Positive electrode material, preparation method therefor and battery

Abstract

A positive electrode material, a preparation method therefor and a battery, the positive electrode material being a single crystal positive electrode material, and the chemical general formula of the positive electrode material being LiaNixMyNzO2}, where 0.98≤a≤1.05, 0.60≤x<1, 0<y≤0.40, 0≤z<0.1, x+y+z=1, M is selected from at least one of Co, Mn and Al, and N is a doped metal. In the particle size distribution map of the positive electrode material, the distribution curve of particles having particle sizes within the range of 1 μm-4 μm has a peak conforming to pulse function distribution, and the particle size distribution width of particles having particle sizes within the range of 1 μm-4 μm is Span(a) and satisfies 0.8<Span(a)<1.6; the distribution curve of particles having particle sizes within the range of 0.1 μm-1 μm (excluding 1 μm) has a peak conforming to Voigt function distribution, and the particle size distribution width of particles having particle sizes within the range of 0.1 μm-1 μm (excluding 1 μm) is Span (b) and satisfies 0.4<Span(b)<0.8. The positive electrode material can have high-compaction density, and strong structural stability and cycling stability, and can exert higher capacity and rate capability.

Description

Positive electrode material and preparation method thereof, and battery

[0001] This application claims priority to the Chinese patent application filed with the State Intellectual Property Office on September 28, 2023, with application number 202311290065.X and invention name “Positive electrode material, preparation method thereof, and battery”, the entire contents of which are incorporated by reference into this application. Technical Field

[0002] The present application belongs to the technical field of positive electrode materials, and in particular relates to a positive electrode material, a preparation method thereof, and a battery. Background Art

[0003] Lithium-ion batteries are widely used in laptops, mobile phones, and digital products due to their high energy density, excellent safety, long cycle life, and environmental friendliness. However, the development of cathode materials has been slower than that of high-capacity anode materials (approximately 800-1000 mAh / g). Therefore, researchers are currently focusing their efforts on developing high-capacity and high-voltage cathode materials to increase the energy density of lithium-ion batteries.

[0004] Commonly used layered ternary cathode materials exhibit high capacity, high voltage, long cycle life, and excellent safety, making them the primary cathode material for power battery development. However, increasing nickel content in ternary cathode materials inevitably leads to problems such as lithium-nickel intermixing, structural degradation, reduced thermal stability, and increased residual alkali. This leads to battery capacity degradation, reduced cycle life, and poor structural stability, compromising safety and high performance.

[0005] At present, the width of the particle size distribution can be increased by crushing to improve the compaction density of the electrode, but this method can only increase the compaction density of the electrode and cannot comprehensively improve the structural stability and cycle stability of the positive electrode material.

[0006] Therefore, what is currently needed is how to make the positive electrode material have a higher compaction density and further improve the structural stability and cycle stability of the material.

[0007] Application Contents

[0008] The purpose of this application is to provide a positive electrode material and a preparation method thereof, and a lithium-ion battery. The positive electrode material of this application can have high compaction density, strong structural stability and cycle stability, so that the positive electrode material can exert higher capacity and rate performance.

[0009] In the first aspect, the present application provides a positive electrode material, the chemical formula of the positive electrode material is Li a Ni x M y N zO2, wherein 0.98≤a≤1.05, 0.60≤x<1, 0<y≤0.40, 0≤z<0.1, x+y+z=1, M is selected from at least one of Co, Mn and Al, and N is a doping metal;

[0010] In the particle size number distribution spectrum of the positive electrode material, the particle distribution curve within the particle size range of 1 μm to 4 μm has a peak that conforms to the Pulse function distribution, and the particle size distribution width of the particles within the particle size range of 1 μm to 4 μm is Span(a), which satisfies 0.8<Span(a)<1.6;

[0011] In the particle size number distribution spectrum of the positive electrode material, the particle distribution curve with a particle size of 0.1 μm to 1 μm and excluding 1 μm has a peak that conforms to the Voigt function distribution, and the particle size distribution width of the particles with a particle size of 0.1 μm to 1 μm and excluding 1 μm is Span(b), satisfying 0.4<Span(b)<0.8.

[0012] In some embodiments, the positive electrode material contains single crystal grains with the same orientation, wherein the average particle size of the single crystal grains is 1 μm to 5 μm.

[0013] In some embodiments, the mass content of the N element in the positive electrode material is 500ppm-10000ppm; and / or, N is selected from at least one of Ti, Zr, Mg, Ca, Sr, Ba, Nb, Ta, Sb, Sn, W and Y.

[0014] In some embodiments, the particle size volume distribution of the positive electrode material satisfies: D min >0.1μm,2.5μm<D 50 <5.5μm, D max <14μm.

[0015] In some embodiments, the particle size volume distribution width of the positive electrode material satisfies: 1.2≤(D 90 -D 10 ) / D 50 , D 10 ≤1.8μm, D 90 ≥5.5μm.

[0016] In some embodiments, in the particle size number distribution spectrum of the positive electrode material, the positive electrode material has at least two particle size distribution peaks.

[0017] In some embodiments, in the XRD pattern of the positive electrode material, the peak intensity of the characteristic peak corresponding to the (003) crystal plane is 1 003 The peak intensity of the characteristic peak corresponding to the crystal plane of the positive electrode material (104) is I 104, I 003 / I 104 It is 1.2 to 1.6.

[0018] In some embodiments, the specific surface area of ​​the positive electrode material is 0.6 m 2 / g~1.5m 2 / g.

[0019] In some embodiments, the positive electrode material has a tap density of ≥1.8 g / cm 3 .

[0020] In some embodiments, the compaction density of the positive electrode material is ≥3.2 g / cm 3 .

[0021] In some embodiments, the bulk density of the positive electrode material is ≥1.2 g / cm 3 .

[0022] In a second aspect, the present application provides a method for preparing a positive electrode material, comprising the following steps:

[0023] A mixed salt solution is spray-dried by a spray pyrolysis method to obtain a precursor, wherein the mixed salt solution contains a nickel source and an M source, and the nozzle pressure-diameter ratio is controlled to be 3.5 MPa / mm to 40 MPa / mm during the spray drying process, and M is selected from at least one of Co, Mn and Al;

[0024] The mixture of the precursor and the lithium source is subjected to a sintering process to obtain a positive electrode material.

[0025] In some embodiments, the precursor has the general chemical formula Ni x M y O2, where 0.60≤x<1, 0<y≤0.40.

[0026] In some embodiments, the nickel source includes at least one of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate.

[0027] In some embodiments, the M source includes at least one of M nitrate, M acetate, M chloride, and M sulfate.

[0028] In some embodiments, during the spray drying process, the temperature in the reaction chamber is 550°C to 1050°C.

[0029] In some embodiments, the concentration of the mixed salt solution is 0.5 mol / L-4 mol / L.

[0030] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate.

[0031] In some embodiments, the added amounts of the lithium source and the precursor satisfy the following ratio: the molar amount of Li to the total molar amount of metal in the precursor is (1.01-1.1):1.

[0032] In some embodiments, the primary sintering process is performed in an oxygen-containing atmosphere, and the oxygen content in the oxygen-containing atmosphere is ≥95%;

[0033] In some embodiments, the temperature of the primary sintering process is 600°C to 1000°C.

[0034] In some embodiments, the time of the primary sintering treatment is 6 hours to 16 hours.

[0035] In some embodiments, the method further includes mixing the primary sintered product with a dopant containing metal N and performing a secondary sintering treatment to obtain a secondary sintered product; wherein the temperature of the secondary sintering treatment is 600°C to 1000°C, and the time of the secondary sintering treatment is 6h to 16h; and / or, N is selected from at least one of Ti, Zr, Mg, Ca, Sr, Ba, Nb, Ta, Sb, Sn, W and Y.

[0036] In some embodiments, the method further comprises reacting the primary sintered product or the secondary sintered product with boric acid to obtain a positive electrode material, and based on 100% by mass of the positive electrode material, the amount of boric acid added is 500 ppm to 2000 ppm.

[0037] In a third aspect, the present application provides a battery comprising a positive electrode material.

[0038] This application has at least the following beneficial effects:

[0039] The positive electrode material provided in this application effectively increases the compacted density of the material while also improving the packing density of the particles by controlling the particle size distribution width of the particles in the range of 1μm to 4μm in the particle size number distribution spectrum as Span(a), and the particle size distribution width of the particles in the range of 0.1μm to 1μm (excluding 1μm) in the particle size number distribution spectrum as Span(b). The positive electrode material can be understood as a type of granular powder. Particle powders typically carry varying degrees of energy on their surface, inside, or between particles, which can cause the entire positive electrode particle system to be in an energy-unstable state, leading to aggregation, polarization, or trace chemical reactions. This makes it difficult for technicians to obtain the desired particle distribution of the positive electrode material during actual operation. Therefore, in order to maintain relative equilibrium of the positive electrode particle system as a whole, this application controls the particle size distribution curve to conform to the Pulse function and the Voigt function, making the particle system energy relatively stable. Furthermore, Span(a) and Span(b) are controlled to achieve the densest packing mode of the two monodispersed particles, that is, to use multi-stage dispersed particles to achieve self-mixing and improve the packing density. Among them, the particle distribution curve with a particle size of 0.1μm to 1μm and excluding the range of 1μm has a peak that conforms to the Voigt function distribution. The Voigt function is composed of two independent functions (i.e., introduced by the Lorentz function and the Gaussian function). While comprehensively controlling the stability of the particle system from different dimensions, it is easier to achieve multi-level filling of the particles themselves, further forming an ideal densest packing mode. In addition, the positive electrode material particles of the present application have more stable physical and chemical properties and better particle strength, which can provide better cycle stability and safety for lithium-ion batteries, and can also significantly reduce the cracking of particles during the pole piece pressing process, thereby improving the pole piece compaction density and volume energy density.

[0040] The preparation method of the positive electrode material provided in the present application adopts a spray drying process and controls the nozzle pressure-diameter ratio to 3.5-40 MPa / mm. During the spray drying process, the formation of particles is continuous, and the particle size of the precursor is in a multi-level dispersion state, so that the particle size number distribution spectrum of the prepared positive electrode material presents a multi-peak distribution curve; the positive electrode material particles of the present application have more stable physical and chemical properties and better particle strength, can provide lithium-ion batteries with better cycle stability and safety, and can also significantly reduce particle cracking during the electrode pressing process, thereby improving the electrode compaction density and volume energy density. BRIEF DESCRIPTION OF THE DRAWINGS

[0041] In order to more clearly illustrate the embodiments of the present application or the technical solutions of the prior art, the following is a brief introduction to the drawings required for use in the embodiments or the description of the prior art. Obviously, the drawings described below are only some embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on these drawings without any creative work.

[0042] FIG1 is a schematic flow chart of a method for preparing a positive electrode material provided in an embodiment of the present application.

[0043] FIG2 is the first peak in the particle size distribution diagram of the positive electrode material provided in Example 1 of the present application.

[0044] FIG3 is the second peak in the particle size distribution diagram of the positive electrode material provided in Example 1 of the present application.

[0045] FIG4 is a particle size distribution diagram of the positive electrode material provided in Example 1 of the present application.

[0046] FIG5 is a particle size distribution diagram of the positive electrode material provided in Comparative Example 1 of the present application.

[0047] FIG6 is a comparison diagram of the compaction density curves of the positive electrode materials provided in Example 1 of the present application and Comparative Example 1. DETAILED DESCRIPTION

[0048] In order to better understand the technical solution of the present application, the embodiments of the present application are described in detail below with reference to the accompanying drawings.

[0049] It should be clear that the embodiments described are only part of the embodiments of this application, not all of the embodiments. Based on the embodiments in this application, all other embodiments obtained by ordinary technicians in this field without making creative work are within the scope of protection of this application.

[0050] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or to implicitly indicate the quantity of the technical features indicated. Thus, a feature specified as "first" or "second" may explicitly or implicitly include one or more of the features.

[0051] In order to facilitate understanding of the present application, specific terms are appropriately defined in the present application. Unless otherwise defined herein, the scientific terms and technical terms used in the present application have the meanings commonly understood by those skilled in the art to which the present application belongs.

[0052] As used herein, the term "matrix" refers to a lithium composite oxide synthesized by mixing a precursor with a lithium salt through a high-temperature solid-phase reaction, and includes lithium and metal elements.

[0053] As used herein, the term "primary particles" refers to particles that exist individually without forming agglomerates.

[0054] As used herein, the term "secondary particles" refers to particles formed by agglomeration of the above-mentioned primary particles.

[0055] Currently, the electrode packing density can be increased by increasing the width of the particle size distribution through pulverization. However, this method only increases the packing density of the electrode and does not comprehensively improve the structural stability and cycle stability of the positive electrode material. The current demand is to achieve a higher packing density for the positive electrode material while further improving the structural stability and cycle stability of the material.

[0056] The present application provides a positive electrode material, the chemical formula of which is Li a Ni x M y N z O2, wherein 0.98≤a≤1.05, 0.60≤x<1, 0<y≤0.40, 0≤z<0.1, x+y+z=1, M is selected from at least one of Co, Mn and Al, and N is a doping metal;

[0057] In the particle size number distribution spectrum of the positive electrode material, the particle distribution curve within the particle size range of 1 μm to 4 μm has a peak that conforms to the Pulse function distribution, and the particle size distribution width of the particles within the particle size range of 1 μm to 4 μm is Span(a), which satisfies 0.8<Span(a)<1.6;

[0058] In the particle size number distribution spectrum of the positive electrode material, the particle distribution curve with a particle size of 0.1 μm to 1 μm and excluding 1 μm has a peak that conforms to the Voigt function distribution, and the particle size distribution width of the particles with a particle size of 0.1 μm to 1 μm and excluding 1 μm is Span(b), satisfying 0.4<Span(b)<0.8.

[0059] In the above scheme, by controlling the particle size distribution width of the particles in the range of 1μm to 4μm in the particle size number distribution spectrum as Span(a), and the particle size distribution width of the particles in the range of 0.1μm to 1μm but not including 1μm in the particle size number distribution spectrum as Span(b), the material compaction density can be effectively increased while improving the packing density of the particles. Since the number distribution spectrum of the above positive electrode material has multiple peaks, and different peaks have Pulse function distribution and Voigt function distribution morphology, the above single crystal particle size distribution is not a simple filling of large and small particles, but can achieve the closest packing mode of a monodispersion of particles. Then, the particles are dispersed and mixed in multiple stages, and the gaps between the particles can always be filled to the greatest extent by particles of appropriate size. For example, when smaller particles are filled between larger particles, there are still gaps between the larger and smaller particles. When the above particle distribution is met, it can still be achieved that particles of appropriate size can fill the gaps between the larger and smaller particles, thereby achieving the maximum cyclic filling and stacking of particles of different particle sizes, thereby improving the packing density. Furthermore, the cathode material of the present application can provide lithium-ion batteries with better cycle stability and safety, and can also significantly reduce particle cracking during the electrode pressing process, thereby increasing the electrode compaction density and volume energy density.

[0060] In the present application, in the particle size distribution spectrum of the positive electrode material, the particle distribution curve in the particle size range of 1 μm to 4 μm has a peak that conforms to the Pulse function distribution, and the particle size distribution width of the particles in the particle size range of 1 μm to 4 μm is Span(a), which satisfies 0.8<Span(a)<1.6; Span(a) can specifically be 0.81, 0.85, 0.89, 0.92, 0.98, 1.01, 1.05, 1.2, 1.25, 1.3, 1.39, 1.4, 1.42, 1.45, 1.5 or 1.59, etc., without limitation herein. Preferably, Span(a) satisfies 0.8<Span(a)<1.4.

[0061] That is, the peak in the range of 1 μm to 4 μm in the number distribution spectrum conforms to the half-normal distribution of the Pulse function. Specifically, the Pulse function is shown in formula (1):

[0062] Where x0 and y0 are the additive correction coefficients of x and P(x) respectively, t1 and t2 are the multiplicative correction coefficients of x; A is the multiplicative correction coefficient of y, and p is the exponential coefficient.

[0063] In the present application, in the particle size distribution spectrum of the positive electrode material, the particle distribution curve of the particles with a particle size of 0.1 μm to 1 μm and excluding 1 μm has a peak that conforms to the Voigt function distribution, and the particle size distribution width of the particles with a particle size of 0.1 μm to 1 μm and excluding 1 μm is Span(b), which satisfies 0.4<Span(b)<0.8. Span(b) can specifically be 0.41, 0.42, 0.45, 0.58, 0.62, 0.7, 0.72, 0.75 or 0.795, etc., and is not limited here.

[0064] That is, the peak in the range of 0.1 μm to 1 μm (excluding 1 μm) in the number distribution spectrum conforms to the peak of the Voigt function distribution, and the peak height of the Voigt function distribution is greater than the peak height of the Pulse function. Specifically, the Voigt function is shown in formula (2):

[0065] In formula (2), t is the peak coefficient. The smaller the t value, the sharper the peak and the narrower the half-width, indicating that the number of small particles is large and the monodispersity is good, which can better fill the gaps between large particles to improve the packing density of the positive electrode material.

[0066] Therefore, the cathode material of the present application has at least two peak characteristics, and the distribution of the two peaks conforms to the above rules.

[0067] In some embodiments, in the particle size number distribution spectrum of the positive electrode material, the positive electrode material has at least two particle size distribution peaks.

[0068] In some embodiments, the positive electrode material contains single grains with the same orientation, wherein the average particle size of the single grains is 1 μm to 5 μm. The positive electrode material particles of the present application contain particles of 1 to 5 μm as single grains with the same orientation, which can further stabilize the distribution of the positive electrode particle system and achieve its own high filling, while preventing the particles from being squeezed after reaching their densest packing. The particles of 1-5 μm have the same orientation, which can enable the positive electrode particles to obtain a further stable structure, a more uniform distribution of bulk components, and better particle strength. It can significantly reduce the cracking of the particles during the pole piece pressing process and improve the pole piece compaction density and volume energy density.

[0069] It should be noted that the grain orientation of the positive electrode material can at least be tested by electron backscatter diffraction (EBSD), and ten single grains with the same orientation are randomly selected to measure the particle size of each grain, and the arithmetic average is taken as the average particle size of the above single grains.

[0070] It is understood that a single crystal grain in the present application can be a single particle composed of a primary particle, or a secondary particle formed by the agglomeration of several primary particles. "Primary particle" refers to the smallest particle unit identified when observing the positive electrode active material through a scanning electron microscope, while "secondary particle" refers to a secondary structure formed by the agglomeration of multiple primary particles.

[0071] In some embodiments, the particle size volume distribution width of the positive electrode material satisfies: 1.2≤(D 90 -D 10 ) / D 50 , where (D 90 -D 10 ) / D 50 Specifically, it can be 1.2, 1.3, 1.4, 1.5, 1.6, 1.7 or 1.8, etc., and of course it can be other values ​​within the above range, which is not limited here. It should be noted that the particle size volume distribution width of the positive electrode material here is measured based on all particles, that is, the particle size volume distribution is calculated from negative infinity to positive infinity based on all particles.

[0072] In some embodiments, N is selected from at least one of Ti, Zr, Mg, Ca, Sr, Ba, Nb, Ta, Sb, Sn, W, and Y.

[0073] In some embodiments, the mass content of the N element in the positive electrode material is 500ppm-10000ppm; specifically, it can be 500ppm, 1000ppm, 1500ppm, 2500ppm, 5000ppm, 7000ppm, 8000ppm, or 10000ppm. Of course, it can also be other values ​​within the above range, which is not limited here. N within the above range can improve the crystal structure of the single crystal material and control the preferred orientation of crystal growth.

[0074] In some embodiments, in the particle size distribution of the positive electrode material, the particle size distribution curve of particles with a particle size range of 1 μm to 4 μm satisfies the following: 1 μm ≤ D 50 ≤4μm, specifically 1μm, 1.5μm, 1.8μm, 2.0μm, 2.5μm, 2.8μm, 3.5μm or 4μm, etc., and of course other values ​​within the above range are also possible and are not limited here. Particle sizes within the range of 1μm to 4μm meet the above range, which is conducive to increasing the compaction density and comprehensively improving the electrochemical performance of the positive electrode material.

[0075] In some embodiments, in the particle size distribution of the positive electrode material, the particle size distribution curve of particles with a particle size range of 0.1 μm to 1 μm satisfies the following conditions: 0.1 μm ≤ D 50≤1μm, specifically 0.1μm, 0.2μm, 0.5μm, 0.6μm, 0.7μm, 0.8μm, 0.9μm or 0.99μm, etc., and of course other values ​​within the above range are also possible and are not limited here. The particle size within the range of 0.1μm to 1μm is within the above range, which is conducive to increasing the compaction density and comprehensively improving the electrochemical performance of the positive electrode material.

[0076] In some embodiments, in the particle size distribution spectrum of the positive electrode material, the peak value of the distribution curve of particles with a particle size range of 0.1 μm to 1 μm is ≥15%, specifically 15%, 16%, 17%, 18%, 19%, 20% or 25%, etc., and of course it can also be other values ​​within the above range, which is not limited here.

[0077] In some embodiments, the particle size volume distribution of the positive electrode material satisfies: D min >0.1μm,2.5μm<D 50 <5.5μm, D max <14μm;D min Specifically, it can be 0.11 μm, 0.12 μm, 0.15 μm, 0.2 μm, 0.5 μm, 0.8 μm, 0.9 μm or 0.99 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0078] In some embodiments, the particle size volume distribution of the positive electrode material satisfies: 2.5 μm < D 50 <5.5μm, specifically it can be 2.51μm, 2.8μm, 3.0μm, 3.2μm, 3.5μm, 3.8μm, 4.2μm, 4.5μm, 4.8μm or 5.5μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0079] In some embodiments, the particle size volume distribution of the positive electrode material satisfies: D max <14μm, D max Specifically, it can be 13.9 μm, 12 μm, 11 μm, 8 μm, 5 μm or 4.99 μm, etc. Of course, it can also be other values ​​within the above range, which is not limited here.

[0080] In some embodiments, the particle size D of the positive electrode material is 10 ≤1.8μm; specifically, it can be 1.0μm, 1.1μm, 1.2μm, 1.3μm, 1.4μm, 1.5μm, 1.6μm, 1.7μm or 1.8μm, etc., and of course, it can also be other values ​​within the above range, which is not limited here. The particle size D of the positive electrode material 90≥5.5μm; specifically, it can be 5.5μm, 5.8μm, 6.2μm, 6.3μm, 6.4μm, 6.5μm, 6.6μm, 7.0μm or 8.0μm, etc., and of course, it can also be other values ​​within the above range, which is not limited here. When the particle size of the positive electrode material is controlled within the above range, especially with a smaller D10 and a larger D90, it means that the positive electrode material has a wider particle size distribution, which is beneficial to improving the gram capacity of the positive electrode material. It should be noted that the positive electrode material here is obtained by measuring the particle size volume distribution based on all particles, that is, the particle size volume distribution is calculated based on all particles from negative infinity to positive infinity.

[0081] In some embodiments, in the XRD pattern of the positive electrode material, the peak intensity of the characteristic peak corresponding to the (003) crystal plane is 1 003 The peak intensity of the characteristic peak corresponding to the crystal plane of the positive electrode material (104) is I 104 , I 003 / I 104 It is 1.2 to 1.6, specifically 1.2, 1.25, 1.3, 1.35, 1.4, 1.45, 1.5, 1.55 or 1.6, etc., which is not limited here. 003 / I 104 Within the above range, the morphology of the single crystal particles can be made round, thereby increasing the stacking vacancies of small particles and further improving the compaction density.

[0082] In some embodiments, the specific surface area of ​​the positive electrode material is 0.6 m 2 / g~1.5m 2 / g, specifically 0.6m 2 / g, 0.7m 2 / g, 0.9m 2 / g, 1.0m 2 / g, 1.1m 2 / g, 1.2m 2 / g, 1.3m 2 / g, 1.4m 2 / g or 1.5m 2 / g, etc., and of course, it can also be other values ​​within the above range, which is not limited here.

[0083] In some embodiments, the positive electrode material has a tap density of ≥1.8 g / cm 3 , specifically 1.8 g / cm 3 , 1.9g / cm 3 , 2.0g / cm 3 , 2.1g / cm 3 , 2.2g / cm 3Of course, other values ​​within the above range are also possible and are not limited here. Controlling the Quanta tap density of the positive electrode material within the above range is beneficial to improving the energy density of the electrode sheet.

[0084] In some embodiments, the cathode material compaction density is ≥3.2 g / cm 3 , specifically 3.2 g / cm 3 、3.6g / cm 3 、3.8g / cm 3 , 4.0g / cm 3 , 4.2g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here.

[0085] In some embodiments, the bulk density of the positive electrode material is ≥1.2 g / cm 3 , specifically 1.2 g / cm 3 , 1.3g / cm 3 , 1.4g / cm 3 , 1.5g / cm 3 , 1.6g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here. A higher bulk density is beneficial to material transportation and storage.

[0086] In a second aspect, the present application provides a method for preparing a positive electrode material, as shown in FIG1 , the method for preparing a positive electrode material comprises the following steps:

[0087] S10: spray drying the mixed salt solution by spray pyrolysis to obtain a precursor, wherein the mixed salt solution contains a nickel source and an M source, and the nozzle pressure-diameter ratio is controlled to be 3.5 MPa / mm to 40 MPa / mm during the spray drying process, and M is selected from at least one of Co, Mn and Al;

[0088] S20: sintering the mixture of the precursor and the lithium source to obtain a positive electrode material.

[0089] The preparation method of the positive electrode material provided in the present application adopts a spray drying process and controls the nozzle pressure-diameter ratio to 3.5-40 MPa / mm. During the spray drying process, the formation of particles is continuous, and the particle size of the precursor is in a multi-level dispersion state, so that the particle size number distribution diagram of the prepared positive electrode material presents a multi-peak distribution curve; the positive electrode material particles of the present application have more stable physical and chemical properties and better particle strength, can provide lithium-ion batteries with better cycle stability and safety, and can also significantly reduce particle cracking during the electrode pressing process, thereby improving the electrode compaction density and volume energy density.

[0090] The preparation method of the present application is described in detail below with reference to the examples:

[0091] S10, preparing a mixed salt solution containing a nickel source and an M source, and spray-drying the mixed salt solution by a spray pyrolysis method to obtain a precursor.

[0092] In some embodiments, the precursor has the general chemical formula Ni x M y O, wherein 0.60≤x<1, 0<y≤0.40, and x+y=1. That is, appropriate amounts of nickel source and M source are weighed according to the chemical formula of the precursor. The M source can be at least one of a cobalt source, a manganese source, and an aluminum source.

[0093] In some embodiments, the precursor has the general chemical formula Ni x (CoMn) y (OH)2, the precursor of nickel-cobalt-manganese ternary material.

[0094] In some embodiments, the nickel source comprises at least one of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate. Preferably, the nickel source comprises nickel chloride.

[0095] In some embodiments, the M source includes at least one of a nitrate of M, an acetate of M, a chloride of M, and a sulfate of M. Preferably, the M source includes a chloride of M.

[0096] In some embodiments, during the spray drying process, the temperature in the reaction chamber is 550°C to 1050°C. Specifically, it can be 550°C, 600°C, 650°C, 700°C, 750°C, 800°C, 900°C, 1000°C, or 1050°C. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature in the reaction chamber is 850°C to 1000°C.

[0097] In some embodiments, the concentration of the mixed salt solution is 0.5 mol / L-4 mol / L, specifically 0.5 mol / L, 1.0 mol / L, 1.5 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L or 4.0 mol / L, etc., which is not limited here.

[0098] S20: sintering the mixture of the precursor and the lithium source to obtain a positive electrode material.

[0099] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate.

[0100] In some embodiments, the amount of lithium source and precursor added satisfies the following ratio: the molar amount of Li to the total molar amount of metal in the precursor is (1.01-1.1):1; specifically, it can be 1.01:1, 1.02:1, 1.05:1, 1.08:1, 1.09:1, or 1.1:1, etc., and of course, other values ​​within the above range are also possible and are not limited here. Within this range, the degree of Li / Ni cation mixing can be reduced, and the excessive amount of residual lithium on the surface of the sintered material that affects the processing performance and safety performance can be reduced.

[0101] In some embodiments, the primary sintering process is performed in an oxygen-containing atmosphere, where the oxygen content in the oxygen-containing atmosphere is ≥ 95%; the oxygen-containing atmosphere can be air or a mixture of air and oxygen.

[0102] In some embodiments, the primary sintering temperature is 600°C to 1000°C; specifically, it may be 600°C, 700°C, 750°C, 800°C, 900°C, 950°C, or 1000°C, but is not limited to the listed values. Other values ​​not listed within this range are also applicable. Within this range, sufficient air can promote the oxidation of divalent nickel to trivalent nickel, reduce Li / Ni cation mixing, and increase the capacity of the positive electrode material. At the same time, this temperature range is conducive to the formation of a layered structure without causing material decomposition.

[0103] In some embodiments, the time for a single sintering treatment is 6 hours to 16 hours, specifically 6 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 15 hours, or 16 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0104] In some embodiments, the method further comprises mixing the primary sintered product with a dopant containing metal N, and performing a secondary sintering process to obtain a secondary sintered product.

[0105] In some embodiments, N is selected from at least one of Ti, Zr, Mg, Sr, Ba, Nb, W, and Y.

[0106] In some embodiments, the metallic N-containing dopant includes at least one of Ta2O5, Sb2O5, SnO2, Nb2O5, Nb2O3, BaO, CaO, Ca(OH)2, Mg(OH)2, MgO, Sr(OH)2, SrO, TiO2, ZrO2, Zr(OH)4, WO3, and Y2O3.

[0107] In some embodiments, based on the mass of the final product positive electrode material as 100%, the mass content of the N element in the positive electrode material is 500ppm-10000ppm, specifically 500ppm, 1000ppm, 1500ppm, 2500ppm, 5000ppm, 7000ppm, 8000ppm, or 10000ppm. Of course, it can also be other values ​​within the above range, which is not limited here.

[0108] Furthermore, in order to enable the dopant to better enter the lattice of the positive electrode material, the temperature of the secondary sintering treatment is 600°C to 1000°C; specifically, it can be 600°C, 700°C, 750°C, 800°C, 900°C, 950°C or 1000°C, etc., but is not limited to the listed values, and other unlisted values ​​within this numerical range are also applicable.

[0109] In some embodiments, the secondary sintering treatment time is 6 hours to 16 hours, specifically 6 hours, 8 hours, 9 hours, 10 hours, 12 hours, 14 hours, 15 hours, or 16 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0110] In some embodiments, the solid phase mixing method can be dry grinding, ball milling, etc., which is not limited here, as long as the components are mixed evenly.

[0111] In some embodiments, the mixing device may be at least one of a ball mill, a three-dimensional mixer, a high-speed mixer, and a VC mixer.

[0112] In some embodiments, the secondary sintering process is performed in an oxygen-containing atmosphere, which may be air or a mixture of air and oxygen.

[0113] Furthermore, the method further comprises:

[0114] The primary sintered product or the secondary sintered product is reacted with boric acid to obtain a positive electrode material.

[0115] In some embodiments, the amount of boric acid added is 500ppm to 2000ppm, specifically 500ppm, 600ppm, 800ppm, 1000ppm, 1300ppm, 1500ppm, 1800ppm or 2000ppm, etc., which are not limited here. The boric acid coating treatment can effectively neutralize the residual alkali on the surface of the positive electrode material, reduce the residual alkali content on the surface of the positive electrode material, and improve the surface structure of the positive electrode material.

[0116] It should be noted that, since the parameters of spray drying can be controlled in this preparation method, the particle size of the precursor can be controlled, and no additional pulverization of the positive electrode material is required.

[0117] The positive electrode material prepared according to the preparation method of the present application contains single grains with the same orientation, wherein the average particle size of the single grains is 1μm to 5μm, and the average particle size of the single grains can specifically be 1μm, 1.5μm, 2μm, 2.5μm, 3μm, 3.5μm, 4μm, 5μm, etc., and of course it can also be other values ​​within the above range, which is not limited here. Compared with polycrystalline, single crystals have more stable physical and chemical properties and better particle strength, can provide lithium-ion batteries with better cycle stability and safety, and can also significantly reduce particle cracking during the pole piece pressing process, thereby improving the pole piece compaction density and volume energy density.

[0118] In a third aspect, the present application provides a battery, which includes a positive electrode plate, and the positive electrode plate includes the above-mentioned positive electrode material or the positive electrode material prepared by the above-mentioned preparation method.

[0119] In some embodiments, the positive electrode plate further includes a conductive agent, which is one of conductive carbon black, Ketjen black, graphite, and acetylene black.

[0120] In some embodiments, the positive electrode plate further includes a binder, and the binder is one of sodium carboxymethyl cellulose, cyclopentane, and polyvinylidene fluoride.

[0121] The above are only preferred embodiments of the present application and are not intended to limit the present application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the present application should be included in the scope of protection of the present application.

[0122] The following further illustrates the embodiments of the present application in multiple embodiments. The embodiments of the present application are not limited to the following specific embodiments. Within the scope of the unchanged main rights, appropriate changes can be made to the implementation.

[0123] Test method:

[0124] (1) Mastersizers 3000 were used to characterize the particle size distribution of the positive electrode material. The specific method is as follows:

[0125] The particle size test method refers to GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd., UK.

[0126] In the particle size distribution spectrum of the positive electrode material, the particle size distribution width functions Span(a) and Span(b) of the two peaks are expressed as:

[0127] D90 p1 、D10 p1 、D50p1 They are the particle size ratio parameters of the peak with x in the range of 1μm-4μm;

[0128] D90 p2 、D10 p2 、D50 p2 are the particle size ratio parameters of the peaks with x in the range of 0.1μm-1μm.

[0129] (2) Testing method for specific surface area of ​​cathode material precursor:

[0130] The specific surface area of ​​the cathode material was tested using a Micromeritics Tristar 3020 specific surface area and pore size analyzer. A certain mass of powder was weighed and completely degassed under vacuum heating to remove surface adsorbents. The specific surface area of ​​the particles was calculated using the nitrogen adsorption method based on the amount of nitrogen adsorbed. The unit is m 2 / g.

[0131] (3) Kanta tap density test of cathode material:

[0132] Use the American Quantacon tap density tester (model: DAT-4-220) and the steps are as follows:

[0133] 1. Clean the measuring cylinder and weigh its mass as m1;

[0134] 2. Add about 50g of sample into the measuring cylinder, make the sample surface as level as possible, and wipe the surrounding area with a paper towel;

[0135] 3. Weigh the total mass of the sample and graduated cylinder to m2;

[0136] 4. Place the measuring cylinder on the vibration table and secure it with three symmetrical fixing feet;

[0137] 5. Turn on the instrument and set the vibration frequency to 5000 times; turn on the vibration switch, and the instrument will automatically stop vibrating after the specified number of times;

[0138] 6. Remove the graduated cylinder and read the volume of the sample. If the sample surface is horizontal after tapping, read the volume directly. If it is diagonal, take the average of the highest and lowest readings (V). Tap density = (m² - m¹) / V.

[0139] (4) Compaction density test of positive electrode material:

[0140] The compaction density of the positive electrode material is tested using the American carver 4350. The steps are as follows: weigh 1g of sample and put it into a mold and press it with a pressure of 3T for 30s. After pressing, the height is measured to calculate the compaction.

[0141] (5) Bulk density test of positive electrode material:

[0142] The compacted density of the positive electrode material is tested using a loose density meter BT101. The steps are as follows: take an appropriate amount of sample, let it flow naturally into the distribution box, alternately pass through the four glass plates with an inclination angle of 25° and the square funnel in the distribution box, and flow into a cylindrical cup of known volume (25 ml). Finally, weigh the mass of the powder in the cylindrical cup.

[0143] (6) XRD test of positive electrode materials:

[0144] The cathode material was characterized using an XRD diffractometer (RIGAICU UITIMAIV), and the diffraction intensity of the (003) crystal plane of the cathode material was obtained to be I 003 The diffraction intensity of the (104) crystal plane is I 104 Calculate I 003 / I 104 .

[0145] (7) Electrochemical performance test:

[0146] The positive electrode material, conductive carbon and polyvinylidene fluoride are dispersed in N-methylpyrrolidone in a mass ratio of 93:5:2 to prepare a positive electrode slurry with a solid content of 50%. After coating on aluminum foil and drying, it is used as the positive electrode sheet. Lithium sheet is used as the negative electrode sheet, and the electrolyte is sodium hexafluorophosphate-diethylene glycol dimethyl ether (NaPF6 concentration is 1 mol / L) to assemble into a button battery.

[0147] Power-off test

[0148] After standing for 12 hours, the battery test was carried out according to the following system: 0.1C charge and 0.1C discharge for 2 weeks (first effect), constant voltage cut-off current 0.005C; 0.5C charge and 0.5C discharge for 1 week (rate), constant voltage cut-off current 0.05C, 0.5C charge and 1C discharge for 1 week (rate), constant voltage cut-off current 0.05C; 0.5C charge and 2C discharge for 1 week (rate), constant voltage cut-off current 0.05C; 0.5C charge and 1C discharge for 50 weeks (cycle).

[0149] (8) Particle size distribution curve fitting method:

[0150] Obtain the particle size distribution curve data of the positive electrode material measured by the laser particle size analyzer, intercept the data with the horizontal coordinate of 1 μm-4 μm, import the above 1-4 μm data into Origin, release the Pulse function for fitting, and when the computer fitting degree chi-square is less than or equal to 10 (χ 2 ≤10), the particle distribution curve in the range of 1μm to 4μm is considered to have a peak that conforms to the Pulse function distribution; the data with the horizontal coordinate of 0.1μm-1μm (excluding 1μm) are intercepted and imported into Origin, and the Voigt function is released for fitting. When the computer fitting degree χ2 If the value is ≤10, it is considered that the particle distribution curve within the range of 0.1 μm to 1 μm (excluding 1 μm) has a peak that conforms to the Voigt function distribution.

[0151] (9) The particle size volume distribution of the positive electrode material was characterized using Mastersizers 3000. The specific method is as follows:

[0152] The particle size test method refers to GB / T 19077-2016. It can be conveniently measured using a laser particle size analyzer, such as the Mastersizer 3000 laser particle size analyzer from Malvern Instruments Ltd. in the UK, which can measure the particle size volume distribution curve of the positive electrode material particles.

[0153] (10) Electron backscatter diffraction (EBSD) test:

[0154] The cathode material samples were first embedded in a carbon lacquer (PELCO) graphite block, and then the cross-section of the block was polished using an argon ion beam. Electron backscatter diffraction (EBSD) imaging was performed using a JEOL JSM-7000F scanning electron microscope. The EBSD image was set to a step size of 250 nm (each pixel was 250 nm × 250 nm).

[0155] Example 1

[0156] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.6 Co 0.1 Mn 0.3 O, control the nozzle pressure-diameter ratio to 3.5MPa / mm;

[0157] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 900° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0158] (3) Weigh 300 g of the matrix material and 10 g of zirconium oxide, mix them evenly, place them in an atmosphere furnace, and perform secondary sintering at 800° C. for 5 h, and then cool them to room temperature to obtain a secondary sintered product.

[0159] (4) After the above materials are fully dispersed with a blender, 200g of the secondary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.6 Co 0.09 Mn 0.3 Zr 0.01 O2.

[0160] As shown in Figure 2, the particle size distribution curve of the positive electrode material of this embodiment 1 has the above-mentioned bimodal distribution characteristics, wherein the first sharp and high peak represents the distribution of particles with a particle size of 0.1 μm to 1 μm and does not include particles in the range of 1 μm. Its distribution curve has a peak that conforms to the Voigt function distribution, and the particle size D50 of these particles is about 0.5 μm.

[0161] The second smoother peak is the distribution of larger particles. The particle distribution curve within the particle size range of 1μm to 4μm has a peak that conforms to the Pulse function distribution. The particle size D50 of these particles is around 2.0μm. The accumulation of particles within the particle size range of 1μm to 4μm will produce gaps. Particles with a particle size of 0.1μm to 1μm and not including 1μm fill the gaps between particles within the particle size range of 1μm to 4μm, further reducing the void ratio of the positive electrode material, effectively improving the compaction density of the electrode sheet, and making the electrolyte infiltration more uniform, so that the material can exert higher capacity and rate performance.

[0162] As shown in Figure 2, the first peak of the double peak of the positive electrode material is long and narrow, with a peak value greater than 15%, and the second peak is short and wide, with a peak value less than 10%.

[0163] Example 2

[0164] The difference from Example 1 is that:

[0165] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.6 Co 0.1 Mn 0.3 O, control the nozzle pressure-diameter ratio to 20 MPa / mm.

[0166] Example 3

[0167] The difference from Example 1 is that:

[0168] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.6 Co 0.1 Mn 0.3 O, control the nozzle pressure-diameter ratio to 40 MPa / mm.

[0169] Example 4

[0170] The difference from Example 1 is that:

[0171] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 1000° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0172] Example 5

[0173] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.94 Co 0.035 Mn 0.25 O, control the nozzle pressure-diameter ratio to 40MPa / mm;

[0174] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 680° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0175] (3) After the above materials are fully dispersed with a blender, 200g of the primary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.94 Co 0.035 Mn 0.025 O2.

[0176] Example 6

[0177] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.825 Co 0.065 Mn 0.11 O, control the nozzle pressure-diameter ratio to 15MPa / mm;

[0178] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 850° C. in an oxygen atmosphere for 8 h to obtain a positive electrode material.

[0179] Example 7

[0180] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.6 Co 0.1 Mn 0.3 O, control the nozzle pressure-diameter ratio to 30MPa / mm;

[0181] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 950° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0182] (3) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of cobalt oxide, place it in an atmosphere furnace, and perform a secondary sintering treatment at 800° C. for 5 h, and then cool it to room temperature to obtain a secondary sintered product.

[0183] (4) After the above materials are fully dispersed with a blender, 200g of the secondary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.6 Co 0.1 Mn0.3 O2.

[0184] Example 8

[0185] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.6 Co 0.1 Mn 0.3 O, control the nozzle pressure-diameter ratio to 10MPa / mm;

[0186] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 890° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0187] (3) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of cobalt oxide, place it in an atmosphere furnace, and perform a secondary sintering treatment at 800° C. for 5 h, and then cool it to room temperature to obtain a secondary sintered product.

[0188] (4) After the above materials are fully dispersed with a blender, 200g of the secondary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0189] Example 9

[0190] The difference from Example 8 is that:

[0191] (5) To finished product LiNi 0.6 Co 0.1 Mn 0.3 Add 50g of O2, Span value is 1.2, D 50 5.1μm single crystal positive electrode material LiNi 0.6 Co 0.1 Mn 0.3 O2.

[0192] Example 10

[0193] (1) Take 500g of conventional single crystal positive electrode material Ni prepared by coprecipitation method 0.6 Co 0.1 Mn 0.3 O, Span(a) value is 1.2, D50 is 3.8 μm;

[0194] (2) Take 100g of LiNi powder single crystal positive electrode material with Span(b) value of 0.5 and D50 of 0.8μm 0.6 Co 0.1 Mn 0.3 O2;

[0195] (3) The positive electrode materials of steps (1) and (2) are mixed uniformly to obtain a positive electrode material.

[0196] Comparative Example 1

[0197] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.925 Co 0.045 Mn 0.03 O, control the nozzle pressure-diameter ratio to 45MPa / mm;

[0198] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 750° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0199] (3) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of zirconium oxide, place it in an atmosphere furnace, and perform a secondary sintering treatment at 600° C. for 5 h, and then cool it to room temperature to obtain a secondary sintered product.

[0200] (4) After the above materials are fully dispersed with a blender, 200g of the secondary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.925 Co 0.035 Mn 0.03 Zr 0.01 O2.

[0201] Comparative Example 2

[0202] (1) Weigh appropriate amounts of nickel chloride, cobalt chloride, and manganese chloride, and obtain the precursor Ni by spray pyrolysis. 0.925 Co 0.045 Mn 0.03 O, control the nozzle pressure-diameter ratio to 3MPa / mm;

[0203] (2) Weigh 1 kg of the precursor and mix it evenly with 503.6 g of lithium carbonate, and then sinter it at 730° C. in an oxygen atmosphere for 8 h to obtain a primary sintered product.

[0204] (3) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of zirconium oxide. Place it in an atmosphere furnace and perform a secondary sintering treatment at 800° C. for 5 h. Then cool it to room temperature to obtain a secondary sintered product.

[0205] (4) After the above materials are fully dispersed with a blender, 200g of the secondary sintered product is mixed with 2g of boric acid, transferred to an atmosphere furnace, and heat treated at 550℃ for 5h. The finished product LiNi 0.925 Co 0.035 Mn 0.03 Zr 0.01 O2.

[0206] Comparative Example 3

[0207] (1) Weigh 1 kg of coprecipitation single crystal ternary precursor Ni 0.60 Co 0.10 Mn 0.30 O and 503.6 g of lithium carbonate were mixed evenly, and then sintered at 900° C. in an oxygen atmosphere for 10 h to obtain a primary sintered product.

[0208] (2) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of cobalt oxide, place it in an atmosphere furnace, and perform a secondary sintering treatment at 800° C. for 5 h, and then cool it to room temperature to obtain a secondary sintered product.

[0209] (3) After the active material is fully dispersed with a blender, 200 g of the secondary sintered product is mixed with 2 g of boric acid, transferred to an atmosphere furnace, and heat treated at 550 °C for 5 h to obtain the positive electrode material.

[0210] FIG4 shows the particle size distribution curve of the positive electrode material prepared in Comparative Example 1. The curve has only one peak, has a typical normal distribution law, is applicable to the Pulse function, and has only one peak.

[0211] Comparative Example 4

[0212] (1) Weigh 1 kg of polycrystalline positive electrode material LiNi with a particle size of 12 μm 0.6 Co 0.1 Mn 0.3 O2.

[0213] (2) Weigh 300g of polycrystalline positive electrode material LiNi with a particle size of 6.5μm 0.6 Co 0.1 Mn 0.3 O2.

[0214] (3) The above materials are mixed evenly using a blender to obtain a positive electrode material.

[0215] Comparative Example 5

[0216] (1) Weigh 1 kg of co-precipitation ternary precursor Ni 0.6 Co 0.1 Mn 0.3 O and 503.6 g of lithium carbonate were mixed evenly, and then sintered at 880° C. in an oxygen atmosphere for 10 h to obtain a primary sintered product.

[0217] (2) Weigh 300 g of the primary sintered product and mix it evenly with 10 g of cobalt oxide, place it in an atmosphere furnace, and perform a secondary sintering treatment at 800° C. for 5 h, and then cool it to room temperature to obtain a secondary sintered product.

[0218] (3) After the secondary sintered product is fully dispersed with a blender, 200 g of the secondary sintered product is mixed with 2 g of boric acid, transferred to an atmosphere furnace, and heat treated at 550 ° C for 5 h to obtain the positive electrode material LiNi 0.6 Co 0.15 Mn 0.3 O2.

[0219] (4) LiNi cathode material 0.6 Co 0.1 Mn 0.3 O2 and 1kg of polycrystalline positive electrode material LiNi with a D50 of 12μm 0.6 Co 0.1 Mn 0.3 O2 is mixed evenly to finally obtain the positive electrode material.

[0220] Table 1 Comparison of performance parameters of positive electrode materials of embodiment and comparative example

[0221] Table 2 Comparison of positive electrode sheets of the embodiment and the comparative example

[0222] According to the data in Tables 1 and 2, by controlling the particle size distribution width of particles in the range of 1 μm to 4 μm as Span(a), and the particle size distribution width of particles in the range of 0.1 μm to 1 μm but not including 1 μm as Span(b), the compaction density of the material can be effectively improved while improving the packing density of the particles. Since the above two particle distribution curves conform to different Pulse function distributions and Voigt function distribution forms, the densest packing mode of the monodisperse can be achieved, that is, multi-stage dispersed particles are used to achieve mixing and improve the packing density.

[0223] The parameters of the raw materials and nozzle aperture ratio of the comparative example 1 are adjusted so that the D of the particles in the range of 0.1 μm to 1 μm in the final positive electrode material is 50 The Span (b) is out of range, which affects the packing density of the positive electrode material particles. Moreover, due to the significant increase in the Ni content, although the initial coulombic efficiency of the material is improved, the capacity deteriorates more during the cycle charge and discharge process, and thus the capacity retention rate decreases.

[0224] The parameters of the raw materials and nozzle aperture ratio of the comparative example 2 are adjusted so that the D of the particles in the range of 1 μm to 4 μm in the final positive electrode material is 50 The Span (b) is out of range, which affects the packing density of the positive electrode material particles. Moreover, due to the significant increase in the Ni content, although the initial coulombic efficiency of the material is improved, the capacity deteriorates more during the cycle charge and discharge process, and thus the capacity retention rate decreases.

[0225] The particle size distribution curve of the positive electrode material prepared in Comparative Example 3 has only one peak, has a typical normal distribution law, and conforms to the Pulse function distribution. The content of small particles and large particles is very small, and the medium particles are relatively large. There are not enough small particles inserted into the gaps between large particles to further increase the packing density. It is difficult for the positive electrode material to achieve a higher packing density, resulting in low Kanta tap density, compacted density and loose density of the positive electrode material.

[0226] The positive electrode material prepared in Comparative Example 4 is a polycrystalline material, and a bimodal distribution characteristic is achieved by mixing large and small particles. There are two peaks, but in the particle size number distribution spectrum of the positive electrode material, the peak with a particle size of 0.1μm to 1μm and not including the peak in the range of 1μm does not conform to the Voigt function, and the numerical ranges of Span(b) and Span(a) are out of the appropriate range. The stability of the particles themselves is poor, the cracking of the particles increases during the electrode pressing process, the electrode compaction density decreases, and the cycle capacity retention rate also decreases.

[0227] For the positive electrode material prepared in Comparative Example 5, the values ​​of span (a) and span (b) are not within the scope of this application. The particles are generally large, making it difficult to achieve effective dense stacking, resulting in a significant decrease in the density of the positive electrode material, and a significant decrease in the first efficiency, cycle retention rate and capacity retention rate of the material.

[0228] The above description is merely a preferred embodiment of the present application and is not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, or improvements made within the spirit and principles of the present application shall be included within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that: The chemical formula of the positive electrode material is Li a Ni x M y N z O2, wherein 0.98≤a≤1.05, 0.60≤x<1, 0<y≤0.40, 0≤z<0.1, x+y+z=1, M is selected from at least one of Co, Mn and Al, and N is a doping metal; In the particle size distribution spectrum of the positive electrode material, the particle distribution curve in the particle size range of 1 μm to 4 μm has a peak that conforms to the Pulse function distribution, and the particle size distribution width of the particles in the particle size range of 1 μm to 4 μm is Span(a), which satisfies 0.8<Span(a)<1.6; In the particle size number distribution spectrum of the positive electrode material, the particle distribution curve with a particle size of 0.1 μm to 1 μm and excluding 1 μm has a peak that conforms to the Voigt function distribution, and the particle size distribution width of the particles with a particle size of 0.1 μm to 1 μm and excluding 1 μm is Span(b), satisfying 0.4<Span(b)<0.

8.

2. The positive electrode material according to claim 1, characterized in that The positive electrode material contains single crystal grains with the same orientation, wherein the average grain size of the single crystal grains is 1 μm to 5 μm.

3. The positive electrode material according to claim 2, characterized in that The mass content of N element in the positive electrode material is 500ppm-10000ppm; and / or N is selected from at least one of Ti, Zr, Mg, Ca, Sr, Ba, Nb, Ta, Sb, Sn, W and Y.

4. The positive electrode material according to claim 1, characterized in that The particles in the positive electrode material with a size of 1 μm to 4 μm have a size of 1 μm≤D 50 ≤4μm.

5. The positive electrode material according to claim 1, characterized in that The particles in the positive electrode material with a size of 0.1 μm to 1 μm have a size of 0.1 μm≤D 50 ≤1μm.

6. The positive electrode material according to claim 1, characterized in that The peak value of the distribution curve of particles in the range of 0.1 μm to 1 μm in the positive electrode material is ≥15%.

7. The positive electrode material according to claim 1, characterized in that It meets at least one of the following technical features: (1) The particle size volume distribution of the positive electrode material satisfies: D min >0.1μm,2.5μm<D 50 <5.5μm, D max <14μm; (2) The particle size volume distribution width of the positive electrode material satisfies: 1.2≤(D 90 -D 10 ) / D 50 , D 10 ≤1.8μm, D 90 ≥5.5μm; (3) In the particle size number distribution spectrum of the positive electrode material, the positive electrode material has at least two particle size distribution peaks.

8. The positive electrode material according to any one of claims 1 to 7, characterized in that In the XRD spectrum of the positive electrode material, the peak intensity of the characteristic peak corresponding to the (003) crystal plane is I 003 The peak intensity of the characteristic peak corresponding to the crystal plane of the positive electrode material (104) is I 104 , I 003 / I 104 It is 1.2 to 1.

6.

9. The positive electrode material according to any one of claims 1 to 7, characterized in that The specific surface area of ​​the positive electrode material is 0.6 m 2 / g~1.5m 2 / g.

10. The positive electrode material according to any one of claims 1 to 7, characterized in that It meets at least one of the following technical features: (1) The positive electrode material has a tap density of ≥1.8 g / cm 3 ; (2) The compaction density of the positive electrode material is ≥3.2 g / cm 3 ; (3) The bulk density of the positive electrode material is ≥1.2 g / cm 3 .

11. A method for preparing a positive electrode material, characterized in that: The following steps are involved: The mixed salt solution is spray-dried by a spray pyrolysis method to obtain a precursor, wherein the mixed salt solution contains a nickel source and an M source, and the nozzle pressure-diameter ratio is controlled to be 3.5MPa / mm to 40MPa / mm during the spray drying process, and M is selected from at least one of Co, Mn and Al; The mixture of the precursor and the lithium source is subjected to a sintering treatment to obtain a positive electrode material.

12. The preparation method according to claim 11, characterized in that: It meets at least one of the following technical features: (1) The chemical formula of the precursor is Ni x M y O, where 0.60≤x<1, 0<y≤0.40; (2) The nickel source includes at least one of nickel nitrate, nickel acetate, nickel chloride, and nickel sulfate; (3) The M source includes at least one of a nitrate of M, an acetate of M, a chloride of M, and a sulfate of M; (4) During the spray drying process, the temperature in the reaction chamber is 550° C. to 1050° C.; (5) The concentration of the mixed salt solution is 0.5 mol / L-4 mol / L.

13. The preparation method according to claim 11, characterized in that: It meets at least one of the following technical features: (1) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate and lithium oxalate; (2) The amount of the lithium source and the precursor added satisfies: the ratio of the molar amount of Li to the total molar amount of the metal in the precursor is (1.01-1.1):1; (3) The temperature of the primary sintering treatment is 600° C. to 1000° C., and the time of the primary sintering treatment is 6 h to 16 h.

14. The preparation method according to claim 11, characterized in that: The method also includes mixing the primary sintering product with a dopant containing metal N, and performing a secondary sintering treatment to obtain a secondary sintering product; wherein the temperature of the secondary sintering treatment is 600° C. to 1000° C., and the time of the secondary sintering treatment is 6 hours to 16 hours; and / or N is selected from at least one of Ti, Zr, Mg, Ca, Sr, Ba, Nb, Ta, Sb, Sn, W and Y.

15. The preparation method according to claim 14, characterized in that: The method further comprises reacting the primary sintering product or the secondary sintering product with boric acid to obtain a positive electrode material, wherein the amount of the boric acid added is 500ppm to 2000ppm based on 100% mass of the positive electrode material.

16. A battery, characterized in that: The battery comprises the positive electrode material according to any one of claims 1 to 10 or the positive electrode material prepared by the method for preparing the positive electrode material according to any one of claims 11 to 15.

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