Secondary battery manufacturing method

Abstract

To provide a method of manufacturing a secondary battery capable of suppressing a deterioration in high-rate performance and breakdown voltage performance.SOLUTION: A method of manufacturing a secondary battery 1 according to one embodiment of the present invention includes the steps of: determining an initial gas charging amount that makes inner pressure of the secondary battery 1 in manufacture and use larger than a lower limit gas volume indicating a minimum gas volume capable of being stored in the secondary battery 1 and smaller than an upper limit gas volume indicating a maximum gas volume capable of being permitted by the secondary battery 1; and setting the gas volume within the secondary battery 1 as the determined initial gas charging amount.SELECTED DRAWING: Figure 1

Description

[Technical Field]

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

[0002] Conventionally, in the development of secondary batteries for use in vehicles such as hybrid vehicles, plug-in hybrid vehicles, and electric vehicles, miniaturization of electrodes has been required. However, miniaturization of electrodes increases the dead space within the secondary battery, increasing the possibility of negative internal pressure. This leads to uneven salt concentration in the electrolyte, raising concerns about a decline in the high-rate performance of the secondary battery. To prevent this, it has been considered to inject gas into the secondary battery, but injecting an excessive amount of gas may reduce the pressure resistance of the secondary battery against electrode expansion.

[0003] In this regard, the method for manufacturing a secondary battery disclosed in Patent Document 1 is intended to suppress deterioration of battery performance by replacing part of the gas in the battery case with an inert gas so that the proportion of active gas in the battery case after discharge is less than a predetermined proportion. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Publication No. 2019-61823 Summary of the Invention [Problem to be solved by the invention]

[0005] However, the manufacturing method of a secondary battery disclosed in Patent Document 1 is not intended to suppress the deterioration of the high-rate performance and the withstand voltage performance of the secondary battery. Therefore, there is a demand for a technology that suppresses the deterioration of both the high-rate performance and the withstand voltage performance of the secondary battery.

[0006] The present invention has been made to solve such problems, and an object of the present invention is to provide a method for manufacturing a secondary battery that can suppress a decrease in high-rate performance and pressure resistance performance. [Means for solving the problem]

[0007] A method for manufacturing a secondary battery according to one embodiment of the present invention includes the steps of: determining an initial gas charge amount such that the internal pressure of the secondary battery during manufacture and use is greater than a lower limit gas amount indicating the minimum amount of gas that the secondary battery can contain and less than an upper limit gas amount indicating the maximum amount of gas that the secondary battery can tolerate; and adjusting the amount of gas in the secondary battery to the determined initial gas charge amount.

[0008] The initial gas charge amount can be determined so that the difference between the sum of the amount of gas generated in the secondary battery and the initial gas charge amount and the amount of gas that permeates through the sealing member installed in the secondary battery is greater than the lower limit gas amount and less than the upper limit gas amount.

[0009] The amount of gas generated can be determined based on the rate of gas generation within the secondary battery.

[0010] Furthermore, the gas permeation amount can be determined based on the gas permeability coefficient of the sealing member, the volume and width of the sealing member, and the internal and external pressures of the secondary battery.

[0011] Furthermore, the lower limit gas amount may correspond to the size of the dead space in the secondary battery.

[0012] Furthermore, the upper limit of the gas amount can be determined by the size of the dead space and the upper limit of the withstand pressure of the secondary battery. [Effects of the Invention]

[0013] According to the present invention, it is possible to provide a method for manufacturing a secondary battery that can suppress a decrease in high-rate performance and pressure resistance performance. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a flowchart showing a method for manufacturing a secondary battery according to an embodiment of the present invention. [Figure 2] 1 is a perspective view illustrating an example of a secondary battery according to an embodiment of the present invention. [Figure 3] FIG. 3 is a cross-sectional view taken along line II in FIG. 2. [Figure 4] FIG. 1 is a graph showing the relationship between the gas permeability coefficient Q and the gas generation rate ΔP and the temperature T. [Figure 5] FIG. 2 is a perspective view showing an example of a sealing member according to an embodiment of the present invention. [Figure 6] FIG. 4 is a diagram showing the change over time in the amount of gas permeation θ that occurs in a secondary battery according to one embodiment of the present invention. [Figure 7] FIG. 4 is a diagram showing the change over time in the amount P of gas generated in a secondary battery according to one embodiment of the present invention. [Figure 8] FIG. 4 is a diagram showing a change over time in the amount of gas in a secondary battery according to one embodiment of the present invention. [Figure 9] FIG. 2 is a diagram showing an example of changes over time in withstand voltage and internal pressure of a secondary battery according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0015] Hereinafter, exemplary embodiments of the present invention will be described with reference to the drawings. Fig. 1 is a diagram showing an example of a method for manufacturing a secondary battery according to an embodiment of the present invention. In step S1, an X-ray imaging device is used to measure the dimensions of a sealing member installed in a secondary battery.

[0016] Fig. 2 is a diagram showing an example of a secondary battery 1 according to one embodiment of the present invention. The secondary battery 1 includes a battery case 10 and a cover 11. As shown in Fig. 2, a pair of external terminals 12 are provided on the cover 11.

[0017] 3 is a cross-sectional view taken along line II in FIG. 2. As shown in FIG. 3, the external terminal 12 is connected to the current collector terminal 14. A sealing member 13 such as a gasket is disposed between the external terminal 12 and the cover 11, and an insulator 15 is disposed between the cover 11 and the current collector terminal 14. The sealing member 13 is a member for sealing the secondary battery 1. The sealing member 13 is compressed when the external terminal 12 and the current collector terminal 14 are connected. In step S1, the dimensions of the sealing member 13 in its compressed state are measured.

[0018] In step S2, an inert gas such as nitrogen is sealed in the secondary battery 1, and the amount of inert gas sealed in the secondary battery 1, the gas partial pressure inside the secondary battery 1 (hereinafter referred to as "internal pressure"), and the gas partial pressure outside the secondary battery 1 (hereinafter referred to as "external pressure") are measured. In step S2, the inert gas is sealed in the entire dead space inside the secondary battery 1.

[0019] In step S3, the amount of gas permeated through the sealing member 13, θ, is calculated based on Equation 1 using the measured dimensions of the sealing member 13 and the internal and external pressures of the secondary battery 1.

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[0020] A in Equation 1 represents the volume of the seal member 13 and is defined by Equation 3.

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[0021] d in Equation 1 represents the width of the seal member 13 shown in FIG.

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[0022] In Equation 1, p1 represents the internal pressure (MPa) of the secondary battery 1. p2 represents the external pressure (MPa) of the secondary battery 1. t represents the elapsed time from when the inert gas is sealed into the secondary battery 1 in step S7, which will be described later.

[0023] FIG. 6 is a diagram showing the change over time in the amount of gas permeation θ that occurs in the secondary battery 1. D1 is the period from the time the secondary battery 1 is manufactured until the secondary battery 1 is put into use. D1 is assumed to be a high temperature state during aging treatment, for example, 50 to 90°C. D2 is the period during which the secondary battery 1 is used. D2 is assumed to be a temperature of, for example, -40 to 60°C.

[0024] 6 shows the change over time in the gas permeation rate θ when the value of the height h of the sealing member 13 is large and when the value of h is small. In D1, the gas permeation rate θ tends to increase as the value of h increases. On the other hand, in D2, the gas permeation rate θ increases as the value of h increases up to t1, but thereafter the gas permeation rate θ tends to increase as the value of h decreases.

[0025] In step S4, the size (cc) of the dead space of the secondary battery 1 is calculated based on Equation 5.

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[0026] In step S5, the amount of gas P generated in the secondary battery 1 after step S7 (to be described later) is calculated based on Equation 6.

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[0027] FIG. 7 is a diagram showing the change over time in the amount of gas generated in the secondary battery 1, P. D1 is the period from the time the secondary battery 1 is manufactured until the secondary battery 1 is put into use. D1 is assumed to be a high temperature state during aging treatment, for example, 50 to 90°C. D2 is the period during which the secondary battery 1 is used. D2 is assumed to be a temperature of, for example, -40 to 60°C. As shown in FIG. 7, the amount of gas generated P decreases over time. The amount of gas generated P at D1 tends to be larger than the amount of gas generated P at D2.

[0028] In step S6, an initial gas charge amount b of the secondary battery 1 is determined. The initial gas charge amount b is the amount of inert gas present in the battery case 10 of the secondary battery 1 immediately after execution of step S7, which will be described later. Specifically, as shown in Equation 8, the initial gas charge amount b is determined so that the internal pressure of the secondary battery 1 during manufacture and use is greater than the lower limit gas charge, which indicates the minimum amount of gas that the secondary battery 1 can contain, and less than the upper limit gas charge, which indicates the maximum amount of gas that the secondary battery 1 can tolerate.

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[0029] P represents the amount of gas generated in the secondary battery 1, and the amount of gas generated calculated in step S5 is used. θ represents the amount of inert gas that permeates the sealing member 13, and the amount of gas permeation calculated in step S3 is used.

[0030] Equation 8 means that the difference between the sum of the amount of gas generated in the secondary battery 1 (P) and the initial gas charge (b) and the amount of gas permeated through the sealing member 13 installed in the secondary battery 1 (θ) is determined to be greater than the lower limit gas amount (X) and less than the upper limit gas amount (Z).

[0031] Fig. 8 is a diagram showing the change over time in the amount of gas inside the secondary battery 1. As shown in Fig. 8, the initial gas charge amount b is determined so that the internal pressure of the secondary battery 1 during manufacture and use is greater than the lower limit gas amount X and less than the upper limit gas amount Z. When the size of the dead space and the amount of gas inside the secondary battery 1 are the same, the pressure difference between the pressure inside the secondary battery 1 and the atmosphere is 0 (Mpa).

[0032] In step S7, the amount of gas in the secondary battery 1 is adjusted to the initial gas charge amount determined in step S6. In addition to inert gas, active gas and air may be contained in the secondary battery 1. In step S7, the total amount of gas in the secondary battery 1 is adjusted to the initial gas charge amount.

[0033] In the above-described embodiment, an initial gas charge amount is determined so that the internal pressure of the secondary battery 1 during manufacture and use is greater than the lower limit gas amount X and less than the upper limit gas amount Z. Then, the amount of gas in the secondary battery 1 is set to the determined initial gas charge amount. This prevents the amount of gas in the secondary battery 1 from becoming equal to or less than the lower limit gas amount X, and prevents the internal pressure of the secondary battery 1 from becoming negative. This makes it possible to suppress a decrease in the high-rate performance of the secondary battery 1. Furthermore, since it is possible to prevent the amount of gas in the secondary battery 1 from becoming equal to or greater than the upper limit gas amount Z, it is possible to suppress a decrease in the pressure resistance performance of the secondary battery 1.

[0034] The present invention is not limited to the above-described embodiment, and can be modified as appropriate within the scope of the invention. [Explanation of symbols]

[0035] 1 Secondary battery 10 Battery case 11 Cover 12 External terminal 13 Sealing material 14 Current collector terminal 15 Insulators

Claims

1. determining an initial gas charge amount such that the internal pressure of the secondary battery during manufacture and use is greater than a lower limit gas amount indicating the minimum amount of gas that can be contained in the secondary battery and less than an upper limit gas amount indicating the maximum amount of gas that can be tolerated by the secondary battery; a step of adjusting the amount of gas in the secondary battery to the determined initial gas charge amount; Including, the lower limit gas amount corresponds to the size of a dead space in the secondary battery, The upper limit gas amount is determined by the size of the dead space in the secondary battery and the upper limit pressure of the secondary battery. A method for manufacturing a secondary battery.

2. 2. The method for manufacturing a secondary battery according to claim 1, wherein the initial gas charge amount is determined so that the difference between the sum of the amount of gas generated in the secondary battery and the initial gas charge amount and the amount of gas permeating through a sealing member installed in the secondary battery is greater than the lower limit gas amount and less than the upper limit gas amount.

3. The method for manufacturing a secondary battery according to claim 2 , wherein the amount of gas generated is determined based on a gas generation rate within the secondary battery.

4. 4. The method for manufacturing a secondary battery according to claim 2, wherein the gas permeation amount is determined based on a gas permeability coefficient of the sealing member, a volume and width of the sealing member, and an internal pressure and an external pressure of the secondary battery.

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