Method for evaluating electrode distance in non-aqueous electrolyte secondary battery and method for manufacturing non-aqueous electrolyte secondary battery

Abstract

To provide a method for evaluating an inter-electrode distance of a nonaqueous electrolyte secondary battery, capable of simply evaluating the propriety of an inter-electrode distance of an electrode body in a short time, and a method for manufacturing the nonaqueous electrolyte secondary battery.SOLUTION: During a manufacturing process of a nonaqueous electrolyte secondary battery 10 in which an electrode body 1, a nonaqueous electrolyte 2 permeated into the electrode body, and a surplus electrolyte 2Y not permeated into the electrode body are housed in a case 3, a method for evaluating an inter-electrode distance of the nonaqueous electrolyte secondary battery includes: an electrolyte injection step S1 of injecting a nonaqueous electrolyte into the case; an electrolyte forcible permeation step S3 of forcibly permeating the surplus electrolyte in the case; a first liquid volume measurement step S2 of measuring a liquid amount L0 of the surplus electrolyte after the electrolyte injection step and before the electrolyte forcible permeation step; a second liquid volume measurement step S4 of measuring a liquid amount L1 of the surplus electrolyte after the electrolyte forcible permeation step; and an evaluation step S5 of, when a liquid change amount ΔL that is a difference of liquid amounts measured in the first liquid volume measurement step and the second liquid volume measurement step is equal to or less than a reference value KJ, evaluating that an inter-electrode distance DL of the electrode body is appropriate.SELECTED DRAWING: Figure 7

Description

[Technical Field]

[0001] The present disclosure relates to a method for evaluating the inter-electrode distance in an electrode assembly of a non-aqueous electrolyte secondary battery, and a method for manufacturing a non-aqueous electrolyte secondary battery using the method for evaluating the inter-electrode distance. [Background technology]

[0002] For example, Patent Document 1 discloses a lithium ion secondary battery including an electrode assembly having a positive electrode, a negative electrode, and a separator, a non-aqueous electrolyte, and a battery case that accommodates the electrode assembly and the non-aqueous electrolyte. It is known that when such a lithium ion secondary battery is charged with a large current for a long period of time, metallic lithium (dendrites) may precipitate on the negative electrode side, which may lead to a short circuit or deterioration of the electrode assembly.

[0003] There are various possible reasons for the deposition of metallic lithium, but it has been found that one of the reasons is that the inter-electrode distance of the electrode body is partially wide. That is, when the inter-electrode distance is partially wide, a local overcharge state occurs at the point where the inter-electrode distance changes, and lithium ions that have gathered in excess near the negative electrode receive electrons from the negative electrode and are likely to deposit on the negative electrode as metallic lithium. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-67699 Summary of the Invention [Problem to be solved by the invention]

[0005] However, although the inter-electrode distance of the electrode body involved in the deposition of metallic lithium can be measured by, for example, CT (computed tomography) image analysis, the need to measure multiple cross sections increases the measurement and analysis time, making it difficult to measure all of the electrodes in a manufacturing process where productivity is required. Furthermore, the inter-electrode distance of the electrode body can vary within the electrode depending on, for example, the condition of the metal foil or the coating condition of the active material layer, making it difficult to measure from the outside. The problem of dendrite deposition is not limited to lithium-ion secondary batteries, but is a common problem with non-aqueous electrolyte secondary batteries, including sodium-ion secondary batteries.

[0006] The presently disclosed technology has been made in consideration of the above-mentioned problems, and an object of the present invention is to provide a method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery, which can easily evaluate the suitability of the inter-electrode distance of an electrode assembly in a short time during the manufacturing stage of a non-aqueous electrolyte secondary battery, including a lithium-ion secondary battery, and a method for manufacturing a non-aqueous electrolyte secondary battery using the inter-electrode distance evaluation method. [Means for solving the problem]

[0007] (1) One aspect of the disclosed technique for solving the above problem is a method for manufacturing a nonaqueous electrolyte secondary battery, the method comprising: housing, in a case, an electrode assembly in which a positive electrode body and a negative electrode body are stacked with a separator sandwiched therebetween; a nonaqueous electrolyte solution that has permeated between the electrodes of the electrode assembly; and an excess of the nonaqueous electrolyte solution that has not permeated between the electrodes of the electrode assembly; The method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery includes: an electrolyte injection step of injecting the non-aqueous electrolyte so that the surplus electrolyte remains in the case; a forced electrolyte penetration step of forcibly penetrating the surplus electrolyte in the case between the electrodes of the electrode body; a first liquid volume measurement step of measuring the liquid volume of the surplus electrolyte in the case after the electrolyte injection step and before the forced electrolyte volume penetration step; a second liquid volume measurement step of measuring the liquid volume of the surplus electrolyte in the case after the forced electrolyte volume penetration step; and an evaluation step of evaluating the inter-electrode distance of the electrode body as appropriate when a change in the liquid volume of the surplus electrolyte, obtained by subtracting the liquid volume measured in the second liquid volume measurement step from the liquid volume measured in the first liquid volume measurement step, is equal to or less than a predetermined reference value.

[0008] (2) In the method for evaluating the inter-electrode distance of a nonaqueous electrolyte secondary battery described in (1), the second liquid amount measuring step is preferably performed after the forced electrolyte penetration step, a conditioning step in which the nonaqueous electrolyte secondary battery is charged and discharged multiple times at room temperature, and an aging step in which the battery is left at a high temperature for a predetermined time.

[0009] (3) Another aspect of the disclosed technique for solving the above problems is a method for manufacturing a nonaqueous electrolyte secondary battery using the method for evaluating the inter-electrode distance of a nonaqueous electrolyte secondary battery described in (1) or (2). [Brief explanation of the drawings]

[0010] [Figure 1] 1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to one aspect of the present embodiment. [Figure 2] 2 is a schematic perspective view showing a state in the middle of winding the positive electrode body and the negative electrode body of the electrode assembly shown in FIG. 1, with a separator sandwiched between them. FIG. [Figure 3] 2 is a schematic cross-sectional view showing the stacked state of the electrode body in the present embodiment at part A shown in FIG. 1. FIG. [Figure 4] 2 is a schematic cross-sectional view showing a stacked state of an electrode body in a comparative example of part A shown in FIG. 1. FIG. [Figure 5]2 is a schematic cross-sectional view of a measuring device for measuring the amount of excess electrolyte in the case of the nonaqueous electrolyte secondary battery shown in FIG. 1 and an evaluation device for the interelectrode distance. [Figure 6] FIG. 6 is a schematic cross-sectional view of a modified example of the measuring device shown in FIG. 5, in which the amount of excess electrolyte is measured while the nonaqueous electrolyte secondary battery is tilted. [Figure 7] 2 is a flowchart showing the steps of a method for evaluating the inter-electrode distance of the nonaqueous electrolyte secondary battery shown in FIG. 1. FIG. [Figure 8] 2 is a flowchart showing the steps of a method for manufacturing the nonaqueous electrolyte secondary battery shown in FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0011] <Description of the Non-Aqueous Electrolyte Secondary Battery> Next, the configuration of a nonaqueous electrolyte secondary battery that is the subject of the interelectrode distance evaluation method according to the embodiment of the disclosed technology will be described in detail with reference to the drawings. FIG. 1 shows a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to one aspect of this embodiment. FIG. 2 shows a schematic perspective view of the electrode assembly shown in FIG. 1 in the middle of being stacked and wound with a separator sandwiched between the positive electrode body and the negative electrode body. FIG. 3 shows a schematic cross-sectional view of the stacked state of the electrode assembly in this example at part A shown in FIG. 1. FIG. 4 shows a schematic cross-sectional view of the stacked state of the electrode assembly in a comparative example at part A shown in FIG. 1.

[0012] 1 to 3, one embodiment (this embodiment) of the nonaqueous electrolyte secondary battery 10 is a nonaqueous electrolyte secondary battery 10 (10B) that houses, in a case 3, an electrode assembly 1 in which a positive electrode body 11 and a negative electrode body 12 are stacked with a separator 13 sandwiched therebetween, a nonaqueous electrolyte 2 that has permeated into the inter-electrode DK of the electrode assembly 1, and an excess electrolyte 2Y that is the same nonaqueous electrolyte 2 but has not permeated into the inter-electrode DK of the electrode assembly 1. There are no limitations on the type of this nonaqueous electrolyte secondary battery 10 (10B) (for example, a lithium-ion secondary battery, a sodium secondary battery, etc.).

[0013] 1, the case 3 is made of, for example, an aluminum alloy and is composed of a case body 31 having an opening 313 and a case lid 32 that seals the opening 313. Here, the case body 31 has a rectangular bottom plate 311 and side plates 312 that stand vertically from the outer periphery of the bottom plate 311, and is formed as a single unit. The case lid 32 is formed as a rectangular plate, and is provided with an injection port 321 for injecting the electrolyte 2 and a safety valve 322 near the center. The case body 31 and the case lid 32 are not limited to the shapes described above, and may have various other shapes.

[0014] Furthermore, terminal insertion holes 323 are formed at both longitudinal ends of the case lid 32, and positive and negative current collector terminals 4 (41, 42) are coupled via insulating members 5 fitted into the terminal insertion holes 323. A positive electrode external connection part 411 is formed at the upper end of the positive current collector terminal 41, and an internal connection part 412 electrically connected to the positive electrode body 11 of the electrode body 1 is formed at its lower end. A negative electrode external connection part 421 is formed at the upper end of the negative electrode collector terminal 42, and an internal connection part 422 electrically connected to the negative electrode body 12 of the electrode body 1 is formed at its lower end.

[0015] 2 and 3, the electrode body 1 is formed by stacking a positive electrode body 11 and a negative electrode body 12 with a separator 13 sandwiched therebetween and winding them in a flat, pressure-bonded state. The electrode body 1 is not limited to a wound-type electrode body, and may be, for example, a sheet-laminated electrode body. The positive electrode body 11 is coated with a positive electrode active material layer 112 of a substantially uniform thickness on both sides of a current collector foil (e.g., aluminum foil) 111, except for one end (uncoated portion). The negative electrode body 12 is coated with a negative electrode active material layer 122 of a substantially uniform thickness on both sides of a current collector foil (e.g., copper foil) 121, except for one end (uncoated portion). The uncoated portion of the positive electrode body 11 is connected to an internal connection portion 412 of a positive electrode current collector terminal 41, and the uncoated portion of the negative electrode body 12 is connected to an internal connection portion 422 of a negative electrode current collector terminal 42.

[0016] Here, the inter-electrode distance DL of the electrode body 1 refers to the distance between the current collector foil 111 of the positive electrode body 11 and the current collector foil 121 of the negative electrode body 12. Fig. 3 shows a state in which the positive electrode body 11, separator 13, and negative electrode body 12 are stacked at an appropriate inter-electrode distance DL1. The electrolyte 2 permeates the small gaps between the positive electrode active material layer 112, separator 13, and negative electrode active material layer 122, the minute gaps between the active materials of the active material layers 112, 122, and the pores of the separator 13. The separator 13 is bonded to the positive electrode active material layer 112 and the negative electrode active material layer 122 via an adhesive applied to allow charge carriers (e.g., lithium ions, etc.) to pass through (not shown).

[0017] 3, when the positive electrode body 11, separator 13, and negative electrode body 12 are stacked with an appropriate inter-electrode distance DL1, the internal resistance between the positive electrode body 11 and the negative electrode body 12 becomes substantially constant, the current flowing during charging and discharging is uniform, and local overcharging is less likely to occur. Therefore, in a nonaqueous electrolyte secondary battery (e.g., a lithium ion secondary battery), dendrites (e.g., metallic lithium) are less likely to precipitate on the surface of the negative electrode body 12.

[0018] In contrast, when the positive electrode body 11, separator 13, and negative electrode body 12B are stacked with a partially wide inter-electrode distance DL2, as in the electrode body 1B of the comparative nonaqueous electrolyte secondary battery 10B shown in FIG. 4, the internal resistance between the positive electrode body 11 and the negative electrode body 12B increases in the region of the wide inter-electrode distance DL2, reducing the current flow during charging and discharging. Meanwhile, localized overcharging is likely to occur in the convex region HP at the distance change point of the inter-electrode distance DL2, and dendrites (e.g., metallic lithium) are likely to precipitate in the convex region HP of the negative electrode body 12B. This region of partially wide inter-electrode distance DL2 can occur during the manufacturing process of the electrode body 1B due to deformation of the negative electrode current collector foil 121B of the electrode body 1B, variations in the coating thickness of the negative electrode active material layer 122B, and the like. Therefore, in order to provide a high-quality nonaqueous electrolyte secondary battery 10 that is highly resistant to precipitation of dendrites (e.g., metallic lithium), it is important to evaluate whether there are many regions with a relatively wide inter-electrode distance DL during the manufacturing stage of the nonaqueous electrolyte secondary battery 10.

[0019] The nonaqueous electrolyte secondary batteries 10 and 10B are not limited to any particular type (e.g., lithium ion secondary battery, sodium secondary battery, etc.), but the positive electrode active material layer 112, separator 13, negative electrode active material layer 122, and electrolyte 2 vary depending on the type of nonaqueous electrolyte secondary battery 10, and known materials can be used for each of them.

[0020] <Method for Evaluating the Distance Between Electrodes of the Present Non-Aqueous Electrolyte Secondary Battery> Hereinafter, a method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery, which can quickly and easily evaluate the suitability of the inter-electrode distance of an electrode assembly involved in the dendrite deposition during the manufacturing stage of the non-aqueous electrolyte secondary battery, will be described with reference to Figs. 1 to 7. Fig. 5 shows a schematic cross-sectional view of a measuring device that measures the amount of excess electrolyte in the case of the non-aqueous electrolyte secondary battery shown in Fig. 1, and an inter-electrode distance evaluating device. Fig. 6 shows a schematic cross-sectional view of a modified version of the measuring device shown in Fig. 5, in which the amount of excess electrolyte is measured with the non-aqueous electrolyte secondary battery in an inclined state. Fig. 7 is a flowchart showing the steps in the method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery shown in Fig. 1.

[0021] As shown in FIGS. 1 to 7 , the method SS for evaluating the inter-electrode distance DL of the nonaqueous electrolyte secondary battery 10 (10B) includes the following steps during the manufacturing stage of the nonaqueous electrolyte secondary battery 10, in which an electrode body 1 formed by stacking a positive electrode body 11 and a negative electrode body 12 with a separator 13 sandwiched therebetween, a nonaqueous electrolyte 2 that has permeated into the inter-electrode DK of the electrode body 1, and an excess electrolyte 2Y that is the nonaqueous electrolyte 2 but has not permeated into the inter-electrode DK of the electrode body 1 are housed in a case 3.

[0022] That is, the evaluation method SS for the inter-electrode distance DL of the nonaqueous electrolyte secondary battery 10 includes: (a) an electrolyte injection step S1 in which the nonaqueous electrolyte 2 is injected so that excess electrolyte 2Y remains in the case 3; (b) an electrolyte forced penetration step S3 in which the excess electrolyte 2Y in the case 3 is forced to penetrate into the inter-electrode distance DK of the electrode body 1; and (c) measuring the liquid volume L0 of the excess electrolyte 2Y in the case 3 after the electrolyte injection step S1 and before the electrolyte forced penetration step S3. The method includes (d) a first liquid volume measurement process S2, (e) a second liquid volume measurement process S4 for measuring the liquid volume L1 of the excess electrolyte 2Y in the case 3 after the electrolyte forced penetration process S3, and (f) an evaluation process S5 for evaluating that the inter-electrode distance DL of the electrode body 1 is appropriate if the liquid change amount ΔL of the excess electrolyte 2Y, which is obtained by subtracting the liquid volume L1 measured in the second liquid volume measurement process S4 from the liquid volume L0 measured in the first liquid volume measurement process S2, is equal to or less than a predetermined reference value KJ.

[0023] (a) In the electrolyte injection step S1, an electrolyte discharge nozzle (not shown) is inserted through the injection port 321 of the case lid 32 between the upper end of the electrode assembly 1 housed in the case 3 and the case lid 32, and a required amount of nonaqueous electrolyte 2 is injected from the electrolyte discharge nozzle into the case 3. At this stage, some of the injected nonaqueous electrolyte 2 permeates into the inter-electrode spaces DK on the outer periphery of the electrode assembly 1, but it is difficult to permeate into the inter-electrode spaces DK on the inner periphery of the electrode assembly 1, and excess electrolyte 2Y that does not permeate into the inter-electrode spaces DK of the electrode assembly 1 remains in the case 3.

[0024] (b) In the forced electrolyte penetration step S3, the excess electrolyte 2Y in the case 3 is forced to penetrate into the inter-electrode gaps DK of the electrode assembly 1. At this time, the excess electrolyte 2Y in the case 3 decreases more as the number of regions with a wide inter-electrode distance DL increases on the inner circumferential side of the electrode assembly 1. Therefore, the greater the amount of change in the liquid level ΔL of the excess electrolyte 2Y in the case 3, the more regions with a wide inter-electrode distance DL of the electrode assembly 1 increase on the inner circumferential side, and the lower the resistance to dendrite (e.g., lithium metal) deposition. Note that the method for forcibly penetrating the excess electrolyte 2Y into the inter-electrode gaps DK of the electrode assembly 1 is not particularly limited, and examples include a method of increasing or decreasing the internal pressure of the case 3 to cause penetration by pressure difference, or a method of vibrating the case 3 to cause penetration by inertial force.

[0025] (c) In a first liquid volume measurement step S2, the liquid volume L0 of the excess electrolyte 2Y in the case 3 is measured after the electrolyte injection step S1 and before the electrolyte forced penetration step S3. Also, in a (d) second liquid volume measurement step S4, the liquid volume L1 of the excess electrolyte 2Y in the case 3 is measured after the electrolyte forced penetration step S3. Unlike CT image analysis, the liquid volumes L0 and L1 can be measured easily and quickly during the manufacturing stage of the nonaqueous electrolyte secondary battery 10 to fit the takt time (for example, several tens of seconds) of the manufacturing line.

[0026] 5, the measuring device 6 used in the first liquid volume measuring step S2 and the second liquid volume measuring step S4 includes, for example, a fluoroscopic line irradiating device 61, a fluoroscopic image measuring device 62, and a table device 63 on which the nonaqueous electrolyte secondary battery 10 (10B) to be measured is placed. Here, the fluoroscopic line irradiating device 61 is a device (e.g., an X-ray irradiating device) that irradiates a fluoroscopic line 64 that allows the interior of the nonaqueous electrolyte secondary battery 10 (10B) to be seen through. The fluoroscopic image measuring device 62 is a device that measures the liquid volumes L0 and L1 of the excess electrolyte 2Y using the liquid level heights H1 and H2 of the excess electrolyte 2Y relative to the bottom plate 311 of the case body 31, measured based on the fluoroscopic image of the fluoroscopic line 64, and the volumes R1 and R2 of the electrode assembly 1 present below the liquid level of the excess electrolyte 2Y, using the following formulas (1) and (2): L0 = H1 × D1 × D2 - R1 Formula (1) L1=H2×D1×D2-R2... Equation (2)

[0027] Note that D1 is the longitudinal length of the bottom plate 311 of the case body 31, D2 is the transverse length of the bottom plate 311 of the case body 31, R1 is the volume of the electrode body 1 present below the liquid surface of the excess electrolyte 2Y measured in the first liquid volume measurement process S2, and R2 is the volume of the electrode body 1 present below the liquid surface of the excess electrolyte 2Y measured in the second liquid volume measurement process S4.

[0028] (e) In the evaluation step S5, if the amount of change in the liquid volume ΔL of the excess electrolyte 2Y, which is obtained by subtracting the liquid volume L1 measured in the second liquid volume measurement step S4 from the liquid volume L0 measured in the first liquid volume measurement step S2, is equal to or less than a predetermined reference value KJ, the inter-electrode distance DL of the electrode body 1 is evaluated as appropriate. The evaluation device 7 used in this evaluation step S5 is connected to the measurement device 6 (fluoroscopic image measurement device 62). The evaluation device 7 includes, for example, an arithmetic circuit 71 that calculates the liquid change amount ΔL of the excess electrolyte 2Y from the difference (L0-L1) between the liquid volume L0 of the excess electrolyte 2Y measured in the first liquid volume measurement process S2 and the liquid volume L1 of the excess electrolyte 2Y measured in the second liquid volume measurement process S4, an input / storage circuit 72 that inputs a predetermined reference value KJ and stores the input reference value KJ, and a judgment circuit 73 that compares the liquid change amount ΔL with the reference value KJ to judge whether the inter-electrode distance DL of the electrode body 1 is appropriate or inappropriate.

[0029] The reference value KJ is set to a value of the amount of solution change that provides good resistance to dendrite (e.g., lithium metal) precipitation, depending on the type, form, battery capacity, etc. of the nonaqueous electrolyte secondary battery 10. For example, it is known that good resistance to dendrite (e.g., lithium metal) precipitation is achieved when the ratio (capacity retention rate) of the discharge capacity after a high-rate charge-discharge test to the discharge capacity after the conditioning step S6, which will be described later, is 90% or higher. Therefore, for example, the value of the amount of solution change ΔL when the capacity retention rate is 90% or higher can be set as the reference value KJ.

[0030] Furthermore, when the amount of excess electrolyte 2Y in the case 3 is small, it is preferable to measure the amount of excess electrolyte 2Y while tilting the case 3 so that the excess electrolyte 2Y of the nonaqueous electrolyte secondary battery 10 (10B) gathers at one case corner 314, as shown in FIG. 6 . In this case, the mounting surface of a table device 63B on which the bottom plate 311 of the case 3 is mounted is formed as an inclined surface that opens upward in a V shape (e.g., inclination angle θ = 45°). Then, with the bottom plate 311 and side plate 312 of the case 3 mounted on this inclined surface, a fluoroscopic line irradiation device 61 shown in FIG. 5 irradiates a fluoroscopic line 64 from the normal direction of the drawing, and a fluoroscopic image measurement device 62 performs measurement based on a fluoroscopic image of the fluoroscopic line 64. In this case, the amounts L0 and L1 of the excess electrolyte 2Y can be accurately measured using the following formulas (3) and (4). L0=1 / 2×H1×W1×D2-T1 Formula (3) L1=1 / 2×H2×W2×D2-T2...Formula (4)

[0031] Here, W1 is the liquid surface length of the excess electrolyte 2Y measured in the first liquid volume measurement step S2, W2 is the liquid surface length of the excess electrolyte 2Y measured in the second liquid volume measurement step S4, T1 is the volume of the electrode assembly 1 present below the liquid surface of the excess electrolyte 2Y measured in the first liquid volume measurement step S2, and T2 is the volume of the electrode assembly 1 present below the liquid surface of the excess electrolyte 2Y measured in the second liquid volume measurement step S4. Also, D2 is the length of the bottom plate 311 of the case body 31 in the short direction.

[0032] 7, in the method SS for evaluating the inter-electrode distance DL of the nonaqueous electrolyte secondary battery 10, the second liquid level measurement step S4 is preferably performed after the forced electrolyte penetration step S3, and after a conditioning step S6 in which the nonaqueous electrolyte secondary battery 10 is charged and discharged multiple times at room temperature and an aging step S7 in which the battery is left at a high temperature for a predetermined time. In the conditioning step S6, a protective coating 12H (see FIG. 3) derived from the electrolyte 2 can be formed near the surface of the negative electrode body 12 by repeating charge and discharge multiple times at room temperature. In the aging step S7, the battery is left at a high temperature for a predetermined time, allowing for dissolution of metallic foreign matter and stabilization of the protective coating 12H. In this case, the excess electrolyte 2Y in the case 3 decreases slightly due to the expansion and contraction of the electrode body 1 and the formation of the protective coating 12H that occur during the conditioning process S6 and the aging process S7, so that the appropriateness of the inter-electrode distance DL of the electrode body 1 can be determined based on a more accurate liquid change amount ΔL of the excess electrolyte 2Y.

[0033] <Method for manufacturing a non-aqueous electrolyte secondary battery using an interelectrode distance evaluation method> Next, a method for manufacturing a nonaqueous electrolyte secondary battery using the above-described method for evaluating the interelectrode distance will be described with reference to Fig. 8. Fig. 8 is a flowchart showing the steps in the method for manufacturing the nonaqueous electrolyte secondary battery shown in Fig. 1.

[0034] The method for manufacturing the nonaqueous electrolyte secondary battery 10 uses the above-described method SS for evaluating the inter-electrode distance DL of the nonaqueous electrolyte secondary battery 10. That is, as shown in Fig. 8, the method for manufacturing the nonaqueous electrolyte secondary battery 10 sequentially performs a battery assembly step Q1, an electrolyte injection step S1, a first liquid level measurement step S2, a forced electrolyte permeation step S3, an initial charging step Q2, a conditioning step S6, an aging step S7, a second liquid level measurement step S4, an evaluation step S5, and an appearance inspection step Q3.

[0035] Here, the battery assembly process Q1 is a process of housing the electrode assembly 1, in which the cathode body 11 and the anode body 12 are stacked with the separator 13 sandwiched between them, in the case body 31 and sealing the case lid 32. At this stage, the injection port 321 for the electrolyte 2 is open. The initial charging process Q2 is a process of connecting the electrode assembly 1 to an external power source to perform an initial charge and releasing gas generated by decomposition of part of the electrolyte and water contained inside the battery to the outside of the case. The appearance inspection process Q3 is a process of inspecting for external scratches and the like to determine whether or not the battery can be shipped.

[0036] Then, nonaqueous electrolyte secondary batteries 10 for which the inter-electrode distance DL of the electrode assembly 1 is evaluated as appropriate in the evaluation step S5 are sent to the appearance inspection step Q3, and are shipped if they pass the appearance inspection (OK). In contrast, nonaqueous electrolyte secondary batteries 10 for which the inter-electrode distance DL of the electrode assembly 1 is evaluated as inappropriate in the evaluation step S5 are stopped from being shipped. Furthermore, even if the inter-electrode distance DL of the electrode assembly 1 is evaluated as appropriate in the evaluation step S5, if it fails the appearance inspection (NG) in the appearance inspection step Q3, shipping is also stopped.

[0037] As described above, the manufacturing method for the nonaqueous electrolyte secondary battery 10 uses the evaluation method SS for the inter-electrode distance DL of the nonaqueous electrolyte secondary battery 10 in the manufacturing process of the nonaqueous electrolyte secondary battery 10, and therefore can evaluate the suitability of the inter-electrode distance DL of the electrode assembly 1 involved in dendrite precipitation for all nonaqueous electrolyte secondary batteries 10. Therefore, it is possible to consistently provide high-quality nonaqueous electrolyte secondary batteries with excellent dendrite precipitation resistance.

[0038] <Modification> The present embodiment described in detail above is merely an example and does not limit the disclosed technology in any way. Therefore, the disclosed technology can be improved and modified in various ways without departing from the spirit and scope of the present invention. [Explanation of symbols]

[0039] 1 Electrode body 2 Non-aqueous electrolyte 2Y Surplus electrolyte 3 cases 10, 10B non-aqueous electrolyte secondary battery 11 Cathode 12 negative electrode body 13 Separator DK Polarity DL distance between poles KJ standard value L0, L1 liquid volume ΔL Fluid change amount S1 Electrolyte injection process S2 First liquid volume measurement process S3 Forced electrolyte penetration process S4 Second liquid volume measurement process S5 Evaluation process S6 Conditioning process S7 Aging process

Claims

1. In a manufacturing stage of a nonaqueous electrolyte secondary battery, an electrode assembly in which a positive electrode body and a negative electrode body are stacked with a separator sandwiched therebetween, a nonaqueous electrolyte solution that has permeated between the electrodes of the electrode assembly, and excess electrolyte solution of the nonaqueous electrolyte solution that has not permeated between the electrodes of the electrode assembly are housed in a case, an electrolyte injection step of injecting the nonaqueous electrolyte so that excess electrolyte remains in the case; an electrolyte forced penetration step of forcibly penetrating the excess electrolyte in the case between the electrodes of the electrode body; a first liquid volume measuring step of measuring the volume of the excess electrolyte in the case after the electrolyte injection step and before the electrolyte forced penetration step; a second liquid volume measuring step of measuring the volume of the excess electrolyte in the case after the electrolyte forced penetration step; an evaluation step of evaluating the inter-electrode distance of the electrode body as appropriate when a change in the amount of excess electrolyte obtained by subtracting the amount of liquid measured in the second liquid volume measurement step from the amount of liquid measured in the first liquid volume measurement step is equal to or less than a predetermined reference value, The predetermined reference value is the value of the liquid change amount at which resistance to dendrite precipitation is good. A method for evaluating the electrode distance of a non-aqueous electrolyte secondary battery.

2. 2. The method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery according to claim 1, The second liquid amount measuring step is performed after the electrolyte forced penetration step, and after a conditioning step in which the nonaqueous electrolyte secondary battery is charged and discharged multiple times at room temperature, and an aging step in which metal foreign matter can be dissolved and a protective film formed near the surface of the negative electrode body due to the electrolyte in the conditioning step can be stabilized. A method for evaluating the electrode distance of a non-aqueous electrolyte secondary battery.

3. The method for evaluating the electrode distance of a non-aqueous electrolyte secondary battery according to claim 1 or 2 is used. A method for manufacturing a non-aqueous electrolyte secondary battery.

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