POSITIVE ELECTRODE AND METHOD OF MANUFACTURING IT

Abstract

A positive electrode may include both a first active positive electrode material having an olivine-type crystalline structure and a second active positive electrode material having a layered crystalline structure in the active positive electrode layer, resulting in high safety and excellent charge / discharge capacity of the positive electrode. Furthermore, the positive electrode may have the advantage of excellent energy and power density, which can result from including a first active positive electrode material represented by a chemical formula as defined herein and comprising three or more metals in addition to lithium.

Description

Anode and its manufacturing method

[0001] The present invention relates to a cathode and a method for manufacturing the same.

[0002] This application claims the benefit of priority from Republic of Korea Patent Application No. 10-2024-0003889, dated January 10, 2024, the entire contents of which are incorporated herein by reference.

[0003]

[0004] Lithium secondary batteries are now widely used not only in small devices like portable electronic devices, but also in medium- to large-sized devices like battery packs for hybrid and electric vehicles and power storage systems. In particular, with growing concern over environmental issues, research is being conducted on electric vehicles and hybrid electric vehicles as alternatives to fossil fuel-powered vehicles like gasoline and diesel, which are major contributors to air pollution.

[0005] Typically, lithium secondary batteries have an electrode assembly structure comprising a positive electrode, a negative electrode, and a separator, each of which is impregnated with a lithium electrolyte. Each electrode is manufactured by coating a current collector with an electrode slurry. The electrode slurry is manufactured by mixing an electrode active material for storing energy, a conductive material for imparting electrical conductivity, and a binder for adhering the electrode active material to the current collector and providing bonding strength between the electrode active material and the current collector, in a solvent such as NMP (N-methyl pyrrolidone).

[0006] The cathode can be a lithium-ion battery such as LCO (LiCoO2), LMO (LiMn2O4), LFP (LiFePO4), or NCM (LiNi) that can reversibly insert or de-insert lithium. 1 / 3 Co 1 / 3 Mn 1 / 3 It includes metal oxides such as O2 as positive electrode active materials.

[0007] Among these, NCM, LCO, and NCA compounds with layered crystal structures facilitate lithium ion storage and exhibit high lithium ion diffusion rates, making them suitable as cathode active materials for high-capacity / high-power secondary batteries. However, compounds with layered crystal structures exhibit poor chemical and structural stability, making them prone to decomposition under high-temperature conditions. This reduces the safety of secondary batteries.

[0008] In contrast, LFP compounds with an olivine crystal structure exhibit high structural stability due to their hexahedral crystal form, in which phosphorus (P) and oxygen (O) are strongly bonded. Therefore, compounds with an olivine crystal structure can easily maintain their crystal structure even when all lithium ions are desorbed during charging, and their crystal structure is not easily decomposed even under high-temperature conditions.

[0009] However, compounds with an olivine crystal structure have low energy densities, which represent the amount of energy a battery can store per unit weight / volume. Therefore, for compounds with an olivine crystal structure to achieve high energy densities, the weight / volume of the cathode active material must be increased, which leads to excessive increases in the size and weight of the secondary battery. Furthermore, the LFP compounds have low ion diffusivity and electrical conductivity, which significantly limits charge / discharge performance.

[0010] Accordingly, to increase the energy density of LFP compounds with a conventional olivine crystal structure, cathode active materials containing metals such as manganese have been developed. These cathode active materials have a structure in which manganese is partially substituted at the iron valence position, thereby improving the energy density of iron phosphate by approximately 5% or more. However, despite these effects, there is a need for additional energy density expression of LFP compounds applicable to medium- to large-sized secondary batteries.

[0011] Therefore, in order to realize high safety of lithium secondary batteries, there is a need for technology development for a lithium secondary battery cathode active material that can realize high energy density and charge / discharge performance such as output and lifespan while including an LFP compound having an olivine structure as a cathode active material, and a cathode including the same.

[0012]

[0013] [Prior Art Literature]

[0014] Republic of Korea Patent Publication No. 10-2013-0136796

[0015] Republic of Korea Patent Publication No. 10-2016-0111213

[0016]

[0017] Accordingly, the purpose of the present invention is to provide a cathode active material for a lithium secondary battery capable of realizing high energy density and charge / discharge performance while including an LFP compound having an olivine structure as a cathode active material to achieve high safety, and a cathode including the same.

[0018]

[0019] To solve the above-mentioned problem,

[0020] The present invention,

[0021] positive current collector,

[0022] Including a positive electrode active layer provided on at least one surface of the positive electrode current collector,

[0023] The above positive electrode active layer provides a positive electrode including a first positive electrode active material represented by the following chemical formula 1 and a second positive electrode active material represented by the following chemical formula 2:

[0024] [Chemical Formula 1]

[0025] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0026] [Chemical Formula 2]

[0027] Lip Ni q Co r Mn t M 2 w O2

[0028] In the above chemical formulas 1 and 2,

[0029] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0030] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2,

[0031] M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0032] p, q, r, t, and w are 1.0≤p≤1.30, 0, respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

[0033] At this time, the compound represented by the chemical formula 1 may include at least one of the compounds represented by the following chemical formulas 3 to 6:

[0034] [Chemical Formula 3]

[0035] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0036] [Chemical Formula 4]

[0037] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0038] [Chemical Formula 5]

[0039] Li 1+a Mn 1-b-x-y-z Fe b Tix V y Nb z PO4

[0040] [Chemical Formula 6]

[0041] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0042] In the above chemical formulas 3 to 6,

[0043] a, b, x, y, and z are -0.5≤a≤0.5, 0.1≤b≤0.8, 0 <x≤0.2, 0<y≤0.1, 0<z≤0.1이되, 0.001≤x+y≤0.2 또는 0.001≤x+y+z≤0.2이다.

[0044] In addition, the first cathode active material may have a lattice constant c of 4.69165 Å to 4.80 Å when analyzed by X-ray diffraction and may satisfy the following equation 1:

[0045] [Formula 1]

[0046] y=-px+q

[0047] In the above equation 1,

[0048] y represents the lattice constant c,

[0049] x is , where a and b are lattice constants a and b, respectively.

[0050] p and q are -0.08≤p≤-0.07 and 5≤q≤6, respectively.

[0051] The average particle diameter (D) of the first cathode active material 50 ) can be 0.5㎛ to 10㎛.

[0052] In addition, the first cathode active material may have a structure in which a carbon layer is coated on the surface, and the average thickness of the carbon layer may be 50 nm or less.

[0053] In addition, the positive electrode active layer may include a first positive electrode active layer in contact with the positive electrode current collector, and a second positive electrode active layer provided on the second positive electrode active layer.

[0054] At this time, the first positive electrode active material may be included in at least one of the first positive electrode active layer and the second positive electrode active layer.

[0055] In addition, when the first positive electrode active material is included in the first positive electrode active layer and the second positive electrode active layer, the content included in the first positive electrode active layer may be greater than the content included in the second positive electrode active layer.

[0056]

[0057] In addition, the present invention,

[0058] A step of applying a cathode slurry to at least one surface of a cathode current collector of a cathode current collector, and

[0059] A step of drying the applied positive electrode slurry to form a positive electrode active layer;

[0060] The above positive electrode slurry provides a method for manufacturing a positive electrode including a first positive electrode active material represented by the following chemical formula 1 and a second positive electrode active material represented by the following chemical formula 2:

[0061] [Chemical Formula 1]

[0062] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0063] [Chemical Formula 2]

[0064] Li p Ni q Co r Mn t M 2 w O2

[0065] In the above chemical formulas 1 and 2,

[0066] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0067] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2,

[0068] M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0069] p, q, r, t, and w are 1.0≤p≤1.30, 0, respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

[0070] Here, the first cathode active material can be manufactured by a step of calcining a mixture of lithium manganese iron phosphate and a metal precursor compound represented by the following chemical formula 7 at a temperature of 500°C or higher:

[0071] [Chemical Formula 7]

[0072] Li 1+m Mn 1-n Fe n PO4

[0073] In the above chemical formula 7,

[0074] m and n are -0.5≤m≤0.5, 0.1≤n≤0.8.

[0075] Additionally, the lithium manganese iron phosphate represented by the above chemical formula 7 can be heat treated at 500°C to 900°C before being mixed with the metal precursor compound.

[0076] In addition, the first cathode active material has a structure in which a carbon layer is coated on the surface, and the carbon layer can be formed by chemical vapor deposition (CVD) under inert gas conditions.

[0077] The above chemical vapor deposition (CVD) can use a carbon structure including at least one of a point-like carbon compound and a linear carbon compound as a carbon source; and at least one of a polymer compound.

[0078]

[0079] Furthermore, the present invention,

[0080] An electrode assembly comprising an anode, a cathode, and a separator provided between the anode and the cathode according to the present invention described above is provided.

[0081]

[0082] The positive electrode according to the present invention comprises a first positive electrode active material having an olivine crystal structure and a second positive electrode active material having a layered crystal structure, thereby exhibiting high safety and excellent positive electrode charge / discharge capacity. Furthermore, the positive electrode comprises a first positive electrode active material represented by Chemical Formula 1 comprising three or more metals other than lithium, thereby exhibiting the advantages of excellent energy density and output.

[0083]

[0084] Figure 1 is a graph showing the correlation between the lattice constant c of a cathode active material and the lattice constants a and b during X-ray diffraction (XRD) analysis.

[0085]

[0086] The present invention can be modified in various ways and has many embodiments, and specific embodiments will be described in detail in the detailed description.

[0087] However, this is not intended to limit the present invention to a specific embodiment, but should be understood to include all modifications, equivalents, or substitutes included in the technical scope of the present invention.

[0088] In the present invention, it should be understood that terms such as “include” or “have” are intended to specify the presence of a feature, number, step, operation, component, part or combination thereof described in the specification, but do not exclude in advance the possibility of the presence or addition of one or more other features, numbers, steps, operations, components, parts or combinations thereof.

[0089] Also, in this specification, "average particle diameter (D 50 )" means the particle diameter at which the integrated value is 50% in the particle diameter distribution of the particles, and is also called the median diameter. The above average particle diameter can be measured by a method commonly applied in the art. For example, the above average particle diameter can be measured using an analysis device that utilizes a laser diffraction scattering particle size distribution measurement method.

[0090]

[0091] Hereinafter, the present invention will be described in more detail.

[0092]

[0093] anode

[0094] The present invention,

[0095] anode current collector, and

[0096] A positive electrode is provided, which includes a positive electrode active layer provided on at least one surface of the positive electrode current collector and including the positive electrode active material according to the present invention described above.

[0097]

[0098] The positive electrode according to the present invention may refer to a positive electrode applied to a lithium secondary battery. The positive electrode includes a positive electrode active layer provided on at least one surface of a positive electrode current collector. Here, the positive electrode active layer is a layer that implements electrical activity of the positive electrode, and includes a positive electrode active material that implements an electrochemical redox reaction during charge and discharge of the battery as a main component. Specifically, the positive electrode active material may be included in an amount of 80 parts by weight to 99.8 parts by weight based on the total weight of the positive electrode active layer, and specifically, may be included in an amount of 95 parts by weight or more, 98 parts by weight or more, 84 parts by weight to 99.8 parts by weight, 90 parts by weight to 99.8 parts by weight, 94 parts by weight to 99.8 parts by weight, 88 parts by weight to 96 parts by weight, or 92 parts by weight to 97.5 parts by weight.

[0099] The above-described positive electrode active layer includes a first positive electrode active material and a second positive electrode active material as positive electrode active materials, which include metal oxides having different crystal structures. Specifically, the first positive electrode active material and the second positive electrode active material each include a compound having an olivine structure represented by the following chemical formula 1 and a compound having a layered structure represented by the following chemical formula 2:

[0100] [Chemical Formula 1]

[0101] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0102] [Chemical Formula 2]

[0103] Li p Ni q Co r Mn t M 2 w O2

[0104] In the above chemical formulas 1 and 2,

[0105] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0106] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2,

[0107] M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0108] p, q, r, t, and w are 1.0≤p≤1.30, 0, respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

[0109] Generally, the cathode active materials used in the cathode for lithium secondary batteries are compounds represented by the chemical formulas 1 and 2.

[0110] Among these, the compound represented by the above chemical formula 2 is a lithium composite metal oxide with a layered crystal structure. It facilitates lithium ion storage and has a high lithium ion diffusion rate, making it suitable for use as a cathode active material for high-capacity / high-power secondary batteries. However, compounds with a layered crystal structure have low chemical and structural stability, making them prone to decomposition under high-temperature conditions. This reduces the safety of secondary batteries.

[0111] On the other hand, lithium manganese iron phosphate having the olivine crystal structure represented by the above chemical formula 1 has a hexahedral crystal form in which phosphorus (P) and oxygen (O) are strongly bonded, and exhibits high structural stability. Therefore, compounds having the olivine crystal structure can easily maintain their crystal structure even when all lithium ions are desorbed during charging, and the crystal structure does not easily decompose even under high-temperature conditions. However, compounds having the olivine crystal structure have low energy density, which indicates the amount of energy that a battery can store per unit weight / volume. Therefore, in order for compounds having the olivine crystal structure to realize high energy density, the weight / volume of the positive electrode active material must be increased, which has the limitation that the size or weight of the secondary battery must increase excessively.

[0112] Accordingly, the present invention includes a first cathode active material having an olivine structure and a second cathode active material having a layered structure in the cathode active layer. Accordingly, the safety and electrical performance of the cathode can be further improved by complementing or alleviating the limitations of metal oxides having different crystal structures.

[0113] Here, the lithium composite metal oxide having a layered structure represented by the above chemical formula 2 is a metal oxide containing nickel (Ni), cobalt (Co) and manganese (Mn) together with lithium, and in some cases, other transition metals (M 2) may have a doped form. For example, the lithium composite metal oxide may be Li(Ni 0.6 Co 0.2 Mn 0.2 )O2, Li(Ni 0.7 Co 0.15 Mn 0.15 )O2, Li(Ni 0.8 Co 0.1 Mn 0.1 )O2, Li(Ni 0.9 Co 0.05 Mn 0.05 )O2, Li(Ni 0.6 Co 0.2 Mn 0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Mn 0.15 Zr 0.05 )O2, Li(Ni 0.7 Co 0.1 Mn 0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Al 0.2 )O2, Li(Ni 0.7 Co 0.15 Al 0.15 )O2, Li(Ni 0.8 Co 0.1 Al 0.1 )O2, Li(Ni 0.9 Co 0.05 Al 0.05 )O2, Li(Ni 0.6 Co 0.2 Al 0.1 Zr 0.1 )O2, Li(Ni 0.6 Co 0.2 Al 0.15 Zr 0.05 )O2 and Li(Ni 0.7 Co 0.1 Al 0.1 Zr 0.1 ) may contain one or more types of O2.

[0114] The second cathode active material including the above lithium composite metal oxide has high charge / discharge capacity and is a transition metal (M 2) doping has the advantage of improving safety at high temperatures because structural stability is further improved. In particular, Li(Ni 0.6 Co 0.1 Mn 0.3 )O2 etc. compounds (i.e., 0.5≤q≤0.7, 0.05≤r≤0.15, 0.2≤t≤0.3) have the advantage of improving the life characteristics and output characteristics of a secondary battery under high voltage conditions when mixed with the first cathode active material.

[0115] In addition, lithium manganese iron phosphate represented by the above chemical formula 1 is lithium manganese iron phosphate (LiMn 1-b Fe b One or more metals (M) in PO4 1 ) can be doped and / or substituted to realize a high energy density at a predetermined molar fraction. More specifically, the cathode active material according to the present invention can have a structure in which lithium manganese iron phosphate is doped and / or substituted with at least one metal, specifically titanium (Ti), vanadium (V), zirconium (Zr), and niobium (Nb).

[0116] As an example, the lithium manganese iron phosphate may include one or more of the compounds represented by the following chemical formulas 3 to 6:

[0117] [Chemical Formula 3]

[0118] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0119] [Chemical Formula 4]

[0120] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0121] [Chemical Formula 5]

[0122] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nbz PO4

[0123] [Chemical Formula 6]

[0124] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0125] In the above chemical formulas 3 to 6,

[0126] a, b, x, y, and z are -0.5≤a≤0.5, 0.1≤b≤0.8, 0 <x≤0.2, 0<y≤0.1, 0<z≤0.1이되, 0.001≤x+y≤0.2 또는 0.001≤x+y+z≤0.2이다.

[0127] The compounds represented by the above chemical formulas 3 to 6 are lithium manganese iron phosphate (LiMn 1-b Fe bPO4) is doped or substituted with titanium (Ti), vanadium (V), and / or niobium (Nb). At this time, the doped or substituted metals may be doped or substituted in an amount of 0.1 molar fraction or less based on the total 1 molar fraction of metals excluding lithium (Li), and the ratio of lithium (Li) to these metals (Me) (Li / Me) may be 1.01 to 1.50, specifically 1.01 to 1.30; 1.01 to 1.20; or 1.01 to 1.15. The concentration of lithium (Li) in the cathode active material is closely related to the density of the particles. Specifically, the higher the concentration of lithium, the higher the density, and in this case, the easier it is to remove pores within the particles, so that a high rolling density can be realized. However, an excessively high lithium concentration may reduce the movement of lithium ions, which may deteriorate the electrical performance. In addition, the significantly low lithium concentration not only results in a low particle density and thus a low rolling density, but also has the problem of low energy density per unit volume / mass during the manufacture of the positive electrode. The present invention can overcome this problem by controlling the ratio of lithium (Li) to metal (Me) contained in the positive electrode active material (Li / Me) within the above-described range.

[0128] For example, the first cathode active material is LiMn 0.8 Fe 0.19 Ti 0.01 PO4, LiMn 0.7 Fe 0.29 Ti 0.01 PO4, LiMn 0.6 Fe 0.39 Ti 0.01 PO4, LiMn 0.8 Fe 0.17 Ti 0.03 PO4, LiMn 0.7 Fe 0.27 Ti 0.03 PO4, LiMn 0.6 Fe 0.37 Ti 0.03 PO4, LiMn 0.8 Fe 0.15 Ti 0.05 PO4, LiMn 0.7 Fe0.25 Ti 0.05 PO4, LiMn 0.6 Fe 0.35 Ti 0.05 Compound represented by chemical formula 3 such as PO4; LiMn 0.8 Fe 0.18 Ti 0.01 V 0.01 PO4, LiMn 0.7 Fe 0.28 Ti 0.01 V 0.01 PO4, LiMn 0.6 Fe 0.38 Ti 0.01 V 0.01 PO4, LiMn 0.8 Fe 0.15 Ti 0.025 V 0.025 PO4, LiMn 0.7 Fe 0.25 Ti 0.025 V 0.025 PO4, LiMn 0.6 Fe 0.35 Ti 0.025 V 0.025 PO4, LiMn 0.8 Fe 0.1 Ti 0.05 V 0.05 PO4, LiMn 0.7 Fe 0.2 Ti 0.05 V 0.05 PO4, LiMn 0.6 Fe 0.3 Ti 0.05 V 0.05 Compound represented by chemical formula 4 such as PO4; LiMn 0.8 Fe 0.17 Ti 0.01 V 0.01 Nb 0.01 PO4, LiMn 0.7 Fe 0.27 Ti 0.01 V 0.01 Nb 0.01 PO4, LiMn 0.6 Fe 0.37 Ti 0.01 V 0.01 Nb 0.01 PO4, LiMn 0.8 Fe 0.12 Ti0.03 V 0.025 Nb 0.025 PO4, LiMn 0.7 Fe 0.22 The 0.03 V 0.025 Nb 0.025 PO4, LiMn 0.6 Fe 0.32 The 0.03 V 0.025 Nb 0.025 PO4, LiMn 0.8 Fe 0.05 The 0.05 V 0.05 Nb 0.05 PO4, LiMn 0.7 Fe 0.15 The 0.05 V 0.05 Nb 0.05 PO4, LiMn 0.6 Fe 0.25 The 0.05 V 0.05 Nb 0.05 PO4등의 화학식 5; 및 LiMn 0.8 Fe 0.17 The 0.01 Zr 0.01 Nb 0.01 PO4, LiMn 0.7 Fe 0.27 The 0.01 Zr 0.01 Nb 0.01 PO4, LiMn 0.6 Fe 0.37 The 0.01 Zr 0.01 Nb 0.01 PO4, LiMn 0.8 Fe 0.12 The 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.7 Fe 0.22 The 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.6 Fe 0.32 The 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.8 Fe 0.05 The 0.05 Zr0.05 Nb 0.05 PO4, LiMn 0.7 Fe 0.15 Ti 0.05 Zr 0.05 Nb 0.05 PO4, LiMn 0.6 Fe 0.25 Ti 0.05 Zr 0.05 Nb 0.05 It may include at least one compound represented by chemical formula 6, such as PO4.

[0129] The first cathode active material has a form in which at least one of titanium (Ti), vanadium (V), and niobium (Nb) is doped and / or substituted in lithium manganese iron phosphate, so that the size of the cathode active material can satisfy a predetermined condition depending on the number of doped and / or substituted metals and / or the molar fraction of the metals. The first cathode active material includes lithium manganese iron phosphate doped and / or substituted with at least one metal, such as lithium iron phosphate (LiFePO4) or lithium manganese iron phosphate (LiMn). 1-b Fe b Compared to PO4), it can have a smaller size. Accordingly, the first cathode active material has a larger specific surface area, and thus has higher charge-discharge efficiency and lifespan characteristics during charge-discharge of the secondary battery.

[0130] In the present invention, "particle" refers to a grain in the unit of micrometers, and when observed under magnification, it can be distinguished into a "grain" having a crystal in the unit of several tens of nanometers. When the grain is further magnified, a unit area (i.e., a crystal lattice) in which atoms form a lattice structure in a certain direction can be confirmed, which is called a "crystallite." The first cathode active material according to the present invention has a form in which at least one of titanium (Ti), vanadium (V), and niobium (Nb) is doped and / or substituted into lithium manganese iron phosphate, so that the size of the crystal grains and / or the size of the particles can be controlled to satisfy a predetermined range.

[0131] For example, as the type or mole fraction of the metal doped or substituted in the first cathode active material increases, the lattice constant c of the lithium manganese iron phosphate constituting the cathode active material may increase, and the grain size of the first cathode active material may decrease. Here, the crystal grain size of the first cathode active material may be measured in the form of lattice constants a, b, c, etc., which represent the length of each side of the crystal grain during X-ray spectroscopy analysis.

[0132] More specifically, the first cathode active material according to the present invention is lithium manganese iron phosphate (LiMn) which is doped or substituted with titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc., and does not contain the transition metal. 1-b Fe b PO4) may have a lattice constant c greater than the lattice constant c (about 4.6916 Å). For example, the first cathode active material may have a lattice constant c of 4.69165 Å to 4.80 Å upon X-ray diffraction analysis, specifically, 4.69165 Å to 4.80 Å; 4.69165 Å to 4.75 Å; 4.69165 Å to 4.70 Å; 4.69165 Å to 4.695 Å; 4.69165 Å to 4.694 Å; 4.69165 Å to 4.693 Å; 4.6917 Å to 4.6925 Å; or 4.6918 Å to 4.6925 Å.

[0133] "Lattice constant" is a value that represents the edge length of a crystal grain, and is used to describe the size and arrangement of a material, and can be expressed in various forms depending on the crystal structure. In the case of the olivine structure, it has an orthorhombic crystal structure, and therefore can have lattice constants of a, b, and c. Among these, the lattice constant c is a factor that represents the unit cell size in the c-axis direction of the crystal, and is closely related to the structural and chemical properties of the crystal grain. For example, lithium manganese iron phosphate (LiMn) with an olivine structure1-b Fe b In the case of PO4), the c-axis direction can act as the main movement path of lithium ions. The lattice constant c, which indicates the size of the c-axis direction, is Fe 2+ and Mn 2+ Ti has a larger ionic radius 4+ , V 5+ , Nb 5+ The back can be doped and increase. An increase in the lattice constant c can expand the lithium ion path and increase the diffusion coefficient of lithium ions. Therefore, the cathode active material according to the present invention can have excellent electrical performance within the range of the lattice constant c described above. However, if it exceeds the upper limit of the above range, a secondary phase can be formed within the olivine structure. If a secondary phase is formed within the olivine structure, the electrochemical activity can be reduced. In addition, if it is below the lower limit of the above range, the electrical performance of the cathode active material can be significantly reduced.

[0134] Here, the first cathode active material may exhibit a linear relationship when the lattice constant c is expressed in relation to the lattice constants a and b, which may follow Vegard's law. Specifically, the lattice constant c of the first cathode active material may have a predetermined correlation with the square root of (the sum of the squares of the lattice constant a and the squares of the lattice constant b), and this correlation may be expressed by the following equation 1:

[0135] [Formula 1]

[0136] y=-px+q

[0137] In the above equation 1,

[0138] y represents the lattice constant c,

[0139] x is , where a and b are lattice constants a and b, respectively.

[0140] p and q are -0.08≤p≤-0.07 and 5≤q≤6, respectively.

[0141]

[0142] The above formula 1 shows the correlation between the lattice constants a and b and the lattice constant c of lithium manganese iron phosphate represented by chemical formula 1. The lattice constants a, b and c and their correlation may vary depending on the type or mole fraction of the doped and / or substituted metal, as well as the manufacturing method or process conditions of lithium manganese iron phosphate. In the case of the present invention, as shown in Fig. 1, the lattice constant a, b and c tends to increase as the number or mole fraction of the metal doped and / or substituted in lithium manganese iron phosphate increases. That is, the first cathode active material of the present invention satisfies the range of the lattice constant c described above, and lithium manganese iron phosphate (LiMn 1-b Fe b Metal (M) doped and / or substituted in PO4 1 ) tends to increase as the number or mole fraction thereof increases, so that the above equation 1 can be satisfied. When the lattice constant c is expressed for the lattice constants a and b, it shows a linear relationship, which means that lithium manganese iron phosphate (LiMn 1-b Fe b This means that the olivine crystal structure can be maintained even when multiple components (e.g., Ti, V, Zr, Sr, Sb, B, Nb, etc.) are doped or substituted in PO4. That is, this indirectly indicates that the structural stability of the cathode active material according to the present invention is maintained at a high level even when multiple components are doped or substituted.

[0143] In addition, the grains of the first positive electrode active material formed by gathering lattice units can be confirmed in size through the X-axis size during X-ray diffraction analysis. The size of the grains may be about 70 nm or more and less than 120 nm. More specifically, the size of the grains may be about 70 nm to 115 nm; about 70 nm to 105 nm; about 70 nm to 99 nm; about 70 nm to 95 nm; or about 80 nm to 99 nm. The positive electrode active material according to the present invention can increase the specific surface area of ​​the grains while minimizing agglomeration between particles by controlling the grain size within the above-described range. Through this, the positive electrode active material can implement high electrical performance. In addition, the positive electrode active material has the characteristic of high rolling density because it is advantageous to form a dense structure by pressure during rolling by including grains having the above-described range. In addition, since grains having the above size range can evenly distribute pressure during rolling, the cathode active material including them can evenly implement a rolling density throughout the active layer. Meanwhile, the grains are particles formed by gathering crystal grains, and generally, as the size of the crystal grains increases, the size of the grains may increase. However, when multiple components are doped or substituted, as in the cathode active material according to the present invention, an interference effect within their lattices may occur. In this case, a structural change in the crystal grain boundary occurs or the crystal grain boundary increases, so an increase in the crystal grain size may not tend to increase the grain size.

[0144] In addition, the first cathode active material may have a predetermined size. For example, the first cathode active material may have an average particle diameter (D 50) may be 0.5 ㎛ to 10 ㎛, and specifically, 0.5 ㎛ to 8 ㎛; 0.5 ㎛ to 6 ㎛; 0.5 ㎛ to 4 ㎛; 0.5 ㎛ to 2 ㎛; 1 ㎛ to 5 ㎛; 2 ㎛ to 4 ㎛; 4 ㎛ to 8 ㎛; 5 ㎛ to 9 ㎛; 3 ㎛ to 6 ㎛; 0.5 ㎛ to 1.5 ㎛; or 0.7 ㎛ to 1.4 ㎛.

[0145] The present invention relates to an average particle diameter (D) of a first cathode active material 50 ) can be controlled to the above-described range, thereby preventing the agglomeration of positive electrode active materials due to particle sizes lower than the lower limit of the above-described range, which reduces the processability and reliability of the positive electrode during positive electrode manufacturing. In addition, there is a problem in that the positive electrode active materials are damaged, such as broken, during the rolling process due to particle sizes higher than the upper limit of the above-described range, which reduces the electrical performance.

[0146] Additionally, the first cathode active material may have a structure in which a carbon layer is coated on its surface. The carbon layer may have a porous structure, thus not only having a high surface area but also having a form in which it uniformly surrounds the core surface with high crystallinity. A carbon layer with such a structure can further enhance the electrochemical reactivity and electrical properties of the cathode active material, thereby improving the output and lifespan characteristics of the cathode active material.

[0147] Here, the thickness of the carbon layer can be controlled within a range that does not lower the energy density of the positive electrode active material. Specifically, the carbon layer can have an average thickness of 50 nm or less, and more specifically, an average thickness of 40 nm or less; 30 nm or less; 20 nm or less; 10 nm or less; 5 nm to 40 nm; 5 nm to 20 nm; 10 nm to 30 nm; 20 nm to 45 nm; 10 nm to 20 nm; 5 nm to 10 nm; 1 nm to 10 nm; or 3 nm to 9 nm.

[0148] Meanwhile, the positive electrode active layer may have a two-layer structure in which a first positive electrode active layer and a second positive electrode active layer are sequentially laminated on a positive electrode current collector. Since the composition of each layer of the positive electrode active layer having a two-layer structure can be easily controlled, the performance of the negative electrode can be improved by varying the type or content of components contained in each layer or controlling the physical properties differently according to specific purposes such as increasing the energy efficiency of the battery or improving the adhesion between the active layer and the current collector.

[0149] At this time, at least one of the first positive electrode active layer and the second positive electrode active layer may include the first positive electrode active material. For example, the positive electrode active layer according to the present invention may have the following structure:

[0150] (1) A structure in which the first positive electrode active layer, which is the lower layer, includes a first positive electrode active material, and the second positive electrode active layer, which is the upper layer, includes a second positive electrode active material.

[0151] (2) A structure in which the first positive electrode active layer, which is the lower layer, includes a second positive electrode active material, and the second positive electrode active layer, which is the upper layer, includes a first positive electrode active material.

[0152] (3) A structure in which the first positive electrode active layer, which is the lower layer, includes a first positive electrode active material, and the second positive electrode active layer, which is the upper layer, includes a first positive electrode active material and a second positive electrode active material.

[0153] (4) A structure in which the first positive electrode active layer, which is the lower layer, includes a first positive electrode active material and a second positive electrode active material, and the second positive electrode active layer, which is the upper layer, includes the first positive electrode active material.

[0154] (5) The first positive electrode active layer and the second positive electrode active layer each contain a first positive electrode active material and a second positive electrode active material, but the first positive electrode active layer has a structure in which the weight ratio of the first positive electrode active material is higher than that of the second positive electrode active layer, and

[0155] (6) The first positive electrode active layer and the second positive electrode active layer each contain a first positive electrode active material and a second positive electrode active material, but the second positive electrode active layer has a structure in which the weight ratio of the first positive electrode active material is higher than that of the first positive electrode active layer.

[0156]

[0157] The first cathode active material according to the present invention has an olivine crystal structure as described above, and thus has high structural stability, and thus has excellent high-temperature safety. In addition, it contains three or more types of metals other than lithium, and thus has excellent energy density and lifespan characteristics, and thus can be included in at least one layer of a two-layer cathode active layer.

[0158] In addition, the content / weight ratio of the first positive electrode active material and the second positive electrode active material can be controlled depending on the location where they are included. Specifically, the first positive electrode active material can be included in a high content / weight ratio in the first positive electrode active layer adjacent to the positive electrode current collector, and the second positive electrode active material can be included in a high content / weight ratio in the second positive electrode active layer adjacent to the negative electrode.

[0159] As an example, the positive electrode according to the present invention may have a structure (1) in which a first positive electrode active layer including a first positive electrode active material and a second positive electrode active layer including a second positive electrode active material are sequentially provided on a positive electrode current collector.

[0160] As another example, the positive electrode according to the present invention may have a structure (3) in which a first positive electrode active layer including a first positive electrode active material and a second positive electrode active layer including a second positive electrode active material are sequentially provided on a positive electrode current collector. In this case, the content / weight ratio of the first positive electrode active material included in the first positive electrode active layer may be 100 wt% based on the total weight of the positive electrode active material included in the layer, but the content / weight ratio of the first positive electrode active material included in the second positive electrode active layer may be less than 100 wt%.

[0161] As another example, the positive electrode according to the present invention may have a structure of (5) including a first positive electrode active material and a second positive electrode active material in the first positive electrode active layer and the second positive electrode active layer, respectively. In this case, the content / weight ratio of the first positive electrode active material included in the first positive electrode active layer may exceed 50 wt% based on the total weight of the positive electrode active material included in the layer, and the content / weight ratio of the first positive electrode active material included in the second positive electrode active layer may be less than 50 wt%.

[0162] The first cathode active material may have low lithium mobility and high electrical resistance, including lithium manganese iron phosphate represented by chemical formula 1 having an olivine structure. Therefore, the cathode according to the present invention can easily release heat generated due to high resistance during charge / discharge of the secondary battery through the cathode current collector by controlling the content / weight ratio of the first cathode active material included in the first cathode active layer to be higher than that of the second cathode active layer as described above. Accordingly, the cathode can improve deterioration due to heat generation of the cathode active material, and thus the lifespan characteristics can be improved. In addition, the concentration of the second cathode active material included in the second cathode active layer can be increased compared to that of the first cathode active layer. This has a form in which the second cathode active material having high energy density and capacity is arranged adjacent to the cathode, so that the efficiency of the electrochemical reaction with the cathode during charge / discharge of the secondary battery can be increased, thereby improving the electrical properties of the secondary battery.

[0163] Meanwhile, the above-mentioned positive electrode active layer may optionally further include a conductive agent, a binder, other additives, etc., along with the positive electrode active material as the main component.

[0164] At this time, the above-mentioned conductive material may include one or more of acetylene black, channel black, furnace black, lamp black, summer black, graphene, carbon nanotubes, and carbon fibers, but is not limited thereto.

[0165] The content of the conductive material may be 0.1 to 10 parts by weight based on 100 parts by weight of the entire electrode active layer, and specifically, may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, 2 to 6 parts by weight, or 0.5 to 2 parts by weight. By controlling the content of the conductive material within the above range, the present invention can prevent the electrode resistance from increasing due to a low content of the conductive material, thereby reducing the charging capacity, and can prevent the problem of the charging capacity from decreasing due to a decrease in the content of the electrode active material due to an excessive amount of the conductive material, or the rapid charging characteristics from decreasing due to an increase in the loading amount of the electrode active layer.

[0166] In addition, the binder may be appropriately applied as a component that assists in the bonding of the positive electrode active material and the conductive material and the bonding to the current collector, and may be applied within a range that does not deteriorate the electrical properties of the positive electrode, but specifically may include at least one of vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber (SBR), and fluororubber.

[0167] The content of the binder may be 0.1 to 10 parts by weight based on 100 parts by weight of the entire positive electrode active layer, and specifically, may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. By controlling the content of the binder contained in the positive electrode active layer within the above range, the present invention can prevent the adhesive strength of the active layer from being lowered due to a low content of binder or the electrical properties of the positive electrode from being lowered due to an excessive amount of binder.

[0168] In addition, the average thickness of the positive electrode active layer may be 50 ㎛ to 500 ㎛. Specifically, the average thickness of the positive electrode active layer may be 100 ㎛ to 400 ㎛; 200 ㎛ to 350 ㎛; 50 ㎛ to 180 ㎛; 80 ㎛ to 150 ㎛; 100 ㎛ to 250 ㎛; 100 ㎛ to 250 ㎛; or 130 ㎛ to 190 ㎛. The present invention can not only implement high adhesion between the positive electrode active layer and the positive electrode current collector by controlling the average thickness of the positive electrode active layer within the above range, but also implement high energy density of the positive electrode.

[0169] Furthermore, the positive electrode current collector may be one having high conductivity without causing chemical changes in the battery. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. may be used. In the case of aluminum or stainless steel, a surface-treated material such as carbon, nickel, titanium, or silver may also be used. In addition, the average thickness of the positive electrode current collector may be appropriately applied within the range of 3 to 500 μm, taking into account the conductivity and total thickness of the positive electrode being manufactured.

[0170]

[0171] The anode according to the present invention has the advantages of excellent safety and life characteristics by having the above-described configuration.

[0172]

[0173] Method for manufacturing anode

[0174] In addition, the present invention,

[0175] A step (S1) of applying a cathode slurry to at least one surface of a cathode current collector of a cathode current collector, and

[0176] A step (S2) of drying the applied positive electrode slurry to form a positive electrode active layer;

[0177] The above positive electrode slurry provides a method for manufacturing a positive electrode including a first positive electrode active material represented by the following chemical formula 1 and a second positive electrode active material represented by the following chemical formula 2:

[0178] [Chemical Formula 1]

[0179] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0180] [Chemical Formula 2]

[0181] Li p Ni q Co r Mn t M 2 w O2

[0182] In the above chemical formulas 1 and 2,

[0183] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0184] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2,

[0185] M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and

[0186] p, q, r, t, and w are 1.0≤p≤1.30, 0, respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

[0187]

[0188] The method for manufacturing a positive electrode according to the present invention refers to the method for manufacturing the positive electrode of the present invention described above. The method for manufacturing the positive electrode can manufacture an anode in which a positive electrode active layer is formed on a positive electrode collector (S2) by applying a positive electrode slurry on a positive electrode current collector (S1) and drying the applied positive electrode slurry.

[0189] Here, the step (S1) of applying the positive electrode slurry is a step of discharging and coating the positive electrode slurry containing the first positive electrode active material represented by Chemical Formula 1 and the second positive electrode active material represented by Chemical Formula 2 onto the surface of the moving positive electrode current collector. This step (S1) can be applied without particular limitation as long as it is a method commonly applied in the art, but preferably, a die coating method can be used. The die coating method can be performed through a slot die having a shim for controlling the discharging conditions of the positive electrode slurry. In this case, by controlling the shape, position, etc. of the shim, the loading amount, coating thickness, etc. of the positive electrode slurry applied on the positive electrode current collector can be easily controlled.

[0190] In particular, in the present invention, a first positive electrode slurry and a second positive electrode slurry can be sequentially and simultaneously applied onto a positive electrode current collector using a dual die. The dual die has the advantage of significantly increasing process efficiency compared to applying each slurry separately. In this case, the first positive electrode slurry and the second positive electrode slurry fed into the dual die can have the types and / or content ratios of the first positive electrode active material and the second positive electrode active material adjusted according to the configurations of the first positive electrode active layer and the second positive electrode active layer to be prepared therefrom.

[0191] For example, the first cathode active material may be included in a high content / weight ratio in the first cathode slurry to be formed as the first cathode active layer, and the second cathode active material may be included in a high content / weight ratio in the second cathode slurry to be formed as the second cathode active layer.

[0192] Meanwhile, the positive electrode slurry is for forming the positive electrode active layer of the positive electrode. Accordingly, the positive electrode slurry mainly includes a first positive electrode active material and a second positive electrode active material, and may further include a conductive material, a binder, etc., as needed. Here, since the composition of the first positive electrode active material, the second positive electrode active material, the conductive material, the binder, etc., included in the positive electrode slurry is the same as that of the positive electrode active layer of the positive electrode for a lithium secondary battery, a detailed description thereof is omitted.

[0193] However, the first cathode active material may be manufactured through a predetermined process. Specifically, the first cathode active material may be manufactured by a step of calcining a mixture of lithium manganese iron phosphate and a metal precursor compound represented by the following chemical formula 7 at a temperature of 500°C or higher, more specifically, 500°C to 1,000°C; 500°C to 900°C; 500°C to 800°C; or 500°C to 750°C:

[0194] [Chemical Formula 7]

[0195] Li 1+m Mn 1-n Fe n PO4

[0196] In the above chemical formula 7,

[0197] m and n are -0.5≤m≤0.5, 0.1≤n≤0.8.

[0198] Typically, conventional olivine-structured cathode active materials are manufactured by mixing precursor compounds containing each transition metal with lithium phosphate, which is a lithium raw material, and calcining the mixture at high temperatures. However, the cathode active material of the present invention can be manufactured by first generating lithium manganese iron phosphate represented by Chemical Formula 7 by calcining a mixture of a manganese precursor compound, an iron precursor compound, and lithium phosphate, and then mixing and calcining precursor compounds of metals to be doped and / or substituted.

[0199] At this time, the compound represented by the chemical formula 7 may be primarily heat-treated at 500°C to 900°C for 0.1 to 20 hours before being mixed with the metal precursor compound. Specifically, the compound represented by the chemical formula 6 may be subjected to a pre-sintering process for 1 to 6 hours; or 1 to 3 hours; before being mixed with the metal precursor compound. At this time, the pre-sintering process may be performed at a temperature of 500°C to 800°C; or 550°C to 750°C. The present invention can significantly reduce the moisture content present in the lithium manganese iron phosphate by performing the heat treatment of the lithium manganese iron phosphate represented by the chemical formula 7 under the above-described conditions before being mixed with the metal precursor compound. Through this, the metals contained in the metal precursor compound can be easily doped into the lithium manganese iron phosphate or substituted at the iron atom position. However, at temperatures lower than the above-described temperature range, there is a limit to which moisture in the lithium manganese iron phosphate is not sufficiently removed, and at temperatures higher than the above-described temperature range, the crystallinity of the lithium manganese iron phosphate increases further, making doping and / or substitution of the metal rather difficult.

[0200] The compound of chemical formula 7, which has been heat-treated in this way, can be mixed with metal precursor compounds and calcined, thereby producing the cathode active material of the present invention. Here, the metal precursor compounds refer to raw materials that supply titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc. to the lithium manganese iron phosphate represented by chemical formula 7. The metal precursor compounds are not particularly limited as long as they can provide titanium (Ti), vanadium (V), zirconium (Zr), and / or niobium (Nb).

[0201] Preferably, the titanium (Ti) precursor compound may include at least one of titanium oxide and titanium alkoxide containing titanium (Ti) as a component. For example, the titanium (Ti) precursor compound may include titanium oxide such as TiO, TiO2, or titanium alkoxide such as Ti[OCH(CH3)2]4, but is not limited thereto.

[0202] Additionally, the vanadium (V) precursor compound may be a vanadium-containing oxide, a vanadium-containing ammonium salt, or a combination thereof. For example, the vanadium (V) precursor compound may include, but is not limited to, vanadium oxide such as VO2, V2O3, V2O5, or ammonium vanadate (NH4VO3).

[0203] The zirconium (Zr) precursor compound may be a zirconium-containing oxide, a zirconium-containing acetate, or a combination thereof. For example, the zirconium (Zr) precursor compound may be a zirconium oxide such as ZrO2, or Zr6O4(OH)4(O2CCH3). 12 May include, but is not limited to, the following:

[0204] In addition, the niobium (Nb) precursor compound may be a niobium-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. For example, the niobium (Nb) precursor compound may be, but is not limited to, a niobium oxide such as NbO, NbO2, Nb2O5; a niobium salt such as NbCO3, Nb(NO3)2, NbSO4, niobium acetate, niobium dicarboxylate, niobium citrate, niobium fatty acid salt; a niobium oxyhydroxide; niobium chloride; or a combination thereof.

[0205] Furthermore, the surface of the first cathode active material may be coated with a carbon layer, and the carbon layer may be chemical vapor deposition (CVD) under inert gas conditions to form a uniform layer.

[0206] Chemical Vapor Deposition (CVD) refers to a method of depositing a vaporized raw material as a thin film on a substrate injected into a reactor under vacuum or inert gas conditions. The present invention has the advantage of forming a thin carbon layer more uniformly on the surface of the first cathode active material represented by Chemical Formula 1 by utilizing this chemical vapor deposition (CVD).

[0207] At this time, the chemical vapor deposition (CVD) can be performed under conditions in which the inside of the reactor is replaced with an inert gas such as nitrogen gas, argon gas, or helium gas to prevent the inflow of impurities into the carbon layer during carbon layer deposition and to prevent side reactions from occurring on the surface of the carbon layer.

[0208] In addition, the chemical vapor deposition (CVD) may be performed by mixing some hydrogen gas into a reactor filled with an inert gas during deposition. For example, the chemical vapor deposition (CVD) may be performed by first depositing while supplying argon gas at a flow rate of 150 to 250 sccm into a reactor replaced with argon gas, and then continuously supplying hydrogen gas at a flow rate of 10 to 20 sccm and argon gas at a flow rate of 250 to 350 sccm to the reactor together for second deposition. In this case, carbon seeds for depositing a carbon layer on the core surface may be generated during the first deposition, and the growth of the carbon seeds generated during the second deposition may be promoted.

[0209] The above chemical vapor deposition (CVD) can be performed within 100 minutes, and specifically, can be performed for 1 minute to 100 minutes; 1 minute to 75 minutes; 1 minute to 50 minutes; 1 minute to 30 minutes; 1 minute to 20 minutes; 1 minute to 10 minutes; and 10 minutes to 70 minutes.

[0210] Additionally, when hydrogen gas is mixed during deposition as described above, the first deposition can be performed within 30 minutes, and the second deposition can be performed for 30 to 70 minutes thereafter.

[0211] As an example, the chemical vapor deposition (CVD) may be performed in such a manner that the first deposition is performed under inert gas conditions for 10 minutes, and the second deposition is performed under conditions in which hydrogen gas is partially mixed with the inert gas for 30 to 40 minutes.

[0212] The present invention can effectively control the thickness of a carbon layer on a core surface by controlling the chemical vapor deposition (CVD) performance time within the above-described range.

[0213] In addition, the chemical vapor deposition (CVD) may be performed at a high temperature for vaporizing a carbon source to form a carbon layer. Specifically, the temperature at which the chemical vapor deposition (CVD) is performed may be 500°C to 1,500°C, and more specifically, 500°C to 1,300°C; 500°C to 1,100°C; 500°C to 1,000°C; 500°C to 900°C; 600°C to 1,300°C; 800°C to 1,100°C; 1,000°C to 1,500°C; 750°C to 990°C; or 600°C to 900°C.

[0214] The present invention not only enables uniform formation of a carbon layer on a first cathode active material by controlling the chemical vapor deposition (CVD) temperature within the above-described range, but also converts the carbon deposited on the surface of the first cathode active material into a carbon layer having high crystallinity. The carbon layer having high crystallinity can significantly improve the electrical properties of the first cathode active material, such as electrical conductivity, and thus has the advantage of enhancing the output performance of the cathode during charge / discharge of a secondary battery.

[0215] As an example, the first cathode active material according to the present invention includes a carbon layer chemical vapor deposited (CVD) in the temperature range described above, and has a Raman spectroscopy analysis of 1580±50 cm -1 The area of ​​the peak appearing in is 1360±50 cm -1 may be larger than the area of ​​the peak appearing in .

[0216] 1360±50 cm for Raman spectroscopy -1 and 1580±50 cm -1 The peaks that appear in each are peaks observed in carbon compounds such as graphite, carbon black, graphene, and carbon nanotubes (CNT). Among these, 1360±50 cm -1The peaks appearing at 1580±50 cm are peaks that appear when inelastic scattering by phonons and elastic scattering occur around the defect / substitution point of carbon compounds during Raman spectroscopy. The higher the intensity and / or area ratio of the peak, the more defects or substitutions the compound has, and the lower the crystallinity. In contrast, -1 The peak appearing in is a peak due to the first Raman scattering phenomenon, and a higher intensity and / or area ratio of the peak indicates a higher crystallinity. That is, the first cathode active material according to the present invention has a higher crystallinity of the carbon layer since the area of ​​the peak indicating the crystallinity of the carbon contained in the carbon layer is larger than the area of ​​the peak indicating the amorphousness of the carbon compound when analyzed by Raman spectroscopy.

[0217] In this case, the carbon coating layer is 1360±50 cm -1 The area of ​​the peak appearing in is 1580±50 cm -1 The peak area may have a ratio of 30% to 90%, and more specifically, a ratio of 50% to 90%; 60% to 90%; 70% to 90%; 60% to 85%; or 55% to 80%.

[0218] Furthermore, the chemical vapor deposition (CVD) can be performed using a solid-state carbon source. Specifically, the chemical vapor deposition (CVD) can use a carbon structure and a polymer compound, each including at least one of a point-like carbon compound and a linear carbon compound, as a carbon source, either alone or in combination.

[0219] More specifically, the dot-shaped carbon compound may include one or more of acetylene black, channel black, furnace black, lamp black, summer black, and graphene. In addition, the linear carbon compound may include one or more of carbon nanotubes and carbon fibers.

[0220] In addition, the polymer compound may include at least one of polyvinylpyrrolidone (PVP), polyacrylonitrile (PAN), polypyrrole (PPy), polyvinyl alcohol (PVA), polyacrylic acid (PAA), polymethylacrylate (PMA), and polymethylmethacrylate (PMMA).

[0221] As an example, the carbon source may be a point-like carbon compound, and the point-like carbon compound may comprise acetylene black.

[0222] As another example, the carbon source may include a point-like carbon compound and a linear carbon compound. In this case, the point-like carbon compound may include acetylene black, and the linear carbon compound may include carbon nanotubes (CNTs). In addition, in this case, the point-like carbon compound and the linear carbon compound may be included in a weight ratio of 1:10 to 10:1, and specifically, may be included in a weight ratio of 1:5 to 5:1, 1:3 to 3:1, 1:2 to 2:1, 1:5 to 1:1.5, 1:1.5 to 1.5, or 1:1.5 to 1.5:1.

[0223] As another example, the carbon source may include a point-like carbon compound, a linear carbon compound, and a polymer compound. In this case, the point-like carbon compound may include acetylene black, the linear carbon compound may include carbon nanotubes (CNTs), and the polymer compound may include polyvinylpyrrolidone (PVP). In this case, the linear carbon compound and the polymer compound may each be included in an amount of 10 to 90 parts by weight per 100 parts by weight of the point-like carbon compound, and specifically, may each be included in an amount of 10 to 80 parts by weight; 10 to 70 parts by weight, 10 to 60 parts by weight, 10 to 50 parts by weight, 10 to 40 parts by weight, 30 to 70 parts by weight, 60 to 80 parts by weight, or 20 to 40 parts by weight per 100 parts by weight of the point-like carbon compound.

[0224] Conventionally, chemical vapor deposition (CVD) for forming a carbon layer has been performed using hydrocarbon gases such as methane (CH4), ethane (CH3CH3), propane (CH3CH2CH3), ethylene (CH2CH2), and acetylene (CHCH). In this case, since a process for gasifying the carbon source is not required, it can be performed at a low temperature. However, it is not easy to control the gaseous carbon source during deposition, and there is a limitation that the high reactivity of the carbon source induces side reactions on the core surface, which reduces the activity of the positive electrode active layer. In addition, the formed carbon layer is an amorphous layer with low crystallinity, so the specific surface area is not large. However, the present invention not only has high workability during deposition using a solid-state carbon source, but also has excellent electrical properties such as electrical conductivity due to the high crystallinity of the carbon layer. In particular, when using a polymer compound such as polyvinylpyrrolidone (PVP) as a carbon source, a porous carbon layer can be formed, allowing for the formation of a carbon layer with a high surface area on the core surface. In this case, the ion transport capacity of the carbon layer increases, improving the lithium diffusion coefficient, and thus the manufactured cathode active material exhibits excellent output performance.

[0225] Meanwhile, the method for manufacturing the positive electrode includes a step (S2) of forming a positive electrode active layer from the applied positive electrode slurry. This step (S2) may refer to a process of drying the positive electrode slurry. At this time, the drying of the positive electrode slurry may be applied without particular limitation as long as it is a method commonly applicable in the art. For example, the drying may be performed by applying heat energy to the positive electrode slurry using a hot air dryer, a vacuum oven, or the like, thereby drying the positive electrode slurry.

[0226] In addition, the manufacturing method according to the present invention may further include a step of rolling the positive electrode active layer formed by drying the positive electrode slurry. The rolling refers to a process of increasing the density of the entire positive electrode active layer by applying pressure to the surface of the positive electrode active layer formed using a roll press or the like. To this end, the rolling may be performed under predetermined pressure and speed conditions at a temperature higher than room temperature.

[0227] Specifically, the rolling can be performed at a temperature of 50°C to 100°C, more specifically, 60°C to 100°C; 75°C to 100°C; 85°C to 100°C; 50°C to 90°C; 60°C to 80°C; or 65°C to 90°C.

[0228] In addition, the rolling can be performed at a rolling speed of 2 m / s to 7 m / s, and more specifically, 2 m / s to 6.5 m / s; 2 m / s to 6 m / s; 2 m / s to 5.5 m / s; 2 m / s to 5 m / s; 2 m / s to 4.5 m / s; 2 m / s to 4 m / s; 2.5 m / s to 4 m / s; 2.5 m / s to 3.5 m / s; 3.5 m / s to 5 m / s; 5 m / s to 7 m / s; 5.5 m / s to 6.5 m / s or 6 m / s to 7 m / s.

[0229] In addition, the rolling can be performed under a pressure condition of 50 MPa to 200 MPa, and specifically, it can be performed under a pressure condition of 50 MPa to 150 MPa; 50 MPa to 100 MPa; 100 MPa to 200 MPa; 150 MPa to 200 MPa or 80 MPa to 140 MPa.

[0230] The present invention can maximize the energy density of the positive electrode active layer while minimizing damage to the positive electrode active layer formed by performing rolling under the above temperature, speed and / or pressure conditions.

[0231]

[0232] Electrode assembly for lithium secondary batteries

[0233] Furthermore, the present invention,

[0234] An electrode assembly comprising an anode, a cathode, and a separator provided between the anode and the cathode according to the present invention described above is provided.

[0235]

[0236] The electrode assembly according to the present invention may refer to an electrode assembly for a lithium secondary battery. The electrode assembly includes the positive electrode and negative electrode according to the present invention described above, and a separator provided therebetween. More specifically, the electrode assembly has a structure in which a plurality of positive electrodes and negative electrodes are alternately arranged, with a separator interposed therebetween. The electrode assembly includes the positive electrode of the present invention described above, and has the characteristics of high energy density and charge / discharge capacity, as well as excellent safety.

[0237] Here, since the above anode has the same configuration as the anode described above, a description of the detailed configuration is omitted.

[0238] In addition, the negative electrode, like the positive electrode, includes a negative electrode active layer on at least one surface of the negative electrode current collector. The negative electrode active layer is a layer that implements the electrical activity of the negative electrode, and includes as its main component a negative electrode active material that implements an electrochemical redox reaction during charging and discharging of the battery.

[0239] The above negative electrode active material may include those commonly applied in the art. For example, the above negative electrode active material may include carbon-based materials such as crystalline artificial graphite, crystalline natural graphite, amorphous hard carbon, low-crystalline soft carbon, acetylene black, graphene, and fibrous carbon, silicon-based materials such as Si, SiO, and SiO2, tin-based materials such as Sn, SnO, and SnO2, LixFe2O3(0≤x≤1), LixWO2(0≤x≤1), Sn x M 1 1-x M 2 y O z (M1 : Mn, Fe, Pb or Ge; M 2 : Al, B, P, Si, elements of group 1, 2, 3 of the periodic table, or halogens; 0 <x≤1; 1≤y≤3; 1≤z≤8임) 등의 금속 복합 산화물; PbO, PbO2, Pb2O3, Pb3O4, Sb2O3, Sb2O4, Sb2O5, GeO, GeO2, Bi2O3, Bi2O4, Bi2O5등의 금속 산화물 등 중에서 선택된 어느 하나 이상을 포함할 수 있다.

[0240] In addition, the negative electrode active layer may optionally include a binder, other additives, etc., along with the negative electrode active material, as needed.

[0241] The above binder is a component that assists in bonding between negative electrode active materials and bonding between the negative electrode active layer and the electrode current collector, and can be appropriately applied within a range that does not deteriorate the electrical properties of the electrode. Specifically, the binder may include at least one selected from vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVdF), polyacrylonitrile, polymethylmethacrylate, polyvinyl alcohol, carboxymethyl cellulose (CMC), starch, hydroxypropyl cellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene butadiene rubber (SBR), and fluoroelastomer.

[0242] The content of the binder may be 0.1 to 10 parts by weight based on 100 parts by weight of the entire negative electrode active layer, and specifically, may be 0.1 to 8 parts by weight, 0.1 to 5 parts by weight, 0.1 to 3 parts by weight, or 2 to 6 parts by weight. The present invention can prevent the adhesive strength of the negative electrode active layer from being lowered due to a low content of binder or the electrical properties of the electrode from being lowered due to an excessive amount of binder by controlling the content of the binder contained in the electrode active layer within the above range.

[0243] In addition, the negative electrode current collector is not particularly limited as long as it has high conductivity without causing chemical changes in the battery, and for example, copper, aluminum, stainless steel, nickel, titanium, calcined carbon, etc. can be used. In the case of copper or stainless steel, a surface-treated one with carbon, nickel, titanium, silver, etc. can also be used. In addition, the average thickness of the electrode current collector can be appropriately applied from 1 to 500 ㎛ in consideration of the conductivity and total thickness of the electrode to be manufactured.

[0244] In addition, the separator interposed between the positive and negative electrodes of each unit cell is an insulating thin film having high ion permeability and mechanical strength, and is not particularly limited as long as it is commonly used in the art, but specifically, one including at least one polymer selected from the group consisting of polypropylene, polyethylene, and polyethylene-propylene copolymers having chemical resistance and hydrophobicity can be used. The separator may have a porous polymer substrate form such as a sheet or non-woven fabric including the above-described polymer, and in some cases, may have a composite separator form in which organic or inorganic particles are coated on the porous polymer substrate using an organic binder. In addition, the separator may have an average pore diameter of 0.01 to 10 μm, and an average thickness of 5 to 300 μm.

[0245] Meanwhile, the electrode assembly is not particularly limited in type, but may be a secondary battery that may specifically include a stacked, zigzag, or zigzag-stacked electrode assembly. As an example, the lithium secondary battery according to the present invention may be a pouch-type secondary battery or a square-shaped secondary battery.

[0246] Pouch-type secondary batteries and / or square secondary batteries have the advantage of high utilization in terms of energy density because the unit cells of the secondary batteries can be packed at a high density in a limited space.

[0247] The lithium secondary battery according to the present invention has the above-described configuration, and thus has the advantages of a large charge / discharge capacity and excellent life characteristics.

[0248]

[0249] Hereinafter, the present invention will be described in more detail through examples and comparative examples.

[0250] However, the following examples and comparative examples are only illustrative of the present invention, and the content of the present invention is not limited to the following examples and comparative examples.

[0251]

[0252] Manufacturing Examples 1 to 5. Manufacturing of the first cathode active material

[0253] First, a compound represented by chemical formula 1 to be used as the first cathode active material was prepared. For this purpose, lithium manganese iron phosphate (LiMn 0.7 Fe 0.3 PO4) was purchased commercially. Lithium manganese iron phosphate (LiMn) was purchased 0.7 Fe 0.3After heat-treating PO4) at 700°C for 1 hour, titanium dioxide (TiO2), ammonium vanadate (NH4VO3), and niobium oxide (Nb2O5) were mixed and calcined at 700±20°C under a nitrogen atmosphere to prepare a compound powder represented by chemical formula 1. At this time, the mixing amounts of titanium dioxide (TiO2), ammonium vanadate (NH4VO3), and niobium oxide (Nb2O5) were adjusted so that the mole fraction of the metal included in the metal precursor compound satisfied Table 1 based on the mole fraction of 1 of the total metal excluding lithium in the prepared compound.

[0254] X-ray diffraction (XRD) was performed on the manufactured compound powder to measure ① lattice constants a, bc and ② X-axis size representing grain size. Specifically, lithium manganese iron phosphate (LiMn 0.7 Fe 0.3Considering the doped and / or substituted metals in PO4), X-ray diffraction spectroscopic analysis was performed using the Rietveld refinement method. At this time, the X-ray diffraction analysis was performed using a Bruker D8 Endeavor (Cu-Kα, λ=1.54Å) equipped with a LynxEye XE-T position sensitive detector or a LynxEye position sensitive detector, and the sample was placed in the groove of a general powder holder. After that, the sample surface was smoothed using a slide glass, and the sample was filled so that the sample height matched the edge of the holder, and then the measurement was performed under the conditions of FDS 0.5°, 2θ=15°~90° range, step size=0.02°, and total scan time=approximately 20 minutes. When analyzing the grain size, instrumental broadening was considered using the Fundamental Parameter Approach (FPA) built into the Bruker TOPAS program, and the entire peaks of the measurement range were used for fitting. The peak shape was fitted using the Lorentzian contribution as the first principle (FP) among the peak shapes available in TOPAS. Strain was not considered at this time. The measured lattice constant c and the grain size (i.e., X-axis size) are shown in Table 1, and the correlation between the lattice constant c and the lattice constants a and b is shown in Fig. 1. Referring to Fig. 1, the lattice constant c shows a linear relationship when plotted against the lattice constants a and b, and it was confirmed that it moves toward the lower right as the concentration of lithium (Li) in the structure increases. In addition, it was confirmed that as the type of metal doped and / or substituted in the positive electrode active material increases, a linear relationship appears, and it follows Vegard's law.

[0255] In addition, particle size distribution analysis (PSD) was performed on each manufactured core to determine the D of the core. 50 was measured. Specifically, particle size distribution analysis (PSD) was performed by laser diffraction method. The particle size distribution analysis (PSD) device used was Malvern's Mastersizer 3000, and the laser refractive index was adjusted to 2.0 to 2.2. Each core weighing less than 1 g was dispersed in deionized (DI) water using an ultrasonic irradiator installed inside the device, and then the particle size distribution was calculated by measuring the difference in diffraction pattern according to particle size when the dispersed particles pass through the laser beam. At this time, by calculating the particle diameter at the point where it becomes 50% of the area cumulative distribution according to particle size in the measuring device, D 50 was measured. The measured results are shown in Table 1 below.

[0256] Manufacturing Example 1 Manufacturing Example 2 Manufacturing Example 3 Manufacturing Example 4 Manufacturing Example 5 Metal precursor compound TiO2-0.060.030.020.02 NH4VO3--0.030.020.02 Nb2O5---0.020.02 Whether or not heat treatment was performed before mixing the metal precursor compound (700℃, 1 hour) XXXXOXRD Lattice constant c4.69162 Å4.69184 Å4.69202 Å4.69209 Å4.69214 Å X-axis size120nm100nm96nm91nm88nmAverage particle diameter (D 50 )1.40㎛1.20㎛1.03㎛0.90㎛0.81㎛

[0257]

[0258]

[0259] Manufacturing Example 6. Manufacturing of the first cathode active material

[0260] The compound manufactured in Manufacturing Example 5 above was introduced into a chemical vapor deposition reactor, and the interior of the reactor was replaced with argon gas. Thereafter, the interior of the reactor was heated to 800°C at a heating rate of 50°C / min, and chemical vapor deposition was performed for 15 to 20 minutes while supplying argon gas at 180 to 220 sccm. Thereafter, hydrogen gas and argon gas were continuously supplied at 10 to 20 sccm and 280 to 320 sccm, respectively, while additionally performing chemical vapor deposition for 25 to 35 minutes, thereby manufacturing a first cathode active material having a carbon layer formed on the surface.

[0261] At this time, the carbon source used in the chemical vapor deposition was a mixture of point-like carbon compounds, linear carbon compounds, and polymer compounds, including 50 wt% acetylene black, 35 wt% carbon nanotubes (CNTs), and 15 wt% polyvinylpyrrolidone (PVP) particles. The carbon source was used in an amount of 4 to 6 wt% based on the total weight of the cathode active material.

[0262] Particle size distribution analysis (PSD) was performed on the manufactured first cathode active material. D of the first cathode active material 50 It was confirmed to be approximately 0.7 to 1.6 ㎛. Furthermore, transmission electron microscopy (TEM) analysis was performed on the manufactured cathode active materials to measure the average thickness of the carbon layer formed on the core surface. The results confirmed that the average thickness of the carbon layer formed on the core surface was approximately 5 to 10 nm.

[0263]

[0264] Manufacturing Example 7. Manufacturing of the first cathode active material

[0265] A cathode active material was manufactured using the same method as Manufacturing Example 6, except that calcination was performed at 800±50°C for 5 minutes.

[0266] Particle size distribution analysis (PSD) was performed on the manufactured first cathode active material. D of the first cathode active material 50 It was confirmed to be approximately 1.4 to 1.9 ㎛. Furthermore, transmission electron microscopy (TEM) analysis was performed on the manufactured cathode active materials to measure the average thickness of the carbon layer formed on the core surface. The results confirmed that the average thickness of the carbon layer formed on the core surface was approximately 11 to 15 nm.

[0267]

[0268] Examples 1 to 12 and Comparative Examples 1 to 3. Manufacturing of lithium secondary batteries

[0269] N-methylpyrrolidone solvent was injected into a homo mixer, and 96 parts by weight of the prepared positive electrode active material; 1.5 parts by weight of carbon black as a conductive material; and 2.5 parts by weight of polyvinylidene fluoride (PVdF) as a binder were each added.

[0270] At this time, the positive electrode active material is the first positive electrode active material manufactured in Manufacturing Examples 1 to 7 (hereinafter referred to as 'LMFM 1 P') and LiNi as the second cathode active material 0.6 Co 0.1 Mn 0.3 O2 (hereinafter referred to as 'NCM', average particle size: approximately 3 to 5 μm) was used in a weight ratio as shown in Table 2 based on the total weight of the corresponding cathode slurry. Then, each slurry was mixed at 3,000 rpm for 60 minutes to prepare a first cathode slurry and a second cathode slurry with a solid content of 50%.

[0271] An aluminum foil (average thickness: 12 μm) was prepared as a cathode current collector, and a first cathode slurry and a second cathode slurry were simultaneously cast on one side of the prepared aluminum foil using a dual die to the same thickness. The aluminum foil on which the first cathode slurry and the second cathode slurry were cast was dried in a vacuum oven at 130°C and then rolled to manufacture a cathode. At this time, the total thickness of the rolled cathode active layer was 150 μm.

[0272] First anode slurrySecond anode slurryLMFM 1 P type content [weight %] LMFM 1 P type content [weight %] LMFM 1 PNCMLMFM 1 PNCM Comparative Example 1-0100-0100 Comparative Example 2 Manufacturing Example 51000 Manufacturing Example 51000 Comparative Example 3 Manufacturing Example 17030 Manufacturing Example 17030 Example 1 Manufacturing Example 55050 Manufacturing Example 55050 Example 2 Manufacturing Example 51000-0100 Example 3-0100 Manufacturing Example 51000 Example 4 Manufacturing Example 51000 Manufacturing Example 55050 Example 5 Manufacturing Example 55050 Manufacturing Example 51000 Example 6 Manufacturing Example 53070 Manufacturing Example 57030 Example 7 Manufacturing Example 57030 Manufacturing Example 53070 Example 8 Manufacturing Example 27030 Manufacturing Example 23070 Example Manufacturing Example 9 Manufacturing Example 37030 Manufacturing Example 33070 Embodiment 10 Manufacturing Example 47030 Manufacturing Example 43070 Embodiment 11 Manufacturing Example 67030 Manufacturing Example 63070 Embodiment 12 Manufacturing Example 77030 Manufacturing Example 73070

[0273]

[0274]

[0275] Experimental example.

[0276] To evaluate the performance of the positive electrode according to the present invention, a lithium metal disk was first prepared as an anode. The prepared negative electrode was placed opposite the positive electrode prepared in Examples 1 to 12 and Comparative Examples 1 to 3, respectively, and an 18 μm polypropylene separator was interposed therebetween to manufacture an electrode assembly. Each manufactured electrode assembly was inserted into a battery case, an electrolyte composition was injected into the battery case, and the case was sealed to manufacture a half cell. At this time, as the electrolyte composition, a solution in which lithium hexafluorophosphate (LiPF6, 1.0 M) was mixed in a mixture of ethylene carbonate (EC): ethyl methyl carbonate (EMC) = 1:1 (volume ratio) was used.

[0277] The following experiments were performed on each of the manufactured half-cells.

[0278]

[0279] 1) Output characteristics of lithium secondary batteries

[0280] Each half-cell was subjected to constant current / constant voltage charging (CC / CV charging) at 25°C, followed by constant current discharge (CC discharge) to measure the initial discharge capacity. The constant current / constant voltage charging was performed with a constant current of 0.1C rate until the voltage reached 4.2 V, and then cut-off at a current of 0.1C rate in constant voltage mode to maintain 4.2 V. In addition, the constant current discharge was performed with a 1.0C rate until the voltage reached 1.5 V.

[0281] Then, each half-cell was fully charged at 1.0C rate at 25℃ to a terminal voltage of 4.2–4.25V, and the high-rate discharge capacity was measured while discharging at a rate ranging from 1.0C to 5.0C. The high-rate discharge characteristics of each lithium secondary battery were evaluated by calculating the relative discharge capacity ratio based on the initial discharge capacity at each discharge rate from the measured discharge capacity. The measured results are shown in Table 3.

[0282]

[0283] 2) High temperature life characteristics

[0284] Each half-cell was measured for its charge-discharge capacity retention under high-temperature conditions. Specifically, one cycle was defined as charging at a constant current of 1C at 45°C until the voltage reached 4.25 V, and then discharging at a constant current of 1C until the voltage reached 2.5 V. Each half-cell was then subjected to 300 charge-discharge cycles.

[0285] At this time, when charging and discharging each half battery, 1 st Charging capacity of the cycle and 300 th The charging capacity of the cycle was measured. The measured 1 st 300 based on the charging capacity of the cycle th The high-temperature life of each half-cell was evaluated by calculating the charge capacity retention rate over the cycle. The results are shown in Table 3 below.

[0286] Unit: % Initial discharge capacity by discharge rate Relative discharge capacity ratio 300 thCycle Capacity Retention Rate [%] 1C 2 C 3 C 5 C Comparative Example 197.99 2.78 7.88 5.26 3.7 Comparative Example 293.48 5.68 2.57 2.38 9.1 Comparative Example 394.28 3.58 1.87 7.57 8.6 Exemplary Example 196.58 9.48 3.178 58 1.4 Exemplary Example 295.28 8.18 4.379 28 2.8 Exemplary Example 396.79 0.88 4.179 88 0.5 Exemplary Example 495.88 9.78 4.98 0.185.3 Exemplary Example 594.78 8.78 3.379 08 3.4 Exemplary Example 693.98 8.28 2.77 8.78 3.0 Exemplary Example 797.290.186.281.586.8 Example 894.684.382.578.180.2 Example 995.588.484.578.683.6 Example 1096.989.585.779.284.1 Example 1197.391.087.282.586.7 Example 1295.687.282.377.879.3

[0287]

[0288] As shown in Table 3 above, it can be seen that the anode according to the present invention has excellent output performance and high-temperature life characteristics.

[0289] Specifically, the half-cells of the examples including both the first cathode active material represented by Chemical Formula 1 and the second cathode active material represented by Chemical Formula 2 at the positive electrode exhibited a high discharge capacity ratio of about 78.0% or more even under high-rate conditions of 5C or more, and it was confirmed that the capacity retention ratio was about 79% or more even after 300 cycles of charge and discharge were performed under high-temperature conditions.

[0290] From these results, it can be seen that the positive electrode according to the present invention has excellent output performance during charge and discharge and excellent life characteristics.

[0291]

[0292] Although the present invention has been described above with reference to preferred embodiments thereof, it will be understood by those skilled in the art or having ordinary knowledge in the art that the present invention can be variously modified and changed within a scope that does not depart from the technical scope of the present invention as set forth in the claims to be described below.

[0293] Therefore, the technical scope of the present invention should not be limited to the contents described in the detailed description of the specification, but should be defined by the patent claims.

Claims

1. A cathode current collector, and a cathode active layer provided on at least one surface of the cathode current collector, The above positive electrode active layer is a positive electrode including a first positive electrode active material represented by the following chemical formula 1 and a second positive electrode active material represented by the following chemical formula 2: [Chemical Formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4 [Chemical formula 2] Li p Ni q Co r Mr t M 2 w O2 In the above chemical formulas 1 and 2, M 1 is at least one of Ti, V, Zr, Sr, Sb, B and Nb, a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2, M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p, q, r, t and w are 1.0≤p≤1.30, 0 respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

2. In paragraph 1, The compound represented by the above chemical formula 1 is an anode including at least one of the compounds represented by the following chemical formulas 3 to 6: [Chemical Formula 3] Li 1+a Mn 1-b-x Fe b You x PO4 [Chemical Formula 4] Li 1+a Mn 1-b-x-y Fe b You x V y PO4 [Chemical Formula 5] Li 1+a Mn 1-b-x-y-z Fe b You x V y Nb z PO4 [Chemical formula 6] Li 1+a Mn 1-b-x-y-z Fe b You x Zr y Nb z PO4 In the above chemical formulas 3 to 6, a, b, x, y and z are -0.5≤a≤0.5, 0.1≤b≤0.8, 0 <x≤0.2, 0<y≤0.1, 0<z≤0.1이되, 0.001≤x+y≤0.2 또는 0.001≤x+y+z≤0.2이다.

3. In paragraph 1, The above first cathode active material is a cathode having a lattice constant c of 4.69165 Å to 4.80 Å when analyzed by X-ray diffraction and satisfying the following equation 1: [Formula 1] y=-px+q In the above equation 1, y represents the lattice constant c, x is , where a and b are lattice constants a and b, respectively. p and q are -0.08≤p≤-0.07 and 5≤q≤6, respectively.

4. In paragraph 1, The average particle diameter (D) of the first cathode active material 50 ) is an anode with a range of 0.5㎛ to 10㎛.

5. In paragraph 1, The above first cathode active material is a cathode having a structure in which a carbon layer is coated on the surface.

6. In paragraph 1, An anode having an average thickness of the carbon layer of less than 50 nm.

7. In paragraph 1, The above positive active layer is, A first positive electrode active layer in contact with the positive electrode current collector, and An anode comprising a second anode active layer provided on the second anode active layer.

8. In paragraph 7, A cathode in which the first cathode active material is included in at least one of the first cathode active layer and the second cathode active layer.

9. In paragraph 8, A cathode, characterized in that when the first cathode active material is included in the first cathode active layer and the second cathode active layer, the content included in the first cathode active layer is greater than the content included in the second cathode active layer.

10. A step of applying a cathode slurry to at least one surface of a cathode current collector of a cathode current collector, and Comprising a step of drying the applied positive electrode slurry to form a positive electrode active layer; The above cathode slurry is a method for manufacturing a cathode including a first cathode active material represented by the following chemical formula 1 and a second cathode active material represented by the following chemical formula 2: [Chemical Formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4 [Chemical formula 2] Li p Ni q Co r Mr t M 2 w O2 In the above chemical formulas 1 and 2, M 1 is at least one of Ti, V, Zr, Sr, Sb, B and Nb, a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2, M 2 is at least one of W, Cu, Fe, V, Cr, Ti, Zr, Zn, Al, In, Ta, Y, La, Sr, Ga, Sc, Gd, Sm, Ca, Ce, Nb, Mg, B, and Mo, and p, q, r, t and w are 1.0≤p≤1.30, 0 respectively. <q≤0.9, 0<r≤0.3, 0≤t≤0.3 및 0≤w≤0.2이되, q+r+t+w=1이다.

11. In paragraph 10, The above first cathode active material is a method for producing a cathode by a step of calcining a mixture of lithium manganese iron phosphate and a metal precursor compound represented by the following chemical formula 7 at a temperature of 500°C or higher: [Chemical formula 7] Li 1+m Mn 1-n Fe n PO4 In the above chemical formula 7, m and n are -0.5≤m≤0.5, 0.1≤n≤0.

8.

12. In paragraph 11, A method for manufacturing a cathode, characterized in that the lithium manganese iron phosphate represented by the chemical formula 7 is heat-treated at 500°C to 900°C before being mixed with a metal precursor compound.

13. In paragraph 11, The above first cathode active material has a structure in which a carbon layer is coated on the surface, A method for manufacturing a cathode active material, wherein the carbon layer is formed by chemical vapor deposition (CVD) under inert gas conditions.

14. In paragraph 13, The above chemical vapor deposition (CVD) is a method for producing a cathode active material using a carbon structure including at least one of a point-like carbon compound and a linear carbon compound as a carbon source; and at least one of a polymer compound.

15. An electrode assembly comprising an anode, a cathode, and a separator provided between the anode and the cathode according to paragraph 1.