Electrodes for lithium secondary batteries, methods for manufacturing the same, and lithium secondary batteries containing the same

Abstract

The present invention relates to an electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the same. According to the present invention, there are provided an electrode for a lithium secondary battery in which the binding between the porous layer and the electrode active material layer is dense while the porous layer is given high flexibility and can exhibit excellent durability during charge and discharge, a method for manufacturing the same, and a lithium secondary battery including the electrode.

Description

[Technical Field]

[0001] [Cross-reference of related applications] This application claims priority rights based on Republic of Korea Patent Application No. 10-2023-0053337 dated April 24, 2023, and Republic of Korea Patent Application No. 10-2024-0042820 dated March 28, 2024, and all content disclosed in the literature of said Republic of Korea Patent Applications is included as part of this Specification.

[0002] This invention relates to an electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery containing the same. [Background technology]

[0003] Recently, with the increasing technological development and demand for mobile devices, the demand for rechargeable secondary batteries as an energy source has been rapidly increasing. As a result, much research is being conducted on secondary batteries that can meet diverse requirements. Secondary batteries are also attracting attention as a power source for electric vehicles (EVs), hybrid electric vehicles (HEVs), and plug-in hybrid electric vehicles (Plug-in HEVs), which have been proposed as solutions to address air pollution caused by existing gasoline and diesel vehicles that use fossil fuels.

[0004] In lithium-ion batteries, a short circuit caused by contact between the positive and negative electrodes leads to intense heat generation and subsequent explosion. Therefore, porous separators have been applied to lithium-ion batteries. However, due to the material properties and manufacturing process characteristics, including stretching, these porous separators exhibit severe thermal contraction behavior at temperatures above approximately 100°C, which can cause a short circuit between the positive and negative electrodes.

[0005] Therefore, there is a need for research into lithium secondary batteries that can achieve stability and long battery life characteristics at high temperatures, and that include a separation membrane with excellent coating properties. [Overview of the project] [Problems that the invention aims to solve]

[0006] This invention provides an electrode for lithium secondary batteries that has excellent bonding durability between a porous layer and an electrode substrate.

[0007] The present invention provides a method for manufacturing electrodes for lithium secondary batteries.

[0008] Furthermore, the present invention provides a lithium secondary battery including the aforementioned electrodes. [Means for solving the problem]

[0009] According to one embodiment of the present invention, It includes an electrode active material layer and a porous layer laminated on an electrode current collector layer, The porous layer comprises a polymer binder containing a copolymer comprising a hard segment of the following chemical formula 1 and a soft segment of the following chemical formula 2, and inorganic fine particles dispersed on the polymer binder. Electrodes for lithium secondary batteries are provided.

[0010] [ka]

[0011] In the aforementioned chemical formula 1, R 1 and R 3 Each of them operates independently.

[0012] [ka]

[0013] A 1 Or A 3 Each is independently either hydrogen or an alkyl group having 1 to 3 carbon atoms, L 1 is a chemical bond or methylene group, R 2 This is an alkylene group having 1 to 5 carbon atoms.

[0014] [ka]

[0015] In the aforementioned chemical formula 2, R 4 This is an alkylene group having 3 to 6 carbon atoms.

[0016] According to another embodiment of the present invention, The steps include: applying an electrode material composition containing an electrode active material onto an electrode current collector layer to form an electrode active material layer; The steps include: preparing an inorganic fine particle dispersion liquid by dispersing inorganic fine particles and a dispersant in a solvent; The steps include preparing a binder solution by dissolving a polymer binder containing a copolymer comprising the hard segment of chemical formula 1 and the soft segment of chemical formula 2 in a solvent, The steps include: preparing a slurry for forming a porous layer by mixing the binder solution with the inorganic fine particle dispersion; The steps include applying the porous layer forming slurry onto the electrode active material layer to form a porous layer, A method for manufacturing the electrode for the lithium secondary battery is provided, including the above.

[0017] Another embodiment of the present invention provides a slurry for forming a porous layer of an electrode for a lithium secondary battery, comprising a polymer binder and inorganic fine particles dispersed on the polymer binder.

[0018] According to yet another embodiment of the present invention, a lithium secondary battery including the electrodes for the lithium secondary battery is provided.

[0019] The following describes in more detail the electrode for a lithium secondary battery, its manufacturing method, and a lithium secondary battery containing the same, which are examples of the realization of the present invention.

[0020] According to one embodiment of the present invention, It includes an electrode active material layer and a porous layer laminated on an electrode current collector layer, The porous layer contains a polymer binder containing a copolymer including a hard segment of the following Chemical Formula 1 and a soft segment of the following Chemical Formula 2, and inorganic fine particles dispersed on the polymer binder. An electrode for a lithium secondary battery is provided.

[0021]

Chem.

[0022] In the above Chemical Formula 1, R 1 and R 3 are each independently

[0023]

Chem.

[0024] [[ID=�3]]and A 1 to A 3 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, and L 1 is a chemical bond or a methylene group, R 2 is an alkylene group having 1 to 5 carbon atoms,

[0025]

Chem.

[0026] In the above Chemical Formula 2, R 4 is an alkylene group having 3 to 6 carbon atoms.

[0027] As a result of the inventors' continuous research, it was confirmed that an electrode for a lithium secondary battery satisfying the above configuration has a dense binding between the porous layer and the electrode active material layer, while giving high flexibility to the porous layer and showing excellent durability during charge and discharge.

[0028] According to one embodiment of the present invention, the electrode for the lithium secondary battery may be a negative electrode or a positive electrode.

[0029] The electrode current collector layer can be made of an electrode current collector known to be conductive without inducing chemical changes in the lithium secondary battery within the art to which the present invention belongs. For example, the electrode current collector may be made of stainless steel; aluminum; nickel; titanium; calcined carbon; or aluminum or stainless steel with a surface treatment of carbon, nickel, titanium, silver, etc.

[0030] Preferably, the electrode current collector may have a thickness of 3 μm to 500 μm. To enhance adhesion to the electrode material, the electrode current collector may have fine irregularities formed on its surface. The electrode current collector can take various forms, such as film, sheet, foil, net, porous body, foam, or nonwoven fabric.

[0031] The electrode active material layer comprises an electrode material composition which is a mixture of an electrode active material, a conductive material, and a binder.

[0032] The conductive material can be used to impart electronic conductivity to the electrode.

[0033] The conductive material can be any material that has electronic conductivity without causing a chemical change in the lithium secondary battery, without any special limitations. Non-limiting examples of the conductive material include carbon-based materials such as carbon black, acetylene black, Ketjen black, channel black, furnace black, lamp black, thermal black, and carbon fiber; graphite such as natural graphite or artificial graphite; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. One or more of the above-mentioned examples may be used as the conductive material.

[0034] The content of the conductive material may be adjusted to a range that exhibits an appropriate level of conductivity without causing a decrease in the capacity of the lithium secondary battery. Preferably, the content of the conductive material may be 1% to 10% by weight or 1% to 5% by weight based on the total weight of the electrode material composition.

[0035] The binder is used to ensure that the electrode material composition adheres well to the electrode current collector.

[0036] As non-limiting examples, the binder may be polyvinyl alcohol, polyacrylate, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylic styrene-butadiene rubber, epoxy resin, nylon resin, etc. One or more of the above-mentioned examples may be used as the binder.

[0037] The binder content may be adjusted to a range that exhibits an appropriate level of adhesion without inducing a decrease in the capacity of the lithium secondary battery. Preferably, the binder content may be 1% to 10% by weight or 1% to 5% by weight based on the total weight of the electrode material composition.

[0038] When the electrode for the lithium secondary battery is the positive electrode, the positive electrode active material can be any material that allows for the reversible insertion and removal of lithium ions without any special restrictions.

[0039] As an example, the positive electrode active material may be a composite oxide or phosphorus oxide containing a metal such as cobalt, manganese, nickel, iron, or a combination thereof, and lithium.

[0040] As another example, the positive electrode active material may be a compound represented by any one of the following chemical formulas: Li a A 1-b R b D2(0.90≦a≦1.8, 0≦b≦0.5);Li a E 1-b R b O 2-c D c (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05);LiE 2-b R b O 4-c D c (0≦b≦0.5, 0≦c≦0.05);Li a Ni 1-b-c Co b R c D d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d≦2);Li a Ni 1-b-c Co b R c O 2-d Z d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Co b R c O 2-d Z2(0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Mn b R c D d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d≦2);Li a Ni 1-b-c Mn b R c O 2-d Z d (0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Ni 1-b-c Mn b R c O 2-d Z2(0.90≦a≦1.8, 0≦b≦0.5, 0≦c≦0.05, 0 <d<2);Li a Nib E c G d O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0.001≦d≦0.1.);Li a Ni b Co c Mn d G e O2(0.90≦a≦1.8, 0≦b≦0.9, 0≦c≦0.5, 0≦d≦0.5, 0.001≦e≦0.1);Li a NiG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a CoG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a MnG b O2(0.90≦a≦1.8, 0.001≦b≦0.1);Li a Mn2G b O4(0.90≦a≦1.8, 0.001≦b≦0.1);QO2;QS2;LiQS2;V2O5;LiV2O5;LiTO2;LiNiVO4;Li (3-f) J2(PO4)3(0≦f≦2);Li (3-f) Fe2(PO4)3 (0≦f≦2); and LiFePO4.

[0041] In the above chemical formulas, A is Ni, Co, Mn or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, rare earth elements or a combination thereof; D is O, F, S, P or a combination thereof; E is Co, Mn or a combination thereof; Z is F, S, P or a combination thereof; G is Al, Cr, Mn, Fe, Mg, La, Ce, Sr, V or a combination thereof; Q is Ti, Mo, Mn or a combination thereof; T is Cr, V, Fe, Sc, Y or a combination thereof; J is V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0042] The positive electrode active material may also have a coating layer on its surface, or the positive electrode active material and the positive electrode active material having a coating layer may be mixed and used. The coating elements included in the coating layer may be Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or mixtures thereof.

[0043] According to one embodiment, the positive electrode active material may be present in an amount of 80% to 95% by weight relative to the total weight of the electrode material composition. Preferably, the content of the positive electrode active material may be 82% to 95% by weight, or 82% to 93% by weight, or 85% to 93% by weight, or 85% to 90% by weight, relative to the total weight of the electrode material composition.

[0044] When the electrode for the lithium secondary battery is the negative electrode portion, the negative electrode active material may include a substance capable of reversibly intercalating and deintercalating lithium ions, lithium metal, an alloy of lithium metal, a substance capable of doping and dedoping lithium, and a transition metal oxide.

[0045] Examples of materials capable of reversibly intercalating and deintercalating lithium ions include crystalline carbon, amorphous carbon, or mixtures thereof as carbonaceous materials. Specifically, the carbonaceous material may be natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch-based carbon fiber, meso-carbon microbeads, petroleum or coal tar pitch-derived cokes, soft carbon, and hard carbon.

[0046] The alloy of the lithium metal may be an alloy of lithium and a metal selected from the group consisting of Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, Sn, Bi, Ga, and Cd.

[0047] The substance capable of doping and undoping lithium may be Si, Si-C composite, SiOx (0 < x < 2), Si-Q alloy (where Q is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Si is excluded), Sn, SnO2, Sn-R alloy (where R is an element selected from the group consisting of alkali metals, alkaline earth metals, group 13 elements, group 14 elements, group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof; provided that Sn is excluded), etc. And as the substance capable of doping and undoping lithium, at least one of the above examples and SiO2 can be mixed and used. Q and R may be 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, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, etc.

[0048] And the transition metal oxide may be vanadium oxide, lithium vanadium oxide, lithium titanium oxide, etc.

[0049] Preferably, the negative electrode active material may contain one or more compounds selected from the group consisting of carbonaceous materials and silicon compounds. Here, the carbonaceous material is one or more substances selected from the group consisting of natural graphite, artificial graphite, kish graphite, pyrolytic carbon, mesophase pitch, mesophase pitch-based carbon fiber, carbon microspheres, petroleum or coal-based coke, softened carbon, and hardened carbon, as exemplified above. And the silicon compound may be a compound containing Si exemplified above, that is, Si, Si-C composite, SiOx (0 < x < 2), the Si-Q alloy, a mixture thereof, or a mixture of at least one of these and SiO2.

[0050] According to one embodiment, the negative electrode active material may be contained at 85% to 98% by weight based on the total weight of the electrode material composition. Preferably, the content of the negative electrode active material may be 85% to 97% by weight, or 87% to 97% by weight, or 87% to 95% by weight, or 90% to 95% by weight based on the total weight of the negative electrode material.

[0051] According to one embodiment, the thickness of the electrode active material layer is preferably adjusted in the range of 5 μm to 500 μm, or 5 μm to 450 μm, or 10 μm to 450 μm for the expression of appropriate performance.

[0052] On the other hand, the electrode for the lithium secondary battery includes a porous layer laminated on the electrode current collector layer.

[0053] According to one embodiment, the porous layer includes a polymer binder and inorganic fine particles dispersed on the polymer binder.

[0054] In particular, the polymer binder includes a copolymer containing a hard segment of the following Chemical Formula 1 and a soft segment of the following Chemical Formula 2.

[0055]

Chemical Formula

[0056] In the aforementioned chemical formula 1, R 1 and R 3 Each of them operates independently.

[0057] [ka]

[0058] A 1 Or A 3 Each is independently either hydrogen or an alkyl group having 1 to 3 carbon atoms, L 1 is a chemical bond or methylene group, R 2 This is an alkylene group having 1 to 5 carbon atoms.

[0059] [ka]

[0060] In the aforementioned chemical formula 2, R 4 This is an alkylene group having 3 to 6 carbon atoms.

[0061] The copolymer has a hard segment capable of hydrogen bonding with the electrode active material layer and a soft segment that provides high flexibility within the copolymer. As a result, the bonding between the porous layer and the electrode active material layer is dense, while the porous layer is given high flexibility, allowing it to exhibit excellent durability during charging and discharging.

[0062] In the copolymer, the R 1 and R 3 Each of them operates independently.

[0063] [ka]

[0064] That is the case.

[0065] Here, the above-mentioned A 1 or A 3 is each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, and the above-mentioned L 1 is a chemical bond or a methylene group. Preferably, the above-mentioned A 1 or A 3 may each be hydrogen, a methyl group, or an ethyl group. Preferably, the above-mentioned L 1 may be a methylene group.

[0066] According to one embodiment, the above-mentioned R 1 and R 3 can each have the above-mentioned structure derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI), 1,4-phenylene diisocyanate, 1,3-phenylene diisocyanate, 2,4-toluene diisocyanate (2,4-TDI), 2,6-toluene diisocyanate (2,6-TDI), or 1,5-naphthalene diisocyanate.

[0067] According to one embodiment, the above-mentioned R 1 and R 3 are each independently

[0068]

Chemical formula

[0069] and may be like this.

[0070] According to one embodiment, the above-mentioned R 1 and R 3 each have the

[0071]

Chemical formula

[0072] structure derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI) and can have it.

[0073] In the copolymer, the R 2 is an alkylene group having 1 to 5 carbon atoms. According to one embodiment, the R 2 The structure may be derived from methylenediamine, ethylenediamine, 1,3-diaminopropane, 1,4-diaminobutane, or 1,5-diaminopentane. Preferably, the R 2 R may be a methylene group (*-CH2-*), an ethylene group (*-CH2-CH2-*), or a propylene group (*-CH2-CH2-CH2-*). According to one embodiment, 2 It can have a structure with an ethylene group (*-CH2-CH2-*) derived from ethylenediamine (EDA).

[0074] In the above chemical formula 2, the R 4 is an alkylene group having 3 to 6 carbon atoms. Preferably, the R 4 R may be a propylene group (*-CH2-CH2-CH2-*) or a butylene group (*-CH2-CH2-CH2-CH2-*). According to one embodiment, 4 The structure may be derived from polytrimethylene ether glycol or polytetramethylene ether glycol. According to one embodiment, the R 4 It can have a structure of butylene groups (*-CH2-CH2-CH2-CH2-*) derived from polytetramethylene ether glycol (PTMEG).

[0075] As a non-restrictive example, the copolymer is the hard segment of chemical formula 1, and the R 1 and R 3 These are each derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI).

[0076] [ka]

[0077] It is a structure, and the R 2This is the structure of an ethylene group (*-CH2-CH2-*) derived from ethylenediamine (EDA), and is the soft segment of the above chemical formula 2, and R 4 It may also be a copolymer having a butylene group (*-CH2-CH2-CH2-CH2-*) structure derived from polytetramethylene ether glycol (PTMEG).

[0078] According to one embodiment, the copolymer may contain the hard segment and the soft segment in a molar ratio of 80:20 to 95:5.

[0079] In order to ensure proper bonding with the electrode active material layer while imparting appropriate mechanical properties to the polymer binder containing the copolymer, the molar ratio of the hard segment to the soft segment is preferably 80:20 or higher. Furthermore, in order to provide high flexibility to the porous layer, the molar ratio of the hard segment to the soft segment is preferably 95:5 or lower.

[0080] Specifically, the molar ratio of the hard segment to the soft segment may be 80:20 or higher, or 85:15 or higher, and 95:5 or lower, or 90:10 or lower.

[0081] Preferably, the molar ratio of the hard segment to the soft segment may be 80:20 to 95:5, or 85:15 to 95:5, or 85:15 to 90:10.

[0082] According to one embodiment, the copolymer is 100.00 0 1,000,000 0 It has a weight-average molecular weight (Mw).

[0083] In order to achieve the improvement effect resulting from the application of the copolymer, the weight-average molecular weight (Mw) of the copolymer is set to 100,000. 0 or more Above or 150,000 0 or more Above, and 1,000,00 0 or moreBelow, or 800,000 0 or more Below, or 600,000 0 or more Below, or 400,000 0 or more It may be lower. Preferably, the weight-average molecular weight (Mw) of the copolymer is 100,000. 0 1,000,000 0、 Or 150,000 0 1,000,000 0、 Or 150,000 0 ishi800,00 0、 Or 150,000 0 stone 600,00 0、 Or 150,000 0 stone 400,00 0 It's okay to have it.

[0084] As a non-restrictive example, the weight-average molecular weight (Mw) can be measured using an Agilent PL-GPC 220 instrument fitted with a 300 mm long Polar Gel MIXED-L column (Polymer Laboratories). The measurement temperature is 65°C, tetrahydrofuran or dimethylformamide is used as the solvent, and the flow rate is 1 mL / min. The sample is prepared to a concentration of 10 mg / 10 mL and supplied in a volume of 100 μL. The Mw and Mn values ​​are derived by referring to the calibration curve formed using a polystyrene standard. Quantity Eight types are used: 580 / 3,940 / 8,450 / 31,400 / 70,950 / 316,500 / 956,000 / 4,230,000.

[0085] According to one embodiment, the copolymer can be one manufactured to satisfy the aforementioned structure and weight-average molecular weight, or a commercially available product (e.g., spandex).

[0086] The polymer binder, along with the copolymer, contains polyetherimide, polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, and ethylene vinyl acetate. The product may further contain one or more binder compounds selected from the group consisting of styrene-butadiene copolymers, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethylcellulose, cyanoethylsucrose, pullulan, carboxymethylcellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene polymer, sulfonated ethylene-propylene-diene polymer, styrene-butadiene rubber, fluororubber, and polyimide.

[0087] According to one embodiment, in order to exhibit the improvement effect of applying the copolymer, it is preferable that the binder compound be present in an amount of 10% by weight or more, or 10% to 100% by weight, or 30% to 100% by weight, or 50% to 100% by weight, based on the total weight of the polymer binder containing the copolymer comprising the hard segment of chemical formula 1 and the soft segment of chemical formula 2.

[0088] The inorganic fine particles form micropores due to the empty spaces between the particles, maintain their physical form at high temperatures, and are electrochemically stable.

[0089] It is preferable that the inorganic fine particles do not undergo oxidation and / or reduction reactions within the operating voltage range of the secondary battery (for example, 0 to 5V based on Li / Li+). It is preferable that the inorganic fine particles have a high electrolyte ion transfer capacity. It is preferable that the inorganic fine particles have as low a density as possible so that they can be well dispersed in the polymer binder. Furthermore, it is preferable that the inorganic fine particles have a high dielectric constant so that they can contribute to increasing the degree of dissociation of the electrolyte salt in the electrolyte.

[0090] Preferably, the inorganic fine particles may be one or more selected from the group consisting of inorganic particles having a dielectric constant of 1 or more, piezoelectric inorganic particles, and inorganic particles having lithium ion transport capability.

[0091] As an example, inorganic particles such as SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, boehmite (AlO(OH)), Al(OH)3, TiO2, and SiC have a dielectric constant of 1 or more and can be preferably applied as the inorganic fine particles.

[0092] As another example, the piezoelectric inorganic particles are insulators at normal pressure, but exhibit conductivity due to a change in their internal structure when a certain pressure is applied. The piezoelectric inorganic particles have a high dielectric constant, with a dielectric constant of 100 or more. Furthermore, when a certain pressure is applied to the piezoelectric inorganic particles for tension or compression, electric charge is generated, causing one side to become positively (+) charged and the other side negatively (-), resulting in a potential difference between the two sides. Due to the properties of the piezoelectric inorganic particles, when an internal short circuit occurs in the electrodes of a secondary battery due to external shock, direct contact between the positive and negative electrodes can be prevented, leading to a gradual decrease in voltage and improved safety. Examples of the piezoelectric inorganic particles include BaTiO3, Pb(Zr,Ti)O3(PZT), and Pb 1-x La x Zr 1-y Ti y O3(PLZT), Pb(Mg 1 / 3 Nb 2 / 3)Inorganic particles such as O3-PbTiO3 (PMN-PT) and HfO2 can be preferably applied.

[0093] As another example, the inorganic particles having the lithium ion transfer ability refer to inorganic particles that contain lithium elements and have a function of moving lithium ions without storing lithium. The inorganic particles having the lithium ion transfer ability can improve the conductivity of lithium ions in the battery. Such inorganic particles include Li3PO4, Li x Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li x Ge y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li x N y (0 < x < 4, 0 < y < 2), Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), and Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), etc.

[0094] Preferably, the inorganic fine particles are SrTiO3, SnO2, CeO2, MgO, NiO, CaO, ZnO, ZrO2, Y2O3, Al2O3, AlO(OH), Al(OH)3, TiO2, SiC, BaTiO3, Pb(Zr, Ti)O3, Pb 1-x La x Zr 1-y Ti y O3, Pb(Mg 1 / 3 Nb 2 / 3 )O3-PbTiO3, HfO2, Li3PO4, Lix Ti y (PO4)3 (0 < x < 2, 0 < y < 3), Li x Al y Ti z (PO4)3 (0 < x < 2, 0 < y < 1, 0 < z < 3), (LiAlTiP) x O y (0 < x < 4, 0 < y < 13), Li x La y TiO3 (0 < x < 2, 0 < y < 3), Li x Ge y P z S w (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5), Li x N y (0 < x < 4, 0 < y < 2), Li x Si y S z (0 < x < 3, 0 < y < 2, 0 < z < 4), and Li x P y S z It may be one or more selected from the group consisting of (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0095] Preferably, the inorganic fine particles have a particle size of 0.001 μm to 10 μm. In order to ensure the dispersibility in the porous layer, it is preferable that the inorganic fine particles have a particle size of 0.001 μm or more. However, when the particle size of the inorganic fine particles is excessively large, the thickness of the porous layer increases and the mechanical properties deteriorate, and there is a possibility of internal short circuit occurring during charge and discharge of the secondary battery due to the excessively large pore size. Therefore, it is preferable that the inorganic fine particles have a particle size of 10 μm or less.

[0096] According to one embodiment, the porous layer may contain 0.5 to 45% by weight of the polymer binder and 55 to 99.5% by weight of the inorganic fine particles.

[0097] In order to provide the porous layer with appropriate porosity and insulating properties, the inorganic fine particles are preferably included in an amount of 55% by weight or more, or 60% by weight or more, or 65% by weight or more, or 70% by weight or more, or 75% by weight or more, or 80% by weight or more. However, if the inorganic fine particles are included in excess, the mechanical properties of the porous layer may deteriorate due to weakening of the adhesive strength. Therefore, it is preferable that the inorganic fine particles are included in an amount of 99.5% by weight or less, or 99% by weight or less, or 95% by weight or less.

[0098] Specifically, the porous layer may contain 55 to 99.5% by weight of the inorganic fine particles, or 60 to 99.5% by weight, or 65 to 99.5% by weight, or 70 to 99.5% by weight, or 75 to 99.5% by weight, or 80 to 99.5% by weight, or 80 to 99% by weight, or 80 to 95% by weight, and the remainder of the polymer binder.

[0099] According to one embodiment, the porosity of the porous layer may be 40 to 80%.

[0100] In terms of ensuring lithium ion permeability, the porosity of the porous layer is preferably 40% or more, or 45% or more, or 50% or more. However, if the porosity of the porous layer is excessively high, it may be difficult to ensure sufficient adhesion between the porous layer and the electrode, which could lead to an internal short circuit during charging and discharging of the lithium secondary battery. Therefore, the porosity of the porous layer is preferably 80% or less, or 75% or less, or 70% or less.

[0101] Specifically, the porosity of the porous layer may be 40 to 80%, 45 to 80%, 45 to 75%, 50 to 75%, or 50 to 70%.

[0102] The porosity can be measured by preparing the slurry for forming the porous layer, then applying it to a shaped film to produce an independent porous layer. In other words, a composition and process conditions that can ensure a porosity within the aforementioned range can be established experimentally and applied to actual manufacturing.

[0103] The porosity can be measured using scanning electron microscope (SEM) images, using an adsorbed gas such as nitrogen and a BET apparatus, or by methods such as mercury intrusion porosimetry or capillary flow porosimetry. Alternatively, the porosity can be calculated from the thickness, weight, and theoretical density of the obtained porous layer.

[0104] The porous layer preferably has a porosity within an appropriate range for the characteristics of the porous layer to be expressed. If the porosity of the porous layer is excessively high, an internal short circuit may occur during the charging and discharging of the lithium secondary battery. Therefore, it is preferable that the porosity of the porous layer be 60% or less.

[0105] According to one embodiment, the thickness of the porous layer is preferably adjusted to a range of 5 μm to 100 μm, 5 μm to 50 μm, or 10 μm to 50 μm in order to achieve appropriate performance.

[0106] On the other hand, an interface layer can exist in the entire region between the electrode active material layer and the porous layer, in which the electrode material composition contained in the electrode active material layer and the porous composition contained in the porous layer are mixed.

[0107] As an example, the interface layer is a layer comprising the electrode material composition in a quantity exceeding 0% by weight but less than 100% by weight and the porous composition in a quantity less than 100% by weight but exceeding 0% by weight.

[0108] According to another embodiment of the present invention, The steps include: applying an electrode material composition containing an electrode active material onto an electrode current collector layer to form an electrode active material layer; The steps include: preparing an inorganic fine particle dispersion liquid by dispersing inorganic fine particles and a dispersant in a solvent; The steps include preparing a binder solution by dissolving a polymer binder containing a copolymer comprising the hard segment of chemical formula 1 and the soft segment of chemical formula 2 in a solvent, The steps include: preparing a slurry for forming a porous layer by mixing the binder solution with the inorganic fine particle dispersion; The steps include applying the porous layer forming slurry onto the electrode active material layer to form a porous layer, A method for manufacturing an electrode for a lithium secondary battery according to the foregoing is provided, including the above.

[0109] The aforementioned electrodes for lithium secondary batteries can be provided through the manufacturing method described above.

[0110] First, a step may be performed in which an electrode material composition containing an electrode active material is applied to the electrode current collector layer to form an electrode active material layer. In this step, the electrode current collector and the electrode material composition are replaced with those described above. The electrode active material layer can be formed by coating the electrode material composition onto the electrode current collector layer and drying it.

[0111] In addition to the above steps, the following steps may be performed: preparing an inorganic fine particle dispersion by dispersing inorganic fine particles and a dispersant in a solvent; preparing a binder solution by dissolving a polymer binder in a solvent; and preparing a slurry for forming a porous layer by mixing the inorganic fine particle dispersion with the binder solution.

[0112] As a result of the inventors' ongoing research, it has been confirmed that the presence or absence of aggregation of inorganic fine particles and the distribution state of polymer binder and inorganic fine particles can change depending on the mixing order and mixing method of the constituent components when preparing the slurry for forming the porous layer. Furthermore, it has been confirmed that the distribution state of polymer binder and inorganic fine particles can have a significant impact on the binding force between the porous layer and the electrode active material layer.

[0113] For example, when preparing a binder solution by dissolving a polymer binder in a solvent, and then adding inorganic fine particles to prepare a slurry for forming a porous layer, the dispersibility of the inorganic fine particles decreases significantly, making it impossible to provide an electrode for a lithium secondary battery that satisfies the aforementioned characteristics.

[0114] According to one embodiment, the manufacturing method of the present invention is performed by the steps of preparing the inorganic fine particle dispersion, preparing the binder solution, and mixing the binder solution with the inorganic fine particle dispersion to prepare a slurry for forming a porous layer, thereby providing an electrode for a lithium secondary battery in which the porous layer and the electrode active material layer are densely bonded while the porous layer is given high flexibility.

[0115] In the above step, the inorganic fine particles and polymer binder are replaced with those described above.

[0116] As the dispersant, compounds known to be suitable for dispersing inorganic fine particles in the art to which the present invention belongs, such as carboxylic acid-modified polyester copolymers and acetic acid, may be used.

[0117] Furthermore, non-aqueous organic solvents may be used as the solvent. Specifically, the non-aqueous organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; N-methyl-2-pyrrolidone (NMP), dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes may also be used. Among the above examples, the carbonate solvents suitable for dispersing inorganic fine particles can be preferably used as the non-aqueous organic solvent.

[0118] According to one embodiment, the porous layer forming slurry preferably contains 30% to 95% by weight of solids including the inorganic fine particles.

[0119] If the solid content of the porous slurry is excessively high, it can induce an increase in viscosity, preventing it from easily penetrating the pore regions of the electrode active material layer, and thus preventing the formation of an interface layer 25 with an appropriate structure. However, if the solid content of the porous slurry is excessively low, a pinhole phenomenon may occur when it is applied onto the electrode active material layer.

[0120] Specifically, the solid content of the porous slurry may be 30% by weight or more, or 35% by weight or more, and 95% by weight or less, or 90% by weight or less. Preferably, the solid content of the porous slurry may be 30% by weight to 95% by weight, or 30% by weight to 90% by weight, or 35% by weight to 90% by weight.

[0121] Next, the porous layer-forming slurry is applied to the electrode active material layer to form a porous layer. The porous layer can be formed by coating the porous layer-forming slurry onto the electrode active material layer and drying it. This step can be carried out taking into consideration the thickness of the electrode active material layer and the porous layer as described above.

[0122] In the above step, drying is preferably carried out at temperatures of 50°C to 150°C, 60°C to 150°C, 60°C to 120°C, or 65°C to 110°C, respectively. If the drying temperature does not meet the above range, drying efficiency may decrease or changes in the morphology of each layer may occur, potentially leading to defects.

[0123] Another embodiment of the present invention provides a slurry for forming a porous layer of an electrode for a lithium secondary battery, comprising a polymer binder and inorganic fine particles dispersed on the polymer binder.

[0124] In the porous layer forming slurry, the polymer binder and the inorganic fine particles are replaced with those described above.

[0125] As described above, the slurry for forming a porous layer is obtained by the steps of: preparing an inorganic fine particle dispersion by dispersing inorganic fine particles and a dispersant in a solvent; preparing a binder solution by dissolving a polymer binder containing a copolymer of the hard segment of chemical formula 1 and the soft segment of chemical formula 2 in a solvent; and preparing a slurry for forming a porous layer by mixing the binder solution with the inorganic fine particle dispersion.

[0126] According to yet another embodiment of the present invention, a lithium secondary battery including the aforementioned electrodes is provided.

[0127] As an example, the lithium secondary battery may include an electrode assembly including a counter electrode disposed on the porous layer of the electrode, an electrolyte impregnated in the electrode assembly, and a battery case that seals and houses the electrode assembly and the electrolyte.

[0128] The aforementioned lithium secondary battery, by incorporating the electrode assembly described above, can exhibit excellent durability and stable performance.

[0129] The aforementioned lithium secondary battery can have various forms, such as prismatic, cylindrical, or pouch-type.

[0130] The aforementioned lithium secondary battery can be used as an energy source with improved performance and safety in the field of portable electronic devices such as mobile phones, laptop computers, tablet computers, mobile batteries, and digital cameras, as well as in the field of means of transportation such as electric vehicles, electric motorcycles, and personal mobility devices.

[0131] According to one embodiment, the electrolyte can be any electrolyte known to be applicable to lithium secondary batteries in the art to which the present invention belongs, without any special limitations. For example, the electrolyte may be an organic liquid electrolyte, an inorganic liquid electrolyte, a solid polymer electrolyte, a gel-type polymer electrolyte, a solid inorganic electrolyte, a molten inorganic electrolyte, and the like.

[0132] Specifically, the electrolyte may include a non-aqueous organic solvent and a lithium salt.

[0133] The aforementioned non-aqueous organic solvent can be used without any special limitations, as long as it can serve as a medium through which ions involved in the electrochemical reaction of the battery can move.

[0134] Specifically, the non-aqueous organic solvents include ester solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether solvents such as dibutyl ether and tetrahydrofuran; ketone solvents such as cyclohexanone; aromatic hydrocarbon solvents such as benzene and fluorobenzene; dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (propylene Carbonate solvents such as carbonate (PC); alcoholic solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and can include a double-bonded aromatic ring or ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolanes may also be used.

[0135] Among the above examples, carbonate-based solvents are preferably used as the non-aqueous organic solvent.

[0136] In particular, considering the battery's charge / discharge performance and compatibility with the sacrificial cathode material, a mixture of cyclic carbonates (e.g., ethylene carbonate, propylene carbonate) having high ionic conductivity and high dielectric constant, and low-viscosity linear carbonates (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) can be preferably used as the non-aqueous organic solvent. In this case, using a mixture of the cyclic carbonate and the linear carbonate in a volume ratio of 1:1 to 1:9 may be advantageous for achieving the aforementioned performance.

[0137] Furthermore, as the non-aqueous organic solvent, a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a volume ratio of 1:2 to 1:10; or a mixture of ethylene carbonate (EC), ethyl methyl carbonate (EMC), and dimethyl carbonate (DMC) in a volume ratio of 1 to 3:1 to 9:1 can be preferably used.

[0138] The lithium salt contained in the electrolyte dissolves in the non-aqueous organic solvent and acts as a source of lithium ions within the battery, enabling the basic operation of a lithium secondary battery and promoting the movement of lithium ions between the positive and negative electrodes.

[0139] Specifically, the lithium salt may be LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiFSI, LiTFSI, LiCl, LiI, and LiB(C2O4)2, etc. Preferably, the lithium salt may be LiPF6, LiFSI, LiTFSI, and mixtures thereof.

[0140] The lithium salt may be included in the electrolyte at a concentration of 0.1 M to 2.0 M. The lithium salt included within this concentration range imparts appropriate conductivity and viscosity to the electrolyte, thereby enabling it to exhibit excellent electrolyte performance.

[0141] Selectively, the electrolyte may contain additives aimed at improving battery life characteristics, suppressing battery capacity reduction, and improving battery discharge capacity.

[0142] For example, the additive may be a haloalkylene carbonate compound such as difluoroethylene carbonate, pyridine, triethyl phosphate, triethanolamine, cyclic ether, ethylenediamine, n-glyme, hexaphosphate triamide, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. The additive may be present in an amount of 0.1 to 5% by weight relative to the total weight of the electrolyte. [Effects of the Invention]

[0143] According to the present invention, an electrode for a lithium secondary battery is provided in which the bonding between the porous layer and the electrode active material layer is dense, yet the porous layer is given high flexibility, and which exhibits excellent durability during charging and discharging. The present invention also provides a method for manufacturing the same, and a lithium secondary battery including the electrode. [Brief explanation of the drawing]

[0144] [Figure 1] Figure 1 is a scanning electron microscope (SEM) image of the lithium secondary battery electrode according to Example 1. [Figure 2] Figure 2 is an SEM image of the lithium secondary battery electrode according to Example 2. [Figure 3] Figure 3 is an SEM image of the lithium secondary battery electrode according to Example 3. [Figure 4] Figure 4 is an SEM image of the lithium secondary battery electrode according to Example 4. [Figure 5] Figure 5 is an SEM image of the lithium secondary battery electrode according to Example 5. [Figure 6]Figure 6 shows an SEM image of the lithium secondary battery electrode according to Comparative Example 1. [Figure 7] Figure 7 shows an SEM image of the lithium secondary battery electrode according to Comparative Example 2. [Modes for carrying out the invention]

[0145] The operation and effects of the invention will be described in more detail below through specific embodiments of the present invention. However, these are presented as examples to aid in understanding the invention. It is not intended that the scope of the invention is limited in any sense through the following embodiments, and it will be obvious to a person of the skill that various changes and modifications are possible within the scope and technical concept of the present invention.

[0146] Example 1 An electrode material composition was prepared consisting of 95.6% by weight of an active material composed of 90% by weight of graphite active material and 10% by weight of SiO, which is a mixture of artificial graphite and natural graphite in a ratio of 3:7; 1% by weight of acetylene black as a conductive material; and 1.1% by weight of carboxymethylcellulose (CMC) and 2.3% by weight of styrene-butadiene rubber (SBR) as binders. The electrode material composition was applied to one surface of a copper current collector with a thickness of 8 μm using a comma coater. This was dried and rolled at 130°C to prepare a negative electrode plate with a laminated negative electrode active material layer. The negative electrode active material layer was formed with a porosity of 24% and a thickness of 44 μm.

[0147] An inorganic fine particle dispersion with a solid content of 40% was prepared by mixing inorganic fine particles, AlO(OH), and a dispersant (BYK, DISPERBYK-111) with N-methyl-2-pyrrolidone (NMP). At this time, the particle size (D60) of the inorganic fine particles was analyzed to be 400 nm using a particle size analyzer.

[0148] Spandex (weight-average molecular weight 200,000) is used as a polymer binder. 0)A 10% by weight binder solution was prepared by mixing poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) in a 50:50 weight ratio and dissolving it in NMP.

[0149] Here, the spandex is a block copolymer consisting of a hard segment of chemical formula 1 and a soft segment of chemical formula 2. The spandex is made of the hard segment of chemical formula 1, and the R 1 and R 3 These are each derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI).

[0150] [ka]

[0151] It is a structure, and the R 2 This is the structure of an ethylene group (*-CH2-CH2-*) derived from ethylenediamine (EDA), and is the soft segment of the above chemical formula 2, and R 4 This copolymer has a structure of butylene groups (*-CH2-CH2-CH2-CH2-*) derived from polytetramethylene ether glycol (PTMEG). In the spandex, the molar ratio of the hard segment to the soft segment is 85:15.

[0152] A porous layer-forming slurry was obtained by uniformly mixing the inorganic fine particle dispersion and the binder solution using a homomixer.

[0153] After applying the porous layer-forming slurry onto the negative electrode active material layer, the material was dried at 130°C to obtain a negative electrode plate in which a porous layer was formed on the negative electrode active material layer. The composition of the porous layer was 90% by weight of the inorganic fine particles and 10% by weight of the polymer binder. The porous layer was formed to a thickness of 20 μm.

[0154] The negative electrode plate was punched out to a size of 31 x 43 mm using a die punching machine to prepare the negative electrode portion.

[0155] A slurry was prepared by uniformly dispersing a mixture consisting of 94 wt% LiNiCoMnO2 (Ni:Co:Mn=8:1:1) as the positive electrode active material, 3 wt% conductive carbon black (Super P; IMERYS Graphite & Carbon) as the conductive material, and 3 wt% polyvinylidene fluoride as the binder in an NMP (Natural Microwave Optic). The slurry was applied to one surface of an aluminum current collector, and this was dried and rolled to prepare a positive electrode plate with a laminated positive electrode active material layer. The positive electrode portion was prepared by punching out the positive electrode plate to a size of 30 × 42 mm using a die punching machine.

[0156] An electrode assembly was manufactured by arranging the positive electrode active material layer of the positive electrode portion in contact with the porous layer of the negative electrode portion.

[0157] The electrode assemblies were placed in pouches to form small cells, and electrolyte was injected into the pouches to produce five lithium secondary batteries.

[0158] In this case, the electrolyte used was a non-aqueous organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed in a volume ratio of 3:7, in which 1.0 M LiPF6 and 2% by weight of vinylene carbonate (VC) were dissolved.

[0159] Example 2 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 1, except that only spandex was used as the polymer binder instead of the mixture of spandex and PVdF-HFP.

[0160] Example 3 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition of the porous layer was adjusted so that the composition of the porous layer consisted of 92% by weight of the inorganic fine particles and 8% by weight of the polymer binder.

[0161] Example 4 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 3, except that only spandex was used as the polymer binder instead of the mixture of spandex and PVdF-HFP.

[0162] Example 5 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition of the porous layer was adjusted so that the composition of the porous layer was 85% by weight of the inorganic fine particles and 15% by weight of the polymer binder.

[0163] Comparative Example 1 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixture of polyetherimide and PVdF-HFP in a 50:50 weight ratio was used as the polymer binder instead of the mixture of spandex and PVdF-HFP.

[0164] Comparative Example 2 The negative electrode, positive electrode, and lithium secondary battery were manufactured in the same manner as in Example 1, except that PVdF-HFP alone was used as the polymer binder instead of the mixture of spandex and PVdF-HFP.

[0165] Experimental Example 1 The weight-average molecular weight (Mw) and number-average molecular weight (Mn) of the copolymer produced in the above production example were measured using gel permeation chromatography (GPC, Waters E2640).

[0166] Specifically, the copolymer was dissolved in HFIP (hexafluoroisopropanol) to a concentration of 2 mg / ml, and 20 μl was injected into the GPC. The GPC mobile bed was supplied with HFIP at a flow rate of 1.0 mL / min, and the analysis was performed at 40°C. Two Agilent Mixed-B columns were connected in series. An RI Detector was used as the detector. The Mw value was derived using a calibration curve formed with polystyrene standard specimens. The weight-average molecular weight of the polystyrene standard specimens was 2,000. 0、 10.00 0、 30,00 0、 70,00 0、 200.00 0、 700,00 0、 2,000,00 0、 4,000,00 0、 and 10,000,00 0 Nine types were used.

[0167] Experimental Example 2 The bending characteristics of the negative electrode plates according to the above examples and comparative examples were evaluated using the mandrel method, and the diameters of the rods in which cracks occurred are shown in Table 1 below.

[0168] Experimental Example 3 The porous layers according to the above examples and comparative examples were formed on the negative electrode active material layer of the negative electrode plate, and the results were observed using a scanning electron microscope. The results are shown in Figures 1 (Example 1), 2 (Example 2), 3 (Example 3), 4 (Example 4), 5 (Example 5), 6 (Comparative Example 1), and 7 (Comparative Example 2). In Figures 1, 2, 6, and 7, (a) is a 1000x magnification SEM image and (b) is a 5000x magnification SEM image. Figures 3, 4, and 5 are 5000x magnification SEM images.

[0169] Referring to Figures 1 to 5, a uniform surface condition without fine cracks was observed in the negative electrode plate according to the embodiment.

[0170] Referring to Figure 6, cracks were easily observed in the negative electrode plate of Comparative Example 1 due to the inflexible polymer binder properties. Specifically, in Comparative Example 1, the surface was rougher compared to Example 1, and relatively large pores of about 1 μm were observed to be unevenly distributed.

[0171] Referring to Figure 7, the negative electrode plate in Comparative Example 2 showed a slight decrease in surface roughness compared to Comparative Example 1, but surface cracks could still be easily observed.

[0172] Experimental Example 4 The open-circuit voltage (OCV) of the lithium secondary batteries obtained in the above examples and comparative examples (five samples each) was measured immediately after fabrication, and the average value of the five samples is shown in Table 1 below.

[0173] The lithium secondary batteries obtained in the above examples and comparative examples (5 samples each) were subjected to a CC-CV mode test at 25°C at 0.1C (reference capacity 4.5mAh / cm²). 2 The batteries were charged to 4.2V and maintained in CV mode until they reached 0.05C. Subsequently, they were discharged to 2.5V at 0.1C to perform a formation process, and the discharge capacity (mAh) was calculated as the average value of five samples, as shown in Table 1 below.

[0174] During the formation process, the number of defective samples among the five samples produced in each of the above examples and comparative examples that did not perform charging and discharging properly due to short circuits, etc., was confirmed and is shown in Table 1 below.

[0175] [Table 1]

[0176] Based on the results of the aforementioned experimental example, the lithium secondary battery of the embodiment exhibited high discharge capacity and excellent assembly stability, with no defects occurring due to short circuits between the negative and positive electrodes.

[0177] The lithium secondary battery of Comparative Example 1 had a low initial open-circuit voltage due to the poor bending characteristics and surface cracks of the negative electrode plate, resulting in a defect rate of approximately 60% and low assembly stability.

[0178] Furthermore, while the lithium secondary battery of Comparative Example 2 showed a slight advantage over Comparative Example 1 in terms of negative electrode plate bending characteristics and surface cracking, its initial open-circuit voltage was still lower than that of the example, its defect rate was approximately 40%, and its assembly stability was low.

[0179] Although the present invention has been described above with reference to limited embodiments and drawings, it goes without saying that the present invention is not limited thereto, and that various modifications and variations are possible within the equivalent scope of the technical concept of the present invention and the claims described below by persons with ordinary skill in the art to which the present invention pertains.

Claims

1. It includes an electrode active material layer and a porous layer laminated on an electrode current collector layer, The porous layer comprises a polymer binder containing a copolymer comprising a hard segment of the following chemical formula 1 and a soft segment of the following chemical formula 2, and inorganic fine particles dispersed on the polymer binder. The copolymer comprises the hard segment and the soft segment in a molar ratio of 80:20 to 95:5, and the copolymer has a weight-average molecular weight (Mw) of 100,000 to 1,000,000. The inorganic fine particles have a particle size of 0.001 μm to 10 μm. Electrodes for lithium-ion secondary batteries. 【Chemistry 1】 In the aforementioned chemical formula 1, R １ and R ３ Each is independent of the others. 【Chemistry 2】 A １ A ３ Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, L １ is a chemical bond or methylene group, R ２ This is an alkylene group having 1 to 5 carbon atoms. 【Transformation 3】 In the aforementioned chemical formula 2, R ４ This is an alkylene group having 3 to 6 carbon atoms.

2. Said R １ and R ３ are each independently 【Chemistry 4】 The electrode for a lithium secondary battery according to claim 1.

3. The polymer binders include polyetherimide, polyvinylidene fluoride, poly(vinylidene fluoride-co-trichloroethylene), poly(vinylidene fluoride-co-chlorotrifluoroethylene), poly(vinylidene fluoride-co-trifluoroethylene), poly(vinylidene fluoride-co-tetrafluoroethylene), poly(vinylidene fluoride-co-hexafluoropropylene), butyl acrylate, polymethyl methacrylate, polyacrylonitrile, polyvinylpyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxy The electrode for a lithium secondary battery according to claim 1, further comprising one or more binder compounds selected from the group consisting of cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethylcellulose, cyanoethyl sucrose, pullulan, carboxymethylcellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene polymer, sulfonated ethylene-propylene-diene polymer, styrene-butadiene rubber, fluororubber, and polyimide.

4. The electrode for a lithium secondary battery according to claim 3, wherein the binder compound contains 10% by weight or more of the polymer binder, based on the total weight of a polymer binder containing a copolymer comprising the hard segment of chemical formula 1 and the soft segment of chemical formula 2.

5. The inorganic fine particles are SrTiO ３ 、SnO ２ 、CeO ２ 、MgO, NiO, CaO, ZnO, ZrO ２ 、Y ２ O ３ 、Al ２ O ３ 、AlO(OH), Al(OH) ３ 、TiO ２ 、SiC, BaTiO ３ 、Pb(Zr,Ti)O ３ 、Pb １－ｘ La ｘ Zr １－ｙ Ti ｙ O ３ 、Pb(Mg １／３ Nb ２／３ )O ３ -PbTiO ３ 、HfO ２ 、Li ３ PO ４ 、Li ｘ Ti ｙ (PO ４ ) ３ (0 < x < 2, 0 < y < 3)、Li ｘ Al ｙ Ti ｚ (PO ４ ) ３ (0 < x < 2, 0 < y < 1, 0 < z < 3)、(LiAlTiP) ｘ O ｙ (0 < x < 4, 0 < y < 13)、Li ｘ La ｙ TiO ３ (0 < x < 2, 0 < y < 3)、Li ｘ Ge ｙ P ｚ S ｗ (0 < x < 4, 0 < y < 1, 0 < z < 1, 0 < w < 5)、Li ｘ N ｙ (0 < x < 4, 0 < y < 2)、Li ｘ Si ｙ S ｚ (0 < x < 3, 0 < y < 2, 0 < z < 4)、およびLi ｘ P ｙ S ｚ An electrode for a lithium secondary battery according to claim 1, which is one or more selected from the group consisting of (0 < x < 3, 0 < y < 3, 0 < z < 7).

6. The electrode for a lithium secondary battery according to claim 1, wherein the porous layer comprises 0.5 to 45% by weight of the polymer binder and 55 to 99.5% by weight of the inorganic fine particles.

7. The steps include: applying an electrode material composition containing an electrode active material onto an electrode current collector layer to form an electrode active material layer; The steps include: preparing an inorganic fine particle dispersion liquid by dispersing inorganic fine particles and a dispersant in a solvent; The steps include: preparing a binder solution by dissolving a polymer binder containing a copolymer comprising a hard segment of chemical formula 1 and a soft segment of chemical formula 2 in a solvent; The steps include: preparing a slurry for forming a porous layer by mixing the binder solution with the inorganic fine particle dispersion; The steps include applying the porous layer forming slurry onto the electrode active material layer to form a porous layer, A method for manufacturing an electrode for a lithium secondary battery according to claim 1, including the method described in claim 1. 【Transformation 5】 In the aforementioned chemical formula 1, R １ and R ３ Each of them operates independently. 【Transformation 6】 A １ A ３ Each of these is an alkyl group having 1 to 3 carbon atoms, L １ is a chemical bond or methylene group, R ２ This is an alkylene group having 1 to 5 carbon atoms. 【Transformation 7】 In the aforementioned chemical formula 2, R ４ This is an alkylene group having 3 to 6 carbon atoms.

8. The method for manufacturing an electrode for a lithium secondary battery according to claim 7, wherein the slurry for forming the porous layer contains 30% to 95% by weight of solids including the inorganic fine particles.

9. The polymer binder comprises a copolymer containing a hard segment of the following chemical formula 1 and a soft segment of the following chemical formula 2, and inorganic fine particles dispersed on the polymer binder. The copolymer comprises the hard segment and the soft segment in a molar ratio of 80:20 to 95:5, and the copolymer has a weight-average molecular weight (Mw) of 100,000 to 1,000,000. The inorganic fine particles have a particle size of 0.001 μm to 10 μm. Slurry for forming porous layers in electrodes for lithium secondary batteries. 【Transformation 8】 In the aforementioned chemical formula 1, R １ and R ３ Each is independent of the others. 【Chemistry 9】 A １ A ３ Each is independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms, L １ is a chemical bond or methylene group, R ２ This is an alkylene group having 1 to 5 carbon atoms. 【Chemistry 10】 In the aforementioned chemical formula 2, R ４ This is an alkylene group having 3 to 6 carbon atoms.

10. The slurry for forming a porous layer of an electrode for a lithium secondary battery according to claim 9, wherein the polymer binder and the inorganic fine particles are contained in the porous layer in an amount of 0.5 to 45% by weight of the polymer binder and 55 to 99.5% by weight of the inorganic fine particles.

11. A lithium secondary battery comprising an electrode for a lithium secondary battery as described in claim 1.

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