KR20220109699A - Method for manufacturing secondary battery - Google Patents

Abstract

The present invention relates to a method for manufacturing a secondary battery, including the steps of: forming an electrode assembly including a negative electrode containing a silicon-based active material, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode; impregnating the electrode assembly by injecting an electrolyte into the electrode assembly; activating the impregnated electrode assembly by charging and discharging the same in at least one cycle; mounting the activated electrode assembly at 55 to 85 ℃ for 1 to 10 hours; and removing gas generated from the electrode assembly after the mounting step.

Description

Secondary battery manufacturing method {METHOD FOR MANUFACTURING SECONDARY BATTERY}

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

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.

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 active material or a negative 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.

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 silicone-based active material is not widely used due to the problem 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.

Meanwhile, the secondary battery is manufactured through a process of assembling the secondary battery, a process of activating the secondary battery, and the like. 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.

Lithium is inserted into the negative electrode included in the secondary battery through the activation, 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 referred to as a solid electrolyte interface layer (hereinafter, SEI layer). After the SEI layer is formed, it acts as an ion tunnel to allow lithium ions to pass through, the lithium ions do not react with the negative electrode or other materials again, and the amount of charge consumed in the SEI layer is irreversible and does not react reversibly when discharging. 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.

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.

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.

Korean Patent Application 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 are limits to solving it.

Korean Patent Publication No. 10-2017-0074030

One object of the present invention is to provide a method for manufacturing a secondary battery exhibiting improved lifespan characteristics.

The present invention comprises the steps of: forming an electrode assembly including a negative electrode including a silicon-based active material, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode; impregnating the electrode assembly by injecting an electrolyte into the electrode assembly; activating the impregnated electrode assembly by charging and discharging it in at least one cycle; placing the activated electrode assembly at 55° C. to 85° C. for 1 hour to 10 hours; and removing the gas generated from the electrode assembly after the mounting step.

In the method for manufacturing a secondary battery of the present invention, after performing charge and discharge for activation of an electrode assembly containing a silicon-based active material, a process of mounting the electrode assembly at a specific temperature and time is performed, thereby providing an SEI layer having stable and excellent strength on the negative electrode can be formed, so that it is possible to manufacture a secondary battery with improved lifespan performance.

In addition, in the manufacturing method of the secondary battery of the present invention, after charging and discharging for activation of the electrode assembly including the silicon-based active material is performed, the electrode assembly is mounted at a specific temperature and time, thereby accelerating side reactions due to residual moisture. A large amount of gas may be generated, and then the gas is removed by a degassing process. According to the manufacturing method of the secondary battery of the present invention, since the gas generated by the negative electrode side reaction can be maximally removed through the above-mentioned deferment, gas generation can be suppressed when the product is applied to the secondary battery after that, which is preferable for improving life performance do.

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.

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.

In the present specification, terms such as "comprise", "comprising" or "having" 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 the existence or addition of numbers, steps, elements, or combinations thereof is not precluded in advance.

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. The laser diffraction method is generally capable of measuring a particle diameter of several mm from a submicron region, and can obtain results of high reproducibility and high resolution.

Hereinafter, the present invention will be described in detail.

<Method for manufacturing secondary battery>

The present invention relates to a method for manufacturing a secondary battery, specifically, to a method for manufacturing a lithium secondary battery.

Specifically, the method of manufacturing a secondary battery of the present invention comprises: forming an electrode assembly including a negative electrode including a silicon-based active material, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode; impregnating the electrode assembly by injecting an electrolyte into the electrode assembly; activating the impregnated electrode assembly by charging and discharging it in at least one cycle; placing the activated electrode assembly at 55° C. to 85° C. for 1 hour to 10 hours; and removing the gas generated from the electrode assembly after the mounting step.

The method for manufacturing a secondary battery of the present invention is SEI having stable and excellent strength on the surface of the anode by performing a process of mounting the electrode assembly at a specific temperature and time after charging and discharging for activation of an electrode assembly containing a silicon-based active material. By forming a layer, it is possible to manufacture a secondary battery with improved lifespan performance.

In addition, in the method of manufacturing a secondary battery of the present invention, after charging and discharging for activation of an electrode assembly containing a silicon-based active material is performed, a process of mounting the electrode assembly at a specific temperature and time is performed, thereby accelerating side reactions due to residual moisture and gas can be generated a lot, and then the gas is removed by a degassing process. According to the manufacturing method of the secondary battery of the present invention, since the gas generated by the negative electrode side reaction can be maximally removed through the above-mentioned deferment, gas generation can be suppressed when the product is applied to the secondary battery after that, which is preferable for improving life performance do.

<Production of electrode assembly>

The method of manufacturing a secondary battery of the present invention includes forming an electrode assembly including a negative electrode including a silicon-based active material, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode.

The negative electrode includes a silicon-based active material. Silicon-based active materials have a higher capacity than carbon-based active materials, but due to volume expansion/contraction during charging and discharging, cracking of the active material, and deterioration of contact, excessive generation of SEI layer and gas generation due to side reactions are a problem. may lead to a decrease in the lifespan of However, since the present invention enables the formation of a stable SEI layer by processes such as activation and post-processing at high temperature, which will be described later, it is possible to realize the capacity characteristics of a silicon-based active material and to manufacture a secondary battery having excellent lifespan performance. .

The negative electrode may include a negative electrode current collector and a negative electrode active material layer disposed on the negative electrode current collector, and the negative electrode active material layer may include the silicon-based active material.

The negative current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. Specifically, the negative electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, fired carbon, and an aluminum-cadmium alloy, preferably copper.

The thickness of the negative electrode current collector may be 3 to 500 μm, and preferably 5 to 50 μm to realize a thin film of a silicon-based active material-containing negative electrode.

The negative electrode current collector may form fine concavities and convexities on the surface to strengthen the bonding strength of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body, and the like.

The anode active material layer may be disposed on at least one surface of the anode current collector. Specifically, the negative active material layer may be disposed on one side or both sides of the negative electrode current collector.

The silicon-based active material may include a compound represented by SiO _x (0≤x<2). Since SiO ₂ does not react with lithium ions to store lithium, x is preferably within the above range.

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 (for example, SiO _x (0<x<2)), but the degree of volume expansion/contraction according to charging and discharging of Si is not that of silicon oxide. Since it is much larger than the case, it is not easy to commercialize it. However, in the present invention, since a stable and strong SEI layer can be formed on Si by performing a high-temperature fermenting process under specific conditions after the activation process, the problem of deterioration in lifespan characteristics can be effectively solved, and the high capacity, energy density, and The advantage of the rate characteristic can be realized more preferably. Specifically, most of the silicon-based active material may be made of Si, and more specifically, the silicon-based active material may be made of Si.

The average particle diameter (D ₅₀ ) of the silicon-based active material is for structural stability of the active material during charging and discharging, and can more smoothly form a conductive network for maintaining electrical conductivity, or a binder for binding the active material and the current collector It may be 1 μm to 10 μm, preferably 1.5 μm to 4 μm, in terms of making it easier to access.

The negative active material is 60% to 90% by weight in the negative active material layer in terms of sufficiently realizing the high capacity of the silicon-based active material in a secondary battery while minimizing the effect of volume expansion/contraction of the silicone-based active material on the battery, preferably It may be included in an amount of 70 wt% to 80 wt%.

The anode active material layer may further include a conductive material and/or a binder together with the anode active material.

The binder may be used to improve adhesion between the negative electrode active material layer and a negative electrode current collector to be described later or to improve bonding strength between the silicon-based active material.

Specifically, the binder further improves electrode adhesion and provides sufficient resistance to volume expansion/contraction of the silicone-based active material, styrene butadiene rubber (SBR), acrylonitrile butadiene rubber (acrylonitrile butadiene rubber) ), acrylic rubber, butyl rubber, fluoro rubber, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinyl alcohol (PVA: polyvinyl alcohol), polyacrylic acid (PAA: polyacrylic acid), polyethylene glycol (PEG: polyethylene glycol), polyacrylonitrile (PAN: polyacrylonitrile), and polyacryl amide (PAM: polyacryl amide) at least one selected from the group consisting of may include

Preferably, the binder has high strength, has excellent resistance to volume expansion/contraction of the silicone-based active material, and provides excellent flexibility to the binder to prevent distortion and warpage of the electrode. At least one selected from the group consisting of acrylic acid, polyacrylonitrile and polyacrylamide, preferably polyvinyl alcohol and polyacrylic acid, and more preferably a copolymer of polyvinyl alcohol and polyacrylic acid. can When the binder includes a copolymer of polyvinyl alcohol and polyacrylic acid, the copolymer of polyvinyl alcohol and polyacrylic acid contains a vinyl alcohol monomer and an acrylic acid monomer in a weight ratio of 50:50 to 90:10, preferably 55: It may be included in a weight ratio of 45 to 80:20.

The binder is to be better dispersed in an aqueous solvent such as water during the preparation of the slurry for forming the negative electrode active material layer, and to improve the binding force by coating the active material more smoothly, hydrogen in the binder is converted to Li, Na or Ca. It may include substituted ones.

The binder may be included in the anode active material layer in an amount of 5 wt% to 30 wt%, preferably 7 wt% to 15 wt%, and when in the above range, the silicone-based active material is better bound to minimize the problem of volume expansion of the active material At the same time, it is possible to facilitate dispersion of the binder during the preparation of the slurry for forming the anode active material layer, and to improve coatability and phase stability of the slurry.

The conductive material may be used to assist and improve conductivity in the secondary battery, and is not particularly limited as long as it has conductivity without causing chemical change. Specifically, the conductive material may include graphite such as natural graphite or artificial graphite; carbon black such as acetylene black, Ketjen black, channel black, farness black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; fluorocarbon; metal powders such as aluminum and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and at least one selected from the group consisting of polyphenylene derivatives.

Specifically, the conductive material may include a first conductive material including carbon nanotubes; a second conductive material including carbon black; and a third conductive material including graphite.

When the conductive material includes the first conductive material, the second conductive material, and the third conductive material, the conductive material may be located on the surface of the silicon-based active material particles, between the silicone-based active material particles, and between the aggregates when the silicone-based active material is aggregated. Thus, the conductive material can be distributed with a high dispersion rate in the negative electrode. On the other hand, even if the silicon-based active material expands and contracts due to charging and discharging, the conductive material can be distributed on the surface of the particles, between the particles, and between the aggregates of the particles, which is preferable for maintaining the conductive network.

The first conductive material may include carbon nanotubes, and may be smoothly distributed and positioned on the surface of the silicon-based active material and between the silicon-based active materials due to a high specific surface area. The first conductive material is specifically at least one selected from a multi-walled carbon nanotube (MWCNT, Multi-Walled Carbon NanoTube, MWCNT), and a single-walled carbon nanotube (SWCNT), more specifically a single-walled carbon nanotube (SWCNT). carbon nanotubes.

The second conductive material may include carbon black, and may be uniformly dispersed among particles of the silicon-based active material to enable maintenance of the conductive network despite volume expansion and contraction of the silicon-based active material.

The third conductive material may include graphite, specifically, plate-shaped graphite. The third conductive material may assist in maintaining a conductive network of aggregates formed by binding of the silicon-based active material and the binder.

The conductive material includes the first conductive material, the second conductive material, and the third conductive material in a weight ratio of (1 to 5): (80 to 120): (80 to 120), preferably (1 to 3) It may be included in a weight ratio of :(95~110):(95~110). When the conductive material is in the above range, the conductive material may be located at a certain amount or more in the section connecting the particles when the active material particles are attached to each other, the space generated between the particles or the active material particles are separated, so that the conductive path is formed It is preferable because it can be formed stably.

The conductive material may be included in the anode active material layer in an amount of 5 wt% to 20 wt%, preferably 7 wt% to 15 wt%, and when in the above range, an excellent conductive network can be formed while mitigating the increase in resistance due to the binder. It is preferable in that there is

The thickness of the negative active material layer may be 20 μm to 100 μm, preferably 30 μm to 60 μm, in terms of implementation of a thin film electrode and high energy density.

The negative electrode may be prepared by coating a negative electrode slurry including a negative electrode active material and optionally a binder, a conductive material and a solvent for forming the negative electrode slurry on the negative electrode current collector, followed by drying and rolling.

The solvent for forming the negative electrode slurry is, for example, in terms of facilitating the dispersion of the negative electrode active material, the binder and/or the conductive material, at least one selected from the group consisting of distilled water, ethanol, methanol and isopropyl alcohol, preferably distilled water. may include

In the solvent for forming the negative electrode slurry, in consideration of the viscosity, coating property, dispersibility, etc. of the negative electrode slurry, the concentration of the solid content including the negative electrode active material, and optionally the binder and the conductive material is 15% to 45% by weight, preferably 20 It may be included in the negative electrode slurry so as to be in an amount of from 24 wt% to 30 wt%, more preferably from 24 wt% to 27 wt%.

The anode faces the cathode.

The positive electrode may include a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector.

The positive electrode current collector is not particularly limited as long as it has high conductivity without causing a chemical change in the battery. Specifically, the positive electrode current collector may include at least one selected from the group consisting of copper, stainless steel, aluminum, nickel, titanium, calcined carbon, and an aluminum-cadmium alloy, and specifically may include aluminum.

The positive electrode current collector may typically have a thickness of 3 to 500 μm.

The positive electrode current collector may form fine concavities and convexities on the surface to strengthen the bonding strength of the negative electrode active material. For example, the negative electrode current collector may be used in various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a nonwoven body, and the like.

The positive electrode active material layer may be disposed on at least one surface of the positive electrode current collector. Specifically, the positive electrode active material layer may be disposed on one side or both sides of the positive electrode current collector.

The positive active material layer may include a positive active material.

The positive active material is a compound capable of reversible intercalation and deintercalation of lithium, and specifically, a lithium transition metal composite oxide containing lithium and at least one transition metal consisting of nickel, cobalt, manganese and aluminum. may include More specifically, the lithium transition metal composite oxide may include lithium and a transition metal including nickel, cobalt, and manganese.

Specifically, as the lithium transition metal composite oxide, lithium-manganese oxide (eg, LiMnO ₂ , LiMn ₂ O ₄ , etc.), lithium-cobalt-based oxide (eg, LiCoO ₂ , etc.), lithium-nickel-based oxide Oxides (eg, LiNiO ₂ , etc.), lithium-nickel-manganese oxides (eg, LiNi _1-Y Mn _Y O ₂ (where 0<Y<1), LiMn _2-z Ni _z O ₄ ) (here, 0<Z<2), etc.), lithium-nickel-cobalt-based oxide (eg, LiNi _1-Y1 Co _Y1 O ₂ (here, 0<Y1<1), etc.), lithium-manganese- Cobalt-based oxides (eg, LiCo _1-Y2 Mn _Y2 O ₂ (here, 0<Y2<1), LiMn _2-z1 Co _z1 O ₄ (here, 0<Z1<2), etc.), lithium- Nickel-manganese-cobalt oxide (for example, Li(Ni _p Co _q Mn _r1 )O ₂ (here, 0<p<1, 0<q<1, 0<r1<1, p+q+r1) =1) or Li(Ni _p1 Co _q1 Mn _r2 )O ₄ (where 0<p1<2, 0<q1<2, 0<r2<2, p1+q1+r2=2), etc.), or lithium -nickel-cobalt-transition metal (M) oxide (eg, Li(Ni _p2 Co _q2 Mn _r3 M _S2 )O ₂ , where M is Al, Fe, V, Cr, Ti, Ta, Mg and Mo is selected from the group consisting of, and p2, q2, r3 and s2 are atomic fractions of each independent element, 0<p2<1, 0<q2<1, 0<r3<1, 0<s2<1, p2+ q2+r3+s2=1) and the like), and any one or two or more of these compounds may be included. Among them, the lithium transition metal composite oxide is LiCoO ₂ , LiMnO ₂ , LiNiO ₂ , lithium nickel-manganese-cobalt oxide (for example, Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ , etc.), or lithium nickel cobalt aluminum oxide (eg For example, it may be Li(Ni _0.8 Co _0.15 Al _0.05 )O ₂ etc.), and the lithium transition metal in consideration of the significant improvement effect by controlling the type and content ratio of the element forming the lithium transition metal composite oxide. The composite oxide is Li(Ni _0.6 Mn _0.2 Co _0.2 )O ₂ , Li(Ni _0.5 Mn _0.3 Co _0.2 )O ₂ , Li(Ni _0.7 Mn _0.15 Co _0.15 )O ₂ or Li(Ni _0.8 Mn _0.1 Co _0.1 )O ₂ and the like, and any one or a mixture of two or more thereof may be used.

The positive active material may be included in an amount of 80 wt% to 99 wt%, preferably 92 wt% to 98.5 wt% in the cathode active material layer in consideration of the sufficient capacity of the cathode active material.

The positive active material layer may further include a binder and/or a conductive material together with the above-described positive active material.

The binder is a component that assists in the binding of the active material and the conductive material and the binding to the current collector, specifically polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose selected from the group consisting of wood, recycled cellulose, polyvinylpyrrolidone, tetrafluoroethylene, polyethylene, polypropylene, ethylene-propylene-diene terpolymer (EPDM), sulfonated EPDM, styrene-butadiene rubber and fluororubber. at least one, preferably polyvinylidenefluoride.

The binder may be included in an amount of 1 wt% to 20 wt%, preferably 1.2 wt% to 10 wt%, in the cathode active material layer in terms of sufficiently securing binding force between components such as the cathode active material.

The conductive material may be used to assist and improve conductivity in the secondary battery, and is not particularly limited as long as it has conductivity without causing chemical change. Specifically, the conductive material may include graphite such as natural graphite or artificial graphite; carbon black, such as carbon black, acetylene black, Ketjen black, channel black, farness black, lamp black, and thermal black; conductive fibers such as carbon fibers and metal fibers; conductive tubes such as carbon nanotubes; metal powders such as fluorocarbon, aluminum, and nickel powder; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and at least one selected from the group consisting of polyphenylene derivatives, and preferably carbon black in view of improving conductivity.

The conductive material facilitates dispersion of the conductive material during the preparation of the slurry for forming the positive electrode active material layer, and in terms of further improving the electrical conductivity, the conductive material has a specific surface area of 80 m ² /g to 200 m ² /g, preferably 100 m ² /g to 150m ² /g.

The conductive material may be included in an amount of 1 wt% to 20 wt%, preferably 1.2 wt% to 10 wt%, in the cathode active material layer in terms of sufficiently ensuring electrical conductivity.

The thickness of the positive active material layer is 30 μm to 400 μm, preferably 50 μm to 110 μm in consideration of the capacity balance between the negative electrode and the positive electrode, and to minimize the effect of volume expansion/contraction of the silicon-based active material in the negative electrode. can

The positive electrode may be prepared by coating a positive electrode slurry including a positive electrode active material and optionally a binder, a conductive material, and a solvent for forming a positive electrode slurry on the positive electrode current collector, followed by drying and rolling.

The solvent for forming the positive electrode slurry may include an organic solvent such as N-methyl-2-pyrrolidone (NMP), and may be used in an amount having a desirable viscosity when the positive electrode active material and, optionally, a binder and a conductive material are included. can For example, the solvent for forming the positive electrode slurry is the positive electrode slurry such that the concentration of the solids including the positive active material, and optionally the binder and the conductive material is 50 wt% to 95 wt%, preferably 70 wt% to 90 wt% can be included in

The secondary battery may have an N/P ratio calculated by Equation 1 below from 1.5 to 3.5, more preferably from 2.2 to 2.5.

[Equation 1]

N/P ratio = discharge capacity per unit area of negative electrode/discharge capacity per unit area of positive electrode.

In the present invention, the "discharge capacity per unit area" means the discharge capacity per unit area in the first cycle of the negative electrode or the positive electrode.

The discharge capacity per unit area of the cathode may be obtained by the following method. Prepare the same negative electrode sample as the negative electrode. A half-cell is prepared using the negative electrode sample and a counter electrode (eg, a lithium metal electrode) facing the negative electrode sample. The discharge capacity per unit area of the negative electrode may be obtained by dividing the measured discharge capacity by charging and discharging the half-cell by the area of the negative electrode sample.

The discharge capacity per unit area of the anode may be obtained by the following method. Prepare the same positive electrode sample as the positive electrode. A half-cell is prepared using the positive electrode sample and a counter electrode (eg, a lithium metal electrode) facing the positive electrode sample. The discharge capacity per unit area of the positive electrode may be obtained by dividing the measured discharge capacity by charging and discharging the half-cell by the area of the positive electrode sample.

When the N/P ratio (the ratio of the discharge capacity of the positive electrode and the negative electrode) of the secondary battery of the present invention is adjusted to the above range, the discharge capacity of the negative electrode is designed to be larger than the discharge capacity of the positive electrode to a specific level, and When lithium is injected into the negative electrode, the proportion of lithium to the total silicon-based active material in the negative electrode may be reduced. Accordingly, it is possible to reduce the use ratio of the silicon-based active material in the negative electrode to a specific level, and thus, it is possible to minimize deterioration of lifespan characteristics due to volume expansion in the negative electrode at the level of the entire battery. In addition, by adjusting the N/P ratio to the above-mentioned level, the deterioration of the lifespan characteristics of the battery due to the aforementioned volume expansion is minimized, and at the same time, the secondary battery having high energy density, rate characteristics and capacity characteristics due to the silicon-based active material. implementation is possible.

The separator separates the anode and the anode and provides a passage for lithium ions to move, and can be used without any particular limitation as long as it is normally used as a separator in a lithium secondary battery. Excellent is preferred. Specifically, a porous polymer film, for example, a porous polymer film made of a polyolefin-based polymer such as an ethylene homopolymer, a propylene homopolymer, an ethylene/butene copolymer, an ethylene/hexene copolymer, and an ethylene/methacrylate copolymer, or these A laminated structure of two or more layers of may be used. In addition, a conventional porous nonwoven fabric, for example, a nonwoven fabric made of high melting point glass fiber, polyethylene terephthalate fiber, etc. may be used. In addition, in order to secure heat resistance or mechanical strength, a coated separator containing a ceramic component or a polymer material may be used, and may optionally be used in a single-layer or multi-layer structure.

<Impregnation of electrode assembly>

The present invention includes the step of impregnating the electrode assembly by injecting an electrolyte into the electrode assembly. As the electrode assembly is immersed in the electrolyte, the electrode assembly may be activated by charging and discharging to be described later.

The electrolyte may include an organic solvent and a lithium salt.

The organic solvent may be used without any particular limitation as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, as the organic solvent, ester solvents such as methyl acetate, ethyl acetate, gamma-butyrolactone, ε-caprolactone; ether solvents such as dibutyl ether or tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; Carbonates such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), propylene carbonate (PC), and fluoroethylene carbonate (FEC) menstruum; alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (R is a C2-C20 linear, branched or cyclic hydrocarbon group, which may include a double bond aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; Or sulfolane may be used. Among these, carbonate-based solvents are preferable, and cyclic carbonates (eg, ethylene carbonate, propylene carbonate, fluoroethylene carbonate, etc.) having high ionic conductivity and high dielectric constant capable of increasing the charging and discharging performance of the battery, and low viscosity A mixture of a linear carbonate-based compound (eg, ethylmethyl carbonate, dimethyl carbonate or diethyl carbonate, etc.) is more preferable. In this case, when the cyclic carbonate and the chain carbonate are mixed in a volume ratio of about 1:9 to about 5:5, the performance of the electrolyte may be excellent. More preferably, mixing fluoroethylene carbonate as a cyclic carbonate and diethyl carbonate as a linear carbonate is preferable in terms of improving electrolyte performance.

The lithium salt may be used without particular limitation as long as it is a compound capable of providing lithium ions used in a lithium secondary battery. Specifically, the lithium salt is LiPF ₆ , LiClO ₄ , LiAsF ₆ , LiBF ₄ , LiSbF ₆ , LiAlO ₄ , LiAlCl ₄ , LiCF ₃ SO ₃ , LiC ₄ F ₉ SO ₃ , LiN(C ₂ F ₅ SO ₃ ) ₂ , LiN(C ₂ F ₅ SO ₂ ) ₂ , LiN(CF ₃ SO ₂ ) ₂ , LiCl, LiI, or LiB(C ₂ O ₄ ) ₂ , etc. may be used. The concentration of the lithium salt is preferably used within the range of 0.1 to 2.0M. When the concentration of the lithium salt is included in the above range, since the electrolyte has an appropriate conductivity and viscosity, excellent electrolyte performance may be exhibited, and lithium ions may move effectively.

The electrolyte may further include an additive for forming a stable and flexible SEI layer on a negative electrode using a silicon-based active material. Specifically, the additive is at least one selected from the group consisting of vinylene carbonate (VC), polystyrene (PS), succinonitrile, ethylene glycol bis(propionnitrile) ether, and lithium bis(fluorosulfonyl)imide, preferably For example, in terms of being able to easily and stably form an SEI layer through ring opening polymerization, an additive including vinylene carbonate may be further included.

The additive may be included in an amount of 0.1 wt% to 15 wt%, preferably 0.5 wt% to 5 wt% in the electrolyte.

The step of impregnating the electrode assembly is 12 hours to 48 hours, more preferably in terms of sufficiently wetting the electrode assembly with the electrolyte solution and enabling the activation according to charging and discharging of the electrode assembly to be performed more smoothly may be performed for 18 to 30 hours.

The step of impregnating the electrode assembly may be performed at 15° C. to 30° C., more specifically at 23° C. to 27° C., and it is possible to improve the impregnation property of the electrode assembly when the range is in the range, and the temperature is excessively high. It is preferable because it is possible to prevent the formation of dendrites in the anode and the occurrence of a low voltage accordingly.

<Activate>

The present invention includes the step of activating the impregnated electrode assembly by charging and discharging in at least one cycle.

The charging and discharging may be performed using an electrochemical charging/discharging device.

The charging and discharging may be performed at a C-rate of 0.05C to 1C, preferably 0.05C to 0.5C. When charging and discharging is performed within the above range, non-uniform insertion and desorption of lithium ions due to rapid charging and discharging can be prevented, so that the lifespan performance of the negative electrode can be further improved.

Charging and discharging for activation of the electrode assembly may be preferably performed in two or more cycles, more specifically, in cycles of 2 to 8. 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 electrode assembly in the cycle of the above-described range so that the SEI layer by activation can be sufficiently formed on the surface of the newly formed anode. In addition, when an aqueous binder such as polyacrylic acid or polyvinyl alcohol is used for the negative electrode in order to suppress the volume expansion and contraction of the silicone-based active material, the aqueous binder has poor electrolyte wettability, so activation is not easy. Accordingly, when the anode is activated by charging and discharging in two or more cycles, the water-based binder is sufficiently wetted with the electrolyte so that the activation can be performed well.

Specifically, the charging/discharging may be performed in two or more cycles, and the C-rate when charging in the first cycle may be lower than the C-rate when charging in the second or more cycles. For example, when the charging/discharging is performed in 2 cycles, the C-rate during charging in the first cycle may be lower than the C-rate during charging in the second cycle. In this case, it is preferable because the charging of the negative electrode can be uniformly performed by performing the charging at a low C-rate in the first cycle, and the formation of the SEI layer by activation can be preferably made in the charging in the second or more cycles. .

The charging and discharging may be performed at 10°C to 80°C. Preferably, in terms of preventing excessive volume expansion/contraction during the charging and discharging, and preventing the continuous generation of the SEI layer, the charging/discharging is performed at 15° C. to 40° C., more preferably at 23° C. to 30° C. can

The charging and discharging may be performed while pressing the impregnated electrode assembly. As lithium is inserted/desorbed from the silicon-based active material by the charging and discharging, the volume expansion/contraction of the anode active material is made. In addition, when the charging and discharging process is performed while the electrode assembly is pressurized, the voids of the negative electrode or the negative electrode active material layer can be realized at an appropriate level, so that the decrease in voids due to excessive pressure is prevented, and the electrolyte is depleted according to the decrease in the voids. can be eliminated, which is preferable for improving the lifespan characteristics.

The pressurization may be performed at 5 MPa to 15 MPa, preferably at 8 MPa to 11 MPa. When the pressure is within 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, and thus the lifespan characteristics of the battery can be further improved.

<High-temperature fermentation stage>

The present invention includes the step of placing the activated electrode assembly at 55°C to 85°C for 1 hour to 10 hours.

The manufacturing method of the secondary battery of the present invention may include the step of mounting the activated electrode assembly under specific conditions, thereby enabling the formation of a stable and strong SEI layer on the surface of the negative electrode. In addition, a new surface may be formed by volume expansion/contraction of the silicon-based active material according to the activation by the charging/discharging, and the SEI layer may be stably formed by the deferment. In addition, when performing the deferment step, the movement of the gas generated at the initial stage of activation can be increased to release the gas in the SEI layer to the outside of the SEI layer, which is preferable because the density of the SEI layer can be increased accordingly. If the deferment step is not performed, there is a risk that the gas in the SEI layer may remain, so that the SEI layer may not be firmly and stably formed.

In addition, in the method of manufacturing a secondary battery of the present invention, after charging and discharging for activation of an electrode assembly including a silicon-based active material is performed, a process of mounting the electrode assembly under the above conditions is performed, so that a side reaction caused by residual moisture is accelerated to release gas. It can be generated a lot, and then the gas is removed by a degassing process. Since the gas generated by the negative electrode side reaction can be maximally removed through the above-mentioned mounting, gas generation can be suppressed when the product is applied to the secondary battery after that, which is preferable for improving life performance.

The fermenting step is carried out at 55°C to 85°C. When the deferring step is performed at less than 55° C., it is difficult to stably form the SEI layer, it is not possible to sufficiently generate a gas due to a side reaction in the deferring step, and the gas removal in the SEI layer is not sufficient. When the deferring step is performed at more than 85° C., there is a risk of metal elution by increasing the reactivity of the metal in the negative electrode current collector, and the low voltage occurrence probability of the secondary battery increases as dendrites of the metal are formed, which is undesirable, high When mounted at a temperature, the adhesive strength of the binder is lowered, causing detachment of the electrode, increasing resistance due to an increase in the distance between active materials, and decreasing lifespan performance due to local lithium precipitation.

Preferably, the fermenting step may be performed at 75°C to 85°C. In the above range, since the viscosity of the electrolyte is reduced, gas generation due to side reactions may be accelerated, so that the gas may be removed as much as possible in the subsequent degassing process. In addition, when it is within the above range, it is preferable to activate the movement of the gas to prevent gas trapping in the SEI layer, and to easily discharge the gas to the outside.

The fermenting step is performed for 1 hour to 10 hours. When it is within the above range, it is possible to sufficiently generate gas through the deferment, and it is preferable that the elution of the metal in the negative electrode current collector, the generation of dendrites, etc. can be prevented.

When the fermenting is performed for less than 1 hour, it is difficult to form a stable SEI layer, it is not possible to sufficiently generate a gas due to a side reaction in the fermenting step, and the gas removal in the SEI layer is not sufficient, which is not preferable. When the deferring is performed for more than 10 hours, damage to the silicon-based active material occurs as the silicon-based active material is exposed to high temperature for a long time, and there is a problem of increasing the resistance by increasing the generation of gas due to damage to the active material and side reactions. A problem of lowering the lifespan characteristics may occur.

Specifically, the passing may be performed for 2 to 6 hours, and when it is in the above range, while forming the SEI layer at a desired level on the negative electrode, it is possible to sufficiently generate gas, and at the same time to prevent damage to the silicon-based active material. This can further improve the lifespan characteristics.

<degassing>

The present invention includes the step of removing the gas generated from the electrode assembly after the step of mounting.

In the degassing step, a gas may be generated as a by-product of the generation of the SEI layer after activation of the electrode assembly, 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.

In particular, the present invention can remove the gas generated by acceleration by the above-described high-temperature deferment step by the gas removing step, can suppress the gas generation when applying the product to the secondary battery, and improve the life performance of the battery. can

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 removing of the gas may be performed by partially opening the electrode assembly to remove the gas, and sealing the electrode assembly in a vacuum state.

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), in particular, 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.

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.

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.

Example

Example 1: Preparation of secondary battery

<Production of electrode assembly>

1. Preparation of anode

Silicon-based active material Si (average particle diameter (D ₅₀ ): 2.3 μm), single-walled carbon nanotubes (average diameter 1.5 nm, average length 10-15 μm) as a conductive material, carbon black (product name: Super C65, manufacturer: TIMCAL), and a mixture of plate-shaped graphite in a weight ratio of 0.2:10:9.8, a copolymer of polyvinyl alcohol and polyacrylic acid as a binder (specifically, a copolymer of vinyl alcohol monomer and acrylic acid monomer in a weight ratio of 66:34, weight average Molecular weight: about 360,000 g/mol) was added to a solvent (distilled water) for forming anode slurry in a weight ratio of 70:20:10 and mixed to prepare an anode slurry (the solid content was 25% by weight based on the total weight of the anode slurry).

As a negative electrode current collector, the negative electrode slurry was coated on both sides of a copper current collector (thickness: 8 μm) in a loading amount of 100 mg/25 cm ² , rolled, and dried in a vacuum oven at 130° C. for 10 hours to dry the negative electrode. An active material layer (thickness: 25 µm) was formed, and this was used as a negative electrode (thickness of the negative electrode: 58 µm).

2. Preparation of anode

Li[Ni _0.6 Co _0.2 Mn _0.2 ]O ₂ (average particle diameter (D ₅₀ ): 10 μm) as a cathode active material, carbon black (product name: Super C65, manufacturer: TIMCAL) as a cathode conductive material, and polyvinylidene fluoride as a cathode binder Ride (PVdF) was added to an N-methylpyrrolidone (NMP) solvent in a weight ratio of 97.5:1.0:1.5 and mixed to prepare a positive electrode slurry. As a positive electrode current collector, the positive electrode slurry was coated on both sides of an aluminum current collector (thickness: 15 μm) in a loading amount of 600 mg/25 cm ² , rolled, and dried in a vacuum oven at 130° C. for 10 hours. An active material layer (thickness: 73.5 µm) was formed, and this was used as a positive electrode (anode thickness: 162 µm).

3. Fabrication of the electrode assembly

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 to prepare an electrode assembly, and the electrode assembly was accommodated in a pouch.

4. N/P ratio

(1) Measurement of discharge capacity per unit area of cathode

A negative electrode sample was prepared in the same manner as in the method of manufacturing the negative electrode except that the negative electrode active material layer was formed only on one surface of the current collector.

A lithium metal electrode having the same size as 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, a lithium salt in which LiPF ₆ was added at a concentration of 1M to an organic solvent in which ethylene carbonate and ethylmethyl carbonate were mixed in a volume ratio of 50:50 was used. The discharge capacity obtained by charging/discharging the coin-shaped half-cell at 0.1 C was divided by the area of the negative electrode sample to obtain the discharge capacity per unit area of the negative electrode.

(2) Measurement of the discharge capacity per unit area of the anode

A positive electrode sample was prepared in the same manner as in the method of manufacturing the positive electrode except that the positive electrode active material layer was formed only on one surface of the current collector.

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, a lithium salt in which LiPF ₆ was added at a concentration of 1M to an organic solvent in which ethylene carbonate and ethylmethyl carbonate were mixed in a volume ratio of 50:50 was used. The discharge capacity obtained by charging/discharging the coin-shaped half-cell at 0.1 C was divided by the area of the positive electrode sample to obtain the discharge capacity per unit area of the positive electrode.

(3) Calculation of N/P ratio

The N/P ratio (= 2.01) 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.

<Impregnation of electrode assembly>

An electrolyte solution was injected into the pouch and the electrode assembly was impregnated.

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 the lithium salt, LiPF ₆ added at a concentration of 1M was used.

The temperature when the electrode assembly was impregnated was 25° C., and the impregnation was performed for 24 hours.

<Activate>

The electrode assembly was activated by placing the impregnated electrode assembly prepared above between a pair of pressure plates and performing charging and discharging while pressing at a pressure of 9.1 MPa using a torque wrench.

The charging and discharging were activated by charging and discharging at 25° C. in 2 cycles with an electrochemical charging/discharging device (manufacturer: PNE Solution).

The charging and discharging were performed under the following conditions.

Charging conditions: 0.33C, CC/CV (4.2V, 0.05C cut-off)

Discharge conditions: 0.33C, CC (2.5V cut-off)

<Position>

The activated electrode assembly was placed in a fully charged state at 60° C. for 4 hours.

<Degassing>

A degassing process was performed on the electrode assembly on which the mounting was completed.

Example 2: Preparation of secondary battery

A secondary battery of Example 2 was prepared in the same manner as in Example 1, except that the above-mentioned fermentation was performed at 80°C.

Example 3: Preparation of secondary battery

A secondary battery of Example 3 was prepared in the same manner as in Example 2, except that the above-mentioned fermentation was performed for 8 hours.

Example 4: Preparation of secondary battery

A secondary battery of Example 4 was manufactured in the same manner as in Example 1, except that the activation step in Example 1 was performed as follows.

<Activate>

The electrode assembly was activated by placing the impregnated electrode assembly prepared above between a pair of pressure plates and performing charging and discharging while pressing at a pressure of 9.1 MPa using a torque wrench.

The charging and discharging were activated by charging and discharging at 25° C. in 2 cycles with an electrochemical charging/discharging device (manufacturer: PNE Solution).

The charging and discharging were performed under the following conditions.

<First cycle>

Charging conditions: 0.10C, CC/CV (4.2V, 0.05C cut-off)

Discharge conditions: 0.33C, CC (2.5V cut-off)

<Second cycle>

Charging conditions: 0.33C, CC/CV (4.2V, 0.05C cut-off)

Discharge conditions: 0.33C, CC (2.5V cut-off)

Example 5: Preparation of secondary battery

The negative electrode slurry prepared in Example 1 was coated on both sides of the negative electrode current collector in a loading amount of 92.3 mg/25 cm ² , rolled, and dried in a vacuum oven at 130° C. for 10 hours to obtain a negative electrode active material layer (thickness). : 23.5 μm), and a negative electrode and a secondary battery of Example 5 were prepared in the same manner as in Example 1 except that this was used as a negative electrode (thickness of the negative electrode: 55 μm).

As a result of measuring the N/P ratio in the same manner as in Example 1, the N/P ratio of the secondary battery of Example 5 was 1.85.

Example 6: Preparation of secondary battery

The negative electrode slurry prepared in Example 1 was coated on both sides of the negative electrode current collector in a loading amount of 119.4 mg/25 cm ² , rolled, and dried in a vacuum oven at 130° C. for 10 hours to obtain a negative electrode active material layer (thickness). : 30 μm), and a negative electrode and a secondary battery of Example 6 were prepared in the same manner as in Example 1 except that this was used as a negative electrode (thickness of the negative electrode: 68 μm).

As a result of measuring the N/P ratio in the same manner as in Example 1, the N/P ratio of the secondary battery of Example 6 was 2.40.

Comparative Example 1: Preparation of secondary battery

<Production of electrode assembly>

An electrode assembly was prepared in the same manner as in Example 1.

<Impregnation of electrode assembly>

The electrode assembly was immersed in the electrolyte in the same manner as in Example 1.

<Activate>

The impregnated electrode assembly prepared above was placed between a pair of pressure plates, and while pressing at a pressure of 9.1 MPa using a torque wrench, it was activated by charging the electrode assembly at 0.1 C so that the SOC was 30%.

<Degassing>

A gas removal process was performed on the activated electrode assembly.

Unlike Example 1, in Comparative Example 1, a deferment process was not performed after the activation process.

Comparative Example 2: Preparation of secondary battery

A secondary battery of Comparative Example 2 was prepared in the same manner as in Example 1, except that the fermenting was performed for 0.5 hours.

Comparative Example 3: Preparation of secondary battery

A secondary battery of Comparative Example 3 was prepared in the same manner as in Example 1, except that the above-mentioned fermenting was performed for 12 hours.

Comparative Example 4: Preparation of secondary battery

A secondary battery of Comparative Example 4 was prepared in the same manner as in Example 1, except that the above-mentioned fermentation was performed at 40°C.

Comparative Example 5: Preparation of secondary battery

A secondary battery of Comparative Example 5 was prepared in the same manner as in Example 1, except that the fermentation was performed at 95°C.

Comparative Example 6: Preparation of secondary battery

A secondary battery of Comparative Example 6 was prepared in the same manner as in Example 1, except that the deferment step was not performed.

Experimental Example 1: Lifespan characteristic evaluation

For the secondary batteries prepared in Examples 1 to 6 and Comparative Examples 1 to 6, the capacity retention rate was evaluated using an electrochemical charger/discharger.

The secondary battery was charged and discharged up to the 200th cycle under the conditions of charging (1.0C CC/CV charging 4.2V, 0.05C cut) and discharging (0.5C CC discharging, 3.2V cut) conditions.

The capacity retention rate was evaluated by the following formula. In addition, the capacity retention rates in the 200th cycle of Examples and Comparative Examples are shown in Table 1 below.

Capacity retention rate (%) = {(discharge capacity in Nth cycle)/(discharge capacity in 1st cycle)} × 100

(wherein N is an integer greater than or equal to 1)

Capacity retention rate@200cycle(%) Example 1 80.1 Example 2 83.0 Example 3 79.4 Example 4 83.4 Example 5 81.5 Example 6 84.7 Comparative Example 1 43.2 Comparative Example 2 72.3 Comparative Example 3 71.2 Comparative Example 4 72.4 Comparative Example 5 33.4 Comparative Example 6 70.4

Referring to Table 1, in the case of the secondary batteries of Examples 1 to 6 manufactured by performing the deferment process at a specific temperature and time during the activation process of the negative electrode and the secondary battery including the silicon-based active material, Comparative Examples 1 to 6, which is not It can be seen that the lifespan performance is significantly improved compared to that of the secondary battery.

Claims (10)

forming an electrode assembly including a negative electrode including a silicon-based active material, a positive electrode facing the negative electrode, and a separator interposed between the negative electrode and the positive electrode;
impregnating the electrode assembly by injecting an electrolyte into the electrode assembly;
activating the impregnated electrode assembly by charging and discharging it in at least one cycle;
placing the activated electrode assembly at 55° C. to 85° C. for 1 hour to 10 hours; and
A method of manufacturing a secondary battery comprising a; removing the gas generated from the electrode assembly after the mounting step.
The method according to claim 1,
The method of manufacturing a secondary battery wherein the charging and discharging is performed in two or more cycles.
The method according to claim 1,
The charging/discharging method of manufacturing a secondary battery is performed while pressing the impregnated electrode assembly.
4. The method of claim 3,
The method of manufacturing a secondary battery wherein the pressurization is performed at a pressure of 5 MPa to 15 MPa.
The method according to claim 1,
The method of manufacturing a secondary battery wherein the charging and discharging is performed at a C-rate of 0.05C to 1C.
The method according to claim 1,
The silicon-based active material is a method of manufacturing a secondary battery comprising a compound represented by SiO _x (0≤x<2).
The method according to claim 1,
The method of manufacturing a secondary battery wherein the silicon-based active material is Si.
The method according to claim 1,
The negative electrode includes a negative electrode current collector, and a negative electrode active material layer disposed on the negative electrode current collector,
The negative active material layer is a method of manufacturing a secondary battery comprising the silicon-based active material, a binder, and a conductive material.
9. The method of claim 8,
The thickness of the negative active material layer is 10㎛ to 100㎛ method of manufacturing a secondary battery.
The method according to claim 1,
A method of manufacturing a secondary battery in which the N/P ratio calculated by Equation 1 below of the electrode assembly is 1.5 to 3.5:
[Equation 1]
N/P ratio = discharge capacity per unit area of negative electrode/discharge capacity per unit area of positive electrode.