POSITIVE ELECTRODE AND METHOD OF MANUFACTURING IT

Abstract

This disclosure relates to a positive electrode and a method for its manufacture. The positive electrode incorporates lithium manganese iron phosphate with an olivine structure as the active positive electrode material, providing high structural stability. Furthermore, the lithium manganese iron phosphate particle size distribution can be easily controlled by doping and / or substitution with one or more metals, resulting in a positive electrode that includes it with the advantages of excellent lamination density and energy density.

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 to Republic of Korea Patent Application No. 10-2024-0003888, dated January 10, 2024, and Republic of Korea Patent Application No. 10-2024-0183777, dated December 11, 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] On the other hand, LFP compounds having an olivine crystal structure have a hexahedral crystal form in which phosphorus (P) and oxygen (O) are strongly bonded, and thus exhibit high structural stability. Therefore, LFP compounds having an 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, the compound has a low energy density, which indicates the amount of energy that a battery can store per unit weight / volume. Therefore, in order for LFP compounds having an olivine crystal structure to realize high energy density, the weight / volume of the cathode active material must be increased, which has the limitation that the size or weight of the secondary battery must increase excessively.

[0009] Accordingly, a manganese-containing cathode active material has been developed to increase the energy density of LFP compounds with a conventional olivine crystal structure. This cathode active material, with a structure in which manganese is partially substituted at the iron valence position, has the effect of improving the energy density of iron phosphate by approximately 5% or more. Despite these effects, there is a need for additional energy density expression of LFP compounds applicable to medium- to large-sized secondary batteries.

[0010] Therefore, in order to achieve high safety of lithium secondary batteries, there is a need for technology development for a lithium secondary battery cathode that can achieve high energy density while including an LFP compound having an olivine structure as a cathode active material.

[0011]

[0012] [Prior Art Literature]

[0013] Republic of Korea Patent Publication No. 10-2016-0064136

[0014]

[0015] The purpose of the present invention is to provide a lithium secondary battery cathode capable of realizing high energy density while including an LFP compound having an olivine structure as a cathode active material in order to realize high safety of a lithium secondary battery, and a method for manufacturing the same.

[0016]

[0017] To solve the above-mentioned problem,

[0018] The present invention,

[0019] anode current collector, and

[0020] Provided is a positive electrode including a positive electrode active layer provided on at least one surface of the positive electrode current collector and including a compound represented by the following chemical formula 1 as a positive electrode active material:

[0021] [Chemical Formula 1]

[0022] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0023] In the above chemical formula 1,

[0024] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0025] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2.

[0026]

[0027] At this time, the positive electrode active material may include at least one of the compounds represented by the following chemical formulas 2 to 5:

[0028] [Chemical Formula 2]

[0029] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0030] [Chemical Formula 3]

[0031] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0032] [Chemical Formula 4]

[0033] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0034] [Chemical Formula 5]

[0035] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0036] In the above chemical formulas 2 to 5,

[0037] 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.

[0038] In addition, the cathode active material has a lattice constant c of 4.69165 Å to 4.80 Å when analyzed by X-ray diffraction and can satisfy the following equation 1:

[0039] [Formula 1]

[0040] y=-px+q

[0041] In the above equation 1,

[0042] y represents the lattice constant c,

[0043] x is , where a and b are lattice constants a and b, respectively.

[0044] p and q are -0.08≤p≤-0.07 and 5≤q≤6, respectively.

[0045]

[0046] In addition, the above cathode active material has an average particle diameter (D 50 ) may be 0.7 ㎛ to 1.3 ㎛.

[0047] In addition, the above cathode active material has a D of 5.5 to 9.0 when analyzing particle size distribution. 90 / D 10 , and D of 0.2 ㎛ or more and less than 0.6 ㎛ 10 can have

[0048] In addition, the above-mentioned positive electrode active material may have a rolling density of 2.3 g / cc or more when pressurized at 9,000 kgf.

[0049]

[0050] Furthermore, in one embodiment of the present invention,

[0051] A step of applying a cathode slurry containing a compound represented by the following chemical formula 1 as a cathode active material to at least one surface of a cathode current collector, and

[0052] A method for manufacturing a cathode according to the present invention is provided, comprising the step of drying the applied cathode slurry to form a cathode active layer.

[0053] [Chemical Formula 1]

[0054] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0055] In the above chemical formula 1,

[0056] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0057] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2.

[0058] Here, the positive electrode active material may include at least one of the compounds represented by the following chemical formulas 2 to 5:

[0059] [Chemical Formula 2]

[0060] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0061] [Chemical Formula 3]

[0062] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0063] [Chemical Formula 4]

[0064] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0065] [Chemical Formula 5]

[0066] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0067] In the above chemical formulas 2 to 5,

[0068] 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.

[0069] In addition, the above 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 6 at a temperature of 500°C or higher:

[0070] [Chemical Formula 6]

[0071] Li 1+m Mn 1-n Fe n PO4

[0072] In the above chemical formula 6,

[0073] m and n are -0.5≤m≤0.5, 0.1≤n≤0.8.

[0074] At this time, the lithium manganese iron phosphate represented by the above chemical formula 6 can be heat treated at 500°C to 900°C before being mixed with the metal precursor compound.

[0075]

[0076] The cathode according to the present invention comprises lithium manganese iron phosphate with an olivine structure as the cathode active material, thereby exhibiting high structural stability. Furthermore, the lithium manganese iron phosphate is doped and / or substituted with one or more metals, facilitating controllable particle distribution. Therefore, a cathode comprising the same exhibits superior energy density and rolling density.

[0077]

[0078] 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.

[0079]

[0080] 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.

[0081] 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 spirit and technical scope of the present invention.

[0082] 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.

[0083] 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 a particle size analyzer or an analysis device using a laser diffraction scattering particle size distribution measurement method, but is not limited thereto.

[0084]

[0085] Hereinafter, the present invention will be described in more detail.

[0086]

[0087] anode

[0088] The present invention,

[0089] A positive electrode is provided, comprising a positive electrode current collector, and a positive electrode active layer provided on at least one surface of the positive electrode current collector and including a compound represented by the following chemical formula 1 as a positive electrode active material:

[0090] [Chemical Formula 1]

[0091] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0092] In the above chemical formula 1,

[0093] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0094] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2.

[0095]

[0096] The positive electrode according to the present invention may refer to a positive electrode for 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.

[0097] In addition, the positive electrode active material includes a compound represented by chemical formula 1:

[0098] [Chemical Formula 1]

[0099] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0100] In the above chemical formula 1,

[0101] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0102] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2.

[0103]

[0104] The compound represented by the above chemical formula 1 has an olivine structure. The olivine structure has a hexahedral crystal form in which phosphorus (P) and oxygen (O) are strongly bonded, and exhibits high structural stability. Therefore, the compound having the olivine crystal structure can easily maintain its crystal structure even when all lithium ions are desorbed during charging, and the crystal structure does not easily decompose even under high-temperature conditions. Therefore, the positive electrode active material has excellent life characteristics and excellent safety characteristics including overcharge and overdischarge. In addition, since the positive electrode active material contains iron, which is abundant and inexpensive, it is LiNi 1 / 3 Co 1 / 3 Mn 1 / 3 It is cheaper than lithium composite oxides such as O2, LiCoO2, LiNiO2, or LiMn2O4, and has less toxicity, so it has less impact on the environment.

[0105] However, lithium manganese iron phosphate (LiMn) containing only lithium (Li), manganese (Mn) and iron (Fe) as metals 1-b Fe bPO4) has a slightly higher energy density than lithium iron phosphate (LiFePO4), but not significantly. In addition, lithium manganese iron phosphate, like the lithium composite oxide described above, has a low rolling density, and therefore, there is a limit to further increasing the energy density through a rolling process, etc. Here, the "rolling density" refers to a parameter indicating the degree of particle deformation of the cathode active material when pressed. The rolling density may mean that the lower the rolling density under the same pressure conditions, the higher the compressive strength and the lower the energy density. Accordingly, the present invention has the characteristic of having a high rolling density by doping and / or substituting one or more metals into lithium manganese iron phosphate, which is a cathode active material. Specifically, the cathode active material according to the present invention may have a structure in which lithium manganese iron phosphate is doped and / or substituted with one or more metals, specifically, titanium (Ti), vanadium (V), zirconium (Zr), and niobium (Nb).

[0106] As an example, the lithium manganese iron phosphate may include one or more of the compounds represented by the following chemical formulas 2 to 5:

[0107] [Chemical Formula 2]

[0108] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0109] [Chemical Formula 3]

[0110] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0111] [Chemical Formula 4]

[0112] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0113] [Chemical Formula 5]

[0114] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0115] In the above chemical formulas 2 to 5,

[0116] 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.

[0117] The compounds represented by the above chemical formulas 2 to 5 are lithium manganese iron phosphate (LiMn 1-b Fe b PO4) is doped or substituted with titanium (Ti), vanadium (V), zirconium (Zr) 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, when the concentration of lithium is high, the density is high, and in this case, it is easy to remove pores in the particles, so that a high rolling density can be implemented. However, an excessively high lithium concentration may reduce the movement of lithium ions, which may reduce 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 metals (Me) contained in the positive electrode active material (Li / Me) within the above-described range.

[0118] These positive electrode active materials include 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 Fe 0.25 Ti 0.05 PO4, LiMn 0.6 Fe 0.35 Ti 0.05 Compound represented by chemical formula 2 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 Ti0.05 V 0.05 PO4, LiMn 0.6 Fe 0.3 Ti 0.05 V 0.05 Compound represented by chemical formula 3 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 Ti 0.03 V 0.025 Nb 0.025 PO4, LiMn 0.7 Fe 0.22 Ti 0.03 V 0.025 Nb 0.025 PO4, LiMn 0.6 Fe 0.32 Ti 0.03 V 0.025 Nb 0.025 PO4, LiMn 0.8 Fe 0.05 Ti 0.05 V 0.05 Nb 0.05 PO4, LiMn 0.7 Fe 0.15 Ti 0.05 V 0.05 Nb 0.05 PO4, LiMn 0.6 Fe 0.25 Ti 0.05 V 0.05 Nb 0.05 Chemical formula 4, such as PO4; and LiMn 0.8 Fe 0.17 Ti 0.01 Zr 0.01 Nb 0.01 PO4, LiMn 0.7 Fe 0.27 Ti 0.01 Zr 0.01 Nb0.01 PO4, LiMn 0.6 Fe 0.37 Ti 0.01 Zr 0.01 Nb 0.01 PO4, LiMn 0.8 Fe 0.12 Ti 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.7 Fe 0.22 Ti 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.6 Fe 0.32 Ti 0.03 Zr 0.025 Nb 0.025 PO4, LiMn 0.8 Fe 0.05 Ti 0.05 Zr 0.05 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 5, such as PO4.

[0119] The above cathode active material has a form in which at least one of titanium (Ti), vanadium (V), zirconium (Zr), and niobium (Nb) is doped and / or substituted in lithium manganese iron phosphate, so that the size of the cathode active material can satisfy predetermined conditions depending on the number of doped and / or substituted metals and / or the molar fraction of the metals.

[0120] Specifically, in the cathode active material, the term "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 cathode active material according to the present invention has a form in which one or more of titanium (Ti), vanadium (V), zirconium (Zr), 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.

[0121] For example, as the type or mole fraction of the metal doped or substituted in the positive electrode active material increases, the lattice constant c of the lithium manganese iron phosphate constituting the positive electrode active material may increase, and the grain size of the positive electrode active material may decrease. Here, the crystal grain size of the positive electrode 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.

[0122] More specifically, the cathode active material according to the present invention is lithium manganese iron phosphate (LiMn) that is doped or substituted with titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc., and does not contain the transition metal. 1-b Fe bPO4) may have a lattice constant c greater than about 4.6916 Å. For example, the cathode active material may have a lattice constant c of 4.69165 Å to 4.80 Å in X-ray diffraction analysis. Specifically, the cathode active material may have a lattice constant c of 4.69165 Å to 4.80 Å in X-ray diffraction analysis; 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 in X-ray diffraction analysis. there is.

[0123] "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 structure 1-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.

[0124] In addition, the 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 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:

[0125] [Formula 1]

[0126] y=-px+q

[0127] In the above equation 1,

[0128] y represents the lattice constant c,

[0129] x is , where a and b are lattice constants a and b, respectively.

[0130] p and q are -0.08≤p≤-0.07 and 5≤q≤6, respectively.

[0131]

[0132] 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, and the a, b and c may be measured values ​​according to X-ray spectroscopy. 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 the 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 the 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 is 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.

[0133] The grains formed by these lattice units can be identified in size through the X-axis size during X-ray diffraction analysis. The size of the grains may be about 70 nm to 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 present invention can implement high electrical performance by controlling the grain size of the positive electrode active material within the above-described range. In addition, the positive electrode active material has the characteristic of high rolling density because it is advantageous to form a dense structure by the applied pressure by including grains having the above-described size range. In addition, since the pressure can be uniformly distributed during rolling when the grains having the above-described size range are present, the positive electrode active material including them can implement a uniform rolling density throughout the active layer. However, excessively small grains with a size below the lower limit may actually increase rolling resistance, thereby reducing process efficiency. Furthermore, when grains with a size exceeding the upper limit are included, the effect of increasing rolling density is minimal.

[0134] Meanwhile, the grains are particles formed by the aggregation of crystal grains, and generally, as the size of the crystal grains increases, the grain size may also increase. However, when multiple components are doped or substituted, as in the cathode active material according to the present invention, interference effects within their lattices may occur. In this case, structural changes occur at the crystal grain boundaries or the crystal grain boundaries increase, so an increase in crystal grain size may not tend to increase the grain size.

[0135] The above cathode active material may have a tendency for the particle size and size distribution to be constant. Accordingly, when analyzing the particle size distribution of the above cathode active material, D 10 , D50 and D 90 / D 10 This specific range can be satisfied.

[0136] Specifically, the above cathode active material has an average particle diameter (D) of 0.7 ㎛ to 1.3 ㎛ when analyzing the particle diameter distribution. 50 ) may have. For example, the cathode active material may have an average particle diameter (D) of 0.7 ㎛ to 1.15 ㎛; 0.7 ㎛ to 1.1 ㎛; 0.75 ㎛ to 1.05 ㎛; 0.75 ㎛ to 1.0 ㎛; or 0.75 ㎛ to 0.95 ㎛ when analyzing particle size distribution. 50 ) can have.

[0137] In addition, the above cathode active material has a D of 5.5 to 9.0 when analyzing particle size distribution. 90 / D 10 may have. For example, the cathode active material may have a D of 6.0 to 8.5; 6.0 to 8.0; 6.1 to 8.0; 6.5 to 8.5; or 6.5 to 7.9 when analyzing the particle size distribution. 90 / D 10 can have

[0138] The above cathode active material has an average particle diameter (D) of 0.2 ㎛ or more and less than 0.6 ㎛ when analyzing particle diameter distribution. 10 ) may have. For example, when analyzing the particle size distribution, the positive electrode active material may have an average particle size (D) of 0.25 ㎛ or more and less than 0.60 ㎛; 0.25 ㎛ to 0.55 ㎛; 0.25 ㎛ to 0.49 ㎛; 0.30 ㎛ to 0.45 ㎛; 0.35 ㎛ to 0.40 ㎛; 0.41 ㎛ to 0.49 ㎛; or 0.35 ㎛ to 0.49 ㎛. 10 ) can have.

[0139] The positive electrode includes a positive electrode active layer prepared by applying a positive electrode slurry containing a positive electrode active material onto a positive electrode current collector and then drying it. At this time, the particle size of the positive electrode active material can affect the density of the positive electrode active layer. In addition, the energy density of the positive electrode can be further increased through a rolling process of the positive electrode active layer during manufacturing. During this process, a high pressure is applied to the positive electrode active material included in the positive electrode active layer, and here, the particle size of the positive electrode active material can affect the deformation of the positive electrode active material particles due to the pressure. For example, if the particle size of the positive electrode active material is large, the particles may be broken during the rolling process, which may result in a loss of the electron transfer path within the positive electrode, and the surface area where a side reaction with the electrolyte may occur may increase, which may result in deterioration of the life characteristics. On the other hand, if the particle size of the positive electrode active material is small, the porosity between the positive electrode active materials increases, which has a limitation in that the rolling density of the positive electrode active layer cannot be sufficiently increased during the rolling process. Therefore, the present invention provides a method for controlling the particle size (D) of the positive electrode active material by controlling the number or mole fraction of metals doped and / or substituted in lithium manganese iron phosphate. 10 and D 50 ) and size distribution (D 90 / D 10 ) is characterized by being adjusted to the above-described range. The cathode active material according to the present invention has a particle size (D 10 and D 50 ) and size distribution (D 90 / D 10 ) is adjusted to the above-described range to increase the energy density of the positive electrode active layer and at the same time minimize particle deformation of the positive electrode active material during the rolling process, thereby achieving a high rolling density.

[0140] For example, the cathode active material according to the present invention may have the above-described particle size and size distribution, and thus may have a rolling density of 2.3 g / cc or more when pressed at a pressure of 9,000 kgf. Specifically, the cathode active material may have a rolling density of 2.30 g / cc to 2.60 g / cc; 2.30 g / cc to 2.50 g / cc; 2.31 g / cc to 2.49 g / cc; 2.35 g / cc to 2.49 g / cc; or 2.36 g / cc to 2.45 g / cc when pressed at a pressure of 9,000 kgf.

[0141] 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.

[0142] At this time, the above-mentioned conductive material may include one or more of acetylene black, super-P, channel black, furnace black, lamp black, summer black, graphene, carbon nanotubes, and carbon fibers, but is not limited thereto.

[0143] 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.

[0144] 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.

[0145] 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.

[0146] 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.

[0147] 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.

[0148]

[0149] The anode according to the present invention has the above-described configuration, and thus has excellent high-temperature safety and life characteristics, as well as the advantages of excellent energy density and rolling density.

[0150]

[0151] Method for manufacturing anode

[0152] Furthermore, the present invention provides a method for manufacturing the anode according to the present invention described above.

[0153] Specifically, the method for manufacturing the positive electrode includes a step (S1) of applying a positive electrode slurry containing lithium manganese iron phosphate represented by the following chemical formula 1 to at least one surface of a positive electrode current collector, and a step (S2) of drying the applied positive electrode slurry to form a positive electrode active layer:

[0154] [Chemical Formula 1]

[0155] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0156] In the above chemical formula 1,

[0157] M 1 is at least one of Ti, V, Zr, Sr, Sb, B, and Nb,

[0158] a, b, and c are -0.5≤a≤0.5, 0.1≤b≤0.8, 0.001≤c≤0.2.

[0159]

[0160] Here, the application of the positive electrode slurry (S1) refers to a process of discharging and coating the surface of the moving positive electrode current collector with a positive electrode slurry containing a carbon-based negative electrode active material. This process 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 discharge 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.

[0161] In addition, the positive electrode slurry is intended to form the positive electrode active layer of the positive electrode. Accordingly, the positive electrode slurry comprises a positive electrode active material as its main component, and may further comprise conductive materials, binders, etc., as needed. Here, since the composition of the positive electrode active material, conductive materials, binders, etc., contained in the positive electrode slurry is identical to that of the positive electrode active layer of the positive electrode, a detailed description thereof will be omitted.

[0162] However, the cathode active material may be manufactured through a predetermined process. In general, conventional cathode active materials with an olivine structure are manufactured by mixing precursor compounds containing each transition metal and lithium phosphate, which is a lithium raw material, and calcining the mixture at a high temperature. However, the cathode active material of the present invention can be manufactured by first generating lithium manganese iron phosphate represented by chemical formula 6 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.

[0163] Specifically, the cathode active material can be manufactured by a step of calcining a mixture of a compound represented by the following chemical formula 6 and a metal precursor compound 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:

[0164] [Chemical Formula 6]

[0165] Li 1+m Mn 1-n Fe n PO4

[0166] In the above chemical formula 56,

[0167] m and n are -0.5≤m≤0.5, 0.1≤n≤0.8.

[0168]

[0169] The present invention can prevent over-sintering of the material due to a temperature exceeding the upper limit by performing firing in the temperature range described above when manufacturing a cathode active material. In addition, since the bonding between the compound represented by Chemical Formula 6 and the metal precursor compound can be promoted in the temperature range described above, and the evaporation of lithium during firing can be minimized, the density of the cathode active material manufactured can be further increased. The density of particles having a high density refers to the density of particles arranged within a specific volume, and the higher the density of particles, the higher the rolling density and strength can be implemented after rolling.

[0170] The compound represented by the above chemical formula 6 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 6 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.

[0171] The compound of chemical formula 6, 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 compound refers to raw materials that supply titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc. to the lithium manganese iron phosphate represented by chemical formula 6. The metal precursor compounds are not particularly limited as long as they can provide titanium (Ti), vanadium (V), zirconium (Zr), and / or niobium (Nb).

[0172] 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.

[0173] 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).

[0174] 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:

[0175] 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.

[0176] Meanwhile, the method for manufacturing the positive electrode may include a process of forming a positive electrode active layer from the applied positive electrode slurry. The process of forming the positive electrode active layer may refer to a process of drying the positive electrode slurry. In this case, 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.

[0177] 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.

[0178] 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.

[0179] 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.

[0180] 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.

[0181] 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.

[0182]

[0183] The method for manufacturing an anode according to the present invention can manufacture an anode having excellent energy density by having the above-described configuration.

[0184]

[0185] Hereinafter, the present invention will be described in more detail through examples and comparative examples.

[0186] 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.

[0187]

[0188] Manufacturing Example 1-7. Manufacturing of positive electrode active material

[0189] First, the cathode active material was prepared. Specifically, lithium manganese iron phosphate (LiMn0.7 Fe 0.3 PO4) was purchased commercially. Titanium dioxide (TiO2), ammonium vanadate (NH4VO3), and niobium oxide (Nb2O5) were mixed with the purchased lithium manganese iron phosphate, and calcined at 700±20℃ under a nitrogen atmosphere to manufacture a cathode active material. 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 manufactured cathode active material. In addition, whether the lithium manganese iron phosphate purchased commercially was heat treated before mixing the metal precursor compound is shown in Table 1.

[0190] X-ray diffraction (XRD) was performed on the manufactured cathode active material to measure ① lattice constants a, b, and c 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, and 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.

[0191] In addition, particle size distribution analysis (PSD) was performed on the above cathode active material to determine ③ D of the cathode active material. 10 , D 50 and D 90 Measure and D from the measured value 90 / D 10 was calculated. Specifically, particle size distribution analysis (PSD) was performed by laser diffraction method. Malvern's Mastersizer 3000 was used as the particle size distribution analysis (PSD) device, and the laser refractive index was adjusted to 2.0 to 2.2. After dispersing each cathode active material less than 1 g in deionized (DI) water using an ultrasonic irradiator installed inside the device, 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 10% of the area cumulative distribution according to particle diameter in the measuring device, D 10 can be measured, D 50 and D 90 The same method was used to measure the same amount of water. The measured and calculated results are shown in Table 1 below.

[0192] Finally, the rolling density of each cathode active material was measured. Specifically, 5 g of the cathode active material was weighed and placed in a cylindrical holder. The powder density was measured while increasing the pressure from 400 kgf to 9,000 kgf at intervals of 400 kgf. As a result, the rolling density of the cathode active material at 9,000 kgf is shown in Table 1 below.

[0193] Manufacturing Example 1 Manufacturing Example 2 Manufacturing Example 3 Manufacturing Example 4 Manufacturing Example 5 Manufacturing Example 6 Manufacturing Example 7 Metal precursor compound TiO2 0.06 0.03 0.02 0.01 0.02 0.04 -NH4VO3 - 0.03 0.02 0.01 0.02 0.04 -Nb2O5 - 0.02 0.01 0.02 0.04 - Whether or not heat treatment was performed before mixing the metal precursor compound (700℃ 1 hour) XXXOOO - XRD lattice constant c 4.69184 Å 4.69202 Å 4.69209 Å 4.69205 Å 4.69214 Å 4.69218 Å 4.69162 Å X-axis size 100 nm 96 nm 91 nm 89 nm 88 nm 87 nm 120 nm PSDD 10 0.50㎛0.47㎛0.42㎛0.43㎛0.38㎛0.36㎛0.60㎛D 50 1.20㎛1.03㎛0.90㎛0.85㎛0.81㎛0.78㎛1.40㎛D 90 / D 10 6.06.26.97.27.67.85.0Rolled density (@ 9000 kgf)2.34 g / cc2.37 g / cc2.41 g / cc2.41 g / cc2.43 g / cc2.45 g / cc2.28 g / cc

[0194]

[0195] Examples 1 to 6 and Comparative Example 1. Preparation of anode

[0196] N-methylpyrrolidone solvent was injected into a homo mixer, and 90 parts by weight of each of the positive electrode active materials manufactured in Manufacturing Examples 1 to 7, 5 parts by weight of carbon black as a conductive material, and 5 parts by weight of polyvinylidene fluoride (PVdF) as a binder were added, respectively. Then, the mixture was mixed at 3,000 rpm for 60 minutes to prepare a positive electrode slurry. An aluminum foil (average thickness: 12 μm) was prepared as a positive electrode current collector, and the positive electrode slurry manufactured previously was cast on one side of the prepared aluminum foil. The aluminum foil on which the positive electrode slurry was cast was dried in a vacuum oven at 130°C and then rolled to manufacture a positive electrode. At this time, the total thickness of the rolled positive electrode active layer was 150 μm.

[0197] Types of applied positive electrode active materials Example 1 Positive electrode active material manufactured in Manufacturing Example 1 Example 2 Positive electrode active material manufactured in Manufacturing Example 2 Example 3 Positive electrode active material manufactured in Manufacturing Example 3 Example 4 Positive electrode active material manufactured in Manufacturing Example 4 Example 5 Positive electrode active material manufactured in Manufacturing Example 5 Example 6 Positive electrode active material manufactured in Manufacturing Example 6 Comparative Example 1 Positive electrode active material manufactured in Manufacturing Example 7

[0198]

[0199] Experimental example.

[0200] In order to evaluate the performance of the anode according to the present invention, the following experiments were conducted.

[0201] First, a lithium metal disk was prepared as a negative electrode. The prepared negative electrode and the positive electrode prepared in Examples 1 to 6 and Comparative Example 1 were placed face to face, and an 18 μm polypropylene separator was interposed between them 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.

[0202] The fabricated half-cell was charged at a constant current of 0.1 C at 25°C until the voltage reached 4.25 V, and then discharged at a constant current of 0.1 C until the voltage reached 2.5 V. At this time, each capacity was measured during charging and discharging to confirm the initial charge capacity and initial discharge capacity, and the initial charge-discharge efficiency (@0.1 C) was calculated by estimating the ratio of the initial discharge capacity to the initial charge capacity.

[0203] Separately, to evaluate the output characteristics of each anode, the previously discharged half-cell was charged at 25°C until the SOC reached 50%, and the resistance was measured. At this time, the resistance was measured as the range of voltage drop when current was applied, and the results are shown in Table 3 below.

[0204] Initial Charge / Discharge (@0.1C) Room Temperature Resistance Charge Capacity Discharge Capacity Efficiency Example 1 150.5 mAh / g 146.0 mAh / g 97.0% 18.2 mΩ Example 2 153.4 mAh / g 149.1 mAh / g 97.2% 16.4 mΩ Example 3 155.2 mAh / g 151.2 mAh / g 97.4% 15.2 mΩ Example 4 156.3 mAh / g 151.7 mAh / g 97.4% 14.6 mΩ Example 5 158.1 mAh / g 154.1 mAh / g 97.5% 14.0 mΩ Example 6 159.8 mAh / g 155.5 mAh / g 97.6% 13.9 mΩ Comparative Example 1 145.0 mAh / g 140.0 mAh / g96.5%22.4 mΩ

[0205]

[0206] As shown in Table 3 above, it can be seen that the positive electrode according to the present invention has high energy density and excellent output performance.

[0207] Specifically, the half-cells including the positive electrode of the embodiment had excellent energy density, with initial charge / discharge capacities of 150 mAh / g or more and 145 mAh / g or more, respectively, and the initial charge / discharge efficiency was confirmed to be high at 97% or more.

[0208] Additionally, half-cells including the cathode of the embodiment were found to have a low resistance of less than 19 mΩ at room temperature of 25°C.

[0209] From this, it can be seen that the cathode active material according to the present invention not only has high structural stability by including lithium manganese iron phosphate with an olivine structure, but also facilitates control of particle size distribution by doping and / or substituting one or more metals within the crystal structure. Accordingly, it can be seen that the cathode including this has significantly improved energy density.

[0210]

[0211] 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 various modifications and changes to the present invention can be made without departing from the spirit and technical scope of the present invention as set forth in the claims to be described below.

[0212] 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. Anode current collector, and A cathode comprising a cathode active layer provided on at least one surface of the cathode current collector and including a compound represented by the following chemical formula 1 as a cathode active material: [Chemical Formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4 In the above chemical formula 1, 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.

2. In paragraph 1, The above cathode active material is a cathode including at least one compound represented by the following chemical formulas 2 to 5: [Chemical formula 2] Li 1+a Mn 1-b-x Fe b You x PO4 [Chemical Formula 3] Li 1+a Mn 1-b-x-y Fe b You x V y PO4 [Chemical Formula 4] Li 1+a Mn 1-b-x-y-z Fe b You x V y Nb z PO4 [Chemical Formula 5] Li 1+a Mn 1-b-x-y-z Fe b You x Zr y Nb z PO4 In the chemical formulas 2 to 5 above, 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 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 above cathode active material has an average particle diameter (D 50 ) is 0.7 ㎛ to 1.3 ㎛.

5. In paragraph 1, The above lithium manganese iron phosphate has a particle size distribution of D of 5.5 to 9.

0. 90 / D 10 A bipolar having .

6. In paragraph 5, The above cathode active material has a D of 0.2 ㎛ or more and less than 0.6 ㎛. 10 A bipolar having .

7. In paragraph 1, The above cathode active material is a cathode having a rolling density of 2.3 g / cc or more when pressurized at 9,000 kgf.

8. A step of applying a cathode slurry containing a compound represented by the following chemical formula 1 as a cathode active material to at least one surface of a cathode current collector, and A method for manufacturing a cathode according to claim 1, comprising the step of drying the applied cathode slurry to form a cathode active layer: [Chemical Formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4 In the above chemical formula 1, 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.

9. In paragraph 8, The above cathode active material is a method for manufacturing a cathode comprising at least one compound represented by the following chemical formulas 2 to 5: [Chemical formula 2] Li 1+a Mn 1-b-x Fe b You x PO4 [Chemical Formula 3] Li 1+a Mn 1-b-x-y Fe b You x V y PO4 [Chemical Formula 4] Li 1+a Mn 1-b-x-y-z Fe b You x V y Nb z PO4 [Chemical Formula 5] Li 1+a Mn 1-b-x-y-z Fe b You x Zr y Nb z PO4 In the chemical formulas 2 to 5 above, a, b, x, y and z are -0.5≤a≤0.5, 0.1≤b≤0.8, 0 <x≤0.1, 0<y≤0.1, 0<z≤0.1이되, 0.001≤z+y+z≤0.2이다.

10. In paragraph 8, The above 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 6 at a temperature of 500°C or higher: [Chemical formula 6] Li 1+m Mn 1-n Fe n PO4 In the above chemical formula 6, m and n are -0.5≤m≤0.5, 0.1≤n≤0.

8.

11. In paragraph 10, A method for manufacturing a cathode, characterized in that the lithium manganese iron phosphate represented by the chemical formula 6 is heat-treated at 500°C to 900°C before being mixed with a metal precursor compound.