JP7765442B2 - Method for evaluating electrode distance in non-aqueous electrolyte secondary battery and method for manufacturing non-aqueous electrolyte secondary battery - Google Patents

Description

The disclosed technology 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 inter-electrode distance evaluation method.

For example, Patent Document 1 discloses a lithium-ion secondary battery comprising an electrode assembly having a positive electrode, a negative electrode, and a separator, a non-aqueous electrolyte, and a battery case that houses the electrode assembly and the non-aqueous electrolyte. It is known that when such lithium-ion secondary batteries are charged with a large current for a long period of time, metallic lithium (dendrites) may precipitate on the negative electrode, potentially leading to short-circuiting or deterioration of the electrode assembly.

There are various possible reasons why metallic lithium is deposited, but it is known that one of the reasons is that the inter-electrode distance of the electrode assembly is partially wide. In other words, when the inter-electrode distance is partially wide, a localized overcharge state occurs at the point where the inter-electrode distance changes, and excess lithium ions that gather near the negative electrode accept electrons from the negative electrode, making it more likely for metallic lithium to deposit on the negative electrode.

JP 2019-67699 A

However, while the inter-electrode distance of the electrode body involved in this metallic lithium deposition can be measured using, 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 electrodes in manufacturing processes where productivity is essential. 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 issue with non-aqueous electrolyte secondary batteries, including sodium-ion secondary batteries.

The disclosed technology was developed in consideration of these problems, and aims to provide 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 during the manufacturing stage of non-aqueous electrolyte secondary batteries, including lithium-ion secondary batteries, and a method for manufacturing a non-aqueous electrolyte secondary battery using this inter-electrode distance evaluation method.

(1) One aspect of the disclosed technique for solving the above problem is to provide a non-aqueous electrolyte secondary battery in a manufacturing stage, in which an electrode assembly in which a positive electrode body and a negative electrode body are stacked with a separator sandwiched therebetween, a non-aqueous electrolyte solution that has permeated between the electrodes of the electrode assembly, and an excess electrolyte solution of the non-aqueous electrolyte solution that has not permeated between the electrodes of the electrode assembly are housed in a case,
a forced electrolyte penetration step of forcibly penetrating the excess electrolyte in the case between the electrodes of the electrode body; a first liquid volume measurement step of measuring the liquid volume of the excess electrolyte in the case after the electrolyte injection step and before the forced electrolyte penetration step; a second liquid volume measurement step of measuring the liquid volume of the excess electrolyte in the case after the forced electrolyte 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 excess electrolyte, calculated 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.

(2) In the method for evaluating the inter-electrode distance of a nonaqueous electrolyte secondary battery described in (1), the second liquid volume measurement step is preferably performed after the forced electrolyte 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 the battery is left at a high temperature for a predetermined period of time.

(3) Another aspect of the disclosed technology for solving the above problem 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).

1 is a schematic cross-sectional view of a nonaqueous electrolyte secondary battery according to one aspect of the present embodiment. 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 therebetween. FIG. 2 is a schematic cross-sectional view showing a stacked state of the electrode body in the present embodiment of the part A shown in FIG. 1. FIG. 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 . 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. FIG. 6 is a schematic cross-sectional view showing 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. FIG. 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. 2 is a flowchart showing steps in a method for manufacturing the nonaqueous electrolyte secondary battery shown in FIG. 1 .

<Description of the Non-Aqueous Electrolyte Secondary Battery>
Next, the configuration of a nonaqueous electrolyte secondary battery that is the subject of the inter-electrode 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.

As shown in FIGS. 1 to 3, one embodiment (this embodiment) of the nonaqueous electrolyte secondary battery 10 is a nonaqueous electrolyte secondary battery 10 (10B) that contains, in a case 3, an electrode assembly 1 in which a cathode body 11 and an anode body 12 are stacked with a separator 13 sandwiched therebetween, a nonaqueous electrolyte 2 that has permeated the inter-electrode DK of the electrode assembly 1, and surplus electrolyte 2Y of the same nonaqueous electrolyte 2 that has not permeated the inter-electrode DK of the electrode assembly 1. There are no limitations on the type of this nonaqueous electrolyte secondary battery 10 (10B) (e.g., lithium-ion secondary battery, sodium secondary battery, etc.).

As shown in FIG. 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 edge 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 inlet 321 for injecting the electrolyte 2 and a safety valve 322 near its center. Note that the case body 31 and case lid 32 are not limited to the shapes described above and may have various other shapes.

In addition, 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 connected via insulating members 5 fitted into the terminal insertion holes 323. A positive electrode external connection portion 411 is formed at the upper end of the positive current collector terminal 41, and an internal connection portion 412 that is electrically connected to the positive electrode body 11 of the electrode body 1 is formed at its lower end. A negative electrode external connection portion 421 is formed at the upper end of the negative current collector terminal 42, and an internal connection portion 422 that is electrically connected to the negative electrode body 12 of the electrode body 1 is formed at its lower end.

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 rolling them in a flat, pressure-bonded state. The electrode body 1 is not limited to a wound-type electrode body, but may be, for example, a sheet-laminated electrode body. The positive electrode body 11 has a current collector foil (e.g., aluminum foil) 111 coated with a positive electrode active material layer 112 of approximately uniform thickness on both sides thereof, except for one end (uncoated portion) of the current collector foil (e.g., copper foil). The negative electrode body 12 has a current collector foil (e.g., copper foil) 121 coated with a negative electrode active material layer 122 of approximately uniform thickness on both sides thereof, except for one end (uncoated portion) of the current collector foil. The uncoated portion of the positive electrode body 11 is connected to the internal connection portion 412 of the positive electrode collector terminal 41, and the uncoated portion of the negative electrode body 12 is connected to the internal connection portion 422 of the negative electrode collector terminal 42.

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. Figure 3 shows the positive electrode body 11, separator 13, and negative electrode body 12 stacked at the 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 each active material layer 112, 122, and the pores of the separator 13. The separator 13 is adhered to the positive electrode active material layer 112 and negative electrode active material layer 122 via an adhesive applied to allow charge carriers (e.g., lithium ions, etc.) to pass through (not shown).

As shown in Figure 3, when the positive electrode body 11, separator 13, and negative electrode body 12 are stacked with the appropriate inter-electrode distance DL1, the internal resistance between the positive electrode body 11 and the negative electrode body 12 becomes approximately constant, the current flowing during charging and discharging is uniform, and localized overcharging is less likely to occur. Therefore, in non-aqueous electrolyte secondary batteries (e.g., lithium ion secondary batteries), dendrites (e.g., metallic lithium) are less likely to precipitate on the surface of the negative electrode body 12.

In contrast, when the cathode body 11, separator 13, and anode 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 Figure 4, the internal resistance between the cathode body 11 and the anode 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 where the inter-electrode distance DL2 changes, and dendrites (e.g., metallic lithium) are likely to precipitate in the convex region HP of the anode body 12B. This partially wide inter-electrode distance DL2 region can arise during the manufacturing process of the electrode body 1B due to deformation of the anode current collector foil 121B of the electrode body 1B, variations in the coating thickness of the anode active material layer 122B, and other factors. Therefore, in order to provide a high-quality nonaqueous electrolyte secondary battery 10 that is highly resistant to dendrite (e.g., metallic lithium) precipitation, 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.

The nonaqueous electrolyte secondary batteries 10 and 10B are not limited to any particular type (e.g., lithium-ion secondary batteries, sodium secondary batteries, 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.

<Method for Evaluating the Distance Between Electrodes of the Present Non-Aqueous Electrolyte Secondary Battery>
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 below with reference to FIGS. 1 to 7. FIG. 5 shows a schematic cross-sectional view of a measuring device for measuring 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 shows a flowchart illustrating the steps in the method for evaluating the inter-electrode distance of the non-aqueous electrolyte secondary battery shown in FIG. 1.

As shown in Figures 1 to 7, the evaluation method SS for 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, which contains, 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 between them, nonaqueous electrolyte 2 that has permeated the inter-electrode DK of the electrode assembly 1, and excess electrolyte 2Y that is nonaqueous electrolyte 2 but has not permeated the inter-electrode DK of the electrode assembly 1.

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 nonaqueous electrolyte 2 is injected so that excess electrolyte 2Y remains in the case 3; (b) a forced electrolyte 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 forced electrolyte 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 the inter-electrode distance DL of the electrode body 1 as appropriate if the liquid volume change ΔL of the excess electrolyte 2Y, 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.

(a) In the electrolyte injection process 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 body 1 housed in the case 3 and the case lid 32, and the required amount of nonaqueous electrolyte 2 is injected into the case 3 from the electrolyte discharge nozzle. At this stage, some of the injected nonaqueous electrolyte 2 penetrates into the inter-electrode DK on the outer periphery of the electrode body 1, but it does not penetrate easily into the inter-electrode DK on the inner periphery of the electrode body 1, and excess electrolyte 2Y that does not penetrate into the inter-electrode DK of the electrode body 1 remains in the case 3.

(b) In the forced electrolyte penetration step S3, excess electrolyte 2Y in the case 3 is forced to penetrate into the inter-electrode gap DK of the electrode body 1. At this time, the excess electrolyte 2Y in the case 3 decreases more as the number of regions with a wider inter-electrode distance DL increases on the inner circumferential side of the electrode body 1. Therefore, the greater the amount of solution change ΔL of the excess electrolyte 2Y in the case 3, the more regions with a wider inter-electrode distance DL exist on the inner circumferential side of the electrode body 1, and the lower the resistance to dendrite (e.g., lithium metal) precipitation. Note that the method for forcibly penetrating excess electrolyte 2Y into the inter-electrode gap DK of the electrode body 1 is not particularly limited, but includes, for example, 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.

(c) In the 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 forced electrolyte penetration step S3. (d) In the second liquid volume measurement step S4, the liquid volume L1 of the excess electrolyte 2Y in the case 3 is measured after the forced electrolyte penetration step S3. Unlike CT image analysis, these 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 (e.g., several tens of seconds) of the manufacturing line.

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, H2, etc. of the excess electrolyte 2Y relative to the bottom plate 311 of the case body 31, and the volumes R1 and R2 of the electrode body 1 present below the liquid level of the excess electrolyte 2Y, measured based on the fluoroscopic image of the fluoroscopic line 64, using the following formulas (1) and (2).
L0 = H1 x D1 x D2 - R1 Formula (1)
L1 = H2 x D1 x D2 - R2 Formula (2)

Note that D1 is the longitudinal length of the bottom plate 311 of the case body 31, D2 is the lateral 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.

(e) In the evaluation step S5, if the liquid change amount ΔL of the excess electrolyte 2Y, calculated 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 less than or equal to 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, a calculation circuit 71 that calculates the amount of change in the liquid level ΔL of the excess electrolyte 2Y from the difference (L0-L1) between the liquid level L0 of the excess electrolyte 2Y measured in the first liquid level measurement process S2 and the liquid level L1 of the excess electrolyte 2Y measured in the second liquid level 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 amount of change in the liquid level ΔL with the reference value KJ to judge whether the inter-electrode distance DL of the electrode body 1 is appropriate.

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 described below 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.

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 placed 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 plates 312 of the case 3 placed 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)

W1 is the liquid surface length of the excess electrolyte 2Y measured in the first liquid volume measurement process S2, W2 is the liquid surface length of the excess electrolyte 2Y measured in the second liquid volume measurement process S4, T1 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 T2 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. Also, D2 is the short-side length of the bottom plate 311 of the case body 31.

As shown in Figure 7, in the evaluation method SS for the interelectrode distance DL of the nonaqueous electrolyte secondary battery 10, the second liquid volume measurement step S4 is preferably performed after the forced electrolyte penetration step S3, and after the conditioning step S6 in which the nonaqueous electrolyte secondary battery 10 is charged and discharged multiple times at room temperature and the aging step S7 in which the battery is left at a high temperature for a predetermined period of time. In the conditioning step S6, a protective coating 12H (see Figure 3) derived from the electrolyte 2 can be formed near the surface of the negative electrode body 12 by repeatedly charging and discharging the battery at room temperature multiple times. In the aging step S7, the battery is left at a high temperature for a predetermined period of time, allowing for the dissolution of metallic foreign matter and the 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 step S6 and the aging step S7. Therefore, the appropriateness of the inter-electrode distance DL of the electrode body 1 can be determined more accurately based on the amount of change ΔL in the excess electrolyte 2Y.

<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.

The manufacturing method for this 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 manufacturing method for this nonaqueous electrolyte secondary battery 10 sequentially includes a battery assembly process Q1, an electrolyte injection process S1, a first liquid level measurement process S2, a forced electrolyte penetration process S3, an initial charging process Q2, a conditioning process S6, an aging process S7, a second liquid level measurement process S4, an evaluation process S5, and an appearance inspection process Q3.

The battery assembly process Q1 involves housing the electrode body 1, which is made up of a stack of cathode bodies 11 and anode bodies 12 sandwiched between separators 13, in the case body 31 and sealing the case lid 32. At this stage, the electrolyte 2 inlet 321 is open. The initial charging process Q2 involves connecting the electrode body 1 to an external power source for initial charging, allowing gas generated by decomposition of part of the electrolyte and water contained within the battery to escape outside the case. The appearance inspection process Q3 involves inspecting for external damage and determining whether or not the battery can be shipped.

Then, nonaqueous electrolyte secondary batteries 10 for which the inter-electrode distance DL of the electrode body 1 is evaluated as appropriate in the evaluation process S5 are sent to the visual inspection process Q3, and are shipped if they pass the visual inspection (OK). In contrast, nonaqueous electrolyte secondary batteries 10 for which the inter-electrode distance DL of the electrode body 1 is evaluated as inappropriate in the evaluation process S5 are suspended from shipment. Furthermore, even if the inter-electrode distance DL of the electrode body 1 is evaluated as appropriate in the evaluation process S5, if it fails the visual inspection (NG) in the visual inspection process Q3, they are also suspended from shipment.

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 during the manufacturing process of the nonaqueous electrolyte secondary battery 10, so the suitability of the inter-electrode distance DL of the electrode body 1, which is involved in dendrite precipitation, can be evaluated 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.

<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.

REFERENCE SIGNS LIST 1 Electrode body 2 Nonaqueous electrolyte 2Y Surplus electrolyte 3 Case 10, 10B Nonaqueous electrolyte secondary battery 11 Cathode body 12 Negative electrode body 13 Separator DK Interelectrode distance DL Interelectrode distance KJ Reference value L0, L1 Liquid volume ΔL Liquid change amount S1 Electrolyte injection step S2 First liquid volume measurement step S3 Electrolyte forced penetration step S4 Second liquid volume measurement step S5 Evaluation step S6 Conditioning step S7 Aging step

Claims (3)

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 liquid 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. The method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery according to claim 1,
The second liquid volume measuring step is a method for evaluating an inter-electrode distance of a nonaqueous electrolyte secondary battery, which is performed after the electrolyte forced 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 metallic foreign matter can be dissolved and a protective coating formed in the vicinity of the surface of the negative electrode body due to the electrolyte in the conditioning step can be stabilized . 3. A method for manufacturing a non-aqueous electrolyte secondary battery using the method for evaluating the inter-electrode distance of a non-aqueous electrolyte secondary battery according to claim 1.