direction of the separator 60. Moreover, each fixed region F2 overlaps the R portion of the separator 60 arranged on the innermost side of the wound body 30 when viewed in the thickness direction of the separator 60.

[0060] 9(A) and 9(B), the portions of the separators on the outermost and innermost sides that overlap with the electrode sheets can be set as non-constrained regions that are not fixed by the jig 80. This makes it possible to improve the spring properties of the wound body 30 in the portions where the separators 60 and the electrode sheets overlap.

[0061] From the viewpoint of shortening the drying time, the drying temperature is preferably 80° C. or more. In addition, from the viewpoint of setting the cell drying temperature at 80° C. or more and suppressing internal short circuit due to direct contact between electrode sheets, miswinding of winding phase difference, error in the pressing position of the jig 80, and damage to the separator 60 due to the restraining load of the jig 80, it is desirable that the protrusion amount S of the separator protrusion 60B is 4 mm or more. Furthermore, from the viewpoint of suppressing damage to the separator 60 due to the restraining load of the jig 80, it is desirable to provide a gap T of 1 mm or more between the widthwise ends (40A, 40B) of the electrode sheet and the fixing areas F1, F2 of the jig 80 when viewed from the thickness direction of the separator. Moreover, the restraining load applied by the jig 80 is preferably 0.2 kN or more.

[0062] After the above drying process, as shown in FIG. 9(C), a concave fixing portion 64 recessed in the thickness direction of the separator 60 may be formed at the end of the outermost separator 60 by pressure from a jig 80.

[0063] (Case insertion / can sealing process) In the case insertion / sealing process, the negative current collecting terminal 22 is joined to the negative current collecting part 32 of the wound body 30 by, for example, ultrasonic welding, and the positive current collecting terminal 23 is joined to the positive current collecting part 33 of the wound body 30 by, for example, resistance welding. Then, the lid assembly 20 is inserted into the battery case 70, and the lid member 21 is attached to close the opening of the battery case 70 by, for example, laser welding (step S4).

[0064] (liquid injection process) In the liquid injection step, the electrolyte is injected from injection port 21B formed in lid member 21, and cap 26 is attached to injection port 21B by, for example, laser welding to seal it (step S5).

[0065] (activation process) In the activation process, the lithium ion secondary battery 10 is initially charged and then stored at high temperature for a certain period of time to perform high-temperature aging treatment to dissolve metallic foreign matter and stabilize the SEI (Solid Electrolyte Interphase) coating (step S6). Specifically, in the activation step, the end of the separator 60 of the wound body 30 is fixed with a jig 90 (see FIG. 10(B)) or the like, and the wound body 30 is stored at a predetermined environmental temperature for a predetermined time.

[0066] Here, Fig. 10(A) shows an example of a fixing region F3 of a separator 60 fixed using a jig 90. Fig. 10(A) is a schematic diagram of the wound body 30 seen from the front-rear direction shown in Fig. 1. Fig. 10(A) also shows a boundary L2 between a flat portion and an R portion of the separator 60 arranged on the outermost peripheral side.

[0067] 10(A), the jig 90 is set at a position corresponding to the flat portion 30B of the separator 60 on the outermost side of the wound body 30, and is configured to apply a predetermined restraining load along the thickness direction of the separator 60 (the front-rear direction in FIG. 1). Note that the "thickness direction of the separator 60" here can also be rephrased as the "stacking direction" of the electrode sheet and the separator 60.

[0068] The fixed region F3 by the jig 90 includes at least a part of a position corresponding to the end of the outermost separator 60 in the width direction (the left-right direction in FIG. 1).

[0069] Meanwhile, on the outermost side of the wound body 30, the temperature rise caused by heating in the activation process is large, and the separator is likely to shrink. Also, on the outermost side, the R portion of the wound body 30 has a large curvature of the electrode sheet, and is therefore in a position that is difficult to absorb stress caused by the separator shrinkage. Therefore, from the viewpoint of suppressing buckling of the electrode sheet caused by the shrinkage of the separator 60, it is desirable that the vicinity of the R portion of the separator 60 arranged on the outermost side be fixed by the restraining load input from the jig 80.

[0070] 10(A), the fixing region F3 of the jig 80 is set at positions corresponding to the upper and lower ends of the flat portion 30B of the separator 60 arranged on the innermost periphery of the wound body 30. Moreover, the fixing region F3 is set as a band-shaped region extending along the boundary L2 of the separator 60 arranged on the outermost periphery. By forming the fixing region F3 as a band-shaped region, the electrode sheet can be fixed linearly in the width direction together with the outermost separator 60. Therefore, when the separator 60 shrinks in the flat portion 30B of the wound body 30, the buckling of the electrode sheet as shown in FIG.

[0071] 10(A), the inside of the fixed region F3 set in an upper and lower pair, i.e., the center of the flat portion 30B of the wound body 30, is set as an unconstrained region that is not fixed by the jig 90. Therefore, most of the overlapping portion between the separator 60 and the electrode sheet is in an unconstrained state, and it is possible to suppress a decrease in the spring property of the wound body 30 due to heating in the activation process.

[0072] From the viewpoint of suppressing buckling of the electrode sheet due to shrinkage of the separator 60, it is desirable to set the width of the band-shaped fixing region F3 to 2 mm or more. Moreover, the restraining load by the jig 80 is preferably 0.43 kN or more.

[0073] The activation process is performed after the wound body 30 is housed in the battery case 70 in the case insertion / sealing process. Therefore, as shown in Fig. 10(B) , the restraint load input from the jig 90 is applied to the wound body 30 via the battery case 70. At this time, in order to stabilize the position of the jig 90, a recess 94 corresponding to the fixing region F3 may be provided in the battery case 70. After such an activation process, a fixing portion 64 having a recessed shape recessed in the thickness direction of the separator 60 by pressure from the jig 80 may be formed at the end of the separator 60 on the outermost side.

[0074] In the above embodiment, the jig 90 is used to apply a restraining load in the activation step as well, but this is not limiting. For example, a recess 94 corresponding to the fixing region F3 may be provided in advance in the battery case 70, so that after the wound body 30 is press-fitted into the battery case 70 in the case insertion / sealing step, a predetermined restraining load is applied to the fixing region F3 by the recess 94 formed in the battery case 70.

[0075] (Inspection process) In the inspection process, cell voltage, battery resistance, etc. are inspected (step S7) to select lithium-ion secondary batteries 10 that exhibit predetermined performance. In vehicle-mounted lithium-ion secondary batteries, multiple lithium-ion secondary batteries 10 are stacked to form a battery module.

[0076] [Effect] In the manufacturing method of the lithium ion secondary battery 10 of the embodiment, a predetermined restraining load is applied along the thickness direction of the separator 60 at a position corresponding to the flat portion 30B formed on the outermost peripheral side of the wound body 30. This allows the wound body 30 to be dried while at least a part of the end portion in the width direction of the separator 60 is fixed.

[0077] Here, it is desirable that the end in the width direction of the separator 60 in the fixed state includes a separator protrusion 60B protruding from the negative electrode sheet 40 arranged on the innermost periphery side of the wound body 30. This prevents the protrusion 60B of the separator 60 provided in contact with the innermost negative electrode sheet 40 of the wound body 30 from shrinking due to heating in the drying process. As a result, it is possible to reduce interference between the end 40A of the innermost negative electrode sheet 40 and the separator protrusion 60B, and to prevent damage to the separator 60.

[0078] In addition, in this process, the end of the separator 60 that is fixed is preferably the end corresponding to the position of the R portion 30A on the innermost periphery of the wound body 30. This makes it possible to suppress contraction of the end of the separator in the portion that contacts the sharp portion of the negative electrode sheet 40 arranged on the innermost periphery. As a result, it is possible to suppress damage to the easily damaged portion of the separator.

[0079] In the embodiment, in the activation process of the lithium-ion secondary battery 10, a predetermined restraining load is applied along the thickness direction of the separator 60 at a position corresponding to the flat portion 30B formed on the outermost peripheral side of the wound body 30. This allows the wound body 30 to be heated at a predetermined environmental temperature and stored for a predetermined time while at least a part of the end portion in the width direction of the separator 60 is fixed.

[0080] Here, it is desirable that the end portions in the width direction of the separator 60 that are in a fixed state include the end portions located at the boundary with the R portion formed on the outermost peripheral side of the wound body 30. In this way, the end portions of the separator located at the boundary with the R portion where the curvature of the electrode sheet is large are fixed, and contraction is suppressed, thereby making it possible to effectively suppress buckling of the electrode sheet.

[0081] In the embodiment, the drying step is performed between the winding step and the case insertion / sealing step. This allows the drying step to be performed after the wound body 30 is formed into a flat shape in the winding step. Therefore, in the drying step, the vertical widths of the negative electrode current collector 32 and the positive electrode current collector 33 of the wound body 30 to be welded to the negative and positive electrode current collector terminals 22, 23 are determined. This allows the end of the separator 60 to be set at a restraining position without damaging the opposing portion between the separator 60 and the electrode sheet.

[0082] In the above embodiment, the drying step is performed before welding the negative electrode current collecting portion 32 and the positive electrode current collecting portion 33 of the wound body 30 to the negative and positive electrode current collecting terminals 22, 23 in the case insertion / sealing step. This makes it possible to easily adjust the restraining load for suppressing the shrinkage of the separator, since there is no need to consider the tension that will be applied from the welded portions after the electrode sheet and the current collecting terminals 22, 23 are welded together when restraining the separator 60 in the drying step.

[0083] The lithium ion secondary battery of the present invention has been described above based on the above embodiment. However, the specific configuration is not limited to this embodiment, and design changes and the like are permitted as long as they do not deviate from the gist of the invention according to each claim of the claims.

[0084] In the above embodiment, an example has been shown in which the electrode sheet arranged on the innermost periphery side of the wound body 30 is the negative electrode sheet 40. However, the electrode sheet arranged on the innermost periphery side of the wound body may be a positive electrode sheet.

[0085] In the above embodiment, the battery is a lithium ion secondary battery, but the battery is not limited to this and may be a battery including a wound body having a separator. [Explanation of symbols]

[0086] 10 Lithium-ion secondary battery (example of battery) 30 Wound body 30A R section 30B Flat part 40 Negative electrode sheet (an example of an electrode sheet) 40A Width direction one end 50 Positive electrode sheet (an example of an electrode sheet) 60 Separator 60B Width direction edge 64 Fixed part

Claims

1. A method for manufacturing a battery having a wound body in which a positive electrode sheet as an electrode sheet, a negative electrode sheet as the electrode sheet, and a separator are wound in a stacked state, and flat portions and R portions are alternately formed, comprising: a drying step of applying a predetermined restraining load along a thickness direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the wound body to fix at least a part of an end portion in a width direction of the separator, and heating the wound body at a predetermined drying temperature to dry the wound body; the end portion in the width direction of the separator includes an end portion protruding from the electrode sheet disposed on the innermost periphery side of the winding body, How batteries are manufactured.

2. the end portion in the width direction of the separator is an end portion protruding from the electrode sheet arranged on the innermost periphery side of the wound body and includes an end portion overlapping with the R portion of the separator arranged on the innermost periphery side of the wound body, A method for producing the battery according to claim 1 .

3. The method further includes an activation step of initially charging a secondary battery including the wound body, and storing the secondary battery for a predetermined period of time by heating the secondary battery at a predetermined environmental temperature, In the activation step, a predetermined restraining load is applied along a thickness direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the winding body, thereby fixing at least a part of an end portion in a width direction of the separator; The end portion in the width direction of the separator includes an end portion located at the boundary with the R portion formed on the outermost peripheral side of the wound body. A method for producing the battery according to claim 1 .

4. a wound body in which a positive electrode sheet as an electrode sheet, a negative electrode sheet as the electrode sheet, and a separator are wound in a stacked state, and flat portions and R portions are alternately formed; a fixing portion having a concave shape that is formed on at least a part of an end portion in a width direction of the separator at a position corresponding to the flat portion formed on the outermost peripheral side of the winding body and is depressed in a thickness direction of the separator by pressing, the end portion in the width direction of the separator includes an end portion protruding from the electrode sheet disposed on the innermost periphery side of the winding body, battery.

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