Cathode material precursor, cathode material and preparation method thereof, battery

Abstract

The application relates to a positive electrode material precursor, a positive electrode material and a preparation method thereof, a battery, and a chemical general formula of the positive electrode material precursor is Ni a Co b Mn c M1 d (OH)2, wherein a+b+c+d=1, 0 The positive electrode material precursor has a core-shell separation structure, can relieve oxygen release of the positive electrode material under high voltage, relieve phase structure change of the positive electrode material, and improve rate performance of the positive electrode material.

Description

Technical Field

[0001] This invention relates to the field of cathode material technology, and in particular to cathode material precursors, cathode materials and their preparation methods, and batteries. Background Technology

[0002] Lithium-rich manganese-based cathode materials possess advantages such as low cost, high capacity, and high energy density, making them highly promising cathode materials for lithium-ion batteries. However, the Li₂MnO₃ phase in lithium-rich manganese-based cathode materials exhibits poor conductivity, and during high-voltage charging, Li₂MnO₃ readily decomposes to produce oxygen. This irreversible process leads to the material structure easily transforming into a spinel phase and eventually into an inactive rock salt phase. This process is also accompanied by problems such as oxygen release and discharge voltage decay.

[0003] Therefore, how to stabilize the phase structure of cathode materials and improve their rate performance remains a technical problem that needs to be solved. Summary of the Invention

[0004] The purpose of this application is to provide a cathode material precursor, a cathode material, a method for preparing the same, and a battery. The cathode material has a core-shell separated structure, which can alleviate oxygen release under high voltage, mitigate phase structure changes in the cathode material, and improve the rate performance of the cathode material.

[0005] Firstly, this application relates to a cathode material precursor, wherein the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)₂, wherein a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2, and M1 is a metallic element; the cathode material precursor has a core-shell structure, comprising:

[0006] The kernel, wherein the radius of the kernel is r1; and

[0007] A shell is located on the outer surface of the core, and there is an interface between the shell and the core. The thickness of the shell is r2, where 1 / 6 < r2 / (r1+r2) < 5 / 6.

[0008] In some embodiments, the shell layer includes an inner shell layer and an outer shell layer, and there is an interface between the inner shell layer and the outer shell layer.

[0009] In some embodiments, the particle size D50 of the cathode material precursor is 2 μm to 25 μm.

[0010] In some embodiments, the particle size D90 of the cathode material precursor is <30 μm.

[0011] In some embodiments, the specific surface area of ​​the cathode material precursor is 5 m². 2 / g~30m 2 / g.

[0012] In some embodiments, M1 includes at least one of Al, Zr, Y, Ti, W, and Sb.

[0013] Secondly, this application provides a cathode material, the general chemical formula of which is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2 e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1, and M1 and M2 are metallic elements;

[0014] The positive electrode material includes a core and a shell located on the outer surface of the core. The radius of the core is r3, and the thickness of the shell is r4. A first void layer exists between the shell and the core. The thickness of the first void layer is d, where 1 / 6 < r4 / (r3+r4+d) < 5 / 6.

[0015] In some embodiments, the housing includes a first housing and a second housing, with a second void layer between the first housing and the second housing.

[0016] In some embodiments, the shell and at least a portion of the core body extend and connect within the first void layer.

[0017] In some implementations, 0 < d ≤ 0.5 μm.

[0018] In some embodiments, M1 includes at least one of Al, Zr, Y, Ti, W, and Sb.

[0019] In some embodiments, M2 includes at least one of Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd, and Ta.

[0020] In some embodiments, based on 100 wt% of the positive electrode material, the mass content of the metal elements M1 and / or M2 is 0.01 wt% to 10 wt%.

[0021] In some embodiments, the mass content of nickel in the core of the cathode material near the surface of the first void layer is greater than the mass content of manganese.

[0022] In some embodiments, the particle size D50 of the cathode material is 6 μm to 15 μm.

[0023] In some embodiments, the particle size D90 of the cathode material is less than 30 μm.

[0024] In some embodiments, the specific surface area of ​​the positive electrode material is 0.2 m². 2 / g~2.5m 2 / g.

[0025] In some embodiments, the tap density of the positive electrode material is >2.0 g / cm³. 3 .

[0026] In some embodiments, the compaction density of the cathode material is >2.0 g / cm³. 3 .

[0027] Thirdly, this application provides a method for preparing a cathode material, comprising the following preparation steps:

[0028] A mixed salt solution containing nickel and manganese salts was mixed with an alkaline solution to carry out a co-precipitation reaction, and then dried to obtain seed crystals.

[0029] Seed crystals are added to a mixed salt solution containing nickel and manganese salts for a secondary co-precipitation reaction to obtain a cathode material precursor with a core-shell structure.

[0030] A mixture containing a cathode material precursor and a lithium source is subjected to a single sintering process to obtain a cathode material with a core-shell separation structure.

[0031] In some embodiments, the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)2, where a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2, and M1 is a metallic element.

[0032] In some embodiments, the concentrations of nickel and manganese salts in the mixed salt solution are each independently selected from 1.0 mol / L to 4.0 mol / L.

[0033] In some embodiments, the mixed salt solution further includes a complexing agent with a concentration of 0.1 mol / L to 0.5 mol / L.

[0034] In some embodiments, the mixed salt solution further includes a salt of metal M1, wherein the concentration of the salt of metal M1 is selected from 1.0 mol / L to 4.0 mol / L.

[0035] In some embodiments, the mixed salt solution further includes a salt of metal M1, wherein metal M1 includes at least one of Al, Zr, Y, Ti, W and Sb.

[0036] In some embodiments, the mixed salt solution further includes a cobalt salt, the concentration of which is selected from 1.0 mol / L to 4.0 mol / L.

[0037] In some embodiments, the coprecipitation reaction is carried out under stirring.

[0038] In some embodiments, the coprecipitation reaction is carried out under stirring at a rate of 20 r / min to 100 r / min.

[0039] In some embodiments, the temperature of the coprecipitation reaction is 20°C to 60°C.

[0040] In some embodiments, the coprecipitation reaction takes 10 h to 150 h.

[0041] In some embodiments, the pH of the mixed salt solution is 8 to 11.

[0042] In some implementations, the products after the coprecipitation reaction are aged and then separated into solid and liquid components.

[0043] In some embodiments, the aging time is 5 hours to 30 hours.

[0044] In some embodiments, the solid-liquid separation includes at least one of filtration separation and centrifugal separation.

[0045] In some embodiments, the nickel salt includes at least one of nickel carbonate, nickel acetate, nickel oxalate, and nickel sulfate.

[0046] In some embodiments, the mixed salt solution further includes a cobalt salt, which includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, and cobalt sulfate.

[0047] In some embodiments, the manganese salt includes at least one of manganese carbonate, manganese acetate, manganese oxalate, and manganese sulfate.

[0048] In some embodiments, the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, and ammonia.

[0049] In some embodiments, the concentration of hydroxide ions in the alkaline solution is 1.0 mol / L to 5.0 mol / L.

[0050] In some embodiments, the median grain size of the seed crystals is 1.5 μm to 4.5 μm.

[0051] In some embodiments, the particle size D50 of the cathode material precursor is 2 μm to 25 μm.

[0052] In some embodiments, the particle size D90 of the cathode material precursor is <30 μm.

[0053] In some embodiments, the specific surface area of ​​the cathode material precursor is 5 m². 2 / g~30m 2 / g.

[0054] In some embodiments, the lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate.

[0055] In some embodiments, the addition amounts of the cathode material precursor and lithium source satisfy the following: the molar ratio of the total molar amount of Ni and Mn to the molar amount of Li is 1:(1.0 to 1.5); or the molar ratio of the total molar amount of Ni, Co and Mn to the molar amount of Li is 1:(1.0 to 1.5); or the molar ratio of the total molar amount of Ni, Co, Mn and M1 to the molar amount of Li is 1:(1.0 to 1.5).

[0056] In some embodiments, the mixing conditions for obtaining the mixture are: solid-phase mixing at 10°C to 50°C for 0.3h to 3h.

[0057] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere.

[0058] In some embodiments, the temperature of the primary sintering process is 800°C to 1000°C.

[0059] In some embodiments, the duration of the first sintering process is 6 hours to 48 hours.

[0060] In some embodiments, after the mixture comprising the cathode material precursor and the lithium source is subjected to a first sintering process, the method further includes: solid-phase mixing of the first sintering product with a dopant containing the metal element M2 and a second sintering process to obtain a cathode material with a core-shell separation structure.

[0061] In some embodiments, the dopant containing the metal element M2 includes at least one of a salt of M2 and an oxide of M2.

[0062] In some embodiments, the dopant containing the metal element M2 includes at least one of the following: carbonate of M2, hydroxide of M2, acetate of M2, oxalate of M2, and sulfate of M2.

[0063] In some embodiments, the metallic element M includes at least one selected from Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd, and Ta.

[0064] In some embodiments, based on 100 wt% of the mass of the primary sintering product, the mass content of the metal element M2 in the dopant is 0.01 wt% to 5 wt%.

[0065] In some embodiments, the solid phase is mixed at 10°C to 50°C for 0.3 to 3 hours.

[0066] In some embodiments, the secondary sintering process is carried out in an oxygen-containing atmosphere.

[0067] In some embodiments, the temperature of the secondary sintering process is 600°C to 800°C.

[0068] In some embodiments, the secondary sintering process takes 6 to 20 hours.

[0069] In some embodiments, the general chemical formula of the cathode material is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2 e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1.

[0070] Thirdly, this application provides a battery comprising the positive electrode material described in the first aspect or the positive electrode material prepared by the method described in the second aspect.

[0071] Compared with the prior art, the present invention has at least the following beneficial effects:

[0072] The cathode material precursor proposed in this application includes a core and a shell, with an interface between them. Controlling r2 / (r1+r2) within the aforementioned range facilitates interface collapse during the lithiation process of the cathode material precursor, thereby forming a void layer. This core-shell separated structure of the lithium-rich manganese-based cathode material can alleviate the release of oxygen at high voltages, mitigate the crystal structure transformation of the cathode material, slow down the voltage drop problem, and improve the capacity and cycle life of the cathode material. The void layer formed at the interface of the cathode material precursor can also effectively alleviate the mechanical stress caused by the volume change between primary particles during charging and discharging, inhibit the formation of internal crystal cracks, effectively isolate the electrolyte from the corrosion of primary particles, and improve the thermal stability and cycle stability of the cathode material.

[0073] The cathode material provided in this application includes a core and a shell located on the outer surface of the core. A void layer exists between the shell and the core. By controlling r4 / (r3+r4+d) within the aforementioned range, a void layer of suitable thickness is formed at the interface of the cathode material precursor. This core-shell separated structure of the lithium-rich manganese-based cathode material can alleviate the release of oxygen at high voltages, mitigate the crystal structure transformation of the cathode material, slow down the voltage drop problem, and improve the capacity and cycle life of the cathode material. Furthermore, it can effectively alleviate the mechanical stress caused by the volume change between primary particles during charging and discharging, effectively suppress the generation of internal crystal cracks, effectively isolate the electrolyte from the corrosion of primary particles, and improve the thermal stability and cycle stability of the cathode material. In addition, doping with metal elements M1 and / or M2 can give the cathode material more lithium intercalation sites, making the cathode material more structurally stable during charging and discharging and improving the rate performance of the cathode material.

[0074] The method for preparing the cathode material provided in this application involves co-precipitating a mixed salt solution containing nickel, cobalt, and manganese salts with an alkaline solution, followed by drying to obtain seed crystals. The seed crystals are then placed in the mixed salt solution for a second co-precipitation reaction. Due to the consumption of hydroxide ions during co-precipitation, the pH of the reaction system changes, and the deposition rates of hydroxides of different metal elements differ. This results in the hydroxides deposited on the seed crystal surface exhibiting stratification at different deposition rates, yielding a cathode material precursor with interfaces. The cathode material precursor is further sintered with a lithium source, causing interface collapse and forming a void layer, resulting in a cathode material with a core-shell separation structure. This core-shell separation structure of the lithium-rich manganese-based cathode material can alleviate the release of oxygen at high voltages, mitigate the crystal structure transformation of the cathode material, reduce voltage drop, and improve the capacity and cycle life of the cathode material. Furthermore, this preparation method is simple and controllable, reducing production costs. Attached Figure Description

[0075] The present invention will be further described below with reference to the accompanying drawings and embodiments.

[0076] Figure 1 This is a schematic diagram of the structure of the cathode material precursor provided in the embodiments of this application.

[0077] Figure 2a as well as Figure 2b These are schematic diagrams of the cathode materials provided in the embodiments of this application.

[0078] Figure 3 This is a schematic flowchart illustrating the preparation method of the cathode material provided in the embodiments of this application.

[0079] Figure 4 A scanning electron microscope cross-sectional view of the cathode material precursor provided in Embodiment 1 of this application.

[0080] Figure 5 This is a scanning electron microscope image of the cathode material provided in Embodiment 1 of this application.

[0081] Figure 6a This is a scanning electron microscope cross-sectional view of the cathode material provided in Embodiment 1 of this application.

[0082] Figure 6b The image shows the distribution of elements in a cross-sectional view of the cathode material provided in Embodiment 1 of this application using a scanning electron microscope.

[0083] Figure 7 A scanning electron microscope cross-sectional view of the cathode material precursor provided in Embodiment 2 of this application.

[0084] Figure 8 This is a scanning electron microscope cross-sectional view of the cathode material provided in Embodiment 2 of this application.

[0085] Figure 9 This is a scanning electron microscope cross-sectional view of the cathode material provided in Embodiment 3 of this application.

[0086] Figure 10 These are the results of 50 cycles of coining in Embodiment 1 and Comparative Example 1 of the present invention.

[0087] Figure label:

[0088] 10-nucleosome;

[0089] 20 - Shell; 21 - First shell, 22 - Second shell;

[0090] 30 - First void layer. Detailed Implementation

[0091] To better understand the technical solution of the present invention, the embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

[0092] It should be understood that the described embodiments are merely some, not all, of the embodiments of the present invention. All other embodiments obtained by those skilled in the art based on the embodiments of the present invention without inventive effort are within the scope of protection of the present invention.

[0093] The terminology used in the embodiments of this invention is for the purpose of describing particular embodiments only and is not intended to limit the invention. The singular forms “a,” “the,” and “the” as used in the embodiments of this invention and the appended claims are also intended to include the plural forms unless the context clearly indicates otherwise.

[0094] It should be understood that the term "and / or" used in this article is merely a description of the relationship between related objects, indicating that three relationships can exist. For example, A and / or B can represent: A existing alone, A and B existing simultaneously, and B existing alone. Additionally, the character " / " in this article generally indicates that the preceding and following related objects have an "or" relationship.

[0095] This application provides a cathode material precursor, such as... Figure 1 As shown, the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)₂, wherein a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2, and M1 is a metallic element; the cathode material precursor has a core-shell structure, comprising:

[0096] The kernel, wherein the radius of the kernel is r1; and

[0097] A shell is located on the outer surface of the core, and there is an interface between the shell and the core. The thickness of the shell is r2, where 1 / 6 < r2 / (r1+r2) < 5 / 6.

[0098] The cathode material precursor proposed in this application includes a core and a shell, with an interface between them. Controlling r2 / (r1+r2) within the aforementioned range facilitates interface collapse during the lithiation process of the cathode material precursor, thereby forming a void layer. This core-shell separated structure of the lithium-rich manganese-based cathode material can alleviate the release of oxygen at high voltages, mitigate the crystal structure transformation of the cathode material, slow down the voltage drop problem, and improve the capacity and cycle life of the cathode material. The void layer formed at the interface of the cathode material precursor can also effectively alleviate the mechanical stress caused by the volume change between primary particles during charging and discharging, inhibit the formation of internal crystal cracks, effectively isolate the electrolyte from the corrosion of primary particles, and improve the thermal stability and cycle stability of the cathode material.

[0099] In some embodiments, the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)2, where a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2.

[0100] In some implementations, the value of 'a' can be 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, or 0.1, etc.; the value of 'b' can be 0.1, 0.15, 0.17, 0.19, 0.2, 0.25, 0.29, or 0.3, etc.; the value of 'c' can be 0.5, 0.6, 0.7, or 0.8, etc.; and the value of 'd' can be 0, 0.01, 0.02, 0.05, 0.1, 0.12, 0.15, 0.19, or 0.2, etc., or other values ​​within the above ranges, which are not limited here.

[0101] In some embodiments, M1 includes at least one of Al, Zr, Y, Ti, W, and Sb.

[0102] In some embodiments, the cathode material precursor is a hydroxide precursor.

[0103] In some implementations, the specific ratio of r2 / (r1+r2) can be 1.1 / 6, 1.5 / 6, 1.8 / 6, 2.0 / 6, 2.2 / 6, 2.5 / 6, 3.0 / 6, 3.5 / 6, 4.0 / 6, 4.5 / 6, or 4.9 / 6, etc., or other values ​​within the above range, which are not limited here. When the ratio deviates from the above range, the interface between the shell and core of the cathode material precursor becomes blurred, and after the size ratio is out of balance, the precursor and lithium source are not easy to collapse into a void layer during sintering, resulting in a less than ideal core-shell separation structure of the cathode material.

[0104] In some embodiments, the shell layer includes an inner shell layer and an outer shell layer, with an interface between the inner shell layer and the outer shell layer. It is understood that when the shell layer has two shell layers, the sum of the thicknesses of the two shell layers is r2, and the size ratio of the shell layer to the core still satisfies 1 / 6 < r2 / (r1+r2) < 5 / 6.

[0105] In some implementations, the mass content of nickel at the interface of the cathode material precursor is greater than the mass content of manganese.

[0106] In some embodiments, the sphericity of the cathode material precursor is 0.8 to 0.99. Good sphericity in the cathode material precursor indicates that the deposition rate around the grains is relatively uniform during grain growth, and this relatively uniform growth rate is beneficial for forming a well-defined interface layer.

[0107] In some embodiments, the particle size D50 of the cathode material precursor is 2μm to 25μm, specifically 2μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 15μm, 18μm, 20μm, 23μm, or 25μm, or other values ​​within the above range, which are not limited here. Preferably, the particle size D50 of the cathode material precursor is 4μm to 20μm.

[0108] In some embodiments, the particle size D90 of the cathode material precursor is <30 μm, specifically 29 μm, 28 μm, 27 μm, 26 μm, 25 μm, or other values ​​within the above range, which are not limited here.

[0109] In some embodiments, the specific surface area of ​​the cathode material precursor is 5 m². 2 / g~30m 2 / g, specifically 5m 2 / g、6m 2 / g、7m 2 / g、9m 2 / g, 10m 2 / g, 15m 2 / g、17m 2 / g、19m 2 / g、20m 2 / g、25m 2 / g、27m 2 / g、29m 2 / g or 30m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Preferably, the specific surface area of ​​the cathode material precursor is 8m². 2 / g~25m2 / g.

[0110] Secondly, this application provides a cathode material, the general chemical formula of which is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2 e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1, and M1 and M2 are metallic elements; Figure 2a As shown,

[0111] The positive electrode material includes a core 10 and a shell 20 located on the outer surface of the core 10. The radius of the core is r3 and the thickness of the shell is r4. A first void layer 30 exists between the shell 20 and the core 10. The thickness of the first void layer 30 is d, where 1 / 6 < r4 / (r3+r4+d) < 5 / 6.

[0112] The cathode material provided in this application includes a core and a shell located on the outer surface of the core. A void layer exists between the shell and the core, thereby achieving core-shell separation. By controlling r4 / (r3+r4+d) within the aforementioned range, a void layer of suitable thickness is formed at the interface of the cathode material precursor. This core-shell separated lithium-rich manganese-based cathode material can alleviate the release of oxygen at high voltages, mitigate the crystal structure transformation of the cathode material, slow down the voltage drop problem, and improve the capacity and cycle life of the cathode material. Furthermore, it can effectively alleviate the mechanical stress caused by the volume change between primary particles during charging and discharging, effectively suppress the generation of internal crystal cracks, effectively isolate the electrolyte from the corrosion of primary particles, and improve the thermal stability and cycle stability of the cathode material. In addition, doping with metal elements M1 and / or M2 can give the cathode material more lithium intercalation sites, making the cathode material more structurally stable during charging and discharging, and improving the rate performance of the cathode material.

[0113] In some embodiments, the cathode material is a lithium-rich metal composite oxide, which combines high capacity, excellent thermal stability, and long cycle stability. Specifically, the general chemical formula of the cathode material is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2 e1For O2, a1 can take values ​​of 0.45, 0.4, 0.35, 0.3, 0.25, 0.2, 0.15, or 0.1, etc.; b1 can take values ​​of 0.1, 0.15, 0.17, 0.19, 0.2, 0.25, 0.29, or 0.3, etc.; c1 can take values ​​of 0.5, 0.6, 0.7, or 0.8, etc.; and d1 can take values ​​of 0, 0.01, 0.02, 0, etc. The values ​​of e1 can be 0, 0.01, 0.02, 0.05, 0.1, 0.12, 0.15, 0.19, or 0.2, etc., and x can be 1.0, 1.1, 1.20, 1.30, 1.35, 1.40, or 1.45, etc., or other values ​​within the above range, which are not limited here.

[0114] In some implementations, 1 / 6 < r4 / (r3+r4+d) < 5 / 6, where the specific ratio of r4 / (r3+r4+d) can be 1.1 / 6, 1.5 / 6, 1.8 / 6, 2.0 / 6, 2.2 / 6, 2.5 / 6, 3.0 / 6, 3.5 / 6, 4.0 / 6, 4.5 / 6, or 4.9 / 6, etc., or other values ​​within the above range, which are not limited here. When the ratio deviates from the above range, if the thickness of the void layer between the shell and the core of the cathode material is insufficient or excessive, the cathode material will not have a significant void layer, i.e., it will not exhibit core-shell separation. This will increase the voltage decay effect of the cathode material, cause severe gas generation, and be detrimental to improving the rate performance of the cathode material. Therefore, by controlling r4 / (r3+r4+d) within the above range, a balance can be achieved between the electrochemical performance and structural stability of the cathode material, enabling the cathode material to have both superior electrochemical performance and improved crystal structure stability, thus mitigating the voltage drop problem of lithium-rich manganese-based cathode materials and improving the capacity and cycle life of the cathode material.

[0115] In some implementations, such as Figure 2b As shown, the shell 20 includes a first shell 21 and a second shell 22, with a second void layer between the first shell 21 and the second shell 22. The thickness of the second void layer is d2. It can be understood that when the shell has two shells, the sum of the thicknesses of the first shell and the second shell is the thickness r4 of the shell. The dimensional ratio of the shell to the core and the first void layer d1 still satisfies 1 / 6 < r4 / (r3 + r4 + d1 + d2) < 5 / 6.

[0116] In some embodiments, the shell and at least a portion of the core extend and connect within the first void layer. Understandably, a portion of the core may extend and connect to the shell through the first void layer. In this application, the thickness of the first void layer is d, where 0 < d ≤ 1 μm, specifically 0.1 μm, 0.2 μm, 0.25 μm, 0.3 μm, 0.35 μm, 0.4 μm, 0.45 μm, 0.5 μm, 0.6 μm, 0.7 μm, 0.8 μm, 0.9 μm, or 1 μm, etc., and of course, other values ​​within the above range are also possible and are not limited here. To achieve both the electrochemical performance and crystal structure stability of the cathode material, preferably, 0 < d ≤ 0.5 μm.

[0117] In some embodiments, M1 includes at least one of Al, Zr, Y, Ti, W, and Sb.

[0118] In some embodiments, M2 includes at least one of Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd, and Ta.

[0119] In some embodiments, the cathode material includes secondary particles composed of primary particles. The secondary particles have a spherical structure with a sphericity of 0.8 to 0.99. When the sphericity of the secondary particles is controlled within the above range, the primary particles in the secondary particles are tightly bonded to form secondary particles, which is beneficial to improving the specific capacity of the cathode material. Furthermore, the secondary particles have a relatively obvious core-shell separation structure, i.e., they have a first void layer.

[0120] In some embodiments, the crystal structure of the cathode material belongs to the hexagonal crystal system.

[0121] In some embodiments, the mass content of nickel in the core of the cathode material near the surface of the first void layer is greater than the mass content of manganese.

[0122] In some embodiments, the particle size D50 of the positive electrode material is 6μm to 15μm, specifically 6μm, 7μm, 8μm, 9μm, 10μm, 11μm, 12μm, 13μm, 14μm, or 15μm, etc., and of course, other values ​​within the above range are also possible, and are not limited here. Preferably, the particle size D50 of the positive electrode material is 7μm to 14μm.

[0123] In some embodiments, the particle size D90 of the cathode material is <30 μm, specifically it can be 29 μm, 28 μm, 27 μm, 26 μm, or 25 μm, or other values ​​within the above range, which are not limited here. When the particle size D90 of the cathode material is controlled within the above range, the sphericity of the cathode material particles is close to 0.8 to 0.99, which is beneficial to improving the specific capacity of the cathode material.

[0124] In some embodiments, the specific surface area of ​​the positive electrode material is 0.2 m². 2 / g~2.5m 2 / g, specifically 0.2m 2 / g, 0.5m 2 / g, 0.7m 2 / g, 0.9m 2 / g、1m 2 / g, 1.5m 2 / g, 1.7m 2 / g, 1.9m 2 / g、2m 2 / g or 2.5m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Preferably, the specific surface area of ​​the positive electrode material is 0.5m². 2 / g~1.5m 2 / g.

[0125] In some embodiments, the tap density of the positive electrode material is >1.8 g / cm³. 3 Specifically, it could be 1.9 g / cm³ 3 2.0g / cm 3 2.1g / cm 3 2.3g / cm 3 2.5g / cm 3 2.7g / cm 3 2.9g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0126] In some embodiments, the compaction density of the cathode material is >2.0 g / cm³. 3 Specifically, it could be 2.1 g / cm³. 3 2.2g / cm 3 2.5g / cm 3 2.8g / cm 3 3.0g / cm 3 3.2g / cm 3 "etc." can also be other values ​​within the above range, and no restrictions are imposed here.

[0127] Secondly, this application provides a method for preparing a cathode material, such as... Figure 3 As shown, the preparation method of this cathode material includes the following steps:

[0128] S10: A mixed salt solution containing nickel and manganese salts is mixed with an alkaline solution to carry out a co-precipitation reaction, and then dried to obtain seed crystals;

[0129] S20: Seed crystals are added to a mixed salt solution containing nickel and manganese salts for a secondary co-precipitation reaction to obtain a cathode material precursor with a core-shell structure;

[0130] S30: A mixture containing a cathode material precursor and a lithium source is sintered once to obtain a cathode material with a core-shell separation structure.

[0131] The method for preparing the cathode material provided in this application involves co-precipitating a mixed salt solution containing nickel, cobalt, and manganese salts with an alkaline solution, followed by drying to obtain seed crystals. The seed crystals are then placed in the mixed salt solution for a second co-precipitation reaction. Due to the consumption of hydroxide ions during co-precipitation, the pH of the reaction system changes, and the deposition rates of hydroxides of different metal elements differ. This results in the hydroxides deposited on the seed crystal surface exhibiting stratification at different deposition rates, yielding a cathode material precursor with interfaces. The cathode material precursor is further sintered with a lithium source, causing interface collapse and forming a void layer, resulting in a cathode material with a core-shell separation structure. This core-shell separation structure of lithium-rich manganese-based cathode material can alleviate oxygen release at high voltages, mitigate crystal structure transformation, reduce voltage drop, and improve capacity, structural stability, and cycle life. Furthermore, this preparation method is simple and controllable, reducing production costs.

[0132] The preparation method of this application is described in detail below with reference to the embodiments:

[0133] S10 involves mixing a mixed salt solution containing nickel and manganese salts with an alkaline solution to undergo a co-precipitation reaction, followed by drying to obtain seed crystals.

[0134] In some embodiments, the concentrations of nickel and manganese salts in the mixed salt solution are each independently selected from 1.0 mol / L to 4.0 mol / L, specifically 1.0 mol / L, 1.5 mol / L, 1.6 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, or 4.0 mol / L, etc., and are not limited here.

[0135] In some embodiments, the mixed salt solution further includes a cobalt salt, the concentration of which is selected from 1.0 mol / L to 4.0 mol / L, specifically 1.0 mol / L, 1.5 mol / L, 1.6 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L or 4.0 mol / L, etc., and is not limited here.

[0136] In some embodiments, the mixed salt solution further includes a salt of metal M1, the concentration of which is selected from 1.0 mol / L to 4.0 mol / L, specifically 1.0 mol / L, 1.5 mol / L, 1.6 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, or 4.0 mol / L, etc., and is not limited here.

[0137] In some embodiments, the metal M1 includes at least one of Al, Zr, Y, Ti, W, and Sb; specifically, it may be aluminum sulfate, yttrium sulfate, titanium sulfate, etc.

[0138] In some embodiments, the mixed salt solution further includes a complexing agent with a concentration of 0.1 mol / L to 0.5 mol / L, specifically 0.1 mol / L, 0.2 mol / L, 0.3 mol / L, 0.4 mol / L, or 0.5 mol / L, etc., which is not limited here. Specifically, the complexing agent can be an aqueous ammonia solution, diethanolamine, ethylenediaminetetraacetic acid, sodium ethylenediaminetetramethylene phosphate, etc.

[0139] In some embodiments, the coprecipitation reaction is carried out under stirring.

[0140] In some embodiments, the coprecipitation reaction is carried out under a protective atmosphere, which includes at least one of nitrogen, neon, helium, argon, and krypton.

[0141] In some embodiments, the stirring rate is 20 r / min to 100 r / min, specifically 20 r / min, 30 r / min, 40 r / min, 50 r / min, 60 r / min, 70 r / min, 80 r / min, 90 r / min or 100 r / min, etc., and is not limited here.

[0142] In some embodiments, the temperature of the coprecipitation reaction is 20°C to 60°C, specifically 20°C, 25°C, 30°C, 40°C, 45°C, 50°C, or 60°C, or other values ​​within the above range, which are not limited here. Preferably, the temperature of the coprecipitation reaction is 30°C to 50°C.

[0143] In some embodiments, the coprecipitation reaction time is 10h to 150h, specifically 10h, 20h, 30h, 50h, 60h, 70h, 80h, 90h, 100h, 120h, 130h, or 150h, or other values ​​within the above range, which are not limited here. Preferably, the coprecipitation reaction time is 20h to 48h.

[0144] In some embodiments, the pH value of the mixed salt solution is 8-11, specifically 8, 9, 10, 10.5, or 11, or other values ​​within the above range, which are not limited here. Preferably, controlling the pH value of the mixed salt solution within the above range is beneficial for the co-precipitation reaction between metal ions and hydroxide ions in the mixed salt. Preferably, the pH value of the mixed salt solution is 9-10.

[0145] In some implementations, the products after the coprecipitation reaction are aged and then separated into solid and liquid components.

[0146] In some embodiments, the aging time is 5h to 30h, specifically 5h, 8h, 10h, 15h, 20h, 25h, 28h or 30h, etc., and of course other values ​​within the above range are also possible, which are not limited here.

[0147] In some embodiments, the solid-liquid separation includes at least one of filtration separation and centrifugal separation.

[0148] In some embodiments, the nickel salt includes at least one of nickel carbonate, nickel acetate, nickel oxalate, and nickel sulfate; the cobalt salt includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, and cobalt sulfate; and the manganese salt includes at least one of manganese carbonate, manganese acetate, manganese oxalate, and manganese sulfate.

[0149] In some embodiments, the alkaline solution includes at least one of sodium hydroxide, potassium hydroxide, and ammonia.

[0150] In some embodiments, the concentration of hydroxide ions in the alkaline solution is 1.0 mol / L to 5.0 mol / L, specifically 1.0 mol / L, 1.5 mol / L, 1.6 mol / L, 2.0 mol / L, 2.5 mol / L, 3.0 mol / L, 3.5 mol / L, or 4.0 mol / L, etc., and is not limited here.

[0151] In some embodiments, the median grain size of the seed crystal is 1.5 μm to 4.5 μm, specifically it can be 1.5 μm, 1.8 μm, 2 μm, 2.5 μm, 2.8 μm, 3 μm, 3.5 μm, 3.8 μm, 4.0 μm or 4.5 μm, etc. Of course, it can also be other values ​​within the above range, which are not limited here.

[0152] In step S20, the seed crystal is added to a mixed salt solution containing nickel and manganese salts for a secondary co-precipitation reaction to obtain the cathode material precursor.

[0153] The formulation of the mixed salt solution and the coprecipitation reaction conditions in step S20 are the same as those in step S10, and will not be repeated here.

[0154] In some embodiments, the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)₂ where a + b + c + d = 1, 0 < a ≤ 0.45, 0 ≤ b ≤ 0.3, 0.5 ≤ c < 1.0, and 0 ≤ d ≤ 0.2. Typical examples of combinations include: Ni 0.25 Mn 0.75 (OH)2, Ni 0.10 Co 0.1 Al 0.05 Mn 0.75 (OH)2, Ni 0.30 Co 0.05 Mn 0.65 (OH)2, Ni 0.44 Co 0.01 Mn 0.55 (OH)2, etc.

[0155] In some embodiments, the sphericity of the cathode material precursor is 0.8 to 0.99, exhibiting a spherical or near-spherical structure. Good sphericity in the cathode material precursor facilitates the formation of a clearly defined interface layer.

[0156] In some embodiments, the particle size D50 of the cathode material precursor is 2μm to 25μm, specifically 2μm, 4μm, 5μm, 6μm, 7μm, 8μm, 9μm, 10μm, 15μm, 18μm, 20μm, 23μm, or 25μm, or other values ​​within the above range, which are not limited here. Preferably, the particle size D50 of the cathode material precursor is 4μm to 20μm.

[0157] In some embodiments, the particle size D90 of the cathode material precursor is <30 μm, specifically 29 μm, 28 μm, 27 μm, 26 μm, 25 μm, or other values ​​within the above range, which are not limited here.

[0158] In some embodiments, the specific surface area of ​​the cathode material precursor is 5 m². 2 / g~30m 2 / g, specifically 5m 2 / g、6m 2 / g、7m 2 / g、9m 2 / g, 10m 2 / g, 15m 2 / g、17m 2 / g、19m 2 / g、20m 2 / g、25m 2 / g、27m 2 / g、29m 2 / g or 30m 2 / g, etc., can also be other values ​​within the above range, and are not limited here. Preferably, the specific surface area of ​​the cathode material precursor is 8m². 2 / g~25m 2 / g.

[0159] Step S30: The mixture containing the cathode material precursor and the lithium source is subjected to a first sintering process to obtain a cathode material with a core-shell structure.

[0160] In some embodiments, the lithium source includes at least one selected from lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate, and lithium oxalate. Preferably, the lithium source is lithium carbonate.

[0161] In some embodiments, the addition amounts of the cathode material precursor and lithium source satisfy the following: the molar ratio of the total molar amount of Ni and Mn to the molar amount of Li is 1:(1.0~1.5); or the molar ratio of the total molar amount of Ni, Co, and Mn to the molar amount of Li is 1:(1.0~1.5); or the molar ratio of the total molar amount of Ni, Co, Mn, and M1 to the molar amount of Li is 1:(1.0~1.5). Specifically, it can be 1:1, 1:1.1, 1:1.2, 1:1.3, 1:1.4, or 1:1.5, etc., and of course, other values ​​within the above range are also possible and are not limited here. Within this range, the Li / Ni cation mixing degree can be reduced, and excessive residual lithium on the surface of the calcined product can be prevented from affecting the processing performance and safety performance.

[0162] In some embodiments, the solid-phase mixing is performed at 10°C to 50°C for 0.3 to 3 hours. The solid-phase mixing temperature can be 10°C, 15°C, 20°C, 25°C, 30°C, 35°C, 40°C, 45°C, or 50°C, and the solid-phase mixing time can be 0.3 hours, 0.4 hours, 0.5 hours, 0.6 hours, 0.8 hours, 1 hour, 1.5 hours, 1.8 hours, 2.5 hours, or 3 hours, etc., and of course, other values ​​within the above ranges are also possible and are not limited here. Preferably, the solid-phase mixing temperature is 10°C to 35°C.

[0163] In some implementations, the solid-phase mixing method can be dry grinding, ball milling, etc., which is not limited here, as long as the components are mixed evenly.

[0164] In some implementations, the mixing equipment may be at least one of a ball mill, a three-dimensional mixer, a high-speed mixer, and a VC mixer.

[0165] In some embodiments, solid-phase mixing is performed using a high-speed mixer with a stirring rate of 500 r / min to 1000 r / min, specifically 500 r / min, 550 r / min, 600 r / min, 650 r / min, 700 r / min, 750 r / min, 800 r / min, 900 r / min, or 1000 r / min, etc., which are not limited here. The stirring time is 10 min to 100 min, specifically 10 min, 20 min, 30 min, 40 min, 50 min, 60 min, 70 min, or 100 min, etc., which are not limited here.

[0166] In some embodiments, the primary sintering process is carried out in an oxygen-containing atmosphere. The oxygen-containing atmosphere can be air or a mixture of air and oxygen.

[0167] In some embodiments, the temperature of the primary sintering treatment is 800℃ to 1000℃, specifically 800℃, 850℃, 880℃, 900℃, 920℃, 940℃, 950℃, or 1000℃, but not limited to the listed values; other unlisted values ​​within this range are also applicable. Within this range, sufficient air can promote the oxidation of divalent nickel to trivalent nickel, reduce Li / Ni cation mixing, and increase the capacity of lithium-rich manganese-based materials. Simultaneously, this temperature range is conducive to the formation of a layered structure without causing material decomposition. Preferably, the temperature of the primary sintering treatment is 850℃ to 950℃.

[0168] In some embodiments, the sintering time for the first sintering process is 6 hours to 48 hours, specifically 6 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 24 hours, 36 hours, or 48 hours, but is not limited to the listed values; other unlisted values ​​within this range are also applicable. Within this range, a layered structure and a uniform primary particle coating layer can be effectively formed, thereby ensuring the various performance indicators of the cathode material are met. Preferably, the sintering time for the first sintering process is 12 hours to 24 hours.

[0169] Furthermore, after the initial sintering treatment of the mixture comprising the cathode material precursor and the lithium source, the method further includes:

[0170] S40 involves solid-state mixing of the primary sintering product with a dopant containing metal element M2, followed by secondary sintering to obtain a cathode material with a core-shell structure.

[0171] The solid-phase mixing method is the same as that described in step S30, and will not be repeated here.

[0172] In some embodiments, the dopant containing the metal element M2 includes at least one of a salt of M2 and an oxide of M2.

[0173] In some embodiments, the dopant containing the metal element M2 includes at least one of the following: carbonate of M2, hydroxide of M2, acetate of M2, oxalate of M2, and sulfate of M2.

[0174] In some embodiments, the dopant containing the metal element M2 is an oxide of M2. Understandably, adding an oxide of the oxygen-containing metal M2 can form LiM2O2 with high lithium-ion conductivity at the grain boundaries between primary particles, reducing grain boundary transport impedance and thus improving the rate performance of the cathode material.

[0175] In some embodiments, the metal element M2 includes at least one selected from Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd, and Ta.

[0176] In some embodiments, based on the mass of the primary sintering product as 100 wt%, the mass content of the metal element M in the dopant is 0.01 wt% to 5 wt%, specifically it can be 0.01 wt%, 0.05 wt%, 0.08 wt%, 0.1 wt%, 0.5 wt%, 1 wt%, 1.5 wt%, 2 wt%, 3 wt%, 4 wt%, or 5 wt%, etc., and is not limited here.

[0177] In some embodiments, the secondary sintering process is carried out in an oxygen-containing atmosphere. The oxygen-containing atmosphere can be air or a mixture of oxygen.

[0178] In some embodiments, the temperature of the secondary sintering treatment is 600℃ to 800℃, specifically 600℃, 650℃, 680℃, 700℃, 720℃, 740℃, 750℃ or 800℃, but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0179] In some embodiments, the secondary sintering treatment time is 6h to 20h, specifically 6h, 8h, 10h, 12h, 15h, 18h or 20h, etc., but is not limited to the listed values. Other unlisted values ​​within this range are also applicable.

[0180] In some embodiments, the preparation method further includes cooling, shaping, and sieving the product after secondary sintering. The shaping includes at least one of crushing, grinding, ball milling, or air crushing.

[0181] In some embodiments, the general chemical formula of the cathode material is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1. Specific embodiments of the positive electrode material can include Li... 1.45 Ni 0.24 Mn 0.74 Zr 0.02 O2, Li 1.30 Ni 0.28 Co 0.04 Mn 0.65 Y 0.03 O2, Li 1.40 Ni 0.39 Co 0.01 Mn 0.55 Mo 0.05 O2, Li 1.40 Ni 0.10 Co 0.05 Al 0.05 Mn 0.75 Mo 0.05 O2, etc.

[0182] Thirdly, this application provides a battery comprising the above-described positive electrode material or the positive electrode material prepared by the above-described preparation method.

[0183] The above are merely preferred embodiments of the present invention and are not intended to limit the present invention. Any modifications, equivalent substitutions, improvements, etc., made within the spirit and principles of the present invention should be included within the scope of protection of the present invention.

[0184] Example 1

[0185] (1) Prepare a 2 mol / L mixed salt solution of NiSO4 and MnSO4 in a ratio of Ni:Mn = 25:75. Prepare a 2 mol / L solution of NaOH. Select 0.24 mol / L ammonia water as a complexing agent. Under nitrogen atmosphere protection, add the above three solutions to a 50L reactor at a flow rate of 2 L / min. The stirring speed is 20 r / min, the reaction temperature is controlled at 40℃, the pH value is controlled at 10, the reaction is carried out for 24 h, and then aged for 10 h. During the process, the particle size is sampled and tested in stages. When the seed crystal particle size reaches 3.0 μm, the reactants are filtered, washed, and dried to obtain the precursor seed crystals.

[0186] (2) Prepare a 2 mol / L mixed salt solution of NiSO4 and MnSO4 in a Ni:Mn ratio of 25:75. Prepare a 2 mol / L NaOH solution. Use 0.24 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 20 r / min, the reaction temperature at 40℃, and the pH value at 11. React for 48 h and then age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.9, and the specific surface area reaches 18 m². 2 At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.25 Mn 0.75 (OH)2.

[0187] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Mn) molar ratio of 1.25. 0.25 Mn 0.75 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered at 900 °C for 12 h in air atmosphere with a heating rate of 1 °C / min. The sintered product was removed when the furnace temperature dropped to approximately 100 °C, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.45 Ni 0.25 Mn 0.75 O2,

[0188] (4) Weigh out lithium-rich manganese-based oxide Li 1.45 Ni 0.25 Mn 0.75 O2 was mixed with Al2O3 and ZrO2 (with elemental mass fractions of Al and Zr of 0.1wt% and 0.2wt%, respectively) in a high-speed mixer at a stirring rate of 800 r / min for 30 min. After being mixed evenly, the mixture was sintered again at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0189] The cathode material prepared in this embodiment has the general formula Li. 1.45 Ni 0.24 Mn 0.73 Al 0.01 Zr 0.02 O2.

[0190] Figure 4 Ni, the cathode material precursor prepared in Example 1 of this application 0.25 Mn 0.75SEM cross-section of (OH)₂. (See image.) Figure 4 It can be seen that the precursor has a clear interface in cross-sectional analysis.

[0191] Figure 5 This is a scanning electron microscope image of the positive electrode material prepared in Example 1 of this application, as shown. Figure 5 As shown, the cathode material has good sphericity and the primary particles are tightly packed together without gaps. Figure 6a These are scanning electron microscope (SEM) cross-sectional images of the positive electrode material prepared in Example 1 of this application. Figure 6a As shown, the cathode material has a distinct core-shell structure, with the core and shell separated, and a first void layer between the core and the shell.

[0192] Figure 6b The elemental distribution diagram of the scanning electron microscope cross-section of the cathode material provided in Embodiment 1 of this application is shown below. Figure 6b As shown, the mass content ρ of nickel in the core of the cathode material near the surface of the first void layer is... Ni The mass content of manganese is greater than ρ Mn .

[0193] Example 2

[0194] (1) A 2 mol / L mixed salt solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 24:1:75. A 1.5 mol / L NaOH solution was prepared. A 0.3 mol / L ammonia solution was selected as the complexing agent. Under a nitrogen atmosphere, the above three solutions were added to a 50L reactor at a flow rate of 2 L / min. The stirring speed was 20 r / min, the reaction temperature was controlled at 40℃, the pH value was controlled at 10, and the reaction was carried out for 24 h, followed by aging for 10 h. During the process, the particle size was sampled and tested at stages. When the seed crystal particle size reached 3.0 μm and the surface morphology was relatively dense, the reactants were filtered, washed, and dried to obtain the precursor seed crystals.

[0195] (2) Prepare a 2 mol / L mixed salt solution of NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 24:1:75. Prepare a 2 mol / L NaOH solution. Use 0.3 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 30 r / min, the reaction temperature at 40℃, and the pH at 10. React for 48 h and then age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.9, and the specific surface area reaches 18 m². 2At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.24 Co 0.01 Mn 0.75 (OH)2.

[0196] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Mn) molar ratio of 1.25. 0.24 Co 0.01 Mn 0.75 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered once at 910 °C for 12 h in air atmosphere, with a heating rate of 1 °C / min. The sintered product was removed when the furnace temperature dropped to approximately 100 °C, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.25 Ni 0.24 Co 0.01 Mn 0.75 O2.

[0197] (4) Weigh out lithium-rich manganese-based oxide Li 1.25 Ni 0.24 Co 0.01 Mn 0.75 O2 and D 50 Y₂O₃ with a particle size of 1 μm (Y elemental mass fraction of 0.5 wt%) was mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min and then sintered twice at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0198] The cathode material prepared in this embodiment has the general formula Li. 1.25 Ni 0.24 Co 0.01 Mn 0.74 Y 0.01 O2.

[0199] Figure 7 The Ni cathode material precursor prepared in Example 2 of this application 0.24 Co 0.01 Mn 0.75 SEM cross-section of (OH)₂. (See image.) Figure 7 It can be seen that the precursor has a clear bilayer interface in the cross-sectional analysis.

[0200] Figure 8 This is a scanning electron microscope cross-sectional image of the positive electrode material prepared in Example 2 of this application, by... Figure 8As shown, the cathode material has a distinct core-shell structure, with the core and shell separated. There is a first void layer between the core and the shell, and the shell includes a first shell and a second shell, with a second void layer between the first shell and the second shell.

[0201] Example 3

[0202] (1) A 2 mol / L mixed salt solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 30:2:68. A 2 mol / L NaOH solution was prepared. A 0.35 mol / L ammonia solution was selected as the complexing agent. Under a nitrogen atmosphere, the above three solutions were added to a 50L reactor at a flow rate of 2 L / min. The stirring speed was 40 r / min, the reaction temperature was controlled at 45℃, the pH value was controlled at 10, and the reaction was carried out for 24 h, followed by aging for 10 h. During the process, the particle size was sampled and tested at stages. When the seed crystal particle size reached 3.0 μm and the surface morphology was relatively dense, the reactants were filtered, washed, and dried to obtain the precursor seed crystals.

[0203] (2) Prepare a 2 mol / L mixed salt solution of NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 30:2:68. Prepare a 2 mol / L NaOH solution. Use 0.24 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 30 r / min, the reaction temperature at 40℃, and the pH value at 10. React for 48 h and age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.92, and the specific surface area reaches 18 m². 2 At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.30 Co 0.02 Mn 0.68 (OH)2.

[0204] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Mn) molar ratio of 1.25. 0.30 Co 0.02 Mn 0.68 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered at 920 °C for 12 h in air atmosphere with a heating rate of 1 °C / min. The sintered product was removed when the furnace temperature dropped to approximately 100 °C, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.25 Ni 0.30Co 0.02 Mn 0.68 O2,

[0205] (4) Weigh out lithium-rich manganese-based oxide Li 1.25 Ni 0.30 Co 0.02 Mn 0.68 O2 and D 50 MoO3 with a particle size of 1 μm (Mo with an elemental mass fraction of 0.7 wt%) was mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min and then sintered twice at 730 °C for 10 h in air atmosphere to obtain the cathode material.

[0206] The cathode material prepared in this embodiment has the general formula Li. 1.25 Ni 0.30 Co 0.02 Mn 0.65 Mo 0.03 O2.

[0207] Figure 9 This is a scanning electron microscope cross-sectional image of the positive electrode material prepared in Example 3 of this application. Figure 9 As shown, the cathode material has a distinct core-shell structure, with the core and shell separated, and a first void layer between the core and the shell.

[0208] Example 4

[0209] (1) A 2 mol / L mixed salt solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 40:3:57. A 2 mol / L NaOH solution was prepared. A 0.24 mol / L ammonia solution was selected as the complexing agent. Under a nitrogen atmosphere, the above three solutions were added to a 50L reactor at a flow rate of 2 L / min. The stirring speed was 20 r / min, the reaction temperature was controlled at 45℃, the pH value was controlled at 10, and the reaction was carried out for 24 h, followed by aging for 10 h. During the process, the particle size was sampled and tested at stages. When the seed crystal particle size reached 3.0 μm and the surface morphology was relatively dense, the reactants were filtered, washed, and dried to obtain the precursor seed crystals.

[0210] (2) Prepare a 2 mol / L mixed salt solution of NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 40:3:57. Prepare a 2 mol / L NaOH solution. Use 0.24 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 30 r / min, the reaction temperature at 60℃, and the pH at 10. React for 48 h and then age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.92, and the specific surface area reaches 18 m². 2 At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.40 Co 0.03 Mn 0.57 (OH)2.

[0211] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Mn) molar ratio of 1.30. 0.40 Co 0.03 Mn 0.57 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered at 900℃ for 24 h in air atmosphere with a heating rate of 1℃ / min. The sintered product was removed when the furnace temperature dropped to approximately 100℃, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.30 Ni 0.40 Co 0.03 Mn 0.57 O2,

[0212] (4) Weigh out lithium-rich manganese-based oxide Li 1.30 Ni 0.40 Co 0.03 Mn 0.57 O2 and D 50 Al₂O₃ and ZrO₂ with a particle size of 1 μm (the elemental mass fractions of Al and Zr are 0.1 wt% and 0.2 wt% respectively) were mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min, and then sintered twice at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0213] The cathode material prepared in this embodiment has the general formula Li. 1.30 Ni 0.39 Co 0.03 Mn 0.55 Al 0.01 Zr0.02 O2.

[0214] Example 5

[0215] (1) A 2 mol / L mixed salt solution was prepared by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 44.5:0.5:55. A 2 mol / L NaOH solution was prepared. A 0.24 mol / L ammonia solution was selected as the complexing agent. Under a nitrogen atmosphere, the three solutions were added to a 50L reactor at a flow rate of 2 L / min. The stirring speed was 20 r / min, the reaction temperature was controlled at 40℃, and the pH value was controlled at 10.5. The reaction was carried out for 24 h and then aged for 10 h. During the process, the particle size was tested at stages. When the seed crystal particle size reached 3.5 μm and the surface morphology was relatively dense, the reactants were filtered, washed, and dried to obtain the precursor seed crystals.

[0216] (2) Prepare a 2 mol / L mixed salt solution by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 44.5:0.5:55. Prepare a 2 mol / L NaOH solution. Use 0.24 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 30 r / min, the reaction temperature at 60℃, and the pH at 10.5. React for 48 h and age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.9, and the specific surface area reaches 18 m². 2 At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.445 Co 0.005 Mn 0.55 (OH)2.

[0217] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Mn) molar ratio of 1.40. 0.445 Co 0.005 Mn 0.55 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered at 900℃ for 24 h in air atmosphere with a heating rate of 1℃ / min. The sintered product was removed when the furnace temperature dropped to approximately 100℃, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.40 Ni 0.445 Co 0.005 Mn 0.57 O2,

[0218] (4) Weigh out lithium-rich manganese-based oxide Li 1.40 Ni 0.445 Co 0.005 Mn 0.57 O2 and D 50 TiO2 with a particle size of 1 μm (Ti element mass fraction of 0.6 wt%) was mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min and then sintered twice at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0219] The cathode material prepared in this embodiment has the general formula Li. 1.40 Ni 0.445 Co 0.005 Mn 0.54 Ti 0.01 O2.

[0220] Example 6

[0221] The difference from Example 1 is:

[0222] (4) Weigh out lithium-rich manganese-based oxide Li 1.45 Ni 0.25 Mn 0.75 O2 and Sr(OH)2 with D50 = 1 μm (Sr elemental mass fraction of 0.1 wt%) were mixed uniformly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min and then sintered at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0223] The cathode material prepared in this embodiment has the general formula Li. 1.45 Ni 0.24 Mn 0.73 Sr 0.02 O2.

[0224] Example 7

[0225] The difference from Example 1 is:

[0226] In steps (1) and (2), the pH value is maintained at 11.

[0227] The performance test results of the cathode material prepared in this embodiment are shown in Table 1.

[0228] Example 8

[0229] The difference from Example 1 is:

[0230] In steps (1) and (2), the stirring rate is 50 r / min.

[0231] The performance test results of the cathode material prepared in this embodiment are shown in Table 1.

[0232] Example 9

[0233] The difference from Example 1 is:

[0234] In steps (1) and (2), the concentration of ammonia is 0.48 mol / L.

[0235] The performance test results of the cathode material prepared in this embodiment are shown in Table 1.

[0236] Example 10

[0237] The difference from Example 1 is:

[0238] In steps (1) and (2), the coprecipitation reaction temperature is 60℃.

[0239] The performance test results of the cathode material prepared in this embodiment are shown in Table 1.

[0240] Example 11

[0241] The difference from Example 1 is:

[0242] In steps (1) and (2), the coprecipitation reaction time is 72 hours.

[0243] The performance test results of the cathode material prepared in this embodiment are shown in Table 1.

[0244] Example 12

[0245] Unlike Example 1, the sintering temperature in step (3) of the lithium-rich manganese-based oxide preparation process is 850°C.

[0246] The performance test results of the cathode material prepared in this comparative example are shown in Table 1.

[0247] Example 13

[0248] Unlike Example 1, the sintering time for the lithium-rich manganese-based oxide preparation process in step (3) is 48 hours.

[0249] The performance test results of the cathode material prepared in this comparative example are shown in Table 1.

[0250] Example 14

[0251] (1) A 2 mol / L mixed salt solution was prepared by mixing NiSO4, CoSO4, Al2(SO4)3, and MnSO4 in a ratio of Ni:Co:Al:Mn = 23:1:1:75. A 1.5 mol / L NaOH solution was prepared, and 0.3 mol / L ammonia water was selected as the complexing agent. Under a nitrogen atmosphere, the above four solutions were added to a 50L reactor at a flow rate of 2 L / min. The stirring speed was 20 r / min, the reaction temperature was controlled at 40℃, the pH value was controlled at 10, and the reaction was carried out for 24 h, followed by aging for 10 h. During the process, the particle size was tested at stages. When the seed crystal particle size reached 3.0 μm and the surface morphology was relatively dense, the reactants were filtered, washed, and dried to obtain the precursor seed crystals.

[0252] (2) Prepare a 2 mol / L mixed salt solution by mixing NiSO4, CoSO4, Al2(SO4)3, and MnSO4 in a ratio of Ni:Co:Al:Mn = 23:1:1:75. Prepare a 2 mol / L NaOH solution. Use 0.3 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above four solutions to a 100L reactor at a flow rate of 2 L / min. Simultaneously, add precursor seed crystals to the reactor. Control the stirring speed at 30 r / min, the reaction temperature at 40℃, and the pH at 10. React for 48 h and then age for 20 h. Take samples for testing during the reaction. When the particle size D... 50 The particle size reaches 10.0 μm, the particle sphericity reaches 0.9, and the specific surface area reaches 18 m². 2 At / g, the process of receiving, washing, and drying begins to obtain Ni cathode material precursor with a layered structure. 0.23 Co 0.01 Al 0.01 Mn 0.75 (OH)2.

[0253] (3) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Al+Mn) molar ratio of 1.25. 0.23 Co 0.01 Al 0.01 Mn 0.75 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered at 920 °C for 12 h in air atmosphere with a heating rate of 1 °C / min. The sintered product was removed when the furnace temperature dropped to approximately 100 °C, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.25 Ni 0.23 Co 0.01 Al 0.01 Mn 0.75 O2.

[0254] (4) Weigh out lithium-rich manganese-based oxide Li 1.25 Ni 0.23 Co 0.01 Al 0.01 Mn 0.75 O2 and D 50 Y₂O₃ with a particle size of 1 μm (Y elemental mass fraction of 0.5 wt%) was mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min and then sintered twice at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0255] The cathode material prepared in this embodiment has the general formula Li. 1.25 Ni 0.23 Co 0.01 Al 0.01 Mn 0.74 Y 0.01 O2.

[0256] Comparative Example 1

[0257] (1) Prepare a 2 mol / L mixed salt solution by mixing NiSO4, CoSO4, and MnSO4 in a ratio of Ni:Co:Mn = 24:1:75. Prepare a 1.5 mol / L NaOH solution. Select 0.3 mol / L ammonia water as a complexing agent. Under a nitrogen atmosphere, add the above three solutions to a 50L reactor at a flow rate of 2 L / min. The stirring speed is 20 r / min, the reaction temperature is controlled at 40℃, the pH value is controlled at 10, and the reaction is carried out for 24 h, followed by aging for 10 h (without introducing oxygen or air). During the process, sample and test the particle size at stages. When the seed crystal particle size reaches 3.0 μm and the surface morphology is relatively dense, filter, wash, and dry the reactants to obtain the cathode material precursor seed crystals.

[0258] (2) Weigh out an appropriate amount of Li2CO3 and Ni, the precursor of the cathode material, according to a Li / (Ni+Co+Mn) molar ratio of 1.25. 0.24 Co 0.01 Mn 0.75 (OH)₂ was mixed evenly in a high-speed mixer at a stirring rate of 1000 r / min for 20 min. The mixture was then transferred to a high-temperature box furnace and sintered once at 910 °C for 12 h in air atmosphere, with a heating rate of 1 °C / min. The sintered product was removed when the furnace temperature dropped to approximately 100 °C, yielding a lithium-rich manganese-based oxide (Li₂) with a core-shell structure. 1.45 Ni 0.24 Co 0.01 Mn 0.75 O2.

[0259] (3) Weigh out lithium-rich manganese-based oxide Li 1.45 Ni0.24 Co 0.01 Mn 0.75 O2 and D 50 Y₂O₃ with a particle size of 1 μm (Y elemental mass fraction of 0.5 wt%) was mixed uniformly in a high-speed mixer at a stirring rate of 800 r / min for 30 min and then sintered twice at 700 °C for 10 h in air atmosphere to obtain the cathode material.

[0260] The cathode material prepared in this embodiment has the general formula Li. 1.45 Ni 0.24 Co 0.01 Mn 0.74 Y 0.01 O2.

[0261] Test method:

[0262] (1) Test methods for the particle size of cathode material precursors and cathode materials:

[0263] The particle size distribution range of the cathode material was tested using a Malvern laser particle size analyzer.

[0264] (2) Test methods for the specific surface area of ​​cathode material precursors and cathode materials:

[0265] The dynamic specific surface area was measured using the JW-DX dynamic specific surface area rapid measuring instrument from Beijing Jingwei Gaobo Scientific Technology Co., Ltd., and the unit is m. 2 / g.

[0266] (3) SEM testing methods for cathode material precursors and cathode materials:

[0267] Scanning electron microscopy characterization was performed on a transmission electron microscope at an operating voltage of 200 kV. The thickness of the shell and the thickness of the void layer were obtained by measuring six points in the SEM cross-section of the cathode material particles using DigitalMicrograph software and then taking the average value.

[0268] (4) Test methods for the interface between the cathode material precursor and the cathode material shell, as well as the mass content of nickel and manganese:

[0269] By examining the SEM cross-section along the radial direction, the interface between the inner and outer shell layers was tested using an electron probe X-ray microscopy analyzer. The mass content of nickel and manganese in the particle cross-section was also determined using an electron probe X-ray microscopy analyzer.

[0270] (5) Electrochemical performance testing

[0271] The positive electrode materials obtained in Examples 1-14 and Comparative Example 1 were assembled into coin cells: the positive electrode material, conductive carbon, and polyvinylidene fluoride (PVDF) were added to N-methyl-2-pyrrolidone (NMP) at a mass ratio of 96:2:2, and uniformly mixed to form a positive electrode slurry. This slurry was then coated onto a positive electrode current collector and vacuum dried to form a positive electrode sheet (the sheet compaction density was 2.8 g / cm³). 3 Using lithium foil as the negative electrode, 2016 button batteries are assembled in a glove box.

[0272] The battery was tested using the CT2001A battery testing system from Wuhan Landian Electronics Co., Ltd., under the conditions of a discharge range of 3.0V-4.3V and a theoretical capacity of 250mAh / g at 0.1C. The test results are detailed in Tables 1 and 2.

[0273] Table 1. Physicochemical properties of materials in comparative examples and embodiments.

[0274]

[0275]

[0276] Table 2 Electrochemical performance testing of materials

[0277]

[0278]

[0279] As shown in Table 2, the positive electrode materials prepared in the embodiments of this application have excellent electrochemical performance, with a discharge capacity of over 280 mAh / g, an initial efficiency of about 87.5%, good rate performance, and outstanding long-cycle performance.

[0280] According to the data from Example 2 and Comparative Example 1, the cathode material with a core-shell separation structure can increase the lithium-ion diffusion rate by nearly 8 times. This shows that the formation of the layered structure has a great promoting effect on lithium-ion diffusion and can also improve the cycle stability of the material.

[0281] like Figure 10 As shown in the cycling data of Example 1 and Comparative Example 1, the cathode material prepared in Example 1 has a void layer, which can effectively improve the cycle retention rate of the cathode material. This is because the core-shell separated structure of the cathode material can alleviate the release of oxygen from the cathode material at high voltage, alleviate the crystal structure transformation of the cathode material, slow down the voltage drop problem of the cathode material, and improve the capacity, structural stability and cycle life of the cathode material.

[0282] 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 positive electrode material, characterized in that, The general chemical formula of the cathode material is Li. x Ni a1 Co b1 Mn c1 M1 d1 M2 e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1, and M1 and M2 are metallic elements; The positive electrode material includes a core and a shell located on the outer surface of the core. The radius of the core is r3, and the thickness of the shell is r4. A first void layer exists between the shell and the core. The thickness of the first void layer is d, where 0 < d ≤ 0.5 μm, and 1.8 / 6 < r4 / (r3 + r4 + d) < 5 / 6.

2. The cathode material according to claim 1, characterized in that, The cathode material satisfies at least one of the following characteristics: (1) The housing includes a first housing and a second housing, and a second void layer exists between the first housing and the second housing; (2) The shell and at least a portion of the core body extend and connect within the first void layer; (3) M1 includes at least one of Al, Zr, Y, Ti, W and Sb; (4) The M2 includes at least one of Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd and Ta; (5) Based on the mass of the positive electrode material being 100 wt%, the mass content of the metal elements M1 and / or M2 is 0.01 wt% to 10 wt%. (6) The mass content of nickel in the core of the cathode material near the surface of the first void layer is greater than the mass content of manganese. (7) The particle size D50 of the positive electrode material is 6μm to 15μm; (8) The particle size D90 of the positive electrode material is less than 30 μm; (9) The specific surface area of ​​the positive electrode material is 0.2 m². 2 / g~2.5m 2 / g; (10) The tap density of the positive electrode material is > 2.0 g / cm³. 3 ; (11) The compaction density of the cathode material is > 2.0 g / cm³. 3 .

3. A cathode material precursor, characterized in that, The cathode material precursor is used to prepare the cathode material according to claim 1 or 2; the general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)₂, wherein a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2, and M1 is a metallic element; the cathode material precursor has a core-shell structure, comprising: The kernel, wherein the radius of the kernel is r1; and A shell is located on the outer surface of the core, and there is an interface between the shell and the core. The thickness of the shell is r2, where 1 / 6 < r2 / (r1+r2) < 5 / 6.

4. The cathode material precursor according to claim 3, characterized in that, The cathode material precursor satisfies at least one of the following characteristics: (1) The shell layer includes an inner shell layer and an outer shell layer, and there is an interface between the inner shell layer and the outer shell layer; (2) The particle size D50 of the cathode material precursor is 2μm to 25μm; (3) The particle size D90 of the cathode material precursor is less than 30 μm; (4) The specific surface area of ​​the cathode material precursor is 5m². 2 / g~30m 2 / g; (5) M1 includes at least one of Al, Zr, Y, Ti, W and Sb.

5. A method for preparing the cathode material as described in claim 1 or 2, characterized in that, The preparation steps include the following: A mixed salt solution containing nickel and manganese salts was mixed with an alkaline solution to carry out a co-precipitation reaction, and then dried to obtain seed crystals. Seed crystals are added to a mixed salt solution containing nickel and manganese salts for a secondary co-precipitation reaction to obtain a cathode material precursor with a core-shell structure. The general chemical formula of the cathode material precursor is Ni. a Co b Mn c M1 d (OH)2, wherein a+b+c+d=1, 0<a≤0.45, 0≤b≤0.3, 0.5≤c<1.0, 0≤d≤0.2, and M1 is a metallic element; the cathode material precursor has a core-shell structure, including: a core with a radius of r1; and a shell layer located on the outer surface of the core, with an interface between the shell layer and the core, and the shell layer having a thickness of r2, wherein 1 / 6<r2 / (r1+r2)<5 / 6; A mixture containing a cathode material precursor and a lithium source is subjected to a single sintering process to obtain a cathode material with a core-shell separation structure.

6. The preparation method according to claim 5, characterized in that, The method includes at least one of the following features (1) to (22): (1) The concentrations of nickel and manganese salts in the mixed salt solution are each independently selected from 1.0 mol / L to 4.0 mol / L; (2) The mixed salt solution further includes a complexing agent, the concentration of which is 0.1 mol / L to 0.5 mol / L; (3) The mixed salt solution also includes a salt of metal M1, wherein the concentration of the salt of metal M1 is selected from 1.0 mol / L to 4.0 mol / L; (4) The mixed salt solution further includes a salt of metal M1, wherein metal M1 includes at least one of Al, Zr, Y, Ti, W and Sb; (5) The mixed salt solution further includes a cobalt salt, the concentration of which is selected from 1.0 mol / L to 4.0 mol / L; (6) The coprecipitation reaction is carried out under stirring. (7) The coprecipitation reaction is carried out under stirring, and the stirring rate is 20 r / min to 100 r / min; (8) The temperature of the coprecipitation reaction is 20℃~60℃; (9) The coprecipitation reaction time is 10h to 150h; (10) The pH value of the mixed salt solution is 8 to 11; (11) The product after the coprecipitation reaction is aged and then separated into solid and liquid components; (12) The product after the coprecipitation reaction is aged and separated into solid and liquid, and the aging time is 5h to 30h. (13) The product after the coprecipitation reaction is aged and then separated into solid and liquid components, wherein the solid-liquid separation includes at least one of filtration separation and centrifugation separation. (14) The nickel salt includes at least one of nickel carbonate, nickel acetate, nickel oxalate, and nickel sulfate; (15) The mixed salt solution further includes a cobalt salt, which includes at least one of cobalt carbonate, cobalt acetate, cobalt oxalate, and cobalt sulfate; (16) The manganese salt includes at least one of manganese carbonate, manganese acetate, manganese oxalate, and manganese sulfate; (17) The alkaline solution includes at least one of sodium hydroxide, potassium hydroxide and ammonia water; (18) The concentration of hydroxide ions in the alkaline solution is 1.0 mol / L to 5.0 mol / L; (19) The median grain size of the seed crystal is 1.5 μm to 4.5 μm; (20) The particle size D50 of the cathode material precursor is 2μm to 25μm; (21) The particle size D90 of the cathode material precursor is <30 μm; (22) The specific surface area of ​​the cathode material precursor is 5m². 2 / g~30m 2 / g.

7. The preparation method according to claim 6, characterized in that, The method includes at least one of the following features (1) to (6): (1) The lithium source includes at least one of lithium hydroxide, lithium carbonate, lithium nitrate, lithium acetate, lithium sulfate and lithium oxalate; (2) The addition amounts of the cathode material precursor and lithium source satisfy the following: the molar ratio of the total molar amount of Ni and Mn to the molar amount of Li is 1:(1.0~1.5); or the molar ratio of the total molar amount of Ni, Co and Mn to the molar amount of Li is 1:(1.0~1.5); or the molar ratio of the total molar amount of Ni, Co, Mn and M1 to the molar amount of Li is 1:(1.0~1.5); (3) The mixing conditions for obtaining the mixture are: solid-phase mixing at 10℃~50℃ for 0.3h~3h; (4) The first sintering process is carried out in an oxygen-containing atmosphere; (5) The temperature of the first sintering treatment is 800℃~1000℃; (6) The time for the first sintering process is 6h to 48h.

8. The preparation method according to claim 5 or 6, characterized in that, After the mixture containing the cathode material precursor and the lithium source is subjected to a first sintering process, the method further includes: performing solid-phase mixing and a second sintering process on the first sintering product and a dopant containing the metal element M2 to obtain a cathode material with a core-shell separation structure.

9. The preparation method according to claim 8, characterized in that, The method includes at least one of the following features (1) to (9): (1) The dopant containing the metal element M2 includes at least one of the salt of M2 and the oxide of M2; (2) The dopant containing metal element M2 includes at least one of the following: carbonate of M2, hydroxide of M2, acetate of M2, oxalate of M2, and sulfate of M2. (3) The metal element M2 includes at least one of Al, Zr, Y, Mo, Sr, Ti, La, W, Nb, Gd and Ta; (4) Based on the mass of the first sintering product being 100 wt%, the mass content of the metal element M2 in the dopant is 0.01 wt% to 5 wt%. (5) The solid phase mixture is mixed at 10℃~50℃ for 0.3h~3h; (6) The secondary sintering process is carried out in an oxygen-containing atmosphere; (7) The temperature of the secondary sintering treatment is 600℃~800℃; (8) The duration of the secondary sintering treatment is 6h to 20h; (9) The general chemical formula of the cathode material is Li x Ni a1 Co b1 Mn c1 M1 d1 M2 e1 O2, where 1.0≤x≤1.5, 0<a1≤0.45, 0≤b1≤0.3, 0.5≤c1<1.0, 0≤d1≤0.2, 0≤e1≤0.2, a1+b1+c1+d1+e1=1.

10. A lithium-ion battery, characterized in that, The lithium-ion battery includes the cathode material according to any one of claims 1 to 2 or the cathode material prepared by the preparation method according to any one of claims 5 to 9.

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