Positive electrode active material composite, and positive electrode for secondary battery and lithium secondary battery comprising same

Abstract

A positive electrode active material composite according to one embodiment of the present invention comprises: positive electrode active material particles containing a lithium composite oxide; and a coating layer located on the surface of the positive electrode active material particles, wherein the coating layer contains a polymer containing a first repeating unit derived from an ionic material and represented by chemical formula 1.

Description

Anode active material composite, anode for a secondary battery including the same, and a lithium secondary battery

[0001] The present invention relates to a positive electrode active material composite, a positive electrode for a secondary battery comprising the same, and a lithium secondary battery.

[0002] Recently, as the required energy density of batteries has increased rapidly, the development of high-capacity lithium-ion batteries has become urgent. To this end, research is actively underway to replace conventional anode materials, such as graphite or silicon, with lithium metal, or to incorporate cathode materials with high energy density into the electrodes.

[0003] However, as the anode becomes thicker for high energy density, it is difficult to secure stable battery performance and lifespan characteristics, so there is practically a limit to increasing the thickness.

[0004] For example, such thick-film cathodes have a problem in that the cathode active material is non-uniformly dispersed. This problem causes non-uniform lithium ion flow characteristics and leads to non-uniform charge / discharge characteristics and polarization phenomena along the thickness direction.

[0005] Therefore, research and development are required for cathode active materials that can be uniformly dispersed in thick-film cathodes to induce uniform lithium ion flow characteristics.

[0006] One aspect of the present invention is to provide a positive electrode active material composite having excellent dispersibility in the positive electrode, a positive electrode for a secondary battery including the same, and a lithium secondary battery.

[0007] The problems of the present invention are not limited to those described above. A person skilled in the art to which the present invention pertains will have no difficulty understanding additional problems of the present invention from the overall contents of this specification.

[0008] A positive electrode active material composite according to one embodiment of the present invention comprises positive electrode active material particles comprising a lithium composite oxide; and a coating layer located on the surface of the positive electrode active material particles, wherein the coating layer comprises a polymer comprising a first repeating unit derived from an ionic material represented by the following chemical formula 1.

[0009] [Chemical Formula 1]

[0010]

[0011] (In the above Chemical Formula 1, R1 is a substituted or unsubstituted (C1-C10) hydrocarbon group with n, n is an integer from 1 to 3, X is N(CF3SO2)2, N(FSO2)2 or CF3SO3, L1 is each independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene or a combination thereof, and the hydrogen of L1 may each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.)

[0012] In addition, in the above-mentioned positive active material composite, the polymer may further include a second repeating unit derived from a compound containing an acrylate group.

[0013] In addition, in the above-mentioned positive active material composite, the compound may contain three or more acrylate groups.

[0014] In addition, in the above-described positive electrode active material composite, the polymer may include the first repeating unit and the second repeating unit in a molar ratio of 1:0.01 to 0.5.

[0015] In addition, in the above-mentioned positive active material composite, the coating layer may be included in an amount of 0.1 to 5.0 weight% based on the total weight of the positive active material composite.

[0016] In addition, in the above-mentioned positive active material composite, the thickness of the coating layer may be 0.001 to 0.1 μm.

[0017] In addition, in the above-mentioned positive active material composite, the positive active material particles may include one or more of a single-crystal active material and a polycrystalline active material.

[0018] In addition, in the above-mentioned positive active material composite, the positive active material particles may include a positive active material represented by the following chemical formula 2.

[0019] [Chemical Formula 2]

[0020] Li x [Ni a Co b Mn c M 1 d ]O2

[0021] (In the above chemical formula 2, M 1 ...is one or more selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, P, Y, Na, and Ca, and 0.8≤x≤1.3, 0.5≤a≤1.0, 0≤b≤0.5, 0≤c≤0.5, 0≤d≤0.2, and a+b+c+d=1.)

[0022] In addition, in the above-described positive active material composite, the positive active material particles may include a first positive active material particle having an average particle size (D50) of 10 to 20 μm; and a second positive active material particle having an average particle size (D50) of 1 to 10 μm.

[0023] In addition, in the above-described positive active material composite, the weight ratio of the first positive active material particle and the second positive active material particle may be 1:0.1 to 0.5.

[0024] In addition, in the above-mentioned positive active material composite, the ionic material may be represented by the following chemical formula 3 or chemical formula 4.

[0025] [Chemical Formula 3]

[0026]

[0027] [Chemical Formula 4]

[0028]

[0029] (In the above chemical formulas 3 and 4, R2 is a substituted or unsubstituted (C1-C10) hydrocarbon group, X is N(CF3SO2)2, N(FSO2)2, or CF3SO3, L1 is each independently a directly bonded (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, L2 is (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, and the hydrogens of L1 and L2 may each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.)

[0030] A positive electrode for a secondary battery according to one embodiment of the present invention comprises the aforementioned positive electrode active material composite, binder, and conductive material.

[0031] A lithium secondary battery according to one embodiment of the present invention includes the aforementioned positive electrode.

[0032] The positive electrode active material composite according to the present invention can have excellent dispersibility and rapid electrolyte wettability. A positive electrode for a secondary battery and a lithium secondary battery comprising the above positive electrode active material composite can maintain smooth lithium ion flow, have excellent ion conductivity characteristics, and have charge / discharge efficiency at high temperatures.

[0033] The various and beneficial advantages and effects of the present invention are not limited to those described above and will be more easily understood in the process of explaining specific embodiments of the present invention.

[0034] Figure 1 shows photographs of the dispersibility evaluation of Example 1 and Comparative Example 1.

[0035] Figure 2 is a graph showing the FT-IR analysis results of Example 1 and Comparative Example 1.

[0036] Figure 3 is a graph showing the capacity realization rate for the discharge rate of Examples 1 to 5 and Comparative Example 1.

[0037] Figure 4 is a graph showing the high-temperature charge / discharge capacity retention rates of Examples 1 to 5 and Comparative Example 1.

[0038] Preferred embodiments of the present invention are described below. However, embodiments of the present invention may be modified in various other forms, and the scope of the present invention is not limited to the embodiments described below.

[0039] In addition, embodiments of the present invention are provided to more fully explain the present invention to those with average knowledge in the relevant technical field.

[0040] In describing the embodiments of the present invention, if it is determined that a detailed description of known technology related to the present invention may unnecessarily obscure the essence of the present invention, such detailed description will be omitted. Furthermore, the terms described below are defined considering their functions in the present invention, and these may vary depending on the intentions or conventions of the user or operator. Therefore, such definitions should be based on the content throughout this specification. The terms used in the detailed description are merely for describing the embodiments of the present invention and should not be limited in any way. Unless explicitly stated otherwise, expressions in the singular form include the meaning of the plural form.

[0041] In this specification, expressions such as “include” or “comprising” are intended to refer to certain characteristics, numbers, steps, actions, elements, parts or combinations thereof, and should not be interpreted to exclude the existence or possibility of one or more other characteristics, numbers, steps, actions, elements, parts or combinations thereof other than those described.

[0042] Unless otherwise specifically defined in this specification, % units mean weight %.

[0043] The term "CA-CB" in this specification may mean "having a carbon number of A or more and B or less."

[0044] The present invention will be described in detail below through each embodiment or example of the invention. It should be noted that each embodiment or example described in this specification is not limited to a single embodiment or example, but may also be combined with other embodiments or examples. Accordingly, the citation of claims in the patent claims is merely an example of an embodiment, and the technical concept of the present invention should not be interpreted as being limited only to a combination with the cited claims; rather, combinations with various claims are also included within the scope of the technical concept of the present invention.

[0045] According to one embodiment of the present invention, a positive active material composite is provided.

[0046] A positive electrode active material composite according to one embodiment of the present invention comprises positive electrode active material particles comprising a lithium composite oxide; and a coating layer located on the surface of the positive electrode active material particles, wherein the coating layer comprises a polymer comprising a first repeating unit derived from an ionic material represented by the following chemical formula 1.

[0047] [Chemical Formula 1]

[0048]

[0049] In the above chemical formula 1, R1 is a substituted or unsubstituted (C1-C10) hydrocarbon group of n, n is an integer from 1 to 3, X is N(CF3SO2)2, N(FSO2)2 or CF3SO3, L1 is each independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene or a combination thereof, and the hydrogen of L1 can each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.

[0050] In this specification, "hydrocarbon group" may include a linear or branched alkyl group; a linear or branched alkylene group; a saturated cyclic aliphatic hydrocarbon group; an unsaturated cyclic aliphatic hydrocarbon group; an aryl group; an arylene group; an arylalkyl group; an arylalkylene group; or a combination thereof. Additionally, the hydrocarbon group may be substituted with one or more substituents selected from the group consisting of -O-, -OC(O)-, -OC(O)O-, -NHCO-, and -NHC(O)O-. Specifically, the "hydrocarbon group" may include a linear or branched (C1-C10)alkyl group; a linear or branched (C1-C10)alkylene group; a (C3-C10)cycloalkyl group; a (C3-C10)cycloalkylene group; a (C3-C10)cycloalkenylene group; or a combination thereof.

[0051] In this specification, "substitution" may mean that one or more hydrogen atoms bonded to a hydrocarbon group are substituted with a halogen, nitro, cyano, (C1-C7)alkoxy, hydroxy, or carboxyl.

[0052] As a specific example, in the above chemical formula 1, the substituted or unsubstituted (C1-C10) hydrocarbon group of R1 may be a (C1-C10) alkyl or a (C1-C10) alkylene. Additionally, as a specific example, R1 may be a substituted or unsubstituted (C1-C8) hydrocarbon group of n, more specifically a (C1-C6) hydrocarbon group, and may be, for example, a (C1-C6) alkyl or a (C1-C6) alkylene.

[0053] As a specific example, in the above chemical formula 1, R1 is a substituted or unsubstituted (C1-C6) hydrocarbon group of n, n is 1 or 2, X is N(CF3SO2)2, N(FSO2)2 or CF3SO3, and L1 may each be independently a direct bond.

[0054] In one embodiment of the present invention, the positive active material composite has excellent dispersibility in the positive electrode as the coating layer containing the polymer is composited with the positive active material particles. In addition, by including the positive active material composite as the active material of the positive electrode, the affinity of the positive electrode to the electrolyte is improved by the coating layer of the positive active material composite, thereby enabling rapid electrolyte wettability. Accordingly, a lithium secondary battery including the positive active material composite can maintain a smooth flow of lithium ions and can have excellent ion conductivity, lifespan characteristics, and charge / discharge efficiency at high temperatures.

[0055] The coating layer located on the surface of the positive active material particles may be a coating layer composed of a linear polymer or a network polymer coating layer having crosslinking points. Specifically, when forming an electrode using a slurry containing a positive active material composite, a network polymer coating layer may be preferred in terms of maintaining the structural safety of the coating layer. The coating layer may be an conformal coating layer conformally coated on the surface of the positive active material particles.

[0056] The positive electrode active material particles include a lithium composite oxide, and the lithium composite oxide may use a compound capable of reversibly intercalating and deintercalating lithium (a lithated intercalation compound). For example, the positive electrode active material particles are not particularly limited as long as they are known as conventional positive electrode active materials, and the positive electrode active material particles may include one or more selected from single-crystal active materials and polycrystalline active materials.

[0057] For example, the positive electrode active material particles may use one or more of the composite oxides of lithium and a metal selected from cobalt, manganese, nickel, and combinations thereof, and specific examples may include compounds represented by any one of the following chemical formulas.

[0058] Li a A 1-b B bD2(wherein 0.90 ≤ a ≤ 1.8, and 0 ≤ b ≤ 0.5); Li a E 1-b B b O 2-c D c (In the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); LiE 2-b B b O 4-c D c (In the above equation, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05); Li a Ni 1-b-c Co b B c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Co b B c O 2-α T α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Co b B c O 2-α T2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni 1-b-c Mn b B c D α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α ≤ 2); Li a Ni 1-b-c Mn b B c O 2-α T α (In the above equation, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Lia Ni 1-b-c Mn b B c O 2-α T2(wherein, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.5, 0 ≤ c ≤ 0.05, 0 < α < 2); Li a Ni b E c G d O2(wherein 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 GeO2(wherein the above formula, 0.90 ≤ a ≤ 1.8, 0 ≤ b ≤ 0.9, 0 ≤ c ≤ 0.5, 0 ≤ d ≤ 0.5, 0.001 ≤ e ≤ 0.1); Li a NiG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a CoG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a MnG b O2(in the above equation, 0.90 ≤ a ≤ 1.8, 0.001 ≤ b ≤ 0.1); Li a Mn2G b O4(wherein 0.90 ≤ a ≤ 1.8 and 0.001 ≤ b ≤ 0.1); QO2; QS2; LiQS2; V2O5; LiV2O5; LiIO2; LiNiVO4; Li (3-f) J2(PO4)3(0 ≤ f ≤ 2); and Li (3-f)Fe2(PO4)3(0 ≤ f ≤ 2); in the preceding formula, A is Ni, Co, Mn or a combination thereof; B 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; T 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; I is Cr, V, Fe, Sc, Y or a combination thereof; and J may be V, Cr, Mn, Co, Ni, Cu or a combination thereof.

[0059] More specifically, the positive active material particles may include a positive active material represented by the following chemical formula 2.

[0060] [Chemical Formula 2]

[0061] Li x [Ni a Co b Mn c M 1 d ]O2

[0062] In the above chemical formula 2, M 1 is one or more selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, P, Y, Na and Ca, and 0.8≤x≤1.3, 0.5≤a≤1.0, 0≤b≤0.5, 0≤c≤0.5, 0≤d≤0.2, and a+b+c+d=1.

[0063] Specifically, M in the above chemical formula 2 1 It may be a doping element that can be included in the positive electrode active material particles and may be appropriately selected as needed. In addition, in the above chemical formula 2, x represents the molar ratio of lithium in the positive electrode active material and may be 0.8≤x≤1.3, 0.85≤x≤1.25, or 0.9≤x≤1.2.

[0064] In the above Chemical Formula 2, a represents the molar ratio of nickel among the metals excluding lithium in the positive electrode active material, and may be 0.5 ≤ a ≤ 1.0, 0.52 ≤ a ≤ 0.98, or 0.55 ≤ a ≤ 0.95. In the above Chemical Formula 2, b represents the molar ratio of cobalt among the metals excluding lithium in the positive electrode active material, and may be 0 ≤ b ≤ 0.5, 0.01 ≤ b ≤ 0.58, or 0.01 ≤ b ≤ 0.55. In the above Chemical Formula 2, c represents the molar ratio of manganese among the metals excluding lithium in the positive electrode active material, and may be 0 ≤ c ≤ 0.5, 0.01 ≤ c ≤ 0.58, or 0.01 ≤ c ≤ 0.55. In the above Chemical Formula 2, d represents the doping element (M) among the metals excluding lithium in the positive electrode active material. 1 It represents the molar ratio of ), which can be 0≤d≤0.2, 0≤d≤0.18, or 0≤d≤0.15.

[0065] For example, the positive active material particles may be included in an amount of 70 to 99 weight%, 80 to 99 weight%, or 85 to 99 weight% with respect to the total weight of the positive active material composite.

[0066] For example, the positive active material particles may include a first positive active material particle having an average particle size (D50) of 10 to 20 μm; and a second positive active material particle having an average particle size (D50) of 1 to 10 μm. By including the first positive active material particle and the second positive active material particle having different average particle sizes (D50), the particle size distribution of the positive active material particles may have a bimodal distribution. By including the positive active material particles having the bimodal distribution, the lithium secondary battery containing the positive active material composite may have a more significant energy density.

[0067] For example, the average particle size (D50) of the first positive active material particle may be 10 to 20 μm, specifically 10.5 to 18 μm, more specifically 11 to 16 μm, and the average particle size (D50) of the second positive active material particle may be 1 to 10 μm, specifically 1.5 to 8 μm, more specifically 2 to 6 μm.

[0068] For example, the weight ratio of the first positive active material particle and the second positive active material particle may be 1:0.1 to 0.5, specifically 1:0.12 to 0.45, more specifically 1:0.15 to 0.4. When the weight ratio of the first positive active material particle and the second positive active material particle satisfies the above range, the dispersibility of the positive active material composite and the wettability of the electrolyte at the positive electrode may be improved.

[0069] For example, an ionic substance can be represented by the following chemical formula 3 or chemical formula 4.

[0070] [Chemical Formula 3]

[0071]

[0072] [Chemical Formula 4]

[0073]

[0074] In the above chemical formulas 3 and 4, R2 is a substituted or unsubstituted (C1-C10) hydrocarbon group, X is N(CF3SO2)2, N(FSO2)2, or CF3SO3, L1 is each independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, L2 is (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, and the hydrogens of L1 and L2 can each be independently substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.

[0075] The substituted or unsubstituted (C1-C10) hydrocarbon group of the above R2 may include a linear or branched (C1-C10) alkyl, a (C3-C10) cycloalkyl group, a (C3-C10) cycloalkenylene group, or a combination thereof, and the methylene group of the substituent may be substituted with one or more substituents selected from the group consisting of -O-, -OC(O)-, -OC(O)O-, -NHCO-, and -NHC(O)O-. Specifically, the above R2 may be a linear or branched (C1-C10) alkyl or a (C3-C10) cycloalkyl group, and more specifically, may be a linear or branched (C1-C8) alkyl, a linear or branched (C1-C6) alkyl, or a linear or branched (C1-C4) alkyl.

[0076] In the above chemical formulas 3 and 4, L1 may each independently be a direct bond or a (C1-C6)alkylene. Additionally, L2 may be a (C1-C6)alkylene, specifically a (C1-C4)alkylene.

[0077] As a specific example, in the above chemical formulas 3 and 4, R2 is (C1-C4)alkyl, X is N(CF3SO2)2, N(FSO2)2 or CF3SO3, L1 is a direct bond, and L2 may be (C2-C6)alkylene.

[0078] For example, the polymer included in the coating layer may further include a second repeating unit derived from a compound containing an acrylate group. When the second repeating unit is included, the aforementioned dispersibility and electrolyte wettability at the anode are improved, and at the same time, it may be possible to realize a cathode for a secondary battery and a lithium secondary battery having high power and high capacity.

[0079] For example, the above compound may include two or more acrylate groups, specifically three or more. For example, the above compound may include one or more selected from the group consisting of ethoxylated trimethylolpropane tri(meth)acrylate, dipentaerythritol hexa(meth)acrylate, pentaerythritol tri(meth)acrylate, propoxylated trimethylolpropane tri(meth)acrylate, propoxylated glyceryl tri(meth)acrylate, ethoxylated pentaerythritol tetra(meth)acrylate, pentaerythritol tetra(meth)acrylate, ditrimethylolpropane tetra(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tri(meth)acrylate, trimethylolpropane tris(3-mercaptopropionate), and dipentaerythritol penta(meth)acrylate, and specifically may include ethoxylated trimethylolpropane tri(meth)acrylate.

[0080] For example, the molar ratio of the first repeating unit and the second repeating unit is not particularly limited, and by appropriately considering the number of functional groups of the monomer from which the first repeating unit and the second repeating unit are derived, the polymer may include the first repeating unit and the second repeating unit in a molar ratio of 1:0.01 to 0.5, specifically 1:0.05 to 0.35, and more specifically 1:0.08 to 0.25. When the molar ratio of the first repeating unit and the second repeating unit satisfies the above range, the dispersibility of the anode active material composite and the wettability of the electrolyte at the anode may be improved.

[0081] For example, the coating layer may be included in an amount of 0.1 to 5.0 wt%, 0.1 to 4.0 wt%, 0.1 to 3.0 wt%, or 0.1 to 2.0 wt%, more specifically 0.35 to 0.75 wt% based on the total weight of the positive active material composite. For another example, the thickness of the coating layer may be 0.001 to 0.1 μm, 0.005 to 0.05 μm, or 0.01 to 0.03 μm. When the content and / or thickness of the coating layer each satisfy the above ranges, the dispersibility of the positive active material composite can be secured at an excellent level without excessive reduction in electron transport resistance.

[0082] According to another embodiment of the present invention, a method for manufacturing a positive electrode active material composite is provided. A method for manufacturing a positive electrode active material composite according to one embodiment of the present invention comprises the steps of: preparing positive electrode active material particles comprising a lithium composite oxide; mixing an ionic material represented by the following chemical formula 1 and an initiator to obtain a coating composition; and mixing the positive electrode active material particles and the coating composition to manufacture a positive electrode active material composite.

[0083] [Chemical Formula 1]

[0084]

[0085] In the above Chemical Formula 1, R1 is a substituted or unsubstituted (C1-C10) hydrocarbon group of n, n is an integer from 1 to 3, X is N(CF3SO2)2, N(FSO2)2, or CF3SO3, and L1 is each independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, and the hydrogen of L1 can each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy. A specific description of Chemical Formula 1 can be described in the same way as previously described in the cathode active material composite.

[0086] In the step of preparing the positive active material particles, the positive active material particles can be described in the same way as previously described in the positive active material complex.

[0087] For example, when the positive active material particles comprise a first positive active material particle and a second positive active material particle, the weight ratio of the first positive active material particle and the second positive active material particle in this step may be 1:0.1 to 0.5, specifically 1:0.12 to 0.45, more specifically 1:0.15 to 0.4. When the weight ratio of the first positive active material particle and the second positive active material particle satisfies the above range, the dispersibility of the manufactured positive active material composite and the wettability of the electrolyte at the positive electrode may be improved.

[0088] For example, in the step of obtaining a coating composition, the ionic material may be represented by the following chemical formula 3 or 4.

[0089] [Chemical Formula 3]

[0090]

[0091] [Chemical Formula 4]

[0092]

[0093] In the above chemical formulas 3 and 4, R2 is a substituted or unsubstituted (C1-C10) hydrocarbon group, X is N(CF3SO2)2, N(FSO2)2, or CF3SO3, L1 is independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, L2 is (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, and the hydrogens of L1 and L2 may each be independently substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy. The specific description of chemical formulas 3 and 4 can be described in the same way as previously described in the cathode active material composite.

[0094] For example, in the step of obtaining a coating composition, an ionic substance represented by Formula 3 or Formula 4 can be prepared through a counter-ion exchange reaction of a compound represented by Formula 5 or Formula 6 below, respectively. In Formula 5 below, R2 and L1 can be described as identical to R2 and L1 of Formula 3, and in Formula 6, L1 and L2 can be described as identical to L1 and L2 of Formula 4, and in Formulas 5 and 6, Y can mean a halogen.

[0095] [Chemical Formula 5]

[0096]

[0097] [Chemical Formula 6]

[0098]

[0099] For example, an ionic substance can be prepared by reacting a compound represented by Chemical Formula 5 (or a compound represented by Chemical Formula 6) with a lithium salt (LiX, where X is N(CF3SO2)2, N(FSO2)2, or CF3SO3). In this case, the reaction between the compound represented by Chemical Formula 5 (or a compound represented by Chemical Formula 6) and the lithium salt can be carried out in a molar ratio of 1:0.5 to 5.0, specifically 1:1.0 to 4.0, more specifically 1:1.0 to 3.0.

[0100] For example, in the step of obtaining a coating composition, the initiator may include a photoinitiator or a thermal initiator, and specifically, may include an azo compound as the thermal initiator. For example, the azo compound is not particularly limited as long as it is a material conventionally used as an initiator, and specific examples may include azobis(isobutyronitrile) or azobis(2,4-dimethylvaleronitrile).

[0101] For example, in the step of obtaining a coating composition, the coating composition may further include a compound containing an acrylate group. The compound containing an acrylate group can be described in the same way as previously described in the anode active material composite.

[0102] For example, in the step of obtaining a coating composition, the ionic material and the compound containing acrylate groups may be mixed in a weight ratio of 1:0.05 to 0.3, specifically 1:0.05 to 0.25, and more specifically 1:0.05 to 0.2. When the weight ratio of the ionic material and the compound containing acrylate groups satisfies the above range, a more uniform coating layer may be formed on the surface of the positive active material particles in the process described below.

[0103] In the step of manufacturing the cathode active material composite, mixing can be performed by stirring at a speed of 1500 rpm or higher. In this case, as frictional heat is generated while mixing the cathode active material particles and the coating composition at a high speed, a cross-linking reaction of the raw materials included in the coating composition is performed, and finally, a uniform coating layer can be formed on the surface of the cathode active material particles. For example, the mixing speed may be 1500 to 5000 rpm, specifically 1500 to 4500 rpm, and more specifically 1500 to 4000 rpm.

[0104] For example, the positive electrode active material particles and the coating composition may be mixed in a weight ratio of 1:0.001 to 0.06, 1:0.002 to 0.04, 1:0.002 to 0.02, or 1:0.003 to 0.01, more specifically in a weight ratio of 1:0.004 to 0.008. When the weight ratio of the positive electrode active material particles and the coating composition satisfies the above range, the dispersibility of the positive electrode active material composite being manufactured can be improved.

[0105] For example, prior to the step of manufacturing the positive electrode active material composite, the method may further include a step of heat-treating the coating composition at a temperature of 30 to 150°C. For example, the heat-treatment temperature may be 40 to 130°C, and more specifically, 50 to 100°C.

[0106] The cathode active material composite manufactured by the above-described method exhibits excellent dispersibility in the cathode as the coating layer containing a polymer is composited with the cathode active material particles. In addition, the cathode containing the cathode active material composite can have rapid electrolyte wettability as the affinity of the cathode is enhanced by the coating layer of the cathode active material composite. Accordingly, the lithium secondary battery containing the cathode active material composite can maintain a smooth flow of lithium ions and can have excellent ion conductivity, lifespan characteristics, and charge / discharge efficiency at high temperatures.

[0107] According to another embodiment of the present invention, a positive electrode for a secondary battery is provided. The positive electrode for a secondary battery according to one embodiment of the present invention comprises the positive electrode active material composite, a binder, and a conductive material described above. Since the positive electrode for a secondary battery includes the positive electrode active material composite described above, the affinity of the positive electrode to the electrolyte is improved by the coating layer of the positive electrode active material composite, thereby enabling rapid electrolyte wettability. Accordingly, work efficiency can be increased by shortening the injection time or aging time of the manufacturing process, and the uniformity of battery performance can be improved.

[0108] The binder can impart adhesion between the active material and the conductive material particles. The binder is not particularly limited to any binder used in conventional cathodes for secondary batteries. Specific examples of binders include polyvinylidene fluoride (PVdF), polyimide (PI), fluoropolyimide (FPI), polyacrylic acid (PAA), polyvinyl alcohol (PVA), carboxymethylcellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone (PVP), tetrafluoroethylene (PTFE), polyethylene, polypropylene, polyurethane, ethylene-propylene-diene polymer (EPDM), sulfonated ethylene-propylene-diene polymer (S-EPDM), styrene-butadiene rubber (SBR), fluorinated rubber or copolymers thereof, algin, etc., and one of these alone or a mixture of two or more may be used, but this is merely an example and is not necessarily limited thereto.

[0109] A conductive material is used to impart conductivity to the anode, and may be one that does not cause chemical changes and possesses electronic conductivity. The conductive material is not particularly limited as long as it is a conductive material used in conventional anodes for secondary batteries. Specific examples of conductive materials include carbon-based materials such as graphite, carbon black, super py, acetylene black, ketjen black, channel black, furnace black, lamp black, thermal black, carbon fiber, carbon nanotube, carbon nanowire, graphene, graphitized mesocarbon microbeads, fullerene, and amorphous carbon; metal powders or metal fibers such as copper, nickel, aluminum, and silver; conductive whiskers such as zinc oxide and potassium titanate; conductive metal oxides such as titanium oxide; and conductive polymers such as polyphenylene derivatives. Among these, one type alone or a mixture of two or more types may be used, but this is merely an example and is not necessarily limited thereto.

[0110] For example, a positive electrode for a secondary battery may further include a positive current collector. The positive current collector can provide an electrical path between the powdered positive active material and the power source. The positive current collector is not particularly limited as long as it is a positive current collector used in conventional secondary battery positive electrodes, but stainless steel, aluminum, nickel, titanium, calcined carbon, or aluminum or stainless steel surface treated with carbon, nickel, titanium, silver, etc. may be used. For example, the positive current collector can be used in various forms such as a film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. In addition, for example, the positive current collector may have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the positive current collector to increase adhesion with the components included in the positive electrode.

[0111] For example, the method for manufacturing a positive electrode for a secondary battery may include the step of manufacturing a positive electrode slurry comprising a positive electrode active material composite, a binder, and a conductive material; and the step of coating the positive electrode slurry onto a positive electrode current collector. Of course, the method of coating the positive electrode slurry can be manufactured through conventional manufacturing methods known in the past, such as applying the positive electrode slurry onto a positive electrode current collector, drying it, and rolling it.

[0112] A lithium secondary battery is provided according to another embodiment of the present invention. A lithium secondary battery according to one embodiment of the present invention includes the anode described above. That is, by including a anode comprising the anode active material composite described above, a smooth flow of lithium ions can be maintained, and excellent ion conductivity, lifespan characteristics, and charge / discharge efficiency at high temperatures can be achieved.

[0113] For example, a lithium secondary battery may include the anode described above; a cathode positioned opposite to the anode; a separator interposed between the anode and the cathode; and an electrolyte. Additionally, the lithium secondary battery may optionally further include a battery container housing an electrode assembly of the anode, cathode, and separator described above, and a sealing member sealing the battery container.

[0114] For example, the cathode may include a cathode current collector; and a cathode active material layer located on the cathode current collector.

[0115] The negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and copper, stainless steel, aluminum, nickel, titanium, calcined carbon, copper or stainless steel surface-treated with carbon, nickel, titanium, silver, etc., and aluminum-cadmium alloys may be used. For example, the negative electrode current collector may be used in various forms such as film, sheet, foil, net, porous body, foam, nonwoven fabric, etc. In addition, for example, the negative electrode current collector may have a thickness of 3 to 500 μm, and fine irregularities may be formed on the surface of the negative electrode current collector to strengthen the bonding force with the negative electrode active material.

[0116] The negative active material layer may optionally include a binder and a conductive material along with the negative active material. For example, the negative active material layer may be manufactured by applying a negative slurry containing the negative active material along with the binder and a conductive material to a negative current collector and drying it, or by casting the negative slurry onto a separate support and then laminating the film obtained by peeling it off from the support onto the negative current collector.

[0117] As the negative electrode active material, a compound capable of reversible intercalation and deintercalation of lithium may be used. The negative electrode active material is not particularly limited as long as it is a negative electrode active material used in conventional lithium secondary batteries, but specific examples include carbonaceous materials such as artificial graphite, natural graphite, graphitized carbon fiber, and amorphous carbon; metallic compounds capable of alloying with lithium such as Si, Al, Sn, Pb, Zn, Bi, In, Mg, Ga, Cd, Si alloys, Sn alloys, or Al alloys; and SiO₂ β Examples include metal oxides capable of doping and dedoping lithium, such as (0 < β < 2), SnO2, vanadium oxide, and lithium vanadium oxide; or composites comprising the metal compound and carbonaceous material, such as Si-C composites or Sn-C composites, and any one or more of these may be used.

[0118] The binder and conductive material may be the same as those previously described for the anode.

[0119] The separator can separate the negative electrode and the positive electrode and provide a pathway for the movement of lithium ions. The separator is not particularly limited to any separator used in conventional lithium secondary batteries, and specifically, it may include one that has low resistance to the movement of electrolyte ions and excellent electrolyte wettability. Specific examples of the separator may include porous polymer films, such as porous polymer films made from polyolefin-based polymers like ethylene homopolymer, propylene homopolymer, ethylene / butene copolymer, ethylene / hexene copolymer, and ethylene / methacrylate copolymer, or laminated structures of two or more layers thereof. Additionally, porous nonwoven fabrics, such as nonwoven fabrics made of high-melting-point glass fibers or polyethylene terephthalate fibers, may be used as separators. Furthermore, to ensure heat resistance or mechanical strength, a coated separator containing ceramic components or polymer materials may be used, and it may optionally be used in a single-layer or multi-layer structure.

[0120] Examples of electrolytes that can be used in the manufacture of lithium secondary batteries include organic liquid electrolytes, inorganic liquid electrolytes, solid polymer electrolytes, gel-type polymer electrolytes, solid inorganic electrolytes, molten inorganic electrolytes, etc., but are not limited thereto.

[0121] For example, the electrolyte may include an organic solvent and a lithium salt.

[0122] Organic solvents may be used without special restrictions as long as they can serve as a medium through which ions involved in the electrochemical reaction of the battery can move. Specifically, organic solvents include ester-based solvents such as methyl acetate, ethyl acetate, γ-butyrolactone, and ε-caprolactone; ether-based solvents such as dibutyl ether or tetrahydrofuran; ketone-based solvents such as cyclohexanone; and aromatic hydrocarbon-based solvents such as benzene and fluorobenzene. Carbonate-based 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-based solvents such as ethyl alcohol and isopropyl alcohol; nitriles such as R-CN (where R is a straight-chain, branched, or cyclic hydrocarbon group having C2 to C20 structures and may include a double bond, a directional ring, or an ether bond); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane; or sulfolanes may be used.

[0123] Lithium salts can be used without special restrictions as long as they are compounds capable of providing lithium ions used in lithium secondary batteries. Specific examples of lithium salts include LiPF6, LiClO4, LiAsF6, LiBF4, LiSbF6, LiAlO4, LiAlCl4, LiCF3SO3, LiC4F9SO3, LiN(C2F5SO3)2, LiN(C2F5SO2)2, LiN(CF3SO2)2, LiCl, LiI, or LiB(C2O4)2. For example, the concentration of the lithium salt may be 0.1 to 2.0 M. When the concentration of the lithium salt falls within the above range, the electrolyte has appropriate conductivity and viscosity, so it can exhibit excellent electrolyte performance and allow lithium ions to move effectively.

[0124] In addition to the above electrolyte components, the electrolyte may further include additives for the purpose of improving the lifespan characteristics of the battery, suppressing the decrease in battery capacity, and improving the discharge capacity of the battery. For example, the additives may further include one or more additives such as haloalkylene carbonate compounds like difluoroethylene carbonate, pyridine, triethylphosphite, triethanolamine, cyclic ether, ethylene diamine, n-glyme, triamide hexaphosphate, nitrobenzene derivative, sulfur, quinone imine dye, N-substituted oxazolidinone, N,N-substituted imidazolidine, ethylene glycol dialkyl ether, ammonium salt, pyrrole, 2-methoxyethanol, or aluminum trichloride.

[0125] The present invention will be described in detail below through examples. However, it should be noted that the examples described below are intended merely to illustrate and embody the present invention and are not intended to limit the scope of the present invention. This is because the scope of the present invention is determined by the matters described in the patent claims and matters reasonably inferred therefrom.

[0126] (Example 1)

[0127] (1) Preparation of a positive electrode active material complex

[0128] (Preparation of positive electrode active material particles) LiNi with an average particle size (D50) of 13.5 µm 0.9 Mn 0.07 Co 0.03 First cathode active material particles of O2 and LiNi having an average particle size (D50) of 4.3㎛ 0.94 Mn 0.04 Co 0.02 The second positive active material particles of O2 were mixed in a weight ratio of 80:20 to prepare the positive active material particles.

[0129] (Obtaining a coating composition) 90% by weight of 3-Ethyl-1-vinyl-1H-imidazol-3-ium bis(trifluoromethanesulfonyl)imide (EVImTFSI), an ionic substance represented by the following chemical formula 3 (R2=ethyl, L1=direct bond, X=N(CF3SO2)2), and 10% by weight of ethoxylated trimethylolpropane triacrylate were mixed, and then azobisisobutyronitrile (1 part by weight of initiator per 100 parts by weight of ethoxylated trimethylolpropane triacrylate) was added as an initiator.

[0130] [Chemical Formula 3]

[0131]

[0132] (Preparation of positive electrode active material composite) Positive electrode active material particles and a coating composition were mixed in a weight ratio of 99.7:0.3, mixed using a self-rotating mixer at 2000 rpm for 3 minutes, and then naturally cooled to prepare a positive electrode active material composite.

[0133] (2) Manufacturing of the anode

[0134] A cathode material was prepared by mixing 96.5 wt% of the cathode active material composite prepared in (1), 1.5 wt% of carbon black (Super-P, average particle size: 40 nm) as a conductive material, and 2 wt% of polyvinylidene fluoride as a binder. A cathode slurry was prepared by adding the cathode material to an N-methyl-2-pyrrolidone solvent so that the cathode material was 65 wt%. The cathode slurry was applied to an aluminum film with a thickness of 20 μm using a doctor blade, and after hot air drying at 100°C, vacuum drying at 130°C for 24 hours and rolling with a roll press to produce a cathode containing a 45 μm thick cathode active material layer. At this time, the cathode active material loading amount of the cathode was 3.5 mAh / cm² and the composite density was 3.6 g / cc.

[0135] (3) Manufacturing of lithium secondary batteries

[0136] A battery assembly was manufactured by laminating the positive electrode, negative electrode (a negative electrode with a thickness of 100 μm attached to a copper thin film with a thickness of 20 μm), and separator (thickness: 13 μm, SC13-D4-BP, Gellec) manufactured in (2). An aluminum battery tab (0.1 T x 7 mm) was ultrasonically welded to the unbuilt part of the positive electrode assembly, and a nickel battery tab (0.1 T x 7 mm) was welded to the unbuilt part of the negative electrode assembly. Then, the assembly was placed into a battery pouch film (153 μm, DNP) formed to fit the battery assembly and sealed. Subsequently, a lithium secondary battery was manufactured by injecting 2.5 g / Ah of a liquid electrolyte containing 1 mole of LiPF6 dissolved in a solvent mixed with ethylene carbonate and dimethyl carbonate in a volume ratio of 1:1.

[0137] (Example 2)

[0138] A positive electrode active material composite, a positive electrode, and a lithium secondary battery were prepared in the same manner as in Example 1, except that in the step of preparing the positive electrode active material composite of Example 1, the positive electrode active material particles and the coating composition were mixed in a weight ratio of 99.5:0.5.

[0139] (Example 3)

[0140] A positive active material composite, a positive electrode, and a lithium secondary battery were prepared in the same manner as in Example 1, except that in the step of preparing the positive active material composite of Example 1, the positive active material particles and the coating composition were mixed in a weight ratio of 99.2:0.8.

[0141] (Example 4)

[0142] A positive electrode active material composite, a positive electrode, and a lithium secondary battery were prepared in the same manner as in Example 2, except that in the step of preparing the positive electrode active material composite of Example 2 (obtaining the coating composition), 3,3'-(Butane-1,4-diyl)bis(1-vinyl-3-imidazolium) Bis(trifluoromethanesulfonyl)imide (BVImTFSI2), which is an ionic material represented by the following chemical formula 4 (L1=direct bonding, L2=butylene, X=N(CF3SO2)2), was used.

[0143] [Chemical Formula 4]

[0144]

[0145] (Example 5)

[0146] In the preparation of the positive active material composite of Example 4, the positive active material particles and the coating composition were mixed in a weight ratio of 99.2:0.8 in the (preparation of positive active material composite) step, except that the positive active material particles and the coating composition were mixed in the same way as in Example 4, the positive active material composite, the positive electrode, and the lithium secondary battery were prepared.

[0147] (Comparative Example 1)

[0148] (1) Preparation of positive active material particles

[0149] LiNi with an average particle size (D50) of 13.5㎛ 0.9 Mn 0.07 Co 0.03 First cathode active material particles of O2 and LiNi having an average particle size (D50) of 4.3㎛0.94 Mn 0.04 Co 0.02 The second positive active material particles of O2 were mixed in a weight ratio of 80:20 to prepare the positive active material particles.

[0150] (2) Manufacturing of positive electrodes and lithium secondary batteries

[0151] Using the positive active material particles prepared in (1), a positive electrode and a lithium secondary battery were manufactured in the same manner as in Example 1.

[0152] (Experimental Example 1: Evaluation of Dispersibility)

[0153] The positive active material composite of Example 1 and the positive active material particles of Comparative Example 1 were each mixed with polyvinylidene fluoride (Example 1 or Comparative Example 1 : polyvinylidene fluoride = 99 : 1). Subsequently, each mixture was added to an N-methyl-2-pyrrolidone solvent such that the mixture was 88% by weight, and the dispersibility was evaluated, and the results are shown in FIG. 1.

[0154] Referring to FIG. 1, it can be seen that in the case of Example 1, unlike Comparative Example 1, the dispersibility is excellent.

[0155] (Experimental Example 2: FT-IR Analysis)

[0156] For the positive electrode active material composite of Example 1 and the positive electrode active material particles of Comparative Example 1, the formation of a coating layer on the positive electrode active material composite was confirmed through FT-IR analysis (equipment name: ALPHA II FT-IR Base Spectrometer, manufacturer: Bruker), and the results are shown in FIG. 2.

[0157] Referring to FIG. 2, in the case of Example 1, unlike Comparative Example 1, peaks of bonds (CF bonds, SN bonds, SO bonds) derived from the coating composition were observed, and it can be confirmed that a coating layer was formed on the surface of the positive active material particles.

[0158] (Experimental Example 3: Evaluation of Physical Properties of the Anode)

[0159] For the anodes of the above examples and comparative examples, the anode porosity, anode wettability, and ionic conductivity within the anode were evaluated using the following evaluation method.

[0160] (1) Anode porosity

[0161] The density (apparent density) of the anode was measured using a thickness gauge (equipment name: μ-HITE, manufacturer: TESA) and a balance (equipment name: EX125, manufacturer: OHAUS), and the true density of the anode was calculated from the composition ratio of the materials contained in the anode and the density of each component. Subsequently, the porosity of the anode was calculated from the difference between the apparent density and the true density (net density) using the following relationship, and the results are shown in Table 1 below.

[0162] [Relationship]

[0163] Volume of each component within the anode (cc) = Measured weight of the anode (g) × Composition of the material / True density of the material (g / cc)

[0164] Porosity (%) = [1 - (Volume of active material in anode + Volume of conductive material in anode + Volume of binder in anode + Volume of additives in anode)] / Measured apparent volume of anode × 100

[0165] (2) Bipolar wettability

[0166] After dropping 1 μl of propylene carbonate (PC) solvent onto the surface of the anode at a dew point temperature of -40℃ and relative humidity of 1% or less, the time required for the solvent to penetrate into the electrode and completely disappear was measured, and the results are shown in Table 1 below. At this time, the point at which the solvent completely disappears was observed visually through an optical microscope and refers to the point at which the solvent titrated on the surface of the anode completely disappears from the surface of the anode.

[0167] (3) Ionic conductivity within the anode

[0168] A symmetric cell was prepared using an anode, and a cell for measuring ion conductivity was prepared by injecting a liquid electrolyte containing 1 mole of LiPF6 dissolved in a solvent mixed with ethylene carbonate (EC) and dimethyl carbonate (DEC) in a 1:1 volume ratio. The ion resistance was measured through impedance analysis of the cell for measuring ion conductivity, and the ion conductivity value within the anode was calculated. The results are shown in Table 1 below.

[0169] Classification Porosity (%) Time Required (sec) Ionic Conductivity (mS / cm) Example 1 19.32 7 3.2 0.47 Example 2 19.32 4 0.8 0.49 Example 3 19.32 6 0.3 0.47 Example 4 19.32 3 7.5 0.51 Example 5 19.32 5 2.5 0.49 Comparative Example 119.35 9 3.8 0.43

[0170] Referring to Table 1, in the case of Examples 1 to 5, it was found that a shorter time was required for the electrolyte to completely penetrate compared to Comparative Example 1, and the ion conductivity within the electrode was improved.

[0171] (Experimental Example 4: Electrochemical Evaluation of Lithium Secondary Battery)

[0172] For the lithium secondary batteries of the above examples and comparative examples, the initial efficiency, capacity realization rate with respect to discharge rate, and high-temperature charge / discharge capacity retention rate were evaluated using the following evaluation method.

[0173] (1) Initial efficiency

[0174] A lithium secondary battery was charged to 4.3V at a C-rate of 0.1 under constant current / constant voltage (CC / CV) conditions at 25℃ and then cut off. Subsequently, it was discharged to 3.0V at a C-rate of 0.1 (CC conditions). The percentage of the discharge capacity divided by the charge capacity was calculated as the initial efficiency, and the results are shown in Table 2.

[0175] (2) Capacity realization rate (output characteristics) relative to discharge rate

[0176] A lithium secondary battery was charged to 4.3V at a C-rate of 0.2 under constant current / constant voltage (CC / CV) conditions at 25°C and then cut off. Subsequently, it was discharged (CC conditions) to 3.0V at different discharge rates of 0.2, 0.33, 0.5, 1.0, 2.0, 3.0, and 5.0 C-rates. The capacity realization rate for each discharge rate was calculated by dividing the discharge capacity for each discharge rate by the initial discharge capacity to determine the percentage, and the results are shown in Figure 3. At this time, the initial discharge capacity was obtained by charging the lithium secondary battery to 4.3V at a C-rate of 0.2 under the above constant current / constant voltage conditions, cutting it off, and then discharging it to 3.0V at a C-rate of 0.2.

[0177] (3) High temperature charge / discharge capacity retention rate

[0178] A lithium secondary battery was charged to 4.3V at a C-rate of 0.5 under constant current / constant voltage (CC / CV) conditions at 45℃, and then cut off. Subsequently, it was discharged to 3.0V at a C-rate of 1.0 (CC conditions). The high-temperature charge / discharge capacity retention rate was calculated by determining the percentage of the discharge capacity for each charge / discharge cycle divided by the initial discharge capacity, and the results are shown in Figure 4 below. In this case, the initial discharge capacity refers to the capacity measured during a single high-temperature charge / discharge cycle.

[0179] Classification Initial Efficiency (%) Example 190.7 Example 291.1 Example 390.5 Example 491.4 Example 590.8 Comparative Example 189.7

[0180] Referring to Table 2 and Figures 3 and 4, Examples 1 to 5 showed higher initial efficiency, capacity realization rate (output characteristics) at a discharge rate of 3.0 C-rate or higher, and high-temperature charge / discharge capacity retention rate than Comparative Example 1.

[0181] The above embodiments are merely examples, and the present invention is not limited thereto. Any configuration having substantially the same structure as the technical concept described in the claims of the present invention and achieving the same functional effect is included within the technical scope of the present invention.

Claims

1. Positive active material particles comprising a lithium composite oxide; and It includes a coating layer located on the surface of the above positive active material particles, and The above coating layer comprises a polymer having a first repeating unit derived from an ionic material represented by the following chemical formula 1, an anode active material composite. [Chemical Formula 1] (In the above Chemical Formula 1, R1 is a substituted or unsubstituted (C1-C10) hydrocarbon group with n, n is an integer from 1 to 3, X is N(CF3SO2)2, N(FSO2)2 or CF3SO3, L1 is each independently a direct bond, (C1-C8)alkylene, (C1-C8)alkenylene or a combination thereof, and the hydrogen of L1 may each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.) 2. In Paragraph 1, The above polymer is a positive electrode active material composite further comprising a second repeating unit derived from a compound containing an acrylate group.

3. In Paragraph 2, The above compound is a positive electrode active material composite comprising three or more acrylate groups.

4. In Paragraph 2, The above polymer is an anode active material composite comprising the first repeating unit and the second repeating unit in a molar ratio of 1:0.01 to 0.

5.

5. In Paragraph 1, The anode active material composite, wherein the coating layer is included in an amount of 0.1 to 5.0 weight% based on the total weight of the anode active material composite.

6. In Paragraph 1, A positive electrode active material composite having a coating layer thickness of 0.001 to 0.1 μm.

7. In Paragraph 1, The above positive active material particles comprise one or more of a single-crystal active material and a polycrystalline active material, forming a positive active material composite.

8. In Paragraph 1, The above positive active material particles comprise a positive active material composite comprising a positive active material represented by the following chemical formula 2. [Chemical Formula 2] Li x [Ni a Co b Mr c M 1 d ]O2 (In the above chemical formula 2, M 1 ...is one or more selected from Al, Zr, B, W, Mo, Cr, Nb, Mg, Hf, Ta, La, Ti, Sr, Ba, Ce, P, Y, Na, and Ca, and 0.8≤x≤1.3, 0.5≤a≤1.0, 0≤b≤0.5, 0≤c≤0.5, 0≤d≤0.2, and a+b+c+d=1.) 9. In Paragraph 1, The positive active material particles comprise a first positive active material particle having an average particle size (D50) of 10 to 20 μm; and a second positive active material particle having an average particle size (D50) of 1 to 10 μm, comprising a positive active material composite.

10. In Paragraph 9, A positive electrode active material composite having a weight ratio of the first positive electrode active material particle and the second positive electrode active material particle of 1:0.1 to 0.

5.

11. In Paragraph 1, The above ionic material is a positive active material complex represented by the following chemical formula 3 or chemical formula 4. [Chemical Formula 3] [Chemical Formula 4] (In the above chemical formulas 3 and 4, R2 is a substituted or unsubstituted (C1-C10) hydrocarbon group, X is N(CF3SO2)2, N(FSO2)2, or CF3SO3, L1 is each independently a directly bonded (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, L2 is (C1-C8)alkylene, (C1-C8)alkenylene, or a combination thereof, and the hydrogens of L1 and L2 may each independently be substituted with one or more substituents selected from halogen, nitro, cyano, and (C1-C7)alkoxy.) 12. A positive electrode for a secondary battery comprising a positive electrode active material composite, a binder, and a conductive material according to any one of claims 1 to 11.

13. A lithium secondary battery comprising a positive electrode according to paragraph 12.

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