Positive electrode material and preparation method therefor, and battery

Abstract

A positive electrode material and a preparation method therefor, and a lithium ion battery. The volume particle size distribution width of the positive electrode material is Span, the dissociation degree of the positive electrode material is β, and the positive electrode material meets the following relationship: 1.1≤β<1.65, and 0.9≤Span≤1.53. The dissociation degree and the volume particle size distribution width of the positive electrode material meet the conditions, so that it can be guaranteed that the positive electrode material has a certain electrode sheet compaction density to improve the energy density, the integrity of the crystal structure of the positive electrode material in the charging and discharging process of the lithium ion battery can be guaranteed, and the gas production value is reduced, and thus the positive electrode material has excellent cycle performance and safety performance.

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 December 27, 2023, with application number 2023118150356 and application name “Positive electrode material, preparation method thereof, lithium-ion battery”, parts of which are incorporated by reference in this application. Technical Field

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

[0003] Lithium-ion batteries have the advantages of high energy density, wide operating temperature range and long cycle life. They are widely used in consumer electronics, power tools, electric vehicles, industrial energy storage and other fields. Currently, the most commonly used positive electrode material in lithium-ion batteries is ternary positive electrode material.

[0004] However, the inventors found that in the prior art, simply increasing the powder compaction density of the positive electrode material not only fails to effectively improve the electrode compaction density of the positive electrode sheet and the energy density of the lithium-ion battery, but also affects the efficiency of lithium ion insertion and extraction, resulting in a decrease in the cycle performance of the lithium-ion battery.

[0005] Application Contents

[0006] The present application provides a positive electrode material, a preparation method thereof, and a lithium-ion battery. By controlling the volume particle size distribution width and dissociation degree of the positive electrode material, it is possible to ensure that the positive electrode material has a certain electrode sheet compaction density to improve the energy density while ensuring the gas production value of the positive electrode material during the charge and discharge process of the lithium-ion battery, so that the positive electrode material also has excellent cycle performance and safety performance.

[0007] In a first aspect, the present application provides a positive electrode material, wherein the number distribution median particle size of the positive electrode material is D n50 μm, the volume particle size distribution width of the positive electrode material is Span, The degree of dissociation of the positive electrode material is β, The true density of the positive electrode material is ρg / cm 3 , the repose angle of the positive electrode material is αrad, P 等 The calculated value of the equivalent density of the positive electrode material, in g / cm 3 ; Wherein, the positive electrode material satisfies at least one of the following relationships:

[0008] 1) 1.1≤β<1.65, and 0.9≤Span≤1.53;

[0009] 2) 3.2≤P等 ≤3.7.

[0010] In a second aspect, the present application provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0011] A mixture comprising a cathode material precursor and a lithium source is subjected to a staged sintering process to obtain a matrix material; wherein the staged sintering process includes a first stage, a second stage, and a third stage performed sequentially, the sintering temperature T1 of the first stage is 100° C. to 300° C., the sintering temperature T2 of the second stage is 400° C. to 800° C., and the sintering temperature T3 of the third stage is 700° C. to 1000° C.;

[0012] After the base material and the coating agent are mixed, a secondary sintering process is performed, and the secondary sintering product is subjected to a micron-sized particle dissociation process to obtain a positive electrode material.

[0013] In a third aspect, the present application provides a battery, comprising the positive electrode material described in the first aspect or the positive electrode material prepared according to the second aspect.

[0014] The technical solution of this application has at least the following beneficial effects:

[0015] In this application, the degree of dissociation of the positive electrode material is controlled within the range of 1.1 to 1.65 (excluding 1.65), and the Span value of the positive electrode material is controlled within the range of 0.9 to 1.53. This can ensure the width of the particle size distribution of the positive electrode material, help improve the compaction density, and at the same time ensure the degree of dissociation of the positive electrode material, reduce the soft agglomeration of particles, and improve the capacity and cycle performance of the positive electrode material. The positive electrode material provided in this application can have high capacity, excellent cycle performance and high energy density.

[0016] The calculated equivalent density, volume particle size distribution width, number distribution median particle size, true density, degree of dissociation, volume distribution median particle size and repose angle of the positive electrode material of the present application also meet the following conditions: And 3.2g / cm 3 ≤P 等 ≤3.7g / cm 3When the calculated equivalent density of the positive electrode material is within the above range, the volume energy density of the positive electrode sheet prepared therefrom can be increased, thereby increasing the battery capacity of the lithium-ion battery. At the same time, by balancing the relationship between the volume particle size distribution width, the median particle size of the number distribution, the true density, the degree of dissociation, the median particle size of the volume distribution, and the angle of repose using the above relationship and the calculated equivalent density of the positive electrode material, each performance parameter is within a reasonable range. This ensures that the positive electrode material has a certain sheet compaction density to increase the energy density while maintaining the integrity of the positive electrode material's crystal structure during the charge and discharge process of the lithium-ion battery, reducing gas generation, and ensuring that the positive electrode material also has excellent cycle performance and safety performance.

[0017] The preparation method of the positive electrode material provided in the present application obtains a positive electrode material in which the volume particle size distribution width, number distribution median particle size, true density, degree of dissociation, volume distribution median particle size, repose angle and electrode compaction density satisfy a balanced relationship through segmented sintering treatment and micron-level particle dissociation treatment. While ensuring that the positive electrode material has a certain electrode compaction density to improve the energy density, it also ensures the integrity of the crystal structure of the positive electrode material during the charge and discharge process of the lithium-ion battery, reduces the gas production value, and makes the positive electrode material also have excellent cycle performance and safety performance. BRIEF DESCRIPTION OF THE DRAWINGS

[0018] FIG1 is a schematic diagram of the discharge state of a battery provided in an embodiment of the present application.

[0019] FIG2 is a SEM image of the positive electrode material provided in this application.

[0020] FIG3 is a SEM image of a positive electrode material provided by the prior art. DETAILED DESCRIPTION

[0021] The present invention is explained below through examples. The examples are illustrative and are only used to explain the present application, and should not be construed as limiting the present application.

[0022] Since simply increasing the powder compaction density of the positive electrode material cannot effectively increase the electrode compaction density of the positive electrode sheet and the energy density of the lithium-ion battery, it will also affect the efficiency of lithium ion deintercalation and desorption, resulting in a decrease in the cycle performance of the lithium-ion battery. To this end, the inventors improved the product process and increased the compaction density of the positive electrode material and the energy density of the lithium-ion battery by controlling the heat treatment temperature at different stages. After research, the inventors found that the performance change of the positive electrode material can be reflected not only from the value range of the particle size distribution width span value and the dissociation degree β value of the positive electrode material, but also from the particle size distribution width span value and the dissociation degree β value of the positive electrode material, the true density of the positive electrode material is ρg / cm 3, the relationship between the angle of repose of the positive electrode material is αrad. On the one hand, the degree of dissociation of the positive electrode material is controlled within the range of 1.1 to 1.65 (excluding 1.65), and the Span value of the positive electrode material is controlled within the range of 0.9 to 1.53. This can not only ensure the width of the particle size distribution of the positive electrode material, but also help to improve the compaction density, while ensuring the degree of dissociation of the positive electrode material, reducing the soft agglomeration of particles, and improving the capacity and cycle performance of the positive electrode material. On the other hand, the equivalent density calculated value, volume particle size distribution width, number distribution median particle size, true density, dissociation degree, volume distribution median particle size and the angle of repose of the positive electrode material also meet the following conditions: And 3.2g / cm 3 ≤P 等 ≤3.7g / cm 3 When the calculated equivalent density of the positive electrode material is within the above range, the volume energy density of the positive electrode sheet prepared therefrom can be increased, thereby increasing the battery capacity of the lithium-ion battery. At the same time, by balancing the relationship between the volume particle size distribution width, the median particle size of the number distribution, the true density, the degree of dissociation, the median particle size of the volume distribution, and the angle of repose using the above relationship and the calculated equivalent density of the positive electrode material, each performance parameter is within a reasonable range. This ensures that the positive electrode material has a certain sheet compaction density to increase the energy density while maintaining the integrity of the positive electrode material's crystal structure during the charge and discharge process of the lithium-ion battery, reducing gas generation, and ensuring that the positive electrode material also has excellent cycle performance and safety performance.

[0023] In a first aspect, the present application provides a positive electrode material, wherein the volume particle size distribution width of the positive electrode material is Span, The degree of dissociation of the cathode material is β, The positive electrode material satisfies the following relationships: 1.1≤β<1.65, and 0.9≤Span≤1.53.

[0024] It is generally believed that the volume particle size distribution width Span of the positive electrode material has no necessary connection with the degree of dissociation β. In general, the higher the Span of the positive electrode material, the wider the particle size distribution width, the larger the difference in particle size, and the higher the degree of dissociation of the positive electrode material. At this time, the small particles in the positive electrode material fill the gaps between the large particles, and the compaction density of the positive electrode sheet will also be higher. However, in the actual preparation process, due to the soft agglomeration phenomenon between the particles of the positive electrode material, the particles formed by soft agglomeration will result in a lower Span value of the positive electrode material and a narrower particle size distribution width, so the particle sizes are closer. Moreover, compared with the secondary particles formed by hard agglomeration of primary particles, the particles formed by soft agglomeration have a lower connection strength between the primary particles. During the rolling process of the electrode sheet preparation, the soft agglomerated particles will spread out, causing the surface of the uncoated primary particles to be exposed to the electrolyte, affecting the cycle performance of the positive electrode material. It should be noted that during the preparation of positive electrode materials, the coating agent can usually only coat the surface of soft agglomerated particles, while the surfaces of multiple primary particles in the soft agglomerated particles are difficult to be coated by the coating agent. Therefore, after the soft agglomerated particles are dispersed, the surfaces of multiple primary particles are exposed to the electrolyte.

[0025] Therefore, in the present application, by controlling the degree of dissociation of the positive electrode material within the range of 1.1 to 1.65 (excluding 1.65), and controlling the Span value of the positive electrode material within the range of 0.9 to 1.53, on the one hand, it is possible to ensure the width of the particle size distribution of the positive electrode material, which helps to improve the compaction density, while ensuring the degree of dissociation of the positive electrode material, reducing the soft agglomeration of the particles, and improving the capacity and cycle performance of the positive electrode material. The positive electrode material provided in the present application can have high capacity, excellent cycle performance and high energy density.

[0026] In some embodiments, the volume particle size distribution width Span value of the positive electrode material is 0.9 to 1.53. Optionally, the volume particle size distribution width Span of the positive electrode material can be specifically 0.9, 1.0, 1.1, 1.2, 1.3, 1.4, 1.5 and 1.53, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the volume particle size distribution width Span of the positive electrode material is within the above range, the particle size distribution of the positive electrode material is appropriate, and the difference in particle size between large particles and small particles is not too large. In the process of preparing the positive electrode sheet, the small particles can effectively fill the gaps between the large particles to increase the compaction density of the positive electrode sheet. At the same time, the specific surface area of ​​the positive electrode material and the increase in the reaction with the electrolyte due to the small volume of the small particles will not be increased, effectively reducing the gas production value of the positive electrode material during the charge and discharge process, ensuring the crystal structure stability of the positive electrode material during the charge and discharge process, and improving the cycle performance and safety performance of the positive electrode material. Preferably, the volume particle size distribution width Span value of the positive electrode material is 1.0 to 1.3.

[0027] In some embodiments, the degree of dissociation β of the positive electrode material is 1.1 to 1.65 (excluding 1.65). Optionally, the degree of dissociation β of the positive electrode material can be specifically 1.1, 1.2, 1.3, 1.4, 1.5, 1.6, 1.62 and 1.63, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the degree of dissociation of the positive electrode material is within the above range, there are fewer soft agglomerated particles between the positive electrode material particles, and the possibility of particle breakage during the rolling process is reduced, thereby reducing the problem of increased electrolyte reaction caused by particle breakage, thereby effectively reducing the gas production value of the positive electrode material during the charge and discharge process. That is, the appropriate degree of dissociation can improve the safety performance and cycle performance of the positive electrode material while ensuring the compaction density of the positive electrode material's diode. Preferably, the degree of dissociation β of the positive electrode material is 1.2 to 1.6.

[0028] In some embodiments, the number distribution median particle size of the positive electrode material is D n50 μm, the true density of the positive electrode material is ρg / cm 3 , the repose angle of the positive electrode material is αrad; P 等 The calculated value of the equivalent density of the positive electrode material, in g / cm 3 Among them, P 等 The volume particle size distribution width Span of the positive electrode material and the median particle size D of the positive electrode material are n50 The relationship between the true density ρ, the degree of dissociation β and the angle of repose α satisfies the formula (I):

[0029] And 3.2≤P 等 ≤3.7.

[0030] In the above scheme, the calculated equivalent density, volume particle size distribution width, number distribution median particle size, true density, degree of dissociation, volume distribution median particle size and repose angle of the positive electrode material of this application meet the following requirements: 3.2g / cm 3 ≤P 等 ≤3.7g / cm 3 When the calculated equivalent density of the positive electrode material is within the above range, the volume energy density of the positive electrode sheet prepared therefrom can be increased, thereby increasing the battery capacity of the lithium-ion battery. At the same time, by balancing the relationship between the volume particle size distribution width, the median particle size of the number distribution, the true density, the degree of dissociation, the median particle size of the volume distribution, and the angle of repose using the above relationship and the calculated equivalent density of the positive electrode material, each performance parameter is within a reasonable range. This ensures that the positive electrode material has a certain sheet compaction density to increase the energy density while maintaining the integrity of the positive electrode material's crystal structure during the charge and discharge process of the lithium-ion battery, reducing gas generation, and ensuring that the positive electrode material also has excellent cycle performance and safety performance.

[0031] In some embodiments, P 等 Specifically, it can be 3.2g / cm 3 , 3.3g / cm 3 、3.4g / cm 3 , 3.5g / cm 3 、3.6g / cm 3 、3.65g / cm 3 , or 3.7g / cm 3 Of course, it can also be other values ​​within the above range, which is not limited here. Preferably, P 等 Satisfy: 3.5≤P 等 ≤3.7.

[0032] In some embodiments, the volume distribution median particle size D of the positive electrode material is v50 3μm~15μm, optional, the volume distribution median particle size D of the positive electrode material v50 Specifically, it can be 3μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm and 15μm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the volume distribution median particle size D of the positive electrode material is v50Within the above range, the number of large-volume particles and small-volume particles is appropriate. In the process of preparing the positive electrode sheet, the small particles can effectively fill the gaps between the large particles, thereby improving the compaction density of the positive electrode sheet. Moreover, the increase in specific surface area and the increase in the reaction with the electrolyte caused by the excessive number of small particles will not be increased, thereby effectively reducing the gas production value of the positive electrode material during the charge and discharge process, ensuring the stability of the crystal structure of the positive electrode material during the charge and discharge process, and improving the cycle performance and safety performance of the positive electrode material. Preferably, the volume distribution median particle size D of the positive electrode material is 1 / 4 of the positive electrode material. v50 3μm~11μm.

[0033] In some embodiments, the number distribution median particle size D of the positive electrode material is n50 1.0 μm to 2.5 μm, optionally, the number distribution median particle size Dv50 of the positive electrode material can be specifically 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm and 2.5 μm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the number distribution median particle size Dv50 of the positive electrode material can be 1.0 μm, 1.1 μm, 1.2 μm, 1.3 μm, 1.4 μm, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2.0 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm and 2.5 μm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. n50 Within the above range, the number of large particles and small particles is appropriate. In the process of preparing the positive electrode sheet, the small particles can effectively fill the gaps between the large particles, thereby improving the compaction density of the positive electrode sheet. Moreover, the increase in specific surface area and the increase in electrolyte reaction caused by the excessive number of small particles will not effectively reduce the gas production value of the positive electrode material during the charge and discharge process, thereby ensuring the crystal structure stability of the positive electrode material during the charge and discharge process and improving the cycle performance and safety performance of the positive electrode material. Preferably, the median particle size D of the positive electrode material is 1 / 4 of the positive electrode material. n50 It is 1.1μm~2.4μm.

[0034] In some embodiments, the true density p of the positive electrode material is 4.5 g / cm 3 ~4.8g / cm 3 Optionally, the true density ρ of the positive electrode material can be 4.5 g / cm 3 , 4.6g / cm 3 , 4.7g / cm 3 and 4.8g / cm 3It can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that when the true density of the positive electrode material is within the above range, the contact between the positive electrode material particles is relatively close, and the transmission of lithium ions during the charge and discharge process is smoother, resulting in a decrease in the impedance of the positive electrode material, which can improve the efficiency of lithium ion insertion and extraction, reduce the polarization phenomenon of the positive electrode material, ensure the normal performance of the battery capacity, and improve the charge and discharge efficiency of the battery. Preferably, the true density ρ of the positive electrode material is 4.6g / cm 3 ~4.7g / cm 3 .

[0035] In some embodiments, the angle of repose α of the positive electrode material is 0.70rad to 1.22rad. Optionally, the angle of repose α of the positive electrode material can be 0.7rad, 0.8rad, 0.9rad, 1.0ad, 1.1ad, 1.2rad, 1.22ad, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that the angle of repose is related to the fluidity of the positive electrode material particles. The angle of repose of the positive electrode material of the present application is within the above range, which can improve the fluidity of the positive electrode material particles and further reduce the gaps between adjacent positive electrode material particles to improve the compaction density of the positive electrode sheet prepared from the positive electrode material. Preferably, the angle of repose α of the positive electrode material is 0.87rad to 1.05rad.

[0036] In some embodiments, the positive electrode material has the general chemical formula Li a Ni x Co y M z D b O2, 0.9≤a≤1.05, 0.5≤x≤1, 0≤y≤0.5, 0≤b≤0.3, x+y+z+b=1; wherein M is selected from at least one of Mn and Al, and D is a doping element. The type of positive electrode material can be selected according to actual needs and is not limited here. Preferably, 0.95≤a≤1.01, 0.6≤x≤0.98, 0≤y≤0.2, and 0≤b≤0.2.

[0037] Specifically, the value of a can be 0.95, 0.98, 0.99, 1.0, 1.01, 1.03, 1.035, 1.04 or 1.05, etc., the value of x can be 0.5, 0.6, 0.7, 0.8, 0.85, 0.9, 0.92, 0.93, 0.95, 0.98 or 1, etc., the value of y can be 0, 0.05, 0.08, 0.1, 0.15, 0.2, 0.25, 0.3 or 0.5, etc., and the value of b can be 0, 0.01, 0.05, 0.1, 0.2, 0.25, 0.28 or 0.3, etc., and of course it can also be other values ​​within the above range, which is not limited here. It should be noted that the content of each element in the positive electrode material can be measured by a known instrument for qualitative analysis and / or quantitative analysis of each element, such as ICP and ICP-MS.

[0038] In some embodiments, the doping element D includes at least one of Ni, Co, Mn, Ta, Mo, W, Mg, La, Al, Y, Ti, Zr, V, Nb, Ce, Sr, and B. The type of doping element D can be selected according to actual needs and is not limited here. These doping elements can change the lattice constant of the positive electrode material or the valence state of the elements in the material, reduce cation mixing, improve the electronic conductivity and ionic conductivity of the material, improve the stability of the material structure, and inhibit the collapse of the positive electrode material crystal structure, thereby improving the cycle performance of the positive electrode material.

[0039] In some embodiments, the specific surface area of ​​the positive electrode material is 0.5 m 2 / g~1.0m 2 / g, optionally, the specific surface area of ​​the positive electrode material can be specifically 0.5m 2 / g, 0.6m 2 / g, 0.7m 2 / g, 0.8m 2 / g, 0.9m 2 / g and 1.0m 2 / g, etc., and can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the specific surface area of ​​the positive electrode material within the above range can provide more embedding sites for lithium ions, thereby increasing the capacity of the lithium ion battery. Preferably, the specific surface area of ​​the positive electrode material is 0.7m 2 / g~0.9m 2 / g.

[0040] In some embodiments, the positive electrode material includes a plurality of primary particles, and the average particle size of the primary particles is 2.0 μm to 2.2 μm. Optionally, the average particle size of the primary particles can be 2.0 μm, 2.03 μm, 2.06 μm, 2.09 μm, 2.12 μm, 2.15 μm, 2.18 μm and 2.2 μm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It is understandable that when the average particle size of the primary particles is within the above range, the compaction density of the positive electrode sheet prepared from the positive electrode material is high, and the contact area between adjacent primary particles of the positive electrode material is increased, which can accelerate the conduction rate of lithium ions and enhance the ionic conductivity of the positive electrode material.

[0041] In some embodiments, the particle size range of the primary particles is less than 2 μm. Optionally, the particle size range of the primary particles can be specifically 1.99 μm, 1.8 μm, 1.6 μm, 1.4 μm, 1.2 μm and 1 μm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the range of the primary particles is within the above range, the difference in particle size between the large primary particles and the small primary particles will not be too large, reducing the inconsistent charge and discharge rates caused by the large difference in the particle size of the primary particles. Since the small primary particles have high reaction activity and aggravate the side reactions with the electrolyte, controlling the particle size range of the primary particles within the above range is beneficial to improving the capacity of the positive electrode material, reducing the reaction between the positive electrode material and the electrolyte during charging and discharging, reducing the gas production value, and thus ensuring the cycle performance and safety performance of the positive electrode material.

[0042] In some embodiments, in the particle size distribution pattern of the positive electrode material, the volume particle size distribution curve of the positive electrode material is normally distributed. It can be understood that the particle size of the positive electrode material is normally distributed, which reduces the micropowder defects caused by the large difference in the particle size of the positive electrode material particles (that is, small particles exist on the surface of the particles, resulting in the intensified reaction between the positive electrode material and the electrolyte), thereby reducing the reaction between the positive electrode material and the electrolyte during the charge and discharge process, reducing the gas production value, and thus ensuring the cycle performance and safety performance of the positive electrode material.

[0043] In some embodiments, the actual electrode sheet compaction density of the positive electrode material at a pressure of 3T is P 实 , of which 0.75P 等 ≤P 实 ≤1.3P 等 It can be understood that according to the ratio range of the actual electrode sheet compaction density and the equivalent density calculated value mentioned above, the electrode sheet compaction density of the positive electrode material that meets the preparation requirements can be selected, which can reduce the adverse effects of the compaction density deviation caused by process errors in the preparation process of the positive electrode material, and further ensure that the electrode sheet compaction density of the positive electrode material meets the production requirements.

[0044] In some embodiments, the primary particles have a single crystal structure, that is, the positive electrode material is a single crystal positive electrode material. It is understood that primary particles with a single crystal structure have advantages such as high mechanical strength and small specific surface area. The high mechanical strength can ensure that the primary particles can withstand greater mechanical pressure than polycrystalline positive electrode material particles, reducing the probability of positive electrode material particle breakage, thereby increasing the compaction density of the positive electrode material. The small specific surface area can effectively reduce the contact between the positive electrode material and the electrolyte, reduce the probability of side reactions, and reduce the consumption of lithium ions due to side reactions, thereby improving the electrochemical performance of the positive electrode material. At the same time, the high orientation of the primary particles with a single crystal structure can effectively reduce intergranular cracks caused by anisotropic stress, further reduce side reactions between the positive electrode material and the electrolyte, and enhance interfacial stability. It can effectively reduce the irreversible phase transition of the positive electrode material from a layered structure to a rock salt phase structure, thereby improving the structural stability and cycle performance of the positive electrode material.

[0045] It should be noted that the difference between single-crystal cathode materials and polycrystalline cathode materials (i.e., polycrystalline secondary particles) is that polycrystalline secondary particles are secondary particles whose smallest particles are aggregates of nanometer-sized primary particles. In contrast, the smallest particles of single-crystal cathode materials are typically micrometer-sized individual primary particles. Generally speaking, in addition to EBSD testing, characterization methods such as scanning electron microscopy (SEM) can also be used to determine whether the resulting cathode product is a single-crystal material. For example, for single-crystal cathode materials, the morphology of single-crystal particles can be characterized by SEM. It can be seen that the appearance of single-crystal particles generally appears as regular or irregular polyhedrons or spheres, with no significant particle agglomeration. EBSD can also be used to characterize the orientation of single-crystal cathode materials. EBSD can be used to observe that the color within at least one grain is the same, which indicates that the orientation within at least one grain is the same. Grains with the same orientation are single crystals. It should be noted that the term "single-crystal cathode material" as known to those skilled in the art is not a "single crystal" in the strict crystallographic sense. In crystallography, an ideal single crystal refers to a crystal with completely identical arrangement and orientation. However, due to limitations in impurities, strain, and crystal defects, ideal single crystals are extremely rare and difficult to produce in the laboratory. Therefore, the single crystal cathode materials known in the art are actually more like "single crystal-like" cathode materials, which differ only in size from polycrystals, which are composed of numerous small primary particles, due to their large single crystal-like particles.

[0046] In a second aspect, the present application provides a method for preparing a positive electrode material, the preparation method comprising the following steps:

[0047] Step S10, performing a staged sintering process on a mixture containing a cathode material precursor and a lithium source to obtain a matrix material; wherein the staged sintering process includes a first stage, a second stage, and a third stage performed sequentially, wherein the sintering temperature T1 of the first stage is 100° C. to 300° C., the sintering temperature T2 of the second stage is 400° C. to 800° C., and the sintering temperature T3 of the third stage is 700° C. to 1000° C.;

[0048] Step S20 , after mixing the base material and the coating agent, performing a secondary sintering process, and performing a micron-sized particle dissociation process on the secondary sintered product to obtain a positive electrode material.

[0049] In the above scheme, the preparation method of the positive electrode material provided in the present application is obtained through a staged sintering treatment and a micron-sized particle dissociation treatment (i.e., the process of dissociating the secondary sintering product to obtain micron-sized particles) to obtain a positive electrode material in which the volume particle size distribution width, the median particle size of the number distribution, the true density, the degree of dissociation, the median particle size of the volume distribution, the angle of repose and the electrode compaction density satisfy a balanced relationship. While ensuring that the positive electrode material has a certain electrode compaction density to improve the energy density, it ensures the integrity of the crystal structure of the positive electrode material during the charge and discharge process of the lithium-ion battery, reduces the gas production value, and makes the positive electrode material also have excellent cycle performance and safety performance.

[0050] The preparation method of the present application is explained in detail below with reference to the examples:

[0051] In step S10, the mixture containing the positive electrode material precursor and the lithium source is subjected to a staged sintering treatment to obtain a matrix material; wherein the staged sintering treatment includes a first stage, a second stage and a third stage performed in sequence, the sintering temperature T1 of the first stage is 100°C to 300°C, the sintering temperature T2 of the second stage is 400°C to 800°C, and the sintering temperature T3 of the third stage is 700°C to 1000°C.

[0052] In some embodiments, the cathode material precursor includes Ni x Co y M 1-x-y oxides and Ni x Co y M 1-x-y At least one of the hydroxides of , wherein 0.33≤x<1, 0≤y≤0.33, M is selected from at least one of Mn and Al, and the type of positive electrode material precursor can be selected according to actual needs and is not limited here.

[0053] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate. The type of lithium source can be selected according to actual needs and is not limited here.

[0054] In some embodiments, the molar ratio of the positive electrode material precursor to the lithium source is 1:(1~1.06). Optionally, the molar ratio of the positive electrode material precursor to the lithium source can be 1:1, 1:1.01, 1:1.02, 1:1.03, 1:1.04, 1:1.05 and 1:1.06, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0055] In some embodiments, the mixture further includes an additive, and the elements in the additive include at least one of Ni, Co, Mn, Ta, Mo, W, Mg, La, Al, Y, Ti, Zr, V, Nb, Ce, Sr and B. The elements contained in the additive can be selected according to actual needs and are not limited here.

[0056] In some embodiments, the mixture also includes additives, and the mass ratio of the positive electrode material precursor to the additive is 100:(0.05~0.40). Optionally, the mass ratio of the positive electrode material precursor to the additive can be 100:0.05, 100:0.10, 100:0.15, 100:0.20, 100:0.25, 100:0.30, 100:0.35 and 100:0.40, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0057] In some embodiments, the graded sintering process is performed in an oxygen-containing atmosphere.

[0058] In some embodiments, the heating rate of the first stage is V1, the heating rate of the second stage is V2, the heating rate of the third stage is V3, and 0<V3<V2<V1<5°C / min.

[0059] In some embodiments, the insulation time t1 of the first stage is 1h to 2h. Optionally, the insulation time of the first stage can be 1h, 1.2h, 1.4h, 1.6h, 1.8h and 2h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0060] In some embodiments, the insulation time t2 of the second stage is optional, and 4h to 6h. The insulation time of the second stage can specifically be 4h, 4.2h, 4.4h, 4.6h, 4.8h, 5h, 5.2h, 5.4h, 5.6h, 5.8h and 6h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0061] In some embodiments, the insulation time t3 of the third stage is optional, and 5h to 10h. The insulation time of the third stage can be specifically 5h, 6h, 7h, 8h, 9h and 10h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0062] In some embodiments, the staged sintering process further includes: crushing the base material, wherein the volume distribution median particle size Dv of the crushed product is 50 3.3μm~4.0μm, optionally, the volume distribution median particle size Dv of the crushed product 50 Specifically, it can be 3.3μm, 3.4μm, 3.5μm, 3.6μm, 3.7μm, 3.8μm, 3.9μm and 4.0μm, etc., or other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the volume distribution median particle size Dv of the crushed product is 50 Within the above range, the particles of the matrix material are uniform, which facilitates subsequent coating treatment and micron-sized particle dissociation treatment.

[0063] In some embodiments, the median particle size D of the crushed product is n50 0.6μm~2.5μm, optionally, the number distribution median particle size D of the crushed product n50 Specifically, it can be 0.6μm, 0.8μm, 1μm, 1.2μm, 1.4μm, 1.6μm, 1.8μm, 2.0μm, 2.2μm, 2.4μm and 2.5μm, etc. It can also be other values ​​within the range, which can be selected according to actual needs and are not limited here. It can be understood that the median particle size D of the crushed product is n50 Within the above range, the particles of the matrix material are uniform, which facilitates subsequent coating treatment and micron-sized particle dissociation treatment.

[0064] In some embodiments, the crushing process is gas crushing, and the pressure range of the gas crushing process is 0.3MPa to 0.8MPa. Optionally, the pressure range of the gas crushing process can be 0.3MPa, 0.4MPa, 0.5MPa, 0.6MPa, 0.7MPa and 0.8MPa, or other values ​​within the range. It can be selected according to actual needs and is not limited here. It can be understood that when the pressure range of the gas crushing process is within the above range, the volume distribution median particle size Dv50 and the number distribution median particle size D n50 Can meet the required requirements.

[0065] In some embodiments, the gas pulverization frequency is between 35 Hz and 60 Hz. Optionally, the gas pulverization frequency can be 35 Hz, 40 Hz, 45 Hz, 46 Hz, 47 Hz, 48 Hz, 49 Hz, 50 Hz, and 60 Hz, or other values ​​within this range. This frequency can be selected based on practical needs and is not limited herein. It is understood that the pulverization frequency will affect the particle size of the substrate material after gas pulverization. The preparation method of the present application employs a pulverization frequency within this range, resulting in particles of a moderate size, which facilitates subsequent coating processing.

[0066] Step S20 , after mixing the base material and the coating agent, performing a secondary sintering process, and performing a micron-sized particle dissociation process on the secondary sintered product to obtain a positive electrode material.

[0067] In some embodiments, the elements in the coating agent include at least one of Ni, Co, Mn, Ta, Mo, W, Mg, La, Al, Y, Ti, Zr, V, Nb, Ce, Sr and B. The elements in the coating agent can be selected according to actual needs and are not limited here.

[0068] In some embodiments, the mass ratio of the base material to the coating agent is 100:(0.05~3.0). Optionally, the mass ratio of the base material to the coating agent can be 100:0.05, 100:0.06, 100:0.07, 100:0.08, 100:0.09, 100:0.10, 100:0.20, 100:0.30, 100:0.40, 100:0.50, 100:1.0, 100:1.5, 100:2.0, 100:2.5 and 100:3.0, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0069] In some embodiments, the secondary sintering process is performed in an oxygen-containing atmosphere.

[0070] In some embodiments, the heating rate V4 of the secondary sintering treatment is 2°C / min to 8°C / min. Optionally, the heating rate V4 of the secondary sintering treatment can be 2°C / min, 3°C / min, 4°C / min, 5°C / min, 6°C / min, 7°C / min and 8°C / min, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0071] In some embodiments, the sintering temperature T4 of the secondary sintering treatment is 350°C to 600°C. Optionally, the sintering temperature T4 of the secondary sintering treatment can be specifically 350°C, 380°C, 410°C, 440°C, 470°C, 500°C, 530°C, 560°C, 590°C and 600°C, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0072] In some embodiments, the holding time t4 of the secondary sintering treatment is 5h to 10h. Optionally, the holding time t4 of the secondary sintering treatment can be 5h, 6h, 7h, 8h, 9h and 10h, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0073] In some embodiments, the micron-sized particle dissociation process includes a grinding process, and the grinding frequency of the grinding process is 20 Hz to 50 Hz. Optionally, the grinding frequency of the grinding process can be specifically 20 Hz, 25 Hz, 30 Hz, 35 Hz, 40 Hz, 45 Hz and 50 Hz, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0074] In some embodiments, the spacing between the grinding discs during grinding is 30 μm to 150 μm. Optionally, the spacing between the grinding discs during grinding can be 30 μm, 40 μm, 50 μm, 60 μm, 70 μm, 80 μm, 90 μm, 100 μm, 110 μm, 120 μm, 130 μm, 140 μm and 150 μm, etc., or other values ​​within the range. It can be selected according to actual needs and is not limited here.

[0075] In some embodiments, the preparation method further comprises: performing screening and demagnetization processes on the secondary sintered product to obtain a positive electrode material.

[0076] In a third aspect, the present application provides a battery. An embodiment of the present application further provides a battery. FIG1 is a schematic diagram of the discharge state of the battery provided in an embodiment of the present application. As shown in FIG1 , the battery includes a housing and an electrode assembly. The electrode assembly includes a positive electrode sheet 1, a negative electrode sheet 2, and a separator 3. The separator 3 is disposed between the positive electrode sheet 1 and the negative electrode sheet 2. The electrode assembly can be a laminated structure, which is formed by alternatingly stacking the positive electrode sheet 1, the separator 3, and the negative electrode sheet 2 in sequence. In other embodiments, the electrode assembly can also be a wound structure, which is formed by stacking the positive electrode sheet, the separator, and the negative electrode sheet in sequence and then winding them.

[0077] In some embodiments, the positive electrode sheet 1 includes a positive electrode current collector 101 and a positive electrode active layer 102 disposed on at least one surface of the positive electrode current collector 101 .

[0078] In some embodiments, the positive electrode current collector 101 may be aluminum foil or nickel foil, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil (aluminum foil or nickel foil, etc.) and a polymer substrate. The positive electrode active layer 102 comprises the positive electrode material of the first aspect described above or the positive electrode material prepared by the above-described preparation method.

[0079] In some embodiments, the negative electrode sheet 2 includes a negative electrode current collector 201 and a negative electrode active material layer 202 disposed on at least one surface of the negative electrode current collector.

[0080] In some embodiments, the negative electrode current collector 201 can be made of at least one of copper foil, nickel foil, stainless steel foil, titanium foil, or a carbon-based current collector, or any composite current collector disclosed in the prior art, such as, but not limited to, a current collector formed by combining the aforementioned conductive foil and a polymer substrate. The negative electrode active material layer 202 includes a negative electrode material, which includes at least one of a silicon negative electrode material, a silicon-carbon negative electrode material, and a graphite negative electrode material.

[0081] The battery provided in the embodiments of the present application has the advantages of high capacity, high initial efficiency, long cycle life, excellent rate performance, and low expansion. The battery can be a lithium-ion battery, a sodium-ion battery, a solid electrolyte battery, etc., without limitation.

[0082] 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.

[0083] Example 1

[0084] (1) Ni 0.6 Co 0.1 Mn 0.3 (OH)2, Li2CO3 and ZrO2 were uniformly mixed in a molar ratio of 1:1.03:0.0026, and a staged sintering treatment was performed under an oxygen atmosphere according to the following sintering parameters to obtain a staged sintering treatment product: the heating rate of the first stage was 5°C / min, the sintering temperature was 300°C, and the holding time was 1 h; the heating rate of the second stage was 3°C / min, the sintering temperature was 800°C, and the holding time was 5 h; the heating rate of the third stage was 1.5°C / min, the sintering temperature was 950°C, and the holding time was 8 h;

[0085] (2) The stepwise sintered product was subjected to roller, gas crushing, and sieving processes to obtain a matrix material, wherein the volume distribution median particle size Dv50 of the matrix material was 3.7 μm; wherein the gas pressure range set during gas crushing was 0.55 MPa, and the grading frequency was 40 Hz;

[0086] (3) the matrix material was mixed with Al2O3 and WO3 in a weight ratio of 1:0.002:0.003, and then subjected to secondary sintering in an oxygen atmosphere to obtain a secondary sintered product; wherein the secondary sintering process had a heating rate of 2°C / min, a sintering temperature of 500°C, and a holding time of 6 h;

[0087] (4) The secondary sintered product is subjected to dynamic dissociation of micron-sized particles, the grinding frequency of the equipment is set to 25 Hz, and the grinding disc spacing is set to 40 μm to obtain a crushed product, which is then screened and demagnetized to obtain the positive electrode material.

[0088] Example 2

[0089] The difference from Example 1 is that Li2CO3 is replaced by LiOH.

[0090] Example 3

[0091] The difference from Example 1 is that the cathode material precursor is Ni 0.5 Co 0.2 Mn 0.3 (OH)2, and the sintering temperature of the third stage is 970℃.

[0092] Example 4

[0093] The difference from Example 1 is that the positive electrode material precursor is Ni0 .7 Co 0.1 Mn 0.2 (OH)2, and the sintering temperature of the third stage is 930℃.

[0094] Example 5

[0095] The difference from Example 1 is that the cathode material precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH)2, and the sintering temperature of the third stage is 900℃.

[0096] Example 6

[0097] The difference from Example 1 is that the heating rate in the first stage is 3° C. / min.

[0098] Example 7

[0099] The difference from Example 1 is that the heating rate in the second stage is 1.5° C. / min.

[0100] Example 8

[0101] The difference from Example 1 is that the heating rate in the third stage is 3° C. / min.

[0102] Example 9

[0103] The difference from Example 1 is that the cathode material precursor is Ni 0.8 Co 0.1 Mn 0.1 (OH)2, the sintering temperature of the first stage is 100℃, the sintering temperature of the second stage is 400℃, and the sintering temperature of the third stage is 800℃.

[0104] Example 10

[0105] The difference from Example 1 is that the sintering temperature of the first stage is 300°C, the sintering temperature of the second stage is 800°C, and the sintering temperature of the third stage is 1000°C.

[0106] Example 11

[0107] The difference from Example 1 is that the holding time of the first stage is 1 hour, the holding time of the second stage is 4 hours, and the holding time of the third stage is 5 hours.

[0108] Example 12

[0109] The difference from Example 1 is that the holding time of the first stage is 2 hours, the holding time of the second stage is 6 hours, and the holding time of the third stage is 10 hours.

[0110] Example 13

[0111] The difference from Example 1 is that the holding time of the first stage is 0.5 h, the holding time of the second stage is 3 h, and the holding time of the third stage is 4 h.

[0112] Example 14

[0113] The difference from Example 1 is that the insulation time of the first stage is 3 hours, the insulation time of the second stage is 7 hours, and the insulation time of the third stage is 11 hours.

[0114] Example 15

[0115] The difference from Example 1 is that the gas pressure range of the gas crushing treatment is 0.3 MPa, the classification frequency is 35 Hz, and the volume distribution median particle size Dv50 of the obtained matrix material is 3.8 μm.

[0116] Example 16

[0117] The difference from Example 1 is that the gas pressure range of the gas crushing treatment is 0.8 MPa, the classification frequency is 60 Hz, and the volume distribution median particle size Dv50 of the obtained matrix material is 3.5 μm.

[0118] Example 17

[0119] The difference from Example 1 is that the gas pressure range of the gas crushing treatment is 0.1 MPa, the classification frequency is 30 Hz, and the volume distribution median particle size Dv50 of the obtained matrix material is 4 μm.

[0120] Example 18

[0121] The difference from Example 1 is that the gas pressure range of the gas crushing treatment is 0.9 MPa, the classification frequency is 65 Hz, and the volume distribution median particle size Dv50 of the obtained matrix material is 3.3 μm.

[0122] Example 19

[0123] The difference from Example 1 is that the grinding frequency for dynamic dissociation of micron-sized particles is 20 Hz, and the grinding disc spacing is 30 μm.

[0124] Example 20

[0125] The difference from Example 1 is that the grinding frequency for dynamic dissociation of micron-sized particles is 50 Hz, and the grinding disc spacing is 150 μm.

[0126] Example 21

[0127] The difference from Example 1 is that the grinding frequency for dynamic dissociation of micron-sized particles is 10 Hz, and the grinding disc spacing is 20 μm.

[0128] Example 22

[0129] The difference from Example 1 is that the grinding frequency for dynamic dissociation of micron-sized particles is 70 Hz, and the grinding disc spacing is 170 μm.

[0130] Example 23

[0131] The differences from Example 1 are as follows: the first stage sintering temperature is 300°C, the holding time is 1 hour; the second stage sintering temperature is 800°C, the holding time is 4 hours; the third stage sintering temperature is 1000°C, the holding time is 5 hours. The gas pressure range of the gas crushing process is 0.9 MPa, and the classification frequency is 65 Hz.

[0132] Comparative Example 1

[0133] The difference from Example 1 is that a single sintering process is performed, but a staged sintering process is not performed, wherein the heating rate of the single sintering process is 3° C. / min, the sintering temperature is 950° C., and the holding time is 8 h.

[0134] Comparative Example 2

[0135] The difference from Example 1 is that a single sintering process is performed, but a staged sintering process is not performed, wherein the heating rate of the single sintering process is 1.5° C. / min, the sintering temperature is 950° C., and the holding time is 6 h.

[0136] Comparative Example 3

[0137] The difference from Example 1 is that the secondary sintered product is not subjected to dynamic dissociation treatment of micron-sized particles.

[0138] Comparative Example 4

[0139] The difference from Example 5 is that the cathode material precursor Ni 0.8 Co 0.1 Mn 0.1 The Dv50 of large particles in (OH)2 is 11.0 μm, the Dv50 of small particles is 3.0 μm, and the ratio of large particles to small particles is 9:1.

[0140] Comparative Example 5

[0141] The difference from Example 5 is that the cathode material precursor Ni 0.8 Co 0.1 Mn 0.1 The Dv50 of large particles in (OH)2 is 11.0μm, the Dv50 of small particles is 3.0μm, and the ratio of large particles to small particles is 1:9. A single sintering treatment is performed, but no segmented sintering treatment is performed. The heating rate of the single sintering treatment is 3℃ / min, the sintering temperature is 900℃, and the holding time is 8h. The secondary sintering product in Comparative Example 5 is not subjected to dynamic dissociation treatment of micron-sized particles.

[0142] Test method description:

[0143] Actual compaction density test: A Carver 4350L was used for the compaction test. After the instrument was calibrated, 1g of material was weighed and placed into the mold. The mold was then fitted with a push rod and placed into the manual compaction density meter. After 30 seconds, the sample was removed and the pressure was released after pressing the push rod for another 30 seconds. The data was then recorded.

[0144] Cathode material true density test: Use a 3H-2000TD fully automatic true density meter. After calibrating the instrument, weigh 7g of material and add it to the sample tube. After setting the number of sample rinses, click Start Test. After the test is completed, record the data.

[0145] Positive electrode material specific surface area test: The dynamic specific surface area rapid tester JW-DX of Beijing Jingwei Gaobo Science and Technology Co., Ltd. is used for testing, and the unit is m 2 / g.

[0146] Positive electrode material repose angle test: The material is slowly added from 5 cm above the funnel. The material falls through the funnel onto a horizontal metal plate to form a cone. When the surface of the powder slides, the angle between the cone surface and the bottom surface is measured, which is the material's repose angle.

[0147] The volume distribution median particle size and number distribution median particle size test of the positive electrode material: The test was carried out using MS3000, the sample mass was 3g, the dispersant was 2-3 drops of sodium hexametaphosphate, the ultrasonic time was 30s, and the volume distribution particle size D was obtained. v 10. D v50 、D v 90 and the volume particle size distribution curve, according to the formula Calculate the Span value; the volume distribution median particle size D v50 The median particle size Dn50 was obtained after conversion in MS3000.

[0148] Average particle size and particle size range testing for primary particles: Five SEM images of the sample at 3000x magnification were taken using a Hitachi S4800 scanning electron microscope. NanoMeasure software was then used to measure at least 200 particles within the SEM images to determine the average particle size. Software analysis revealed that the maximum particle size minus the minimum particle size determined the particle size range.

[0149] Capacity, rate, and cycle are measured using button batteries:

[0150] The positive electrode material and SP:PVDF glue were mixed in a mass ratio of 93:5:2 and then evenly slurried. The slurry was then evenly coated on a 16μm-thick aluminum foil and dried in a 100°C oven for 12 hours. A 16mm-diameter, 1mm-thick lithium metal sheet was used as the negative electrode. A 20μm-thick polyethylene porous membrane was used as the separator. The electrolyte was a mixture of equal parts ethylene carbonate (EC) and diethyl carbonate (DEC) with 1 mol / L LiPF6. The positive electrode sheet, separator, negative electrode sheet, and electrolyte were assembled into a 2016-type button cell in an Ar glove box with water and oxygen concentrations below 5ppm.

[0151] Capacity test: The electrical performance test was conducted using a blue electric test system (charge and discharge voltage of 2.8-4.35V, temperature condition of 25°C), 0.1C charge, 0.1C discharge, constant voltage cutoff current of 0.005C, and the discharge capacity (CmAh / g) was calculated based on the discharge capacity.

[0152] Cycle test: At 25°C, with a charge and discharge voltage of 2.8-4.35V, charge at 0.5C and discharge at 1C for 50 cycles, with a constant voltage cutoff current of 0.05C. The final capacity retention rate after 50 cycles is the cycle performance.

[0153] Test results:

[0154] Table 1

[0155] Table 2

[0156] Test result analysis:

[0157] According to the test results of Examples 11 to 23 of the present application, the degree of dissociation of the positive electrode material is controlled within the range of 1.1 to 1.8, and the Span value of the positive electrode material is controlled within the range of 0.9 to 1.5. This can ensure the width of the positive electrode material particle size distribution, help improve the compaction density, and at the same time ensure the degree of dissociation of the positive electrode material, reduce the soft agglomeration of particles, and improve the capacity and cycle performance of the positive electrode material. The positive electrode material provided by this application can have high capacity, excellent cycle performance and high energy density.

[0158] From the test results of Example 1 and Examples 2 to 5, it can be seen that under the premise of keeping the same preparation process conditions in the present application, the compaction density of the positive electrode material obtained by using different positive electrode material precursors or lithium sources is at a higher level, and P 等 The volume particle size distribution width Span and the number distribution median particle size D n50 The relationship between true density ρ, dissociation degree β and repose angle α can still satisfy formula (I), 3.2≤P 等 Under the condition of ≤3.7, the positive electrode material can be guaranteed to have a suitable compaction density to improve the energy density, and the integrity of the crystal structure of the positive electrode material during the charge and discharge process of the lithium-ion battery can be guaranteed, the gas production value can be reduced, and the cycle performance or safety performance of the positive electrode material can be better. And the volume particle size distribution width Span and the number distribution median particle size D can be controlled. n50 , true density ρ, dissociation degree β and repose angle α are within the scope of this application, and the cathode material's pole sheet compaction density P 等 Meet the preferred range: 3.5≤P 等 ≤3.7.

[0159] The test results of Example 1 and Examples 6-8 show that during the preparation of the positive electrode material, when the heating rates in the first, second, and third stages satisfy 0 < V3 < V2 < V1 < 5°C / min, the prepared positive electrode material has a certain electrode sheet compaction density and good discharge capacity. In Examples 6-8, when the heating rates in the first, second, and third stages do not meet these limits, both the electrode sheet compaction density and discharge capacity are reduced.

[0160] The test results of Examples 1 and 9-10 show that during the preparation of the positive electrode material, when the sintering temperatures in the first, second, and third stages meet the requirements of T1 of 100°C to 300°C, T2 of 400°C to 800°C, and T3 of 700°C to 1000°C, respectively, the prepared positive electrode material has a certain electrode sheet compaction density and good discharge capacity. In Example 11, the sintering temperatures in the first, second, and third stages do not meet the above requirements. Excessively high sintering temperatures increase particle size, which results in reduced electrode sheet compaction density and discharge capacity.

[0161] The test results of Examples 1 and 11-12 show that during the preparation of the positive electrode material, when the holding times in the first, second, and third stages meet the requirements of t1 being 1-2 hours, t2 being 4-6 hours, and t3 being 5-10 hours, respectively, the prepared positive electrode material has a certain electrode sheet compaction density and a good discharge capacity. In Examples 14-15, the holding times in the first, second, and third stages do not meet the above requirements, resulting in a decrease in both the electrode sheet compaction density and the discharge capacity.

[0162] It can be seen from the test results of Example 1 and Examples 15 to 16 that during the preparation of the positive electrode material, when the air pressure range and the grading frequency of the base material during the crushing treatment meet 0.3MPa to 0.8MPa and 35Hz to 60Hz, the degree of dissociation of the obtained base material is within a reasonable range, and as the grading frequency increases, the amount of micropowder increases accordingly, the Span is significantly improved, but the compaction density of the electrode is slightly reduced. However, the increase in the amount of micropowder will cause the specific surface area of ​​the positive electrode material to increase slightly, the activity of the side reaction between the positive electrode material and the electrolyte is enhanced during the cycle, and the cycle performance is reduced.

[0163] In Examples 17 and 18, the pressure range and grading frequency of Example 17 were too small, resulting in a smaller span of the positive electrode material, which reduced the compaction density of the positive electrode material and slightly decreased the capacity of the positive electrode material. In Example 18, the pressure range and grading frequency were too large, resulting in a larger span of the positive electrode material. Although the compaction density of the positive electrode material increased, and the capacity of the positive electrode material increased, the increase in small particles of the positive electrode material intensified the side reaction between the positive electrode material and the electrolyte, resulting in a slight decrease in cycle performance.

[0164] The test results of Examples 1 and 19-20 show that during the preparation of the positive electrode material in Example 1, when the grinding frequency and grinding spacing for dynamic dissociation of micron-sized particles meet the range of 20 Hz to 50 Hz and 30 μm to 150 μm, the resulting positive electrode material has a reasonable degree of dissociation and compaction density. In Examples 21-22, the grinding disc spacing is too small and the grinding frequency is too large, resulting in excessive changes in the degree of friction between the particles of the secondary sintered product, a decrease in the compaction density of the electrode sheet, and the discharge capacity and cycle performance of the lithium-ion battery are affected.

[0165] From the test results of Example 1 and Example 23, it can be seen that during the preparation of the positive electrode material of Example 23, the sintering temperature and the holding time are both minimized, which limits the growth of the primary particles, thereby significantly reducing the median particle size Dv50 of the positive electrode material and increasing the angle of repose α; the grinding pressure and the classification frequency of the gas crushing are maximized, and the collision between the primary particles is intensified, but the primary particle size is small due to sintering (that is, the particle strength is high and it is not suitable to produce fine powder), so the Span is reduced to a certain extent. The span value of the obtained positive electrode material is 1.04, and the separation degree β is 1.31. However, due to the influence of the too small Dn50, the final obtained electrode compaction density P 等 It has decreased to 3.16, which does not meet the requirement of 3.2≤P 等 ≤3.7, the discharge capacity and cycle performance of lithium-ion batteries are also affected.

[0166] From the test results of Example 1 and Comparative Examples 1-2, it can be seen that in Comparative Examples 1-2, no staged sintering treatment is performed, and a one-stage heating rate is used for sintering. Regardless of whether the constant temperature time is extended or shortened, the degree of dissociation and Span of the positive electrode material particles are significantly smaller than the positive electrode material prepared in Example 1. Correspondingly, the discharge capacity and cycle performance also have obvious differences.

[0167] From the test results of Example 1 and Comparative Example 3, it can be seen that the dissociation degree of the positive electrode material obtained without the dynamic dissociation treatment of micron-sized particles is low, and soft agglomeration easily occurs between the particles, resulting in poor discharge capacity and cycle performance.

[0168] It can be seen from the test results of Example 5 and Comparative Example 4 that when the small particles in the positive electrode material account for a large proportion, the Span value increases slightly, but the fluidity of the resulting positive electrode material deteriorates, the angle of repose increases, the degree of dissociation is significantly reduced, and the small particles fill the gaps between the large particles. Although the electrode compaction density is significantly improved, at an excessively large electrode compaction density, large particles are prone to microcracks during the preparation of the positive electrode, and the specific surface area of ​​the positive electrode material increases, affecting the cycle performance of the lithium-ion battery.

[0169] From the test results of Example 5 and Comparative Example 5, it can be seen that when the large particles in the positive electrode material account for a large proportion of 90% and the particle size of the large particles is 13 μm, since the positive electrode material is a conventional high-nickel polycrystalline material, although it has not undergone dynamic dissociation treatment of micron-level particles, the dissociation degree of the polycrystalline positive electrode material itself is high, and the single sintering treatment adopts a one-stage heating rate, the compaction of the pole piece of the obtained positive electrode material is significantly reduced, which in turn affects the energy density of the lithium-ion battery.

[0170] The above describes in detail the structure, features and effects of the present application based on the embodiments shown in the drawings. The above is only a preferred embodiment of the present application, but the present application does not limit the scope of implementation to what is shown in the drawings. Any changes made in accordance with the concept of the present application, or modifications to equivalent embodiments with equivalent changes, which still do not exceed the spirit covered by the description and drawings, should be within the scope of protection of the present application.

Claims

1. A positive electrode material, characterized in that: The median particle size of the positive electrode material is D n50 μm, the volume particle size distribution width of the positive electrode material is Span, The degree of dissociation of the positive electrode material is β, The true density of the positive electrode material is ρg / cm 3 , the repose angle of the positive electrode material is αrad, P 等 is the calculated value of the equivalent density of the positive electrode material, in g / cm 3 ; Wherein, the positive electrode material satisfies at least one of the following relationships: 1), 1.1≤β<1.65, and 0.9≤Span≤1.53; 2), 2. The positive electrode material according to claim 1, characterized in that: The median particle size of the positive electrode material is D n50 μm, the true density of the positive electrode material is ρg / cm 3 , the repose angle of the positive electrode material is αrad, P 等 is the calculated value of the equivalent density of the positive electrode material, in g / cm 3 ; Among them, P 等 The volume particle size distribution width Span of the positive electrode material and the median particle size D of the number distribution of the positive electrode material n50 , the relationship between true density ρ, dissociation degree β and repose angle α satisfies:

3. The positive electrode material according to claim 1 or 2, characterized in that The volume particle size distribution width of the positive electrode material is Span, The degree of dissociation of the positive electrode material is β, Wherein, the positive electrode material satisfies the following relationship: 1.1≤β<1.65, and 0.9≤Span≤1.

53.

4. The positive electrode material according to claim 1, characterized in that: The chemical formula of the positive electrode material is Li a Ni x Co y M z D b O2, 0.9≤a≤1.05, 0.5≤x≤1, 0≤y≤0.5, x+y+z+b=1, 0≤b≤0.3; wherein M is selected from at least one of Mn and Al, and D includes at least one of Ni, Co, Mn, Ta, Mo, W, Mg, La, Al, Y, Ti, Zr, V, Nb, Ce, Sr and B.

5. The positive electrode material according to claim 1, characterized in that: The volume distribution median particle size D of the positive electrode material v50 3 μm to 15 μm; and / or, the number distribution median particle size D of the positive electrode material n50 It is 1.0μm~2.5μm.

6. The positive electrode material according to claim 1, characterized in that: The true density ρ of the positive electrode material is 4.5 g / cm 3 ~4.8g / cm 3 ; and / or, the repose angle α of the positive electrode material is 0.70rad~1.22rad.

7. The positive electrode material according to claim 1, characterized in that: The actual electrode sheet compaction density of the positive electrode material under 3T pressure is P 实 , of which 0.75P 等 ≤P 实 ≤1.3P 等 .

8. The positive electrode material according to claim 1, characterized in that: The positive electrode material includes a plurality of primary particles, and the positive electrode material has at least one of the following characteristics: (1) The primary particles have a single crystal structure; (2) The average particle size of the primary particles is 2.0 μm to 2.2 μm; (3) The particle size range of the primary particles is less than 2 μm.

9. The positive electrode material according to claim 1, characterized in that: The specific surface area of ​​the positive electrode material is 0.5 m 2 / g~1.0m 2 / g.

10. The positive electrode material according to claim 1, characterized in that: In the particle size distribution pattern of the positive electrode material, the volume particle size distribution curve of the positive electrode material presents a normal distribution.

11. A method for preparing a positive electrode material, characterized in that: The preparation method comprises the following steps: A mixture containing a positive electrode material precursor and a lithium source is subjected to a staged sintering process to obtain a matrix material; wherein the staged sintering process includes a first stage, a second stage and a third stage performed in sequence, the sintering temperature T1 of the first stage is 100°C to 300°C, the sintering temperature T2 of the second stage is 400°C to 800°C, and the sintering temperature T3 of the third stage is 700°C to 1000°C; After the base material and the coating agent are mixed, a secondary sintering process is performed, and the secondary sintering product is subjected to a micron-level particle dissociation process to obtain a positive electrode material.

12. The method for preparing the positive electrode material according to claim 11, characterized in that: The preparation method has at least one of the following characteristics: (1) The positive electrode material precursor includes Ni x Co y M 1-x-y Oxide and Ni x Co y M 1-x-y At least one of the hydroxides of , wherein 0.33≤x<1, 0≤y≤0.33, and M is selected from at least one of Mn and Al; (2) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate and lithium oxalate; (3) The molar ratio of the positive electrode material precursor to the lithium source is 1:(1-1.06); (4) The mixture also includes an additive, and the elements in the additive include at least one of Ni, Co, Mn, Ta, Mo, W, Mg, La, Al, Y, Ti, Zr, V, Nb, Ce, Sr and B; and / or the mass ratio of the positive electrode material precursor to the additive is 1: (0.05% to 0.40%).

13. The method for preparing the positive electrode material according to claim 11, characterized in that: The heating rate of the first stage is V1, the heating rate of the second stage is V2, the heating rate of the third stage is V3, and 0<V3<V2<V1<5℃ / min; and / or, The heat preservation time t1 of the first stage is 1 h to 2 h, the heat preservation time t2 of the second stage is 4 h to 6 h, and the heat preservation time t3 of the third stage is 5 h to 10 h.

14. The method for preparing the positive electrode material according to claim 11, characterized in that: The method further comprises crushing the base material, wherein the volume distribution median particle size Dv of the crushed product is 50 3.3 μm to 4.0 μm; and / or the number distribution median particle size D of the product of the crushing treatment n50 0.6μm~2.5μm.

15. 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 preparation method according to any one of claims 11 to 14.

Images