Lithium cathode active material

Abstract

The present invention relates to a lithium positive electrode active material for a high-voltage secondary battery. the lithium cathode active material comprises at least 94% by weight of spinel; The spinel is Li x Ni y Mn 2-y O4, where: 0.95 ≤ x ≤ 1.05; 0.43≦y≦0.47; wherein the lithium positive electrode active material has a capacity of at least 138 mAh / g, where y is measured by a method selected from the group consisting of electrochemical measurement, X-ray diffraction, and scanning transmission electron microscopy (STEM) combined with energy dispersive X-ray spectroscopy (EDS). The present invention also relates to a lithium positive electrode active material for a high-voltage secondary battery of the present invention, as well as a method for producing a secondary battery comprising the lithium positive electrode active material of the present invention.

Description

[Technical Field]

[0001] Field of Invention This invention relates to lithium cathode active materials for use in high-voltage lithium secondary batteries. In particular, this invention relates to such materials having high capacity, high voltage, and low decomposition properties relative to the Li / Li+ standard. Furthermore, this invention relates to a method for producing such materials. [Background technology]

[0002] background Lithium cathode active material can be characterized by the following formula: Li x Ni y Mn 2-y O 4-δ In the formula, 0.9 ≤ x ≤ 1.1, 0.4 ≤ y ≤ 0.5, and 0 ≤ δ ≤ 0.1. Such materials can be used, for example, in portable devices (US8,404,381B2); electric vehicles, energy storage systems, auxiliary power units, and uninterruptible power supplies. Lithium cathode active materials are recognized as future successors to lithium-ion secondary battery cathode materials such as LiCoO2 and LiMn2O4.

[0003] Lithium cathode active materials can be produced from one or more precursors obtained by co-deposition. Both the precursors and the product are spherical due to the co-deposition process. Electrochimica Acta (2014), pp. 290-296 discloses a material produced by sequential sintering (heat treatment) at 500°C and then 800°C after an initial heat treatment step (500°C). The resulting product exhibits high crystallinity and a spinel structure after the initial heat treatment step (500°C). The product has a uniform morphology and a tap density of 2.03 g / cm³. -3 A uniform secondary particle size of 5.6 μm is observed. According to Electrochimica Acta (2004), pp. 939-948, when spherical particles are uniformly distributed, they exhibit a higher tap density in terms of fluidity and ease of packing compared to disordered particles. 0.5 Mn1.5 In O4, it is speculated that the hierarchical morphology obtained and the large size of the secondary particles were factors contributing to the increase in tap density.

[0004] As disclosed in US8,404,381B2 and US7,754,384B2, the lithium cathode active material can also be produced from a precursor obtained by mechanically mixing starting materials to form a homogeneous mixture. The precursor is heated at 600 °C, annealed at 700 - 950 °C, and cooled in a medium containing oxygen. It is disclosed that the heat treatment step at 600 °C is necessary to fully incorporate lithium into the mixed nickel and manganese oxide precursor. Also, it is disclosed that annealing is generally carried out at a temperature of 800 °C or higher to remove oxygen while forming the desired spinel form. Furthermore, it is disclosed that oxygen can be partially restored by cooling in a medium containing oxygen. US7,754,384B2 does not describe the tap density of the material. It is disclosed that an excess amount of lithium of 1 - 5 mol% is used to produce the precursor.

[0005] J. Electrochem. Soc. (1997)144,144、pp205 - 213) also discloses the production of spinel LiNi 0.5 Mn 1.5 O4 from a precursor produced by mechanically mixing starting materials to obtain a homogeneous mixture. The precursor is heated three times at 750 °C and once at 800 °C in air. When heated above 650 °C, LiNi 0.5 Mn 1.5 O4 loses oxygen and disproportionates, but it is disclosed that when cooled slowly in an oxygen-containing atmosphere, the LiNi 0.5 Mn 1.5 O4 stoichiometry is restored. The particle size and tap density are not disclosed. Also, it is disclosed that the production of spinel phase materials by mechanically mixing starting materials to obtain a homogeneous mixture is difficult, and precursors produced by the sol-gel method are preferred.

Prior Art Documents

[0006] [Patent Document 1] US8,404,381B2 [Patent Document 2] US7,754,384B2 [Patent Document 3] US7,754,384B2 [Non-patent literature]

[0007] [Non-Patent Document 1] Electrochimica Acta (2004), pp939-948 [Non-Patent Document 2] J. Electrochem. Soc. (1997)144,144, pp205-213) [Overview of the Initiative] [Problems that the invention aims to solve]

[0008] It is desirable to provide a lithium cathode active material with high phase purity and high capacity. It is also desirable to provide a lithium cathode active material with high stability, where the capacity degradation of the material is 4% or less over 100 cycles between 3.5 and 5.0 V at 55°C, and 2% or less over 100 cycles between 3.5 and 5.0 V at room temperature. Furthermore, since tap density can increase the energy density of the battery, it is desirable to provide a lithium cathode active material with high tap density. Finally, it is desirable to provide a lithium cathode active material with an optimal Ni content to balance energy density and material decomposition. [Means for solving the problem]

[0009] summary The present invention relates to a lithium positive electrode active material for a high-voltage secondary battery, wherein the lithium positive electrode active material comprises at least 94% by mass of spinel, and the spinel is Lix Ni y Mn 2-y It has the net chemical composition of O4, where, 0.95 ≤ x ≤ 1.05; 0.43 ≤ y ≤ 0.47; Here, the lithium cathode active material has a capacity of at least 138 mAh / g, and y is measured by a method selected from the group consisting of electrochemical measurements, X-ray diffraction, and scanning transmission electron microscopy (STEM) in combination with energy-dispersive X-ray spectroscopy (EDS).

[0010] The inventors have found that particularly high capacity and low discoloration can be obtained when the Ni content in the lithium cathode active material is within a relatively narrow range, i.e., 0.43 ≤ y ≤ 0.47, and when the lithium cathode active material contains at least 94% by mass of spinel, i.e., up to 6% by mass, impurities or a phase other than spinel, such as a sodium chloride type. The range of y is selected to provide a lithium cathode active material with good performance while maintaining a balance between high energy density and low decomposition. If y exceeds 0.47, the degree of decomposition (degradation) of the lithium cathode active material increases, while if y is less than 0.43, the Mn content of the lithium cathode active material increases, resulting in a decrease in the energy density of the battery using the lithium-positive electrode material. Thus, it has been found that a range of 0.43 ≤ y ≤ 0.47 provides the optimal Ni content in balance with high energy density and low decomposition. Preferably, 0.43 ≤ y < 0.45.

[0011] It should be noted that the Ni content in the spinel of the lithium cathode active material may differ from the total Ni content of the lithium cathode active material, as some of the Ni may be in the form of impurities such as sodium chloride. Such differences depend, for example, on the calcination process carried out in the manufacture of the lithium cathode active material, and consequently, on the amount of impurities or non-spinel phases in the lithium cathode active material. To obtain the correct y value for spinel, it is important to use a method suitable for this purpose, which includes the following three methods: electrochemical measurement (quantitative), X-ray diffraction measurement, and a combination of energy-dispersive X-ray spectroscopy (EDS) with scanning transmission electron microscopy (STEM). Methods for measuring the Ni content of the total lithium cathode active material and the spinel in the lithium cathode active material are described in more detail in Example C, and it should be noted that the determination of capacity is described as in Example A. [Modes for carrying out the invention]

[0012] A "spinel" is a crystal lattice in which oxygen atoms are arranged in a slightly distorted cubic close-packed lattice, with cations occupying octahedral and tetrahedral sites in the interstitial gaps within the lattice. Oxygen and octahedral-coordinate cations form a skeletal structure with a three-dimensional channel system that occupies the tetrahedral-coordinate cations. In a spinel-type structure, the ratio of tetrahedral-coordinate cations to octahedral-coordinate cations is approximately 1:2, and the ratio of cations to oxygen is approximately 3:4. The cations at the octahedral sites may consist of a single element or a mixture of different elements. When a mixture of different types of octahedral-coordinate cations forms a three-dimensional periodic lattice on its own, the spinel is called an ordered spinel. When the cations are more randomly distributed, the spinel is called a disordered spinel. Examples of ordered and disordered spinels described in the P4332 space group and the Fd-3m space group, respectively, are disclosed in Adv. Mater. (2012) 24, pp 2109-2116.

[0013] A "salt-type" crystal lattice is one in which oxygen atoms are arranged in a slightly distorted cubic close-packed lattice, and cations completely occupy the octahedral sites in the lattice. Cations can consist of a single element or a mixture of different elements. Mixtures of different types of cations can be statistically disordered, maintaining cubic symmetry (Fm-3m), or ordered, resulting in lower symmetry. The cation / oxygen ratio is 1:1 in a rock salt-type structure.

[0014] The phase composition of the lithium cathode active material can be determined based on the X-ray diffraction pattern obtained using a Phillips PW1800 instrument system with CuKα emission (λ=1.541 Å) in a θ-2θ configuration operating in Bragg-Brentano mode. Experimental parameters contributing to shifts in the observed data need to be corrected. This is achieved using a complete profile fundamental parameter approach, as implemented in Bruker's TOPAS software. The phase composition obtained from Rietveld analysis is given with a typical uncertainty of 1-2 percentage points by mass and represents the relative composition of all crystalline phases. Therefore, no amorphous phases are included in the phase composition.

[0015] The discharge capacity and discharge current described herein are specific values ​​based on the mass of the lithium cathode active material.

[0016] Furthermore, the lithium cathode active material may contain small amounts of elements other than Li, Ni, Mn, and O. Such elements may be one or more of the following, for example, B, N, F, Mg, Al, Si, P, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, and W. Such small amounts of elements may originate from impurities in the starting materials used to produce the lithium cathode active material, or they may be added as dopants to improve some of the properties of the lithium cathode active material.

[0017] The value of x is related to the Li content of the original lithium cathode active material, i.e., the synthesized lithium cathode active material. When the material is incorporated into a battery, the x value typically changes compared to the x value in the original lithium cathode active material. This change in the x value also changes the value of the lattice parameter a. The advantages described herein are based on the original lithium cathode active material, i.e., the x value in the original lithium cathode active material.

[0018] When lithium cathode active material is extracted from a battery, the extracted lithium cathode active material in a half-cell having a lithium metal anode as described in Example A is measured at a current of less than 29 mA / g and a voltage of 3.5 V versus Li / Li + Discharge to the potential of 3.5V vs Li / Li + By maintaining the potential for 5 hours, the x-value of the original material, i.e., the x-value before the lithium cathode active material was incorporated as part of the battery, can be measured.

[0019] In one embodiment, at least 90% by mass of the spinel in the lithium cathode active material is crystallized in the disordered space group Fd-3m. Disordered materials have been observed to have lower decomposition compared to materials manufactured as ordered materials with similar stoichiometry. Ordering is typically characterized by techniques such as Raman spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy, as described in Ionics (2006) 12, pp117-126. As further described in Example D, quantitative ordering parameters can be extracted based on Raman spectroscopy or electrochemistry, as a measurement of separation between two Ni-plates at approximately 4.7 V. This is illustrated in Figure 6b. As shown in Figure 3, the two parameters are very well correlated. Figure 4 shows a comparison of plateau separation dV and decomposition for lithium cathode active materials. While ordering is not the only parameter that affects decomposition (degradation), it can be seen that there is a minimum decomposition at a certain plateau separation, and thus at a certain degree of order. If the spinel is too ordered, it is impossible to achieve a low degree of resolution. A significant increase in the degree of resolution is observed when the plateau separation is less than 40 mV. Preferably, the plateau separation should be at least 50 mV, and preferably around 60 mV.

[0020] In one embodiment, the lithium cathode active material in the half-cell has a potential difference of at least 50 mV between 25% and 75% of the capacity above 4.3 V during discharge at a discharge current of approximately 29 mA / g. When the potential difference between 25% and 75% of the capacity during discharge exceeds 4.3 V, it typically reaches a maximum of 75-80 mV. The potential difference between 25% and 75% of the capacity above 4.3 V during discharge is also expressed as "plateau separation" or dV, and is a measure of the free energy related to the insertion and removal of lithium in a given charge state, which is influenced by whether the spinel phase is disordered or ordered. Without being bound by any theory, a plateau separation of at least 50 mV would be favorable because it relates to whether the lithium cathode active material is in an ordered or disordered phase, and to the rate of half-cell discoloration by the lithium cathode active material. The plateau separation is preferably about 60 mV.

[0021] In one embodiment, the lithium cathode active material is calcined so that the lattice parameter a is between 8.171 Å and 8.183 Å. These values ​​of the lattice parameter a are related to lithium cathode active materials with a low degree of decomposition.

[0022] In particular, the lithium cathode active material has a lattice constant a, which is between (-0.1932y+8.2613)Å and 8.183Å. Preferably, the lattice constant a is between (-0.1932y+8.2613)Å and 8.2667)Å. More preferably, the lattice constant a is between (-0.1932y+8.2613)Å and 8.2641)Å. These values ​​of the lattice constant a are related to a lithium cathode active material with low decomposition and high energy density. In the embodiment, the parameter a is between (-0.1932y+8.2613)Å and 8.183Å, and 0.43≦y<0.45. Preferably, parameter a is between (-0.1932y+8.2613)Å and (-0.1932y+8.2667)Å, and between 0.43≦y<0.45. These combinations of lattice parameter a and y values ​​correspond particularly to lithium cathode active materials with low resolution.

[0023] In one embodiment, the lithium cathode active material has a tap density of 2.2 g / cm³. 3 That concludes the explanation. Preferably, the tap density of the lithium cathode active material is 2.25 g / cm³. 3 Above; 2.3 g / cm³ or more, for example, 2.5 g / cm³ 3 That is the case.

[0024] "Tap density" is a term used to describe the bulk density of powder (or granular solid) after compaction and compression, usually by "tapping" it a specified number of times from a predetermined height. The tapping method is best described as "lifting and dropping." In this context, tapping should not be confused with tamping, lateral striking, or vibration. Since the measurement method can affect the tap density value, the same method should be used when comparing the tap densities of different materials. The tap density of this invention is measured by weighing a 10 mm inner diameter graduated cylinder before and after adding approximately 5 g of powder, recording the quality of the added substance, then tapping the cylinder on a table for a while, and then reading the volume of the tapped substance. Typically, tapping should continue until the volume no longer changes with further tapping. As an example, tapping may be performed for 1 minute and approximately 120 or 180 times.

[0025] One method for quantifying particle size in a slurry or powder is to measure the size of a large number of particles and calculate the characteristic particle size as a weighted average of all measurements. Another method for characterizing particle size is to plot the overall particle size distribution, i.e., the volume fraction of particles of a certain size as a function of particle size. In such a distribution, D10 is defined as the particle size at which 10% of the population's volume fraction falls below the value of D10, D50 is defined as the particle size at which 50% of the population's volume fraction falls below the value of D50 (i.e., the median), and D90 is defined as the particle size at which 90% of the population's volume fraction falls below the value of D90. Methods commonly used to measure particle size distribution include laser diffraction and scanning electron microscopy, often combined with image analysis.

[0026] The lithium positive electrode active material is a powder composed of particles or consisting of particles. Such particles are formed, for example, by the close aggregation of primary particles. In this case, it can be defined as "secondary particles". Alternatively, the particles can be single crystals. Such single crystal particles are quite small and typically have a D50 of 5 μm or less. Therefore, the term "particle" means covering both primary particles such as single crystals and secondary particles.

[0027] In one embodiment, the D50 of the particles constituting the lithium positive electrode active material satisfies: 3 μm < D50 < 12 μm. Preferably, 5 μm < D50 < 10 μm, for example, about 7 μm. When D50 is between 3 and 12 μm, it is advantageous that the handling of the powder becomes easy, enabling a low surface area while maintaining a sufficient surface area for transporting lithium and electrons inside and outside the structure during discharge and charge. In one embodiment, the particle size distribution is characterized in that the ratio between D90 and D10 is 4 or less. This corresponds to a narrow size distribution. Such a narrow size distribution, combined with the fact that the D50 of the particles is between 3 and 12 μm, indicates that the number of fine powders of the lithium positive electrode material, that is, the number of particles with a particle diameter of less than 1 μm, is small, and thus the surface area is small. The small number of particles with a particle diameter of less than 1 μm and the narrow particle diameter distribution ensure that the electrochemical responses of all particles of the lithium positive electrode material are essentially the same. As a result, during charging and discharging, it is avoided that some of the particles receive significantly more stress than other particles.

[0028] The particle size distribution values ​​D10, D50, and D90 are defined and measured as described in Jillavenkatesa A, Dapkunas SJ, Lin-Sien Lum: Particle Size Characterization, NIST (National Institute of Standards and Technology) Special Publication 960-1, 2001. Commonly used methods for determining particle size distribution include laser diffraction and scanning electron microscopy, often combined with image analysis.

[0029] In one embodiment, the lithium cathode active material is 1.5m 2 The betting area is less than / g. The betting area is 1.0m². 2 Less than / g or 0.5m 2 The BET may be reduced to less than 0.3 m / g, or down to 0.2 m / g. A low BET surface area is advantageous because it corresponds to a low-porosity, high-density material. Since the decomposition reaction occurs on the surface of the material, such materials are typically stable materials, i.e., materials that decompose slowly.

[0030] In one embodiment, the lithium cathode active material is composed of particles, which are characterized by an average aspect ratio of less than 1.6 and / or a roughness of less than 1.35. This corresponds to substantially spherical particles.

[0031] The shape of a particle can be characterized using its aspect ratio, which is defined as the ratio of the particle's length to its width. Here, the length is the maximum distance between two points on the periphery, and the width is the maximum distance between two periphery points connected by a line perpendicular to the length.

[0032] Lithium cathode active materials having an aspect ratio of less than 1.6 and / or a roughness of less than 1.35 have the advantage of being stable due to their low surface area. Preferably, the average aspect ratio is less than 1.5, and more preferably less than 1.4. Furthermore, such aspect ratios and roughness provide a material with high tap density. The aspect ratio and roughness values ​​can be measured from scanning electron microscope images of polished particles embedded in epoxy to reveal the particle cross-section, as described in Example B.

[0033] Particle shape can be further characterized using particle circularity or sphericity and shape. J. Almeida-Prieto et al., in J. Pharmaceutical Sci., 93 (2004) 621, list many morphological factors proposed in the literature for evaluating sphericity: Heywood factor, aspect ratio, roughness, pellips, rectangle, modelx, elongation, circularity, roundness, and the Vp and Vr factors proposed in this paper. Particle circularity is given by 4·π·(area) / (perimeter). 2 It is defined as follows, where area is the projected area of ​​the particle. Thus, an ideal spherical particle has a circularity of 1, and particles of other shapes have a circularity value between 0 and 1.

[0034] In one embodiment, the lithium cathode active material is composed of particles, characterized by having a circularity greater than 0.55. In another embodiment, the lithium cathode active material is composed of particles, characterized by having an area envelope (solidity) greater than 0.6 or greater than 0.8. In yet another embodiment, the lithium cathode active material is composed of particles, characterized by having a porosity of less than 3%. The ranges of these parameters relate to lithium cathode active materials with low degradability. The values ​​of circularity, area envelope, and porosity can be measured from scanning electron microscope images of polished particles embedded in epoxy to reveal the particle cross-section, as described in Example B.

[0035] In one embodiment, Li x Ni y Mn 2-y In formula O4, 0.99 ≤ x ≤ 1.01. The crystal structure of the lithium cathode active material is often utilized and preferred when there is approximately one lithium ion for every two transition metal ions for every four oxygen atoms in the spinel crystal. In this case as well, the value of x is related to the Li content of the original lithium cathode active material, i.e., the synthesized lithium cathode active material. When this material is in a battery, the x value typically changes compared to the x value in the original lithium cathode active material. The change in the x value also changes the value of the lattice parameter a. The advantages described herein are based on the original lithium cathode active material, i.e., the x value in the original lithium cathode active material.

[0036] When lithium cathode active material is extracted from a battery, the lithium cathode active material extracted in a half-cell having a lithium metal anode, as described in Example A, is measured at a current of less than 29 mA / g and 3.5V vs. Li / Li + Discharge to the potential of 3.5V vs Li / Li + By maintaining the potential for 5 hours, the x-value of the original material, i.e., the x-value before the lithium cathode active material was incorporated as part of the battery, can be measured.

[0037] In one embodiment, the specific capacity of the lithium cathode active material in the half-cell decreases to 8% or less over 100 cycles between 3.5 and 5.0 V at 55°C. Preferably, the specific capacity of the lithium cathode active material decreases to 6% or less over 100 charge-discharge cycles between 3.5 and 5.0 V; more preferably, when cycled at 55°C with charge-discharge currents of 74 mA / g and 147 mA / g, it decreases to 4% or less over 100 charge-discharge cycles between 3.5 and 5.0 V. The cell (battery) type and test parameters are shown in Example A.

[0038] In one embodiment, the lithium cathode active material is synthesized from a precursor containing Li, Ni, and Mn in the ratio Li:Ni:Mn:X:Y:2-Y, where 0.95≦X≦1.05 and 0.42≦Y<0.5. As used herein, the content of Li, Ni, and Mn in the spinel of the lithium cathode active material, i.e., in the net chemical composition, is Li x Ni y Mn 2-y O 4, x and y are denoted by lowercase x and y, respectively. In contrast, the Li and Ni content in the precursor used to synthesize the lithium cathode active material is denoted by the letters X and Y, and is denoted by uppercase. If x and y differ significantly from X and Y, it signifies low phase purity. Therefore, to obtain high capacity, it is desirable that x be close to or equal to X, and y be close to or equal to Y. Furthermore, impurity phases within the lithium cathode active material, i.e., non-spinel phases, may contain considerable amounts of lithium or different amounts of Mn and Ni. This can decrease x within the spinel and significantly alter y. Such impurity phases further reduce the capacity and stability of the spinel. The presence of impurities can further increase the degree of electrolyte decomposition when the lithium cathode active material is incorporated into a battery cell, and can also increase the dissolution of Mn and Ni from the lithium cathode active material. Both effects are known to increase the capacity fade of the battery cell.

[0039] The Li, Ni, and Mn content in the precursor used to synthesize the lithium cathode active material, indicated by the letters X and Y, can be determined by measuring the amounts of Li, Ni, and Mn in the lithium cathode active material, i.e., in a sample containing both spinel and impurities in amounts representative of the entire sample. Such measurements may be performed using inductively coupled plasma or EDS, as described in Example C.

[0040] Another embodiment of the present invention relates to a method for producing a lithium cathode active material. The method includes the following steps: a.Li x Ni yMn 2-y A step of providing a precursor for producing a lithium cathode active material comprising at least 94 mass% spinel having a chemical composition O4, where 0.95 ≤ x ≤ 1.05; and 0.43 ≤ y ≤ 0.47; b. A step of heating the precursor to a temperature of 500°C to 1200°C to sinter the precursor and obtain a sintered product. c. A step of cooling the sintered product from step b to room temperature.

[0041] As used herein, “precursor” means a composition produced by mechanically mixing or co-depositing starting materials to obtain a homogeneous mixture (Journal of Power Sources (2013) 238, 245-250); a composition produced by mechanically mixing starting materials to obtain a homogeneous mixture (Journal of Power Sources (2013) 238, 245-250); or a composition produced by mixing a lithium source with a composition produced by co-depositing starting materials (Electrochimica Acta (2014) 115, 290-296). Preferably, step a includes providing a precursor by co-depositing the precursor.

[0042] The starting material is selected from one or more compounds selected from the group consisting of metal oxides, metal carbonates, metal oxalates, metal acetates, metal nitrates, metal sulfates, metal hydroxides, and pure metals; where the metal is selected from the group consisting of nickel (Ni), manganese (Mn), and lithium (Li) and mixtures thereof. Preferably, the starting material is selected from one or more compounds selected from the group consisting of manganese oxide, nickel oxide, manganese carbonate, nickel carbonate, manganese sulfate, nickel sulfate, manganese nitrate, nickel nitrate, lithium hydroxide, lithium carbonate, and mixtures thereof. The metal oxidation state of the starting material metal can vary, for example, MnO, Mn3O4, Mn2O3, MnO2, Mn(OH), MnOOH, Ni(OH)2, NiOOH, etc.

[0043] To obtain a good lithium cathode active material, it is naturally necessary to start with good starting materials. Preferably, the precursor includes a co-deposited Ni-Mn precursor, as described in WO2018015207 or WO2018015210, as well as a Li precursor. Alternatively, the Ni-Mn precursor can also be produced by mechanically mixing the starting materials.

[0044] In one embodiment of the method of the present invention, the precipitated compound is a co-deposited compound of Ni and Mn formed in the Ni-Mn co-deposit step. It has been found that in order to obtain a lithium cathode active material, it is desirable to use a precursor in the form of co-deposited Ni-Mn such that the average aspect ratio of the particles is less than 1.6, the roughness is less than 1.35, and the circularity is greater than 0.55.

[0045] Preferably, the Mn-containing precursor that can become a co-deposited Ni-Mn precursor consists of spherical particles having a morphology similar to that of the lithium cathode active material. Therefore, the Mn-precursor and / or Ni-Mn precursor used in the production of the lithium cathode active material is a particle having an aspect ratio of less than 1.6, a roughness of less than 1.35, and / or a circularity greater than 0.55. Preferably, such particles also have an area envelope degree greater than 0.8.

[0046] Ni and Mn can be precipitated with suitable precipitation anions such as carbonates. Preferably, the precursor in the form of co-precipitated Ni-Mn is produced by a precipitation process, in which a first solution of Ni-containing starting material, a second solution of Mn-containing starting material, and a third solution of precipitation anions are simultaneously added to the liquid reaction medium in the reactor, but with respect to the added Ni, the Mn and precipitation anions are added in a ratio of 1:10 to 10:1, preferably 1:5 to 5:1, more preferably 1:3 to 3:1, more preferably 1:2 to 2:1, more preferably 1:1.5 to 1.5:1, or 1:1.2 to 1.2:1 relative to the stoichiometric amount of precipitate.

[0047] Preferably, the first, second, and third solutions are added to the reaction medium in amounts calibrated to maintain the pH of the reaction mixture at an alkaline pH, for example, between 8.0 and 10.0, preferably between 8.5 and 10.0. Preferably, the first, second, and third solutions are added to the reaction mixture over a period of time, for example, between 2.0 and 11 hours, preferably between 4.0 and 10.0 hours, more preferably between 5.0 and 9.0 hours. Preferably, the first, second, and third solutions are added to the reaction mixture under vigorous stirring, providing a power input of 2 W / L to 25 W / L, preferably 4 W / L to 20 W / L, more preferably 6 W / L to 15 W / L, more preferably 8 W / L to 12 W / L.

[0048] To obtain a lithium cathode active material having particles with an average aspect ratio of less than 1.6, a roughness of less than 1.35, and a circularity greater than 0.55, it has been found that it is desirable to use a precursor in the form of co-deposited Ni-Mn produced by the deposition process described above, that is, one or more of the following: The first and second solutions are added simultaneously over a long period of time while vigorously stirring and controlling the indicated pH.

[0049] In contrast to adding the first and second solutions to the third solution, adding the first, second, and third solutions simultaneously offers the possibility of ensuring that the Ni and Mn on one side and the precipitated anions on the other side are present in the reaction mixture at the same level, or at least of the same order of magnitude. Furthermore, although not bound by any theory, it is thought that adding the three solutions simultaneously means that the precipitated particles grow in size during the precipitation process, and a new layer of precipitated material continuously precipitates on the surface of the growing particles. Such stepwise construction of particles is thought to facilitate the formation of the desired properties of the precursor particles and ultimately promote the formation of lithium cathode active material particles. Moreover, performing the precipitation process over a long period of time is also thought to contribute to facilitating the stepwise construction of the particles.

[0050] Furthermore, although not bound by any theory, vigorous stirring of the reaction mixture is also thought to help in the formation of a precursor with the desired properties. In particular, vigorous stirring is thought to move particles in opposite directions, resulting in a grinding effect that makes the particles more spherical.

[0051] Furthermore, it has been found that by performing the precipitation process as described above, and adding the first and second liquids simultaneously over a long period of time while vigorously stirring and controlling the pH, a greater number of spherical particles are produced, and particles with improved chemical compositional uniformity are also generated.

[0052] Ultimately, as described above, it was found that adding the first and second solutions simultaneously over a long period of time while vigorously stirring and controlling the pH produced not only more spherical particles but also precursor particles. When used to produce lithium cathode active material particles, the level of impurities decreases as described above. These are particles containing Li, Ni, and Mn in the ratio Li:Ni:Mn:X:Y:2-Y, where 0.95≦X≦1.05 and 0.42≦Y<0.5, in other words, x is close to or equal to X, and y is close to or equal to Y.

[0053] In relation to the present invention, the expression "stoichiometric amount" refers to the ratio of the amounts of elements present in the precipitated compound.

[0054] In one embodiment, the precursor of the lithium cathode active material is produced from two or more starting materials, such as nickel-manganese carbonate and lithium carbonate, or nickel-manganese carbonate and lithium hydroxide, or nickel-manganese hydroxide and lithium hydroxide, or nickel-manganese hydroxide and lithium carbonate, or manganese oxide, nickel carbonate and lithium carbonate.

[0055] In one embodiment, part of step b is carried out in a reducing atmosphere. For example, the first part of step b is carried out in a reducing atmosphere such as N2, and the next part of step b is carried out in air.

[0056] In one embodiment, the temperature in step b is between 850°C and 1100°C.

[0057] In one embodiment, during the cooling of step c, the temperature is maintained at intervals of 750 to 650°C for a time sufficient to obtain at least 94% phase purity of the lithium cathode active material. The time sufficient to obtain at least 94% phase purity is, for example, as shown in Examples 1 to 3 below; however, other combinations of temperature and time are known to those skilled in the art.

[0058] In another aspect, the present invention further relates to a secondary battery comprising a lithium cathode active material according to the present invention. [Brief explanation of the drawing]

[0059] A brief explanation of the diagram: Figure 1a shows experimental data on the relationship between nickel content in spinel and the degree of decomposition for a series of lithium cathode active materials;

[0060] Figure 1b shows experimental data regarding the relationship between the 4V plateau of lithium cathode active material in a half-cell and the degree of decomposition of lithium cathode active material for a certain range of lithium cathode active materials;

[0061] Figure 1c shows experimental data regarding the relationship between the lattice constant a in the spinel of the lithium cathode active material and the degree of decomposition of the lithium cathode active material within the range of a;

[0062] Figure 2a shows experimental data regarding the relationship between the nickel content in spinel and the lattice constant a of spinel for a certain range of lithium cathode active materials;

[0063] Figure 2b shows experimental data regarding the relationship between the 4V plateau of lithium cathode active materials in half-cells and the lattice constant a of spinel for a certain range of lithium cathode active materials;

[0064] Figure 3 shows experimental data on the relationship between cation ordering parameters measured using Raman spectroscopy and electrochemistry;

[0065] Figure 4 shows experimental data regarding the relationship between the degree of half-cell resolution and the difference in discharge between 25% and 75% potentials with a capacity of 4.3V or higher when discharging at a current of approximately 29 mA / g within the range of lithium cathode active materials;

[0066] Figure 5a shows the relationship between circularity and resolution for four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry;

[0067] Figure 5b shows the relationship between roughness and resolution in four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry;

[0068] Figure 5c shows the relationship between average diameter and resolution for four samples of lithium cathode active material according to the present invention and substantially identical spinel stoichiometry;

[0069] Figure 5d shows the relationship between aspect ratio and resolution for four samples of lithium cathode active material according to the present invention and substantially identical spinel stoichiometry;

[0070] Figure 5e shows the relationship between area envelope and resolution for four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry;

[0071] Figure 5f shows the relationship between porosity and resolution for four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry;

[0072] Figures 6a and 6b show the relationship between capacity and voltage during discharge and charging, respectively, for measuring the 4V plateau and dV, for a half-cell using the lithium cathode active material according to the present invention.

[0073] Figures 7a and 7b are SEM images of one of the materials shown in Figures 5a to 5f at different magnification levels;

[0074] Figures 8a and 8b are SEM images of the second material shown in Figures 5a to 5f at different magnification levels;

[0075] Figures 9a and 9b are SEM images of the third material shown in Figures 5a to 5f at different magnification levels;

[0076] Figures 10a and 10b are SEM images of the fourth material shown in Figures 5a to 5f at different magnification levels;

[0077] Figure 11 shows a comparison of the Ni content (Niy) of spinel, measured by scanning transmission electron microscopy energy-dispersive X-ray spectroscopy (STEM-EDS), with the electrochemical (EC) value for three samples with different Niy content.

[0078] Figure 12 shows the heating profile used to obtain the cathode electrode active material described in Example 2;

[0079] Figure 13 shows the Raman spectrum of the ordered sample. The degree of ordering is calculated using the four gray regions.

[0080] Figures 14a and 14b show SEM images of the material of the present invention, in perspective and cross-sectional views, respectively.

[0081] Figures 15a and 15b show SEM images of commercially available materials, in perspective and cross-sectional views, respectively.

[0082] Detailed explanation of the diagram: Figure 1a shows the degree of decomposition and nickel content (indicated as "Niy" in Figure 1a) in spinel for the lithium cathode active material range. x Ni y Mn 2-y This is experimental data regarding the relationship between the O4 value (y). All samples exhibit a capacity of at least 138 mAh / g when discharged at 74 mA / g (0.5C) in a half-cell between 3.5V and 5V at 55°C, as described in Example A. The degree of degradation is measured in a half-cell at 55°C and is described as the degree of degradation per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Since the degree of degradation is influenced by several factors, there will be variability, but a guideline line or curve is provided to emphasize that a minimum degree of degradation exists at a given Ni content of spinel, and that the minimum degradation rate decreases as the Ni content decreases. Therefore, it is not possible to provide lithium cathode active materials with a degree of degradation lower than the minimum degree of degradation; however, heterogeneity, morphology / or excessive ordering in the lithium cathode active material may make it difficult to reach the minimum degree of degradation. To illustrate some of these other parameters, four samples (black squares) were prepared to investigate how they affect the degree of morphological degradation, as shown in Example 4.

[0083] Figure 1b shows experimental data regarding the relationship between the 4V plateau of lithium cathode active material in a half-cell and the degree of resolution for a certain range of lithium cathode active material. All samples exhibit a capacity of at least 138 mAh / g when discharged at 74 mA / g (0.5C) in a half-cell between 3.5V and 5V at 55°C, as described in Example A. The degree of resolution is measured in a half-cell at 55°C and is described as the degree of resolution per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Figure 1b also includes guide lines or curves to emphasize that there is a minimum degree of resolution at a given 4V plateau, and that the minimum degree of resolution decreases as the 4V plateau increases. The four samples shown as black squares in Figure 1a are also shown as black squares in Figure 1(b).

[0084] Figure 1c shows experimental data regarding the relationship between the lattice constant a ("a-axis") in the spinel of the lithium cathode active material and the degree of resolution of the lithium cathode active material within a certain range. All samples exhibit a capacity of at least 138 mAh / g when discharged at 74 mA / g (0.5C) in a half-cell between 3.5V and 5V at 55°C, as described in Example A. The degree of resolution is measured in a half-cell at 55°C and is described as the degree of resolution per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Figure 1c also includes guide lines or curves to emphasize that for a given lattice parameter, there exists a minimum degree of resolution, and that the minimum degree of resolution decreases as the lattice parameter a increases. The four samples shown as black squares in Figures 1a and 1b are also shown as black squares in Figure 1c. Figures 1a, 1b, and 1c show the relationships between different parameters of the same sample.

[0085] Figure 2a shows the amount of nickel in spinel (Li, which is shown as "Niy" in Figure 2a). x Ni y Mn 2-y This is experimental data concerning the relationship between the value y) in O4 and the lattice parameter a of spinel for lithium cathode active material. All samples exhibit a capacity of at least 138 mAh / g when discharged at 74 mA / g (0.5C) in a half-cell at 55°C and between 3.5V and 5V, as described in Example A. From Figure 2a, it can be seen that there is a linear dependence between the nickel content and the lattice constant a for the experimental data. Slight variations may occur due to variations in lithium content.

[0086] Figure 2b shows experimental data regarding the relationship between the 4V plateau of lithium cathode active materials in a half-cell and the lattice constant a of spinel for a certain range of lithium cathode active materials. All samples exhibit a capacity of at least 138 mAh / g when discharged at 74 mA / g (0.5C) in a half-cell at 55°C between 3.5V and 5V, as described in Example A. Figures 2a and 2b show the relationship between different parameters for the same sample.

[0087] As shown in Example C, if Ni is low, Mn 3+ Since the content increases, there is a correlation between the Ni content in spinel and the lattice parameters of the spinel.

[0088] Through this, the inventors found a close correlation between the degree of decomposition of lithium cathode active material, parameter a, Ni content, and the 4V plateau. This correlation can be used to select appropriate values ​​for the parameter and Ni content in order to optimize lithium cathode active material for specific applications.

[0089] Figure 3 shows experimental data relating cation ordering parameters measured using Raman spectroscopy and electrochemistry, respectively. The two methods are described in Example D, and a correlation is observed. Disordered lithium cathode active materials have been observed to exhibit lower decomposition compared to similar materials produced as ordered materials. While there is some variation in the samples shown in Figure 3, there is a tendency for higher dV values, which corresponds to lower Raman ordering values. The voltage difference dV is measured as described in relation to Figure 6b. As used herein, the term “Raman ordering” refers to the measurement of cation ordering in lithium cathode active materials based on Raman spectroscopy as described in Example D.

[0090] Figure 4 shows experimental data on the relationship between the degree of half-cell resolution and the discharge difference between potentials at 25% and 75% of the capacity above 4.3V during discharge, using a current of approximately 29 mA / g for a range of lithium cathode active materials. This difference dV is measured as in Example D. Figure 4 shows that a relationship exists between the difference dV and the degree of resolution of the lithium cathode active material. The difference dV is also expressed as "plateau separation" and is a measure of the free energy related to the insertion and removal of lithium in a given charge state, which is influenced by whether the spinel phase is disordered or ordered. Although there is some variation in the samples shown in Figure 4, there is a tendency for higher dV values ​​to indicate lower resolution. Without being bound by theory, a plateau separation of at least 50 mV seems favorable because this is related to whether the lithium cathode active material is in an ordered or disordered phase, and the rate of half-cell discoloration by the lithium cathode active material.

[0091] Figures 5a-5f show the relationship between the degree of resolution and the parameter range for the four samples indicated by black squares in Figures 1a-1c, 2a-2b, and 4. These four lithium cathode active materials differ in degree of resolution, as is evident from Figures 1a-1c and 2a-2b, but their spinel stoichiometry is very similar. Of the four samples shown in Figures 5a-5f, the spinel stoichiometry for three samples is LiNi 0.454 Mn 1.546 The fourth sample of spinel has O4, and the spinel stoichiometry is LiNi 0.449 Mn 1.551 Having O4 。 All four samples were prepared based on the co-deposited precursor, and the particles are secondary particles.

[0092] Figure 5a shows the relationship between the circularity and resolution of secondary particles for four samples of lithium cathode active material according to the present invention and substantially identical spinel stoichiometry. The circularity of secondary particles is calculated from the area and circumference (outer circumference) of the particle shape using 4π. * [Area] / [Perimeter] 2It is measured as follows. The circumference represents both the overall shape and the surface roughness; a higher value means it is more perfectly round and has a smoother surface. A perfectly smooth circle has a circularity of 1. Average circularity is the arithmetic mean of the circularity of all secondary particles measured in the sample. It was calculated using the ImageJ software (https: / / imagej.nih.gov). Figure 5a shows that a higher circularity corresponds to a lower resolution.

[0093] Figure 5b shows the relationship between secondary particle roughness and resolution for four samples of lithium cathode active material according to the present invention, and under substantially the same spinel stoichiometry. Secondary particle roughness is measured as the ratio of the particle shape to the circumference of an ellipse fitted to the particle shape. Roughness represents how rough the surface is. A higher value indicates a rougher surface. Average roughness is the arithmetic mean of the roughness of all secondary particles measured in the sample. It was calculated using ImageJ software (https: / / imagej.nih.gov). In Figure 5b, it can be seen that a lower roughness value corresponds to a lower resolution.

[0094] Figure 5c shows the relationship between the average diameter of secondary particles and the degree of resolution for four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry. The diameter of the secondary particles is measured as the equivalent circle diameter, i.e., the diameter of a circle with the same area as the particle. The average diameter is the arithmetic mean of the diameters of all secondary particles measured in the sample. It was calculated using the ImageJ software (https: / / imagej.nih.gov). In Figure 5c, it can be seen that the average diameter is reduced to suppress the degree of resolution. The average diameter of the secondary particles is given in μm.

[0095] Figure 5d shows the relationship between the aspect ratio and resolution of secondary particles in four samples of lithium cathode active material according to the present invention and substantially the same spinel stoichiometry. The aspect ratio of secondary particles was measured from an ellipse fitted to the particle shape. The aspect ratio is defined as [principal axis] / [minor axis], where [principal axis] and [minor axis] are the major and minor axes of the fitted ellipse. The average aspect ratio is the arithmetic mean of the aspect ratios of all secondary particles measured in the sample. It was calculated using ImageJ software (https: / / imagej.nih.gov). In Figure 5d, it can be seen that, in general, lower aspect ratios correspond to lower resolution.

[0096] Figure 5e shows the relationship between the area envelope and resolution of secondary particles for four samples of lithium cathode active material according to the present invention, and under substantially the same spinel stoichiometry. The area envelope of secondary particles is defined as the ratio of the particle area to the convex surface area, i.e., [area] / [convex surface area]. The convex surface area can be thought of as the shape produced by wrapping a rubber band around the particle. The more concave features there are on the particle surface, the higher the convex surface area and the lower the area envelope. The average area envelope is the arithmetic mean of the area envelopes of all secondary particles measured in the sample. It was calculated using the ImageJ software (https: / / imagej.nih.gov). Figure 5e shows that a higher area envelope value indicates less resolution.

[0097] Figure 5f shows the relationship between the porosity and resolution of secondary particles for four samples of lithium cathode active material according to the present invention and for substantially identical spinel stoichiometry. The porosity of secondary particles is the percentage of the internal region that appears with dark contrast in the SEM image, and the dark contrast is interpreted as porosity, i.e., pores inside the particle. The average porosity is the arithmetic mean of the porosity of all secondary particles measured in the sample. It was calculated using the ImageJ software (https: / / imagej.nih.gov). Figure 5f shows that, generally, lower porosity corresponds to less resolution.

[0098] Figures 6a and 6b show the relationship between the capacity and voltage of a half-cell with lithium cathode active material during discharge and charge, for measuring the 4V plateau and dV, respectively. The measurements used as examples for calculating the two parameters are based on the lithium cathode active material described in Example 2. The 4V plateau is used to describe the capacity around 4V compared to the total capacity. Since this ratio can fluctuate slightly between discharge and charge, its value is determined as the average of the two. Using the variable names from the figures, the 4V plateau is (Q 4V cha +(Q tot dis -Q 4V dis )) / (2 * Q tot dis It is calculated as follows: Based on the example, the value is calculated as follows: (11.0 + (138.8 - 123.1)) / (2 * 138.8) = 9.6%. The plateau separation between the two plateaus around 4.7V, dV, was calculated as the voltage difference between 25% and 75% of the discharge capacity between 4.3V and 5V during discharge at 29.6mA / g. Calculating this using the example shown in Figure 6b, we get 4.718V - 4.662V = 56mV.

[0099] Figures 7a–10b are SEM images at two different magnification levels for four samples indicated by black squares in Figures 1a–1c and 2a–2b. As is clear from Figures 1a–1c and 2a–2b, these four substances have different resolutions. In the samples in Figures 7a, 7b, 9a, 9b, 10a, and 10b, the stoichiometry of spinel is LiNi 0.454 Mn 1.546 The spinel of the samples in Figures 8a and 8b, which contain O4, has a stoichiometry of LiNi 0.449 Mn 1.551 O 4. It has.

[0100] Figures 7a and 7b are SEM images of one of the samples shown in Figures 1a-1c, 2a-2b, and 5a-5f at two different magnification levels. The sample shown in Figures 7a and 7b is a lithium cathode active material with a resolution of 7.2%. The sample material was embedded in epoxy, polished to a flat surface, and the cross-section of the secondary particles of the lithium cathode active material was imaged. Images were acquired using an 8kV accelerating voltage and a backscatter electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0101] Figures 8a and 8b are second SEM images of the sample shown in Figures 1a-1c, 2a-2b, and 5a-5f at two different magnification levels. The sample shown in Figures 8a and 8b is a lithium cathode active material with a resolution of 6.2%. The sample material was embedded in epoxy, polished to a flat surface, and the cross-section of the secondary particles of the lithium cathode active material was imaged. Images were acquired using an 8kV accelerating voltage and a backscatter electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0102] Figures 9a and 9b are SEM images of the sample shown in Figures 1a-1c, 2a-2b, and 5a-5f at two different magnification levels. The sample shown in Figures 9a and 9b is a lithium cathode active material with a resolution of 4.6%. The sample material was embedded in epoxy, polished to a flat surface, and the cross-section of the secondary particles of the lithium cathode active material was imaged. Images were acquired using an 8kV accelerating voltage and a backscatter electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0103] Figures 10a and 10b are SEM images of the sample shown in Figures 1a-1c, 2a-2b, and 5a-5f at two different magnification levels. The sample shown in Figures 10a and 10b is a lithium cathode active material with a resolution of 3.2%. The sample material was embedded in epoxy, polished to a flat surface, and the cross-section of the secondary particles of the lithium cathode active material was imaged. Images were acquired using an 8kV accelerating voltage and a backscatter electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0104] Figure 11 compares the Ni content (Niy) in spinel, measured by energy-dispersive X-ray spectroscopy (STEM-EDS) using a scanning transmission electron microscope, with values ​​obtained by electrochemistry (EC) for three samples with different Niy values. STEM-EDS directly measures the elemental composition of a material, while EC indirectly measures the composition from the size of a 4V charging plateau. The comparison results showed that the two methods were consistent, indicating that the 4V charging plateau is indeed directly related to the composition of the spinel phase. Therefore, measuring the 4V charging plateau is an effective method for determining the composition of spinel.

[0105] Figure 12 shows the heating profile used to obtain the cathode electrode active material described in Example 2. The temperature is measured using a thermocouple in close proximity to the powder bed. The heating is divided into two stages, as in Example 2.

[0106] Figure 13 shows the Raman spectrum of ordered spinel. 151 cm⁻¹ -1 ~172cm -1 , is 385cm -1 ~420cm -1 , 482cm -1 ~505cm -1 , 627cm -1 ~639cm -1 The degree of ordering is calculated using these four gray areas. [Examples]

[0107] example: In the following, exemplary and non-limiting embodiments of the present invention are described in the form of experimental data. Examples 1 to 5 relate to methods for producing lithium cathode active materials. Example A describes a method for electrochemical testing, Example B describes SEM-based measurements of morphological parameters, Example C describes three methods for measuring the Mn and Ni content in spinel, and Example D describes two methods used to measure the degree of cation ordering in spinel.

[0108] Example 1: Synthesis of lithium cathode active material Dissolve 7.1 kg of NiSO4·7H2O and 15.1 kg of MnSO4·H2O in 48.5 kg of water to prepare an aqueous solution of NiSO4 and MnSO4 metal ions with a Ni:Mn atomic ratio of 1:3.18. In a separate container, dissolve 11.2 kg of Na2CO3 in 51.0 kg of water to prepare an aqueous carbonate solution. No ammonia or other chelating agents are used. Add the metal ion solution and the carbonate solution separately at approximately 3 L / h and insert into a reactor with vigorous stirring (400 rpm), pH 8.8-9.5, and temperature 35°C. The reactor volume is 40 liters. After 4 hours, remove the product from the reactor and divide it into 6 batches. Continue precipitation in one of the 6 batches for approximately 4 hours, then divide it into 2 batches. Continue precipitation in each of the 2 batches until the desired Ni,Mn-carbonate precursor is obtained. Follow this procedure for the remaining 5 samples. To remove Na2SO4, the precursor is filtered and washed.

[0109] As described above, 4667 g of the co-precipitation Ni,Mn-carbonate precursor (Ni: 0.478, Mn: 1.522) and 716 g of Li2CO3 (corresponding to Li:Ni:Mn = 1.00:0.478:1.522) are mixed with ethanol to form a viscous slurry. The slurry is shaken in a paint shaker for 3 minutes to completely deagglomerate and obtain a mixture of granular material. The slurry is poured into a tray and dried at 80°C. The dried material is further deagglomerated by shaking in a paint shaker for 1 minute to obtain a homogeneous powder mixture with free flow.

[0110] The powder mixture is heated in a furnace with nitrogen flowing through it at a gradient of 2.5°C / min to 550°C. The powder is heated at 550°C for 4 hours. Thereafter, the powder is treated in 550°C air for 9 hours. The temperature is raised to 950°C at a gradient of 2.5°C / min. 950°C is maintained for 10 hours, then the temperature is reduced to 700°C at a gradient of 2.5°C / min. 700°C is maintained for 4 hours, then the temperature is reduced to room temperature at a gradient of 2.5°C / min.

[0111] Next, 20g of the powder is heated to 900°C in oxygen-enriched air (90% O2) at a rate of 2.5°C / min. The temperature is maintained at 900°C for 1 hour, then reduced to 750°C at a rate of 2.5°C / min. The temperature is maintained at 750°C for 4 hours, then reduced to room temperature at a rate of 2.5°C / min.

[0112] This powder was shaken in a paint shaker for 6 minutes to deagglomerate again, and then passed through a 45 micron sieve to obtain a lithium cathode active material consisting of 97.7% LNMO, 1.5% O3, and 0.8% rock salt. Using the methods described in Examples A and C, the stoichiometry of spinel was determined to be LiNi 0.47 Mn 1.53 It was measured to be O4, the 4V plateau constituted 6% of the total discharge capacity, and the degree of decomposition at 55°C was measured to be 4% per 100 cycles for a half-cell. The relevant parameters are shown in Table 1 below.

[0113] Example 2: Synthesis of lithium cathode active material A precursor in the form of co-precipitation Ni,Mn-carbonate (Ni:0.46, Mn:1.54), prepared in the same manner as in Example 1, and 83.1 g of Li2CO3 (corresponding to Li:Ni:Mn=1.00:0.46:1.54) were mixed with ethanol to form a viscous slurry. The slurry was shaken in a paint shaker for 3 minutes to completely deagglomerate and obtain a mixture of granular material. The slurry was poured into a tray and dried at 80°C. The dried material was further deagglomerated by shaking it in a paint shaker for 1 minute to obtain a freely flowing, homogeneous powder mixture.

[0114] The powder mixture is heated in a muffle furnace at a gradient of approximately 1°C / min to 550°C under a nitrogen flow. The temperature is maintained at 550°C for 3 hours, and then cooled to room temperature at a gradient of approximately 1°C / min.

[0115] The product is shaken in a paint shaker for 6 minutes to deagglomerate, then passed through a 45-micron sieve and dispersed in an alumina crucible in a layer of 10-25 mm. This powder is heated in a muffle furnace in air at a gradient of 2.5°C / min to 670°C. The temperature is maintained at 670°C for 6 hours, then further increased to 900°C at a gradient of 2.5°C / min. The temperature is maintained at 900°C for 10 hours, then decreased to 700°C at a gradient of 2.5°C / min. The temperature is maintained at 700°C for 4 hours, then decreased to room temperature at a gradient of 2.5°C / min.

[0116] This powder was shaken in a paint shaker for 6 minutes to deagglomerate again, and then passed through a 45-micron sieve to obtain a lithium cathode active material consisting of 98.9% LNMO, 0.5% O3, and 0.6% rock salt. Using the methods described in Examples A and C, the stoichiometry of spinel was LiNi 0.45 Mn 1.55 It was determined to be O4, with the 4V plateau constituting 10% of the total discharge capacity, and the degree of decomposition at 55°C was measured to be 3% per 100 cycles for a half-cell. The relevant parameters are shown in Table 1 below.

[0117] Example 3: Synthesis of lithium cathode active material Similar to Example 1, 1400 g of the co-precipitated Ni,Mn-carbonate precursor (Ni:0.47, Mn:1.53) and 211 g of Li2CO3 (corresponding to Li:Ni:Mn=0.98:0.47:1.53) are mixed with ethanol to form a viscous slurry. The slurry is shaken in a paint shaker for 3 minutes to completely deagglomerate and obtain a mixture of granular material. The slurry is poured into a tray and dried at 80°C. The dried material is further deagglomerated by shaking in a paint shaker for 1 minute to obtain a homogeneous powder mixture with free flow.

[0118] The powder mixture is heated in a furnace with a nitrogen flow at a gradient of 2°C / min to 600°C. The temperature is maintained at 600°C for 6 hours. Thereafter, the powder is heated in 600°C air for 12 hours. The temperature is increased to 900°C at a gradient of 2°C / min. The temperature is maintained at 900°C for 5 hours, then the temperature is reduced to 750°C at a gradient of 2°C / min. The temperature is maintained at 750°C for 8 hours, then the temperature is reduced to room temperature at a gradient of 2°C / min.

[0119] This powder was shaken in a paint shaker for 6 minutes to deagglomerate again, and then passed through a 45-micron sieve to obtain a lithium cathode active material consisting of 98.1% LNMO, 1.4% O3, and 0.5% rock salt. Using the methods described in Examples A and C, the stoichiometry of spinel was determined to be LiNi 0.43 Mn 1.57 It was determined to be O4, with the 4V plateau accounting for 13% of the total discharge capacity, and the degree of decomposition at 55°C was measured to be 2% per 100 cycles in the half-cell. The relevant parameters are shown in Table 1 below.

[0120] Example 4: Synthesis of lithium cathode active material Four samples were synthesized to obtain different particle morphologies while maintaining the same Ni content in the spinel. The four samples are included in Figures 1a-1c, 2a-2b, and 4 as black squares, and Figures 7a-10b show SEM images of the particle cross-sections. Figures 5a-5f show the relationship between the degree of resolution and a series of parameters related to morphology for the four samples. The relevant parameters are shown in Table 1 below. The precursors for all samples were co-deposited using slightly different variations as described in Example 1. For example, the precursor for Sample 2 in Table 2, as shown in Figures 8a and 8b, was produced by stirring at 200 rpm in a packed reactor at approximately 2.6 W / L, and the precursor for Sample 4 in Table 2, as shown in Figures 10a and 10b, was produced by stirring at 400 rpm in a packed reactor at approximately 10 W / L.

[0121] Example 5: Synthesis of lithium cathode active material Additional samples were prepared as Examples 1-3 using separate precursors and different calcination programs. Figure 1a shows the correlation between the degree of decomposition per 100 cycles at 55°C, measured in the half-cell described in Example A, and the Ni content in the spinel. The Ni content in the spinel is measured electrochemically as described in Example C. Figure 1b shows the correlation between the degree of decomposition per 100 cycles at 55°C, measured in the half-cell, as described in Calcination A and the 4V plateau. Figure 1c shows the correlation between the degree of decomposition at 55°C, measured in the half-cell described in Example A, and the lattice parameter a in the spinel. Table 1 below contains the Ni content, Niy, lattice parameter, a, 4V plateau, capacity, degree of decomposition, and difference, dV, between the two Ni-plateaus described in Example D for the samples described in Examples 1-5.

[0122] [Table 1]

[0123] Example 6: Morphological measurement using a scanning electron microscope: Comparison of a sample according to the present invention (sample 4) and a commercially available sample. Sample 4 discussed in Example 4 and a commercially available sample of lithium cathode active material were compared using a scanning electron microscope (SEM).

[0124] Figures 14a and 14b show SEM images of sample 4 as a perspective view and cross-section view, respectively, while Figures 15a and 15b show SEM images of a commercially available sample as a perspective view and cross-section view, respectively. As is clear from Figures 14a and 14b, the particles of sample 4 are highly spherical and highly uniform in their internal structure. In contrast, the particles of the commercially available sample (Figures 15a and 15b) are not spherical and appear to have a high degree of aggregation.

[0125] Example: Electrochemical test method for lithium cathode active material manufactured from Examples 1-5: Electrochemical tests were performed using thin composite positive electrodes and metallic lithium negative electrodes (half-cells) with 2032 types of coin-type batteries. The thin composite positive electrodes were manufactured by completely mixing 84% by mass of lithium positive electrode active material (manufactured according to Examples 1-4), 8% by mass of SuperC65 carbon black (Timcal), and 8% by mass of PVdF binder (polyvinylidene difluoride, sigma-Aldrich) in NMP (N-methyl-pyrrolidone) to form a slurry. This slurry was spread onto carbon-coated aluminum foil using a doctor blade with a gap of 100-200 μm and dried at 80°C for 12 hours to form a film. From the dried film, electrodes with a diameter of 14 mm and filled with approximately 8 mg of lithium positive electrode active material were cut out, pressed in a hydraulic pellet press (20 mm diameter, 3 tons), and dried under vacuum at 120°C for 10 hours in an argon-filled glove box.

[0126] Coin cells were assembled in a glove box filled with argon gas (<1 ppm O2 and H2O) using two polymer separators (Toray V25EKD and Freudenberg FS2192-11SG) and an electrolyte containing 1 mole of LiPF6 in EC:DMC (weight ratio 1:1). Two 250 μm thick lithium disks were used as the counter electrodes, and the pressure inside the cell was regulated by two stainless steel disk spacers and a disk spring on the negative electrode side. Electrochemical lithium insertion and extraction were monitored using an automated cycle data recording system (Maccor) operating in galvanostatic mode.

[0127] The electrochemical test includes 6 generation cycles (3 cycles 0.2C / 0.2C (charge / discharge) and 3 cycles 0.5C / 0.2C), 25 output test cycles (5 cycles 0.5C / 0.5C, 5 cycles 0.5C / 1C, 5 cycles 0.5C / 2C, 5 cycles 0.5C / 5C, 5 cycles 0.5C / 10C), and 120 0.5C / 1C cycles to measure the degree of decomposition. The C rate is 147mAhg. -1 The positive electrode active material (for example, 0.2C is 29.6mAg) -1The calculations were based on the theoretical specific capacity of lithium (corresponding to 10C, where 10C corresponds to 1.47mAg). Voltage isolation of two 4.7V plateaus, dV, and voltage isolation of a 4V plateau were calculated based on cycle 3, capacity was calculated based on cycle 7, and resolution was calculated between cycles 33 and 133.

[0128] Example B: Method for measuring particle size and shape using a scanning electron microscope: To prepare samples for scanning electron microscopy (SEM), lithium cathode active material was embedded in epoxy and polished to a flat surface for imaging of particle cross-sections. To evaluate the correlation between particle shape and resolution for samples with substantially the same spinel phase stoichiometry, particle size and shape were measured for different samples using SEM images of the embedded cross-sections. In the samples shown in Figures 7a, 7b, 9a, 9b, 10a, and 10b, the spinel phase was stoichiometric LiNi 0.454 Mn 1.546 The spinel in the samples in Figures 8a and 8b contains O4, and the stoichiometric value of LiNi 0.449 Mn 1.551 It has O4.

[0129] SEM images were acquired using an 8kV accelerating voltage and a backscatter electron detector. Images were acquired at low and high magnification, with pixel sizes of 0.216 μm / pixel (Figures 7a, 8a, 9a, 10a) and 0.054 μm / pixel (Figures 7b, 8b, 9b, 10b), respectively. Low-magnification images were used to measure particle size and shape.

[0130] SEM images were analyzed using the ImageJ software (https: / / imagej.nih.gov). The procedure was as follows: • Center filter, radius 1 pixel; • Sharpening; • Thresholding using the Otsu algorithm; • Analyze particles: Area 3μm 2 Only particles exceeding a certain threshold are considered.

[0131] The particle analysis process involves measuring the area and perimeter (circumference) of each particle and calculating the best-fitting ellipse that has the same area as the particle. Then, using the area, perimeter, and fitted ellipse, a number of size and shape descriptors are calculated for each particle in the SEM image: • Diameter: The equivalent diameter of a circle, i.e., the diameter of a circle with the same area as the particle. • Aspect ratio: The aspect ratio of the particle's fitted ellipse, i.e., [major axis] / [minor axis]. • Roughness: The ratio between the measured circumference and the circumference of the fitted ellipse. Describes the surface roughness of the particles. • Circularity: 4π * [Area] / [Perimeter] 2 Circularity describes the overall shape and surface roughness. A smooth, circular surface has a circularity of 1. • Area Envelopment: [Area] / [Area of ​​Convex Surfaces]. The area of ​​convex surfaces can be thought of as the shape resulting from wrapping a rubber band around a particle. The more concave features there are on the surface of the particle, the higher the area of ​​convex surfaces and the lower the area envelope. • Porosity: The percentage of the interior region of a particle that appears as a dark contrast in SEM images. The dark contrast is interpreted as porosity, or holes, inside the particle.

[0132] The sample mean values ​​of these descriptors are shown in the table below for four samples that are substantially identical in spinel stoichiometry but differ in resolution. Resolution was measured in half-cells as the decrease in capacity after 100 cycles between 3.5 and 5.0 V at 55°C.

[0133] [Table 2]

[0134] As described in connection with FIGS. 5a-5f, the resolution as a function of six descriptors shows a correlation such that a lithium positive electrode active material having a low resolution is characterized by one or more of the following parameters: short diameter, low roughness, low aspect ratio, high circularity, high area coverage, and low porosity. Optimally, the lithium positive electrode active material will meet most or all of the six descriptors of short diameter, low roughness, low aspect ratio, high circularity, high area coverage, and low porosity. Preferably, the diameter is less than 10 μm, the roughness is less than 1.35, the circularity is greater than 0.55, and the area coverage is greater than 0.8.

[0135] Example C: Measurement of Ni and Mn content in spinel As described above, depending on the production of the lithium positive electrode active material, the contents of Ni and Mn in the spinel of the lithium positive electrode active material may differ from the bulk values that can be determined, especially using ICP. Example C shows that the contents of Ni and Mn in the spinel of the lithium positive electrode active material can be measured using three different methods based on electrochemistry, diffraction, and electron microscopy, respectively.

[0136] The methods based on electrochemistry and diffraction utilize the change in the ratio of Mn 3+ and Mn 4+ which changes due to the change in the Mn / Ni ratio. This becomes clear by calculating the average oxidation state of Mn in Li x Ni y Mn 2-y O4 to be (4 * 2 - 1 * x - 2 * y) / (2 - y), assuming the oxidation state of Li is 1+, the oxidation state of Ni is 2+, and the oxidation state of O is -2. Using this, when x is 1, the formula can be written as Li +1 Ni +2 y Mn +3 1-2y Mn +4 1+y O4, and when x is other than 1, a similar formula can be written.

[0137] Electrochemically, during cycling, Li+ Extraction and insertion of Mn 3+ is Mn 4+ It can be reversibly oxidized back to its original state, and also in the circulating Li + Through extraction and insertion, Ni 2+ is Ni 4+ It can be reversibly oxidized back to its original state. In this way, Ni 2+ For two Li + Mn 3+ One Li + It is possible to extract (and subsequently insert) it. When x=1, equation Li +1 Ni +2 y Mn +3 1-2y Mn +4 1+y Based on O4, the percentage of the total volume attributable to Mn activity is given by (1-2y) / (1-2y+2y)=(1-2y). For example, y=0 corresponds to 0% of the volume attributable to Mn activity, while y=0.45 and 0.4 correspond to 10% and 20% of the total volume being attributable to Mn activity, respectively.

[0138] In LNMO, Mn 3+ / Mn 4+ The reaction is approximately 4V vs Li / Li + Observed at Ni 2+ / Ni 4+ The reaction was approximately 4.7V vs Li / Li + Observed at 3.5V to 5V vs Li / Li + Compared to the total capacity up to 3.5V~4.3V vs Li / Li +The capacity measured up to this point is expected to correspond to the Mn activity. The capacity around 4V is determined using the third discharge at 29mA / g (0.2C) as described in Example A. During charging and discharging, the battery is not in equilibrium, and due to the internal resistance within the battery, the measured voltage may shift upward during charging and downward during discharging. This effect is particularly pronounced near sudden changes in battery voltage, and therefore the proportion of Mn activity appears to differ depending on whether the analysis is based on charging or discharging. Figure 6a shows the discharge and charging voltage curves as a function of capacity for the third charge at 29mA / g (0.2C) described in Example A. The capacity Q corresponds to a voltage of 4.3V between charging and discharging, respectively. 4V cha and Q 4V dis Using this, the total discharge capacity Q tot dis Using this method, the proportion of Mn activity is (Q 4V cha +(Q tot dis -Q 4V dis )) / (2*Q tot dis This value is given by (Q). This value is expressed as the "4V plateau". The maximum and minimum values ​​of the 4V plateau are given by (Q). tot dis -Q 4V dis ) / (Q tot dis ) and (Q 4V cha ) / (Q tot dis It is given by ).

[0139] diffraction Mn 3 Ions and Mn 4+The ion sizes differ, which affects the spinel lattice parameters. Powder X-ray diffraction data were collected on a Phillips PW1800 instrument system in Bragg-Brentano mode with θ~2θ geometry using CuKα emission (λ=1.541 Å). Experimental parameters contributing to the observed peak position shifts need to be corrected from the observed data, which is used in the calculation of lattice parameters. This is achieved using the full-profile fundamental parameter approach implemented in Bruker's TOPAS software. As a result, the spinel lattice constant is Mn 3+ The amount of [substance], and consequently the amounts of Mn and Ni, is determined with an uncertainty of nearly 5 / 10000 Å, which is sufficient to determine the amounts of [substance].

[0140] Electron microscope By combining scanning transmission electron microscopy (STEM) and energy-dispersive X-ray spectroscopy (EDS) to perform elemental mapping, the amounts of Mn and Ni in spinel can be directly measured. STEM-EDS was used to measure the amounts of Ni and Mn in three different samples to compare the composition of the spinel phase with values ​​calculated from a 4V charging plateau in electrochemical measurements.

[0141] STEM-EDS measurements were performed using an FEI Talos transmission electron microscope equipped with a ChemiSTEM EDS detector system. The microscope was operated in STEM mode with an acceleration voltage of 200 kV. Elemental maps were acquired and analyzed using Bruker's Esprit 1.9 software. Standard quantification was performed using automated background subtraction, series deconvolution, and the Cliff-Lorimer method. Impurities or non-spinel phases in the sample were easily identified due to their significantly different composition from spinel, namely, their richness in Mn or Ni, and their small proportion in the overall sample. These non-spinel phases were not included in the quantification in order to accurately measure the composition of the spinel phase. In the quantification, the atomic percentage of elements contained in the spinel phase was shown. The amount of Ni in spinel, Niy, is Niy = 2 * Ni at% / (Ni at% +Mn at% ) was calculated as follows. Here Ni at% and Mna at% These are the atomic percentages of Ni and Mn measured in spinel.

[0142] Analysis of three samples prepared with varying Niy values ​​yielded the results shown in Table 3 and Figure 11 below. Ni net chemical composition refers to the overall Ni content in the sample, while Niy refers to the Ni content of the spinel phase measured using STEM-EDS and a 4V charging plateau. The table shows good agreement between the two Niy measurements, confirming that the 4V charging plateau is indeed directly related to the spinel phase composition. Furthermore, this data indicates that Niy is not necessarily identical to the net chemical composition, but rather is determined by the calcination conditions.

[0143] [Table 3]

[0144] As shown in Figure 2a, there is a relationship between the a-axis, obtained using XRD measurement, and the ratio of Mn to Ni, given by y, which is obtained from the 4V plateau. This correspondence is a = -0.1932 * This can be applied to the straight line y+8.2627. Figure 2(b) shows the analogous correspondence between the a-axis and the 4V plateau.

[0145] Example D: Quantification of ordering The cation ordering of Ni and Mn in the spinel of lithium cathode active material can be determined by Raman spectroscopy, as described in Ionics (2006) 12, pp. 117-126. To quantify the degree of ordering, two peaks related to cation ordering are observed at 162 cm⁻¹. -1 (151cm -1 ~172cm -1 ) and 395cm -1 (385cm -1 ~420cm -1) and 496cm independent of order -1 (482cm -1 ~505cm -1 ) and 636cm (627cm~639cm) -1 Two peaks near ) are used. A simple method is to calculate the area of ​​each peak as shown in Figure 13 and calculate the ordering parameter as the ratio (A1+A2) / (A3+A4). This method compensates for variations in background and signal intensity. A perfectly ordered spinel shows a value of around 0.4, and a perfectly disordered spinel shows a value of around 0.1.

[0146] Another method for determining the degree of ordering is to measure the difference dV between two voltage plateaus at approximately 4.7V during a 29.6mA / g (0.2C) discharge. This method requires sufficiently good material and electrode fabrication to obtain flat and well-separated plateaus, as seen in Figures 6a and 6b. As shown in Figure 6b, calculate the difference between the centers of the two plateaus around 4.7V. Q 4V dis It is determined as shown in Example C, and the center of each of the two plateaus is Q 4V dis 25% of Q 4V dis This is determined by 75% of the factors. A perfectly ordered spinel has a value of around 30mV, while a perfectly disordered spinel has a value of around 60mV.

[0147] Figure 3 shows a comparison of two ordering parameters for which a correlation was confirmed. In Figure 4, using the correlation between dV and ordering, it is determined that cation ordering causes an increase in the degree of decomposition. The present invention includes the following items. [Item 1] A lithium positive electrode active material for high-voltage secondary batteries, The lithium cathode active material comprises at least 94% by mass of spinel, The spinel is Li x Ni y Mn 2-y O 4 It has the following net chemical composition, where, 0.95≦x≦1.05; 0.43 ≤ y ≤ 0.47; Herein, the lithium cathode active material has a capacity of at least 138 mAh / g, where y is measured by a method selected from the group consisting of electrochemical measurements, X-ray diffraction, and scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy (EDS). [Item 2] The lithium cathode active material according to item 1, wherein at least 90 mass% of the spinel is crystallized in a disordered space group Fd-3m. [Item 3] The lithium cathode active material in the half-cell has a potential difference of at least 50 mV between 25% and 75% of its capacity, and is greater than 4.3 V during discharge at a current of about 29 mA / g. [Item 4] The lithium cathode active material described in any one of items 1 to 3, wherein the lithium cathode active material is calcined so that its lattice constant a is between 8.171 and 8.183 Å. [Item 5] A lithium cathode active material as described in item 4, wherein the lattice constant a is between (-0.1932y + 8.2613) Å and 8.183 Å. [Item 6] A lithium cathode active material as described in item 4, wherein the lattice constant a is between (-0.1932y+8.2613)Å and (-0.1932y+8.2667)Å. [Item 7] A lithium cathode active material as described in item 4, wherein the lattice constant a is between (-0.1932y+8.2613)Å and (-0.1932y+8.2641)Å. [Item 8] The lithium cathode active material is 2.2 g / cm³ 3 A lithium cathode active material having the above tap density, as described in any one of items 1 to 7. [Item 9] The lithium positive electrode active material according to any one of Items 1 to 8, wherein the D50 of the particles of the lithium positive electrode active material satisfies 3 μm < D50 < 12 μm. [Item 10] The lithium positive electrode active material according to any one of Items 1 to 9, wherein the BET specific surface area of the lithium positive electrode active material is less than 1.5 m 2 / g. [Item 11] The lithium positive electrode active material according to any one of Items 1 to 10, wherein the lithium positive electrode active material is composed of particles, and the particles have an average aspect ratio of less than 1.6. [Item 12] The lithium positive electrode active material according to any one of Items 1 to 11, wherein the lithium positive electrode active material is composed of particles, and the particles have a roughness of less than 1.35. [Item 13] The lithium positive electrode active material according to any one of Items 1 to 12, wherein the lithium positive electrode active material is composed of particles, and the particles have a circularity exceeding 0.55. [Item 14] The lithium positive electrode active material according to any one of Items 1 to 13, wherein the lithium positive electrode active material is composed of particles, and the particles have an area envelope degree exceeding 0.8. [Item 15] The lithium positive electrode active material according to any one of Items 1 to 10, wherein the lithium positive electrode active material is composed of particles, and the particles have a porosity of less than 3%. [Item 16] The lithium positive electrode active material according to any one of Items 1 to 15, wherein 0.99 ≤ x ≤ 1.01. [Item 17] The lithium positive electrode active material according to any one of Items 1 to 16, wherein the decrease in the capacity of the lithium positive electrode active material in the half cell is 4% or less in 100 cycles between 3.5 and 5.0 V at 55 °C. [Item 18] The lithium positive electrode active material according to any one of Items 1 to 17, wherein the lithium positive electrode active material is synthesized from a precursor containing Li, Ni, and Mn in a ratio of Li:Ni:Mn:X:Y:2 - Y, where 0.95 ≤ X ≤ 1.05; and 0.42 ≤ Y < 0.5. [Item 19] The lithium positive electrode active material according to any one of Items 1 to 18, wherein 0.43 ≤ y < 0.45. [Item 20] a. Li x Ni y Mn 2-y O 4 (where 0.95 ≤ x ≤ 1.05; and 0.43 ≤ y ≤ 0.47), providing a precursor for producing a lithium positive electrode active material containing at least 94% by mass of spinel having a chemical composition of b. Heating the precursor of step a to a temperature of 500 °C to 1200 °C to sinter the precursor and obtaining a sintered product. c. A step of cooling the sintered product from step b to room temperature. A method for producing a lithium cathode active material as described in any one of items 1 to 17, including the method described in item 1 to 17. [Item 21] The manufacturing method described in item 20, wherein part of step b is carried out in a reducing atmosphere. [Item 22] The manufacturing method according to item 20 or 21, wherein the temperature of step b is between 850°C and 1100°C. [Item 23] The manufacturing method according to any one of items 20 to 22, wherein during the cooling of step c, the temperature is maintained at intervals of 750 to 650°C for a time sufficient to obtain at least 94% phase purity of the lithium cathode active material. [Item 24] The method for producing a product according to any one of items 20 to 23, wherein at least one of the precursors is a precipitated compound. [Item 25] The manufacturing method according to any one of items 20 to 24, wherein the precipitated compound is a co-precipitated compound of Ni and Mn formed in the Ni-Mn co-precipitation step. [Item 26] The manufacturing method according to item 25, wherein the precursor in the form of co-deposited Ni-Mn is produced in a precipitation step, and the first solution of the starting material containing Ni, the second solution of the starting material containing Mn, and the third solution of the precipitated anion are simultaneously added to the liquid reaction medium in the reactor in amounts such that, with respect to the added Ni, Mn and the precipitated anion are each added in a ratio of 1:10 to 10:1, preferably 1:5 to 5:1, more preferably 1:3 to 3:1, more preferably 1:2 to 2:1, more preferably 1:1.5 to 1.5:1, and more preferably 1:1.2 to 1.2:1 with respect to the stoichiometric amount of precipitate. [Item 27] The method for producing the product according to item 26, wherein the first, second, and third solutions are added to the reaction medium in amounts adjusted to maintain the pH of the reaction mixture at an alkaline pH, for example, between 8.0 and 10.0, preferably between 8.5 and 10.0. [Item 28] The method for producing the reaction according to any one of items 26 to 27, wherein the first, second, and third solutions are added to the reaction mixture over a long period of time, for example, 2.0 to 11 hours. [Item 29] The method of production according to any one of items 26 to 28, wherein the first, second, and third solutions are added to the reaction mixture under vigorous stirring, providing an input of 2 w / L to 25 w / L. [Item 30] A secondary battery containing a lithium cathode active material as described in any one of items 1 through 19.

Claims

1. A lithium positive electrode active material for high-voltage secondary batteries, The lithium cathode active material comprises at least 94% by mass of spinel. The spinel is Li ｘ Ni ｙ Mn ２－ｙ O ４ It has the following net chemical composition, where, 0.95 ≤ x ≤ 1.05; 0.43 ≤ y ≤ 0.47; Here, the lithium cathode active material has a capacity of at least 138 mAh / g and a maximum of 142 mAh / g when discharged at 74 mA / g (0.5 C) in a half-cell between 3.5 V and 5 V at 55°C, where y is measured by a method selected from the group consisting of electrochemical measurements, X-ray diffraction, and scanning transmission electron microscopy (STEM) combined with energy-dispersive X-ray spectroscopy (EDS). The D50 of the lithium cathode active material particles satisfies 3 μm < D50 < 12 μm, The BET area of ​​the lithium cathode active material is 1.5 m². ２ The lithium cathode active material is less than / g.

2. The lithium cathode active material according to claim 1, wherein at least 90% by mass of the spinel is crystallized in a disordered space group Fd-3m.

3. The lithium cathode active material according to claim 1 or 2, wherein the lithium cathode active material in the half-cell has a potential difference of at least 50 mV between 25% and 75% of its capacity, at more than 4.3 V during discharge at a current of 29 mA / g.

4. The lithium cathode active material according to any one of claims 1 to 3, wherein the lithium cathode active material is calcined so that its lattice constant a is between 8.171 and 8.183 Å.

5. The lithium cathode active material according to claim 4, wherein the lattice constant a is between (-0.1932y + 8.2613) Å and 8.183 Å.

6. The lithium cathode active material according to claim 4, wherein the lattice constant a is between (-0.1932y + 8.2613) Å and (-0.1932y + 8.2667) Å.

7. The lithium cathode active material according to claim 4, wherein the lattice constant a is between (-0.1932y + 8.2613) Å and (-0.1932y + 8.2641) Å.

8. The lithium cathode active material is 2.2 g / cm³. ３ A lithium cathode active material according to any one of claims 1 to 7, having the above tap density.

9. The lithium cathode active material according to any one of claims 1 to 8, characterized in that the lithium cathode active material is composed of particles, and the particles have an average aspect ratio of less than 1.

6.

10. The lithium cathode active material according to any one of claims 1 to 9, characterized in that the lithium cathode active material is composed of particles, and the particles have a roughness of less than 1.

35.

11. The lithium cathode active material according to any one of claims 1 to 10, characterized in that the lithium cathode active material is composed of particles, and the particles have a circularity of 0.55 or greater.

12. The lithium cathode active material according to any one of claims 1 to 11, characterized in that the lithium cathode active material is composed of particles, and the particles have an area envelope degree greater than 0.

8.

13. The lithium cathode active material according to any one of claims 1 to 12, characterized in that when the lithium cathode active material is discharged at 74 mA / g (0.5 C) in a half-cell between 3.5 V and 5 V at 55°C, it has a capacity of at least 138 mAh / g and a maximum of 140 mAh / g.

14. A lithium cathode active material according to any one of claims 1 to 13, wherein 0.99 ≤ x ≤ 1.

01.

15. The lithium cathode active material according to any one of claims 1 to 14, wherein the decrease in capacity of the lithium cathode active material in the half-cell is 4% or less over 100 cycles between 3.5 and 5.0 V at 55°C.

16. A lithium cathode active material according to any one of claims 1 to 15, wherein 0.43 ≤ y < 0.

45.

17. a. Li ｘ Ni ｙ Mn ２－ｙ O ４ Providing a precursor for producing a lithium positive electrode active material containing at least 94% by mass of spinel having a chemical composition of (where 0.95 ≦ x ≦ 1.05; and 0.43 ≦ y ≦ 0.47); b. A step of heating the precursor from step a to a temperature of 500°C to 1200°C to sinter the precursor and obtain the sintered product. c. A step of cooling the sintered product from step b to room temperature. Includes, Part of process b is carried out in a reducing atmosphere. A method for producing a lithium cathode active material according to any one of claims 1 to 16.

18. a. Li ｘ Ni ｙ Mn ２－ｙ O ４ A step of providing a precursor for producing a lithium cathode active material comprising at least 94 mass% spinel having a chemical composition of (where 0.95 ≤ x ≤ 1.05; and 0.43 ≤ y ≤ 0.47); b. A step of heating the precursor from step a to a temperature of 500°C to 1200°C to sinter the precursor and obtain the sintered product. c. A step of cooling the sintered product from step b to room temperature. Includes, During the cooling process of step c, the temperature is maintained at intervals of 750°C to 650°C for a sufficient amount of time to obtain at least 94% phase purity of the lithium cathode active material. A method for producing a lithium cathode active material according to any one of claims 1 to 16.

19. The manufacturing method according to claim 18, wherein part of step b is carried out in a reducing atmosphere.

20. The manufacturing method according to any one of claims 17 to 19, wherein the temperature of step b is between 850°C and 1100°C.

21. The manufacturing method according to any one of claims 17, 19 to 20, wherein during the cooling of step c, the temperature is maintained at intervals of 750 to 650°C for a time sufficient to obtain at least 94% phase purity of the lithium cathode active material.

22. The manufacturing method according to any one of claims 18 to 21, wherein at least one of the precursors is a precipitated compound.

23. The manufacturing method according to claim 22, wherein the precipitated compound is a co-precipitated compound of Ni and Mn formed in the Ni-Mn co-precipitation step.

24. The manufacturing method according to claim 23, wherein the precursor in the form of co-deposited Ni-Mn is produced in a precipitation step, and in which, with respect to the added Ni, the amounts of Mn and precipitated anions are added in a ratio of 1:10 to 10:1 with respect to the stoichiometric amount of precipitate, and a first solution of the starting material containing Ni, a second solution of the starting material containing Mn, and a third solution of the precipitated anion are simultaneously added to the liquid reaction medium in the reactor.

25. The manufacturing method according to claim 24, wherein the first, second, and third solutions are added to the reaction medium in amounts adjusted to maintain the pH of the reaction mixture at an alkaline pH between 8.0 and 10.

0.

26. The manufacturing method according to any one of claims 24 to 25, wherein the first, second, and third solutions are added to the reaction mixture over a period of 2.0 to 11 hours.

27. A secondary battery comprising the lithium cathode active material according to any one of claims 1 to 16.

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