Method for manufacturing non-aqueous secondary battery

Abstract

To provide a manufacturing method for a non-aqueous secondary battery that can suppress deterioration of the spring constant of an electrode body.SOLUTION: A non-aqueous secondary battery includes an electrode body having a negative electrode plate, a positive electrode plate, and a separator provided between the negative electrode plate and the positive electrode plate. A manufacturing method of the non-aqueous secondary battery includes an inter-electrode distance measurement step of measuring an inter-electrode distance at a predetermined timing during an unrestrained period in which an electrode body is in an unrestrained state, and an adjustment step of adjusting the restraining force on the electrode body according to the distance between the electrodes measured in the inter-electrode distance measurement step.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a nonaqueous secondary battery, and more particularly to a method for manufacturing a nonaqueous secondary battery that can suppress deterioration of the spring constant of an electrode assembly. [Background technology]

[0002] Conventionally, non-aqueous secondary batteries include an electrode assembly having a negative electrode plate, a positive electrode plate, and a separator. Such an electrode assembly is wound in a winding direction while the negative electrode plate, the positive electrode plate, and the separator are stacked in a stacking direction, and is housed in a battery case together with a non-aqueous electrolyte solution in a state in which the electrode assembly has a flat region and a curved region.

[0003] As a method for manufacturing such a nonaqueous secondary battery, for example, Patent Document 1 discloses a method for making the distance between the electrode plates in each region of the electrode assembly constant by inserting a spacer having ribs with different spring constants in the flat region and the curved region. With this manufacturing method, even if the flat region of the electrode assembly expands, the distance between the electrode plates can be kept constant in the flat region and the curved region of the electrode assembly, and metal deposition in the flat region of the electrode assembly can be suppressed. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2017-98107 Summary of the Invention [Problem to be solved by the invention]

[0005] However, in the invention described in Patent Document 1, if the distance between the electrode plates of an electrode assembly is shorter than expected, the electrode assembly will be constrained more than necessary, and in such a case, there is a risk that the spring constant of the electrode assembly will deteriorate due to the constraining of the electrode assembly. [Means for solving the problem]

[0006] Various aspects of the method for manufacturing a nonaqueous secondary battery that solves the above problems will be described. [Aspect 1] A method for manufacturing a nonaqueous secondary battery comprising an electrode assembly having a negative electrode plate, a positive electrode plate, and a separator disposed between the negative electrode plate and the positive electrode plate, the method including: an inter-electrode measurement step of measuring the distance between the electrode plates at a predetermined timing during an unconstrained period in which the electrode assembly is not constrained; and an adjustment step of adjusting the constraint force on the electrode assembly in accordance with the distance between the electrode plates measured in the inter-electrode measurement step.

[0007] According to the above configuration, the restraining force on the electrode assembly can be adjusted according to the state of the electrode assembly, i.e., the distance between the electrode plates actually measured during the non-restraint period, thereby suppressing metal deposition due to an increase in the distance between the electrode plates and suppressing deterioration of the spring constant of the electrode assembly.

[0008] [Aspect 2] In the method for manufacturing a nonaqueous secondary battery according to [Aspect 1], the adjustment step may not restrain the electrode assembly when the distance between the electrode plates measured in the electrode-to-electrode measurement step is equal to or less than a first distance, and may restrain the electrode assembly when the distance between the electrode plates measured in the electrode-to-electrode measurement step is longer than the first distance.

[0009] According to the above configuration, when the distance between the electrode plates actually measured during the non-constraint period is equal to or shorter than the first distance, the electrode assembly is not constrained, thereby minimizing the constraint on the electrode assembly and suppressing deterioration of the spring constant of the electrode assembly. On the other hand, when the distance between the electrode plates is longer than the first distance, the electrode assembly is constrained, thereby suppressing metal deposition. Therefore, metal deposition due to an increase in the distance between the electrode plates can be suppressed, and deterioration of the spring constant of the electrode assembly can be suppressed.

[0010] [Aspect 3] In the method for manufacturing a nonaqueous secondary battery according to [Aspect 2], the adjustment step may restrain the electrode assembly with a stronger restraining force when the distance between the electrode plates measured in the electrode-to-electrode measurement step is longer than the second distance, compared to when the distance is greater than the first distance and equal to or less than a second distance longer than the first distance.

[0011] According to the above configuration, when the distance between the electrode plates actually measured during the non-restraint period is longer than the second distance, the electrode assembly is restrained with a stronger restraining force than when the distance between the electrode plates is longer than the first distance and equal to or shorter than the second distance, thereby suppressing metal deposition due to the longer distance between the electrode plates. On the other hand, when the distance between the electrode plates actually measured during the non-restraint period is longer than the first distance and equal to or shorter than the second distance, the electrode assembly is restrained with a weaker restraining force than when the distance between the electrode plates is longer than the second distance. This suppresses metal deposition due to the longer distance between the electrode plates and also suppresses deterioration of the spring constant of the electrode assembly.

[0012] [Aspect 4] In the method for manufacturing a nonaqueous secondary battery according to any one of [Aspect 1] to [Aspect 3], the electrode gap measurement step may measure the distance between the electrode plates at a timing when a predetermined time has elapsed since the electrode plates entered the unconstrained state during the unconstrained period.

[0013] According to the above configuration, by measuring the distance between the electrode plates at a timing when a predetermined time has elapsed since the electrode plates were put into the unconstrained state, it is possible to suppress measurement errors due to the timing of measuring the distance between the electrode plates.

[0014] [Aspect 5] In the method for manufacturing a nonaqueous secondary battery described in [Aspect 1], the electrode gap measurement step may measure the distance between the electrode plates at a first timing and a second timing that is a specified time after the first timing during the non-constraint period, and the adjustment step may be capable of adjusting the constraint force on the electrode body according to the distance between the electrode plates measured at the first timing and the distance between the electrode plates measured at the second timing in the electrode gap measurement step.

[0015] According to the above configuration, the restraining force on the electrode assembly can be adjusted according to the distance between the electrode plates measured at a first timing and a second timing, which is a predetermined time after the first timing. This improves the accuracy of adjusting the restraining force on the electrode assembly. Therefore, it is possible to suppress metal deposition caused by an increase in the distance between the electrode plates and to suppress deterioration of the spring constant of the electrode assembly.

[0016] [Aspect 6] [Aspect 5] may further include a pole-to-pole prediction step of predicting a third time when the distance between the pole plates will be the first distance, based on the distance between the pole plates measured at the first timing in the pole-to-pole measurement step and the distance between the pole plates measured at the second timing, and the adjustment step may include restraining the electrode assembly at the third time predicted in the pole-to-pole prediction step.

[0017] According to the above configuration, by predicting the third timing at which the distance between the electrode plates becomes the first distance, the electrode assembly can be restrained at the third timing. This allows the distance between the electrode plates to be adjusted to the first distance. Therefore, metal deposition due to an increase in the distance between the electrode plates can be suppressed, and deterioration of the spring constant of the electrode assembly can be suppressed.

[0018] A method for manufacturing a non-aqueous secondary battery comprising an electrode assembly having a negative electrode plate, a positive electrode plate, and a separator disposed between the negative electrode plate and the positive electrode plate, a non-aqueous electrolyte, and a battery case containing the electrode assembly and the non-aqueous electrolyte, the method comprising: an inter-electrode measurement step of measuring the distance between the electrode plates at a predetermined timing during an unconstrained period in which the electrode assembly is not constrained; an injection step of injecting the non-aqueous electrolyte into the battery case with the electrode assembly contained therein; and a sealing step of sealing the battery case with the electrode assembly and the non-aqueous electrolyte contained therein, wherein the sealing step shortens the time from when the non-aqueous electrolyte is injected into the battery case in the injection step to when the battery case is sealed, in accordance with the distance between the electrode plates measured in the inter-electrode measurement step.

[0019] According to the above configuration, the time from when the nonaqueous electrolyte is poured into the battery case to when the battery case is sealed can be shortened depending on the state of the electrode assembly, i.e., the distance between the electrodes actually measured during the unconstrained period. This allows the pressure inside the battery case to be intentionally reduced. This increases the self-constraint force acting on the electrode assembly, preventing the distance between the electrodes from increasing in the electrode assembly. This prevents metal deposition due to an increase in the distance between the electrodes, minimizes the constraint on the electrode assembly, and prevents deterioration of the spring constant of the electrode assembly.

[0020] In the method for manufacturing a nonaqueous secondary battery according to [Aspect 8] or [Aspect 7], the sealing step may shorten the time from when the nonaqueous electrolyte is injected into the battery case in the liquid injection step to when the distance between the electrode plates measured in the liquid inter-electrode measurement step is equal to or less than a predetermined distance.

[0021] According to the above configuration, when the distance between the electrodes actually measured during the non-constraint period is equal to or less than a predetermined distance, the pressure inside the battery case can be intentionally reduced. This increases the self-constraint force acting on the electrode assembly, effectively preventing the distance between the electrodes from increasing. This effectively prevents metal deposition due to the increased distance between the electrodes.

[0022] [Aspect 9] The method for producing a nonaqueous secondary battery according to [Aspect 7] or [Aspect 8] may further include a charging step of charging the nonaqueous secondary battery after the sealing step is completed, and an aging step of storing the nonaqueous secondary battery after the charging step is completed, wherein the aging step may store the nonaqueous secondary battery in the unconstrained state when the time from when the nonaqueous electrolyte is injected into the battery case to when the battery case is sealed is shortened.

[0023] According to the above configuration, when the time from when the nonaqueous electrolyte is poured into the battery case until when the battery case is sealed is shortened, the nonaqueous secondary battery is stored in an unconstrained state during the aging process, which minimizes the constraint on the electrode assembly and suppresses deterioration of the spring constant of the electrode assembly. [Effects of the Invention]

[0024] According to the present invention, it is possible to suppress deterioration of the spring constant of the electrode body. [Brief explanation of the drawings]

[0025] [Figure 1] 1 is a perspective view of a lithium ion secondary battery according to an embodiment of the present invention; [Figure 2] FIG. 2 is a schematic diagram showing the configuration of a laminate of electrode bodies of a lithium ion secondary battery. [Figure 3] 1 is a flowchart showing a manufacturing process of a lithium ion secondary battery. [Figure 4] FIG. 2 is a schematic diagram showing a restraint table. [Figure 5] FIG. 1 is a schematic diagram showing an embodiment. [Figure 6] 1 is a flowchart showing a manufacturing process of a lithium ion secondary battery. [Figure 7] FIG. 10 is a schematic diagram showing a prediction result based on a measurement result of the electrode distance. [Figure 8] 1 is a flowchart showing a manufacturing process of a lithium ion secondary battery. DETAILED DESCRIPTION OF THE INVENTION

[0026] [First embodiment] Hereinafter, one embodiment of a method for manufacturing a nonaqueous secondary battery will be described. <Lithium-ion secondary battery 10> As an example of a nonaqueous secondary battery, the structure of a lithium ion secondary battery will be described.

[0027] As shown in FIG. 1, the lithium ion secondary battery 10 is configured as a cell battery. The lithium ion secondary battery 10 includes a battery case 11. The battery case 11 includes a lid 12. The battery case 11 includes an opening (not shown) on the upper side. The lid 12 seals the opening. The battery case 11 is made of a metal such as an aluminum alloy. The lid 12 includes a negative electrode external terminal 13 and a positive electrode external terminal 14 used for charging and discharging power. The negative electrode external terminal 13 and the positive electrode external terminal 14 may have any shape.

[0028] The lithium ion secondary battery 10 includes an electrode assembly 15. The lithium ion secondary battery 10 includes a negative electrode current collector 16 and a positive electrode current collector 17. The negative electrode current collector 16 connects the negative electrode of the electrode assembly 15 to a negative electrode external terminal 13. The positive electrode current collector 17 connects the positive electrode of the electrode assembly 15 to a positive electrode external terminal 14. The electrode assembly 15 is housed inside a battery case 11.

[0029] The lithium ion secondary battery 10 includes a non-aqueous electrolyte 18. The non-aqueous electrolyte 18 is injected into the battery case 11 through a filling hole (not shown). The lithium ion secondary battery 10 is configured as a sealed battery container by attaching a lid 12 to the opening of the battery case 11. In this manner, the battery case 11 accommodates the electrode assembly 15 and the non-aqueous electrolyte 18.

[0030] <Nonaqueous electrolyte 18> The nonaqueous electrolyte 18 is a composition in which a supporting salt is contained in a nonaqueous solvent. In this embodiment, ethylene carbonate (EC) can be used as the nonaqueous solvent. The nonaqueous solvent may be one or more materials selected from the group consisting of propylene carbonate (PC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), etc.

[0031] The supporting electrolyte may be LiPF, LiBF, LiClO, LiAsF, LiCF, SO, LiC, F, SO, LiN(CF, SO), LiC(CF, SO), LiI, or the like. Alternatively, one or more lithium compounds (lithium salts) selected from these may be used. Thus, the nonaqueous electrolyte 18 contains a lithium compound.

[0032] <Electrode body 15> As shown in FIG. 2, the electrode assembly 15 includes a negative electrode plate 20, a positive electrode plate 30, and a separator 40. The longitudinal direction of the electrode assembly 15 is referred to as the "lengthwise direction Z." The thickness direction of the electrode assembly 15 is referred to as the "thickness direction D." The direction intersecting the lengthwise direction Z and the thickness direction D of the electrode assembly 15 is referred to as the "widthwise direction W." One direction of the widthwise directions W is referred to as the "first widthwise direction W1," and the other direction of the widthwise directions W is referred to as the "second widthwise direction W2." In other words, the second widthwise direction W2 is the opposite direction to the first widthwise direction W1.

[0033] The electrode body 15 is formed by stacking a negative electrode plate 20, a positive electrode plate 30, and a separator 40 in the thickness direction D. The separator 40 is provided between the negative electrode plate 20 and the positive electrode plate 30. Specifically, the electrode body 15 is formed by stacking the separator 40, the positive electrode plate 30, the separator 40, and the negative electrode plate 20 in this order.

[0034] The electrode assembly 15 is formed by stacking a negative electrode plate 20, a positive electrode plate 30, and a separator 40 in a thickness direction D and then winding them in a length direction Z. The electrode assembly 15 has a flat shape in the thickness direction D at the center in the length direction Z.

[0035] In this way, the thickness direction D in which the negative electrode plate 20, the positive electrode plate 30, and the separator 40 are stacked can also be referred to as the stacking direction. Also, the length direction Z in which the negative electrode plate 20, the positive electrode plate 30, and the separator 40 are wound can also be referred to as the winding direction.

[0036] The electrode body 15 has a flat shape in the thickness direction D. The electrode body 15 has a flat region and a curved region in the length direction Z. The flat region is a region that has a flat shape in the thickness direction D. The curved region is a region that has a curved shape in the thickness direction D. The curved regions are located at both ends of the flat region in the length direction Z.

[0037] <Negative electrode plate 20> The negative electrode plate 20 functions as an example of a negative electrode of the lithium ion secondary battery 10. The negative electrode plate 20 includes a negative electrode substrate 21 and a negative electrode mixture layer 22. The negative electrode mixture layer 22 is provided on both sides of the negative electrode substrate 21.

[0038] The negative electrode substrate 21 has a negative electrode connecting portion 23. The negative electrode connecting portion 23 is a region where the negative electrode composite layer 22 is not provided on either side of the negative electrode substrate 21. The negative electrode connecting portion 23 is provided at an end portion in the first width direction W1 of the electrode body 15. The negative electrode connecting portion 23 is exposed from the positive electrode plate 30 and the separator 40 in the first width direction W1.

[0039] In this embodiment, negative electrode substrate 21 is made of Cu foil. Negative electrode substrate 21 serves as a base for the aggregate of negative electrode composite layer 22. Negative electrode substrate 21 functions as a current collecting member that collects electricity from negative electrode composite layer 22.

[0040] Negative electrode mixture layer 22 contains a negative electrode active material. In this embodiment, the negative electrode active material is a material capable of absorbing and releasing lithium ions, and a powdered carbon material such as graphite is used. Negative electrode plate 20 is produced, for example, by kneading the negative electrode active material, a solvent, and a binder, applying the kneaded negative electrode mixture paste to negative electrode substrate 21, and drying the mixture.

[0041] <Positive electrode plate 30> The positive electrode plate 30 functions as an example of a positive electrode of the lithium ion secondary battery 10. The positive electrode plate 30 includes a positive electrode substrate 31 and a positive electrode mixture layer 32. The positive electrode mixture layer 32 is provided on both sides of the positive electrode substrate 31.

[0042] The positive electrode substrate 31 includes a positive electrode connection portion 33. The positive electrode connection portion 33 is a region where the positive electrode composite layer 32 is not provided on either side of the positive electrode substrate 31. The positive electrode connection portion 33 is provided at an end portion of the electrode body 15 in the second width direction W2. The positive electrode connection portion 33 is exposed from the negative electrode plate 20 and the separator 40 in the second width direction W2.

[0043] In this embodiment, positive electrode substrate 31 is made of Al foil or Al alloy foil. Positive electrode substrate 31 serves as a base for the aggregate of positive electrode mixture layer 32. Positive electrode substrate 31 functions as a current collecting member that collects electricity from positive electrode mixture layer 32.

[0044] The positive electrode mixture layer 32 contains a positive electrode active material. The positive electrode active material is a material capable of absorbing and releasing lithium, such as lithium cobalt oxide (LiCoO), lithium manganese oxide (LiMnO), or lithium nickel oxide (LiNiO). Alternatively, a material obtained by mixing LiCoO, LiMnO, and LiNiO in any ratio may be used. The positive electrode mixture layer 32 contains a conductive material. Examples of the conductive material include carbon black such as acetylene black (AB) or ketjen black, and graphite. The positive electrode plate 30 is produced, for example, by kneading a positive electrode active material, a conductive material, a solvent, and a binder, and then applying the resulting positive electrode mixture paste to the positive electrode substrate 31 and drying it.

[0045] <Separator 40> The separator 40 is disposed between the negative electrode plate 20 and the positive electrode plate 30. The separator 40 holds the non-aqueous electrolyte 18. The separator 40 is a nonwoven fabric made of a porous resin such as polypropylene. The separator 40 may be a porous polymer membrane such as a porous polyethylene membrane, a porous polyolefin membrane, or a porous polyvinyl chloride membrane, or a lithium ion or ion conductive polymer electrolyte membrane, either singly or in combination. When the electrode assembly 15 is immersed in the non-aqueous electrolyte 18, the non-aqueous electrolyte 18 permeates the separator 40 from the edges toward the center.

[0046] <Manufacturing Process of Lithium-ion Secondary Battery 10> Here, the manufacturing process of the lithium ion secondary battery 10 of this embodiment will be described with reference to Fig. 3. The manufacturing process of the lithium ion secondary battery 10 of this embodiment includes steps S10 to S22. That is, the manufacturing method of the lithium ion secondary battery 10 of this embodiment includes steps S10 to S22.

[0047] 3, in this embodiment, a source process is performed in step S10. The source process is a process for fabricating battery elements of the lithium-ion secondary battery 10. Specifically, the source process is a process for fabricating the negative electrode plate 20 and the positive electrode plate 30 that constitute the battery elements of the lithium-ion secondary battery 10.

[0048] After the assembly process is completed, an assembly process is performed in step S11. The assembly process is a process for assembling the lithium-ion secondary battery 10. Specifically, the assembly process includes a winding process, a flattening press process, a case insertion process, a liquid injection process, and a sealing process.

[0049] The assembly process begins with a winding step in step S12. In the winding step, the electrode body 15 is wound with the positive electrode plate 30 and the negative electrode plate 20 stacked with the separator 40 interposed therebetween. Specifically, the electrode body 15 is wound in the longitudinal direction Z while being supported around the winding axis, with the negative electrode plate 20 and the positive electrode plate 30 stacked with the separator 40 interposed therebetween.

[0050] Next, in step S13, a flattening press process is performed. In the flattening press process, pressure is applied from the thickness direction D, so that the end portions, as viewed from the width direction W, are shaped into a flattened shape resembling a racing track. In addition, the negative electrode connecting portion 23 is pressure-welded, and the positive electrode connecting portion 33 is pressure-welded. Through the above procedure, the electrode body 15 is manufactured.

[0051] Next, in step S14, a case insertion step is performed. In the case insertion step, the electrode assembly 15 is inserted into the battery case 11. At this time, the positive electrode connection portion 33 is electrically connected to the positive electrode external terminal 14 via the positive electrode current collector 17. The negative electrode connection portion 23 is electrically connected to the negative electrode external terminal 13 via the negative electrode current collector 16. Then, the battery case 11 and the lid 12 are sealed by laser welding or the like, and the opening in the battery case 11 is closed by the lid 12. At this stage, the nonaqueous electrolyte 18 has not yet been poured, and the pouring hole in the lid 12 is open.

[0052] Next, in step S15, a liquid injection process is performed. The liquid injection process is a process of injecting nonaqueous electrolyte 18 into battery case 11 through an injection hole (not shown). In other words, the liquid injection process is a process of injecting nonaqueous electrolyte 18 into battery case 11 with electrode assembly 15 housed therein. As a result, electrode assembly 15 and nonaqueous electrolyte 18 are housed in battery case 11.

[0053] Next, in step S16, a sealing process is performed. In the sealing process, after the injection of the nonaqueous electrolyte 18 into the battery case 11 is completed, the injection hole is sealed to hermetically seal the battery case 11. In other words, the sealing process is a process of sealing the battery case 11 in a state in which the electrode assembly 15 and the nonaqueous electrolyte 18 are housed in the battery case 11. Through the above procedure, the lithium-ion secondary battery 10 is assembled.

[0054] After the assembly process is completed, an activation process is performed in step S17. The activation process is a process for activating the lithium ion secondary battery 10. More specifically, the activation process includes a charging process and an aging process.

[0055] In the activation process, first, in step S18, a charging process is performed. The charging process is a process of charging the lithium-ion secondary battery 10 after the sealing process is completed. In particular, the charging process is a process of initially charging the lithium-ion secondary battery 10 assembled in the assembly process for the purpose of forming an SEI (Solid Electrolyte Interphase) coating, etc. The charging process is performed in a constrained state in which the lithium-ion secondary battery 10 is constrained. In this way, when the lithium-ion secondary battery 10 is in a constrained state, the electrode body 15 housed in the lithium-ion secondary battery 10 is also in a constrained state. "Constraining" refers to applying pressure to the electrode body 15 directly or indirectly from the thickness direction D.

[0056] Next, in step S19, an aging process is performed. The aging process is a process of storing the charged lithium ion secondary battery 10 after the charging process is completed. In the aging process, the lithium ion secondary battery 10 is chemically stabilized and activated. One of the purposes of the aging process is to detect minute short circuits between the electrodes caused by minute metal particles present in the electrodes. In this embodiment, the aging process may be performed by keeping the battery at a high temperature of about 60°C, but it may also be performed at an ambient temperature of about 20°C. In this embodiment, the aging process is performed in a constrained state in which the lithium ion secondary battery 10 is constrained.

[0057] When the activation process is completed, the lithium-ion secondary battery 10 is changed from a constrained state to an unconstrained state in which the lithium-ion secondary battery 10 is not constrained. In this way, the lithium-ion secondary battery 10 is brought into an unconstrained state, and the electrode body 15 housed in the lithium-ion secondary battery 10 is brought into an unconstrained state. Then, the lithium-ion secondary battery 10 is completed as a cell battery, and after a shipping inspection, it is ready to be assembled into a stack.

[0058] <Lithium deposition resistance and spring constant> When the lithium ion secondary battery 10 changes from a constrained state to an unconstrained state after the activation process is completed, the electrode body 15 housed in the lithium ion secondary battery 10 may swell over time, increasing the distance between the negative electrode plate 20 and the positive electrode plate 30. Hereinafter, the distance between the negative electrode plate 20 and the positive electrode plate 30 will be referred to as the inter-electrode distance.

[0059] One of the reasons for the increase in the inter-electrode distance is that the wound electrode body 15 physically loosens over time, and another reason for the increase in the inter-electrode distance is that gas is generated in the wound electrode body 15 due to a chemical reaction over time.

[0060] As described above, when the inter-electrode distance is increased, the nonaqueous electrolyte 18 present between the negative electrode plate 20 and the positive electrode plate 30 is less likely to be pushed out of the electrode assembly 15. As a result, the amount of nonaqueous electrolyte 18 present between the negative electrode plate 20 and the positive electrode plate 30 becomes excessively large. This promotes metal elution, which deteriorates the lithium deposition resistance as a result of the metal deposition resistance.

[0061] On the other hand, by keeping the electrode body 15 in a constrained state even after the activation step is completed, it is possible to prevent the interelectrode distance from becoming longer, thereby preventing a deterioration in resistance to lithium deposition.

[0062] However, if the electrode body 15 is constrained more than necessary, the electrode body 15 will be crushed excessively. This may result in a deterioration in the spring constant of the electrode body 15. In particular, if an electrode body 15 in which the inter-electrode distance is not long is constrained, the spring constant of the electrode body 15 will be deteriorated even though the lithium deposition resistance is not deteriorated. However, constraining an electrode body 15 in which the inter-electrode distance is excessively long does not pose a major problem from the viewpoints of both lithium deposition resistance and spring constant.

[0063] <Measuring process between electrodes> Therefore, in this embodiment, in step S20, it is determined whether a predetermined time has elapsed since the lithium ion secondary battery 10 entered an unconstrained state after the activation process was completed. In this embodiment, the predetermined time is, for example, about 480 hours (20 days), but is not limited to this.

[0064] The electrode gap measurement step of step S21 is not performed until a predetermined time has elapsed since the electrode assembly 15 entered the unconstrained state, and once the predetermined time has elapsed since the electrode assembly 15 entered the unconstrained state, the electrode gap measurement step is performed in step S21. The electrode gap measurement step is a step of measuring the electrode gap at a predetermined timing after the activation step is completed and a predetermined time has elapsed since the electrode assembly 15 entered the unconstrained state during the unconstrained period. The unconstrained period is a period during which the electrode assembly 15 is in the unconstrained state. In the electrode gap measurement step, the electrode gap distance may be measured from an image captured by CT (Computed Tomography).

[0065] In the inter-electrode measuring step, the inter-electrode distance may be measured at a predetermined position on the electrode assembly 15. The predetermined position may be a curved region of the electrode assembly 15 and an end of the negative electrode substrate 21 in the second width direction W2. In particular, because the electrode assembly 15 is wound, the inter-electrode distance tends to be longer in the curved region than in the flat region. For this reason, measuring the inter-electrode distance in the curved region of the electrode assembly 15 provides higher measurement accuracy than measuring the inter-electrode distance in the flat region of the electrode assembly 15. Alternatively, the distance between the negative electrode substrate 21 of the negative electrode plate 20 and the positive electrode substrate 31 of the positive electrode plate 30 that are adjacent in the thickness direction D may be measured as the inter-electrode distance.

[0066] <Restriction process> Next, in step S22, a restraint process is performed according to the measurement results. The restraint process is a process in which the lithium-ion secondary battery 10 is placed in a restraint state, thereby allowing the electrode assembly 15 housed in the lithium-ion secondary battery 10 to be placed in a restraint state for a restraint period. The restraint period may be a predetermined period, or may be the period until assembly into a stack. In the restraint process, the lithium-ion secondary battery 10 as a cell battery is restrained individually, but multiple lithium-ion secondary batteries 10 may also be restrained together. In the restraint process, the lithium-ion secondary battery 10 can be restrained in a restraint mode based on the restraint table TA shown in FIG. 4.

[0067] <Restraint table TA> 4, the constraint table TA is a table in which the inter-electrode distance measured in the inter-electrode measurement process corresponds to the constraint mode. In the figure, the inter-electrode distance measured in the inter-electrode measurement process will be described using the symbol DP.

[0068] The inter-electrode distance thresholds include a first distance D1 and a second distance D2. The first distance D1 is a suitable upper limit of the inter-electrode distance, and is, for example, but not limited to, 150 μm. The second distance D2 is an inter-electrode distance that does not require consideration of the spring constant of the electrode assembly 15, and is, for example, but not limited to, 200 μm.

[0069] The constraint modes include "no constraint," "medium constraint," and "strong constraint." "No constraint" is a mode in which the lithium ion secondary battery 10 is not constrained. "Medium constraint" and "strong constraint" are modes in which the lithium ion secondary battery 10 is constrained. "Strong constraint" is a mode in which the lithium ion secondary battery 10 is constrained with a stronger constraint force than "medium constraint."

[0070] In this embodiment, "medium restraint" refers to a small restraint force that shortens the inter-electrode distance to some extent, for example, about 3 kN, but is not limited to this. In this embodiment, "strong restraint" refers to a large restraint force that shortens the inter-electrode distance to some extent, for example, about 8 kN, but is not limited to this.

[0071] In the restraint table TA, when the inter-electrode distance measured in the inter-electrode measurement step is equal to or shorter than the first distance D1, the restraint mode corresponds to "no restraint." As a result, the restraint step does not restrain the electrode assembly 15 when the inter-electrode distance is equal to or shorter than the first distance D1.

[0072] When the inter-electrode distance measured in the inter-electrode measurement process is greater than the first distance D1 and equal to or less than the second distance D2, the constraint state corresponds to "medium constraint." When the inter-electrode distance measured in the inter-electrode measurement process is longer than the second distance D2, the constraint state corresponds to "strong constraint."

[0073] As a result, the restraining step restrains the electrode assembly 15 when the inter-electrode distance is longer than the first distance D1. In particular, when the inter-electrode distance is greater than the first distance D1, the restraining step restrains the electrode assembly 15 with a stronger restraining force when the inter-electrode distance is longer than the second distance D2 than when the inter-electrode distance is equal to or shorter than the second distance D2.

[0074] In this way, in the restraining step, the lithium ion secondary battery 10 can be restrained according to the inter-electrode distance measured in the inter-electrode measuring step. Furthermore, in the restraining step, the restraining force on the electrode body 15 can be adjusted according to the measured inter-electrode distance. Such a restraining step corresponds to an example of an adjusting step.

[0075] <Example> Here, referring to FIG. 5, an example of the lithium-ion secondary battery 10 of this embodiment will be described. In this example, the first distance D1 is 150 μm and the second distance D2 is 200 μm. Also, in this example, the electrode distance is measured under the same conditions as in the electrode distance measurement process. In this example, a predetermined charge / discharge cycle was repeatedly performed, and whether or not lithium deposition resistance deteriorated was evaluated based on whether or not lithium deposition occurred on the negative electrode plate 20. Also, in this example, the lithium-ion secondary battery 10 was compressed to measure the spring constant, and whether or not the spring constant deteriorated was evaluated based on whether or not the standard was met. In the figure, lithium deposition resistance is indicated as "Li deposition resistance."

[0076] First, a case where the inter-electrode distance measured when a predetermined time has elapsed since the non-constrained state was established is equal to or shorter than the first distance D1 will be described with reference to a first and second examples. As shown in FIG. 5, in the first example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was set and the electrode spacing was 139 μm, the lithium deposition resistance and the spring constant did not deteriorate when the electrode was not constrained.

[0077] On the other hand, in the second example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was set to 142 μm, when the constraint was performed at a medium constraint, the lithium deposition resistance did not deteriorate, but the spring constant deteriorated.

[0078] Next, the case where the inter-electrode distance measured when a predetermined time has elapsed since the non-constrained state was established is greater than the first distance D1 and less than the second distance D2 will be explained with reference to the third, fourth and fifth examples.

[0079] In the third example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was reached was 170 μm, the spring constant did not deteriorate when the sensor was not constrained, but the lithium deposition resistance deteriorated.

[0080] On the other hand, in the fourth example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was established was 172 μm, when the constraint was performed at a medium constraint, the lithium deposition resistance did not deteriorate and the spring constant did not deteriorate either.

[0081] In addition, in the fifth example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was set to 175 μm, when the strong constraint was applied, the lithium deposition resistance did not deteriorate, but the spring constant deteriorated.

[0082] Next, a case where the inter-electrode distance measured when a predetermined time has elapsed since the non-constrained state was established is longer than the second distance D2 will be described with reference to a sixth embodiment. In the sixth example, when the inter-electrode distance measured after a predetermined time had elapsed since the non-constrained state was set to 207 μm, when the strong constraint was applied, the lithium deposition resistance did not deteriorate and the spring constant did not deteriorate either.

[0083] From these examples, the constraint table TA determines the first distance D1 and the second distance D2 and the constraint mode according to the measured inter-electrode distance so that both the lithium precipitation resistance and the spring constant do not deteriorate.

[0084] <Actions and Effects of the First Embodiment> The operation and effects of the first embodiment will be described. (1-1) The restraining force on the electrode body 15 can be adjusted according to the state of the electrode body 15, that is, the inter-electrode distance actually measured during the non-restraint period. Therefore, lithium deposition due to an increase in the inter-electrode distance can be suppressed, and deterioration of the spring constant of the electrode body 15 can be suppressed.

[0085] (1-2) When the inter-electrode distance actually measured during the non-constraint period is equal to or shorter than the first distance D1, by not constraining the electrode assembly 15, it is possible to minimize the constraint on the electrode assembly 15 and suppress deterioration of the spring constant of the electrode assembly 15. On the other hand, when the inter-electrode distance is longer than the first distance D1, it is possible to suppress lithium deposition by constraining the electrode assembly 15. Therefore, it is possible to suppress lithium deposition due to an increase in the inter-electrode distance and suppress deterioration of the spring constant of the electrode assembly 15.

[0086] (1-3) When the inter-electrode distance actually measured during the non-constraint period is longer than the second distance D2, the electrode assembly 15 is constrained with a stronger constraining force than when the inter-electrode distance is longer than the first distance D1 and equal to or shorter than the second distance D2. This makes it possible to suppress lithium deposition due to an increase in the inter-electrode distance. On the other hand, when the inter-electrode distance actually measured during the non-constraint period is longer than the first distance D1 and equal to or shorter than the second distance D2, the electrode assembly 15 is constrained with a weaker constraining force than when the inter-electrode distance is longer than the second distance D2. This makes it possible to suppress lithium deposition due to an increase in the inter-electrode distance while also suppressing deterioration in the spring constant of the electrode assembly 15.

[0087] (1-4) By measuring the inter-electrode distance at a timing when a predetermined time has elapsed since the non-constrained state was established, measurement errors due to the timing of measuring the inter-electrode distance can be suppressed. [Second embodiment] A second embodiment will now be described. In the following description, the same reference numerals will be used to designate the same configurations and the same control contents as those in the already described embodiments, and redundant description thereof will be omitted or simplified.

[0088] In the second embodiment, the inter-electrode distance is measured at both the first timing and the second timing during the period when the lithium ion secondary battery 10 is in the unconstrained state. Then, the lithium ion secondary battery 10 can be constrained according to the inter-electrode distance measured at the first timing and the inter-electrode distance measured at the second timing.

[0089] <Measuring process between electrodes> 6, in this embodiment, in step S30, a first electrode-to-electrode measurement process is performed when the lithium-ion secondary battery 10 is in an unconstrained state after the activation process is completed. The first electrode-to-electrode measurement process is a process for measuring the electrode gap under conditions similar to those of the electrode-to-electrode measurement process of the first embodiment. The timing at which the electrode gap is measured in the first electrode-to-electrode measurement process corresponds to an example of the first timing.

[0090] Then, in step S31, it is determined whether a specified time has elapsed since the end of the first inter-electrode measurement step while the lithium ion secondary battery 10 is in an unconstrained state. In this embodiment, the specified time is shorter than the predetermined time in the first embodiment, and is, for example, about 240 hours (10 days), but is not limited to this.

[0091] The second electrode gap measurement step in step S32 is not performed until a specified time has elapsed since the end of the first electrode gap measurement step, and once the specified time has elapsed since the end of the first electrode gap measurement step, the second electrode gap measurement step is performed in step S32. The second electrode gap measurement step is performed in step S32. The second electrode gap measurement step is a step of measuring the electrode gap under conditions similar to those of the first electrode gap measurement step. The timing at which the electrode gap distance is measured in the second electrode gap measurement step corresponds to an example of the second timing. The second timing can also be considered to be the timing at which a specified time has elapsed since the first timing.

[0092] As described above, in the second embodiment, the electrode gap measuring step includes a first electrode gap measuring step and a second electrode gap measuring step, and measures the electrode gap at a first timing and a second timing during the non-constraint period.

[0093] <Gap prediction process> Next, in step S33, a pole-to-pole distance prediction process is performed. In the pole-to-pole distance prediction process, since the elapsed time in the non-constraint period and the pole-to-pole distance are proportional to each other, a correlation line is created based on the pole-to-pole distance measured in the first pole-to-pole distance measurement process and the pole-to-pole distance measured in the second pole-to-pole distance measurement process. The correlation line shows the relationship between the elapsed time in the non-constraint period and the pole-to-pole distance.

[0094] Then, in the electrode gap prediction process, it is possible to predict the timing when the electrode gap will become the first distance D1 based on the created correlation line. That is, in the electrode gap prediction process, it is possible to predict the timing when the electrode gap will become the first distance D1 based on the electrode gap measured at the first timing and the electrode gap measured at the second timing. The timing when the electrode gap will become the first distance D1 corresponds to an example of the third timing.

[0095] Furthermore, in the electrode gap prediction process, it is possible to predict, based on the created correlation line, that the electrode gap will not become the first distance D1 until a predetermined time has elapsed since the electrode gap became unconstrained. That is, in the electrode gap prediction process, it is possible to predict, based on the electrode gap measured at the first timing and the electrode gap measured at the second timing, that the electrode gap will not become the first distance D1 until a predetermined time has elapsed since the electrode gap became unconstrained.

[0096] <Restriction process> Next, in step S34, a constraint process is performed according to the prediction result. If the inter-pole distance prediction process predicts that the inter-pole distance will become the first distance D1, the constraint process performs constraint with medium constraint at the timing when the inter-pole distance is predicted to become the first distance D1. On the other hand, if the inter-pole distance prediction process predicts that the inter-pole distance will not become the first distance D1 until a predetermined time has elapsed since the non-constrained state was entered, the constraint process does not perform constraint.

[0097] In this way, the restraining step can adjust the restraining force on the electrode body 15 in accordance with the inter-electrode distance measured at the first timing and the inter-electrode distance measured at the second timing. Such a restraining step corresponds to an example of an adjusting step.

[0098] When the inter-electrode distance measured in the first inter-electrode measurement process and the second inter-electrode measurement process is equal to or less than the first distance D1, the process proceeds as described above. On the other hand, when the inter-electrode distance measured in the first inter-electrode measurement process is greater than the first distance D1 and equal to or less than the second distance D2, restraint may be performed with a medium restraint after completion of the first inter-electrode measurement process. When the inter-electrode distance measured in the first inter-electrode measurement process is greater than the second distance D2, restraint may be performed with a strong restraint after completion of the second inter-electrode measurement process.

[0099] When the inter-electrode distance measured in the first inter-electrode measurement step is equal to or less than the first distance D1 but the inter-electrode distance measured in the second inter-electrode measurement step is greater than the first distance D1 and equal to or less than the second distance D2, restraint with a medium restraint may be performed after completion of the second inter-electrode measurement step. When the inter-electrode distance measured in the first inter-electrode measurement step is equal to or less than the first distance D1 but the inter-electrode distance measured in the second inter-electrode measurement step is greater than the second distance D2, restraint with a strong restraint may be performed after completion of the second inter-electrode measurement step.

[0100] <Example> An example of the lithium ion secondary battery 10 of this embodiment will now be described with reference to Fig. 7. In this example, the relationship between the elapsed time in the non-constraint period and the inter-electrode distance will be described.

[0101] As shown in Fig. 7, in graph 50, the vertical axis represents the inter-electrode distance, and the horizontal axis represents the elapsed time. The timing at which the first inter-electrode measurement process is performed is when the elapsed time is 0. The timing at which the second inter-electrode measurement process is performed is when the elapsed time is t1. Time t1 corresponds to the specified time. In the first embodiment, the timing at which a predetermined time has elapsed since the non-constrained state was entered is when the elapsed time is t3.

[0102] Graph 50 shows a first correlation line 51. First correlation line 51 is a straight line that passes through a point where the inter-electrode distance is distance DA in the first inter-electrode measurement process and a point where the inter-electrode distance is distance DB in the second inter-electrode measurement process. In this case, first correlation line 51 intersects with first distance D1 at time t2, before time t3. Therefore, in the inter-electrode distance prediction process, time t2 is predicted as the time when the inter-electrode distance will become first distance D1. Then, in the constraint process, constraint is performed with medium constraint from time t2.

[0103] The graph 50 also shows a second correlation line 52. The second correlation line 52 is a straight line that passes through a point where the inter-electrode distance is distance DA in the first inter-electrode measurement process and a point where the inter-electrode distance is distance DA in the second inter-electrode measurement process. In this case, the second correlation line 52 does not intersect with the first distance D1 before time t3. Therefore, in the inter-electrode prediction process, it is predicted that the inter-electrode distance will not become the first distance D1 until a predetermined time has elapsed since the non-constrained state was entered in the inter-electrode prediction process. Then, in the constraint process, constraint is not performed.

[0104] <Actions and Effects of the Second Embodiment> The operation and effects of the second embodiment will be described. (2-1) According to the lithium ion secondary battery 10 of this embodiment, the restraining force on the electrode assembly 15 can be adjusted according to the inter-electrode distance measured in the first inter-electrode measurement step and the second inter-electrode measurement step. This increases the accuracy of adjusting the restraining force on the electrode assembly 15. Therefore, lithium deposition due to an increase in the inter-electrode distance can be suppressed, and deterioration of the spring constant of the electrode assembly 15 can be suppressed.

[0105] (2-2) By predicting the timing at which the inter-electrode distance becomes the first distance D1, it is possible to restrain the electrode assembly 15 at that timing. This allows the inter-electrode distance to be adjusted to the first distance D1. Therefore, lithium deposition due to an increase in the inter-electrode distance is suppressed, and the electrode assembly 15 is not restrained more than necessary, thereby suppressing deterioration in the spring constant of the electrode assembly 15.

[0106] [Third embodiment] A third embodiment will be described. In the third embodiment, the sealing step is performed before the liquid injection step and in a period in which the lithium ion secondary battery 10 is in an unconstrained state, based on the results of measuring the inter-electrode distance. In addition, in the assembly process, at least the case insertion step, the liquid injection step, and the sealing step are in an unconstrained period in which the battery is in an unconstrained state.

[0107] <Each process> 8, in this embodiment, after the case insertion process is completed, a gap measurement process is performed in step S40. The gap measurement process is a process for measuring the gap under conditions similar to those of the gap measurement process in the first embodiment. That is, the gap measurement process measures the gap during the non-constraint period at a predetermined timing, i.e., after the case insertion process is completed.

[0108] Next, after the electrode gap measuring step is completed, a liquid injection step is performed in step S15. In the present embodiment, the liquid injection step may be a step of injecting the nonaqueous electrolyte solution 18 into the battery case 11 after creating a vacuum inside the battery case 11. In this case, creating a vacuum inside the battery case 11 applies a negative pressure to the electrode assembly 15 housed in the battery case 11.

[0109] After the liquid injection step is completed, a sealing step is performed in step S41 according to the measurement results. In the sealing step, the battery case 11 is sealed by sealing the liquid injection hole based on the inter-electrode distance measured in the inter-electrode measurement step.

[0110] Specifically, when the inter-electrode distance measured in the inter-electrode measurement step is equal to or shorter than the first distance D1, the battery case 11 is sealed by sealing the liquid injection hole after the shortened sealing time has elapsed. The shortened sealing time is a predetermined time that is shorter than the normal sealing time. The shortened sealing time is a time during which negative pressure is applied to the electrode assembly 15. The normal sealing time is a time during which negative pressure is not applied to the electrode assembly 15.

[0111] In this way, when the measured inter-electrode distance is equal to or less than the predetermined first distance D1, the sealing step shortens the time from when the non-aqueous electrolyte solution 18 is poured into the battery case 11 to when the battery case 11 is sealed. In other words, the sealing step shortens the time from when the non-aqueous electrolyte solution 18 is poured into the battery case 11 to when the battery case 11 is sealed, in accordance with the measured inter-electrode distance.

[0112] This makes it possible to intentionally apply negative pressure to the electrode assembly 15 housed in the battery case 11 when the inter-electrode distance measured in the inter-electrode measurement step is equal to or less than the first distance D1. Therefore, when the inter-electrode distance is equal to or less than the first distance D1, it is possible to prevent the electrode assembly 15, which is wound by an appropriate negative pressure in the battery case 11, from loosening. Furthermore, even when the lithium-ion secondary battery 10 changes from a constrained state to an unconstrained state after the activation step is completed, it is possible to prevent the inter-electrode distance from increasing over time.

[0113] Therefore, even if the lithium-ion secondary battery 10 changes from a constrained state to an unconstrained state after the activation process is completed, there is no need to constrain the lithium-ion secondary battery 10. Furthermore, there is no need to constrain the lithium-ion secondary battery 10 during the aging process either. In this manner, the aging process stores the nonaqueous secondary battery in an unconstrained state when the time until sealing the battery case 11 is shortened. This prevents deterioration of lithium deposition resistance, prevents the electrode body 15 from being constrained more than necessary, and also prevents deterioration of the spring constant. Furthermore, if a self-discharge process is performed after the aging process to check whether the lithium-ion secondary battery 10 is normal based on the voltage drop value per hour of the lithium-ion secondary battery 10, the self-discharge process may also be performed in an unconstrained state.

[0114] <Actions and Effects of the Third Embodiment> The operation and effects of the third embodiment will be described. (3-1) According to the lithium-ion secondary battery 10 of this embodiment, the time from when the nonaqueous electrolyte solution 18 is poured into the battery case 11 to when the battery case 11 is sealed can be shortened depending on the state of the electrode assembly 15, i.e., the inter-electrode distance actually measured during the unconstrained period. This allows the pressure inside the battery case 11 to be intentionally reduced. This increases the self-constraint force acting on the electrode assembly 15, making it possible to prevent the inter-electrode distance in the electrode assembly 15 from increasing. This therefore prevents lithium deposition due to an increase in the inter-electrode distance, and minimizes the constraint on the electrode assembly 15, thereby preventing deterioration of the spring constant of the electrode assembly 15.

[0115] (3-2) When the inter-electrode distance actually measured during the non-constrained period is equal to or shorter than the first distance D1, the pressure inside the battery case 11 can be intentionally reduced. This increases the self-constraint force acting on the electrode assembly 15, effectively preventing the inter-electrode distance in the electrode assembly 15 from increasing. This effectively prevents lithium deposition due to an increase in the inter-electrode distance.

[0116] (3-3) When the time from when the nonaqueous electrolyte solution 18 is poured into the battery case 11 until when the battery case 11 is sealed is shortened, the lithium ion secondary battery 10 is stored in an unconstrained state during the aging process. Therefore, the constraint on the electrode assembly 15 can be minimized, and deterioration of the spring constant of the electrode assembly 15 can be suppressed.

[0117] [Example of change] This embodiment can be modified as follows: This embodiment and the following modifications can be combined and implemented within the scope of technical compatibility.

[0118] In the second embodiment, for example, if the inter-electrode distance becomes longer than the first distance D1 before a predetermined time has elapsed, the electrode assembly 15 may not be constrained after the second inter-electrode measurement step is completed, rather than at the time when the inter-electrode distance becomes the first distance D1. Alternatively, for example, the electrode assembly 15 may be constrained when a predetermined time has elapsed. For example, when the inter-electrode distance is longer than the first distance D1 and equal to or shorter than the second distance D2 after the predetermined time has elapsed, the electrode assembly 15 may be constrained with a medium constraint, or when the inter-electrode distance is longer than the second distance D2. In other words, it is sufficient that the constraint force on the electrode assembly 15 can be adjusted based on the inter-electrode distance measured at the first timing and the inter-electrode distance measured at the second timing.

[0119] In the second embodiment, for example, even if the inter-electrode distance does not become longer than the first distance D1 before the predetermined time has elapsed, the electrode body 15 may be restrained at a timing when it is predicted that the inter-electrode distance will become the first distance D1 after the predetermined time has elapsed. For example, the predetermined time in the second embodiment may be the same as or different from the predetermined time in the first embodiment, and may be any time.

[0120] In the second embodiment, for example, the first inter-electrode measurement step may be performed some time after the activation step is completed, rather than immediately after the activation step is completed. Specifically, the inspection step may be performed after the activation step is completed, or the first inter-electrode measurement step may be performed after the inspection step is completed. In other words, the first inter-electrode measurement step may be performed during the non-constraint period. Furthermore, the second inter-electrode measurement step may be performed when a specified time has elapsed since the inter-electrode distance was measured in the first inter-electrode measurement step, regardless of whether the specified time has elapsed since the non-constraint state was established.

[0121] In the third embodiment, for example, when the inter-electrode distance measured in the inter-electrode measuring step of step S40 is longer than the first distance D1, the lithium-ion secondary battery 10 may be manufactured using the same process as in the first embodiment. In the third embodiment, for example, when the inter-electrode distance measured in the inter-electrode measuring step of step S40 is longer than the first distance D1, the lithium-ion secondary battery 10 may be manufactured using the same process as in the second embodiment. In these cases, when the normal sealing time has elapsed in step S41, the battery case 11 is sealed by sealing the liquid injection hole, so that it is not necessary to apply negative pressure to the electrode body 15.

[0122] In the third embodiment, for example, the time from when the nonaqueous electrolyte solution 18 is poured into the battery case 11 until when the battery case 11 is sealed may be shortened in stages according to the inter-electrode distance. In other words, it is only necessary to shorten the time from when the nonaqueous electrolyte solution 18 is poured into the battery case 11 until when the battery case 11 is sealed according to the inter-electrode distance.

[0123] In this embodiment, for example, "no constraint" may be changed to "weak constraint," which has a weaker constraint force than "medium constraint" and "strong constraint." In other words, the constraint process may constrain the electrode assembly 15 with a weaker constraint force when the inter-electrode distance is equal to or shorter than the first distance D1, compared to when the inter-electrode distance is longer than the first distance D1. Furthermore, the constraint force on the electrode assembly 15 includes intentionally constraining the electrode assembly 15 and not intentionally constraining the electrode assembly 15. In other words, the constraint force on the electrode assembly 15 includes not constraining the electrode assembly 15.

[0124] In this embodiment, for example, the predetermined position of the electrode assembly 15 measured in the electrode gap measurement step may be a planar region of the electrode assembly 15. For example, the predetermined position of the electrode assembly 15 measured in the electrode gap measurement step may be the center of the electrode assembly 15 in the width direction W, or may be on the second width direction W2 side of the electrode assembly 15. For example, in the electrode gap measurement step, the electrode gap may be measured based on the distance between the negative electrode substrates 21 of the negative electrode plates 20 that are adjacent in the thickness direction D. For example, in the electrode gap measurement step, the electrode gap may be measured based on the distance between the positive electrode substrates 31 of the positive electrode plates 30 that are adjacent in the thickness direction D.

[0125] In this embodiment, for example, the electrode gap measurement process may be performed after the activation process is completed, as in the first and second embodiments, or may be performed before the activation process is started, as in the third embodiment.

[0126] In the present embodiment, the inter-electrode distance is measured for each lithium ion secondary battery 10, but this is not limited thereto. For example, the inter-electrode distance may be measured for an extracted lithium ion secondary battery 10 from among a plurality of lithium ion secondary batteries 10 manufactured in the same lot.

[0127] In the present embodiment, the present invention has been described using the lithium ion secondary battery 10 as an example, but it can also be applied to other secondary batteries. In the present embodiment, a thin-plate lithium-ion secondary battery 10 for vehicle use is illustrated, but the present invention can also be applied to cylindrical batteries. Furthermore, the present invention is not limited to vehicle use, and can also be applied to batteries for ships, aircraft, and even stationary use.

[0128] The phrase "at least any" used herein means one or more of the desired options. As an example, when the number of options is two, the phrase "at least any" used herein means only one option or both options. As another example, when the number of options is three or more, the phrase "at least any" used herein means only one option or any combination of two or more options.

[0129] It goes without saying that those skilled in the art can add, delete, or modify the components of the present invention, and change the order of the components, without departing from the scope of the claims. [Explanation of symbols]

[0130] D: Thickness direction W: Width direction Z: Length direction 10...Lithium-ion secondary battery 11...Battery case 12...lid body 13...Negative external terminal 14...Positive external terminal 15...Electrode body 16...Negative electrode current collector 17...Positive electrode current collector 18...Nonaqueous electrolyte 20...Negative electrode plate 21...Anode substrate 22...Negative electrode composite material layer 23...Negative electrode connection part 30...Positive electrode plate 31...Positive electrode substrate 32...Positive electrode mixture layer 33...Positive electrode connection part 40...Separator 50...Graph 51...First correlation line 52...Second correlation line

Claims

1. A method for manufacturing a nonaqueous secondary battery including an electrode assembly having a negative electrode plate, a positive electrode plate, and a separator provided between the negative electrode plate and the positive electrode plate, comprising: an electrode gap measurement step of measuring the distance between the electrode plates at a predetermined timing during an unconstrained period in which the electrode assembly is not constrained; an adjusting step of adjusting the restraining force on the electrode assembly in accordance with the distance between the electrode plates measured in the electrode spacing measuring step, A method for manufacturing a non-aqueous secondary battery.

2. The method for producing a nonaqueous secondary battery according to claim 1, The adjustment step does not restrain the electrode assembly when the distance between the electrode plates measured in the electrode gap measurement step is equal to or shorter than a first distance, and restrains the electrode assembly when the distance between the electrode plates measured in the electrode gap measurement step is longer than the first distance. A method for manufacturing a non-aqueous secondary battery.

3. The method for producing a nonaqueous secondary battery according to claim 2, In the adjustment step, the electrode assembly is constrained with a stronger constraining force when the distance between the electrode plates measured in the electrode gap measurement step is longer than the second distance, compared to when the distance between the electrode plates measured in the electrode gap measurement step is longer than the first distance and is equal to or shorter than a second distance longer than the first distance. A method for manufacturing a non-aqueous secondary battery.

4. The method for producing a nonaqueous secondary battery according to any one of claims 1 to 3, the electrode gap measuring step measures the distance between the electrode plates at a timing when a predetermined time has elapsed since the non-constrained state was established during the non-constrained period. A method for manufacturing a non-aqueous secondary battery.

5. The method for producing a nonaqueous secondary battery according to claim 1, the electrode gap measuring step measures the distance between the electrode plates at a first timing and at a second timing when a specified time has elapsed since the first timing during the non-constraint period; the adjusting step can adjust the restraining force on the electrode body according to the distance between the electrode plates measured at the first timing and the distance between the electrode plates measured at the second timing in the electrode gap measuring step. A method for manufacturing a non-aqueous secondary battery.

6. 6. The method for producing a nonaqueous secondary battery according to claim 5, a pole-gap prediction step of predicting a third timing at which the distance between the pole plates will become the first distance, based on the distance between the pole plates measured at the first timing in the pole-gap measurement step and the distance between the pole plates measured at the second timing; The adjusting step restrains the electrode assembly at the third timing predicted in the electrode gap prediction step. A method for manufacturing a non-aqueous secondary battery.

7. A method for manufacturing a non-aqueous secondary battery comprising: an electrode assembly having a negative electrode plate, a positive electrode plate, and a separator provided between the negative electrode plate and the positive electrode plate; a non-aqueous electrolyte; and a battery case that accommodates the electrode assembly and the non-aqueous electrolyte, an electrode gap measurement step of measuring the distance between the electrode plates at a predetermined timing during an unconstrained period in which the electrode assembly is not constrained; a liquid injection step of injecting the nonaqueous electrolyte into the battery case with the electrode assembly housed therein; a sealing step of sealing the battery case with the electrode assembly and the nonaqueous electrolyte solution accommodated in the battery case, the sealing step shortens the time from when the nonaqueous electrolyte is poured into the battery case in the pouring step to when the battery case is sealed, in accordance with the distance between the electrode plates measured in the electrode gap measuring step. A method for manufacturing a non-aqueous secondary battery.

8. The method for producing a nonaqueous secondary battery according to claim 7, the sealing step shortens the time from when the nonaqueous electrolyte is injected into the battery case in the liquid injection step to when the battery case is sealed when the distance between the electrode plates measured in the electrode gap measurement step is equal to or shorter than a predetermined distance; A method for manufacturing a non-aqueous secondary battery.

9. The method for producing a nonaqueous secondary battery according to claim 7 or 8, a charging step of charging the nonaqueous secondary battery after the sealing step is completed; an aging step of storing the nonaqueous secondary battery after the charging step is completed, the aging step includes storing the nonaqueous secondary battery in the unconstrained state when the time from when the nonaqueous electrolyte solution is poured into the battery case until when the battery case is sealed is shortened; A method for manufacturing a non-aqueous secondary battery.

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