Manufacturing method of secondary battery using split injections of electrolyte

Abstract

The present invention relates to a method for manufacturing a secondary battery, wherein the method for manufacturing a secondary battery involves injecting a large amount of electrolyte in two separate injections, and by correcting the amount of the second injection of the electrolyte by reflecting the average value of the amount of the first injection of the electrolyte previously injected, the electrolyte can be injected quantitatively within a short period of time. Therefore, when manufacturing a battery in which 200g or more of electrolyte is injected, such as a large-capacity secondary battery or a long-cell model secondary battery, the defect rate can be significantly reduced, and the performance of the secondary battery can be further improved.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a secondary battery comprising the split injection of an electrolyte. Background Technology

[0003] With the development of electronic devices, secondary batteries are gaining prominence as an energy source. Recently, as lithium-ion batteries and similar types are being utilized as power sources for medium and large-sized devices such as electric vehicles, the performance of secondary batteries is being considered a major factor determining the performance of electronic devices and medium-to-large-sized devices.

[0004] Rechargeable batteries are manufactured by fabricating and assembling an electrode assembly consisting of a positive electrode, a negative electrode, and a separator, inserting this assembly into a battery case such as a pouch, injecting an electrolyte into the case, and then sealing it. In this process, since the battery's performance is determined by the impregnation state of the electrolyte injected into the battery case, it is important to inject the electrolyte quantitatively; consequently, this requires a significant amount of time during the battery manufacturing process.

[0005] However, with the recent increase in the use of batteries such as high-capacity secondary batteries or long cell models that require a significant amount of electrolyte, there have been ongoing attempts to inject an accurate amount of electrolyte within a shorter timeframe. For example, a technology has been developed to perform electrolyte injection and impregnation in a short time by injecting the electrolyte into a fixed battery case at a high vacuum pressure and high pressure at a rapid injection speed. However, this technology has a problem in that the electrolyte is not injected quantitatively when the amount of electrolyte is increased to 200g or more. To solve this problem, injection is performed in two separate stages; while increasing the injection speed allows for quantitative control of the injected electrolyte amount, this method has limitations in that the rapid injection speed causes the battery cells to collide, resulting in the injected electrolyte splashing out and causing electrolyte loss and contamination of the inside and outside of the case. Therefore, there is a need for a technology that can quantitatively inject electrolyte within a short timeframe without contamination of the inside and outside of the battery when injecting large-capacity electrolytes of 200g or more. Prior art literature

[0007] Republic of Korea Published Patent Application No. 10-2019-0060214 The problem to be solved

[0008] Accordingly, the objective of the present invention is to provide a technology that can quantitatively inject a large-capacity electrolyte of 200g or more into a battery case in a short period of time during the manufacture of a secondary battery. means of solving the problem

[0010] In order to solve the aforementioned problem,

[0011] In one embodiment of the present invention,

[0012] A step of first injecting an electrolyte into a battery case into which an electrode assembly is inserted, at a preset injection amount;

[0013] A step of injecting the electrolyte a second time into the battery case into which the electrolyte has been injected a first time; and

[0014] The step of sealing the battery case into which the electrolyte has been secondarily injected, wherein

[0015] The present invention provides a method for manufacturing a secondary battery in which, when the electrolyte injection is performed for the n+1th time, a correction value is calculated from the average value of the electrolyte injection amounts injected for the first time from the nath time (where 10≤a≤20 is an integer) to the nth time, and the calculated correction value is reflected in a preset amount of the second electrolyte injection.

[0017] Here, the average value of the first injected electrolyte amount is,

[0018] A step of calculating the average injection value (A) and standard deviation (σ) of the first-stage electrolyte injection amounts from the na-th (wherein an integer of 10≤a≤20) to the n-th;

[0019] A step of establishing a confidence interval from the calculated average main value (A) and standard deviation (σ);

[0020] The above average injection value (A) and standard deviation (σ) can be obtained by the step of selecting only the values ​​belonging to the set confidence interval among the a primary electrolyte injection amounts used in calculating the above average injection value (A) and standard deviation (σ), and calculating the confidence interval average value, which is the average value of the selected values.

[0021] In addition, the above correction value may be the average value of the confidence interval of the primary electrolyte injection amount, the sum of the preset secondary electrolyte injection amount and the deviation of the total electrolyte injection amount.

[0022] In addition, the method for manufacturing the above secondary battery is performed using a pump-type injection device that injects an electrolyte through a syringe, and the amount of electrolyte injected secondarily can be controlled by calculating a driving value of the syringe according to a correction value, and operating the syringe by reflecting the calculated driving value in a preset syringe driving value.

[0023] Meanwhile, the method for manufacturing a secondary battery according to the present invention may further include a step of measuring the amount of the first injected electrolyte after the step of first injecting the electrolyte into the battery case, and may further include a step of storing the measured amount of the first injected electrolyte after the step of measuring the amount of the first injected electrolyte.

[0024] In addition, the amount of the second electrolyte injected may be 10 to 60 weight percent of the total amount of electrolyte injected, and specifically, 20 to 40 weight percent of the total amount of electrolyte injected.

[0025] In addition, the total amount of electrolyte injected into the battery case may be 200g or more.

[0026] In addition, the total time for injecting the total electrolyte into the battery case may be less than 3 seconds. Effects of the invention

[0028] The secondary battery manufacturing method according to the present invention injects a large amount of electrolyte in two separate injections, and by correcting the amount of the second injection of the electrolyte by reflecting the average value of the first injection amount of the electrolyte injected in the previous injection, the electrolyte can be injected quantitatively within a short period of time. Therefore, when manufacturing a battery in which more than 200g of electrolyte is injected, such as a large-capacity secondary battery or a long-cell model secondary battery, the defect rate can be significantly reduced, and the performance of the secondary battery can be further improved. Specific details for implementing the invention

[0030] The present invention is capable of various modifications and may have various embodiments, and specific embodiments are to be described in detail in the detailed description.

[0031] However, this is not intended to limit the invention to specific embodiments, and it should be understood that it includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0032] In the present invention, terms such as "comprising" or "having" are intended to specify the existence of the features, numbers, steps, actions, components, parts, or combinations thereof described in the specification, and should be understood as not excluding in advance the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof.

[0033] Furthermore, in the present invention, when a part such as a layer, film, region, or plate is described as being "on" another part, this includes not only cases where it is "immediately above" the other part, but also cases where there is another part in between. Conversely, when a part such as a layer, film, region, or plate is described as being "under" another part, this includes not only cases where it is "immediately below" the other part, but also cases where there is another part in between. Additionally, in the present application, being "placed on" may include cases where it is placed on the lower part as well as on the upper part.

[0034] In the present invention, "ppm" refers to the number of secondary batteries produced per minute, which can represent process efficiency. For example, 15 ppm may mean producing 15 secondary batteries per minute.

[0035] In addition, in the present invention, "total injection time" refers to the time during which the electrolyte is injected into the battery case through the syringe of the injection device when the electrolyte is injected into the battery case, and the time during which the amount of electrolyte injected is calculated and the piston of the syringe is adjusted according to the calculated amount of electrolyte may be excluded.

[0037] The present invention will be described in more detail below.

[0039] Method for manufacturing a secondary battery

[0040] In one embodiment of the present invention,

[0041] A step of first injecting an electrolyte into a battery case into which an electrode assembly is inserted, at a preset injection amount;

[0042] A step of injecting the electrolyte a second time into the battery case into which the electrolyte has been injected a first time; and

[0043] The step of sealing the battery case into which the electrolyte has been secondarily injected, wherein

[0044] The present invention provides a method for manufacturing a secondary battery in which, when the electrolyte injection is performed for the n+1th time, a correction value is calculated from the average value of the electrolyte injection amounts injected for the first time from the nath time (where 10≤a≤20 is an integer) to the nth time, and the calculated correction value is reflected in a preset electrolyte injection amount to determine the amount of electrolyte injected for the second time.

[0046] A method for manufacturing a secondary battery according to the present invention is a method for injecting an electrolyte through a pump-type injection device that injects the electrolyte through a syringe, and includes the step of injecting the electrolyte twice into a battery case into which an electrode assembly is inserted. Specifically, the manufacturing method includes the step of first injecting the electrolyte into the battery case into which the electrode assembly is inserted with a preset injection amount; the step of secondarily injecting the electrolyte into the battery case into which the electrolyte was first injected; and the step of sealing the battery case into which the electrolyte was secondarily injected.

[0047] The present invention allows for more quantitative control of the total amount of electrolyte injected compared to the case where the electrolyte is injected at once by injecting a large volume of electrolyte in two stages, and can improve the processability and productivity of the operation compared to the case where the electrolyte is injected in three or more stages.

[0048] In addition, in the above manufacturing method, the step of first injecting the electrolyte is a process in which the electrolyte is first injected according to a preset amount of electrolyte injection, and the preset amount of electrolyte injected at this time may be 40 to 90 weight% with respect to the total amount of electrolyte, and specifically may be 60 to 20 weight%. By adjusting the first injection amount of the electrolyte to 40 weight% or more of the total amount of electrolyte, the present invention can prevent the accuracy of the electrolyte injection amount from decreasing due to an increased correction error in the second injection amount.

[0049] Conventional technologies for split-dose electrolyte injection mostly involve injecting most of the electrolyte during the first injection and then supplementing the shortfall in the total electrolyte amount during the second injection, resulting in a first electrolyte injection amount exceeding 95%. However, in this case, although the total amount of electrolyte injected is quantitatively controlled, since additional electrolyte is injected using a high-pressure pump into a battery case that has already been injected with a significant amount of electrolyte, the electrolyte splashes out, potentially causing electrolyte loss and contamination of the inside and outside of the case. Furthermore, the production efficiency of the battery may decrease depending on the electrolyte injection speed due to the excessive first electrolyte injection. However, the present invention can improve these problems by controlling the first electrolyte injection amount to 90% by weight or less of the total electrolyte amount.

[0050] The present invention allows for the injection of an excess amount of electrolyte in divided doses, and by using the average value of the amounts of electrolyte previously injected into the battery case when injecting the second electrolyte, the electrolyte can be injected quantitatively at a rapid speed without contamination by the electrolyte.

[0051] Specifically, when the electrolyte injection is performed for the n+1th time, the present invention calculates a correction value from the average value of the electrolyte injection amounts injected first from the nath time (wherein an integer of 10 ≤ a ≤ 20) to the nth time, and determines the amount of electrolyte injected secondly by reflecting the calculated correction value.

[0052] Here, the average value of the first injected electrolyte amount may be derived from the amount of electrolyte first injected into the previous battery case, and specifically, may be derived from the first electrolyte injection amount of the previous 10 to 20 battery cases of the battery case in which the electrolyte is being injected.

[0053] For example, in the secondary battery manufacturing process, the amount of secondary electrolyte injected into the 21st battery case can be obtained from the 10 amounts of primary electrolyte injected from the 11th battery case to the 20th battery case in which the electrolyte was previously injected.

[0054] In addition, the average value of the first injected electrolyte amount is,

[0055] A step of calculating the average injection value (A) and standard deviation (σ) of the first-stage electrolyte injection amounts from the na-th (wherein an integer of 10≤a≤20) to the n-th;

[0056] A step of establishing a confidence interval from the calculated average main value (A) and standard deviation (σ);

[0057] The above average injection value (A) and standard deviation (σ) can be obtained by selecting only the values ​​belonging to the set confidence interval among the a primary electrolyte injection amounts used in calculating the above average injection value (A) and standard deviation (σ), and calculating the confidence interval average value, which is the average value of these.

[0058] Specifically, first, the average injection value (A) and standard deviation (σ) of the primary injection amount of electrolyte for 10 to 20 previous battery cases injected with electrolyte are calculated, and a confidence interval (CI) can be established from the calculated average injection value (A) and standard deviation (σ). Here, the confidence interval is a range reflecting the standard deviation (σ) in the calculated average injection value (A), wherein the lower limit is greater than the value obtained by subtracting the standard deviation (σ) from the average injection value (A), and the upper limit is smaller than the value obtained by adding the standard deviation (σ) to the average injection value (A) (A-σ). <CI<A+σ). 다음으로, 평균 주액값(A)과 표준 편차(σ)을 산출하는데 사용된 10~20개의 1차 전해액 주입량 중 설정된 신뢰구간(CI)에 존재하는 값만을 선별하고, 선별된 1차 전해액 주입량들의 평균값을 계산하여 신뢰구간 평균값(CIA)을 산출할 수 있다.

[0059] The present invention can significantly reduce the defect rate of a battery compared to the case where the amount of the second electrolyte injected is determined by reflecting only the amount of the first electrolyte injected into the battery case, by using the average value of the confidence interval (CIA) calculated in this way as the average value of the amount of the first injected electrolyte.

[0060] In addition, the average value of the first injected electrolyte amount, i.e., the confidence interval mean value (CIA), is used to calculate a correction value. Specifically, the present invention can calculate a correction value by the deviation of the total electrolyte injection amount from the sum of the confidence interval mean value of the first electrolyte injection amount and the preset second electrolyte injection amount.

[0061] For example, if the preset values ​​for the primary electrolyte injection amount and the secondary electrolyte injection amount are 200g and 100g, respectively, and the confidence interval average value (CIA) of the primary electrolyte injection amount injected into the previous battery cases is 200.1, a deviation of 0.1g of the total electrolyte injection amount (300g) can be calculated as a correction value.

[0062] The correction value calculated in this way is reflected in the preset secondary electrolyte injection amount, and the electrolyte can be secondarily injected into the battery case with the secondary electrolyte injection amount reflecting the correction value.

[0063] Specifically, the method for manufacturing a secondary battery according to the present invention utilizes a pump-type injection device in which an electrolyte is injected into a battery case through a syringe. The pump-type injection device includes a first syringe for primarily injecting an electrolyte into a battery case; and a second syringe for secondarily injecting an electrolyte into a battery case into which the electrolyte has been primarily injected. The first syringe and the second syringe are each equipped with a high-pressure pump to inject an electrolyte into the battery case in a preset amount. Here, the movement value of a piston provided inside each syringe is set in units of the electrolyte injection amount per mm according to the preset electrolyte injection amount. The present invention converts a correction value into the electrolyte injection amount per mm of the piston movement distance provided in the second syringe, and reflects this in the preset piston movement value of the second syringe to operate it, thereby allowing it to be reflected in the secondary electrolyte injection amount injected into the battery case.

[0065] Meanwhile, the total amount of electrolyte injected into the battery case in the present invention may be 200g or more, and specifically, 250g or more, 300g or more, 400g or more, 200~1,000g, 300~1,000g, 200~500g, 300~800g, or 300~500g.

[0066] In addition, the amount of the secondary electrolyte injected may be 10 to 60 weight percent of the total amount of electrolyte injected, and specifically, 20 to 40 weight percent. By controlling the secondary amount of electrolyte injection to 10 weight percent or more of the total amount of electrolyte, the present invention can prevent the accuracy of the electrolyte injection amount from decreasing due to an increased correction error in the secondary injection amount. Furthermore, by controlling the secondary amount of electrolyte injection to 60 weight percent or less of the total amount of electrolyte, it is possible to prevent the battery case from being contaminated internally or externally by the electrolyte during the secondary electrolyte injection, or to prevent a decrease in the production efficiency of the battery.

[0067] In addition, the time required for the battery case into which the electrode assembly is inserted to be fixed and for the electrolyte to be fully injected may be less than 3 seconds, specifically 2.5 seconds or less, 2 seconds or less, 0.5 to 2.5 seconds, 1 to 2.5 seconds, or 1.5 to 2.5 seconds. In the present invention, the time required from the first injection step of injecting the electrolyte to the sealing step of the secondary battery into which the electrolyte has been injected includes the time for injecting the electrolyte into the secondary battery case (the sum of the first injection and second injection times) and the time for calculating and controlling the injection amount for the second injection after the first injection. The present invention can maximize the manufacturing efficiency and productivity of the secondary battery by controlling the total time for the electrolyte injection to be less than 3 seconds, and can prevent the degradation of the battery's performance by minimizing the time the electrolyte is exposed to air.

[0068] Furthermore, in the method for manufacturing a secondary battery according to the present invention, after the step of first injecting an electrolyte into the battery case, the method may further include a step of measuring the amount of the first injected electrolyte.

[0069] Specifically, in the present invention, when a battery case is fixed / mounted to a pump-type injection device used to inject an electrolyte into a battery case through a syringe, the weight of the battery case with the electrode assembly inserted is measured before injecting the electrolyte, and the amount of the first injected electrolyte can be measured by continuously measuring the weight after injecting the electrolyte into the battery case with the measured weight.

[0070] At this time, the measured amount of primary electrolyte injected does not affect the amount of secondary electrolyte injected into the battery case, but it may be measured to correct the amount of secondary electrolyte injected into the battery cases to which the electrolyte will be injected thereafter. To this end, after the step of measuring the amount of primary injected electrolyte, a step of storing the measured amount of primary electrolyte injected may be further included.

[0072] The method for manufacturing a secondary battery according to the present invention involves injecting a large volume of electrolyte in two separate injections, and by correcting the second injection amount of the electrolyte by reflecting the average value of the first injection amount of the electrolyte injected in the previous injection, the electrolyte can be injected quantitatively within a short period of time. Therefore, when manufacturing a battery in which 200g or more of electrolyte is injected, such as a large-capacity secondary battery or a long-cell model secondary battery, the defect rate can be significantly reduced to a level of 15 ppm or less, and the performance of the secondary battery can be further improved.

[0074] The present invention will be explained in more detail below through examples and comparative examples.

[0075] However, the following examples and comparative examples are merely illustrative of the present invention, and the content of the present invention is not limited to the following examples and comparative examples.

[0077] Examples 1 to 3.

[0078] A secondary battery was manufactured using a pump-type electrolyte injection device that includes a first syringe for first injecting an electrolyte into a battery case and a second syringe for second injecting an electrolyte into the battery case into which the electrolyte was first injected, wherein the first syringe and the second syringe are each equipped with a high-pressure pump.

[0079] Specifically, 100 battery cases with electrode assemblies inserted were prepared, and the prepared battery cases were mounted on the pump-type electrolyte injection device described above. Then, 300g of electrolyte was injected into each battery case, and the battery cases with the injected electrolyte were sealed to manufacture a secondary battery. At this time, when injecting the secondary electrolyte, the average injection value (A) and standard deviation (σ) were calculated from the primary injection amount of the 10 battery cases (n-th to n+10-th batteries) into which the electrolyte was injected prior to the injection of the electrolyte into the corresponding battery case (n+1-th battery). After establishing a confidence interval using the calculated average injection value (A) and standard deviation (σ), values ​​satisfying the confidence interval were selected from the 10 primary electrolyte injection amounts used to calculate the average injection value (A), and their average value was derived as the confidence interval average value (CIA). The derived average value (CIA) was added to the preset secondary electrolyte injection amount, and the deviation from the total electrolyte injection amount (300g) was calculated as a correction value. The correction value was converted into an electrolyte injection amount per mm of piston movement distance of the second syringe equipped in the electrolyte injection device, and the amount of secondary electrolyte injected into the battery case was controlled by reflecting this in the preset piston movement value of the second syringe and operating it.

[0080] In addition, the conditions for the first and second electrolyte injections were pre-set as shown in Table 1 below, and electrolytes were injected into 100 battery cases each. The total amount of electrolyte finally injected was measured for the fabricated secondary batteries to evaluate pump accuracy and injection volume dispersion, which are shown in Table 1. Furthermore, upon visual inspection of the exterior of each manufactured secondary battery, it was confirmed that the interior and exterior of the secondary battery of Example 3 were contaminated.

[0081] 1st injection 2nd injection Pump accuracy Fluid volume variation Injection volume Weekly payment time Injection volume Weekly payment time Example 1 200g 2 seconds 100g 1 second ±0.5% ±0.5g Example 2 150g 1.5 seconds 150g 1.5 seconds ±0.5% ±0.75g Example 3 285g 3 seconds 15g 0.2 seconds ±0.5% ±0.08g

[0083] Comparative Example 1.

[0084] A secondary battery was manufactured by including a syringe for injecting electrolyte into a battery case, and using a pump-type electrolyte injection device combined with a high-pressure pump for the syringe.

[0085] Specifically, 100 battery cases with electrode assemblies inserted were prepared, and the prepared battery cases were mounted on the pump-type electrolyte injection device described above. Then, 300g of electrolyte was injected into each battery case at once for 3 seconds, and the battery cases injected with electrolyte were sealed to manufacture a secondary battery.

[0086] As a result of measuring the total amount of electrolyte finally injected into 100 manufactured secondary batteries, it was confirmed that the pump accuracy and the variation in injection volume were ±0.5% and ±1.5g, respectively. These results indicate that when injecting a large volume of electrolyte of 200g or more in a short period of time, the pump accuracy is high, but the actual amount of electrolyte injected into the battery case is not uniform.

[0088] Comparative Example 2.

[0089] A secondary battery was manufactured using a pump-type electrolyte injection device that includes a first syringe for first injecting an electrolyte into a battery case and a second syringe for second injecting an electrolyte into the battery case into which the electrolyte was first injected, wherein the first syringe and the second syringe are each equipped with a high-pressure pump.

[0090] Specifically, 100 battery cases with electrode assemblies inserted were prepared, and the prepared battery cases were mounted on the pump-type electrolyte injection device described above. Then, 300g of electrolyte was injected into each battery case, and the battery cases with the injected electrolyte were sealed to manufacture a secondary battery. At this time, when injecting the secondary electrolyte, the amount of primary electrolyte injected into the corresponding battery case was measured, and the difference between the measured amount of primary electrolyte injected and the total amount of electrolyte injected (300g) was applied as the amount of secondary electrolyte injected.

[0091] As a result of measuring the total amount of electrolyte finally injected into 100 manufactured secondary batteries, it was confirmed that the pump accuracy and the variation in injection volume were ±0.5% and ±1.9g, respectively. These results indicate that when injecting a large volume of electrolyte of 200g or more in a short period of time, the pump accuracy is high, but the actual amount of electrolyte injected into the battery case is not uniform.

[0093] Although the present invention has been described above with reference to preferred embodiments, those skilled in the art or those with ordinary knowledge in the art will understand that various modifications and changes can be made to the present invention without departing from the spirit and technical scope of the invention as described in the claims set forth below.

[0094] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be determined by the claims.

Claims

Claim 1 A step of first injecting an electrolyte into a battery case into which an electrode assembly is inserted with a preset injection amount; a step of secondarily injecting an electrolyte into the battery case into which the electrolyte has been first injected; The method includes the step of sealing a battery case into which electrolyte is secondarily injected, wherein, when the electrolyte injection is performed as the n+1th time, the amount of the secondly injected electrolyte is determined by calculating a correction value from the average value of the firstly injected electrolyte amounts from the nath (where n is an integer greater than a) to the nth, and reflecting the calculated correction value in a preset secondly injected electrolyte amount; the average value of the firstly injected electrolyte amounts comprises the steps of: calculating the average injection value (A) and standard deviation (σ) of the firstly injected electrolyte amounts from the nath (where n is an integer greater than a) to the nth; setting a confidence interval from the calculated average injection value (A) and standard deviation (σ); selecting only the values ​​belonging to the set confidence interval among the a firstly injected electrolyte amounts used in calculating the average injection value (A) and standard deviation (σ), and the average value thereof A method for manufacturing a secondary battery, wherein the total amount of electrolyte injected into the battery case is 200g or more, obtained by the step of calculating the average value of the confidence interval. Claim 2 delete Claim 3 A method for manufacturing a secondary battery according to claim 1, characterized in that the correction value is the average value of the confidence interval of the primary electrolyte injection amount, the sum of the preset secondary electrolyte injection amount and the deviation of the total electrolyte injection amount. Claim 4 A method for manufacturing a secondary battery according to claim 1, wherein the method is performed using a pump-type injection device that injects an electrolyte through a syringe, and the amount of electrolyte injected secondarily is controlled by calculating a driving value of the syringe according to a correction value and operating the syringe by reflecting the calculated driving value in a preset syringe driving value. Claim 5 A method for manufacturing a secondary battery according to claim 1, further comprising the step of measuring the amount of the first injected electrolyte after the step of first injecting the electrolyte into the battery case. Claim 6 A method for manufacturing a secondary battery according to claim 5, further comprising the step of storing the measured amount of primary electrolyte injected after the step of measuring the amount of primary electrolyte injected. Claim 7 A method for manufacturing a secondary battery according to claim 1, wherein the amount of the electrolyte injected secondarily is 10 to 60 weight% of the total amount of electrolyte injected. Claim 8 A method for manufacturing a secondary battery according to claim 1, wherein the amount of the electrolyte injected secondarily is 20 to 40 weight% of the total amount of electrolyte injected. Claim 9 delete Claim 10 A method for manufacturing a secondary battery according to claim 1, wherein the total injection time of the electrolyte is less than 3 seconds.