Electrode for lithium secondary battery, method for manufacturing the same, and lithium secondary battery including 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 to Related Applications] This application claims the benefit of priority based on Korean Patent Application Nos. 10 - 2023 - 0053337 filed on April 24, 2023 and 10 - 2024 - 0042820 filed on March 28, 2024, and all the contents disclosed in the documents of the Korean patent applications are included as part of this specification.

[0002] 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.

Background Art

[0003] Recently, as the technology development and demand for mobile devices have increased, the demand for secondary batteries that can be charged and discharged as an energy source has been rapidly increasing. Accordingly, many studies on secondary batteries that can meet various requirements have been conducted. In addition, secondary batteries have been presented as a solution for solving air pollution such as existing gasoline vehicles and diesel vehicles using fossil fuels, and are also attracting attention as power sources for electric vehicles (EVs), hybrid electric vehicles (HEVs), plug - in hybrid electric vehicles (Plug - in HEVs), etc.

[0004] When a short - circuit occurs due to the contact between the positive electrode and the negative electrode in a lithium secondary battery, an explosion continues along with intense heat generation. Therefore, a porous separator is applied to the lithium secondary battery. However, the porous separator of the secondary battery shows intense heat - shrinkage behavior at a temperature of about 100 °C or higher due to its material properties and manufacturing process characteristics including stretching, resulting in a problem of causing a short - circuit between the positive electrode and the negative electrode.

[0005] Therefore, there is a need for research on lithium secondary batteries including a separator with excellent stability and long battery life characteristics at high temperatures and excellent coating properties.

Summary of the Invention

Problems to be Solved by the Invention

[0006] The present invention provides an electrode for a lithium secondary battery having excellent bonding durability between a porous layer and an electrode substrate.

[0007] The present invention provides a method for manufacturing the electrode for a lithium secondary battery.

[0008] And the present invention provides a lithium secondary battery including the electrode.

Means for Solving the Problems

[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 includes 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.

[0010]

Chem.

[0011] In the above Chemical Formula 1, R 1 and R 3 are each independently,

[0012]

Chem.

[0013] is, A 1 to A 3 are each independently hydrogen or an alkyl group having 1 to 3 carbon atoms, L 1 is a chemical bond or a methylene group, R 2 is an alkylene group having 1 to 5 carbon atoms,

[0014]

Chem.

[0015] In the above Chemical Formula 2, R 4 is an alkylene group having 3 to 6 carbon atoms.

[0016] According to another embodiment of the present invention, forming an electrode active material layer by applying an electrode material composition containing an electrode active material on an electrode current collector layer; preparing an inorganic fine particle dispersion liquid obtained by dispersing inorganic fine particles and a dispersant in a solvent; preparing a binder solution in which a polymer binder containing the hard segment of the above Chemical Formula 1 and the soft segment of the above Chemical Formula 2 is dissolved in a solvent; preparing a slurry for forming a porous layer by mixing the binder solution with the inorganic fine particle dispersion liquid; forming a porous layer by applying the slurry for forming a porous layer on the electrode active material layer; A method for manufacturing the electrode for a lithium secondary battery including the above is provided.

[0017] According to still another embodiment of the present invention, there is provided a slurry for forming a porous layer of an electrode for a lithium secondary battery, including the polymer binder and inorganic fine particles dispersed on the polymer binder.

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

[0019] Hereinafter, the electrode for a lithium secondary battery, a manufacturing method thereof, and a lithium secondary battery including the same according to embodiments of the present invention will be described in more detail.

[0020] According to an embodiment of the present invention, including an electrode active material layer and a porous layer laminated on an electrode current collector layer, The porous layer contains a polymer binder including 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. 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] 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 has been 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 can exhibit excellent durability during charge and discharge.

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

[0029] For the electrode current collector layer, an electrode current collector known to have conductivity in the technical field to which the present invention pertains without inducing chemical changes in the lithium secondary battery can be applied. As an example, the electrode current collector may be stainless steel; aluminum; nickel; titanium; fired carbon; or one obtained by surface treatment with carbon, nickel, titanium, silver, etc. on the surface of aluminum or stainless steel.

[0030] Preferably, the electrode current collector can have a thickness of 3 μm to 500 μm. In order to enhance the adhesive force with the electrode material, the surface of the electrode current collector may have fine irregularities. The electrode current collector can have various forms such as a film, a sheet, a foil, a net, a porous body, a foam, a non-woven fabric body, etc.

[0031] The electrode active material layer contains an electrode material composition that 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] As the conductive material, any material having electronic conductivity without causing chemical changes in the lithium secondary battery can be used without particular limitation. As non-limiting examples, the conductive material may be carbon-based substances such as carbon black, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber; graphite such as natural graphite and artificial graphite; metal powders or metal fibers such as copper, nickel, aluminum, silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; or conductive polymers such as polyphenylene derivatives. As the conductive material, one or a mixture of two or more of the above-described examples may be used.

[0034] The content of the conductive material may be adjusted within a range that does not induce a decrease in the capacity of the lithium secondary battery while exhibiting an appropriate level of conductivity. Preferably, the content of the conductive material may be 1% by weight to 10% by weight or 1% by weight to 5% by weight based on the total weight of the electrode material composition.

[0035] The binder is used to make the electrode material composition adhere well to the electrode current collector.

[0036] As a non-limiting example, the binder may be polyvinyl alcohol, polyacrylate, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, a polymer containing ethylene oxide, polyvinyl pyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, acrylated styrene-butadiene rubber, epoxy resin, nylon resin, etc. As the binder, one or a mixture of two or more of the aforementioned examples may be used.

[0037] The content of the binder may be adjusted within a range that does not induce a decrease in the capacity of the lithium secondary battery while exhibiting an appropriate level of adhesiveness. Preferably, the content of the binder may be 1% by weight to 10% by weight or 1% by weight to 5% by weight based on the total weight of the electrode material composition.

[0038] When the electrode for the lithium secondary battery is a positive electrode, as the positive electrode active material, any material capable of reversible insertion and desorption of lithium ions can be used without particular limitation.

[0039] As an example, the positive electrode active material may be a composite oxide or phosphate containing cobalt, manganese, nickel, iron, or a combination of these metals 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 D 2 (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 Z 2 (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 Z 2(0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < d < 2); Li a Ni b E c G d O 2 (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 O 2 (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 O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O 2 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn 2 G b O 4 (0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); QO 2 ; QS 2 ; LiQS 2 ; V 2 O 5 ; LiV 2 O 5 ; LiTO 2 ; LiNiVO 4 ; Li (3-f) J 2 (PO 4 ) 3 (0 ≤ f ≤ 2); Li (3-f) Fe 2 (PO 4 ) 3 (0 ≤ f ≤ 2); and LiFePO 4 。

[0041] In the above chemical formula, A is Ni, Co, Mn, or a combination thereof; R is Al, Ni, Co, Mn, Cr, Fe, Mg, Sr, V, a rare earth element, 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] Those having a coating layer on the surface of the positive electrode active material may also be used, or the positive electrode active material and the positive electrode active material having a coating layer may be mixed and used. As the coating element contained in the coating layer, Mg, Al, Co, K, Na, Ca, Si, Ti, V, Sn, Ge, Ga, B, As, Zr, or a mixture thereof may be used.

[0043] According to one embodiment, the positive electrode active material may be contained in an amount of 80% to 95% by weight based on 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 based on the total weight of the electrode material composition.

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

[0045] Examples of substances that can reversibly intercalate and deintercalate lithium ions include crystalline carbon, amorphous carbon, or mixtures thereof as carbonaceous substances. Specifically, the carbonaceous substance may be natural graphite, artificial graphite, Kish graphite, pyrolytic carbon, mesophase pitches, mesophase pitch-based carbon fibers, meso-carbon microbeads, petroleum or coal tar pitch-derived cokes, soft carbon, hard carbon, and the like.

[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] Examples of substances that can be doped and undoped with lithium include Si, Si-C composites, SiOx (0 < x < 2), Si-Q alloys (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, SnO 2 , Sn-R alloys (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), and the like. And examples of substances that can be doped and undoped with lithium include at least one of the above examples and SiO 2They can be used in admixture. The 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 exemplified above. And the silicon compound is 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 SiO 2 and may be a mixture.

[0050] According to one embodiment, the negative electrode active material may be contained in an amount of 85% by weight 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% by weight to 97% by weight, or 87% by weight to 97% by weight, or 87% by weight to 95% by weight, or 90% by weight 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 manifestation of appropriate performance.

[0052] On the one hand, the electrode for the lithium secondary battery includes a porous layer laminated on an 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 including 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 above Chemical Formula 1, R 1 and R 3 are each independently

[0057]

Chemical formula

[0058] 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,

[0059]

Chemical formula

[0060] In the above Chemical Formula 2, R 4 is an alkylene group having 3 to 6 carbon atoms.

[0061] The copolymer has the hard segment capable of forming a hydrogen bond with the electrode active material layer and the soft segment providing high flexibility within the copolymer. Thereby, binding between the porous layer and the electrode active material layer is dense while high flexibility is imparted to the porous layer, and excellent durability can be exhibited during charge and discharge.

[0062] In the copolymer, the R 1 and R 3 are each independently,

[0063]

Chemical formula

[0064] as follows.

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

[0066] According to one embodiment, the R 1 and R 3 can each have the 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 R 1 and R 3 are each independently,

[0068] [Chemical formula]

[0069] may also be.

[0070] According to one embodiment, the R 1 and R 3 each may have a structure derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI).

[0071] [Chemical formula]

[0072] can have a structure.

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

[0074] In Chemical Formula 2 above, the R 4 is an alkylene group having 3 to 6 carbon atoms. Preferably, the R 4 is a propylene group (*-CH 2 -CH 2 -CH 2-*) or a butylene group (*-CH 2 -CH 2 -CH 2 -CH 2 -*) may also be used. According to one embodiment, the R 4 can have the structure derived from polytetramethylene ether glycol or polytetramethylene ether glycol. According to one embodiment, the R 4 is a butylene group (*-CH 2 -CH 2 -CH 2 -CH 2 -*) derived from polytetramethylene ether glycol (PTMEG).

[0075] As a non-limiting example, the copolymer has the hard segment of the above Chemical Formula 1, and the R 1 and R 3 are each derived from 4,4'-diphenylmethane diisocyanate (4,4'-MDI)

[0076]

Chemical formula

[0077] structure, the R 2 is an ethylene group (*-CH 2 -CH 2 -*) derived from ethylenediamine (EDA), and in the soft segment of the above Chemical Formula 2, the R 4 is a butylene group (*-CH 2 -CH 2 -CH 2 -CH 2 -*) 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 endow the polymer binder containing the copolymer with appropriate mechanical properties and ensure the binding property with the electrode active material layer, the molar ratio of the hard segment to the soft segment is preferably 80:20 or more. And in order to endow the porous layer with high flexibility, the molar ratio of the hard segment to the soft segment is preferably 95:5 or less.

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

[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 has a weight average molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol.

[0083] In order to enable the improvement effect by the application of the copolymer to be manifested, the weight average molecular weight (Mw) of the copolymer may be 100,000 g / mol or more, or 150,000 g / mol or more, and 1,000,000 g / mol or less, or 800,000 g / mol or less, or 600,000 g / mol or less, or 400,000 g / mol or less. Preferably, the weight average molecular weight (Mw) of the copolymer may be 100,000 g / mol to 1,000,000 g / mol, or 150,000 g / mol to 1,000,000 g / mol, or 150,000 g / mol to 800,000 g / mol, or 150,000 g / mol to 600,000 g / mol, or 150,000 g / mol to 400,000 g / mol.

[0084] As a non-limiting example, the weight average molecular weight (Mw) can be measured using an Agilent PL-GPC 220 instrument equipped with a Polar Gel MIXED-L column (Polymer Laboratories) with a length of 300 mm. The measurement temperature is 65 °C. Tetrahydrofuran or dimethylformamide is used as the solvent, and the flow rate is measured at a rate of 1 mL / min. The sample is prepared at a concentration of 10 mg / 10 mL and then supplied in an amount of 100 μL. The Mw value and the Mn value are derived with reference to a calibration curve formed using polystyrene standards. The molecular weights (g / mol) of the polystyrene standards used are eight types: 580 / 3,940 / 8,450 / 31,400 / 70,950 / 316,500 / 956,000 / 4,230,000.

[0085] According to one embodiment, as the copolymer, those manufactured or commercial products (for example, spandex, etc.) that satisfy the above-described structure and weight average molecular weight can be applied.

[0086] And the polymer binder may further contain one or more binder compounds selected from the group consisting of 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, polyvinyl pyrrolidone, polyvinyl acetate, ethylene vinyl acetate copolymer, polyethylene oxide, cellulose acetate, cellulose acetate butyrate, cellulose acetate propionate, cyanoethyl pullulan, cyanoethylated polyvinyl alcohol, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene butadiene rubber, fluororubber, and polyimide together with the copolymer.

[0087] According to one embodiment, in order to enable the improvement effect by the application of the copolymer to be manifested, the binder compound preferably contains 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 containing the hard segment of the chemical formula 1 and the soft segment of the chemical formula 2.

[0088] The inorganic fine particles form fine pores 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 5 V based on Li / Li+). The inorganic fine particles preferably have a high electrolyte ion transfer ability. The inorganic fine particles preferably have as small a density as possible so that they can be well dispersed within the polymer binder. Further, the inorganic fine particles preferably have a high dielectric constant so that they can contribute to an increase in the dissociation degree of the electrolyte salt in the electrolyte.

[0090] Preferably, the inorganic fine particles may be at least one selected from the group consisting of inorganic particles having a dielectric constant of 1 or more, inorganic particles having piezoelectricity, and inorganic particles having lithium ion transfer ability.

[0091] As an example, SrTiO 3 、SnO 2 、CeO 2 、MgO, NiO, CaO, ZnO, ZrO 2 、Y 2 O 3 、Al 2 O 3 、boehmite (AlO(OH)), Al(OH) 3 、TiO 2 、and inorganic particles such as SiC have a dielectric constant of 1 or more and can be preferably applied as the inorganic fine particles.

[0092] As another example, the inorganic particles having piezoelectricity are substances that are insulators under normal pressure but exhibit conductivity due to a change in internal structure when a certain pressure is applied. The piezoelectric inorganic particles have a high dielectric constant characteristic with a dielectric constant of 100 or more. Further, when a certain pressure is applied to the piezoelectric inorganic particles to stretch or compress them, charges are generated and one surface becomes positively (+) charged and the other surface becomes negatively (-) charged, thereby generating a potential difference between both surfaces. Due to the characteristics of the piezoelectric inorganic particles, when an internal short circuit occurs at the electrode of the secondary battery due to an external impact, direct contact between the positive electrode and the negative electrode can be prevented, and a gradual decrease in voltage and an improvement in safety can be achieved. Examples of the piezoelectric inorganic particles include BaTiO 3, Pb(Zr, Ti)O 3 (PZT), Pb 1-x La x Zr 1-y Ti y O 3 (PLZT), Pb(Mg 1 / 3 Nb 2 / 3 )O 3 -PbTiO 3 (PMN-PT), and inorganic particles such as HfO 2 can be preferably applied.

[0093] As another example, the inorganic particles having the lithium ion transfer ability contain a lithium element and are inorganic particles having 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. Examples of such inorganic particles include 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), and Li x P y S z (0 < x < 3, 0 < y < 3, 0 < z < 7), etc.

[0094] Preferably, 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), and Li x P y S zIt may be one or more selected from the group consisting of (0 < x < 3, 0 < y < 3, 0 < z < 7).

[0095] The inorganic fine particles preferably have a particle size of 0.001 μm to 10 μm. In order to ensure dispersibility in the porous layer, the inorganic fine particles preferably 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 during charge and discharge of the secondary battery due to the excessively large pore size. Therefore, the inorganic fine particles preferably 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 give appropriate porosity and insulation to the porous layer, the inorganic fine particles are preferably contained 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, when the inorganic fine particles are contained in excess, the mechanical properties of the porous layer may deteriorate due to weakening of the adhesive force. Therefore, the inorganic fine particles are preferably contained 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, 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 of the inorganic fine particles and the balance 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 the lithium ion permeability, the porosity of the porous layer is preferably 40% or more, or 45% or more, or 50% or more. However, when the porosity of the porous layer is excessively large, it may be difficult to ensure the adhesion between the porous layer and the electrode, and there may be a possibility of internal short circuit during charge and discharge 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%, or 45 to 80%, or 45 to 75%, or 50 to 75%, or 50 to 70%.

[0102] The porosity can be measured after preparing the slurry for forming the porous layer, applying this to a shaped film to manufacture an independent porous layer. That is, it is possible to establish the composition and process conditions that can ensure the porosity within the above range by an experimental method, and apply this to actual production.

[0103] The porosity can be measured using a scanning electron microscope image (SEM), or measured using an adsorbing gas such as nitrogen and a BET apparatus, or measured by methods such as mercury intrusion porosimetry or capillary flow porosimetry. Or 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 exhibited. When the porosity of the porous layer is excessively large, there may be a possibility of internal short circuit during charge and discharge of the lithium secondary battery. Therefore, the porosity of the porous layer is preferably 60% or less.

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

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

[0107] As an example, the interface layer is a layer composed of the electrode material composition of more than 0% by weight and less than 100% by weight and the porous composition of less than 100% by weight and more than 0% by weight.

[0108] According to another implementation example of the present invention, forming an electrode active material layer by applying an electrode material composition containing an electrode active material on an electrode current collector layer; preparing an inorganic fine particle dispersion liquid in which inorganic fine particles and a dispersant are dispersed in a solvent; preparing a binder solution in which a polymer binder containing the hard segment of Chemical Formula 1 and the soft segment of Chemical Formula 2 is dissolved in a solvent; mixing the binder solution with the inorganic fine particle dispersion liquid to prepare a slurry for forming a porous layer; applying the slurry for forming a porous layer on the electrode active material layer to form a porous layer; A method for manufacturing an electrode for a lithium secondary battery according to the above is provided.

[0109] The above-described electrode for a lithium secondary battery can be provided through the above manufacturing method.

[0110] First, a step of forming an electrode active material layer by applying an electrode material composition containing an electrode active material on an electrode current collector layer may be performed. In the above step, the electrode current collector and the electrode material composition may be replaced with the contents described above, respectively. The electrode active material layer can be formed by applying the electrode material composition on the electrode current collector layer and drying it.

[0111] Separately from the above step, a step of preparing an inorganic fine particle dispersion liquid in which inorganic fine particles and a dispersant are dispersed in a solvent, a step of preparing a binder solution in which a polymer binder is dissolved in a solvent, and a step of mixing the binder solution with the inorganic fine particle dispersion liquid to prepare a slurry for forming a porous layer may be performed.

[0112] As a result of the inventors' continuous research, it was confirmed that in preparing the slurry for forming the porous layer, the presence or absence of the aggregation phenomenon of the inorganic fine particles and the distribution state of the polymer binder and the inorganic fine particles can vary depending on the mixing order and mixing method of the components. And it was confirmed that the distribution state of the polymer binder and the inorganic fine particles may significantly affect the adhesion force between the porous layer and the electrode active material layer.

[0113] As an example, when a binder solution in which a polymer binder is dissolved in a solvent is produced and then inorganic fine particles are added thereto to prepare a slurry for forming a porous layer, the dispersibility of the inorganic fine particles is significantly reduced, and thus it becomes impossible to provide an electrode for a lithium secondary battery that satisfies the above 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 liquid, preparing the binder solution, and mixing the binder solution with the inorganic fine particle dispersion liquid to prepare a slurry for forming a porous layer, so that a lithium secondary battery electrode can be provided in which the porous layer and the electrode active material layer are tightly bonded while the porous layer is given high flexibility.

[0115] In the above step, with respect to the inorganic fine particles and the polymer binder, the above-described content is respectively substituted.

[0116] As the dispersant, a carboxylic acid-modified polyester copolymer and a compound known to be suitable for the dispersion of inorganic fine particles in the technical field to which the present invention pertains, such as acetic acid, may be used.

[0117] And as the solvent, a non-aqueous organic solvent may be used. Specifically, the non-aqueous organic solvent includes 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; carbonate solvents such as 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 (PC); alcohol 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 may contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolane. Among the above examples, the carbonate solvent suitable for the dispersion of inorganic fine particles can be preferably used as the non-aqueous organic solvent.

[0118] According to one embodiment, the slurry for forming the porous layer preferably has a solid content containing the inorganic fine particles of 30% by weight to 95% by weight.

[0119] When the solid content of the porous slurry is excessively high, it induces an increase in viscosity and cannot easily penetrate into the pore region of the electrode active material layer, so that an interface layer 25 with an appropriate structure may not be formed. 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 may be 95% by weight or less or 90% by weight or less. Preferably, the solid content of the porous slurry may be 30% to 95% by weight, or 30% to 90% by weight, or 35% to 90% by weight.

[0121] Next, a step of applying the porous layer-forming slurry onto the electrode active material layer to form a porous layer is performed. The porous layer can be formed by applying the porous layer-forming slurry onto the electrode active material layer and drying it. In this step, it can be performed in consideration of the thicknesses of the electrode active material layer and the porous layer described above.

[0122] In this step, drying is preferably performed at a temperature of 50°C to 150°C, or 60°C to 150°C, or 60°C to 120°C, or 65°C to 110°C. If the drying temperature does not satisfy the above range, the drying efficiency may decrease, or morphological changes of each layer may occur, inducing defects.

[0123] According to another embodiment of the present invention, there is provided a slurry for forming a porous layer of an electrode for a lithium secondary battery, which includes the polymer binder and inorganic fine particles dispersed on the polymer binder.

[0124] Regarding the polymer binder and the inorganic fine particles in the porous layer-forming slurry, they are respectively substituted with the contents described above.

[0125] As described above, the slurry for forming the porous layer is obtained through the steps of preparing an inorganic fine particle dispersion liquid in which inorganic fine particles and a dispersant are dispersed in a solvent, preparing a binder solution in which a polymer binder containing the hard segment of Chemical Formula 1 and the soft segment of Chemical Formula 2 is dissolved in a solvent, and mixing the binder solution with the inorganic fine particle dispersion liquid to prepare a slurry for forming the porous layer.

[0126] According to another embodiment of the present invention, a lithium secondary battery including the above-described electrode 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 for sealing and housing the electrode assembly and the electrolyte.

[0128] By including the above-described electrode assembly, the lithium secondary battery can exhibit excellent durability and stable performance.

[0129] The lithium secondary battery can have various forms such as a square type, a cylindrical type, and a pouch type.

[0130] The lithium secondary battery can be used as an energy supply source having improved performance and safety in the fields of portable electronic devices such as mobile phones, notebook computers, tablet computers, mobile batteries, and digital cameras, and in the fields of transportation means such as electric vehicles, electric bicycles, and personal mobility devices.

[0131] According to one embodiment, as the electrolyte, any electrolyte known to be applicable to lithium secondary batteries in the technical field to which the present invention pertains can be used without particular limitation. 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, or the like.

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

[0133] As the non-aqueous organic solvent, any medium that can play a role in allowing the ions involved in the electrochemical reaction of the battery to move can be used without particular limitation.

[0134] Specifically, the non-aqueous organic solvent includes 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; carbonate solvents such as dimethyl carbonate (DMC), diethyl carbonate (DEC), methyl ethyl carbonate (MEC), ethyl methyl carbonate (EMC), ethylene carbonate (EC), and propylene carbonate (PC); alcohol solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group with 2 to 20 carbon atoms and can contain a double bond aromatic ring or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; and sulfolane, etc.

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

[0136] In particular, considering the charge-discharge performance of the battery and the compatibility with the sacrificial positive electrode material, as the non-aqueous organic solvent, a mixture of a cyclic carbonate having high ionic conductivity and high dielectric constant (e.g., ethylene carbonate, propylene carbonate) and a linear carbonate having low viscosity (e.g., ethyl methyl carbonate, dimethyl carbonate, diethyl carbonate) can be preferably used. In this case, mixing the cyclic carbonate and the linear carbonate at a volume ratio of 1:1 to 1:9 may be advantageous for the manifestation of the above-described performance.

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

[0138] The lithium salt contained in the electrolyte is dissolved in the non-aqueous organic solvent and acts as a supply source of lithium ions in the battery to enable the operation of a basic lithium secondary battery, and plays a role in promoting the movement of lithium ions between the positive electrode and the negative electrode.

[0139] Specifically, the lithium salt is LiPF 6 、LiClO 4 、LiAsF 6 、LiBF 4 、LiSbF 6 、LiAlO 4 、LiAlCl 4 、LiCF 3 SO 3 、LiC 4 F 9 SO 3 、LiN(C 2 F 5 SO 3 ) 2 、LiN(C 2 F 5 SO 2 ) 2 、LiN(CF 3 SO 2 )2 , LiFSI, LiTFSI, LiCl, LiI, and LiB(C 2 O 4 ) 2 etc. may also be used. Preferably, the lithium salt is LiPF 6 , LiFSI, LiTFSI, or a mixture thereof.

[0140] The lithium salt may be contained in the electrolyte at a concentration of 0.1 M to 2.0 M. By imparting appropriate conductivity and viscosity to the electrolyte, the lithium salt contained within this concentration range can exhibit excellent electrolyte performance.

[0141] Optionally, the electrolyte may contain additives for the purpose of improving the battery life characteristics, suppressing the reduction of battery capacity, improving the discharge capacity of the battery, etc.

[0142] For example, the additives may be haloalkylene carbonate compounds such as difluoroethylene carbonate, pyridine, triethyl phosphate, triethanolamine, cyclic ethers, ethylenediamine, n-glyme, hexamethylphosphoric triamide, nitrobenzene derivatives, sulfur, quinoneimine dyes, N-substituted oxazolidinones, N,N-substituted imidazolidines, ethylene glycol dialkyl ethers, ammonium salts, pyrrole, 2-methoxyethanol, aluminum trichloride, etc. The additives may be contained at 0.1 to 5% by weight based on the total weight of the electrolyte.

Advantages of the Invention

[0143] According to the present invention, there are provided an electrode for a lithium secondary battery, a method for manufacturing the same, and a lithium secondary battery including the electrode, which can give high flexibility to the porous layer while having a dense binding between the porous layer and the electrode active material layer, and can exhibit excellent durability during charge and discharge.

Brief Description of the Drawings

[0144]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

Mode for Carrying Out the Invention

[0145] Hereinafter, the actions and effects of the invention will be described more specifically through specific examples of the present invention. However, this is presented as an exemplification for assisting the understanding of the invention. It is not intended that the scope of the rights of the invention be limited in any sense through the following examples, and it is obvious to those skilled in the art that various changes and modifications are possible within the scope and technical idea scope of the present invention.

[0146] Example 1 A negative electrode active material layer was prepared by mixing artificial graphite and natural graphite at a ratio of 3:7 to form 90% by weight of a graphite active material, and 10% by weight of SiO to form 95.6% by weight of an active material, 1% by weight of acetylene black as a conductive material, 1.1% by weight of carboxymethyl cellulose (CMC) and 2.3% by weight of styrene butadiene rubber (SBR) as binders. Using a comma coater, the electrode material composition was applied to one side of a copper current collector having a thickness of 8 μm. This was dried and rolled at 130 °C to prepare a negative electrode plate with a negative electrode active material layer laminated thereon. The negative electrode active material layer was formed with a porosity of 24% and a thickness of 44 μm.

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

[0148] As a polymer binder, spandex (weight average molecular weight 200,000 g / mol) and poly(vinylidene fluoride-co-hexafluoropropylene) (PVdF-HFP) were mixed at a weight ratio of 50:50 and dissolved in NMP to prepare a 10% by weight binder solution.

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

[0150]

Chemical Formula

[0151] structure, and the R2 is an ethylene group (*-CH 2 -CH 2 -*) derived from ethylenediamine (EDA), which is a soft segment of the chemical formula 2 above, and the R 4 is a butylene group (*-CH 2 -CH 2 -CH 2 -CH 2 -*) derived from polytetramethylene ether glycol (PTMEG). It is a copolymer having the structure. In the spandex, the molar ratio of the hard segment to the soft segment is 85:15.

[0152] Using a homomixer, a slurry for forming a porous layer in which the inorganic fine particle dispersion and the binder solution were uniformly mixed was obtained.

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

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

[0155] As a positive electrode active material, LiNiCoMnO 2 (Ni:Co:Mn = 8:1:1) 94% by weight, 3% by weight of conductive carbon black (Super P; IMERYS Graphite & Carbon) as a conductive material, and 3% by weight of polyvinylidene fluoride as a binder were put into NMP and uniformly dispersed to prepare a slurry. The slurry was applied to one surface of an aluminum current collector, and this was dried and rolled to prepare a positive electrode plate on which a positive electrode active material layer was laminated. The positive electrode plate was punched out using a die punching machine to a size of 30 × 42 mm to prepare a positive electrode portion.

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

[0157] The electrode assembly was housed in a pouch to form a small cell, and an electrolytic solution was injected into the pouch to fabricate five lithium secondary batteries.

[0158] At this time, as the electrolytic solution, 1.0 M LiPF was added to a non-aqueous organic solvent in which ethylene carbonate (EC) and ethyl methyl carbonate (EMC) were mixed at a volume ratio of 3:7. 6 And a solution in which 2 wt% of vinylene carbonate (VC) was dissolved was used.

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

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

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

[0162] Example 5 A negative electrode part, a positive electrode part, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that the composition of the porous layer-forming slurry 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 A negative electrode part, a positive electrode part, and a lithium secondary battery were manufactured in the same manner as in Example 1, except that a mixture of polyetherimide and PVdF-HFP at a weight ratio of 50:50 was used instead of the mixture of spandex and PVdF-HFP as the polymer binder.

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

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

[0166] Specifically, after dissolving the copolymer to a concentration of 2 mg / ml in HFIP (hexafluoroisopropanol), 20 μl was injected into GPC. The mobile phase of GPC was flowing in at a flow rate of 1.0 mL / min using HFIP, 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. Nine types of polystyrene standard specimens with weight average molecular weights of 2,000 g / mol, 10,000 g / mol, 30,000 g / mol, 70,000 g / mol, 200,000 g / mol, 700,000 g / mol, 2,000,000 g / mol, 4,000,000 g / mol, and 10,000,000 g / mol were used.

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

[0168] Experimental Example 3 The negative electrode plates with the porous layer formed on the negative electrode active material layer according to the above Examples and Comparative Examples were observed with a scanning electron microscope, and the results are shown in Fig. 1 (Example 1), Fig. 2 (Example 2), Fig. 3 (Example 3), Fig. 4 (Example 4), Fig. 5 (Example 5), Fig. 6 (Comparative Example 1), and Fig. 7 (Comparative Example 2). In Figs. 1, 2, 6, and 7, (a) is an SEM image at a magnification of 1000, and (b) is an SEM image at a magnification of 5000. Figs. 3, 4, and 5 are SEM images at a magnification of 5000, respectively.

[0169] Referring to Figs. 1 to 5, a uniform surface state without fine cracks could be observed in the negative electrode plates according to the Examples.

[0170] Referring to FIG. 6, in the negative electrode plate according to Comparative Example 1, cracks were easily observed due to the characteristics of the non-flexible polymer binder. Specifically, in Comparative Example 1, the surface was rougher than that in Example 1, and relatively large pores of about 1 μm were observed to be unevenly distributed.

[0171] Referring to FIG. 7, in the negative electrode plate according to Comparative Example 2, although the surface roughness decreased somewhat compared to Comparative Example 1, cracks on the surface could still be easily observed.

[0172] Experimental Example 4 For the lithium secondary batteries obtained in the above Examples and Comparative Examples (5 samples each), the open circuit voltage (OCV) was measured immediately after production, and the average value of the 5 samples was shown in Table 1 below.

[0173] The lithium secondary batteries obtained in the above Examples and Comparative Examples (5 samples each) were charged at 0.1C (reference capacity 4.5 mAh / cm 2 ) in the CC-CV mode at 25°C until 4.2V was reached, and the voltage was maintained in the CV mode until 0.05C was reached. Thereafter, discharge was performed at 0.1C until 2.5V, and the formation process was carried out. The discharge capacity (mAh) was shown in Table 1 below as the average value of the 5 samples.

[0174] During the formation process, the number of defective samples among the 5 samples each manufactured in the above Examples and Comparative Examples, in which charge and discharge could not be performed normally due to short circuit or the like, was confirmed and shown in Table 1 below.

[0175]

Table 1

[0176] Referring to the results of the above experimental examples, the lithium secondary batteries of the Examples showed high discharge capacity and excellent assembly stability without occurrence of defects due to short circuit between the negative electrode part and the positive electrode part.

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

[0178] And, the lithium secondary battery of Comparative Example 2 was slightly superior to Comparative Example 1 in terms of the bending characteristics and surface cracks of the negative electrode plate. However, the initial open-circuit voltage was still lower than that of the Example, the defective rate was about 40%, and the assembly stability was low.

[0179] As described above, the present invention has been described with reference to the limited examples and drawings. However, the present invention is not limited thereto, and it goes without saying that various modifications and variations can be made within the equivalent scope of the technical idea of the present invention and the scope of the claims described below by those having ordinary knowledge in the technical field to which the present invention pertains.

Claims

1. The electrode active material layer and the porous layer are laminated on an electrode current collector layer, The porous layer includes a polymer binder including a copolymer including a hard segment represented by the following Chemical Formula 1 and a soft segment represented by the following Chemical Formula 2, and inorganic fine particles dispersed on the polymer binder: Electrode for lithium secondary batteries. 【Chemistry 1】 In the above formula 1, R １ and R ３ are each independently 【Chemistry 2】 And A １ Or A ３ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; L １ is a chemical bond or a methylene group, R ２ is an alkylene group having 1 to 5 carbon atoms, 【Chemistry 3】 In the above formula 2, R ４ is an alkylene group having 3 to 6 carbon atoms.

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

3. 2. The electrode for a lithium secondary battery according to claim 1, wherein the copolymer contains the hard segment and the soft segment in a molar ratio of 80:20 to 95:

5.

4. 2. The electrode for a lithium secondary battery according to claim 1, wherein the copolymer has a weight average molecular weight (Mw) of 100,000 g / mol to 1,000,000 g / mol.

5. The polymeric binder may be selected from the group consisting of 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, polyethyleneoxy.

2. 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, cyanoethyl cellulose, cyanoethyl sucrose, pullulan, carboxymethyl cellulose, acrylonitrile-styrene-butadiene copolymer, ethylene-propylene-diene terpolymer, sulfonated ethylene-propylene-diene terpolymer, styrene butadiene rubber, fluororubber, and polyimide.

6. 6. The electrode for a lithium secondary battery according to claim 5, wherein the binder compound is present in an amount of 10 wt % or more based on the total weight of the polymer binder including a copolymer including the hard segment of Formula 1 and the soft segment of Formula 2.

7. 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), and Li ｘ P ｙ S ｚ 2. The electrode for a lithium secondary battery according to claim 1, wherein the x and y are one or more elements selected from the group consisting of: (0<x<3, 0<y<3, 0<z<7).

8. 2. The electrode for a lithium secondary battery according to claim 1, wherein the inorganic fine particles have a particle size of 0.001 to 10 μm.

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

10. applying an electrode material composition containing an electrode active material onto an electrode current collector layer to form an electrode active material layer; A step of preparing an inorganic fine particle dispersion liquid obtained by dispersing inorganic fine particles and a dispersant in a solvent; A step of preparing a binder solution by dissolving a polymer binder including a copolymer including a hard segment of the following Chemical Formula 1 and a soft segment of the following Chemical Formula 2 in a solvent; preparing a slurry for forming a porous layer by mixing the inorganic fine particle dispersion liquid with the binder solution; applying the porous layer forming slurry onto the electrode active material layer to form a porous layer; The method for producing an electrode for a lithium secondary battery according to claim 1 , comprising: 【Chemistry 5】 In the above formula 1, R １ and R ３ are each independently 【Chemistry 6】 And A １ Or A ３ are each independently an alkyl group having 1 to 3 carbon atoms; L １ is a chemical bond or a methylene group, R ２ is an alkylene group having 1 to 5 carbon atoms, 【Chemistry 7】 In the above formula 2, R ４ is an alkylene group having 3 to 6 carbon atoms.

11. 11. The method of claim 10, wherein the porous layer forming slurry has a solid content including the inorganic fine particles of 55 to 99.5 wt%.

12. The present invention comprises a polymer binder including a copolymer including a hard segment represented by the following formula 1 and a soft segment represented by the following formula 2, and inorganic fine particles dispersed on the polymer binder: Slurry for forming porous layers of electrodes for lithium secondary batteries. 【Chemistry 8】 In the above formula 1, R １ and R ３ are each independently 【Chemistry 9】 And A １ Or A ３ are each independently a hydrogen atom or an alkyl group having 1 to 3 carbon atoms; L １ is a chemical bond or a methylene group, R ２ is an alkylene group having 1 to 5 carbon atoms, 【Chemistry 10】 In the above formula 2, R ４ is an alkylene group having 3 to 6 carbon atoms.

13. The slurry for forming a porous layer of an electrode for a lithium secondary battery according to claim 12, wherein the copolymer contains the hard segment and the soft segment in a molar ratio of 80:20 to 95:

5.

14. 13. The slurry for forming a porous layer of an electrode for a lithium secondary battery according to claim 12, wherein the polymer binder and the inorganic fine particles are contained in a ratio of 0.5 to 45 wt %:55 to 99.5 wt %.

15. A lithium secondary battery comprising the electrode for lithium secondary batteries according to claim 1.

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