Lithium-ion battery positive electrode material and manufacturing method thereof, lithium-ion battery

Abstract

The present invention relates to the field of lithium-ion batteries, and discloses a cathode material for a lithium-ion battery, a method for manufacturing the same, and a lithium-ion battery. The Ni 3+ content on the surface of the cathode material and the Ni 3+ content inside the cathode material have a ratio of 0.95-1:1. In the cathode material, the content of mixed-array nickel is 3% or less. The Ni 3+ content on the surface and inside of the cathode material of the lithium-ion battery is close, and the content of mixed-array nickel is low. As a result, the generation of a NiO passivation layer on the cathode material is avoided, the phenomenon of loss of surface-active lithium is reduced, and the lithium-ion battery including the cathode material has improved capacity, rate performance, and cycle performance.

Description

[Technical Field]

[0001] The present invention relates to the field of lithium ion batteries, and more particularly to a positive electrode material for lithium ion batteries and a method for producing the same, and a lithium ion battery. [Background technology]

[0002] In recent years, with the oil energy crisis and worsening environmental pollution problems, electric vehicles have been rapidly developed around the world as a replacement for traditional automobiles in new circuits. At the same time, the performance demands for high energy density and long cycle life of the power batteries installed in electric vehicles are also increasing.

[0003] As the most expensive and most impactful part of a battery, cathode materials have been widely researched, developed, and applied in lithium-ion power battery systems, among which layered lithium nickel cobalt manganese aluminate multi-component materials have high specific capacity and stability, and have great potential for development. In order to meet the increasingly urgent demand for high energy density and safety, increasing the Ni content in multi-component materials to increase energy density and combining doping and coating methods to control the speed and cycling performance of materials have become the common choice of the market and researchers.

[0004] As nickel content increases, traditional wet coating methods tend to result in the loss of surface-active lithium, and the formation of an electrochemically active passivation layer when the material comes into contact with water, further increasing the material's impedance and affecting its energy density and rate performance. Furthermore, the water washing process is complex, with numerous influencing factors, and the cost of filtrate recovery is high. For this reason, increasing research is turning to dry coating processes for high-nickel materials, which not only effectively avoids the above issues but also offers a simpler manufacturing process, lower costs, and higher consistency and reproducibility. For example, CN106784675A proposes a dry coating method for lithium battery positive electrode materials, in which the coating material is first premixed with boric acid, then mixed with the primary sintering material and sintered to obtain the finished positive electrode material. During this process, the coating material is intimately contacted to form a solid melt, resulting in a uniform coating effect and a tight bond after sintering, making the coating less likely to fall off. This method not only shortens the production cycle, but also ensures uniformity of the coating. It also allows the coating material to be exposed to high temperatures to form an ideal glassy coating, improving the stability of the material.

[0005] However, direct dry coating of primary sintered material still faces many challenges, one of the most significant being that the specific surface area and porosity of the primary sintered material that has not been washed with water cannot be fully developed, and the particles that undergo subsequent coating have a further reduced specific surface area and filled pores, resulting in a large difference in the specific surface area of ​​the finished dry-coated product compared to that of wet-coated products. The small specific surface area and porosity reduce the contact area between the material and the electrolyte, affecting the lithium ion mass transfer process and affecting discharge capacity and rate performance.

[0006] Therefore, it is very important to provide a positive electrode material that has a uniform coating effect, an appropriate specific surface area and porosity, no passivation layer, a high energy density, and good rate performance. Summary of the Invention [Problem to be solved by the invention]

[0007] The present invention aims to provide a lithium-ion battery positive electrode material and a manufacturing method thereof, and a lithium-ion battery, in order to overcome the problems that the surface active lithium of the positive electrode material is lost due to the traditional wet coating and water washing, and the positive electrode material properties cannot meet actual needs due to the existence of a NiO passivation layer on the surface of the positive electrode material. 3+ The close content and low mixed-arrangement nickel content can avoid the formation of a NiO passivation layer on the positive electrode material and reduce the phenomenon of loss of surface active lithium, so that lithium-ion batteries containing this positive electrode material have improved capacity, rate performance, and cycle performance. [Means for solving the problem]

[0008] In order to achieve the above object, a first aspect of the present invention provides a cathode material for a lithium ion battery, comprising: a surface of the cathode material; 3+ The content and internal Ni of the cathode material 3+ The content ratio is 0.95-1:1, In the positive electrode material, the content of mixed-arrangement nickel is 3% or less.

[0009] A second aspect of the present invention provides a method for producing a cathode material for a lithium ion battery, the method comprising: S1: Mixing a cathode material precursor, a lithium source, and an optional dopant, and then performing primary sintering under a first oxygen-containing atmosphere, followed by cooling, crushing, and sieving to obtain a primary sintered material; S2. After mixing the primary sintering material and the coating agent, secondary sintering is carried out under a second oxygen-containing atmosphere, and the resulting cathode material for lithium ion batteries is obtained after screening and iron removal; The oxygen concentration in the second oxygen-containing atmosphere is 90 vol % or more.

[0010] A third aspect of the present invention provides a positive electrode material for a lithium ion battery produced by the above method.

[0011] A fourth aspect of the present invention provides a lithium ion battery comprising the above-described positive electrode material for lithium ion batteries.

[0012] According to the above technical solutions, the positive electrode material of the lithium ion battery and the manufacturing method thereof, and the lithium ion battery according to the present invention achieve the following beneficial effects:

[0013] Ni on the surface and inside of the lithium ion cathode material according to the present invention 3+ The close content and low mixed-arrangement nickel content can avoid the formation of a NiO passivation layer on the positive electrode material and reduce the phenomenon of loss of surface active lithium, so that lithium-ion batteries containing this positive electrode material have improved capacity, rate performance, and cycle performance.

[0014] Furthermore, the positive electrode material of the present invention for lithium ion batteries has a specific porosity, and even when a coating layer is applied to the surface of the positive electrode material, the surface can still maintain a loose and porous structure, the coating layer is in uniform contact with the surface of the material, there are many reaction sites, and there is no local concentration on the surface of the coating layer, which is helpful in reducing the impedance of the positive electrode material and improving the cycle performance of lithium ion batteries containing the positive electrode material. In addition, the specific porosity is advantageous for the material to be fully infiltrated with the electrolyte, resulting in higher initial charge / discharge efficiency and rate performance.

[0015] Furthermore, the material has a specific porosity distribution, specifically, the core of the positive electrode material has a low porosity and the shell has a high porosity, the dense structure of the low-porosity core contributes to improving the crushing strength of the positive electrode material, and the high-porosity shell can ensure the coating effect and electrolyte infiltration effect. Furthermore, the shell is prone to microcracks and powdering during the charge and discharge process, and the large porosity in the shell provides space for the expansion and contraction of the unit cell volume during the charge and discharge process, relieves stress, and improves the cycle life of lithium-ion batteries containing this positive electrode material.

[0016] Furthermore, the primary particles of the cathode material of the lithium-ion battery according to the present invention have a specific arrangement. The arrangement of the primary particles of the material is adjusted by combined doping, and the primary particles are radially arranged at least in the shell portion (different doping can also be extended to the core). The orderly arrangement effectively alleviates the compression and cracking caused by the expansion and contraction in different directions of crystal grains with different crystal plane orientations, thereby improving the cycle performance of lithium-ion batteries containing the cathode material.

[0017] Furthermore, the cathode material for lithium-ion batteries according to the present invention has an appropriate grain boundary density, and the present method adjusts the core-shell structure of the material to have different grain boundary densities through combinatorial doping. In the shell layer, the primary particles absorb and release lithium frequently and are in sufficient contact with the electrolyte, which makes it easy for microcracks to form and develop during cycling, resulting in surface powdering. Therefore, a low grain boundary density can reduce the formation and development of microcracks at the grain boundaries. In the core, there is relatively little contact between the primary particles and the electrolyte, and a higher interface density provides channels for lithium ion diffusion, resulting in higher capacity and better rate performance. The differentiated grain boundary densities in the core-shell structure of the cathode material according to the present invention enable the material to have high capacity and long cycle times.

[0018] The method for manufacturing a positive electrode material for a lithium-ion battery according to the present invention uses dry coating in an atmosphere with a high oxygen concentration content, thereby avoiding the formation of an inactive passivation layer caused by contact of the surface of a high-nickel ternary material with water and delithiation in the conventional water washing process, and maximizing the same structure and trivalent active nickel content in the surface and bulk phase, and further providing higher capacity and lower electrochemical impedance.

[0019] Furthermore, by selecting a specific combination of dopants and combining it with dry coating, porous secondary particles having a core-shell structure consisting of well-ordered primary particles are produced, which results in a positive electrode material with high particle strength. When used in a lithium ion battery, this significantly improves the specific capacity, cycle performance, and rate performance of the lithium ion battery, while also extending the cycle life.

[0020] Furthermore, in the method for manufacturing a positive electrode material for a lithium-ion battery according to the present invention, the specific surface area of ​​the primary sintered material is adjusted by combined doping, and by controlling the specific surface area of ​​the primary sintered material, not only can the surface of the obtained positive electrode material be sufficiently infiltrated with the electrolyte, but also no excess surface lithium remains on the surface of the positive electrode material, so that the positive electrode material obtained after dry-coating the primary sintered material can exhibit high discharge capacity. [Brief explanation of the drawings]

[0021] [Figure 1] FIG. 2 is a cross-sectional SEM image of the positive electrode material obtained in Example 1. [Figure 2] FIG. 2 is a surface SEM image of the positive electrode material obtained in Example 1. [Figure 3] FIG. 10 is a cross-sectional SEM image of the positive electrode material obtained in Example 9. [Figure 4] FIG. 10 is a surface SEM image of the positive electrode material obtained in Example 9. [Figure 5] FIG. 1 is a cross-sectional SEM image of the positive electrode material obtained in Example 10. [Figure 6] FIG. 1 is a surface SEM image of the positive electrode material obtained in Example 10. [Figure 7] FIG. 2 is a cross-sectional SEM image of the positive electrode material obtained in Example 2. [Figure 8] FIG. 2 is a surface SEM image of the positive electrode material obtained in Example 2. [Figure 9] FIG. 2 is a cross-sectional SEM image of the positive electrode material obtained in Example 3. [Figure 10] FIG. 2 is a surface SEM image of the positive electrode material obtained in Example 3. [Figure 11]FIG. 1 is a cross-sectional SEM image of the positive electrode material obtained in Example 4. [Figure 12] FIG. 1 is a surface SEM image of the positive electrode material obtained in Example 4. [Figure 13] FIG. 1 is a comparison diagram of the initial discharge capacities of Example 1, Example 9, Comparative Example 1, and Comparative Example 3. [Figure 14] FIG. 1 is a diagram comparing dQ / dV in Example 1, Example 9, Comparative Example 1, and Comparative Example 3. [Figure 15] FIG. 10 is a graph comparing the rate performance of Examples 1-3, 9, and 10. [Figure 16] FIG. 1 is a graph comparing cycle performances of Examples 1-3, 9, and 10. DETAILED DESCRIPTION OF THE INVENTION

[0022] In order to achieve the above-mentioned effects, a first aspect of the present invention provides a cathode material for a lithium ion battery, comprising: a surface of the cathode material; 3+ The content and internal Ni of the cathode material 3+ The content ratio is 0.95-1:1, In the positive electrode material, the content of mixed-arrangement nickel is 3% or less.

[0023] In the present invention, the content of the mixed arrangement nickel is Ni in which the lithium-nickel mixed arrangement occurs. 2+ refers to the percentage of total Ni, and can be measured by XRD finishing.

[0024] In the present invention, the surface of the positive electrode material Ni 3+ Content and internal Ni 3+ The content was measured by XPS and the surface Ni 3+ The content is the result of direct XPS testing of a sample of the finished product, and the internal Ni 3+ The content was measured by crushing a sample of the finished product into primary particles using an airflow mill, then etching it to a depth of 30 nm, followed by XPS testing.

[0025] In layered ternary positive electrode materials, such as nickel-cobalt-manganese ternary positive electrode materials, Ni, Co, and Mn are located in the transition metal layer of the lattice, and the theoretical valence of active Ni is +3. 2+ and Ni 3+ coexist in the lattice, and Ni 2+ A portion of the lithium is released between the layers and absorbed in the reversible Li layer, resulting in a lithium-nickel mixed array, which affects the capacity and cycle life of lithium-ion batteries manufactured from the cathode material. Furthermore, in the traditional cathode material manufacturing process, the contact between the surface of the cathode material and water during the water washing process causes a large amount of delithiation from the surface of the cathode material, ultimately forming NiOOH. The NiOOH is then deoxidized during the subsequent heating process to form a non-electrochemical rock salt phase NiO passivation layer. XPS detection reveals that the Ni on the surface of the cathode material is 3+ The content drops significantly, and Ni 2+ It was found that as the content increased, the electrochemical performance of the lithium ion battery manufactured from the cathode material ultimately deteriorated, specifically, the battery capacity decreased and the impedance and polarization significantly increased.

[0026] The inventor of the present invention has conducted research and found that Ni on the surface and inside of the positive electrode material of a lithium-ion battery 3+ By controlling the content of nickel to be close to the content of nickel and having a low mixed-arrangement nickel content, specifically within the range defined in the present invention, the formation of a NiO passivation layer on the positive electrode material can be avoided, the phenomenon of loss of surface active lithium can be reduced, and the lithium ion battery containing this positive electrode material can have improved capacity, rate performance, and cycle performance.

[0027] Furthermore, the surface of the positive electrode material is Ni 3+ The content and internal Ni of the cathode material 3+ The content ratio is 0.97-0.99:1, In the positive electrode material, the content of mixed-arrangement nickel is 1.5% or less.

[0028] According to the present invention, the positive electrode material contains Ni 3+ Content and Ni 2+ The ratio of the content is 2 or more.

[0029] In the present invention, Ni in the positive electrode material 3+ Content and Ni 2+ When the content ratio satisfies the above range, the positive electrode material has higher activity and fewer lattice defects, which can significantly improve the electrochemical activity of the positive electrode material. When used in a lithium-ion battery, the capacity and rate performance of the battery can be significantly improved. At the same time, the less divalent nickel in the positive electrode material, the less mixed-arrangement nickel, which reduces the risk of lithium-nickel mixed-arrangement, improves the structural stability of the positive electrode material, and extends the cycle life of the positive electrode material in the battery.

[0030] In the present invention, the positive electrode material Ni 3+ Content and Ni 2+ The content is measured by XPS.

[0031] Furthermore, in the positive electrode material, Ni 3+ Content and Ni 2+ The content ratio is 3-8.

[0032] According to the present invention, the specific surface area S of the positive electrode material is 0.1-0.5 m 2 / g.

[0033] In the present invention, the positive electrode material of the lithium ion battery has a specific surface area, which can ensure that the surface of the positive electrode material is sufficiently wetted by the electrolyte, and at the same time, can ensure that the surface of the positive electrode material has a low residual lithium content, so that the lithium ion battery containing this positive electrode material has a high discharge capacity.

[0034] Furthermore, the specific surface area S0 of the positive electrode material is 0.1-0.45 m 2 / g.

[0035] According to the present invention, after being crushed under a pressure of 3.5 T, the specific surface area of ​​the cathode material is S 3.5 and the rate of change of the specific surface area SSA = (S 3.5 -S0) / S0×100% is 0-50%.

[0036] In the present invention, when the specific surface area of ​​the positive electrode material before and after compression at a pressure of 3.5 T meets the above range, the positive electrode material has certain pressure resistance characteristics, and its high compression strength can avoid the risk of ball cracking during the compression of the material in the process of making the pole pieces, improving the safety and stability of lithium-ion batteries containing the positive electrode material, while allowing the positive electrode material to withstand higher compression densities and have the potential for higher energy density.

[0037] Furthermore, (S 3.5 -S0) / S0×100% is 20-50%, preferably 30-45%.

[0038] According to the present invention, the particle size corresponding to 10% of the volume distribution in the particle size test of the positive electrode material is D 10 0 After being crushed under a pressure of 3.5 T, the particle size corresponding to 10% of the volume distribution in the particle size test of the multi-component positive electrode material is D 10 1 and where (D 10 0 -D 10 1 ) / D 10 0 ×100% is 0-30%. Furthermore, (D 10 0 -D 10 1 ) / D 10 0 ×100% is 0-20%.

[0039] According to the present invention, the particle size corresponding to 50% of the volume distribution in the particle size test of the positive electrode material is D 50 0 After being crushed under a pressure of 3.5 T, the particle size corresponding to 50% of the volume distribution in the particle size test of the multi-component positive electrode material is D 50 1 and where (D 50 0 -D 50 1 ) / D 500 ×100% is 0-15%. Furthermore, (D 50 0 -D 50 1 ) / D 50 0 ×100% is 0-10%.

[0040] According to the present invention, the particle size corresponding to 90% of the volume distribution in the particle size test of the positive electrode material is D 90 0 After being crushed under a pressure of 3.5 T, the particle size corresponding to 90% of the volume distribution in the particle size test of the multi-component positive electrode material is D 90 1 and where (D 90 0 -D 90 1 ) / D 90 0 ×100% is 0-8%. Furthermore, (D 90 0 -D 90 1 ) / D 90 0 ×100% is 0-7%.

[0041] In the present invention, the D before and after the cracking of the positive electrode material under a pressure of 3.5 T 10 , D 50 and D 90 If at least one of the above conditions is satisfied, the positive electrode material has pressure resistance properties, and small pressure cracking fine powder will not occur under strong pressure, which indicates that the safety and stability of the positive electrode material can be improved during the manufacturing process.

[0042] In the present invention, the particle size corresponding to 10% of the volume distribution in the particle size test of the positive electrode material is D 10 0 After being crushed under a pressure of 2.5 T, the particle size corresponding to 10% of the volume distribution in the particle size test of the multi-component positive electrode material is D 10 2.5 and where (D 10 0 -D 10 2.5 ) / D 10 0 ×100% is 0-10%, preferably (D 10 0 -D 10 2.5 ) / D 10 0 ×100% is 0-6%.

[0043] In the present invention, the particle size corresponding to 50% of the volume distribution in the particle size test of the positive electrode material is D 50 0 After being crushed under a pressure of 2.5 T, the particle size corresponding to 50% of the volume distribution in the particle size test of the multi-component positive electrode material is D 50 2.5 and where (D 50 0 -D 50 2.5 ) / D 50 0 ×100% is 0-6%, preferably (D 50 0 -D 50 2.5 ) / D 50 0 ×100% is 0-5%.

[0044] In the present invention, the particle size corresponding to 90% of the volume distribution in the particle size test of the positive electrode material is D 90 0 After being crushed under a pressure of 2.5 T, the particle size corresponding to 90% of the volume distribution in the particle size test of the multi-component positive electrode material is D 90 2.5 and where (D 90 0 -D 90 2.5 ) / D 90 0 × 100% is 0-4%, preferably (D 90 0 -D 90 2.5 ) / D90 0 ×100% is 0-3%.

[0045] In the present invention, the particle size corresponding to 10% of the volume distribution in the particle size test of the positive electrode material is D 10 0 After being crushed under a pressure of 4.5 T, the particle size corresponding to 10% of the volume distribution in the particle size test of the multi-component positive electrode material is D 10 4.5 and where (D 10 0 -D 10 4.5 ) / D 10 0 ×100% is 0-50%, preferably (D 10 0 -D 10 4.5 ) / D 10 0 ×100% is 0-40%.

[0046] In the present invention, the particle size corresponding to 50% of the volume distribution in the particle size test of the positive electrode material is D 50 0 After being crushed under a pressure of 4.5 T, the particle size corresponding to 50% of the volume distribution in the particle size test of the multi-component positive electrode material is D 50 4.5 and where (D 50 0 -D 50 4.5 ) / D 50 0 ×100% is 0-30%, preferably (D 50 0 -D 50 4.5 ) / D 50 0 ×100% is 0-20%.

[0047] In the present invention, the particle size corresponding to 90% of the volume distribution in the particle size test of the positive electrode material is D 90 0After being crushed under a pressure of 4.5 T, the particle size corresponding to 90% of the volume distribution in the particle size test of the multi-component positive electrode material is D 90 4.5 and where (D 90 0 -D 90 4.5 ) / D 90 0 ×100% is 0-15%, preferably (D 90 0 -D 90 4.5 ) / D 90 0 ×100% is 0-10%.

[0048] According to the present invention, the porosity of the positive electrode material is 1-8%.

[0049] In the present invention, the positive electrode material of the lithium ion battery has a specific porosity, particularly a porosity distribution, so that the cycle life of the lithium ion battery containing the positive electrode material can be extended.

[0050] In the present invention, the porosity was measured using multiple cross-sectional SEM images and software statistical methods.

[0051] Furthermore, the porosity of the positive electrode material is 2-7%, preferably 3-6%.

[0052] According to the present invention, the positive electrode material is a secondary particle having a core-shell structure.

[0053] According to the present invention, in the positive electrode material, the porosity of the core is 0.1-2%.

[0054] According to the present invention, in the positive electrode material, the porosity of the shell is 3-8%.

[0055] In the present invention, the positive electrode material of the lithium ion battery has a specific porosity. In particular, the core of the positive electrode material has a low porosity, while the shell has a high porosity. The dense structure of the core with low porosity contributes to improving the crushing strength of the positive electrode material, and the shell with high porosity can provide space for the expansion and contraction of the unit cell volume during charging and discharging, thereby relieving stress and extending the cycle life of the lithium ion battery including the positive electrode material.

[0056] Furthermore, in the positive electrode material, the porosity of the core is 0.13-2%.

[0057] Furthermore, in the positive electrode material, the shell porosity is 4-7%.

[0058] According to the present invention, in the positive electrode material, the ratio of the radius of the core to the radius of the shell layer is 0.5-9:1.

[0059] In the present invention, when the radius ratio of the core and shell layers in the positive electrode material satisfies the above range, it can ensure that the material has a certain porosity in the outer layer, as well as a certain compressive strength. When used in a lithium ion battery, the lithium ion battery has excellent overall performance, such as high capacity, excellent cycleability, and excellent stability.

[0060] Furthermore, in the positive electrode material, the ratio of the radius of the core to the radius of the shell layer is 0.5-3:1.

[0061] According to the present invention, in the positive electrode material, the aspect ratio of the core primary particles is 1-2:1.

[0062] According to the present invention, in the positive electrode material, the aspect ratio of the primary particles of the shell layer is 3-7:1.

[0063] In the present invention, when at least one of the aspect ratios of the primary particles of the core and the shell layer in the positive electrode material satisfies the above range, the core of the positive electrode material is composed of an accumulation of oblate primary particles with a small aspect ratio, and the primary particles are closely and disorderly accumulated to form a dense structure with low porosity and high grain boundary density. The shell layer is composed of elongated primary particles with a relatively large aspect ratio, arranged radially, with relatively little contact surface between the primary particles and many holes formed between them, forming a relatively sparse structure. At the same time, the primary particles of the positive electrode material have a proper arrangement and orientation, which relieves stress generated during the charge and discharge process and prevents microcracks from occurring between the primary particle interfaces, ultimately extending the cycle life of the positive electrode material.

[0064] Furthermore, in the positive electrode material, the aspect ratio of the core primary particles is 1.2-1.8:1.

[0065] Furthermore, in the positive electrode material, the aspect ratio of the primary particles of the shell layer is 3-6:1.

[0066] According to the present invention, the aspect ratio of the primary particles of the positive electrode material is 1-6:1.

[0067] Furthermore, the aspect ratio of the primary particles of the positive electrode material is 1-5:1.

[0068] According to the present application, the positive electrode material includes a matrix and a coating layer coated on the matrix, the matrix has a structure shown in formula I, and the coating layer contains a J element-containing lithium oxygen compound and / or a J element-containing oxide; Li 1+a1 (Ni x Co y Mn z M m )O2 formula I Here, -0.1 ≦ a1 ≦ 0.2, 0 < x < 1, 0 ≦ y ≦ 0.4, 0 < z ≦ 0.6, 0 ≦ m ≦ 0.1, M is selected from at least one of Ta, Cr, Mo, W, Al, Y, Ti, Zr, V, Nb, Ca, P, Co, Ce, Er, Mg, B, Sr, Ba, and La, and J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo, and Mn.

[0069] In the present invention, the positive electrode material includes a coating layer composed of a lithium oxygen compound and / or an oxide of a specific element, and the specific element is bonded or attached to the surface of the positive electrode material to form a protective layer on the surface of the positive electrode material, reducing the side reaction between the material and the electrolyte, reducing the phenomenon of powdering of the material to a certain extent, and improving the cycle stability of the lithium-ion battery including the positive electrode material.

[0070] In the present invention, the J element-containing lithium oxygen compound and / or the J element-containing oxide may also contain at least one element of Ni, Co, Mn, and M from the matrix.

[0071] In one specific embodiment of the present invention, preferably, -0.1 ≦ a1 ≦ 0.15, 0 < x < 0.99, 0 < y ≦ 0.3, 0 < z ≦ 0.4, 0 < m ≦ 0.05, M is selected from at least one of Ti, B, La, P, and W and optionally at least one of Al, Nb, Cr, V, Mg, Sr, Y, Ce, Ca, V, Ta, Co, Zr, and Mo, and J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo, and Mn.

[0072] In the present invention, when the positive electrode material contains a specific type of M element, the preferential growth of the primary particles of the positive electrode material in the preferential plane direction is promoted, the primary particles exhibit a more elongated structure, many pores are formed between the particles, and the porosity of the entire material becomes larger. The specific pore structure not only provides more storage and reaction space by the coating layer of the dry coating, but also helps the material to be sufficiently infiltrated by the electrolyte and exhibit higher initial charge-discharge efficiency and rate performance.

[0073] According to the present invention, the element J in the coating layer accounts for 0.05 wt%-1.5 wt% of the total mass of the positive electrode material.

[0074] In the present invention, when the content of element J in the coating layer of the positive electrode material satisfies the above range, the surface of the positive electrode material can be protected and modified to a certain extent, and the coating layer can be prevented from being too thick and affecting the conductivity and gram capacity of the positive electrode material.

[0075] Furthermore, the element J in the coating layer accounts for 0.05 wt%-1 wt% of the total mass of the positive electrode material.

[0076] According to the present invention, in the positive electrode material, surface free Li accounts for 3%-6% of the total Li element molar ratio.

[0077] In the present invention, surface free Li is the total lithium content of lithium carbonate and lithium hydroxide on the surface of the positive electrode material, which is measured by potentiometric titration with a 905 potentiometric titrator.

[0078] When the surface free Li content in the positive electrode material satisfies the above range, it not only provides an effective active lithium content, reduces the risk of lithium deficiency in the material lattice, and ensures high capacity of the material, but also prevents excessive surface free lithium from increasing the material impedance and causing serious storage gas production.

[0079] Furthermore, in the positive electrode material, surface free Li accounts for 3.5%-5% of the total Li element molar ratio.

[0080] According to the present invention, the water content of the positive electrode material is 0-100 ppm.

[0081] In the present invention, when the water content of the positive electrode material satisfies the above range, the positive electrode material contains little water of crystallization and adsorbed water, and the side reactions with water are few, indicating high electrochemical activity. When used in a lithium ion battery, the battery has excellent cycle stability.

[0082] In the present invention, the moisture content of the positive electrode material was measured using a precision moisture meter.

[0083] Furthermore, the water content of the positive electrode material is 0-80 ppm.

[0084] A second aspect of the present invention provides a method for producing a cathode material for a lithium ion battery, the method comprising: S1: Mixing a cathode material precursor, a lithium source, and an optional dopant, and then performing primary sintering under a first oxygen-containing atmosphere, followed by cooling, crushing, and sieving to obtain a primary sintered material; S2. After mixing the primary sintering material and the coating agent, secondary sintering is carried out under a second oxygen-containing atmosphere, and the resulting cathode material for lithium ion batteries is obtained after screening and iron removal; The oxygen concentration in the second oxygen-containing atmosphere is 90 vol % or more.

[0085] In the present invention, the method for producing a positive electrode material for a lithium ion battery is carried out by dry coating in an atmosphere with a high oxygen concentration content, which avoids the contact of the surface of the high-nickel ternary material with water and the formation of an inactive passivation layer due to delithiation in the conventional water washing process, and maximizes the same structure and trivalent active nickel content in the surface and bulk phase. Specifically, a positive electrode material for a lithium ion battery according to the first aspect of the present invention is produced, which has a lower electrochemical impedance and can effectively improve the capacity, rate performance and cycle performance of a lithium ion battery when used in the lithium ion battery.

[0086] Furthermore, the oxygen concentration in the second oxygen-containing atmosphere is 98 vol % or more.

[0087] According to the present invention, in step S1, the dopant is a compound containing a doping element M, where M is selected from at least one of Ta, Cr, Mo, W, Al, Y, Ti, Zr, V, Nb, Ca, P, Co, Ce, Er, Mg, B, Sr, Ba and La.

[0088] According to the present invention, the oxygen concentration in the first oxygen-containing atmosphere is 95 vol % or more, preferably 98-100 vol %.

[0089] According to the present invention, the primary sintering conditions include heating from room temperature to 600-900°C at a heating rate of 2-8°C / min, and sintering for 8-14 hours.

[0090] In the present invention, when the primary sintering is carried out under the above conditions, a reasonable melting and migration time of lithium hydroxide can be ensured, and the solid-state reaction of lithiation and doping can be more fully achieved. The high oxygen concentration also contributes to the maximum oxidation of divalent nickel in nickel cobalt manganese hydroxide to trivalent nickel in lithium nickel cobalt manganese oxide, thereby forming a layered electrochemically active material with fewer defects.

[0091] Furthermore, the primary sintering conditions include heating from room temperature to 650-850°C at a heating rate of 3-6°C / min, and sintering for 8-12 hours.

[0092] According to the present invention, in step S2, the coating agent is a compound containing a coating element J, where J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo and Mn.

[0093] According to the present invention, the conditions of the secondary sintering include a sintering temperature of 200-600°C and a sintering time of 8-14 hours.

[0094] In the present invention, when the secondary sintering is performed under the above conditions, the coating material can fully react and bond with the material substrate, protecting and modifying the material surface, and improving the cycle stability of the material. Some coating materials can react with residual alkali on the surface under the above conditions, consuming the insulating material on the surface to improve the discharge capacity and rate performance of lithium-ion batteries containing the positive electrode material, while reducing gas production during storage and cycling of the material.

[0095] Furthermore, the conditions for the secondary sintering include a sintering temperature of 300-600°C and a sintering time of 8-12h.

[0096] According to the present invention, in step S1, the addition amount of the lithium source is in a stoichiometric ratio of 0.9≦n(Li) / n(Me)≦1.2, preferably added in a range of 1≦n(Li) / n(Me)≦1.1, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

[0097] According to the present invention, in step S1, the addition amount of the dopant is in a stoichiometric ratio of 0≦n(M) / n(Me)≦0.1, preferably added in a range of 0<n(M) / n(Me)≦0.05, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

[0098] According to the present invention, in step S2, the addition amount of the coating agent is added in a mass ratio of 0.05wt%≦m(J) / [m(BM)]≦1.5wt%, where m(J) is the mass of element J in the coating agent and m(BM) is the mass of the primary sintered material of the cathode material.

[0099] Furthermore, in step S2, the addition amount of the coating agent is added in a mass ratio of 0.05wt%≦m(J) / [m(BM)]≦1wt%.

[0100] In a specific embodiment of the present invention, in step S1, the dopant includes at least one of a first dopant, a second dopant, and a third dopant. The first dopant is a compound containing a doping element M1, where M1 is selected from at least one of Al, Nb, Cr, V, Mg, and Sr. The second dopant is a compound containing a doping element M2, where M2 is selected from at least one of Ti, B, La, P, and W. The third dopant is a compound containing a doping element M3, where M3 is selected from at least one of Y, Ce, Ca, V, Ta, Co, Zr, and Mo.

[0101] In the present invention, the terms first dopant, second dopant and third dopant are used only to distinguish between different dopant types and types of doping elements.

[0102] In the present invention, a specific combination of dopants is selected and combined with dry coating, where the first type of dopant M1 is a basic conventional dopant that stabilizes the layered oxide structure, the second type of dopant is the primary particles of the fine-grained material, which creates large porosity between the particles, forming a special dopant of sparse secondary particles, and the third type of dopant is a special dopant that makes the material arrangement more compact and orderly, especially the arrangement inside the core, forming a core-shell structure with a sparse exterior and a dense interior. In the present invention, the combination of dopants produces porous secondary particles with a core-shell structure consisting of orderly arranged primary particles. The resulting positive electrode material has high particle strength, and when used in lithium-ion batteries, it significantly improves the specific capacity, cycle performance, and rate performance of the lithium-ion battery, while also extending the cycle life.

[0103] In one preferred embodiment of the present invention, the dopant is a combination of a second dopant with a first dopant and / or a third dopant.

[0104] According to the present invention, in step S1, the amount of the first dopant added is in a stoichiometric ratio of 0≦n(M1) / n(Me)≦0.1, preferably 0≦n(M1) / n(Me)≦0.05, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

[0105] According to the present invention, in step S1, the amount of the second dopant added is in a stoichiometric ratio of 0≦n(M2) / n(Me)≦0.1, preferably 0≦n(M2) / n(Me)≦0.05, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

[0106] According to the present invention, in step S1, the third dopant is added in an amount in a stoichiometric ratio of 0≦n(M3) / n(Me)≦0.1, preferably 0≦n(M3) / n(Me)≦0.05, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

[0107] In one specific embodiment of the present invention, the specific surface area of ​​the primary sintered material is 0.3-0.8 m 2 / g.

[0108] In the present invention, when the primary sintered material has a specific surface area within the above range, the surface of the primary sintered material has a porous and sparse structure. When the primary sintered material is coated, the coating agent can better penetrate into the pores of the primary sintered material, allowing for good coating of the primary sintered material. The finally obtained positive electrode material has low electrochemical impedance, and when the positive electrode material is used in a lithium ion battery, the discharge capacity and rate performance of the lithium ion battery can be significantly improved.

[0109] Furthermore, the specific surface area of ​​the primary sintered material is 0.35-0.65m 2 / g, preferably 0.35-0.6m 2 / g.

[0110] According to the present invention, in step S2, the particle size corresponding to 10% of the volume distribution in the particle size test of the coating material is D 10 and the particle size corresponding to 50% of the volume distribution is D 50 and the particle size corresponding to 90% of the volume distribution is D 90 and 1.85≦K 90 =(D 90 -D 10 ) / D 50 ≦2.83.

[0111] In the present invention, K 90When a coating agent satisfying the above range is selected to dry coat the primary sintered material, the uniformity of the coating can be improved. Specifically, the small particles of the coating agent are more likely to melt and enter the pores on the surface of the primary sintered material, while the large particles of the coating agent can be melted and dispersed evenly on the surface of the primary sintered material, ultimately improving the coating effect of the coating agent.

[0112] In one specific embodiment of the present invention, the coating agent is a compound containing a coating element B, and the D 10 is 5-15 μm, and D 50 is 30-40 μm, and D 90 is 80-90 μm.

[0113] In the present invention, the positive electrode material precursor can be a conventional positive electrode material precursor in this field, and preferably, the positive electrode material precursor is: The positive electrode material precursor can be produced by the steps of preparing a mixed salt solution of a nickel salt, a cobalt salt, and a manganese salt, passing the mixed salt solution, a precipitant solution, and a complexing agent solution through a reaction vessel, respectively, to carry out a co-precipitation reaction in an inert gas atmosphere, and then aging, washing, and drying the resulting mixture to obtain the positive electrode material precursor.

[0114] In the present invention, the types of nickel salt, cobalt salt, and manganese salt are not particularly limited, and conventional nickel salt, cobalt salt, and manganese salt in this field can be used, for example, the nickel salt is nickel sulfate, the cobalt salt is cobalt sulfate, and the manganese salt is manganese sulfate.

[0115] In the present invention, the amounts of the nickel salt, the cobalt salt, and the manganese salt used satisfy the relationship n(Ni):n(Co):n(Mn)=x:y:z, and 0 <x<1、0<y≦0.4、0<z≦0.6である。

[0116] According to the present invention, the concentration of the mixed salt solution is 1-3 mol / L.

[0117] In the present invention, there is no particular limitation on the type of the precipitant solution, and any conventional precipitant solution in this field, such as a sodium hydroxide solution, can be used.

[0118] In the present invention, there is no particular limitation on the type of the complexing agent solution, and a conventional complexing agent solution in this field, such as aqueous ammonia, can be used.

[0119] According to the present invention, the concentration of the precipitant solution is 7-10 mol / L.

[0120] According to the present invention, the concentration of the complexing agent solution is 5 mol / L or more.

[0121] According to the present invention, the conditions for the co-precipitation reaction include: pH 10.5-11.5, stirring speed 200-800 rpm, reaction temperature 50-80°C, and flow rate of mixed salt solution into the reactor 100-400 mL / h.

[0122] In the present invention, by controlling the pH value, the introduction rate of the mixed salt solution into the reaction vessel, the reaction temperature, and the stirring rate during the co-precipitation reaction so as to satisfy the above-mentioned ranges, the primary fibers of the precursor can be grown into an elongated structure, and the precursor structure having this radial arrangement is sparse, regularly arranged, and a layered oxide positive electrode material with few defects is formed, which is advantageous for sufficient lithiation.

[0123] Furthermore, the conditions for the co-precipitation reaction include a pH of 10.6-11.4, a stirring speed of 300-700 rpm, a reaction temperature of 55-80°C, preferably 55-75°C, and a supply rate of the mixed salt solution into the reaction vessel of 100-300 mL / h.

[0124] A third aspect of the present invention provides a positive electrode material for a lithium ion battery produced by the above method.

[0125] A fourth aspect of the present invention provides a lithium ion battery comprising the above-mentioned positive electrode material for lithium ion batteries.

[0126] In the present invention, unless otherwise specified, room temperature refers to 25°C.

[0127] The present invention will now be described in detail with reference to examples. (1) Morphological test: Obtained by scanning electron microscope test of Hitachi S-4800 model, Japan. (2) Particle size D 10 , D 50 , D 90 : Obtained by testing with Marvern Hydro 2000mu laser particle size distribution analyzer, (3) Specific surface test: obtained by testing with a Micromeritics Tristar 3020 specific surface meter, (4) XRD finish: obtained by testing with Smart Lab9 KW from Nippon Rigakusha, (5) Particle strength test: obtained by Shimadzu Instruments' microcompression tester MCT-210 test particle, (6) XPS: Obtained using an ESCALAB 250 spectrometer from Perkin Elmer, USA. (7) The surface free Li content was measured by potentiometric titration with a 905 potentiometric titrator. (8) The matrix composition in the positive electrode material is measured by ICP. (9) The moisture content of the positive electrode material is measured using a precision moisture meter. (10) Electrochemical performance test: In the above examples and comparative examples, the electrochemical performance of the multi-component positive electrode materials is tested using a CR2025 button cell battery.

[0128] The manufacturing process of the 2025 button battery is as follows:

[0129] Electrode piece preparation: The multi-component positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were thoroughly mixed with an appropriate amount of N-methylpyrrolidone (NMP) in a mass ratio of 95:3:2 to form a uniform slurry. The slurry was applied to an aluminum foil and dried at 120°C for 12 hours. The aluminum foil was then pressed under a pressure of 100 MPa to prepare a positive electrode piece with a diameter of 12 mm and a thickness of 120 μm. The loading of the multi-component positive electrode material was 15.5 mg / cm. 2 is.

[0130] Battery assembly: In a gas glove box filled with argon gas with a water and oxygen content of less than 5 ppm, the positive electrode pieces, separator, negative electrode pieces, and electrolyte were assembled into a 2025-type button cell battery and allowed to stand for 6 hours. The negative electrode pieces were made of lithium metal sheet with a diameter of 17 mm and a thickness of 1 mm, the separator was made of 25 μm-thick polyethylene porous film (Celgard 2325), and the electrolyte was a mixture of equal parts of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0131] 2025 Button Cell Test: In the following examples and comparative examples, the electrochemical performance test was carried out on a 2025 button battery using a Shenzhen Newwell battery test system, and the 0.1C charge / discharge current density was 200mA / g.

[0132] The charge / discharge voltage range is controlled to 3-4.3V, and the button cell is charged / discharged at room temperature under 0.1C to evaluate the initial charge / discharge specific capacity and initial charge / discharge efficiency of the multi-component positive electrode material.

[0133] Cycle performance test: The charge / discharge voltage range was controlled to 3-4.3V, and the button battery was charged / discharged at 0.1C for two cycles at a constant temperature of 45°C, and then charged / discharged at 1C for 80 cycles to evaluate the high-temperature capacity retention of the multi-component positive electrode material.

[0134] Rate performance test: The charge / discharge voltage range was controlled to 3.0-4.3V, and the button battery was charged / discharged at 0.1C for two cycles at room temperature, followed by one cycle at 0.2C, 0.33C, 0.5C, and 1C. The rate performance of the multi-component positive electrode material was evaluated by the ratio of the initial discharge specific capacity at 0.1C to the discharge specific capacity at 1C. The initial discharge specific capacity at 0.1C was the discharge specific capacity of the first cycle of the button battery, and the discharge specific capacity at 1C was the discharge specific capacity of the sixth cycle of the button battery.

[0135] Example 1 (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in pure water in a molar ratio of n(Ni):n(Co):n(Mn) of 98:1:1 to obtain a 2.2 mol / L mixed salt solution A. An 8 mol / L sodium hydroxide solution was prepared as precipitant solution B, and a 6 mol / L ammonia water was prepared as complexing agent solution C. The bottom solution was added to the reactor to adjust the pH to 11. Nitrogen gas was introduced for protection, and the system temperature was controlled at 60°C. Solutions A, B, and C were added to the reactor through the inlet pipes, respectively. The stirring speed was 500 rpm, the mixed salt solution A flow rate was controlled at 200 mL / h, and the flow rates of solutions B and C were adjusted to stabilize the pH of the reaction system at 11±0.05. The process was terminated after the average particle size D50 of the particles in the solution reached 14 μm. The cathode material precursor was obtained through aging, separation, washing, and drying.

[0136] (2) The above cathode material precursor, lithium hydroxide, alumina and niobium oxide as the first dopants, boric acid as the second dopant, and yttrium oxide as the third dopant were weighed out and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(Nb):n(B):n(Y) = 1:1.03:0.01:0.002:0.001:0.002. The mixture was then sintered at constant temperature in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.45 m. 2 / g.

[0137] (3) The B element in boric acid I and the primary sintering material were mixed uniformly in a high-speed mixer at a mass ratio of m(B) / [m(BM)]=0.15 wt%, and then sintered in an oxygen furnace at a constant temperature of 350°C, with an oxygen concentration of 99%, for 10 hours. After cooling, sieving, and iron removal, the cathode material A1 was obtained, with a composition of Li 1.03 (Ni 0.965 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 Y 0.002 )O2 matrix, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0138] Boric Acid I D 10 is 10.2 μm, and D 50 is 32.1 μm, and D 90 is 83.3 μm, and the distribution coefficient K 90 is 2.27.

[0139] Surface Ni of cathode material A1 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0140] The cross-sectional and surface SEM images of the cathode material A1 obtained in Example 1 are shown in Figures 1 and 2, respectively. The cathode material has a core-shell structure, with the core and shell layers having different porosities, and the primary particles in the shell layer are radially arranged. For cathode material A1, the aspect ratio and porosity of the core primary particles, the aspect ratio and porosity of the shell primary particles, the aspect ratio and porosity of the cathode material primary particles, and the ratio of the core radius to the shell radius are shown in Table 2.

[0141] Example 2 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, the first dopants (alumina and niobium oxide), the second dopant (boric acid), and the third dopant (yttrium oxide) were weighed and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(Nb):n(B):n(Y) = 1:1.03:0.01:0.002:0.001:0.005. The mixture was then isothermally sintered in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.39 m. 2 / g.

[0142] In step (3), a positive electrode material A2 is obtained in the same manner as in Example 1, and the composition is Li 1.03 (Ni 0.962 Co 0.01 Mn 0.01 Al 0. Nb 0.002 B 0.001 Y 0.005 )O2 matrix, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0143] Surface Ni of cathode material A2 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0144] The cross-sectional and surface SEM images of the cathode material A2 prepared in Example 2 are shown in Figures 7 and 8, respectively, which show that the cathode material has a core-shell structure, with the core and shell layers having different porosities, and the primary particles in the shell layer being radially arranged. Compared with the cathode material A1 of Example 1, the core and shell layers of cathode material A2 have lower porosity, the primary particles in the core are more densely arranged, the primary particles in the shell layer are more regularly arranged radially, and the aspect ratio of the primary particles is larger.

[0145] For positive electrode material A2, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0146] Example 3 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, alumina as the first dopant, ammonium dihydrogen phosphate as the second dopant, and yttrium oxide as the third dopant were weighed and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(P):n(Y) = 1:1.03:0.01:0.001:0.002. The mixture was then isothermally sintered in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.41 m. 2 / g.

[0147] In step (3), a positive electrode material A3 was prepared in the same manner as in Example 1, and the composition was Li 1.03 (Ni 0.967 Co 0.01 Mn 0.01 Al 0.01 P 0.001 Y 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0148] Surface Ni of cathode material A3 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0149] The cross-sectional and surface SEM images of cathode material A3 obtained in Example 3 are shown in Figures 9 and 10, respectively. The cathode material has a core-shell structure, with the core and shell layers having different porosities, and the primary particles in the shell layer are radially arranged. Compared to cathode material A1 in Example 1, the difference in porosity between the core and shell layers of cathode material A3 is slightly smaller, and there are some pores in the core region.

[0150] For positive electrode material A3, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0151] Example 4 Step (1) is the same as step (1) of Example 1, In step (2), the positive electrode material precursor, lithium hydroxide, alumina as a first dopant, boric acid as a second dopant, and zirconia as a third dopant were weighed in a molar ratio of n(Me):n(Li):n(Al):n(B):n(Zr)=1:1.03:0.01:0.001:0.002, and then uniformly mixed. Primary sintering was performed according to the conditions of Example 1 to obtain a primary sintered material. The specific surface area of ​​the primary sintered material was 0.39 m. 2 / g.

[0152] In step (3), a positive electrode material A4 was prepared in the same manner as in Example 1, and its composition was Li 1.03 (Ni 0.967 Co 0.01 Mn 0.01 Al 0.01 B 0.001 Zr 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0153] Surface Ni of cathode material A4 3+ Content, internal Ni 3+The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0154] The cross-sectional and surface SEM images of cathode material A4 obtained in Example 4 are shown in Figures 11 and 12, respectively. The results show that the cathode material has a core-shell structure, with the core and shell layers having different porosities, and the primary particles in the shell layer are radially arranged. Compared with cathode material A1 in Example 1, the shell layer of cathode material A4 has a slightly smaller porosity and a smaller particle aspect ratio.

[0155] For positive electrode material A4, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0156] Example 5 (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in pure water in a molar ratio of n(Ni):n(Co):n(Mn) of 82:10:8 to obtain a 2 mol / L mixed salt solution A. An 8 mol / L sodium hydroxide solution was prepared as precipitant solution B, and a 5.4 mol / L ammonia water was prepared as complexing agent solution C. The bottom solution was added to the reactor to adjust the pH to 11. Nitrogen gas was introduced for protection, and the system temperature was controlled at 60°C. Solutions A, B, and C were added to the reactor through the inlet pipes, respectively. The stirring speed was 500 rpm, and the mixed salt solution A flow rate was controlled at 200 mL / h. The flow rates of solutions B and C were adjusted to stabilize the pH of the reaction system at 11±0.05. The process was terminated after the average particle size D50 of the particles in the solution reached 14 μm. The solution was then aged, separated, washed, and dried to obtain the cathode material precursor.

[0157] (2) The cathode material precursor, lithium hydroxide, alumina as the first dopant, boric acid as the second dopant, and yttrium oxide as the third dopant were weighed out and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(B):n(Y) = 1:1.03:0.01:0.004:0.002. The mixture was then isothermally sintered in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 750°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.35 m. 2 / g. (3) The procedure is almost the same as step (3) of Example 1, except that the B element in boric acid I and the primary sintering material are mixed in a mass ratio of m(B) / [m(BM)]=0.12 wt% to prepare a positive electrode material A5, and the composition is Li 1.03 (Ni 0.804 Co 0.1 Mn 0.08 Al 0.01 B 0.004 Y 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.12 wt% of the total mass of the positive electrode material.

[0158] Surface Ni of cathode material A5 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0159] For positive electrode material A5, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0160] Example 6 (1) Nickel sulfate, cobalt sulfate, and manganese sulfate were dissolved in pure water in a molar ratio of n(Ni):n(Co):n(Mn) of 60:20:20 to obtain a 1.6 mol / L mixed salt solution A. An 8 mol / L sodium hydroxide solution was prepared as precipitant solution B, and a 4.8 mol / L ammonia water was prepared as complexing agent solution C. The bottom solution was added to the reactor to adjust the pH to 11. Nitrogen gas was introduced for protection, and the system temperature was controlled at 60°C. Solutions A, B, and C were added to the reactor through the inlet pipes, respectively. The stirring speed was 500 rpm, the mixed salt solution A flow rate was controlled at 200 mL / h, and the flow rates of solutions B and C were adjusted to stabilize the pH of the reaction system at 11±0.05. The process was terminated when the average particle size D50 of the particles in the solution reached 14 μm. The cathode material precursor was obtained after aging, separation, washing, and drying. (2) The cathode material precursor, lithium hydroxide, alumina as the first dopant, boric acid as the second dopant, and yttrium oxide as the third dopant were weighed out and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(B):n(Y) = 1:1.03:0.01:0.005:0.001. The mixture was then isothermally sintered in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 850°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.35 m. 2 / g. (3) The mass ratio of B element in boric acid I and the primary sintering material was m(B) / [m(BM)]=0.1 wt% to obtain a positive electrode material A6, which is almost the same as step (3) in Example 1, and the composition is Li 1.03 (Ni 0.584 Co 0.2 Mn 0.2 Al 0.01 B 0.005 Y 0.001 )O2, and a coating layer coated on the surface of the matrix, the coating layer containing an oxide of B and / or a lithium oxygen compound of B. The coating layer accounts for 0.1 wt% of the total mass of the positive electrode material.

[0161] Surface Ni of counter cathode material A6 3+ Content, internal Ni 3+The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0162] For positive electrode material A6, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0163] Example 7 Steps (1) and (2) are the same as steps (1) and (2) in Example 1, Step (3) is to use boric acid II instead of boric acid I to obtain cathode material A7, the composition of which is Li 1.03 (Ni 0.965 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 Y 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0164] Boric Acid II D 10 is 20.1 μm, and D 50 is 43.2 μm, and D 90 is 67.2 μm, and the distribution coefficient K 90 is 1.09.

[0165] Surface Ni of cathode material A7 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0166] For positive electrode material A7, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0167] Example 8 Steps (1) and (2) are the same as steps (1) and (2) in Example 1, In step (3), tungsten oxide was used instead of boric acid I. The W element in tungsten oxide and the primary sintering material were mixed uniformly in a high-speed mixer at a mass ratio of m(W) / [m(BM)] = 0.2 wt%, and then sintered at 460 °C in an oxygen furnace with an oxygen concentration of 99% for 10 h. After cooling, sieving, and iron removal, Li 1.03 (Ni 0.965 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 Y 0.002 ) O2 matrix, and a coating layer containing an oxide of W and / or a lithium oxygen compound of W coated on the surface of the matrix. The coating layer accounts for 0.20 wt% of the total mass of the positive electrode material.

[0168] Distribution coefficient K of tungsten oxide 90 is 1.51.

[0169] Surface Ni of cathode material A8 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0170] For positive electrode material A8, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0171] In Example 8, tungsten oxide is used as a coating agent. The tungsten oxide reacts with excess Li on the surface of the positive electrode material, reducing the amount of free Li on the surface of the positive electrode material, thereby improving the rate performance and cycle performance of lithium-ion batteries containing the positive electrode material.

[0172] Example 9 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, and the first dopants, alumina and niobium oxide, were weighed in a molar ratio of n(Me):n(Li):n(Al):n(Nb) = 1:1.03:0.01:0.002, then uniformly mixed and sintered in an oxygen furnace at a constant temperature. The oxygen concentration was 99% and the temperature was increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.19 m. 2 / g. In step (3), a positive electrode material A9 was prepared in the same manner as in Example 1, and the composition was Li 1.03 (Ni 0.968 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0173] Surface Ni of cathode material A9 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0174] The cross-sectional and surface SEM images of cathode material A9 obtained in Example 9 are shown in Figures 3 and 4, respectively, demonstrating that the cathode material does not have a core-shell structure. Furthermore, compared with cathode material A1 in Example 1, cathode material A9 has a smaller aspect ratio of the primary particles, a more rounded particle morphology, and the primary particles of the core and shell layers are more closely aligned, with smaller voids formed between the particles and a lower porosity.

[0175] For positive electrode material A9, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0176] Example 10 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, the first dopants alumina and niobium oxide, and the second dopant boric acid were weighed out and mixed uniformly in a molar ratio of n(Me):n(Li):n(Al):n(Nb):n(B) = 1:1.03:0.01:0.002:0.001. The mixture was then isothermally sintered in an oxygen furnace with an oxygen concentration of 99%. The temperature was increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.48 m. 2 / g.

[0177] In step (3), a positive electrode material A10 was prepared in the same manner as in Example 1, and the composition was Li 1.03 (Ni 0.967 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0178] Surface Ni of cathode material A10 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0179] Cross-sectional and surface SEM images of cathode material A10 obtained in Example 10 are shown in Figures 5 and 6, respectively. Cathode material A10 does not have a core-shell structure, and the entire material has high porosity. Furthermore, compared with cathode material A1 in Example 1, the primary particles of cathode material A10 are more elongated and have a larger aspect ratio. The disordered arrangement between the primary particles forms many pores, and the specific surface area of ​​the formed secondary particles is larger.

[0180] For the positive electrode material A10, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0181] Example 11 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, and second dopant boric acid are weighed in a molar ratio of n(Me):n(Li):n(B) = 1:1.03:0.001, then uniformly mixed and sintered in an oxygen furnace at a constant temperature. The oxygen concentration is 99% and the temperature is increased from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material is obtained. The specific surface area of ​​the primary sintered material is 0.51 m. 2 / g. In step (3), a positive electrode material A11 was prepared in the same manner as in Example 1, and the composition was Li 1.03 (Ni 0.979 Co 0.01 Mn 0.01 B 0.001 )O2 matrix, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material. Surface Ni of counter cathode material A11 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0182] For the positive electrode material A11, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0183] Example 12 Step (1) is the same as step (1) of Example 1, In step (2), the cathode material precursor, lithium hydroxide, second dopant boric acid, and third dopant yttrium oxide were weighed out in a molar ratio of n(Me):n(Li):n(B):n(Y) = 1:1.03:0.001:0.002, mixed uniformly, and sintered at constant temperature in an oxygen furnace with an oxygen concentration of 99%. The mixture was heated from room temperature to 700°C at a rate of 5°C / min for 12 hours. After cooling, crushing, and sieving, the primary sintered material was obtained. The specific surface area of ​​the primary sintered material was 0.47 m. 2 / g. In step (3), a positive electrode material A12 was prepared in the same manner as in Example 1, and the composition was Li 1.03 (Ni 0.977 Co 0.01 Mn 0.01 B 0.001 Y 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0184] Surface Ni of cathode material A12 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0185] For the positive electrode material A12, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0186] Comparative Example 1 Steps (1) and (2) are the same as steps (1) and (2) in Example 1, In step (3), the primary sintering material was mixed with water in a solid-liquid ratio of 3:1, washed with water while stirring for 2 minutes, then compressed, filtered, and dried to obtain a water-washed pre-treated material. The B element in boric acid I, which was used as a coating agent, and this pre-treated material were added in a mass ratio of m(B) / [m(BM)] = 0.15 wt%, mixed uniformly in a high-speed mixer, and sintered at a constant temperature of 350°C in an oxygen furnace with an oxygen concentration of 99% for 10 hours. After cooling, sieving, and iron removal, the cathode material D1 was obtained, with a composition of Li. 1.03 (Ni 0.965 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 Y 0.002 )O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0187] Surface Ni of cathode material D1 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0188] For positive electrode material D1, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0189] Comparative Example 2 Steps (1) and (2) are the same as steps (1) and (2) of Example 9, Step (3) is the same as step (3) of Comparative Example 1, and a positive electrode material D2 is obtained. 1.03 (Ni 0.968 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002)O2, and a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. The B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

[0190] Surface Ni of cathode material D2 3+ Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0191] For positive electrode material D2, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0192] Comparative Example 3 Steps (1) and (2) are the same as steps (1) and (2) in Example 1, In step (3), boric acid I is replaced with oxide, and the W element in tungsten oxide and the primary sintering material are mixed uniformly in a high-speed mixer at a mass ratio of m(W) / [m(BM)]=0.2 wt%, and then sintered at 460°C in an oxygen furnace with an oxygen concentration of 50% and air as the other atmosphere. The sintering time is 10 h. After cooling, sieving, and iron removal, the cathode material D3 is obtained, with a composition of Li. 1.03 (Ni 0.965 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 B 0.001 Y 0.002 )O 2の The positive electrode material comprises a matrix, and a coating layer containing an oxide of W and / or a lithium oxygen compound of W coated on the surface of the matrix, wherein the W element in the coating layer accounts for 0.2 wt% of the total mass of the positive electrode material.

[0193] Distribution coefficient K of tungsten oxide 90 is 1.51.

[0194] Surface Ni of the cathode material D3 3+Content, internal Ni 3+ The content, mixed-arrangement nickel content, surface free Li content, specific surface area and water content were tested, and the results are shown in Table 1.

[0195] For positive electrode material D3, the aspect ratio and porosity of the primary particles of the core, the aspect ratio and porosity of the primary particles of the shell layer, the aspect ratio and porosity of the primary particles of the positive electrode material, and the ratio of the radius of the core to the shell layer are shown in Table 2.

[0196] [Table 1-1]

[0197] [Table 1-2]

[0198] [Table 2-1]

[0199] [Table 2-2]

[0200] The positive electrode materials of the examples and comparative examples were crushed under conditions of 2.5T, 3.5T and 4.5T, respectively, and the specific surface area and particle size of the positive electrode materials after crushing were tested. The change rates of the specific surface area and particle size before and after crushing are shown in Table 3.

[0201] [Table 3-1]

[0202] [Table 3-2]

[0203] The cathode materials were assembled into 2025-type button cells, and the electrochemical performance of the cells was tested, with the results shown in Table 4.

[0204] [Table 4]

[0205] As can be seen from Tables 1 to 4, in Examples 1 to 10 of the present invention, dry coating was performed and the oxygen concentration in the oxygen-containing atmosphere during the coating process was controlled, and the Ni on the surface and inside of the obtained positive electrode material was 3+ The closeness of the content and the low content of mixed-arrangement nickel can avoid the formation of a NiO passivation layer on the positive electrode material and reduce the phenomenon of loss of surface active lithium, so that the lithium ion battery containing the positive electrode material has improved capacity, rate performance and cycle performance.

[0206] In Comparative Example 1-2, wet coating is used, and the primary sintered material is washed with water during the coating process, so that active lithium such as lithium carbonate and lithium hydroxide on the surface of the positive electrode material is washed away, and some active Ni 3+ Ni 4+ converted to Ni 2+ This decomposes and converts the surface Ni 3+ The content and internal ratio decrease, the mixed-arrangement nickel content increases, and a NiO passivation layer forms on the surface of the positive electrode material, ultimately resulting in poor capacity, rate performance, and cycle performance of the lithium-ion battery manufactured using the positive electrode material.

[0207] Furthermore, in the cathode materials obtained in Examples 1-8 of the present invention, by selecting specific doping elements, the cathode material forms a specific core-shell structure, specifically, the core and shell layers have different porosities, the core comprises primary particles with a small aspect ratio, and the shell layer comprises primary particles with a large aspect ratio, and at the same time, the primary particles in the shell layer are radially arranged. When the cathode material with this specific core-shell structure ensures sufficient contact between the cathode material and the electrolyte, it can improve the particle strength of the cathode material, and the primary particles in the shell layer are radially arranged, which is advantageous for mitigating compression and cracking caused by the expansion and contraction of crystal grains with different crystal plane orientations in different directions. In addition, the low grain boundary density in the shell layer reduces the generation and development of microcracks at the grain boundaries, thereby improving the charge-discharge cycle performance and service life of lithium-ion batteries containing this cathode material.

[0208] Compared with Examples 1 and 2, the doping rate of the third doping element is increased, and therefore the porosity of the core, shell layer and overall porosity of the positive electrode material are all reduced, the arrangement of the primary particles in the core and shell layer is more compact, the radial arrangement of the primary particles in the shell layer is more regular, the aspect ratio of the primary particles is larger, the positive electrode material has a smaller specific surface area, the positive electrode material has better particle strength, and lithium ion batteries containing this positive electrode material have better cycle performance.

[0209] As can be seen from Examples 1 and 3-4, the cathode materials containing different doping elements have the same structural effect as Example 1, and can also improve the electrochemical performance of lithium-ion batteries.

[0210] As can be seen from Examples 1 and 5-6, the preparation method of the present invention can be applied to different types of precursor materials, and the cathode materials obtained with different types of precursor materials can all improve the electrochemical performance of lithium-ion batteries.

[0211] As can be seen from Examples 1 and 7, coating agents with different particle sizes, especially those with the preferred particle size distribution of the present invention, can achieve better results.

[0212] As can be seen from Examples 1 and 8, different coating elements can be selected and coated onto the substrate material using the dry coating system of the present invention to form a finished cathode material with a high trivalent Ni content and improved performance.

[0213] FIG. 13 is a graph comparing the initial discharge capacities of Example 1, Example 9, Comparative Example 1, and Comparative Example 3, and FIG. 14 is a graph comparing dQ / dV of Example 1, Example 9, Comparative Example 1, and Comparative Example 3. As can be seen from FIGS. 13 and 14, lithium ion batteries containing the positive electrode material of the present invention have low charge voltages, small charge / discharge polarization, and excellent rate performance and initial discharge capacities.

[0214] FIG. 15 is a graph comparing the rate performance of Examples 1, 9, 10, and 2 and 3, and FIG. 16 is a graph comparing the cycle performance of Examples 1, 9, 10, and 2 and 3. As can be seen from FIGS. 15 and 16, the lithium ion batteries containing the positive electrode material having a core-shell structure have better cycle performance and rate performance than Examples 9 and 10, which do not have a core-shell structure.

[0215] Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited thereto. Within the technical concept of the present invention, the technical solutions of the present invention may be modified in a number of simple ways, including the combination of each technical feature in any other suitable manner, and these simple modifications and combinations are also considered to be the contents disclosed in the present invention, and all fall within the protection scope of the present invention.

Claims

1. 1. A method for producing a cathode material for a lithium ion battery, the method comprising: S1: Mixing a cathode material precursor, a lithium source, and an optional dopant, and then performing primary sintering under a first oxygen-containing atmosphere, followed by cooling, crushing, and sieving to obtain a primary sintered material; S2. After mixing the primary sintering material and the coating agent, secondary sintering is carried out under a second oxygen-containing atmosphere, and after sieving and removing iron, a positive electrode material for a lithium ion battery is obtained; the oxygen concentration in the second oxygen-containing atmosphere is 90 vol% or more; the dopant is a compound containing a doping element M, wherein M is selected from at least one of Ta, Cr, Mo, W, Al, Y, Ti, Zr, V, Nb, Ca, P, Ce, Er, Mg, B, Sr, Ba, and La; The primary sintering conditions were to increase the temperature from room temperature to 600-900°C at a temperature increase rate of 2-8°C / min, and sinter for 8-14 hours. the coating material is a compound containing a coating element J, where J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo, and Mn; D is the particle size corresponding to 10% of the volume distribution in the particle size test of the coating material. １０ , D, which is the particle size corresponding to 50% volume distribution ５０ and D, which is the particle size corresponding to 90% of the volume distribution ９０ is 1.5≦K ９０ = (D ９０ -D １０ ) / D ５０ 2.8≦2.8

2. 2. The method of claim 1, wherein in step S1, the lithium source is added in an amount such that the stoichiometric ratio is 0.9≦n(Li) / n(Me)≦1.2, where n(Me) is the total molar amount of metal elements in the cathode material precursor.

3. In step S1, the dopant includes at least one of a first dopant, a second dopant, and a third dopant; Here, the first dopant is a doping element M １ It is a compound containing M １ is selected from at least one of Al, Nb, Cr, V, Mg and Sr, and the second dopant is a doping element M ２ It is a compound containing M ２ is selected from at least one of Ti, La, P and W, and the third dopant is a doping element M ３ It is a compound containing M ３ is selected from at least one of Y, Ce, Ca, V, Ta, Co, Zr, and Mo, and the first dopant, the second dopant, and the third dopant are different in dopant type; The method of claim 1.

4. The positive electrode material precursor is The positive electrode material precursor is prepared by the steps of preparing a mixed salt solution of nickel salt, cobalt salt, and manganese salt, introducing the mixed salt solution, precipitant solution, and complexing agent solution into a reactor respectively, and carrying out a co-precipitation reaction in an inert gas atmosphere, followed by aging, washing, and drying. The method of claim 1.

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