Ternary material, preparation method thereof, positive plate and lithium ion battery

Abstract

The invention provides a ternary material and a preparation method thereof, a positive plate and a lithium ion battery. The chemical equation of the ternary material is LiNi < x > Co < y > Mn < y > M < 1-x-y > O < 2 >, x is larger than or equal to 0.6, y is smaller than or equal to 0.1, the cobalt content of the surface of the ternary material is higher than that of the interior of the ternary material, and the ternary material further comprises a first doping element, a second doping element and a third doping element, the first doping element is selected from at least two of a group IIIA element, a group IVB element, a group IIA element, a group VB element, a group VIB element and a group IIIB element, and the second doping element is a combination of a second cobalt element and an A element; and the third doping element is selected from any one or more of a group IIIA element, a group VB element, a group IIIB element, a group VIB element, a group IVA element, a group IVB element and a group IIA element. The ternary material has relatively high structural stability.

Description

TECHNICAL FIELD

[0001] The present application relates to the technical field of batteries, in particular to a ternary material, a preparation method thereof, a positive plate and a lithium ion battery. BACKGROUND

[0002] As a new energy carrier to help China implement the major strategy of "carbon peak and carbon neutrality", lithium ion batteries have shown great potential in the field of new energy vehicles and electrochemistry. The rapid development of electric vehicles has put forward higher requirements for the performance of power lithium ion batteries. The positive electrode material is particularly crucial in lithium ion batteries and is the main factor determining the energy density, service life, cycle stability, safety and cost of lithium ion batteries. Among the many positive electrode materials of lithium ion batteries, ternary materials are highly expected by the industry due to their high energy density, stable low-temperature performance, excellent charge and discharge performance and other advantages. However, high-nickel ternary positive electrode materials also have problems such as surface residual alkali, electrolyte corrosion side reaction, structural instability, lithium-nickel mixing and micro-cracks, which need to be solved urgently. These problems seriously affect the cycle performance, rate performance and safety of the battery, thereby restricting the commercial development scale.

[0003] The ternary positive electrode material mainly has the following problems: (1) surface composition reacts with air; (2) reacts with electrolyte; (3) lithium-nickel cation mixing and surface space group structure transformation; (4) lattice oxygen precipitation and migration of transition metal ions; (5) mechanical fracture of the material leading to the formation of micro-cracks. These problems change the material matrix structure and interface properties during the charging and discharging process, thereby leading to the failure of high-nickel ternary positive electrode materials. Surface composition reacts with air: compared with low-nickel ternary positive electrode materials, the surface composition of high-nickel ternary positive electrode materials is more unstable. First, the surface layer Ni 3+ ion is easy to slowly change into lower valence Ni 2+ ion during storage, and at the same time, due to the change in valence, the O 2- in the internal lattice of the nickel-cobalt-manganese oxide is easy to transform into O - , greatly weakening the TM-O bond (TM is Ni, Co, Mn); secondly, more LiOH is introduced in the preparation of NCM, which leads to the contact of surface residual lithium salt impurities with H2O and CO2 in the air and further reaction to form Li2CO3 and LiOH and other basic impurities; in addition, O2 needs to be continuously introduced during high-temperature sintering to promote the transformation of Ni 2+ ion to Ni 3+ ion, which also leads to the combination of excessive Li + impurities and O to form Li2O, which will eventually form Li2CO3 and LiOH. Lithium-nickel mixing in ternary materials is unavoidable, because and The ionic radii of Ni are very close, and during charging, Ni... 2+ It is easy to migrate to Li + The site leads to Ni 2+ Vacancies are generated during the discharge process in Li + Enter Ni 2+ The vacancy caused Li + / Ni 2+ Lithium-nickel blending. This process begins during the synthesis of ternary materials. Although studies have shown that appropriate lithium-nickel blending is beneficial to the stability of the layered structure, the degree of lithium-nickel blending increases with battery cycling, leading to capacity degradation in ternary materials. 2+ Occupy Li + Sites that hinder lithium-ion diffusion, leading to increased impedance; Li + Enter Ni 2+ After intercalation / deintercalation, the material loses activity due to the inability to intercalate or deintercalate, leading to capacity decay. Interfacial side reactions cause irreversible phase transitions from the outside in and electrolyte decomposition, which is a major factor in the capacity decay of high-nickel ternary materials. The degradation of ternary materials begins at the surface. Interfacial side reactions between high-nickel ternary materials and the electrolyte begin as soon as the lithium-ion battery is assembled, with the electrolyte LiPF6 undergoing a complex decomposition process. The irreversible phase transition of ternary materials is a significant cause of increased impedance and capacity decay. Under high Ni content, Ni, with its strong oxidizing properties... 3+ / 4+ Ni can oxidize the electrolyte in surface contact. 3+ / 4+ Reduced to Ni 2+ Under these conditions, due to Ni 2+ The binding force on oxygen atoms is relatively weak, allowing oxygen atoms to escape from the crystal lattice. This causes a phase transformation in the original layered lattice (R-3m), converting it into an M3O4-type spinel phase (Fd3m), which further deoxidizes into an inactive rock salt phase (Fm3m). Compared to the layered phase, the spinel phase is denser and lacks electrochemical activity. Lithium ions need to overcome a significant barrier to pass through it, which is detrimental to improving the cycle stability and rate performance of high-nickel ternary materials. Both the spinel and rock salt phase transformations result in the release of lattice oxygen, producing O2, which is a major reason for gas expansion in lithium-ion batteries.

[0004] The ternary positive electrode material has many advantages, but higher requirements are put forward for the ternary positive electrode material in order to adapt to different application occasions, such as in order to improve the energy density, the ternary positive electrode material needs to be high-nickelized, or the upper limit of the battery charging voltage is improved; the battery needs to have fast charging performance, and the material needs to have excellent rate performance. In the modification of high-nickel ternary positive electrode materials, the stability of the ternary material is closely related to the content of nickel, and the higher the content is, the more conducive to the improvement of the specific capacity, but the lower the material stability is. In order to give full play to the advantages of high energy density of high-nickel ternary positive electrode material, therefore, the currently commercialized high-nickel ternary material has basically been modified, and the common modification methods include element doping and surface coating. The element doping of the ternary positive electrode material can generally be carried out in two stages, that is, the soluble salt of the doping element is added in the salt solution configuration stage of the precursor synthesis, or the nano-oxide particles of the doping element are added in the lithium mixing stage. Doping trace metal ions or non-metal ions into the crystal lattice can improve the electronic conductivity and ionic conductivity of the material to some extent, and can also improve the cycle and thermal stability of the material. Since single element doping can only improve the performance of the material in some aspects, multiple elements are generally used for co-doping to improve the comprehensive performance of the material. The surface of the material particles is an important place for electrode reaction, and the Li + Through the deintercalation and intercalation of the particle surface, other side reactions are also accompanied, such as the deposition of electrolyte decomposition products on the particle surface, the reaction of trace H2O in the electrolyte with LiPF6 to generate HF to corrode the material, etc. Therefore, coating the surface of the material is an effective method to prevent the surface side reaction from damaging the material. Since other coating materials such as oxides often cause the impedance of the material to increase, the cycle stability of the material is improved at the same time, and part of the capacity is sacrificed. Lithium-containing compounds are also often used as coating materials, which can effectively reduce the surface impedance as fast ion conductors. The surface coating of the ternary material requires a suitable coating amount and uniformity, so the coating process is very important. SUMMARY

[0005] The main purpose of the present application is to provide a kind of ternary material and its preparation method, positive plate and lithium ion battery, to solve the problem of poor cycle stability of battery due to poor stability of high-nickel ternary material in prior art.

[0006] In order to achieve the above purpose, according to one aspect of the present application, a ternary material is provided, and the chemical equation of the ternary material is LiNi x Co y Mn y M 1-x-yO2, x is greater than or equal to 0.6, y is less than or equal to 0.1, M is selected from Mn elements and / or Al elements, and the cobalt content of the surface of the ternary material is higher than the cobalt content inside the ternary material, the ternary material further comprising a first doping element, a second doping element and a third doping element, the first doping element being selected from at least two of Group IIIA elements, Group IVB elements, Group IIA elements, Group VB elements, Group VIB elements and Group IIIB elements, the second doping element being a combination of a second cobalt element and an A element, the A element being selected from any one or more of tungsten elements, zirconium elements and calcium elements, and the third doping element being selected from any one or more of Group IIIA elements, Group VB elements, Group IIIB elements, Group VIB elements, Group IVA elements, Group IVB elements and Group IIA elements.

[0007] By increasing the surface cobalt content, the structural stability of the material surface is strengthened, and the lithium-nickel mixing is reduced, which helps to maintain the layered structure of the material during the cycle process, improve the cycle performance and stability. The surface enrichment of cobalt content can form a relatively stable coating layer, reduce the direct contact of the surface with the electrolyte, inhibit the surface side reaction, and improve the interface stability and overall electrochemical performance of the material. The presence of multiple doping elements helps to effectively adjust the crystal structure of the material, so that the lithiumation degree, surface free lithium content, crystallinity and lithium-nickel mixing of the ternary material reach a balance, so that the ternary material can have excellent electrochemical performance, which helps to improve the structural stability of the ternary material, thereby helping to improve the cycle stability and rate performance of the ternary material.

[0008] According to another aspect of the present application, a preparation method of a ternary material is provided, comprising: S1, preparing a Ni x Co y M 1-x-yS1, mixing the (OH)2, the first lithium source and the first doping source to perform a first sintering to obtain a first sintered product; wherein x≥0.6, y≤0.1, M is selected from Mn element and / or Al element; the first doping source is selected from at least two of group IIIB element source, group IVB element source, group IIA element source, group VB element source, group VIB element source and group IIIB element source; S2, mixing the first sintered product, a second lithium source and a first cobalt source to perform a second sintering to obtain a second sintered product; S3, mixing the second sintered product and a second doping source to perform a third sintering to obtain a third sintered product; wherein the second doping source is a combination of a second cobalt source and an A source, the A source is selected from any one or more of tungsten source, zirconium source and calcium source; S4, mixing the third sintered product and a third doping source to perform a fourth sintering to obtain the ternary material; wherein the third doping source is selected from any one or more of group IIIB element source, group VB element source, group IIIB element source, group VIB element source, group IVA element source, group IVB element source and group IIA element source.

[0009] In steps S2 and S3, by using the first cobalt source and the second doping source, it is helpful to form a uniform surface coating layer, especially the enrichment of cobalt element on the surface, which can reduce the side reaction between the electrolyte and the material surface, reduce the residual alkali amount of the material surface, thereby reducing the surface impedance, improving the processing performance and cycle stability of the ternary material. The addition of the third doping source helps to improve the electronic conductivity and ionic conductivity of the material, thereby improving the transmission efficiency of lithium ions in the material, reducing the polarization phenomenon in the battery charging and discharging process, and further improving the rate performance and cycle stability of the material.

[0010] Further, the average particle size of the ternary material is 1.5-4.5 μm.

[0011] Controlling the average particle size of the ternary material within the above range helps to make the diffusion distance of lithium ions moderate, which can provide good electrochemical performance.

[0012] Further, 0.7≥x≥0.6, 0.05≤y≤0.1; and / or, Ni x Co y M 1-x-y The D50 of the (OH)2 is 3-5.5 μm; and / or, the D50 of the first lithium source is 300-800 μm; and / or, the average particle size of the first doping source is 10-200 nm; and / or, the lithium element in the first lithium source and the Ni x Co y M 1-x-y The molar ratio of the (OH)2 is (0.8-1):1; and / or, the first doping source and the Ni x Co y M1-x-y the mass ratio of Li2CO3:(Ni(OH)2+Co(OH)2+M(OH)2) is (0.1-1):100; and / or, the first lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate, and lithium phosphate; and / or, the first doping source is selected from at least two of Al2O3, ZrO2, MgO, TiO2, Nb2O5, WO3, SrCO3, Y2O3, La2O3, and MoO3.

[0013] Controlling the values of x and y within the above ranges helps to balance the energy density and thermal stability of the material. Controlling the value of x within the above range helps to improve the electronic conductivity of the material. x Co y M 1-x-y Controlling the D50 of Li2CO3 within the above range helps to improve the tap density and cycle stability of the material. Controlling the D50 of the first lithium source within the above range helps to reduce the cost of the material on the one hand, and to improve the uniform distribution and effective transmission of lithium ions during the sintering process on the other hand. Controlling the average particle size of the first doping source within the above range helps to improve the uniformity of the distribution of the doping source. Controlling the lithium element in the first lithium source and the Ni x Co y M 1-x-y Controlling the molar ratio of Li2CO3:(Ni(OH)2+Co(OH)2+M(OH)2) within the above range helps to reduce lithium-nickel mixing and improve the efficiency of lithium ion intercalation and deintercalation. Controlling the molar ratio of the first doping source and Ni x Co y M 1-x-y Controlling the mass ratio of Li2CO3:(Ni(OH)2+Co(OH)2+M(OH)2) within the above range helps to improve the electronic conductivity and ionic conductivity of the material.

[0014] Further, the above-mentioned temperature of the first sintering is 350-700°C; and / or, the time of the first sintering is 2-16h; and / or, the heating rate of the first sintering is 1-10°C / min; and / or, the atmosphere of the first sintering is an oxygen-rich atmosphere with an oil content of less than 5ppm and a humidity of less than 30%, the oxygen content in the oxygen-rich atmosphere being greater than 30%. x Co y M 1-x-y The ratio of the D50 of Li2CO3 to the D50 of the first lithium source is 1:(100-200).

[0015] Controlling the value of x within the above range helps to improve the electronic conductivity of the material. x Co y M 1-x-y Controlling the ratio of the D50 of Li2CO3 to the D50 of the first lithium source within the above range helps the first lithium source to be fully dissociated and react with the active metal ions in the precursor under high-temperature sintering, forming a uniformly distributed lithiation layer.

[0016] Further, the above-mentioned temperature of the first sintering is 350-700°C; and / or, the time of the first sintering is 2-16h; and / or, the heating rate of the first sintering is 1-10°C / min; and / or, the atmosphere of the first sintering is an oxygen-rich atmosphere with an oil content of less than 5ppm and a humidity of less than 30%, the oxygen content in the oxygen-rich atmosphere being greater than 30%.

[0017] Controlling the temperature, time and heating rate of the first sintering within the above ranges helps to improve the uniformity of the lithiation layer. Controlling the atmosphere of the first sintering within the above ranges helps to effectively reduce the formation of impurities on the surface of the material.

[0018] Further, the mass ratio of the first sintering product to the second lithium source is 100:(0.1-20); and / or, the mass ratio of the first cobalt source to the first sintering product is (0.1-3):100; and / or, the second lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate and lithium phosphate; and / or, the first cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH.

[0019] Controlling the mass ratio of the first sintering product to the second lithium source within the above ranges helps to optimize the degree of lithiation of the material and maintain the stability of the structure of the material. Controlling the mass ratio of the first cobalt source to the first sintering product within the above ranges improves the surface stability of the material.

[0020] Further, the temperature of the second sintering is 750-1000°C; and / or, the time of the second sintering is 8-25h; and / or, the atmosphere of the second sintering is an atmosphere with an oxygen content of ≥50%; and / or, the D10 of the second sintering product is ≤2μm, the D50 is 2.5-4.5μm, and the D90 is ≤14μm.

[0021] Controlling the temperature and time of the second sintering within the above ranges helps to reorganize and strengthen the crystal lattice structure inside the material and improve the overall stability of the material. Controlling the atmosphere of the second sintering within the above ranges helps to enable the surface of the material to react with oxygen and form a protective layer, reducing direct contact with the electrolyte. Controlling the particle size distribution of the second sintering product within the above ranges helps to improve the diffusion speed of lithium ions and shorten the transport path of lithium ions.

[0022] Further, the mass ratio of the second doping source to the second sintering product is (0.1-3):100; and / or, the mass ratio of the second cobalt source to the A source is (1-5):1; and / or, the second cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH; and / or, the temperature of the third sintering is 350-700°C; and / or, the time of the third sintering is 8-25h; and / or, the atmosphere of the third sintering is an atmosphere with an oxygen content of ≥50%.

[0023] Controlling the mass ratio of the second doping source to the second sintering product within the above range helps to further improve the electrical conductivity and thermal stability of the material. Controlling the mass ratio of the second cobalt source to the A source within the above range helps to form a more uniform and stable coating layer, improving the electronic and ionic conductivity of the material. Controlling the temperature and time of the third sintering within the above range helps to make the second doping source more uniformly distributed and coated on the surface of the material. Controlling the atmosphere of the third sintering within the above range helps to enable the material surface to react with oxygen to form a dense oxide layer.

[0024] Further, the mass ratio of the third doping source to the third sintering product is (4-10): 100; and / or, the third doping source is selected from any one or more of a B source, an Al source, a Ta source, a Ce source, a W source, a Nb source, a Ge source, a Y source, a Zr source, a Ca source, and a Sr source; and / or, the temperature of the fourth sintering is 300-400°C; and / or, the time of the fourth sintering is 3-10 h.

[0025] Controlling the mass ratio of the third doping source to the third sintering product within the above range helps to further improve the structural stability of the ternary material. Controlling the type of the third doping source within the above range helps to further improve the cycle stability and rate performance of the ternary material. Controlling the temperature and time of the fourth sintering within the above range helps to promote the uniform distribution of the doping elements and the formation of a stable coating layer.

[0026] According to yet another aspect of the present application, there is provided a positive electrode sheet containing the aforementioned ternary material.

[0027] Since the aforementioned positive electrode sheet contains the ternary material of the present application, the positive electrode sheet has high cycle stability and rate performance.

[0028] According to yet another aspect of the present application, there is provided a lithium ion battery comprising a positive electrode sheet, an electrolyte, and a negative electrode sheet, wherein the positive electrode sheet is the aforementioned positive electrode sheet.

[0029] Since the aforementioned positive electrode sheet contains the ternary material of the present application, the positive electrode sheet has high cycle stability and rate performance.

[0030] By the technical solution of the present application, the cobalt content on the surface of the ternary material is higher than that in the interior, which can increase the electronic conductivity of the material surface, reduce the surface impedance, and accelerate the surface diffusion rate of lithium ions, thereby improving the rate performance and cycle stability of the material. The high-nickel ternary material is prone to structural instability problems under high charge state, especially lithium-nickel mixing, and by increasing the surface cobalt content, the structural stability of the material surface is strengthened, and lithium-nickel mixing is reduced, which helps to maintain the layered structure of the material during the cycle process and improve the cycle performance and stability. The material surface is often where electrochemical reactions and side reactions occur. The surface enrichment of cobalt content can form a relatively stable coating layer, reduce the direct contact of the surface with the electrolyte, inhibit the surface side reaction, and improve the interface stability and overall electrochemical performance of the material. The presence of multiple doping elements helps to effectively adjust the crystal structure of the material, so that the lithiumation degree, surface free lithium content, crystallinity, and lithium-nickel mixing of the ternary material are balanced, thereby enabling the ternary material to have excellent electrochemical performance, helping to improve the structural stability of the ternary material, and thereby helping to improve the cycle stability and rate performance of the ternary material. BRIEF DESCRIPTION OF DRAWINGS

[0031] The accompanying drawings, which form a part of the present description, illustrate the present application and, together with the written description, serve to explain the application. In the drawings:

[0032] Figure 1 The SEM diagram of the ternary material in Example 1 of the present application is shown;

[0033] Figure 2 The XRD diagram of the ternary material in Example 1 of the present application is shown. DETAILED DESCRIPTION

[0034] It should be noted that the embodiments in the present application and the features in the embodiments can be combined with each other without conflict. The present application will be described in detail below with reference to the accompanying drawings and in combination with the embodiments.

[0035] As analyzed in the background art of the present application, the existing technology has the problem of poor battery cycle stability due to poor stability of high-nickel ternary materials. In order to solve the above problems, the present application provides a ternary material, a preparation method thereof, a positive electrode sheet, and a lithium ion battery.

[0036] In a typical embodiment of the present application, a ternary material is provided, and the chemical formula of the ternary material is LiNi x Co y Mn y M 1-x-yO2, x≥0.6, y≤0.1, M is selected from Mn element and / or Al element, and the cobalt content of the surface of the ternary material is higher than the cobalt content inside the ternary material, the ternary material further comprises a first doping element, a second doping element and a third doping element, the first doping element is selected from at least two of group IIIA elements, group IVB elements, group IIA elements, group VB elements, group VIB elements and group IIIB elements, the second doping element is a combination of a second cobalt element and an A element, the A element is selected from any one or more of tungsten element, zirconium element and calcium element, and the third doping element is selected from any one or more of group IIIA elements, group VB elements, group IIIB elements, group VIB elements, group IVA elements, group IVB elements and group IIA elements.

[0037] The application controls the cobalt content of the surface of the ternary material to be higher than the inside, which can increase the electronic conductivity of the material surface, reduce the surface impedance, and accelerate the surface diffusion rate of lithium ions, thereby improving the rate performance and cycle stability of the material. The high-nickel ternary material is prone to structural instability problems, especially lithium-nickel mixing, at a high charge state. By increasing the surface cobalt content, the structural stability of the material surface is strengthened, and lithium-nickel mixing is reduced, which helps to maintain the layered structure of the material during the cycle process and improve the cycle performance and stability. The material surface is often where electrochemical reactions and side reactions occur. The surface enrichment of cobalt content can form a relatively stable coating layer, reduce the direct contact of the surface with the electrolyte, inhibit the surface side reaction, and improve the interface stability and overall electrochemical performance of the material. The presence of multiple doping elements helps to effectively adjust the crystal structure of the material, so that the lithiumation degree, surface free lithium content, crystallinity and lithium-nickel mixing of the ternary material are balanced, thereby enabling the ternary material to have excellent electrochemical performance, helping to improve the structural stability of the ternary material, and thereby helping to improve the cycle stability and rate performance of the ternary material.

[0038] In an embodiment of the application, the pH of the ternary material is 11.54-11.92; and / or, the mass content of residual LiOH on the surface of the ternary material is 0.08-0.2%; and / or, the mass content of residual Li2CO3 on the surface of the ternary material is 0.05-0.2%; and / or, the mass content of free Li on the surface of the ternary material is 340-746 ppm.

[0039] In another typical embodiment of the application, a preparation method of a ternary material is provided, comprising: S1, preparing a precursor of the ternary material by mixing a first precursor, a second precursor and a third precursor, wherein the first precursor comprises a first element, the second precursor comprises a second element, and the third precursor comprises a third element; and S2, preparing the ternary material by mixing the precursor and a fourth precursor, wherein the fourth precursor comprises a fourth element. x Co y M 1-x-yS1, mixing (OH)2, a first lithium source and a first doping source after the mixing to perform a first sintering to obtain a first sintering product; wherein x≥0.6, y≤0.1, M is selected from Mn element and / or Al element; the first doping source is selected from at least two of a group IVB element source, a group IIIB element source, a group IVA element source, a group VB element source, a group VIB element source and a group IIIB element source; S2, mixing the first sintering product, a second lithium source and a first cobalt source after the mixing to perform a second sintering to obtain a second sintering product; S3, mixing the second sintering product and a second doping source after the mixing to perform a third sintering to obtain a third sintering product; wherein the second doping source is a combination of a second cobalt source and an A source, and the A source is selected from any one or more of a tungsten source, a zirconium source and a calcium source; S4, mixing the third sintering product and a third doping source after the mixing to perform a fourth sintering to obtain a ternary material; wherein the third doping source is selected from any one or more of a group IIIB element source, a group VB element source, a group VIB element source, a group IVB element source, a group IVA element source and a group IIIB element source.

[0040] By introducing the first lithium source, the second lithium source and the plurality of doping sources in different sintering steps, the crystal structure of the material can be effectively adjusted, the degree of lithiation, the content of free lithium on the surface, the crystallinity and the lithium-nickel mixing of the ternary material can be balanced, so that the ternary material can have excellent electrochemical performance, and is not affected by the reduction of the cobalt content of the precursor, which helps to improve the structural stability of the ternary material, thereby helping to improve the cycle stability and rate performance of the ternary material. In steps S2 and S3, by using the first cobalt source and the second doping source, a uniform surface coating layer can be formed, especially the enrichment of cobalt elements on the surface, which can reduce the side reaction between the electrolyte and the material surface, reduce the residual alkali content on the surface of the material, thereby reducing the surface impedance, improving the processing performance and cycle stability of the ternary material. The addition of the third doping source helps to improve the electronic conductivity and ionic conductivity of the material, thereby improving the transmission efficiency of lithium ions in the material, reducing the polarization phenomenon in the battery charging and discharging process, and further improving the rate performance and cycle stability of the material. The ternary material prepared by the preparation method has good uniformity in particle size, has high crystallinity, helps to improve the rate cycle performance of the material, and can still maintain this performance under high pressure conditions.

[0041] The tungsten source is selected from tungsten oxide and / or tungsten acid; the zirconium source is selected from zirconium oxide and / or zirconium hydroxide; the calcium source is selected from any one or more of calcium oxide, calcium hydroxide and calcium carbonate.

[0042] In an embodiment of the present application, the average particle size of the ternary material is 1.5-4.5 μm.

[0043] Controlling the average particle size of the ternary material within the above range helps to make the diffusion distance of lithium ions moderate, which can reduce the excessive increase of specific surface area caused by too small particle size, thereby increasing the risk of surface side reactions, while providing good electrochemical performance.

[0044] In an embodiment of the present application, 0.7≥x≥0.6, 0.05≤y≤0.1; and / or, Ni x Co y M 1-x-y The D50 of the (OH)2 is 3-5.5 μm; and / or, the D50 of the first lithium source is 300-800 μm; and / or, the average particle size of the first doping source is 10-200 nm; and / or, the molar ratio of lithium element in the first lithium source to Ni x Co y M 1-x-y The molar ratio of the (OH)2 is (0.8-1):1; and / or, the mass ratio of the first doping source to Ni x Co y M 1-x-y The mass ratio of the (OH)2 is (0.1-1):100; and / or, the first lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate and lithium phosphate; and / or, the first doping source is selected from at least two of Al2O3, ZrO2, MgO, TiO2, Nb2O5, WO3, SrCO3, Y2O3, La2O3 and MoO3.

[0045] Controlling the values of x and y within the above range helps to balance the energy density and thermal stability of the material, and reduces structural instability and impedance increase caused by lithium-nickel mixing. Controlling the Ni x Co y M 1-x-y The D50 of the (OH)2 within the above range helps to improve the compaction density and cycle stability of the material. Controlling the D50 of the first lithium source within the above range helps to reduce the cost of the material on the one hand, and to improve the uniform distribution and effective transmission of lithium ions during the sintering process on the other hand, thereby reducing the insufficient reaction of the lithium source and the precursor, and improving the electrochemical performance and cycle stability of the material. Controlling the average particle size of the first doping source within the above range helps to improve the uniformity of the distribution of the doping source. Controlling the molar ratio of lithium element in the first lithium source to Ni x Co y M 1-x-y The molar ratio of the (OH)2 within the above range helps to reduce lithium-nickel mixing and improve the intercalation and deintercalation efficiency of lithium ions. Controlling the mass ratio of the first doping source to Ni x Co y M 1-x-yThe mass ratio of Al2O3 and ZrO2 is (0.1-1):1, which helps to improve the electronic conductivity and ionic conductivity of the material, thereby helping to improve the electrochemical activity and thermal stability of the ternary material. Controlling the type of the first lithium source within the above range helps to improve the lithiation efficiency. Controlling the type of the first doping source within the above range helps to improve the electronic conductivity and thermal stability of the material, while reducing electrolyte decomposition and surface side reactions through surface coating.

[0046] In an embodiment of the present application, the first lithium source is selected from lithium carbonate and / or lithium hydroxide; and / or, the first doping source is a combination of Al2O3 and ZrO2, and the mass ratio of Al2O3 and ZrO2 is (0.1-1):1.

[0047] Lithium carbonate and lithium hydroxide have good chemical stability and good lithiation ability during sintering, which helps to reduce energy consumption and improve the purity of the material. Aluminum and zirconium oxides as doping sources can form stable lattice structures inside the material, reduce lithium-nickel mixing, and improve the thermal stability and electrochemical stability of the material.

[0048] In an embodiment of the present application, the above-mentioned Ni x Co y M 1-x-y The ratio of D50 of Al2O3 and D50 of the first lithium source is 1:(100-200).

[0049] Controlling the type of Ni x Co y M 1-x-y The ratio of D50 of Al2O3 and D50 of the first lithium source is within the above range, which helps the first lithium source to fully dissociate and react with active metal ions in the precursor under high-temperature sintering, forming a uniformly distributed lithiation layer, reducing local over-lithiation or under-lithiation, thereby improving the consistency and electrochemical performance of the material.

[0050] In an embodiment of the present application, the temperature of the first sintering is 350-700℃; and / or, the time of the first sintering is 2-16h; and / or, the heating rate of the first sintering is 1-10℃ / min; and / or, the atmosphere of the first sintering is an oxygen-rich atmosphere with an oil content of less than 5ppm and a humidity of less than 30%, and the oxygen content in the oxygen-rich atmosphere is greater than 30%.

[0051] Controlling the temperature, time and heating rate of the first sintering within the above range helps to improve the uniformity of the lithiation layer and reduce lithium-nickel mixing. Controlling the atmosphere of the first sintering within the above range helps to effectively reduce the formation of impurities on the surface of the material.

[0052] It should be noted that the base gas in the oxygen-containing atmosphere of the present application is selected from any one or more of helium, argon and nitrogen.

[0053] In an embodiment of the present application, the mass ratio of the first sintered product to the second lithium source is 100:(0.1-20); and / or, the mass ratio of the first cobalt source to the first sintered product is (0.1-3):100; and / or, the second lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate and lithium phosphate; and / or, the first cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH.

[0054] Controlling the mass ratio of the first sintered product to the second lithium source within the above range helps to optimize the degree of lithiation of the material and maintain the stability of the material structure. Controlling the mass ratio of the first cobalt source to the first sintered product within the above range improves the surface stability of the material, reduces side reactions between the material and the electrolyte, reduces the surface impedance, and thus improves the cycle stability and rate capability of the material. Controlling the type of the second lithium source within the above range helps to optimize the lithiation process of the material, reduces the generation of by-products, and improves the purity and lithiation efficiency of the material. Controlling the type of the first cobalt source within the above range helps to make cobalt more uniformly distributed on the surface of the material, form an effective coating layer, and improve the surface stability of the material.

[0055] In an embodiment of the present application, the temperature of the second sintering is 750-1000°C; and / or, the time of the second sintering is 8-25h; and / or, the atmosphere of the second sintering is an atmosphere with an oxygen content of ≥50%; and / or, the D10 of the second sintered product is ≤2μm, the D50 is 2.5-4.5μm, and the D90 is ≤14μm.

[0056] Controlling the temperature and time of the second sintering within the above range helps to reorganize and strengthen the crystal lattice structure inside the material, promote the perfection of the material's crystallization, reduce structural defects, and improve the overall stability of the material. Controlling the atmosphere of the second sintering within the above range helps to enable the material surface to react with oxygen and form a protective layer, reduce direct contact with the electrolyte, reduce side reactions occurring during battery cycling, and improve the cycle stability and safety of the material. Controlling the particle size distribution of the second sintered product within the above range helps to improve the diffusion speed of lithium ions and shorten the transport path of lithium ions.

[0057] In an embodiment of the present application, the mass ratio of the second doping source to the second sintering product is (0.1-3):100; and / or, the mass ratio of the second cobalt source to the A source is (1-5):1; and / or, the second cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH; and / or, the temperature of the third sintering is 350-700°C; and / or, the time of the third sintering is 8-25h; and / or, the atmosphere of the third sintering is an atmosphere with an oxygen content of ≥50%.

[0058] Controlling the mass ratio of the second doping source to the second sintering product within the above range helps to further improve the electrical conductivity and thermal stability of the material, reduce lithium-nickel cation mixing, inhibit lattice oxygen precipitation, and at the same time improve the cycle stability and safety of the material. Controlling the mass ratio of the second cobalt source to the A source within the above range helps to form a more uniform and stable coating layer, improve the electronic and ionic conductivity of the material, reduce side reactions between the material and the electrolyte, and improve the surface stability of the material. Controlling the type of the second cobalt source within the above range helps to enrich the selectivity of the type of cobalt source. Controlling the temperature and time of the third sintering within the above range helps to make the second doping source more uniformly distributed and coated on the surface of the material. Controlling the atmosphere of the third sintering within the above range helps to enable the surface of the material to react with oxygen to form a dense oxide layer, which not only protects the material from direct contact with the electrolyte, but also further optimizes the surface structure and properties of the material, improves the transmission efficiency of lithium ions, and improves the cycle stability of the material.

[0059] In an embodiment of the present application, the A source is a tungsten source.

[0060] When the second doping source is a combination of the second cobalt source and the tungsten source, cobalt helps to maintain the electronic transmission path of the material, while tungsten enhances the structural strength of the material through doping, and the synergistic effect of the two can further improve the cycle stability and rate performance of the material. The two form a composite coating layer on the surface of the material, the oxide coating layer of tungsten can enhance the corrosion resistance of the material, while the doping of cobalt can enhance the uniformity and density thereof, and this coating can reduce the side reactions between the material and the electrolyte, reduce the surface impedance, and improve the surface stability and electrochemical activity of the material.

[0061] In an embodiment of the present application, the mass ratio of the third doping source to the third sintering product is (4-10):100; and / or, the third doping source is selected from any one or more of a B source, an Al source, a Ta source, a Ce source, a W source, a Nb source, a Ge source, a Y source, a Zr source, a Ca source and a Sr source; and / or, the temperature of the fourth sintering is 300-400°C; and / or, the time of the fourth sintering is 3-10h.

[0062] The third doping source and the mass ratio of the third sintering product are controlled in the above range, which helps to further improve the structural stability of the ternary material. The type of the third doping source is controlled in the above range, which helps to further improve the cycle stability and rate performance of the ternary material. The temperature and time of the fourth sintering are controlled in the above range, which helps to promote the uniform distribution of the doping elements and the formation of a stable coating layer.

[0063] For example, the B source is selected from boron oxide and / or boron fluoride; the Al source is selected from aluminum oxide and / or aluminum fluoride; the Ta source is selected from tantalum oxide and / or tantalum fluoride; the Ce source is selected from cerium oxide and / or cerium fluoride; the W source is selected from tungsten oxide and / or tungsten fluoride; the Nb source is selected from niobium oxide and / or niobium fluoride; the Ge source is selected from germanium oxide and / or germanium fluoride; the Y source is selected from yttrium oxide and / or yttrium fluoride; the Zr source is selected from zirconium oxide and / or zirconium fluoride; the Ca source is selected from calcium oxide and / or calcium fluoride; and the Sr source is selected from strontium oxide and / or strontium fluoride.

[0064] In order to further improve the stability of the ternary material, in an embodiment of the present application, the third doping source is a combination of an Al source and a B source, and the mass ratio of the Al source to the B source is (1-3):3.

[0065] In another typical embodiment of the present application, a positive electrode sheet is provided, which contains the ternary material of the present application.

[0066] Since the positive electrode sheet contains the ternary material of the present application, the positive electrode sheet has high cycle stability and rate performance.

[0067] In an embodiment of the present application, the positive electrode sheet includes a positive electrode active layer and a current collector, the positive electrode active layer includes the ternary material, a conductive agent and a binder, and the mass ratio of the ternary material, the conductive agent and the binder is (90-99):(0.1-5):(0.1-5).

[0068] For example, the conductive agent is super-conductive carbon black, and the binder is polyvinylidene fluoride.

[0069] In another typical embodiment of the present application, a lithium ion battery is provided, which includes a positive electrode sheet, an electrolyte and a negative electrode sheet, the positive electrode sheet is the positive electrode sheet as described above.

[0070] Since the positive electrode sheet of the lithium ion battery contains the ternary material of the present application, the lithium ion battery has a long service life and safety.

[0071] The beneficial effects of the present application will be further illustrated in the following examples.

[0072] Example 1

[0073] S1, a ternary material precursor Ni0.65 Co 0.07 Mn 0.28 (OH)2(D50 is 3.5 μm), lithium hydroxide (D50 is 350 μm) and the first doping source are mixed to perform the first sintering, wherein the molar ratio of lithium element in the lithium hydroxide to Ni 0.65 Co 0.07 Mn 0.28 (OH)2is 0.98:1, the first doping source is a combination of Al2O3 and ZrO2, and the mass ratio of Al2O3 (average particle size is 15 nm) to ZrO2 (average particle size is 30 nm) is 0.5:1, the first doping source and Ni 0.65 Co 0.07 Mn 0.28 (OH)2is 0.2:100, the temperature of the first sintering is 600°C, the time is 5 hours, the heating rate is 5°C / min, and the atmosphere is an oxygen-rich nitrogen atmosphere (oxygen content is 90%) with an oil content of less than 5 ppm and a humidity of less than 30%, to obtain a first sintering product;

[0074] S2, the first sintering product, lithium carbonate and CoOOH are mixed to perform the second sintering, wherein the mass ratio of the first sintering product to lithium carbonate is 100:1, the mass ratio of CoOOH to the first sintering product is 1:100, the temperature of the second sintering is 850°C, the sintering time is 11.5h, the atmosphere is a nitrogen atmosphere with an oxygen content of 90%, and then crushing is performed to obtain a second sintering product with a D10 of 1.75 μm, a D50 of 3.64 μm and a D90 of 11.67 μm;

[0075] S3, the second sintering product and the second doping source are mixed to perform the third sintering, wherein the mass ratio of the second doping source to the second sintering product is 0.5:100, the second doping source is a combination of CoOOH and tungsten oxide, and the mass ratio of CoOOH to tungsten oxide is 2:1, the sintering temperature is 650°C, the sintering time is 11.5h, and the atmosphere is a nitrogen atmosphere with an oxygen content of 90%, to obtain a third sintering product;

[0076] S4, the third sintering product and the third doping source are mixed to perform the fourth sintering, wherein the mass ratio of the third doping source to the third sintering product is 5:100, the third doping source is a combination of aluminum oxide (average particle size is 15 nm) and boric acid, the mass ratio of aluminum oxide to boric acid is 2:3, the temperature of the fourth sintering is 350°C, and the sintering time is 3h, to obtain a ternary material with an average particle size of 2.2 μm.

[0077] Example 2

[0078] S1, the ternary material precursor Ni 0.6 Co 0.1 Mn0.3 (OH)2(D50 is 3.5 μm), lithium hydroxide (D50 is 350 μm) and the first doping source are mixed and then first sintering is performed, wherein the molar ratio of lithium element in lithium hydroxide to Ni 0.65 Co 0.07 Mn 0.28 (OH)2is 0.98:1, the first doping source is a combination of Al2O3 and ZrO2, and the mass ratio of Al2O3 (average particle size is 20 nm) to ZrO2 (average particle size is 20 nm) is 0.5:1, the first doping source and Ni 0.65 Co 0.07 Mn 0.28 (OH)2is 0.2:100, the temperature of the first sintering is 600℃, the time is 5 hours, the heating rate is 5℃ / min, and the atmosphere is an oxygen-rich nitrogen atmosphere (oxygen content is 90%) with an oil content of less than 5 ppm and a humidity of less than 30%, to obtain a first sintering product;

[0079] S2, the first sintering product, lithium carbonate and CoOOH are mixed and then second sintering is performed, wherein the mass ratio of the first sintering product to lithium carbonate is 100:1, the mass ratio of CoOOH to the first sintering product is 1:100, the temperature of the second sintering is 850℃, the sintering time is 11.5h, the atmosphere is a nitrogen atmosphere with an oxygen content of 90%, and then crushing is performed to obtain a second sintering product with a D10 of 1.75 μm, a D50 of 3.64 μm and a D90 of 11.67 μm;

[0080] S3, the second sintering product and the second doping source are mixed and then third sintering is performed, wherein the mass ratio of the second doping source to the second sintering product is 0.5:100, the second doping source is a combination of CoOOH and tungsten oxide, and the mass ratio of CoOOH to tungsten oxide is 2:1, the sintering temperature is 650℃, the sintering time is 11.5h, and the atmosphere is a nitrogen atmosphere with an oxygen content of 90%, to obtain a third sintering product;

[0081] S4, the third sintering product and the third doping source are mixed and then fourth sintering is performed, wherein the mass ratio of the third doping source to the third sintering product is 4:100, the third doping source is a combination of aluminum oxide (average particle size is 15 nm) and lithium niobate, the mass ratio of aluminum oxide to lithium niobate is 1:3, the temperature of the fourth sintering is 400℃, and the sintering time is 3h, to obtain a ternary material with an average particle size of 1.97 μm.

[0082] Example 3

[0083] The difference from Example 1 is that the Ni 0.65 Co 0.07 Mn 0.28The D50 of (OH)₂ is 3.5 μm, the D50 of lithium hydroxide is 700 μm, and Ni 0.65 Co 0.07 Mn 0.28 The ratio of the D50 of (OH)2 to the D50 of lithium hydroxide is 1:200, resulting in a ternary material.

[0084] Example 4

[0085] The difference from Example 1 is that Ni 0.65 Co 0.07 Mn 0.28 The D50 of (OH)₂ is 3.5 μm, the D50 of lithium hydroxide is 800 μm, and Ni 0.65 Co 0.07 Mn 0.28 The ratio of the D50 of (OH)2 to the D50 of lithium hydroxide is 1:228, resulting in a ternary material.

[0086] Example 5

[0087] The difference from Example 1 is that the lithium element in lithium hydroxide reacts with Ni. 0.65 Co 0.07 Mn 0.28 The molar ratio of (OH)₂ is 0.8:1, the mass ratio of Al₂O₃ to ZrO₂ is 1:1, and the first dopant source is Ni. 0.65 Co 0.07 Mn 0.28 The mass ratio of (OH)2 is 0.1:100, and a ternary material is finally obtained.

[0088] Example 6

[0089] The difference from Example 1 is that the lithium element in lithium hydroxide reacts with Ni. 0.65 Co 0.07 Mn 0.28 The molar ratio of (OH)₂ is 1:1, the mass ratio of Al₂O₃ to ZrO₂ is 0.1:1, and the first dopant source is related to Ni. 0.65 Co 0.07 Mn 0.28 The mass ratio of (OH)2 is 1:100, and a ternary material is finally obtained.

[0090] Example 7

[0091] The difference from Example 1 is that the lithium element in lithium hydroxide reacts with Ni. 0.65 Co 0.07 Mn 0.28 The molar ratio of (OH)₂ is 1.1:1, the mass ratio of Al₂O₃ to ZrO₂ is 2:1, and the first dopant source is Ni. 0.65 Co0.07 Mn 0.28 The mass ratio of (OH)2 to Li2CO3 is 1.2:100, and finally the ternary material is obtained.

[0092] Example 8

[0093] The difference from Example 1 is that the mass ratio of the first sintered product to Li2CO3 is 100:0.1, and the mass ratio of CoOOH to the first sintered product is 0.1:100, and finally the ternary material is obtained.

[0094] Example 9

[0095] The difference from Example 1 is that the mass ratio of the first sintered product to Li2CO3 is 100:20, and the mass ratio of CoOOH to the first sintered product is 3:100, and finally the ternary material is obtained.

[0096] Example 10

[0097] The difference from Example 1 is that the mass ratio of the first sintered product to Li2CO3 is 100:25, and the mass ratio of CoOOH to the first sintered product is 4:100, and finally the ternary material is obtained.

[0098] Example 11

[0099] The difference from Example 1 is that the mass ratio of the second doping source to the second sintered product is 0.1:100, the second doping source is a combination of CoOOH and tungsten oxide, and the mass ratio of CoOOH to tungsten oxide is 1:1, and finally the ternary material is obtained.

[0100] Example 12

[0101] The difference from Example 1 is that the mass ratio of the second doping source to the second sintered product is 3:100, the second doping source is a combination of CoOOH and tungsten oxide, and the mass ratio of CoOOH to tungsten oxide is 5:1, and finally the ternary material is obtained.

[0102] Example 13

[0103] The difference from Example 1 is that the mass ratio of the second doping source to the second sintered product is 4:100, the second doping source is a combination of CoOOH and tungsten oxide, and the mass ratio of CoOOH to tungsten oxide is 0.5:1, and finally the ternary material is obtained.

[0104] Example 14

[0105] The difference from Example 1 is that the mass ratio of the third doping source to the third sintered product is 10:100, and the mass ratio of aluminum oxide to boric acid in the third doping source is 1:1, and finally the ternary material is obtained.

[0106] Example 15

[0107] The difference from Example 1 is that the mass ratio of the third dopant source to the third sintering product is 1.1:100, and the mass ratio of alumina to boric acid in the third dopant source is 1:0.1, thus obtaining a ternary material.

[0108] Example 16

[0109] The difference from Example 1 is that, in S1, the ternary material precursor Ni... 0.65 Co 0.07 Mn 0.28 The first sintering process involves mixing (OH)₂ (D50 of 3.5 μm), lithium hydroxide (D50 of 350 μm), and a first dopant source, wherein the lithium element in the lithium hydroxide reacts with Ni. 0.65 Co 0.07 Mn 0.28 The molar ratio of (OH)₂ is 0.98:1. The first doping source is a combination of TiO₂ and WO₃, and the mass ratio of TiO₂ (average particle size 40 nm) to WO₃ (average particle size 50 nm) is 1:1. The first doping source and Ni 0.65 Co 0.07 Mn 0.28 The mass ratio of (OH)2 was 0.2:100. The first sintering temperature was 350℃, the time was 16 hours, the heating rate was 1℃ / min, and the atmosphere was an oxygen-rich nitrogen atmosphere (oxygen content of 90%) with an oil content of less than 5ppm and a humidity of less than 30%. The first sintered product was obtained.

[0110] S2. The first sintered product, lithium carbonate, and cobalt carbonate are mixed and then subjected to a second sintering. The mass ratio of the first sintered product to lithium carbonate is 100:1, and the mass ratio of cobalt carbonate to the first sintered product is 1:100. The second sintering temperature is 750℃, the sintering time is 25h, and the atmosphere is a nitrogen atmosphere with an oxygen content of 90%. Then, the mixture is pulverized to obtain the second sintered product with D10 of 1.5μm, D50 of 2.5μm, and D90 of 10μm.

[0111] S3 involves mixing the second sintered product and the second dopant source and then performing a third sintering. The mass ratio of the second dopant source to the second sintered product is 0.5:100. The second dopant source is a combination of cobalt acetate and calcium oxide, and the mass ratio of cobalt acetate to calcium oxide is 2:1. The sintering time is 8 hours at 700°C, and the atmosphere is a nitrogen atmosphere with an oxygen content of 90%, to obtain the third sintered product.

[0112] S4: the third sintered product is mixed with strontium oxide, and then fourth sintering is performed, wherein the mass ratio of strontium oxide to the third sintered product is 5:100, the temperature of the fourth sintering is 300°C, and the sintering time is 10h, to obtain a ternary material with an average particle size of 2.6μm.

[0113] Comparative Example 1

[0114] The difference from Example 1 is that step S2 is cancelled, and in step S3, the first sintered product, lithium carbonate, CoOOH and the second doping source are mixed and then third sintering is performed, to finally obtain a ternary material.

[0115] Comparative Example 2

[0116] The difference from Example 1 is that step S3 is cancelled, and in step S4, the second sintered product, the second doping source and the third doping source are mixed and then fourth sintering is performed, to finally obtain a ternary material.

[0117] Comparative Example 3

[0118] The difference from Example 1 is that steps S2, S3 and S4 are cancelled, and the ternary material precursor Ni 0.65 Co 0.07 Mn 0.28 (OH)2, lithium hydroxide, the first doping source, lithium carbonate, CoOOH, the second doping source and the third doping source are mixed and then first sintering is performed, to obtain a ternary material.

[0119] pH and residual alkali detection

[0120] Test method: see the “Nickel-cobalt-manganese lithium analysis and determination method” of Hunan Helyong Technology Co., Ltd., as follows:

[0121] (1) pH test: the lithium ion battery cathode material is mixed with distilled water according to a solid-liquid ratio of 1:10, and then a pH meter is used for testing, which can be specifically seen in Part 4 of the “Nickel-cobalt-manganese lithium analysis and determination method”;

[0122] (2) Residual alkali determination: an acid-base titration method is used, which can be specifically seen in Part 5 of the “Nickel-cobalt-manganese lithium analysis and determination method”.

[0123] The ternary materials prepared in the examples and comparative examples are subjected to pH and residual alkali detection, and the test results are shown in Table 1. It should be noted that the free lithium content in Table 1 is the sum of the lithium ion content in the residual alkali (lithium carbonate and lithium hydroxide).

[0124] The ternary material prepared in the example and the comparative example is respectively assembled into a 2016 button cell, wherein the ternary material: superconductive carbon black: polyvinylidene fluoride with a mass ratio of 90:5:5 is dissolved in N-methyl pyrrolidone, and a uniformly dispersed slurry is obtained by stirring the slurry, uniformly coated on an aluminum foil, and dried at 120 DEG C for 12 hours to obtain; the negative electrode is a lithium sheet; the separator is Celgard 2400; the electrolyte is 1M LiPF6 dissolved in ethylene carbonate / dimethyl carbonate / diethyl carbonate (volume ratio 1:1:1). The battery assembly process is completed in a glove box.

[0125] The battery test conditions are as follows: tested on a blue instrument in a 25 DEG C constant temperature box; test current: 0.2C, 0.33C, 1C, 2C, 3C, constant current and constant voltage charging, 0.2C, 0.33C, 1C, 2C, 3C constant current discharge, constant voltage charging stage cutoff condition: cutoff current 0.05C; test voltage range: 2.8-4.5V. The cycle test is 1C rate cycle for 50 times, and the test results are shown in Table 2.

[0126] Table 1

[0127]

[0128] Table 2

[0129]

[0130] Figure 1 The SEM diagram of the ternary material in Example 1 of the present application is shown in Figure 1, and it can be seen from Figure 1 that the ternary material of the present application has a single crystal morphology, and the particle size is uniform, has good crystallinity, and the average particle size of the particles is 2.2 μm. Figure 1

[0131] The XRD diagram of the ternary material in Example 1 of the present application is shown in Figure 2, and it can be seen from Figure 2 that the ternary material of the present application has an α-NaFeO2 type layered structure; the (006) / (102) and (108) / (110) peaks are obviously split, indicating that the material has a good layered structure. Figure 2 Figure 2 From the above description, it can be seen that the above-mentioned examples of the present application achieve the following technical effects:

[0132] From the above description, it can be seen that the above-mentioned examples of the present application achieve the following technical effects:

[0133] ​The cobalt content of the surface of the ternary material is higher than the inside in the application, which can increase the electronic conductivity of the material surface, reduce the surface impedance, and accelerate the surface diffusion rate of lithium ions, thereby improving the rate performance and cycle stability of the material. High-nickel ternary materials are prone to structural instability problems at high charge states, especially lithium-nickel mixing. By increasing the surface cobalt content, the structural stability of the material surface is strengthened, and lithium-nickel mixing is reduced, which helps to maintain the layered structure of the material during the cycle process and improve the cycle performance and stability. The material surface is often where electrochemical reactions and side reactions occur. Surface enrichment of cobalt content can form a relatively stable coating layer, reduce direct contact between the surface and the electrolyte, inhibit surface side reactions, and improve the interface stability and overall electrochemical performance of the material. The presence of multiple doping elements helps to effectively adjust the crystal structure of the material, balances the lithiumation degree, surface free lithium content, crystallinity, and lithium-nickel mixing of the ternary material, so that the ternary material can have excellent electrochemical performance, which helps to improve the structural stability of the ternary material, thereby improving the cycle stability and rate performance of the ternary material.

[0134] The above is only an embodiment of the application and is not intended to limit the application. Those skilled in the art can make various modifications and changes to the application. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principles of the application shall be included in the protection scope of the application.

Claims

1. A ternary material characterized in that, The chemical formula of the ternary material is LiNi x Co y Mn y M 1-x-y O2, x≥0.6, y≤0.1, M is selected from Mn element and / or Al element, and the cobalt content of the surface of the ternary material is higher than the cobalt content inside the ternary material, the ternary material further comprises a first doping element, a second doping element and a third doping element, the first doping element is selected from at least two of Group IIIA elements, Group IVB elements, Group IIA elements, Group VB elements, Group VIB elements and Group IIIB elements, the second doping element is a combination of a second cobalt element and an A element, the A element is selected from any one or more of tungsten element, zirconium element and calcium element, and the third doping element is selected from any one or more of Group IIIA elements, Group VB elements, Group IIIB elements, Group VIB elements, Group IVA elements, Group IVB elements and Group IIA elements.

2. A method of producing the ternary material of claim 1, characterized in that, Comprise: S1, Ni x Co y M 1-x-y (OH)2, a first lithium source and a first doping source are mixed to perform a first sintering to obtain a first sintering product; wherein x≥0.6, y≤0.1, M is selected from Mn element and / or Al element; the first doping source is selected from at least two of a group IVA element source, a group IVB element source, a group IIA element source, a group VB element source, a group VIB element source and a group IIIB element source; S2, the first sintering product, a second lithium source and a first cobalt source are mixed and then subjected to a second sintering to obtain a second sintering product; S3, the second sintering product and a second doping source are mixed and then subjected to a third sintering to obtain a third sintering product; wherein the second doping source is a combination of a second cobalt source and an A source, and the A source is selected from any one or more of a tungsten source, a zirconium source and a calcium source; S4, the third sintering product and a third doping source are mixed and then subjected to a fourth sintering to obtain the ternary material; wherein the third doping source is selected from any one or more of a group IIIA element source, a group VB element source, a group IIIB element source, a group VIB element source, a group IVA element source, a group IVB element source and a group IIA element source.

3. The preparation method according to claim 2, characterized in that, The average particle size of the ternary material is 1.5-4.5 μm.

4. The preparation method according to claim 2, characterized in that, 0.7 > x > 0.6, 0.05 < y < 0.1 ; and / or, the Ni x Co y M 1-x-y D50 of the (OH)2 is 3-5.5 pm; And / or, the D50 of the first lithium source is 300-800 μm; And / or, the average particle size of the first doping source is 10-200 nm; and / or the molar ratio of lithium element in the first lithium source to the Ni x Co y M 1-x-y (OH)2 is (0.8-1): 1; and / or the first dopant source and the Ni x Co y M 1-x-y (OH)2is (0.1-1):

100. And / or, the first lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate and lithium phosphate; And / or, the first doping source is selected from at least two of Al2O3, ZrO2, MgO, TiO2, Nb2O5, WO3, SrCO3, Y2O3, La2O3 and MoO3.

5. The preparation method according to claim 4, characterized in that, said Ni x Co y M 1-x-y the ratio of the D50 of said (OH)2 to the D50 of said first lithium source is 1 : (100-200).

6. The production method according to any one of claims 2 to 5, characterized by, The temperature of the first sintering is 350-700 ℃; and / or, the time of the first sintering is 2-16 h; and / or, the temperature rising rate of the first sintering is 1-10 ℃ / min; and / or, the atmosphere of the first sintering is an oxygen-rich atmosphere with an oil content of less than 5 ppm and a humidity of less than 30%, and the oxygen content in the oxygen-rich atmosphere is greater than 30%.

7. The production method according to any one of claims 2 to 5, characterized by, The mass ratio of the first sintering product to the second lithium source is 100:(0.1-20); And / or, the mass ratio of the first cobalt source to the first sintering product is (0.1-3):100; And / or, the second lithium source is selected from any one or more of lithium carbonate, lithium hydroxide, lithium nitrate, lithium oxalate, lithium fluoride, lithium bromide, lithium chloride, lithium acetate, lithium oxide, lithium dihydrogen phosphate and lithium phosphate; And / or, the first cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH.

8. The production method according to any one of claims 2 to 5, characterized by, The temperature of the second sintering is 750-1000 ℃; and / or, the time of the second sintering is 8-25 h; and / or, the atmosphere of the second sintering is an atmosphere with an oxygen content of ≥50%; And / or, the D10 of the second sintering product is ≤2 μm, the D50 is 2.5-4.5 μm, and the D90 is ≤14 μm.

9. The production method according to any one of claims 2 to 5, characterized by, The mass ratio of the second doping source to the second sintering product is (0.1-3):100; and / or, the mass ratio of the second cobalt source to the A source is (1-5):1; And / or, the second cobalt source is selected from any one or more of cobalt oxalate, cobalt acetate, cobalt carbonate, cobalt hydroxide, CoO and CoOOH. And / or, the third sintering temperature is 350-700 DEG C; and / or, the third sintering time is 8-25h; and / or, the third sintering atmosphere is an atmosphere with oxygen content >=50%.

10. The production method according to any one of claims 2 to 5, characterized by, The mass ratio of the third doping source to the third sintering product is (4-10):100; And / or, the third doping source is selected from any one or more of a B source, an Al source, a Ta source, a Ce source, a W source, an Nb source, a Ge source, a Y source, a Zr source, a Ca source and a Sr source; And / or, the fourth sintering temperature is 300-400 DEG C; and / or, the fourth sintering time is 3-10h.

11. A positive electrode sheet characterized by comprising: The positive electrode sheet contains the ternary material of claim 1.

12. A lithium-ion battery comprising a positive electrode sheet, an electrolyte, and a negative electrode sheet, characterized by, The positive electrode sheet is the positive electrode sheet of claim 11.

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