Title of Invention: Secondary Battery Manufacturing Method technical field [One] Cross Citation with Related Applications [2] This application claims the benefit of priority based on Korean Patent Application No. 10-2019-0088452 dated July 22, 2019, and all contents disclosed in the literature of the Korean patent application are incorporated as a part of this specification. [3] technical field [4] The present invention relates to a method for manufacturing a secondary battery. background [5] Recently, with the rapid spread of electronic devices using batteries, such as mobile phones, notebook computers, and electric vehicles, the demand for small, lightweight and relatively high-capacity secondary batteries is rapidly increasing. In particular, a lithium secondary battery has been in the spotlight as a driving power source for a portable device because it is lightweight and has a high energy density. Accordingly, research and development efforts for improving the performance of lithium secondary batteries are being actively conducted. [6] In general, a lithium secondary battery includes a positive electrode, a negative electrode, a separator interposed between the positive electrode and the negative electrode, an electrolyte, an organic solvent, and the like. In addition, the positive electrode and the negative electrode may have an active material layer including a positive electrode active material or a negative electrode active material on a current collector. In general, a lithium-containing metal oxide such as LiCoO 2 , LiMn 2 O 4 is used as a positive electrode active material for the positive electrode, and a carbon-based active material or silicon-based active material that does not contain lithium is used as the negative electrode active material for the negative electrode. [7] In particular, silicon-based active materials are attracting attention in that they have a capacity that is about 10 times higher than that of carbon-based active materials, and due to their high capacity, a high energy density can be realized even with a thin electrode. However, the silicon-based active material is not widely used due to the problems of volume expansion due to charging and discharging, cracking/damage of the active material particles due to this, and deterioration of life-span properties by this. [8] Meanwhile, the secondary battery is manufactured through a process of assembling the secondary battery and a process of activating the secondary battery. In this case, the activation may be performed by injecting an electrolyte into the assembled secondary battery and impregnating it, and charging and discharging the impregnated secondary battery through a charging and discharging device. [9] Through the activation, lithium is inserted into the negative electrode included in the secondary battery, and the electrolyte and lithium salt react on the surface of the negative electrode to generate compounds such as Li 2 Co 3 , Li 2 O, and LiOH. These compounds form a kind of passivation layer on the surface of the anode, and the passivation layer is called a solid electrolyte interface layer (hereinafter referred to as a SEI layer). After the SEI layer is formed, it acts as an ion tunnel to allow lithium ions to pass through, and the lithium ions do not react with the negative electrode or other materials again. has no characteristics. Therefore, through the formation of the SEI layer, no further decomposition of the electrolyte occurs and the amount of lithium ions in the electrolyte is reversibly maintained, so that stable charging and discharging can be maintained. [10] In this regard, when the activation process is performed on the negative electrode to which the silicon-based active material is applied, as described above, since the silicon-based active material has a large degree of volume expansion/contraction due to charging and discharging, the active material is broken or the contact between the active materials is reduced. A new cathode surface can be continuously created. Accordingly, the SEI layer formation reaction continuously occurs on the surface of the new anode. Excessive SEI layer formation may increase the gas generated during the SEI layer formation reaction, and increase the local resistance of the negative electrode due to this gas generation, lithium There is a problem in that the lifespan characteristics of the battery are deteriorated due to precipitation. [11] Therefore, there is a need to develop a silicon-based active material-applied negative electrode and a secondary battery that realizes the high capacity and energy density of the silicon-based active material while improving the stable formation of the SEI layer, charging and discharging performance, and lifespan characteristics. [12] Korean Patent Laid-Open No. 10-2017-0074030 relates to a negative active material for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same, and discloses a negative active material including a porous silicon-carbon composite, but solves the above problems There is a limit to solving it. [13] [Prior art literature] [14] [Patent Literature] [15] Korean Patent Publication No. 10-2017-0074030 DETAILED DESCRIPTION OF THE INVENTION technical challenge [16] One object of the present invention is to provide a method of manufacturing a secondary battery capable of forming a stable SEI layer and improving lifespan characteristics upon activation in a negative electrode and a secondary battery including a silicon-based active material. means of solving the problem [17] The present invention comprises the steps of: forming a secondary battery structure including an electrode assembly including a negative electrode, a positive electrode and a separator, and an electrolyte; and activating the secondary battery structure by charging and discharging in at least one cycle while pressurizing the secondary battery structure to 1.5 MPa to 3.5 MPa, wherein the negative electrode includes a silicon-based active material. Effects of the Invention [18] The method for manufacturing a secondary battery of the present invention is characterized in that in manufacturing a secondary battery including a negative electrode including a silicon-based active material, the secondary battery is pressurized to a specific pressure range during the activation process. According to the present invention, by performing the activation process while pressurizing in the above pressure range, it is possible to suppress the volume expansion of the silicon-based active material and form a stable SEI layer, and to secure a certain level of voids in the negative electrode so that the electrolyte inside is not depleted can do. Accordingly, the lifespan characteristics of the secondary battery manufactured by the above-described method can be remarkably improved. Brief description of the drawing [19] 1 is a graph evaluating the capacity retention rate of secondary batteries of Examples and Comparative Examples. Modes for carrying out the invention [20] The terms or words used in the present specification and claims should not be construed as being limited to their ordinary or dictionary meanings, and the inventor may properly define the concept of the term in order to best describe his invention. Based on the principle that there is, it should be interpreted as meaning and concept consistent with the technical idea of ​​the present invention. [21] The terminology used herein is used to describe exemplary embodiments only, and is not intended to limit the present invention. The singular expression includes the plural expression unless the context clearly dictates otherwise. [22] In the present specification, terms such as "comprise", "comprising" or "have" are intended to designate the presence of an embodied feature, number, step, element, or a combination thereof, but one or more other features or It should be understood that it does not preclude the possibility of the presence or addition of numbers, steps, elements, or combinations thereof. [23] In the present specification, the average particle diameter (D 50 ) may be defined as a particle diameter corresponding to 50% of the cumulative volume in the particle size distribution curve of the particles. The average particle diameter (D 50 ) may be measured using, for example, a laser diffraction method. In general, the laser diffraction method can measure a particle diameter of several mm from a submicron region, and can obtain results of high reproducibility and high resolution. [24] Hereinafter, the present invention will be specifically described. [25] [26] [27] The present invention relates to a method for manufacturing a secondary battery, specifically, to a method for manufacturing a lithium secondary battery. [28] Specifically, the method of manufacturing a secondary battery of the present invention comprises: forming a secondary battery structure including an electrode assembly including a negative electrode, a positive electrode, and a separator, and an electrolyte; and activating the secondary battery structure by charging and discharging in at least one cycle while pressurizing the secondary battery structure to 1.5 MPa to 3.5 MPa, wherein the negative electrode includes a silicon-based active material. [29] According to the manufacturing method of the secondary battery of the present invention, it is characterized in that the secondary battery structure is pressurized to a specific pressure range when the activation process is performed. That is, for activation, the secondary battery structure is pressurized to a specific pressure range during the charging and discharging process to suppress the volume expansion due to the charging and discharging of the silicon-based active material, thereby breaking the active material due to the volume expansion/contraction of the silicon-based active material. It is possible to prevent the falling phenomenon of the active material, the occurrence of the continuous SEI layer generation reaction, the excessive generation of gas due to the reaction, the increase in the local resistance of the negative electrode due to the gas generation, and the deterioration of the lifespan characteristics due to lithium precipitation can be prevented. In addition, when the activation process is performed while pressurizing within the specific pressure range, it is possible to secure an appropriate level of voids in the negative electrode while preventing volume expansion due to charging and discharging of the silicon-based active material, and depletion of the electrolyte due to a decrease in the porosity can be prevented. Therefore, it is preferable to improve the lifespan characteristics. [30] [31] [32] The method for manufacturing a secondary battery of the present invention includes forming an electrode assembly including a negative electrode, a positive electrode, and a separator, and a secondary battery structure including an electrolyte. [33] The electrode assembly includes an anode, an anode, and a separator. Specifically, the electrode assembly may include a negative electrode, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode. [34] The negative electrode includes a silicon-based active material. [35] The silicone-based active material may be a compound represented by the following formula (1). [36] [Formula 1] [37] SiO x (0≤x<2) [38] In Formula 1, SiO 2 does not react with lithium ions and thus cannot store lithium, so x is preferably within the above range. [39] Specifically, the silicon-based active material may be Si. Conventionally, Si is advantageous in that its capacity is about 2.5 to 3 times higher than that of silicon oxide (eg, SiO x (0 [107] The method of manufacturing a secondary battery of the present invention includes activating the secondary battery structure by charging and discharging in at least one cycle while pressurizing the secondary battery structure to 1.5 MPa to 3.5 MPa. [108] In the method of manufacturing a secondary battery of the present invention, a pressurization process is performed together during charging and discharging for activation of a secondary battery structure. According to the present invention, the volume expansion/contraction of the anode active material occurs while lithium is inserted/desorbed from the anode active material through charging and discharging. [109] In addition, in the method of manufacturing a secondary battery of the present invention, pressure is applied to 1.5 MPa to 3.5 MPa during charging and discharging for activation of the secondary battery structure. If the charging and discharging processes are performed while pressurizing the secondary battery structure in the above pressure range, the volume expansion of the silicon-based active material can be sufficiently controlled, thereby preventing cracking due to volume expansion/contraction of the silicon-based active material and increasing the distance between the active materials. . In addition, in general, when the silicon-based active material is activated, due to cracking due to volume expansion/contraction of the silicon-based active material and increasing the distance between the active materials, the SEI layer formation reaction continues to occur, resulting in excessive gas generation, resistance increase, and lifespan decrease. In the present invention, since charging and discharging are performed while pressurizing within the above pressure range, it is possible to prevent breakage of the active material and maintain the distance between the active materials, so that an appropriate level of SEI layer can be formed and gas generation can be minimized. can In addition, when the charging and discharging process is performed while pressurizing the secondary battery structure within the above pressure range, the voids of the negative electrode or the negative electrode active material layer can be implemented at an appropriate level, thereby preventing the decrease in voids due to excessive pressurization, and the electrolyte solution according to the decrease in voids This depletion problem can be solved, which is preferable for improving lifespan characteristics. [110] If the pressure is less than 1.5 MPa during activation of the secondary battery structure, since volume expansion of the silicon-based active material cannot be sufficiently prevented, damage to the active material and an increase in the distance between the active materials may occur, and lifespan characteristics due to excessive increase of the SEI layer degradation may occur. If the pressure is greater than 3.5 MPa during activation of the secondary battery structure, the volume-expanded silicon-based active material fills the pores of the negative electrode during charging and discharging, so that the pores of the negative electrode may be reduced more than necessary, and the electrolyte There is a risk of exhaustion, and excessive pressure may cause damage to the silicon-based active material, which may lead to a decrease in the lifespan of the battery. [111] Preferably, the pressurization may be performed at 2 MPa to 3 MPa, and when pressurized in the above pressure range, the voids of the negative electrode can be maintained at an appropriate level while sufficiently controlling the volume expansion of the silicon-based active material, so that the lifespan characteristics of the battery can be further improved. can [112] The activating step may be performed by, for example, placing the secondary battery structure between a pair of pressure plates and then pressurizing it to 25 kgf·cm to 55 kgf·cm, preferably 35 kgf·cm to 45 kgf·cm, and thus Accordingly, the above-mentioned 1.5 MPa to 3.5 MPa, preferably, a pressure range of 2 MPa to 3 MPa may be implemented. The pressing pressure by the pressing plate may be adjusted through a torque wrench. [113] [114] The activating step is performed by charging and discharging in at least one cycle while pressurizing to the above-mentioned pressure range. [115] The charging and discharging may be performed using an electrochemical charger/discharger. [116] Charging and discharging for activation of the secondary battery structure may be preferably performed at least 2 or more cycles, more preferably 2 to 8 cycles, even more preferably 3 to 6 cycles. In general, in the case of a silicon-based active material, the degree of volume expansion/contraction due to charging and discharging is greater than that of a carbon-based active material, and accordingly, a new negative electrode surface may be created by the structural change of the silicon-based active material. Accordingly, it is preferable to perform charging and discharging to the secondary battery structure in the cycle of the above-described range so that the SEI layer by activation can be sufficiently formed even on the surface of the newly formed anode. [117] The voltage range in which the charging and discharging are performed may be appropriately set in consideration of the type of the positive electrode or positive electrode active material used to face the negative electrode. Specifically, in the activating step, the charging and discharging may be performed in a voltage range of 2.5V to 4.35V. More specifically, the positive electrode may include a positive electrode current collector and a positive electrode active material layer formed on the positive electrode current collector, and the positive electrode active material layer may include a positive electrode active material including a lithium-nickel-cobalt-manganese composite oxide. And, in the activating step, the charging and discharging may be performed in a voltage range of 2.5V to 4.2V, preferably 3V to 4.2V. In addition, the cathode active material layer may include a cathode active material including a lithium-cobalt-based oxide, and in the activating step, the charging and discharging may be performed in a voltage range of 3V to 4.35V. [118] The activating step may be performed at room temperature, specifically, may be performed at 23°C to 27°C. [119] [120] In the present invention, the negative electrode includes a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material layer includes the silicon-based active material, and the porosity of the negative electrode after activation is 55% to 70% , preferably 56% to 62%. When the negative electrode after activation has a porosity within the above range, the electrolyte solution can be sufficiently present in the negative electrode to realize lithium insertion/desorption and electrical conductivity at an excellent level, and excessive reduction of voids due to volume expansion of the silicon-based active material can be prevented. [121] In the present specification, the porosity of the negative electrode after the activation is defined as a value calculated by Equation 3 below. [122] [Equation 3] [123] Porosity of negative electrode after activation (%) = [1-b (electrode density of negative electrode active material layer before activation × d 1 /d 2 )/(true density of negative electrode active material layer before activation) ] × 100 [124] In Equation 3, d 1 is the thickness of the negative active material layer before activation, d 2 is the thickness of the negative active material layer after activation, and the electrode density of the negative active material layer before activation is the negative electrode active material layer measured with the negative electrode before activation. density, and the true density of the negative electrode active material layer before activation is the density of the negative electrode active material layer measured when the negative electrode before activation is pressed with a press device until the thickness of the negative electrode does not change. [125] According to Equation 3, since it may be difficult to directly measure the porosity of the negative electrode after activation, the true density and electrode density of the negative electrode active material layer before activation, and the thickness ratio of the negative electrode active material layer before and after activation (d 1 /d 2 ) can be hypothetically calculated using Specifically, according to Equation 3 below, the true density of the negative active material layer after activation and the true density of the negative active material layer after activation are assumed to be the same, and the electrode density of the negative electrode active material layer after activation is the electrode density of the negative electrode active material layer before activation It is assumed to be a value multiplied by the ratio d 1 /d 2 of the thickness of the anode active material layer before activation (d 1 ) to the thickness of the anode active material layer after activation (d 2 ). [126] In the secondary battery structure of the present invention, since the negative electrode includes a silicon-based active material, the thickness of the negative electrode active material layer may be increased due to volume expansion of the silicon-based active material during charging and discharging for activation of the secondary battery structure. Considering this, the porosity of the negative electrode after the activation may be greater than the porosity of the negative electrode before the activation. [127] [128] The method of manufacturing a secondary battery of the present invention may further include removing the gas generated in the activating step. [129] After activation of the secondary battery structure, a gas may be generated as a by-product by generation of an SEI layer, generation of an irreversible capacity, and the like. Accordingly, a process of removing by-products may be performed for use of the activated secondary battery, and the secondary battery may be manufactured in a usable form through the gas removal process. [130] As the step of removing the gas, a method generally used in the field of secondary batteries may be performed without limitation. For example, the step of removing the gas may be performed by partially opening the secondary battery structure to remove the gas, and sealing in a vacuum state. [131] [132] The secondary battery manufactured by the manufacturing method of the secondary battery of the present invention is useful in the field of portable devices such as mobile phones, notebook computers, digital cameras, and electric vehicles such as hybrid electric vehicles (HEVs), particularly medium and large-sized batteries It can be preferably used as a component battery of a module. Accordingly, the present invention also provides a medium and large-sized battery module including the secondary battery as described above as a unit battery. [133] These medium and large-sized battery modules can be preferably applied to power sources that require high output and large capacity, such as electric vehicles, hybrid electric vehicles, and power storage devices. [134] [135] Hereinafter, embodiments of the present invention will be described in detail so that those of ordinary skill in the art can easily carry out the present invention. However, the present invention may be embodied in several different forms and is not limited to the embodiments described herein. [136] [137] Example [138] Example 1: Preparation of secondary battery [139] [140] 1. Preparation of anode [141] A mixture of silicon-based active material Si (average particle diameter (D 50 ): 2.5 μm), carbon black (product name: Super C65, manufacturer: TIMCAL) as an anode conductive material, and polyvinyl alcohol and polyacrylic acid in a weight ratio of 66:34 as an anode binder (weight average molecular weight: about 360,000 g/mol) was added to a solvent (distilled water) for forming the negative electrode slurry and mixed to prepare a negative electrode slurry (the solid content was 25% by weight based on the total weight of the negative electrode slurry). The silicon-based active material, the negative electrode conductive material, and the negative electrode binder were mixed in a weight ratio of 75:10:15. [142] As a negative electrode current collector, the negative electrode slurry was coated on one side of a copper current collector (thickness: 8 μm) in a loading amount of 68.4 mg/25 cm 2 , rolled, and dried in a vacuum oven at 130° C. for 10 hours. A negative electrode active material layer (thickness: 44 µm) was formed, and this was used as a negative electrode (thickness of the negative electrode: 52 µm, porosity of the negative electrode: 39.8%). [143] The porosity of the negative electrode (porosity of the negative electrode before activation) was measured by Equation 2 below. [144] [Equation 2] [145] Porosity of negative electrode (%) = ｛1-(electrode density of negative electrode active material layer/true density of negative electrode active material layer) × 100 [146] In Equation 2, the electrode density of the negative electrode active material layer is the density of the negative electrode active material layer measured with the negative electrode (the negative electrode before activation), and the true density of the negative electrode active material layer is the negative electrode (the negative electrode before activation) with a press equipment It is the density of the anode active material layer measured when the thickness of the anode does not change when pressed. [147] [148] 2. Preparation of anode [149] LiNi 0.6 Co 0.2 Mn 0.2 O 2 (average particle diameter (D 50 ): 11㎛) as a cathode active material, carbon black (product name: Super C65, manufacturer: TIMCAL) as a cathode conductive material, and polyvinylidene fluoride (PVdF) as a cathode binder ) was added to N-methylpyrrolidone (NMP) solvent in a weight ratio of 97:1.5:1.5 and mixed to prepare a positive electrode slurry. As a positive electrode current collector, the positive electrode slurry was coated on one side of an aluminum current collector (thickness: 12 μm) in a loading amount of 458 mg/25 cm 2 , rolled, and dried in a vacuum oven at 130° C. for 10 hours. An active material layer (thickness: 110 μm) was formed, and this was used as a positive electrode (anode thickness: 122 μm). [150] [151] 3. Formation of secondary battery structure [152] A separator (thickness: 17.5 μm) having a laminated structure of ethylene polymer (PE)/propylene polymer (PP)/ethylene polymer (PE) between the negative electrode and the positive electrode, wherein the negative electrode and the positive electrode prepared above are disposed to face each other An electrode assembly was prepared through the. [153] The electrode assembly was accommodated in a pouch, an electrolyte solution was injected into the pouch, and the electrode assembly was impregnated to form a secondary battery structure. [154] The electrolyte is an organic solvent in which fluoroethylene carbonate (FEC) and diethyl carbonate (DMC) are mixed in a volume ratio of 30:70, and a vinylene carbonate (VC) additive is added in an amount of 3% by weight based on the total weight of the electrolyte, As a lithium salt, LiPF 6 added at a concentration of 1M was used. [155] The temperature when the electrode assembly was impregnated was 25° C., and the impregnation was performed for 24 hours. [156] [157] 4. N/P ratio [158] A negative electrode sample was prepared by cutting the prepared negative electrode to a predetermined size. A lithium metal electrode having the same size as that of the negative electrode sample was prepared, and it was opposed to the negative electrode sample. After interposing a polyethylene separator between the negative electrode sample and the lithium metal electrode, an electrolyte was injected to prepare a coin-type half-cell. As the electrolyte, an organic solvent in which ethylene carbonate and ethylmethyl carbonate were mixed in a volume ratio of 50:50 was used as a lithium salt in which LiPF 6 was added at a concentration of 1M. The discharge capacity obtained by charging/discharging the coin-type half-cell at 0.1 C was divided by the weight of the silicon-based active material contained in the negative electrode sample to obtain the discharge capacity of the negative electrode sample per unit weight of the silicon-based active material. [159] In addition, the positive electrode prepared above was cut to a predetermined size to prepare a positive electrode sample. A lithium metal electrode having the same size as the positive electrode sample was prepared, and it was opposed to the positive electrode sample. After interposing a polyethylene separator between the positive electrode sample and the lithium metal electrode, an electrolyte was injected to prepare a coin-type half-cell. As the electrolyte, an organic solvent in which ethylene carbonate and ethylmethyl carbonate were mixed in a volume ratio of 50:50 was used as a lithium salt in which LiPF 6 was added at a concentration of 1M. The discharge capacity obtained by charging/discharging the coin-type half-cell at 0.1 C was divided by the weight of the positive active material contained in the positive electrode sample to obtain the discharge capacity of the positive electrode sample per unit weight of the positive electrode active material. [160] The discharge capacity of the negative electrode sample per unit weight of the negative electrode active material measured above was multiplied by the weight of the silicon-based active material and divided by the area of ​​the negative electrode to obtain the discharge capacity per unit area of ​​the negative electrode. In addition, the discharge capacity of the positive electrode sample per unit weight of the positive electrode active material was multiplied by the weight of the positive electrode active material and divided by the area of ​​the positive electrode to obtain the discharge capacity per unit area of ​​the positive electrode. [161] The N/P ratio (=2) was obtained by dividing the discharge capacity per unit area of ​​the negative electrode by the discharge capacity per unit area of ​​the positive electrode. [162] [163] [164] The secondary battery structure prepared above is placed between a pair of pressure plates, and while pressurizing with a torque of 30 kgf·cm using a torque wrench (pressure 1.87 MPa), an electrochemical charger (manufacturer: PNE Solution) is used for 5 cycles. It was activated by charging and discharging at 25°C. [165] The charging and discharging were performed under the following conditions. [166] Charging conditions: 0.2C, CC/CV (4.2V, 0.05C cut-off) [167] Discharge conditions: 0.2C, CC (3.0V cut-off) [168] [169] A gas removal process was performed on the activated secondary battery structure, which was used as the secondary battery of Example 1. [170] [171] Example 2: Preparation of secondary battery [172] A secondary battery of Example 2 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was 40 kgf·cm and the pressure at the time of pressurization was 2.49 MPa. [173] [174] Example 3: Preparation of secondary battery [175] A secondary battery of Example 3 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was set to 50 kgf·cm and the pressure at the time of pressurization was set to 3.12 MPa. [176] [177] Example 4: Preparation of secondary battery [178] A secondary battery of Example 4 was manufactured in the same manner as in Example 2, except that only one cycle of charging and discharging was performed during activation of the secondary battery structure. [179] [180] Comparative Example 1: Preparation of secondary battery [181] A secondary battery of Comparative Example 1 was manufactured in the same manner as in Example 1, except that a pressurization process was not performed during activation of the secondary battery structure. [182] [183] Comparative Example 2: Preparation of secondary battery [184] A secondary battery of Comparative Example 2 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was 5 kgf·cm and the pressure during pressurization was 0.31 MPa. [185] [186] Comparative Example 3: Preparation of secondary battery [187] A secondary battery of Comparative Example 3 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was 10 kgf·cm and the pressure during pressurization was 0.62 MPa. [188] [189] Comparative Example 4: Preparation of secondary battery [190] A secondary battery of Comparative Example 4 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was 20 kgf·cm and the pressure at the time of pressurization was 1.25 MPa. [191] [192] Comparative Example 5: Preparation of secondary battery [193] A secondary battery of Comparative Example 5 was manufactured in the same manner as in Example 1, except that the torque of the torque wrench was set to 60 kgf·cm and the pressure at the time of pressurization was set to 3.74 MPa. [194] [195] Comparative Example 6: Preparation of secondary battery [196] Before activating the secondary battery structure prepared in Example 1, it was placed between a pair of pressure plates, and was pressurized at 40 kgf·cm using a torque wrench for 24 hours (pressure: 2.49 MPa). [197] After the pressurization, the pressure plate was removed from the secondary battery structure, and the secondary battery structure was activated by charging and discharging at 25° C. in 5 cycles using an electrochemical charger and discharger (manufactured by PNE Solution). The charging and discharging conditions are as follows. [198] Charging conditions: 0.2C, CC/CV (4.2V, 0.05C cut-off) [199] Discharge conditions: 0.2C, CC (3.0V cut-off) [200] [201] A gas removal process was performed on the activated secondary battery structure, which was used as the secondary battery of Comparative Example 6. [202] [203] Comparative Example 7: Preparation of secondary battery [204] The secondary battery prepared in Comparative Example 1 was placed between a pair of pressure plates, and pressurized to 40 kgf·cm using a torque wrench (pressure: 2.49 MPa) [205] The secondary battery after the pressurization was used as the secondary battery of Comparative Example 7. [206] [207] Experimental Example 1: Evaluation of porosity of the negative electrode after activation [208] The porosity of the negative electrode after activation of the secondary batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 7 was evaluated. [209] The porosity of the negative electrode after activation was measured by Equation 3 below. [210] [Equation 3] [211] Porosity of negative electrode after activation (%) = [1-b (electrode density of negative electrode active material layer before activation × d 1 /d 2 )/(true density of negative electrode active material layer before activation) ] × 100 [212] In Equation 3, d 1 is the thickness of the negative active material layer before activation, d 2 is the thickness of the negative active material layer after activation, and the electrode density of the negative active material layer before activation is the negative electrode active material layer measured with the negative electrode before activation. density, and the true density of the negative electrode active material layer before activation is the density of the negative electrode active material layer measured when the negative electrode before activation is pressed with a press device until the thickness of the negative electrode does not change. [213] [214] [Table 1] [215] [216] Referring to Table 1, the secondary batteries of Examples 1 to 4 activated by charging and discharging while pressurizing the secondary battery structure to a pressure range according to the present invention were evaluated to secure an appropriate level of voids in the negative electrode, but The secondary battery did not. [217] [218] Experimental Example 2: Lifespan characteristic evaluation [219] For the secondary batteries prepared in Examples 1 to 4 and Comparative Examples 1 to 7, capacity retention rates were evaluated using an electrochemical charger/discharger. [220] The secondary battery was charged and discharged up to the 100th cycle under the conditions of charging (0.5C CC/CV charging 4.2V, 0.05C cut) and discharging (0.5C CC discharging, 3.0V cut) conditions. [221] The capacity retention rate was evaluated by Equation 4 below. 1 is a graph showing the capacity retention rate according to the cycles of Examples 1 to 4, and Comparative Examples 1 to 7, respectively. [222] In addition, the capacity retention rates in the 100th cycle of Examples and Comparative Examples are shown in Table 2 below. [223] [Equation 4] [224] Capacity retention rate (%) = {(discharge capacity in Nth cycle)/(discharge capacity in 1st cycle)} × 100 [225] (in Equation 4, N is an integer from 1 to 100) [226] [227] [Table 2] [228] [229] 1 and Table 2, the secondary batteries of Examples 1 to 4 activated by charging and discharging while pressurizing the secondary battery structure to a pressure range according to the present invention appropriately control thickness increase due to initial volume expansion during activation In addition, it can be confirmed that a stable SEI layer can be formed, and lifespan characteristics are improved compared to Comparative Examples by securing an appropriate level of voids in the anode. However, in the case of the secondary batteries of Comparative Examples 1 to 4 pressurized at a low pressure or not pressurized during activation, the volume expansion of the active material cannot be controlled, and thus it is difficult to form a stable SEI layer, and it is difficult to form a side reaction. It can be seen that due to excessive gas generation, a rapid decrease in lifespan characteristics is observed from the beginning of the cycle. [230] In addition, it can be seen that even in the case of the secondary battery of Comparative Example 5 that was pressurized at an excessively high pressure during activation, the lifespan characteristics were remarkably deteriorated. It is considered that this deterioration of the life characteristics is due to the occurrence of damage to the active material due to high pressurization pressure. In addition, the deterioration of the lifespan characteristics is caused by a phenomenon in which the active material, which has expanded in volume due to the high pressurization pressure, blocks the pores in the negative electrode, and the electrolyte inside the negative electrode is reduced or depleted according to the decrease in the pores in the negative electrode, thereby reducing the lifespan characteristics of the battery It is thought to be according to [231] In addition, in the case of the secondary batteries of Comparative Examples 6 and 7 in which the pressurization and activation of the secondary battery structure were not simultaneously performed, the volume expansion of the active material during activation could not be controlled to an appropriate level, resulting in a rapid deterioration in lifespan characteristics. Claims [Claim 1] forming a secondary battery structure including an electrode assembly including a negative electrode, a positive electrode, and a separator, and an electrolyte; and activating the secondary battery structure by charging and discharging in at least one cycle while pressurizing the secondary battery structure to 1.5 MPa to 3.5 MPa, wherein the negative electrode includes a silicon-based active material. [Claim 2] The method according to claim 1, wherein in the step of activating, the pressurization is performed at 2 MPa to 3 MPa. [Claim 3] The method according to claim 1, wherein the silicon-based active material is a compound represented by the following formula (1). [Formula 1] SiO x (0≤x<2) [Claim 4] The method according to claim 1, wherein the silicon-based active material is Si. [Claim 5] The method according to claim 1, wherein the average particle diameter (D 50 ) of the silicon-based active material is 1㎛ to 10㎛ the secondary battery manufacturing method. [Claim 6] The method according to claim 1, wherein the secondary battery structure has an N/P ratio of 1.5 to 4 according to Equation 1 below. [Equation 1] N/P ratio = discharge capacity per unit area of ​​negative electrode / discharge capacity per unit area of ​​positive electrode [Claim 7] The method according to claim 1, wherein the activating step is performed by placing the secondary battery structure between a pair of pressure plates and then pressurizing the secondary battery structure to 25kgf·cm to 55kgf·cm. [Claim 8] The method according to claim 1, wherein the negative electrode comprises a negative electrode current collector and a negative electrode active material layer formed on the negative electrode current collector, the negative electrode active material layer includes the silicon-based active material, the porosity of the negative electrode after activation calculated by the following Equation (3) A method of manufacturing a secondary battery containing 55% to 70% silver. [Equation 3] Porosity (%) of the negative electrode after activation = [1-b (electrode density of the negative electrode active material layer before activation × d 1 /d 2 )/(true density of the negative electrode active material layer before activation)] x 100 above In Equation 3, d 1 is the thickness of the negative active material layer before activation, d 2 is the thickness of the negative active material layer after activation, and the electrode density of the negative active material layer before activation is the density of the negative electrode active material layer measured with the negative electrode before activation , and the true density of the anode active material layer before activation is the density of the anode active material layer measured when the anode before activation is pressed with a press device until the thickness of the anode does not change. [Claim 9] The method according to claim 1, wherein the activating step is performed at 23 °C to 27 °C. [Claim 10] The method according to claim 1, wherein in the step of activating, the charging and discharging are performed in 2 to 8 cycles. [Claim 11] The method according to claim 1, wherein the positive electrode includes a positive electrode current collector and a positive electrode active material including a lithium-nickel-cobalt-manganese composite oxide formed on the positive electrode current collector, and in the activating step, the charging and discharging are 2.5 A method of manufacturing a secondary battery performed in a voltage range of V to 4.2V.