Positive electrode active material and its manufacturing method, positive electrode, and secondary battery

Abstract

One embodiment provides a cathode active material having a disordered rock salt structure, improving the migration rate of lithium ions, and enabling excellent capacity characteristics and life characteristics, a cathode including the same, and a secondary battery. 【Solution means】A cathode active material having a disordered rock salt structure and containing a compound represented by Chemical Formula 1, where M 1 has an oxidation number of +2 for the whole, 1 provides a cathode active material with a ratio of 25 at% or less, a method for producing the same, a cathode, and a secondary battery. [Chemical Formula 1] A x M 1 2-x-y M 2 y O 2-a X a (In Chemical Formula 1, A is one or more elements selected from Li and Na, M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W, X is a halogen element, x / (2 - x)>1.1, 0

Description

[Technical Field]

[0001] This invention relates to positive electrode active material, its manufacturing method, positive electrode, and secondary battery. [Background technology]

[0002] Lithium-ion batteries, which have high energy density and are easily portable, are primarily used as power sources for mobile information terminals such as mobile phones, laptops, and smartphones. Recently, research has been actively conducted on using high-energy-density lithium-ion batteries as power sources or energy storage sources for hybrid and electric vehicles.

[0003] To realize lithium secondary batteries that meet these applications, a variety of positive electrode active materials are being considered. Among them, lithium nickel oxides, lithium nickel manganese cobalt composite oxides, lithium nickel cobalt aluminum composite oxides, and lithium cobalt oxides are mainly used as positive electrode active materials.

[0004] Incidentally, the recent increase in demand for larger, higher-capacity, higher-energy-density, or more productive lithium-ion batteries has created a need for the development of new methods for manufacturing cathode active materials. [Overview of the project] [Problems that the invention aims to solve]

[0005] One embodiment provides a positive electrode active material having a disordered rock salt structure, which improves the lithium ion migration rate and enables excellent capacity and life characteristics, as well as a positive electrode and a secondary battery containing the same. [Means for solving the problem]

[0006] In one embodiment, the positive electrode active material contains a compound represented by the following chemical formula 1, M 1 M has an oxidation state of +2 relative to the whole. 1 The ratio of this material is 25 at% or less, providing a positive electrode active material. [Chemical Formula 1] A x M 1 2-x-y M 2 y O 2-a X a

[0007] In the above Chemical Formula 1, A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr and V, and M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta and W, X is a halogen element, x / (2 - x)>1.1, 0<y<1 and 0≦a≦0.5.

[0008] In another embodiment, a positive electrode active material containing a lithium manganese composite oxide is provided, and in the whole manganese, the ratio of manganese having an oxidation number of +2 is 25 at% or less.

[0009] In still another embodiment, a mixture is obtained by mixing an A-containing carbonate, an M 1 -containing oxide and an M 2 -containing oxide in an alcoholic solvent, and the mixture is heat-treated at 900°C to 1500°C in an inert gas atmosphere. The A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr and V, and M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta and W. The M 1 -containing oxide contains M 1 2O3 and M 1 O2, and a method for manufacturing a positive electrode active material is provided.

[0010] In still another embodiment, a positive electrode is provided, which includes a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector and containing the above-mentioned positive electrode active material.

[0011] Another embodiment provides a secondary battery including the positive electrode, negative electrode, and electrolyte described above. [Effects of the Invention]

[0012] One embodiment provides a positive electrode active material having a disordered rock salt structure, which improves the lithium ion migration rate and enables excellent capacity and life characteristics, as well as a positive electrode and a secondary battery containing the same. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 2] Figure 2 is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 3] Figure 3 is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 4] Figure 4 is a schematic cross-sectional view showing a lithium secondary battery according to one embodiment. [Figure 5] Figure 5 shows the XPS measurement results for the positive electrode active material produced in Comparative Example 1. [Figure 6] Figure 6 shows the XPS measurement results for the positive electrode active material produced in Example 1. [Figure 7] Figure 7 shows the XPS measurement results for the positive electrode active material produced in Example 2. [Figure 8] Figure 8 shows the XRD measurement results for the positive electrode active materials produced in Example 1 and Comparative Example 1. [Figure 9] Figure 9 shows, as a reference example, the results of measuring the difference between the maximum and minimum volume values ​​of the octahedrons formed by lithium and the nearest oxygen atoms in the crystal structure for LiCoO2 and the cathode active materials produced in Examples 3 and 4. [Figure 10] Figure 10 shows the results of measuring the activation barrier for the cathode active materials produced in Examples 3 and 4, which were evaluated in Figure 9. [Figure 11]Figure 11 shows the results of measuring the difference between the maximum and minimum volume values ​​of the octahedrons formed by lithium and the nearest oxygen atoms in the crystal structure for the positive electrode active materials produced in Examples 3 and 5. [Figure 12] Figure 12 shows the results of measuring the change in discharge capacity over cycles for lithium secondary batteries manufactured in Example 1, Example 2, and Comparative Example 1. [Modes for carrying out the invention]

[0014] Embodiments of the present invention will be described in detail below. However, these are presented as examples only and are not limited thereto; the present invention is defined solely by the scope of the claims.

[0015] Unless otherwise specified herein, when a part such as a layer, film, region, or plate is said to be "on top of" another part, this includes not only the case where it is "directly on top" of the other part, but also the case where there is yet another part in between.

[0016] Unless otherwise specified, singular nouns may also include plural nouns. Similarly, unless otherwise specified, "A or B" may mean "including A, including B, or including both A and B."

[0017] In this specification, “these combinations” may mean mixtures, laminates, composites, copolymers, alloys, blends, and reaction products of the constituents.

[0018] Unless otherwise defined herein, particle size may be average particle size. Also, particle size refers to the average particle size (D) where the cumulative volume of the particle is 50% by volume in the particle size distribution. 50 ) means average particle size (D 50The measurement can be performed using methods widely known to those skilled in the art, for example, by measuring with a particle size analyzer, or by measuring with a transmission electron microscope or scanning electron microscope. Alternatively, the measurement can be performed using a measuring device employing dynamic light scattering, and after performing data analysis to count the number of particles for each particle size range, the average particle size (D) can be calculated based on this. 50 The ) value can be obtained. Alternatively, it can be measured using the laser diffraction method. More specifically, in the laser diffraction method, the particles to be measured are dispersed in a dispersion medium, then introduced into a commercially available laser diffraction particle size analyzer (for example, the MT 3000 from Microtrac), and ultrasonic waves of approximately 28 kHz are irradiated at an output of 60 W, and the average particle size (D) at the 50% reference of the particle size distribution in the measuring device is obtained. 50 It is possible to calculate ).

[0019] Here, terms such as “include,” “equip,” or “possess” are intended to specify the existence of implemented features, figures, steps, components, or combinations thereof, and should be understood not to preemptively exclude the existence or possibility of adding one or more other features, figures, steps, components, or combinations thereof.

[0020] The term "metal" is interpreted as a concept that includes general metals, transition metals, and metalloids.

[0021] positive electrode active material In one embodiment, the positive electrode active material contains a compound represented by the following chemical formula 1, M 1 M has an oxidation state of +2 relative to the whole. 1 The ratio of this material is 25 at% or less, providing a positive electrode active material. [Chemical formula 1] Ax M 1 2-x-y M 2 y O 2-a X a

[0022] In Chemical Formula 1, A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W, X is a halogen element, and x / (2 - x)>1.1, 0 < y < 1, and 0 ≤ a ≤ 0.5.

[0023] In one embodiment, the positive electrode active material has a disordered rock salt (DRX) structure, and the disordered rock salt structure is a new structure of a positive electrode active material different from existing layered, spinel, olivine, etc., and is characterized in that the path of insertion / desorption of lithium ions in the crystal structure is disordered.

[0024] The positive electrode active material having such a disordered rock salt structure has an advantage that it can achieve a higher capacity of 300 mAh / g or more than the positive electrode active material having a layered crystal structure that realizes a capacity of approximately 270 mAh / g.

[0025] However, the positive electrode active material having a disordered rock salt structure has a disadvantage that the ionic conductivity is low because the movement speed of lithium ions is slow, there is a side reaction problem with the electrolyte due to a very high upper limit voltage of 4.6 V or more required for driving, and the life characteristics are inferior due to an unstable crystal structure.

[0026] Therefore, in one embodiment, a positive electrode active material having a disordered rock salt structure is proposed that can solve the problems of low ionic conductivity and low life characteristics due to elution of transition metals, improve the movement speed of lithium ions, and improve the capacity characteristics and life characteristics.

[0027] The low ionic conductivity of cathode active materials with a disordered rock salt structure slows the diffusion rate of lithium within the cathode active material, which limits its application to high-rate charge / discharge cells, or necessitates limiting particle size to the nanoscale to shorten the ion diffusion distance when applied to high-rate charge / discharge cells. Limiting particle size to the nanoscale in this way significantly reduces the electrode plate density, makes it difficult to control the properties of the slurry, and makes it difficult to manufacture high-quality electrode plates.

[0028] Furthermore, cathode active materials with a disordered rock salt structure are inferior to existing materials because their extremely short lifespan during charging and discharging limits the number of usable charge-discharge cycles to only a few tens of cycles.

[0029] The oxidation states of transition metal elements such as Mn, Fe, Co, Ni, Cr, and V, which constitute the cathode active material having such a disordered rock salt structure and directly participate in the redox reaction to contribute to capacity development, are not a single value but can have various values ​​such as +2, +3, +4, +5, and +6. In one embodiment, it was confirmed that the ionic conductivity and charge / discharge performance are improved by controlling the proportion of such transition metal elements with an oxidation state of +2 to a low level, and a cathode active material to which this is applied is proposed.

[0030] Existing research has employed a strategy to increase ionic conductivity by increasing the Li / Me ratio by adding an excess of Li to a cathode active material with a disordered rock salt structure, thereby increasing the connectivity of the Li ion diffusion pathway. However, this strategy has disadvantages, such as the side effect of increasing the specific gravity of O-redox reactions, which induce degradation of the crystal structure, and the decrease in the volume density of the material as the amount of Li increases.

[0031] Therefore, in one embodiment, even without an increase in the amount of Li, M 1 M has an oxidation state of +2 relative to the whole. 1By controlling the ratio at a low ratio, a positive electrode active material is proposed that can improve the ionic conductivity and both the capacity characteristics and the life characteristics.

[0032] The positive electrode active material according to one embodiment contains a compound represented by the following chemical formula 1. [Chemical formula 1] A x M 1 2-x-y M 2 y O 2-a X a

[0033] In the chemical formula 1, A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, and M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W, X is a halogen element, and x / (2 - x)>1.1, 0 < y < 1, and 0 ≤ a ≤ 0.5.

[0034] As an example, in the chemical formula 1, the M 1 may be one or more elements selected from Mn, Co, and Ni. As a typical example, the M 1 may be Mn. When this is satisfied, a positive electrode active material having a disordered rock salt structure and excellent ionic conductivity can be ensured.

[0035] As an example, in the chemical formula 1, the M 2 may be one element selected from Ti and Zr, or the M [[ID=4\2]] 2 may be one or more elements selected from Ti and Zr. As a typical example, the M 2 may be Ti. When this is satisfied, a positive electrode active material having a disordered rock salt structure and excellent ionic conductivity can be ensured.

[0036] As an example, in the chemical formula 1, 1 ≦ x ≦ 1.33, 1.1 ≦ x ≦ 1.3, or 1.15 ≦ x ≦ 1.25 may be satisfied. When this is satisfied, it may be advantageous for the expression of excellent capacity characteristics and life characteristics.

[0037] As an example, in the chemical formula 1, 0.1 ≦ y ≦ 0.8, 0.1 ≦ y ≦ 0.5, or 0.1 ≦ y ≦ 0.4 may be satisfied. When this is satisfied, it may be advantageous for the expression of excellent capacity characteristics and life characteristics.

[0038] As an example, in the chemical formula 1, 0 ≦ a ≦ 0.5, 0 < a ≦ 0.5, 0.1 ≦ a ≦ 0.3, or 0.1 ≦ a ≦ 0.2 may be satisfied. When this is satisfied, it may be advantageous for the expression of excellent capacity characteristics and life characteristics.

[0039] In the positive electrode active material, M 1 As a whole, M having an oxidation number of +2 1 The ratio is 25 at% or less. For example, it may be 0 at% to 25 at%, 2 at% to 25 at%, 9 at% to 25 at%, 12 at% to 19 at%, 15 at% to 19 at%, or 16 at% to 18.5 at%. When calculating the energy required for lithium to diffuse within the disordered rock salt structure of the positive electrode active material through first-principles calculations, it is understood that the greater the energy difference between adjacent positions within the crystal structure, the greater the energy required to move between two adjacent positions. The energy difference between adjacent positions is due to the volume difference of each position, and the volume occupied by one of the transition metal elements is greatly affected by the oxidation number. Therefore, the more diverse the distribution of the oxidation numbers of the transition metals within the positive electrode active material having a disordered rock salt structure, the greater the energy required for lithium to diffuse, which hinders diffusion. At the same time, the positive electrode active material having a disordered rock salt structure has a decrease in oxidation number due to the over-reduction reaction during charge and discharge. By the way, M 1 Compared with a positive electrode active material having a disordered rock salt structure composed of two types with an oxidation number of +3 or +4, M 1In the case of a cathode active material having a disordered rock salt structure in which the oxidation states of the transition metal are distributed in three types: +2, +3, and +4, 2+ ions are easily eluted through the electrolyte. When transition metals are eluted in this way, the crystal structure deteriorates compared to the existing structure, adversely affecting lifetime characteristics such as capacity retention. Therefore, increasing the overall oxidation state to prevent the generation of 2+ ions through over-reduction is suitable for improving the lifetime characteristics of cathode active material materials having a disordered rock salt structure. Accordingly, in one embodiment, as a cathode active material having a disordered rock salt structure, the transition metal element M 1 M has an oxidation state of +2 relative to the whole. 1 By controlling the ratio to a low level of 25 at% or less, the conductivity characteristics of the ions can be improved, thereby enhancing the capacity characteristics and lifetime characteristics.

[0040] As an example, the aforementioned M 1 The oxidation number of may be one or more selected from +2, +3, and +4. The more diverse the distribution of oxidation numbers of transition metals in a cathode active material with a disordered rock salt structure, the greater the energy required for lithium to diffuse, thus hindering diffusion. Therefore, reducing the number of different oxidation numbers in a cathode active material with a disordered rock salt structure can be an advantageous strategy for improving the ionic conductivity characteristics of the cathode active material. In other words, improving the ionic conductivity characteristics requires a strategy of reducing the number of different transition metal oxidation numbers, while improving the lifetime characteristics requires increasing the oxidation number overall. Therefore, M 1 A cathode active material having a disordered rock salt structure with oxidation states limited to +2, +3, and +4 can be said to be a material to which all of the above strategies can be applied, resulting in improved ionic conductivity and lifetime characteristics.

[0041] For example, M 1 M has an oxidation state of +3 relative to the whole. 1 The ratio may be 35 at% or more, for example, 35 at% to 60 at%, 35 at% to 55 at%, or 35 at% to 51 at%. 1 Overall, M 1 Since the life characteristics can be improved by increasing the oxidation number of M1 M has an oxidation state of +3 relative to the whole. 1 When the ratio satisfies the aforementioned range, the effect of improving both capacity characteristics and lifespan characteristics can be achieved in a harmonious manner.

[0042] For example, M 1 M has an oxidation state of +4 relative to the whole. 1 The ratio may be 25 at% or more, for example, 25 at% to 60 at%, 30 at% to 50 at%, or 30 at% to 45 at%. 1 Overall, M 1 Since the life characteristics can be improved by increasing the oxidation number of M 1 M has an oxidation state of +4 relative to the whole. 1 When the ratio satisfies the aforementioned range, the effect of improving both capacity characteristics and lifespan characteristics can be achieved in a harmonious manner.

[0043] As an example, in the above chemical formula 1, M 1 The average oxidation number may be +3 or higher, for example, +3 to +5, +3.1 to +4, or +3.1 to +3.5. When this condition is met, it can efficiently improve the ionic conductivity of the positive electrode active material having a disordered rock salt structure, which can be advantageous in ensuring excellent capacity and lifetime characteristics.

[0044] In one embodiment, the positive electrode active material can satisfy the following formula 1. When this is satisfied, the effect of improving capacity characteristics and lifetime characteristics can be maximized. [Formula 1] 0.35 ≤ R1 / (R2+R3) ≤ 0.65

[0045] In the above equation 1, R1 is M 1 M has an oxidation state of +4 relative to the whole. 1 This shows the ratio, and R2 is M 1 M has an oxidation state of +2 relative to the whole. 1 This shows the ratio, and R3 is M 1 M has an oxidation state of +3 relative to the whole. 1 This shows the ratio.

[0046] At this time, the positive electrode active material is M 1 The oxidation number of can be determined by manufacturing a battery (for example, a half-cell manufactured using a lithium counter electrode as the negative electrode) that includes a positive electrode active material layer containing the positive electrode active material, performing one charge-discharge cycle in the range of 1.5V to 4.8V, then disassembling the battery, recovering only the positive electrode, and measuring the XPS.

[0047] As an example, the positive electrode active material has a difference of 3.6 Å between the maximum and minimum volume values ​​of the octahedron formed by lithium and the nearest adjacent oxygen in its crystal structure. 3 It may also be less than or equal to, for example, 3.0 Å 3 ~3.6Å 3 , 3.1 Å 3 ~3.6Å 3 , or 3.1 Å 3 ~3.36Å 3 That's fine.

[0048] A cathode active material having a disordered rock salt structure is known to have an octahedral crystal structure, with oxygen atoms located at each of the eight vertices of the octahedron. The difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and its nearest oxygen atom within the disordered rock salt structure of such a cathode active material can be understood as a pathway for lithium movement. Therefore, it is presumed that the larger the difference between the maximum and minimum values, the slower the lithium ion movement rate, and the smaller the difference, the faster the lithium ion movement rate. In other words, if the difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and its nearest oxygen atom within the crystal structure satisfies the aforementioned range, the lithium ion movement rate can be improved, effectively contributing to the securing of excellent capacity characteristics.

[0049] As an example, the positive electrode active material may further include a coating layer containing a conductive material on its surface. The conductive material is used to impart conductivity to the electrode and can be any electron conductive material that does not cause a chemical change. 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; or mixtures thereof. As a representative example, carbon black can be used.

[0050] Another embodiment provides a positive electrode active material containing a lithium manganese-based composite oxide, wherein the ratio of manganese having an oxidation number of +2 in the total manganese is 25 at% or less. On the other hand, since the above description of the positive electrode active material can be similarly applied, duplicate descriptions are omitted.

[0051] As an example, the positive electrode active material has a disordered rock salt structure, and the lithium manganese-based composite oxide can mean a composite oxide containing lithium and manganese, and can further contain additional transition metals in addition to the manganese.

[0052] Method for manufacturing positive electrode active material In yet another embodiment, a mixture of a carbonate containing A, an oxide containing M 1 and an oxide containing M 2 is obtained by mixing in an alcoholic solvent, and the mixture is heat-treated at 900 °C to 1500 °C in an inert gas atmosphere. The A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, and M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W. The oxide containing M 1 is M 1 2O3 and M 1Provided is a method for manufacturing a positive electrode active material containing O2.

[0053] The above description relates to a method for manufacturing a positive electrode active material according to an embodiment. Hereinafter, overlapping descriptions of the positive electrode active material will be omitted, and the steps for manufacturing the positive electrode active material of one embodiment will be described in detail.

[0054] First, a mixture in which a carbonate containing A, an oxide containing M 1 and an oxide containing M 2 are mixed is obtained in an alcoholic solvent. Here, the A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, and M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W.

[0055] As an example, the mixture may further contain a halide containing A.

[0056] The oxide containing M 1 contains M 1 2O3 and M 1 O2. For example, the oxide containing M 1 may be Mn2O3 and MnO2.

[0057] As an example, the carbonate containing A may be Li2CO3, the halide containing A may be LiF, and the oxide containing M 2 may be TiO2, Zr(OH)4, or a combination thereof.

[0058] As an example, the alcoholic solvent may be an alcoholic solvent having 1 to 10 carbon atoms. For example, ethanol, propanol, butanol, etc. may be mentioned, and as a representative example, absolute ethanol may also be used.

[0059] In one embodiment, the mixing can be carried out by a wet process using a ball mill. Existing cathode active materials having a disordered rock salt structure are manufactured using the planetary ball milling method. Such existing methods involve placing raw material powder and balls into special equipment that applies high energy, applying a dry high-energy milling method, and manufacturing the cathode active material using the physical and thermal energy added during crushing.

[0060] In contrast, in one embodiment, a special manufacturing method is used in which a ball mill is applied at low energy using an alcoholic solvent in a wet process for simple mixing, followed by heat treatment. This reduces process costs compared to existing methods and can be advantageous when applied to mass production processes.

[0061] For example, the ball mill can be performed using YSZ (yttria-stabilized zirconia) balls. For example, the diameter of the balls may be 1 mm to 10 mm or 3 mm to 8 mm, and the ball milling can be performed at a speed of 100 rpm to 1000 rpm, 150 rpm to 700 rpm, or 200 rpm to 500 rpm, for 2 to 20 hours, 5 to 18 hours, or 10 to 15 hours. If these conditions are met, of the positive electrode active material obtained at the end, M 1 The oxidation state can be efficiently adjusted within the desired range.

[0062] In one embodiment, after obtaining the mixture, the process may further include a drying step, through which the mixture can be obtained in powder form. The drying can be carried out at 50°C to 200°C, 60°C to 150°C, or 70°C to 100°C, and for 5 to 30 hours, 8 to 20 hours, or 10 to 15 hours. If these conditions are met, of the final positive electrode active material, M 1 The oxidation state can be efficiently adjusted within the desired range.

[0063] Next, the mixture is heat-treated under an inert gas atmosphere. For example, the inert gas may include He, Ar, N2, or a combination thereof.

[0064] In one embodiment, the heat treatment can be carried out at 900°C to 1500°C, 1000°C to 1400°C, or 1100°C to 1300°C, for 2 to 10 hours, 3 to 9 hours, or 4 to 8 hours. If these conditions are met, of the resulting positive electrode active material, M 1 The oxidation state can be efficiently adjusted within the desired range.

[0065] As an example, the heat treatment can be carried out within the heat treatment temperature range after raising the temperature at a heating rate of 1°C / min to 10°C / min, 3°C / min to 8°C / min, or 5°C / min to 7°C / min. If this condition is met, then among the resulting positive electrode active material, M 1 The oxidation state can be efficiently adjusted to the desired range.

[0066] positive electrode In one embodiment, a positive electrode is provided that includes a positive electrode current collector and a positive electrode active material layer located on the positive electrode current collector and containing the positive electrode active material described above.

[0067] The positive electrode active material layer may further include, in addition to the positive electrode active material described above, a binder, a conductive material, or a combination thereof.

[0068] positive electrode active material As the positive electrode active material, the aforementioned positive electrode active material can be used as a compound (lithiated insertion compound) that allows for reversible insertion and removal of lithium or sodium.

[0069] binder The binder plays a role in making it easier for positive electrode active material particles to adhere to each other and for the positive electrode active material to adhere to the current collector. Typical examples of binders include, but are not limited to, polyvinyl alcohol, carboxymethylcellulose, hydroxypropylcellulose, diacetylcellulose, polyvinyl chloride, carboxylated polyvinyl chloride, polyvinyl fluoride, polymers containing ethylene oxide, polyvinylpyrrolidone, polyurethane, polytetrafluoroethylene, polyvinylidene fluoride, polyethylene, polypropylene, styrene-butadiene rubber, (meth)acrylicated styrene-butadiene rubber, epoxy resin, (meth)acrylic resin, polyester resin, and nylon.

[0070] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes in the battery that is constructed can be used. Examples of conductive materials include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0071] The content of the binder and conductive material may be 0.5% to 5% by weight, respectively, based on 100% by weight of the positive electrode active material layer.

[0072] Al may be used as the positive electrode current collector, but it is not limited to this.

[0073] For example, the electrode plate density of the positive electrode may be 1.8 g / cc or more, for example, 1.8 g / cc to 2.5 g / cc, 1.85 g / cc to 2.2 g / cc, or 1.86 g / cc to 2.0 g / cc.

[0074] secondary battery In one embodiment, a secondary battery is provided comprising a positive electrode; a negative electrode; and an electrolyte; wherein the positive electrode comprises a positive electrode current collector; and a positive electrode active material layer located on the positive electrode current collector and containing a positive electrode active material manufactured by the manufacturing method described above.

[0075] As an example, a secondary battery may include a positive electrode, a negative electrode, a separator located between the positive and negative electrodes, and an electrolyte.

[0076] The secondary battery mentioned above includes lithium secondary batteries and can be classified into cylindrical, prismatic, pouch-type, coin-type, etc., depending on its form. Figures 1 to 4 are schematic diagrams showing a lithium secondary battery according to one embodiment, where Figure 1 is cylindrical, Figure 2 is prismatic, and Figures 3 and 4 are pouch-type battery forms. Referring to Figures 1 to 4, the lithium secondary battery 100 may include an electrode assembly 40 with a separator 30 interposed between a positive electrode 10 and a negative electrode 20, and a case 50 in which the electrode assembly 40 is housed. The positive electrode 10, negative electrode 20, and 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 Figure 1. Also, in Figure 2, the lithium secondary battery 100 may include a positive electrode lead tap 11 and a positive electrode terminal 12, a negative electrode lead tap 21 and a negative electrode terminal 22. As shown in Figures 3 and 4, the lithium secondary battery 100 may include electrode taps 70, namely a positive electrode tap 71 and a negative electrode tap 72, which serve as electrical pathways for guiding the current formed in the electrode assembly 40 to the outside.

[0077] negative electrode The negative electrode may include a negative electrode current collector; and a negative electrode active material layer located on the negative electrode current collector; and the negative electrode active material layer may include a negative electrode active material, and further include a binder, a conductive material, or a combination thereof.

[0078] negative electrode active material The negative electrode active material includes a material capable of reversibly inserting / desorbing lithium ions, lithium metal, an alloy of lithium metal, a material capable of doping and undoping lithium, or a transition metal oxide.

[0079] As the material capable of reversibly inserting / desorbing the lithium ions, a carbon-based negative electrode active material can be used, for example, including crystalline carbon, amorphous carbon, or a combination thereof. Examples of the crystalline carbon include graphite such as amorphous, plate-shaped, flaky, spherical or fibrous natural graphite or artificial graphite, and examples of the amorphous carbon include soft carbon or hard carbon, mesophase pitch carbide, fired coke, and the like.

[0080] 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 can be used.

[0081] As the material capable of doping and undoping lithium, a Si-based negative electrode active material or a Sn-based negative electrode active material can be used. As the Si-based negative electrode active material, silicon, a silicon-carbon composite, SiOx (0 < x ≤ 2), a 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 may be used. As the Sn-based negative electrode active material, Sn, SnO2, a Sn alloy, or a combination thereof may be used.

[0082] The silicon-carbon composite may also be a composite of silicon and amorphous carbon. The average particle size (D 50 The thickness of the silicon-carbon composite 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 amorphous carbon coated on the surface of the silicon particles. For example, it may include secondary particles (core) which are aggregates of primary silicon particles and amorphous carbon coating layers (shell) located on the surface of these 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 the amorphous carbon matrix.

[0083] The silicon-carbon composite may further contain 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 surface of this core. The crystalline carbon may be artificial graphite, natural graphite, or a combination thereof. The amorphous carbon may be soft carbon or hard carbon, mesophase pitch carbide, calcined coke, etc.

[0084] When the silicon-carbon composite contains silicon and amorphous carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, and the amorphous carbon content may be 50% to 90% by weight. Furthermore, when the composite contains silicon, amorphous carbon, and crystalline carbon, the silicon content may be 10% to 50% by weight per 100% by weight of the silicon-carbon composite, the crystalline carbon content may be 10% to 70% by weight, and the amorphous carbon content may be 20% to 40% by weight.

[0085] Furthermore, the thickness of the amorphous carbon coating layer may be 5 nm to 100 nm. The average particle size (D) of the silicon particles (primary particles) 50) may be from 10 nm to 1 μm, or may be from 10 nm to 200 nm. The silicon particles may exist alone as silicon, may exist in the form of a silicon alloy, or may exist in an oxidized form. The oxidized form of silicon can be represented by SiOx (0 < x ≦ 2). At this time, the atomic content ratio of Si:O indicating the degree of oxidation may be from 99:1 to 33:67. In this specification, unless otherwise defined, the average particle size (D 50 ) means the diameter of the particles with a cumulative volume of 50% in the particle size distribution.

[0086] 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 mixed and used, the mixing ratio may be from 1:99 to 90:10 by weight.

[0087] binder The binder serves to make the negative electrode active material particles adhere to each other easily and make the negative electrode active material adhere to the current collector easily. As the binder, a non-aqueous binder, an aqueous binder, a dry binder, or a combination thereof can be used.

[0088] 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.

[0089] The water-based binder may be selected from styrene-butadiene rubber, (meth)acrylicated 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.

[0090] When an aqueous binder is used as the negative electrode binder, it may further contain a cellulosic compound that can impart viscosity. This cellulosic compound can be a mixture of one or more carboxymethylcellulose, hydroxypropylmethylcellulose, methylcellulose, or alkali metal salts thereof. The alkali metal can be Na, K, or Li.

[0091] The dry binder is a polymeric substance that can be formed into fibers, and may be, for example, polytetrafluoroethylene, polyvinylidene fluoride, polyvinylidene fluoride-hexafluoropropylene copolymer, polyethylene oxide, or a combination thereof.

[0092] conductive material Conductive materials are used to impart conductivity to electrodes, and any electronically conductive material that does not cause chemical changes in the battery that is constructed can be used. Specific examples include carbon-based materials such as natural graphite, artificial graphite, carbon black, acetylene black, Ketjenblack, carbon fibers, carbon nanofibers, and carbon nanotubes; metallic materials containing copper, nickel, aluminum, silver, etc., in the form of metal powders or metal fibers; conductive polymers such as polyphenylene derivatives; or mixtures thereof.

[0093] The content of the negative electrode active material may be 95% to 99.5% by weight relative to 100% by weight of the negative electrode active material layer, and the content of the binder may be 0.5% to 5% by weight relative to 100% by weight of the negative electrode active material layer. For example, the negative electrode active material layer may contain 90% to 99% by weight of the negative electrode active material, 0.5% to 5% by weight of the binder, and 0.5% to 5% by weight of the conductive material.

[0094] The negative electrode current collector may 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 alloys thereof, and may be in the form of foil, sheet, or foam. The thickness of the negative electrode current collector may be, for example, 1 μm to 20 μm, 5 μm to 15 μm, or 7 μm to 10 μm.

[0095] electrolyte The electrolyte for lithium secondary batteries may, for example, be an electrolyte solution, which may contain a non-aqueous organic solvent and a lithium salt.

[0096] Non-aqueous organic solvents serve as a medium through which ions involved in the electrochemical reactions of the battery can move. Non-aqueous organic solvents may be carbonate-based, ester-based, ether-based, ketone-based, or alcohol-based solvents, aprotic solvents, or combinations thereof.

[0097] As carbonate-based solvents, 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. can be used. As ester-based solvents, methyl acetate, ethyl acetate, n-propyl acetate, dimethyl acetate, methyl propionate, ethyl propionate, decanolide, mevalonolactone, valerolactone, caprolactone, etc. can be used. As ether-based solvents, dibutyl ether, tetraglyme, diglyme, dimethoxyethane, 2-methyltetrahydrofuran, 2,5-dimethyltetrahydrofuran, and tetrahydrofuran can be used. As ketone-based solvents, cyclohexanone can be used. As alcohol-based solvents, ethyl alcohol and isopropyl alcohol can be used, and as aprotic solvents, nitriles such as R-CN (where R is a linear, branched, or cyclic hydrocarbon group having 2 to 20 carbon atoms, and may include double bonds, aromatic rings, or ether groups); amides such as dimethylformamide; dioxolanes such as 1,3-dioxolane and 1,4-dioxolane; and sulfolanes can be used.

[0098] Non-aqueous organic solvents can be used alone or in combination of two or more. When using a mixture of two or more, the mixing ratio can be appropriately adjusted according to the desired battery performance, and this is generally understood by those working in this field.

[0099] When using carbonate-based solvents, cyclic carbonates and linear carbonates can be mixed, and the cyclic carbonates and linear carbonates can be mixed in a volume ratio of 1:1 to 1:9.

[0100] The non-aqueous organic solvent may further contain an aromatic hydrocarbon organic solvent. For example, the carbonate solvent and the aromatic hydrocarbon organic solvent can be mixed and used in a volume ratio of 1:1 to 30:1.

[0101] The electrolyte may further contain vinyl ethyl carbonate, vinylene carbonate, or ethylene carbonate compounds to improve battery life.

[0102] Typical examples of the aforementioned ethylene carbonate compounds include fluoroethylene carbonate, difluoroethylene carbonate, chloroethylene carbonate, dichloroethylene carbonate, bromoethylene carbonate, dibromoethylene carbonate, nitroethylene carbonate, and cyanoethylene carbonate.

[0103] Lithium salts dissolve in organic solvents and act as a source of lithium ions within batteries, enabling the operation of basic lithium secondary batteries and facilitating the movement of lithium ions between the positive and negative electrodes. Typical 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 F 2x+1 SO2)(C y F 2y+1 It may contain one or more selected from SO2) (where x and y are integers from 1 to 20), lithium trifluoromethanesulfonate, lithium tetrafluoroethanesulfonate, lithium difluorobis(oxalate)phosphate (LiDFOB), and lithium bis(oxalate)borate (LiBOB).

[0104] The lithium salt concentration should preferably be within the range of 0.1 M to 2.0 M. When the lithium salt concentration is within this range, the electrolyte has appropriate ionic conductivity and viscosity, allowing it to exhibit excellent performance and enabling effective lithium ion movement.

[0105] Separator Depending on the type of lithium secondary battery, a separator may be present between the positive and negative electrodes. Such separators can be polyethylene, polypropylene, polyvinylidene fluoride, or multilayer films of two or more layers thereof. Mixed multilayer films such as polyethylene / polypropylene two-layer separators, polyethylene / polypropylene / polyethylene three-layer separators, or polypropylene / polyethylene / polypropylene three-layer separators are also commonly used.

[0106] The separator may include a porous substrate and a coating layer containing organic, inorganic, or a combination thereof located on one or both sides of the porous substrate.

[0107] The porous substrate may be a polymer film formed from any polymer selected from polyethylene, polyolefins such as polypropylene, polyesters such as polyethylene terephthalate and polybutylene terephthalate, polyacetal, polyamide, polyimide, polycarbonate, polyetherketone, polyaryletherketone, polyetherimide, polyamideimide, polybenzimidazole, polyethersulfone, polyphenylene oxide, cyclic olefin copolymer, polyphenylene sulfide, polyethylene naphthalate, glass fiber, and polytetrafluoroethylene (e.g., Teflon®), or from a copolymer or mixture of two or more of these polymers.

[0108] The porous substrate can have a thickness of approximately 1 μm to 40 μm, for example, 1 μm to 30 μm, 1 μm to 20 μm, 5 μm to 15 μm, or 10 μm to 15 μm.

[0109] The organic substance may include a (meth)acrylic copolymer comprising a first structural unit derived from (meth)acrylamide, and a second structural unit comprising at least one of a structural unit derived from (meth)acrylic acid or (meth)acrylate and a structural unit derived from (meth)acrylamide sulfonic acid or a salt thereof.

[0110] The inorganic material may include, but is not limited to, inorganic particles selected from Al2O3, SiO2, TiO2, SnO2, CeO2, MgO, NiO, CaO, GaO, ZnO, ZrO2, Y2O3, SrTiO3, BaTiO3, Mg(OH)2, boehmite, and combinations thereof. The average particle size (D 50 ) may be 1 nm to 2000 nm, for example, 100 nm to 1000 nm or 100 nm to 700 nm.

[0111] The organic and inorganic materials can exist mixed together in a single coating layer, or in a form in which a coating layer containing organic materials and a coating layer containing inorganic materials are stacked.

[0112] The thickness of the coating layer may be 0.5 μm to 20 μm, for example, 1 μm to 10 μm, or 1 μm to 5 μm.

[0113] The following describes examples and comparative examples of the present invention. The following examples are merely illustrative of the present invention and are not limited to the following examples.

[0114] Example 1 1. Manufacturing of positive electrode active material After weighing out 2.498g, 2.205g, 0.486g, 0.893g, and 0.145g of Li2CO3, Mn2O3, MnO2, TiO2, and LiF, respectively, the mixture was wet-milled with anhydrous ethanol at 200 rpm for 12 hours with 200g of 5mm balls made of YSZ material added to the weighed-out weighed-out weighed-out weighed-out weighed-out weighed-out weighed-out weighed-out weighed out with 200g of YSZ material. The mixture was dried at 70°C for 12 hours to obtain only the powder. 2g of the powder was compressed to a diameter of 20mm under a pressure of 20MPa to make pellets. The resulting pellets were heat-treated in a tube furnace under an Ar atmosphere at a heating rate of 5°C / min to 1100°C for 4 hours to obtain Li 1.2 Mn 0.6 Ti 0.2 O 1.9 F 0.1 A substance with the desired composition was obtained. Next, the Li 1.2 Mn 0.6 Ti 0.2 O 1.9 F 0.1 Weighed out 0.7g and 0.1g of the constituent material and carbon black, respectively, and added five 10mm silicon nitride balls. The mixture was then dry-ground at 300rpm for 6 hours. 1.2 Mn 0.6 Ti 0.2 O 1.9 F 0.1 A positive electrode active material was manufactured in which a carbon black-containing coating layer was formed on the surface of the particles of the composition.

[0115] 2. Manufacturing of lithium-ion batteries A positive electrode active material layer slurry was prepared by mixing 80% by weight of the manufactured positive electrode active material, 10% by weight of polyvinylidene fluoride binder, and 10% by weight of carbon black conductive material. The positive electrode active material layer slurry was coated onto an aluminum foil current collector, dried, and rolled to produce a positive electrode with a plate density of 1.86 g / cc.

[0116] Next, a half-cell was manufactured using a lithium metal counter electrode, and a lithium secondary battery was manufactured using a conventional method with a polytetrafluoroethylene separator between the positive electrode and the lithium metal counter electrode, and an electrolyte solution prepared by dissolving 1M LiPF6 in a solvent containing a 1:1 volume mixture of ethylene carbonate and dimethyl carbonate.

[0117] Example 2 During the production of the positive electrode active material, Li2CO3, Mn2O3, MnO2, TiO2, and LiF are weighed and mixed in masses of 2.482g, 2.191g, 0.965g, 0.444g, and 0.144g, respectively. 1.2 Mn 0.7 Ti 0.1 O 1.9 F 0.1 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a positive electrode active material of a specific composition was obtained.

[0118] Example 3 During the production of the positive electrode active material, Li2CO3, Mn2O3, MnO2, and TiO2 are weighed and mixed in masses of 2.570g, 1.308g, 0.480g, and 1.765g, respectively. 1.2 Mn 0.4 Ti 0.4 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a positive electrode active material with an O2 composition was obtained.

[0119] Example 4 During the production of the positive electrode active material, Li2CO3, Mn2O3, MnO2, and Zr(OH)4 are weighed and mixed in masses of 1.854g, 0.943g, 0.346g, and 2.945g, respectively. 1.2 Mn 0.4 Zr 0.4 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a positive electrode active material with an O2 composition was obtained.

[0120] Comparative Example 1 During the production of the positive electrode active material, Li2CO3, Mn2O3, TiO2, and LiF are weighed and mixed in masses of 2.514g, 2.220g, 1.348g, and 0.146g, respectively. 1.2 Mn 0.5 Ti 0.3 O 1.9 F 0.1 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a positive electrode active material of a specific composition was obtained.

[0121] Example 5 During the production of the positive electrode active material, Li2CO3, MnO, Mn2O3, and TiO2 are weighed and mixed in masses of 2.730g, 0.397g, 0.884g, and 2.237g, respectively. 1.2 Mn 0.3 Ti 0.5 A positive electrode active material and a lithium secondary battery were manufactured in substantially the same manner as in Example 1, except that a positive electrode active material with an O2 composition was obtained.

[0122] Evaluation Example 1: Evaluation of Oxidation Number The lithium secondary batteries produced in Comparative Example 1, Example 1, and Example 2 were charged to 4.8V at 25°C with a constant current of 0.2C using a WBCS 3000, and then discharged to 1.5V with the same current. The discharged batteries were disassembled, and only the positive electrode was recovered. XPS measurements were taken over a 400μm × 400μm area using an X-ray photoelectron spectrometer (NEXSA, Thermo Fisher Scientific) under conditions of a pass energy of 50eV and steps of 0.1eV intervals for 50ms, and the results are shown in Figures 5 to 7. From the XPS results in Figures 5 to 7, Mn 2+ Mn 3+ and Mn 4+ The area corresponding to each was measured, the oxidation number ratio of Mn was determined, and the average oxidation number was calculated from the oxidation number ratio of Mn to obtain the average oxidation number of Mn, which is shown in Table 1 below. At this time, the average oxidation number of Mn is defined by the following equation 2. e This was calculated as the value of [the variable].

[0123] [Formula 2] Mn e =[(2×R2)+(3×R3)+(4×R4)] / (R2+R3+R4) In the above equation 2, Mn e R1 represents the average oxidation state of Mn, R2 represents the at% ratio of Mn with an oxidation state of +2, R3 represents the at% ratio of Mn with an oxidation state of +3, and R4 represents the at% ratio of Mn with an oxidation state of +4.

[0124] [Table 1]

[0125] Referring to Table 1, it can be confirmed that in Examples 1 and 2, the ratio of Mn with an oxidation state of +2 to the total Mn is 25 at% or less.

[0126] In contrast, in Comparative Example 1, it can be confirmed that the proportion of Mn with an oxidation state of +2 relative to the total Mn exceeds 25 at%.

[0127] Evaluation Example 2: XRD Evaluation For the positive electrode active materials produced in Comparative Example 1 and Example 1, XRD measurements were taken in the 2θ range of 10° to 70° using a Bruker D6 Phaser apparatus. The X-ray wavelength was 1.54 Å, and the voltage and current were set to 40 kV / 20 mA, respectively. The results are shown in Figure 8.

[0128] Referring to Figure 8, it can be seen that in the case of the positive electrode active materials produced in Comparative Example 1 and Example 1, all three peaks observed around 2θ=35~40°, 2θ=41~45°, and 2θ=60~65° are present.

[0129] From the XRD measurement results, it can be confirmed that both the positive electrode active material of Comparative Example 1 and Example 1 have a disordered rock salt structure.

[0130] Evaluation Example 3: Evaluation of the difference between the maximum and minimum volume values ​​of octahedra within a crystal structure. As a reference example, the electronic structure and mechanical and thermodynamic properties of LiCoO2 and the cathode active materials manufactured in Examples 3 and 4 were calculated using density functional theory based on first-principles calculations as the theoretical framework. The initial structure of the cathode active material was determined using VASP software on a supercomputer capable of large-scale parallel processing. The energy convergence criterion was 10 -6 Set to eV and the energy change in the electronic structure calculation is 10 -6 The simulation was repeated until the force converged to below eV, using force convergence criteria 10. -2 The force acting on each atom is 10 when the eV / Å condition is set. -2 Structural optimization simulations were performed using a method that optimizes atomic positions until they decrease to less than eV / Å. The volume values ​​of the octahedra formed by lithium and the nearest oxygen atoms in the optimized crystal structure obtained through the simulations were measured, and the difference between the maximum and minimum values ​​of these volume values ​​was calculated and is shown in Figure 9.

[0131] Furthermore, elastic band simulation calculations were performed to measure the reaction pathway and activation barrier for the positive electrode active materials manufactured in Examples 3 and 4, which were evaluated in Figure 9. The minimum energy path between the initial state and the final state was determined through elastic band simulation, and the image between the initial state and the final state was generated by interpolation using a linear path. The spring constant, which determines the strength of the elastic band, was set to the standard value of -5, and the simulation was repeated until the forces acting on the five intermediate images converged. The results of measuring the activation barrier are shown in Figure 10.

[0132] Referring to Figure 9, for the positive electrode active materials produced in Examples 3 and 4, the difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and the nearest oxygen atom in the crystal structure is 3.6 Å. 3 It can be confirmed that the following is true.

[0133] Referring to Figure 10, observing the difference between the maximum and minimum values ​​of the activation barrier measured for each case during volume measurement in Figure 9, it can be confirmed that the case in Example 4 is larger than that in Example 3. Therefore, it can be confirmed that the smaller the difference between the maximum and minimum values ​​of the volume of the octahedron formed by lithium and the nearest oxygen in the crystal structure, the smaller the activation barrier, and this reduces the energy required for lithium ions to diffuse, thereby improving the conductivity characteristics of the ions. This is the case for Li in Example 4. 1.2 Mn 0.4 Zr 0.4 In the case of Zr in O, the Li in Example 3 1.2 Mn 0.4 Ti 0.4 This is presumably because the size of the ions themselves is larger compared to the size of the Ti ions in O.

[0134] Furthermore, for the positive electrode active materials produced in Examples 3 and 5, the volume values ​​of the octahedra formed by lithium and the nearest oxygen in the crystal structure, and the difference between the maximum and minimum values ​​of these volume values ​​were determined in the same manner as described above, and are shown in Figure 11.

[0135] Referring to Figure 11, in the case of the positive electrode active materials produced in Example 5 and Example 3, both M 1 Even though it is LMTO corresponding to Mn, in the case of the positive electrode active material manufactured in Example 5, the difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and the nearest oxygen in the crystal structure is 3.36 Å. 3 In contrast to the above, in the case of the positive electrode active material manufactured in Example 3, the difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and the nearest adjacent oxygen in the crystal structure is 3.36 Å. 3 It can be confirmed that the following is true.

[0136] This suggests that, in Example 3, the activation barrier is smaller compared to Example 5, and the energy required for lithium ions to diffuse is also smaller, thus improving the ion conductivity characteristics.

[0137] Evaluation Example 4: Evaluation of Charge / Discharge Performance The lithium secondary batteries manufactured in Comparative Example 1 and Examples 1 and 2 were charged to 4.8V at 25°C with a constant current of 0.2C, and then discharged to 1.5V at 0.2C. This cycle was repeated 50 times. Figure 12 shows the change in discharge capacity over the cycles, and Table 2 below shows the initial discharge capacity and the capacity retention rate, which is the ratio of the discharge capacity after 50 cycles to the initial discharge capacity.

[0138] [Table 2]

[0139] Referring to Figure 12 and Table 2, it can be confirmed that in Examples 1 and 2, the capacity retention rate is higher and the lifetime characteristics are superior compared to Comparative Example 1. Comparing Example 1 and Comparative Example 1, even though the amount of transition metal oxidation and reduction is the same, in Example 1, the capacity degradation is suppressed more effectively than in Comparative Example 1. This is judged to be because the reduction reaction to Mn2+ was mitigated, reducing the dissolution phenomenon.

[0140] In particular, in the case of Example 1, which satisfies Equation 1, the discharge capacity is sufficiently higher than 250 mAh / g or more compared to Example 2, which does not satisfy Equation 1, and the capacity retention rate is also excellent, confirming that both the capacity characteristics and life characteristics are superior.

[0141] Although preferred embodiments have been described in detail above, the scope of the present invention is not limited thereto. Various modifications and improvements made by those skilled in the art using the basic concepts defined in the claims also fall within the scope of the present invention. [Explanation of Symbols]

[0142] 100: Lithium-ion rechargeable battery 10: Positive electrode 11: Positive lead tap 12: Positive terminal 20: Negative electrode 21: Negative lead tap 22: Negative terminal 30: Separator 40: Electrode assembly 50: Case 60: Sealing member 70: Electrode Tap 71: Positive Tap 72: Negative Tap

Claims

1. The positive electrode active material contains a compound represented by the following chemical formula 1, M 1 M has an oxidation state of +2 relative to the whole. 1 The ratio of this material is 25 at% or less, which is the positive electrode active material. [Chemical formula 1] A x M 1 2-x-y M 2 y O 2-a X a (In the above chemical formula 1, A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, and M 2 (where x is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W, and x is a halogen element with x / (2-x) > 1.1, 0 < y < 1, and 0 ≤ a ≤ 0.5.)

2. M 1 M has an oxidation state of +3 relative to the whole. 1 The positive electrode active material according to claim 1, wherein the ratio is 35 at% or more.

3. M 1 M has an oxidation state of +4 relative to the whole. 1 The positive electrode active material according to claim 1, wherein the ratio is 25 at% or more.

4. In the aforementioned chemical formula 1, M 1 The positive electrode active material according to claim 1, wherein the average oxidation number is +3 or higher.

5. Said M 1 The positive electrode active material according to claim 1, wherein the oxidation number of is one or more selected from +2, +3, and +4.

6. Said M 1 The positive electrode active material of the element according to claim 1, wherein is one or more selected from Mn, Co, and Ni.

7. Said M 2 The positive electrode active material of the element according to claim 1, wherein is one selected from Ti, Zr, Nb, Mo, Ta, and W.

8. The difference between the maximum and minimum volume values ​​of the octahedron formed by lithium and its nearest neighbor oxygen atoms in the crystal structure is 3.6 Å. 3 The positive electrode active material according to claim 1, which is as follows:

9. A positive electrode active material according to claim 1, satisfying the following formula 1. [Formula 1] 0.35≦R 1 / (R 2 +R 3 )≦0.65 (In the above formula 1, R 1 M 1 M has an oxidation state of +4 relative to the whole. 1 The ratio of R 2 M 1 M has an oxidation state of +2 relative to the whole. 1 The ratio of R 3 M 1 M has an oxidation state of +3 relative to the whole. 1 (This shows the ratio.)

10. The positive electrode active material according to claim 1, having a disordered rock salt structure.

11. This is a positive electrode active material containing a lithium manganese-based composite oxide. The positive electrode active material has a manganese content of +2 oxidation state of 25 at% or less in the total manganese content.

12. The positive electrode active material according to claim 11, having a disordered rock salt structure.

13. In an alcoholic solvent, A-containing carbonate, M 1 Containing oxides and M 2 A mixture of contained oxides is obtained, The process includes heat-treating the mixture at 900°C to 1500°C under an inert gas atmosphere. A is one or more elements selected from Li and Na, and M 1 is one or more elements selected from Mn, Fe, Co, Ni, Cr, and V, and the M 2 is one or more elements selected from Ti, Zr, Nb, Mo, Ta, and W. Said M 1 The contained oxides are M 1 2 O 3 and M 1 O 2 A method for producing a positive electrode active material containing the active material.

14. The method for producing a positive electrode active material according to claim 13, wherein the mixture further comprises an A-containing halide.

15. The method for producing a positive electrode active material according to claim 13, wherein the mixing is carried out by a wet method using a ball mill.

16. The process further includes a drying step after obtaining the aforementioned mixture. The method for producing a positive electrode active material according to claim 13, wherein the drying is carried out at 50°C to 200°C.

17. The method for producing a positive electrode active material according to claim 13, wherein the heat treatment is performed within the heat treatment temperature range after raising the temperature at a heating rate of 1°C / min to 10°C / min.

18. Positive electrode current collector; and A positive electrode active material layer located on the positive electrode current collector, comprising the positive electrode active material described in any one of claims 1 to 12; The positive electrode, including the positive electrode.

19. The positive electrode according to claim 18, wherein the plate density of the positive electrode is 1.8 g / cc or more.

20. The positive electrode according to claim 18; Negative electrode; and Electrolyte; Rechargeable batteries, including those mentioned above.

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