Positive electrode and method for manufacturing the same

Abstract

This invention relates to a cathode and a method for manufacturing the same. The cathode contains manganese iron lithium phosphate with an olivine structure as the cathode active material and is characterized by high structural safety. Furthermore, since the particle size distribution of the manganese iron lithium phosphate can be easily controlled by doping and / or substitution with one or more metals, a cathode containing it has the advantage of excellent rolling density and energy density.

Description

[Technical Field]

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

[0002] This application claims priority rights under Korean Patent Application No. 10-2024-0003888 dated January 10, 2024, and Korean Patent Application No. 10-2024-0183777 dated December 11, 2024, and all content disclosed in the documents of said patent applications is incorporated herein by reference. [Background technology]

[0003] In recent years, lithium-ion batteries have been widely applied not only to small devices such as portable electronic devices, but also to medium and large-scale devices such as battery packs for hybrid and electric vehicles, and power storage devices. In particular, with the growing concern for environmental issues in recent years, there has been a great deal of research into electric vehicles and hybrid electric vehicles that can replace vehicles that use fossil fuels such as gasoline and diesel vehicles, which are one of the main causes of air pollution.

[0004] Generally, lithium secondary batteries have a structure in which an electrode assembly consisting of a positive electrode, a negative electrode, and a separator membrane is impregnated with a lithium electrolyte. In this case, 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 providing electrical conductivity, and a binder for adhering it to the current collector and providing bonding force, in a solvent such as NMP (N-methyl pyrrolidone).

[0005] The positive electrode can be made of LCO (LiCoO2), LMO (LiMn2O4), LFP (LiFePO4), or NCM (LiNi), which can reversibly insert or remove lithium. 1 / 3 Co 1 / 3 Mn 1 / 3 It contains metal oxides such as O2 as the positive electrode active material.

[0006] Among these, NCM, LCO, and NCA compounds, which have a layered crystalline structure, are suitable as positive electrode active materials for high-capacity / high-power secondary batteries because they easily store lithium ions and have a high lithium ion diffusion rate. However, compounds with a layered crystalline structure have low chemical and structural stability and can easily decompose under high-temperature conditions. This acts as a factor that reduces the safety of secondary batteries.

[0007] On the other hand, LFP compounds with an olivine crystal structure have a hexahedral crystal form in which phosphorus (P) and oxygen (O) are strongly bonded, and exhibit high structural stability. Therefore, LFP compounds with an olivine crystal structure can easily maintain their crystal structure even when all lithium ions are desorbed during charging, and decomposition of the crystal structure is less likely to occur even under high-temperature conditions. However, these compounds have 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 with an olivine crystal structure to achieve high energy density, the weight / volume of the positive electrode active material must be increased, which limits the size and weight of the secondary battery to an excessive increase.

[0008] As a result, a form of positive electrode active material containing manganese was developed to increase the energy density of conventional LFP-based compounds with an olivine crystal structure. This positive electrode active material has a structure in which manganese is partially substituted at the valence positions of iron atoms, achieving an effect of improving the energy density of iron phosphate by approximately 5% or more. Despite this effect, there is a need for LFP-based compounds that can exhibit additional energy density when applied to medium- and large-scale secondary batteries.

[0009] Therefore, in order to achieve high safety in lithium secondary batteries, there is a need for technological development of lithium secondary battery cathodes that can achieve high energy density while containing LFP-based compounds having an olivine structure as the cathode active material. [Prior art documents] [Patent Documents]

[0010] [Patent Document 1] Korean Published Patent Application No. 10-2016-0064136 Summary of the Invention Problem to be Solved by the Invention

[0011] An object of the present invention is to provide a positive electrode for a lithium secondary battery that can achieve high energy density while containing an LFP-based compound having an olivine structure as a positive electrode active material, and a method for producing the same, in order to achieve high safety of the lithium secondary battery. Means for Solving the Problem

[0012] In order to solve the above problem, the present invention a positive electrode current collector, and provides a positive electrode comprising a positive electrode active layer provided on at least one surface of the positive electrode current collector and containing a compound represented by the following Chemical Formula 1 as a positive electrode active material.

[0013] [Chemical Formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0014] In the above Chemical Formula 1, M 1 is one or more selected from the group consisting of Ti, V, Zr, Sr, Sb, B and Nb, a, b and c satisfy -0.5≦a≦0.5, 0.1≦b≦0.8, and 0.001≦c≦0.2.

[0015] In this case, the positive electrode active material may contain one or more selected from compounds represented by the following Chemical Formulas 2 to 5.

[0016] [Chemical Formula 2] Li 1+a Mn1-b-x Fe b Ti x PO4

[0017] [Chemical formula 3] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0018] [Chemical formula 4] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0019] [Chemical formula 5] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0020] In the above chemical formulas 2 to 5, a, b, x, y, and z are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0 <x≦0.2、0<y≦0.1、0<z≦0.1であり、かつ、0.001≦x+y≦0.2、または0.001≦x+y+z≦0.2である。

[0021] Furthermore, the above positive electrode 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.

[0022] [Formula 1] y = -px + q

[0023] In the above formula 1, y represents the lattice constant c, x is √(a 2 +b 2 ) is expressed as, 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.

[0024] Furthermore, the above positive electrode active material has an average particle size (D 50 The size of the particle can be between 0.7 μm and 1.3 μm.

[0025] Furthermore, the above positive electrode active material had a particle size distribution of 5.5 to 9.0 during particle size distribution analysis. 90 / D 10 It can have a D of 0.2 μm or more and less than 0.6 μm. 10 It can have.

[0026] Furthermore, 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.

[0027] Furthermore, in one embodiment, the present invention The steps include: applying a positive electrode slurry containing a compound represented by the following chemical formula 1 as a positive electrode active material to at least one surface of the positive electrode current collector, and The present invention provides a method for producing a positive electrode, which includes the step of drying the coated positive electrode slurry to form a positive electrode active layer.

[0028] [Chemical formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0029] In the above chemical formula 1, M 1 It is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. a, b, and c are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.2.

[0030] Here, the positive electrode active material may contain one or more compounds represented by the following chemical formulas 2 to 5.

[0031] [Chemical formula 2] Li1+a Mn 1-b-x Fe b Ti x PO4

[0032] [Chemical formula 3] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0033] [Chemical formula 4] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0034] [Chemical formula 5] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0035] In the above chemical formulas 2 to 5, a, b, x, y, and z are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0 <x≦0.2、0<y≦0.1、0<z≦0.1であり、かつ、0.001≦x+y≦0.2、または0.001≦x+y+z≦0.2である。

[0036] Furthermore, the above-mentioned positive electrode active material can be produced by a step of calcining a mixture of lithium iron manganese phosphate, represented by the following chemical formula 6, and a metal precursor compound at a temperature of 500°C or higher.

[0037] [Chemical formula 6] Li 1+m Mn 1-n Fe n PO4

[0038] In the above chemical formula 6, m and n are -0.5 ≤ m ≤ 0.5 and 0.1 ≤ n ≤ 0.8, respectively.

[0039] In this case, the lithium iron manganese 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. [Effects of the Invention]

[0040] The positive electrode according to the present invention contains manganese iron lithium phosphate with an olivine structure as the positive electrode active material and is characterized by high structural safety. Furthermore, the particle distribution of the manganese iron lithium phosphate can be easily controlled by doping and / or substitution with one or more metals. Therefore, a positive electrode containing this has the advantage of excellent energy density and rolling density. [Brief explanation of the drawing]

[0041] [Figure 1] This graph shows the correlation between the lattice constant c of the positive electrode active material and the lattice constants a and b during X-ray diffraction (XRD) analysis. [Modes for carrying out the invention]

[0042] Since the present invention can be modified in various ways and has many different embodiments, specific embodiments will be described in detail.

[0043] However, this is not intended to limit the present invention to any particular embodiment, but rather to be understood to include all modifications, equivalents, or substitutions that fall within the spirit and technical scope of the present invention.

[0044] In the present invention, terms such as “includes” or “having” are intended to specify the presence of features, numbers, steps, operations, components, parts, or combinations thereof as described in the specification, without prejudice to the presence or possibility of adding one or more other features, numbers, steps, operations, components, parts, or combinations thereof.

[0045] Furthermore, in this specification, "average particle size (D 50 "Average particle size" refers to the particle size at which the integrated value in the particle size distribution becomes 50%, and this is also called the median diameter. The above average particle size can be measured using methods commonly applied in this industry. For example, the above average particle size can be measured using a particle size analyzer or an analytical instrument using laser diffraction scattering particle size distribution measurement, but is not limited to these.

[0046] The present invention will be described in more detail below.

[0047] <Positive electrode>

[0048] The present invention The present invention provides a positive electrode comprising a positive electrode current collector and a positive electrode active layer provided on at least one surface of the positive electrode current collector, the active layer containing a compound represented by the following chemical formula 1 as the positive electrode active material.

[0049] [Chemical formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0050] In the above chemical formula 1, M 1 It is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. a, b, and c are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.2.

[0051] The positive electrode according to the present invention may mean 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 embodies the electrical activity of the positive electrode and mainly contains a positive electrode active material that embodies an electrochemical oxidation-reduction reaction during charging and discharging of the battery. Specifically, the positive electrode active material can be included in an amount of 80 to 99.8 parts by weight relative to the total weight of the positive electrode active layer, more specifically in amounts of 95 parts by weight or more, 98 parts by weight or more, 84 to 99.8 parts by weight, 90 to 99.8 parts by weight, 94 to 99.8 parts by weight, 88 to 96 parts by weight, or 92 to 97.5 parts by weight.

[0052] Furthermore, the above-mentioned positive electrode active material includes a compound represented by chemical formula 1.

[0053] [Chemical formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0054] In the above chemical formula 1, M 1 It is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. a, b, and c are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.2.

[0055] 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 above compound having an olivine crystal structure can easily maintain its crystal structure even when all lithium ions are desorbed during charging, and decomposition of the crystal structure is unlikely to occur even under high temperature conditions. Therefore, the above positive electrode active material has excellent lifespan characteristics and excellent safety features in all aspects, including overcharging and over-discharging. Furthermore, since the positive electrode active material contains iron, which is abundant and inexpensive as a resource, LiNi 1 / 3 Co 1 / 3 Mn 1 / 3It is cheaper than lithium composite oxides such as O₂, LiCoO₂, LiNiO₂, or LiMn₂O₄, has low toxicity, and thus has less impact on the environment.

[0056] However, lithium manganese iron phosphate (LiMn 1-b Fe b PO₄) that contains only lithium (Li), manganese (Mn) and iron (Fe) as metals has a slightly higher energy density than lithium iron phosphate (LiFePO₄), but the energy density is still not very high. In addition, lithium manganese iron phosphate has a low rolling density similar to the aforementioned lithium composite oxides, so there is a limit to further increasing the energy density through processes such as a rolling step. Here, the "rolling density" refers to a parameter indicating the degree to which particle deformation of the positive electrode active material occurs when pressurized. The rolling density can mean that under the same pressure condition, a lower rolling density corresponds to higher compressive strength and lower energy density. Therefore, the present invention is characterized in that one or more metals are doped and / or substituted into the positive electrode active material lithium manganese iron phosphate to achieve a high rolling density. Specifically, the positive electrode 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 selected from the group consisting of titanium (Ti), vanadium (V), zirconium (Zr) and niobium (Nb).

[0057] As an example, the lithium manganese iron phosphate may include one or more of the compounds represented by the following Chemical Formula 2 to Chemical Formula 5.

[0058] [Chemical Formula 2] Li 1+a Mn 1-b-x Fe b Ti x PO4

[0059] [Chemical Formula 3] Li 1+a Mn 1-b-x-y Fe b Ti x V y PO4

[0060] [Chemical Formula 4] Li 1+a Mn 1-b-x-y-z Fe b Ti x V y Nb z PO4

[0061] [Chemical Formula 5] Li 1+a Mn 1-b-x-y-z Fe b Ti x Zr y Nb z PO4

[0062] In the above Chemical Formulas 2 to 5, a, b, x, y, and z satisfy -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0 < x ≤ 0.2, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and 0.001 ≤ x+y ≤ 0.2, or 0.001 ≤ x+y+z ≤ 0.2.

[0063] The compound represented by any one of the above Chemical Formulas 2 to 5 is lithium manganese iron phosphate (LiMn 1-b Fe bPO4) is doped or substituted with titanium (Ti), vanadium (V), zirconium (Zr), and / or niobium (Nb). In this case, the doping or substitution of each metal can be limited to 0.1 mole fraction or less, based on 1 mole fraction of the total metal excluding lithium (Li), and the ratio of lithium (Li) to these metals (Me) (Li / Me) can 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 positive electrode active material is closely related to the particle density. Specifically, a higher lithium concentration results in higher density, and in this case, void removal within the particles is easier, thus enabling the realization of a high rolling density. However, excessively high lithium concentrations can reduce lithium ion movement and decrease electrical performance. Furthermore, extremely low lithium concentrations not only result in low particle density and low rolling density, but also pose problems such as low energy density per unit volume / mass during cathode manufacturing. The present invention can overcome these problems by adjusting the ratio of lithium (Li) to metal (Me) contained in the cathode active material (Li / Me) to the above range.

[0064] LiMn is an example of such a positive electrode active material. 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 0.05PO4, LiMn 0.6 Fe 0.35 Ti 0.05 Compounds 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 Ti 0.05 V 0.05 PO4, LiMn 0.6 Fe 0.3 Ti 0.05 V 0.05 Compounds 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, LiMn0.7 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 PO4 is the range of 4;and 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 Zr 0.05 Nb 0.05 PO4、LiMn 0.7 Fe 0.15Ti 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 contain one or more compounds represented by chemical formula 5, such as PO4.

[0065] The above-mentioned positive electrode active material has a form in which manganese iron lithium phosphate is doped and / or substituted with one or more of titanium (Ti), vanadium (V), zirconium (Zr), and niobium (Nb), so that the size of the positive electrode active material can satisfy predetermined conditions depending on the number of doped and / or substituted metals and / or the mole fraction of the metals.

[0066] Specifically, in positive electrode active materials, "particles" refer to particles on the micrometer scale, and when observed under magnification, they can be divided into "grains" having crystals on the nanometer scale. When these grains are magnified further, a unit region in which atoms form a lattice structure in a certain direction (i.e., a crystal lattice) can be observed, and this is called a "crystallite." The positive electrode active material according to the present invention has a form in which manganese iron lithium phosphate is doped and / or substituted with one or more of titanium (Ti), vanadium (V), zirconium (Zr), and niobium (Nb), and the size of the crystallite and / or particles can be controlled to satisfy a predetermined range.

[0067] For example, the lattice constant c of the lithium iron manganese phosphate constituting the positive electrode active material can increase as the type and mole fraction of the doping or substitution metal increase, and the grain size of the positive electrode active material can decrease. Here, the grain size of the positive electrode active material can be measured in the form of lattice constants a, b, c, etc., which indicate the length of each side of the crystal grain during X-ray spectroscopy.

[0068] More specifically, the positive electrode active material according to the present invention is doped or substituted with manganese (Mn) along with titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc., and does not contain the above transition metals. 1-b Fe b The positive electrode active material can have a lattice constant c greater than that of PO4 (approximately 4.6916 Å). For example, the positive electrode active material may have a lattice constant c of 4.69165 Å to 4.80 Å when analyzed by X-ray diffraction. Specifically, the positive electrode active material may have a lattice constant c of 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 when analyzed by X-ray diffraction.

[0069] A "lattice constant" is a value that represents the length of the edges of crystal grains and is used to describe the size and arrangement of a substance. It can be expressed in various forms depending on the crystal structure. In the case of an olivine structure, it has an orthorhombic crystal structure and can have lattice constants a, b, and c accordingly. Of these, the lattice constant c is a factor that indicates 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 grains. For example, lithium iron manganese phosphate (LiMn), which has an olivine structure. 1-b Fe b In the case of PO4), the c-axis direction can act as the main migration path for lithium ions. The lattice constant c, which indicates the magnitude in the c-axis direction, is Fe 2+ and Mn 2+ Ti has a larger ionic radius. 4+ , V 5+ Nb 5+These can be increased by doping. Increasing the lattice constant c expands the lithium ion pathway and increases the lithium ion diffusion coefficient. Therefore, the positive electrode active material according to the present invention can exhibit 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 inside the olivine structure. If a secondary phase is formed inside the olivine structure, the electrochemical activity may actually be reduced. Also, if it is below the lower limit of the above range, the electrical performance of the positive electrode active material may be significantly reduced.

[0070] Furthermore, the positive electrode active material can exhibit a linear relationship when the lattice constant c is expressed in relation to the lattice constants a and b, and this can be governed by Vegard's law. Specifically, the lattice constant c of the positive electrode active material can have a predetermined correlation with the square root of (the sum of the squares of lattice constant a and lattice constant b), and such a correlation can be expressed by the following equation 1.

[0071] [Formula 1] y = -px + q

[0072] In the above formula 1, y represents the lattice constant c, x is √(a 2 +b 2 ) is expressed as, 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.

[0073] Formula 1 above 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, where a, b, and c may be measured values ​​obtained by X-ray spectroscopy. The lattice constants a, b, and c and their correlations can change depending not only on the type and mole fraction of the metals doped and / or substituted into lithium manganese iron phosphate, but also on the manufacturing method and process conditions. In the present invention, as shown in Figure 1, the correlation tends to increase as the number and mole fraction of the metals doped and / or substituted into lithium manganese iron phosphate increases. That is, the first positive electrode active material of the present invention satisfies the range of lattice constant c described above, and lithium manganese iron phosphate (LiMn 1-b Fe b PO4) doped and / or substituted with metal (M 1 Since the lattice constant c tends to increase as the number or mole fraction of ) increases, the above equation 1 can be satisfied. The fact that the lattice constant c shows a linear relationship when expressed with respect to the lattice constants a and b means that manganese iron lithium 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 into or substituted into PO4). In other words, it indirectly indicates that the structural safety of the cathode active material according to the present invention is maintained at a high level even when multiple components are doped into or substituted into it.

[0074] Grains, formed by such lattice units, can be confirmed by their size through the X-axis size during X-ray diffraction analysis. The size of these grains may be between approximately 70 nm and less than 120 nm. More specifically, the grain sizes may be approximately 70 nm to 115 nm, approximately 70 nm to 105 nm, approximately 70 nm to 99 nm, approximately 70 nm to 95 nm, or approximately 80 nm to 99 nm. The present invention can achieve high electrical performance by adjusting the grain size of the positive electrode active material to the above range. Furthermore, the positive electrode active material contains grains having the above size range, which is advantageous for forming a dense structure by applied pressure, and therefore has the characteristic of high rolling density. In addition, since the pressure can be uniformly distributed during rolling of grains having the above size range, the positive electrode active material containing them can achieve a uniform rolling density throughout the active layer. However, excessively small grains with a size below the above lower limit may actually increase rolling resistance and reduce process efficiency. Furthermore, there is a limitation in that if the grain size exceeds the above upper limit, the effect of increasing the rolling density is minimal.

[0075] On the other hand, the grains described above are particles formed by the aggregation of crystal grains, and generally, the grain size can increase as the size of the crystal grains increases. However, when multiple components are doped or substituted, as in the positive electrode active material according to the present invention, intralattice interference effects between them can occur. In this case, structural changes occur at the crystal grain boundaries, or the number of crystal grain boundaries increases, so the tendency for an increase in crystal grain size to increase grain size may not be observed.

[0076] The above positive electrode active material can have a consistent particle size and size distribution. As a result, when analyzing the particle size distribution of the above positive electrode active material, D 10 , D 50 , and D 90 / D 10 This can satisfy the specified range.

[0077] Specifically, the above positive electrode active material has an average particle size of 0.7 μm to 1.3 μm (D) when analyzed for particle size distribution. 50 ) can have. For example, the above positive electrode active material may have an average particle size (D) of 0.7 μm to 1.15 μm, 0.7 μm to 1.1 μm, 0.75 μm to 1.05 μm, 0.75 μm to 1.0 μm, or 0.75 μm to 0.95 μm when analyzed for particle size distribution. 50 ) can have.

[0078] Furthermore, the above positive electrode active material had a particle size distribution of 5.5 to 9.0 during particle size distribution analysis. 90 / D 10 It can have the following characteristics. For example, the above positive electrode active material may have a particle size distribution of 6.0-8.5, 6.0-8.0, 6.1-8.0, 6.5-8.5, or 6.5-7.9 when analyzed. 90 / D 10 It can have.

[0079] The above positive electrode active material has an average particle size (D) of 0.2 μm or more and less than 0.6 μm when analyzed for particle size distribution. 10 ) may have. For example, the above positive electrode active material may have an average particle size (D) of 0.25 μm or more and less than 0.60 μm, 0.25 μm to 0.55 μm, 0.25 μm to 0.49 μm, 0.30 μm to 0.45 μm, 0.35 μm to 0.40 μm, 0.41 μm to 0.49 μm, or 0.35 μm to 0.49 μm when analyzed for particle size distribution. 10 ) can have.

[0080] The positive electrode includes a positive electrode active layer, which is formed by coating a positive electrode slurry containing positive electrode active material onto a positive electrode current collector and then drying it. In this case, the particle size of the positive electrode active material may affect the density of the positive electrode active layer. Furthermore, the energy density of the positive electrode can be increased through the rolling process of the positive electrode active layer during manufacturing. During this process, the positive electrode active material contained in the positive electrode active layer is subjected to high pressure, and here the particle size of the positive electrode active material may affect the particle deformation of the positive electrode active material in response to pressure. For example, if the particle size of the positive electrode active material is large, the particles may break during the rolling process, resulting in the loss of electron transfer pathways within the positive electrode, an increased surface area where side reactions with the electrolyte can occur, and potentially poor lifetime characteristics. On the other hand, if the particle size of the positive electrode active material is small, the porosity between positive electrode active material particles increases, which limits the rolling density of the positive electrode active layer to not be sufficiently high during the rolling process. Therefore, the present invention controls the number and mole fraction of metals doped and / or substituted into lithium iron manganese phosphate to control the particle size (D) of the positive electrode active material. 10 and D 50 ) and size distribution (D 90 / D 10 The positive electrode active material according to the present invention is characterized by adjusting the particle size (D 10 and D 50 ) and size distribution (D 90 / D 10 The invention features a high rolling density while simultaneously minimizing particle deformation of the positive electrode active material during the rolling process by adjusting the value within the above-mentioned range to increase the energy density of the positive electrode active layer.

[0081] As an example, the positive electrode active material according to the present invention, having the above-mentioned particle size and size distribution, may have a rolling density of 2.3 g / cc or more when pressurized at a pressure of 9,000 kgf. Specifically, the positive electrode 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 pressurized at a pressure of 9,000 kgf.

[0082] On the other hand, the positive electrode active layer may selectively further contain conductive materials, binders, and other additives in addition to the positive electrode active material, which is the main component.

[0083] In this case, the conductive material may include, but is not limited to, one or more of the following: acetylene black, Super P, channel black, furnace black, lamp black, thermal black, graphene, carbon nanotubes, and carbon fibers.

[0084] The content of the conductive material can be 0.1 to 10 parts by weight per 100 parts by weight of the entire electrode active layer, specifically 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 and the charging capacity from decreasing due to a low content of conductive material, and can prevent problems such as the charging capacity decreasing due to a decrease in the content of the electrode active material due to an excessive amount of conductive material, or the rapid charging characteristics decreasing due to an increase in the loading amount of the electrode active layer.

[0085] Furthermore, the above-mentioned binder is a component that assists in the bonding of the positive electrode active material to conductive materials and to the current collector, and can be appropriately applied within a range that does not degrade the electrical properties of the positive electrode. Specifically, it may contain one or more of the following: vinylidene fluoride-hexafluoropropylene copolymer (PVDF-co-HFP), polyvinylidene fluoride (PVDF), polyacrylonitrile, polymethyl methacrylate, polyvinyl alcohol, carboxymethylcellulose (CMC), starch, hydroxypropylcellulose, regenerated cellulose, polyvinylpyrrolidone, polytetrafluoroethylene, polyethylene, polypropylene, polyacrylic acid, ethylene-propylene-diene monomer, sulfonated ethylene-propylene-diene monomer, styrene-butadiene rubber (SBR), and fluororubber.

[0086] The binder content may be 0.1 to 10 parts by weight per 100 parts by weight of the entire positive electrode active layer, specifically 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 binder content in the positive electrode active layer within the above range, the present invention can prevent a decrease in the adhesive strength of the active layer due to a low binder content or a decrease in the electrical properties of the positive electrode due to an excessive amount of binder.

[0087] Furthermore, the average thickness of the positive electrode active layer may be between 50 μm and 500 μm. Specifically, the average thickness of the positive electrode active layer may be between 100 μm and 400 μm, 200 μm and 350 μm, 50 μm and 180 μm, 80 μm and 150 μm, 100 μm and 250 μm, 100 μm and 250 μm, or 130 μm and 190 μm. By adjusting the average thickness of the positive electrode active layer within the above range, the present invention can not only achieve high adhesion between the positive electrode active layer and the positive electrode current collector, but also achieve a high energy density of the positive electrode.

[0088] Furthermore, the positive electrode current collector can be made of a material that does not induce chemical changes in the battery and has high conductivity. For example, stainless steel, aluminum, nickel, titanium, calcined carbon, etc. can be used, and in the case of aluminum or stainless steel, materials that have been surface-treated with carbon, nickel, titanium, silver, etc. may be used. The average thickness of the current collector can be appropriately set between 3 μm and 500 μm, taking into consideration the conductivity and total thickness of the manufactured positive electrode.

[0089] The positive electrode according to the present invention, having the above-described configuration, not only has excellent high-temperature safety and lifespan characteristics, but also has the advantage of excellent energy density and rolling density.

[0090] <Manufacturing method for positive electrode>

[0091] Furthermore, the present invention provides a method for manufacturing the positive electrode according to the present invention as described above.

[0092] Specifically, the above method for manufacturing a positive electrode includes the steps of: applying a positive electrode slurry containing manganese iron lithium phosphate represented by the following chemical formula 1 to at least one surface of a positive electrode current collector (S1); and drying the applied positive electrode slurry to form a positive electrode active layer (S2).

[0093] [Chemical formula 1] Li 1+a Mn 1-b-c Fe b M 1 c PO4

[0094] In the above chemical formula 1, M 1 It is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. a, b, and c are such that -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.2.

[0095] Here, the application of the positive electrode slurry (S1) refers to the process of discharging the positive electrode slurry onto the surface of a moving positive electrode current collector to coat it. This process can be applied without particular limitations as long as it is a method commonly used in the industry, but preferably a die coating method can be used. The die coating method can be performed via a slot die equipped with shims for controlling the discharge conditions of the positive electrode slurry. In this case, by controlling the shape, position, etc., of the shims, the loading amount and coating thickness of the positive electrode slurry applied onto the positive electrode current collector can be easily controlled.

[0096] Furthermore, the above-mentioned positive electrode slurry is intended to form the positive electrode active layer of the positive electrode. Therefore, the above-mentioned positive electrode slurry mainly contains positive electrode active material and may further contain conductive materials, binders, etc., as needed. Here, the composition of the positive electrode active material, conductive materials, binders, etc. contained in the positive electrode slurry is the same as that of the positive electrode active layer of the positive electrode described above, so a detailed explanation is omitted.

[0097] However, the above-mentioned positive electrode active material may be manufactured by a predetermined process. Generally, conventional olivine-structured positive electrode active materials are manufactured by mixing precursor compounds containing each transition metal with lithium phosphate, which is a lithium raw material, and calcining these mixtures at high temperatures. However, the positive electrode active material of the present invention can be manufactured by first producing manganese iron lithium phosphate represented by chemical formula 6 by calcining a mixture of manganese precursor compound, iron precursor compound, and lithium phosphate, and then mixing in precursor compounds of the doping and / or substitution metals and calcining the mixture.

[0098] Specifically, the above-mentioned positive electrode active material can be produced 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 at 500°C to 1,000°C, 500°C to 900°C, 500°C to 800°C, or 500°C to 750°C.

[0099] [Chemical formula 6] Li 1+m Mn 1-n Fe n PO4

[0100] In the above chemical formula 6, m and n are -0.5 ≤ m ≤ 0.5 and 0.1 ≤ n ≤ 0.8, respectively.

[0101] The present invention prevents over-sintering of the material due to temperatures exceeding the upper limit by performing firing within the temperature range described above during the manufacturing of the positive electrode active material. Furthermore, by promoting bonding between the compound represented by chemical formula 6 and the metal precursor compound within the temperature range described above, while minimizing the evaporation of lithium during firing, the density of the manufactured positive electrode active material can be increased. Highly dense particles refer to densely packed particles arranged within a specific volume, and the higher the density of the particles, the higher the rolling density and strength after rolling can be realized.

[0102] The compound represented by chemical formula 6 can be pre-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 chemical formula 6 can undergo a total calcination process for 1 to 6 hours, or 1 to 3 hours, before being mixed with the metal precursor compound. In this case, the temperature at which the total calcination process is carried out may be 500°C to 800°C, or 550°C to 750°C. The present invention significantly reduces the water content present in the manganese iron lithium phosphate by performing the heat treatment of the manganese iron lithium phosphate represented by chemical formula 6 under the above conditions before mixing with the metal precursor compound. As a result, the metal contained in the metal precursor compound can be easily doped or substituted at the iron atomic positions within the manganese iron lithium phosphate. However, at temperatures lower than the above-mentioned temperature range, there is a limitation that the water in the manganese iron lithium phosphate cannot be sufficiently removed, and at temperatures higher than the above-mentioned temperature range, the crystallinity of the manganese iron lithium phosphate increases further, making metal doping and / or substitution rather difficult.

[0103] The heat-treated compound of chemical formula 6 can be mixed with a metal precursor compound and calcined, thereby producing the positive electrode active material of the present invention. Here, the metal precursor compound refers to a raw material that supplies titanium (Ti), vanadium (V), zirconium (Zr), niobium (Nb), etc., to manganese iron lithium phosphate represented by chemical formula 6. The metal precursor compound is not particularly limited as long as it can provide titanium (Ti), vanadium (V), zirconium (Zr), and / or niobium (Nb).

[0104] Preferably, the titanium (Ti) precursor compound may contain one or more titanium oxides or titanium alkoxides containing titanium (Ti) as a component. For example, the titanium (Ti) precursor compound may, but is not limited to, titanium oxides such as TiO and TiO2 or titanium alkoxides such as Ti[OCH(CH3)2]4.

[0105] Furthermore, 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 oxides such as VO2, V2O3, and V2O5, or ammonium vanadate (NH4VO3).

[0106] The above zirconium (Zr) precursor compound may be a zirconium-containing oxide, a zirconium-containing acetate, or a combination thereof. For example, the above zirconium (Zr) precursor compound may be zirconium oxide such as ZrO2, or Zr6O4(OH)4(O2CCH3) 12 This may include, but is not limited to, the following:

[0107] Furthermore, the above niobium (Nb) precursor compound may be a niobium-containing acetate, nitrate, sulfate, halide, sulfide, hydroxide, oxide, oxyhydroxide, or a combination thereof. For example, the above niobium (Nb) precursor compound may be, but is not limited to, niobium oxide such as NbO, NbO2, Nb2O5; niobium salts such as NbCO3, Nb(NO3)2, NbSO4, niobium acetate, niobium dicarboxylic acid salt, niobium citrate, niobium fatty acid salt; niobium oxyhydroxide; niobium chloride; or a combination thereof.

[0108] On the other hand, the above method for manufacturing the positive electrode may include a step of forming a positive electrode active layer from the coated positive electrode slurry. The step of forming the positive electrode active layer may mean a step of drying the positive electrode slurry. In this case, the drying of the positive electrode slurry can be applied without particular limitations as long as it is a method that is commonly applied in the industry. For example, the drying can be performed by applying thermal energy to the positive electrode slurry using a hot air dryer, a vacuum oven, or the like.

[0109] Furthermore, 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 overall density of the positive electrode active layer by applying pressure to the surface of the formed positive electrode active layer using a roll press or the like. For this purpose, the rolling can be carried out under predetermined pressure and speed conditions under a temperature higher than room temperature.

[0110] Specifically, the rolling described above can be carried out at temperatures of 50°C to 100°C, more specifically at temperatures of 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.

[0111] Furthermore, the above rolling can be carried out at rolling speeds of 2 m / s to 7 m / s, more specifically at rolling speeds of 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.

[0112] Furthermore, the rolling described above can be carried out under pressure conditions of 50 MPa to 200 MPa, specifically under pressure conditions 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.

[0113] The present invention makes it possible to maximize the energy density of the positive electrode active layer while minimizing damage to the positive electrode active layer formed by rolling under the above temperature, speed, and / or pressure conditions.

[0114] The method for manufacturing a positive electrode according to the present invention, having the above-described configuration, can produce a positive electrode with excellent energy density.

[0115] The present invention will be described in more detail below with reference to examples and comparative examples.

[0116] However, the following examples and comparative examples are illustrative of the present invention, and the content of the present invention is not limited to the following examples and comparative examples.

[0117] <Manufacturing Example 1-7. Manufacturing of Cathode Active Material>

[0118] First, the positive electrode active material was prepared. Specifically, manganese iron lithium (LiMn) phosphate. 0.7 Fe 0.3Lithium iron manganese phosphate (PO4) was purchased from the market. Titanium dioxide (TiO2), ammonium vanadate (NH4VO3), and niobium oxide (Nb2O5) were mixed with the purchased lithium iron manganese phosphate and calcined at 700±20°C under a nitrogen atmosphere to produce a positive electrode active material. At this time, the amounts of titanium dioxide (TiO2), ammonium vanadate (NH4VO3), and niobium oxide (Nb2O5) mixed were adjusted so that the mole fraction of the metal contained in the metal precursor compound satisfies Table 1, based on a mole fraction of 1 for the total metal excluding lithium in the produced positive electrode active material. Table 1 also shows whether or not the lithium iron manganese phosphate purchased from the market was heat-treated before mixing with the metal precursor compound.

[0119] X-ray diffraction (XRD) was performed on the manufactured positive electrode active material to measure (1) lattice constants a, b, and c, and (2) the X-axis size indicating the grain size. Specifically, manganese iron lithium phosphate (LiMn) 0.7 Fe 0.3X-ray diffraction spectroscopy was performed using the Rietveld refinement method, taking into account the doped and / or substituted metals within PO4. For this analysis, the sample was placed in the groove of a general powder holder using a LynxEye XE-T position-sensitive detector or a Bruker D8 Endeavor (Cu-Kα, λ=1.54Å) equipped with a LynxEye position-sensitive detector. The sample surface was then homogenized using a slide glass, and after filling the holder so that the sample height matched the edge, measurements were taken under the conditions of FDS 0.5°, step size = 0.02° for the 2θ = 15°~90° region, and total scan time = approximately 20 minutes. When analyzing grain size, instrumental broadening was considered using the Fundamental Parameter Approach (FPA) built into the Bruker TOPAS program, and the overall peak of the measurement range was used during fitting. The peak shape was fitted using the Lorentzian contribution as the first principle (FP) from the peak shapes available in TOPAS, without considering strains. The measured lattice constant c and grain size (i.e., X-axis size) are shown in Table 1, and the correlation between lattice constant c and lattice constants a and b is shown in Figure 1. Referring to Figure 1, it was confirmed that lattice constant c shows a linear relationship with lattice constants a and b, and that it moves towards the lower right end as the lithium (Li) concentration in the structure increases. Furthermore, it was confirmed that the linear relationship appears as the type of metal doping and / or substitution in the positive electrode active material increases, and that it follows Vegard's law.

[0120] In addition, particle size distribution (PSD) analysis was performed on the above positive electrode active material to determine the (3)D of the positive electrode active material. 10 , D 50 and D 90Measure and from the measured value D 90 / D 10 The particle size distribution was calculated. Specifically, particle size distribution analysis (PSD) was performed using the laser diffraction method. A Malvern Mastersizer 3000 was used as the PSD analyzer, and the laser refractive index was adjusted to 2.0-2.2. Using an ultrasonic irradiator installed inside the device, each positive electrode active material weighing less than 1g was dispersed in deionized water (DI water). Then, the difference in diffraction patterns corresponding to the particle size as the dispersed particles passed through the laser beam was measured to calculate the particle size distribution. At this time, the diameter of the particle at the point where the cumulative area distribution by particle size in the measuring device reaches 10% was calculated, and D 10 It can measure D 50 and D 90 The same method was used for measurement. The measured and calculated results are shown in Table 1 below.

[0121] Finally, the rolling density of each positive electrode active material was measured. Specifically, 5g of positive electrode active material was weighed and filled into a cylindrical holder, and the powder density was measured while increasing the pressure in 400kgf increments from 400kgf to 9,000kgf. As a result, the rolling density of the positive electrode active material at 9,000kgf is shown in Table 1 below.

[0122] [Table 1]

[0123] <Examples 1-6 and Comparative Example 1. Manufacturing of the positive electrode>

[0124] N-methylpyrrolidone solvent was injected into a homo mixer, and 90 parts by weight of each positive electrode active material produced in Production Examples 1-7 above, 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. The mixture was then mixed at 3,000 rpm for 60 minutes to prepare a positive electrode slurry. An aluminum sheet (average thickness: 12 μm) was prepared as a positive electrode current collector, and the previously produced positive electrode slurry was cast onto one side of the prepared aluminum sheet. The aluminum sheet with the cast positive electrode slurry was dried in a vacuum oven at 130°C, and then rolled to produce a positive electrode. At this time, the total thickness of the rolled positive electrode active layer was 150 μm.

[0125] [Table 2]

[0126] <Example of experiment>

[0127] The following experiment was conducted to evaluate the performance of the positive electrode according to the present invention.

[0128] First, a lithium metal disk was prepared as the negative electrode. The prepared negative electrode was placed opposite the positive electrodes prepared in Examples 1-6 and Comparative Example 1, respectively, and an electrode assembly was fabricated by interposing a separator made of 18 μm polypropylene between them. Each of the fabricated electrode assemblies was inserted into a battery case, and after injecting the electrolyte composition into the battery case, the case was sealed to produce a half-cell. At this time, the electrolyte composition used was a solution prepared by mixing lithium hexafluorophosphate (LiPF6, 1.0 M) with a mixture of ethylene carbonate (EC) and ethyl methyl carbonate (EMC) in a 1:1 (volume ratio).

[0129] The fabricated half-cell was charged at 25°C with a constant current of 0.1C until the voltage reached 4.25V, and then discharged with a constant current of 0.1C until the voltage reached 2.5V. During this time, the capacities during charging and discharging were measured to confirm the initial charging capacity and initial discharging capacity, and the initial charge-discharge efficiency (@0.1C) was calculated by estimating the ratio of the initial discharging capacity to the initial charging capacity.

[0130] Separately, in order to evaluate the output characteristics of each positive electrode, the previously discharged half-cells were charged at 25°C until the State of Charge (SOC) reached 50%, and their resistance was measured. At this time, the voltage drop when current was applied was measured as the resistance, and the results are shown in Table 3 below.

[0131] [Table 3]

[0132] As shown in Table 3 above, the positive electrode according to the present invention has a high energy density and excellent output performance.

[0133] Specifically, the half-cells including the positive electrode in the examples exhibited excellent energy density, with initial charge / discharge capacities of 150 mAh / g or more and 145 mAh / g or more, respectively, and a high initial charge / discharge efficiency of 97% or more.

[0134] Furthermore, the half-cell including the positive electrode of the example was shown to have a low resistance of less than 19 mΩ at room temperature of 25°C.

[0135] From this, it can be seen that the cathode active material according to the present invention contains manganese iron lithium phosphate with an olivine structure, which not only provides high structural safety, but also allows for easy control of the particle size distribution by doping and / or substituting one or more metals within the crystal structure. Therefore, it can be seen that a cathode containing this material exhibits a significant improvement in energy density.

[0136] While preferred embodiments of the present invention have been described above with reference to those preferred in the art, a person skilled in the art or a person with ordinary knowledge of the art will understand that the present invention can be modified and altered in various ways without departing from the spirit and technical domain of the invention as described in the claims below.

[0137] Therefore, the technical scope of the present invention is not limited to what is described in the summary of the invention in the specification, but can be defined by the claims.

Claims

1. Positive electrode current collector, and The positive electrode current collector is provided on at least one surface and includes a positive electrode active layer containing a compound represented by the following chemical formula 1 as the positive electrode active material, [Chemical formula 1] Li １＋ａ Mn １－ｂ－ｃ Fe ｂ M １ ｃ PO ４ In the aforementioned chemical formula 1, M １ is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. a, b, and c are positive poles where -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.

2.

2. The positive electrode active material includes one or more compounds represented by the following chemical formulas 2 to 5: [Chemical formula 2] Li １＋ａ Mn １－ｂ－ｘ Fe ｂ Today ｘ PO ４ [Chemical formula 3] Li １＋ａ Mn １－ｂ－ｘ－ｙ Fe ｂ Today ｘ V ｙ PO ４ [Chemical formula 4] Li １＋ａ Mn １－ｂ－ｘ－ｙ－ｚ Fe ｂ Today ｘ V ｙ N﹂ ｚ PO ４ [Chemical formula 5] Li １＋ａ Mn １－ｂ－ｘ－ｙ－ｚ Fe ｂ Today ｘ Zr ｙ N﹂ ｚ PO ４ In the aforementioned chemical formulas 2 to 5, The positive electrode according to claim 1, wherein a, b, x, y, and z satisfy -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0 < x ≤ 0.2, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and 0.001 ≤ x + y ≤ 0.2 or 0.001 ≤ x + y + z ≤ 0.

2.

3. The positive electrode active material has a lattice constant c of 4.69165 Å to 4.80 Å as determined by X-ray diffraction analysis, and satisfies the following equation 1. [Formula 1] y = -px + q In the above formula 1, y represents the lattice constant c, x is √(a ２ +b ２ ) is expressed as, where a and b are lattice constants a and b, respectively. The positive electrode according to claim 1 or 2, wherein p and q are -0.08 ≤ p ≤ -0.07 and 5 ≤ q ≤ 6, respectively.

4. The average particle size (D) of the positive electrode active material ５０ The positive electrode according to claim 1, wherein the diameter is 0.7 μm to 1.3 μm.

5. The aforementioned positive electrode active material has a particle size distribution of 5.5 to 9.0 D ９０ / D １０ A positive electrode according to claim 1 or 2, having the following characteristics.

6. The positive electrode active material is D, which is 0.2 μm or more and less than 0.6 μm. １０ The positive electrode according to claim 5, having the following characteristics.

7. The positive electrode according to claim 1, wherein the rolling density of the positive electrode active material when pressurized at 9,000 kgf is 2.3 g / cc or more.

8. The steps include: applying a positive electrode slurry containing a compound represented by the following chemical formula 1 as a positive electrode active material to at least one surface of the positive electrode current collector, and The process includes the step of drying the coated positive electrode slurry to form a positive electrode active layer, [Chemical formula 1] Li １＋ａ Mn １－ｂ－ｃ Fe ｂ M １ ｃ PO ４ In the aforementioned chemical formula 1, M １ is one or more of Ti, V, Zr, Sr, Sb, B, and Nb. A method for manufacturing a positive electrode according to claim 1, wherein a, b, and c satisfy -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, and 0.001 ≤ c ≤ 0.

2.

9. The positive electrode active material includes one or more compounds represented by the following chemical formulas 2 to 5: [Chemical formula 2] Li １＋ａ Mn １－ｂ－ｘ Fe ｂ Today ｘ PO ４ [Chemical formula 3] Li １＋ａ Mn １－ｂ－ｘ－ｙ Fe ｂ Today ｘ V ｙ PO ４ [Chemical formula 4] Li １＋ａ Mn １－ｂ－ｘ－ｙ－ｚ Fe ｂ Today ｘ V ｙ N﹂ ｚ PO ４ [Chemical formula 5] Li １＋ａ Mn １－ｂ－ｘ－ｙ－ｚ Fe ｂ Today ｘ Zr ｙ N﹂ ｚ PO ４ In the aforementioned chemical formulas 2 to 5, A method for manufacturing a positive electrode according to claim 8, wherein a, b, x, y, and z satisfy -0.5 ≤ a ≤ 0.5, 0.1 ≤ b ≤ 0.8, 0 < x ≤ 0.2, 0 < y ≤ 0.1, 0 < z ≤ 0.1, and 0.001 ≤ z + y + z ≤ 0.

2.

10. The positive electrode active material is produced by a step of calcining a mixture of manganese iron lithium phosphate, represented by the following chemical formula 6, and a metal precursor compound at a temperature of 500°C or higher. [Chemical formula 6] Li １＋ｍ Mn １－ｎ Fe ｎ PO ４ In the aforementioned chemical formula 6, A method for manufacturing a positive electrode according to claim 8, wherein m and n are -0.5 ≤ m ≤ 0.5 and 0.1 ≤ n ≤ 0.

8.

11. The method for producing a positive electrode according to claim 10, wherein the lithium iron manganese phosphate represented by chemical formula 6 is heat-treated at 500°C to 900°C before being mixed with the metal precursor compound.

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