Cathode active material having a spinel structure

Abstract

The present invention relates to a cathode active material comprising: a first crystalline particle having a spinel structure and the formula Li x Ni y Mn 3-x-y-z D z (b) A first crystalline particle, represented by O4, where 0.95≦x≦1.05; 0.45≦y≦0.50 and 0≦z≦0.20, where D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof; (b) a first crystalline particle having a particle size of 3 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope; (b) a second crystalline particle, the second crystalline particle containing a material having a spinel structure, which is given by the formula Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ Represented by O4, where 0.95≦x'≦1.05;0.43≦y'≦0.47 and 0≦z'≦0.20, D' is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof, and the second crystalline grain has an average particle diameter at least three times that of the first crystalline grain, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope.

Description

[Technical Field]

[0001] Field of Invention This invention relates to a cathode active material used in lithium batteries. [Background technology]

[0002] Background of the Invention The development of high-energy-density rechargeable battery materials is a major research challenge, with applications ranging from electric vehicles and portable electronic devices to grid-scale energy storage. Since its first commercialization in the early 1990s, lithium-ion batteries (LIBs) have offered many advantages over other commercial battery technologies. In particular, their high specific energy and specific power make LIBs the best candidate for electric mobile transport applications.

[0003] Lithium nickel manganese oxide (LNMO), or lithium nickel manganese oxide, is a cathode material that is attracting attention in the battery industry due to its promising electrochemical performance and relatively low cost compared to other high-energy-density cathode materials such as NCA and LCO.

[0004] LNMO has a similar crystal structure to LMO, but the addition of nickel improves its energy density and thermal stability. Furthermore, LNMO is less toxic than other nickel-containing cathode materials, making it a more environmentally friendly option.

[0005] One of the main advantages of LNMO is its high capacity retention rate and cycle stability, which means it can maintain a high energy capacity over many charge-discharge cycles. This characteristic makes it a promising candidate for applications in electric vehicle batteries where long cycle life is crucial.

[0006] Lithium cathode active material is characterized by the following equation: Li x Ni y Mn 2-y O 4-δHere, 0.9 ≤ x ≤ 1.1, 0.4 ≤ y ≤ 0.5, and 0 ≤ δ ≤ 0.1. Such materials are used in applications such as: portable devices (US8404381); electric vehicles, energy storage systems, auxiliary power units, and uninterruptible power supplies. Lithium cathode active materials are considered promising successors to current lithium secondary battery cathode materials (e.g., LiCoO2, LiMn2O4). 。

[0007] Lithium cathode active materials can be produced from precursors obtained by coprecipitation. Coprecipitation results in spherical precursors and products. Electrochimica Acta (2014), pp. 290-296 discloses a material obtained by sequentially sintering (heat treating) a precursor obtained by coprecipitation at 500°C and then at 800°C. The resulting product exhibits high crystallinity after the first heat treatment step (500°C) and possesses a spinel structure. This product has a uniform morphology and a tap density of 2.03 g / cm³. -3 They exhibit a uniform secondary particle size of 5.6 μm. According to Electrochimica Acta (2004), pp939-948, spherical particles have high fluidity and are easy to fill, resulting in a higher tap density than irregular particles.

[0008] Lithium cathode active materials can also be produced from precursors obtained by mechanically mixing starting materials to form a homogeneous mixture, as disclosed in US8404381. The precursor is heated to 600°C, annealed between 700 and 950°C, and cooled in an oxygen-containing medium. The 600°C heat treatment step is disclosed to be necessary to ensure good integration of lithium into the mixed nickel-manganese oxide precursor. The annealing step is also disclosed to be generally carried out at temperatures above 800°C to allow oxygen to be lost while forming the desired spinel morphology. Furthermore, it is disclosed that subsequent cooling in an oxygen-containing medium allows for partial return of oxygen. US7754384 does not mention the tap density of the material. It is also disclosed that a lithium excess of 1 to 5 mole percent is used in the production of the precursor.

[0009] US7754384 also describes materials of chemical formula LiNi 0.4 Mn 1.6 O 4-δ (δ > 0). It is disclosed that this chemical formula, i.e., a material with a lower Ni content compared to Mn, has high cycle stability.

[0010] [[ID= (13)]]J.Electrochem.Soc.(1997)144,pp205 - 213 discloses a method for producing spinel - type LiNi 0.5 Mn 1.5 O4 from a precursor produced by mechanically mixing materials to obtain a homogeneous mixture. The precursor is heated three times at 750 °C and once at 800 °C in air. It is disclosed that LiNi 0.5 Mn 1.5 O4 loses oxygen and disproportionates when heated above 650 °C. However, by using a slow cooling rate in an oxygen - containing atmosphere, the stoichiometric composition of LiNi 0.5 Mn 1.5 O4 is restored.

[0011] WO2020 / 127543 discloses a lithium cathode active material for high - voltage secondary batteries. The lithium cathode active material contains at least 94% by mass of spinel, and the spinel has a net chemical composition of Li x Ni y Mn 2-y O4, where 0.95 ≤ x ≤ 1.05 and 0.43 ≤ y ≤ 0.47 are satisfied. The lithium cathode active material is composed of spherical particles. This material has high capacity, high voltage with respect to the Li / Li + reference, and low degradation property. [Prior Art Documents] [Patent Documents]

[0012] [Patent Document 1] US8404381 [Patent Document 2] US7754384 [Patent Document 3] WO2020 / 127543 [Non-patent literature]

[0013] [Non-Patent Document 1] Electrochimica Acta (2014),pp 290-296 [Non-Patent Document 2] J.Electrochem.Soc.(1997)144,pp205-213 [Overview of the project] [Problems that the invention aims to solve]

[0014] It is desirable to provide a cathode active material with improved volumetric energy density and / or higher voltage and / or high energy density. It is also desirable to provide a cathode active material with improved performance over multiple charge-discharge cycles. [Means for solving the problem]

[0015] Summary of the Invention In one embodiment, a cathode active material comprising the following is provided: (a) A first crystal grain having a spinel structure and the formula Li x Ni y Mn 3-x-y-z D z Represented by O4, where 0.95≦x≦1.05;0.45≦y≦0.50 and 0≦z≦0.20, and D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof; the first crystalline grain is a first crystalline grain having a particle size of 3 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. (b) A second crystalline particle, the second crystalline particle comprising a material having a spinel structure, wherein the material is of the formula Li x’ Ni y’ Mn3-x’-y’-z’ D' z’ Represented by O4, where 0.95≦x'≦1.05;0.43≦y'≦0.47 and 0≦z'≦0.20, D' is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof, and the second crystalline grain has an average particle diameter at least three times that of the first crystalline grain, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. Here, y > y'.

[0016] The material of the present invention can be manufactured by two different methods for forming first crystalline particles and second crystalline particles, after which the first crystalline particles and second crystalline particles can be combined.

[0017] In another embodiment, the present invention provides a method for producing the cathode active material described herein, which includes: A. A method for producing single crystals of one or more first components, comprising the following steps: (i) A step of supplying one or more lithium precursor compounds and one or more transition metal precursor compounds; (ii) The step of contacting the precursor compound and grinding it to form a pulverized mixture; (iii) A step of calcining the pulverized mixture to provide a calcined mixture; B. A method for producing a second crystalline particle of the cathode active material, comprising the following steps: (i) A step of providing one or more transition metal compounds; (ii) Precipitating a transition metal to form a precipitate, and washing the precipitate to form a first precursor mixture; (iii) The step of contacting the first precursor mixture with one or more lithium precursor compounds to form a second precursor mixture; (iv) A step of calcining the second precursor mixture, C. Combine the products obtained in A and B. [Effects of the Invention]

[0018] A surprising discovery was that by mixing the above materials, the cathode active materials of the present invention, which have different Ni content, can achieve a high Ni content in the cathode without impairing electrochemical stability. As a result, it is possible to simultaneously achieve improved packing density and increased average voltage, and to increase energy density without impairing other properties of the cathode active material.

[0019] Furthermore, it was found that this material has higher stability compared to conventional cathode active materials, particularly those containing only "polycrystalline materials" as disclosed in WO2020 / 127543. In fact, in several respects, the cathode active material of the present invention was found to have the same stability as single-crystal materials. In addition, the cathode active material of the present invention is improved in terms of reducing manufacturing costs and / or wastewater generation.

[0020] Brief explanation of the drawing [Brief explanation of the drawing]

[0021] [Figure 1] Figure 1 shows an SEM image of the Small-Ni435 sample from Example 1. [Figure 2] Figure 2 shows an SEM image of the Large-Ni435 sample from Example 3. [Figure 3] Figure 3: SEM image of a Small-Ni435 sample after embedding in epoxy resin and polishing the flat surface. [Figure 4] Figure 4: Cross-sectional SEM image of an electrode prepared by mixing Small-Ni435 and Large-Ni435 in a 50:50 ratio. [Figure 5] Figure 5: Compression densities of materials Small-Ni435 (light gray symbols), Large-Ni435 (black symbols), and a 50:50 mixture of Large-Ni435 and Small-Ni435 are shown as a function of compressed pressure. [Figure 6]Figure 6: LNMO-Li half-cells using individual materials. Voltage curves recorded during 0.1C charging and 0.1C discharging are shown. [Figure 7] Figure 7: LNMO-Li half-cells using individual materials. Shows the change in discharge capacity at 23°C recorded during 0.5C charging and 1C discharging. [Figure 8] Figure 8: LNMO-Li half-cell using mixed materials. Voltage curves recorded during 0.1C charging and 0.1C discharging are shown. [Figure 9] Figure 9: LNMO-Li half-cell using mixed materials. Shows the change in discharge capacity at 23°C recorded during 0.5C charging and 0.1C discharging. [Figure 10] Figure 10: LNMO-LTO total battery. Voltage curves recorded during 0.1C charging and 0.1C discharging are shown. [Figure 11] Figure 11: All LNMO-LTO batteries. Shows the change in discharge capacity during 1C charge and 1C discharge cycles at 23°C. The reference cycle was recorded at 0.1C charge and 0.1C discharge. Capacity loss corresponds to 1.4% per 100 cycles from 1.7V to 3.4V and 1.1% from 2.8V to 3.4V. [Figure 12] Figure 12: Shows the degradation rate of Small and Large LNMO cathode active materials as a function of the Ni content of spinel. [Figure 13] Figure 13: Discharge and charge voltage curves of an LNMO-Li battery against its capacity. [Figure 14] Figure 14: Shows the correspondence between the electrochemically determined 4V plateau and the lattice constant a determined by X-ray diffraction. [Figure 15] Figure 15: This figure shows the correspondence between the nickel content in spinel, determined electrochemically, and the lattice constant a, determined by X-ray diffraction. [Modes for carrying out the invention]

[0022] Detailed description of the invention A cathode active material having the following configuration is provided, as described herein: (a) A first crystal grain, where the first crystal grain has a spinel structure and is given by formula Li x Ni y Mn (3-x-y-z) Represented as DzO4, where 0.95≦x≦1.05, 0.45≦y≦0.50, 0≦z≦0.20, and D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, and mixtures thereof, and the first crystalline grain has a particle size of 3 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. (b) A second crystalline particle, where the second crystalline particle comprises a material having a spinel structure and its chemical formula is Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ Represented as O4 、 Here, 0.95≦x'≦1.05; 0.43≦y'<0.47, and 0≦z'≦0.20, and D' is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof, and the second crystalline grain has an average particle diameter at least three times that of the first crystalline grain, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope, and y>y'.

[0023] By providing a mixture of these materials, we found that it is possible to provide a cathode active material that simultaneously achieves improved packing density and increased average voltage without impairing other properties of the cathode active material, and as a result, the energy density can be increased.

[0024] As described herein, the cathode active material comprises particles formed from one or more single crystals of a first crystalline grain whose particle size, as measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope, is 3 μm or less.

[0025] As those skilled in the art will understand, the Ferret diameter is the distance between two parallel lines positioned opposite each other as tangents on the contour of a particle. The minimum Ferret is the minimum distance between such two tangents and can be considered the smallest sieve opening through which the particle can pass. For example, in a rectangular particle, the minimum Ferret diameter corresponds to the shorter side, and in a circular particle, the minimum Ferret diameter corresponds to the diameter of the circle.

[0026] The Ferret diameter of particles is well understood by those skilled in the art. The Ferret diameter is used in the analysis of particle size and its distribution, and has been commonly used in scientific literature since the 1970s. The Ferret diameter is a measure of object size defined as the distance between two parallel planes that restrict the object perpendicular to its direction. Therefore, it is also called the caliper diameter, deriving from the measurement of object size with a caliper.

[0027] The Ferret diameter of the first or second crystalline grain can be evaluated using a scanning electron microscope (SEM). For example, to prepare a sample for this measurement, it is embedded in epoxy resin, polished to a flat surface, and the cross-section of the individual particles constituting the sample is imaged. The resulting image is then analyzed to measure the size and shape of the particles. The minimum Ferret diameter is the minimum distance between two tangents and can be considered the smallest sieve opening through which the particle can pass. For example, in a rectangular particle, the minimum Ferret diameter corresponds to the shorter side, and in a circular particle, it corresponds to the circumference.

[0028] The size of irregularly shaped particles can also be quantified by referring to the diameter of a circle with an equal projected area. For a particle with a projected area A, an equal-area circle has a diameter d=2 * √(A / (2 * π))

[0029] The Ferret diameter of the particles can be determined according to the following method. The sample is prepared by encapsulating it in epoxy resin for scanning electron microscopy (SEM) and polishing it to a flat surface. SEM images are acquired using a Zeiss GeminiSEM 500 equipped with a field emission gun (FEG), with an acceleration voltage of 10 kV and an energy-selective backscatter (ESB) detector (backscatter electron detector type). The pixel size is 0.01 μm / pixel. A total of 25 images are acquired and stitched together into a high-resolution image of 4930 pixels × 3697 pixels (corresponding to an image area of ​​48 μm × 36 μm). The images are analyzed according to the following procedure to detect and analyze a total of 663 particles. ImageJ software (https: / / imagej.nih.gov) is used for image analysis. The procedure is as follows: - Thresholding and segmentation using "Otsu's algorithm" - Apply binary processing (binarization) "Fill hole". - Apply the binary process "Erode" 8 times. - Apply the binary process "Dilate" six times. - Perform "particle analysis" without size limitations

[0030] The "Fill holes" process is used to fill potential holes within particles. Subsequently, the "Dilate" process from Erode is applied to remove noise and ensure the separation of adjacent particles.

[0031] A "spinel" refers to a crystal lattice in which oxygen is arranged in a slightly distorted cubic close-packed lattice, where distortion can occur, and cations (positive ions) occupy interstitial octahedral and tetrahedral sites within the lattice. Oxygen and octahedral-coordinated cations form a skeletal structure with a three-dimensional channel system, in which tetrahedral-coordinated cations are present. The ratio of tetrahedral-coordinated cations to octahedral-coordinated cations is approximately 1:2, and the ratio of cations to oxygen (ratio of cations to oxygen) in a spinel-type structure is approximately 3:4. The cations on the octahedral sites can consist of a single element or a mixture of multiple elements. If a mixture of different types of octahedral-coordinated cations forms a three-dimensional periodic lattice on its own, the spinel is called an ordered spinel. If the distribution of cations is more random, the spinel is called a disordered spinel. Examples of ordered and disordered spinels (described by the P4332 space group and the Fd-3m space group, respectively) are given in Adv. Mater. (2012) 24, pp 2109-2116.

[0032] The phase composition of the cathode-active material can be measured based on X-ray diffraction patterns acquired using a Phillips PW1800 instrument system operating in θ-2θ geometry of Bragg-Brentno modes with Cu Kα radiation (λ=1.541 Å). The observed data needs to be corrected for experimental parameters that contribute to the shift in the observed data. This is achieved using the full-profile fundamental parameter method implemented in Bruker's TOPAS software. The phase composition determined from the Rietveld analysis is expressed as mass percent (wt%) with a typical uncertainty of 1-2 percent points and represents the relative composition of all crystalline phases. Therefore, amorphous phases are not included in the phase composition.

[0033] For convenience of reference, these and further aspects of the invention are discussed under appropriate section headings. However, the teachings in each section are not necessarily limited to each specific section.

[0034] First crystal particle - small LNMO The first crystal grain of the present invention has a spinel structure and is of the formula Li x Ni y Mn 3-x-y-z D z O 4v This is expressed as follows, where 0.95≦x≦1.05, 0.45≦y≦0.50, and 0≦z≦0.20. D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, and mixtures thereof. The first crystalline grain has a particle size of 3 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. The first crystalline grain may be ordered (space group P4332) or disordered.

[0035] In one embodiment, the first crystal grain has a particle diameter of 2.5 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. For example, 2 μm or less, 1 μm or less, 1.6 μm or less, 1.4 μm or less, 1.2 μm or less, 1 μm or less, or 0.8 μm or less.

[0036] In one embodiment, the first crystal grain has a particle size of at least 0.1 μm, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope, for example, at least 0.2 μm, for example at least 0.3 μm, for example at least 0.4 μm, for example at least 0.5 μm, for example at least 0.6 μm, for example at least 0.7 μm.

[0037] In one embodiment, the first crystal grain has a particle size measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope, which is at least 0.1 to 2.5 μm, e.g., 0.1 to 2 μm, e.g., 0.1 to 1.8 μm, e.g., 0.1 to 1.6 μm, e.g., 0.1 to 1.4 μm, e.g., 0.1 to 1.2 μm, e.g., 0.1 to 1 μm, e.g., 0.1 to 0.8 μm.

[0038] In one embodiment, the first crystalline grain has a particle size measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope, which is at least 0.2–2.5 μm. For example, 0.3–2.5 μm, 0.4–2.5 μm, 0.5–2.5 μm, 0.6–2.5 μm, or 0.7–2.5 μm.

[0039] As discussed herein, the size of irregularly shaped particles can also be quantified by referring to the diameter of a circle with equal projected area. For a particle with projected area A, a circle with equal area has a diameter d=2 * √(A / (2 * π)) is obtained. In one embodiment, the cathode active material includes first crystal particles, and the average equivalent circle diameter of the particles measured using a scanning electron microscope is 3 μm or less. In one embodiment, the average equivalent circle diameter of the particles measured using a scanning electron microscope is 2.5 μm or less, for example 2 μm or less, for example 1.8 μm or less, for example 1.6 μm or less, for example 1.4 μm or less, for example 1.2 μm or less, for example 1 μm or less, for example 0.9 μm or less.

[0040] In one embodiment, the average equivalent circle diameter of the first crystal grain, measured using a scanning electron microscope, is at least 0.1 μm, e.g., at least 0.2 μm, e.g., at least 0.3 μm, e.g., at least 0.4 μm, e.g., at least 0.5 μm, e.g., at least 0.6 μm, e.g., at least 0.7 μm.

[0041] In one embodiment, the average equivalent circle diameter of the first crystal grain, measured using a scanning electron microscope, is 0.1–2.5 μm, e.g., 0.1–2 μm, e.g., 0.1–1.8 μm, e.g., 0.1–1.6 μm, e.g., 0.1–1.4 μm, e.g., 0.1–1.2 μm, e.g., 0.1–1 μm, e.g., 0.1–0.9 μm.

[0042] In one embodiment, the average equivalent circle diameter of the first crystal grain, measured using a scanning electron microscope, is 0.2–2.5 μm, e.g., 0.3–2.5 μm, e.g., 0.4–2.5 μm, e.g., 0.5–2.5 μm, e.g., 0.6–2.5 μm, e.g., 0.7–2.5 μm.

[0043] Formula Li x Ni y Mn 3-x-y-z D z In O4, x is between 0.95 and 1.05. In one embodiment, x is in the range of 0.95 to 1.04. For example, the range is 0.95 to 1.03, 0.95 to 1.02, 0.95 to 1.01, 0.95 to 1. In one embodiment, x is in the range of 0.96 to 1.05, for example, 0.97 to 1.05, 0.98 to 1.05, 0.99 to 1.05, 1 to 1.05. In one embodiment, x is in the range of 0.96 to 1.04, for example, 0.97 to 1.03, 0.98 to 1.02, 0.99 to 1.01, 0.97 to 1.02, 0.97 to 1.01, 0.97 to 1, 1.

[0044] Formula Li x Ni y Mn 3-x-y-z D z In O4, y is between 0.45 and 0.50. In one embodiment, y is in the range of 0.46 to 0.50, for example, in the range of 0.47 to 0.50, for example, in the range of 0.48 to 0.50, for example, in the range of 0.49 to 0.50, for example, in the range of 0.50. In one embodiment, y is in the range of 0.45 to 0.49, for example, in the range of 0.45 to 0.48, for example, in the range of 0.45 to 0.47, for example, in the range of 0.45 to 0.46, for example, in the range of 0.45.

[0045] Formula Li x Ni y Mn 3-x-y-z D zIn O4, z is between 0 and 0.20. In one embodiment, z is in the range of 0 to 0.18, for example, 0 to 0.16, for example, 0 to 0.15, for example, 0 to 0.14, for example, 0 to 0.12, for example, 0 to 0.1, for example, 0 to 0.08, for example, 0 to 0.06, for example, 0 to 0.05, for example, 0 to 0.04, for example, 0 to 0.03, for example, 0 to 0.02, for example, 0 to 0.01, for example, 0.

[0046] D is a dopant, and it is clear that D does not exist when z is 0. D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof. In one embodiment, D is selected from the group consisting of B, Mg, Al, Nb, Si, P, La, S, Ti, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof.

[0047] In one embodiment, the first crystal grain is a single crystal grain. As described herein, the first crystal grain of the present invention has a spinel structure and is of the formula Li x Ni y Mn 3-x-y-z D z It is represented as O4. Those skilled in the art will understand that while crystalline grains having a spinel structure are primarily spinel, other non-spinel structural materials may also be present in the crystal. In one embodiment 、 The first crystal grain has a spinel structure, and the formula is Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ The material contains at least 94% by mass, for example, at least 96% by mass, for example, at least 98% by mass, for example, at least 99% by mass, for example, at least 99.5% by mass, for example, at least 99.9% by mass, for example, at least 99.99% by mass.

[0048] Second crystal particle: Large LNMO The second crystalline particle of the present invention comprises a material having a spinel structure, Li x’ Niy’ Mn 3-x’-y’-z’ D' z’ Represented by O4; where 0.95 ≤ x' ≤ 1.05; 0.43 ≤ y' < 0.47, and 0 ≤ z' ≤ 0.20. D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, and mixtures thereof. The second crystalline grain may have disorder (space group Fd-3m).

[0049] In one embodiment, the second crystalline grain is formed from an aggregated single crystal. In another embodiment, the second crystalline grain is a polycrystalline secondary grain.

[0050] The secondary particles can be of any suitable size, provided that the average particle diameter of the second crystal particles is at least three times the average particle diameter of the first crystal particles. In one embodiment, one or more secondary particles have an average particle diameter (D50) of less than 50 μm, for example less than 45 μm, for example less than 40 μm, for example less than 35 μm, for example less than 30 μm, for example less than 25 μm, for example less than 20 μm, for example less than 15 μm, for example less than 10 μm.

[0051] In one embodiment, one or more secondary particles have an average particle diameter (D50) of at least 1 μm, for example, at least 2 μm, for example, at least 3 μm, for example, at least 4 μm, for example, at least 5 μm, for example, at least 10 μm.

[0052] In one embodiment, one or more secondary particles have an average particle diameter (D50) of 4-50 μm, e.g., 4-45 μm, e.g., 4-40 μm, e.g., 4-35 μm, e.g., 4-30 μm, e.g., 4-25 μm, e.g., 4-20 μm, e.g., 4-15 μm, e.g., 4-10 μm.

[0053] One way to quantify particle size is to plot the entire particle size distribution, i.e., the volume fraction of particles of a particular size, as a particle size function. In such a distribution, D10 is defined as the particle size at which 10% of the distribution is less than the D10 value, D50 as the particle size at which 50% of the distribution is less than the D50 value (i.e., the median), and D90 as the particle size at which 90% of the distribution is less than the D90 value. Common methods for determining particle size distribution include laser diffraction measurements and combinations of scanning electron microscopy measurements and image analysis. The particle size distribution value D50 is defined and measured according to the method described in "Particle Size Characterization" by Jillavenkatesa A, Dapkunas SJ, and Lin-Sien Lum (NIST Special Publication 960-1, 2001).

[0054] Formula Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ In O4, x' is between 0.95 and 1.05. In one embodiment, x' is in the range of 0.95 to 1.04, for example, the range of 0.95 to 1.03, for example, the range of 0.95 to 1.02, for example, the range of 0.95 to 1.01, for example, the range of 0.95 to 1. In one embodiment, x' is in the range of 0.96 to 1.05, for example, the range of 0.97 to 1.05, for example, the range of 0.98 to 1.05, for example, the range of 0.99 to 1.05, for example, the range of 1 to 1.05. In one embodiment, x' is in the range of 0.96 to 1.04, for example, the range of 0.97 to 1.03, for example, the range of 0.98 to 1.02, for example, the range of 0.99 to 1.01, for example, the range of 0.97 to 1.02, for example, the range of 0.97 to 1.01, for example, the range of 0.97 to 1, for example, the range of 1.

[0055] Formula Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’In O4, y' is between 0.43 and 0.47. In one embodiment, y' is in the range of 0.44 to 0.47, for example, in the range of 0.45 to 0.47, for example, in the range of 0.46 to 0.47, for example, in the range of 0.45 to 0.46, for example, in the range of 0.45 to 0.44. In one embodiment, y' is in the range of 0.43 to 0.46, for example, in the range of 0.43 to 0.45, for example, in the range of 0.43 to 0.44.

[0056] Formula Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ In O4, z' is between 0 and 0.20. In one embodiment, z' is in the range of 0 to 0.18, for example, 0 to 0.16, for example, 0 to 0.15, for example, 0 to 0.14, for example, 0 to 0.12, for example, 0 to 0.1, for example, 0 to 0.08, for example, 0 to 0.06, for example, 0 to 0.05, for example, 0 to 0.04, for example, 0 to 0.03, for example, 0 to 0.02, for example, 0 to 0.01, for example, 0.

[0057] D' is a dopant, and it is clear that D' does not exist when z is 0. D' is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof. In one embodiment, D' is selected from the group consisting of B, Mg, Al, Nb, Si, P, La, S, Ti, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof.

[0058] As described herein, the second crystalline grain of the present invention has a spinel structure and is of the formula Li x’ Ni y’ Mn 3-x’-y’-z’ D' z’ It contains a material represented by O4. In one embodiment, the second crystalline grain has a spinel structure and is of the formula Li x’ Ni y’ Mn 3-x’-y’-z’ D'z’ It contains a material represented by the formula O4 and contains it in an amount of at least 50% by mass, for example at least 55% by mass, for example at least 60% by mass, for example at least 65% by mass, for example at least 70% by mass, for example at least 75% by mass, for example at least 80% by mass, for example at least 85% by mass, for example at least 90% by mass, for example at least 92% by mass, for example at least 94% by mass, for example at least 96% by mass, for example at least 98% by mass, for example at least 99% by mass, for example at least 99.5% by mass based on the mass of the second crystal particles.

[0059] Cathode active material As described herein, as one aspect, the general formula Li x Ni y Mn 3-x-y There is provided a cathode active material containing two types of lithium transition metal oxide particles having O4 and further containing an optional dopant (D). The lithium transition metal oxide may have a spinel crystal structure. The cathode active material includes the following: (i) Particles formed from one or more single crystals, the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope is 3 μm or less, 0.95 ≦ x ≦ 1.05; and 0.45 ≦ y ≦ 0.50 (ii) Secondary particles that can be formed from aggregated single crystal particles, 0.95 ≦ x ≦ 1.05; 0.43 ≦ y < 0.47.

[0060] In a certain aspect, the first crystal particles have a particle size measured as the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope of 0.5 to 2 μm; and the second crystal particles have an average particle size measured as the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope of 5 to 10 μm.

[0061] In one embodiment, the first crystalline grain has a particle size of 1 μm or less, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope; and the second crystalline grain has an average particle size of at least 3 μm, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope.

[0062] In one embodiment, the secondary particles of the cathode active material have a porosity (porosity) of less than 8%, for example, less than 6%, for example, less than 4%, and for example, 1-3%. As those skilled in the art will understand, the porosity can be determined by measuring the particle density using a hydrometer with ethanol. The porosity of the material is equal to 1 - (particle density / skeleton density). For reference, the skeleton density of LNMO is 4.43 g / cm³. 3 That is the case.

[0063] In one embodiment, based on the mass of the cathode active material, the first crystalline particles are present in an amount of 20-80% by mass, for example, 30-80% by mass, for example, 30-70% by mass, for example, 35-70% by mass, for example, 35-65% by mass, for example, 35-60% by mass, for example, 35-55% by mass, for example, 35-50% by mass.

[0064] In one embodiment, based on the mass of the cathode active material, the second crystalline particles are present in an amount of 20-80% by mass, for example 30-80% by mass, for example 30-70% by mass, for example 35-70% by mass, for example 35-65% by mass, for example 35-60% by mass, for example 35-55% by mass, for example 35-50% by mass.

[0065] Manufacturing method The material of the present invention can be manufactured by two different methods for forming first crystalline particles and second crystalline particles, after which the first crystalline particles and second crystalline particles can be combined.

[0066] The first method includes a method for producing one or more single crystals of a first component, and includes the following steps: (i) A step of providing one or more lithium precursor compounds and one or more transition metal precursor compounds; (ii) The step of contacting the precursor compound and grinding it to form a pulverized mixture; (iii) A step of calcining the pulverized mixture to provide a calcined mixture.

[0067] The lithium precursor compound of the first method may be selected from Li2CO3 or LiOH·H2O.

[0068] The transition metal precursor compound of the first method may be selected from oxides of Mn and Ni, carbonates of Mn and Ni, and hydroxides of Mn and Ni. In one embodiment, the transition metal precursor compound of the first method is selected from MnO2, Mn3O4, MnCO3, NiCO3, and basic Ni carbonates such as (Ni(CO3)x(OH)y·zH2O (where 2x+y=2)), as well as mixtures thereof.

[0069] In one embodiment, the pulverized mixture is calcined at a temperature of at least 800°C. In embodiments of this method, the pulverized mixture is calcined at a temperature of 300 to 1200°C, for example 400 to 1100°C, for example 500 to 1100°C, for example 500 to 1000°C, for example 600 to 1000°C, for example 700 to 950°C.

[0070] The pulverized mixture can be calcined for any suitable period of time. In one embodiment, the pulverized mixture is calcined for a period of at least 10 minutes, for example, at least 30 minutes, for example, at least 1 hour, for example, at least 2 hours, for example, at least 3 hours. In one embodiment, the pulverized mixture is calcined for 10 minutes to 10 hours, for example, 30 minutes to 10 hours, for example, 1 hour to 10 hours, for example, 2 hours to 10 hours, for example, 3 hours to 10 hours.

[0071] After the calcination of the pulverized mixture, cooling is typically performed. "Cooling" means gradually lowering the temperature or temperature range to reduce the temperature of the material. Typical cooling conditions include cooling at a rate of 1°C to 5°C per minute when lowering the temperature from 900°C to 700°C. Optionally, the material can be cooled to, for example, 600°C, 500°C, 400°C, 300°C, 200°C, 100°C, 50°C, or room temperature (i.e., approximately 25°C).

[0072] The second method is for producing a second crystalline particle of the cathode active material. This method includes the following steps: (i) A step of supplying one or more transition metal compounds, (ii) Precipitating a transition metal to form a precipitate, and washing the precipitate to form a first precursor mixture; (iii) The step of contacting the first precursor mixture with one or more lithium precursor compounds to form a second precursor mixture; (iv) A step of calcining the second precursor mixture.

[0073] As those skilled in the art will understand, in step (ii), wastewater is generated by washing.

[0074] The lithium precursor compound can be selected from Li2CO3, LiOH·H2O, LiNO3, and mixtures thereof.

[0075] The transition metal precursor compound in the second method may be selected from water-soluble Ni and Mn compounds. In one embodiment, the transition metal precursor compound is selected from MnSO4, Mn(NO3)2, NiSO4, Ni(NO3)2, and mixtures thereof.

[0076] In one embodiment, the second precursor mixture is dried before step (iv), i.e., before calcination of the second precursor mixture.

[0077] In one embodiment, the second precursor mixture is calcined at a temperature of at least 500°C in a reducing atmosphere, and then calcined in air at a temperature of at least 800°C.

[0078] In embodiments of this method, the second precursor mixture is calcined at 300-1200°C, for example 400-1100°C, for example 500-1100°C, for example 500-1000°C, for example 600-1000°C, for example 700-900°C.

[0079] The second precursor mixture can be calcined for any suitable period of time. In one embodiment, the second precursor mixture is calcined for a period of at least 10 minutes, for example, at least 30 minutes, for example, at least 1 hour, for example, at least 2 hours, for example, at least 3 hours, for example, at least 4 hours, for example, at least 5 hours, for example, at least 6 hours, for example, at least 7 hours, for example, at least 8 hours, for example, at least 9 hours, for example, at least 10 hours. In one embodiment, the second precursor mixture is calcined for a period of 10 minutes to 20 hours, for example, 30 minutes to 20 hours, for example, 1 hour to 20 hours, for example, 2 hours to 20 hours, for example, 3 hours to 20 hours, for example, 4 hours to 20 hours, for example, 5 hours to 20 hours, for example, 6 hours to 20 hours, for example, 7 hours to 20 hours, for example, 8 hours to 20 hours, for example, 9 hours to 20 hours, for example, 10 hours to 20 hours.

[0080] The second precursor mixture is typically cooled after calcination. "Cooling" means treating the material by gradually lowering the temperature or temperature range to reduce the material's temperature. Typical cooling conditions involve cooling from 900°C to 700°C at a rate of 1°C to 5°C per minute. Optionally, the material can be cooled to, for example, 600°C, 500°C, 400°C, 300°C, 200°C, 100°C, 50°C, or room temperature (i.e., approximately 25°C).

[0081] In one embodiment, the intermediate further contains up to 3 mol% of elements other than Li, Ni, Mn, and O. These are characterized in the patent formula as elements D and D', and such elements are, for example, one or more of the following: B, N, F, Mg, Al, Si, P, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, mixtures thereof, or one or more compounds thereof. The dopants are added or derived from impurities in the raw materials.

[0082] A "precursor" refers to a composition produced by processes such as mechanical mixing or coprecipitation before heat treatment at temperatures of approximately 300°C to 1000°C.

[0083] "Compressed density" is the measurement used to define powder density in this application. Powders can be compressed or decompressed to a much wider range of bulk densities than coarse-grained materials. Vibration or compression can make them extremely dense, even losing their fluidity. The method for measuring the "compressed density" of the cathode-active material powder in this invention is described in Example 7, and the results are shown in Figure 5 and Tables 1-3.

[0084] A "reducing atmosphere" refers to an atmosphere that, at the relevant heat treatment temperature, shifts the thermodynamic equilibrium of a solid to a phase distribution where the average oxidation state of the metal is lower than that of the spinel phase. A reducing atmosphere can be provided by the type of gas present in the reaction vessel during heating. This gas can be provided by the presence of a reducing gas. For example, a reducing gas is one or more gases selected from hydrogen, carbon monoxide, carbon dioxide, nitrogen, less than 15 vol% oxygen in an inert gas, and mixtures thereof. The term "less than 15 vol% oxygen in an inert gas" is intended to encompass a range from 0 vol% oxygen, corresponding to an inert gas without oxygen, to 15 vol% oxygen in an inert gas. The amount of oxygen in a reducing atmosphere is preferably low, less than 1000 ppm, and most preferably less than 10 ppm. Normally, oxygen is not added to the atmosphere, but oxygen may be generated during heating.

[0085] An "inert gas" refers to a gas that does not participate in the process. Examples of inert gases include one or more gases selected from argon, nitrogen, helium, and mixtures thereof.

[0086] Furthermore, the term "reducing atmosphere" refers to a composition consisting of two or more gases, one of which is considered a non-reducing atmosphere gas when used alone, and the other being a second gas or substance that reduces the oxidizing capacity of the gas mixture. The total reducing capacity of the atmosphere corresponds to a reducing atmosphere. Such compositions can be selected from the following groups: nitrogen, less than 15% by volume of oxygen in an inert gas, air and hydrogen; air and CO; air and methanol; air and carbon dioxide.

[0087] Furthermore, a "reducing atmosphere" can be obtained by adding a substance to the precursor composition or adding a gaseous composition to the atmosphere in order to remove some or all of the oxidizing species present in the atmosphere of the reaction vessel during heating. The substance can be added to the precursor during the preparation of the precursor or before heat treatment. The substance is any oxidizable material, preferably containing carbon, and for example, the substance can be one or more compounds selected from the group consisting of graphite, acetic acid, carbon black, oxalic acid, wood fiber, and plastic materials.

[0088] A "non-reducing atmosphere" refers to an atmosphere at temperatures below 700°C that completely shifts the thermodynamic equilibrium of a solid to the spinel phase.

[0089] In one embodiment, the non-reducing atmosphere is a gaseous composition selected from air and compositions containing at least 5 volume% oxygen in an inert gas. The non-reducing atmosphere can be provided by the type of gas present in the reaction vessel during heating. Preferably, the non-reducing gas is air.

[0090] "Casturing" means treating a material at a specific temperature or temperature range to obtain the desired crystallinity. The temperature or temperature range is intended to represent the temperature of the material being heat-treated. Typical calcination temperatures are approximately 500°C, 600°C, 700°C, 800°C, 900°C, and 1000°C, and temperature ranges are approximately 300°C to 1200°C, 500°C to 1000°C, and 650°C to 950°C. The term "calcination in the temperature range of X°C to Y°C" is not intended to be limited to a specific single temperature between X and Y. Rather, the term also includes calcination to a temperature range within the X to Y temperature range during the heating time.

[0091] In another aspect, the present invention provides a method for producing the cathode active material described herein, which includes: A. A process for producing one or more single crystals of a first component, comprising the following steps: (i) A step of providing one or more lithium precursor compounds and one or more transition metal precursor compounds; (ii) A step of contacting the precursor compound and grinding it to form a pulverized mixture; (iii) A step of calcining the pulverized mixture to provide a calcined mixture; B. A method for producing a second crystalline particle of the cathode active material, comprising the following steps: (i) A step of providing one or more transition metal compounds; (ii) Precipitating a transition metal to form a precipitate, and washing the precipitate to form a first precursor mixture; (iii) The step of contacting the first precursor mixture with one or more lithium precursor compounds to form a second precursor mixture; (iv) A step of calcining the second precursor mixture; C. Mix the products obtained in A and B.

[0092] In this method, the products obtained in A and B can be mixed in a slurry state.

[0093] In this method, the products obtained at A and B can be mixed in a mass ratio ranging from 30:70 to 70:70, for example, in a mass ratio ranging from 40:60 to 60:40, for example, in a ratio of 50:50.

[0094] The method of the present invention can include one or more additional steps. These one or more additional steps can be performed before, after, or in the middle of the steps described herein.

[0095] In another aspect, the present invention provides a cell (battery) having a cathode active material comprising: (a) A first crystal particle, wherein the first crystal particle has a spinel structure and is represented by the formula Li x Ni y Mn 3-x-y-z D z O4, where 0.95 ≦ x ≦ 1.05; 0.45 ≦ y ≦ 0.50, and 0 ≦ z ≦ 0.20, and D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, and mixtures thereof; the first crystal particle has a particle size of 3 μm or less as measured by the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope, (b) A second crystal particle, wherein the second crystal particle contains a material having a spinel structure and is represented by the formula Li x’ Ni y’ Mn 3-x’-y’-z’ D’ z’ O4, where 0.95 ≦ x’ ≦ 1.05; 0.43 ≦ y’ ≦ 0.47, and 0 ≦ z’ ≦ 0.20, and D’ is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W, and mixtures thereof, and the second crystal particle has an average particle size of at least three times the average particle size of the first crystal particle as measured by the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope, where y > y’. [Examples]

[0096] Experiment Section The following describes exemplary and non-limiting embodiments of the present invention with experimental data. Examples 1-4 relate to methods for producing cathode active materials. Example 5 describes a method for measuring the minimum Ferret diameter. Example 6 describes a method for acquiring SEM images of electrode cross-sections. Example 7 describes a method for determining the compressed density of cathode active materials. Example 8 relates to electrochemical characterization. Example 9 describes the determination of Ni and Mn content in spinel, and Example 10 presents data, results, and comparative data relating to the claimed products.

[0097] Example 1 - Synthesis of Cathode Active Material - Small-Ni435 MnO2 (269.5 g, equivalent to 3.1 mol of Mn), basic Ni(OH)x(CO3)y (133 g, equivalent to 0.9 mol of Ni), and Li2CO3 (73.9 g, equivalent to 2.0 mol of Li), along with 1 L of water, were weighed and subjected to ball milling in a planetary ball mill (reverse rotation at 600 rpm for 30 minutes) to form a slurry with a molar ratio of Li:Ni:Mn = 1.00:0.45:1.55. The mixture was dried at 120°C for 12 hours. The powder was mixed in a mortar for 15 minutes to obtain a precursor. 20 g of the precursor was placed in a 50 mL crucible and heated at 900°C for 3 hours, then cooled to room temperature at a rate of 1.5°C / min. The product was ground in a mortar for 15 minutes and sieved through a 45 micron sieve to obtain a cathode active material consisting of LNMO. A representative SEM image of the sample is shown in Figure 1. The arithmetic mean of the minimum Ferret diameter of the material was determined to be 0.66 μm by the method described in Example 5. Based on the electrochemical characterization described in Example 6, the stoichiometric composition of the obtained LNMO material is Li 1.00 Ni 0.435 Mn 1.565 It was determined to be O4. 。 Therefore, this sample is identified as Small-Ni435.

[0098] Example 2 - Synthesis of Cathode Active Material - Small-Ni470 MnO2 (264.3 g, equivalent to 3.04 mol of Mn), basic Ni(OH)x(CO3)y (141.9 g, equivalent to 0.96 mol of Ni), and Li2CO3 (73.9 g, equivalent to 2.0 mol of Li) and 1 L of water were weighed and ball-milled in a planetary ball mill (600 rpm, 30 minutes, reverse rotation) to form a slurry with a molar ratio of Li:Ni:Mn = 1.00:0.48:1.52. The mixture was dried at 120°C for 12 hours. The powder was mixed in a mortar for 15 minutes to obtain a precursor. 20 g of the precursor was placed in a 50 mL crucible and heated at 900°C for 3 hours, then cooled to room temperature at a rate of 0.5°C / min. The product was ground in a mortar for 15 minutes and sieved through a 45 micron sieve to obtain a cathode active material consisting of LNMO. The particle morphology and particle size of this material are the same as those of the Small-Ni435 sample in Example 1. Based on the electrochemical characterization described in Example 6, the stoichiometric composition of the obtained LNMO material is Li 1.00 Ni 0.47 Mn 1.53 It was determined to be O4. 。 Therefore, this sample is identified as Small-Ni470.

[0099] Example 3 - Synthesis of Cathode Active Material - Large-Ni435 Mix NiSO4 and MnSO4 solutions corresponding to a molar ratio of Ni:Mn=0.45:1.55 to co-precipitate Ni,Mn carbonate, and then mix with Na2CO3 under stirring to combine the two solutions. + and SO4 2-The mixture is washed and dried to remove ions, thereby forming spherical particles of co-precipitated Ni,Mn carbonate. 150 g of Li2CO3 (corresponding to Li:Ni:Mn = 1.00:0.45:1.55) and ethanol are added to 940 g of the mixed co-precipitated Ni,Mn carbonate particles to form a viscous slurry. The slurry is stirred in a paint shaker for 3 minutes to obtain complete deagglomeration of the particulate material and a mixture. The slurry is poured into a tray and dried at 80°C. The dried material is stirred in a paint shaker for 1 minute to obtain a homogeneous powder mixture with free flow. The powder mixture is heated in a reactor under a nitrogen atmosphere and heated to 550°C at a heating rate of 2.5°C / min. The powder is heated at 550°C for 10 hours. The powder is then treated in air at 550°C for 10 hours. The temperature is increased to 950°C at a heating rate of 2.5°C / min. After maintaining a temperature of 950°C for 10 hours, the system is cooled to room temperature at a rate of 1.5°C / minute.

[0100] The powder was shaken in a paint shaker for 6 minutes to redisperse it, and then passed through a 45-micron sieve to obtain a cathode active material consisting of LNMO. The SEM image of the sample is shown in Figure 2. The arithmetic mean of the minimum Ferret diameter of the material is 8 μm. Based on the electrochemical characterization described in Example 6, the stoichiometric composition of the obtained LNMO material is Li 1.00 Ni 0.435 Mn 1.565 It was determined to be O4. 。 Therefore, this sample is identified as Large-Ni435.

[0101] Example 4 - Synthesis of Cathode Active Material Mix NiSO4 and MnSO4 solutions corresponding to a molar ratio of Ni:Mn = 0.48:1.52, co-precipitate the Ni,Mn carbonate, and mix it with Na2CO3 under stirring to combine the two solutions. + and SO4 2-The mixture is washed and dried to remove ions, thereby forming spherical particles of co-precipitated Ni,Mn carbonate. 150 g of Li2CO3 (corresponding to Li:Ni:Mn = 1.00:0.48:1.52) and ethanol are mixed with 940.5 g of the mixed co-precipitated Ni,Mn carbonate particles to form a viscous slurry. The slurry is stirred in a paint shaker for 3 minutes to obtain complete deagglomeration and mixing of the particulate material. The slurry is poured into a tray and dried at 80°C. The dried material is then stirred in a paint shaker for 1 minute to obtain a homogeneous powder mixture with free flow. The powder mixture is heated in a reactor under a nitrogen atmosphere, and heated to 550°C at a heating rate of 2.5°C / min. The powder is heated at 550°C for 10 hours. The powder is then treated in air at 550°C for 10 hours. The temperature is increased to 950°C at a heating rate of 2.5°C / min. After maintaining a temperature of 950°C for 10 hours, the system is cooled to room temperature at a rate of 0.5°C / minute.

[0102] The powder is shaken in a paint shaker for 6 minutes to redisperse it, and then passed through a 45-micron sieve to obtain a cathode active material consisting of LNMO. The particle morphology and particle size of this material are the same as those of the Large-Ni435 sample in Example 3. Based on the electrochemical characterization described in Example 6, the stoichiometric composition of the obtained LNMO material is Li 1.00 Ni 0.47 Mn 1.53 It was determined to be O4. Therefore, this sample is classified as Large-Ni470.

[0103] Example 5 - Material property evaluation The material was encapsulated in epoxy resin and polished to a flat surface. A scanning electron microscope (SEM) of the Zeiss Gemini SEM 500 (equipped with a field emission gun (FEG)) was used to acquire SEM images with an acceleration voltage of 10 kV and an energy-selective backscatter (ESB) detector (backscatter electron detector type). The pixel size was 0.01 μm / pixel. A total of 25 images were acquired and stitched together into a high-resolution image of 4930 pixels × 3697 pixels (image area 48 μm × 36 μm). Figure 3 shows an image of Small-Ni435 prepared using the method described in Example 1. A total of 663 particles were detected and analyzed according to the following procedure.

[0104] The images will be analyzed using the ImageJ software (https: / / imagej.nih.gov). The procedure is as follows: • Thresholding and segmentation using "Otsu's algorithm" • Apply the binary process "Fill Hole". • Apply the binary process "Erode" 8 times. • Apply the binary process "Dilate" six times. • Use "particle analysis" without size limitations

[0105] The "fill holes" process is used to fill potential holes within particles. Then, noise is removed by applying "Erode" followed by "Dilate," ensuring reliable separation of adjacent particles.

[0106] Size measurement results: Average minimum ferret diameter: 0.66 μm Average equivalent circle diameter: 0.84 μm Particle count: 663

[0107] Example 6 - Characterization of mixed material electrodes Figure 4 shows SEM images of electrode cross-sections using mixture 1 (Small-Ni435 and Large-Ni435). The cross-sections of the compressed electrodes were prepared by embedding them in epoxy resin and polishing them to create a flat surface perpendicular to the electrode surface.

[0108] Example 7 - Compression Density The compressed density of the cathode active material powder was measured by the following method: 3.00 g of material was loaded into a die with a cylindrical hole (16 mm in diameter). A punch that fit the hole in the die was subjected to pressure (1-2 ton / cm²). 2 The powder is compressed by adding (). The powder volume is calculated by measuring the punch position and the compressed density is determined. Figure 5 and Tables 1-3 show the relationship between compressed density and pressurizing pressure for Example 1, Example 2, and a 50:50 mixture of these two materials.

[0109] Example 8 - Electrochemical Characterization Electrochemical tests were performed using a 2032 coin cell. Thin-film composite cathode materials and thin-film composite anode materials of metallic lithium (half-cell, half-cell) and lithium titanate (LTO) (full-cell, full-cell) were used, respectively. The thin-film composite cathode material was prepared by completely mixing 92% by mass of cathode-active LNMO material with 4% by mass of Super C65 carbon black (Timcal) and 4% by mass of PVdF binder (polyvinylidene fluoride, Arkema) in NMP (N-methylpyrrolidone) to form a slurry. The slurry was applied 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 12 mg of cathode active material were cut from the dried film, compressed using a hydraulic pellet press (20 mm diameter, 3 tons), and then dried in an argon-filled glove box at 120°C under vacuum for 10 hours. The LTO electrodes were sourced from Custom Cells Itzehoe GmbH.

[0110] Coin-type cells were assembled in an argon-filled glove box (<1 ppm O2 and H2O) using a glass fiber separator, an electrolyte containing 1 mole of LiPF6 (mass ratio 1:1) in EC:DEC (mass ratio 1:1), and a 500 μm thick lithium disk as the anode electrode in the case of a half-cell, and a Celgard H2010 separator, an electrolyte containing 1 mole of LiPF6 (mass ratio 1:1) in EC:DEC (mass ratio 1:1), and a 15 mm diameter LTO electrode with a load corresponding to a balance N / P of 1.2 (in the case of a full cell).

[0111] Electrochemical lithium insertion and extraction were monitored using an automated cycle data recording system (Maccor) operating in constant current mode. Charge and discharge currents are expressed in C. 1 C is defined as the theoretical current required to charge and discharge the cell in one hour.

[0112] The electrochemical test of the half-cell involves four formation cycles (one 0.2C / 0.2C (charge / discharge) cycle, one 0.5C / 0.5C cycle, two 0.5C / 1C cycles, and 0.5C / 0.2C cycles), nine power test cycles (three 0.5C / 1C cycles, three 0.5C / 5C cycles, and three 0.5C / 10C cycles), followed by one 0.1C / 0.1C cycle for capacity measurement, and then 50 0.5C / 1C cycles for degradation measurement. The electrochemical testing of all batteries includes three formation cycles at 0.1C / 0.1C for cell capacity measurement.

[0113] The half-cell is cycled within a voltage range of 3.5 to 5.0V, with an upper cutoff voltage of 5.0V for charging and a lower cutoff voltage of 3.5V for discharging. LNMO-LTO cells are cycled in the voltage ranges of 1.7–3.4V and 2.8–3.4V.

[0114] The LNMO materials tested shown in Figures 6-11 are small particles produced according to Examples 1 (Small-Ni435) and 2 (Small-Ni470), as well as large particles produced according to Examples 3 (Large-Ni435) and 4 (Large-Ni470), and mixtures thereof, where the numbers refer to the nickel content in the spinel material as determined by the electrochemical characterization described in Example 9.

[0115] In the mixture tests, both LNMO materials were added to the slurry simultaneously in a mass ratio of 50:50. The test results for three material mixtures are shown below. These are Large-Ni435 + Small-Ni435 (Mixture 1), Large-Ni470 + Small-Ni435 (Mixture 2), and Large-Ni435 + Small-Ni470 (Mixture 3).

[0116] The tested LNMO material shown in Figure 12 was synthesized using the methods described in Examples 1 and 3, but with slight modifications to the formulation to alter the nickel content in the spinel.

[0117] Capacity is expressed as the amount of charge accumulated during discharge from the upper voltage limit to the lower voltage limit, relative to the LNMO content in the electrode. The unit of capacity is mAh / (gLNMO).

[0118] Cell degradation is expressed as relative capacity loss after 100 charge-discharge cycles. The unit of degradation is % / 100 cycles.

[0119] Electrochemical data for half-cells are shown in Figures 6-9 and 12, and data for LNMO-LTO cells are shown in Figures 10-11.

[0120] The voltage curves shown in Figures 6, 8, and 10 were collected with a battery tester and used to calculate capacity and average voltage.

[0121] Figures 7, 9, and 11 plot the change in capacity against the number of charge-discharge cycles. This data is used to evaluate cell degradation.

[0122] The calculated degradation rates for multiple samples with different particle sizes and nickel content in spinel are shown in Figure 12.

[0123] The specific energy density of the cathode active material within the cell is determined by multiplying the average voltage by the capacitance.

[0124] The energy density of the cathode active material within the cell is determined by multiplying the specific energy density by the compressibility density. The method for determining the compressibility density is described in Example 7.

[0125] Capacity, average voltage, degradation, and energy density are summarized in Tables 1-4.

[0126] Example 9 - Determination of Ni and Mn content in spinel Depending on the manufacturing method of the lithium cathode active material, the Ni and Mn content in the spinel of the lithium cathode active material may differ from the bulk values ​​that can be measured by methods such as ICP. In this example, we demonstrate that the Ni and Mn content in the spinel of the lithium cathode active material can be measured using two different methods based on electrochemistry and diffraction.

[0127] This method is based on the change in the Mn / Ni ratio. 3+ and Mn 4+ This utilizes the property of changing the ratio. 、 Li x Ni y Mn 2-y The average oxidation state of Mn in O4 is given by (4) under the assumption that the oxidation state of Li is 1+, Ni is 2+, and O is -2. * 2-1 * x-2 * This can be seen by calculating y) / (2-y). Using this formula, when x=1, Li +1 Ni +2 1-y) Mn +3 1-2y Mn +4 1+y It can be expressed as O4, and the same formula can be obtained when x is not equal to 1.

[0128] Electrochemically, Mn 3+ Li during the cycle + Extraction and insertion of Mn 4+ It can be reversibly oxidized to Ni, and can also be restored to its original state. 2+ teeth 、 Li during the cycle + Extraction and insertion of Ni 4+ It can be reversibly oxidized and then restored to its original state. Therefore, Ni 2+ Each contains 2 Li + Mn 3+ Each unit contains 1 Li + It is possible to extract (and then insert) each of them. Therefore, equation Li +1 Ni +2 1-y) Mn +3 1-2y Mn+4 1+y In O4, when x=1, the ratio of the volume related to manganese activity to the total volume is given by (1-2y) / (1-2y+2y)=(1-2y). For example, y=0 indicates that the volume related to Mn activity is 0%, while y=0.45 and 0.4 indicate that 10% and 20% of the total volume are derived from Mn activity, respectively.

[0129] In LNMO, Mn 3+ / Mn 4+ The reaction occurs at approximately 4V (vsLi / Li + ) was observed at Ni 2+ / Ni 4+ The reaction is observed at approximately 4.7V. Therefore, between 3.5V and 4.3V (vsLi / Li + The total capacity of ) was compared with the 3.5V to 4.3V range (vsLi / Li + The capacitance measured is expected to correspond to the Mn activity. The capacitance around 4V is determined using a second discharge with a current of 74mA / g (0.5C), as described in Example 8. During charging and discharging, the cell is not in equilibrium, so the measured voltage rises during charging and falls during discharging due to the effect of the cell's internal resistance. This effect is particularly pronounced near the point of abrupt change in cell voltage, and the manganese activity ratio appears to differ depending on whether the analysis is based on charging or discharging. The true value is midway between these two values, and a reasonable estimate is the average of the two. Figure 13 shows the discharge voltage curve and charging voltage curve for capacitance during the second charge and discharge with a current of 74mA / g (0.5C) as described in Example 8. The capacitance Q corresponds to the charging and discharging voltage of 4.3V, respectively. 4V cha and Q 4V di) , and total discharge capacity Q tot dis) The m-manganese activity fraction is given by the following formula: (Q 4V cha) +(Q tot dis- Q 4V dis )) / (2 * Q tot disThis value is represented as "4V plateau".

[0130] diffraction Mn 3+ Ions and Mn 4+ The size of the ions differs, Mn 3+ This is the maximum value. This affects the lattice constant of spinel. Powder X-ray diffraction data were collected using a Phillips PW1800 instrument system with Cu Kα radiation (λ=1.541 Å) in Bragg-Brentano mode and θ-2θ geometry. The observational data require correction for experimental parameters that contribute to the shift in the observed peak position used in lattice constant calculations. This is achieved using the full-profile fundamental parameter method implemented in Bruker TOPAS software. As a result, the spinel lattice constant was determined with an uncertainty of approximately 5 / 10000 Å, which is Mn 3+ This is sufficient to determine the amount of [substance], and consequently the amounts of Mn and Ni.

[0131] The validity of both methods is demonstrated by comparing the electrochemically determined 4V plateau with the a-axis determined by XRD. Figure 14 shows this comparison, and the linear correlation between volume increase and Mn 3+ This shows a direct correlation with the increase. Figure 15 shows the same data as Figure 14, but the x-axis is converted to the nickel content y of spinel, taking advantage of the fact that the 4V plateau is given by (1-2y) as mentioned above. The relationship between the a-axis determined by XRD and the ratio between Mn and Ni, given by y determined from the electrochemically determined 4V plateau, is given by the straight line a = -0.1932 * It can be approximated by y + 8.2627. The tested and existing LNMO materials shown in Figures 14 and 15 were synthesized using the methods described in Examples 1 and 3, but the formulations were fine-tuned to change the nickel content in the spinel.

[0132] Furthermore, the two methods were further validated by comparing the measured nickel content of selected samples with the results obtained by directly measuring the Ni and Mn content inside the particles using scanning transmission electron microscopy-energy-dispersive X-ray spectroscopy.

[0133] Example 10 - Data Comparison

[0134] [Table 1]

[0135] [Table 2]

[0136] [Table 3]

[0137] [Table 4]

[0138] Based on Tables 1-4 and Figures 1-12, the following observations are highlighted to reveal the optimization of high energy density and low degradation by varying the particle size and nickel content of the LNMO spinel cathode active material: ● Energy density can be maximized by increasing the average voltage, specific capacity, and powder density at the electrode. ○ The average voltage increases with increasing nickel content in the spinel. For example, as shown in Table 1, changing the nickel content of the spinel from y=0.435 to y=0.470 increases the voltage from 4.60V to 4.66V, a 1.3% increase. While there is little change in specific capacitance due to the nickel content of spinel, as shown in Figure 11 and Table 3, it can be beneficial to limit the voltage range to suppress degradation. In this case, the specific capacitance within the limited range increases with increasing nickel content in the spinel. For example, in an LNMO-LTO cell, as shown in Table 3, increasing the nickel content of small particles in the 50:50 mixture from y=0.435 to y=0.470 resulted in a 5% increase in specific capacitance from 116mAh / g to 122mAh / g in the 2.8V to 3.4V range. ○ Powder density increases when small and large particles are mixed. For example, as is clear from the comparison between Table 1 and Table 2, when small and large particles are mixed in a 50:50 mixture, the density is 2.5 g / cm³ compared to large particles alone. 3 From 3.0 g / cm³ 3 It increases by 20%. ● As the nickel content increases, degradation also increases, but if the particles are sufficiently small, the degradation remains constant regardless of the nickel content in the spinel. This can be confirmed in particular in Table 1, Table 2, Figures 7, 9, 11, and 12. ● Therefore, the optimal solution is to mix small particles with a high nickel content with large particles with a low nickel content. From the materials described in Examples 1-4, the optimal combination is a mixture of Large-Ni435 and Small-Ni470.

[0139] Table 4 compares the effects of particle size and nickel content in spinel on energy density. Generally, using a combination of small and large particles improves energy density by approximately 20%. Surprisingly, increasing the nickel content in small-particle LNMOs can further increase energy density by 1-6%, depending on the cell's chemical composition and operating conditions.

[0140] Those skilled in the art will understand that various modifications and variations are possible without departing from the scope and spirit of the present invention. Although the present invention has been described in relation to certain preferred embodiments, it should be understood that the invention described in the claims should not be unduly limited to such specific embodiments. In fact, various modifications of the described embodiments for carrying out the present invention, which are obvious to those skilled in the chemistry or related art, are intended to fall within the scope of the following claims.

Claims

1. (a) A first crystal grain having a spinel structure and the formula Li ｘ Ni ｙ Mn ３－ｘ－ｙ－ｚ D ｚ O ４ Represented by the formula, where 0.95 ≤ x ≤ 1.05; 0.45 ≤ y ≤ 0.50, and 0 ≤ z ≤ 0.20, where D is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof; the first crystalline grain is a first crystalline grain having a particle size of 3 μm or less, measured as the arithmetic mean of the minimum Ferret diameter of the particles measured using a scanning electron microscope. (b) A second crystal particle, the second crystal particle containing a material having a spinel structure, which is represented by the formula Li ｘ’ Ni ｙ’ Mn ３－ｘ’－ｙ’－ｚ’ D’ ｚ’ O ４ where 0.95 ≦ x’ ≦ 1.05; 0.43 ≦ y’ ≦ 0.47, and 0 ≦ z’ ≦ 0.20, D’ is a dopant selected from B, N, F, Mg, Al, Nb, Si, P, La, S, Ca, Ti, Cr, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof, and the second crystal particle has an average particle diameter at least three times the average particle diameter of the first crystal particle, measured as the arithmetic mean value of the minimum Feret diameter of the particles measured using a scanning electron microscope, the second crystal particle A cathode active material containing and having y > y'.

2. The cathode active material according to claim 1, wherein 0.98 ≤ x ≤ 1.

02.

3. The cathode active material according to claim 1 or 2, wherein x is 1.

4. A cathode active material according to any one of claims 1 to 3, wherein 0.46 ≤ y ≤ 0.

50.

5. A cathode active material according to any one of claims 1 to 4, wherein 0.48 ≤ y ≤ 0.

50.

6. A cathode active material according to any one of claims 1 to 5, wherein 0 ≤ z ≤ 0.

05.

7. The cathode active material according to any one of claims 1 to 6, wherein D is a dopant selected from B, Mg, Al, Nb, Si, P, La, S, Ti, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof.

8. A cathode active material according to any one of claims 1 to 5, wherein z = 0.

9. The cathode active material according to any one of claims 1 to 8, wherein the first crystalline particles have a particle size of 2 μm or less.

10. The cathode active material according to any one of claims 1 to 9, wherein the second crystalline particle is a polycrystalline secondary particle.

11. A cathode active material according to any one of claims 1 to 10, wherein 0.98 ≤ x' ≤ 1.

02.

12. A cathode active material according to any one of claims 1 to 11, wherein x' is 1.

13. A cathode active material according to any one of claims 1 to 12, wherein 0.44 ≤ y' < 0.

47.

14. A cathode active material according to any one of claims 1 to 13, wherein 0.45 ≤ y' < 0.

46.

15. A cathode active material according to any one of claims 1 to 14, wherein 0 ≤ z' ≤ 0.

05.

16. The cathode active material according to any one of claims 1 to 15, wherein D' is a dopant selected from B, Mg, Al, Nb, Si, P, La, S, Ti, Fe, Co, Cu, Zn, Zr, Mo, Sn, W and mixtures thereof.

17. A cathode active material according to any one of claims 1 to 15, wherein z' = 0.

18. The cathode active material according to any one of claims 1 to 17, wherein the first crystalline particles have a particle diameter of 0.5 to 2 μm, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope; and the second crystalline particles have an average particle diameter of 5 to 10 μm, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope.

19. The cathode active material according to any one of claims 1 to 18, wherein the first crystalline particles have a particle diameter of 1 μm or less, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope; and the second crystalline particles have an average particle diameter of at least 3 μm, measured as the arithmetic mean of the minimum Ferret diameters of the particles measured using a scanning electron microscope.

20. The cathode active material according to any one of claims 1 to 19, wherein the first crystal grain is a single crystal grain.

21. Based on the mass of the second crystal grain, the second crystal grain contains a material in an amount of at least 94% by mass, for example, at least 96% by mass, for example, at least 98% by mass, in which the second crystal grain has a spinel structure, and which is of the formula Li ｘ’ Ni ｙ’ Mn ３－ｘ’－ｙ’－ｚ’ D' ｚ’ O ４ The cathode active material according to any one of claims 1 to 20.

22. A cell comprising a cathode active material as defined in any one of claims 1 to 21.

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