Lithium positive electrode active material

Abstract

To provide a positive electrode active material for a high voltage lithium secondary battery, having an optimum Ni-content in order to balance the energy density and degradation of the material, and a method of producing the same.SOLUTION: The present invention relates to a lithium positive electrode active material including at least 94 mass% spinel. The spinel has a net chemical composition of LixNiyMn2-yO4 where 0.95≤x≤1.05 and 0.43≤y≤0.47 are satisfied. The lithium positive electrode active material has a capacity of at least 138 mAh / g. In the chemical composition, y is measured by means of a method selected from the group consisting of electrochemical measurement, X-ray diffraction, and scanning transmission electron microscopy (STEM) in combination with energy dispersive X-ray spectroscopy (EDS). The present invention also relates to a method of producing a lithium positive electrode active material for a high voltage secondary battery of the present invention as well as a secondary battery including a lithium positive electrode active material according to the present invention.SELECTED DRAWING: Figure 10a

Description

Technical Field

[0001] Field of the Invention The present invention relates to a lithium positive electrode active material used in a high-voltage lithium secondary battery. In particular, the present invention relates to such a material having a high capacity, a high voltage, and a low decomposability with respect to the Li / Li+ standard. Furthermore, the present invention relates to a method for manufacturing such a material.

Background Art

[0002] Background The lithium positive electrode active material (positive electrode active material) can be characterized by the following formula: Li x Ni y Mn 2-y O 4-δ , where 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 supply devices. The lithium positive electrode active material is recognized as a future successor material to current lithium secondary battery cathode materials such as LiCoO2 and LiMn2O4.

[0003] The lithium positive electrode active material can be manufactured from one or more precursors obtained by a coprecipitation method. The precursors and the product are spherical by the coprecipitation process. Electrochimica Acta (2014), pp290-296 discloses a material manufactured by sequentially sintering (heat-treating) at 500 °C and then at 800 °C after the first heat treatment step (500 °C). The obtained product has high crystallinity and a spinel structure after the first heat treatment step (500 °C). A uniform morphology of the product, a tap density of 2.03 gcm -3 , and a uniform secondary particle diameter of 5.6 μm are observed. According to Electrochimica Acta (2004), pp939-948, when spherical particles are uniformly distributed, they exhibit a higher tap density in terms of fluidity and ease of filling than disordered particles. This LiNi 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 sufficiently incorporate lithium into the mixed nickel and manganese oxide precursor. Also, it is disclosed that annealing is generally performed 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 at 650 °C or higher, LiNi 0.5 Mn 1.5 O4 loses oxygen and disproportionates, however, when cooled slowly in an oxygen-containing atmosphere, the LiNi 0.5 Mn 1.5 O4 stoichiometry is disclosed to recover. 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

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Non-Patent Documents

[0007]

Non-Patent Document 1

Non-Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0008] It is desirable to provide a lithium positive electrode active material with high phase purity and large capacity. Also, it is desirable to provide a highly stable lithium positive electrode active material, where the capacity reduction 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 the tap density may increase the energy density of the battery, it is desirable to provide a lithium positive electrode active material with a high tap density. Finally, in order to balance the energy density and the decomposition of the material, it is desirable to provide a lithium positive electrode active material with an optimal Ni content.

Means for Solving the Problems

[0009] Summary The present invention relates to a lithium positive electrode active material for a high-voltage secondary battery, and the lithium positive electrode active material contains at least 94% by mass of spinel, and the spinel is Lix Ni y Mn 2-y having a net chemical composition of O4, where 0.95 ≦ x ≦ 1.05; 0.43 ≦ y ≦ 0.47; and wherein the lithium positive electrode active material has a capacity of at least 138 mAh / g, and wherein 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 realized that when the content of Ni in the lithium positive electrode active material is in a relatively narrow range, i.e., 0.43 ≦ y ≦ 0.47, and when the lithium positive electrode active material contains at least 94% by mass of spinel, i.e., a maximum of 6% by mass of impurities or a phase other than spinel, such as a rock salt type, particularly high capacity and low fading can be obtained. The range of the value of y is selected to provide a lithium positive electrode active material having good performance while maintaining a balance between high energy density and low decomposition. When y exceeds 0.47, the lithium positive electrode active material has an increased degree of decomposition (deterioration), while when y is less than 0.43, the Mn content of the lithium positive electrode active material increases, and as a result, the energy density of the battery using the lithium positive electrode material decreases. Thus, it has been found that in the range of 0.43 ≦ y ≦ 0.47, an optimal Ni content is provided in the balance between high energy density and low decomposition. Preferably, 0.43 ≦ y < 0.45.

[0011] It should be noted here that the Ni content in the spinel of the lithium positive electrode active material may be in the form of impurities such as a rock salt type for some Ni, so it may be different from the Ni content in the total lithium positive electrode active material. Such differences depend, for example, on the calcination (firing) performed in the production of the lithium positive electrode active material, and thus on the amount of impurities or non-spinel phases in the lithium positive electrode active material. To obtain the correct y value for the spinel, it is important to use a method suitable for this purpose, which applies to the following three methods: electrochemical measurement (quantification), X-ray diffraction measurement, and a combination of energy-dispersive X-ray spectroscopy (EDS) with scanning transmission electron microscopy (STEM). The methods for measuring the Ni content in the total lithium positive electrode active material and in the spinel in the lithium positive electrode active material are described in more detail in Example C, and it should be noted that the determination of the capacity is described as described in Example A.

Embodiments for Carrying Out the Invention

[0012] "Spinel" refers to a crystal lattice in which oxygen is arranged in a slightly distorted cubic close-packed lattice and cations occupy octahedral sites and tetrahedral sites in the lattice. Oxygen and octahedrally coordinated cations form a skeletal structure having a three-dimensional channel system that occupies tetrahedrally coordinated cations. In the spinel-type structure, the ratio of tetrahedrally coordinated cations to octahedrally coordinated cations is about 1:2, and the ratio of cations to oxygen is about 3:4. The cations in the octahedral sites may consist of a single element or a mixture of different elements. When a mixture of different types of octahedrally coordinated cations forms its own three-dimensional periodic lattice, the spinel is called an ordered spinel. When the cations are more randomly distributed, the spinel is called a disordered spinel. Examples of ordered spinels 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] The "rock salt type" refers to a crystal lattice in which oxygen is arranged in a slightly distorted face-centered cubic lattice and the cations completely occupy the octahedral sites in the lattice. The cations can consist of a single element or a mixture of different elements. A mixture of different types of cations can be statistically disordered, maintaining cubic symmetry (Fm-3m), or ordered, resulting in a lower symmetry. The cation / oxygen ratio is 1:1 in the rock salt structure.

[0014] The phase composition of the lithium positive electrode active material can be determined based on the X-ray diffraction pattern obtained by the θ-2θ arrangement operating in the Bragg-Brentano mode using CuKα radiation (λ = 1.541 Å) with a PW1800 device system manufactured by Phillips. For experimental parameters that contribute to the shift of the observed data, it is necessary to correct the observed data. This is achieved using a full profile fundamental parameter approach as implemented in Bruker's TOPAS software. The phase composition determined from the Rietveld analysis is given with a typical uncertainty of 1 to 2 percentage points in mass%, representing the relative composition of the total crystalline phase. Therefore, any amorphous phase is not included in the phase composition.

[0015] The discharge capacity and discharge current described in this specification are described as specific values based on the mass of the lithium positive electrode active material.

[0016] Note that the lithium positive electrode active material may contain a small amount of elements other than Li, Ni, Mn, and O. Such elements may be, for example, one or more of B, N, F, Mg, Al, Si, P, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W. Such a small amount of elements may be derived from impurities in the starting materials for manufacturing the lithium positive electrode active material, or may be added as dopants for the purpose of improving some properties of the lithium positive electrode 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 within the original lithium cathode active material. The change in the x value will also change 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 the lithium cathode active material is extracted from a battery, the x value of the original material, i.e., the x value before the lithium cathode active material is incorporated as part of the battery, can be measured by discharging the lithium cathode active material extracted in a half-cell having a lithium metal anode as described in Example A at a current of less than 29 mA / g to a potential of 3.5 V vs. Li / Li + and maintaining the potential of 3.5 V vs. Li / Li + for 5 hours.

[0019] In one embodiment, at least 90 mass % of the spinel of the lithium positive electrode active material is crystallized in the disordered space group Fd-3m. The disordered material has been observed to have lower decomposability compared to materials having a similar stoichiometry or materials produced as ordered materials. 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, the quantitative ordering parameter can be extracted based on Raman spectroscopy or electrochemistry as a measurement of the separation between two Ni-layers at about 4.7V. This is illustrated in FIG. 6b. As shown in FIG. 3, the two parameters are very well correlated. FIG. 4 shows a comparison of the plateau separation dV and the degree of decomposition of the lithium positive electrode active material. Although ordering is not the only parameter that affects the degree of decomposition (deterioration), it can be seen that there is a minimum degree of decomposition at a certain plateau separation and thus a certain degree of order. If the spinel is too ordered, it is impossible to achieve a low degree of decomposition. When the plateau separation is less than 40 mV, a significant increase in the degree of decomposition is observed. Preferably, the plateau separation should be at least 50 mV, preferably around 60 mV.

[0020] In one embodiment, the lithium positive electrode active material in the half-cell has a difference of at least 50 mV between the 25% and 75% potentials of the capacity exceeding 4.3V during discharge at a discharge current of about 29 mA / g. When the potential difference between 25% and 75% of the capacity during discharge exceeds 4.3V, it typically reaches a maximum of 75 - 80 mV. The potential difference between 25% and 75% of the capacity above 4.3V 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 at a given state of charge, which is affected 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 advantageous. This is because it is related to whether the lithium positive electrode active material is in an ordered or disordered phase and the fading rate of the half-cell by the lithium positive electrode active material. The plateau separation is preferably about 60 mV.

[0021] In one embodiment, the lithium positive electrode active material is calcined such that the lattice parameter a is between 8.171 Å and 8.183 Å. These values of the lattice constant a are related to a lithium positive electrode active material with low decomposition.

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

[0023] In one embodiment, the tap density of the lithium positive electrode active material is 2.2 g / cm 3 or more. Preferably, the tap density of the lithium positive electrode active material is 2.25 g / cm 3 or more; 2.3 g / cm or more, for example 2.5 g / cm 3 or the like.

[0024] "Tap density" is a term used to describe the bulk density of a powder (or granular solid) after consolidation and compression by "tapping" a certain number of times from a usually predetermined height. The method of "tapping" is best expressed as "lifting and dropping". Tapping in this context should not be confused with tamping, lateral impact, 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 the present invention is measured by weighing a graduated cylinder with an inner diameter of 10 mm before and after adding about 5 g of powder, recording the mass of the added substance, then tapping (tapping) the cylinder on the table for a while, and then reading the volume of the tapped substance. Usually, tapping should be continued until the volume no longer changes with further tapping. As an example, tapping may be performed for 1 minute and may be about 120 or 180 times.

[0025] One way to quantify the size of particles in a slurry or powder is to measure the sizes of a large number of particles and calculate the characteristic particle size as the weighted average of all the measured values. Another way to characterize the particle size is to plot the entire particle size distribution, i.e., the volume fraction of particles having 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 volume fraction of the population is below the value of D10, D50 is defined as the particle size (i.e., the median) at which 50% of the volume fraction of the population is below the value of D50, and D90 is defined as the particle size at which 90% of the volume fraction of the population is below the value of D90. Commonly used methods for measuring particle size distribution include laser diffraction measurement and scanning electron microscope measurement, 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 dense 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 powder is easy to handle, enables a low surface area, and can maintain a surface area sufficient to transport lithium and electrons in and out of the structure during discharge and charge. In one embodiment, the size distribution of the particles 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, in combination with the fact that the D50 of the particles is between 3 and 12 μm, indicates that the number of fine powder particles 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 the 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 S J, Lin-Sien Lum: Particle Size Characterization, NIST (National Institute of Standards and Technology) Special Publication 960-1, 2001. Methods commonly used to determine the particle size distribution include laser diffraction measurement and scanning electron microscope measurement, which are combined with image analysis.

[0029] In one embodiment, the lithium positive electrode active material has a BET surface area of less than 1.5 m 2 / g. The BET surface area may be less than 1.0 m 2 / g or less than 0.5 m 2 / g or less, down to 0.3 m / g or down to 0.2 m / g. Since a low BET surface area corresponds to a low-porosity, high-density material, it is advantageous to have a low BET surface area. Since the decomposition reaction occurs on the surface of the material, such materials are typically stable materials, i.e., materials with a slow decomposition rate.

[0030] In one embodiment, the lithium positive electrode active material is composed of particles, where the particles 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 the particles can be characterized using the aspect ratio, which is defined as the ratio of the length of the particle to the width of the particle. Here, the length is the maximum distance between two points on the perimeter, and the width is the maximum distance between two perimeter 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, more preferably less than 1.4. Furthermore, such aspect ratios and roughnesses provide materials with a high tap density. The values of the aspect ratio and roughness can be measured from scanning electron micrographs of polished particles, which are embedded in epoxy and reveal the particle cross-section as described in Example B.

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

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

[0035] In one embodiment, in the formula of Li x Ni y Mn 2-y O4, 0.99 ≦ x ≦ 1.01. When there is about one lithium ion for two transition metal ions with respect to four oxygen atoms in the spinel crystal, the crystal structure of the lithium positive electrode active material is well utilized, which is preferable. Also in this case, the value of x is related to the Li content of the original lithium positive electrode active material, that is, the synthesized lithium positive electrode active material. When this material is in the battery, the x value typically changes compared to the x value in the original lithium positive electrode active material. The change in the x value also causes a change in the value of the lattice parameter a. The advantages described in this specification are based on the original lithium positive electrode active material, that is, the x value in the original lithium positive electrode active material.

[0036] When the lithium positive electrode active material is extracted from the battery, the lithium positive electrode active material extracted in a half-cell having a lithium metal anode as described in Example A is discharged at a current of less than 29 mA / g at a potential of 3.5 V vs. Li / Li + and the potential of 3.5 V vs. Li / Li + is maintained for 5 hours, whereby the x value of the original substance, that is, the x value before the lithium positive electrode active material is incorporated as part of the battery can be measured.

[0037] In one embodiment, the specific capacity of the lithium positive electrode 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 positive electrode active material decreases to 6% or less over 100 charge-discharge cycles between 3.5 and 5.0 V; more preferably, when cycling 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 types of cells (batteries) 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 a ratio of Li:Ni:Mn:X:Y:2 - Y, where 0.95 ≦ X ≦ 1.05; and 0.42 ≦ Y < 0.5. As used herein, the contents of Li, Ni, and Mn in the spinel of the lithium cathode active material, i.e., in the net chemical composition, are Li x Ni y Mn 2-y O 4, are represented by lowercase x and y, respectively. In contrast, the contents of Li and Ni in the precursor used to synthesize the lithium cathode active material are represented by the uppercase letters X and Y. If x and y are significantly different from X and Y, it means 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. Further, the impurity phases in the lithium cathode active material, i.e., the phases that are not spinel, may contain a significant amount of lithium or different amounts of Mn and Ni. This can thereby reduce x and significantly change y within the spinel. Such impurity phases further reduce the capacity of the spinel and reduce its stability. The presence of impurities may further increase the degree of electrolyte decomposition when the lithium cathode active material is incorporated into a battery cell, and may 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 contents of Li, Ni, and Mn in the precursor used to synthesize the lithium cathode active material represented 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 an amount representative of the entire sample. Such measurements may be by inductively coupled plasma or EDS as described in Example C.

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

[0041] As used herein, "precursor" means a composition produced by mechanically mixing or co-precipitating 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 composition produced by co-precipitation of starting materials with a lithium source (Electrochimica Acta (2014) 115, 290 - 296). Preferably, step a includes providing the precursor by co-precipitation of 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 metal in the starting material can change, 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 from good starting materials. Preferably, the precursor includes a co-precipitated Ni-Mn precursor and a Li precursor as described in, for example, WO2018015207 or WO2018015210. 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-precipitated compound of Ni and Mn formed in the Ni-Mn co-precipitation step. To obtain a lithium cathode active material, it has been found that it is desirable to use a precursor in the form of co-precipitated 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 exceeds 0.55.

[0045] Preferably, the Mn-containing precursor that can be a co-precipitated Ni-Mn precursor is composed 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 are particles 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 exceeding 0.8.

[0046] Ni and Mn can be precipitated with a suitable precipitating anion such as carbonate. Preferably, the precursor in the form of co-precipitated Ni-Mn is produced in a precipitation step, where a first solution of a Ni-containing starting material, a second solution of a Mn-containing starting material, and a third solution of a precipitating anion are simultaneously added to a liquid reaction medium in a reactor, but with respect to the added Ni, the Mn and the precipitating anion 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, 1:1.2 to 1.2:1 with respect to the stoichiometric amount of precipitation.

[0047] Preferably, the first, second, and third solutions are added to the reaction medium in calibrated amounts such that the pH of the reaction mixture is maintained 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, for example, over a period of 2.0 to 11 hours, preferably 4.0 to 10.0 hours, more preferably 5.0 to 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, even more preferably 8 W / L to 12 W / L.

[0048] In order to obtain a lithium positive electrode active material having 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 desirable to use a precursor in the form of co-precipitated Ni-Mn produced in the precipitation step shown above, i.e., one produced using one or more of the following. That is, while controlling the indicated pH and with vigorous stirring, the first and second solutions are simultaneously added over a long period of time.

[0049] In contrast to the case where the first and second solutions are added to the third solution, adding the first, second, and third solutions simultaneously offers the possibility of ensuring that in the reaction mixture, Ni and Mn on one side and the precipitated anions on the other side are present at the same level or at least of the same order of magnitude. Furthermore, without being bound by any theory, adding the above three solutions simultaneously is thought to mean that the precipitated particles grow in size during the precipitation step and new layers of the precipitated material continuously precipitate on the surface of the growing particles. Such a stepwise construction of the particles is thought to facilitate the formation of the desired properties of the precursor particles and ultimately promote the formation of the lithium positive electrode active material particles. Furthermore, performing the precipitation step over a long period of time is also thought to contribute to facilitating such a stepwise construction of the particles.

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

[0051] Also, when the precipitation step is carried out as described above, while controlling the pH and adding the first and second liquids simultaneously over a long period with vigorous stirring, it has been found that more spherical particles are formed, and particles with enhanced chemical composition uniformity also occur.

[0052] Finally, as described above, that is, while controlling the pH and adding the first and second solutions simultaneously over a long period with vigorous stirring, it was found that in addition to producing more spherical particles, precursor particles were also produced. This results in a reduction in the level of impurities as described above when used to produce lithium positive electrode active material particles. That is, particles containing Li, Ni, and Mn in the ratio of 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 connection with the present invention, the expression "stoichiometric amount" means the ratio of the amounts of elements present in the precipitated compound.

[0054] In one embodiment, the precursor of the lithium positive electrode active material is such that the starting materials are produced from two or more starting materials, and the starting materials are, for example, 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 and nickel carbonate and lithium carbonate.

[0055] In one embodiment, a 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 the air.

[0056] In one embodiment, the temperature of 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 - 650 °C for a time sufficient to obtain at least 94% phase purity of the lithium positive electrode active material. The time sufficient to obtain at least 94% phase purity is, for example, as shown in Examples 1 - 3 below; however, other combinations of temperature and time are known to those skilled in the art.

[0058] According to another aspect, the present invention further relates to a secondary battery including the lithium positive electrode active material according to the present invention.

Brief Description of the Drawings

[0059] Brief Description of the Drawings: Figure 1a shows experimental data regarding the relationship between the nickel content in spinel and the degree of decomposition for a series of lithium positive electrode active materials;

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

[0061] Figure 1c is experimental data regarding the relationship between the lattice constant a in the spinel of the lithium positive electrode active material and the degree of decomposition of the lithium positive electrode active material in 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 positive electrode active materials;

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

[0064] Figure 3 shows experimental data regarding the relationship between the cation ordering parameter measured using Raman spectroscopy and electrochemistry, respectively;

[0065] Figure 4 is experimental data regarding the relationship between the degree of decomposition and the difference in discharge of a half-cell between 25% and 75% of the potential with a capacity of 4.3V or more when discharging at a current of about 29 mA / g within the range of the lithium positive electrode active material;

[0066] Figure 5a shows the relationship between circularity and degree of decomposition regarding four samples of the lithium positive electrode active material according to the present invention and substantially the same spinel stoichiometry;

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

[0068] Figure 5c shows the relationship between the average diameter and the degree of decomposition regarding four samples of the lithium positive electrode active material according to the present invention and substantially the same spinel stoichiometry;

[0069] Figure 5d shows the relationship between the aspect ratio and the degree of decomposition regarding four samples of the lithium positive electrode active material according to the present invention and substantially the same spinel stoichiometry;

[0070] Figure 5e shows the relationship between the area envelope degree and the degree of decomposition regarding four samples of the lithium positive electrode active material according to the present invention and substantially the same spinel stoichiometry;

[0071] Figure 5f shows the relationship between porosity and degree of decomposition regarding four samples of the lithium positive electrode active material according to the present invention and substantially the same spinel stoichiometry;

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

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

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

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

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

[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 value by electrochemistry (EC) for three different samples of Niy;

[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. Four gray regions are used to calculate the degree of order.

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

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

[0082] Detailed Description of the Drawings: Figure 1a shows experimental data on the degree of decomposition and the amount of nickel (the value of y in Li x x Ni y Mn 2-y O4) in spinel within the 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 between 3.5V and 5V at 55°C, as described in Example A. The degree of decomposition is measured in a half-cell at 55°C and is described as the degree of decomposition per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Since the degree of decomposition is affected by several factors, there is variation. However, for a given Ni content in the spinel, there is a minimum degree of decomposition, and a reference line or curve is described to emphasize that as the Ni content decreases, the minimum degradation rate decreases. Therefore, it is not possible to provide a lithium cathode active material with a degree of decomposition lower than the minimum; however, due to inhomogeneities, morphology / morphology, or excessive ordering in the lithium cathode active material, it may be difficult to reach the minimum degree of decomposition. To illustrate some of these other parameters, four samples (black squares) were fabricated, as shown in Example 4, to investigate how they affect the degree of morphological decomposition (degradation).

[0083] Figure 1b shows experimental data on the relationship between the 4V plateau of the lithium cathode active material in a half-cell and the degree of decomposition 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 between 3.5V and 5V at 55°C, as described in Example A. The degree of decomposition is measured in a half-cell at 55°C and is described as the degree of decomposition per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Also in Figure 1b, for a given 4V plateau, there is a minimum degree of decomposition, and a reference line or curve is described to emphasize that as the 4V plateau increases, the minimum degree of decomposition decreases. 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 on the relationship between the lattice constant a “a-axis” in the spinel of the lithium positive electrode active material and the degree of decomposition of a certain range of lithium positive electrode 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 between 3.5V and 5V at 55°C, as described in Example A. The degree of decomposition is measured in a half-cell at 55°C and is described as the degree of decomposition per 100 full charge and discharge cycles between 3.5V and 5V, as described in Example A. Also, in Figure 1c, for a given lattice parameter, there is a minimum degree of decomposition, and a reference line or curve is described to emphasize that the minimum degree of decomposition decreases as the lattice parameter a increases. The four samples indicated by black squares in Figures 1a and 1b are also indicated by black squares in Figure 1c. Figures 1a, 1b, and 1c show the relationships between different parameters of the same sample.

[0085] Figure 2a shows experimental data on the relationship between the amount of nickel in the spinel (the value of y in Li x Ni y Mn 2-y O4 shown as “Niy” in Figure 2a) and the lattice parameter a of the spinel with respect to the positive electrode active material of lithium. 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. 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. There may be slight variations due to fluctuations in the lithium content.

[0086] Figure 2b shows experimental data on the relationship between the 4V plateau of the lithium positive electrode active material in the half-cell and the lattice parameter a of the spinel for a certain range of lithium positive electrode 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 between 3.5V and 5V at 55°C, as described in Example A. Figures 2a and 2b show the relationships between different parameters of the same sample.

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

[0088] Thereby, the inventors have found that there is a close correlation between the low degree of decomposition, parameter a, Ni content rate, and 4V plateau of the lithium positive electrode active material. This correlation can be used to select appropriate values of the parameter, Ni content, in order to optimize the lithium positive electrode active material for a specific application.

[0089] Figure 3 shows the experimental data regarding the relationship of the cation ordering parameter measured using Raman spectroscopy and electrochemistry, respectively. The two methods are described in Example D, and it can be seen that there is a correlation. It has been observed that the disordered lithium positive electrode active material has a lower degree of decomposition compared to a similar material manufactured as an ordered material. Although there are some variations in the samples shown in Figure 3, there is a tendency for the dV value to be high, which corresponds to a low Raman ordering value. The voltage difference dV is measured as described in relation to Figure 6b. The term "Raman order" used herein means the measurement of cation ordering in the lithium positive electrode active material based on the Raman spectroscopy described in Example D.

[0090] Figure 4 shows experimental data regarding the relationship between the degree of decomposition of a half-cell and the difference in discharge for 25% and 75% of the capacity above 4.3 V during discharge at a current of about 29 mA / g with respect to the range of the lithium positive electrode active material. This difference dV is measured as in Example D. In Figure 4, it is shown that there is a relationship between the difference dV and the degree of decomposition of the lithium positive electrode active material. The difference dV is also referred to as "plateau separation" and is a measure of the free energy related to the insertion and removal of lithium at a given state of charge, which is affected by whether the spinel phase is disordered or ordered. Although there are some variations in the samples shown in Figure 4, there is a tendency that the higher the dV value, the lower the degree of decomposition. Without being bound by theory, a plateau separation of at least 50 mV seems to be advantageous. This is because it is related to whether the lithium positive electrode active material is in an ordered phase or a disordered phase and the fading rate of the half-cell due to the lithium positive electrode active material.

[0091] Figures 5a - 5f show the relationship between the degree of decomposition and the range of parameters for the four samples indicated by the black squares in Figures 1a - 1c, 2a - 2b, and 4. These four samples of the lithium positive electrode active material have different degrees of decomposition as is clear from Figures 1a - 1c and 2a - 2b, but the spinel stoichiometry is very similar. Among the four samples shown in Figures 5a - 5f, the spinels of three samples have the spinel stoichiometry LiNi 0.454 Mn 1.546 O4, and the spinel of the fourth sample has the spinel stoichiometry LiNi 0.449 Mn 1.551 O4. 。 All four samples are manufactured based on a co-precipitation precursor, and the particles are secondary particles.

[0092] Figure 5a shows the relationship between the circularity of secondary particles and the degree of decomposition for four samples of the lithium positive electrode active material according to the present invention and with respect to a substantially identical spinel stoichiometry. The circularity of the secondary particles is 4π from the area and the perimeter (outer perimeter) of the particle shape * [area] / [outer perimeter] 2It is measured as such. The circularity represents both the overall shape and the surface roughness. The higher the value, the more circular it is and the smoother the surface. A circular shape with a smooth surface has a circularity of 1. The average circularity is the arithmetic mean of the circularities of all the secondary particles measured in the sample. It was calculated using ImageJ software (https: / / imagej.nih.gov). In Figure 5a, it can be seen that the higher the circularity, the lower the resolution.

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

[0094] Figure 5c shows the relationship between the average diameter and resolution of secondary particles for four samples of the lithium positive electrode active material according to the present invention and in a substantially the same spinel stoichiometry. The diameter of the secondary particles is measured as the equivalent circular 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 the secondary particles measured in the sample. It was calculated using ImageJ software (https: / / imagej.nih.gov). In Figure 5c, it can be seen that the average diameter is decreased to suppress the resolution. The average diameter of the secondary particles is given in μm.

[0095] Figure 5d shows the relationship between the aspect ratio and the degree of decomposition of four samples of the lithium positive electrode active material according to the present invention and secondary particles with substantially the same spinel stoichiometry. The aspect ratio of the secondary particles was measured from an ellipse fitted to the particle shape. The aspect ratio is defined as [major axis] / [minor axis]. Here, [major axis] and [minor axis] are the major axis and minor axis 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 Soft ImageJ (https: / / imagej.nih.gov). In Figure 5d, it can generally be seen that a lower aspect ratio corresponds to less decomposition.

[0096] Figure 5e shows the relationship between the area envelope degree and the degree of decomposition of four samples of the lithium positive electrode active material according to the present invention and secondary particles with substantially the same spinel stoichiometry. The area envelope degree of the secondary particles is defined as the ratio of the particle area to the convex area, i.e., [area] / [convex area]. The convex area can be considered as the shape formed by winding a rubber band around the particle. The more concave the surface of the particle, the higher the convex area and the lower the area envelope degree. The average area envelope degree is the arithmetic mean of the area envelope degrees of all secondary particles measured in the sample. It was calculated using Soft ImageJ (https: / / imagej.nih.gov). In Figure 5e, it can be seen that the higher the value of the area envelope degree, the less decomposition.

[0097] Figure 5f shows the relationship between the porosity and the degree of decomposition of four samples of the lithium positive electrode active material according to the present invention and secondary particles with substantially the same spinel stoichiometry. The porosity of the secondary particles is the ratio of the internal area that appears with a dark contrast in the SEM image, and the dark contrast is interpreted as porosity, i.e., pores inside the particles. The average porosity is the arithmetic mean of the porosities of all secondary particles measured in the sample. It was calculated using Soft ImageJ (https: / / imagej.nih.gov). In Figure 5f, it can generally be seen that lower porosity corresponds to less decomposition.

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

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

[0100] Figures 7a and 7b are SEM images at two different magnification levels of one of the samples shown in Figures 1a - 1c, 2a - 2b, and 5a - 5f. 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 acceleration voltage of 8 kV and a backscattered electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0101] Figures 8a and 8b are the second two different magnification level second SEM images of the samples shown in Figures 1a - 1c, 2a - 2b, and 5a - 5f. The samples shown in Figures 8a and 8b are lithium cathode active materials 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. 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 acceleration voltage of 8 kV and a backscattered electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0102] Figures 9a and 9b are SEM images at the third two different magnification levels of the samples shown in Figures 1a - 1c, 2a - 2b, and 5a - 5f. The samples shown in Figures 9a and 9b are lithium cathode active materials 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 acceleration voltage of 8 kV and a backscattered electron detector. Pixel size: a) 0.216 μm / pixel, b) 0.054 μm / pixel.

[0103] Figures 10a and 10b are SEM images of two different magnification levels of the fourth of the samples shown in Figures 1a - 1c, 2a - 2b, and 5a - 5f. The samples shown in Figures 10a and 10b are lithium cathode active materials 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 acceleration voltage of 8 kV and a backscattered 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 the values obtained by electrochemistry (EC) for three samples with different Niy values. STEM-EDS directly measures the elemental composition of a substance, while EC indirectly measures the composition from the magnitude of the 4V charge plateau. As a result of the comparison, the two methods are in agreement, and it was found that the 4V charge plateau is indeed directly related to the composition of the spinel phase. Therefore, the measurement of the 4V charge 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 with 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 the ordered spinel. 151 cm -1 ~172 cm -1 、 is 385 cm -1 ~420 cm -1 、 482 cm -1 ~505 cm -1 、 627 cm -1 ~639 cm -1 Using four gray regions of, the degree of ordering is calculated.

Examples

[0107] Examples: 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 a method for producing a lithium cathode active material. Example A describes a method for electrochemical testing, Example B describes measurements based on SEM of morphological parameters, Example C describes three methods for measuring the content of Mn and Ni in spinel, and Example D describes two methods used to measure the degree of cation ordering in spinel.

[0108] Example 1: Synthesis of Lithium Positive Electrode Active Material Dissolve 7.1 kg of NiSO4·7H2O and 15.1 kg of MnSO4·H2O in 48.5 kg of water to produce an aqueous metal ion solution of NiSO4 and MnSO4 with a Ni:Mn atomic ratio of 1:3.18. In another container, dissolve 11.2 kg of Na2CO3 in 51.0 kg of water to produce a carbonate aqueous solution. No ammonia or other chelating agents are used. The metal ion solution and the carbonate solution are separately added at about 3 L / h, vigorously stirred (400 rpm), and inserted into a reactor at pH 8.8 - 9.5 and a temperature of 35°C. The volume of the reactor is 40 liters. After 4 hours, the product is taken out of the reactor and divided into 6 portions. For one of the 6 batches, precipitation is continued for about 4 hours and then divided into 2 portions. For each of the 2 batches, precipitation is continued until the desired Ni,Mn-carbonate precursor is obtained. The remaining 5 samples follow this procedure. The precursor is filtered and washed to remove Na2SO4.

[0109] Mix 4667 g of the precursor in the form of co-precipitated Ni,Mn-carbonate (Ni: 0.478, Mn: 1.522) produced as described above and 716 g of Li2CO3 (corresponding to Li:Ni:Mn = 1.00:0.478:1.522) with ethanol to form a viscous slurry. Shake the slurry in a paint shaker for 3 minutes to obtain a completely de-aggregated mixture of particulate matter. Pour the slurry into a tray and dry it at 80°C. The dried material is further de-aggregated by shaking it in a paint shaker for 1 minute to obtain a free-flowing homogeneous powder mixture.

[0110] The powder mixture is heated to 550 °C at a rate of 2.5 °C / min in a furnace with a nitrogen flow. The powder is heated at 550 °C for 4 hours. Subsequently, the powder is treated in air at 550 °C for 9 hours. The temperature is raised to 950 °C with a rate of 2.5 °C / min. Maintain at 950 °C for 10 hours and decrease to 700 °C at a rate of 2.5 °C / min. Maintain at 700 °C for 4 hours and decrease to room temperature at a rate of 2.5 °C / min.

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

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

[0113] Example 2: Synthesis of Lithium Positive Electrode Active Material A precursor in the form of 529 g of co-precipitated Ni,Mn-carbonate (Ni: 0.46, Mn: 1.54) produced 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) are mixed with ethanol to form a viscous slurry. The slurry is shaken in a paint shaker for 3 minutes to obtain a completely dispersed mixture of particulate matter. The slurry is poured into a tray and dried at 80 °C. The dried material is further dispersed by shaking in a paint shaker for 1 minute to obtain a free-flowing and homogeneous powder mixture.

[0114] The powder mixture is heated in a muffle furnace at a rate of about 1 °C / min up to 550 °C under a nitrogen flow. Maintain at 550 °C for 3 hours and cool to room temperature at a rate of around 1 °C / min.

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

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

[0117] Example 3: Synthesis of Lithium Positive Electrode Active Material A precursor in the form of 1400 g of co-precipitated Ni,Mn-carbonate (Ni: 0.47, Mn: 1.53) produced as in Example 1 and 211 g of Li2CO3 (equivalent 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 fully deagglomerate and obtain a mixture of particulate matter. 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 free-flowing homogeneous powder mixture.

[0118] Heat the powder mixture in a furnace with a nitrogen flow at a ramp rate of 2 °C / min to 600 °C. Maintain 600 °C for 6 hours. Thereafter, heat the powder in air at 600 °C for 12 hours. Raise the temperature to 900 °C with a ramp rate of 2 °C / min. Maintain 900 °C for 5 hours and lower it to 750 °C at a ramp rate of 2 °C / min. Maintain 750 °C for 8 hours and lower it to room temperature at a ramp rate of 2 °C / min.

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

[0120] Example 4: Synthesis of Lithium Positive Electrode 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 as black squares in Figures 1a - 1c, 2a - 2b and 4, and Figures 7a - 10b show SEM images of the particle cross-sections. Figures 5a - 5f show the relationship between the degree of decomposition and a series of parameters related to the morphology for the four samples. The relevant parameters are shown in Table 1 below. The precursors of all samples were co-precipitated as described in Example 1 using slightly different variations. As an example, the precursor of Sample 2 in Table 2 as shown in Figures 8a and 8b was produced by stirring at 200 rpm corresponding to approximately 2.6 W / L in a filled reactor, and the precursor of Sample 4 in Table 2 as shown in Figures 10a and 10b was produced by stirring at 400 rpm corresponding to approximately 10 W / L in a filled reactor.

[0121] Example 5: Synthesis of Lithium Positive Electrode Active Material Additional samples were produced 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-cells described in Example A and the Ni content in the spinel. The Ni content in the spinel is electrochemically measured as described in Example C. Figure 1b shows the correlation of the degree of decomposition per 100 cycles at 55 °C measured in half-cells as described in Example Calcination A and the 4V plateau. Figure 1c shows the correlation between the degree of decomposition at 55 °C measured in the half-cells described in Example A and the lattice parameter a in the spinel. Table 1 below includes the Ni content, Niy, lattice parameter, a, 4V plateau, capacity, degree of decomposition, and difference, dV, between two Ni-plateaus described in Example D for the samples described in Examples 1 - 5.

[0122]

Table 1

[0123] Example 6: Measurement of Morphology Using a Scanning Electron Microscope: Comparison of a Sample (Sample 4) According to the Present Invention with a Commercially Available Sample The sample 4 discussed in Example 4 and a commercial sample of a lithium positive electrode active material were compared using a scanning electron microscope (SEM).

[0124] Figures 14a and 14b show SEM images of sample 4 in perspective view and cross-sectional view, respectively, and Figures 15a and 15b show perspective view and cross-sectional view of SEM images of the commercial sample, respectively. As is apparent 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 commercial sample (Figures 15a and 15b) do not appear to be spherical and have a high degree of aggregation.

[0125] Example: Electrochemical Test Method for Lithium Positive Electrode Active Material Produced from Examples 1 to 5: Electrochemical tests were realized using 2032 types of coin-shaped batteries with a thin composite positive electrode and a metallic lithium negative electrode (half-cell). The thin composite positive electrode was fabricated by completely mixing 84 wt% of a lithium positive electrode active material (manufactured according to Examples 1 to 4), 8 wt% of SuperC65 carbon black (Timcal), and 8 wt% of a 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. Electrodes with a diameter of 14 mm and filled with approximately 8 mg of the lithium positive electrode active material were cut out from the dried film, pressed using a hydraulic pellet press (diameter 20 mm, 3 tons), and dried under vacuum at 120 °C for 10 hours in an argon-filled glove box.

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

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

[0128] Example B: Method for Measuring Particle Size and Shape Using a Scanning Electron Microscope: To prepare samples for scanning electron microscopy (SEM), the lithium cathode active material was embedded in epoxy and polished to a flat surface to image the cross-section of the particles. To evaluate the correlation between particle shape and degree of decomposition for samples with substantially the same spinel stoichiometry, the particle sizes and shapes of different samples were measured using SEM images of the embedded cross-sections. For the samples in FIGS. 7a, 7b, 9a, 9b, 10a and 10b, the spinel has the stoichiometry LiNi 0.454 Mn 1.546 O4, and the spinel of the samples in FIGS. 8a and 8b has the stoichiometry LiNi 0.449 Mn 1.551 O4.

[0129] SEM images were acquired using an acceleration voltage of 8 kV and a backscattered electron detector. The images were acquired at low magnification and high magnification with pixel sizes of 0.216 μm / pixel (FIGS. 7a, 8a, 9a, 10a) and 0.054 μm / pixel (FIGS. 7b, 8b, 9b, 10b), respectively. The low magnification images were used for measuring particle size and shape.

[0130] The SEM images were analyzed using the software ImageJ (https: / / imagej.nih.gov). The procedure was as follows: · Central filter, radius 1 pixel; · Sharpening; · Threshold using the Otsu algorithm; · Analyze particles: only particles with an area greater than 3 μm 2 were considered.

[0131] The process of analyzing the particles involves measuring the area and outer perimeter (circumference) for each particle and calculating the best-fit ellipse having the same area as the particle. Then, using the area, outer perimeter, and the fitted ellipse, a number of descriptors regarding size and shape are calculated for each particle in the SEM image: · Diameter: The equivalent circular diameter, i.e., the diameter of a circle having the same area as the particle. · Aspect ratio: The aspect ratio of the fitted ellipse of the particle, i.e., [major axis] / [minor axis]. · Roughness: The ratio between the measured outer perimeter and the perimeter of the fitted ellipse. It describes the surface roughness of the particle. · Circularity: 4π * [area] / [outer perimeter] 2 . Circularity describes the overall shape and surface roughness. For a smooth circular surface, the circularity is 1. · Area envelope: [area] / [area of the convex hull]. The area of the convex hull can be thought of as the shape resulting from wrapping a rubber band around the particle. The more concave features on the surface of the particle, the higher the area of the convex hull and the lower the area envelope. · Porosity: The ratio of the internal area of the particle displayed with a dark contrast in the SEM image. The dark contrast is interpreted as the porosity, i.e., the holes (voids) inside the particle.

[0132] The sample mean values of these descriptors are shown in the following table for four samples having substantially the same spinel stoichiometry but different degrees of decomposition. The degree of decomposition was measured in a half-cell 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 envelope, 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 envelope, 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 envelope is greater than 0.8.

[0135] Example C: Measurement of Ni and Mn Contents 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, in particular 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+ 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+ By extraction and insertion, Mn 3+ is Mn 4+ can be reversibly oxidized and returned to, and also during the cycle, Li + By extraction and insertion of, Ni 2+ is Ni 4+ can be reversibly oxidized and returned to. Thus, for Ni 2+ two Li + are, for Mn 3+ one Li + can be extracted (and subsequent insertion). When x = 1, the formula Li +1 Ni +2 y Mn +3 1-2y Mn +4 1+y Based on O4, the ratio of the capacity related to Mn activity to the total capacity is given by (1 - 2y) / (1 - 2y + 2y)=(1 - 2y). As an example, y = 0 corresponds to 0% of the capacity related to Mn activity, and y = 0.45 and 0.4 correspond to 10% and 20% of the total capacity being due to Mn activity, respectively.

[0138] In LNMO, Mn 3+ / Mn 4+ The reaction is observed at about 4 V vs. Li / Li + and Ni 2+ / Ni 4+ The reaction was observed at about 4.7 V vs. Li / Li + . Therefore, compared with the total capacity from 3.5 V to 5 V vs. Li / Li + the capacity from 3.5 V to 4.3 V vs. Li / Li +The capacity measured up to that point is expected to correspond to the Mn activity. The capacity around 4V is determined using the third discharge at 29 mA / g (0.2C) as described in Example A. During charge and discharge, the battery is not in an equilibrium state, 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 prominent near sudden changes in the battery voltage, and thus the proportion of Mn activity may appear to vary depending on whether the analysis is based on charging or discharging. Figure 6a shows the discharge and charge voltage curves as a function of capacity for the third charge at 29 mA / g (0.2C) described in Example A. The capacities Q 4V cha and Q 4V dis corresponding to a voltage of 4.3V during charge and discharge respectively are used to calculate the total discharge capacity Q tot dis . When using Q 4V cha +(Q tot dis -Q 4V dis )) / (2*Q tot dis ), the proportion of Mn - activity is given. This value is referred to 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 ) respectively.

[0139] Diffraction Mn 3 ions and Mn 4+The sizes of the ions are different, which affects the lattice parameters of the spinel. Powder X-ray diffraction data were collected on a Phillips PW1800 instrument system in θ~2θ geometry operating in Bragg-Brentano mode using CuKα radiation (λ = 1.541 Å). For the experimental parameters that contribute to the shift of the observed peak positions, it is necessary to correct the observed data, which is used in the calculation of the 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 determined with an uncertainty of approximately 5 / 10,000 Å, sufficient to determine the amount of Mn 3+ and thus the amounts of Mn and Ni.

[0140] Electron microscopy By combining scanning transmission electron microscopy (STEM) with energy-dispersive X-ray spectroscopy (EDS) for elemental mapping, the amounts of Mn and Ni in the spinel can be directly measured. STEM-EDS measured the amounts of Ni and Mn in three different samples to compare the composition of the spinel phase with the value calculated from the 4V charge plateau in the electrochemical measurement.

[0141] The STEM-EDS measurements were performed using a 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. The elemental maps were acquired and analyzed using Bruker's software Esprit 1.9. Standard quantification was performed using automatic background subtraction, series deconvolution, and the Cliff-Lorimer method. Impurities or non-spinel phases in the sample could be easily identified because of their significantly different composition from the spinel, i.e., a composition rich in Mn or Ni, and their small proportion in the whole sample. These non-spinel phases were not included in the quantification to accurately measure the composition of the spinel phase. The quantification showed the atomic percentages of the elements contained in the spinel phase. The amount of Ni in the spinel, Niy, is Niy = 2 * Ni at% / (Ni at% +Mn at% ) was determined. Here, Ni at% and Mna at% are the atomic percentages of Ni and Mn measured in the spinel.

[0142] As a result of analyzing three samples prepared by changing the value of Niy, as shown in Table 3 and Figure 11 below. The Ni net chemical composition (net chemical composition) refers to the overall Ni content in the sample, and Niy refers to the Ni content of the spinel phase measured using STEM-EDS and the 4V charge plateau. The table shows that the two measured values of Niy are in good agreement, confirming that the 4V charge plateau is directly related to the composition of the spinel phase. Furthermore, this data shows that Niy is not necessarily the same as the net chemical composition, but rather is determined by the firing 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 obtained from the 4V plateau. This correspondence can be fitted to a straight line of a = -0.1932 * y + 8.2627. Figure 2(b) shows a similar 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 the lithium positive electrode active material can be determined by Raman spectroscopy, as described in Ionics (2006) 12, pp117-126. To quantify the degree of ordering, two peaks related to cation order, 162 cm -1 (151 cm -1 ~172 cm -1 ) and 395 cm -1 (385 cm -1 ~420 cm -1and 496 cm independent of order -1 (482 cm -1 ~505 cm -1 ) and two peaks around 636 cm (627 cm - 639 cm -1 ) are used. As a simple method, the area of each peak can be calculated as shown in Fig. 13, and the order parameter can be calculated as the ratio (A1 + A2) / (A3 + A4). This method compensates for fluctuations in background and signal intensity. A fully ordered spinel shows a value around 0.4, and a fully disordered spinel shows a value around 0.1.

[0146] Another method to determine the degree of order is to measure the difference dV between two voltage plateaus at about 4.7 V during discharge at 29.6 mA / g (0.2 C). This method requires the production of sufficiently good materials and electrodes to obtain flat and well-separated plateaus, as seen in Figs. 6a and 6b. As shown in Fig. 6b, calculate the difference between the centers of each of the two plateaus near 4.7 V. Q 4V dis is determined as described in Example C, and the center of each of the two plateaus is Q 4V dis at 25% of and Q 4V dis at 75% of. A fully ordered spinel has a value around 30 mV, and a fully disordered spinel has a value around 60 mV.

[0147] Fig. 3 shows a comparison of two order parameters for which a correlation was confirmed. In Fig. 4, using the correlation between dV and order, it is judged that cation order causes an increase in the degree of decomposition.

Claims

1. A lithium positive electrode active material for a high voltage secondary battery, The lithium positive electrode active material comprises at least 94% by weight of spinel, The spinel is Li ｘ Ni ｙ Mn ２－ｙ O ４ wherein: 0.95≦x≦1.05; 0.43≦y≦0.47; wherein the lithium active cathode 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) in combination with energy dispersive X-ray spectroscopy (EDS).

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

3. 3. The lithium cathode active material of claim 1 or 2, wherein the lithium cathode active material in a half-cell has a difference of at least 50 mV between potentials at 25% and 75% of capacity above 4.3 V during discharge at a current of about 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 the lattice constant a is between 8.171 and 8.183 Å.

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

6. 5. The lithium positive electrode 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. 5. The lithium positive electrode active material of claim 4, wherein the lattice constant a is between (-0.1932y+8.2613) Å and (-0.1932y+8.2641) Å.

8. The lithium positive electrode active material has a density of 2.2 g / cm ３ The lithium positive electrode active material according to any one of claims 1 to 7, having a tap density of at least 100%.

9. The lithium positive electrode active material according to any one of claims 1 to 8, wherein D50 of the particles of the lithium positive electrode active material satisfies 3 μm<D50<12 μm.

10. The BET area of ​​the lithium positive electrode active material is 1.5 m ２ The lithium positive electrode active material according to any one of claims 1 to 9, wherein the Li+ / - is less than 1 / g.

11. 11. The lithium cathode active material of claim 1, wherein the lithium cathode active material is composed of particles, the particles having an average aspect ratio of less than 1.

6.

12. 12. The lithium cathode active material according to claim 1, characterized in that the lithium cathode active material is composed of particles, the particles having a roughness of less than 1.

35.

13. 13. The lithium positive electrode active material according to claim 1, wherein the lithium positive electrode active material is composed of particles, the particles having a circularity of greater than 0.

55.

14. 14. The lithium positive electrode active material according to claim 1, wherein the lithium positive electrode active material is composed of particles, the particles having an area coverage ratio of greater than 0.

8.

15. 11. The lithium positive electrode active material according to claim 1, wherein the lithium positive electrode active material is composed of particles, the particles having a porosity of less than 3%.

16. The lithium positive electrode active material according to any one of claims 1 to 15, wherein 0.99≦x≦1.

01.

17. 17. The lithium positive electrode active material according to claim 1, wherein the capacity loss of the lithium positive electrode active material in a half cell is 4% or less in 100 cycles between 3.5 and 5.0 V at 55° C.

18. 18. The lithium cathode active material of claim 1, wherein the lithium cathode active material is synthesized from a precursor comprising Li, Ni, and Mn in a ratio Li:Ni:Mn:X:Y:2-Y, where 0.95≦X≦1.05; and 0.42≦Y<0.

5.

19. The lithium positive electrode active material according to any one of claims 1 to 18, wherein 0.43≦y<0.

45.

20. Li ｘ Ni ｙ Mn ２－ｙ O ４ providing a precursor for producing a lithium active cathode material comprising at least 94% by weight of a spinel having a chemical composition: b. sintering the precursor of step a by heating to a temperature between 500° C. and 1200° C. to obtain a sintered product; c. Cooling the sintered product of step b to room temperature. The method for producing a lithium positive electrode active material according to any one of claims 1 to 17, comprising:

21. The process according to claim 20, wherein part of step b is carried out in a reducing atmosphere.

22. The method according to claim 20 or 21, wherein the temperature in step b is between 850°C and 1100°C.

23. The method of any one of claims 20 to 22, wherein during the cooling of step c, the temperature is maintained in the interval of 750 to 650°C for an amount of time sufficient to obtain at least 94% phase purity of the lithium active cathode material.

24. The method according to any one of claims 20 to 23, wherein at least one of the precursors is a precipitating compound.

25. The method according to any one of claims 20 to 24, wherein the precipitated compound is a co-precipitation compound of Ni and Mn formed in a Ni-Mn co-precipitation step.

26. 26. A process according to claim 25, wherein said precursor in the form of co-precipitated Ni-Mn has been produced in a precipitation step, in which a first solution of starting material comprising Ni, a second solution of starting material comprising Mn and a third solution of precipitating anions are added simultaneously to the liquid reaction medium in a reactor in amounts such that, relative to the added Ni, each of the Mn and precipitating anions is 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, more preferably 1:1.2 to 1.2:1, with respect to the stoichiometric amount of the precipitate.

27. 27. The process according to claim 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 a pH between 8.0 and 10.0, preferably 8.5 and 10.

0.

28. The process of any one of claims 26 to 27, wherein the first, second and third solutions are added to the reaction mixture over an extended period of time, for example, from 2.0 to 11 hours.

29. The process according to any one of claims 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.

30. A secondary battery comprising the lithium positive electrode active material according to any one of claims 1 to 19.

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