Electrode for secondary battery, method for manufacturing the same, and secondary battery including the same

Abstract

Provided are an electrode for a secondary battery, a method for manufacturing the same, and a secondary battery including the same. The electrode for a secondary battery includes a current collector, an active material layer disposed on the current collector and including an active material, and a protective coating layer covering at least a portion of a surface of the active material layer and including an aryl-ring-containing metal compound.

Description

Technical Field

[0001] This invention relates to an electrode for a secondary battery, a method for manufacturing the same, and a secondary battery including the same. More specifically, it relates to an electrode for a secondary battery including an active material layer, a method for manufacturing the same, and a secondary battery including the same. Background Technology

[0002] Rechargeable batteries are batteries that can be repeatedly charged and discharged. With the development of the information communication and display industries, rechargeable batteries are widely used as power sources for portable electronic communication devices such as portable cameras, mobile phones, and laptops (PCs). In addition, in recent years, battery packs that include rechargeable batteries have been developed for use as power sources for environmentally friendly vehicles such as electric vehicles.

[0003] For example, lithium secondary batteries are being actively researched and developed due to their high operating voltage and energy density per unit weight, as well as their advantages in charging speed and lightweight design.

[0004] A secondary battery may include: an electrode assembly comprising a positive electrode, a negative electrode, and a separator; and an electrolyte impregnating the electrode assembly. The secondary battery may further include an outer casing material housing the electrode assembly and the electrolyte, such as a pouch-type casing material.

[0005] With repeated charging and discharging of secondary batteries, side reactions may occur between the electrolyte components and the positive or negative electrode. For example, due to oxidation / reduction reactions between additives in the electrolyte and active materials in the positive or negative electrode, the electrode surface may be damaged and gas may be generated.

[0006] Therefore, it is necessary to study a method that can reduce side reactions with the electrolyte without hindering the charging / discharging characteristics within the electrode. Summary of the Invention

[0007] (a) Technical problems to be solved One technical problem of the present invention is to provide an electrode for a secondary battery with improved stability and charge / discharge characteristics.

[0008] One technical problem of the present invention is to provide a method for manufacturing an electrode for a secondary battery with improved stability and charge / discharge characteristics.

[0009] One technical problem of the present invention is to provide a secondary battery with improved stability and charge / discharge characteristics.

[0010] (II) Technical Solution The electrode for a secondary battery includes: a current collector; an active material layer disposed on the current collector and containing an active material; and a protective coating covering at least a portion of the surface of the active material or at least a portion of the surface of the active material layer and containing an aryl-cyclic metal compound.

[0011] In some embodiments, the protective coating may comprise a compound represented by the following structural formula 1.

[0012] [Structure 1] (In structural formula 1, R is hydrogen, deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, substituted or unsubstituted C1-C) 60 Alkyl, substituted or unsubstituted C2-C 60 alkenyl, substituted or unsubstituted C2-C 60 Alkyne, substituted or unsubstituted C1-C 60 Alkoxy, substituted or unsubstituted C3-C 60 Carbocyclic groups, substituted or unsubstituted C1-C 60 Heterocyclic groups, substituted or unsubstituted C6-C 60 aryloxy, substituted or unsubstituted C6-C 60 Arylthio, substituted or unsubstituted C7-C 60 Aryl or substituted or unsubstituted C2-C 60 (Heteroaryl alkyl groups, where M represents a metallic element, a is an integer from 1 to 5, and n is an integer from 1 to 4.) In some implementations, in structural formula 1, M can be an alkali metal or an alkaline earth metal, and n can be 1 or 2.

[0013] In some embodiments, the active material layer may further comprise an adhesive, and the protective coating may at least partially cover the surfaces of the active material and adhesive exposed on the outer surface of the active material layer.

[0014] In some embodiments, the protective coating may also be present on the surface of the active material within the active material layer.

[0015] In some embodiments, the protective coating may include a first protective coating covering the outer surface of the active material layer and a second protective coating covering the surface of the active material.

[0016] In some embodiments, the first protective coating and the second protective coating may be merged together at the periphery of the active material layer.

[0017] In some implementations, the protective coating may be in contact with the surface of the current collector.

[0018] In some embodiments, in a solution from which the components of the protective coating are dissolved from the electrodes of the secondary battery... 1 In the H-NMR spectrum, multiplet peaks can be observed in the range of 7.2 ppm to 7.4 ppm, and doublet peaks can be observed in the range of 7.6 ppm to 7.7 ppm.

[0019] The secondary battery includes: a positive electrode; and a negative electrode disposed opposite to the positive electrode. At least one of the positive electrode and the negative electrode includes the electrodes for the secondary battery described above.

[0020] In a method for manufacturing electrodes for secondary batteries, a current collector is prepared. An active material layer is formed on the current collector, the active material layer comprising an active material and a protective coating comprising an aryl-cyclic metal compound. The protective coating may be formed on the outer surface of the active material layer, or it may be formed on the surface of the active material.

[0021] In some embodiments, when forming the protective coating on the outer surface of the active material layer, the active material layer, which is coated on the current collector, can be immersed in a coating solution containing the aryl-cyclic metal compound.

[0022] In some embodiments, when forming the protective coating on the surface of the active material, the active material may be mixed into a coating solution containing the aryl-cyclic metal compound before being coated onto the current collector.

[0023] In some implementations, the active material can be mixed into the coating solution during vacuum drying.

[0024] In some embodiments, the concentration of the aryl-cyclic metal compound in the coating solution may be greater than 0.1% by weight and less than 10% by weight.

[0025] (III) Beneficial Effects An electrode for a secondary battery according to an embodiment of the present invention includes a protective coating formed on an active material layer and / or active material particles. This protective coating can block oxidation / reduction reactions caused by electron migration between the active material layer and the electrolyte.

[0026] The protective coating comprises an aryl-cyclic metal salt compound. This aryl-cyclic metal salt compound can selectively block electron migration while maintaining or enhancing lithium-ion conductivity. Therefore, it can improve the charge / discharge characteristics and rate performance of the secondary battery, while reducing instabilities such as gas generation caused by electrolyte side reactions.

[0027] The secondary batteries according to the above exemplary embodiments can be widely used in green technology fields such as electric vehicles, battery charging stations, and other battery-powered solar and wind power generation. For example, the lithium secondary batteries can be used in eco-friendly electric vehicles and hybrid vehicles to prevent climate change by suppressing air pollution and greenhouse gas emissions. Attached Figure Description

[0028] Figure 1 This is a schematic cross-sectional view showing an electrode for a secondary battery according to an exemplary embodiment.

[0029] Figures 2 to 4 This is a schematic, partially enlarged cross-sectional view showing an electrode for a secondary battery according to an exemplary embodiment.

[0030] Figure 5 and Figure 6 These are schematic plan views and schematic cross-sectional views of a secondary battery according to an exemplary embodiment.

[0031] Figure 7 The composition was measured from the negative electrode components of Example 1 and Comparative Example 1. 1 H-NMR analysis diagram. Detailed Implementation

[0032] Embodiments of the present invention provide an electrode for a secondary battery comprising an active material layer and a protective coating. Furthermore, a lithium secondary battery comprising the aforementioned electrode for a secondary battery is provided.

[0033] The embodiments of the present invention will be described in more detail below. However, the accompanying drawings and embodiments serve to better understand the technical concept of the present invention; therefore, the concept of the present invention should not be construed as being limited to the matters described in such drawings and embodiments.

[0034] Figure 1 These are schematic plan views and schematic cross-sectional views of electrodes for secondary batteries according to exemplary embodiments.

[0035] Reference Figure 1 The electrode for a secondary battery may include a current collector 50 and an active material layer 60 formed on the current collector 50. The electrode for a secondary battery may be a positive electrode or a negative electrode.

[0036] The active material layer 60 can be formed on at least one of the upper and lower surfaces of the current collector 50. For example... Figure 1 As shown, the active material layer 60 can be formed on the top and bottom surfaces of the current collector 50, respectively.

[0037] The current collector 50 may be made of copper, stainless steel, nickel, aluminum, titanium, or alloys thereof. The current collector 50 may also be surface-treated with carbon, nickel, titanium, silver, etc. The thickness of the current collector 50 may range from 5 μm to 50 μm.

[0038] When the electrode for the secondary battery is provided as the positive electrode, the current collector 50 may include aluminum or an aluminum alloy. When the electrode for the secondary battery is provided as the negative electrode, the current collector 50 may include copper or a copper alloy.

[0039] The active material layer 60 may contain either positive or negative active materials.

[0040] The positive electrode active material may contain a lithium-nickel metal oxide. The lithium-nickel metal oxide may further contain at least one of cobalt (Co), manganese (Mn), and aluminum (Al).

[0041] In some embodiments, the positive electrode active material or the lithium-nickel metal oxide may comprise a layered structure or a crystal structure represented by the following chemical formula 1.

[0042] [Chemical Formula 1] Li x Ni a M b O 2+z In chemical formula 1, the values ​​can be 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b≤0.5, and -0.5≤z≤0.1. As mentioned above, M can contain Co, Mn, and / or Al.

[0043] The chemical structure represented by Formula 1 indicates the bonding relationships contained in the layered or crystalline structure of the positive electrode active material, and does not exclude other additional elements. For example, M may contain Co and / or Mn, and Co and Mn may be provided together with Ni as the main active element of the positive electrode active material. Formula 1 is provided to represent the bonding relationships of the main active elements, and it should be understood that Formula 1 includes the introduction and substitution of additional elements.

[0044] In one embodiment, in addition to the primary active element, auxiliary elements may be further included to enhance the chemical stability of the positive electrode active material or the layered / crystal structure. These auxiliary elements may be incorporated into the layered / crystal structure to form a bond, and this should be understood to also include the chemical structures represented by Formula 1.

[0045] For example, the auxiliary element may include at least one selected from Na, Mg, Ca, Y, Ti, Hf, V, Nb, Ta, Cr, Mo, W, Fe, Cu, Ag, Zn, B, Al, Ga, C, Si, Sn, Sr, Ba, Ra, P, and Zr. The auxiliary element may function as an auxiliary active element, working together with Co or Mn, to contribute to the capacity / power activity of the positive electrode active material; for example, Al.

[0046] For example, the positive electrode active material or the lithium-nickel metal oxide may contain a layered structure or a crystal structure represented by the following chemical formula 1-1.

[0047] [Chemical Formula 1-1] Li x Ni a M1 b1 M2 b2 O 2+z In chemical formula 1-1, M1 may contain Co, Mn, and / or Al. M2 may contain the aforementioned auxiliary elements. In chemical formula 1-1, the following conditions may be met: 0.9≤x≤1.2, 0.5≤a≤0.99, 0.01≤b1+b2≤0.5, -0.5≤z≤0.1.

[0048] The positive electrode active material may further include coating elements or doping elements. For example, elements that are substantially the same as or similar to the auxiliary elements described above can be used as coating elements or doping elements. For example, one or more combinations of the elements described above can be used as coating elements or doping elements.

[0049] The coating element or dopant element may exist on the surface of the lithium-nickel metal oxide particles or penetrate through the surface of the lithium-nickel metal oxide particles and be contained in the bonding structure represented by chemical formula 1 or chemical formula 1-1.

[0050] The positive electrode active material may contain nickel-cobalt-manganese (NCM)-based lithium oxide. In this case, NCM-based lithium oxide with increased nickel content can be used.

[0051] Ni can be provided as a transition metal related to the power and capacity of lithium secondary batteries. Therefore, as described above, by using a high-content (High-Ni) composition for the positive electrode active material, a high-capacity positive electrode and a high-capacity lithium secondary battery can be provided.

[0052] However, as the content of Ni increases, the long-term storage stability and life stability of the positive electrode or secondary battery may be relatively reduced, and the side reactions with the electrolyte may also increase. However, according to an exemplary embodiment, the conductivity can be maintained by including Co, and the life stability and capacity retention characteristics can be improved by Mn.

[0053] In some embodiments, the content of Ni in the NCM-based lithium oxide (for example, the mole fraction of Ni in the total moles of nickel, cobalt, and manganese) can be 0.6 or more, 0.7 or more, 0.8 or more, 0.85 or more, 0.87 or more, or 0.90 or more. In some embodiments, the content of Ni can be 0.85 to 0.99, 0.85 to 0.97, 0.85 to 0.95, 0.87 to 0.95, or 0.90 to 0.95. Within the above Ni content range, the capacity characteristics of the positive electrode and lithium secondary battery can be improved.

[0054] In some embodiments, the positive electrode active material may further include a lithium cobalt oxide-based active material, a lithium manganese oxide-based active material, a lithium nickel oxide-based active material, or a lithium iron phosphate (LFP)-based active material (for example, LiFePO4).

[0055] In some embodiments, the positive electrode active material may include, for example, a lithium-rich layered oxide (LLO) / over-lithiated oxide (OLO)-based active material, a Mn-rich-based active material, a Co-less-based active material, etc., having a chemical structure or crystal structure represented by Chemical Formula 2. These can be used alone or in combination of two or more.

[0056] [Chemical Formula 2] p[Li2MnO3]·(1-p)[Li q JO2] In Chemical Formula 2, 0 < p < 1, 0.9 ≤ q ≤ 1.2, and J may include at least one element selected from Mn, Ni, Co, Fe, Cr, V, Cu, Zn, Ti, Al, Mg, and B.

[0057] The negative electrode active material can be used without particular limitation as a material known in the art that can adsorb and intercalate / deintercalate lithium ions as a negative electrode active material. For example, carbon-based materials such as crystalline carbon, amorphous carbon, carbon composites, carbon fibers, etc.; lithium metal; lithium alloys; silicon-containing materials or tin-containing materials, etc. can be used.

[0058] Examples of the amorphous carbon may include hard carbon, soft carbon, coke, mesocarbon microbead (MCMB), mesophase pitch-based carbon fiber (MPCF), etc.

[0059] Examples of the crystalline carbon may include natural graphite, artificial graphite, graphitized coke, graphitized mesocarbon microbead (MCMB), graphitized mesophase pitch-based carbon fiber (MPCF), etc., i.e., graphite-based carbon.

[0060] The lithium metal may include pure lithium metal or lithium metal formed with a protective layer for suppressing dendrite growth, etc. In one embodiment, the lithium metal-containing layer deposited or coated on the negative electrode current collector may be used as the negative electrode active material layer. In one embodiment, the lithium thin film layer may also be used as the negative electrode active material layer.

[0061] Examples of the elements included in the lithium alloy may include aluminum, zinc, bismuth, cadmium, antimony, silicon, lead, tin, gallium, or indium, etc.

[0062] The silicon-containing material may provide further increased capacity characteristics. The silicon-containing material may include Si, SiOx (0 < x < 2), SiOx doped with metal (0 < x < 2), silicon-carbon composite, etc. The metal may include lithium and / or magnesium, and the SiOx doped with metal (0 < x < 2) may include metal silicate.

[0063] For example, the positive electrode active material or the negative electrode active material may be mixed in a solvent to prepare an electrode mixture or an electrode paste (positive electrode paste or negative electrode paste). The electrode paste is coated on the current collector 50, and then dried and calendered, thereby an electrode for a lithium secondary battery can be manufactured.

[0064] The coating process may include gravure coating, slot die coating, multilayer simultaneous die coating, imprinting, doctor blade coating, dip coating, bar coating, casting, etc. The electrode paste may further contain a binder and a conductive material.

[0065] Non-limiting examples of the solvent used in the preparation of the positive electrode paste may include organic solvents such as N-methyl-2-pyrrolidone (NMP), dimethylformamide, dimethylacetamide, N,N-dimethylaminopropylamine, ethylene oxide, tetrahydrofuran, etc. The solvent used in the preparation of the negative electrode paste may include water, alcohol-based solvents, etc.

[0066] The adhesive may include polyvinylidene fluoride (PVDF), poly(vinylidene fluoride-co-hexafluoropropylene) copolymer, polyacrylonitrile, polymethyl methacrylate, nitrile rubber (NBR), polybutadiene rubber (BR), styrene-butadiene rubber (SBR), polyacrylic acid-based adhesives, poly(3,4-ethylenedioxythiophene) (PEDOT)-based adhesives, etc.

[0067] In some embodiments, PVDF-based adhesives can be used as the positive electrode binder. In some embodiments, styrene-butadiene rubber (SBR)-based adhesives, carboxymethyl cellulose (CMC), polyacrylic acid-based adhesives, poly(3,4-ethylenedioxythiophene) (PEDOT)-based adhesives, etc., can be used as the negative electrode binder.

[0068] The conductive material may be added to enhance conductivity and / or the mobility of lithium ions or electrons. For example, non-limiting examples of the conductive material may include carbon-based conductive materials such as graphite, carbon black, acetylene black, Ketjen black, graphene, carbon nanotubes, vapor-grown carbon fiber (VGCF), and carbon fibers, and / or metal-based conductive materials containing perovskite materials such as tin, tin oxide, titanium oxide, LaSrCoO3, and LaSrMnO3.

[0069] According to an embodiment of the present invention, the electrode for a secondary battery includes a protective coating 70. The protective coating 70 may be formed on at least a portion of the surface of the active material layer 60.

[0070] The protective coating 70 can be formed on at least one of the opposing face and two side faces of the current collector 50 of the active material layer 60, and can be at least partially exposed on the surface of the active material layer 60. The opposing face can be a face opposite to the coating surface on the current collector 50 of the active material layer 60 in the thickness direction. The side faces can be surfaces connecting the opposing face and the coating surface.

[0071] The protective coating 70 may contain a material having low electrical conductivity and high ionic conductivity (e.g., high lithium conductivity). By protecting the outer surface of the active material layer 60 at least partially by the protective coating 70, electron migration between the active material layer 60 (or the electrode active material within the active material layer 60) and the electrolyte can be inhibited or blocked.

[0072] Therefore, oxidation / reduction reactions occurring through the outer surface of the active material layer 60 can be suppressed, while lithium conductivity can be increased or maintained. Thus, lithium charge / discharge reactions can be promoted, and the capacity characteristics of the secondary battery can be maintained even during repeated charge / discharge cycles.

[0073] The protective coating 70 may contain a substance that is substantially insoluble in the electrolyte and has high thermal and chemical stability (oxidation / reduction stability). Furthermore, it may contain a substance that improves mechanical strength and impact resistance.

[0074] According to an embodiment of the present invention, the protective coating 70 may contain an aryl-cyclic metal compound, such as a salt containing an aryl-cyclic anion and a metal cation.

[0075] According to an exemplary embodiment, the protective coating 70 may contain a compound represented by the following structural formula 1.

[0076] [Structure 1] In structural formula 1, R can be hydrogen, deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, or a substituted or unsubstituted C1-C group. 60 Alkyl, substituted or unsubstituted C2-C 60 alkenyl, substituted or unsubstituted C2-C 60 Alkyne, substituted or unsubstituted C1-C 60 Alkoxy, substituted or unsubstituted C3-C 60 Carbocyclic groups, substituted or unsubstituted C1-C 60 Heterocyclic groups, substituted or unsubstituted C6-C 60 aryloxy, substituted or unsubstituted C6-C 60 Arylthio, substituted or unsubstituted C7-C 60 Aryl or substituted or unsubstituted C2-C 60 Heteroaryl alkyl groups.

[0077] In one embodiment, R can be hydrogen or substituted or unsubstituted C1-C. 60 Alkyl group. In one embodiment, R can be hydrogen or a substituted or unsubstituted C1-C5 alkyl group.

[0078] M represents a metallic element, a represents the quantity of R, and can be an integer from 1 to 5. n can be an integer from 1 to 4. When a is an integer from 2 to 5, multiple Rs can be the same or different from each other.

[0079] In this specification, unless otherwise defined, "substituted or unsubstituted" can mean substituted or unsubstituted by one or more substituents selected from deuterium, halogen, cyano, nitro, amino, silyl, boron, phosphonooxide, phosphonosulfur, alkyl, alkenyl, aryl, and heterocyclic groups. Furthermore, the substituents exemplified above can be substituted or unsubstituted, respectively. For example, biphenyl can be interpreted as aryl or as a phenyl group substituted with a phenyl group. Heterocyclic groups include aliphatic heterocycles and aromatic heterocycles (heteroaryl groups).

[0080] In one embodiment, the protective coating 70 may comprise a metal benzoate salt. In one embodiment, the protective coating 70 may comprise an alkali metal benzoate salt such as lithium benzoate, sodium benzoate, potassium benzoate (n=1); or a benzoate-based alkaline earth metal salt such as calcium benzoate, magnesium benzoate (n=2).

[0081] In one embodiment, the protective coating 70 may contain an alkali metal salt of benzoate.

[0082] In one embodiment, M in Formula 1 can be an alkali metal other than lithium. The protective coating 70 can comprise a benzoate salt of an alkali metal other than lithium. For example, the protective coating 70 can comprise sodium benzoate and / or potassium benzoate.

[0083] Using an alkali metal with a relatively larger ionic radius than lithium can further enhance the passivation effect on the surface of the active material layer 60 of the lithium secondary battery. For example, it can suppress the formation of lithium impurities on the surface of the active material layer 60 and suppress lithium dissolution.

[0084] In one embodiment, when the protective coating 70 contains a benzoate-based alkaline earth metal salt, multiple benzoate groups are distributed on the surface of the active material layer 60, thereby increasing the passivation effect of the electrode.

[0085] As described above, the protective coating 70 contains ionicly bonded substances, thereby forming a stable solid film on the surface of the active material layer 60. Therefore, compared to the case where a thick polymer protective film is formed, side reactions with the electrolyte can be reduced while promoting rapid charge and discharge. Furthermore, by including organic groups containing aryl rings, the solubility in the electrolyte can be reduced, and stable electrode passivation can be provided.

[0086] Furthermore, a secondary battery can be manufactured with a protective coating 70 formed before charging / discharging, while suppressing the formation of a solid electrolyte interface (SEI) film that occurs during charging / discharging. Therefore, electrolyte consumption can be prevented while effectively suppressing electrolyte side reactions caused by repeated charging / discharging, high temperatures, overvoltage, etc.

[0087] In some embodiments, the composition of the electrode for the secondary battery is measured using the protective coating 70. 1 In the H-NMR spectrum, peaks (e.g., multiplets of quartets or more) were observed in the range of 7.2 ppm to 7.4 ppm, and peaks (doublets) were observed in the range of 7.6 ppm to 7.7 ppm. For example, in a solution from which the components of the protective coating 70 were dissolved from the electrode of the secondary battery... 1 The above peaks can be observed in H-NMR spectra.

[0088] A protective coating 70 may also be formed on the current collector 50. In some embodiments, the protective coating 70 may extend continuously along the surface of the current collector 50, the side surface of the active material layer 60, and the opposite surface of the active material layer 60.

[0089] Figures 2 to 4 This is a schematic, partially enlarged cross-sectional view illustrating an electrode for a secondary battery according to an exemplary embodiment. For example, Figures 2 to 4 yes Figure 1 The diagram shows a schematic enlarged cross-sectional view of region A.

[0090] exist Figures 2 to 4 In this context, the active substances contained in the active substance layer 60 are referred to as active substance particles.

[0091] Reference Figure 2 The protective coating 70 can be formed on the outer surface of the active material layer 60. The protective coating 70 can be a separate coating formed directly on the outer surface of the active material layer 60.

[0092] Within the active material layer 60, active material particles 65 may be distributed together with adhesive 62. Conductive material 64 may be distributed together with adhesive 62 between the active material particles 65. Protective coating 70 may contact and at least partially cover the active material particles 65, adhesive 62, and conductive material 64 exposed on the outer surface of the active material layer 60.

[0093] As described above, an electrode slurry containing active material particles 65, binder 62 and conductive material 64 can be coated onto the current collector 50, and then dried and calendered to form an electrode for a secondary battery.

[0094] The coating material used to form the protective coating 70 can be dissolved in a solvent to prepare a coating solution. The manufactured electrode is immersed in the coating solution and then dried at a specified temperature to form the protective coating 70. According to an exemplary embodiment, the electrode can be immersed in the coating solution while the active material layer 60 is coated on the current collector 50.

[0095] The solvent may include water, alcohol-based solvents such as ethanol, tetrahydrofuran (THF), dimethyl sulfoxide (DMSO), etc.

[0096] The concentration or content of the coating substance in the coating solution can be greater than 0.1% by weight and less than 10% by weight, 0.1% by weight to 5% by weight, 0.5% by weight to 5% by weight, or 1% by weight to 5% by weight. The drying temperature can be 40°C to 100°C, 50°C to 80°C, or 50°C to 70°C.

[0097] Under the above concentration and drying conditions, oxidation / reduction caused by side reactions of the electrolyte can be prevented without hindering the fast charging characteristics, initial efficiency, and rate performance of the secondary battery.

[0098] Reference Figure 3 The protective coating 70 can be formed on the surface of each of the active material particles 65. Therefore, the protective coating 70 formed on the outer surface of the active material particles 65 arranged on the outer surface of the active material layer 60 can be exposed on the outer surface.

[0099] Inside the active material layer 60, an adhesive 62 and / or a conductive material 64 may be distributed between the protective coatings 70 formed on adjacent active material particles 65.

[0100] According to an exemplary embodiment, the coating material described above can be mixed into a solvent used for electrode slurry to prepare a coating solution. Therefore, the coating material particles 65 can be mixed into the coating solution before coating the current collector 50.

[0101] The concentration or content of the coating substance in the coating solution may be greater than 0.1% by weight and less than 10% by weight, 0.1% by weight to 5% by weight, 0.5% by weight to 5% by weight, or 1% by weight to 5% by weight.

[0102] Active material particles 65 can be mixed in the coating solution to form a coating slurry, and stirred using a mixer. The solid content in the coating slurry can be 30% to 90% by weight, 40% to 85% by weight, 40% to 80% by weight, or 50% to 70% by weight.

[0103] Under the above coating conditions, oxidation / reduction caused by side reactions of the electrolyte can be prevented without hindering the initial efficiency and rate characteristics of the secondary battery.

[0104] While stirring for a specified time, the solvent can be removed by vacuum drying, thereby forming a protective coating 70 on the surface of the active material particles 65.

[0105] Electrode slurry can be prepared as described above by using active material particles 65 with a protective coating 70 formed thereon. The electrode slurry is then coated onto a current collector 50, and subsequently dried and calendered to manufacture an electrode for a secondary battery comprising an active material layer 60.

[0106] Reference Figure 4 The protective coating 70 can be formed on the outer surface of the active material layer 60 and on the surface of the active material particles 65.

[0107] The protective coating 70 may include a first protective coating 70a formed on the outer surface of the active material layer 60 and a second protective coating 70b formed on the surface of the active material particles 65. In some embodiments, the first protective coating 70a and the second protective coating 70b may be substantially merged with each other at the periphery of the active material layer 60.

[0108] According to an exemplary implementation, such as referring to Figure 3 As explained, a second protective coating 70b can be formed on the active material particles 65 before the active material layer 60 is formed. The active material particles 65 with the second protective coating 70b formed are dispersed in a solvent together with a binder 62 and a conductive material 64 to prepare an electrode slurry. The electrode slurry is coated on the current collector 50, and then dried and calendered to form the active material layer 60.

[0109] Then, as per reference Figure 2 As explained, the electrodes of the secondary battery, including the active material layer 60, can be impregnated with a coating solution and dried to form a first protective coating 70a.

[0110] Figure 5 and Figure 6 These are schematic plan views and schematic cross-sectional views illustrating a secondary battery according to an exemplary embodiment. For example, Figure 6 It is along Figure 5 A cross-sectional view taken along the thickness direction of line I-I'. Figure 5 and Figure 6 The illustration of the protective coating 70 is omitted.

[0111] Figure 5 and Figure 6The schematic structure of the secondary battery is provided for ease of illustration, and the structure of the secondary battery of the present invention is not limited thereto.

[0112] Reference Figure 5 and Figure 6 The lithium secondary battery may include an electrode assembly 150, which includes a positive electrode 100 and a negative electrode 130. The electrode assembly 150 may further include a separator 140. A plurality of positive electrodes 100 and a plurality of negative electrodes 130 may be stacked with respect to the separator 140 to form the electrode assembly 150. The electrode assembly 150 may be housed together with an electrolyte within a housing 160 and immersed in the electrolyte.

[0113] The positive electrode 100 may include a positive electrode current collector 105 and a positive electrode active material layer 110 formed on at least one side of the positive electrode current collector 105. The positive electrode active material layer 110 may include positive electrode active material particles as active material particles 65.

[0114] The negative electrode 130 may include a negative electrode current collector 125 and a negative electrode active material layer 120 formed on at least one side of the negative electrode current collector 125. The negative electrode active material layer 120 may include negative electrode active material particles as active material particles 65.

[0115] At least one of the positive electrode 100 and the negative electrode 130 may include a reference. Figures 1 to 4 The described electrode includes a protective coating 70 for a secondary battery. In some embodiments, the electrode can be applied to the negative electrode 130 to enhance the mobility of lithium within the negative electrode active material layer and to block oxidation / reduction side reactions caused by electron migration with the electrolyte.

[0116] In some implementations, the electrodes for the secondary battery described above can be applied to the positive electrode 100 and the negative electrode 130, respectively.

[0117] A separator 140 may be disposed between the positive electrode 100 and the negative electrode 130. The separator 140 may include a porous polymer membrane or a porous nonwoven fabric.

[0118] The porous polymer membrane may include polyolefin-based polymers such as ethylene polymers, propylene polymers, ethylene / butene copolymers, ethylene / hexene copolymers, and ethylene / methacrylate copolymers.

[0119] The porous nonwoven fabric may include high-melting-point glass fibers, polyethylene terephthalate fibers, etc. The diaphragm 140 may also include a ceramic-based material. For example, inorganic particles may be coated on the polymer membrane or dispersed within the polymer membrane to improve heat resistance.

[0120] According to an exemplary embodiment, a battery cell can be defined by a positive electrode 100, a negative electrode 130, and a separator 140, and multiple battery cells can be stacked to form, for example, an electrode assembly 150. The electrode assembly 150 can be of the winding type, stacking type, z-folding type, or stack-folding type.

[0121] The electrode assembly 150, together with the electrolyte, is housed in the housing 160, thereby defining a lithium secondary battery. According to an exemplary embodiment, the electrolyte can be a non-aqueous electrolyte.

[0122] Non-aqueous electrolytes may contain a lithium salt as the electrolyte and an organic solvent, said lithium salt being, for example, Li. + X - This indicates that the anion (X) of the lithium salt is... - ), can be exemplified by F - Cl - ,Br - I - NO3 - N(CN)2 - BF4 - ClO4 - PF6 - (CF3)2PF4 - (CF3)3PF3 - (CF3)4PF2 - (CF3)5PF - (CF3)6P - CF3SO3 - CF3CF2SO3 - (CF3SO2)2N - (FSO2)2N - CF3CF2(CF3)2CO - (CF3SO2)2CH - (SF5)3C - (CF3SO2)3C - CF3(CF2)7SO3 - CF3CO2 - CH3CO2 -SCN - (CF3CF2SO2)2N - wait.

[0123] The organic solvents may include, for example, propylene carbonate (PC), ethylene carbonate (EC), diethyl carbonate (DEC), dimethyl carbonate (DMC), ethyl methyl carbonate (EMC), methyl propyl carbonate, dipropyl carbonate, dimethyl sulfoxide, acetonitrile, dimethoxyethane, diethoxyethane, vinylene carbonate, sulfolane, γ-butyrolactone, propylene sulfite, tetrahydrofuran, etc. These may be used alone or in combination of two or more.

[0124] like Figure 5 As shown, the tabs (positive tab and negative tab) can protrude from the positive current collector 105 and negative current collector 125 belonging to each cell and extend to one end of the housing 160. The tabs can be fused to said one end of the housing 160 and connected to electrode leads (positive lead 107 and negative lead 127) extending to or exposed outside the housing 160.

[0125] Although Figure 5 The diagram shows the positive electrode lead 107 and the negative electrode lead 127 protruding from the upper side of the housing 160 in the planar direction, but the position of the electrode leads is not limited to this. For example, the electrode leads may also protrude from at least one of the two sides of the housing 160, or they may protrude from the lower side of the housing 160. Alternatively, the positive electrode lead 107 and the negative electrode lead 127 may also be formed to protrude from different sides of the housing 160, respectively.

[0126] The lithium secondary battery can be manufactured in shapes such as cylindrical, prismatic, pouch, or coin, for example, using a can.

[0127] The following are experimental examples, including embodiments and comparative examples, to help understand the present invention. However, these embodiments are only for illustrating the present invention and are not intended to limit the scope of the claims. Various changes and modifications can be made to the embodiments within the scope of the present invention and the technical concept, which will be obvious to those skilled in the art. Such variations and modifications are naturally within the scope of the claims.

[0128] Example 1 LiNi will be used as the positive electrode active material. 0.8 Co 0.1 Mn 0.1O2 positive electrode active material particles, acetylene black (Denka Black) as a conductive material, and PVDF as a binder are mixed in a mass ratio of 97:2:1 to prepare a positive electrode mixture. The prepared positive electrode mixture is coated onto an aluminum current collector, and then the positive electrode is manufactured by drying and rolling.

[0129] A negative electrode slurry is prepared, comprising 93% by weight of natural graphite particles as the negative electrode active material, 5% by weight of flake-type conductive material KS6 as the conductive material, 1% by weight of styrene-butadiene rubber (SBR) as a binder, and 1% by weight of carboxymethyl cellulose (CMC) as a thickener. The negative electrode slurry is coated onto a copper substrate and then dried and calendered to manufacture the negative electrode.

[0130] The positive and negative electrodes are immersed in an ethanol solution containing sodium benzoate at a concentration of 1% by weight for about 10 seconds, then removed and dried in a convection oven at 60 degrees Celsius to form a protective coating on the surface of the active material layer.

[0131] The positive and negative electrodes manufactured as described above are notched to specified dimensions and stacked. A separator (polyethylene, 15 μm thick) is placed between the positive and negative electrodes to form a battery cell. The tabs of the positive and negative electrodes are then welded together. The welded positive / separator / negative electrode assembly is placed in a soft package, and the three sides except for the electrolyte injection surface are sealed. At this time, the portion with the electrode tabs is contained within the sealed portion. Electrolyte is injected through the electrolyte injection surface, and the electrolyte injection surface is also sealed, then immersed for at least 12 hours. Afterward, formation charging and discharging are performed (charging conditions: CC-CV, 0.25C, 4.2V, 0.05C, cut-off; discharging conditions: CC, 0.25C, 2.5V, cut-off).

[0132] In preparing the electrolyte, a 1M LiPF6 solution was prepared using a mixed solvent of EC / EMC (30 / 70; volume ratio), and 1% by weight of vinylene carbonate (VC), 0.5% by weight of 1,3-propenyl sulfonyl lactone (PRS) and 0.5% by weight of lithium bis(oxalato)borate (LiBOB) were added.

[0133] Example 2 The secondary battery was manufactured using the same method as in Example 1, except that the positive and negative electrodes were manufactured after the active material layer was formed instead of forming a protective coating on the positive and negative active material particles.

[0134] Specifically, the positive electrode active material particles and the negative electrode active material particles are mixed in a planetary mixer with an NMP solution and an aqueous solution of sodium benzoate, respectively, having a concentration of 1% by weight. The solid content of the solution in the mixer is adjusted to 50% by weight, and then stirring / mixing is performed simultaneously with vacuum drying using a vacuum pipeline.

[0135] Example 3 The secondary battery was manufactured using the same method as in Example 1, except that the concentration of sodium benzoate in the coating solution was increased to 10 by weight.

[0136] Example 4 The secondary battery was manufactured using the same method as in Example 1, except that the concentration of sodium benzoate in the coating solution was reduced to 0.09% by weight.

[0137] Example 5 The secondary battery was manufactured using the same method as in Example 1, except that magnesium benzoate was used as the coating material.

[0138] Example 6 The secondary battery was manufactured using the same method as in Example 1, except that lithium benzoate was used as the coating material.

[0139] Comparative Example 1 The secondary battery was manufactured using the same method as in Example 1, except that the formation of the protective coating was omitted.

[0140] Comparative Example 2 The secondary battery was manufactured using the same method as in Example 1, except that lithium bis(oxalatoborate) (LiBOB) was used as the coating material in the coating solution.

[0141] Comparative Example 3 The secondary battery was manufactured using the same method as in Example 1, except that NaCl was used as the coating material contained in the coating solution.

[0142] Evaluation example (1) Protective coating 1 H-NMR analysis The negative electrode was separated from the secondary battery after formation and charge / discharge of Example 1 and Comparative Example 1, and then immersed in dimethyl carbonate (DMC) for 3 days before drying. The active material layer was scraped off from the dried negative electrode and then mixed with D2O at a weight ratio of 1:2 to prepare a sample solution. The sample solution was stirred for 1 day to dissolve the protective coating components, and then filtered through a syringe filter to obtain the measurement solution.

[0143] Figure 7 The composition was measured from the negative electrode components of Example 1 and Comparative Example 1. 1 H-NMR analysis diagram.

[0144] Reference Figure 7 In Example 1 1 In the H-NMR spectrum, multiple peaks were observed in the range of 7.2 ppm to 7.4 ppm, and double peaks were observed in the range of 7.6 ppm to 7.7 ppm.

[0145] (2) Evaluation of fast charging characteristics The secondary batteries manufactured in the examples and comparative examples were subjected to step charging (CC / CV charging at 4.2V to 0.05V cutoff) and 1 / 3C discharging (CC discharging to 2.5V cutoff) cycles at 1.25C / 1.0C / 0.75C / 0.5C rates (C-rate) within a DOD range of 72% (SOC 8-80%), repeated 200 times. A 10-minute rest time was set between each cycle. After 200 cycles, the charge capacity retention rate relative to the discharge capacity of the initial cycle was measured.

[0146] (3) DC-IR evaluation The secondary battery was charged at 25°C (0.3C CC / CV charging to 4.2V, 0.05C cutoff), rested for 10 minutes, and then discharged (0.3C CC discharge to 50% SOC, cutoff). After resting at 50% SOC for 1 hour, a 1C discharge for 10 seconds was performed, followed by another 10-second rest. The difference between the voltage after resting at 50% SOC for 1 hour and the voltage after the 1C discharge for 10 seconds was divided by the 1C current value to calculate the discharge resistance (DC-IR) at 50% SOC.

[0147] The evaluation results are recorded in Table 1 below.

[0148] [Table 1] Referring to Table 1, in embodiments where a protective coating comprising an aryl-cyclic metal compound is formed, improved fast-charge capacity retention and lower discharge resistance are ensured.

[0149] In Example 3, where the concentration of the coating substance in the coating solution was increased, the discharge resistance increased slightly due to the increased coating thickness. In Example 4, where the concentration of the coating substance in the coating solution was decreased, the fast charging stability decreased compared to Example 1.

[0150] In comparative examples where the protective coating was omitted or coated with organic or inorganic substances that do not contain aryl groups, the fast charging capacity retention rate decreased significantly compared to the examples.

[0151] In Example 6, which uses lithium benzoate as the coating material, the fast charging stability decreased and the discharge resistance increased compared to Example 1, which uses sodium benzoate.

Claims

1. An electrode for a secondary battery, comprising: current collector; An active material layer is disposed on the current collector and contains active material; And a protective coating, the protective coating covering at least a portion of the surface of the active material or at least a portion of the surface of the active material layer and comprising an aryl-cyclic metal compound.

2. The electrode for a secondary battery according to claim 1, wherein, The protective coating comprises a compound represented by the following structural formula 1: [Structure 1] ， In structural formula 1, R is hydrogen, deuterium, -F, -Cl, -Br, -I, hydroxyl, cyano, nitro, or a substituted or unsubstituted C1-C group. 60 Alkyl, substituted or unsubstituted C2-C 60 alkenyl, substituted or unsubstituted C2-C 60 Alkyne, substituted or unsubstituted C1-C 60 Alkoxy, substituted or unsubstituted C3-C 60 Carbocyclic groups, substituted or unsubstituted C1-C 60 Heterocyclic groups, substituted or unsubstituted C6-C 60 aryloxy, substituted or unsubstituted C6-C 60 Arylthio, substituted or unsubstituted C7-C 60 Aryl or substituted or unsubstituted C2-C 60 heteroaryl, M represents a metallic element, a is an integer from 1 to 5, and n is an integer from 1 to 4.

3. The electrode for a secondary battery according to claim 2, wherein, In structural formula 1, M is an alkali metal or an alkaline earth metal, and n is 1 or 2.

4. The electrode for a secondary battery according to claim 1, wherein, The active material layer further comprises an adhesive, and the protective coating at least partially covers the surfaces of the active material and the adhesive exposed on the outer surface of the active material layer.

5. The electrode for a secondary battery according to claim 1, wherein, The protective coating also exists on the surface of the active material within the active material layer.

6. The electrode for a secondary battery according to claim 5, wherein, The protective coating includes a first protective coating covering the outer surface of the active material layer and a second protective coating covering the surface of the active material.

7. The electrode for a secondary battery according to claim 6, wherein, The first protective coating and the second protective coating merge with each other at the periphery of the active material layer.

8. The electrode for a secondary battery according to claim 1, wherein, The protective coating is in contact with the surface of the current collector.

9. The electrode for a secondary battery according to claim 1, wherein, In the solution from which the components of the protective coating are dissolved from the electrodes of the secondary battery 1 In the H-NMR spectrum, multiple peaks were observed in the range of 7.2 ppm to 7.4 ppm, and double peaks were observed in the range of 7.6 ppm to 7.7 ppm.

10. A secondary battery, comprising: A positive electrode; and a negative electrode disposed opposite to the positive electrode. Wherein, at least one of the positive electrode and the negative electrode includes the electrode for a secondary battery as described in claim 1.

11. A method for manufacturing an electrode for a secondary battery, comprising the following steps: Prepare the current collector; as well as An active material layer is formed on the current collector, the active material layer comprising an active material and a protective coating comprising an aryl-cyclic metal compound. The step of forming the active material layer includes forming the protective coating on the outer surface of the active material layer, or forming the protective coating on the surface of the active material.

12. The method for manufacturing an electrode for a secondary battery according to claim 11, wherein, The step of forming the protective coating on the outer surface of the active material layer includes immersing the active material layer, which is coated on the current collector, in a coating solution containing the aryl-cyclic metal compound.

13. The method for manufacturing an electrode for a secondary battery according to claim 11, wherein, The step of forming the protective coating on the surface of the active material includes mixing the active material into a coating solution containing the aryl-cyclic metal compound before coating the active material onto the current collector.

14. The method for manufacturing an electrode for a secondary battery according to claim 13, wherein, The step of mixing the active material into the coating solution is carried out together with vacuum drying.

15. A method for manufacturing an electrode for a secondary battery according to any one of claims 12 or 13, wherein, The concentration of the aryl-cyclic metal compound in the coating solution is 0.1% by weight or more and less than 10% by weight.

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