High-nickel positive electrode material, preparation method thereof and lithium ion battery

Abstract

The application relates to a high-nickel positive electrode material, a preparation method thereof and a lithium ion battery, the chemical general formula of the high-nickel positive electrode material is shown in formula (1): Li x Ni 1‑(a+b+c+d+e+f) Co a M1 b M2 c M3 d M4 e M5 f O2(1), wherein 0.95<=x<=1.2, 0<=a<=0.15, 0<=b<=0.10, 0<=c<=0.05, 0<=d<=0.05, 0<=e<=0.05, 0<=f<=0.05, 0 3+ The quantity of the high-nickel material surface Ni 2+ is less, the quantity of Ni is more, the positive electrode material surface can be avoided from being oxidized during delithiation, the stability of the positive electrode material structure is beneficial to being maintained, the loss of the positive electrode active material and the electrolyte is avoided, the capacity of the positive electrode material is further improved, and the high-temperature cycle performance of the high-nickel positive electrode material is obviously improved.

Description

Technical Field

[0001] This invention belongs to the field of cathode material technology, and particularly relates to a high-nickel cathode material and its preparation method, and lithium-ion batteries. Background Technology

[0002] Lithium-ion batteries are widely used in laptops, mobile phones, and digital products due to their high energy density, good safety performance, long cycle life, and environmental friendliness. Simultaneously, with increasing environmental awareness, lithium-ion batteries are gradually being used as power batteries in transportation vehicles, such as electric vehicles and electric buses. The market is placing increasingly higher demands on the specific capacity, energy density, power density, and lifespan of lithium-ion batteries, especially specific capacity. The most commonly used cathode materials in lithium-ion batteries are olivine-structured LiFePO4, layered LiCoO2, and layered lithium nickel oxide materials. Olivine-structured LiFePO4 has reached its capacity limit and its main applications are in energy storage and low-range electric vehicles. Layered LiCoO2 is mainly used in consumer batteries. Lithium nickel oxide materials are widely used in electric vehicles. In lithium nickel oxide materials, nickel is the main redox reaction element; increasing the nickel content can effectively improve the specific capacity of these materials, thus the development of high-nickel materials has become a market trend.

[0003] The main factors currently hindering the widespread application of high-nickel ternary materials in power batteries are poor high-temperature performance, rapid increase in DC internal resistance, and gas production. These unfavorable factors are mainly caused by three factors. Firstly, the intrinsic structure of high-nickel ternary materials undergoes irreversible structural changes during charging and discharging, with higher nickel content resulting in greater structural changes. Secondly, during charging and discharging, the valence of nickel changes accordingly, corresponding to the extraction and insertion of lithium ions. Under the same voltage, higher nickel content results in more lithium ions being extracted, leading to greater volume changes in the material. These volume changes are accompanied by the release of internal stress, causing cracks in the high-nickel material. Especially for high-nickel materials in the charging state, the electrolyte can enter the material through these cracks, reacting with the highly active Ni... 4+ Redox reactions occur, leading to changes in the material structure; secondly, when high-nickel ternary materials undergo delithiation, the Ni on the material surface... 3+ It will be converted into Ni, a strong oxidizing agent. 4+ Ni 4+ It is prone to redox reactions with organic electrolytes, which leads to the loss of positive electrode active material and electrolyte, resulting in capacity decay, increase of DC internal resistance and gas generation. Finally, high-nickel ternary materials are prone to generating alkaline impurities (including residual Li2CO3 and LiOH on the material surface) during the synthesis process. These alkaline impurities are non-conductive and easily react with electrolyte, causing battery gas generation and battery polarization.

[0004] Therefore, in order to promote the widespread use of high-nickel ternary materials in power batteries, there is an urgent need for a high-nickel cathode material that can solve the problems of poor high-temperature performance, rapid increase in DC internal resistance, and gas production. Summary of the Invention

[0005] The purpose of this application is to provide a high-nickel cathode material and its preparation method, as well as a lithium-ion battery. The high-nickel cathode material of this application has Ni content on its surface. 3+ Small quantity, Ni 2+ A larger quantity can prevent the surface of high-nickel cathode materials from being oxidized during delithiation, thereby improving the high-temperature cycle performance and structural stability of high-nickel cathode materials.

[0006] In a first aspect, embodiments of this application provide a high-nickel cathode material, the chemical formula of which is shown in formula (1):

[0007] Li x Ni 1-(a+b+c+d+e+f) Co a M1 b M2 c M3 d M4 e M5 f O2 (1)

[0008] Wherein, 0.95≤x≤1.2, 0≤a≤0.15, 0≤b≤0.10, 0≤c≤0.05, 0≤d≤0.05, 0≤e≤0.05, 0≤f≤0.05, 0<a+b+c+d+e+f≤0.2;

[0009] The high-nickel cathode material was analyzed by AlKα radiation using powder XPS, which showed that Ni2P, which can appear in the range of 850 eV to 870 eV, was incorporated. 3 / 2 After peak separation and fitting, Ni 2+ The peak area is set to S1, Ni 3+ The peak area is set to S2, and Ni 2+ The peak half-width is set to A, and Ni is... 3+ Let the half-peak width be B, and S1, S2, A, and B satisfy the following relationship:

[0010] S1 / (S1+S2)>0.5 and 0.9<A / B<1.5 (2).

[0011] In conjunction with the first aspect, the cathode material includes secondary particles and / or primary particles, at least a portion of the surface of the primary particles is coated with a coating layer, the secondary particles include a plurality of primary particles with coating layers, and the coating layer includes at least one of the following features (1) to (3):

[0012] (1) The coating layer includes a first coating layer and a second coating layer, wherein the first coating layer is formed on the surface of the primary particle and the second coating layer is formed on the surface of the first coating layer;

[0013] (2) The coating layer includes a first coating layer and a second coating layer, wherein the first coating layer includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La;

[0014] (3) The coating layer includes a first coating layer and a second coating layer, wherein the second coating layer includes a boron-containing compound;

[0015] (4) The coating layer includes a first coating layer and a second coating layer. The second coating layer includes a boron-containing compound, which includes B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O. 13 At least one of them.

[0016] In conjunction with the first aspect, the material includes at least one of the following features (1) to (14):

[0017] (1) M1 includes Mn and / or Al;

[0018] (2) M2 and M3 each include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg and Ba, and M2 and M3 are not the same;

[0019] (3) The M4 includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La;

[0020] (4) The M5 includes B;

[0021] (5) The high-nickel cathode material was subjected to powder XPS analysis using AlKα rays: when Ni2P, which can appear in the range of 850 eV to 870 eV, was incorporated... 3 / 2 After peak separation and fitting, Ni 2+ / Ni 3+ The area ratio is greater than 1;

[0022] (6) The high-nickel cathode material was subjected to powder XPS analysis using AlKα rays: when the O1S peak, which appears in the range of 526 eV to 540 eV, was separated and fitted, the O1S peak... 晶格氧 / O1S 杂质氧 The area ratio is greater than 1 / 2;

[0023] (7) The mass content of LiOH in the high-nickel cathode material is less than 0.3 wt%;

[0024] (8) The mass content of Li2CO3 in the high-nickel cathode material is less than 0.3wt%;

[0025] (9) The crystal structure of the high-nickel cathode material belongs to the hexagonal crystal structure or the monoclinic crystal structure.

[0026] (10) The morphology of the high-nickel cathode material crystal particles includes at least one of approximately spherical, approximately cubic and approximately cuboid shapes;

[0027] (11) The pH of the high-nickel cathode material is: 10.5 < pH < 11.7;

[0028] (12) The powder conductivity of the high-nickel cathode material is greater than 0.02 S / cm;

[0029] (13) The specific surface area of ​​the high-nickel cathode material is 0.3 m². 2 / g~0.8m 2 / g;

[0030] (14) The average particle size of the high-nickel cathode material is 2.5 μm to 4.5 μm.

[0031] Secondly, this application discloses a method for preparing a high-nickel cathode material, comprising the following steps:

[0032] The matrix material is obtained by mixing a metal composite hydroxide precursor, a lithium-containing compound and a dopant and then performing a single heat treatment.

[0033] The dopant includes elements M2 and M3. The compound corresponding to element M2 is at least one of oxides, hydroxides and lithium metal oxides containing only M2, and the oxidation state of M2 in the compound is greater than or equal to +4. The compound corresponding to element M3 is at least one of oxides and hydroxides containing only M3, and the oxidation state of M3 in the compound is +2.

[0034] The matrix material is coated to obtain a high-nickel cathode material.

[0035] In conjunction with the second aspect, the method includes at least one of the following features (1) to (10):

[0036] (1) The mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant is 1:(0.46~0.48):(0.001~0.003);

[0037] (2) The ratio of the total metal content Me in the metal composite hydroxide precursor to the atomic ratio of Li in the lithium-containing compound is 1.0 < Li / Me < 1.2;

[0038] (3) The lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate;

[0039] (4) The elements M2 and M3 are both selected from at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg and Ba, and M2 and M3 are not the same;

[0040] (5) The molar ratio of M2 and M3 Greater than or equal to 2:1;

[0041] (6) The average particle size of the dopant is 10 nm to 50 nm;

[0042] (7) The temperature of the first heat treatment is 680℃~900℃;

[0043] (8) The duration of the first heat treatment is 5h to 20h;

[0044] (9) The heating rate of the first heat treatment is 50℃ / h to 550℃ / h;

[0045] (10) The oxygen content of the matrix material is greater than or equal to 85%.

[0046] In conjunction with the second aspect, the method includes the step of mixing the matrix material with a first coating agent and then subjecting it to a secondary heat treatment to obtain a first-coated product, the method comprising at least one of the following features (1) to (10):

[0047] (1) The mass ratio of the matrix material to the first coating agent is 1000:(0.5~3);

[0048] (2) The first coating agent includes a metallic element or a non-metallic element with a valence greater than or equal to +3;

[0049] (3) The first coating agent includes at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide and titanium oxide;

[0050] (4) The average particle size of the first coating agent is 10 nm to 50 nm;

[0051] (5) The temperature of the secondary heat treatment is 600℃~800℃;

[0052] (6) The duration of the secondary heat treatment is 1 hour to 20 hours;

[0053] (7) The heating rate of the secondary heat treatment is 50℃ / h to 550℃ / h;

[0054] (8) The secondary heat treatment further includes washing under constant temperature conditions and drying under vacuum conditions after washing, wherein the temperature of the constant temperature conditions is 10℃~25℃.

[0055] (9) The secondary heat treatment further includes washing under constant temperature conditions and drying under vacuum conditions after washing, wherein the drying temperature is 100℃~200℃.

[0056] (10) The oxygen content of the material obtained by the first coating is greater than or equal to 85%.

[0057] In conjunction with the second aspect, the method further includes a step of mixing the product obtained from the first coating with a second coating agent and then subjecting it to three heat treatments, the method comprising at least one of the following features (1) to (6):

[0058] (1) The second coating agent is a boron-containing compound;

[0059] (2) The second coating agent is a boron-containing compound, including B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O. 13 At least one of them;

[0060] (3) The mass ratio of the product obtained from the first coating to the second coating agent is 1:(1-5);

[0061] (4) The temperature of the three heat treatments is 200℃~600℃;

[0062] (5) The duration of the three heat treatments is 1 hour to 20 hours;

[0063] (6) The heating rate of the three heat treatments is 50℃ / h to 550℃ / h.

[0064] In conjunction with the second aspect, the metal complex hydroxide precursor is obtained by mixing a metal salt solution with a complexing agent and a pH adjuster.

[0065] In conjunction with the second aspect, the method includes at least one of the following features (1) to (10):

[0066] (1) The mass ratio of the metal salt solution, complexing agent, and pH adjuster is 1:(0.01~0.10):(0.1~0.8);

[0067] (2) The metal salt solution includes at least one of nickel salt solution, cobalt salt solution, manganese salt solution and aluminum salt solution;

[0068] (3) The complexing agent includes at least one of ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, hydrazine, ethylenediaminetetraacetic acid, hypozoxytriacetic acid, uracil diacetic acid and glycine;

[0069] (4) The pH adjuster includes at least one of sodium hydroxide and potassium hydroxide;

[0070] (5) The pH of the mixed treatment is 9-13;

[0071] (6) The temperature of the mixing process is 10℃~80℃;

[0072] (7) The mixing treatment time is 10h to 200h;

[0073] (8) The mixing process is carried out under stirring conditions, and the stirring rate is 800 rpm to 1200 rpm;

[0074] (9) The mixing process further includes solid-liquid separation, washing and drying steps;

[0075] (10) The average particle size of the metal composite hydroxide precursor is 3 μm to 10 μm.

[0076] Thirdly, embodiments of this application disclose a lithium-ion battery, the lithium-ion battery comprising the high-nickel cathode material described in the first aspect or the high-nickel cathode material prepared by the method described in the second aspect.

[0077] Compared with the prior art, the present invention has the following beneficial effects: The high-nickel cathode material of this application is analyzed by AlKα radiation using powder XPS, and when combined with Ni2P which can appear in the range of 850 eV to 870 eV... 3 / 2 After peak separation and fitting, Ni 2+ Peak area S1, Ni 3+ Peak area S2, Ni 2+ The peak half-width A and Ni 3+ The peak half-width B satisfies: S1 / (S1+S2)>0.5 and 0.9<A / B<1.5, indicating that the Ni on the surface of the high-nickel cathode material of this application... 3+ Small quantity, Ni 2+ The larger quantity of nickel also helps prevent oxidation of the high-nickel cathode material surface during delithiation, which is beneficial for maintaining the stability of the cathode material structure. This avoids the loss of cathode active material and electrolyte during charge and discharge, further improving the cathode material's capacity and significantly enhancing the high-temperature cycle performance of the high-nickel cathode material. Furthermore, due to the Ni content on the material surface... 3+ The quantity is small, and the surface Ni 2+The large quantity of material reduces the occurrence of internal cracks during charging and discharging, stabilizes the internal structure of the material, and significantly suppresses the increase in DC internal resistance of the battery when the cathode material of this application is used in the battery for long-term cycling.

[0078] This application involves heat-treating a material containing M2 elements with a valence greater than or equal to +4 and M3 elements with a valence equal to +2. This results in M2 elements being doped onto the surface of the material and M3 elements being doped into the interior. Because the M2 elements with a valence greater than or equal to +4 are present on the surface, the valence balance is achieved, resulting in Ni content on the material surface... 3+ The quantity is reduced, while the surface Ni 2+ The increased quantity of M3 elements helps prevent oxidation of the cathode material surface during lithium removal, thus maintaining the stability of the cathode material structure. The entry of M3 elements with a +2 valence into the material can suppress the H2→H3 phase transition during charging and discharging, improving structural stability. Simultaneously, M3 can replace a portion of the Li in the material's internal crystal lattice. + The position of the matrix material is adjusted, but the layered structure of the material is not affected. This application improves the stability of high-nickel cathode materials and further enhances the capacity performance of high-nickel cathode materials by doping with M2 and M3 elements to form the matrix material. Attached Figure Description

[0079] To more clearly illustrate the technical solutions of the embodiments of this application or the prior art, the drawings used in the description of the embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0080] Figure 1 This is a flowchart illustrating the preparation process of the high-nickel cathode material of this application;

[0081] Figure 2 This is a SEM image of the high-nickel cathode material of this application;

[0082] Figure 3 The Ni2P peak of the high-nickel cathode material of Example 1 of this application is located at the Ni bonding portion at a binding energy of 850 eV to 870 eV. 3 / 2 Perform peak segmentation and curve fitting;

[0083] Figure 4 The Ni2P peak of the Ni bonding portion at the binding energy position of 850 eV to 870 eV in the high-nickel cathode material of Example 8 of this application. 3 / 2 Perform peak segmentation and curve fitting;

[0084] Figure 5The peak of Ni2P in the Ni bonding region at the binding energy position of 850 eV to 870 eV is shown in Comparative Example 1 high-nickel cathode material. 3 / 2 Perform peak segmentation and curve fitting;

[0085] Figure 6 The peak of Ni2P in the Ni bonding region at the binding energy position of 850 eV to 870 eV is shown in Comparative Example 2 high-nickel cathode material. 3 / 2 Perform peak segmentation and curve fitting;

[0086] Figure 7 Peak separation and curve fitting diagram of the O1S peak at the position of the O-bonding portion with a binding energy of 526eV to 540eV in the high-nickel cathode material of Example 1 of this application;

[0087] Figure 8 Peak separation and curve fitting diagram of the O1S peak at the position of the O bond portion with a binding energy of 526eV to 540eV in the high nickel cathode material of Example 8 of this application;

[0088] Figure 9 The peak O1S of the O-bonding portion at the binding energy position of 526eV to 540eV is shown in the diagram of Comparative Example 1 high-nickel cathode material.

[0089] Figure 10 Peak separation and curve fitting diagram of the O1S peak in the O-bonding portion of the high-nickel cathode material of Comparative Example 2 at the binding energy position of 526eV to 540eV.

[0090] Figure 11 This is a capacity differential curve of the high-nickel cathode material in Example 1 of this application;

[0091] Figure 12 This is a capacity differential curve of the high-nickel cathode material in Example 8 of this application;

[0092] Figure 13 This is the capacity differential curve of the high-nickel cathode material in Comparative Example 1;

[0093] Figure 14 This is a capacity differential curve of the high-nickel cathode material in Comparative Example 2;

[0094] Figure 15 Argon-ion cross-sectional SEM image of the high-nickel cathode material of Example 1 of this application after 300 cycles;

[0095] Figure 16 Argon-ion cross-sectional SEM image of the high-nickel cathode material of Example 8 of this application after 300 cycles;

[0096] Figure 17Argon-ion cross-sectional SEM image of the high-nickel cathode material of Comparative Example 1 after 300 cycles;

[0097] Figure 18 Argon-ion cross-sectional SEM images of the high-nickel cathode material in Comparative Example 2 after 300 cycles. Detailed Implementation

[0098] To better understand the technical solution of this application, the embodiments of this application will be described in detail below with reference to the accompanying drawings.

[0099] It should be understood that the described embodiments are merely some, not all, of the embodiments in this application. All other embodiments obtained by those skilled in the art based on the embodiments in this application without inventive effort are within the scope of protection of this application.

[0100] Furthermore, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined with "first" or "second" may explicitly or implicitly include one or more of that feature.

[0101] For ease of understanding of this invention, specific terms have been appropriately defined in this application. Unless otherwise defined herein, the scientific and technical terms used in this invention have the meanings commonly understood by one of ordinary skill in the art to which this invention pertains.

[0102] As used herein, the term "matrix" refers to a lithium-based composite oxide synthesized by a high-temperature solid-state reaction of a precursor and a lithium salt, and includes both lithium and metal elements.

[0103] As used in this article, the term "primary particle" refers to a particle that exists alone and does not form a condensate.

[0104] As used in this article, the term "secondary particle" refers to a particle formed by the condensation of the aforementioned primary particles.

[0105] NCM ternary cathode materials can be understood as LiCoO2, LiNi 0.5 Mn 0.5 A solid solution of O2 and LiNiO2, corresponding to the general formula Li 1+a [Ni z (Ni 1 / 2 Mn 1 / 2 ) y CO x ] 1-a O2, where Z represents Ni 3+ Ratio; for example, LiNi 0.6 Co 0.2 Mn 0.2O2 can be understood as 0.2LiCoO2 + 0.4LiNi 0.5 Mn 0.5 O2 + 0.4LiNiO2, therefore Ni 3+ The ratio is 0.4, and other high-nickel materials such as LiNi 0.885 Co 0.09 Mn 0.025 Ni in O2 3+ The ratio is 0.86, LiNi 0.8 Co 0.15 Al 0.05 Ni in O2 3+ The ratio is 0.8. For the synthesis of high-nickel materials, due to the presence of Ni... 3+ A higher proportion of Ni also requires a higher oxygen content in its synthesis process, because only in this way can the Ni in the precursor be converted into Ni. 2+ Oxidized to Ni 3+ For example, LiNi 0.885 Co 0.09 Mn 0.025 O2 and LiNi 0.8 Co 0.15 Al 0.05 O2 can only be synthesized in a high-concentration oxygen atmosphere, while LiNi 0.4 Co 0.2 Mn 0.4 Ni of O2 3+ The ratio is 0, so it can be synthesized in air, and the material surface has very few alkaline impurities. The synthesized high-nickel material is very sensitive to moisture in the air, mainly because of the low Ni content in the high-nickel material. 3+ The high proportion of lithium in high-nickel materials makes it easier for lithium to undergo a proton exchange reaction with water in the air to form LiOH, while Ni... 3+ Low- to medium-nickel materials are less prone to proton exchange reactions; therefore, the production and storage of high-nickel materials must be carried out in a low-humidity environment. When high-nickel materials are used to make batteries, the Ni content in the material increases after charging. 3+ It will be converted into Ni 4+ Ni 4+ Its strong oxidizing properties will cause a redox reaction with the electrolyte in direct contact with Ni. 4+ +electrolyte→Ni 2+ The combination of H₂O and CO₂ produces gases that cause the battery to bulge, while the loss of positive electrode active material leads to a sharp drop in battery capacity. This is because high-nickel materials inevitably contain a high proportion of Ni. 3+ The Ni on the surface layer (5nm~10nm) of high-nickel materials 3+ Since it comes into direct contact with the electrolyte or air, how to control the Ni content of the surface layer of high-nickel materials is crucial. 3+The ratio is of great significance for improving the high-temperature cycling performance of high-nickel materials, reducing material gas production, reducing alkaline impurities on the material surface, and reducing the growth of DC internal resistance.

[0106] Therefore, this application provides a high-nickel cathode material, the general chemical formula of which is shown in formula (1):

[0107] Li x Ni 1-(a+b+c+d+e+f) Co a M1 b M2 c M3 d M4 e M5 f O2 (1)

[0108] Wherein, 0.95≤x≤1.2, 0≤a≤0.15, 0≤b≤0.10, 0≤c≤0.05, 0≤d≤0.05, 0≤e≤0.05, 0≤f≤0.05, 0<a+b+c+d+e+f≤0.2.

[0109] High-nickel cathode materials were analyzed by powder XPS using AlKα rays. This revealed the presence of Ni₂P, which binds to materials in the 850 eV–870 eV range. 3 / 2 After peak separation and fitting, Ni 2+ The peak area is set to S1, Ni 3+ The peak area is set to S2, and Ni 2+ The peak half-width is set to A, and Ni is... 3+ Let the half-peak width be B, and S1, S2, A, and B satisfy the following relationship:

[0110] S1 / (S1+S2)>0.5 and 0.9<A / B<1.5 (2).

[0111] In the above technical solution, the high-nickel cathode material of this application satisfies the following relationship as determined by XPS: S1 / (S1+S2)>0.5 and 0.9<A / B<1.5, indicating that the Ni content on the surface of the high-nickel cathode material of this application is high. 3+ The quantity is small, and the surface Ni 2+ The larger quantity of nickel on the surface of the cathode material prevents oxidation during delithiation, thus maintaining the stability of the cathode material structure and avoiding losses of the cathode active material and electrolyte during charge and discharge. This further increases the capacity of the cathode material and significantly improves the high-temperature cycle performance of the high-nickel cathode material. Furthermore, due to the Ni content on the material surface... 3+ The quantity is small, and the surface Ni 2 +The large quantity of material reduces the occurrence of internal cracks during charging and discharging, stabilizes the internal structure of the material, and significantly suppresses the increase in DC internal resistance of the battery when the cathode material of this application is used in the battery for long-term cycling.

[0112] In some embodiments, the cathode material includes secondary particles and / or primary particles, with at least a portion of the surface of the primary particles coated with a coating layer, and the secondary particles including a plurality of primary particles with coating layers. It is understood that the secondary particles are aggregates of a plurality of primary particles, and the cathode material of this application may include only primary particles, or only secondary particles, or may be a mixture of primary and secondary particles.

[0113] In some embodiments, the coating layer includes a first coating layer and a second coating layer, wherein the first coating layer is formed on the surface of the primary particles, and the second coating layer is formed on the surface of the first coating layer. The first coating layer can improve the stability of the material surface structure, and the second coating layer can effectively improve the material's processability and electrical conductivity.

[0114] In some embodiments, the first coating layer includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr, and La, wherein the oxidation state of the aforementioned elements in the high-nickel cathode material is greater than or equal to +3, resulting in a Ni content in the surface layer of the high-nickel cathode material. 2+ The quantity remains unchanged or is further increased to improve the stability of the cathode material structure, while also reducing the generation of alkaline impurities on the material surface. It is understood that the above-mentioned high-nickel cathode material surface refers to the thickness of 5nm to 10nm on the surface of primary particles.

[0115] In some embodiments, the second coating layer comprises a boron-containing compound, including B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O. 13 At least one of the above-mentioned boron-containing compounds can not only react chemically with alkaline impurities on the surface of high-nickel cathode materials, thus preventing the decomposition of Li2CO3 in the alkaline impurities on the material surface or the side reaction between the alkaline impurities and the electrolyte to generate gas, but also form a stable coating layer on the surface of high-nickel cathode materials, thereby improving the stability of high-nickel cathode materials.

[0116] In some implementations, M1 includes Mn and / or Al. Specifically, M1 can be Mn, Al, or a mixture of Mn and Al.

[0117] In some embodiments, M2 and M3 each include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg, and Ba, and M2 and M3 are not the same.

[0118] In some embodiments, M4 includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr, and La.

[0119] In some implementations, M5 includes B.

[0120] In some embodiments, the high-nickel cathode material is subjected to powder XPS analysis using AlKα rays: when Ni2P, which can appear in the range of 850 eV to 870 eV, is incorporated... 3 / 2 After peak splitting and fitting, the standard deviation of the fit ∑x 2 <10%, Ni 2 + / Ni 3+ The area ratio is greater than 1. Specifically, Ni 2+ / Ni 3+ The area ratio can be 2, 3, 4, and 5, indicating that the Ni content of the high-nickel material surface layer in this application is... 2+ More nickel content can prevent the surface of high-nickel cathode materials from being oxidized during delithiation, which is beneficial to maintaining the stability of the cathode material structure.

[0121] In some embodiments, the high-nickel cathode material is analyzed using AlKα radiation via powder XPS. When the O1S peaks that appear in the 526 eV–540 eV range are separated and fitted, and the standard deviation of the fit is ∑x 2 <10%, O1S 晶格氧 / O1S 杂质氧 The area ratio is greater than 1 / 2. Impurity oxygen refers to oxygen in compounds such as LiOH, Li₂CO₃, and Li₂SO₄; specifically, O₁S... 晶格氧 / O1S 杂质氧 The area can be 0.532, 0.525, and 0.573, etc., for O1S 晶格氧 / O1S 杂质氧 Controlling the area ratio within the above range is beneficial to reducing alkaline impurities (Li2CO3 and LiOH, etc.) on the surface of high-nickel cathode materials and reducing the gas production of batteries made from high-nickel cathode materials.

[0122] In some embodiments, the surface alkaline impurities of the high-nickel cathode material mainly refer to Li₂CO₃ and LiOH. The mass content of Li₂CO₃ in the high-nickel cathode material is less than 0.3 wt%. Specifically, the mass content of Li₂CO₃ in the high-nickel cathode material can be 0.05 wt%, 0.1 wt%, 0.12 wt%, and 0.2 wt%, etc., and of course, other values ​​within the above range are also possible and are not limited here. Preferably, the mass content of Li₂CO₃ in the high-nickel cathode material is less than 0.13 wt%.

[0123] In some embodiments, the mass content of LiOH in the high-nickel cathode material is less than 0.3 wt%. Specifically, the mass content of LiOH in the high-nickel cathode material can be 0.05 wt%, 0.08 wt%, 0.1 wt%, and 0.2 wt%, etc., or other values ​​within the above range, which are not limited here. Preferably, the mass content of LiOH in the high-nickel cathode material is less than 0.1 wt%.

[0124] Controlling the mass content of Li2CO3 and LiOH in high-nickel cathode materials within the above-mentioned range is beneficial to improving the processing performance of high-nickel cathode materials and reducing gas production in batteries made from high-nickel cathode materials.

[0125] In some implementations, the high-nickel cathode material has a hexagonal or monoclinic crystal structure.

[0126] The hexagonal crystal structure belongs to the order of P3, P31, P32, R3, P-3, R-3, P312, P321, P3112, P3121, P3212, P3221, R32, P3m1, P31m, P3c1, P31c, R3m, R3c, P-31m, P-31c, P-3m1, P-3c1, R-3m, R-3c, P6, P61, P65, P Any space group in the group consisting of P62, P64, P63, P-6, P6 / m, P63 / m, P622, P6122, P6522, P6222, P6422, P6322, P6mm, P6cc, P63cm, P63mc, P-6m2, P-6c2, P-62m, P-62c, P6 / mmm, P6 / mcc, P63 / mcm, and P63 / mmc.

[0127] The crystal structure of the monoclinic crystal form belongs to any space group selected from the group consisting of P2, P21, C2, Pm, Pc, Cm, Cc, P2 / m, P21 / m, C2 / m, P2 / c, P21 / c, and C2 / c.

[0128] Preferably, in order to obtain a secondary battery with a high discharge capacity, the high-nickel cathode material has a hexagonal crystal structure with space group R-3m or a monoclinic crystal structure with C2 / m.

[0129] In some embodiments, the morphology of the high-nickel cathode material crystal particles includes at least one of approximately spherical, approximately cubic, and approximately cuboid shapes.

[0130] In some embodiments, the pH of the high-nickel cathode material is 10.5 < pH < 11.7. The pH of the high-nickel cathode material can be 10.6, 10.8, 11.0, 11.2, 11.3, and 11.5, or other values ​​within the above range, which are not limited here. Controlling the pH of the high-nickel cathode material within the above range is beneficial for improving its processing performance. Preferably, the pH of the high-nickel cathode material is 11.0 < pH < 11.5, and more preferably, 11.2 < pH < 11.3.

[0131] In some embodiments, the powder conductivity of the high-nickel cathode material is greater than 0.02 S / cm. Specifically, the powder conductivity of the high-nickel cathode material can be 0.03 S / cm, 0.04 S / cm, 0.05 S / cm, 0.0 S / cm, and 0.07 S / cm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0132] In some implementations, the specific surface area of ​​the high-nickel cathode material is 0.3 m². 2 / g~0.8m 2 / g, the specific surface area of ​​high-nickel cathode material can specifically be 0.3m². 2 / 、0.4m 2 / 、0.5m 2 / 、0.6m 2 / 、0.7m 2 / and 0.8m 2 / etc., of course, can also be other values ​​within the above range, which are not limited here.

[0133] In some embodiments, the median particle size of the high-nickel cathode material is 2.5 μm to 4.5 μm. The median particle size of the high-nickel cathode material can be 2.5 μm, 3 μm, 3.5 μm, 4 μm and 4.5 μm, etc. Controlling the average particle size of the high-nickel cathode material within the above range is beneficial to improving the compaction density, powder conductivity and cycle life of the high-nickel cathode material as a cathode sheet.

[0134] This application provides a method for preparing a high-nickel cathode material, including the following steps:

[0135] Step S100: The metal composite hydroxide precursor, lithium-containing compound and dopant are mixed and subjected to a heat treatment to obtain the matrix material; the dopant includes M2 element and M3 element, the compound corresponding to M2 element is at least one of oxide, hydroxide and lithium metal oxide containing only M2, and the oxidation state of M2 in the compound is greater than or equal to +4, the compound corresponding to M3 element is at least one of oxide and hydroxide containing only M3, and the oxidation state of M3 in the compound is +2;

[0136] Step S200: Coating the substrate material obtained in step S100 to obtain a high-nickel cathode material.

[0137] In the above technical solution, among the dopants containing M2 and M3 elements, M2 has poor elemental migration ability, while M3 has strong ion migration ability. This application involves heat-treating the dopants containing M2 and M3 elements with a metal composite hydroxide precursor and a lithium-containing compound, resulting in M2 element doping onto the material surface. M2 element is mainly enriched at the grain boundaries, while M3 element is doped inside the crystal structure. Since M2 element with a valence greater than or equal to +4 exists on the material surface, valence balance is achieved, resulting in Ni on the material surface... 3+ The quantity is reduced, while the surface Ni 2+ The increased quantity of M3 elements helps prevent oxidation of the cathode material surface during lithium removal, thus maintaining the stability of the cathode material structure. The entry of M3 elements with a +2 valence into the material can suppress the H2→H3 phase transition during charging and discharging, improving structural stability. Simultaneously, M3 can replace a portion of the Li in the material's internal crystal lattice. + The position of the matrix material is adjusted, but the layered structure of the material is not affected. This application improves the stability of the high-nickel cathode material and further enhances its capacity performance by doping the matrix material with M2 and M3 elements.

[0138] The preparation method of this application is described in detail below with reference to the embodiments:

[0139] Before step S100, a metal complex hydroxide precursor is prepared by: using a co-precipitation method to mix and treat a metal salt solution with a complexing agent and a pH adjuster to obtain the metal complex hydroxide precursor.

[0140] In some embodiments, the mass ratio of the metal salt solution, complexing agent, and pH adjuster is 1:(0.01 to 0.10):(0.1 to 0.8). Specifically, the mass ratio of the metal salt solution, complexing agent, and pH adjuster can be 1:0.01:0.1, 1:0.05:0.3, 1:0.1:1.5, and 1:0.08:0.8, etc.

[0141] In some embodiments, the metal salt solution includes at least one of a nickel salt solution, a cobalt salt solution, a manganese salt solution, and an aluminum salt solution.

[0142] Specifically:

[0143] Nickel salt solutions include at least one of nickel sulfate, nickel chloride, nickel sulfamate, nickel bromide, nickel hydroxide, and nickel carbonyl.

[0144] Cobalt salt solutions include at least one of cobalt sulfate, cobalt chloride, and cobalt nitrate.

[0145] Manganese salt solutions include at least one of manganese sulfate, manganese nitrate, and manganese chloride.

[0146] Aluminum salt solutions include at least one of sodium aluminate, aluminum sulfate, aluminum chloride, and potassium aluminate.

[0147] In some embodiments, the complexing agent is selected to be capable of forming a complex with nickel, cobalt, manganese or aluminum ions in an aqueous solution. Specifically, the complexing agent includes at least one of ammonium ion donor, hydrazine, ethylenediaminetetraacetic acid, hypozoxytriacetic acid, uracil diacetic acid and glycine. The ammonium ion donor includes at least one of ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate and ammonium fluoride.

[0148] In some embodiments, the mixing temperature is between 10°C and 80°C. Specifically, the mixing temperature is 10°C, 20°C, 30°C, 40°C, 50°C, 60°C, 70°C, and 80°C, etc., and other values ​​within the above range are also possible and are not limited here. Preferably, the mixing temperature is between 20°C and 70°C. Controlling the temperature of the co-precipitation reaction within the above range is beneficial to the growth of precursor grains.

[0149] In some implementations, the pH adjuster includes alkali metal hydroxides.

[0150] In some embodiments, the alkali metal oxide includes at least one of sodium hydroxide and potassium hydroxide.

[0151] In some embodiments, the pH of the mixed treatment is 9 to 13. Specifically, the pH of the mixed treatment is 9, 10, 11, 12, and 13, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the pH of the mixed treatment is 11 to 13.

[0152] In some embodiments, the mixing process takes place for 10 hours to 200 hours. The specific mixing time can be 10 hours, 20 hours, 30 hours, 40 hours, 50 hours, 60 hours, 70 hours, 80 hours, 90 hours, 100 hours, 110 hours, 120 hours, 130 hours, 140 hours, 150 hours, 160 hours, 180 hours, 180 hours, 190 hours, and 200 hours, or other values ​​within the above range. No limitation is made here.

[0153] In some embodiments, the mixing process is carried out under stirring conditions, with a stirring rate of 800 rpm to 1200 rpm. The stirring rate can be 800 rpm, 900 rpm, 1000 rpm, 1100 rpm, and 1200 rpm, or other values ​​within the above range, which are not limited here.

[0154] In some embodiments, the mixing process is carried out in a reaction vessel, which is at least one of a continuous type that allows the formed metal complex hydroxide to overflow, or an intermittent type that does not discharge to the outside of the system until the reaction is completed.

[0155] In some embodiments, the metal composite hydroxide precursor prepared by the mixing process is a slurry-like suspension, which is then subjected to solid-liquid separation, washing, and drying to obtain the metal composite hydroxide precursor.

[0156] In some embodiments, the solid-liquid separation method includes either centrifugation or filtration, and the purpose of the solid-liquid separation is to separate the metal complex hydroxide from the solvent.

[0157] In some implementations, the washing process involves multiple washes with deionized water to remove impurities.

[0158] In some embodiments, the drying temperature is 100℃ to 130℃. The specific drying temperature can be 100℃, 110℃, 120℃ and 130℃, etc., or other values ​​within the above range, which are not limited here.

[0159] In some embodiments, the drying time is 12h to 24h. The specific drying time can be 12h, 13h, 14h, 15h, 16h, 17h, 18h, 19h, 20h, 21h, 22h, 23h and 24h, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0160] In some embodiments, the average particle size of the metal composite hydroxide precursor is 3 μm to 10 μm, and the median particle size of the metal composite hydroxide precursor can be 3 μm, 4 μm, 5 μm, 6 μm, 7 μm, 8 μm, 9 μm and 10 μm, etc., or other values ​​within the above range, which are not limited here.

[0161] Step S100: The metal composite hydroxide precursor, lithium-containing compound and dopant are mixed and subjected to a heat treatment to obtain the matrix material. The dopant includes a compound containing M2 and M3 elements. The compound corresponding to the M2 element is at least one of oxides, hydroxides and lithium metal oxides containing only M2, and the oxidation state of the M2 element in the compound is greater than or equal to +4. The compound corresponding to the M3 element is at least one of oxides and hydroxides containing only M3, and the oxidation state of the M3 element in the compound is +2.

[0162] In the above steps, the dopant is added and subjected to a heat treatment, so that the M2 element with a valence greater than or equal to +4 is mainly doped on the surface of the material, and the M3 element with a valence of +2 mainly enters the interior of the material. It can be understood that after a heat treatment, the M3 element can directly enter the interior of the crystal and replace some of the Li sites, the M2 element is mainly enriched at the grain boundaries of the material, and a small portion of the M2 element enters the interior of the crystal under the induction of the M3 element, replacing a small amount of element sites inside the crystal.

[0163] In some embodiments, the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant is 1:(0.46 to 0.48):(0.001 to 0.003). Specifically, the mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant can be 1:0.46:0.002, 1:0.47:0.003, 1:0.48:0.001, 1:0.047:0.002, and 1:0.048:0.01, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0164] In some embodiments, the atomic ratio of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound is 1.0 < Li / Me < 1.2. Specifically, Li / Me can be 1.01, 1.05, 1.1, 1.15, and 1.19, etc., where Me represents the sum of the atomic numbers of all metals in the metal composite hydroxide precursor. Controlling the atomic ratio of metal Me in the metal composite hydroxide precursor to Li in the lithium-containing compound within the above range is beneficial to the formation of matrix material grains and the improvement of material electrochemical performance.

[0165] In some embodiments, the lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate, and lithium acetate.

[0166] In some embodiments, both M2 and M3 include at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg, and Ba, and M2 and M3 are not the same.

[0167] In some embodiments, the dopant includes at least one selected from lithium zirconate, lithium titanate, niobium oxide, lithium tungstate, barium oxide, and magnesium hydroxide.

[0168] In some implementations, the molar ratio of element M2 to element M3 is... Greater than or equal to 2:1, Specifically, the ratios can be 2:1, 3:1, 4:1, 5:1, and 6:1, etc. Within these limits, high-valence elements (M2 elements with a valence greater than or equal to +4) can be effectively doped onto the surface layer of the material, while low-valence elements (M3 elements with a valence of +2) only need to be added in small amounts to penetrate into the material. Adding too many low-valence elements will inhibit the electrochemical performance of the material. Preferably, the molar ratio of M2 elements to M3 elements in the dopant is...

[0169] In some embodiments, the average particle size of the dopant is 10 nm to 50 nm. Specifically, the average particle size of the dopant can be 10 nm, 20 nm, 30 nm, 40 nm and 50 nm, etc., or other values ​​within the above range, which are not limited here.

[0170] In some embodiments, the temperature of the primary heat treatment is 680℃ to 900℃. Specifically, the primary heat treatment temperature is 680℃, 700℃, 720℃, 750℃, 780℃, 800℃, 820℃, 850℃, and 900℃, etc., and other values ​​within the above range are also possible and are not limited here. Preferably, the primary heat treatment temperature is 780℃ to 870℃. Controlling the primary heat treatment temperature within the above range is beneficial to the grain growth of the high-nickel cathode material.

[0171] In some embodiments, the heat treatment time is 5 hours to 20 hours. Specifically, the heat treatment time is 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 18 hours, 19 hours, and 20 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the heat treatment time is 8 hours to 15 hours.

[0172] In some embodiments, the heating rate of a single heat treatment is 50℃ / h to 550℃ / h. Specifically, the heating rate of a single heat treatment is 50℃ / h, 100℃ / h, 140℃ / h, 200℃ / h, 250℃ / h, 300℃ / h, 380℃ / h, 400℃ / h, 450℃ / h, 500℃ / h, and 550℃ / h, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the heating rate of a single heat treatment is 100℃ / h to 400℃ / h, and more preferably, the heating rate of a single heat treatment is 140℃ / h to 380℃ / h.

[0173] In some embodiments, the oxygen content of the matrix material is greater than or equal to 85%. Specifically, the oxygen content in the matrix material can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, 97%, etc., or other values ​​within the above range, which are not limited here. Preferably, the oxygen content of the matrix material is greater than or equal to 95%.

[0174] In some implementations, the equipment for primary heat treatment includes a stationary box furnace or a roller kiln-type continuous furnace.

[0175] Step S200: Coating the substrate material obtained in step S100 to obtain a high-nickel cathode material.

[0176] Step 201: Mix the matrix material with the first coating agent and then perform a second heat treatment to obtain the first coating product.

[0177] In some embodiments, the mass ratio of the matrix material to the first coating agent is 1000:(0.5 to 3). Specifically, the mass ratio of the matrix material to the first coating agent can be 1000:0.5, 1000:1, 1000:1.5, 1000:2, 1000:2.5, and 1000:3, etc. Of course, other values ​​within the above range are also possible and are not limited here.

[0178] In some embodiments, the first coating agent includes a metallic or non-metallic element with a valence greater than or equal to +3. This application incorporates a metallic or non-metallic element with a valence greater than or equal to +3 to balance the valence of the Ni on the surface of the high-nickel cathode material. 2+ By keeping the quantity constant or increasing it further, the stability of the material structure is improved, the formation of alkaline impurities from contact between the material and moisture in the air is prevented, and the gas production of the material is reduced.

[0179] In some embodiments, the first coating agent may be at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide, and titanium oxide.

[0180] In some embodiments, the temperature of the secondary heat treatment is 600℃ to 800℃. Specifically, the temperature of the secondary heat treatment is 600℃, 650℃, 680℃, 700℃, 720℃, 750℃, 780℃, and 800℃, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature of the secondary heat treatment is 650℃ to 750℃.

[0181] In some embodiments, the secondary heat treatment time is 1 hour to 20 hours. Specifically, the secondary heat treatment time is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 18 hours, 18 hours, 19 hours, and 20 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the secondary heat treatment time is 3 hours to 10 hours.

[0182] In some embodiments, the heating rate of the secondary heat treatment is 50℃ / h to 550℃ / h. Specifically, the heating rate of the secondary heat treatment is 50℃ / h, 100℃ / h, 140℃ / h, 200℃ / h, 250℃ / h, 300℃ / h, 380℃ / h, 400℃ / h, 450℃ / h, 500℃ / h, and 550℃ / h, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the heating rate of the secondary heat treatment is 100℃ / h to 400℃ / h, and more preferably, the heating rate of the secondary heat treatment is 140℃ / h to 380℃ / h.

[0183] In some embodiments, the oxygen content of the product obtained from a single coating step is greater than or equal to 85%. Specifically, the oxygen content of the product obtained from a single coating step can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, and 97%, etc., and of course, other values ​​within the above range are also possible, which are not limited here. Preferably, the oxygen content of the product obtained from a single coating step is greater than or equal to 95%.

[0184] In some embodiments, the equipment for secondary heat treatment includes stationary box furnaces or roller kiln continuous furnaces.

[0185] In some embodiments, the matrix material is mixed with the first coating agent and then subjected to a second heat treatment, followed by washing under constant temperature conditions. After washing, it is dried under vacuum conditions to obtain the first coating.

[0186] In some embodiments, the temperature of the constant temperature condition is 10℃ to 25℃. Specifically, the temperature of the constant temperature condition can be 10℃, 11℃, 12℃, 13℃, 14℃, 15℃, 16℃, 17℃, 18℃, 19℃, 20℃, 21℃, 22℃, 23℃, 24℃, and 25℃, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0187] In some embodiments, the drying temperature is 100℃ to 200℃. The specific drying temperature can be 100℃, 110℃, 120℃, 130℃, 140℃, 150℃, 160℃, 170℃, 180℃, 190℃ and 200℃, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0188] Step S202: The material obtained from the first coating is mixed with the second coating agent and then subjected to three heat treatments to obtain a high-nickel cathode material.

[0189] In some embodiments, the second coating agent is a boron-containing compound, including B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O. 13 At least one of the following, by adding a boron-containing compound to the coating obtained in one step, the boron-containing compound can not only react chemically with alkaline impurities on the material surface, but also cover the material surface to form a stable coating layer, thereby reducing alkaline impurities on the material surface and protecting the material surface, reducing the decomposition of Li2CO3 in the alkaline impurities on the material surface to produce gas, and reducing the side reaction between the alkaline impurities on the material surface and the electrolyte to produce gas.

[0190] In some embodiments, the mass ratio of the primary coating agent to the second coating agent is 1:(1 to 5). Specifically, the mass ratio of the primary coating agent to the second coating agent can be 1:1, 1:2, 1:3, 1:4, and 1:5, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0191] In some embodiments, the temperature for the three heat treatments is between 200°C and 400°C. Specifically, the temperatures for the three heat treatments are 200°C, 250°C, 280°C, 300°C, 320°C, 360°C, 380°C, and 400°C, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the temperature for the three heat treatments is between 250°C and 360°C.

[0192] In some embodiments, the duration of the three heat treatments is 1 hour to 20 hours. Specifically, the duration of the three heat treatments is 1 hour, 2 hours, 3 hours, 4 hours, 5 hours, 6 hours, 7 hours, 8 hours, 9 hours, 10 hours, 11 hours, 12 hours, 13 hours, 14 hours, 15 hours, 16 hours, 18 hours, 18 hours, 19 hours, and 20 hours, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the duration of the three heat treatments is 5 hours to 10 hours.

[0193] In some embodiments, the heating rate of the three heat treatments is 50℃ / h to 550℃ / h. Specifically, the heating rate of the three heat treatments is 50℃ / h, 100℃ / h, 140℃ / h, 200℃ / h, 250℃ / h, 300℃ / h, 380℃ / h, 400℃ / h, 450℃ / h, 500℃ / h, and 550℃ / h, etc. Of course, other values ​​within the above range are also possible and are not limited here. Preferably, the heating rate of the three heat treatments is 100℃ / h to 400℃ / h, and more preferably, the heating rate of the three heat treatments is 140℃ / h to 380℃ / h.

[0194] In some embodiments, the oxygen content of the high-nickel cathode material is greater than or equal to 85%. Specifically, the oxygen content of the high-nickel cathode material can be 85%, 86%, 87%, 88%, 89%, 90%, 91%, 92%, 93%, 94%, 95%, 96%, and 97%, etc., or other values ​​within the above range, which are not limited here. Preferably, the oxygen content of the high-nickel cathode material is greater than or equal to 95%.

[0195] In some implementations, the equipment for the three heat treatments includes a stationary box furnace or a roller kiln-type continuous furnace.

[0196] In some implementations, the three heat treatments also include sieving and demagnetization steps.

[0197] In some implementations, the purpose of sieving is 200 mesh to 400 mesh. The specific mesh number can be 200 mesh, 210 mesh, 250 mesh, 280 mesh, 300 mesh, 350 mesh, 380 mesh and 400 mesh, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0198] This application also provides a lithium-ion secondary battery, including a positive electrode, a negative electrode, a separator, a non-aqueous electrolyte, and a casing. The positive electrode includes a current collector and a positive electrode material coated on the current collector, such as the high-nickel positive electrode material described above or a positive electrode material prepared by the same method as described above.

[0199] In some embodiments, a positive electrode slurry containing a high-nickel material (the high-nickel positive electrode material of the present invention), a conductive agent, a binder, and NMP is prepared, and the positive electrode slurry is loaded onto the positive electrode current collector, thereby enabling the manufacture of a positive electrode sheet for a secondary battery.

[0200] In some embodiments, the conductive agent can be a carbon material, such as carbon black, acetylene black, Ketjen black, graphite, carbon nanotubes (CNTs), and vapor-deposited carbon (VGCF). These carbon materials can be used alone or in combination of two or more.

[0201] In some embodiments, a thermoplastic resin can be used as the binder. Examples of thermoplastic resins that can be used as the binder for the positive electrode of a lithium-ion secondary battery include polyvinylidene fluoride (hereinafter, sometimes referred to as PVDF), polytetrafluoroethylene (hereinafter, sometimes referred to as PTFE), tetrafluoroethylene / hexafluoropropylene / vinylidene fluoride copolymers, hexafluoropropylene / vinylidene fluoride copolymers, tetrafluoroethylene / perfluorovinyl ether polymers, and other fluoropolymers; and polyolefin resins such as polyethylene and polypropylene. The above-mentioned thermoplastic resins can be used alone, or two or more of the above-mentioned thermoplastic resins can be used simultaneously.

[0202] In some embodiments, the positive current collector can be a strip-shaped component formed from metallic materials such as Al, Ni, or stainless steel. From the viewpoint of ease of processing and low cost, Al is preferred as the forming material, and it is processed into a thin film.

[0203] In some embodiments, the negative electrode only needs to be able to insert and extract lithium ions at a lower potential than the positive electrode. It can be an electrode formed by loading a slurry containing negative electrode active material onto a negative electrode current collector, or an electrode composed solely of negative electrode active material.

[0204] In some embodiments, the negative electrode active material is a material capable of lithium-ion insertion and extraction using carbon materials, chalcogenide compounds (oxides, sulfides, etc.), nitrides, metals, or alloys at a lower potential than that of the positive electrode. Among the aforementioned negative electrode active materials, carbon materials with graphite as the main component, such as natural graphite or artificial graphite, are preferred because the negative electrode potential hardly changes from an uncharged state to a fully charged state during charging (good potential flatness), the average discharge potential is low, and the capacity retention rate during repeated charge and discharge (good cycle characteristics). The shape of the carbon material is not particularly limited; for example, it can be in the form of flakes such as natural graphite, spheres such as medium-carbon microspheres, fibers such as graphitized carbon fibers, or aggregates of micropowders.

[0205] In some embodiments, the binder can be a thermoplastic resin, such as PVDF, thermoplastic polyimide, carboxymethyl cellulose, polyethylene, and polypropylene, etc. The above-mentioned binders can be used alone or two or more at the same time. As the negative electrode current collector of a lithium secondary battery, a strip-shaped component formed of metal materials such as Cu, Ni, and stainless steel can be cited as an example. From the viewpoint of being difficult to alloy with lithium and easy to process, Cu is preferred as the forming material and processed into a thin film.

[0206] In some embodiments, the diaphragm can be made of materials such as polyethylene, polypropylene, or other polyolefin resins, fluoropolymers, or nitrogen-containing aromatic polymers, and can be in the form of a porous membrane, nonwoven fabric, or woven fabric. Alternatively, the diaphragm can be formed using one or more of the aforementioned materials, or it can be formed by stacking the aforementioned materials.

[0207] In some embodiments, the electrolyte contains an electrolyte and an organic solvent. Examples of electrolytes included in the electrolyte include LiClO4, LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, LiN(SO2C2F5)2, LiN(SO2CF3)(COCF3), Li(C4F9SO3), LiC(SO2CF3)3, and Li2B. 10 Cl 10 Lithium salts such as LiBOB (lithium bis(oxalato)borate, LiFSI (lithium bis(fluorosulfonyl)imide), lower aliphatic carboxylic acid lithium salts, and LiAlCl4 can be used. These electrolytes can be used alone or in combination with two or more of them. Preferably, the electrolyte contains at least one electrolyte selected from the group consisting of fluorine-containing compounds such as LiPF6, LiAsF6, LiSbF6, LiBF4, LiCF3SO3, LiN(SO2CF3)2, and LiC(SO2CF3)3. In addition, organic solvents contained in the electrolyte may include, for example, carbonates such as propylene carbonate, ethylene carbonate, dimethyl carbonate, diethyl carbonate, methyl ethyl carbonate, 4-trifluoromethyl-1,3-dioxolane-2-one, and 1,2-di(methoxycarbonyloxy)ethane; 1,2-dimethoxyethane, 1,3-dimethoxypropane, pentafluoropropyl methyl ether, 2,2,3,3-tetrafluoropropyl difluoromethyl ether, tetrahydrofuran, and 2-methyl... Ethers such as tetrahydrofuran; esters such as methyl formate, methyl acetate, and γ-butyrolactone; nitrile compounds such as acetonitrile and butyronitrile; amides such as N,N-dimethylformamide and N,N-dimethylacetamide; carbamates such as 3-methyl-2-oxazolinone; sulfur-containing compounds such as sulfolane, dimethyl sulfoxide, and 1,3-propanesulfonyl lactone; or products in which fluorine groups have been introduced into the above organic solvents (products in which one or more hydrogen atoms in the organic solvent are replaced by fluorine atoms). The above organic solvents can be used alone or two or more of the above organic solvents can be used simultaneously.

[0208] The embodiments of the present invention are described, but the present invention is not limited to these examples as long as it does not depart from its spirit.

[0209] Example 1

[0210] (1) Ni was prepared by co-precipitation method 0.885 Co 0.09 Mn 0.025 (OH)2 precursor, Ni 0.885 Co 0.09 Mn 0.025 (OH)₂ precursor, LiOH * H2O and dopants nano-TiO2, ZrO2, and MgO are mixed evenly, in which The matrix material was then prepared by a first heat treatment at 830℃, wherein Li / Me = 1.05 and M = (Ni, Co and Mn);

[0211] (2) The matrix material prepared in step (1) and nano Al2O3 are mixed evenly, and then subjected to a second heat treatment at 700°C. The material obtained from the second heat treatment is put into distilled water and washed with water while maintaining the temperature at 25°C. After the dehydration process, the mixture is dried in a vacuum atmosphere at 150°C to obtain the second coating.

[0212] (3) The second coating material and H3BO3 are mixed evenly, and a third heat treatment is performed at 300℃. After sieving and demagnetization, a high-nickel cathode material is obtained, such as... Figure 1 The image shown is a SEM image of the high-nickel cathode material in this embodiment.

[0213] Example 2

[0214] Unlike Example 1, in step (1)

[0215] Example 3

[0216] Unlike Example 1, in step (1)

[0217] Example 4

[0218] Unlike Example 1, in step (1)

[0219] Example 5

[0220] Unlike Example 1, in step (1)

[0221] Example 6

[0222] Unlike Example 1, in step (1)

[0223] Example 7

[0224] Unlike Example 1, in step (1)

[0225] Example 8

[0226] Unlike Example 1, in step (1), the dopant was replaced with WO3, ZrO2, and MgO, and

[0227] Example 9

[0228] Unlike Example 1, in step (1), the dopant was replaced with WO3, ZrO2, and Y2O3, and

[0229] Example 10

[0230] Unlike Example 1, in step (1), the dopant was replaced with WO3, ZrO2, and Y2O3, and

[0231] Example 11

[0232] Unlike Example 1, in step (1), the dopant was replaced with MoO3, ZrO2, and Al2O3, and

[0233] Example 12

[0234] Unlike Example 1, in step (1), the dopant was replaced with ZrO2 and MgO, and

[0235] Example 13

[0236] Unlike Example 1, the heat treatment temperature in step (1) is 650°C.

[0237] Example 14

[0238] Unlike Example 1, the heat treatment temperature in step (1) is 680°C.

[0239] Example 15

[0240] Unlike Example 1, the heat treatment temperature in step (1) is 700°C.

[0241] Example 16

[0242] Unlike Example 1, the heat treatment temperature in step (1) is 850°C.

[0243] Example 17

[0244] Unlike Example 1, the heat treatment temperature in step (1) is 900°C.

[0245] Example 18

[0246] Unlike Example 1, the heat treatment temperature in step (1) is 910°C.

[0247] Example 19

[0248] Unlike Example 1, in step (2), Al2O3 is replaced with lithium aluminate.

[0249] Example 20

[0250] Unlike Example 1, in step (2), Al2O3 is replaced with titanium oxide.

[0251] Example 21

[0252] Unlike Example 1, in step (3), H3BO3 is replaced with Li3BO3.

[0253] Example 22

[0254] Unlike Example 1, in step (3), H3BO3 is replaced with B2O3.

[0255] Example 23

[0256] Unlike Example 1, step (3) is not performed.

[0257] Example 24

[0258] Unlike Example 1, step (2) is omitted.

[0259] Comparative Example 1

[0260] Unlike Example 1, the dopant in step (1) is replaced with MgO and Al2O3.

[0261] Comparative Example 2

[0262] Unlike Example 1, the dopant in step (1) is replaced with SrO and MgO.

[0263] Comparative Example 3

[0264] Unlike Example 1, the dopant in step (1) is replaced with Al2O3 and Y2O3.

[0265] Comparative Example 4

[0266] Unlike Example 1, the dopant in step (1) is replaced with Y2O3 and MgO.

[0267] Comparative Example 5

[0268] Unlike Example 1, the dopant in step (1) is replaced with La2O3 and Al2O3.

[0269] Performance testing:

[0270] (1) Alkaline impurity test of high-nickel materials:

[0271] The content of alkaline impurities on the surface of high-nickel materials is a characteristic of the material surface, which can be quantitatively measured by analyzing the reaction products between the surface and water. When high-nickel material powder is immersed in water, a surface reaction occurs. During the reaction, the pH of the water increases (as the alkaline impurities dissolve), and the alkaline content is quantified by pH titration. The titration result is the alkaline impurity content. The alkaline impurity content can be measured as follows: 5.0 g of high-nickel material powder is immersed in 100 ml of deionized water and stirred for 10 minutes in a sealed glass flask. After stirring to dissolve the alkali, the suspension of powder in water is filtered to obtain a clear solution. Then, 90 ml of the clear solution is titrated with 0.1 M HCl at a rate of 0.5 ml / min while stirring, by recording the pH curve until the pH reaches 3. A reference voltage curve is obtained by titrating a suitable mixture of LiOH and Li₂CO₃ dissolved in deionized water at low concentrations. In almost all cases, two distinct plateaus are observed. The upper plateau with an endpoint y₁ (in ml) between pH 8 and 9 is the equilibrium OH group. - / H2O, followed by balancing CO3. 2- / HCO3 - The lower plateau with an endpoint y2 (in ml) between pH 4 and 6 is HCO3. - / H2CO3. The inflection point y1 between the first and second plateaus and the inflection point y2 after the second plateau are obtained by the corresponding minimum values ​​of the derivative dpH / dVol of the pH curve. The second inflection point is generally close to pH 4.7. The results are then expressed as weight percentages of LiOH and Li2CO3 as shown in equations (3) and (4):

[0272]

[0273]

[0274] (2) XPS testing of high-nickel cathode materials:

[0275] X-ray photoelectron spectroscopy (XPS) can analyze materials from the surface down to a depth range of approximately 5 nm to 10 nm (typically around 5 nm), allowing for quantitative analysis of elemental concentrations in about half of the surface layer. Furthermore, narrow-scan analysis allows for analysis of elemental bonding states. X-ray photoelectron spectroscopy (XPS) can be performed using, for example, the ULVAC-PHI X-ray photoelectron spectroscopy analyzer (Quantera II). X-ray source: Al monochromatic 100 μm, 25 W, 15 kV; no surface etching; photoelectron extraction angle: 45°; bonding energy correction: the C1s peak was set to 284.6 eV; XPS was performed on the high-nickel material of this invention. Based on the obtained XPS spectrum, the Ni2P peak appearing at a binding energy of 850 eV to 870 eV was identified. 3 / 2 Peak separation and curve fitting were performed to determine Ni. 2+ Peak area and Ni 3+ Peak area was determined by performing peak separation and curve fitting on the O1S peak appearing in the O-bonded region with binding energies of 526 eV to 540 eV, and calculating the O1S peak area. 晶格氧 Peak area and O1S 杂质氧 Peak area.

[0276] (3) Battery capacity calibration

[0277] First, the battery capacity was calibrated by charging it to 4.25V at 1 / 3C current at room temperature (25℃), letting it stand for 30 minutes, then discharging it to 2.5V at 1 / 3C current, letting it stand for 30 minutes, repeating the cycle twice, and setting the second discharge capacity as C0. This was then used as a benchmark for subsequent DCIR testing.

[0278] (4) DCIR test (protection voltage 1.0V~4.4V, test temperature: 25℃)

[0279] a. Charge at 0.2C0 constant current to 10%C0 at 25℃, let stand for 2 hours [termination voltage recorded as V1], test DCIR (discharge at 1.5C0 for 30 seconds [termination voltage recorded as V2], let stand for 30 minutes [termination voltage recorded as V3]; charge at 1.5C0 for 30 seconds [termination voltage recorded as V4], let stand for 5 minutes), discharge at 0.33C0 to 2.5V / cell, let stand for 30 minutes;

[0280] b. Charge at 25℃ with a constant current of 0.2C0 to 20%C0, let stand for 2 hours [the termination voltage is recorded as V1], test DCIR (discharge at 1.5C0 for 30 seconds [the termination voltage is recorded as V2], let stand for 30 minutes [the termination voltage is recorded as V3]; charge at 1.5C0 for 30 seconds [the termination voltage is recorded as V4], let stand for 5 minutes), discharge at 0.33C0 to 2.5V / cell, let stand for 30 minutes;

[0281] c. Charge at 0.2C0 constant current to 50%C0 at 25℃, let stand for 2 hours [termination voltage recorded as V1], test DCIR (discharge at 1.5C0 for 30 seconds [termination voltage recorded as V2], let stand for 30 minutes [termination voltage recorded as V3]; charge at 1.5C0 for 30 seconds [termination voltage recorded as V4], let stand for 5 minutes), discharge at 0.33C0 to 2.5V / cell, let stand for 30 minutes;

[0282] d. Charge at 0.2C0 constant current to 80%C0 at 25℃, let stand for 2 hours [termination voltage recorded as V1], test DCIR (discharge at 1.5C0 for 30 seconds [termination voltage recorded as V2], let stand for 30 minutes [termination voltage recorded as V3]; charge at 1.5C0 for 30 seconds [termination voltage recorded as V4], let stand for 5 minutes), discharge at 0.33C0 to 2.5V / cell, let stand for 30 minutes;

[0283] Calculate the DCIR values ​​for different SOCs using the following formulas (5) and (6):

[0284] DCIR release = (V1-V2) / 1.5C0*1000 (unit: mΩ) (5)

[0285] DCIR charge = (V1-V2) / 1.5C0*1000 (unit: mΩ) (6)

[0286] The DCIR value was measured after every 100 cycles using the same method as the DCIR measurement before the cycle described above.

[0287] (5) Thickness expansion test of full cells made of high-nickel materials:

[0288] At room temperature, the battery was charged at a constant current of 0.5C to 4.25V, and then charged at a constant voltage to a current of 0.05C. At this point, the battery was in a fully charged state. The initial thickness of the fully charged battery before storage was measured, and then the battery was placed in a 60℃ oven. The thickness of the battery was measured every 20 days, and the battery thickness expansion rate was calculated according to the following formula (7):

[0289] Thickness expansion rate = (thickness after storage - thickness before storage) / (thickness before storage) (7)

[0290] (6) Cross-section testing of high-nickel materials after 300 cycles of high-temperature cycling:

[0291] The high-nickel material after 500 cycles of high-temperature cycling was cut using a Hitachi E-3500 ion mill, and the morphology of its cross-section was observed using a Hitachi S4800 cold field emission scanning electron microscope.

[0292] I. XPS and Fitting Tests for High-Nickel Cathode Materials

[0293] The high-nickel cathode material XPS prepared in each embodiment and comparative example was tested using Ni2P. 3 / 2 The results of peak separation and fitted area ratio of Ni2P in Examples 1, 8, 1, and 2 are shown in Table 1 below. 3 / 2 The peaks and fitting are as follows: Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the peak division and fitting of O1S in Examples 1, 8, Comparative Example 1, and Comparative Example 2 are as follows: Figure 7 , Figure 8 , Figure 9 and Figure 10 As shown.

[0294] Table 1. Testing of XPS in high-nickel cathode materials prepared in each embodiment and comparative example (Ni2P) 3 / 2 Results of O1S peak division and fitted area ratio

[0295]

[0296]

[0297] As shown in Examples 1-24 and Comparative Examples 1-5, the high-nickel cathode material prepared in this application, after measurement, satisfies S1 / (S1+S2)>0.5 and 0.9<A / B<1.5, indicating that the Ni on the surface of the high-nickel material matrix is ​​high. 3+ Small quantity, Ni 2+ The larger quantity of nickel on the cathode material surface prevents oxidation during delithiation, thus maintaining the stability of the cathode material structure and avoiding the loss of cathode active material and electrolyte. This further increases the capacity of the cathode material, resulting in a significant improvement in the high-temperature cycle performance of the high-nickel cathode material. Furthermore, due to the Ni content on the material surface... 3+ The quantity is small, and the surface Ni 2+ The large quantity of material reduces the occurrence of internal cracks during charging and discharging, stabilizes the internal structure of the material, and significantly suppresses the increase in DC internal resistance of the battery when the cathode material of this application is used in the battery for long-term cycling.

[0298] Ni2P in Examples 1, 8, Comparative Example 1, and Comparative Example 2 3 / 2 The peaks and fitting are as follows: Figure 3 , Figure 4 , Figure 5 and Figure 6 As shown, the peak division and fitting of O1S in Examples 1, 8, Comparative Example 1, and Comparative Example 2 are as follows: Figure 7 , Figure 8 , Figure 9and Figure 10 As shown. The S1 / (S1+S2) area ratio of the high-nickel cathode material prepared in this application and the material prepared in the comparative example differed significantly. In the examples of this application, the S1 / (S1+S2) area ratio of the sample was >1, indicating that the Ni on the material surface was significantly higher. 2+ The quantity is significantly higher than Ni 3+ The quantity is large, but the area ratio of S1 / (S1+S2) in the comparative example is <1; O1S 晶格氧 / O1S 杂质氧 The area ratios are all >0.5, which indicates that the alkaline impurities on the surface of the materials in the embodiments are relatively low.

[0299] The surface alkaline impurity test results show that the total surface alkaline impurities of the high-nickel cathode material in this application embodiment are lower, while the total surface alkaline impurities of LiOH and Li2CO3 in the comparative sample are higher.

[0300] Table 2 shows a performance comparison of the high-nickel cathode materials in Examples 1-24 and Comparative Examples 1-5 of this application.

[0301] Table 2. Performance tests of high-nickel cathode materials from Examples 1-24 and Comparative Examples 1-5

[0302]

[0303] Based on the high-nickel cathode materials prepared in Examples 1-24 and Comparative Examples 1-5 of this application, the capacity retention rate of full cells at 45°C for 300 cycles at 1C / 1C under different voltages was tested. High-temperature performance tests showed that the high-temperature cycling performance of the cathode materials in the examples and comparative examples changed significantly. Under conditions of 2.5V to 4.2V, the capacity retention rate of the cathode materials in some examples of this application was around 95%, while the capacity retention rate of the cathode materials in the comparative examples was below 93%. Tests under conditions of 2.5V to 4.25V showed that due to phase transitions, the high-temperature cycling performance of the samples in both examples and comparative examples decreased. However, some examples still showed significantly better performance than the comparative examples.

[0304] The high-nickel cathode materials prepared according to the embodiments and comparative examples of this application were tested for DC internal resistance growth in full cells at 2.5V–4.2V and 45°C at 1C / 1C per 100 cycles. A comparative analysis of the capacity differential curves of Examples 1, 8, Comparative Example 1, and Comparative Example 2 is provided below. Figure 11 , Figure 12 , Figure 13 , Figure 14 As can be seen from Table 1 and the accompanying drawings, the DC internal resistance growth of the cathode materials in the embodiments and comparative examples of this application has changed significantly, with the DC internal resistance growth of the embodiments being significantly lower than that of the comparative examples. Figure 11 , 12As can be seen from 13 and 14, Example 1 has the smallest irreversible phase transition and the smallest voltage difference ΔV after 300 cycles. This shows that the structure with simultaneous doping of high and low valence is more stable, and the structure on the surface and inside of the material is more stable.

[0305] Full cells were fabricated using high-nickel cathode materials prepared according to the embodiments and comparative examples of this application. Then, their gas production during storage at a high temperature of 60°C was tested. The cell thickness was measured every 20 days, and the thickness expansion rate was calculated. As shown in Table 1, the cell thickness growth of the embodiments and comparative examples changed significantly. However, the thickness expansion growth of the embodiments was significantly lower than that of the comparative examples.

[0306] As can be seen from Examples 12 to 18, when the primary synthesis temperature of the material is controlled at around 850°C, the cathode material has excellent electrochemical performance. If the primary heat treatment temperature is less than the range defined in this application (Example 12) or greater than the range defined in this application (Example 18), there will be serious drawbacks such as poor cycle performance and high expansion rate.

[0307] As can be seen from Example 23, the cathode material obtained by coating the substrate material only once has the disadvantage of poor cycle performance.

[0308] As can be seen from Example 24, the cathode material obtained by only coating the matrix material twice will have the disadvantages of poor cycle performance and high expansion rate.

[0309] Argon ion cross-sectional analysis was performed on the high-nickel materials of Examples 1 and 8 and Comparative Examples 1 and 2 after 300 cycles. The cross-sectional analysis results of Examples 1 and 8 and Comparative Examples 1 and 2 are as follows: Figure 15 , 16 , 17, 18 are shown by Figure 15 , 16 As can be seen from 17 and 18, no cracks occurred inside the materials of Examples 1 and 2, while cracks appeared inside the materials of Comparative Examples 1 and 2. This step shows that the simultaneous doping of high valence and low valence in this application is beneficial to the stability of the material structure.

[0310] The above description is merely a preferred embodiment of this application and is not intended to limit this application. Various modifications and variations can be made to this application by those skilled in the art. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of this application should be included within the protection scope of this application.

Claims

1. A high-nickel cathode material, characterized in that, The general chemical formula of the high-nickel cathode material is shown in formula (1): The x Nor 1-(a+b+c+d+e+f) Co a M1 b M2 c M3 d M4 e M5 f O2 (1) Wherein, 0.95≤x≤1.2, 0<a≤0.15, 0<b≤0.10, 0<c≤0.05, 0<d≤0.05, 0≤e≤0.05, 0≤f≤0.05, 0<a+b+c+d+e+f≤0.2, M1 is selected from Mn and / or Al; M2 is selected from at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, and Sn; M3 is selected from at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg, and Ba, and M2 and M3 are not the same; The high-nickel cathode material was analyzed by AlKα radiation using powder XPS, which showed that Ni2P, which can appear in the range of 850 eV to 870 eV, was incorporated. 3 / 2 After peak separation and fitting, Ni 2+ The peak area is set to S1, Ni 3+ The peak area is set to S2, and Ni 2+ The peak half-width is set to A, and Ni is... 3+ Let the half-peak width be B, and S1, S2, A, and B satisfy the following relationship: S1 / (S1+S2)>0.5 and 0.9<A / B<1.5 (2).

2. The cathode material according to claim 1, characterized in that, The cathode material comprises secondary particles and / or primary particles, wherein at least a portion of the surface of the primary particles is coated with a coating layer, and the secondary particles comprise a plurality of primary particles with coating layers, wherein the coating layer comprises at least one of the following features (1) to (4): (1) The coating layer includes a first coating layer and a second coating layer, wherein the first coating layer is formed on the surface of the primary particle and the second coating layer is formed on the surface of the first coating layer; (2) The coating layer includes a first coating layer and a second coating layer, wherein the first coating layer includes at least one of Al, Ti, P, Si, Nb, Y, W, Cr, Zr and La; (3) The coating layer includes a first coating layer and a second coating layer, wherein the second coating layer includes a boron-containing compound; (4) The coating layer includes a first coating layer and a second coating layer. The second coating layer includes a boron-containing compound, which includes B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7, and Li2B8O. 13 At least one of them.

3. The cathode material according to claim 1, characterized in that, The material includes at least one of the following features (1) to (10): (1) The high-nickel cathode material was subjected to powder XPS analysis using AlKα rays: when Ni2P, which can appear in the range of 850eV~870eV, was added... 3 / 2 After peak separation and fitting, Ni 2+ / Ni 3+ The area ratio is greater than 1; (2) The high-nickel cathode material was subjected to powder XPS analysis using AlKα rays: After peak separation and fitting of the O1S peaks that appear in the 526eV~540eV range, the O1S... 晶格氧 / O1S 杂质氧 The area ratio is greater than 1 / 2; (3) The mass content of LiOH in the high-nickel cathode material is less than 0.3 wt%; (4) The mass content of Li2CO3 in the high-nickel cathode material is less than 0.3 wt%; (5) The crystal structure of the high-nickel cathode material belongs to the hexagonal crystal structure or the monoclinic crystal structure; (6) The crystal particle morphology of the high-nickel cathode material includes at least one of approximately spherical, approximately cubic and approximately cuboid shapes; (7) The pH of the high-nickel cathode material is: 10.5 < pH < 11.7; (8) The powder conductivity of the high-nickel cathode material is greater than 0.02 S / cm; (9) The specific surface area of ​​the high-nickel cathode material is 0.3 m². 2 / g ~0.8m 2 / g; (10) The average particle size of the high-nickel cathode material is 2.5 μm to 4.5 μm.

4. A method for preparing a high-nickel cathode material, characterized in that, Includes the following steps: The matrix material is obtained by mixing a metal composite hydroxide precursor, a lithium-containing compound and a dopant and then performing a single heat treatment. The dopant includes elements M2 and M3. The compound corresponding to element M2 is at least one of oxides, hydroxides, and lithium metal oxides containing only M2, and the oxidation state of M2 in the compound is greater than or equal to +4. The compound corresponding to element M3 is at least one of oxides and hydroxides containing only M3, and the oxidation state of M3 in the compound is +2. Element M2 is selected from at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, and Sn. Element M3 is selected from at least one of Zr, Ti, Nb, Ce, Hf, W, Mo, Ta, Ge, Sn, Sr, Mg, and Ba, and M2 and M3 are not the same. The matrix material is coated to obtain a high-nickel cathode material.

5. The preparation method according to claim 4, characterized in that, The method includes at least one of the following features (1) to (9): (1) The mass ratio of the metal composite hydroxide precursor, the lithium-containing compound, and the dopant is 1:(0.46~0.48):(0.001~0.003). (2) The ratio of the total metal content Me in the metal composite hydroxide precursor to the atomic ratio of Li in the lithium-containing compound is 1.0 < Li / Me < 1.2; (3) The lithium-containing compound includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium acetate; (4) The molar ratio of M2 and M3 in the dopant n M2 : n M3 Greater than or equal to 2:1; (5) The average particle size of the dopant is 10 nm to 50 nm; (6) The temperature of the first heat treatment is 680℃~900℃; (7) The duration of the first heat treatment is 5h to 20h; (8) The heating rate of the first heat treatment is 50℃ / h ~ 550℃ / h; (9) The oxygen content of the matrix material is greater than or equal to 85%.

6. The preparation method according to claim 4, characterized in that, The method includes the step of mixing the matrix material with a first coating agent and then performing a secondary heat treatment to obtain a first-coated product, and the method includes at least one of the following features (1) to (10): (1) The mass ratio of the matrix material to the first coating agent is 1000:(0.5~3); (2) The first coating agent includes a metallic element or a non-metallic element with a valence greater than or equal to +3; (3) The first coating agent includes at least one of lithium aluminate, lithium titanate, lithium lanthanum titanate, yttrium oxide, aluminum oxide and titanium oxide; (4) The average particle size of the first coating agent is 10 nm to 50 nm; (5) The temperature of the secondary heat treatment is 600℃~800℃; (6) The duration of the secondary heat treatment is 1 hour to 20 hours; (7) The heating rate of the secondary heat treatment is 50℃ / h to 550℃ / h; (8) After the secondary heat treatment, the process further includes washing under constant temperature conditions and drying under vacuum conditions, wherein the temperature of the constant temperature conditions is 10℃~25℃. (9) After the secondary heat treatment, the process further includes washing under constant temperature conditions and drying under vacuum conditions, wherein the drying temperature is 100℃~200℃. (10) The oxygen content in the material obtained by the first coating is greater than or equal to 85%.

7. The preparation method according to claim 6, characterized in that, The method further includes a step of mixing the first coating product with a second coating agent and then subjecting it to three heat treatments, the method comprising at least one of the following features (1) to (6): (1) The second coating agent includes a boron-containing compound; (2) The second coating agent comprises a boron-containing compound, said boron-containing compound including B2O3, H3BO3, Li2O-B2O3, Li3BO3, Li2B4O7, Li2B2O7 and Li2B8O 13 At least one of them; (3) The mass ratio of the first coating product to the second coating agent is 1:(1~5); (4) The temperature of the three heat treatments is 200℃~600℃; (5) The duration of the three heat treatments is 1 hour to 20 hours; (6) The heating rate of the three heat treatments is 50℃ / h to 550℃ / h.

8. The preparation method according to claim 4, characterized in that, The metal complex hydroxide precursor is obtained by mixing a metal salt solution, a complexing agent, and a pH adjuster.

9. The preparation method according to claim 8, characterized in that, The method includes at least one of the following features (1) to (10): (1) The mass ratio of the metal salt solution, complexing agent and pH adjuster is 1:(0.01~0.10):(0.1~0.8). (2) The metal salt solution includes at least one of nickel salt solution, cobalt salt solution, manganese salt solution and aluminum salt solution; (3) The complexing agent includes at least one of ammonia, ammonium sulfate, ammonium chloride, ammonium carbonate, ammonium fluoride, hydrazine, ethylenediaminetetraacetic acid, hypozoxytriacetic acid, uracil diacetic acid, and glycine; (4) The pH adjuster includes at least one of sodium hydroxide and potassium hydroxide; (5) The pH of the mixed treatment is 9~13; (6) The temperature of the mixing process is 10℃~80℃; (7) The mixing treatment time is 10 h ~ 200 h; (8) The mixing process is carried out under stirring conditions, and the stirring rate is 800 rpm to 1200 rpm; (9) The mixing process further includes solid-liquid separation, washing and drying steps; (10) The average particle size of the metal composite hydroxide precursor is 3 μm to 10 μm.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the high-nickel cathode material according to any one of claims 1 to 3 or the high-nickel cathode material prepared by the method according to claims 4 to 9.

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