Method of manufacturing secondary battery for improving the wetting property of electrolyte

Abstract

The present invention relates to a method for manufacturing a secondary battery for improving the impregnation of an electrolyte, wherein the reactivity of the electrolyte is increased by solidifying the electrolyte during the pre-aging step and then liquefying it, thereby having the effect of increasing the impregnation of the electrolyte into the electrode assembly within the secondary battery.

Description

Technology Field

[0001] The present invention relates to a method for manufacturing a secondary battery for improving the impregnation properties of an electrolyte. Background Technology

[0003] As technology development and demand for mobile devices increase, the demand for batteries as an energy source is rapidly rising, and accordingly, much research is being conducted on batteries that can meet various requirements.

[0004] In terms of battery shape, there is high demand for prismatic and pouch-type rechargeable batteries, which are thin and suitable for applications in products such as mobile phones. In terms of materials, there is high demand for lithium-ion batteries and lithium-ion polymer batteries, which possess advantages such as high energy density, discharge voltage, and output stability.

[0005] In particular, recently it has been attracting a lot of attention due to reasons such as low manufacturing costs, small weight, and easy shape deformation, and its usage is also gradually increasing.

[0006] These secondary batteries are manufactured by embedding an electrode assembly into a battery case, injecting an electrolyte, impregnating it to produce a battery cell, and then undergoing an activation process.

[0007] Conventionally, to manufacture a secondary battery, an electrolyte was injected, and then the electrolyte located at the bottom was drawn up to the top and wetted by injecting the electrolyte into the battery cell. In order to properly wet the active material in the electrode with the electrolyte, the battery cell was placed in a wetting chamber, and an impregnation process was performed by applying vacuum pressure, and then vacuum sealing was performed to manufacture the battery cell.

[0008] In addition, to improve the electrolyte impregnation, the activation process undergoes an aging process at room temperature for 2 to 3 days before the charge / discharge step. The aging process performed before the charge / discharge step is known to have the greatest influence on improving the electrolyte impregnation.

[0009] Meanwhile, in the above aging process, the battery cell is performed while standing upright in a tray. Since the battery cell is standing upright, the electrolyte tends to pool at the bottom of the battery cell, resulting in insufficient impregnation of the entire electrode assembly and thus affecting the performance of the battery cell.

[0010] Therefore, there is a need to develop technology that can improve the impregnation of the electrolyte during the aging process performed prior to the activation process of the battery cell. Prior art literature

[0012] Republic of Korea Published Patent No. 2015-0049479 The problem to be solved

[0013] In order to solve the problems of the prior art as described above, the present invention aims to provide a method for manufacturing a secondary battery for improving the impregnation of an electrolyte during a pre-aging step performed before the activation process of the secondary battery. means of solving the problem

[0015] The present invention provides a method for manufacturing a secondary battery for improving the impregnation properties of an electrolyte. In one example, the method for manufacturing a secondary battery according to the present invention comprises: a first pre-aging step of aging a secondary battery into which an electrolyte has been injected at a temperature (T1) below the freezing point of the electrolyte; a second pre-aging step of aging the secondary battery that has undergone the first pre-aging at a temperature (T2) above the freezing point of the electrolyte; and a charge-discharge step of charging and discharging the secondary battery that has undergone the second pre-aging.

[0016] In a specific example, the first pre-aging step is performed in a temperature range of -50 ℃ to -10 ℃, and the second pre-aging step can be performed in a temperature range of -20 to 60 ℃.

[0017] In addition, the first pre-aging step may be performed for 0.5 to 12 hours, and the second pre-aging step may be performed for 6 to 24 hours.

[0018] In another example, the process includes performing a second pre-aging step after the first pre-aging step, and the process can be repeated n times (n is an integer greater than or equal to 2).

[0019] Meanwhile, the method for manufacturing a secondary battery according to the present invention may further include an aging step of the charged and discharged secondary battery at a temperature range of 20 to 60 ℃ after the charge and discharge step. Furthermore, the method for manufacturing a secondary battery according to the present invention may further include a degassing step of performing a degassing process to remove gas generated inside the secondary battery after the aging step.

[0020] In one example, the electrolyte injected into the secondary battery comprises a non-aqueous solvent and a lithium salt. In a specific example, the non-aqueous solvent may be one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. In addition, the lithium salt is F - , Cl - , Br - , I - , NO3- , N(CN)2 - , BF4 - , ClO4 - , PF6 - , (CF3)2PF4 - , (CF3)3PF3 - , (CF3)4PF2 - , (CF3)5PF - , (CF3)6P - , CF3SO3 - , CF3CF2SO3 - , (CF3SO2)2N - , (FSO2)2N - , CF3CF2(CF3)2CO - , (CF3SO2)2CH - , (SF5)3C - , (CF3SO2)3C - , CF3(CF2)7SO3 - , CF3CO2 - , CH3CO2 - , SCN - and (CF3CF2SO2)2N - It may be one or more types selected from a group consisting of

[0021] In one example, the secondary battery may be a pouch-type battery cell. In a specific example, the pouch-type battery cell may have a structure in which a gas pocket is formed on one side that communicates with the interior of the battery cell.

[0022] Furthermore, the method for manufacturing a secondary battery according to the present invention may include the step of sealing the secondary battery and removing the gas pocket after the charge / discharge step. Effects of the invention

[0024] According to the method for manufacturing a secondary battery for improving the impregnation of an electrolyte according to the present invention, by solidifying the electrolyte during the pre-aging step and then liquefying it, the reactivity of the electrolyte is increased, thereby having the effect of increasing the impregnation of the electrolyte into the electrode assembly within the secondary battery. Brief explanation of the drawing

[0026] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. FIG. 2 is a flowchart schematically illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. Figure 3 is a graph showing the cycle evaluation results of the embodiments and comparative examples of the present invention. Specific details for implementing the invention

[0027] The present invention is capable of various modifications and may take various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. However, this is not intended to limit the invention to the specific disclosed forms, and it should be understood that the invention includes all modifications, equivalents, and substitutions that fall within the spirit and scope of the invention.

[0028] In this application, 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 precluding the existence or addition of one or more other features, numbers, steps, actions, components, parts, or combinations thereof. Furthermore, 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 this application, being placed "on" may include cases where it is placed on the lower part as well as on the upper part.

[0030] The present invention relates to a method for manufacturing a secondary battery for improving the impregnation properties of an electrolyte.

[0031] Conventionally, to manufacture a secondary battery, an electrode assembly is placed in an electrode case, an electrolyte is injected, the electrolyte is impregnated into the electrode assembly, and then the battery is manufactured through an activation process. Meanwhile, to improve the electrolyte impregnation of the electrode assembly, the secondary battery injected with the electrolyte undergoes an aging process at room temperature for 2 to 3 days before the charge-discharge stage during the activation process of the secondary battery. In particular, the aging process performed before the charge-discharge is known to have a significant impact on improving the electrolyte impregnation.

[0032] However, in the above aging process, the secondary battery is performed while standing upright in a tray. In this case, the electrolyte tends to accumulate at the bottom of the secondary battery, resulting in insufficient impregnation of the electrolyte throughout the electrode assembly and thus affecting the performance of the battery cell.

[0033] Accordingly, the present invention provides a method for manufacturing a secondary battery to improve the impregnation of an electrolyte during a pre-aging step performed prior to the activation process of the secondary battery. More specifically, the method for manufacturing a secondary battery according to the present invention can increase the impregnation of the electrolyte into an electrode assembly within the secondary battery by increasing the reactivity of the electrolyte by solidifying and then liquefying the electrolyte during the pre-aging step.

[0035] Hereinafter, a method for manufacturing a secondary battery for improving the impregnation properties of an electrolyte according to the present invention will be described in detail.

[0036] FIG. 1 is a flowchart schematically illustrating a method for manufacturing a secondary battery according to one embodiment of the present invention.

[0037] Referring to FIG. 1, a method for manufacturing a secondary battery according to the present invention comprises: a first pre-aging step (S10) of aging a secondary battery into which an electrolyte has been injected at a temperature (T1) below the freezing point of the electrolyte; a second pre-aging step (S20) of aging the secondary battery that has undergone the first pre-aging at a temperature (T2) above the freezing point of the electrolyte; and a charge / discharge step (S30) of charging and discharging the secondary battery that has undergone the second pre-aging.

[0038] The method for manufacturing a secondary battery according to the present invention can induce a phase transition of the electrolyte according to a temperature change during the pre-aging step, and increase the reaction rate of the electrolyte in this process to increase the impregnation of the electrolyte into the electrode assembly within the secondary battery. In a specific example, in the method for manufacturing a secondary battery according to the present invention, the pre-aging step performed before the charge / discharge step can be divided into a first pre-aging step and a second pre-aging step. In the first pre-aging step, the aging temperature can be cooled to a temperature (T1) below the freezing point to solidify the electrolyte. Then, in the second pre-aging step, the aging temperature can be increased to a temperature (T2) exceeding the freezing point of the electrolyte to liquefy the solidified electrolyte.

[0039] At this time, during the second pre-aging stage, a phase change of the electrolyte occurs due to an endothermic reaction. In a specific example, during the second pre-aging stage, the solidified electrolyte undergoes a phase change from solid to liquid due to an endothermic reaction. During this phase change process, the internal energy of the electrolyte increases, and the entropy also increases. Accordingly, the reaction rate of the electrolyte impregnating the electrode assembly during the second pre-aging stage increases, thereby increasing the impregnation of the electrolyte into the electrode assembly.

[0040] Furthermore, the method for manufacturing a secondary battery according to the present invention can also increase the performance of the battery cell by increasing the impregnation of the electrolyte into the electrode assembly.

[0041] The above secondary battery may be configured in a form in which an electrode assembly and an electrolyte are housed within a battery case. Meanwhile, the pre-aging step may include a process for manufacturing the secondary battery. Specifically, an electrode assembly comprising an electrode active material and a binder is coated onto an electrode current collector to manufacture a positive electrode and a negative electrode, respectively, and then a separator is interposed between the positive electrode and the negative electrode to prepare an electrode assembly.

[0042] After placing the electrode assembly prepared in this way into a battery case, the electrolyte is injected, and the battery case is sealed to manufacture the battery.

[0043] The steps for manufacturing such batteries are not particularly limited and can be performed according to known methods.

[0044] In addition, the electrode assembly is not particularly limited as long as it has a structure including an anode, a cathode, and a separator interposed between the anode and the cathode, and may be, for example, a jelly-roll type, a stack type, or a stack / folding type.

[0045] The above-mentioned battery case is not particularly limited as long as it is used as an outer material for packaging the battery, and may be cylindrical, prismatic, or pouch-type. For example, in the present invention, the secondary battery may be a pouch-type battery.

[0046] The above electrolyte comprises an organic solvent and a lithium salt, and may optionally further comprise an additive.

[0047] The above organic solvent is not limited as long as it minimizes decomposition due to oxidation reactions, etc. during the charging and discharging process of the battery, and may be, for example, cyclic carbonates, linear carbonates, esters, ethers, or ketones. These may be used alone or two or more may be used in combination.

[0048] Among the above organic solvents, carbonate-based organic solvents may be particularly preferred. Examples of cyclic carbonates include ethylene carbonate (EC), propylene carbonate (PC), and butylene carbonate (BC), while examples of linear carbonates include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), ethylmethyl carbonate (EMC), methylpropyl carbonate (MPC), and ethylpropyl carbonate (EPC).

[0049] The above lithium salts may be used without limitation as lithium salts commonly used in the electrolytes of lithium secondary batteries, such as LiPF6, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiBF4, LiBF6, LiSbF6, LiN(C2F5SO2)2, LiAlO4, LiAlCl4, LiSO3CF3, and LiClO4, and may be used individually or in combination of two or more types.

[0050] Additionally, the electrolyte may optionally contain additional additives. For example, to stably form the SEI film, any one selected from the group consisting of vinylene carbonate, vinylethylene carbonate, fluoroethylene carbonate, cyclic sulfite, saturated sulfone, unsaturated sulfone, acyclic sulfone, lithium oxalyl difluoroborate (LiODFB), and derivatives thereof, or a mixture of two or more of these, may be used as the additive, but is not limited thereto.

[0051] Examples of the above-mentioned cyclic sulfites include ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, 1,3-butylene glycol sulfite, etc. Examples of saturated sulfones include 1,3-propane sulfone, 1,4-butane sulfone, etc. Examples of unsaturated sulfones include ethene sulfone, 1,3-propene sulfone, 1,4-butene sulfone, 1-methyl-1,3-propene sulfone, etc. Examples of acyclic sulfones include divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, methyl vinyl sulfone, etc. there is.

[0052] These additives are added to the electrolyte to improve low-temperature output characteristics by forming a robust SEI film on the cathode, as well as to suppress the decomposition of the anode surface that may occur during high-temperature cycle operation and to prevent oxidation reactions of the electrolyte.

[0053] Meanwhile, in the present invention, the term "aging step" refers to the process of storing the manufactured secondary battery at a predetermined temperature. In a specific example, when the secondary battery is charged, electrons travel along a wire to the negative electrode and become charged; in order to achieve charge neutrality, lithium ions are intercalated at the negative electrode. At this time, lithium ions can be intercalated in the area where the electrolyte is impregnated, that is, the area where the ion movement path is maintained (wetting area), but intercalation becomes relatively difficult in the non-wetting area where the electrolyte is not impregnated. Therefore, the battery can be aged through a pre-aging step so that the electrolyte can permeate well into the positive and negative electrodes.

[0054] In one example, the method for manufacturing a secondary battery according to the present invention includes a first pre-aging step (S10) of aging a secondary battery injected with an electrolyte at a temperature (T1) below the freezing point of the electrolyte. At this time, the first pre-aging step may include a process of aging at room temperature so that the electrolyte wets the electrode assembly. However, it is not limited thereto.

[0055] In a specific example, the first pre-aging step (S10) may perform a process of aging at room temperature to wet the electrode assembly with the electrolyte, and then cooling to a temperature range of -50 ℃ to -10 ℃. For example, the first pre-aging step (S10) may be performed at a temperature of -50 ℃ to -10 ℃, -45 ℃ to -12 ℃, -40 ℃ to -14 ℃, -35 ℃ to -16 ℃, -30 ℃ to -18 ℃, -25 ℃ to -20 ℃, or an average temperature of -20 ℃. If the aging temperature in the first pre-aging step exceeds -10 ℃, the freezing point of the electrolyte may be exceeded, and solidification of the electrolyte may not occur. However, the temperature of the pre-aging may vary depending on the type of electrolyte injected into the secondary battery.

[0056] Meanwhile, the first pre-aging step (S10) may be performed for 0.5 to 12 hours. More specifically, the first pre-aging step (S10) may be performed for 0.7 to 6 hours, 0.9 to 3 hours, and 1.3 to 2 hours.

[0057] In one example, the method for manufacturing a secondary battery according to the present invention includes a second pre-aging step (S20) of aging the secondary battery, which has undergone first pre-aging, at a temperature (T2) exceeding the freezing point of the electrolyte. As previously described, the second pre-aging step (S20) is a step for changing the phase of the solidified electrolyte inside the secondary battery into a liquid.

[0058] In a specific example, the second pre-aging step may be performed in a temperature range of -20 to 60 ℃. For example, the second pre-aging step (S20) may be performed at a temperature of -20 ℃ to 60 ℃, -10 ℃ to 55 ℃, 10 ℃ to 50 ℃, 30 ℃ to 45 ℃, 35 ℃ to 42 ℃, or an average of 40 ℃. If the aging temperature in the second pre-aging step is below -20 ℃, the temperature is too low and the solidified electrolyte may not melt, and if it exceeds 60 ℃, the temperature is too high and the electrode assembly inside the secondary battery may be damaged. However, the temperature of the pre-aging may vary depending on the type of electrolyte injected into the secondary battery.

[0059] Meanwhile, the second pre-aging step (S20) may be performed for 6 to 24 hours. More specifically, the second pre-aging step (S20) may be performed for 6 to 24 hours, 8 to 20 hours, 10 to 16 hours, or an average of 12 hours. In particular, during the second pre-aging step, the electrolyte undergoes a phase change from solid to liquid, and accordingly, the reaction rate of wetting the electrode assembly increases, allowing the electrolyte to be easily impregnated into the electrode assembly. In particular, by increasing the reaction rate of the electrolyte, there is an effect of reducing the pre-aging time compared to conventional methods.

[0060] Furthermore, it is preferable to perform the above first and second pre-aging steps before the charge / discharge steps described later. Specifically, if the electrolyte is solidified in the charged state, a short circuit between the positive and negative electrodes may occur due to structural changes in the secondary battery.

[0061] Next, the method for manufacturing a secondary battery according to the present invention includes a charge / discharge step (S30) for charging and discharging a secondary battery that has undergone secondary pre-aging.

[0062] The above charge / discharge step (S30) is a process of stabilizing the battery structure and making the secondary battery, which has undergone the pre-aging step, usable through processes such as charging and discharging. In addition, it is intended to remove defective batteries by measuring the standard deviation of the delta voltage and the OCV (Open Circuit Voltage, no-load voltage), and finally to select the capacity. During the activation process of this secondary battery, a Solid Electrolyte Interface (SEI) film is formed on the surface of the negative electrode. Through this process, the movement of lithium ions at the electrolyte-electrode interface is facilitated, and the decomposition of the electrolyte is suppressed. At this time, regarding the SEI film, reference is made to what is known in the art.

[0063] In one example, the method for manufacturing a lithium secondary battery according to the present invention may further include an aging process step for stabilizing the battery as needed after the formation process and before the degassing step. In a specific example, the aging step may be performed at a temperature of 60°C or lower. Specifically, the aging step may be performed for 3 days at room temperature (25±5°C) or for one day at a temperature of 60°C or lower, specifically between 40°C and 60°C.

[0064] At this time, if the aging process is performed at a low temperature of less than 20℃, the effect of improving the wettability of the secondary battery may be negligible, and if the aging process is performed at a temperature exceeding 60℃, the electrolyte may evaporate or side reactions between the electrolyte and the anode may occur.

[0065] In addition, the method may further include a degassing step for performing a degassing process to remove gases generated inside the secondary battery after the aging step. In a specific example, the method for manufacturing a secondary battery according to the present invention may perform a degassing process to remove gases after the aging process. The degassing process may be performed by a conventional method, thereby removing gases such as carbon dioxide and methane generated during the formation of the SEI film in the charge / discharge stage, as well as gases generated during the aging stage that may cause swelling of the battery later.

[0066] Meanwhile, the method for manufacturing a secondary battery according to the present invention may be a pouch-type battery cell having a structure in which a gas pocket is formed on one side in communication with the interior of the battery cell, and may further include the step of sealing the secondary battery that has undergone the charge / discharge step or the aging step and removing the gas pocket.

[0068] FIG. 2 is a flowchart schematically illustrating a method for manufacturing a secondary battery according to another embodiment of the present invention. Referring to FIG. 2, the method for manufacturing a secondary battery according to the present invention includes a process of performing a second pre-aging step after a first pre-aging step, and the process may be repeated n times (n is an integer greater than or equal to 2). Although the number of repetitions is not fixed, the process may be repeated 2 to 6 times, and for example, may be repeated 2 times.

[0069] The method for manufacturing a secondary battery according to the present invention is intended to improve the impregnation of the electrolyte during the pre-aging process and may repeatedly include the process of solidifying and liquefying the electrolyte.

[0070] For example, the above process may be repeated twice. Specifically, the method for manufacturing a secondary battery according to the present invention may include a first pre-aging step (S11) of aging a secondary battery injected with an electrolyte at a temperature (T1) below the freezing point of the electrolyte, a second pre-aging step (S21) of aging the secondary battery that has undergone first pre-aging at a temperature (T2) above the freezing point of the electrolyte, a first pre-aging step (S12) of aging the secondary battery injected with an electrolyte at a temperature (T1) below the freezing point of the electrolyte, a second pre-aging step (S22) of aging the secondary battery that has undergone first pre-aging at a temperature (T2) above the freezing point of the electrolyte, and a charge / discharge step (S30) of charging and discharging the secondary battery that has undergone second pre-aging. That is, by performing the solidification → liquefaction → solidification → liquefaction process of the electrolyte during the pre-aging process of the present invention, the reactivity of the electrolyte can be increased, thereby increasing the impregnation of the electrolyte into the electrode assembly in the secondary battery.

[0071] As the process for each stage has been explained previously, specific details regarding each stage will be omitted.

[0073] The content of the present invention is described in detail below through examples and drawings, but the following examples and drawings are intended to illustrate the present invention and do not limit the scope of the present invention.

[0075] <Example>

[0076] Example 1.

[0077] Manufacturing of the cathode

[0078] A cathode slurry was prepared by weighing 92.6 parts by weight of graphite as a carbon-based active material, 2.4 parts by weight of SiO as a silicon-based active material, 1 part by weight of carbon black and 0.5 parts by weight of MWCNT as a conductive material, and 3.5 parts by weight of SBR, CMC, and PVP as binders, adding them to distilled water, and mixing. Then, the cathode slurry was applied to a copper (Cu) thin film on the cathode current collector using a slot die, and the cathode was manufactured by drying and rolling.

[0080] Manufacturing of anodes

[0081] Li(Ni as a positive electrode active material 0.8 Mn 0.1 Co 0.1 97.55 parts by weight of O2 (NCM-811), 1 part by weight of carbon black as a conductive material, and 1.45 parts by weight of polyvinylidene fluoride (PVdF) and a conductive material dispersant as binders were mixed and added to N-methylpyrrolidone (NMP) as a solvent to prepare an anode active material slurry. Then, the slurry was coated onto one side of an aluminum current collector with a thickness of 15 μm, and an anode was manufactured by performing drying and rolling under the same conditions as the cathode.

[0083] Manufacturing of lithium secondary batteries

[0084] A non-aqueous electrolyte was prepared by dissolving LiPF6 and LiFSi to a concentration of 1.2 M in an organic solvent mixed with ethylene carbonate (EC), propylene carbonate (PC), and ethyl methyl carbonate (EMC) in a composition of 25:5:70 (volume ratio). Meanwhile, some additives may be additionally included to ensure battery performance.

[0085] Then, a polyolefin separator was interposed between the anode and cathode prepared above, and lamination was performed to first realize a Bi-cell form. Then, 26 Bi-cells were stacked, and a packaging cell was fabricated through welding and packaging processes. At this time, to minimize moisture inside the cell, the cell was stored in a 55°C drying chamber for at least 3 days, and then the electrolyte was injected to manufacture a lithium secondary battery.

[0087] Activation process

[0088] First, the secondary battery injected with electrolyte was stored upright at room temperature for 5 hours. Then, a first pre-aging step was performed at an average temperature of -20°C for an average of 2 hours. Next, a second pre-aging step was performed at an average temperature of 40°C for an average of 12 hours. After that, a degassing process was performed in a vacuum for an average of 15 seconds. Subsequently, a charge-discharge step was carried out. A detailed explanation of this is omitted.

[0090] Example 2.

[0091] A secondary battery was manufactured in the same manner as in Example 1, except that after performing the first pre-aging and second pre-aging, the first pre-aging and second pre-aging processes were performed again.

[0093] Comparative Example 1.

[0094] A secondary battery was manufactured in the same manner as in Example 1, except that the secondary battery injected with electrolyte was stored at room temperature while standing upright for 2 days.

[0096] <Experimental Example>

[0097] Secondary battery cycle evaluation

[0098] A cycle evaluation was performed using the secondary batteries prepared in Examples 1 and 2 and Comparative Example 1. The results are shown in FIG. 3.

[0099] Referring to FIG. 3, it was confirmed that the efficiency of the secondary batteries manufactured in Examples 1 and 2 was superior compared to Comparative Example 1. This appears to be an effect resulting from increased impregnation of the electrolyte into the electrode assembly during the manufacturing of the secondary battery.

[0101] Although the present invention has been described above by limited embodiments and drawings, the present invention is not limited thereto, and it is obvious that various modifications and variations are possible within the scope of the technical spirit of the present invention and the equivalent scope of the claims described below by those skilled in the art to which the present invention belongs.

Claims

Claim 1 A method for manufacturing a secondary battery comprising: a first pre-aging step of aging a secondary battery injected with an electrolyte at a temperature (T1) below the freezing point of the electrolyte; a second pre-aging step of aging the secondary battery that has undergone the first pre-aging at a temperature (T2) above the freezing point of the electrolyte; and a charge / discharge step of charging and discharging the secondary battery that has undergone the second pre-aging, wherein the second pre-aging step is performed in a temperature range of -20 ℃ to 60 ℃. Claim 2 A method for manufacturing a secondary battery according to claim 1, wherein the first pre-aging step is performed in a temperature range of -50 ℃ to -10 ℃. Claim 3 delete Claim 4 A method for manufacturing a secondary battery according to claim 1, wherein the first pre-aging step is performed for 0.5 to 12 hours and the second pre-aging step is performed for 6 to 24 hours. Claim 5 A method for manufacturing a secondary battery according to claim 1, comprising a process of performing a second pre-aging step after a first pre-aging step, wherein the process is repeated n times (n is an integer greater than or equal to 2). Claim 6 A method for manufacturing a secondary battery according to claim 1, further comprising, after the charge-discharge step, an aging step of the charged and discharged secondary battery at a temperature range of 20 to 60 ℃. Claim 7 A method for manufacturing a secondary battery according to claim 6, further comprising a degassing step for performing a degassing process to remove gas generated inside the secondary battery after an aging step. Claim 8 A method for manufacturing a secondary battery according to claim 1, wherein the electrolyte injected into the secondary battery comprises a non-aqueous solvent and a lithium salt. Claim 9 A method for manufacturing a secondary battery according to claim 8, wherein the non-aqueous solvent is one or more selected from the group consisting of ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethylmethyl carbonate (EMC), methylpropyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, gamma-butyrolactone, propylene sulfite, and tetrahydrofuran. Claim 10 A method for manufacturing a secondary battery according to claim 8, wherein the lithium salt is one or more selected from the group consisting of LiPF6, LiAsF6, LiCF3SO3, LiN(CF3SO2)2, LiBF4, LiBF6, LiSbF6, LiN(C2F5SO2)2, LiAlO4, LiAlCl4, LiSO3CF3, and LiClO4. Claim 11 A method for manufacturing a secondary battery according to claim 1, wherein the secondary battery is a pouch-type battery cell and has a structure in which a gas pocket communicating with the interior of the battery cell is formed on one side. Claim 12 A method for manufacturing a secondary battery according to claim 11, comprising the steps of sealing the secondary battery and removing gas pockets after the charge / discharge step.

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