Positive electrode material for lithium ion battery, method for producing the same, and 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, specifically to the cathode material of lithium-ion batteries and its manufacturing method, and lithium-ion batteries.

Background Art

[0002] In recent years, with the deepening of the oil energy crisis and environmental pollution problems, electric vehicles around the world have been rapidly developing in a new circuit as an alternative to traditional vehicles. At the same time, the performance requirements for high energy density and long cycle life of the power batteries installed in electric vehicles are also increasing.

[0003] As the most costly and performance-impacting part of the battery, the cathode material has been widely researched and applied in the lithium-ion power battery system. Among them, the layered lithium nickel cobalt manganese aluminum multi-element material has high specific capacity and stability, and has great potential for development. In order to meet the increasingly urgent requirements for high energy density and safety, increasing the Ni content in the multi-element material to increase the energy density, and combining doping and coating means to control the rate and cycle performance of the material have become the common choices of the market and researchers.

[0004] As the nickel content increases, traditional wet coating methods are prone to cause loss of surface-active lithium, and an electrochemically active passivation layer is formed due to the contact between the material and water. Furthermore, the impedance of the material increases, affecting the energy density and rate performance. In addition, the operation process during water washing is complex, with many influencing factors, and the cost of filtrate recovery is high. Therefore, more and more research is focusing on the dry coating process of high-nickel materials, which can not only effectively avoid the above problems, but also has a simple manufacturing process, low cost, high consistency and reproducibility. For example, CN106784675A provides a dry coating method for lithium battery cathode materials. First, the coating material is premixed with boric acid, and then mixed with the primary sintered material and fired to obtain the finished cathode material. During the process, the coating materials are in sufficient contact to form a solid melt, the coating effect is uniform, and they are tightly bonded after firing, and the coating layer is not easily detached. This method not only shortens the production cycle, ensures the uniformity of coating, can also expose the coating material to high temperature to form an ideal glassy coating, and improves the stability of the material.

[0005] However, directly dry-coating the primary sintered material still faces many challenges. One of the most major problems is that the specific surface area and porosity of the non-water-washed primary sintered material cannot be opened, and the particles for subsequent coating have a further reduced specific surface and are filled with pores. There is a large difference between the specific surface area of the dry-coated finished product and that of the wet-coated one. The small specific surface area and porosity reduce the contact area between the material and the electrolyte, affect the lithium-ion mass transfer process, and influence the discharge capacity and rate performance.

[0006] Therefore, it is very important to provide a cathode material with a uniform coating effect, appropriate specific surface area and porosity, no passivation layer, high energy density and good rate performance.

Summary of the Invention

Problems to be Solved by the Invention

[0007] The present invention aims to provide a positive electrode material for a lithium-ion battery, a method for manufacturing the same, and a lithium-ion battery, in order to overcome the problems that the loss of surface-active lithium of the positive electrode material due to water washing of traditional wet coating and the presence of a NiO passivation layer on the surface of the positive electrode material result in the inability of the positive electrode material properties to meet the actual requirements. The Ni on the surface and inside of the positive electrode material of the lithium-ion battery 3+ Since the content is close and the content of mixed-array nickel is low, the generation of a NiO passivation layer on the positive electrode material can be avoided, and the phenomenon of loss of surface-active lithium can be reduced. As a result, the lithium-ion battery including the positive electrode material has improved capacity, rate performance, and cycle performance.

Means for Solving the Problems

[0008] To achieve the above object, a first aspect of the present invention provides a positive electrode material for a lithium-ion battery, and the ratio of the Ni 3+ content on the surface of the positive electrode material to the Ni 3+ content inside the positive electrode material is 0.95 - 1:1, and in the positive electrode material, the content of mixed-array nickel is 3% or less.

[0009] A second aspect of the present invention provides a method for manufacturing a positive electrode material for a lithium-ion battery, and the method includes: S1. After mixing a positive electrode material precursor, a lithium source, and a dopant as required, performing primary sintering in a first oxygen-containing atmosphere, cooling, pulverizing, and sieving to obtain a primary sintered material; S2. After mixing the primary sintered material and a coating agent, performing secondary sintering in a second oxygen-containing atmosphere, sieving, and removing iron to obtain a positive electrode material for a lithium-ion battery, and 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 manufactured by the above method.

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

[0012] By the above technical solution, the positive electrode material of the lithium-ion battery according to the present invention, its manufacturing method, and the lithium-ion battery achieve the following beneficial effects.

[0013] Since the Ni content on the surface and inside of the lithium-ion positive electrode material according to the present invention is close, and the content of mixed-array nickel is low, it is possible to avoid generating a NiO passivation layer on the positive electrode material and reduce the phenomenon of loss of surface-active lithium. As a result, the lithium-ion battery including the positive electrode material has improved capacity, rate performance, and cycle performance. 3+ Furthermore, the positive electrode material of the lithium-ion battery according to the present invention has a specific porosity. Even when there is a coating layer on the surface of the positive electrode material, the surface can still maintain a loose porous structure, the coating layer contacts the surface of the material uniformly, there are many reaction sites, and there is no local concentration on the surface of the coating layer. This indicates that it can reduce the impedance of the positive electrode material and contribute to improving the cycle performance of the lithium-ion battery including the positive electrode material. In addition, the specific porosity is advantageous for sufficiently infiltrating the material with the electrolyte and releasing higher initial charge-discharge efficiency and rate performance.

[0014] Moreover, 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 core with a low porosity contributes to improving the cracking strength of the positive electrode material, and the shell with a high porosity can ensure the coating effect and the electrolyte infiltration effect. It should be noted that the shell is prone to micro-cracking and powdering phenomena during the charge-discharge process. The large porosity in the shell provides space for the expansion and contraction of the unit cell volume during the charge-discharge process, releases stress, and improves the cycle life of the lithium-ion battery including the positive electrode material.

[0015] Moreover, 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 core with a low porosity contributes to improving the cracking strength of the positive electrode material, and the shell with a high porosity can ensure the coating effect and the electrolyte infiltration effect. It should be noted that the shell is prone to micro-cracking and powdering phenomena during the charge-discharge process. The large porosity in the shell provides space for the expansion and contraction of the unit cell volume during the charge-discharge process, releases stress, and improves the cycle life of the lithium-ion battery including the positive electrode material.

[0016] Furthermore, the primary particles of the positive electrode material of the lithium-ion battery according to the present invention have a specific arrangement state. By means of combined doping, the arrangement state of the primary particles of the material is adjusted, and the primary particles are arranged radially at least in the shell portion (different doping can also extend to the core). Arranging them in an orderly manner can effectively relieve the pressure and cracks caused by the expansion and contraction in different directions of crystal grains with different crystal plane orientations, and improve the cycle performance of the lithium-ion battery including the positive electrode material.

[0017] Furthermore, the positive electrode material of the lithium-ion battery according to the present invention has an appropriate grain boundary density, and the method adjusts the core-shell structure of the material to have different grain boundary densities by means of combined doping. In the shell layer, the number of lithium insertion and extraction times of the primary particles is large and they are in sufficient contact with the electrolyte, and it is easy to form, develop, and powder the surface with microcracks during cycling. Therefore, a small grain boundary density can reduce the generation and development of microcracks at the grain boundaries. In the core, the contact between the primary particles and the electrolyte is relatively small, and a higher interface density provides channels for lithium-ion diffusion, obtaining higher capacity and better rate performance. The differentiation of the grain boundary density in the core-shell structure of the positive electrode material of the present invention enables high capacity and long cycles of the material.

[0018] In the method for manufacturing the positive electrode material of the lithium-ion battery according to the present invention, in an atmosphere with a high oxygen concentration content, by means of dry coating, the contact between the surface of the high-nickel ternary system material and water and the formation of an inactive passivation layer due to delithiation in the conventional water washing process are avoided, and the same structure and trivalent active nickel content in the surface and the bulk phase are retained to the maximum extent, and furthermore, higher capacity and lower electrochemical impedance are provided.

[0019] Furthermore, by selecting a specific combination of dopants and combining it with dry coating, porous secondary particles having a core-shell structure composed of primary particles arranged in an orderly manner are produced. As a result, when the positive electrode material has high particle strength and is used in a lithium-ion battery, the specific capacity, cycle performance, and rate performance of the lithium-ion battery are significantly improved, and at the same time, the cycle life is extended.

[0020] Furthermore, in the method for manufacturing the positive electrode material of the 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 does the surface of the obtained positive electrode material and the electrolyte sufficiently infiltrate, but also no excessive surface lithium remains on the surface of the positive electrode material. The positive electrode material obtained after dry coating the primary sintered material can exhibit a high discharge capacity.

Brief Description of the Drawings

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Mode for Carrying Out the Invention

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

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

[0024] In the present invention, the surface Ni content and the internal Ni content of the positive electrode material are measured by XPS. The surface Ni content of the positive electrode material is the result of directly performing an XPS test on the sample of the finished product, and the internal Ni content is the result of pulverizing the sample of the finished product into primary particles with an air flow mill, etching by 30 nm, and then performing an XPS test. 3+ 3+ 3+ 3+

[0025] ​​​​​​​In the case of a layered ternary cathode material, such as a nickel cobalt manganese ternary cathode material, Ni, Co, and Mn are located in the transition metal layer of the lattice, and the theoretical valence of active Ni is +3. In actual production, Ni 2+ and Ni 3+ coexist in the lattice, and the Ni 2+ portion is free between the layers and occluded in the reversible Li layer, resulting in a lithium nickel mixed arrangement, which affects the capacity and cycle life of the lithium-ion battery manufactured from the cathode material. In addition, in the manufacturing process of traditional cathode materials, in the water washing process, the surface of the cathode material is in contact with water, causing a large amount of de-lithiation on the surface of the cathode material, and finally forming NiOOH. NiOOH deoxygenates in the subsequent heating process to generate a non-electrochemical rock salt phase NiO passivation layer. According to XPS detection, the Ni 3+ content on the surface of the cathode material decreases significantly, the Ni 2+ content increases, and finally it is found that the electrochemical performance of the lithium-ion battery manufactured from the cathode material deteriorates. Specifically, the battery capacity decreases, and the impedance and polarization increase significantly.

[0026] According to the research of the inventors of the present invention, by making the Ni 3+ content on the surface and inside of the cathode material of the lithium-ion battery close, and having a low content of mixed arrangement nickel, specifically controlling to meet the range limited in the present invention, the generation of the NiO passivation layer on the cathode material can be avoided, the phenomenon of loss of surface active lithium can be reduced, and the lithium-ion battery including the cathode material has improved capacity, rate performance and cycle performance.

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

[0028] According to the present invention, in the cathode material, the ratio of the Ni 3+ content to the Ni 2+ content is 2 or more.

[0029] In the present invention, Ni in the cathode material 3+ content and Ni 2+ When the ratio of the contents satisfies the above range, the cathode material has higher activity and fewer lattice defects, and can significantly improve the electrochemical activity of the cathode material. When it is used in a lithium-ion battery, the capacity and rate performance of the battery can be significantly improved. At the same time, when there is less divalent nickel in the cathode material, there is less mixed arrangement nickel, reducing the risk of lithium-nickel mixed arrangement, improving the structural stability of the cathode material, and extending the cycle life of the cathode material in the battery.

[0030] In the present invention, Ni of the cathode material 3+ content and Ni 2+ content are measured by XPS.

[0031] Furthermore, in the cathode material, the ratio of the Ni 3+ content to the Ni 2+ content is 3 - 8.

[0032] According to the present invention, the specific surface area S0 of the cathode material is 0.1 - 0.5 m 2 / g.

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

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

[0035] According to the present invention, after being cracked at a pressure of 3.5 T, the specific surface area of the cathode material is S 3.5 , and the change rate 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 cracking under a pressure of 3.5 T satisfies the above range, the positive electrode material has certain pressure resistance characteristics. With a large cracking strength, it can avoid the risk of spherical cracking during the pole piece compaction of the material in the process of manufacturing the pole piece, improve the safety and stability of the lithium-ion battery including the positive electrode material, while enabling the positive electrode material to withstand a higher compaction density and have the potential for a 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 by the particle size test of the positive electrode material is D 10 0 After cracking under a pressure of 3.5 T, the particle size corresponding to 10% of the volume distribution by the particle size test of the multi-component positive electrode material is D 10 3.5 Here, (D -D 10 0 ) / D 10 3.5 ×100% is 0 - 30%. 10 0 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 by the particle size test of the positive electrode material is D 50 0 After cracking under a pressure of 3.5 T, the particle size corresponding to 50% of the volume distribution by the particle size test of the multi-component positive electrode material is D 50 3.5 Here, (D -D 50 0 ) / D 50 3.5 ) / D 50 0×100% is 0 - 15%. Furthermore, (D 50 0 -D 50 3.5 ) / D 50 0 ×100% is 0 - 10%.

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

[0041] In the present invention, among D 10 , D 50 and D 90 before and after cracking of the positive electrode material at a pressure of 3.5 T, when at least one of them satisfies the above range, it indicates that the positive electrode material has pressure resistance characteristics, generates small pressure crack fine powder under strong pressure, and thereby can improve the safety and stability in the top-level manufacturing process of the positive electrode material.

[0042] In the present invention, the particle size corresponding to 10% of the volume distribution by the particle size test of the positive electrode material is D 10 0 After being cracked at a pressure of 2.5 T, the particle size corresponding to 10% of the volume distribution by the particle size test of the multi-component positive electrode material is D 10 2.5 and where (D 10 0 -D10 2.5 ) / D 10 0 ×100% is from 0 to 10%, preferably, (D 10 0 -D 10 2.5 ) / D 10 0 ×100% is from 0 to 6%.

[0043] In the present invention, the particle size corresponding to 50% of the volume distribution by the particle size test of the positive electrode material is D 50 0 and after cracking under a pressure of 2.5 T, the particle size corresponding to 50% of the volume distribution by 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 from 0 to 6%, preferably, (D 50 0 -D 50 2.5 ) / D 50 0 ×100% is from 0 to 5%.

[0044] In the present invention, the particle size corresponding to 90% of the volume distribution by the particle size test of the positive electrode material is D 90 0 and after cracking under a pressure of 2.5 T, the particle size corresponding to 90% of the volume distribution by 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 from 0 to 4%, preferably, (D 90 0 -D 90 2.5 ) / D 90 0 ×100% is from 0 to 3%.

[0045] In the present invention, the particle size corresponding to 10% of the volume distribution by the particle size test of the positive electrode material is D 10 0 After being cracked under a pressure of 4.5 T, the particle size corresponding to 10% of the volume distribution by 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 by the particle size test of the positive electrode material is D 50 0 After being cracked under a pressure of 4.5 T, the particle size corresponding to 50% of the volume distribution by 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 by the particle size test of the positive electrode material is D 90 0 After being cracked under a pressure of 4.5 T, the particle size corresponding to 90% of the volume distribution by the particle size test of the multi-component positive electrode material is D 904.5 and where (D 90 0 -D 90 4.5 ) / D 90 0 × 100% is from 0 to 15%, preferably, (D 90 0 -D 90 4.5 ) / D 90 0 × 100% is from 0 to 10%.

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

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

[0050] In the present invention, the porosity was measured using a plurality of cross-sectional SEM images and a software statistics method.

[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 secondary particles 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 cathode material of the lithium-ion battery has a specific porosity. In particular, the core of the cathode material has a low porosity, while the shell has a high porosity. The dense structure of the core with a low porosity contributes to the improvement of the cracking strength of the cathode material, and the shell with a high porosity can provide space for the expansion and contraction of the unit cell volume during charge and discharge, thereby releasing stress and extending the cycle life of the lithium-ion battery including the cathode material.

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

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

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

[0059] In the present invention, when the ratio of the radius of the core to the shell layer in the cathode material satisfies the above range, not only can it ensure that the material has a certain porosity in the outer layer, but also it can ensure that the material has a certain cracking strength. When it is used in a lithium-ion battery, the lithium-ion battery has excellent comprehensive performance, such as high capacity, excellent cycle performance, and excellent stability.

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

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

[0062] According to the present invention, in the cathode 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 ratio of the primary particles of the core in the positive electrode material or the aspect ratio of the primary particles of the shell layer satisfies the above range, the core of the positive electrode material has a structure in which primary particles with a small aspect ratio and an oblate shape are deposited. The primary particles are deposited closely and disorderly, forming a dense structure with a small porosity and a large grain boundary density. The shell layer is laminated with a relatively sparse structure in which primary particles with a relatively large aspect ratio and an elongated shape are radially arranged, the contact surface between the primary particles is relatively small, and many holes are formed between the particles. At the same time, the primary particles of the positive electrode material have an appropriate arrangement orientation, release the stress generated during the charge and discharge process, avoid the occurrence of microcracks between the primary particle interfaces, and finally extend the cycle life of the positive electrode material.

[0064] Furthermore, in the positive electrode material, the aspect ratio of the primary particles of the core 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 includes 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 made of a lithium oxygen compound and / or an oxide of a specific element, the specific element is bonded or adhered to the surface of the positive electrode material, forms a protective layer on the surface of the positive electrode material, reduces the side reaction between the material and the electrolyte, reduces the phenomenon of powdering of the material to a certain extent, and improves 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 a 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 whole 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 cathode material.

[0074] In the present invention, for the cathode material, when the content of the element J in the coating layer satisfies the above range, to a certain extent, it can protect and modify the surface of the cathode material while preventing the coating layer from being too thick and affecting the conductivity and gram capacity of the cathode material.

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

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

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

[0078] When the content of the surface free Li in the cathode material satisfies the above range, it can provide an effective active lithium content, reduce the risk of lithium deficiency in the lattice of the material, ensure the high capacity of the material, and prevent the surface free lithium from being too much to increase the material impedance and cause serious storage gas production.

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

[0080] According to the present invention, the moisture content of the cathode material is 0 - 100 ppm.

[0081] In the present invention, when the moisture content of the cathode material satisfies the above range, it contains less crystal water and adsorbed water, has fewer side reactions with water, and shows 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 moisture content of the positive electrode material is 0 - 80 ppm.

[0084] A second aspect of the present invention provides a method for manufacturing a positive electrode material of a lithium - ion battery, the method comprising: S1: After mixing a positive electrode material precursor, a lithium source, and a dopant as required, performing primary sintering in a first oxygen - containing atmosphere, cooling, pulverizing, and sieving to obtain a primary sintered material; S2: After mixing the primary sintered material with a coating agent, performing secondary sintering in a second oxygen - containing atmosphere, sieving, and removing iron to obtain a positive electrode material of a lithium - ion battery. The oxygen concentration in the second oxygen - containing atmosphere is 90 vol% or more.

[0085] In the present invention, in the method for manufacturing a positive electrode material of a lithium - ion battery, in an atmosphere with a high oxygen - concentration content, by dry coating, the contact between the surface of the high - nickel ternary system material and water and the formation of an inactive passivation layer due to delithiation in the conventional water - washing process are avoided, and the same structure and trivalent active nickel content in the surface and the bulk phase are kept to the maximum. Specifically, the positive electrode material of the lithium - ion battery described in the first aspect of the present invention is manufactured. The positive electrode material has a lower electrochemical impedance. When it is used in a lithium - ion battery, the capacity, rate performance, and cycle performance of the lithium - ion battery can be effectively improved.

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

[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, the solid-phase reaction of lithiation and doping becomes more sufficient, and the high oxygen concentration also contributes to maximizing the oxidation of divalent nickel in nickel cobalt manganese hydroxide to trivalent nickel in lithium nickel cobalt manganese oxide, forming a layered electrochemical active material with fewer defects.

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

[0092] According to the present invention, in step S2, the coating agent is a compound containing a coating element J, and 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 for the secondary sintering include a sintering temperature of 200 - 600 °C and a sintering time of 8 - 14 h.

[0094] In the present invention, when the secondary sintering is carried out under the above conditions, the coating agent can react sufficiently with the material substrate to bond, play a role in protecting and modifying the material surface, and improve the cycle stability of the material. Some coating agents can react with the surface residual alkali under the above conditions, consume the surface insulating substances, improve the discharge capacity and rate performance of the lithium-ion battery including the cathode material, while reducing the gas production during the 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 - 12 h.

[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 at 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 at 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 at a mass ratio of 0.05 wt% ≦ m(J) / [m(BM)] ≦ 1.5 wt%, 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 at a mass ratio of 0.05 wt% ≦ m(J) / [m(BM)] ≦ 1 wt%.

[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 first dopant, the second dopant, and the third dopant are used only for distinguishing 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. The first type of dopant M1 is a basic conventional dopant that stabilizes the layered oxide structure. The second type of dopant is primary particles of a refined material, which form a large porosity between the particles and form a specially selected dopant of sparse secondary particles. The third type of dopant forms a specially selected dopant with a core-shell structure that is sparse on the outside and dense on the inside in order to make the arrangement of the material denser and more orderly, especially the arrangement inside the core denser. In the present invention, porous secondary particles having a core-shell structure composed of primary particles arranged orderly by the combination between dopants are manufactured. The obtained positive electrode material has high particle strength. When it is used in a lithium-ion battery, the specific capacity, cycle performance, and rate performance of the lithium-ion battery are significantly improved, and at the same time, the cycle life is extended.

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

[0104] According to the present invention, in step S1, the addition amount of the first dopant is added at 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 positive electrode material precursor.

[0105] According to the present invention, in step S1, the addition amount of the second dopant is added at 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 positive electrode material precursor.

[0106] According to the present invention, in step S1, the addition amount of the third dopant is added at 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 a 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 becomes porous and hydrophobic. When the coating agent is coated on the primary sintered material, the coating agent can penetrate better through the pores of the primary sintered material, enabling good coating of the primary sintered material. The finally obtained cathode material has low electrochemical impedance. When the cathode 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 - 0.65 m 2 / g, preferably 0.35 - 0.6 m 2 / g.

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

[0111] In the present invention, K 90When a coating agent that satisfies the above range is selected to dry - coat the primary sintered material, the uniformity of the coating can be improved. Specifically, the small - particle coating agent in the coating agent is more likely to melt and enter the pores on the surface of the primary sintered material, and after the large - particle coating agent in the coating agent melts, it can be uniformly dispersed on the surface of the primary sintered material, and finally the coating effect of the coating agent is improved.

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

[0113] In the present invention, the cathode - material precursor can adopt the conventional cathode - material precursor in this field. Preferably, the cathode - material precursor is prepared by mixing nickel salt, cobalt salt, and manganese salt into a mixed - salt solution, passing the mixed - salt solution, the precipitant solution, and the complexing - agent solution into a reaction kettle respectively, performing a coprecipitation reaction in an inert gas, and then obtaining the cathode - material precursor through aging, washing, and drying steps.

[0114] In the present invention, the types of nickel salt, cobalt salt, and manganese salt are not particularly limited, and the 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 usage amounts of the nickel salt, the cobalt salt, and the manganese salt satisfy n(Ni):n(Co):n(Mn)=x:y:z, where 0 < x < 1, 0 < y ≤ 0.4, and 0 < z ≤ 0.6.

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

[0117] In the present invention, the type of the precipitant solution is not particularly limited, and a conventional precipitant solution in this field, such as a sodium hydroxide solution, can be employed.

[0118] In the present invention, the type of the complexing agent solution is not particularly limited, and a conventional complexing agent solution in this field, such as aqueous ammonia, can be employed.

[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 of the coprecipitation reaction include that the pH is 10.5 - 11.5, the stirring speed is 200 - 800 rpm, the reaction temperature is 50 - 80 °C, and the flow rate of the mixed salt solution into the reaction kettle is 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 kettle, the reaction temperature, and the stirring rate in the coprecipitation reaction process to meet the above ranges, the primary fibers of the precursor can be grown into an elongated structure, radially arranged, and the precursor structure having such a structure is porous, regularly arranged, favorable for sufficient lithiation, and forms a layered oxide cathode material with few defects.

[0123] Furthermore, the conditions of the coprecipitation reaction include that the pH is 10.6 - 11.4, the stirring speed is 300 - 700 rpm, the reaction temperature is 55 - 80 °C, preferably 55 - 75 °C, and the introduction rate of the mixed salt solution into the reaction kettle is 100 - 300 mL / h.

[0124] The third aspect of the present invention provides a cathode material for a lithium-ion battery manufactured by the above method.

[0125] The fourth aspect of the present invention provides a lithium-ion battery characterized by including the above cathode material for a lithium-ion battery.

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

[0127] Hereinafter, the present invention will be described in detail by way of examples. In the following examples, (1) Morphology test: Obtained from the test of a scanning electron microscope of model S-4800 manufactured by Hitachi, Ltd., Japan. (2) Particle size D 10 、D 50 、D 90 : Obtained from the test of a laser particle size distribution analyzer of model Hydro 2000mu manufactured by Malvern. (3) Specific surface area test: Obtained from the test of a specific surface area meter of model Tristar 3020 manufactured by Micromeritics. (4) XRD finish: Obtained from the test of a Smart Lab9 KW manufactured by Rigaku Corporation, Japan. (5) Particle strength test: Obtained from the test of particles using a micro compression tester MCT-210 manufactured by Shimadzu Corporation. (6) XPS: Obtained from an ESCALAB 250 spectrometer manufactured by PerkinElmer, USA. (7) The surface free Li content is measured by potentiometric titration using a 905 potentiometric titrator. (8) The composition of the matrix in the positive electrode material is measured by ICP. (9) The moisture content of the positive electrode material is measured by a precision moisture meter. (10) Electrochemical performance test: In the above examples and comparative examples, the electrochemical performance of the multi-component positive electrode material is tested using a CR2025 button cell.

[0128] The manufacturing process of the 2025 type button cell is specifically as follows.

[0129] Manufacture of the positive electrode sheet: A multi-component positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were sufficiently mixed with an appropriate amount of N-methylpyrrolidone (NMP) at a mass ratio of 95:3:2 to form a uniform slurry. The slurry was coated on an aluminum foil and dried at 120 °C for 12 h, and then pressed and formed at a pressure of 100 MPa to manufacture a positive electrode sheet with a diameter of 12 mm and a thickness of 120 μm. The loading amount of the multi-component positive electrode material was 15.5 mg / cm 2 is.

[0130] Assembly of the battery: Inside a gas glove box filled with argon gas with both the water content and the oxygen content less than 5 ppm, after assembling the positive electrode sheet, the separator, the negative electrode sheet, and the electrolyte into a 2025-type button battery, it was left standing for 6 h. The negative electrode sheet used a lithium metal sheet with a diameter of 17 mm and a thickness of 1 mm. The separator used a polyethylene porous film (Celgard 2325) with a thickness of 25 μm. The electrolyte used an equal-volume mixture of 1 mol / L LiPF6, ethylene carbonate (EC), and diethyl carbonate (DEC).

[0131] 2025-type button battery test: In the following examples and comparative examples, an electrochemical performance test was performed on the 2025-type button battery using a Shensen Neware battery test system. The charge-discharge current density at 0.1C was 200 mA / g.

[0132] The charge-discharge voltage range was controlled to 3 - 4.3V. At room temperature, the button battery was subjected to a charge-discharge test at 0.1C to evaluate the initial charge-discharge specific capacity and the 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. At a constant temperature of 45 °C, the button battery was subjected to 2 cycles of charge-discharge at 0.1C, and then 80 cycles of charge-discharge at 1C to evaluate the high-temperature capacity retention rate of the multi-component positive electrode material.

[0134] Rate performance test: Control the charge-discharge voltage range to 3.0 - 4.3V. At room temperature, charge and discharge the button cell at 0.1C for 2 cycles, and then charge and discharge it at 0.2C, 0.33C, 0.5C, and 1C for 1 cycle each. Evaluate the rate performance of the multi-component cathode material 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 is the discharge specific capacity of the first cycle of the button cell, and the discharge specific capacity at 1C is the discharge specific capacity of the sixth cycle of the button cell.

[0135] Example 1 (1) Dissolve nickel sulfate salt, cobalt sulfate salt, and manganese sulfate salt in pure water at a molar ratio of n(Ni):n(Co):n(Mn) of 98:1:1 to obtain a mixed salt solution A with a concentration of 2.2 mol / L. Prepare an 8 mol / L sodium hydroxide solution as the precipitant solution B and a 6 mol / L ammonia water as the complexing agent solution C. Add the bottom liquid to the reaction kettle and adjust the pH to 11. Introduce nitrogen gas for protection, control the system temperature at 60°C, add solutions A, B, and C to the reaction kettle from the inlet pipes respectively, with the stirring rotation speed being 500 rpm, control the feeding rate of the mixed salt solution A at 200 mL / h, adjust the flow rates of solutions B and C to stabilize the pH of the reaction system at 11 ± 0.05. After the average particle size D50 in the solution grows to 14 μm, end the reaction, and obtain the cathode material precursor through aging, separation, washing, and drying.

[0136] (2) Weigh the above cathode material precursor, lithium hydroxide, alumina and niobium oxide as the first dopant, boric acid as the second dopant, and yttrium oxide as the third dopant respectively at 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, and then mix them uniformly. Sinter them at a constant temperature in an oxygen furnace. The oxygen concentration is 99%. Heat up from room temperature to 700°C at a heating rate of 5°C / min, and the sintering time is 12 h. After cooling, pulverizing, and sieving, obtain the primary sintered material. The specific surface area of the primary sintered material is 0.45 m 2 / g.

[0137] (3) Put the B element in boric acid I and the primary sintered material into a high-speed mixer at a mass ratio of m(B) / [m(BM)] = 0.15 wt% and mix them uniformly. Sinter at a constant temperature of 350 °C in an oxygen furnace, with an oxygen concentration of 99% and a sintering time of 10 h. After cooling, sieving, and iron removal, the cathode material A1 is obtained, and the composition 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 matrix, and a coating layer including 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 cathode material.

[0138] The D of boric acid I 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] The surface Ni 3+ content, internal Ni 3+ content, the content of mixed array nickel, the content of surface free Li, the specific surface area, and the moisture content of the cathode material A1 are tested, and the results are shown in Table 1.

[0140] The cross-sectional SEM and surface SEM of the cathode material A1 obtained in Example 1 are shown in Figure 1 and Figure 2 respectively. The cathode material has a core-shell structure, and the core and shell layers have different porosities. At the same time, it shows that the primary particles in the shell layer are radially arranged. For the cathode material A1, the aspect ratio and porosity of the primary particles in the core, the aspect ratio and porosity of the primary particles in the shell layer, the aspect ratio and porosity of the primary particles of the cathode material, and the ratio of the radii of the core and shell layers are shown in Table 2.

[0141] Example 2 Step (1) is the same as step (1) in Example 1, In step (2), the positive electrode material precursor, lithium hydroxide, the first dopant alumina and niobium oxide, the second dopant boric acid, and the third dopant yttrium oxide are weighed 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, and then mixed uniformly. The mixture is sintered at a constant temperature in an oxygen furnace, where the oxygen concentration is 99%, and the mixture is heated from room temperature to 700°C at a heating rate of 5°C / min, and the sintering time is 12h. After cooling, crushing, and sieving, the primary sintered material is obtained. The specific surface area of the primary sintered material is 0.39m 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, 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 B element in the coating layer accounts for 0.15 wt% of the total mass of the positive electrode material.

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

[0144] The cross-sectional SEM and surface SEM 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, and the core and shell layers have different porosities, and at the same time, the primary particles in the shell layer are radially arranged. Compared with the cathode material A1 in Example 1, the core and shell layers of the cathode material A2 have lower porosities, and the arrangement of the primary particles in the core is more compact, the radial arrangement of the primary particles in the shell layer is more regular, and the aspect ratio of the primary particles is larger.

[0145] For the positive electrode material A2, Table 2 shows 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.

[0146] Example 3 Step (1) is the same as step (1) of Example 1, In step (2), the positive electrode 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 respectively at a molar ratio of n(Me):n(Li):n(Al):n(P):n(Y)=1:1.03:0.01:0.001:0.002 and then uniformly mixed, and sintered at a constant temperature in an oxygen furnace. The oxygen concentration was 99%. The temperature was raised from room temperature to 700 °C at a heating rate of 5 °C / min, and the sintering time was 12 h. After cooling, pulverizing, and sieving, a primary sintered material was obtained. The specific surface area of the primary sintered material is 0.41 m 2 / g.

[0147] Step (3) manufactures the positive electrode material A3 in the same manner as in Example 1, and the composition is 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 including 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] The surface Ni 3+ content, internal Ni 3+ content, the content of mixed array nickel, the content of surface free Li, the specific surface area, and the moisture content of the positive electrode material A3 were tested, and the results are shown in Table 1.

[0149] As shown in FIGS. 9 and 10 which are the cross-sectional SEM and surface SEM of the positive electrode material A3 obtained in Example 3 respectively, the positive electrode material has a core-shell structure, and the core and the shell layer have different porosities. At the same time, it shows that the primary particles in the shell layer are arranged radially. Compared with the positive electrode material A1 of Example 1, the difference in porosity between the core and the shell layer of the positive electrode material A3 is slightly smaller, and there are also certain pores in the core part.

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

[0151] Example 4 Step (1) is the same as step (1) of Example 1. In step (2), after weighing the positive electrode material precursor, lithium hydroxide, alumina as the first dopant, boric acid as the second dopant, and zirconia as the third dopant at a molar ratio of n(Me):n(Li):n(Al):n(B):n(Zr)=1:1.03:0.01:0.001:0.002 and mixing them uniformly, primary sintering is carried out according to the conditions of Example 1 to obtain a primary sintered material, and the specific surface area of the primary sintered material is 0.39 m 2 / g.

[0152] In step (3), the positive electrode material A4 is manufactured in the same manner as in Example 1, and its composition includes a matrix of 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] The Ni 3+ content on the surface of the positive electrode material A4, the internal Ni 3+The content, the content of the mixed array nickel, the content of the surface-free Li, the specific surface area, and the moisture content are tested, and the results are shown in Table 1.

[0154] The cross-sectional SEM and surface SEM of the positive electrode material A4 obtained in Example 4 are shown in FIGS. 11 and 12, respectively. The positive electrode material has a core-shell structure, and the core and the shell layer have different porosities. At the same time, it shows that the primary particles in the shell layer are arranged radially. Compared with the positive electrode material A1 of Example 1, the porosity of the shell layer of the positive electrode material A4 is slightly smaller, and the aspect ratio of the particles is smaller.

[0155] For the positive electrode material A4, Table 2 shows 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 radii of the core and the shell layer.

[0156] Example 5 (1) Nickel sulfate salt, cobalt sulfate salt, and manganese sulfate salt are dissolved in pure water at a molar ratio of n(Ni):n(Co):n(Mn) of 82:10:8 to obtain a mixed salt solution A with a concentration of 2 mol / L. An 8 mol / L sodium hydroxide solution is prepared as a precipitant solution B, and a 5.4 mol / L ammonia water solution is prepared as a complexing agent solution C. Add the bottom liquid to the reaction kettle to adjust the pH to 11, introduce nitrogen gas for protection, control the system temperature at 60 °C, add solutions A, B, and C to the reaction kettle from the inlet pipes respectively, with a stirring rotation speed of 500 rpm, control the feeding rate of the mixed salt solution A at 200 mL / h, adjust the flow rates of solutions B and C so that the pH of the reaction system is stabilized at 11 ± 0.05, and end after the average particle size D50 of the particles in the solution grows to 14 μm. Then carry out aging, separation, washing, and drying to obtain a positive electrode material precursor.

[0157] (2) The precursor of the positive electrode material, lithium hydroxide, alumina as the first dopant, boric acid as the second dopant, and yttrium oxide as the third dopant were weighed respectively at a molar ratio of n(Me):n(Li):n(Al):n(B):n(Y)=1:1.03:0.01:0.004: 0.002 and then uniformly mixed, and sintered at a constant temperature in an oxygen furnace. The oxygen concentration was 99%. The temperature was raised from room temperature to 750 °C at a heating rate of 5 °C / min, and the sintering time was 12 h. After cooling, pulverizing, and sieving, a primary sintered material was obtained. The specific surface area of the primary sintered material is 0.35 m 2 / g. (3) Except for manufacturing the positive electrode material A5 with the mass ratio of B element in boric acid I to the primary sintered material m(B) / [m(BM)] = 0.12 wt%, it is almost the same as step (3) of Example 1, 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 matrix, and a coating layer containing boron oxide and / or lithium oxygen compound of boron 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] The surface Ni 3+ content, internal Ni 3+ content, the content of mixed array nickel, the content of surface free Li, specific surface area, and moisture content of the positive electrode material A5 were tested, and the results are shown in Table 1.

[0159] For the 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) Dissolve nickel sulfate salt, cobalt sulfate salt, and manganese sulfate salt in pure water at a molar ratio of n(Ni):n(Co):n(Mn) of 60:20:20 to obtain a mixed salt solution A with a concentration of 1.6 mol / L. Prepare a sodium hydroxide solution with a concentration of 8 mol / L as a precipitant solution B, and prepare an ammonia water solution with a concentration of 4.8 mol / L as a complexing agent solution C. Add a bottom liquid to the reaction kettle to adjust the pH to 11, introduce nitrogen gas for protection, control the system temperature at 60 °C, add solution A, B, and C to the reaction kettle from the inlet pipes respectively, with a stirring rotation speed of 500 rpm, control the feeding rate of the mixed salt solution A at 200 mL / h, adjust the flow rates of solution B and C so that the pH of the reaction system is stabilized at 11 ± 0.05. After the average particle size D50 in the solution grows to 14 μm, end the reaction, and obtain a cathode material precursor through aging, separation, washing, and drying. (2) Weigh the cathode material precursor, lithium hydroxide, alumina as the first dopant, boric acid as the second dopant, and yttrium oxide as the third dopant respectively at a molar ratio of n(Me):n(Li):n(Al):n(B):n(Y)=1:1.03:0.01:0.005:0.001, then mix them uniformly, and sinter them at a constant temperature in an oxygen furnace. The oxygen concentration is 99%. Heat up from room temperature to 850 °C at a heating rate of 5 °C / min, and the sintering time is 12 h. After cooling, pulverizing, and sieving, a primary sintered material is obtained. The specific surface area of the primary sintered material is 0.35 m 2 / g. (3) Obtain cathode material A6 with a mass ratio of m(B) / [m(BM)] = 0.1 wt% of the B element in boric acid I and the primary sintered material. It is almost the same as step (3) of 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 matrix, and a coating layer containing boron oxide and / or lithium oxygen compound of boron coated on the surface of the matrix. The coating layer accounts for 0.1 wt% of the total mass of the cathode material.

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

[0162] In the cathode 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 cathode 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) of Example 1. In step (3), boric acid II was used instead of boric acid I to obtain the cathode material A7, and the composition 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 matrix, and a coating layer including 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 cathode material.

[0164] The D of boric acid II 10 is 20.1 μm, D 50 is 43.2 μm, D 90 is 67.2 μm, and the distribution coefficient K 90 is 1.09.

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

[0166] For the cathode 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 cathode 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) of Example 1, In step (3), instead of boric acid I, tungsten oxide is used, and the W element in tungsten oxide and the primary sintered material are mixed uniformly in a high-speed mixer at a mass ratio m(W) / [m(BM)] = 0.2 wt%, and sintered at a constant temperature of 460 °C in an oxygen furnace. The oxygen concentration is 99%, and the sintering time is 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 are obtained. The coating layer accounts for 0.20 wt% of the total mass of the cathode material.

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

[0169] The surface Ni 3+ content, internal Ni 3+ content, content of mixed array nickel, content of surface free Li, specific surface area, and moisture content of the cathode material A8 are tested, and the results are shown in Table 1.

[0170] For the cathode 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 cathode 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 the coating agent. Tungsten oxide reacts with the excess Li on the surface of the cathode material, reducing the content of surface free Li in the cathode material and improving the rate performance and cycle performance of the lithium-ion battery containing the cathode material.

[0172] Example 9 Step (1) is the same as step (1) in Example 1, In step (2), a cathode material precursor, lithium hydroxide, alumina and niobium oxide as the first dopant are weighed respectively at a molar ratio of n(Me):n(Li):n(Al):n(Nb)=1:1.03:0.01:0.002 and then uniformly mixed, and isothermally sintered in an oxygen furnace. The oxygen concentration is 99%. It is heated from room temperature to 700 °C at a heating rate of 5 °C / min, and the sintering time is 12 h. After cooling, pulverizing and sieving, a primary sintered material is obtained, and the specific surface area of the primary sintered material is 0.19 m 2 / g. In step (3), cathode material A9 is manufactured in the same manner as in Example 1, and the composition is Li 1.03 (Ni 0.968 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002 )O2 matrix, and a coating layer including 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 cathode material.

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

[0174] The cross-sectional SEM and surface SEM of cathode material A9 obtained in Example 9 are shown in Figure 3 and Figure 4 respectively, indicating that the cathode material does not have a core-shell structure. Furthermore, compared with the cathode material A1 of Example 1, the aspect ratio of the primary particles of cathode material A9 is smaller, the particle morphology is more rounded, the primary particles of the core and the shell layer are more closely arranged, the cavities formed between the particles are small, and the porosity is low.

[0175] For cathode 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 cathode material, and the ratio of the radii of the core and the shell layer are shown in Table 2.

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

[0177] In step (3), the cathode material A10 is manufactured in the same manner as in Example 1, and the composition is 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 including 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 cathode material.

[0178] The Ni 3+ content on the surface of the cathode material A10, the internal Ni 3+ content, the content of mixed array nickel, the content of surface free Li, the specific surface area and the moisture content are tested, and the results are shown in Table 1.

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

[0180] In 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 positive electrode material precursor, lithium hydroxide, and boric acid as the second dopant were each weighed at a molar ratio of n(Me):n(Li):n(B)=1:1.03:0.001 and then uniformly mixed, and sintered at a constant temperature in an oxygen furnace. The oxygen concentration was 99%. The temperature was raised from room temperature to 700°C at a heating rate of 5°C / min, and the sintering time was 12 h. After cooling, pulverizing, and sieving, a primary sintered material was obtained. The specific surface area of the primary sintered material is 0.51 m 2 / g. Step (3) manufactures the positive electrode material A11 in the same manner as in Example 1, and the composition is Li 1.03 (Ni 0.979 Co 0.01 Mn 0.01 B 0.001 )O2, and includes a coating layer including 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. Regarding the surface Ni 3+ content, internal Ni 3+ content, content of mixed array nickel, content of surface free Li, specific surface area, and moisture content of the positive electrode material A11 were tested, and the results are shown in Table 1.

[0182] In 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, Step (2): The precursor of the positive electrode material, lithium hydroxide, boric acid as the second dopant, and yttrium oxide as the third dopant were weighed respectively at a molar ratio of n(Me):n(Li):n(B):n(Y)=1:1.03:0.001:0.002 and then uniformly mixed, and sintered at a constant temperature in an oxygen furnace. The oxygen concentration was 99%. The temperature was raised from room temperature to 700 °C at a heating rate of 5 °C / min, and the sintering time was 12 h. After cooling, pulverizing, and sieving, a primary sintered material was obtained. The specific surface area of the primary sintered material is 0.47 m 2 / g. Step (3) manufactures the positive electrode material A12 in the same manner as in Example 1, and the composition is Li 1.03 (Ni 0.977 Co 0.01 Mn 0.01 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.

[0184] The Ni content on the surface of the positive electrode material A12, the internal Ni 3+ content, the content of mixed array nickel, the content of surface free Li, the specific surface area, and the moisture content were tested, and the results are shown in Table 1. 3+

[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) of Example 1, Step (3): The primary sintered material was mixed with water at a solid-liquid ratio of 3:1, washed with water while stirring for 2 min, then compressed, filtered, and dried to obtain a pre-treated material after water washing. Element B in boric acid I as the coating agent was added to this pre-treated material at a mass ratio of m(B) / [m(BM)] = 0.15 wt%, put into a high-speed mixer and uniformly mixed, and then sintered at a constant temperature of 350 °C in an oxygen furnace. The oxygen concentration was 99% and the sintering time was 10 h. After cooling, sieving, and iron removal, the cathode material D1 was obtained, with the 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 includes a coating layer containing an oxide of B and / or a lithium oxygen compound of B coated on the surface of the matrix. Element B in the coating layer accounts for 0.15 wt% of the total mass of the cathode material.

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

[0188] For the cathode 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 cathode 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): Similar to step (3) of Comparative Example 1, the cathode material D2 was obtained, with the composition of Li 1.03 (Ni 0.968 Co 0.01 Mn 0.01 Al 0.01 Nb 0.002)It includes a matrix that is 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 cathode material.

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

[0191] For cathode material D2, Table 2 shows 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 cathode material, and the ratio of the radius of the core to the shell layer.

[0192] Comparative Example 3 Steps (1) and (2) are the same as steps (1) and (2) of Example 1, In step (3), an oxide was used instead of boric acid I. The W element in tungsten oxide and the primary sintered material were mixed uniformly in a high-speed mixer at a mass ratio of m(W) / [m(BM)] = 0.2 wt%, and sintered at a constant temperature of 460 °C in an oxygen furnace. The oxygen concentration was 50%, and the other atmosphere was air. The sintering time was 10 h. After cooling, sieving, and iron removal, cathode material D3 was obtained, and the composition was 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 It includes 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. The W element in the coating layer accounts for 0.2 wt% of the total mass of the cathode material.

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

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

[0195] For the 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 radii of the core and 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 cracked under the conditions of 2.5T, 3.5T, and 4.5T, respectively. The specific surface area and particle size of the cracked positive electrode materials were tested, and the change rates of the specific surface area and particle size before and after cracking are shown in Table 3.

[0201]

Table 3-1

[0202]

Table 3-2

[0203] The positive electrode material was assembled into a 2025-type button battery, and the electrochemical performance of the battery was tested, and the results are shown in Table 4.

[0204]

Table 4

[0205] As can be seen from Tables 1 - 4, in Examples 1 - 10 of the present invention, during dry coating, the concentration of oxygen in the oxygen-containing atmosphere during the coating process was controlled, and the Ni content on the surface and inside of the obtained cathode material was made to approach and have a low content of mixed-array nickel, avoiding the generation of a NiO passivation layer on the cathode material, and the phenomenon of loss of surface-active lithium could be reduced. Thereby, the lithium-ion battery containing the cathode material has improved capacity, rate performance, and cycle performance. 3+ In Comparative Examples 1 - 2, wet coating was employed. During the coating process, the primary sintered material was washed with water, and active lithium such as lithium carbonate and lithium hydroxide on the surface of the cathode material was washed away, and a part of the active Ni was converted to Ni, decomposed and converted to Ni, whereby the surface Ni content and the internal ratio decreased, the mixed-array nickel content increased, and a NiO passivation layer was formed on the surface of the cathode material, and finally the capacity, rate performance, and cycle performance of the lithium-ion battery manufactured from the cathode material deteriorated.

[0206] 3+ to Ni 4+ and decomposed and converted to Ni 2+ resulting in a decrease in the surface Ni 3+ content and the internal ratio, an increase in the mixed-array nickel content, and the formation of a NiO passivation layer on the surface of the cathode material, and finally the capacity, rate performance, and cycle performance of the lithium-ion battery manufactured from the cathode material deteriorate.

[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 the shell layer have different porosities, and the core contains primary particles with a small aspect ratio, while the shell layer contains primary particles with a large aspect ratio. At the same time, the primary particles in the shell layer are radially arranged. When the cathode material having the above specific core-shell structure ensures sufficient contact between the cathode material and the electrolyte, the particle strength of the cathode material can be improved. The primary particles in the shell layer are radially arranged, which is advantageous for alleviating the pressure and cracks caused by the expansion and contraction in different directions of crystal grains with different crystal plane orientations. Moreover, the low grain boundary density of the shell layer reduces the generation and development of microcracks at the grain boundaries, improving the charge-discharge cycle performance and service life of the lithium-ion battery containing the cathode material.

[0208] Compared with Example 1 and Example 2, due to the improvement in the doping ratio of the third doping element, the porosities of the core, the shell layer, and the whole of the cathode material all decrease, and the arrangement of the primary particles in the core and the shell layer is denser. The radial arrangement of the primary particles in the shell layer is more regular, the aspect ratio of the primary particles is larger, the cathode material has a smaller specific surface area, the cathode material has better particle strength, and the lithium-ion battery containing the cathode material has better cycle performance.

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

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

[0211] As can be seen from Example 1 and Example 7, coating agents with different particle sizes, especially coating agents having a preferred particle size distribution according to the present invention, can obtain better effects.

[0212] As can be seen from Example 1 and Example 8, different coating agent elements can be selected and coated on the substrate material by the dry coating system of the present invention to form a finished positive electrode material having a high trivalent Ni content and having an improvement effect.

[0213] FIG. 13 is a comparison diagram of the initial discharge capacity of Example 1, Example 9, Comparative Example 1 and Comparative Example 3, and FIG. 14 is a dQ / dV comparison diagram of Example 1, Example 9, Comparative Example 1 and Comparative Example 3. As can be seen from FIGS. 13 and 14, the lithium ion battery including the positive electrode material of the present invention has a low charging corresponding voltage, a small charge-discharge polarization, and excellent rate performance and initial discharge capacity.

[0214] FIG. 15 is a comparison diagram of the rate performance of Example 1, Example 9, Example 10 and Examples 2 and 3, and FIG. 16 is a comparison diagram of the cycle performance of Example 1, Example 9, Example 10 and Examples 2 and 3. As can be seen from FIGS. 15 and 16, compared with Example 9 and Example 10 without the core-shell structure, the lithium ion battery including the positive electrode material having the core-shell structure has better cycle performance and rate performance.

[0215] The preferred embodiments of the present invention have been described in detail above, but the present invention is not limited thereto. Within the technical concept scope of the present invention, a plurality of simple modifications are possible to the technical solution means of the present invention, including the combination of each technical feature in any other appropriate manner. These simple modifications and combinations are regarded as the same as the content disclosed in the present invention and all belong to the protection scope of the present invention.

Claims

1. A positive electrode material for a lithium ion battery, wherein the Ni content on the surface of the positive electrode material ３＋ and the Ni content inside the positive electrode material ３＋ have a ratio of 0.95 - 1:1, The positive electrode material is characterized in that the content of mixed array nickel is 3% or less, which is a positive electrode material for a lithium-ion battery.

2. The surface Ni content of the positive electrode material ３＋ and the internal Ni content of the positive electrode material ３＋ have a ratio of 0.97 - 0.99:1, In the positive electrode material, the proportion of the content of mixed array nickel is 1.5% or less, Preferably, in the positive electrode material, Ni ３＋ content and Ni ２＋ The ratio of the content is 2 or more, preferably 3-8. The positive electrode material for a lithium ion battery according to claim 1.

3. The specific surface area S of the positive electrode material ０ is 0.1 - 0.5 m ２ / g, preferably 0.1 - 0.45 m ２ / g, and Preferably, after cracking at a pressure of 3.5 T, the specific surface area of the positive electrode material is S １ where (S １ - S ０ ) / S ０ × 100% is 0 - 50%, preferably 20 - 50%. Preferably, the particle size corresponding to 10% of the volume distribution by the particle size test of the positive electrode material is D １０ ０ After being cracked at a pressure of 3.5 T, the particle size corresponding to 10% of the volume distribution by the particle size test of the multi-component positive electrode material is D １０ １ and Here, (D １０ ０ -D １０ １ ) / D １０ ０ ×100% is 0 - 30%, preferably 0 - 20%, Preferably, the particle size corresponding to 50% of the volume distribution by the particle size test of the positive electrode material is D ５０ ０ After cracking at a pressure of 3.5 T, the particle size corresponding to 50% of the volume distribution by the particle size test of the multi-component positive electrode material is D ５０ １ and Here, (D ５０ ０ -D ５０ １ ) / D ５０ ０ ×100% is 0 - 15%, preferably 0 - 10%, Preferably, the particle size corresponding to 90% of the volume distribution by the particle size test of the positive electrode material is D ９０ ０ After cracking under a pressure of 3.5 T, the particle size corresponding to 90% of the volume distribution by the particle size test of the multi-component positive electrode material is D ９０ １ and Here, (D ９０ ０ -D ９０ １ ) / D ９０ ０ × 100% is from 0 to 8%, preferably from 0 to 7%, Preferably, the porosity of the positive electrode material is 1-8%, and the positive electrode material for a lithium-ion battery according to Claim 1 or 2.

4. The positive electrode material is secondary particles having a core-shell structure, Preferably, in the positive electrode material, the porosity of the core is 0.1-2%, Preferably, in the positive electrode material, the porosity of the shell is 3-8%, Preferably, in the positive electrode material, the ratio of the radius of the core to the shell layer is 0.5-9:1, preferably 0.5-3:1, Preferably, in the positive electrode material, the aspect ratio of the primary particles of the core is 1-2:1, Preferably, in the positive electrode material, the aspect ratio of the primary particles of the shell layer is 3-7:1, Preferably, the aspect ratio of the primary particles of the positive electrode material is 1-6:1, and the positive electrode material for a lithium-ion battery according to any one of Claims 1-3.

5. 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 includes 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 )O ２ Formula I Here, -0.1 ≤ a １ ≤ 0.2, 0 < x < 1, 0 ≤ y ≤ 0.4, 0 < z ≤ 0.6, 0 ≤ m ≤ 0.1, and 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, Preferably, -0.1 ≦ a １ ≦ 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, J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo and Mn, Preferably, the element J in the coating layer occupies 0.05 wt%-1.5 wt%, preferably 0.05 wt%-1 wt% of the total mass of the positive electrode material, and the positive electrode material for a lithium-ion battery according to any one of Claims 1-4.

6. In the positive electrode material, the surface free Li occupies 3%-6% of the total Li element molar ratio, Preferably, the moisture content of the positive electrode material is 0-100 ppm, and the positive electrode material for a lithium-ion battery according to any one of Claims 1-5.

7. A method for manufacturing a positive electrode material for a lithium-ion battery, the method comprising: S1. After mixing a positive electrode material precursor, a lithium source and a dopant as required, performing primary sintering in a first oxygen-containing atmosphere, cooling, pulverizing, and sieving to obtain a primary sintered material. Step S2: After mixing the primary sintered material and the coating agent, perform secondary sintering in a second oxygen-containing atmosphere, followed by sieving, iron removal, and obtaining a cathode material for a lithium-ion battery. The method for manufacturing a cathode material for a lithium-ion battery, characterized in that the oxygen concentration in the second oxygen-containing atmosphere is 90 vol% or more. **Claim 8** In step S1, the dopant is a compound containing a doping element M, and 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. Preferably, the oxygen concentration in the first oxygen-containing atmosphere is 95 vol% or more. Preferably, the conditions for the primary sintering are: heating from room temperature to 600 - 900 °C at a heating rate of 2 - 8 °C / min, and sintering for 8 - 14 h. Preferably, in step S2, the coating agent is a compound containing a coating element J, and J is selected from at least one of Zr, V, B, Al, Sr, Co, W, Mo, and Mn. Preferably, the conditions for the secondary sintering include a sintering temperature of 200 - 600 °C and a sintering time of 8 - 14 h. The method according to claim 7. **Claim 9** In step S1, the addition amount of the lithium source is added at a stoichiometric ratio of 0.9 ≤ n(Li) / n(Me) ≤ 1.2, where n(Me) is the total molar amount of metal elements in the cathode material precursor. Preferably, in step S1, the addition amount of the dopant is added at a stoichiometric ratio of 0 ≤ n(M) / n(Me) ≤ 0.1, where n(Me) is the total molar amount of metal elements in the cathode material precursor. Preferably, in step S2, the addition amount of the coating agent is added at a mass ratio of 0.05 wt% ≤ m(J) / [m(BM)] ≤ 1.5 wt%, 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. The method according to claim 7 or 8. **Claim 10** 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-containing compound, and M is selected from at least one of Al, Nb, Cr, V, Mg, and Sr. The second dopant is a doping element M-containing compound, and M is selected from at least one of Ti, B, La, P, and W. The third dopant is a doping element M-containing compound, and M is selected from at least one of Y, Ce, Ca, V, Ta, Co, Zr, and Mo. １ is a compound containing M １ is selected from at least one of Al, Nb, Cr, V, Mg, and Sr. The second dopant is a doping element M ２ is a compound containing M ２ is selected from at least one of Ti, B, La, P, and W. The third dopant is a doping element M ３ is a compound containing M ３ is selected from at least one of Y, Ce, Ca, V, Ta, Co, Zr, and Mo. Preferably, in step S1, the addition amount of the first dopant is added at a stoichiometric ratio of 0 ≦ n(M １ ) / n(Me) ≦ 0.1, where n(Me) is the total molar amount of metal elements in the cathode material precursor, Preferably, in step S1, the addition amount of the second dopant is added at a stoichiometric ratio of 0 ≦ n(M ２ ) / n(Me) ≦ 0.1, where n(Me) is the total molar amount of metal elements in the cathode material precursor, Preferably, in step S1, the addition amount of the third dopant is added at a stoichiometric ratio of 0 ≦ n(M ３ ) / n(Me) ≦ 0.1, where n(Me) is the total molar amount of metal elements in the cathode material precursor, Preferably, the specific surface area of the primary sintered material is 0.15 - 0.8 m ２ / g, and Preferably, in step S2, D is the particle size corresponding to 10% of the volume distribution by the particle size test of the coating agent １０ , D is the particle size corresponding to 50% of the volume distribution ５０ and D is the particle size corresponding to 90% of the volume distribution ９０ satisfy 1.5 ≦ K ９０ = (D ９０ - D １０ ) / D ５０ ≦ 2.8 Preferably, when the coating agent is a coating element B-containing compound, D of the coating agent １０ is 5 - 15 μm, D ５０ is 30 - 40 μm, D ９０ is 80 - 90 μm, The method according to any one of claims 7 - 9. **Claim 11** The cathode material precursor is prepared by mixing nickel salt, cobalt salt, and manganese salt into a mixed salt solution, introducing the mixed salt solution, the precipitant solution, and the complexing agent solution into a reaction kettle respectively, performing a coprecipitation reaction under an inert gas, and then obtaining the cathode material precursor through aging, washing, and drying. Preferably, the concentration of the mixed salt solution is 1-3 mol / L, Preferably, the concentration of the precipitant solution is 7-10 mol / L, Preferably, the concentration of the complexing agent solution is 5 mol / L or more, Preferably, the conditions of the coprecipitation reaction include that the pH is 10.5-11.5, the stirring speed is 200-800 rpm, the reaction temperature is 50-80 °C, and the introduction rate of the mixed salt solution into the reaction kettle is 100-400 mL / h. The method according to any one of claims 7-10.

12. A positive electrode material for a lithium-ion battery, produced by the method according to any one of claims 7-11.

13. A lithium-ion battery comprising the positive electrode material for a lithium-ion battery according to any one of claims 1-6 and 12.

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