Lithium-ion battery positive electrode material, and preparation method therefor and use thereof

Abstract

The present invention relates to the technical field of lithium-ion battery materials, and specifically to a lithium-ion battery positive electrode material. The positive electrode material satisfies the following relational expression: P=(K*102)+[(C-100)*102 / L]^2, wherein P is the structural stress coefficient of the positive electrode material, and 2.51≤P≤12.00; K is the porosity of the positive electrode material, and 1%≤K≤10%; C is the grain size of the positive electrode material, and 100 nm≤C≤400 nm; L is the particle size D50 of the positive electrode material, and 8 μm≤L≤16 μm. Also provided is a preparation method for the lithium-ion battery positive electrode material. The positive electrode material has high battery capacity, excellent cycle performance, and good thermal stability and structural stability.

Description

A lithium-ion battery cathode material, its preparation method and application Technical Field

[0001] This invention relates to the field of lithium-ion battery materials technology, specifically to a lithium-ion battery cathode material, its preparation method, and its application. Background Technology

[0002] With the rapid development of the electric vehicle market, the requirements for the efficiency and safety performance of lithium-ion batteries are becoming increasingly stringent. As the most crucial component of lithium-ion batteries, the cathode material plays a vital role in their performance. Lithium-ion battery failure is often closely related to the thermal stability and particle breakage of the materials. Volume changes during charging and discharging lead to stress release within the material, ultimately causing particle breakage in the later stages of cycling, exacerbating side reactions in the lithium-ion battery, and creating safety hazards.

[0003] Research has revealed that the porosity, grain size, and particle size of cathode materials are closely related to internal stress. Current cathode materials typically adjust particle size and grain size through precursor design and sintering temperature, but effectively adjusting porosity is challenging. A common method is to adjust porosity by modifying the precursor fabrication process; however, many factors influence porosity during precursor preparation, making it difficult to maintain process stability and reliably control the size and distribution of porosity within the material.

[0004] Patent document CN117317209A discloses a cathode material and its preparation method, aiming to solve the problems of difficult porosity control and poor reproducibility of existing cathode materials. By controlling the porosity of the cathode material, the structural stability of the cathode material can be controlled, thereby improving the performance of the cathode material. However, this cathode material only considers battery capacity and cycle performance, without considering the thermal stability of the material, thus still failing to ensure its safety performance. Summary of the Invention

[0005] The technical problem to be solved by this invention is to overcome the shortcomings and defects mentioned in the background art above, and to provide a lithium-ion battery cathode material with high battery capacity, excellent cycle performance, good thermal stability and structural stability, as well as its preparation method and application. To solve the above technical problem, the technical solution proposed by this invention is: a lithium-ion battery cathode material, wherein the cathode material satisfies the following relationship: P = (K * 10 2 )+[(C-100)*10 2 / L]^2;

[0006] Where P is the structural stress coefficient of the cathode material, 2.51≤P≤12.00;

[0007] K is the porosity of the cathode material, 1%≤K≤10%;

[0008] C represents the grain size of the cathode material, where 100nm ≤ C ≤ 400nm;

[0009] L represents the particle size of the cathode material, D. 50 , 8μm≤L≤16μm.

[0010] In one embodiment, the cathode material matrix is ​​coated with element B, and the general chemical formula of the cathode material matrix is ​​Li. a Ni 1-x-y-z Co x M y N z O2, wherein M is Mn or Al, N is selected from at least one of Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn and Sb, and 0.90≤a≤1.20, 0≤x≤0.30, 0≤y≤0.30, 0≤z≤0.05, x+y+z≤0.30.

[0011] In one embodiment, the cathode material further contains sulfur (S) element, which accounts for 0.01% to 0.30% of the total mass of the cathode material.

[0012] Based on the same inventive concept, a method for preparing the lithium-ion battery cathode material as described above is also provided, comprising the following steps:

[0013] After the cathode material precursor, pore-forming agent and dopant are mixed at high speed, the mixture is heated to the first sintering temperature and then held for sintering. The mixture is then cooled to the holding temperature and held for sintering. Finally, it is naturally cooled to room temperature to obtain a first sintering intermediate.

[0014] The sintering intermediate is washed and dried to obtain a dried intermediate;

[0015] The dried intermediate was mixed with the coating agent to obtain a mixture. The mixture was heated to the second sintering temperature and then sintered for a second time. Finally, it was naturally cooled to room temperature to obtain the lithium-ion cathode material.

[0016] In one embodiment, the pore-forming agent is a sulfate or sulfate salt hydrate containing Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, wherein the molar ratio of sulfate to matrix in the pore-forming agent is 0.002 to 0.05; the dopant is an oxide, hydroxide, or carbonate containing at least one element selected from Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, wherein the molar ratio of metal element to matrix in the dopant is 0 to 0.05.

[0017] In one embodiment, during a single heat-holding sintering process, the temperature is increased to a first sintering temperature of 600-900°C at a rate of 1-5°C / min under an air or oxygen atmosphere, and then held for 8-20 hours. The temperature is then decreased to a holding temperature of 300-450°C at a rate of 0.5-2.5°C / min, and then held for 3-8 hours.

[0018] In one embodiment, during the washing and drying of the primary sintering intermediate, the primary sintering intermediate is washed with deionized water at a mass solid-liquid ratio of 1.0 to 3.0 for 1 to 15 minutes, filtered for 10 to 30 minutes until the moisture content is less than 10%, and then dried in a vacuum drying oven for 5 to 20 hours to obtain the dried intermediate.

[0019] In one embodiment, the coating agent is at least one of boric acid or boron oxide, and element B accounts for 0.01% to 0.30% of the total mass of the dried intermediate.

[0020] In one embodiment, during the secondary heat preservation sintering, the temperature is raised to 250°C-350°C at a second heating rate of 1-5°C / min under an oxygen or air atmosphere and held for sintering for 4-12 hours. After naturally cooling to room temperature, the lithium-ion cathode material is obtained by passing it through a 300-mesh sieve.

[0021] Based on the same inventive concept, an application is also provided: the application of the above-mentioned lithium-ion battery cathode material in lithium-ion batteries.

[0022] Compared with existing technologies, the beneficial effects of this invention are as follows: Through research and testing, the inventors discovered that the performance of lithium battery electrode materials is closely related to their microstructure parameters. These parameters include porosity, grain size, and particle size D. 50 Porosity is a key factor affecting structural stress and material properties. It directly affects the wetting degree of the electrolyte and the effective lithium-ion conductivity. Higher porosity results in a higher electrolyte phase volume fraction, more thorough electrolyte wetting, and a higher effective lithium-ion conductivity. This application experimentally discovered that when particle size and grain size are within a suitable range, as porosity increases, the compressive stress between particles is released spatially, which is beneficial for improving the structural stability of the cathode material; at a particle size D... 50 When porosity is within a suitable range, increasing grain size is beneficial to improving the crystallinity of the material, and also to its stability; however, when porosity and grain size are too large or too small, the structural stability of the cathode material will decrease. Therefore, the structural stress coefficient, porosity, grain size, and particle size D of the cathode material set according to this application are... 50By adjusting the relationship between the cathode material and its structural stress, the thermal stability and safety performance of the material can be enhanced. Furthermore, the cathode material preparation method provided in this application is simple and reliable. By adjusting the heating and cooling during the first sintering stage, the formation and uniform distribution of pores are facilitated, thereby further alleviating the internal structural stress of the material and preventing the pores at the precursor end from being unable to be inherited into the cathode material. In addition, by controlling the cooling rate and temperature of the cooling platform, the influence of dopants on the grain size of the material can be balanced, allowing this method to achieve the same beneficial effects when used with various different dopants. Moreover, the cathode material and its preparation method of this application can be flexibly used with various dopants in actual production, demonstrating high practical value. Attached Figure Description

[0023] To more clearly illustrate the technical solutions in the embodiments of the present invention or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of the present invention. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0024] Figure 1 is a SEM cross-sectional view of the cathode material in Embodiment 1 of this application;

[0025] Figure 2 is a SEM cross-sectional view of the cathode material in Embodiment 3 of this application;

[0026] Figure 3 is a SEM cross-sectional view of the cathode material in Comparative Example 1 of this application;

[0027] Figure 4 is a SEM cross-sectional view of the cathode material in Comparative Example 2 of this application;

[0028] Figure 5 is a SEM cross-sectional view of the cathode material in Embodiment 6 of this application. Detailed Implementation

[0029] To facilitate understanding of the present invention, the present invention will be described more fully and in detail below with reference to the accompanying drawings and preferred embodiments, but the scope of protection of the present invention is not limited to the following specific embodiments.

[0030] Unless otherwise defined, all technical terms used herein have the same meaning as commonly understood by those skilled in the art. The technical terms used herein are for the purpose of describing particular embodiments only and are not intended to limit the scope of the invention.

[0031] Unless otherwise specified, all raw materials, reagents, instruments and equipment used in this invention can be purchased from the market or prepared by existing methods.

[0032] Please refer to Figures 1-5, which illustrate a lithium-ion battery cathode material according to one embodiment. This cathode material satisfies the following relationship: P = (K * 10 2 )+[(C-100)*10 2 / L]^2;

[0033] Wherein, P is the structural stress coefficient of the cathode material, 2.51≤P≤12.00; this structural stress coefficient is related to porosity, grain size and particle size D50, and affects the structural stress and performance of the cathode material.

[0034] K is the porosity of the cathode material, 1%≤K≤10%;

[0035] C represents the grain size of the cathode material, where 100nm ≤ C ≤ 400nm;

[0036] L represents the particle size of the cathode material, D. 50 , 8μm≤L≤16μm.

[0037] In calculations, nanometers are used as the unit of measurement.

[0038] In the aforementioned lithium-ion battery cathode materials, the porosity, grain size, and particle size D are analyzed. 50 The relevant parameters are adjusted to satisfy the above relationship to ensure that the cathode material has suitable porosity, grain size, and particle size D. 50 Furthermore, the structural stress coefficient value obtained by calculation based on the relationship is within a suitable range, which can achieve reasonable control of the structural stress of the cathode material, enhance the capacity and cycle performance of the cathode material, and obtain cathode materials with excellent thermal stability and safety performance.

[0039] Specifically, in one embodiment, the positive electrode material has the general chemical formula Li. a Ni 1-x-y-z Co x M y N z O2, wherein M is Mn or Al, N is selected from at least one of Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn and Sb, and 0.90≤a≤1.20, 0≤x≤0.30, 0≤y≤0.30, 0≤z≤0.05, x+y+z≤0.30.

[0040] Specifically, in one embodiment, the cathode material further contains sulfur (S) element, which accounts for 0.01% to 0.30% of the total mass of the cathode material. The uniform distribution of S element in the cathode material can change the grain growth direction during sintering, thereby increasing the gap between particles.

[0041] This application also provides a method for preparing the above-mentioned lithium-ion battery cathode material, including the following steps:

[0042] S10. After the cathode material precursor, pore-forming agent and dopant are mixed at high speed, the mixture is heated to the first sintering temperature at the first heating rate and then sintered at the first holding temperature. The mixture is then cooled to the holding temperature at the cooling rate and sintered at the first holding temperature. Finally, it is naturally cooled to room temperature to obtain a first sintering intermediate.

[0043] Preferably, in one embodiment, the pore-forming agent is a sulfate or sulfate-water hydrate containing Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, wherein the molar ratio of sulfate to matrix in the pore-forming agent is 0.002–0.05; the dopant is an oxide, hydroxide, or carbonate containing at least one element selected from Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, wherein the molar ratio of metal element to matrix in the dopant is 0–0.05. The metal elements in both the pore-forming agent and the dopant will enter the matrix, and their total amount is equal to the Li in the chemical formula. a Ni 1-x-y-z Co x M y N z The total amount of N in O2.

[0044] Doping elements can optimize the electronic structure of cathode materials, increase their conductivity and ion transport efficiency, and improve the cycle life and stability of cathode materials.

[0045] Specifically, in the above-mentioned first heat preservation sintering, under an air or oxygen atmosphere, the temperature is raised to the first sintering temperature of 600-900℃ at a first heating rate of 1-5℃ / min, and held for sintering for 8-20 hours. Then, the temperature is lowered to the holding temperature of 300-450℃ at a cooling rate of 0.5-2.5℃ / min, and held for sintering for 3-8 hours.

[0046] The sintering temperature, holding temperature, initial heating rate, and cooling rate need to be adjusted according to different dopants to ensure that the grain size of the sintered material is within a suitable range. If the added dopant inhibits crystal growth, the initial heating rate and cooling rate need to be increased; conversely, if the added dopant promotes crystal growth, the sintering temperature, holding temperature, initial heating rate, and cooling rate need to be decreased. This ensures that the material maintains a suitable grain size and porosity distribution under different dopants.

[0047] By first heating up for high-temperature sintering and then cooling down for low-temperature sintering, the pores in the cathode material are formed and evenly distributed. This allows the electrolyte to be evenly wetted inside the material particles, avoiding the situation where excessively concentrated pores lead to excessively fast local reaction rates, resulting in uneven stress inside the particles during charging and discharging.

[0048] S20. Wash and dry the sintering intermediate to obtain a dried intermediate.

[0049] Preferably, in one embodiment, during the washing and drying of the primary sintering intermediate, deionized water is used to wash the primary sintering intermediate for 1-15 minutes at a solid-liquid ratio of 1.0-3.0 by mass, followed by filtration for 10-30 minutes until the moisture content is below 10%, drying in a vacuum drying oven for 5-20 hours, and then sieving to obtain the dried intermediate. Through the washing, filtration, drying, and sieving steps, impurities can be removed, resulting in a product with more uniform particle size and further improving the performance of the cathode material. Filtration can remove residual lithium after water washing.

[0050] S30. After the dry intermediate and the coating agent are mixed at high speed to obtain a mixture, the mixture is heated to the second sintering temperature at the second heating rate and then sintered at the second holding temperature. Then it is naturally cooled to room temperature to obtain the lithium-ion cathode material.

[0051] Preferably, in one embodiment, the coating agent is one or more of boric acid and boron oxide. Preferably, in the secondary heat preservation sintering, under an oxygen or air atmosphere, the temperature is raised to 250℃-350℃ at a second heating rate of 1-5℃ / min and held for sintering for 4-12 hours. After naturally cooling to room temperature, the lithium-ion cathode material is obtained by passing it through a 300-mesh sieve.

[0052] The cathode material obtained by the above method satisfies the following relationship: P = (K * 10 2 )+[(C-100)*10 2 / L]^2;

[0053] P is the structural stress coefficient of the cathode material, 2.51≤P≤12.00;

[0054] K is the porosity of the cathode material, 1%≤K≤10%;

[0055] C represents the grain size of the cathode material, where 100nm ≤ C ≤ 400nm;

[0056] L represents the particle size of the cathode material, D. 50The particle size distribution is 8μm ≤ L ≤ 16μm. The above method can reduce volume changes during intercalation, reduce mechanical stress and fracture risk by controlling particle size and particle size distribution. Furthermore, appropriate porosity can alleviate internal structural stress in the material, and the structural stress coefficient is controlled within this range, ultimately resulting in products with excellent capacity and cycle performance, good thermal stability and high safety performance.

[0057] Example 1:

[0058] This embodiment describes the lithium-ion cathode material of the present invention, wherein sulfur accounts for 0.10% of the total mass of the lithium-ion cathode material. The porosity K = 6.09%, grain size C = 220.4 nm, and particle size L:D were calculated using electron microscopy and software analysis of the pore area. 50 =10μm, according to the relationship P=(K*10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 7.54.

[0059] The preparation method of the above-mentioned lithium-ion cathode material includes the following steps:

[0060] (1) Ni, the precursor of the cathode material 0.90 Co 0.05 Mn 0.05 (OH)2, Zr(SO4)2, SrO and lithium source were added to a high-speed mixer at a molar ratio of 1:0.005:0.002:1.04 and mixed for 30 minutes at a speed of 1500 rpm to obtain a mixture. The mixture was then placed in a sintering furnace and heated to 750°C at a rate of 2°C / min under an oxygen atmosphere. The temperature was maintained for sintering for 13 hours, and then cooled to 300°C at a rate of 2°C / min for 5 hours. Finally, the mixture was allowed to cool naturally to room temperature to obtain a primary sintering intermediate.

[0061] (2) The sintering intermediate prepared in step (1) was washed with deionized water at a mass solid-liquid ratio of 1.8:1. After washing for 10 minutes, it was filtered for 15 minutes until the water content was less than 10%. The sample was placed in a vacuum oven and vacuum dried at 160°C for 8 hours. Then it was naturally cooled to room temperature and sieved to obtain the dried intermediate.

[0062] (3) The dried intermediate and boric acid were mixed in a high-speed mixer at a molar ratio of 1:0.01. The speed of the high-speed mixer was 1500 rpm and the mixture was mixed at high speed for 30 min to obtain a mixture. The mixture was placed in a sintering furnace and heated to 300°C at a heating rate of 2°C / min under an oxygen atmosphere and sintered at that temperature for 8 h. Then it was naturally cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium nickel manganese composite oxide cathode material.

[0063] Example 2:

[0064] This embodiment describes the lithium-ion cathode material of the present invention, wherein sulfur accounts for 0.08% of the total mass of the matrix, porosity K = 5.77%, grain size C = 226.1 nm, and particle size D... 50 L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 7.36.

[0065] The preparation method of the above-mentioned lithium-ion cathode material includes the following steps:

[0066] (1) Ni, the precursor of the cathode material 0.90 Co 0.05 Mn 0.05 (OH)2, MgSO 4、 WO3 and lithium source were mixed in a high-speed mixer at a molar ratio of 1:0.01:0.002:1.04. The high-speed mixer rotated at 1500 rpm for 30 minutes to obtain a mixture. The mixture was then placed in a sintering furnace and heated to 770°C at a rate of 1°C / min under an oxygen atmosphere. The temperature was maintained for sintering for 13 hours. The temperature was then lowered to 320°C at a rate of 0.5°C / min and held for 8 hours. Finally, the mixture was allowed to cool naturally to room temperature to obtain a primary sintering intermediate.

[0067] (2) The sintering intermediate prepared in step (1) was washed with deionized water at a mass solid-liquid ratio of 1.5:1. After washing for 10 minutes, it was filtered for 15 minutes until the water content was less than 10%. The sample was placed in a vacuum oven and vacuum dried at 160°C for 8 hours. Then it was naturally cooled to room temperature and sieved through a 300-mesh sieve to obtain the dried intermediate.

[0068] (3) The dried intermediate and boric acid were mixed in a high-speed mixer at a molar ratio of 1:0.01. The speed of the high-speed mixer was 1500 rpm and the mixture was mixed at high speed for 30 min to obtain a mixture. The mixture was placed in a sintering furnace and heated to 310°C at a heating rate of 2°C / min under an oxygen atmosphere and sintered at that temperature for 8 h. Then it was naturally cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium nickel manganese composite oxide cathode material.

[0069] Example 3:

[0070] This embodiment describes the lithium-ion cathode material of the present invention, wherein sulfur accounts for 0.13% of the total mass of the matrix, porosity K = 8.31%, grain size C = 210.6 nm, and particle size D... 50L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 9.53.

[0071] The preparation method of the above-mentioned lithium-ion cathode material includes the following steps:

[0072] (1) Ni, the precursor of the cathode material 0.90 Co 0.05 Mn 0.05 (OH)2, Ti(SO4)2, Al2O3 and lithium source were added to a high-speed mixer in a molar ratio of 1:0.01:0.002:1.04 and mixed at 1500 rpm for 30 min to obtain a mixture. The mixture was then placed in a sintering furnace and heated to 760°C at a rate of 3°C / min under an oxygen atmosphere. The temperature was maintained for sintering for 13 h, and then cooled to 350°C at a rate of 1.0°C / min for 5 h. Finally, the mixture was allowed to cool naturally to room temperature to obtain a primary sintering intermediate.

[0073] (2) The sintering intermediate prepared in step (1) was washed with deionized water at a mass solid-liquid ratio of 1.2:1. After washing for 10 minutes, it was filtered for 15 minutes until the water content was less than 10%. The sample was placed in a vacuum oven and vacuum dried at 160°C for 8 hours. Then it was naturally cooled to room temperature and sieved to obtain the dried intermediate.

[0074] (3) The dried intermediate and boric acid were mixed in a high-speed mixer at a molar ratio of 1:0.01. The speed of the high-speed mixer was 1500 rpm and the mixture was mixed at high speed for 30 min to obtain a mixture. The mixture was placed in a sintering furnace and heated to 320°C at a heating rate of 1°C / min under an oxygen atmosphere and sintered at that temperature for 8 h. Then it was naturally cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium nickel manganese composite oxide cathode material.

[0075] Example 4:

[0076] This embodiment describes the lithium-ion cathode material of the present invention, wherein sulfur accounts for 0.09% of the total mass of the matrix, porosity K = 5.93%, grain size C = 233.6 nm, and particle size D... 50 L = 13 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained from the calculation of / L]^2 is 6.99.

[0077] The preparation method of the above-mentioned lithium-ion cathode material includes the following steps:

[0078] (1) Ni, the precursor of the cathode material 0.90 Co 0.05 Mn 0.05 (OH)2, Zr(SO4)2, CaCO3 and lithium source were added to a high-speed mixer in a molar ratio of 1:0.005:0.002:1.04 and mixed at 1500 rpm for 30 min to obtain a mixture. The mixture was then placed in a sintering furnace and heated to 760°C at a rate of 3°C / min under an oxygen atmosphere. The temperature was maintained for 13 h, and then the temperature was lowered to 350°C at a rate of 1.0°C / min and held for 5 h. Finally, the mixture was allowed to cool naturally to room temperature to obtain a primary sintering intermediate.

[0079] (2) The sintering intermediate prepared in step (1) was washed with deionized water at a mass solid-liquid ratio of 1.5:1. After washing for 10 minutes, it was filtered for 15 minutes until the water content was less than 10%. The sample was placed in a vacuum oven and vacuum dried at 160°C for 8 hours. Then it was naturally cooled to room temperature and sieved to obtain the dried intermediate.

[0080] (3) The dried intermediate and boric acid were mixed in a high-speed mixer at a molar ratio of 1:0.01. The speed of the high-speed mixer was 1500 rpm and the mixture was mixed at high speed for 30 min to obtain a mixture. The mixture was placed in a sintering furnace and heated to 330°C at a heating rate of 2°C / min under an oxygen atmosphere and sintered at that temperature for 8 h. Then it was naturally cooled to room temperature and passed through a 300-mesh sieve to obtain a lithium nickel manganese composite oxide cathode material.

[0081] Example 5:

[0082] This embodiment describes the lithium-ion cathode material of the present invention, with a porosity K = 6.38%, a grain size C = 260.1 nm, and a particle size D. 50 L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 8.94.

[0083] The specific steps of Example 5 can be referred to in Example 1, except that the constant temperature for the first sintering is increased by 10°C.

[0084] Example 6:

[0085] This embodiment describes the lithium-ion cathode material of the present invention. The lithium-ion cathode material has a porosity K = 4.61%, a grain size C = 216.9 nm, and a particle size D. 50 L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2The structural stress coefficient P obtained from the calculation of / L]^2 is 5.98.

[0086] The specific steps of Example 6 can be referred to in Example 1, except that there is no cooling platform after the first sintering.

[0087] Comparative Example 1:

[0088] The comparative lithium-ion cathode material was used to compare with Example 1 of this application. This lithium-ion cathode material has a porosity K = 14.21%, a grain size C = 200.8 nm, and a particle size D. 50 L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 15.23.

[0089] The specific steps of Comparative Example 1 can be referred to in Example 1, except that the amount of pore-forming agent used is 5 times that of Example 1.

[0090] Comparative Example 2:

[0091] The comparative lithium-ion cathode material was used to compare with Example 1 of this application. This lithium-ion cathode material has a porosity K = 0.43%, a grain size C = 230.5 nm, and a particle size D. 50 L = 10 μm, according to the relationship P = (K * 10 2 )+[(C-100)*10 2 The structural stress coefficient P obtained by calculation is 2.13.

[0092] The specific steps of Comparative Example 2 can be referred to in Example 1, except that no pore-forming agent is added.

[0093] When the cathode materials in the above embodiments and comparative examples are assembled into secondary batteries, and their electrochemical and thermal stability are tested, the test results are shown in Table 1 below.

[0094] Table 1 Performance test results of Examples 1-6 and Comparative Examples 1-2

[0095] As can be seen from the above embodiments and comparative examples, the lithium-ion battery cathode material of this application satisfies the following relationship:

[0096] P = (K * 10) 2 )+[(C-100)*10 2 / L]^2, where P is the structural stress coefficient of the cathode material, 2.51≤P≤12.00; K is the porosity of the cathode material, 1%≤K≤10%; C is the grain size of the cathode material, 100nm≤C≤400nm; L is the particle size D of the cathode material. 50 The particle size distribution is 8μm ≤ L ≤ 16μm. In Examples 1-6, the coin cell discharge capacity at 0.1C reaches 225.1, the coin cell room temperature cycling performance at 100cls reaches 96.2%, the coin cell high temperature cycling performance at 100cls reaches 95.5%, and the DSC peak temperature reaches 208.3°C. In contrast, the cathode material in the comparative examples exhibits lower structural stress coefficient, porosity, grain size, and particle size D. 50 Although not all the conditions for this application are met, the comparative results show that the cathode material of this application outperforms the comparative example in all aspects. In particular, improving the DSC peak temperature is very difficult, while the DSC peak temperature of the cathode material of this application is superior to that of the comparative example. Through the above examples and comparative results, it is evident that the lithium-ion battery cathode material of this application exhibits excellent capacity, cycle performance, thermal stability, and safety performance.

Claims

1. A lithium-ion battery cathode material, characterized in that, The cathode material satisfies the following relationship: P=(K*10 2 )+[(C-100)*10 2 / L]^2; Where P is the structural stress coefficient of the cathode material, 2.51≤P≤12.00; K is the porosity of the cathode material, 1%≤K≤10%; C represents the grain size of the cathode material, where 100nm ≤ C ≤ 400nm; L represents the particle size of the cathode material, D. 50 , 8μm≤L≤16μm.

2. The lithium-ion battery cathode material according to claim 1, characterized in that, The cathode material matrix is ​​coated with element B, and the general chemical formula of the cathode material matrix is ​​Li. a Ni 1-x-y-z Co x M y N z O2, wherein M is Mn or Al, N is selected from at least one of Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn and Sb, and 0.90≤a≤1.20, 0≤x≤0.30, 0≤y≤0.30, 0≤z≤0.05, x+y+z≤0.

30.

3. The lithium-ion battery cathode material according to claim 2, characterized in that, The cathode material also contains sulfur (S), which accounts for 0.01% to 0.30% of the total mass of the cathode material.

4. A method for preparing a lithium-ion battery cathode material as described in any one of claims 1-3, characterized in that: Includes the following steps: After the cathode material precursor, pore-forming agent and dopant are mixed at high speed, the mixture is heated to the first sintering temperature and then held for sintering. The mixture is then cooled to the holding temperature and held for sintering. Finally, it is naturally cooled to room temperature to obtain a first sintering intermediate. The sintering intermediate is washed and dried to obtain a dried intermediate; The dried intermediate is mixed with the coating agent to obtain a mixture. The mixture is heated to the second sintering temperature and then sintered at the same temperature for a second time. Finally, it is naturally cooled to room temperature to obtain the lithium-ion cathode material.

5. The preparation method according to claim 4, characterized in that: The pore-forming agent is a sulfate or sulfate salt hydrate containing Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, with a molar ratio of sulfate to matrix of 0.01 to 0.

05. The dopant is an oxide, hydroxide, or carbonate containing at least one element selected from Zr, Al, Ti, Mg, Y, W, Mo, Sr, Ba, La, Ca, Si, Nb, Ta, Ce, Ga, Sn, and Sb, with a molar ratio of metal element to matrix of 0 to 0.

1.

6. The preparation method according to claim 4, characterized in that: In the first heat preservation sintering process, under an air or oxygen atmosphere, the temperature is raised to the first sintering temperature of 600-900℃ at a heating rate of 1-5℃ / min, and held for sintering for 8-20 hours. Then, the temperature is lowered to the heat preservation temperature of 300-450℃ at a cooling rate of 0.5-2.5℃ / min, and held for sintering for 3-8 hours.

7. The preparation method according to claim 4, characterized in that: In the washing and drying of the primary sintering intermediate, the primary sintering intermediate is washed with deionized water at a mass solid-liquid ratio of 1.0 to 3.0 for 1 to 15 minutes, filtered for 10 to 30 minutes until the moisture content is less than 10%, and then dried in a vacuum drying oven for 5 to 20 hours to obtain the dried intermediate.

8. The preparation method according to claim 4, characterized in that: The coating agent is at least one of boric acid or boron oxide, and element B accounts for 0.01% to 0.30% of the total mass of the dried intermediate.

9. The preparation method according to claim 4, characterized in that: In the secondary heat preservation sintering process, under an oxygen or air atmosphere, the temperature is raised to 250℃-350℃ at a second heating rate of 1-5℃ / min and held for sintering for 4-12 hours. After naturally cooling to room temperature, the lithium-ion cathode material is obtained by passing it through a 300-mesh sieve.

10. The application of a lithium-ion battery cathode material as described in any one of claims 1-3 in a lithium-ion battery.

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