Pretreatment method for positive electrode active material, positive electrode, and lithium secondary battery

Abstract

To provide a method capable of enhancing price competitiveness of a lithium secondary battery and achieving high capacity, high efficiency and long life characteristics by improving initial formation efficiency of a lithium-manganese-rich positive electrode active material to improve processability.SOLUTION: The present invention relates to a pre-treatment method for activating a lithium-manganese-rich positive electrode active material, and more particularly, to a pre-treatment method including performing charging and discharging under a condition that a charging current density (I1) is higher than a discharging current density (I2), and a positive electrode and a lithium rechargeable battery using the same.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for pretreating a positive electrode active material, a positive electrode, and a lithium secondary battery. [Background technology]

[0002] Lithium-manganese-rich (LMR) materials, which are used as cathode active materials for lithium secondary batteries, have a layered structure with an excess of lithium and a relatively high manganese content. LMR materials not only generate capacity through the oxidation-reduction of existing transition metals, but also apply a new principle of oxygen oxidation-reduction (O-redox) to generate high capacity. With a high proportion of low-cost manganese, they are attracting attention as an ultra-low-cost next-generation cathode active material.

[0003] However, LMR materials have the disadvantage of low coulombic efficiency during the formation cycle. This means that a significant portion of the lithium ions that are released from the positive electrode and inserted into the negative electrode during formation charging do not return to the positive electrode during formation discharging, but remain in the negative electrode, causing the battery to operate. This means that when designing a battery, a larger amount of negative electrode must be added than the actual capacity of the battery. Even if a low-cost material is used for the positive electrode, the increased amount of negative electrode increases costs, negating the cost advantage of the positive electrode material.

[0004] Therefore, in lithium secondary batteries using a positive electrode made of LMR material, it is necessary to improve the coulomb efficiency in the initialization cycle in order to reduce the N / P ratio and maximize the low cost advantages of the positive electrode itself. Summary of the Invention [Problem to be solved by the invention]

[0005] The present invention provides a method for improving the initialization efficiency of a lithium-manganese-rich positive electrode active material and improving processability, thereby increasing the price competitiveness of lithium secondary batteries and achieving high capacity, high efficiency, and long life characteristics. [Means for solving the problem]

[0006] In one embodiment, a pretreatment method for activating the lithium-manganese-rich positive electrode active material involves charging the material at a charging current density I 1 is the discharge current density I 2 The present invention provides a pretreatment method including charging and discharging at a higher temperature than the above.

[0007] In another embodiment, a positive electrode for a lithium secondary battery is provided, which has been pretreated by the above method.

[0008] In another embodiment, a lithium secondary battery pretreated by the method is provided, which includes the positive electrode, the negative electrode, and an electrolyte. [Effects of the Invention]

[0009] According to one embodiment of the pretreatment method, the initial formation efficiency of the lithium-manganese-rich positive electrode active material can be increased without increasing the formation time, and the discharge capacity and reversible discharge capacity ratio can be improved. [Brief explanation of the drawings]

[0010] [Figure 1] FIG. 1 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 3] FIG. 3 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. [Figure 4] FIG. 4 is a cross-sectional view schematically illustrating a lithium secondary battery according to an embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0011] Although specific embodiments will be described below in detail so that those skilled in the art can easily implement the present invention, the present invention may be embodied in various different forms and is not limited to the embodiments described herein.

[0012] The terms used herein are merely used to describe exemplary embodiments and are not intended to limit the present invention. The singular expressions include the plural expressions unless the context clearly indicates otherwise.

[0013] As used herein, "combinations thereof" refers to mixtures, laminates, composites, copolymers, alloys, blends, reaction products, and the like of compositions.

[0014] As used herein, the terms "comprise," "comprise," or "have" are intended to specify the presence of embodied features, numbers, steps, components, or combinations thereof, and should be understood as not precluding the possible presence or addition of one or more other features, numbers, steps, components, or combinations thereof.

[0015] In the drawings, the thickness of multiple layers and regions is exaggerated to clearly show them, and similar parts are designated by the same reference numerals throughout the specification. When a layer, film, region, plate, or other part is said to be "on" another part, this includes not only the case where it is "directly on" that other part, but also the case where there is another part between them. Conversely, when a part is said to be "directly on" that other part, it means that there is no other part between them.

[0016] Furthermore, the term "layer" as used herein includes not only shapes formed on the entire surface when observed in a plan view, but also shapes formed on a portion of the surface.

[0017] The average particle size can be measured by methods well known to those skilled in the art, such as using a particle size analyzer or a transmission electron microscope image or a scanning electron microscope image. Alternatively, the average particle size can be calculated by measuring using dynamic light scattering, counting the number of particles in each particle size range, and then calculating the average particle size. Unless otherwise defined, the average particle size may refer to the diameter (D50) of particles that make up 50% of the cumulative volume in a particle size distribution. Furthermore, unless otherwise defined, the average particle size may be determined by measuring the size (diameter or major axis length) of 20 or more randomly selected particles in a scanning electron microscope image to obtain a particle size distribution, and then taking the diameter (D50) of particles that make up 50% of the cumulative volume in the particle size distribution as the average particle size.

[0018] Here, "or" is not to be construed as exclusive; for example, "A or B" is to be construed as including A, B, A+B, etc.

[0019] The term "metal" is understood to include general metals, transition metals, and semimetals (metalloids).

[0020] Unless otherwise specified, "voltage" is a value measured based on the lithium oxidation-reduction reaction voltage (vs. Li / Li + (vs. Li / Li + )) means.

[0021] Pretreatment method for lithium-manganese-rich cathode active material Lithium-manganese-rich cathode active materials refer to cathode active materials for lithium secondary batteries containing a layered lithium-manganese composite oxide containing lithium, manganese, and oxygen. These materials have a lithium excess composition, where the lithium content is greater than 1 relative to the total amount of metals excluding lithium, and contain approximately 30 mol% or more of manganese relative to the total amount of metals excluding lithium. Lithium-manganese-rich materials have the advantages of being cost-competitive due to their high proportion of inexpensive manganese and of achieving high capacity through the oxidation-reduction of oxygen as well as transition metals. However, they suffer from low coulombic efficiency during the chemical formation process (the initial charge and discharge), resulting in high irreversible capacity. While it is possible to increase charge and discharge efficiency during chemical formation by simply reducing the current density, this increases the time required for the chemical formation process and reduces the battery production rate, limiting its practical application. In one embodiment, a pretreatment method is provided that appropriately adjusts the current density during chemical formation charge and discharge to improve the initial coulombic efficiency and discharge capacity without increasing the total chemical formation time.

[0022] The pretreatment can be understood as the first charge / discharge process after battery fabrication, and can be expressed as a chemical formation process or chemical formation cycle. For example, the pretreatment can be understood as a process of fabricating a lithium secondary battery including a positive electrode including the positive electrode active material, an electrode structure including a separator and a negative electrode, and injecting an electrolyte solution including a nonaqueous organic solvent and a lithium salt, and then performing the first one or more charge / discharge cycles.

[0023] The pretreatment process can be said to induce activation of the cathode active material, specifically, the pretreatment can activate an oxidation-reduction reaction of the cathode active material, such as an oxidation-reduction reaction by a transition metal and / or an oxidation-reduction reaction by oxygen. For example, the pretreatment can induce activation of an oxygen oxidation-reduction reaction through a change in the crystal structure of the lithium-manganese-rich cathode active material.

[0024] According to one embodiment, the pretreatment method for the lithium-manganese-rich positive electrode active material is performed at a charging current density I1 is the discharge current density I 2 This includes charging and discharging under conditions higher than the initial charge / discharge rate. The lithium-manganese-rich layered cathode active material may have better rate characteristics during charging than during discharging. By utilizing this characteristic and designing a higher current density during the initial charge than the initial discharge and performing pretreatment, charge / discharge efficiency can be significantly improved without increasing the total formation time, and the discharge capacity and reversible discharge capacity ratio can be improved. The current density can be expressed as a C-rate, for example, and the unit of C-rate can be C.

[0025] As mentioned above, the charging current density I 1 is the discharge current density I 2 The charge / discharge process may be the first charge / discharge process. 1 and discharge current density I 2 The range of each of the above is not particularly limited. For example, I 1 is over 0.1C, and I 2 can be less than 0.1C. In this case, I 1 may be, for example, 0.11C or more and 5C or less, 0.11C or more and 3C or less, 0.11C or more and 2C or less, 0.11C or more and 1C or less, or 0.11C or more and 0.5C or less (e.g., 0.12C or more and 5C or less, 0.12C or more and 3C or less, 0.12C or more and 2C or less, 0.12C or more and 1C or less, or 0.12C or more and 0.5C or less; 0.125C or more and 5C or less, 0.125C or more and 3C or less, 0.125C or more and 2C or less, 0.125C or more and 1C or less, or 0.125C or more and 0.5C or less; 0.2C or more and 5C or less, 0.2C or more and 3C or less, 0.2C or more and 2C or less, 0.2C or more and 1C or less, or 0.2C or more and 0.5C or less). 2 can be 0.001C to 0.09C, 0.005C to 0.09C, 0.01C to 0.09C, 0.05C to 0.085C, 0.055C to 0.08C, or 0.055C to 0.07C.

[0026] As another example, I1 is over 0.2C, and I 2 can be less than 0.2C. 1 For example, I may be 0.21 C or more and 5 C or less, 0.21 C or more and 3 C or less, 0.21 C or more and 2 C or less, or 0.21 C or more and 1 C or less. 2 can be 0.001C to 0.19C, 0.005C to 0.19C, 0.01C to 0.19C, or 0.05C to 0.19C, or 0.1C to 0.185C.

[0027] As an example, I 2 I against 1 Percentage I 1 / I 2 can be 1.1 to 30, e.g., 1.2 to 25, 1.3 to 22, 1.4 to 20, 1.1 to 20, 1.5 to 19, 2 to 15, 2.5 to 10, or 2.9 to 9. 1 / I 2 When the ratio satisfies the above range, the formation time does not increase, while the charge / discharge efficiency during formation can be significantly improved.

[0028] As an example, I 1 and I 2 Difference I 1 -I 2 may be 0.01C to 1.5C, for example, but not limited to, 0.02C to 1.2C, 0.03C to 1.0C, 0.01C to 1.0C, 0.04C to 0.95C, 0.07C to 0.7C, 0.1C to 0.5C, or 0.13C to 0.45C. 1 -I 2 When the value satisfies the above range, the formation time does not increase, while the charge / discharge efficiency during formation can be significantly improved.

[0029] According to one embodiment, I 1 The charging time T is determined by 1 and I 2 Discharge time T determined by 2 The total pretreatment time is I 1 >I 3 >I 2Satisfy I 3 Let the charge current density and discharge current density be I 3 The pretreatment time required may be substantially the same as or shorter than the time required when charging and discharging with the same settings. For example, 1 is set to above 0.1C, and I 2 The total pretreatment time required when the charge / discharge current density is set to less than 0.1 C may be substantially the same as or shorter than the pretreatment time required when charging / discharging is performed at the same charge / discharge current density of 0.1 C. That is, according to one embodiment, by designing the charge current density during formation to be higher than the discharge current density, charge / discharge efficiency can be significantly improved, but this does not increase the time required for formation or reduce the battery production rate, which is advantageous for application to actual processes.

[0030] According to one embodiment, the charge capacity C in the first charge / discharge by the pretreatment method 1 Discharge capacity C 2 Percentage C 2 / C 1 The coulomb efficiency can be 89.0% or more.

[0031] The upper limit voltage of the first charge in the pretreatment method may be 4.55 V or higher. By performing the first charge at an upper limit voltage of 4.55 V or higher, it is possible to activate the reversible capacity of the lithium-manganese-rich positive electrode active material through oxidation-reduction of oxygen as well as oxidation-reduction of the transition metal. The upper limit voltage during the first charge may be, for example, 4.60 V or 4.65 V or higher.

[0032] The pretreatment method may further include performing a second charge / discharge after the above-mentioned charge / discharge, wherein the charge current density and the discharge current density in the second charge / discharge are I 4 For example, I 4 ≧I 1 >I 2 Or I 4 >I 1 >I 2 Or I 1 >I 4 >I 2If the first and second charge / discharge cycles are performed under these conditions for pretreatment, the initial coulomb efficiency can be significantly improved, while the discharge capacity and reversible discharge capacity ratio can be improved.

[0033] The upper limit charge voltage in the second charge / discharge may be set lower than the upper limit charge voltage in the first charge / discharge. For example, the upper limit charge voltage in the second charge / discharge may be less than 4.55 V, such as 4.50 V or less. The upper limit voltage in the second charge / discharge may also be set in a high voltage range of 4.3 V or more, such as 4.3 V to 4.50 V or 4.4 V to 4.45 V. When the first and second charge / discharge cycles are performed under these conditions for pretreatment, the initial coulombic efficiency can be significantly improved, while the discharge capacity and reversible discharge capacity ratio can be increased.

[0034] In one embodiment, the charge capacity in the first charge / discharge is C 1 , discharge capacity is C 2 And I 1 >I 3 >I 2 Satisfy I 3 Assuming that the charge current density and discharge current density in the first charge / discharge are all I 3 The charging capacity in this case is C 3.1 , discharge capacity is C 3.2 The discharge capacity of the second charge / discharge is C 4 In that case, C 2 / C 1 >C 3.2 / C 3.1 can be satisfied, and C 4 / C 1 >C 4 / C 3.1That is, according to one embodiment, when the charge current density in the first charge / discharge is designed to be higher than the discharge current density, the initial charge / discharge efficiency may be higher than the initial charge / discharge efficiency when the charge / discharge is performed at a value between the charge current density and the discharge current density. Also, according to one embodiment, when the charge current density in the first charge / discharge is designed to be higher than the discharge current density, the reversible discharge capacity ratio, which is the ratio of the second discharge capacity to the first charge capacity, may be higher than the reversible discharge capacity ratio when the first charge / discharge is performed at a value between the charge current density and the discharge current density.

[0035] The reversible discharge capacity ratio is the charge capacity C 1 Discharge capacity C in the second charge / discharge 4 Percentage C 4 / C 1 In this regard, the first charge / discharge may refer to the first charge / discharge performed at a voltage of 4.55 V or higher, in which the charge current density is designed to be higher than the discharge current density according to one embodiment, and the second charge / discharge may refer to the first charge / discharge performed at a voltage lower than 4.55 V. According to one embodiment, the reversible discharge capacity ratio may be 81% or higher.

[0036] The reversible discharge capacity ratio can affect the N / P ratio, which is the ratio of the loading levels between the negative and positive electrodes in a full cell design. For example, a lower reversible discharge capacity ratio requires a higher negative electrode loading level to achieve the same positive electrode capacity, resulting in a decrease in total energy density. In other words, a higher reversible discharge capacity ratio can be more advantageous for increasing the energy density of a lithium secondary battery.

[0037] The lithium-manganese-rich cathode active material may exhibit capacity through an oxidation-reduction reaction of a transition metal while simultaneously exhibiting capacity through an oxidation-reduction reaction of oxygen. The pretreatment method may activate the lithium-manganese-rich cathode active material, for example, by activating the oxidation-reduction reaction of the transition metal and oxygen through a change in the crystalline structure of the cathode active material.

[0038] The lithium-manganese-rich positive electrode active material may be represented by, for example, a metal oxide containing at least one of Chemical Formula 1 and Chemical Formula 2.

[0039] [Chemical formula 1] Li 1+x1 (Ni y1 Mn z1 M 1 1-y1-z1 ) 1-x1 O 2-b1 X 1 b1

[0040] In the formula 1, 0.03≦x1≦0.33, 0.1≦y1≦0.7, 0.3≦z1≦0.9, and 0≦b1≦0.1; M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X 1 is one or more elements selected from F, P, and S. According to one embodiment, in the above formula 1, M 1 may not exist (i.e., 1-y1-z1=0). X 1 may not exist (i.e., b1=0), and as an example, M 1 and X 1 may not both exist (i.e., 1-y1-z1=0 and b1=0).

[0041] [Chemical formula 2] x2(LiNi y2 Mn z2 M 2 1-y2-z2 O2-b2 X 2 b2 )+x3(Li2(Mn t1 M 2 1-t1 )O 3-b3 X 2 b3 )

[0042] In the formula 2, 0≦x2≦0.94, 0.06≦x3≦1, 0.5≦x2+x3≦1, 0.5≦y2≦1.0, 0≦z2≦0.5, 0≦b2≦0.1, 0.9≦t1≦1, and 0≦b3≦0.1; M 2 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr, and X 2 is one or more elements selected from F, P, and S. According to one embodiment, in the above formula 2, M 2 may not exist (i.e., 1-y2-z2=0 and 1-t1=0), and X 2 may not exist (i.e., b2=0 and b3=0), and as an example, M 2 and X 2 may not both exist (i.e., 1-y2-z2=0 and 1-t1=0, and b2=0 and b3=0).

[0043] For example, it can be said that Chemical Formula 1 represents a solid-solution phase, and Chemical Formula 2 represents a composite phase. According to an embodiment, the positive electrode active material may include either the solid-solution phase represented by Chemical Formula 1 or the composite phase represented by Chemical Formula 2, or both. For example, the positive electrode active material may be a material in which the composite and the solid solution coexist, or a material in which the composite and the solid solution coexist competitively.

[0044] Here, a solid solution can refer to a solid mixture in which different elements are completely and uniformly mixed, with other elements evenly distributed within the solid crystals, similar to a solution in which a solute is evenly distributed within a solvent. A solid solution can also refer to a continuous quasi-isostructural compound formed by the strong interrelationship of two or more individual components, which has new properties. A solid solution can be homogeneous, have approximately the same composition, and have a single phase or a single crystal structure. In contrast, a composite can be composed of two or more materials that have different physical properties and maintain a physically distinct state. A composite can be heterogeneous, have two or more compositions, and have two or more phases or crystal structures.

[0045] In one embodiment, the lithium-manganese-rich active cathode material may have a lithium to total metals excluding lithium molar ratio of 1.06 or greater and 2 or less, for example, 1.06 to 1.8, 1.06 to 1.6, 1.06 to 1.5, 1.1 to 1.45, 1.1 to 1.4, 1.1 to 1.3, 1.1 to 1.2, 1.2 to 1.8, 1.2 to 1.5, or 1.3 to 1.45.

[0046] In Chemical Formula 1, (1 + x1) is the molar ratio of lithium, and (1 + x1) / (1 - x1) means the ratio of the lithium content to the total metal content excluding lithium. The range of x1 in Chemical Formula 1 is 0.03≦x1≦0.33, for example, 0.03≦x1≦0.30, 0.03≦x1≦0.2, for example, 0.03≦x1≦0.15, 0.03≦x1≦0.13, 0.03≦x1≦0.11, or 0.03≦x1≦0.09.

[0047] According to an embodiment, the lithium-manganese-rich positive electrode active material may contain nickel. In this case, the nickel content may be 10 mol% to 70 mol%, for example, 20 mol% to 65 mol%, 25 mol% to 60 mol%, 25 mol% to 40 mol%, or 40 mol% to 65 mol%, based on 100 mol% of the total metals excluding lithium. For example, the positive electrode active material may be a mid-nickel material having a nickel content of 45 mol% to 70 mol%, a low-nickel material having a nickel content of 10 mol% to less than 45 mol%, or a mixture thereof. Increasing the nickel content in the lithium-manganese-rich positive electrode active material can improve capacity, or decreasing the nickel content can reduce production costs and appropriately limit the specific gravity of oxygen oxidation-reduction.

[0048] In Chemical Formula 1, y1 represents the molar ratio of nickel in the solid solution phase and satisfies 0.1≦y1≦0.7, and may be, for example, 0.2≦y1≦0.66, 0.25≦y1≦0.6, 0.25≦y1≦0.4, or 0.4≦y1≦0.66.

[0049] In Chemical Formula 2, y2 represents the nickel content of the layered material in the composite phase. The range of y2 satisfies 0.5≦y2≦1.0, and may be, for example, 0.5≦y2≦0.94, 0.5≦y2≦0.80, 0.55≦y2≦0.80, or 0.55≦y2≦0.75.

[0050] According to one embodiment, the manganese content in the lithium-manganese-rich cathode active material may be 30 mol% or more, based on 100 mol% of all metals excluding lithium, for example, 30 mol% to 90 mol%, 35 mol% to 80 mol%, 40 mol% to 75 mol%, 35 mol% to 60 mol%, or 60 mol% to 75 mol%. When the manganese content satisfies this range, it is possible to improve capacity while maintaining price competitiveness, and to appropriately adjust the capacity utilization rate due to oxygen oxidation-reduction to achieve long-life characteristics.

[0051] In Chemical Formula 1, z1 represents the molar ratio of manganese and satisfies 0.3≦z1≦0.9, and may be, for example, 0.35≦z1≦0.8, 0.4≦z1≦0.75, 0.35≦z1≦0.6, or 0.6≦z1≦0.75.

[0052] In one embodiment of the lithium-manganese-rich positive electrode active material, the cobalt content relative to 100 mol % of all metals excluding lithium may be 0 mol % to 1 mol %, or 0 mol % to 0.1 mol %, or 0 mol % to 0.01 mol %.

[0053] The positive electrode active material may be in the form of secondary particles formed by agglomeration of a plurality of primary particles. The positive electrode active material may have an average particle size D50 of 1 μm to 20 μm, for example, 5 μm to 15 μm or 8 μm to 12 μm. For example, the positive electrode active material may be a mixture of small particles having an average particle size D50 of 0.5 μm to 8 μm and large particles having an average particle size D50 of 9 μm to 20 μm. Here, the average particle size may be determined by measuring the size (e.g., particle size, major axis, or length) of approximately 20 random particles in an SEM image of the positive electrode active material, obtaining a particle size distribution, and then taking the size of the particles with a cumulative volume of 50% as the average particle size D50.

[0054] positive electrode In one embodiment, a positive electrode for a lithium secondary battery is provided, which is pretreated using the above-described method. The positive electrode includes a positive electrode current collector and a positive electrode active material layer disposed on the positive electrode current collector, the positive electrode active material layer including the lithium-manganese-rich positive electrode active material described above. The positive electrode active material layer may further include other positive electrode active materials in addition to the above-described positive electrode active material, and may optionally further include a binder, a conductive material, or a combination thereof.

[0055] binder The binder serves to firmly adhere the positive electrode active material particles to each other and to firmly adhere the positive electrode active material to the current collector. Representative examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethyl cellulose, hydroxypropyl cellulose, diacetyl cellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, vinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0056] Conductive material The conductive material is used to impart conductivity to the electrodes, and any material that does not cause chemical changes in the constructed battery and is electronically conductive can be used. Examples of the conductive material include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials containing copper, nickel, aluminum, silver, etc. in the form of metal powder or metal fiber; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0057] The content of the binder and the conductive material may be 0.5% by weight to 5% by weight, respectively, relative to 100% by weight of the positive electrode active material layer.

[0058] The positive electrode current collector can be made of Al, but is not limited to this.

[0059] Lithium secondary battery In one embodiment, a lithium secondary battery is provided that has been pretreated using the above-described method. The lithium secondary battery includes a positive electrode containing the lithium-manganese-rich positive electrode active material, a negative electrode, and an electrolyte. The lithium secondary battery may be a lithium ion battery using a liquid electrolyte, or an all-solid-state secondary battery or semi-solid-state secondary battery using a solid electrolyte. For convenience, the configuration of the lithium ion battery will be described in detail below.

[0060] Lithium secondary batteries can be classified into cylindrical, prismatic, pouch, and coin types depending on their shape. FIGS. 1 to 4 are schematic diagrams illustrating a lithium secondary battery according to an embodiment, with FIG. 1 illustrating a cylindrical battery, FIG. 2 illustrating a prismatic battery, and FIGS. 3 and 4 illustrating pouch types. Referring to FIGS. 1 to 4, a lithium secondary battery 100 may include an electrode assembly 40 including a positive electrode 10, a negative electrode 20, and a separator 30 interposed between them, and a case 50 housing the electrode assembly 40. The positive electrode 10, the negative electrode 20, and the separator 30 may be impregnated with an electrolyte (not shown). The lithium secondary battery 100 may include a sealing member 60 that seals the case 50, as shown in FIG. 1. The lithium secondary battery 100 in FIG. 2 may also include a positive electrode lead tab 11, a positive electrode terminal 12, a negative electrode lead tab 21, and a negative electrode terminal 22. As shown in FIGS. 3 and 4, the lithium secondary battery 100 may include electrode tabs 70, i.e., a positive electrode tab 71 and a negative electrode tab 72, which serve as electrical paths for conducting the current generated in the electrode assembly 40 to the outside.

[0061] negative electrode The negative electrode may include a current collector and a negative electrode active material layer disposed on the current collector. The negative electrode may further include a binder, a conductive material, or a combination thereof.

[0062] negative electrode active material The negative electrode active material includes a material capable of reversibly intercalating / deintercalating lithium ions, lithium metal, a lithium metal alloy, a material capable of being doped and dedoped with lithium, or a transition metal oxide.

[0063] As a substance capable of reversibly intercalating / deintercalating the lithium ions, a carbon-based negative electrode active material can be used, and for example, it can contain crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-like, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0064] As the alloy of the lithium metal, an alloy of lithium and a metal selected from Na, K, Rb, Cs, Fr, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ra, Ge, Al, and Sn (for example, Na, K, Rb, Cs, Be, Mg, Ca, Sr, Si, Sb, Pb, In, Zn, Ba, Ge, Al, and Sn) may be used.

[0065] As a substance capable of doping and undoping lithium, an Si-based negative electrode active material or an Sn-based negative electrode active material can be used. The Si-based negative electrode active material can be silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), an Si-Q alloy (where Q is an element selected from alkali metals, alkaline earth metals, group 13 elements, group 14 elements (excluding Si), group 15 elements, group 16 elements, transition metals, rare earth elements, and combinations thereof, for example, Mg, Ca, Sr, Ba, Ra, Sc, Y, Ti, Zr, Hf, Rf, V, Nb, Ta, Db, Cr, Mo, W, Sg, Tc, Re, Bh, Fe, Pb, Ru, Os, Hs, Rh, Ir, Pd, Pt, Cu, Ag, Au, Zn, Cd, B, Al, Ga, Sn, In, Tl, Ge, P, As, Sb, Bi, S, Se, Te, Po, and combinations thereof), or a combination thereof. The Sn-based negative electrode active material can be Sn, SnOx (0 < x ≤ 2), SnO2, an Sn alloy, or a combination thereof.

[0066] The silicon-carbon composite may be a composite of silicon and amorphous carbon. The average particle size D50 of the silicon-carbon composite particles may be, for example, 0.5 μm to 20 μm. According to one embodiment, the silicon-carbon composite may be in the form of silicon particles and the surfaces of the silicon particles coated with amorphous carbon. For example, the silicon-carbon composite may include secondary particles (cores) formed by the aggregation of primary silicon particles and amorphous carbon coating layers (shells) located on the surfaces of the secondary particles. The amorphous carbon may also be located between the primary silicon particles; for example, the primary silicon particles may be coated with amorphous carbon. The secondary particles may be dispersed in an amorphous carbon matrix.

[0067] The silicon-carbon composite may further include crystalline carbon. For example, the silicon-carbon composite may include a core containing crystalline carbon and silicon particles, and an amorphous carbon coating layer located on the core surface. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. Examples of the amorphous carbon include soft carbon, hard carbon, mesophase pitch carbide, and calcined coke.

[0068] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10 to 50 wt % and the amorphous carbon content may be 50 to 90 wt % relative to 100 wt % of the silicon-carbon composite. When the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10 to 50 wt % and the crystalline carbon content may be 10 to 70 wt % and the amorphous carbon content may be 20 to 40 wt % relative to 100 wt % of the silicon-carbon composite.

[0069] Also, the thickness of the amorphous carbon coating layer can be 5 nm to 100 nm. The average particle size D50 of the silicon particles (primary particles) can be 10 nm to 1 μm, or 10 nm to 200 nm. The silicon particles may exist alone as silicon, or may exist in the form of a silicon alloy, or may exist in an oxidized form. The oxidized form of silicon can be represented as SiO x (0 < x ≤ 2). At that time, the atomic content ratio of Si:O indicating the degree of oxidation can be 99:1 to 33:67. Unless otherwise defined in this specification, the average particle size D50 means the diameter of particles with a cumulative volume of 50% in the particle size distribution.

[0070] The Si-based negative electrode active material or the Sn-based negative electrode active material can be used by mixing with a carbon-based negative electrode active material. When the Si-based negative electrode active material or the Sn-based negative electrode active material and the carbon-based negative electrode active material are used in combination, the mixing ratio can be 1:99 to 90:10 as a weight ratio.

[0071] binder The binder serves to make the negative electrode active material particles adhere well to each other and also make the negative electrode active material adhere well to the current collector. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0072] Examples of the non-aqueous binder include polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, ethylene-propylene copolymer, polystyrene, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, polyamideimide, polyimide, or a combination thereof.

[0073] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylate styrene-butadiene rubber, (meth)acrylonitrile-butadiene rubber, (meth)acrylic rubber, butyl rubber, fluororubber, polyethylene oxide, polyvinylpyrrolidone, polyepichlorohydrin, polyphosphazene, poly(meth)acrylonitrile, ethylene propylene diene copolymer, polyvinylpyridine, chlorosulfonated polyethylene, latex, polyester resin, (meth)acrylic resin, phenolic resin, epoxy resin, polyvinyl alcohol, and combinations thereof.

[0074] When an aqueous binder is used as the negative electrode binder, a cellulose-based compound that can impart viscosity can be further included. The cellulose-based compound can be a mixture of one or more of carboxymethyl cellulose, hydroxypropyl methyl cellulose, methyl cellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0075] The dry binder may be a polymeric substance that can be made into a fiber, such as polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0076] Conductive material The conductive material is used to impart conductivity to the electrodes, and any material that does not cause chemical changes in the constructed battery and is electronically conductive can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, ketjen black, carbon fiber, carbon nanofiber, and carbon nanotube; metal-based materials in the form of metal powder or metal fiber, including copper, nickel, aluminum, and silver; conductive polymers such as polyphenylene derivatives; and mixtures thereof.

[0077] The content of the negative electrode active material may be 95 wt% to 99.5 wt% relative to 100 wt% of the negative electrode active material layer, and the content of the binder may be 0.5 wt% to 5 wt% relative to 100 wt% of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90 wt% to 99 wt% of the negative electrode active material, 0.5 wt% to 5 wt% of the binder, and 0.5 wt% to 5 wt% of the conductive material.

[0078] current collector The negative electrode current collector can include, for example, indium (In), copper (Cu), magnesium (Mg), stainless steel, titanium (Ti), iron (Fe), cobalt (Co), nickel (Ni), zinc (Zn), aluminum (Al), germanium (Ge), lithium (Li), or an alloy thereof, and can be in foil, sheet, or foam form. The thickness of the negative electrode current collector can be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0079] electrolyte The electrolyte for a lithium secondary battery may be, for example, an electrolytic solution, which may include a non-aqueous organic solvent and a lithium salt.

[0080] The non-aqueous organic solvent serves as a medium through which ions involved in the electrochemical reaction of the battery can migrate, and may be a carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvent, an aprotic solvent, or a combination thereof.

[0081] Examples of carbonate solvents that may be used include dimethyl carbonate (DMC), diethyl carbonate (DEC), dipropyl carbonate (DPC), methyl propyl carbonate (MPC), ethyl propyl carbonate (EPC), methyl ethyl carbonate (MEC), ethylene carbonate (EC), propylene carbonate (PC), butylene carbonate (BC), etc. Examples of ester solvents that may be used include methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. Examples of ether solvents that may be used include dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran. Examples of ketone solvents that may be used include cyclohexanone. Examples of alcohol solvents that may be used include ethyl alcohol and isopropyl alcohol. Examples of aprotic solvents that may be used include nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, which may contain a double bond, an aromatic ring, or an ether group); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes.

[0082] The non-aqueous organic solvents can be used alone or in combination of two or more kinds. When two or more kinds are used in combination, the mixing ratio can be appropriately adjusted depending on the desired battery performance, which is widely understood by those working in this field.

[0083] When a carbonate-based solvent is used, a cyclic carbonate and a chain carbonate can be mixed and used, and the cyclic carbonate and the chain carbonate can be mixed in a volume ratio of 1:1 to 1:9.

[0084] The non-aqueous organic solvent may further include an aromatic hydrocarbon-based organic solvent, for example, a carbonate-based solvent and an aromatic hydrocarbon-based organic solvent may be mixed in a volume ratio of 1:1 to 30:1.

[0085] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate based compounds to improve battery life.

[0086] Representative examples of the ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0087] Lithium salts are substances that dissolve in organic solvents and act as a source of lithium ions within the battery, enabling basic lithium secondary battery operation and facilitating the movement of lithium ions between the positive and negative electrodes. Representative examples of lithium salts include LiPF6, LiBF4, LiSbF6, LiAsF6, LiClO4, LiAlO2, LiAlCl4, LiPO2F2, LiCl, LiI, LiN(SO3C2F5)2, Li(FSO2)2N (lithium bis(fluorosulfonyl)imide; LiFSI), LiC4F9SO3, and LiN(C x F2 x+1 SO2)(C y F 2y+1 SO2) (x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethersulfonate, lithium difluorobis(oxalato)phosphate (LiDFBOP), and lithium bis(oxalato)borate (LiBOB).

[0088] The concentration of the lithium salt is preferably in the range of 0.1 M to 2.0 M. When the concentration of the lithium salt is within this range, the electrolyte has appropriate ionic conductivity and viscosity, thereby exhibiting excellent performance and allowing lithium ions to migrate effectively.

[0089] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive electrode and the negative electrode. Such separators may be made of polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more of these materials, including mixed multilayer films such as a polyethylene / polypropylene two-layer separator, a polyethylene / polypropylene / polyethylene three-layer separator, or a polypropylene / polyethylene / polypropylene three-layer separator.

[0090] The separator may include a porous substrate and a coating layer including an organic material, an inorganic material, or a combination thereof located on one or both sides of the porous substrate.

[0091] The porous substrate may be a polymer membrane formed from any one polymer selected from polyolefins such as polyethylene and polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyether ketone, polyaryl ether ketone, polyetherimide, polyamide imide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, Teflon (registered trademark), and polytetrafluoroethylene, or a copolymer or mixture of two or more of these polymers.

[0092] The porous substrate can have a thickness of about 1 μm to 40 μm, such as 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0093] The organic material may include a (meth)acrylic copolymer including a first structural unit derived from (meth)acrylamide and a second structural unit including at least one of a structural unit derived from (meth)acrylic acid or a (meth)acrylate and a structural unit derived from (meth)acrylamidosulfonic acid or a salt thereof.

[0094] The inorganic substances include Al2O3, SiO2, TiO2, SnO2 The inorganic particles may include, but are not limited to, inorganic particles selected from CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The inorganic particles may have an average particle size D50 of 1 nm to 2000 nm, for example, 100 nm to 1000 nm, or 100 nm to 700 nm.

[0095] The organic material and the inorganic material may be mixed in one coating layer, or may be stacked in a coating layer containing an organic material and a coating layer containing an inorganic material.

[0096] The thickness of each of the coating layers may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0097] Examples of the present invention and comparative examples are described below. The following examples are merely examples of the present invention, and the present invention is not limited to the following examples.

[0098] Comparative Example 1 1. Manufacture of lithium secondary batteries Ni 0.5 Mn 0.5(OH)2 and LiOH were mixed so that the molar ratio of Li / (Ni+Mn) was 1.1, and the temperature was increased at a rate of 5°C / min in an oxygen atmosphere, and the heat treatment temperature was maintained at 950°C. After that, the temperature was cooled to room temperature at a rate of 5°C / min for a total of 24 hours. 1.05 Ni 0.48 Mn 0.48 O2] + 0.57 [0.85(LiNi 0.56 Mn 0.44 O2) + 0.10(Li2MnO3)] was produced.

[0099] 96 wt% of the prepared positive electrode active material, 2 wt% of polyvinylidene fluoride binder, and 2 wt% of carbon nanotube conductive material were mixed to prepare a positive electrode active material layer slurry, which was then coated on an aluminum foil current collector, dried, and rolled to prepare a positive electrode. At this time, the loading level of the positive electrode active material layer was 10 mg / cm. 2 and the density of the final rolled cathode is about 3.5 g / cc.

[0100] The fabricated positive electrode and lithium counter electrode were inserted into a battery case with a polytetrafluoroethylene separator interposed between them, and an electrolyte solution prepared by dissolving 1M LiPF in a solvent made by mixing ethylene carbonate, ethyl methyl carbonate, and dimethyl carbonate in a volume ratio of 2:4:4, to which 1.5 wt % vinylene carbonate had been added, was poured into the case, and a lithium secondary battery was fabricated in a conventional manner.

[0101] 2. Pretreatment process The lithium secondary battery prepared in Example 1 was charged at a constant current of 0.1 C at 25° C. up to 4.65 V, and then the voltage was maintained until the current value reached 0.05 C. After that, the battery was discharged at a constant current of 0.1 C down to 2.5 V, thereby carrying out the first charge-discharge cycle. The 0.1 C constant current charge took 10 hours, and the 0.1 C constant current discharge took 10 hours, totaling 20 hours.

[0102] Next, the battery was charged to 4.45 V at a constant current of 0.2 C at 25°C, and then the voltage was maintained until the current value reached 0.05 C, after which it was discharged to 2.5 V at a constant current of 0.2 C to perform the second charge-discharge.

[0103] The comparative examples and examples were all carried out under the condition of 1C=200mA / g.

[0104] Example 1 A lithium secondary battery was fabricated and pretreated in substantially the same manner as in Comparative Example 1, except that the first charge / discharge step was performed by charging at a constant current of 0.125 C at 25° C. up to 4.65 V, maintaining the voltage until the current reached 0.05 C, and then discharging at a constant current of 0.083 C down to 2.5 V. The 0.125 C constant current charge took 8 hours, and the 0.083 C constant current discharge took 12 hours, totaling 20 hours.

[0105] Example 2 A lithium secondary battery was fabricated and pretreated in substantially the same manner as in Comparative Example 1, except that the first charge / discharge step was performed by charging at a constant current of 0.2 C at 25° C. up to 4.65 V, maintaining the voltage until the current reached 0.05 C, and then discharging at a constant current of 0.067 C down to 2.5 V. The 0.2 C constant current charge took 5 hours, and the 0.067 C constant current discharge took 15 hours, totaling 20 hours.

[0106] Example 3 A lithium secondary battery was fabricated and pretreated in substantially the same manner as in Comparative Example 1, except that the first charge / discharge step was performed by charging at a constant current of 0.5 C at 25° C. up to 4.65 V, maintaining the voltage until the current reached 0.05 C, and then discharging at a constant current of 0.056 C down to 2.5 V. The 0.5 C constant current charge took 2 hours, and the 0.056 C constant current discharge took 18 hours, totaling 20 hours.

[0107] Example 4 A lithium secondary battery was fabricated and pretreated in substantially the same manner as in Comparative Example 1, except that the first charge / discharge step was performed by charging at a constant current of 1.0 C at 25° C. up to 4.65 V, maintaining the voltage until the current reached 0.05 C, and then discharging at a constant current of 0.053 C down to 2.5 V. The 1.0 C constant current charge took 1 hour, and the 0.053 C constant current discharge took 19 hours, totaling 20 hours.

[0108] Comparative Example 2 A lithium secondary battery was manufactured and pretreated in a manner substantially similar to that of Comparative Example 1, except that in the pretreatment process, the battery was charged to 4.65 V at a constant current of 0.056 C at 25° C., and then the voltage was maintained until the current value reached 0.05 C, and then the battery was discharged to 2.5 V at a constant current of 0.5 C, thereby performing the first charge-discharge step.

[0109] Comparative Example 3 A positive electrode active material and a lithium secondary battery were manufactured and pretreated in substantially the same manner as in Comparative Example 1, except that the molar ratio of Ni and Mn in the preparation of the positive electrode active material precursor was changed to 33:67. The positive electrode active material according to Comparative Example 3 was prepared using a 0.67(LiNi 0.50 Mn 0.50 O2) + 0.33(Li2MnO3).

[0110] Example 5 A lithium secondary battery was fabricated and pretreated in substantially the same manner as in Comparative Example 3, except that in the pretreatment process, the first charge / discharge was performed by charging at a constant current of 0.5 C at 25° C. up to 4.65 V, maintaining the voltage until the current value reached 0.05 C, and then discharging at a constant current of 0.056 C down to 2.5 V. The 0.5 C constant current charge took 2 hours, and the 0.056 C constant current discharge took 18 hours, totaling 20 hours.

[0111] Evaluation example 1 For Examples 1 to 4 and Comparative Examples 1 and 2, the charge capacity and discharge capacity after the first chemical formation were measured and are shown in Table 1 below. The ratio of the discharge capacity to the first charge capacity is shown as the coulomb efficiency in Table 1 below. The charge capacity and discharge capacity after the second chemical formation were also measured and are shown in Table 1 below. The ratio of the second discharge capacity to the first charge capacity is shown as the reversible discharge capacity ratio in Table 1 below.

[0112] [Table 1]

[0113] Referring to Table 1, it can be seen that Examples 1 to 3 were improved in all respects, with an increased discharge capacity and improved coulombic efficiency in the first formation cycle, an increased discharge capacity and improved reversible discharge capacity ratio in the second formation cycle, compared to Comparative Example 1. It can be seen that Example 4 was improved in all respects, with an increased discharge capacity and coulombic efficiency in the first formation cycle, an increased discharge capacity in the second formation cycle, and a comparable reversible discharge capacity ratio, compared to Comparative Example 1.

[0114] Evaluation example 2 For Example 5 and Comparative Example 3, the charge capacity and discharge capacity after the first chemical formation were measured and are shown in Table 2 below. The ratio of the discharge capacity to the first charge capacity is shown as coulomb efficiency in Table 2 below. The charge capacity and discharge capacity after the second chemical formation were measured and are shown in Table 2 below. The ratio of the second discharge capacity to the first charge capacity is shown as reversible discharge capacity ratio in Table 2 below.

[0115] [Table 2]

[0116] Referring to Table 2, it can be seen that Example 5 had an increased discharge capacity and improved coulombic efficiency in the first chemical cycle compared to Comparative Example 3, and an increased discharge capacity and improved reversible discharge capacity ratio in the second chemical cycle.

[0117] Referring to Tables 1 and 2, Evaluation Example 1 is an evaluation of a mid-nickel LMR material, and Evaluation Example 2 is an evaluation of a low-nickel LMR material. However, regardless of the type of material or nickel content, applying a pretreatment method according to an embodiment significantly improves the initial charge / discharge efficiency during formation, increases the first and second discharge capacities, and improves the reversible discharge capacity ratio. It can also be seen that this strategy is applicable to all types of LMR materials.

[0118] Although the preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto, and various modifications and improvements made by those skilled in the art using the basic concepts defined in the following claims also fall within the scope of the present invention. [Explanation of symbols]

[0119] 100: Lithium secondary battery 10: Positive electrode 11: Positive electrode lead tab 12: Positive terminal 20: Negative electrode 21: Negative electrode lead tab 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode tab 71: Positive electrode tab 72: Negative electrode tab

Claims

1. 1. A pretreatment method for activating a lithium-manganese-rich positive electrode active material, comprising: Charging current density (I 1 ) is the discharge current density (I 2 ) charging and discharging at a higher condition than the

2. I 2 I against 1 The ratio (I 1 / I 2 2. The pretreatment method according to claim 1, wherein the ratio of the number of ions to the number of particles is 1.1 to 30.

3. I 1 and I 2 When expressed as C-rate, I 1 and I 2 The difference between (I 1 -I 2 2. The pretreatment method according to claim 1, wherein the temperature is 0.01C to 1.5C.

4. I 1 and I 2 When expressed as C-rate, I 1 is more than 0.1C, and I 2 is less than 0.1 C, or I 1 is over 0.2C, and I 2 The pretreatment method of claim 1 , wherein the temperature is less than 0.2 C.

5. I 1 The charging time (T 1 ) and I 2 The discharge time (T 2 The total pretreatment time is I 1 >I 3 >I 2 Satisfy I 3 Let the charge current density and discharge current density be I 3 2. The pretreatment method according to claim 1, wherein the pretreatment time is substantially the same as or shorter than the time required for pretreatment when charging and discharging are performed under the same settings.

6. The charge capacity (C 1 ) to discharge capacity (C 2 ) ratio (C 2 / C 1 2. The pretreatment method according to claim 1, wherein the coulomb efficiency of the ion exchange reaction is 89.0% or more.

7. The upper limit of the charge voltage in the charge / discharge is 4.55 V (vs. Li / Li + 2. The pretreatment method according to claim 1, wherein the total amount of the sieve is 1000 ppm or more.

8. The pretreatment method further includes performing a second charge / discharge after the charge / discharge; The charge current density and discharge current density in the second charge / discharge are I 4 is the same as I 4 ≧I 1 >I 2 , or I 4 >I 1 >I 2 , or I 1 >I 4 >I 2 The pretreatment method according to claim 1 ,

9. The pretreatment method according to claim 8 , wherein the upper limit charge voltage in the second charge / discharge is lower than the upper limit charge voltage in the first charge / discharge.

10. The upper limit voltage for the first charge / discharge is 4.55V (vs. Li / Li + ) or more, and the upper limit charge voltage of the second charge / discharge is 4.3V to 4.55V (vs. Li / Li + 10. The pretreatment method of claim 9, wherein the total amount of the saturation is less than 100%.

11. The charge capacity in the first charge / discharge is C 1 , discharge capacity is C 2 year, I 1 >I 3 >I 2 Satisfy I 3 As a result, the charge current density and discharge current density in the first charge / discharge are all I 3 The charging capacity in this case is C 3.1 , discharge capacity is C 3.2 year, The discharge capacity of the second charge / discharge is C 4 When I say, C 2 / C 1 >C 3.2 / C 3.1 and C 4 / C 1 >C 4 / C 3.1 The pretreatment method according to claim 8 , wherein the above formula (I) is satisfied.

12. The charge capacity (C 1 ) vs. the discharge capacity (C 4 ) ratio (C 4 / C 1 9. The pretreatment method according to claim 8, wherein the reversible discharge capacity ratio (Rc) is 81% or more.

13. 2. The pretreatment method according to claim 1, wherein the lithium-manganese-rich positive electrode active material exhibits capacity through oxidation-reduction reactions of all transition metals and oxygen.

14. 2. The pretreatment method according to claim 1, wherein the pretreatment induces activation of an oxidation-reduction reaction of oxygen by changing the crystal structure of the lithium-manganese-rich positive electrode active material.

15. 2. The pretreatment method of claim 1, wherein the lithium-manganese-rich positive electrode active material is represented by a metal oxide comprising at least one of Chemical Formula 1 and Chemical Formula 2. [Chemical formula 1] Li 1+x1 (N y1 Mn z1 M 1 1-y1-z1 ) 1-x1 O 2-b1 X 1 b1 (In the above Chemical Formula 1, 0.03≦x1≦0.33, 0.1≦y1≦0.7, 0.3≦z1≦0.9, and 0≦b1≦0.1; M 1 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr; and X 1 is one or more elements selected from F, P, and S. [Chemical formula 2] xr(iiii y2 7N z2 7. 2 1-y2-z2 9 2-b2 8 2 b2 )+x3(i) 2 (7n t1 7. 2 1-t1 )9 3-b3 8 2 b3 ) ) (In the above chemical formula 2, 0≦x2≦0.94, 0.06≦x3≦1, 0.5≦x2+x3≦1, 0.5≦y2≦1.0, 0≦z2≦0.5, 0≦b2≦0.1, 0.9≦t1≦1, and 0≦b3≦0.1; M 2 is one or more elements selected from Al, B, Ba, Ca, Ce, Cr, Cu, Fe, Mg, Mo, Nb, Si, Sn, Sr, Ti, V, W, Y, Zn, and Zr; and X 2 is one or more elements selected from F, P, and S.

16. A positive electrode for a lithium secondary battery, which has been pretreated by the method according to any one of claims 1 to 15.

17. A lithium secondary battery to which pretreatment according to the method of any one of claims 1 to 15 has been applied, the lithium secondary battery comprising a positive electrode, a negative electrode, and an electrolyte.

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