Manufacturing method of secondary battery and manufacturing apparatus of the secondary battery

Abstract

To efficiently impregnate an electrolyte in a case into an electrode body.SOLUTION: A secondary battery houses an electrode body into a housing, and an electrolyte injected into a case is impregnated into the electrode body. Also, a manufacturing apparatus used for manufacturing this secondary battery includes an execution function of a measurement step of measuring an internal resistance of the secondary battery by an AC-IR measurement. In addition, the manufacturing apparatus includes: a pressing step of arranging the secondary battery to a pressure environment; and an open step of returning the pressure environment to an atmospheric environment. Then, on the basis of those functions, the measurement step, the pressing step, and the open step are repeated and executed until a measurement value R of the internal resistance becomes a predetermined target value R0 or less.SELECTED DRAWING: Figure 5

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a secondary battery and a manufacturing apparatus for a secondary battery.

Background Art

[0002] Conventionally, for example, as described in Patent Document 1, there is a method for manufacturing a secondary battery in which an electrolytic solution is poured into a case containing an electrode body, and then the secondary battery is placed in a pressurized environment. That is, by adopting such a configuration, the electrode body accommodated in the case can be impregnated with the electrolytic solution more quickly. In this conventional example, the so-called "vacuum pumping", that is, the injection process is performed in an environment depressurized to a substantially vacuum state. Then, after the secondary battery is opened to the atmosphere, the above-described pressure impregnation process is performed.

[0003] Furthermore, in the manufacturing method of this conventional technology, when returning the pressurized environment to the atmospheric pressure environment after pressure impregnation, the so-called stepped atmospheric release is performed by gradually reducing the pressure. And, thereby, the pressure fluctuation at the time of atmospheric release is suppressed, and the electrolytic solution in the case is less likely to scatter.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, by performing the stepped atmospheric release as described above, the time required until the injection and impregnation processes of the electrolytic solution are completed becomes long. And, thereby, there is a problem that the effect of shortening the time by impregnating under the pressurized environment is diminished.

Means for Solving the Problems

[0006] Described are aspects of a method for manufacturing a secondary battery and a manufacturing apparatus for a secondary battery that solve the above problems. Aspect 1 is a method for manufacturing a secondary battery in which an electrode body is housed in a case and the electrode body is impregnated with an electrolytic solution injected into the case, the method including a measurement step of measuring the internal resistance of the secondary battery by AC-IR measurement, a pressurization step of disposing the secondary battery in a pressurized environment, and a release step of returning the pressurized environment to an atmospheric pressure environment, and repeatedly executing the measurement step, the pressurization step, and the release step until a measured value of the internal resistance becomes equal to or less than a target value of the internal resistance.

[0007] According to the above configuration, by performing AC-IR measurement, it is possible to accurately grasp the impregnation state of the electrolytic solution with respect to the electrode body based on the measured value of the internal resistance. Further, this makes it possible to repeatedly execute the pressurization step and the release step until the impregnation of the electrolytic solution is completed. As a result, by not assuming completion of impregnation by a single pressurized impregnation and atmospheric release, the pressure of the pressurized environment can be set relatively low. Furthermore, by repeating the pressurized impregnation and atmospheric release, an effect that the impregnation of the electrolytic solution into the electrode body proceeds quickly is obtained. And thereby, while suppressing the occurrence of so-called "liquid scattering", that is, a phenomenon in which the electrolytic solution in the case scatters outside the case due to pressure fluctuations during atmospheric release, the required time until the impregnation of the electrolytic solution into the electrode body is completed can be shortened.

[0008] Aspect 2 is the method for manufacturing a secondary battery according to Aspect 1, including a step of setting the pressurized environment based on the measured value of the internal resistance. According to the above configuration, it is possible to set an appropriate pressurized environment according to the impregnation state of the electrolytic solution indicated by the measured value of the internal resistance. And thereby, it is possible to more efficiently impregnate the electrolytic solution in the case into the electrode body.

[0009] Aspect 3 is the method for manufacturing a secondary battery according to Aspect 2, in which the pressure of the pressurized environment and the holding time of the pressure are set based on a difference between the measured value and the target value. According to the above configuration, the pressurizing environment can be appropriately defined by the pressure in the pressurizing environment and the holding time of this pressure. And thereby, the electrolytic solution in the case can be impregnated into the electrode body more efficiently.

[0010] Aspect 4 is the method for manufacturing a secondary battery according to Aspect 3, in which the pressure is set to a first pressure value when the measured value is equal to or higher than a determination threshold value set to a value higher than the target value, and the pressure is set to a second pressure value lower than the first pressure value when the measured value is lower than the determination threshold value.

[0011] According to the above configuration, by comparing the measured value of the internal resistance with a predetermined determination threshold value, it is possible to easily determine the magnitude of the difference between the measured value and the target value. And based on this comparison determination, when it is determined that the difference between the measured value of the internal resistance and the target value is large, by setting a higher pressure in the pressurizing environment, the time required until the impregnation of the electrolytic solution is completed can be shortened.

[0012] Furthermore, when it is determined that the difference between the measured value of the internal resistance and the target value is small, a lower pressure is set. And thereby, by reducing the pressure difference between the pressurizing environment and the atmospheric pressure environment, the pressure fluctuation during the atmospheric release can be suppressed to be small, and the occurrence of "liquid scattering" can be suppressed.

[0013] Aspect 5 is the method for manufacturing a secondary battery according to any one of Aspects 1 to 4, including a step of setting a decompression rate according to the pressurizing environment. That is, the larger the pressure fluctuation during the atmospheric release, the easier it is for the "liquid scattering" to occur. Therefore, the higher the pressure in the pressurizing environment, by slowing down the decompression rate in the release process, the pressurizing environment can be quickly returned to the atmospheric pressure environment while suppressing the occurrence of "liquid scattering".

[0014] Aspect 6 is the method for manufacturing a secondary battery according to Aspect 5, in which an atmospheric release time according to the pressure in the pressurizing environment is set as the decompression rate. According to the above configuration, the higher the pressure in the pressurized environment, the longer the atmospheric release time can be set, so that the pressure reduction rate in the release process can be slowed down. And thereby, while suppressing the occurrence of "liquid scattering", the pressurized environment can be quickly returned to the atmospheric pressure environment.

[0015] Aspect 7 is a method for manufacturing a secondary battery according to any one of Aspects 1 to 6, in which when the measured value is less than or equal to the target value, additional electrolyte is injected into the case in the atmospheric pressure environment.

[0016] That is, by ensuring the electrolyte remaining in the case, that is, the so-called "free liquid", in a state where the impregnation of the electrode body with the electrolyte is completed, it is possible to pre-compensate for the decrease in the electrolyte due to the change over time during the use of the secondary battery. However, when performing pressure impregnation and atmospheric release, it is less likely that "liquid scattering" will occur if there is less electrolyte in the case. Therefore, according to the above configuration, the electrolyte in the case can be more efficiently impregnated into the electrode body, and the high battery performance can be maintained for a longer time.

[0017] Aspect 8 is a manufacturing apparatus for a secondary battery in which an electrode body is housed in a case and the electrode body is impregnated with the electrolyte by disposing the secondary battery in which the electrolyte is injected into the case in a pressurized environment, and includes a resistance measurement unit that measures the internal resistance of the secondary battery by AC-IR measurement, and repeats the measurement of the internal resistance, the pressurization of the secondary battery, and the atmospheric release of returning the pressurized environment of the secondary battery to the atmospheric pressure environment until the measured value of the internal resistance becomes less than or equal to the target value of the internal resistance.

Advantages of the Invention

[0018] According to the present invention, the electrolyte in the case can be efficiently impregnated into the electrode body.

Brief Description of the Drawings

[0019]

Figure 1

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DETAILED DESCRIPTION OF THE INVENTION

[0020] Hereinafter, an embodiment in which a manufacturing method of a secondary battery is embodied will be described with reference to the drawings. (Lithium Ion Secondary Battery) As shown in FIG. 1, the secondary battery 1 includes an electrode body 10 in which a positive electrode 3, a negative electrode 4, and a separator 5 are integrated, and a case 20 that houses the electrode body 10. And the secondary battery 1 of this embodiment has a configuration as a lithium ion secondary battery in which the electrode body 10 in the case 20 is impregnated with a non-aqueous electrolytic solution (not shown).

[0021] Specifically, in the secondary battery 1 of the present embodiment, the positive electrode 3, the negative electrode 4, and the separator 5 have a sheet-like outer shape and are laminated. Then, by winding the laminate of the positive electrode 3, the negative electrode 4, and the separator 5, an electrode body 10 is formed in which the positive and negative electrodes and the separator 5 are alternately arranged in the radial direction with the separator 5 sandwiched between the positive electrode 3 and the negative electrode 4.

[0022] Further, the case 20 of the present embodiment includes a flat substantially rectangular box-shaped case body 21 and a lid member 22 that closes the open end 21x of the case body 21. And the electrode body 10 of the present embodiment has a flat outer shape corresponding to the box shape of the case 20.

[0023] (Electrode Sheet and Electrode Body) More specifically, as shown in FIG. 2, in the secondary battery 1 of the present embodiment, the positive electrode 3 and the negative electrode 4 each have a configuration as an electrode sheet 35 including a current collector foil 31 having a sheet-like outer shape and an electrode active material layer 32 laminated on the current collector foil 31. Specifically, the electrode sheet 35P for the positive electrode 3 is formed by laminating a positive electrode active material layer 32P containing a lithium transition metal oxide serving as a positive electrode active material on a current collector foil 31P serving as a base material made of aluminum or the like. And the electrode sheet 35N for the negative electrode 4 is formed by laminating a negative electrode active material layer 32N containing a carbon-based material serving as a negative electrode active material on a current collector foil 31N serving as a base material made of copper or the like.

[0024] Furthermore, in the secondary battery 1 of the present embodiment, these positive and negative electrode sheets 35P and 35N are each shaped into a strip. And the electrode body 10 of the present embodiment has a configuration as a wound body in which the positive and negative electrode sheets 35P and 35N laminated with the separator 5 therebetween are wound around a winding axis 10x extending in the width direction of the strip shape (the left-right direction in FIG. 2).

[0025] Also, in FIG. 2, the separator 5 and each electrode sheet 35 are wound in such a manner that the electrode sheet 35P constituting the positive electrode 3 is wound inside. However, this figure is an example showing the structure of the electrode body 10, and in some cases, these separator 5 and each electrode sheet 35 may be wound in such a manner that the electrode sheet 35N constituting the negative electrode 4 is wound inside. And thereby, it is determined whether the electrode sheet 35 disposed on the outermost shell of the electrode body 10 is the electrode sheet 35P constituting the positive electrode 3 or the electrode sheet 35N constituting the negative electrode 4.

[0026] Also, as shown in FIGS. 1 to 3, the lid member 22 of the case 20 is provided with a positive electrode terminal 38P and a negative electrode terminal 38N protruding outside the case 20. Further, each electrode sheet 35 is formed with an uncoated portion 39 where the electrode active material layer 32 is not formed on the current collector foil 31. And the secondary battery 1 of the present embodiment is configured such that the electrode sheet 35P constituting the positive electrode 3 and the positive electrode terminal 38P are electrically connected and the electrode sheet 35N constituting the negative electrode 4 and the negative electrode terminal 38N are electrically connected by using these uncoated portions 39.

[0027] Specifically, the electrode body 10 of the present embodiment is housed in the case 20 in a state where its winding axis 10x is along the longitudinal direction (the left - right direction in FIG. 1) of the lid member 22 having a long and substantially rectangular plate shape. Further, in this state, the uncoated portion 39P of the electrode sheet 35P constituting the positive electrode 3 and the positive electrode terminal 38P are connected via a connection member 40P. And similarly, the uncoated portion 39N of the electrode sheet 35N constituting the negative electrode 4 and the negative electrode terminal 38N are connected via a connection member 40N.

[0028] Furthermore, an electrolytic solution 45 is injected into this case 20. That is, as the electrolytic solution 45 of the secondary battery 1 having a configuration as a lithium-ion secondary battery, a solution in which a lithium salt serving as a supporting salt is dissolved in an organic solvent is used. Also, the injection of the electrolytic solution 45 is performed using a liquid injection hole (not shown) provided in the lid member 22. And thus, the secondary battery 1 of the present embodiment is configured such that the electrode body 10 sealed in the case 20 is impregnated with the electrolytic solution 45.

[0029] (Manufacturing apparatus used for impregnation of electrolytic solution) As shown in FIG. 4, in the secondary battery 1 of the present embodiment, a manufacturing apparatus 50 used for impregnation of the electrolytic solution 45 includes a pressure adjustment chamber 55 having a pump device 51 for pressure adjustment and an atmosphere release valve 53. That is, this pressure adjustment chamber 55 is configured such that the pressure inside the chamber can be reduced or increased by the operation of the pump device 51, and the pressure inside the chamber can be returned to atmospheric pressure by the operation of the atmosphere release valve 53. And thus, the secondary battery 1 of the present embodiment is configured such that the injection of the electrolytic solution 45 into the case 20 and the impregnation of the electrolytic solution 45 into the electrode body 10 accommodated in the case 20 are performed while being accommodated in this pressure adjustment chamber 55.

[0030] More specifically, the manufacturing apparatus 50 of the present embodiment includes a control device 60 that controls the operating state of this pressure adjustment chamber 55. Specifically, this control device 60 includes a decompression control unit 61 that controls the operation of the pump device 51 to shift the inside of the pressure adjustment chamber 55 to a decompressed environment based on its function as an exhaust pump. Also, this control device 60 includes a pressurization control unit 62 that controls the operation of the pump device 51 to shift the inside of the pressure adjustment chamber 55 to a pressurized environment based on its function as a compressor. And the control device 60 of the present embodiment includes an opening control unit 63 that controls the operation of the atmosphere release valve 53 to return the inside of the pressure adjustment chamber 55 to an atmospheric pressure environment.

[0031] Also, in the manufacturing apparatus 50 of the present embodiment, a liquid injection device 65 for injecting the electrolytic solution 45 into the case 20 of the secondary battery 1 disposed in the pressure adjustment chamber 55 is provided in the pressure adjustment chamber 55. And the control device 60 of the present embodiment includes a liquid injection control unit 66 that controls the operation of the liquid injection device 65.

[0032] Furthermore, in the manufacturing apparatus 50 of the present embodiment, an AC-IR measurement device 70 is provided in the pressure adjustment chamber 55. And the control device 60 of the present embodiment includes a resistance measurement unit 71 that measures the internal resistance of the secondary battery 1 disposed in the pressure adjustment chamber 55 by using this AC-IR measurement device 70.

[0033] That is, the AC-IR measurement device 70 has a function of obtaining the internal resistance of the secondary battery 1 from the voltage value of its AC voltmeter by applying a measurement current having a predetermined frequency (for example, 1 kHz) to the positive electrode terminal 38P and the negative electrode terminal 38N of the secondary battery 1. And in the secondary battery 1 of the present embodiment, based on the measured value R of the internal resistance using this AC-IR measurement device 70, the impregnation determination of the electrolytic solution 45 with respect to the electrode body 10 housed in the case 20 is executed.

[0034] In general, the measurement of the internal resistance by the above-described AC method is called "AC-IR measurement". On the other hand, the measurement of the internal resistance by the DC method using a DC voltmeter is called "DC-IR measurement". Furthermore, the measured values of the internal resistance obtained by these AC method and DC method may be simply called "AC-IR" and "DC-IR", respectively. And "AC-IR measurement" has advantages such as being able to measure in a short time, having high measurement reproducibility, the charge rate of the secondary battery 1 not changing, and the equipment being small and energy-saving.

[0035] (Method of impregnating electrolytic solution based on AC-IR measurement) Specifically, as shown in FIG. 5, when impregnating the electrode body 10 in the case 20 of the control device 60 of the present embodiment with the electrolytic solution 45, first, the pressure adjustment chamber 55 in which the secondary battery 1 is disposed is subjected to so-called "vacuum pumping". That is, the inside of the pressure adjustment chamber 55 is depressurized to about "0 kPa", thereby disposing the secondary battery 1 in a depressurized environment (step 101). Next, in this depressurized environment, the electrolytic solution 45 is injected into the case 20 of the secondary battery 1 (step 102). Then, after the completion of the liquid injection process in step 102, the inside of the pressure adjustment chamber 55 is returned to atmospheric pressure. That is, by opening to the atmosphere using the atmosphere release valve 53, the secondary battery 1 after the liquid injection is disposed in an atmospheric pressure environment (step 103).

[0036] That is, when returning the depressurized environment to the atmospheric pressure environment after injecting the electrolytic solution 45, the electrolytic solution 45 injected into the case 20 penetrates into the electrode body 10. And in the secondary battery 1 of the present embodiment, the initial impregnation of the electrolytic solution 45 is performed in this way.

[0037] Note that the atmospheric pressure is about "100 kPa" and the vacuum pressure is about "0 kPa". Therefore, the decompression force by the above "vacuum pumping" is about "100 kPa". And when this is expressed as a pressurization force, it becomes about "-100 kPa".

[0038] Next, in the secondary battery 1 of the present embodiment, in a state where the initial impregnation of the electrolytic solution 45 is completed, the AC-IR measurement of the secondary battery 1 is executed (step 104). That is, the control device 60 of the present embodiment obtains the measured value R of the internal resistance of the secondary battery 1 by the AC-IR measurement in step 103. Further, the control device 60 reads out the target value R0 of the internal resistance from its storage area (not shown) (step 105). And the control device 60 of the present embodiment determines whether the measured value R of the internal resistance obtained by the AC-IR measurement in step 104 for the secondary battery 1 in the pressure adjustment chamber 55 is less than or equal to a predetermined target value R0 of the internal resistance (step 106).

[0039] That is, in the secondary battery 1 of the present embodiment, as the impregnation of the electrolytic solution 45 into the electrode body 10 progresses, its internal resistance decreases. And the control device 60 of the present embodiment is configured to determine whether the impregnation of the electrolytic solution 45 is completed based on the above AC-IR measurement and comparison with the target value R0.

[0040] Also, when the measured value R of the internal resistance by the AC-IR measurement of the control device 60 of the present embodiment is greater than the target value R0 (R > R0, step 106: NO), subsequently, based on the measured value R, the pressurization environment of the secondary battery 1 is set (step 107). Specifically, in this step 107, the control device 60 sets the pressurization pressure P of the pressurization environment and the holding time T of the pressurization pressure P. And the control device 60 of the present embodiment is configured to form a pressurization environment in the pressure adjustment chamber 55 based on the settings of these pressurization pressure P and holding time T (step 108).

[0041] Furthermore, the control device 60 of the present embodiment subsequently sets the decompression rate when returning the inside of the pressure adjustment chamber 55 from the pressurization environment to the atmospheric pressure environment based on the pressurization pressure P of the pressurization environment set in step 107 (step 109). Specifically, in this step 109, the control device 60 sets the atmospheric release time t when the decompression rate is constant as the decompression rate. And the control device 60 of the present embodiment is configured to return the inside of the pressure adjustment chamber 55 where the secondary battery 1 is disposed from the pressurization environment to the atmospheric pressure environment by performing atmospheric release at the decompression rate set in this step 109 (step 110).

[0042] More specifically, as shown in FIG. 6, in the pressure setting step (see FIG. 5, step 107) of the control device 60 of the present embodiment, it is determined whether the measured value R of the internal resistance by AC-IR measurement is equal to or greater than a predetermined determination threshold value Rth (step 201). Further, when the measured value R of the internal resistance is equal to or greater than the determination threshold value Rth (R≥Rth, step 201: YES), the control device 60 sets the pressure P of the pressurization environment to the first pressure value P1 (P = P1, step 202). Then, the control device 60 sets the first holding time T1 as the holding time T of this first pressure value P1.

[0043] Also, when the measured value R of the internal resistance of the control device 60 of the present embodiment is lower than the determination threshold value Rth (R < Rth, step 201: NO), the pressure P of the pressurization environment is set to a second pressure value P2 lower than the first pressure value P1 (P = P2 (<P1), step 203). Then, the control device 60 sets the second holding time T2 as the holding time T of this second pressure value P2.

[0044] Specifically, in the secondary battery 1 of the present embodiment, the first pressure value P1 is set to "500 kPa". Also, the second pressure value P2 is set to "300 kPa". And both the first holding time T1 and the second holding time T2 are set to "3 seconds".

[0045] That is, the control device 60 of the present embodiment determines the magnitude of the difference between the measured value R of the internal resistance and the target value R0 by comparing the measured value R of the internal resistance with a predetermined determination threshold value Rth. And thereby, when the magnitude of this difference is large, the secondary battery 1 is arranged in a pressurization environment with a higher pressure P, so that the electrode body 10 can be impregnated with the electrolytic solution 45 more quickly.

[0046] Also, in step 202 of the present embodiment, when the first pressure value P1 is set for the pressure P in the pressurized environment, in the opening setting step (see FIG. 5, step 109), the first opening time t1 is set for the atmospheric opening time t (t = t1, step 204). Then, in step 203, when the second pressure value P2 is set for the pressure P in the pressurized environment, similarly in the opening setting step, the second opening time t2 shorter than the first opening time t1 is set for the atmospheric opening time t (t = t2 (<t1), step 205).

[0047] That is, in the opening step (see FIG. 5, step 110) of returning the pressurized environment to the atmospheric pressure environment, the phenomenon that the electrolytic solution 45 in the case 20 scatters outside the case 20 due to the pressure fluctuation is likely to occur.

[0048] However, as shown in FIG. 7, such scattering of the electrolytic solution 45 lengthens the atmospheric opening time t. That is, by slowing down the pressure reduction rate, its occurrence can be suppressed. And the atmospheric opening time t in which such scattering of the electrolytic solution 45 hardly occurs tends to be longer as the pressure P in the pressurized environment is higher.

[0049] Based on this point, in the secondary battery 1 of the present embodiment, when the pressure P in the pressurized environment is set to the first pressure value P1, that is, "500 kPa" (see FIG. 5, step 201: YES), the first opening time t1 is set to "59 seconds". And when the pressure P in the pressurized environment is set to the second pressure value P2, that is, "300 kPa" (see FIG. 5, step 201: NO), the second opening time t2 is set to "50 seconds".

[0050] In addition, as shown in FIG. 4, in the manufacturing apparatus 50 of the present embodiment, the pressure control unit 62 provided in the control device 60 functions as a pressure setting unit. And similarly, the opening control unit 63 provided in the control device 60 functions as the opening setting unit.

[0051] As shown in FIG. 5, after the control device 60 of the present embodiment executes the pressurization process and the release process of the above steps 107 to 110, it executes the AC-IR measurement of the secondary battery 1 again (step 111). Further, the control device 60 determines whether the measured value R of the internal resistance obtained by this re AC-IR measurement is equal to or less than its target value R0 (step 112). And in this step 112, when the measured value R of the internal resistance by the AC-IR measurement is larger than the target value R0 (R > R0, step 112: NO), the control device 60 of the present embodiment executes the processes of the above steps 107 to 112 again.

[0052] That is, in the secondary battery 1 of the present embodiment, until the measured value R of the internal resistance becomes equal to or less than the target value R0, the measurement process of the internal resistance by the AC-IR measurement, the pressurization process of the secondary battery 1, and the release process thereof are repeatedly executed. And when the measured value R of the internal resistance by the AC-IR measurement becomes equal to or less than the target value R0 (R ≤ R0, step 112: YES), it is determined that the impregnation of the electrolyte 45 into the electrode body 10 is completed.

[0053] Also, in the secondary battery 1 of the present embodiment, after the impregnation of the electrolyte 45 into the electrode body 10 is completed, additional electrolyte 45 is injected into the case 20 in an atmospheric pressure environment (finish filling, step 113). And the secondary battery 1 of the present embodiment is configured such that by executing this finish filling, the decrease of the electrolyte 45 based on the change over time due to the use of the secondary battery 1 is compensated in advance.

[0054] In addition, in the secondary battery 1 of the present embodiment, when the measured value R of the internal resistance by the AC-IR measurement after the initial impregnation becomes equal to or less than the target value R0 (R ≤ R0, step 106: YES), the processes of the above steps 107 to 112 are not executed. And thereby, the finish filling process of step 113 is executed without performing the pressurization process and the release process of the secondary battery 1.

[0055] (Reference Example) In "Reference Example 1" shown in FIG. 8, similar to the secondary battery 1 of the present embodiment, liquid injection and atmospheric opening in a reduced-pressure environment by "vacuum evacuation" are performed (for reduced-pressure liquid injection, refer to FIG. 5, and in the figure, refer to Steps 101 to 103). Also, in the case of this "Reference Example 1", the internal resistance of the secondary battery 81 is not measured by AC-IR measurement. And in this "Reference Example 1", after the initial impregnation of the electrolytic solution 45, one pressurized impregnation and atmospheric opening are performed, that is, the pressurizing step of placing the secondary battery 81 in a pressurized environment and the opening step of returning to the atmospheric pressure environment are performed only once to complete the impregnation of the electrolytic solution 45.

[0056] Specifically, in the case of this "Reference Example 1", considering that there are variations in the permeability of the electrolytic solution 45, in order to complete it with one pressurized impregnation and atmospheric opening, the pressure P in the pressurized environment is set high. Specifically, in FIG. 8, the pressure P is set to "700 kPa (800 kPa - 100 kPa)". Also, the holding time T is set to about "600 seconds". And thereby, the predetermined time until the impregnation is completed is about "800 seconds".

[0057] Furthermore, in the case of this "Reference Example 1", since the pressure P in the pressurized environment is high, the pressure fluctuation during the atmospheric opening is large. For this reason, in the opening step, there is a problem that the electrolytic solution 45 in the case 20 is likely to scatter outside the case 20 due to the pressure fluctuation during the atmospheric opening.

[0058] Incidentally, hereinafter, for convenience of explanation, the scattering of the electrolytic solution 45 occurring in such an opening step is described by omitting it as "liquid scattering". And this "liquid scattering" may also be referred to as "liquid spillage" or the like.

[0059] Also, “Reference Example 2” shown in FIG. 9 also performs liquid injection and atmospheric release in a reduced-pressure environment by “vacuum pumping”, similar to the secondary battery 1 of the present embodiment. Further, the internal resistance of the secondary battery 82 is not measured by AC-IR measurement. And also in this “Reference Example 2”, after the initial impregnation of the electrolytic solution 45, one pressurized impregnation and atmospheric release are performed, that is, the pressurization step of placing the secondary battery 82 in a pressurized environment and the release step of returning to the atmospheric pressure environment are performed only once to complete the impregnation of the electrolytic solution 45.

[0060] Here, in the case of this “Reference Example 2”, in the release step after pressurized impregnation, a so-called “stepwise atmospheric release” is performed. Specifically, the pressure P during pressurized impregnation is set to the same “700 kPa (800 kPa - 100 kPa)” as in the above “Reference Example 1”, and the pressure is decreased by “100 kPa” at a time, and the temporary holding of the reduced pressure P is repeated. That is, also in this “Reference Example 2”, similar to the above “Reference Example 1”, considering the variation in the permeability of the electrolytic solution 45, the pressure P of the pressurized environment is set high in order to complete it with one pressurized impregnation and atmospheric release. However, in this “Reference Example 2”, by performing the above “stepwise atmospheric release”, it is possible to suppress the pressure fluctuation during atmospheric release by taking a longer time to return to the atmospheric pressure environment than in “Reference Example 1”. And thereby, it becomes a configuration that suppresses the occurrence of “liquid scattering”.

[0061] However, on the contrary, in this “Reference Example 2”, by performing the “temporary holding of the reduced pressure P” a plurality of times, the release step after pressurized impregnation takes time. As a result, there is a problem that the required time becomes long until the impregnation of the electrolytic solution 45 into the electrode body 10 is completed.

[0062] (Function) On the other hand, as shown in the embodiment of FIG. 10, in the secondary battery 1 of the present embodiment, by performing AC-IR measurement, it is possible to accurately grasp the impregnation state of the electrolytic solution 45 with respect to the electrode body 10 based on the measured value R of its internal resistance. Further, thereby, until the impregnation of the electrolytic solution 45 is completed, the pressurization process and the release process can be repeatedly executed, that is, without assuming the completion of impregnation by one-time pressurization impregnation and atmospheric release, the pressure P of the pressurization environment can be set relatively low. Furthermore, by repeating the pressurization impregnation and the atmospheric release, an effect that the impregnation of the electrolytic solution 45 with respect to the electrode body 10 proceeds quickly can be obtained. And thereby, while suppressing the occurrence of "liquid scattering", it is possible to shorten the required time until the impregnation of the electrolytic solution 45 with respect to the electrode body 10 is completed.

[0063] Specifically, as shown in FIGS. 10 and 11, for example, the target value R0 corresponding to the internal resistance of the secondary battery 1 in a state where the impregnation of the electrolytic solution 45 with respect to the electrode body 10 is completed is set to "1.20 mΩ". In this embodiment, in the first AC-IR measurement performed after the execution of the liquid injection and release processes in the reduced-pressure environment, the measured value R of the internal resistance is "2.49 mΩ", which is higher than the target value R0 (see FIG. 5, steps 104 to 106). Further, this "2.49 mΩ" is larger than the determination threshold value Rth, "1.25 mΩ", for setting the pressure P of the pressurization environment based on the magnitude of the difference between the measured value R of the internal resistance and the target value R0. And based on this first AC-IR measurement, a pressurization process in which the pressure P of the pressurization environment is set to the first pressure value P1, and a release process in which the first release time t1 is set for the atmospheric release time t are executed (S1, see FIG. 5, steps 107 to 110). Incidentally, the first pressure value P1 is "0.5 MPa (500 kPa)", and the first release time t1 is "59 seconds".

[0064] Furthermore, in this embodiment, even in the second AC-IR measurement (S2, see FIG. 5, steps 111 and 112) performed after the above-mentioned pressure impregnation and air release, the measured value R of the internal resistance is still "1.28 mΩ", which is higher than the target value R0. Furthermore, this "1.28 mΩ" is still greater than the determination threshold value Rth for setting the pressure P of the pressurized environment based on the magnitude of the difference between the measured value R of the internal resistance and the target value R0. Then, based on this second AC-IR measurement, the same conditions as the first pressure impregnation and air release are applied, that is, a pressurization process in which the pressure P of the pressurized environment is set to the first pressure value P1, and an air release process in which the air release time t is set to the first release time t1 are executed.

[0065] Next, in this embodiment, in the third AC-IR measurement (S3) performed after the execution of this second pressure impregnation and air release, the measured value R of the internal resistance has reached the target value R0 of "1.20 mΩ". Thereby, it is confirmed that the impregnation of the electrolytic solution 45 into the electrode body 10 is completed, and additional injection of the electrolytic solution 45 in the atmospheric pressure environment, that is, finish liquid injection, is executed (see FIG. 5, step 113).

[0066] As shown in FIG. 12, for the secondary battery 1 of this embodiment, "liquid scattering" does not occur even during air release after pressure impregnation. Furthermore, in the case of the above embodiment, the required time until the impregnation of the electrolytic solution 45 is completed is about "240 seconds". And this is not only shorter than about "1500 seconds" of "Reference Example 2" in which "stepwise air release" was performed so that "liquid scattering" does not occur, but also shorter than about "800 seconds" of "Reference Example 1" in which air release was performed without aversion to the occurrence of "liquid scattering".

[0067] Next, the effects of this embodiment will be described. (1) When manufacturing the secondary battery 1, the electrode body 10 is accommodated in the case 20, and the electrode body 10 is impregnated with the electrolytic solution 45 injected into the case 20. Further, the manufacturing apparatus 50 used for manufacturing this secondary battery 1 has a function of executing a measurement process for measuring the internal resistance of the secondary battery 1 by AC-IR measurement. Furthermore, this manufacturing apparatus 50 has a function of executing a pressurization process of disposing the secondary battery 1 in a pressurized environment and an opening process of returning this pressurized environment to an atmospheric pressure environment. Then, based on these functions, the measurement process, the pressurization process, and the opening process are repeatedly executed until the measured value R of the internal resistance becomes equal to or less than a predetermined target value R0.

[0068] According to the above configuration, by performing AC-IR measurement, it is possible to accurately grasp the impregnation state of the electrolytic solution 45 with respect to the electrode body 10 based on the measured value R of the internal resistance. Further, this makes it possible to repeatedly execute the pressurization process and the opening process until the impregnation of the electrolytic solution 45 is completed. As a result, by not assuming the completion of impregnation by one-time pressurization impregnation and atmospheric opening, the pressure P of the pressurized environment can be set relatively low. Furthermore, by repeating the pressurization impregnation and the atmospheric opening, an effect that the impregnation of the electrolytic solution 45 with respect to the electrode body 10 proceeds quickly is obtained. And thereby, while suppressing the occurrence of so-called "liquid scattering", that is, the phenomenon that the electrolytic solution 45 in the case 20 scatters outside the case 20 due to the pressure fluctuation during the atmospheric opening, the time required until the impregnation of the electrolytic solution 45 with respect to the electrode body 10 is completed can be shortened.

[0069] (2) When executing the pressurization process, the pressurized environment is set based on the measured value R of the internal resistance by AC-IR measurement. According to the above configuration, it is possible to set an appropriate pressurized environment according to the impregnation state of the electrolytic solution 45 indicated by the measured value R of the internal resistance. And thereby, the electrolytic solution 45 in the case 20 can be impregnated into the electrode body 10 more efficiently.

[0070] (3) In the pressurization environment setting step, when the measured value R of the internal resistance is equal to or higher than the determination threshold value Rth set to a value higher than the target value R0, the pressure P of the pressurization environment is set to the first pressure value P1. And when the measured value R of the internal resistance is lower than the determination threshold value Rth, the pressure P of the pressurization environment is set to the second pressure value P2 lower than the first pressure value P1.

[0071] That is, the pressurization environment of the secondary battery 1 can be defined by the pressure P of the pressurization environment and the holding time T of this pressure P. For example, the greater the pressure P of the pressurization environment, the faster the impregnation of the electrolytic solution 45 into the electrode body 10 progresses. And for the progress of this impregnation, a certain holding time T is required.

[0072] Based on this point, as in the above configuration, by comparing the measured value R of the internal resistance with the predetermined determination threshold value Rth, the magnitude of the difference between the measured value R and the target value R0 is determined. And when it is determined based on this comparison determination that the difference between the measured value R of the internal resistance and the target value R0 is large, by setting a higher pressure P of the pressurization environment, the required time until the impregnation of the electrolytic solution 45 is completed can be shortened.

[0073] Furthermore, when it is determined that the difference between the measured value R of the internal resistance and the target value R0 is small, a lower pressure P of the pressurization environment is set. And thereby, by reducing the pressure difference between the pressurization environment and the atmospheric pressure environment, the pressure fluctuation at the time of atmospheric release can be suppressed to be small, and the occurrence of "liquid scattering" can be suppressed.

[0074] (4) When executing the release step, as the pressure reduction rate corresponding to the pressurization environment, the atmospheric release time t corresponding to the pressure P of the set pressurization environment is set. That is, the greater the pressure fluctuation at the time of atmospheric release, the easier it is for the "liquid scattering" to occur. Therefore, the higher the pressure P of the pressurization environment, the longer the atmospheric release time t is set, and by slowing down the pressure reduction rate in the release step, while suppressing the occurrence of "liquid scattering", the pressurization environment can be quickly returned to the atmospheric pressure environment.

[0075] When the measured value R of the internal resistance is less than or equal to the target value R0, additional electrolyte 45 is injected into the case 20 in an atmospheric pressure environment. That is, by ensuring the electrolyte 45 remaining in the case 20, namely the so-called "free liquid", in a state where the impregnation of the electrode body 10 with the electrolyte 45 is completed, it is possible to pre-compensate for the decrease in the electrolyte 45 due to changes over time during the use of the secondary battery 1. However, when performing pressure impregnation and atmospheric release, it is less likely for the "liquid scattering" to occur if there is less electrolyte 45 in the case 20. Therefore, according to the above configuration, the electrolyte 45 in the case 20 can be impregnated into the electrode body 10 more efficiently, and the high battery performance can be maintained for a longer time.

[0076] (6) When manufacturing the secondary battery 1, an electrolyte injection step of injecting the electrolyte 45 into the case 20 is performed in a state where the secondary battery 1 is placed in a reduced pressure environment. And after the execution of this electrolyte injection step, the first measurement step by the AC-IR measurement is executed.

[0077] That is, when returning the reduced pressure environment to the atmospheric pressure environment after injecting the electrolyte 45 in the reduced pressure environment, the electrolyte 45 injected into the case 20 penetrates into the electrode body 10. And according to the above configuration, by the first AC-IR measurement, it is possible to accurately grasp the impregnation state of the electrolyte 45 with respect to the electrode body 10 in the secondary battery 1 after the initial impregnation by the electrolyte injection and the atmospheric release in the reduced pressure environment.

[0078] Note that the above embodiments can be implemented with the following modifications. The above embodiments and the following modification examples can be implemented in combination with each other within a technically non-conflicting range.

[0079] · In the above embodiment, the first pressure value P1 is set to "500 kPa" and the second pressure value P2 is set to "300 kPa", but these first pressure value P1 and second pressure value P2 can be arbitrarily changed respectively. It is preferable that the second pressure value P2 is lower than the first pressure value P1.

[0080] · Also, in the above embodiment, the first holding time T1 and the second holding time T2 are both set to "3 seconds", but these first holding time T1 and second holding time T2 may also be arbitrarily changed respectively. For example, the higher the applied pressure P of the applied pressure environment to be set, the shorter the holding time T may be set, etc.

[0081] · In the above embodiment, the applied pressure P of the applied pressure environment is set in two steps of the first pressure value P1 and the second pressure value P2 by comparing the measured value R of the internal resistance by AC-IR measurement with a predetermined determination threshold value Rth, but the applied pressure P may also be set in a plurality of steps of three or more steps. Further, the applied pressure P may be set by using a map, a table, etc. in which the difference between the measured value R of the internal resistance and the target value R0 is associated with the applied pressure P to be set. Also, it is not necessarily the case that the higher the difference between the measured value R of the internal resistance and the target value R0, the higher the applied pressure P is set. And the setting of the holding time T may also be configured to be performed by such map calculation.

[0082] · Further, the applied pressure P of the applied pressure environment may be set by a method other than using the measured value R of the internal resistance by AC-IR measurement. For example, a configuration in which the applied pressure P to be set is gradually reduced according to the number of repetitions of the pressurization process and the release process may be used. And the setting of the holding time T may also not necessarily have a relationship with the measured value R of the internal resistance by AC-IR measurement and the applied pressure P of the applied pressure environment.

[0083] · Also, in the above embodiment, the first release time t1 when the applied pressure P of the applied pressure environment is set to the first pressure value P1 is set to "59 seconds", and the second release time t2 when the applied pressure P is set to the second pressure value P2 is set to "50 seconds". However, it is not limited to this, and these first release time t1 and second release time t2 may be arbitrarily changed. Further, the setting of this atmospheric release time t may also be set in a plurality of steps of three or more steps. And the atmospheric release time t may be set by using a map, a table, etc. in which the applied pressure P of the set applied pressure environment is associated with the atmospheric release time t.

[0084] · Also, regarding the pressurization setting and the release setting, for example, parameters other than the pressure P and the holding time T, such as temperature, may be added. Furthermore, these pressurization setting and release setting do not necessarily have to be performed every time the pressurization process and the release process are repeated. And, regardless of the number of repetitions, the pressurization process and the release process may be repeated with a fixed pressurization setting and release setting set in advance.

[0085] · In the above embodiment, the first liquid injection into the case 20 is performed in a reduced-pressure environment where the pressure is reduced to near "0 kPa" by so-called "vacuum pumping". However, the present invention is not limited to this, and the first liquid injection may be performed in an atmospheric pressure environment without performing "vacuum pumping".

[0086] · In the above embodiment, when the measured value R of the internal resistance is equal to or less than the target value R0, additional electrolyte 45 is injected into the case 20 in an atmospheric pressure environment. However, the present invention is not limited to this, and such so-called finish liquid injection does not necessarily have to be performed. At the time of the first liquid injection, for example, the electrolyte 45 may be injected in a larger amount in advance. However, from the viewpoint of suppressing "liquid scattering" at the time of atmospheric release after pressure impregnation, it is preferable that the amount of the electrolyte 45 in the case 20 is small.

[0087] · In the above embodiment, the electrode body 10 of the secondary battery 1 has a configuration as a wound body. However, the positive and negative electrode sheets 35P and 35N laminated with the separator 5 therebetween do not necessarily have to be wound. Further, the secondary battery 1 does not necessarily have to be a lithium ion secondary battery, and may be applied to other non-aqueous electrolyte secondary batteries. And, the terminal shapes of the positive electrode terminal 38P and the negative electrode terminal 38N are also not limited to the shapes shown in FIG. 1 and may be arbitrarily changed.

[0088] Next, the technical idea that can be grasped from the above embodiment and the modification example will be described. (a) A liquid injection step of injecting the electrolyte into the case in a state where the secondary battery is disposed in a reduced-pressure environment, and the first measurement step is executed after the execution of the liquid injection step.

[0089] That is, after injecting the electrolytic solution in a reduced-pressure environment and then returning the reduced-pressure environment to an atmospheric-pressure environment, the electrolytic solution injected into the case penetrates into the electrode body. And according to the above configuration, by the first AC-IR measurement, it is possible to accurately grasp the impregnation state of the electrolytic solution with respect to the electrode body in the secondary battery after initial impregnation by liquid injection and atmospheric opening in the reduced-pressure environment.

[0090] (b) It includes a pressure setting unit that sets the pressurized environment based on the measured value of the internal resistance. (c) It includes an opening setting unit that sets the decompression rate at the time of atmospheric opening based on the pressurized environment of the secondary battery.

Explanation of reference numerals

[0091] 1... Secondary battery 10... Electrode body 20... Case 45... Electrolytic solution 50... Manufacturing apparatus R... Measured value of internal resistance R0... Target value of internal resistance

Claims

1. A method for manufacturing a secondary battery that houses an electrode body in a case and impregnates the electrode body with an electrolytic solution injected into the case, comprising: a measurement step of measuring the internal resistance of the secondary battery by AC-IR measurement; a pressurization step of placing the secondary battery in a pressurized environment; a release step of returning the pressurized environment to an atmospheric pressure environment, and repeating the measurement step, the pressurization step, and the release step until the measured value of the internal resistance becomes equal to or less than a target value of the internal resistance.

2. comprising a step of setting the pressurized environment based on the measured value of the internal resistance The method for manufacturing a secondary battery according to claim 1.

3. The method for manufacturing a secondary battery according to claim 2, wherein the pressure and the holding time of the pressurized environment are set based on the difference between the measured value and the target value.

4. When the measured value is equal to or greater than a determination threshold set to a value higher than the target value, setting the pressure to a first pressure value, and The method for manufacturing a secondary battery according to claim 3, wherein when the measured value is lower than the determination threshold, setting the pressure to a second pressure value lower than the first pressure value.

5. comprising a step of setting a decompression rate according to the pressurized environment The method for manufacturing a secondary battery according to any one of claims 1 to 4.

6. setting an atmospheric release time according to the pressure of the pressurized environment as the decompression rate The method for manufacturing a secondary battery according to claim 5.

7. The method for manufacturing a secondary battery according to claim 1, wherein when the measured value is equal to or less than the target value, additional electrolytic solution is injected into the case in the atmospheric pressure environment.

8. A secondary battery manufacturing apparatus that accommodates an electrode body in a case and impregnates the electrode body with an electrolytic solution by disposing the secondary battery, in which the electrolytic solution is poured into the case, in a pressurized environment. It includes a resistance measurement unit that measures the internal resistance of the secondary battery by AC-IR measurement. A secondary battery manufacturing apparatus that repeatedly performs measurement of the internal resistance, pressurization of the secondary battery, and atmospheric release to return the pressurized environment of the secondary battery to the atmospheric pressure environment until the measured value of the internal resistance becomes equal to or less than the target value of the internal resistance.

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