Method for infiltrating electrode for lithium secondary battery with electrolyte, method for manufacturing lithium secondary battery including electrode infiltrated with electrolyte by method, and lithium secondary battery including electrode

Abstract

The present disclosure provides a method for infiltrating an electrolyte into an electrode for a lithium secondary battery, the method including manufacturing and storing a roll assembly in a state in which a long sheet type electrode and a substrate infiltrated with a liquid electrolyte are wound together; a method for manufacturing a lithium secondary battery using the electrode manufactured by the method; and a lithium secondary battery manufactured as described above.

Description

Technical Field

[0001] Cross-reference to related applications

[0002] This application claims priority and benefit to Korean Patent Application No. 10-2024-0113676, filed on August 23, 2024, and Korean Patent Application No. 10-2025-0117578, filed on August 22, 2025, the disclosure of which is incorporated herein by reference in its entirety.

[0003] This disclosure relates to a method for electrolyte impregnation of an electrode for a lithium secondary battery, a method for manufacturing a lithium secondary battery including an electrode impregnated with an electrolyte by the method, and a lithium secondary battery including the electrode. Background Technology

[0004] Due to the rapid increase in the use of fossil fuels, the demand for alternative or clean energy sources is growing, and as part of this, the most active area of ​​research is the use of electrochemistry for power generation and energy storage.

[0005] Currently, secondary batteries are a representative example of electrochemical devices that utilize such electrochemical energy, and their application is gradually expanding.

[0006] Recently, with the technological advancements and increasing demand for mobile devices such as laptops, mobile phones, and cameras, the demand for secondary batteries as an energy source has increased rapidly. Among such secondary batteries, lithium-ion batteries have been extensively studied. Lithium-ion batteries exhibit high charge / discharge characteristics, long cycle life, and are eco-friendly, and have already been commercialized and widely used.

[0007] Meanwhile, such lithium secondary batteries are mainly used by immersing a liquid electrolyte in an electrode assembly that includes electrodes and separators. However, the extent to which the liquid electrolyte is immersed in such an electrode assembly is always a problem.

[0008] Specifically, the electrode assembly includes porous electrodes and porous separators, and the battery must be manufactured in a state of being fully immersed in liquid electrolyte to ensure proper battery performance without further liquid injection; otherwise, problems such as a significant increase in resistance and a rapid decline in lifetime characteristics exist due to electrolyte depletion.

[0009] Therefore, there is an urgent need to develop a relatively simple method for manufacturing lithium secondary batteries that can solve these problems and ensure adequate electrolyte immersion of battery components. Summary of the Invention

[0010] Technical issues

[0011] One object of this disclosure is to provide a method for simply manufacturing a battery without the need for further electrolyte injection by allowing sufficient electrode wetting in the electrodes.

[0012] Technical solution

[0013] To achieve the above objectives, according to one aspect of this disclosure, a method for immersing an electrolyte into an electrode for a lithium secondary battery is provided, the method comprising manufacturing and storing a roll assembly in which an elongated electrode and a substrate immersed in a liquid electrolyte are wound together.

[0014] In this case, the storage temperature of the roll assembly can be from 30°C to 80°C, and the storage time can be from 20 hours to 48 hours.

[0015] Here, the substrate wetted with liquid electrolyte can be a nonwoven fabric, a polymer membrane, or a separator.

[0016] In a method for wetting an electrolyte into a substrate, the substrate can be manufactured by dip coating in which the substrate is immersed in a liquid electrolyte solution.

[0017] The roll assembly can be manufactured by separately preparing electrodes wound in roll form and a substrate wetted with a liquid electrolyte, which is also wound in roll form, then unwinding them and rewinding them together.

[0018] On the other hand, according to another aspect of this disclosure, a method for manufacturing a lithium secondary battery using an electrode wetted with a liquid electrolyte is provided.

[0019] Specifically, a lithium secondary battery is manufactured by incorporating an electrode assembly, including electrodes and separators, into a secondary battery case, wherein the electrodes are electrolyte-wetted electrodes manufactured by the method described above for wetting the electrolyte.

[0020] In addition, the separator can be an electrolyte-wetted separator that is wetted with liquid electrolyte before manufacturing the electrode assembly.

[0021] In this case, the method for manufacturing a lithium secondary battery according to this disclosure may not include the step of separately injecting the liquid electrolyte into the secondary battery case.

[0022] According to another aspect of this disclosure, a lithium secondary battery manufactured in this manner is provided. Therefore, such a lithium secondary battery is a lithium secondary battery having an electrode assembly, including electrodes wetted with a liquid electrolyte and separators wetted with a liquid electrolyte, incorporated into a secondary battery case.

[0023] Based on the total weight of the electrolyte, the liquid electrolyte present in the secondary battery box that is not wetted into the electrodes or separators may account for 5% by weight or less, particularly 1% by weight or less.

[0024] Based on the total volume of the electrode, the liquid electrolyte immersed in the electrode may be included in an amount of 101% to 150%, and based on the total volume of the separator, the liquid electrolyte immersed in the separator may be included in an amount of 100% to 150%.

[0025] Furthermore, the interface resistance between the electrode and the separator can be from 0.01 Ω·cm² to 0.055 Ω·cm².

[0026] Furthermore, the ion resistance between the electrode and the separator can be from 0.01 Ω·cm² to 0.045 Ω·cm². Attached Figure Description

[0027] Figure 1 This is a schematic diagram illustrating a method for immersing an electrolyte into an electrode for a lithium secondary battery according to one embodiment of the present disclosure.

[0028] Figure 2 This is a cross-sectional schematic diagram of a lithium secondary battery according to another embodiment of this disclosure. Detailed Implementation

[0029] The embodiments of this disclosure will be described in more detail below to facilitate understanding of the invention.

[0030] The terms or words used in this specification and claims should not be construed as limited to their ordinary or dictionary meanings, but rather should be interpreted in a meaning and concept consistent with the technical concept of this disclosure, based on the principle that the inventors can appropriately define the concepts of the terms in order to best describe their own inventions.

[0031] The terminology used herein is provided to describe exemplary embodiments and is not intended to limit the concept of the invention. Unless the context clearly indicates otherwise, the singular form includes the plural form.

[0032] Furthermore, throughout the specification, unless otherwise stated, when a section is referred to as "comprising" or "containing" a component, it means that the section may also include other components without excluding them.

[0033] According to one embodiment of this disclosure,

[0034] A method for wetting an electrolyte into an electrode for a lithium secondary battery is provided.

[0035] The method includes manufacturing and storing roll assemblies in which elongated electrodes and a substrate wetted with a liquid electrolyte are wound together.

[0036] In the following, a method for immersing an electrolyte into an electrode for a lithium secondary battery according to one embodiment of the present disclosure will be described in more detail with reference to the accompanying drawings.

[0037] first, Figure 1 A method for immersing an electrolyte into an electrode for a lithium secondary battery according to one embodiment of the present disclosure is illustrated schematically.

[0038] Reference Figure 1 The elongated electrode 110 and the substrate 120 wetted with liquid electrolyte were prepared in roll form.

[0039] Here, the elongated electrode 110 has a structure in which an electrode mixture layer is formed on one or both surfaces of the electrode current collector.

[0040] Here, the electrode mixture layer is manufactured by dispersing electrode active materials, binders, conductive materials, etc. in a solvent to form an electrode slurry, applying the electrode slurry to one or both surfaces of the electrode current collector, followed by drying and rolling.

[0041] There are no particular restrictions on the electrode current collector, as long as it is conductive and will not cause any chemical changes in the battery. For example, stainless steel, copper, aluminum, nickel, titanium, sintered carbon, or copper, aluminum, or stainless steel with a surface treated with carbon, nickel, titanium, silver, etc. can be used as current collectors.

[0042] The electrode current collector can be 3 μm to 500 μm thick and can have fine protrusions and depressions formed on its surface to enhance adhesion to the electrode mixture layer. For example, the electrode current collector can be used in a variety of forms such as films, sheets, foils, meshes, porous bodies, foams and nonwoven fabrics.

[0043] The type of electrode active material varies depending on whether the elongated electrode 110 is a positive or negative electrode.

[0044] The positive electrode includes a positive electrode active material, which is a compound capable of reversibly inserting and deintercalating lithium, and specifically, it may include lithium metal oxides or lithium metal phosphates containing lithium and at least one metal such as iron, cobalt, manganese, nickel or aluminum.

[0045] Specifically, the lithium metal oxide may include lithium-manganese-based oxides (e.g., LiMnO2, LiMn2O4, etc.), lithium-cobalt-based oxides (e.g., LiCoO2, etc.), lithium-nickel-based oxides (e.g., LiNiO2, etc.), lithium-nickel-manganese-based oxides (e.g., LiNi q2 , r1 , 4-b , 1-x , , s2 , r2 , p2 , b , x , 1+a ,

[0046] Mn Y O2 (where 0 < Y < 1), LiMn 2-Z Ni Z O4 (where 0 < Z < 2), etc.), lithium-nickel-cobalt-based oxides (e.g., LiNi 1-Y1 Co Y1 O2 (where, 0 < Y1 < 1), etc.), lithium-manganese-cobalt-based oxides (e.g., LiCo 1-Y2 Mn Y2 O2 (where, 0 < Y2 < 1), LiMn 2-Z1 Co Z1 O4 (where, 0 < Z1 < 2), etc.), lithium-nickel-manganese-cobalt-based oxides (e.g., Li(Ni p Co q Mn r )O2 (where, 0 < p < 1, 0 < q < 1, 0 < r < 1, p + q + r = 1) or Li(Ni p1 Co q1 Mn r1 )O4 (where, 0 < p1 < 2, 0 < q1 < 2, 0 < r1 < 2, p1 + q1 + r1 = 2), etc.), or lithium-nickel-cobalt-transition metal (M) oxides (e.g., Li(Ni p2 Co q2 Mn r2 M s2 )O2 (where M is selected from Al, Fe, V, Cr, Ti, Ta, Mg, and Mo, and p2, q2, r2, and s_{^{2}} are the atomic fractions of the respective independent elements, where 0 < p2 < 1, 0 < q2 < 1, 0 < r2 < 1, 0 < s2 < 1, p2 + q2 + r2 + s2 = 1), etc.), lithium iron phosphate (e.g., Li 1+a Fe 1-x M x (PO 4-b )X b (where M is at least one selected from Al, Mg, and Ti, X is at least one selected from F, S, and N, and −0 .5 ≤ a ≤ +0.5, 0 ≤ x ≤ 0.5, 0 ≤ b ≤ 0.1), and may include any one of them or a mixture of two or more of them.

[0046] The negative electrode includes a negative electrode active material, and the negative electrode active material may include one or more of the following: lithium metal, carbon material capable of reversibly inserting / de-inserting lithium ions, metal or alloy of lithium with these metals, metal composite oxide, material capable of doping and de-doping lithium, and transition metal oxide.

[0047] Carbon materials capable of reversibly inserting / deintercalating lithium ions can be used without particular restrictions, as long as they are carbon-based anode active materials commonly used in lithium-ion secondary batteries. Typical examples include crystalline carbon, amorphous carbon, or both. Examples of crystalline carbon include graphite such as amorphous, planar, flake, spherical, or fibrous natural or artificial graphite, and examples of amorphous carbon include soft carbon (low-temperature calcined carbon) or hard carbon, mesophase pitch carbides, calcined coke, etc.

[0048] As a metal or an alloy of lithium with these metals, a metal selected from Cu, Ni, Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al and Sn or an alloy of lithium with these metals can be used.

[0049] As a metal composite oxide, at least one of the following can be used: PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5, Li x Fe2O3 (0≤x≤1), Li x WO2 (0≤x≤1) and Sn x Me 1-x Me' y O z (Where Me: Mn, Fe, Pb, Ge; Me': Al, B, P, Si, Group I, Group II and Group III elements of the periodic table, halogens; 0) <x≤1;1≤y≤3;1≤z≤8)。

[0050] Materials capable of doping and dedoping lithium can include Si, SiO2, etc. x(where 0 < x ≤ 2), Si-Y alloy (where Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Si), Sn, SnO2, Sn-Y (where Y is an element selected from alkali metals, alkaline earth metals, Group 13 elements, Group 14 elements, transition metals, rare earth elements, and combinations thereof, and is not Sn), etc., and at least one of these can be used in combination with SnO2. Element Y can be selected from Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Ge, P, As, Sb, Bi, S, Se, Te, Po and combinations thereof.

[0051] The transition metal oxide can include a lithium-containing titanium composite oxide (LTO), vanadium oxide, lithium vanadium oxide, etc.

[0052] In addition, the conductive material is a component for further improving the conductivity of the electrode active material. Such a conductive material is not particularly limited as long as it has conductivity and does not cause any chemical changes in the battery, and for example, the following conductive materials can be used: carbon powder, such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black or thermal cracking carbon black; graphite powder, such as natural graphite, artificial graphite or graphite with a well-formed crystal structure; conductive nanomaterials, such as carbon nanofibers or carbon nanotubes; fluorinated carbon powder; conductive powder, such as aluminum powder and nickel powder; conductive whiskers, such as zinc oxide whiskers and potassium titanate whiskers; conductive metal oxides, such as titanium oxide; or conductive materials, such as polyphenylene derivatives. Among them, the conductive material includes conductive nanomaterials such as carbon nanotubes or carbon nanofibers, which can further reduce the resistance of the lithium metal battery and further enhance the output characteristics.

[0053] Typically, based on the total weight of the electrode mixture layer, the conductive material can be included in an amount of 1 wt% to 20 wt%, or 1 wt% to 15 wt%, or 1 wt% to 10 wt%.

[0054] The binder optionally included in the electrode mixture layer is a component that facilitates bonding between the electrode active material and the conductive material, as well as bonding with the electrode current collector. Examples of binders may include polyvinylidene fluoride, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene (PE), polypropylene, ethylene propylene diene monomer (EPDM), sulfonated EPDM, nitrile rubber, styrene-butadiene rubber, fluororubber, etc. Mixtures or copolymers selected from two or more of these may also be used.

[0055] Typically, the binder may be included in an amount of 1% to 20% by weight, or 1% to 15% by weight, or 1% to 10% by weight, based on the total weight of the electrode mixture layer.

[0056] In addition, fillers may optionally be added as components to suppress their expansion. There are no particular limitations on such fillers, as long as they suppress electrode expansion without causing any chemical changes in the battery, and examples may include: olefinic polymers, such as polyethylene and polypropylene; and fibrous materials, such as glass fiber and carbon fiber.

[0057] Meanwhile, the substrate 120 wetted with liquid electrolyte is manufactured by wetting the substrate with liquid electrolyte.

[0058] There are no restrictions on the substrate, as long as it is any porous material, and it can be, for example, a nonwoven fabric, a polymer membrane, or a separator.

[0059] Nonwoven fabrics can be, for example, nonwoven fabrics made of high melting point glass fibers, polyethylene terephthalate fibers, etc.

[0060] Alternatively, the polymer membrane may be a porous polymer membrane comprising polyolefin-based polymers, such as ethylene homopolymers, propylene homopolymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers, or a stacked structure of two or more of its layers.

[0061] In addition, the separator can be a nonwoven fabric or a polymer membrane, or it can be an SRS (Safety Reinforced Separator) membrane in which a coating containing adhesive material and inorganic particles is formed on one or both surfaces of the substrate, such as a nonwoven fabric or a polymer membrane.

[0062] Inorganic particles allow for the formation of empty spaces between them, acting as micropores and separators that maintain physical properties. Furthermore, inorganic particles retain their physical properties even at temperatures of 200°C or higher, resulting in an organic-inorganic hybrid layer with excellent heat resistance.

[0063] There are no particular limitations on the inorganic particles, as long as they are electrochemically stable. In other words, there are no particular limitations on the inorganic particles that can be used in this disclosure unless they cause oxidation and / or reduction reactions within the operating voltage range of the battery to be used. In particular, when using inorganic particles with ion transfer capabilities, the ion conductivity in the electrochemical element can be increased to improve performance, and therefore, inorganic particles with high ion conductivity are preferred if possible. Furthermore, if the inorganic particles have a high density, it is difficult to disperse such particles during preparation, and there is a problem of weight increase when manufacturing the battery. Therefore, inorganic particles with low density are preferred if possible. In addition, inorganic materials with high dielectric constants help to increase the degree of dissociation of electrolyte salts, such as lithium salts, in liquid electrolytes, thereby improving the ion conductivity of the electrolyte. Finally, inorganic particles with thermal conductivity are more preferred because they have excellent endothermic capacity and thus suppress the phenomenon of localized heat concentration leading to heat spots and thermal runaway.

[0064] For the reasons stated above, the inorganic particles are preferably selected from one or more of the following: (a) inorganic particles with a high dielectric constant of 1 or greater, 5 or greater, preferably 10 or greater; (b) inorganic particles with piezoelectricity; (c) thermally conductive inorganic particles; and (d) inorganic particles with lithium-ion transfer capability.

[0065] Piezoelectric inorganic materials refer to materials that are non-conductive under atmospheric pressure but acquire electrical properties due to changes in their internal structure when pressure is applied. Such inorganic particles exhibit high dielectric properties, with a dielectric constant of 100 or greater, and if such inorganic particles are stretched or compressed under pressure, they generate charges, making one side positively charged and the other negatively charged. Therefore, such particles are materials that can generate a potential difference between their two sides.

[0066] Examples of piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3 (PZT), and Pb 1-x La x Zr 1-y Ti y O3 (PLZT), PB (Mg3Nb) 2 / 3 Hafnium oxide (HfO2), mixtures thereof, etc., but not limited to these.

[0067] Inorganic particles having the ability to transfer lithium ions refer to inorganic particles that contain lithium element but do not store lithium and have the function of transferring lithium ions. The inorganic particles having the ability to transfer lithium ions can transfer lithium ions and make lithium ions move due to certain defects existing inside the particle structure. Therefore, such particles can prevent the reduction of lithium mobility, thereby preventing the reduction of battery capacity.

[0068] Examples of inorganic particles having the ability to transfer lithium ions include: lithium phosphate (Li3PO4); lithium titanium phosphate (Li x Ti y (PO4)3, 0 < x < 2, 0 < y < 3); lithium aluminum titanium phosphate (Li x Al y Ti z (PO4)3, 0 < x < 2, 0 < y < 1, 0 < z < 3); glass based on (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), such as 14Li2O - 9Al2O3 - 38TiO2 - 39P2O5, etc.; lithium lanthanum titanate (Li x La y TiO3, 0 < x < 2, 0 < y < 3); lithium germanium thiophosphate (Li x Ge y P z S w , 0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), such as Li 3.25 Ge 0.25 P 0.75 S4, etc.; lithium nitride (Li x N y , 0 < x < 4, 0 < y < 2), such as Li3N, etc.; glass based on SiS2 (Li x Si y S z , 0 < x < 3, 0 < y < 2, 0 < z < 4), such as Li3PO4 - Li2S - SiS2, etc.; glass based on P2S5 (Li x P y S z , 0 < x < 3, 0 < y < 3, 0 < z < 7), such as LiI - Li2S - P2S5, etc.; their mixtures; and so on, but not limited thereto.

[0069] In addition, examples of inorganic particles having a dielectric constant of 1 or more include SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, TiO2, SiC, their mixtures, etc., but not limited thereto.

[0070] Thermally conductive inorganic particles are materials that provide low thermal resistance but no electrical conductivity and thus have insulating properties, and may be, for example, selected from at least one of aluminum nitride (AlN), boron nitride (BN), aluminum oxide (Al2O3), silicon carbide (SiC) and beryllium oxide (BeO), but are not limited thereto.

[0071] When inorganic materials with high dielectric constants, piezoelectric inorganic particles, thermally conductive inorganic particles, and inorganic particles with lithium-ion transfer capabilities are mixed, their synergistic effect can be doubled.

[0072] There is no limitation on the size of the inorganic particles, but in order to form appropriate pores between the inorganic particles, the size is preferably in the range of 0.001 μm to 10 μm, if possible. If such a size is less than 0.001 μm, the dispersibility deteriorates, and it becomes difficult to adjust the physical properties. If such a size is greater than 10 μm, the thickness increases, thereby reducing the mechanical properties, and the coating cannot function properly due to the excessively large pore size, and the chance of causing internal short circuits increases during battery charging and discharging.

[0073] There is no particular limitation on the content of inorganic particles, but it is preferred that such a content, based on a mixture of inorganic particles and binder material, ranges from 1% to 99% by weight (100% by weight), more preferably from 10% to 95% by weight. If the content is less than 1% by weight, the content of binder material becomes too high, resulting in a decrease in pore size and porosity due to the reduction in the empty spaces formed between the inorganic particles, and thus potentially deteriorating the lithium-ion mobility. Conversely, if the content is greater than 99% by weight, the content of binder material becomes too low, resulting in a deterioration in the mechanical properties of the coating due to weakened adhesive strength between the inorganic materials.

[0074] On the other hand, there are no limitations unless the binder material causes side reactions with the electrolyte. In particular, the binder material can be a material with the lowest possible glass transition temperature (Tg), preferably in the range of -200°C to 200°C. This is because such a binder material can improve the mechanical properties of the final insulating film.

[0075] Furthermore, the adhesive material does not need to have ion conductivity, but it is more preferable to use a polymer with ion conductivity.

[0076] Therefore, it is preferable that the binder material has a high dielectric constant. In fact, the degree of dissociation of salts in an electrolyte depends on the dielectric constant of the electrolyte solvent, and thus, as the dielectric constant of the polymer increases, the degree of dissociation of salts in the electrolyte can be improved. The dielectric constant of the polymer used can be 1 or greater, particularly in the range of 1.0 to 100 (measurement frequency = 1 kHz), and preferably 10 or greater.

[0077] In addition to the aforementioned functions, the binder material can also be gelled to exhibit high electrolyte swelling during liquid electrolyte wetting. In fact, if the binder material is a polymer with excellent electrolyte swelling, the electrolyte injected after battery assembly permeates the polymer, and the polymer retains the absorbed electrolyte, thus exhibiting ion conductivity for the electrolyte. Therefore, if possible, the solubility index of the polymer is preferably 15 MPa. 1 / 2 up to 45 MPa 1 / 2 Within the range, more preferably within 15 MPa 1 / 2 Up to 25 MPa 1 / 2 and 30 MPa 1 / 2 up to 45 MPa 1 / 2 Within the range. If the solubility index is less than 15 MPa 1 / 2 and greater than 45 MPa 1 / 2 If it does not, it becomes difficult to swell in the liquid electrolyte used in conventional batteries.

[0078] Examples of adhesive materials may be selected from one or more of the following: polyvinylidene fluoride-copoly-hexafluoropropylene, polyvinylidene fluoride-copoly-trichloroethylene, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, polyethylene-copoly-vinyl acetate, polyimide, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethyl polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, and polyvinyl alcohol.

[0079] Therefore, the substrate itself, wetted with liquid electrolyte, can be used as a separator for a lithium secondary battery according to one embodiment of the present disclosure, or the separator can be wetted with electrolyte alone and used.

[0080] Meanwhile, the liquid electrolyte can be a lithium non-aqueous electrolyte, and the lithium non-aqueous electrolyte can contain lithium salts and non-aqueous organic solvents.

[0081] In this case, lithium salts are preferably used as the medium for transferring ions within the lithium secondary battery. For example, the lithium salt may contain Li. + It can be a cation and may contain at least one of the following as an anion: F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - B 10 Cl 10- AlCl4 - AlO2 - PF6 - CF3SO3 - CH3CO2 - CF3CO2 - AsF6 - SbF6 - CH3SO3 - (CF3CF2SO2)2N - (CF3SO2)2N - (FSO2)2N - BF2C2O4 - BC4O8 - PF4C2O4 - PF2C4O8 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - C4F9SO3 - CF3CF2SO3 - CF3CF2(CF3)2CO - (CF3SO2)2CH - CF3(CF2)7SO3 - and SCN - .

[0082] Specifically, lithium salts may include those selected from LiCl, LiBr, LiI, LiBF4, LiClO4, and LiB. 10 Cl 10 The lithium salts are selected from one or more of the following: LiAlCl4, LiAlO2, LiPF6, LiCF3SO3, LiCH3CO2, LiCF3CO2, LiAsF6, LiSbF6, LiCH3SO3, LiFSI (lithium bis(fluorosulfonyl)imide, LiN(SO2F)2), LiBETI (lithium bis(perfluoroethanesulfonyl)imide, LiN(SO2CF2CF3)2), and LiTFSI (lithium bis(trifluoromethanesulfonyl)imide, LiN(SO2CF3)2). However, for the sake of excellent stability, lithium salts preferably include Li(N(SO2CF3)2.

[0083] In addition to these, any lithium salt commonly used in lithium secondary battery electrolytes can be used without restriction.

[0084] The concentration of lithium salt can be appropriately varied within the generally applicable range; however, to achieve the best effect in forming a film on the electrode surface to prevent corrosion, lithium salt can be included in the electrolyte at a concentration of 0.5 M to 3 M, particularly 1 M to 2.5 M, and even more particularly 1 M to 2 M. When the concentration of lithium salt meets the above range, the effect of improving the cycle characteristics of lithium secondary batteries during high-temperature storage is sufficient, and the viscosity of the electrolyte is suitable, thereby improving the electrolyte wetting characteristics.

[0085] There are no restrictions on non-aqueous organic solvents, as long as they can minimize decomposition due to oxidation reactions or the like during subsequent charging / discharging of the lithium secondary battery, and can exhibit their properties together with additives. For example, carbonate-based organic solvents, ether-based organic solvents, ester-based organic solvents, etc., can be used alone or in mixtures of both or more thereof, and specifically, carbonate-based organic solvents can be used.

[0086] Among organic solvents, carbonate-based organic solvents may include at least one selected from organic solvents based on cyclic carbonates and organic solvents based on linear carbonates. Specifically, cyclic carbonate-based organic solvents may include at least one selected from ethylene carbonate (EC), propylene carbonate (PC), 1,2-butylene carbonate, 2,3-butylene carbonate, 1,2-pentene carbonate, 2,3-pentene carbonate, vinylene carbonate, and fluoroethylene carbonate (FEC). Specifically, it may include a mixed solvent of ethylene carbonate having a high dielectric constant and propylene carbonate having a relatively low melting point compared to ethylene carbonate.

[0087] Furthermore, the organic solvent based on linear carbonates is a solvent with low viscosity and low dielectric constant, and may include at least one selected from dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate, methyl ethyl carbonate (EMC), methyl propyl carbonate and ethyl propyl carbonate, and more specifically, it may include dimethyl carbonate.

[0088] Ether-based organic solvents may include, but are not limited to, at least one of ethylene glycol dimethyl ether, diethyl ether, dipropyl ether, methyl ethyl ether, methyl propyl ether and ethyl propyl ether, or a mixture of two or more thereof.

[0089] Ester-based organic solvents may include at least one selected from linear ester-based organic solvents and cyclic ester-based organic solvents.

[0090] As a specific example, organic solvents based on linear esters may include, but are not limited to, any one of methyl acetate, ethyl acetate, propyl acetate, methyl propionate, ethyl propionate, propyl propionate and butyl propionate, or mixtures of two or more thereof.

[0091] As a representative example, organic solvents based on cyclic esters may include, but are not limited to, any one of γ-butyrolactone, γ-valerolactone, γ-caprolactone, σ-valerolactone and ε-caprolactone, or mixtures of two or more thereof.

[0092] In ester-based solvents, cyclic carbonate-based compounds are preferred because their high dielectric constant makes them effective at dissociating lithium salts in the electrolyte. When cyclic carbonate-based compounds are mixed in appropriate ratios with low-viscosity, low-dielectric-constant linear carbonate-based compounds (e.g., dimethyl carbonate and diethyl carbonate) and linear ester-based compounds, electrolytes with high conductivity can be prepared, which is even more preferable.

[0093] In addition, lithium non-aqueous electrolytes may also contain functional additives. These additives may be included to prevent damage to the negative electrode in high-power environments, or to further improve low-temperature high-rate discharge characteristics, high-temperature stability, overcharge protection, and swelling reduction during high-temperature storage.

[0094] Specifically, as a representative example, functional additives may include at least one functional additive selected from the following: compounds based on sulfonyl lactones, compounds based on sulfite esters / salts, compounds based on sulfones, compounds based on sulfate esters / salts, compounds based on halogen-substituted carbonates, compounds based on nitriles, compounds based on cyclic carbonates, compounds based on phosphate esters / salts, compounds based on borate esters / salts, and compounds based on lithium salts.

[0095] The sulfonyl-based compound may include at least one compound selected from 1,3-propanesulfonyl (PS), 1,4-butanesulfonyl, ethanesulfonyl, 1,3-propenesulfonyl (PRS), 1,4-butenesulfonyl, and 1-methyl-1,3-propenesulfonyl, and may be included in an amount of 0.3% to 5% by weight, and particularly 1% to 5% by weight, based on the total weight of the liquid electrolyte. When the amount of the sulfonyl-based compound in the liquid electrolyte is greater than 5% by weight, an excessively thick layer may form on the surface of the electrode, resulting in increased resistance and output degradation, and the increased resistance due to excessive additives may degrade the output characteristics.

[0096] The sulfite / salt-based compound may include at least one compound selected from the following: ethylene sulfite, methyl ethylene sulfite, ethyl ethylene sulfite, 4,5-dimethyl ethylene sulfite, 4,5-diethyl ethylene sulfite, propylene sulfite, 4,5-dimethyl propylene sulfite, 4,5-diethyl propylene sulfite, 4,6-dimethyl propylene sulfite, 4,6-diethyl propylene sulfite, and 1,3-butanediol sulfite, and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0097] The sulfone-based compounds may include at least one compound selected from divinyl sulfone, dimethyl sulfone, diethyl sulfone, methyl ethyl sulfone, and methyl vinyl sulfone, and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0098] Compounds based on sulfate esters / salts may include ethylene sulfate (Esa), trimethylol sulfate (TMS), or methyltrimethylol sulfate (MTMS), and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0099] Furthermore, compounds based on halogen-substituted carbonates may include fluoroethylene carbonate (FEC) and may be included in an amount of 5% by weight or less based on the total weight of the liquid electrolyte. When the amount of halogen-substituted carbonate compounds in the liquid electrolyte exceeds 5% by weight, the battery swelling performance may deteriorate.

[0100] In addition, nitrile-based compounds may include at least one compound selected from the following: succinate, adiponitrile (Adn), acetonitrile, propionitrile, butyronitrile, valerate, octanoic acid, heptanonitrile, cyclopentanoic acid, cyclohexanoic acid, 2-fluorobenzyl nitrile, 4-fluorobenzyl nitrile, difluorobenzyl nitrile, trifluorobenzyl nitrile, phenylacetonitrile, 2-fluorophenylacetonitrile, and 4-fluorophenylacetonitrile.

[0101] The cyclic carbonate-based compound may include vinylene carbonate (VC) or ethylene ethylene carbonate, and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte. When the content of the cyclic carbonate-based compound in the liquid electrolyte is greater than 3% by weight, the battery swelling suppression performance may deteriorate.

[0102] The phosphate ester / salt-based compound may include at least one compound selected from lithium difluoro(bis(oxalato)phosphate), lithium difluorophosphate, tetramethyltrimethylsilyl phosphate, trimethylsilyl phosphite, tris(2,2,2-trifluoroethyl) phosphate, and tris(trifluoroethyl) phosphite, and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0103] Compounds based on borate esters / salts may include lithium oxaloyl difluoroborate and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0104] The lithium salt-based compound is a compound that is different from the lithium salt contained in the lithium non-aqueous electrolyte. The lithium salt-based compound may include at least one compound selected from LiPO2F2, LiODFB, LiBOB (lithium bis(oxalatoborate) (LiB(C2O4)2), and LiBF4), and may be included in an amount of 3% by weight or less based on the total weight of the liquid electrolyte.

[0105] Two or more functional additives may be mixed and included in an amount of 20% by weight or less, particularly from 0.1% to 10% by weight, based on the total weight of the liquid electrolyte. When the content of functional additives exceeds 20% by weight, there is a possibility that excessive side reactions may occur in the lithium non-aqueous electrolyte during battery charging and discharging. In particular, they may not decompose sufficiently at high temperatures and may exist as unreacted substances or in a precipitated state in the lithium non-aqueous electrolyte at room temperature. Consequently, side reactions that degrade the life or resistivity characteristics of lithium metal batteries may occur.

[0106] The substrate 120 wetted with liquid electrolyte can be manufactured by dip coating, in which the substrate is immersed in a liquid electrolyte solution and then removed from the liquid electrolyte solution.

[0107] After the elongated electrode 110 and the substrate 120 wetted with liquid electrolyte are manufactured in this manner, the roll assembly 100 can be manufactured by preparing them in a roll form, then unrolling them and rewinding them together.

[0108] In addition, after manufacturing the roll assembly 100, a storage process is required to allow the liquid electrolyte to fully wet the gaps in the elongated electrode 110.

[0109] In this case, the storage temperature can be 30°C or higher, specifically 30°C to 80°C, or more specifically 40°C to 60°C.

[0110] If the storage temperature is too low outside the above range, the liquid electrolyte will take too long to wet the elongated electrode 110, resulting in reduced manufacturing efficiency. If the storage temperature is too high, it may affect the quality of the electrode, which is undesirable.

[0111] Additionally, the storage time can be selected based on the extent to which the liquid electrolyte fully wets the elongated electrode 110. For example, storage can be carried out for 20 hours or longer, specifically 20 to 48 hours, or more specifically 24 to 30 hours.

[0112] If storage is carried out for too short a time outside the above range, sufficient liquid electrolyte immersion may not be achieved, while if storage is carried out for too long, the processing time may be prolonged regardless of the degree of immersion, which is not preferred.

[0113] After the storage process, the liquid electrolyte moves from the substrate 120 wetted with the liquid electrolyte to the elongated electrode 110, and the liquid electrolyte can even fully wet the elongated electrode 110.

[0114] Therefore, according to another embodiment of this disclosure, a method for manufacturing a lithium secondary battery using a long-film electrode 110 and a lithium secondary battery 200 thereby manufactured are provided.

[0115] Figure 2 A schematic cross-sectional view of a lithium secondary battery 200 manufactured in this manner is shown.

[0116] Reference Figure 2 The lithium secondary battery 200 has a structure in which an electrode assembly 210, including an electrode 201 and a separator 202, is incorporated into a secondary battery case 220.

[0117] Here, electrode 201 can be manufactured according to the size of the unit electrode to be produced by cutting from... Figure 1 The long sheet electrode 110 is manufactured using the manufacturing method described above.

[0118] Additionally, the separator 202 can be used Figure 1 The substrate 120 is manufactured by impregnating it with a liquid electrolyte, or by impregnating the liquid electrolyte into a separately used separator. Therefore, the separator 202 may also be an electrolyte-impregnated separator that is impregnated with a liquid electrolyte before the electrode assembly 210 is manufactured.

[0119] In this case, there is no restriction on the wetting of the liquid electrolyte into the separator, but it can be done by dip coating, as in the manufacturing method of the substrate 120 wetted with liquid electrolyte.

[0120] Electrodes 201 and separators 202 manufactured in this manner are already wetted with liquid electrolyte and are joined together by methods such as stacking or winding to form electrode assembly 210. For ease of illustration, electrode 201 is represented as a single unit. However, positive and negative electrodes can be arranged alternately, with separators 202 inserted between them, and both positive and negative electrodes can be those wetted with liquid electrolyte in the same manner as described above.

[0121] Subsequently, the electrode assembly 210 is incorporated into the secondary battery box 220, and the outer portion of the secondary battery box 220 is sealed to manufacture the lithium secondary battery 200.

[0122] That is, according to this disclosure, before manufacturing the electrode assembly 210, the electrode 201 and the separator 202 are wetted with a liquid electrolyte, and then these are stacked or wound and then incorporated into the secondary battery box 220.

[0123] Since the electrolyte is immersed in the electrodes 201 and the separator 202 through this process, the method for manufacturing a lithium secondary battery according to this disclosure may not include the process of separately injecting the liquid electrolyte into the secondary battery case 220.

[0124] Therefore, according to this disclosure, the liquid electrolyte has been fully immersed in the electrode 201 and the separator 202 without the need for separate injection of liquid electrolyte, thereby enabling the lithium secondary battery 200 to fully exhibit its battery performance.

[0125] Therefore, in the lithium secondary battery 200 manufactured in this way, based on the total volume of the electrolyte, the content of liquid electrolyte that exists alone inside the secondary battery case 220 and is not wetted into the electrodes 201 and the separator 202 can be 5% by volume or less, specifically 3% by volume or less, or more specifically 1% by volume or less.

[0126] That is, according to this disclosure, the liquid electrolyte existing alone in this manner corresponds to the degree to which a portion of the liquid electrolyte that is wetted in the electrodes or separators leaks out, for example, during the activation process when pressure is applied to and removed from the lithium secondary battery 200.

[0127] On the other hand, although the liquid electrolyte content inside the secondary battery box 220 is extremely small, the electrodes 201 and the separator 202 are directly exposed to the liquid electrolyte in the electrode unit and separator unit for electrolyte wetting, so that electrolyte wetting can even fully reach the interior of the electrodes 201 or the separator 202. Therefore, based on the total volume of the electrodes, the electrolyte present in the secondary battery box 220 can be 5% by volume or less, or more specifically 1% by volume or less.

[0128] Furthermore, since the electrodes wetted with liquid electrolyte are stored in roll form and then used during manufacturing, the time required for the liquid electrolyte to evaporate can be reduced, allowing the electrodes and separators to exist in a state where they are fully wetted by the liquid electrolyte.

[0129] Specifically, based on the total volume of electrode 201, the liquid electrolyte immersed in electrode 201 may be included in an amount of 101% to 150%, and based on the total volume of separator 202, the liquid electrolyte immersed in separator 202 may be included in an amount of 100% to 150%.

[0130] Specifically, based on the total volume of electrode 201, the liquid electrolyte immersed in electrode 201 may be included in an amount of 105% to 150%, more specifically 110% to 130%, and based on the total volume of separator 202, the liquid electrolyte immersed in separator 202 may be included in an amount of 100% to 130%, more specifically 105% to 130%.

[0131] Therefore, according to this disclosure, by fully immersing the liquid electrolyte in the electrode 201 and the separator 202, the interfacial resistance that may occur due to problems such as reduced lithium-ion mobility between the electrode 201 and the separator 202 can be reduced.

[0132] Specifically, in this disclosure, the interface resistance between electrode 201 and separator 202 can be from 0.01 Ω·cm² to 0.055 Ω·cm², more specifically from 0.05 Ω·cm² to 0.55 Ω·cm², and even more specifically from 0.05 Ω·cm² to 0.054 Ω·cm².

[0133] Interface resistance can be calculated by: activating the manufactured lithium secondary battery; instantaneously applying a high current of 2.0 C to 5.0 C, specifically 2.0 C to 3.0 C; and observing the change in voltage, then applying Ohm's law to the initial rapid change.

[0134] If the interface resistance is too high outside the above range, the output characteristics of the lithium secondary battery may deteriorate, which is not preferred.

[0135] Furthermore, the ion resistance between electrode 201 and separator 202 can be from 0.01 Ω·cm² to 0.045 Ω·cm², specifically from 0.02 Ω·cm² to 0.04 Ω·cm², and more specifically from 0.03 Ω·cm² to 0.04 Ω·cm².

[0136] After observing the voltage change in the same way as the interface resistance, the ionic resistance can be obtained from the voltage change over a period of approximately 5 to 20 seconds, specifically up to 10 seconds.

[0137] Preferred embodiments, comparative examples, and experimental examples for evaluating the invention will be described below. However, the following embodiments are merely preferred embodiments of the invention and are not intended to limit the scope of the invention.

[0138] Example 1

[0139] LiFePO4 was used as the positive electrode active material, carbon nanotubes as the conductive material, and PVDF polymer as the binder. A slurry composition was prepared by mixing the positive electrode active material, conductive material, and binder in an N-methylpyrrolidone solvent at a weight ratio of 96.5:1.5:2. The slurry composition was applied to an aluminum current collector, then dried and rolled in a vacuum furnace at 110°C to fabricate the positive electrode.

[0140] A glass fiber nonwoven fabric with a 50% pore size and a thickness of 200 μm was placed in a water bath (40°C) filled with a liquid electrolyte in which LiPF6 was dissolved at a concentration of 1.0 M in a non-aqueous organic solvent with a composition of ethylene carbonate (EC):γ-butyrolactone (GBL) = 20:80 (volume ratio), and allowed to stand for 24 hours for dip coating. The glass fiber nonwoven fabric and the positive electrode were then wound together in roll form to form a roll assembly, which was then left to stand at 60°C for 24 hours to obtain a positive electrode wetted with the liquid electrolyte.

[0141] Prepare separators (SRS separators coated on both surfaces of a polyethylene substrate with Al2O3:PVDF = 90 wt%: 10 wt%). Place the separators in a water bath (40°C) filled with a liquid electrolyte in a non-aqueous organic solvent containing LiPF6 dissolved at a concentration of 1.0 M in an ethylene carbonate (EC):γ-butyrolactone (GBL) ratio of 20:80 (volume ratio), and allow to stand for 24 hours for dip coating.

[0142] The positive electrode and the separator, both wetted with liquid electrolyte, are cut into unit electrodes / separators. The separators are then stacked between the positive electrode and the lithium metal foil negative electrode to form an assembly, which is then incorporated into a pouch-type secondary battery case to manufacture a half-cell.

[0143] Comparative Example 1

[0144] The half-cell was manufactured in the same manner as in Example 1, except that a liquid electrolyte was simply applied to the positive electrode manufactured in Example 1 and allowed to stand for 24 hours to prepare a positive electrode wetted with the liquid electrolyte, and such a positive electrode was used.

[0145] Comparative Example 2

[0146] Instead of immersing the positive electrode and separator manufactured in Example 1 separately with liquid electrolyte, the separator (an SRS separator coated with Al2O3:PVDF=90 wt%:10 wt% on both surfaces of a polyethylene substrate) was inserted between the positive electrode and the lithium metal negative electrode, and then placed in a pouch-type secondary battery box filled with liquid electrolyte, and allowed to stand for 48 hours to manufacture a half cell.

[0147] Experimental Example 1

[0148] The amount of liquid electrolyte used in Example 1 and Comparative Example 2 was measured respectively.

[0149] The amount of liquid electrolyte used in Example 1 was calculated by subtracting the weight of the remaining liquid electrolyte after adding and removing the separator from the weight of the liquid electrolyte initially placed in the prepared tank. The amount of liquid electrolyte used in Comparative Example 2 was calculated based on the injected weight.

[0150] Subsequently, the half-cells manufactured in Example 1 and Comparative Example 2 were charged at 25°C with a constant current of 0.1 C until the voltage reached 3.85 V, and then discharged with a constant current of 0.1 C until the voltage reached 2.5 V.

[0151] Subsequently, the half-cell was disassembled to remove the battery, and then the total weight of the pouch and the electrolyte remaining in the pouch was measured, where the weight of the liquid electrolyte that was not wetted into the electrodes or separators was calculated by subtracting the weight of the pouch before the half-cell was manufactured.

[0152] Therefore, the ratio of the weight of the unwetting liquid electrolyte inside the bag to the total weight of the electrolyte used is calculated and shown in Table 1 below.

[0153] [Table 1]

[0154]

[0155] Experimental Example 2

[0156] The half-cell manufactured in Experiment Example 1 was disassembled, and the positive electrode and separator were separated. The weights of the positive electrode and separator were measured separately, and then the cell was placed in a vacuum chamber under vacuum conditions to remove the electrolyte.

[0157] The weight of the positive electrode and separator after the electrolyte has been removed is then measured, as well as the weight of the positive electrode and separator before the electrolyte evaporates and after the electrolyte has been removed, to obtain the weight of the electrolyte contained in each component.

[0158] When the weight of the electrolyte is converted into volume using density, the volume occupied by the electrolyte is calculated based on the volume of the electrodes and the volume of the separators, and is shown in Table 2 below.

[0159] The volume of the electrodes and separators is calculated as area × thickness.

[0160] [Table 2]

[0161]

[0162] Experimental Example 3

[0163] The half-cells manufactured in Example 1 and Comparative Examples 1 and 2 were charged at 25°C with a constant current of 0.1 C until the voltage reached 3.85 V, and then discharged with a constant current of 0.1 C until the voltage reached 2.5 V. The resulting initial charge capacity and initial discharge capacity are shown in Table 3 below. The ratio of initial discharge capacity to initial charge capacity is defined as the initial efficiency, and it is also shown in Table 3 below.

[0164] In addition, the battery capacity was measured simultaneously with 30 charge-discharge cycles at 45°C and 0.1 C within a voltage range of 2.5 V to 3.8 V. The capacity retention rate was defined as the ratio of the capacity at the 30th cycle to the capacity at the 1st cycle, and is shown in Table 3 below.

[0165] [Table 3]

[0166]

[0167] Referring to Table 3, it can be determined that when a positive electrode pre-wetting by the manufacturing method of this disclosure is used, it is superior in terms of capacity, efficiency and capacity retention compared to Comparative Example 1, in which liquid electrolyte is simply applied to the positive electrode. Furthermore, it can achieve a similar level of performance compared to Comparative Example 2, which uses a conventional liquid electrolyte injection + wetting process and requires twice the process time of this disclosure, thereby enabling a reduction in process time.

[0168] Experiment Example 4

[0169] The half-cell manufactured as in Example 1 was charged at 25°C with a constant current of 0.1 C until the voltage reached 3.85 V, and then discharged with a constant current of 0.1 C until the voltage reached 2.5 V. This charge-discharge cycle was repeated three times, with a current equivalent to 2.5 C applied instantaneously to observe the voltage change. The resistance was calculated from the voltage change using Ohm's law.

[0170] When a current is applied, the initial rapid change in resistance is defined as the interfacial resistance, and the resistance obtained from the voltage change up to about 10 seconds is defined as the ionic resistance.

[0171] The results are shown in Table 4 below.

[0172] [Table 4]

[0173]

[0174] Referring to Table 4, it can be determined that the half-cell manufactured by the manufacturing method of this disclosure has significantly lower interface resistance and ionic resistance.

[0175] Based on the above disclosure, those skilled in the art can make various applications and modifications without departing from the spirit and scope of this disclosure.

[0176] [Industrial Applicability]

[0177] As described above, according to this disclosure, the electrodes can be fully wetted with a liquid electrolyte before manufacturing a lithium secondary battery, so that the battery can be manufactured without the need for additional electrolyte injection.

[0178] Furthermore, since the electrodes are fully wetted by the electrolyte and no additional wetting time is required, the process is simplified and problems such as increased resistance in areas not wetted by the electrolyte and degradation of lifetime characteristics due to electrolyte depletion are avoided, which effectively improves the performance and safety of lithium secondary batteries.

Claims

1. A method for impregnating an electrolyte into an electrode for a lithium secondary battery. The method includes manufacturing and storing roll assemblies in which elongated electrodes and a substrate wetted with a liquid electrolyte are wound together.

2. The method for wetting electrolytes according to claim 1, The storage temperature is 30℃ to 80℃.

3. The method for wetting electrolytes according to claim 1, The storage time is 20 to 48 hours.

4. The method for wetting electrolytes according to claim 1, The substrate wetted with liquid electrolyte is a nonwoven fabric, a polymer film, or a separator.

5. The method for wetting electrolytes according to claim 1, The substrate wetted with the liquid electrolyte is manufactured by dip coating, wherein the substrate is immersed in a liquid electrolyte solution.

6. The method for wetting electrolytes according to claim 1, The aforementioned roll assembly is manufactured by separately preparing the electrode wound in roll form and the substrate wetted with liquid electrolyte in roll form, then unwinding them and rewinding them together.

7. A method for manufacturing a lithium secondary battery, comprising incorporating an electrode assembly containing electrodes and separators into a secondary battery case. The electrode is an electrolyte-wetted electrode manufactured by the method for wetting electrolyte according to any one of claims 1 to 5.

8. The method for manufacturing a lithium secondary battery according to claim 7, The separator is an electrolyte-wetted separator that is wetted with liquid electrolyte before the electrode assembly is manufactured.

9. The method for manufacturing a lithium secondary battery according to claim 7, The method does not include the step of separately injecting the liquid electrolyte into the secondary battery box.

10. A lithium secondary battery having an electrode assembly, including electrodes wetted with a liquid electrolyte and separators wetted with the liquid electrolyte, incorporated into a secondary battery case. Based on the total weight of the electrolyte, the liquid electrolyte present in the secondary battery box that is not wetted into the electrodes or the separator accounts for 5% or less by weight.

11. The lithium secondary battery according to claim 10, Based on the total weight of the electrolyte, the liquid electrolyte present in the secondary battery box that is not wetted into the electrodes or the separator accounts for 1% or less by weight.

12. The lithium secondary battery according to claim 10, The liquid electrolyte, based on the total volume of the electrode, is included in the electrode in an amount of 100% to 130%, and Based on the total volume of the separator, the liquid electrolyte immersed in the separator is included in an amount of 100% to 150%.

13. The lithium secondary battery according to claim 10, The interface resistance between the electrode and the separator is 0.01 Ω·cm² to 0.055 Ω·cm².

14. The lithium secondary battery according to claim 10, The ionic resistance between the electrode and the separator is 0.01 Ω·cm² to 0.045 Ω·cm².

Images