Lithium-ion secondary battery and method for manufacturing the same

Abstract

To provide a lithium ion secondary battery in which the increase in internal resistance due to repeated charging and discharging can be suppressed.SOLUTION: A lithium ion secondary battery includes as an electrode body, a wound body 20 in which a multilayer body including a stack of a negative electrode plate, a separator 120, and a positive electrode plate is wound in a winding direction Z. The wound body 20 includes: a negative electrode side current collector part 103 that has a flat shape that is pressed and shaped in a direction orthogonal to an axis direction X when wound, in which at one end part in the axis direction X, a negative electrode mixture layer is not provided on both surfaces of a negative electrode base material layer 101, a thickness direction Y in the negative electrode base material layer 101 is an amplitude direction, and the shape is wavy with the winding direction Z corresponding to the wavelength direction; and a positive electrode side current collector part in which at the other end part in the axis direction X, a positive electrode mixture layer is not provided on both surfaces of a positive electrode base material layer, the thickness direction Y in the positive electrode base material layer is the amplitude direction, and the shape is wavy with the winding direction Z corresponding to the wavelength direction.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a lithium ion secondary battery including a wound body formed by stacking a positive electrode plate, a separator, and a negative electrode plate and then winding them, and to a method for manufacturing the lithium ion secondary battery. [Background technology]

[0002] In the secondary battery described in Patent Document 1, a cathode body and an anode body are stacked with a separator interposed therebetween. The secondary battery includes a capacitor element formed by winding the stacked body into a cylindrical shape. The cathode body is an example of a negative electrode plate, the anode body is an example of a positive electrode plate, and the capacitor element formed by winding into a cylindrical shape is an example of a wound body. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] JP 2018-56482 A Summary of the Invention [Problem to be solved by the invention]

[0004] In lithium-ion secondary batteries, an organic solvent with lithium salt dissolved therein is used as the electrolyte, and the electrolyte exhibits high ionic conductivity. During charging, lithium ions are released from the positive electrode, pass through the electrolyte to the negative electrode, and are absorbed by the negative electrode. At this time, the wound body expands. During discharging, lithium ions are released from the negative electrode, pass through the electrolyte to the positive electrode, and are absorbed by the positive electrode. At this time, the wound body contracts.

[0005] In high-rate charging and discharging, in which a large current is instantly charged or discharged, a large amount of lithium ions must be absorbed and released between the electrodes instantly. Therefore, the wound body expands and contracts repeatedly with repeated charging and discharging. During charging, lithium ions are absorbed in the negative electrode on the negative electrode side, and during discharging, lithium ions are absorbed in the positive electrode on the positive electrode side, so that the lithium salt concentration of the electrolyte becomes low at the ends of the negative electrode side and the positive electrode side of the wound body. Then, the electrolyte with the low lithium salt concentration is pushed out of the wound body from the ends of the negative electrode side and the positive electrode side by the large expansion and contraction of the wound body. In the wound body, the ease of movement of the electrolyte tends to differ between the center and the ends due to the flattened shape. Therefore, a difference occurs in the lithium salt concentration of the electrolyte between the center and the ends in the wound body. As a result, the internal resistance during discharge increases, and the battery performance of the lithium ion secondary battery decreases. [Means for solving the problem]

[0006] The lithium ion secondary battery that solves the above problem includes a negative electrode plate having a negative electrode substrate layer that is a substrate for a negative electrode and a negative electrode mixture layer provided on the negative electrode substrate layer, a positive electrode plate having a positive electrode substrate layer that is a substrate for a positive electrode and a positive electrode mixture layer provided on the positive electrode substrate layer, and a separator provided between the negative electrode plate and the positive electrode plate, and a laminate in which the negative electrode plate, the separator, and the positive electrode plate are stacked is wound in a winding direction to form a wound body, and the wound body is configured as an electrode body. The negative electrode base material layer has a flattened shape that has been pressurized and shaped in a direction perpendicular to the axial direction, and at one end in the axial direction, the negative electrode base material layer is not provided on either surface of the negative electrode base material layer, the thickness direction of the negative electrode base material layer is the amplitude direction, and the winding direction is the wavelength direction, and the negative electrode side current collecting part has a corrugated shape, and at the other end in the axial direction, the positive electrode base material layer is not provided on either surface of the positive electrode base material layer, the thickness direction of the positive electrode base material layer is the amplitude direction, and the winding direction is the wavelength direction.

[0007] According to the above configuration, the wavy convex portion makes it difficult for the electrolyte to move in the axial direction of the winding, and therefore it is possible to prevent the electrolyte with a low lithium salt concentration from leaking out of the winding, thereby suppressing unevenness in the lithium salt concentration in the winding and thus suppressing an increase in internal resistance due to repeated charging and discharging.

[0008] In the above configuration, the wavy shape has a smaller amplitude as it is closer to the negative electrode mixture layer or the positive electrode mixture layer, and has a larger amplitude as it is farther from the negative electrode mixture layer or the positive electrode mixture layer.

[0009] According to the above configuration, the wave shape having a smaller amplitude closer to the negative electrode mixture layer or the positive electrode mixture layer and a larger amplitude farther from the negative electrode mixture layer or the positive electrode mixture layer is a shape that can be easily manufactured. The easily manufactured wave shape of the protrusions can prevent the electrolyte with a low lithium salt concentration from leaking out of the wound body.

[0010] In the above configuration, the negative electrode side current collecting portion and the positive electrode side current collecting portion are connected to external terminals of the lithium ion secondary battery by connection portions above their respective planar portions of the flat shape, and the negative electrode side current collecting portion and the positive electrode side current collecting portion have the wavy shape below the lower ends of the connection portions.

[0011] According to the above configuration, it is possible to prevent the electrolyte solution with a reduced lithium salt concentration from leaking out of the wound body from the lower part of the wound body, which is the part that is not connected to the external terminal of the lithium ion secondary battery by the connection part.

[0012] In the above configuration, in the flat planar portion of the flat shape in the negative electrode side current collecting part, two of the negative electrode substrate layers adjacent in the thickness direction of the negative electrode substrate layer both have the wavy shape, so that a position of the gap between the two of the negative electrode substrate layers changes in the thickness direction of the negative electrode substrate layer, and in the flat planar portion of the flat shape in the positive electrode side current collecting part, two of the positive electrode substrate layers adjacent in the thickness direction of the positive electrode substrate layer both have the wavy shape, so that a position of the gap between the two of the positive electrode substrate layers changes in the thickness direction of the positive electrode substrate layer.

[0013] According to the above configuration, the position of the gap changes in the thickness direction of the negative electrode substrate layer and the positive electrode substrate layer, so that the resistance when the electrolyte moves through the gap in the axial direction of the wound body increases, and therefore it is possible to prevent the electrolyte with a low lithium salt concentration from leaking out of the wound body through the gap between the substrate layers.

[0014] The above configuration has a location in the flat planar portion of the negative electrode side current collecting part, where the gap value between two adjacent negative electrode base material layers in the thickness direction of the negative electrode base material layer is 18 μm or less, and a location in the flat planar portion of the positive electrode side current collecting part, where the gap value between two adjacent positive electrode base material layers in the thickness direction of the positive electrode base material layer is 18 μm or less.

[0015] According to the above configuration, in locations where the gap between the base layers is 18 μm or less, it is possible to further prevent the electrolyte solution with a low lithium salt concentration from leaking out of the wound body through the gap between the base layers.

[0016] A method for manufacturing a lithium ion secondary battery that solves the above problem includes a coating process in which a mixture layer is applied to an electrode plate, a drying process in which the mixture layer is dried, a pressing process in which the thickness of the electrode plate is adjusted, a winding process in which a negative electrode plate (which is the electrode plate), a separator, and a positive electrode plate (which is the electrode plate) are stacked and then wound to form a wound body, and a flattening press process in which the wound body is pressurized and shaped in a direction perpendicular to the axial direction when wound, wherein in the coating process, an uncoated portion where the mixture layer is not coated is formed at one or both ends in the width direction of the coated portion where the mixture layer is coated, and in the press process, a value of a first pressure applied to the coated portion and a value of a second pressure applied to the uncoated portion are set so that the amount of elongation in the longitudinal direction of the uncoated portion is greater than the amount of elongation in the longitudinal direction of the coated portion.

[0017] According to the above-mentioned manufacturing method, it is possible to form a negative electrode plate and a positive electrode plate having a corrugated shape that can prevent the electrolyte solution with a low lithium salt concentration from leaking out of the wound body at the current collecting portion of the base material layer. Then, it is possible to form a wound body with the negative electrode plate and the positive electrode plate having the corrugated shape, and to manufacture a lithium ion secondary battery.

[0018] In the above manufacturing method, in the winding process, the tension applied to the negative electrode plate and the positive electrode plate when forming the wound body is set so that the longitudinal length of the uncoated portion of the negative electrode plate and the positive electrode plate is the same as the longitudinal length of the coated portion.

[0019] According to the above manufacturing method, the negative and positive plates bent in the slitting step after the pressing step can be formed into negative and positive plates having a substantially rectangular shape in a plan view from the thickness direction. Then, an undistorted wound body is formed with the negative and positive plates having a wavy shape in the current collecting portion of the base material layer, and a lithium ion secondary battery can be manufactured.

[0020] In the above manufacturing method, in the pressing step, a value of the second pressure applied to the uncoated portion is greater than 1.2 times a value of the first pressure applied to the coated portion. According to the above configuration, the wound body can be formed from the negative electrode plate and the positive electrode plate that have a large effect of suppressing the electrolyte with a low lithium salt concentration from leaking out of the wound body in the current collecting portion of the base material layer. Effect of the Invention

[0021] According to the present invention, in a lithium ion secondary battery, it is possible to suppress unevenness in the lithium salt concentration in the wound body, and therefore it is possible to suppress an increase in internal resistance due to repeated charging and discharging. [Brief description of the drawings]

[0022] [Figure 1] FIG. 1 is a perspective view showing a lithium ion secondary battery in one embodiment. [Diagram 2] FIG. 2 is a schematic diagram showing a layered configuration in a wound body. [Diagram 3] FIG. 4 is a schematic diagram showing the shape of an end portion of a wound body. [Figure 4] FIG. 4 is a schematic enlarged view showing part A in FIG. [Diagram 5] 5 is a schematic cross-sectional view showing a gap between base layers taken along line 5-5 shown in FIG. 4. [Figure 6] 6 is a cross-sectional view showing the wavy shape of the base layer taken along line 6-6 shown in FIG. 4. [Figure 7] 7 is a cross-sectional view showing the wavy shape of the base layer taken along line 7-7 shown in FIG. 4. [Figure 8] 1 is a flowchart showing an electrode plate manufacturing process. [Figure 9] 1 is a flowchart showing a cell assembly process. [Figure 10] FIG. 4 is a schematic cross-sectional view showing a state in which an electrode plate is pressed from both sides. [Figure 11] FIG. 4 is a schematic diagram showing the electrode plate after a pressing process. [Figure 12] FIG. 4 is a schematic diagram showing the electrode plate after a slitting process. [Figure 13] FIG. 13 is a schematic diagram showing an electrode plate to which tension is applied during a winding process. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0023] First, the lithium ion secondary battery 11 in this embodiment will be described. <Configuration of lithium-ion secondary battery> As shown in Fig. 1, the lithium ion secondary battery 11 is configured as a cell battery. A plurality of cell batteries are connected and assembled to be used as a battery. The lithium ion secondary battery 11 includes a rectangular parallelepiped battery case 21 having an opening.

[0024] The battery case 21 includes a lid 22 that seals the opening. In the lithium-ion secondary battery 11, a sealed battery container is formed by attaching the lid 22 to the battery case 21. The battery case 21 and the lid 22 are made of a metal such as an aluminum alloy.

[0025] The lithium ion secondary battery 11 includes a wound body 20 configured as an electrode body. The wound body 20 is accommodated in a battery case 21 together with an electrolyte 27. The lithium ion secondary battery 11 includes a negative electrode external terminal 24 and a positive electrode external terminal 26, which are used for discharging and charging, on a lid 22. The shapes of the negative electrode external terminal 24 and the positive electrode external terminal 26 shown in FIG. 1 are examples of terminal shapes. That is, the shapes of the negative electrode external terminal 24 and the positive electrode external terminal 26 are not limited to the terminal shapes shown in FIG. 1.

[0026] <Winding body configuration> As shown in FIG. 2, the wound body 20 includes a negative electrode plate 100 as an electrode plate, a positive electrode plate 110 as an electrode plate, and a separator 120 provided between the negative electrode plate 100 and the positive electrode plate 110. The separator 120 insulates the electrode plates from each other and holds the electrolyte 27. The negative electrode plate 100, the separator 120, and the positive electrode plate 110 are in the form of a strip. The wound body 20 is formed by winding a laminate in which the negative electrode plate 100, the separator 120, and the positive electrode plate 110 are stacked in a winding direction Z. More specifically, the laminate in which the separator 120, the positive electrode plate 110, the separator 120, and the negative electrode plate 100 are stacked in this order is wound in the winding direction Z and shaped into a flat shape, thereby forming the wound body 20. The winding direction Z is also called the longitudinal direction Z because it is the same as the longitudinal direction of the rectangular strips that constitute each layer.

[0027] The negative electrode plate 100 has a negative electrode base material layer 101, which is a base material of the negative electrode, and a negative electrode mixture layer 102 provided on both sides of the negative electrode base material layer 101. The wound body 20 has a negative electrode side current collector 103 at one end in the axial direction X. The axial direction X is the direction of the winding axis when the negative electrode plate 100 is wound in the winding direction Z in the winding process of the manufacturing process. The negative electrode side current collector 103 is a portion where the negative electrode mixture layer 102 is not provided on both sides of the negative electrode base material layer 101. The negative electrode side current collector 103 takes out electricity from the negative electrode mixture layer 102 of the negative electrode plate 100. The axial direction X is the same direction as the width direction, which is the short side direction of the strips constituting each layer, so the axial direction X is also called the width direction X.

[0028] A portion where the negative electrode mixture layer 102 is provided on both sides of the negative electrode base material layer 101 is a portion where the negative electrode mixture layer 102 is coated in a coating step in the manufacturing process, and is therefore referred to as a coated portion CP. A portion where the negative electrode mixture layer 102 is not provided on both sides of the negative electrode base material layer 101 is a portion where the negative electrode mixture layer 102 is not coated in a coating step in the manufacturing process, and is therefore referred to as an uncoated portion UCP. The uncoated portion UCP, which is a portion where the negative electrode mixture layer 102 is not provided on both sides of the negative electrode base material layer 101, is a portion where the negative electrode base material layer 101 is exposed on both sides.

[0029] The negative electrode substrate layer 101 is made of, for example, copper foil. The negative electrode substrate layer 101 is a substrate with a thickness of about 10 μm for passing electricity through the negative electrode mixture layer 102. The negative electrode mixture layer 102 is made of graphite. Graphite is a material having a crystalline structure in which carbon layers are stacked, and can store lithium between the carbon layers.

[0030] The positive electrode plate 110 has a positive electrode base material layer 111 which is a base material for the positive electrode, and a positive electrode mixture layer 112 provided on both sides of the positive electrode base material layer 111. The wound body 20 has a positive electrode side current collector 113 at the other end in the axial direction X. The positive electrode side current collector 113 is a portion of the positive electrode base material layer 111 on both sides of which the positive electrode mixture layer 112 is not provided. The positive electrode side current collector 113 extracts electricity from the positive electrode mixture layer 112 of the positive electrode plate 110.

[0031] A portion where the positive electrode mixture layer 112 is provided on both sides of the positive electrode base material layer 111 is a portion where the positive electrode mixture layer 112 is coated in a coating step in the manufacturing process, and is therefore referred to as a coated portion CP. A portion where the positive electrode mixture layer 112 is not provided on both sides of the positive electrode base material layer 111 is a portion where the positive electrode mixture layer 112 is not coated in a coating step in the manufacturing process, and is therefore referred to as an uncoated portion UCP. The uncoated portion UCP, which is a portion where the positive electrode mixture layer 112 is not provided on both sides of the positive electrode base material layer 111, is a portion where the positive electrode base material layer 111 is exposed on both sides.

[0032] The positive electrode substrate layer 111 is made of, for example, aluminum foil. The positive electrode substrate layer 111 is a substrate with a thickness of about 15 μm for passing electricity through the positive electrode mixture layer 112. The positive electrode mixture layer 112 is made of a mixture of an active material and a conductive material. The active material is a metal oxide containing lithium, which releases lithium ions during charging and absorbs lithium ions during discharging. Carbon fine particles are used as the conductive material, which comes into contact with the active material to form a path of electricity.

[0033] Separator 120 is a resin sheet having a thickness of about 20 μm. Separator 120 prevents contact between the positive electrode and the negative electrode, and has a large number of minute pores, thereby enabling electrolyte 27 to be held in the pores.

[0034] <End shape of the winding body> 3, the wound body 20 has a flat shape that is pressurized and shaped in a thickness direction Y that is a direction perpendicular to the axial direction X and the winding direction Z when the laminate is wound. The wound body 20 has flat planar portions F on both sides in the thickness direction Y.

[0035] The negative electrode current collector 23 is welded to the negative electrode side current collector 103, which is one end in the axial direction X. More specifically, the negative electrode side current collector 103 has the negative electrode current collector 23 welded to the upper part of each flat surface portion F of the flat shape. As a result, the negative electrode side current collector 103 is connected to the negative electrode external terminal 24, which is an external terminal of the lithium ion secondary battery 11, at the connection part 23a. Note that the upper or upper part refers to the part that is inserted last when the wound body 20 is accommodated in the battery case 21. The lower or lower part refers to the part that is inserted first when the wound body 20 is accommodated in the battery case 21.

[0036] For convenience of explanation, only a portion of the negative electrode current collector 23 overlaps with the negative electrode side current collecting part 103 in the axial direction X; however, in reality, the entire negative electrode current collector 23 overlaps with the negative electrode side current collecting part 103 in the axial direction X and is welded thereto.

[0037] 1, which is the other end in the axial direction X. More specifically, the positive electrode current collector 25 is welded to the positive electrode current collector 113 above each flat surface portion F of the flattened shape. As a result, the positive electrode current collector 113 is connected to the positive electrode external terminal 26 shown in FIG. 1, which is an external terminal of the lithium ion secondary battery 11, at the connection portion 25a.

[0038] <Wavy shape of current collector> As shown in Fig. 4, the negative electrode side current collecting part 103 has a wavy shape at one end of the wound body 20. In Fig. 3, the wavy shape is represented by only thin solid lines in order to show a rough shape of the end of the wound body 20. The negative electrode side current collecting part 103 has a wavy shape in which the thickness direction Y of the negative electrode base material layer 101 is the amplitude direction and the winding direction Z is the wavelength direction.

[0039] Similarly, the positive electrode side current collector 113 has a wavy shape at the other end of the wound body 20. The positive electrode side current collector 113 has a wavy shape in which the thickness direction Y of the positive electrode base material layer 111 is the amplitude direction and the winding direction Z is the wavelength direction.

[0040] The wavy shape has a protrusion 31 and a recess 32. More specifically, the wavy shape is a shape in which the protrusions 31 and the recesses 32 are alternately repeated on the surface of the base layer 101, 111 while maintaining the thickness of the base layer 101, 111. The protrusions 31 are mountain-shaped parts of the surface of the base layer 101, 111, and the recesses 32 are valley-shaped parts of the surface of the base layer 101, 111. Since the current collecting parts 103, 113 are foil-shaped, the back side of the protrusions 31 becomes the recesses 32. If the protrusions 31 are present in the direction in which the electrolyte 27 moves, resistance is generated to change the flow along the protrusions 31, making it difficult for the electrolyte 27 to move in the direction in which the protrusions 31 are present.

[0041] 5, the wound body 20 is laminated in the order of a separator 120, a negative electrode plate 100, a separator 120, and a positive electrode plate 110. Therefore, in the negative electrode side current collecting portion 103, a gap Δ is formed between two adjacent negative electrode base material layers 101 due to the thickness of the two separators 120 and one positive electrode plate 110 sandwiched between the two negative electrode plates 100 and the thickness of the two negative electrode mixture layers 102.

[0042] In the negative electrode side current collector 103 of the wound body 20 having such a layer configuration, the negative electrode base material layer 101 is wavy in the thickness direction Y, so that the negative electrode side current collector 103 has a wavy shape. More specifically, in the flat plane portion F of the negative electrode side current collector 103 shown in Fig. 3 , both of the two negative electrode base material layers 101 adjacent to each other in the thickness direction Y of the negative electrode base material layer 101 have a wavy shape. As a result, the position of the gap Δ between the two negative electrode base material layers 101 changes in the thickness direction Y of the negative electrode base material layer 101.

[0043] Similarly, in the positive electrode side current collecting portion 113, a gap Δ is formed between two adjacent positive electrode base material layers 111 due to the thickness of the two separators 120 and one negative electrode plate 100 sandwiched between the two positive electrode plates 110, and the thickness of the two positive electrode mixture layers 112.

[0044] In the positive electrode side current collecting part 113 of the wound body 20 having such a layer configuration, the positive electrode base material layer 111 is wavy in the thickness direction Y, so that the positive electrode side current collecting part 113 has a wavy shape. More specifically, in the flat plane portion F of the positive electrode side current collecting part 113, both of the two positive electrode base material layers 111 adjacent to each other in the thickness direction Y of the positive electrode base material layer 111 have a wavy shape. As a result, the position of the gap Δ between the two positive electrode base material layers 111 changes in the thickness direction Y of the positive electrode base material layer 111.

[0045] In addition, in the portion where the connection portion 23a and the negative electrode side current collector 103 shown in FIG. 1 are welded, and in the portion where the connection portion 25a and the positive electrode side current collector 113 shown in FIG. 1 are welded, the thickness of the wound body 20 becomes thinner in the thickness direction Y of the wound body 20. More specifically, in the welded portion, the two adjacent negative electrode base material layers 101 are closely attached by welding, so the value of the gap Δ in the connection portion 23a becomes almost "zero". In addition, in the welded portion, the two adjacent positive electrode base material layers 111 are closely attached by welding, so the value of the gap Δ in the connection portion 25a becomes almost "zero". Therefore, the negative electrode side current collector 103 may have a wavy shape below the lower end 23b of the connection portion 23a. In addition, the positive electrode side current collector 113 may have a wavy shape below the lower end 25b of the connection portion 25a.

[0046] 6, in the negative current collecting portion 103, the amplitude Am of the wavy shape is large in a portion farther from the negative electrode mixture layer 102. Similarly, in the positive current collecting portion 113, the amplitude Am of the wavy shape is large in a portion farther from the positive electrode mixture layer 112.

[0047] 7, in the negative electrode current collecting portion 103, the amplitude Am of the wavy shape is small in a portion close to the negative electrode mixture layer 102. Similarly, in the positive electrode current collecting portion 113, the amplitude Am of the wavy shape is small in a portion close to the positive electrode mixture layer 112.

[0048] That is, the closer the wavy shape is to the negative electrode mixture layer 102, the smaller the amplitude Am, and the farther from the negative electrode mixture layer 102, the larger the amplitude Am. Also, the closer the wavy shape is to the positive electrode mixture layer 112, the smaller the amplitude Am, and the farther from the positive electrode mixture layer 112, the larger the amplitude Am. In other words, the closer the wavy shape is to the negative electrode mixture layer 102 or the positive electrode mixture layer 112, the smaller the amplitude Am, and the farther from the negative electrode mixture layer 102 or the positive electrode mixture layer 112, the larger the amplitude Am.

[0049] In this embodiment, the wavy shape is a shape in which the amplitude Am gradually decreases as it approaches the negative electrode mixture layer 102, and the amplitude Am becomes "zero" by the time it reaches the negative electrode mixture layer 102. Moreover, the wavy shape is a shape in which the amplitude Am gradually decreases as it approaches the positive electrode mixture layer 112, and the amplitude Am becomes "zero" by the time it reaches the positive electrode mixture layer 112.

[0050] In the negative electrode plate 100, the portion where the negative electrode mixture layer 102 is provided may have a slightly curved shape. For example, the wavy shape may be a shape in which the amplitude Am does not become "zero" until the negative electrode mixture layer 102 is reached, and the portion where the negative electrode mixture layer 102 is provided has a slight curve, or a shape in which the amplitude Am becomes "zero" after the negative electrode mixture layer 102 is reached. Note that "slightly curved" refers to a curve having an amplitude smaller than the amplitude Am at the current collecting parts 103, 113.

[0051] Similarly, in the positive electrode plate 110, the portion where the positive electrode mixture layer 112 is provided may have a slightly curved shape. For example, the wavy shape may be a shape in which the amplitude Am does not become "zero" until the positive electrode mixture layer 112 is reached, and the portion where the positive electrode mixture layer 112 is provided has a slight curve, or a shape in which the amplitude Am becomes "zero" after the positive electrode mixture layer 112 is reached.

[0052] The wavy shape may be a shape in which the amplitude Am does not change until the position approaches the negative electrode mixture layer 102 to a certain extent, and the amplitude Am suddenly becomes "zero" at the position approaches the negative electrode mixture layer 102 to a certain extent. The wavy shape may be a shape in which the amplitude Am does not change until the position approaches the positive electrode mixture layer 112 to a certain extent, and the amplitude Am suddenly becomes "zero" at the position approaches the positive electrode mixture layer 112 to a certain extent. The wavy shape may have a portion where the amplitude Am increases as it approaches the negative electrode mixture layer 102 or the positive electrode mixture layer 112.

[0053] The amplitude Am may vary between the start and end of the wound body 20. For example, the amplitude Am may be different between the start and end of the wound body 20, or a portion with a large amplitude Am and a portion with a small amplitude Am may be repeated in at least a portion of the section between the start and end of the wound body 20. Furthermore, the amplitude Am may be irregular in at least a portion of the section between the start and end of the wound body 20.

[0054] The wavelength λ may vary between the winding start portion and the winding end portion of the wound body 20. For example, the wavelength λ may be different between the winding start portion and the winding end portion of the wound body 20, or a portion with a large wavelength λ and a portion with a small wavelength λ may be repeated in at least a portion of the section between the winding start portion and the winding end portion. Furthermore, the wavelength λ may be irregular in at least a portion of the section between the winding start portion and the winding end portion of the wound body 20.

[0055] In this embodiment, the wavelength λ is the same in a portion close to the negative electrode mixture layer 102 and in a portion far from the negative electrode mixture layer 102, and the wavelength λ is the same in a portion close to the positive electrode mixture layer 112 and in a portion far from the positive electrode mixture layer 112. The phase of the waveform in the wavy shape is the same in the portion close to the negative electrode mixture layer 102 and in the portion far from the negative electrode mixture layer 102, and the phase of the waveform in the wavy shape is the same in the portion close to the positive electrode mixture layer 112 and in the portion far from the positive electrode mixture layer 112.

[0056] The phase of the waveform in the wavy shape may be shifted between a portion close to the negative electrode mixture layer 102 and a portion far from the negative electrode mixture layer 102. In addition, the phase of the waveform in the wavy shape may be shifted between a portion close to the positive electrode mixture layer 112 and a portion far from the positive electrode mixture layer 112.

[0057] The phases of the waveforms in the wavy shapes of two adjacent negative electrode base material layers 101 may be the same or may be different as in this embodiment. The phases of the waveforms in the wavy shapes of two adjacent positive electrode base material layers 111 may be the same or may be different as in this embodiment.

[0058] Regardless of whether the phases of the waveforms in the wavy shapes of two adjacent negative electrode base material layers 101 are the same or different, at least a part of the surfaces of the negative electrode base material layers 101 may be in contact with each other. Furthermore, regardless of whether the phases of the waveforms in the wavy shapes of two adjacent positive electrode base material layers 111 are the same or different, at least a part of the surfaces of the two positive electrode base material layers 111 may be in contact with each other.

[0059] If the wave shapes of two adjacent negative electrode base material layers 101 differ even slightly, the value of the gap Δ between the two negative electrode base material layers 101 varies depending on the location. Also, if the wave shapes of two adjacent positive electrode base material layers 111 differ even slightly, the value of the gap Δ between the two positive electrode base material layers 111 varies depending on the location. That is, there are locations where the value of the gap Δ is large and locations where the value of the gap Δ is small. In the locations where the value of the gap Δ is small, the electrolyte 27 is less likely to move.

[0060] The wavy shape may be a shape imitating a single wave in which convex portions 31 and concave portions 32 are alternately repeated on the surface of the base layer 101, 111 while maintaining the thickness of the base layer 101, 111 as in this embodiment. Alternatively, the wavy shape may be a shape imitating a composite wave in which two or more waves are overlapped while maintaining the thickness of the base layer 101, 111. Alternatively, the wavy shape may be an uneven shape in which convex portions 31 and concave portions 32 are irregularly arranged while maintaining the thickness of the base layer 101, 111.

[0061] Next, a method for manufacturing the lithium ion secondary battery 11 in this embodiment will be described. <Outline of electrode plate manufacturing process> 8, in the manufacturing method of the lithium ion secondary battery 11, the flow of the electrode plate manufacturing process is performed first. The electrode plate manufacturing process includes a coating process in which the electrode plate is coated with the mixture layers 102, 112, a drying process in which the mixture layers 102, 112 are dried, a pressing process in which the thickness of the electrode plate is adjusted, and a slitting process in which the electrode plate is cut.

[0062] In step S201, a coating process is performed. A paste made by mixing an active material, a conductive material, and a binder is thinly coated on both sides of the central portion in the width direction X of the negative electrode base material layer 101 as an electrode plate and the positive electrode base material layer 111 as an electrode plate. As a result, portions where the mixture layers 102, 112 are not provided on both sides are formed at both ends in the width direction X of the strip-shaped base material layers 101, 111. In other words, in the coating process, uncoated parts UCP where the mixture layers 102, 112 are not coated are formed at both ends in the width direction X of the coated part CP where the mixture layers 102, 112 are coated.

[0063] The paste for the negative electrode and the paste for the positive electrode have different paste compositions. The paste for the negative electrode is applied onto the negative electrode base material layer 101 to form the negative electrode mixture layer 102, and the paste for the positive electrode is applied onto the positive electrode base material layer 111 to form the positive electrode mixture layer 112. The applied paste is adjusted to a predetermined thickness using a roller, doctor blade, or the like.

[0064] In step S202, a drying process is performed. For example, an infrared drying device or the like is used to volatilize the binder solvent, and the applied paste is hardened to a certain degree of hardness.

[0065] In step S203, a pressing process is performed. The negative electrode base layer 101 coated with the negative electrode mixture layer 102 is moved relatively from one end to the other end in the longitudinal direction Z while being pressed by the press rolls from both sides. As a result, the surface of the negative electrode mixture layer 102 is shaped flat, and the thickness of the portion coated with the negative electrode mixture layer 102 is adjusted to a predetermined thickness. In addition, the positive electrode base layer 111 coated with the positive electrode mixture layer 112 is moved relatively from one end to the other end in the longitudinal direction Z while being pressed by the press rolls from both sides. As a result, the surface of the positive electrode mixture layer 112 is shaped flat, and the thickness of the portion coated with the positive electrode mixture layer 112 is adjusted to a predetermined thickness.

[0066] In step S204, a slitting process is performed. The negative electrode base layer 101 coated with the negative electrode mixture layer 102 is cut in the longitudinal direction Z at the center position in the width direction X of the negative electrode mixture layer 102. This completes two rectangular negative electrode plates 100 as electrode plates. In addition, the positive electrode base layer 111 coated with the positive electrode mixture layer 112 is cut in the longitudinal direction Z at the center position in the width direction X of the positive electrode mixture layer 112. This completes two rectangular positive electrode plates 110 as electrode plates.

[0067] In the winding process described below, the laminate formed by stacking the negative electrode plate 100 and the positive electrode plate 110 manufactured in this process and the rectangular separator 120 is wound in the winding direction Z and shaped flat to form the wound body 20.

[0068] The slitting step may not be necessary. The dimensions of the rectangular base layers 101, 111 in the width direction X are approximately halved, and only one end portion in the width direction X is left as an uncoated portion UCP in the coating step. This allows the negative electrode plate 100 and the positive electrode plate 110 to be manufactured in the same shape without performing the slitting step.

[0069] <Outline of cell assembly process> 9, the next step in the manufacturing method of the lithium ion secondary battery 11 is a flow of a cell assembly process, which includes a winding process, a flattening press process, a terminal welding process, a case insertion process, a can sealing welding process, a cell drying process, a liquid injection / sealing process, and an activation / inspection process.

[0070] In step S301, a winding process is performed. A laminate in which the negative electrode plate 100 and the positive electrode plate 110 manufactured according to the flow shown in FIG. 8 and the rectangular separator 120 are stacked is wound in the winding direction Z to form the wound body 20. The negative electrode plate 100, the positive electrode plate 110, and the separator 120 are wound while applying tension T in the longitudinal direction Z to each of them to form the wound body 20. That is, the winding process is performed in which the negative electrode plate 100, the separator 120, and the positive electrode plate 110, which is an electrode plate, are stacked, and then wound to form the wound body 20.

[0071] In step S302, a flattening press process is performed. More specifically, a flattening press process is performed in which the wound body 20 is pressurized and shaped in a thickness direction Y that is a direction perpendicular to the axial direction X when the laminate is wound in the winding process. The wound body 20 is shaped flat to form a flat wound body 20. In other words, flat portions F of the flat wound body 20 are formed on both sides in the thickness direction Y of the wound body 20.

[0072] In step S303, a terminal welding process is performed. A current collector terminal is attached to an end of the wound body 20. More specifically, the negative electrode current collector 23 is welded to one end of the wound body 20 in the axial direction X, and the positive electrode current collector 25 is welded to the other end of the wound body 20 in the axial direction X, thereby connecting the wound body 20 to the negative electrode external terminal 24 and the positive electrode external terminal 26.

[0073] In step S304, a case insertion process is performed. The wound body 20 to which the insulating film is attached is inserted into the battery case 21. In step S305, a can sealing welding process is performed, in which the battery case 21 and the lid 22 are laser welded together.

[0074] In step S306, a cell drying step is performed. Moisture in the wound body 20 is removed by heating. In step S307, a liquid pouring and sealing step is performed. After the electrolyte 27 is poured into the battery case 21 through the liquid pouring hole, the liquid pouring hole is sealed.

[0075] In step S308, the activation and inspection process is carried out. After conditioning, aging, and inspection, the cell battery is completed. <How to form the wavy shape> 10, in the pressing process of step S203, the negative electrode plate 100 moves relatively from one end to the other end in the longitudinal direction Z while pressures P1 and P2 are applied from both sides in the thickness direction Y. In the coated portion CP, a first pressure P1 is applied from both sides in the thickness direction Y. In the uncoated portion UCP, a second pressure P2 is applied from both sides in the thickness direction Y.

[0076] This adjusts the thickness of the coated part CP to a predetermined thickness. In the coated part CP, application of the first pressure P1 shortens the dimension in the thickness direction Y and lengthens the dimension in the longitudinal direction Z. That is, the thickness of the coated part CP is reduced, but the coated part CP extends in the longitudinal direction Z. More specifically, in both the negative electrode substrate layer 101 and the negative electrode mixture layer 102 constituting the coated part CP, the dimension in the thickness direction Y is shortened and the dimension in the longitudinal direction Z is lengthened.

[0077] In the uncoated portion UCP, application of the second pressure P2 also shortens the dimension in the thickness direction Y and lengthens the dimension in the longitudinal direction Z. That is, the thickness of the uncoated portion UCP decreases, but the uncoated portion UCP extends in the longitudinal direction Z. More specifically, since the only layer constituting the uncoated portion UCP is the negative electrode base material layer 101, the dimension in the thickness direction Y of the negative electrode base material layer 101 of the uncoated portion UCP shortens and the dimension in the longitudinal direction Z lengthens.

[0078] In the pressing process, a value of a first pressure P1 applied to the coated portion CP and a value of a second pressure P2 applied to the uncoated portion UCP are set so that an elongation amount of the uncoated portion UCP in the longitudinal direction Z is larger than an elongation amount of the coated portion CP in the longitudinal direction Z. The value of the second pressure P2 applied to the uncoated portion UCP is set larger than the value of the first pressure P1 applied to the coated portion CP.

[0079] As shown in FIG. 11, the state of the negative electrode plate 100 after the pressing process is in an undeformed state such that the amount of elongation of the uncoated portion UCP in the longitudinal direction Z is greater than the amount of elongation of the coated portion CP in the longitudinal direction Z. More specifically, the negative electrode plate 100 has an internal stress indicated by the dashed arrow in FIG. 11 that tends to deform in the longitudinal direction Z in the uncoated portion UCP, but the coated portion CP located in the center in the width direction X suppresses the deformation in the longitudinal direction Z in the uncoated portion UCP. Furthermore, in the pressing process, the pressing process is performed on the portion where the negative electrode plate 100 wound in the longitudinal direction Z is unwound, and the pressing process is completed by winding the negative electrode plate 100 that has been subjected to the pressing process in the longitudinal direction Z again. That is, in the pressing process, the deformation in the longitudinal direction Z in the uncoated portion UCP is suppressed by the state of the negative electrode plate 100 being wound in the longitudinal direction Z. That is, the state of the negative electrode plate 100 after the pressing step is a state in which the negative electrode plate 100 maintains a substantially rectangular shape, and the uncoated portion UCP has an internal stress that tends to deform in the longitudinal direction Z.

[0080] As shown in Fig. 12, in the slitting process of step S204, the negative electrode plate 100 shown in Fig. 11 is cut along the cutting line CL to form two negative electrode plates 100 shown in Fig. 12 in the shape of a gently arched strip. In other words, the negative electrode plate 100 is cut at the center position of the coated portion CP, and the internal stress shown by the dashed arrow in Fig. 12 is released, allowing the uncoated portion UCP to stretch in the longitudinal direction Z. In the negative electrode plate 100 after the slitting process, the amount of stretching of the uncoated portion UCP in the longitudinal direction Z becomes larger than the amount of stretching of the coated portion CP in the longitudinal direction Z. In order to deform the negative electrode plate 100 into such a shape, in the pressing process, the value of the second pressure P2 applied to the uncoated portion UCP is set to be larger than the value of the first pressure P1 applied to the coated portion CP.

[0081] As described above, the dimension of the strip-shaped negative electrode base material layer 101 in the width direction X is approximately halved, and only one end portion in the width direction X is left as an uncoated portion UCP in the coating process. This makes it possible to manufacture a negative electrode plate 100 having the same shape as the negative electrode plate 100 when the slitting process is performed, without performing the slitting process. In this case, the shape of the negative electrode plate 100 after the pressing process becomes the shape of the negative electrode plate 100 shown in FIG. 12.

[0082] 13, in the winding process of step S301, the wound body 20 is formed while the shape of the negative electrode plate 100 is corrected so that the negative electrode plate 100 has a substantially rectangular shape in a plan view from the thickness direction Y. More specifically, in the winding process, the tension T in the longitudinal direction Z of the negative electrode plate 100 when forming the wound body 20 is set so that the length of the uncoated portion UCP in the longitudinal direction Z of the negative electrode plate 100 is the same as the length of the coated portion CP in the longitudinal direction Z.

[0083] The tension T corrects the shape of the negative electrode plate 100 so that it becomes straight when viewed from above in the thickness direction Y. The length of the coated part CP in the longitudinal direction Z has already been extended by the slitting process after the pressing process, so there is little room for the length of the coated part CP in the longitudinal direction Z to extend any further. Therefore, the length of the uncoated part UCP in the longitudinal direction Z is shortened, thereby correcting the shape of the negative electrode plate 100. More specifically, the negative electrode base material layer 101 of the uncoated part UCP does not shrink, but the negative electrode base material layer 101 of the uncoated part UCP is deformed into a wavy shape, so that the length of the uncoated part UCP in the longitudinal direction Z and the length of the coated part CP in the longitudinal direction Z become the same length. A wavy shape is formed in the uncoated portion UCP such that the amplitude Am is smaller closer to the negative electrode mixture layer 102 or the positive electrode mixture layer 112 and the amplitude Am is larger farther from the negative electrode mixture layer 102 or the positive electrode mixture layer 112.

[0084] In this way, a wavy shape is formed in the negative electrode side current collecting part 103. A similar wavy shape is also formed in the positive electrode side current collecting part 113 by a similar manufacturing method. Then, in the pressing process, the value of the first pressure P1 on the coated part CP and the value of the second pressure P2 on the uncoated part UCP are set so that the elongation amount in the longitudinal direction Z of the uncoated part UCP is larger than the elongation amount in the longitudinal direction Z of the coated part CP. Then, in the winding process, the tension T on the positive electrode plate 110 when forming the wound body 20 is set so that the length of the uncoated part UCP in the longitudinal direction Z and the length of the coated part CP in the longitudinal direction Z are the same for the positive electrode plate 110.

[0085] <Operation of the embodiment> The operation of this embodiment will be described. During charging and discharging, the flattened wound body 20 expands and contracts in the axial direction X, which acts as a force that moves the electrolyte 27 in the axial direction X of the wound body 20. However, since the negative electrode side current collecting portion 103 and the positive electrode side current collecting portion 113 have a wavy shape, the flow of the electrolyte 27 in the axial direction X, as indicated by the solid arrow in Fig. 5, is hindered by the protrusions 31 of the wavy shape shown in Fig. 5. In other words, the resistance to the movement of the electrolyte 27 in the axial direction X of the wound body 20 increases, making it possible to make it difficult for the electrolyte 27 to move in the axial direction X of the wound body 20.

[0086] In the negative electrode side current collecting portion 103, the wave shape is a wave shape in which the amplitude Am becomes smaller as it approaches the negative electrode mixture layer 102 and the amplitude Am becomes larger as it moves away from the negative electrode mixture layer 102. This wave shape makes it difficult for the electrolyte 27 to move toward the end of the wound body 20 while the shape of the central part of the negative electrode base material layer 101 remains flat. In addition, in the positive electrode side current collecting portion 113, the wave shape is a wave shape in which the amplitude Am becomes smaller as it approaches the positive electrode mixture layer 112 and the amplitude Am becomes larger as it moves away from the negative electrode mixture layer 102. This wave shape makes it difficult for the electrolyte 27 to move toward the end of the wound body 20 while the shape of the central part of the positive electrode base material layer 111 remains flat.

[0087] A wavy shape in which the amplitude Am is smaller closer to the negative electrode mixture layer 102 or the positive electrode mixture layer 112 and the amplitude Am is larger farther from the negative electrode mixture layer 102 or the positive electrode mixture layer 112 can be easily formed by the above-mentioned manufacturing method.

[0088] The negative electrode side current collecting part 103 is connected to the negative electrode external terminal 24 at the connection part 23a near the center, so that the value of the gap Δ above the wound body 20 becomes almost "zero". The positive electrode side current collecting part 113 is connected to the positive electrode external terminal 26 at the connection part 25a near the center, so that the value of the gap Δ above the wound body 20 becomes almost "zero". Therefore, the electrolyte 27 flows in and out of the end part of the wound body 20 at the lower part of the wound body 20. Since the negative electrode side current collecting part 103 has a wavy shape below the lower end 23b of the connection part 23a, the flow of the electrolyte 27 in and out of the lower part of the wound body 20 at the negative electrode side current collecting part 103 can be reduced. In addition, since the positive electrode side current collecting portion 113 has a wavy shape below the lower end 25b of the connection portion 25a, the inflow and outflow of the electrolyte 27 occurring at the lower part of the wound body 20 in the positive electrode side current collecting portion 113 can be reduced.

[0089] Due to the expansion and contraction of the wound body 20 in the axial direction X, a force acts on the electrolyte 27 to move it in the axial direction X through the gap Δ. Furthermore, in the gap Δ between the negative electrode base material layers 101 in the negative electrode side current collector 103 and the gap Δ between the positive electrode base material layers 111 in the positive electrode side current collector 113, the position of the gap Δ changes in the thickness direction Y perpendicular to the axial direction X in which the electrolyte 27 moves. This increases the resistance when the electrolyte 27 moves in the axial direction X through the gap Δ between the base material layers 101, 111, making it difficult for the electrolyte 27 to move in the axial direction X.

[0090] The corrugated shapes of the negative electrode plate 100 and the positive electrode plate 110 form a location where the value of the gap Δ is large and a location where the value of the gap Δ is small. In the location where the value of the gap Δ is small, the resistance to the electrolyte 27 moving in the axial direction X through the gap Δ between the base material layers 101, 111 becomes large, so that it is possible to make it difficult for the electrolyte 27 to move in the axial direction X.

[0091] By the method for forming the wavy shape in the manufacturing method of the lithium ion secondary battery 11 described above, it is possible to manufacture a negative electrode plate 100 having a wavy shape in the negative electrode side current collecting portion 103 of the negative electrode substrate layer 101. Also, by the method for forming the wavy shape in the manufacturing method of the lithium ion secondary battery 11 described above, it is possible to manufacture a positive electrode plate 110 having a wavy shape in the positive electrode side current collecting portion 113 of the positive electrode substrate layer 111.

[0092] In the pressing process, the value of the first pressure P1 on the coated part CP and the value of the second pressure P2 on the uncoated part UCP are set so that the elongation amount of the uncoated part UCP in the longitudinal direction Z is greater than the elongation amount of the coated part CP in the longitudinal direction Z. Therefore, in the slitting process after the pressing process, the length of the uncoated part UCP in the longitudinal direction Z is shortened, and the length of the coated part CP in the longitudinal direction Z is lengthened. However, in the subsequent winding process, the tension T on the negative electrode plate 100 and the positive electrode plate 110 when forming the wound body 20 is set so that the length of the uncoated part UCP in the longitudinal direction Z and the length of the coated part CP in the longitudinal direction Z are the same. Therefore, the negative electrode plate 100 and the positive electrode plate 110 bent in the slitting process after the pressing process can be made to have a shape that has a substantially rectangular shape in a plan view from the thickness direction Y. That is, in the winding process, the negative electrode plate 100 and the positive electrode plate 110 can be made straight when viewed in a plan view from the thickness direction Y.

[0093] <Confirmation results of the action according to the embodiment> According to the lithium ion secondary battery 11 of this embodiment, the following results were obtained in terms of the transition of the internal resistance during high-rate charging and discharging. When the area ratio of the gap Δ was reduced by 50%, the rate of change of the internal resistance of the lithium ion secondary battery 11 during repeated charging and discharging was reduced by 1.7%. Note that the reduction in the rate of change of the internal resistance can suppress the deterioration of the battery performance.

[0094] According to the manufacturing method of the lithium ion secondary battery 11 of this embodiment, the following results were obtained in the method of forming the corrugated shape. When the value of the second pressure P2 on the uncoated part UCP was set to be greater than 1.2 times the value of the first pressure P1 on the coated part CP, in the slitting process after the pressing process, the elongation amount of the uncoated part UCP in the longitudinal direction Z became greater than the elongation amount of the coated part CP in the longitudinal direction Z. Then, in the subsequent winding process, by adjusting the value of the tension T, the length of the uncoated part UCP in the longitudinal direction Z and the length of the coated part CP in the longitudinal direction Z could be made the same. In the gap Δ, a portion was formed in which the value of the gap Δ was 75% or more smaller than when there was no corrugated shape. Since the rate of change of the internal resistance during high-rate charging and discharging is approximately inversely proportional to the value of the gap Δ, in this embodiment, a corrugated shape in which the rate of change of the internal resistance during repeated charging and discharging is reduced by approximately 2.55% could be formed. The size of the gap Δ when no wavy pattern is formed is 73 μm, whereas in this embodiment, the actual value of the gap Δ in a portion where the value of the gap Δ is 75% or less is 18 μm or less.

[0095] In summary, in the pressing step of the manufacturing method of the lithium ion secondary battery 11 of this embodiment, the value of the second pressure P2 on the uncoated portion UCP is greater than 1.2 times the value of the first pressure P1 on the coated portion CP. The lithium ion secondary battery 11 of this embodiment has a portion in the flat plane portion F of the negative electrode side current collecting portion 103 where the value of the gap Δ between two adjacent negative electrode base material layers 101 in the thickness direction Y of the negative electrode base material layer 101 is 18 μm or less. The lithium ion secondary battery 11 of this embodiment has a portion in the flat plane portion F of the positive electrode side current collecting portion 113 where the value of the gap Δ between two adjacent positive electrode base material layers 111 in the thickness direction Y of the positive electrode base material layer 111 is 18 μm or less.

[0096] <Effects of the embodiment> The effects of this embodiment will be described. (1) At one end in the axial direction X, the negative electrode mixture layer 102 is not provided on both sides of the negative electrode base material layer 101, and the negative electrode side current collector 103 has a wavy shape in which the thickness direction Y of the negative electrode base material layer 101 is the amplitude Am direction and the winding direction Z is the wavelength λ direction. At the other end in the axial direction X, the positive electrode mixture layer 112 is not provided on both sides of the positive electrode base material layer 111, and the positive electrode side current collector 113 has a wavy shape in which the thickness direction Y of the positive electrode base material layer 111 is the amplitude Am direction and the winding direction Z is the wavelength λ direction. Therefore, the wavy convex portion 31 makes it difficult for the electrolyte 27 to move in the axial direction X of the wound body 20, and it is possible to suppress the electrolyte 27 with a low lithium salt concentration from going out of the wound body 20. As a result, the unevenness of the lithium salt concentration in the wound body 20 is suppressed, and the increase in internal resistance due to repeated charging and discharging can be suppressed.

[0097] (2) The wavy shape has a smaller amplitude Am closer to the negative electrode mixture layer 102 or the positive electrode mixture layer 112, and a larger amplitude Am closer to the negative electrode mixture layer 102 or the positive electrode mixture layer 112. A wavy shape having a smaller amplitude Am closer to the negative electrode mixture layer 102 or the positive electrode mixture layer 112 and a larger amplitude Am farther from the negative electrode mixture layer 102 or the positive electrode mixture layer 112 is an easily manufacturable shape. Therefore, the easily manufacturable wavy convex portion 31 can prevent the electrolyte 27 with a low lithium salt concentration from leaking out of the wound body 20.

[0098] (3) The negative electrode side current collector 103 and the positive electrode side current collector 113 are connected to the external terminals 24, 26 of the lithium ion secondary battery 11 at the upper portions of the flat planar portion F of the flat shape by the connection portions 23a, 25a. The negative electrode side current collector 103 and the positive electrode side current collector 113 have a wavy shape below the lower ends 23b, 25b of the connection portions 23a, 25a. This makes it possible to prevent the electrolyte solution 27 with a low lithium salt concentration from flowing out of the wound body 20 from the lower portion of the wound body 20, which is the portion not connected to the external terminals 24, 26 of the lithium ion secondary battery 11 by the connection portions 23a, 25a.

[0099] (4) In the flat plane portion F of the negative electrode side current collecting portion 103, both of the two negative electrode base material layers 101 adjacent in the thickness direction Y of the negative electrode base material layer 101 have a wavy shape. As a result, the position of the gap Δ between the two negative electrode base material layers 101 changes in the thickness direction Y of the negative electrode base material layer 101. Then, in the flat plane portion F of the positive electrode side current collecting portion 113, both of the two positive electrode base material layers 111 adjacent in the thickness direction Y of the positive electrode base material layer 111 have a wavy shape. As a result, the position of the gap Δ between the two positive electrode base material layers 111 changes in the thickness direction Y of the positive electrode base material layer 111. By changing the position of the gap Δ in the thickness direction Y of the negative electrode base material layer 101 and the positive electrode base material layer 111, the resistance when the electrolyte 27 moves through the gap Δ in the axial direction X of the wound body 20 increases. Therefore, it is possible to prevent the electrolyte solution 27 with a reduced lithium salt concentration from leaking out of the wound body 20 through the gap Δ between the base layers 101, 111.

[0100] (5) In the flat planar portion F of the negative electrode side current collecting portion 103, there is a portion where the value of the gap Δ between two adjacent negative electrode base material layers 101 in the thickness direction Y of the negative electrode base material layer 101 is 18 μm or less. In addition, in the flat planar portion F of the positive electrode side current collecting portion 113, there is a portion where the value of the gap Δ between two adjacent positive electrode base material layers 111 in the thickness direction Y of the positive electrode base material layer 111 is 18 μm or less. Therefore, in the portion where the value of the gap Δ between the base material layers 101, 111 is 18 μm or less, it is possible to further suppress the electrolyte solution 27 with a low lithium salt concentration from leaking out of the wound body 20 through the gap Δ between the base material layers 101, 111.

[0101] (6) In the coating step, an uncoated part UCP not coated with the mixture layers 102, 112 is formed at one or both ends in the width direction X of the coated part CP coated with the mixture layers 102, 112. Then, in the pressing step, the value of the first pressure P1 on the coated part CP and the value of the second pressure P2 on the uncoated part UCP are set so that the elongation amount of the uncoated part UCP in the longitudinal direction Z is larger than the elongation amount of the coated part CP in the longitudinal direction Z. This makes it possible to form the negative electrode plate 100 and the positive electrode plate 110 having a wavy shape that can prevent the electrolyte 27 with a low lithium salt concentration from going out of the wound body 20 in the current collecting parts 103, 113 of the base material layers 101, 111. Then, the wound body 20 is formed with the negative electrode plate 100 and the positive electrode plate 110 having the wavy shape, and the lithium ion secondary battery 11 can be manufactured.

[0102] (7) In the winding process, the length of the uncoated portion UCP in the longitudinal direction Z of the negative electrode plate 100 and the positive electrode plate 110 is the same as the length of the coated portion CP in the longitudinal direction Z. The tension T applied to the negative electrode plate 100 and the positive electrode plate 110 when forming the wound body 20 is set in this manner. Therefore, the negative electrode plate 100 and the positive electrode plate 110 bent in the slitting process after the pressing process can be formed into the negative electrode plate 100 and the positive electrode plate 110 having a substantially rectangular shape in a plan view from the thickness direction Y. Then, the wound body 20 is formed of the negative electrode plate 100 and the positive electrode plate 110 having a wavy shape in the current collecting portions 103, 113 of the base layers 101, 111, and the lithium ion secondary battery 11 can be manufactured.

[0103] (8) In the pressing process, the value of the second pressure P2 on the uncoated portion UCP is greater than 1.2 times the value of the first pressure P1 on the coated portion CP. Therefore, the wound body 20 can be formed with the negative electrode plate 100 and the positive electrode plate 110 that have a large effect of suppressing the electrolyte solution 27 with a low lithium salt concentration from leaking out of the wound body 20 in the current collecting portions 103, 113 of the base layers 101, 111.

[0104] <Modifications of this embodiment> The present embodiment can be modified as follows: The present embodiment and the following modified examples can be combined with each other to the extent that there is no technical contradiction.

[0105] In this embodiment, the negative electrode mixture layer 102 is provided on both sides of the negative electrode base material layer 101, but the negative electrode mixture layer 102 may be provided on only one side of the negative electrode base material layer 101. Similarly, in this embodiment, the positive electrode mixture layer 112 is provided on both sides of the positive electrode base material layer 111, but the positive electrode mixture layer 112 may be provided on only one side of the positive electrode base material layer 111.

[0106] The wavy shape is not limited to the wavy shape formed by the manufacturing method described in this embodiment. For example, a concave press mold and a convex press mold may be used to press a plurality of locations on the current collecting portion 103, 113 from both sides in the thickness direction Y, thereby forming a wavy shape on the current collecting portion 103, 113. The plurality of pressed locations may not be aligned in the width direction X or the longitudinal direction Z, and may be irregularly arranged. It is sufficient that the current collecting portion 103, 113 has a convex portion 31 having a shape that prevents the flow of the electrolyte 27 in the axial direction X. In addition, for example, the current collecting portion 103, 113 may be pressed from both sides by a pair of forming rollers having a wavy forming surface, while moving relatively from one end to the other end in the longitudinal direction Z, thereby forming a wavy shape on the current collecting portion 103, 113.

[0107] In the flat plane portion F of the winding 20, even if there is no protrusion 31 on the end edge in the width direction X of the current collecting parts 103, 113, it is sufficient that there is a protrusion 31 having a shape that prevents the flow of the electrolyte 27 in the axial direction X between the end edge and the mixture layers 102, 112. It is sufficient that the current collecting parts 103, 113 have a protrusion 31 having a shape that prevents the flow of the electrolyte 27 in the axial direction X.

[0108] Prior to the winding step, a straightening step may be performed to straighten the shape of the negative electrode plate 100 by applying tension T in the longitudinal direction Z of the negative electrode plate 100 so that the negative electrode plate 100 has a substantially rectangular shape in a plan view from the thickness direction Y. Then, the winding step may be performed after the straightening step. More specifically, in the straightening step, the tension T applied to the negative electrode plate 100 is set so that the length of the uncoated portion UCP in the longitudinal direction Z is equal to the length of the coated portion CP in the longitudinal direction Z. A similar straightening step may also be performed on the positive electrode plate 110.

[0109] In the winding process, the tension on the coated portion CP side may be made stronger than the tension on the uncoated portion UCP side, so that the shape of the negative electrode plate 100 is straight when viewed in a plan view from the thickness direction Y. Note that the shape of the positive electrode plate 110 may also be straightened in a similar manner when viewed in a plan view from the thickness direction Y. [Explanation of symbols]

[0110] 11...Lithium-ion secondary battery 20...Wound body 21…Battery case 22…Cover body 23...Negative electrode current collector 23a…Connection 23b…lower end 24…Negative external terminal 25...Positive electrode current collector 25a…Connection 25b…lower end 26…Positive external terminal 27...Electrolyte 31…Convex part 32…Recess 100: Negative electrode plate 101...Negative electrode base material layer 102...Negative electrode mixture layer 103...Negative electrode current collector 110…Positive electrode plate 111...Positive electrode substrate layer 112...Positive electrode mixture layer 113…Positive electrode current collector 120…Separator Δ…Gap λ...Wavelength Am…Amplitude CL…cutting line CP: Coating department F...Plane part P1…First pressure P2: Second pressure T…Tension UCP: Uncoated section X…Axis direction Y: Thickness direction Z…winding direction

Claims

1. a coating step in which a mixture layer is applied to the electrode plate; a drying step in which the mixture layer is dried; a pressing step in which the thickness of the electrode plate is adjusted; a winding step in which the negative electrode plate, which is the electrode plate, a separator, and the positive electrode plate, which is the electrode plate, are stacked and then wound to form a wound body; a flattening press process in which the wound body is pressurized and shaped in a direction perpendicular to the axial direction when the wound body is pressed; A method for producing a lithium ion secondary battery comprising: In the coating step, uncoated portions not coated with the mixture layer are formed at both ends in a width direction of the coated portion coated with the mixture layer, a value of a first pressure applied to the coated portion and a value of a second pressure applied to the uncoated portion are set so that an elongation amount of the uncoated portion in a longitudinal direction is larger than an elongation amount of the coated portion in the longitudinal direction in the pressing step; After the pressing step, the electrode plate is cut at a center position of the coated portion, and the cut electrode plate is corrected in shape so that a length of the uncoated portion in the longitudinal direction is equal to a length of the coated portion in the longitudinal direction, so that a wavy shape is formed in the uncoated portion, while the wound body is formed; A corrugated protrusion is provided to prevent the flow of the electrolyte moving in the axial direction of the winding body, In the flat planar portion of the negative electrode side current collecting portion, there is a portion in which the value of the gap between two adjacent negative electrode base material layers in the thickness direction of the negative electrode base material layer is 18 μm or less, In the flat plane portion of the positive electrode side current collecting portion, there is a portion where the value of the gap between two adjacent positive electrode base material layers in the thickness direction of the positive electrode base material layer is 18 μm or less. A method for manufacturing a lithium-ion secondary battery.

2. a coating step in which a mixture layer is applied to the electrode plate; a drying step in which the mixture layer is dried; a pressing step in which the thickness of the electrode plate is adjusted; a winding step in which the negative electrode plate, which is the electrode plate, a separator, and the positive electrode plate, which is the electrode plate, are stacked and then wound to form a wound body; a flattening press process in which the wound body is pressurized and shaped in a direction perpendicular to the axial direction when the wound body is pressed; A method for producing a lithium ion secondary battery comprising: In the coating step, uncoated portions not coated with the mixture layer are formed at both ends in a width direction of the coated portion coated with the mixture layer, a value of a first pressure applied to the coated portion and a value of a second pressure applied to the uncoated portion are set so that an elongation amount of the uncoated portion in a longitudinal direction is larger than an elongation amount of the coated portion in the longitudinal direction in the pressing step; After the pressing step, the electrode plate is cut at a center position of the coated portion, and the cut electrode plate is corrected in shape so that a length of the uncoated portion in the longitudinal direction is equal to a length of the coated portion in the longitudinal direction, so that a wavy shape is formed in the uncoated portion, while the wound body is formed; The wavy shape formed in the uncoated portion has a smaller amplitude as the uncoated portion is closer to the mixture layer, and has a larger amplitude as the uncoated portion is farther from the mixture layer. In the flat planar portion of the negative electrode side current collecting portion, there is a portion in which the value of the gap between two adjacent negative electrode base material layers in the thickness direction of the negative electrode base material layer is 18 μm or less, In the flat plane portion of the positive electrode side current collecting portion, there is a portion where the value of the gap between two adjacent positive electrode base material layers in the thickness direction of the positive electrode base material layer is 18 μm or less. A method for manufacturing a lithium-ion secondary battery.

3. In the winding step, tensions applied to the negative electrode plate and the positive electrode plate when the wound body is formed are set so that the length of the uncoated portion in the longitudinal direction of the negative electrode plate and the length of the coated portion in the longitudinal direction of the positive electrode plate are the same. The method for producing the lithium ion secondary battery according to claim 1 or 2.

4. In the pressing step, a value of the second pressure applied to the uncoated portion is greater than 1.2 times a value of the first pressure applied to the coated portion. A method for producing the lithium ion secondary battery according to any one of claims 1 to 3.

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