Positive electrode material precursor and preparation method thereof, positive electrode material and preparation method thereof, lithium ion battery and electric device

Abstract

The invention belongs to the technical field of batteries, and particularly relates to a positive electrode material precursor and a preparation method thereof, a positive electrode material and a preparation method thereof, a lithium ion battery and a power utilization device.The positive electrode material comprises positive electrode material particles, and each positive electrode material particle comprises a first core, a first middle layer and a first shell, the particle size of primary particles of the first core is smaller than that of primary particles of the first middle layer and that of primary particles of the first shell, and the content of nickel and cobalt elements in the first shell is higher than that of nickel and cobalt elements in the first core. The positive electrode material has capacity, rate capability and cycle performance.

Description

Technical Field

[0001] The present application relates to the field of battery technology, and more specifically, to a positive electrode material precursor and a preparation method thereof, a positive electrode material and a preparation method thereof, a lithium-ion battery, and an electrical device. Background Art

[0002] In lithium-ion battery systems, key performance indicators such as energy density, safety, power density and cost are mainly affected by the positive electrode material. Therefore, the research and development of positive electrode materials with low cost, long life, high safety and high energy density has become the core direction of technological breakthroughs in the new generation of lithium-ion batteries. Among them, lithium-rich manganese-based positive electrode materials, due to their unique anion / cation synergistic redox mechanism, can provide a reversible specific capacity of more than 250mAh / g, showing extremely high energy density, and have become one of the current research hotspots. However, the lithium-rich manganese-based positive electrode materials in related technologies are difficult to take into account capacity, rate performance and cycle performance. Therefore, the development of positive electrode materials that take into account capacity, rate performance and cycle performance is one of the challenges currently faced. Summary of the Invention

[0003] The present invention aims to at least partially address one of the technical problems in the related art. To this end, the present invention provides a positive electrode material and a preparation method thereof, a positive electrode material precursor and a preparation method thereof, a lithium-ion battery, and an electrical device that balance capacity, rate capability, and cycle performance.

[0004] In a first aspect, the present application provides a positive electrode material. According to an embodiment of the present application, the positive electrode material includes positive electrode material particles, wherein the positive electrode material particles include: a first inner core, the first inner core including a first core and a first intermediate layer located on at least a portion of an outer surface of the first core; the first core including a compound represented by Formula 1, the first intermediate layer including a compound represented by Formula 2; a first outer shell, the first outer shell located on at least a portion of a surface of the first inner core including a compound represented by Formula 3;

[0005] Li 1+a Ni b Co c Mn d M 1 e O2 Formula 1

[0006] Li 1+a' Ni b' Co c' Mn d' M 2 e' O2 Formula 2

[0007] Li 1+a” Ni b” Co c” Mnd” M 3 e” O2 Formula 3

[0008] Among them, 0.09 <a<0.23,0.0385<b<0.409,0.0385<c<0.2727,0.385<d<0.909,a+b+c+d+e=1;

[0009] 0.09 <a'<0.23,0.0385<b'<0.409,0.0385<c'<0.2727,0.385<d'<0.909,a'+b'+c'+d'+e'=1;

[0010] 0.09 <a”<0.23,0.0385<b”<0.409,0.0385<c”<0.2727,0.385<d”<0.909,a”+b”+c”+d”+e”=1;

[0011] b <b”,c<c”,d”<d;

[0012] M 1 、M 2 、M 3 Each independently includes at least one of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P;

[0013] The first core includes first primary particles, the first intermediate layer includes second primary particles, the first shell includes third primary particles, the particle size of the first primary particles is smaller than the particle size of the second primary particles, and the particle size of the first primary particles is smaller than the particle size of the third primary particles.

[0014] In this positive electrode material, the first core has a smaller primary particle size, constructs an efficient lithium ion transmission network, and has a fast lithium ion diffusion rate, giving the battery using this positive electrode material excellent specific capacity (such as 0.1C specific capacity greater than 290mAh / g) and rate performance (such as 1C specific capacity greater than 250mAh / g); the first intermediate layer and the first shell have a larger primary particle size, less gas release, weaker structural rearrangement and interface side reactions, and the higher nickel and cobalt content of the first shell significantly improves the interface stability. The battery using this positive electrode material has excellent cycle performance. This positive electrode material is based on the synergistic optimization of multi-level structural design and differentiated distribution of internal and external elements. Through the organic combination of microstructure regulation and composition design, it has the advantages of capacity, rate performance, and cycle performance.

[0015] According to an embodiment of the present application, 0.01≤b″-b≤0.02.

[0016] According to an embodiment of the present application, 0.01≤c″-c≤0.02.

[0017] According to an embodiment of the present application, 0.02≤dd″≤0.04.

[0018] According to an embodiment of the present application, the ratio of the radius R1 of the first core, the radius R2 of the first inner core, and the radius R of the positive electrode material particle is 1:(1-3]:[1.2-4].

[0019] According to an embodiment of the present application, 0.75≤R2 / R≤0.9.

[0020] According to an embodiment of the present application, the radius R1 of the first core is 1.5 μm to 3 μm.

[0021] According to an embodiment of the present application, the radius R2 of the first core is 3 μm to 4.5 μm.

[0022] According to an embodiment of the present application, the radius R of the positive electrode material particles is 3.5 μm to 6 μm.

[0023] According to an embodiment of the present application, the median particle size D of the positive electrode material particles is 50 7μm~12μm.

[0024] According to an embodiment of the present application, the first primary particles include spherical primary particles.

[0025] According to an embodiment of the present application, the particle size of the first primary particles is 80 nm to 120 nm.

[0026] According to an embodiment of the present application, the second primary particles and the third primary particles each independently include flake-shaped primary particles.

[0027] According to an embodiment of the present application, the major axis size of the second primary particles is 150 nm to 1500 nm, and the minor axis size is 50 nm to 150 nm.

[0028] According to an embodiment of the present application, the third primary particles have a major axis size of 150 nm to 1200 nm, and a minor axis size of 50 nm to 150 nm.

[0029] According to an embodiment of the present application, a ratio of an average aspect ratio of the third primary particles to an average aspect ratio of the second primary particles is 0.4-1.5:1.

[0030] According to an embodiment of the present application, the average aspect ratio of the second primary particles is greater than the average aspect ratio of the third primary particles.

[0031] According to an embodiment of the present application, the aspect ratio of the second primary particles is 1 to 10:1.

[0032] According to an embodiment of the present application, the average aspect ratio of the second primary particles is 4 to 7:1.

[0033] According to an embodiment of the present application, the aspect ratio of the third primary particles is 1 to 8:1.

[0034] According to an embodiment of the present application, the average aspect ratio of the third primary particles is 3 to 6:1.

[0035] According to an embodiment of the present application, the porosity of the first core is greater than the porosity of the first shell.

[0036] According to an embodiment of the present application, the porosity of the first core is 15% to 25%.

[0037] According to an embodiment of the present application, the porosity of the first intermediate layer is 10% to 20%.

[0038] According to an embodiment of the present application, the porosity of the first shell is 5% to 15%.

[0039] According to an embodiment of the present application, the positive electrode material particles further include a buffer layer, the buffer layer being located between the first intermediate layer and the first outer shell, and the buffer layer meeting at least one of the following conditions:

[0040] The thickness of the buffer layer d is less than 500 nm;

[0041] The buffer layer includes plate-shaped primary particles.

[0042] According to an embodiment of the present application, the positive electrode material further includes a coating layer, which is located on at least a portion of the outer surface of the first shell and / or at least a portion of the outer surface of the first core not covered by the first shell.

[0043] According to the embodiment of the present application, the compaction density of the positive electrode material is 2.4 g / cm 3 ~2.6g / cm 3 .

[0044] According to the embodiment of the present application, the specific surface area of the positive electrode material is 1.5m 2 / g~2.0m 2 / g.

[0045] In a second aspect, the present application provides a positive electrode material precursor. According to an embodiment of the present application, the positive electrode material precursor includes precursor particles, wherein the precursor particles include: a second inner core, the second inner core including a second core and a second intermediate layer located on at least a portion of an outer surface of the second core, the second core including a compound represented by Formula 4, and the second intermediate layer including a compound represented by Formula 5; a second outer shell, the second outer shell located on at least a portion of a surface of the second inner core and including a compound represented by Formula 6;

[0046] Mn x Ni y Co z CO3 formula 4

[0047] Mn x' Ni y' Co z' (OH)2 Formula 5

[0048] Mn x” Ni y” Co z” (OH)2 Formula 6

[0049] Among them, 0.5≤x≤1, 0.05≤y≤0.45, 0.05≤z≤0.3, x+y+z=1;

[0050] 0.5≤x'≤1, 0.05≤y'≤0.45, 0.05≤z'≤0.3, x'+y'+z'=1;

[0051] 0.5≤x”≤1, 0.05≤y”≤0.45, 0.05≤z”≤0.3, x”+y”+z”=1;

[0052] x>x", y <y”,z<z”。

[0053] According to an embodiment of the present application, 0.02≤xx”≤0.04.

[0054] According to an embodiment of the present application, 0.01≤y″-y≤0.02.

[0055] According to an embodiment of the present application, 0.01≤z″-z≤0.02.

[0056] A third aspect of the present application provides a method for preparing the aforementioned positive electrode material precursor. According to an embodiment of the present application, the method comprises: subjecting a mixed salt solution containing nickel, cobalt, and manganese salts, a carbonate precipitant solution, and a first complexing agent solution to a first coprecipitation reaction at pH 1 to obtain a second core; subjecting the mixed salt solution, a hydroxide precipitant solution, and a second complexing agent solution to a second coprecipitation reaction at pH 2 to form a second intermediate layer on the surface of the second core to obtain a second inner core; and subjecting the mixed salt solution, the hydroxide precipitant solution, and the second complexing agent solution to a third coprecipitation reaction at pH 3 to form a second outer shell on the surface of the second inner core to obtain the positive electrode material precursor; wherein pH 2 > pH 3. This method can efficiently prepare the aforementioned positive electrode material precursor, has simple steps, is easy to operate, and is suitable for industrial production. Specifically, by setting pH 2 > pH 3, the deposition rates of nickel, cobalt, and manganese can be adjusted, thereby obtaining a positive electrode material precursor with a high nickel and cobalt content in the outer shell by simply changing the reaction conditions.

[0057] According to the embodiments of the present application, pH 1 is 7-9.

[0058] According to the embodiments of the present application, pH2 is 9-11.

[0059] According to the embodiments of the present application, pH2-pH3=0.4-0.5.

[0060] According to an embodiment of the present application, the temperatures of the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each independently 45° C. to 60° C.

[0061] According to an embodiment of the present application, after the first coprecipitation reaction and the third coprecipitation reaction, the method further comprises: sequentially aging, solid-liquid separation, washing, and drying the reaction slurry obtained by the coprecipitation reaction;

[0062] According to an embodiment of the present application, the aging time is 5 hours to 30 hours.

[0063] According to an embodiment of the present application, the concentration of the mixed salt solution is 0.2 mol / L to 6 mol / L, preferably 1 mol / L to 3 mol / L.

[0064] According to an embodiment of the present application, the concentrations of the carbonate precipitant solution and the hydroxide precipitant solution are independently 0.2 mol / L to 12 mol / L, preferably 1 mol / L to 6 mol / L.

[0065] According to an embodiment of the present application, the concentrations of the first complexing agent solution and the second complexing agent solution are independently 0.1 mol / L to 10 mol / L, preferably 0.2 mol / L to 6 mol / L.

[0066] According to an embodiment of the present application, the nickel salt includes at least one of nickel sulfate, nickel chloride and nickel nitrate.

[0067] According to an embodiment of the present application, the cobalt salt includes at least one of cobalt sulfate, cobalt chloride and cobalt nitrate.

[0068] According to an embodiment of the present application, the manganese salt includes at least one of sulfate, chloride and nitrate.

[0069] According to an embodiment of the present application, the carbonate precipitant includes at least one of sodium carbonate, potassium carbonate and lithium carbonate.

[0070] According to an embodiment of the present application, the hydroxide precipitant includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0071] According to an embodiment of the present application, the first complexing agent and the second complexing agent independently include at least one of ammonia water, ethylenediamine, ammonium bicarbonate, ammonium chloride, ammonium sulfate and ammonium nitrate.

[0072] In a fourth aspect, the present application provides a method for preparing the aforementioned positive electrode material. According to an embodiment of the present application, the method comprises: preparing a positive electrode material precursor using the method described above; performing a first mixing of the positive electrode material precursor, a lithium source, and a dopant, and performing a first sintering of the obtained first mixture to obtain a positive electrode material intermediate; performing a second mixing of the positive electrode material intermediate and a coating agent, and performing a second sintering of the obtained second mixture to obtain the positive electrode material. This method can quickly and efficiently prepare the aforementioned positive electrode material, has simple steps, is easy to operate, and the obtained positive electrode material has both capacity, rate performance, and cycle performance.

[0073] According to an embodiment of the present application, the first sintering includes a first stage sintering and a second stage sintering performed sequentially.

[0074] According to an embodiment of the present application, the temperature of the first sintering stage is 300°C to 500°C.

[0075] According to an embodiment of the present application, the holding time of the first sintering stage is 2 hours to 5 hours.

[0076] According to an embodiment of the present application, the temperature of the second sintering stage is 750°C to 950°C.

[0077] According to an embodiment of the present application, the holding time of the second sintering stage is 5 hours to 15 hours.

[0078] According to an embodiment of the present application, the temperature of the second sintering is 300°C to 700°C.

[0079] According to an embodiment of the present application, the holding time of the second sintering is 2 hours to 12 hours.

[0080] According to an embodiment of the present application, the doping element includes a compound containing element M, and the element M includes one or more of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P.

[0081] According to an embodiment of the present application, the coating agent includes AlF3, Al2O3, ZnO, MgO, Nb2O5, TiO2, V2O5, CuO, ZrO2, MoO3, WO3, Li3PO 4 , B2O3 or more.

[0082] According to an embodiment of the present application, the selected lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium chloride.

[0083] According to an embodiment of the present application, the molar ratio M of the M element in the dopant to the sum of the amounts of lithium element in the lithium source, nickel element in the positive electrode material precursor, cobalt element in the positive electrode material precursor, manganese element in the positive electrode material precursor and the M element: (Li+Ni+Co+Mn+M) is 0~0.05:2, preferably 0.001~0.01:2.

[0084] According to an embodiment of the present application, the molar ratio of the coating agent to the positive electrode material intermediate is 0 to 0.05:1, preferably 0.005 to 0.01:1.

[0085] According to an embodiment of the present application, the molar ratio Li:(Ni+Co+Mn+M) of the lithium element in the lithium source to the sum of the amounts of nickel element in the positive electrode material precursor, cobalt element in the positive electrode material precursor and manganese element in the positive electrode material precursor is 1.2~1.6:1.

[0086] In a fifth aspect of the present application, a lithium-ion battery is provided. According to an embodiment of the present application, the lithium-ion battery includes the aforementioned positive electrode material. As a result, the lithium-ion battery has a high capacity, good rate capability, and good cycle performance.

[0087] The sixth aspect of the present application provides an electrical device comprising the lithium-ion battery described in the fifth aspect of the present application. Thus, the electrical device has a longer battery life, better fast charging performance, and a longer service life. BRIEF DESCRIPTION OF THE DRAWINGS

[0088] Figure 1 This is a SEM photograph of the cross section of the positive electrode material precursor particles in Preparation Example 1 of the present application.

[0089] Figure 2 This is a SEM photograph of the cross section of the positive electrode material precursor particles in Comparative Preparation Example 1 of the present application.

[0090] Figure 3 This is a SEM photograph of the cross section of the positive electrode material particles in Example 1 of the present application.

[0091] Figure 4 This is a SEM photograph of the cross section of the positive electrode material particles in Comparative Example 1 of the present application. DETAILED DESCRIPTION

[0092] The embodiments of the present invention are described in detail below, and examples of the embodiments are shown in the accompanying drawings. The embodiments described below with reference to the accompanying drawings are exemplary and intended to be used to explain the present invention, but should not be understood as limiting the present invention.

[0093] This application is based on the inventor's discovery and understanding of the following facts and problems:

[0094] The inventors have found that the current lithium-rich manganese-based positive electrode materials either have a small primary particle size and a large specific surface area, a fast lithium ion diffusion rate, and excellent rate performance, but the large specific surface area will also lead to more gas release, structural rearrangement, and electrode-electrolyte interface side reactions, thereby affecting the cycle stability; or have a large primary particle size, low porosity, and a relatively small specific surface area, so the kinetic performance is weak and the rate performance is poor, but the gas release is less, the structural rearrangement and interface side reactions are weak, and the cycle performance is relatively better. In summary, the inventors believe that optimizing the relevant technologies of lithium-rich manganese-based positive electrode materials to achieve a balance between capacity, kinetics and cycle stability is a key research direction to promote their commercial application. In view of this, the inventors propose a positive electrode material and its preparation method that have both capacity, rate performance and cycle performance, a positive electrode material precursor and its preparation method, a lithium-ion battery and an electrical device.

[0095] In a first aspect, the present application provides a positive electrode material. According to an embodiment of the present application, the positive electrode material includes positive electrode material particles, wherein the positive electrode material particles include: a first inner core, the first inner core including a first core and a first intermediate layer located on at least a portion of an outer surface of the first core; the first core including a compound represented by Formula 1, the first intermediate layer including a compound represented by Formula 2; a first outer shell, the first outer shell located on at least a portion of a surface of the first inner core including a compound represented by Formula 3;

[0096] Li 1+a Ni b Co c Mn d M 1 e O2 Formula 1

[0097] Li 1+a' Ni b' Co c' Mn d' M 2 e' O2 Formula 2

[0098] Li 1+a” Ni b” Co c” Mn d” M 3 e” O2 Formula 3

[0099] Among them, 0.09 <a<0.23,0.0385<b<0.409,0.0385<c<0.2727,0.385<d<0.909,a+b+c+d+e=1;

[0100] 0.09 <a'<0.23,0.0385<b'<0.409,0.0385<c'<0.2727,0.385<d'<0.909,a'+b'+c'+d'+e'=1;

[0101] 0.09 <a”<0.23,0.0385<b”<0.409,0.0385<c”<0.2727,0.385<d”<0.909,a”+b”+c”+d”+e”=1;

[0102] b <b”,c<c”,d”<d;

[0103] M 1 、M 2 、M 3 Each independently includes at least one of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P;

[0104] The first core includes first primary particles, the first intermediate layer includes second primary particles, the first shell includes third primary particles, the particle size of the first primary particles is smaller than the particle size of the second primary particles, and the particle size of the first primary particles is smaller than the particle size of the third primary particles.

[0105] In this positive electrode material, the first core has a smaller primary particle size, constructs an efficient lithium ion transmission network, and has a fast lithium ion diffusion rate, giving the battery using this positive electrode material excellent specific capacity (such as 0.1C specific capacity greater than 290mAh / g) and rate performance (such as 1C specific capacity greater than 250mAh / g); the first intermediate layer and the first shell have a larger primary particle size, less gas release, weaker structural rearrangement and interface side reactions, and the higher nickel and cobalt content of the first shell significantly improves the interface stability. The battery using this positive electrode material has excellent cycle performance. This positive electrode material is based on the synergistic optimization of multi-level structural design and differentiated distribution of internal and external elements. Through the organic combination of microstructure regulation and composition design, it has the advantages of capacity, rate performance, and cycle performance.

[0106] According to the embodiments of the present application, in the positive electrode material particles, the first intermediate layer completely encapsulates the first core, and the first outer shell completely encapsulates the first intermediate layer. This improves the performance of the positive electrode material. However, it is understood that in the actual preparation process, there may be certain fluctuations or limitations, and it is possible that in some positive electrode material particles, the first intermediate layer does not completely encapsulate the first core, and the first outer shell does not completely include the first inner core.

[0107] According to the embodiments of the present application, a can specifically be 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, etc.; b can specifically be 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.408, etc.; c can specifically be 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.27, etc.; d can specifically be 0.39, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, etc.

[0108] According to the embodiments of the present application, a' can be specifically 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, etc.; b' can be specifically 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.408, etc.; c' can be specifically 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.27, etc.; d' can be specifically 0.39, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, etc.

[0109] According to the embodiments of the present application, a" can be specifically 0.1, 0.12, 0.14, 0.16, 0.18, 0.2, 0.22, etc.; b" can be specifically 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.408, etc.; c" can be specifically 0.039, 0.05, 0.1, 0.15, 0.2, 0.25, 0.27, etc.; d" can be specifically 0.39, 0.4, 0.45, 0.5, 0.55, 0.6, 0.65, 0.7, 0.8, 0.85, 0.9, etc.

[0110] According to an embodiment of the present application, 0.01≤b″-b≤0.02. Specifically, b″-b can be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, etc.

[0111] According to an embodiment of the present application, 0.01≤c″-c≤0.02. Specifically, c″-c can be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, etc.

[0112] According to an embodiment of the present application, 0.02≤dd″≤0.04. Specifically, dd″ can be 0.02, 0.022, 0.024, 0.026, 0.028, 0.03, 0.032, 0.034, 0.036, 0.038, 0.04, etc.

[0113] The nickel, cobalt and manganese elements in the first core and the first shell are within the above-mentioned content difference range. The nickel and cobalt content in the first core can make it have higher capacity and better rate performance, while the nickel and cobalt content in the first shell is higher than that in the first core, which significantly improves its interface stability, thereby making the battery using this positive electrode material have the advantages of capacity, rate performance and cycle performance, and better comprehensive performance.

[0114] According to an embodiment of the present application, in the positive electrode material, the first core may include first primary particles, the first intermediate layer may include second primary particles, and the first shell may include third primary particles. As an example, the first core may be formed by agglomerating a plurality of first primary particles, the first intermediate layer may be formed by agglomerating a plurality of second primary particles, and the first shell may be formed by agglomerating a plurality of third primary particles.

[0115] It can be understood that primary particles refer to the smallest independent units that constitute agglomerates.

[0116] According to an embodiment of the present application, the first primary particles include spherical primary particles, thereby enabling dense stacking of the first primary particles, thereby facilitating increased lithium ion transfer rate, thereby facilitating increased capacity and rate capability of the positive electrode material.

[0117] According to an embodiment of the present application, the particle size of the first primary particles can be 80 nm to 120 nm, specifically 80 nm, 85 nm, 90 nm, 95 nm, 100 nm, 105 nm, 110 nm, 115 nm, 120 nm, etc. Within this particle size range, the nanoscale primary particles of the first core form an efficient lithium ion transport network, which is beneficial to improving the capacity and rate performance of the positive electrode material.

[0118] According to an embodiment of the present application, the second primary particles and the third primary particles each independently comprise flaky primary particles. Thus, the flaky primary particles can be arranged in an orderly manner along the radial direction of the positive electrode material particles to form a radial structure, which has better structural stability, less gas release, and less structural rearrangement and interfacial side reactions, thereby improving the cycling performance of batteries using this positive electrode material.

[0119] According to an embodiment of the present application, the major axis size of the second primary particle can be 150nm~1500nm, specifically 150nm, 250nm, 350nm, 450nm, 550nm, 650nm, 750nm, 850nm, 950nm, 1050nm, 1150nm, 1250nm, 1350nm, 1450nm, 1500nm, etc.; the minor axis size of the second primary particle can be 50nm~150nm, specifically 50nm, 80nm, 100nm, 120nm, 150nm, etc.

[0120] According to an embodiment of the present application, the major axis size of the third primary particle can be 150nm~1200nm, specifically such as 150nm, 250nm, 350nm, 450nm, 550nm, 650nm, 750nm, 850nm, 950nm, 1050nm, 1150nm, 1200nm, etc.; the minor axis size of the third primary particle can be 50nm~150nm, specifically such as 50nm, 80nm, 100nm, 120nm, 150nm, etc.

[0121] In this article, the particle size of primary particles can be measured by analyzing the particle size statistics of scanning electron microscope images. Specifically, the particle size of a spherical particle is the diameter; the major axis of a flake-shaped primary particle is the maximum distance between any two points on its contour line, and the minor axis is the minimum distance between any two points on its contour line.

[0122] According to an embodiment of the present application, the ratio of the average aspect ratio of the third primary particles to the average aspect ratio of the second primary particles is 0.4 to 1.5:1, specifically, 0.4:1, 0.5:1, 0.6:1, 0.7:1, 0.8:1, 0.9:1, 1:1, 1.1:1, 1.2:1, 1.3:1, 1.4:1, 1.5:1, etc. This can further improve the overall performance of the positive electrode material.

[0123] According to an embodiment of the present application, the average aspect ratio of the second primary particles is greater than the average aspect ratio of the third primary particles. The longer aspect ratio of the second primary particles helps slow side reactions and improve structural stability during cycling; the shorter aspect ratio of the third primary particles helps shorten the lithium ion diffusion path and improve the lithium ion transfer rate.

[0124] According to an embodiment of the present application, the aspect ratio of the second primary particles is 1 to 10:1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, 9:1, 10:1, etc.

[0125] According to an embodiment of the present application, the average aspect ratio of the second primary particles is 4 to 7:1, specifically 4:1, 4.5:1, 5:1, 5.5:1, 6:1, 6.5:1, 7:1, etc.

[0126] According to an embodiment of the present application, the aspect ratio of the third primary particles is 1 to 8:1, specifically 1:1, 2:1, 3:1, 4:1, 5:1, 6:1, 7:1, 8:1, etc.

[0127] According to an embodiment of the present application, the average aspect ratio of the third primary particles is 3 to 6:1, specifically 3:1, 3.5:1, 4:1, 4.5:1, 5:1, 5.5:1, 6:1, etc.

[0128] The aspect ratio of the second primary particles to the third primary particles is within the above range, which can further improve the overall performance of the positive electrode material.

[0129] In this article, the aspect ratio of a primary particle refers to the ratio of the longest diameter passing through the interior of the particle to the shortest diameter perpendicular to it. It can be detected by statistical analysis of scanning electron microscope images. The average aspect ratio can be obtained by calculating the aspect ratios of all particles in a photo and taking the average value.

[0130] According to an embodiment of the present application, the ratio of the radius R1 of the first core, the radius R2 of the first inner core, and the radius R of the positive electrode material particle is 1:(1-3]:[1.2-4]. Specifically, such as 1:1.05:1.2, 1:1.1:1.5:1:1.5:2, 1:2:3, 1:3:4, etc. Within the above ratio range, the capacity, rate performance, and cycle performance can be better balanced, thereby improving the comprehensive performance of the positive electrode material.

[0131] In some embodiments, 0.75≤R2 / R≤0.9. Specifically, R2 / R can be 0.75, 0.78, 0.8, 0.82, 0.85, 0.88, 0.9, etc. Thus, the thickness of the first shell is appropriate, and the overall performance of the positive electrode material is better. It is neither too thin to significantly improve the surface stability, nor too thick to affect the lithium ion transmission rate and capacity.

[0132] In some embodiments, the radius R1 of the first core is 1.5 μm to 3 μm (specifically, 1.5 μm, 1.6 μm, 1.7 μm, 1.8 μm, 1.9 μm, 2 μm, 2.1 μm, 2.2 μm, 2.3 μm, 2.4 μm, 2.5 μm, 2.6 μm, 2.7 μm, 2.8 μm, 2.9 μm, 3 μm, etc.); the radius R2 of the first core is 3 μm to 4.5 μm (specifically, 3 μm, 3.1 μm, 3.2 μm, The positive electrode material particles have a radius R of 3.5 μm to 6 μm (specifically, 3.5 μm, 3.5 μm, 4 μm, 4.2 μm, 4.5 μm, 4.8 μm, 5 μm, 5.2 μm, 5.5 μm, 5.8 μm, 6 μm, etc.). When the above radius range is met, the positive electrode material particles can be densely packed, thereby increasing the compaction density of the positive electrode material and facilitating lithium ion transmission, thereby improving rate performance.

[0133] Herein, the radius R1 of the first core, the radius R2 of the first inner core, and the radius R of the positive electrode material particle can be detected by scanning electron microscope images of the cross section of the positive electrode material particle.

[0134] According to an embodiment of the present application, the median particle size D of the positive electrode material particles is 50 The median particle size is 7 μm to 12 μm, specifically 7 μm, 7.5 μm, 8 μm, 8.5 μm, 9 μm, 9.5 μm, 10 μm, 10.5 μm, 11 μm, 11.5 μm, 12 μm, etc. When the above median particle size range is met, the positive electrode material particles can be densely packed, thereby facilitating the improvement of the compaction density of the positive electrode material, while facilitating the transport of lithium ions, thereby improving the rate performance.

[0135] In this paper, in the particle size distribution, the median particle size D 50 Also called the median particle size, it means that 50% of the volume of the positive electrode material has a particle size less than or equal to this value, and 50% of the volume of the positive electrode material has a particle size greater than this value. 50 The measurement can be performed using a Malvern particle size tester: the positive electrode material is dispersed in a dispersant (pure water, ethanol, acetone or other surfactants), ultrasonicated for 30 minutes, and then the sample is added to the Malvern particle size tester to start the test.

[0136] According to the embodiments of the present application, the porosity of the first core is greater than that of the first shell. The higher porosity of the first core indicates that the primary particles are more loosely packed together. The larger porosity inside provides a larger specific surface area, which is beneficial for lithium ion transport and improves specific capacity and rate performance. The smaller porosity and specific surface area of the shell help reduce the contact area with the electrolyte, improve interfacial stability and structural cycling stability, reduce side reactions, and thus improve cycling performance.

[0137] According to an embodiment of the present application, the porosity of the first core is 15% to 25%, specifically such as 15%, 16%, 17%, 18%, 19%, 20%, 21%, 22%, 3%, 24%, 25%, etc.; the porosity of the first intermediate layer can be 10% to 20%, specifically such as 10%, 11%, 12%, 13%, 14%, 15%, 16%, 17%, 18%, 19%, 20%, etc.; the porosity of the first shell is 5%% to 15%, specifically such as 5%, 6%, 7%, 8%, 9%, 10%, 11%, 12%, 13%, 14%, 15%, etc. Within the above porosity range, the higher porosity of the first core indicates that the primary particles are relatively loosely packed, and the larger internal porosity can provide a larger specific surface area, which is beneficial to lithium ion transmission and improves specific capacity and rate performance; the moderate porosity of the first intermediate layer is beneficial to increase the mechanical stability of the structure and improve the compaction density; the lower porosity of the first shell is beneficial to reduce the contact area with the electrolyte and improve the structural cycle stability; thereby further improving the comprehensive performance of the positive electrode material.

[0138] According to an embodiment of the present application, the positive electrode material particles further include a buffer layer located between the first intermediate layer and the first outer shell. The buffer layer can effectively alleviate structural stress caused by volume changes in the positive electrode material during cycling, thereby improving cycling performance.

[0139] According to an embodiment of the present application, the thickness d of the buffer layer is less than 500 nm. Specifically, the thickness d of the buffer layer can be 495 nm, 450 nm, 400 nm, 350 nm, 300 nm, 250 nm, 200 nm, etc. Thus, a good buffering effect can be provided while substantially not causing other negative effects.

[0140] According to an embodiment of the present application, the buffer layer includes flaky primary particles. As a result, the flaky primary particles can be arranged in an orderly manner along the radial direction of the positive electrode material particles to form a radial structure, which has better structural stability, less gas release, and weaker structural rearrangement and interfacial side reactions, thereby improving the cycle performance of batteries using this positive electrode material.

[0141] It can be understood that in some embodiments, the positive electrode material particles of the present application are composed of a first core, a first intermediate layer, a buffer layer and a first shell.

[0142] According to an embodiment of the present application, the positive electrode material particles may further include a coating layer, the coating layer being located on at least a portion of the outer surface of the first shell and / or at least a portion of the outer surface of the first core not covered by the first shell. Thus, surface coating can further improve the interfacial stability of the positive electrode material and further enhance cycling performance.

[0143] According to an embodiment of the present application, the material of the coating layer may include AlF3, Al2O3, ZnO, MgO, Nb2O5, TiO2, V2O5, CuO, ZrO2, MoO3, WO3, Li3PO 4 , B2O3. Thus, the interface stability of the positive electrode material can be further improved, the side reaction can be reduced, and the cycle performance can be improved.

[0144] It can be understood that in some embodiments, the positive electrode material particles of the present application are composed of a first core, a first intermediate layer, a buffer layer, a first shell and a coating layer.

[0145] According to the embodiment of the present application, the compaction density of the positive electrode material is 2.4 g / cm 3 ~2.6g / cm 3 , such as 2.4g / cm 3 , 2.42g / cm 3 , 2.44g / cm 3 , 2.46g / cm 3 , 2.48g / cm 3 , 2.5g / cm 3 , 2.52g / cm 3 , 2.54g / cm 3 , 2.56g / cm 3 , 2.58g / cm 3 , 2.6g / cm 3 Within the above compression density range, the battery using the positive electrode material can have a higher energy density.

[0146] According to the embodiment of the present application, the specific surface area of the positive electrode material is 1.5m 2 / g~2.0m 2 / g, such as 1.5m 2 / g, 1.6m 2 / g, 1.7m 2 / g, 1.8m 2 / g, 1.9m 2 / g, 2m 2 / g, etc. Within the above specific surface area range, the positive electrode material has a higher lithium ion surface structure stability, fewer side reactions, and better cycle performance.

[0147] It can be understood that the current preparation of lithium-rich manganese-based positive electrode materials is mainly to synthesize the precursor by co-precipitation method, and then prepare the final material by high-temperature solid-phase sintering. The inventors have found that in the above preparation process, the type of precursor has a significant effect on the microstructure and electrochemical properties of lithium-rich manganese-based positive electrode materials. At present, lithium-rich manganese-based positive electrode materials are generally prepared by high-temperature solid-phase sintering of carbonate precursors or hydroxide precursors. The lithium-rich manganese-based positive electrode materials prepared with carbonate precursors have a smaller primary particle size and a larger specific surface area, a fast lithium ion diffusion rate, and excellent rate performance, but a larger specific surface area will also lead to more gas release, structural rearrangement and electrode-electrolyte interface side reactions, thereby affecting the cycle stability. The lithium-rich manganese-based positive electrode material prepared with hydroxide precursors has a larger primary particle size, lower porosity, and relatively small specific surface area, so the kinetic performance is weaker and the rate performance is poor, but the gas release is less, the structural rearrangement and interface side reactions are weaker, and the cycle performance is relatively better. Based on the above, the inventors believe that hydroxide precursors and carbonate precursors each have their own advantages, and there is also a certain degree of complementarity. By organically combining the advantages of the two, achieving complementary advantages, and optimizing the preparation process of lithium-rich manganese-based positive electrode materials, a balance can be achieved between capacity, kinetics and cycle stability, and a positive electrode material with higher capacity, better kinetics and better cycle stability can be obtained.

[0148] In view of this, the second aspect of the present application provides a positive electrode material precursor. According to an embodiment of the present application, the positive electrode material precursor includes precursor particles, wherein the precursor particles include: a second inner core, the second inner core including a second core and a second intermediate layer located on at least a portion of the outer surface of the second core, the second core including a compound represented by Formula 4, and the second intermediate layer including a compound represented by Formula 5; a second outer shell, the second outer shell located on at least a portion of the surface of the second inner core, and including a compound represented by Formula 6;

[0149] Mn x Ni y Co z CO3 formula 4

[0150] Mn x' Ni y' Co z' (OH)2 Formula 5

[0151] Mn x” Ni y” Co z” (OH)2 Formula 6

[0152] Among them, 0.5≤x≤1, 0.05≤y≤0.45, 0.05≤z≤0.3, x+y+z=1;

[0153] 0.5≤x'≤1, 0.05≤y'≤0.45, 0.05≤z'≤0.3, x'+y'+z'=1;

[0154] 0.5≤x”≤1, 0.05≤y”≤0.45, 0.05≤z”≤0.3, x”+y”+z”=1;

[0155] x>x", y <y”,z<z”。

[0156] In the positive electrode material precursor, the second core is carbonate, the second intermediate layer and the second outer shell are hydroxide. When it is used to prepare the positive electrode material, the positive electrode material can inherit its three-layer structural characteristics, and the primary particles with smaller particle size formed by thermal decomposition of the carbonate can be tightly stacked, providing a fast lithium ion transmission channel, giving the positive electrode material a higher specific capacity and better rate performance, while the hydroxide can generate lamellar primary particles and arrange them in an orderly manner along the radial direction of the positive electrode material particles to form a radial structure, which can improve the interface stability of the positive electrode material and improve the cycle performance.

[0157] According to the embodiments of the present application, in the precursor particles, the second intermediate layer completely encapsulates the second core, and the second outer shell completely encapsulates the second intermediate layer. As a result, the performance of the positive electrode material precursor is improved. However, it is understood that there may be certain fluctuations or limitations in the actual preparation process, and there may be cases in which the second intermediate layer in some precursor particles does not completely encapsulate the second core, and the second outer shell does not completely include the second inner core.

[0158] According to the embodiments of the present application, x can be 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, etc., y can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, etc.; z can be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc.

[0159] According to the embodiments of the present application, x' can be specifically 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, etc., y' can be specifically 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, etc.; z' can be specifically 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc.

[0160] According to the embodiments of the present application, x" can specifically be 0.5, 0.6, 0.7, 0.8, 0.9, 0.99, etc., y" can specifically be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, 0.35, 0.4, 0.45, etc.; z" can specifically be 0.05, 0.1, 0.15, 0.2, 0.25, 0.3, etc.

[0161] According to an embodiment of the present application, 0.02≤xx”≤0.04. Specifically, xx” can be 0.02, 0.022, 0.024, 0.026, 0.028, 0.03, 0.032, 0.034, 0.036, 0.038, 0.04, etc.

[0162] According to an embodiment of the present application, 0.01≤y″-y≤0.02. Specifically, y″-y can be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, etc.

[0163] According to an embodiment of the present application, 0.02≤z″-z≤0.04. Specifically, z″-z can be 0.01, 0.011, 0.012, 0.013, 0.014, 0.015, 0.016, 0.017, 0.018, 0.019, 0.02, etc.

[0164] The nickel, cobalt and manganese elements in the second core and the second shell are within the above-mentioned content difference range. The nickel and cobalt content in the second core can make it have higher capacity and better rate performance, while the nickel and cobalt content in the second shell is higher than that in the second core, which significantly improves its interface stability. Therefore, when used to prepare positive electrode materials, it can have the advantages of capacity, rate performance and cycle performance, and has better comprehensive performance.

[0165] It can be understood that the cathode material precursor of the second aspect of the present application can be used to prepare the cathode material of the first aspect of the present application.

[0166] A third aspect of the present application provides a method for preparing the aforementioned positive electrode material precursor. According to an embodiment of the present application, the method comprises: subjecting a mixed salt solution containing nickel salt, cobalt salt, and manganese salt, a carbonate precipitant solution, and a first complexing agent solution to a first coprecipitation reaction at pH 1 to obtain a second core; subjecting the mixed salt solution, a hydroxide precipitant solution, and a second complexing agent solution to a second coprecipitation reaction at pH 2 to form a second intermediate layer on the surface of the second core to obtain a second inner core; and subjecting the mixed salt solution, the hydroxide precipitant solution, and the second complexing agent solution to a third coprecipitation reaction at pH 3 to form a second outer shell on the surface of the second inner core to obtain the positive electrode material precursor; wherein pH 2 > pH 3. This method can efficiently prepare the aforementioned positive electrode material precursor, has simple steps, is easy to operate, and is suitable for industrial production. Specifically, by setting pH 2 > pH 3, the deposition rates of nickel, cobalt, and manganese can be adjusted, thereby obtaining a positive electrode material precursor with a high nickel and cobalt content in the outer shell by simply changing the reaction conditions.

[0167] According to the embodiments of the present application, pH1 is 7 to 9, specifically 7, 7.2, 7.4, 7.6, 7.8, 8, 8.2, 8.4, 8.6, 8.8, 9, etc.

[0168] According to the embodiments of the present application, pH2 is 9 to 11, specifically 9, 9.2, 9.4, 9.6, 9.8, 10, 10.2, 10.4, 10.6, 10.8, 11, etc.

[0169] According to the embodiments of the present application, pH2-pH3=0.4-0.5, specifically 0.41, 0.42, 0.43, 0.44, 0.45, 0.46, 0.47, 0.48, 0.49, 0.5, etc.

[0170] Within the above pH range, the coprecipitation reaction can proceed smoothly, with a fast reaction rate and a high raw material utilization rate. In addition, the particle size and morphology of the obtained precursor are suitable, which is beneficial to improving the comprehensive performance of the positive electrode material.

[0171] According to an embodiment of the present application, the temperature of the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each independently 45°C to 60°C, specifically 45°C, 46°C, 47°C, 48°C, 49°C, 50°C, 51°C, 52°C, 53°C, 54°C, 55°C, 56°C, 57°C, 58°C, 59°C, 60°C, etc. Within the above temperature range, the reaction rate is fast, the reaction is sufficient, and side reactions are few.

[0172] It is understood that after the coprecipitation reaction is completed, what is directly obtained is a mixed solution containing the target product. According to an embodiment of the present application, after the first coprecipitation reaction and after the third coprecipitation reaction, it also includes: the reaction slurry obtained by the coprecipitation reaction is aged, filter pressed, washed and dried in sequence. That is to say, after the first coprecipitation reaction, aging, filter press, washing and drying are carried out in sequence; after the third coprecipitation reaction, aging, filter press, washing and drying are also carried out in sequence. Thus, aging can promote the growth and homogenization of precipitated particles, enhance the crystallinity of the precipitate, promote the removal of impurities, improve the chemical stability of the precipitate and optimize the morphology and structure of the precipitate, filter press can perform solid-liquid separation and separate the precipitated particles, washing can remove residues on the surface of the precipitated particles, and drying can dry out moisture and remove impurities such as solvents that can be removed.

[0173] According to the embodiments of the present application, the aging time is 5 hours to 30 hours, specifically 5 hours, 8 hours, 10 hours, 12 hours, 15 hours, 18 hours, 20 hours, 22 hours, 25 hours, 28 hours, 30 hours, etc. Within the above time range, the growth and homogenization of the precipitated particles can be ensured, and the obtained precipitated particles have suitable particle size and morphology, high cleanliness, and good stability.

[0174] According to an embodiment of the present application, the nickel salt includes at least one of nickel sulfate, nickel chloride and nickel nitrate.

[0175] According to an embodiment of the present application, the cobalt salt includes at least one of cobalt sulfate, cobalt chloride and cobalt nitrate.

[0176] According to an embodiment of the present application, the manganese salt includes at least one of sulfate, chloride and nitrate.

[0177] According to an embodiment of the present application, the concentration of the mixed salt solution is 0.2mol / L~6mol / L, specifically 1mol / L~3mol / L, more specifically 0.2mol / L, 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 3.5mol / L, 4mol / L, 4.5mol / L, 5.5mol / L, 6mol / L, etc.

[0178] It can be understood that the concentration of the above-mentioned mixed salt solution refers to the sum of the concentrations of nickel salt, cobalt salt and manganese salt, and the molar ratio of nickel salt, cobalt salt and manganese salt can be formulated according to the molar ratio of nickel, cobalt and manganese elements in the positive electrode material precursor.

[0179] According to an embodiment of the present application, the carbonate precipitant includes at least one of sodium carbonate, potassium carbonate and lithium carbonate.

[0180] According to an embodiment of the present application, the hydroxide precipitant includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide.

[0181] According to an embodiment of the present application, the concentrations of the carbonate precipitant solution and the hydroxide precipitant solution are each independently 0.2 mol / L to 12 mol / L, specifically 1 mol / L to 6 mol / L, more specifically 0.2 mol / L, 0.5 mol / L, 1 mol / L, 1.5 mol / L, 2 mol / L, 2.5 mol / L, 3 mol / L, 3.5 mol / L, 4 mol / L, 4.5 mol / L, 5.5 mol / L, 6 mol / L, 6.5 mol / L, 7 mol / L, 7.5 mol / L, 8 mol / L, 8.5 mol / L, 9 mol / L, 9.5 mol / L, 10 mol / L, 10.5 mol / L, 11 mol / L, 11.5 mol / L, 12 mol / L, etc.

[0182] According to an embodiment of the present application, the first complexing agent and the second complexing agent independently include at least one of ammonia water, ethylenediamine, ammonium bicarbonate, ammonium chloride, ammonium sulfate and ammonium nitrate.

[0183] According to an embodiment of the present application, the concentrations of the first complexing agent solution and the second complexing agent solution are each independently 0.1mol / L to 10mol / L, specifically 0.2mol / L to 6mol / L, more specifically 0.2mol / L, 0.5mol / L, 1mol / L, 1.5mol / L, 2mol / L, 2.5mol / L, 3mol / L, 3.5mol / L, 4mol / L, 4.5mol / L, 5.5mol / L, 6mol / L, 6.5mol / L, 7mol / L, 7.5mol / L, 8mol / L, 8.5mol / L, 9mol / L, 9.5mol / L, 10mol / L, etc.

[0184] In a fourth aspect, the present application provides a method for preparing the aforementioned positive electrode material. According to an embodiment of the present application, the method comprises: preparing a positive electrode material precursor using the method described above; performing a first mixing of the positive electrode material precursor, a lithium source, and a dopant, and performing a first sintering of the obtained first mixture to obtain a positive electrode material intermediate; performing a second mixing of the positive electrode material intermediate and a coating agent, and performing a second sintering of the obtained second mixture to obtain the positive electrode material. This method can quickly and efficiently prepare the aforementioned positive electrode material, has simple steps, is easy to operate, and the obtained positive electrode material has both capacity, rate performance, and cycle performance.

[0185] According to the embodiments of the present application, the specific method of the first mixing is not particularly limited, and a high-speed mixer can be used to mix the positive electrode material precursor, the lithium source and the dopant.

[0186] According to an embodiment of the present application, the selected lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium chloride.

[0187] According to an embodiment of the present application, the molar ratio of lithium in the lithium source to the sum of the amounts of nickel in the positive electrode material precursor, cobalt in the positive electrode material precursor, and manganese in the positive electrode material precursor (Li:(Ni+Co+Mn+M)) is 1.2 to 1.6:1, specifically 1.2:1, 1.3:1, 1.4:1, 1.5:1, 1.6:1, etc. Within the above ratio range, the overall performance of the positive electrode material is improved.

[0188] According to an embodiment of the present application, the doping element includes a compound containing element M, and the element M includes one or more of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P.

[0189] According to an embodiment of the present application, the molar ratio M of the M element in the dopant to the sum of the amount of the lithium element in the lithium source, the nickel element in the positive electrode material precursor, the cobalt element in the positive electrode material precursor, the manganese element in the positive electrode material precursor, and the M element: (Li+Ni+Co+Mn+M) is 0 to 0.05:2, specifically 0.001 to 0.01:2, more specifically 0.001:2, 0.005:2, 0.01:2, 0.02:2, 0.03:2, 0.04:2, 0.05:2, etc. Within the above ratio range, it is beneficial to improve the comprehensive performance of the positive electrode material.

[0190] According to an embodiment of the present application, the first sintering includes a first stage sintering and a second stage sintering performed in sequence. Specifically, the temperature of the first stage sintering is 300°C to 500°C (such as 300°C, 320°C, 340°C, 360°C, 380°C, 400°C, 420°C, 440°C, 460°C, 480°C, 500°C, etc.); the holding time of the first stage sintering is 2h to 5h (specifically 2h, 2.5h, 3h, 3.5h, 4h, 4.5h, 5h, etc.); the second stage The sintering temperature is 750°C to 950°C (specifically, 750°C, 780°C, 800°C, 820°C, 840°C, 860°C, 880°C, 900°C, 920°C, 940°C, 950°C, etc.); the holding time of the second sintering stage is 5h to 15h (specifically, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, 13h, 14h, 15h, etc.). Within the above range, the lithium source can react with the precursor to generate a lithium-rich manganese-based positive electrode material, and the M element in the dopant can be doped into the lattice of the positive electrode material, which is conducive to obtaining a positive electrode material with a stable structure and better performance.

[0191] According to the embodiments of the present application, the specific method of the second mixing is not particularly limited, and a high-speed mixer can be used to mix the positive electrode material intermediate and the coating agent.

[0192] According to an embodiment of the present application, the coating agent includes AlF3, Al2O3, ZnO, MgO, Nb2O5, TiO2, V2O5, CuO, ZrO2, MoO3, WO3, Li3PO 4 As a result, the coating layer formed on the surface of the positive electrode material particles has better stability, fewer side reactions during application, and better cycle performance.

[0193] According to an embodiment of the present application, the molar ratio of the coating agent to the cathode material intermediate is 0 to 0.05:1, specifically 0.005 to 0.01:1, more specifically 0.005:1, 0.01:1, 0.02:1, 0.03:1, 0.04:1, 0.05:1, etc. Within the above ratio range, the overall performance of the cathode material is improved.

[0194] According to an embodiment of the present application, the temperature of the second sintering is 300°C to 700°C (specifically, 300°C, 350°C, 400°C, 450°C, 500°C, 550°C, 600°C, 650°C, 700°C, etc.); the holding time of the second sintering is 2h to 12h (specifically, 2h, 3h, 4h, 5h, 6h, 7h, 8h, 9h, 10h, 11h, 12h, etc.). Within the above temperature range, the coating agent can form a coating layer on the surface of the positive electrode material, thereby further improving the interfacial stability of the positive electrode material and improving the cycle performance.

[0195] In a fifth aspect of the present application, a lithium-ion battery is provided. According to an embodiment of the present application, the lithium-ion battery includes the aforementioned positive electrode material. As a result, the lithium-ion battery has a high capacity, good rate capability, and good cycle performance.

[0196] It is understood that there is no particular limitation on the specific type of the lithium-ion battery, which may be a primary battery or a secondary battery; the shape of the lithium-ion battery may be a cylindrical battery, a square battery, or a battery of any other shape, and according to the outer packaging classification, the lithium-ion battery may be a hard-shell battery, a soft-pack battery, etc.

[0197] Typically, a lithium-ion battery includes a positive electrode sheet, a negative electrode sheet, an electrolyte, and a separator. The positive electrode sheet, the negative electrode sheet, and the separator can be made into an electrode assembly through a winding or lamination process, and the electrode assembly and the electrolyte can be contained in an outer packaging. During the charge and discharge process of the lithium-ion battery, active ions are embedded and released back and forth between the positive electrode sheet and the negative electrode sheet. The electrolyte plays the role of conducting ions between the positive electrode sheet and the negative electrode sheet. The separator is set between the positive electrode sheet and the negative electrode sheet, mainly to prevent the positive and negative electrodes from short-circuiting, while allowing active ions to pass through.

[0198] In some embodiments, the positive electrode sheet may include a positive electrode current collector and a positive electrode active material layer disposed on at least one side of the positive electrode current collector. The positive electrode active material layer includes a positive electrode active material, a conductive agent, and a binder. The positive electrode current collector may include a metal foil, for example, the metal foil may be aluminum foil. The positive electrode active material may include the positive electrode material of the first aspect of the present application. The conductive agent may include acetylene black, single-walled carbon nanotubes, and conventional materials in the art. The binder may be polyvinylidene fluoride (PVDF) and conventional materials in the art.

[0199] In some embodiments, the negative electrode sheet may include a negative electrode current collector and a negative electrode active material layer disposed on at least one side of the negative electrode current collector. The negative electrode active material layer may include a negative electrode active material, a thickener, a conductive agent, and a binder. The negative electrode current collector may be a metal foil, for example, a copper foil. The negative electrode active material may include artificial graphite, natural graphite, a silicon-containing carbon-based composite material, a lithium-containing metal composite material, a lithium metal material, and a negative electrode active material commonly used in the art. The thickener may be a thickener sodium carboxymethyl cellulose (CMC-Na) and a conventional material in the art. The conductive agent may be acetylene black and a conventional material in the art. The binder may be styrene-butadiene rubber and a conventional material in the art.

[0200] In some embodiments, the separator can be a separator known in the art that can be used in lithium-ion batteries and is stable to the electrolyte used, such as a polyethylene separator, a polypropylene separator, a polyethylene / polypropylene composite separator, etc.

[0201] The sixth aspect of the present application provides an electrical device comprising the lithium-ion battery described in the fifth aspect of the present application. Thus, the electrical device has a longer battery life, better fast charging performance, and a longer service life.

[0202] In some embodiments, the lithium-ion battery can be used as a power source or as an energy storage unit for the electrical device. The electrical device may include, but is not limited to, mobile devices (e.g., mobile phones, laptops, etc.), electric vehicles (e.g., pure electric vehicles, hybrid electric vehicles, plug-in hybrid electric vehicles, electric bicycles, electric scooters, electric golf carts, electric trucks, etc.), electric trains, ships, satellites, energy storage systems, etc.

[0203] The embodiments of the present application are described in detail below.

[0204] Preparation Example 1

[0205] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.21:0.12 to prepare a mixed salt solution A with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 3 mol / L ammonia solution was prepared as a complexing agent solution C.

[0206] Solution A, B and C were introduced into the coprecipitation reactor at a certain flow rate to prepare the carbonate precursor. The reaction temperature was 55°C, pH 1 was controlled at 7.7, and the stirring speed was 1000 rpm. 50When the growth reaches 5 μm, the reaction is completed. The reactants are aged for 12 hours, filtered, washed and dried to obtain a carbonate precursor, whose chemical composition is Mn 0.67 Ni 0.21 Co 0.12 CO3.

[0207] Subsequently, the carbonate precursor is used as a seed crystal to grow a hydroxide intermediate layer and a shell on its outer layer.

[0208] Prepare 4 mol / L sodium hydroxide solution as precipitant solution D and 6 mol / L ammonia solution as complexing agent solution E.

[0209] Solutions A, D and E were introduced into an argon-protected reactor at a certain flow rate, and the front-end reaction and the back-end reaction were carried out in sequence. The conditions for the front-end reaction were: reaction temperature 55°C, pH2 controlled at 10.5, and stirring speed 1000 rpm. 50 When the growth reaches 9 μm, the reaction pH and rotation speed are adjusted to carry out the latter stage reaction. The latter stage reaction conditions include: reaction temperature 55 ° C, pH3 controlled at 10.1, stirring speed 800 rpm, when D 50 The reaction is completed when the growth reaches 10 μm. The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor S1, which is composed of Mn 0.68 Ni 0.20 Co 0.12 CO3@Mn 0.67 Ni 0.20 Co 0.13 (OH)2@Mn 0.65 Ni 0.22 Co 0.13 (OH)2, the cross-sectional SEM image of the cathode material precursor S1 is shown in Figure 1 The aspect ratio of the primary particles of the shell is 5.55:1.

[0210] like Figure 1 As shown in Figure 3, the cathode material precursor S1 consists of a core, an intermediate layer, and an outer shell. The core is a carbonate precursor with a small primary particle size, while the intermediate layer and the outer shell are hydroxide precursors and are arranged radially from the center to the outside. The porosity and average aspect ratio of the intermediate layer are significantly higher than those of the outer shell. In addition, elemental analysis shows that the inner and outer layers of S1 have a significant differential distribution of Ni, Co, and Mn concentrations (see Table 3). The outer shell is characterized by high Ni and Co content and low Mn content.

[0211] Preparation Example 2

[0212] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.19:0.14 to prepare a mixed salt solution A1 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 3 mol / L ammonia solution was prepared as a complexing agent solution C.

[0213] Solutions A1, B and C were introduced into the coprecipitation reactor at a certain flow rate to prepare the carbonate precursor. The reaction temperature was 54°C, the pH was controlled at 7.6, and the stirring speed was 1000 rpm. 50 When the growth reaches 5.5 μm, the reaction is completed. After the reaction is completed, the reactants are aged for 12 hours, and then separated, washed and dried to obtain a carbonate precursor material, whose chemical composition is Mn 0.67 Ni 0.19 Co 0.14 CO3.

[0214] Subsequently, the carbonate precursor is used as a seed crystal to grow a hydroxide intermediate layer and an outer layer on its outer layer.

[0215] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.17:0.16 to prepare a mixed salt solution A2 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L sodium hydroxide solution was prepared as a precipitant solution D, and a 6 mol / L ammonia solution was prepared as a complexing agent solution E.

[0216] Solutions A2, D and E were introduced into an argon-protected reactor at a certain flow rate, and the front-end reaction and the back-end reaction were carried out in sequence. The conditions for the front-end reaction were: reaction temperature 54°C, pH2 controlled at 10.3, and stirring speed 1000 rpm. 50 When the growth reaches 9 μm, the reaction pH and rotation speed are adjusted to carry out the latter stage reaction. The latter stage reaction conditions include: reaction temperature 55 ° C, pH3 controlled at 9.9, stirring speed 800 rpm, when D 50 The reaction is completed when the cell grows to 10 μm.

[0217] The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor S2, which is composed of Mn 0.68 Ni 0.18 Co 0.14 CO3@Mn 0.67 Ni 0.18 Co 0.15 (OH)2@Mn 0.65 Ni 0.20 Co 0.15 (OH)2, the aspect ratio of the shell primary particles is 5.2:1.

[0218] Preparation Example 3

[0219] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.19:0.14 to prepare a mixed salt solution A1 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 3 mol / L ammonia solution was prepared as a complexing agent solution C.

[0220] Solutions A1, B and C were introduced into the coprecipitation reactor at a certain flow rate to prepare the carbonate precursor. The reaction temperature was 56°C, the pH was controlled at 7.4, and the stirring speed was 1000 rpm. 50 When the growth reaches 4.8 μm, the reaction is completed. After the reaction is completed, the reactants are aged for 12 hours, and then separated, washed and dried to obtain a carbonate precursor material with a chemical composition of Mn 0.67 Ni 0.17 Co 0.16 CO3.

[0221] Subsequently, the carbonate precursor is used as a seed crystal to grow a hydroxide intermediate layer and an outer layer on its outer layer.

[0222] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.17:0.16 to prepare a mixed salt solution A2 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L sodium hydroxide solution was prepared as a precipitant solution D, and a 6 mol / L ammonia solution was prepared as a complexing agent solution E.

[0223] Solutions A2, D and E were introduced into an argon-protected reactor at a certain flow rate, and the front-end reaction and the back-end reaction were carried out in sequence. The conditions for the front-end reaction were: reaction temperature 56°C, pH2 controlled at 10.0, and stirring speed 1000 rpm. 50 When the growth reaches 9.3 μm, the reaction pH and rotation speed are adjusted to carry out the latter stage reaction. The latter stage reaction conditions include: reaction temperature of 55 ° C, pH3 controlled at 9.55, stirring speed of 800 rpm, when D 50 The reaction is completed when the cell grows to 10 μm.

[0224] The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor S3, which is composed of Mn 0.68 Ni 0.16 Co 0.16 CO3@Mn 0.67 Ni 0.16 Co 0.17 (OH)2@Mn0.65 Ni 0.18 Co 0.17 (OH)2, the aspect ratio of the primary particles of the shell is 4.8:1.

[0225] Preparation Example 4

[0226] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.19:0.14 to prepare a mixed salt solution A1 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 3 mol / L ammonia solution was prepared as a complexing agent solution C.

[0227] Solutions A1, B and C were introduced into the coprecipitation reactor at a certain flow rate to prepare the carbonate precursor. The reaction temperature was 56°C, the pH was controlled at 7.4, and the stirring speed was 1000 rpm. 50 When the growth reaches 4.8 μm, the reaction is completed. After the reaction is completed, the reactants are aged for 12 hours, and then separated, washed and dried to obtain a carbonate precursor material with a chemical composition of Mn 0.67 Ni 0.17 Co 0.16 CO3.

[0228] Subsequently, the carbonate precursor is used as a seed crystal to grow a hydroxide intermediate layer and an outer layer on its outer layer.

[0229] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.17:0.16 to prepare a mixed salt solution A2 with a transition metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L sodium hydroxide solution was prepared as a precipitant solution D, and a 6 mol / L ammonia solution was prepared as a complexing agent solution E.

[0230] Solutions A2, D and E were introduced into an argon-protected reactor at a certain flow rate, and the front-end reaction and the back-end reaction were carried out in sequence. The conditions for the front-end reaction were: reaction temperature 56°C, pH2 controlled at 10.0, and stirring speed 1000 rpm. 50 When the growth reaches 8.2 μm, the reaction pH and rotation speed are adjusted to carry out the latter stage reaction. The latter stage reaction conditions include: reaction temperature 55 ° C, pH3 controlled at 9.55, stirring speed 800 rpm, when D 50 The reaction ends when the cell grows to 10.5 μm.

[0231] The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor S4, which is composed of Mn 0.68 Ni 0.16 Co 0.16CO3@Mn 0.67 Ni 0.16 Co 0.17 (OH)2@Mn 0.65 Ni 0.18 Co 0.17 (OH)2, the aspect ratio of the shell primary particles is 4.75:1.

[0232] Comparative Preparation Example 1

[0233] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.21:0.12 to prepare a mixed salt solution A with a transition metal ion concentration of 2 mol / L. Simultaneously, a 4 mol / L sodium hydroxide solution as a precipitant solution B and a 6 mol / L ammonia solution as a complexing agent solution C were prepared.

[0234] Solutions A, B and C were introduced into an argon-protected reactor at a certain flow rate to synthesize the precursor. The reaction conditions were as follows: reaction temperature 55°C, pH 10.5, and stirring speed 1000 rpm. 50 The reaction was completed when the growth reached 10.0 μm.

[0235] The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor C1, which is composed of Mn 0.67 Ni 0.21 Co 0.12 (OH)2. The cross-sectional SEM image of the cathode material precursor C1 is shown in FIG. Figure 2 As shown, the structure of the cathode material precursor is uniform and does not show obvious core-shell structure distribution characteristics.

[0236] Comparative Preparation Example 2

[0237] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.21:0.12 to prepare a mixed salt solution A with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 0.4 mol / L ammonia solution was prepared as a complexing agent solution C.

[0238] Solutions A, B and C were introduced into the reactor at a certain flow rate to synthesize the precursor. The reaction conditions were as follows: reaction temperature was 55°C, pH was controlled at 7.7, and stirring speed was 1000 rpm. 50 The reaction was completed when the growth reached 10.0 μm.

[0239] The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor C2, which is composed of Mn 0.67 Ni0.21 Co 0.12 CO3.

[0240] Comparative Preparation Example 3

[0241] Manganese sulfate, nickel sulfate, and cobalt sulfate were dissolved in deionized water at a molar ratio of Mn:Ni:Co = 0.67:0.21:0.12 to prepare a mixed salt solution A with a transition metal ion concentration of 2 mol / L. Simultaneously, a 2 mol / L sodium carbonate solution was prepared as a precipitant solution B, and a 3 mol / L ammonia solution was prepared as a complexing agent solution C.

[0242] Solution A, B and C were introduced into the coprecipitation reactor at a certain flow rate to prepare the carbonate precursor. The reaction temperature was 55°C, pH 1 was controlled at 7.7, and the stirring speed was 1000 rpm. 50 When the growth reaches 5 μm, the reaction is completed. The reactants are aged for 12 hours, filtered, washed and dried to obtain a carbonate precursor, whose chemical composition is Mn 0.67 Ni 0.21 Co 0.12 CO3.

[0243] Subsequently, the carbonate precursor is used as a seed crystal to grow hydroxide on its outer layer.

[0244] Prepare 4 mol / L sodium hydroxide solution as precipitant solution D and 6 mol / L ammonia solution as complexing agent solution E.

[0245] Solutions A, D and E were introduced into an argon-protected reactor at a certain flow rate, and the front-end reaction and the back-end reaction were carried out in sequence. The conditions for the front-end reaction were: reaction temperature 55°C, pH2 controlled at 10.5, and stirring speed 1000 rpm. 50 The reaction is completed when the growth reaches 10 μm. The slurry obtained by the above reaction is aged, filtered, washed and dried to obtain the positive electrode material precursor C3, which is composed of Mn 0.67 Ni 0.21 Co 0.12 CO3@Mn 0.67 Ni 0.21 Co 0.12 (OH)2.

[0246] Example 1

[0247] The precursor S1, lithium carbonate, tungsten oxide and molybdenum oxide were accurately weighed in a molar ratio of 0.99:1.5038:0.005:0.005 and mixed evenly in a high mixer. The molar amount of the precursor is calculated as the total molar amount of (Ni+Co+Mn). The molar amount of lithium carbonate is calculated as the molar amount of lithium element. The mixture obtained above was sintered in a muffle furnace. The sintering system is: heating to 500°C at 5°C / min, keeping warm for 4h, then heating to 900°C at 1.33°C / min, keeping warm for 10h, and finally cooling to room temperature with the furnace. After sintering, the product was screened to obtain a positive electrode material intermediate.

[0248] The cathode material intermediate, aluminum oxide, and magnesium fluoride were precisely weighed at a molar ratio of 1:0.0015:0.0015 and mixed thoroughly in a high-speed mixer. The resulting mixture was then sintered in a muffle furnace at 550°C for 10 hours. After sintering, the product was screened and iron removed to obtain cathode material A1, the chemical composition of which is shown in Table 1.

[0249] The median particle size of the positive electrode material A1 is 9.8 μm. Particles with a diameter of 9.8 μm were selected for SEM characterization. The SEM photos are shown in Figure 3 .from Figure 3 As can be seen, the cathode material particles consist of a core, an intermediate layer, and an outer shell. The core, derived from a carbonate precursor, has relatively small primary particles, approximately 100 nm. The intermediate layer and outer shell are arranged radially outward from the center, with a buffer layer approximately 250 nm thick between them. The outer shell's primary particles have an aspect ratio of 5.53:1, similar to that of the precursor.

[0250] Composition analysis results (Table 3) show that the cathode material shell contains high levels of Ni and Co, while containing low levels of Mn, indicating that the cathode material inherits the elemental distribution characteristics of the precursor material. Reducing the Mn content in the cathode material shell helps suppress Mn dissolution caused by the Jan-Taylor effect, thereby improving the cycling stability of the cathode material shell.

[0251] Examples 2 to 8

[0252] The method of Example 1 was followed, except that the processes adopted were as shown in Table 1, and the structural parameters and electrochemical performance results were as shown in Table 2.

[0253] Comparative Example 1

[0254] The method of Example 1 is followed, except that the process adopted is shown in Table 1, and the structural parameters and electrochemical performance results are shown in Table 2. The cross-sectional SEM image of the positive electrode material prepared in Comparative Example 1 is shown in FIG. Figure 4 As shown, it has no obvious core-shell structure.

[0255] Comparative Example 2

[0256] The method of Example 1 was followed, except that the processes adopted were as shown in Table 1, and the structural parameters and electrochemical performance results were as shown in Table 2.

[0257] Comparative Example 3

[0258] The method of Example 1 was followed, except that the processes adopted were as shown in Table 1, and the structural parameters and electrochemical performance results were as shown in Table 2.

[0259] Table 1

[0260]

[0261]

[0262] Performance testing:

[0263] 1. Radius: obtained by SEM testing of the cross section of the cathode material particles. The scanning electron microscope model is S-4800 from HITAI, Japan.

[0264] 2. Aspect ratio, average aspect ratio: The aspect ratio is obtained by analyzing the SEM test results of the cross section of the positive electrode material particles. The average aspect ratio is obtained by calculating the aspect ratios of all particles in a photo and taking the average value.

[0265] 3. Primary particle size: obtained by SEM testing the cross section of the positive electrode material particles.

[0266] 4. Porosity parameters: measured by intelligent lithium battery material image analysis system.

[0267] 5. Median particle size D 50 : Measured by Malvern 3000 particle size analyzer.

[0268] 6. Compaction density: obtained by testing using Mitsubishi Chemical's MCP-PD51 tap density tester.

[0269] 7. Specific surface area test: measured using the Tri-star 3020 specific surface area analyzer from Micromeritics, USA.

[0270] 8. Electrical properties:

[0271] The above cathode materials were assembled into button cells for electrochemical performance testing.

[0272] Weigh and mix the positive electrode material, acetylene black, and polyvinylidene fluoride in a mass ratio of 92:5:3. Add an appropriate amount of NMP and stir evenly to form a positive electrode slurry. Apply it to aluminum foil and dry it. After roller pressing, cut it into small discs with a diameter of 12mm and dry it in a vacuum oven at 120°C overnight to obtain the positive electrode sheet.

[0273] The positive electrode was used as the working electrode, a polyethylene (PE) membrane with a thickness of 25 μm was used, and a lithium metal counter electrode with a diameter of 17 mm and a thickness of 1 mm was matched. 1 mol / L LiPF6 / EC-DEC (volume ratio 1:1) electrolyte was injected and CR2025 button cells were assembled in an argon glove box (H2O / O2 <0.1 ppm).

[0274] Capacity test conditions: After the prepared button battery is left to stand for 6 hours, charge and discharge at room temperature at 1C = 250mA / g, at 0.1C, in the voltage range of 2.5V to 4.6V, and record the discharge specific capacity.

[0275] Rate performance test: In the voltage range of 2.5V ~ 4.6V, charge and discharge cycles were carried out at 0.1C, 0.1C, 0.2C, 0.33C, 0.5C, 1C, and 2C conditions in sequence to test the specific capacity.

[0276] Cycle test conditions: After the battery is activated for two cycles at 0.1C and a voltage range of 2.5V to 4.6V, it is charged and discharged 80 times at a current density of 0.5C and a voltage range of 2.5V to 4.6V, and the capacity retention rate is recorded.

[0277] Table 2

[0278]

[0279]

[0280] Component Analysis:

[0281] The core-shell structure was analyzed using a field scanning electron microscope-energy dispersive spectroscopy system (SEM / EDS, model S-4800, accelerating voltage 15kV):

[0282] Sampling strategy: 6 representative sites were randomly selected in the core, middle layer and outer shell;

[0283] Test method: Quantitative analysis of the atomic percentage (at.%) of Ni, Co, and Mn elements by EDS point scanning mode;

[0284] Data processing: Calculate the average value of element content in each area

[0285] Table 3

[0286]

[0287] By comparing and analyzing the above embodiments and comparative examples, and combining the data results in Tables 1 to 3, the following conclusions can be drawn: This application constructs a positive electrode material with a core-shell structure and differentiated distribution of inner and outer layer elements by precisely controlling the synthesis process of the precursor and combining doping and coating strategies.

[0288] Specifically, the physicochemical characterization and electrochemical performance data in Table 2 demonstrate that the cores formed from the carbonate precursors used in Examples 1 to 6 possess high porosity. This high porosity corresponds to a larger specific surface area and lower compaction density, which facilitates increased lithium ion diffusion, resulting in superior specific capacity and rate performance of the prepared materials compared to the comparative example materials.

[0289] Furthermore, the introduction of a buffer layer between the intermediate layer and the outer shell of the positive electrode material helps mitigate the volume expansion and contraction caused by anisotropic changes in the lattice parameters during charge and discharge, thereby improving the mechanical stability of the material. Furthermore, the increased relative content of Ni and Co in the outer shell, while the reduced relative content of Mn, helps suppress octahedral structural distortion and manganese dissolution caused by the Jahn-Teller effect, thereby enhancing the structural stability of the material.

[0290] In summary, by coordinating the design of material morphology, structure, and element distribution, the mechanical properties and structural stability of the materials during recycling were improved. The recycling retention rates of the materials shown in Examples 1 to 6 all exceeded 90%, significantly higher than the 78% of the comparative example materials.

[0291] Therefore, this application, through the combined application of carbonate precursors and hydroxide precursors, overcomes the difficulty in balancing rate performance and cycle performance due to their own physical and chemical properties, significantly improving the overall electrochemical performance of the positive electrode material. In addition, through the design of the buffer layer structure and the regulation of the surface nickel, cobalt and manganese content, the mechanical and structural stability of the material is further improved, thereby improving its cycle life and the stability of its electrochemical performance.

[0292] In the description of the present invention, it should be understood that the terms "first" and "second" are used for descriptive purposes only and should not be understood to indicate or imply relative importance or implicitly specify the number of the technical features indicated. Therefore, a feature defined as "first" or "second" may explicitly or implicitly include at least one of such features. In the description of the present invention, "plurality" means at least two, for example, two, three, etc., unless otherwise specifically defined.

[0293] In the description of this specification, the reference terms "one embodiment", "some embodiments", "example", "specific example", or "some examples" mean that the specific features, structures, materials or characteristics described in conjunction with the embodiment or example are included in at least one embodiment or example of the present invention. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials or characteristics described can be combined in any one or more embodiments or examples in a suitable manner. In addition, those skilled in the art can combine and combine different embodiments or examples described in this specification and features of different embodiments or examples without contradiction.

[0294] Although the embodiments of the present invention have been shown and described above, it will be understood that the above embodiments are illustrative and are not to be construed as limitations on the present invention. A person skilled in the art may change, modify, replace and modify the above embodiments within the scope of the present invention.

Claims

1. A positive electrode material, characterized in that The positive electrode material particles include: A first inner core, the first inner core comprising a first core and a first intermediate layer located on at least a portion of an outer surface of the first core; the first core comprising a compound represented by Formula 1, and the first intermediate layer comprising a compound represented by Formula 2; a first shell, the first shell being located on at least a portion of the surface of the first core and comprising a compound represented by Formula 3; Li 1+a Ni b Co c Mn d M 1 e O2 Formula 1 Li 1+a' Ni b' Co c' Mn d' M 2 e' O2 formula 2 Li 1+a” Ni b” Co c” Mn d” M 3 e” O2 formula 3 Among them, 0.09 <a<0.23,0.0385<b<0.409,0.0385<c<0.2727,0.385<d<0.909,a+b+c+d+e=1;0.09<a'<0.23,0.0385<b'<0.409,0.0385<c'<0.2727,0.385<d'<0.909,a'+b'+c'+d'+e'=1;0.09<a”<0.23,0.0385<b”<0.409,0.0385<c”<0.2727,0.385<d”<0.909,a”+b”+c”+d”+e”=1;b<b”,c<c”,d”<d; M 1 、M 2 、M 3 Each independently includes at least one of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P; The first core includes first primary particles, the first intermediate layer includes second primary particles, the first shell includes third primary particles, the particle size of the first primary particles is smaller than the particle size of the second primary particles, and the particle size of the first primary particles is smaller than the particle size of the third primary particles.

2. The positive electrode material according to claim 1, characterized in that Meet at least one of the following conditions: 0.01≤b”-b≤0.02; 0.01≤c”-c≤0.02; 0.02≤dd”≤0.

04.

3. The positive electrode material according to claim 1, characterized in that The ratio of the radius R1 of the first core, the radius R2 of the first inner core, and the radius R of the positive electrode material particle is 1:(1-3]:[1.2-4]; Preferably, 0.75≤R2 / R≤0.

9.

4. The positive electrode material according to claim 1, characterized in that Meet at least one of the following conditions: The radius R1 of the first core is 1.5 μm to 3 μm; The radius R2 of the first core is 3 μm to 4.5 μm; The radius R of the positive electrode material particles is 3.5 μm to 6 μm.

5. The positive electrode material according to claim 1, characterized in that The median particle size D of the positive electrode material particles 50 7μm~12μm.

6. The positive electrode material according to claim 1, characterized in that Meet at least one of the following conditions: The first primary particles include spherical primary particles; The particle size of the first primary particles is 80 nm to 120 nm; The second primary particles and the third primary particles each independently comprise a flake-shaped primary particle; The second primary particles have a major axis size of 150 nm to 1500 nm and a minor axis size of 50 nm to 150 nm; The third primary particle has a major axis size of 150 nm to 1200 nm and a minor axis size of 50 nm to 150 nm; The ratio of the average aspect ratio of the third primary particles to the average aspect ratio of the second primary particles is 0.4 to 1.5:

1.

7. The positive electrode material according to claim 6, characterized in that The primary particles meet at least one of the following conditions: The average aspect ratio of the second primary particles is greater than the average aspect ratio of the third primary particles; The aspect ratio of the second primary particles is 1 to 10:1; The average aspect ratio of the second primary particles is 4 to 7:1; The aspect ratio of the third primary particles is 1 to 8:1; The average aspect ratio of the third primary particles is 3 to 6:

1.

8. The positive electrode material according to claim 1, characterized in that The porosity of the first core is greater than the porosity of the first shell.

9. The positive electrode material according to claim 1, characterized in that Meet at least one of the following conditions: The porosity of the first core is 15% to 25%; The porosity of the first intermediate layer is 10% to 20%; The porosity of the first shell is 5% to 15%.

10. The positive electrode material according to any one of claims 1 to 9, characterized in that The positive electrode material particles further include a buffer layer, which is located between the first intermediate layer and the first outer shell, and the buffer layer satisfies at least one of the following conditions: The thickness of the buffer layer d is less than 500 nm; The buffer layer includes plate-shaped primary particles.

11. The positive electrode material according to any one of claims 1 to 10, characterized in that Also comprising a covering layer, the covering layer being located on at least a portion of the outer surface of the first shell and / or at least a portion of the outer surface of the first core not covered by the first shell; Preferably, the coating layer includes AlF3, Al2O3, ZnO, MgO, Nb2O5, TiO2, V2O5, CuO, ZrO2, MoO3, WO3, Li3PO 4 , B2O3 or at least one of the following.

12. The positive electrode material according to claim 1, characterized in that Meet at least one of the following conditions: The compaction density of the positive electrode material is 2.4 g / cm 3 ~2.6g / cm 3 ; The specific surface area of the positive electrode material is 1.5 m 2 / g~2.0m 2 / g.

13. A cathode material precursor, characterized in that: include: a second inner core, the second inner core comprising a second core and a second intermediate layer located on at least a portion of an outer surface of the second core, the second core comprising a compound represented by Formula 4, and the second intermediate layer comprising a compound represented by Formula 5; a second shell, the second shell being located on at least a portion of the surface of the second core and comprising a compound represented by Formula 6; Mn x Ni y Co z CO3 formula 4 Mn x' Ni y' Co z' (OH)2 formula 5 Mn x” Ni y” Co z” (OH)2 Formula 6 Among them, 0.5≤x≤1, 0.05≤y≤0.45, 0.05≤z≤0.3, x+y+z=1; 0.5≤x'≤1, 0.05≤y'≤0.45, 0.05≤z'≤0.3, x'+y'+z'=1; 0.5≤x”≤1, 0.05≤y”≤0.45, 0.05≤z”≤0.3, x”+y”+z”=1; x>x”, y <y”,z<z”。 14. The cathode material precursor according to claim 13, characterized in that: Meet at least one of the following conditions: 0.02≤xx”≤0.04; 0.01≤y”-y≤0.02; 0.01≤z”-z≤0.

02.

15. A method for preparing the cathode material precursor according to claim 13 or 14, characterized in that: include: A mixed salt solution containing nickel salt, cobalt salt and manganese salt, a carbonate precipitant solution and a first complexing agent solution are subjected to a first coprecipitation reaction at pH 1 to obtain a second core; allowing the mixed salt solution, hydroxide precipitant solution, and second complexing agent solution to undergo a second coprecipitation reaction at pH 2 to form a second intermediate layer on the surface of the second core to obtain a second inner core; causing the mixed salt solution, the hydroxide precipitant solution, and the second complexing agent solution to undergo a third coprecipitation reaction at pH 3 to form a second shell on the surface of the second inner core, thereby obtaining the positive electrode material precursor; Among them, pH2>pH3.

16. The method according to claim 15, characterized in that Meet at least one of the following conditions: pH1 is 7-9; pH2 is 9-11; pH2-pH3=0.4~0.

5.

17. The method according to claim 15, characterized in that The temperatures of the first coprecipitation reaction, the second coprecipitation reaction, and the third coprecipitation reaction are each independently 45° C. to 60° C.

18. The method according to claim 15, characterized in that After the first coprecipitation reaction and the third coprecipitation reaction, the method further comprises: The reaction slurry obtained by the coprecipitation reaction is sequentially aged, filtered, washed and dried; Optionally, the aging time is 5 hours to 30 hours.

19. The method according to claim 16, wherein Meet at least one of the following conditions: The concentration of the mixed salt solution is 0.2 mol / L to 6 mol / L, preferably 1 mol / L to 3 mol / L; The concentrations of the carbonate precipitant solution and the hydroxide precipitant solution are independently 0.2 mol / L to 12 mol / L, preferably 1 mol / L to 6 mol / L; The concentrations of the first complexing agent solution and the second complexing agent solution are independently 0.1 mol / L to 10 mol / L, preferably 0.2 mol / L to 6 mol / L; The nickel salt includes at least one of nickel sulfate, nickel chloride and nickel nitrate; The cobalt salt includes at least one of cobalt sulfate, cobalt chloride and cobalt nitrate; The manganese salt includes at least one of sulfate, chloride and nitrate; The carbonate precipitant includes at least one of sodium carbonate, potassium carbonate and lithium carbonate; The hydroxide precipitant includes at least one of sodium hydroxide, potassium hydroxide and lithium hydroxide; The first complexing agent and the second complexing agent independently include at least one of ammonia water, ethylenediamine, ammonium bicarbonate, ammonium chloride, ammonium sulfate and ammonium nitrate.

20. A method for preparing the positive electrode material according to any one of claims 1 to 12, characterized in that: include: A cathode material precursor is prepared by the method according to any one of claims 15 to 19; performing a first mixing of the positive electrode material precursor, the lithium source and the dopant, and performing a first sintering on the obtained first mixture to obtain a positive electrode material intermediate; The positive electrode material intermediate and the coating agent are mixed for a second time, and the obtained second mixture is sintered for a second time to obtain the positive electrode material.

21. The method according to claim 20, characterized in that The first sintering includes a first stage sintering and a second stage sintering performed sequentially, and satisfies at least one of the following conditions: The temperature of the first sintering stage is 300°C to 500°C; The holding time of the first sintering stage is 2h to 5h; The temperature of the second sintering stage is 750°C to 950°C; The holding time of the second sintering stage is 5h to 15h; The second sintering temperature is 300° C. to 700° C.; The second sintering heat preservation time is 2h to 12h.

22. The method according to claim 20, characterized in that Meet at least one of the following conditions: The doping element includes a compound containing an element M, and the element M includes one or more of Mg, Al, Ca, K, Na, Ti, V, Cr, Fe, Cu, Zn, Zr, Nb, Mo, W, and P; The coating agent includes one or more of AlF3, Al2O3, ZnO, MgO, Nb2O5, TiO2, V2O5, CuO, ZrO2, MoO3, WO3, Li3PO4, and B2O3; The selected lithium source includes at least one of lithium carbonate, lithium hydroxide, lithium nitrate and lithium chloride.

23. The method according to claim 20, characterized in that Meet at least one of the following conditions: The molar ratio M of the M element in the dopant to the sum of the amounts of the lithium element in the lithium source, the nickel element in the positive electrode material precursor, the cobalt element in the positive electrode material precursor, the manganese element in the positive electrode material precursor, and the M element is (Li+Ni+Co+Mn+M) in the range of 0 to 0.05:2, preferably 0.001 to 0.01:2; The molar ratio of the coating agent to the positive electrode material intermediate is 0 to 0.05:1, preferably 0.005 to 0.01:1; The molar ratio Li:(Ni+Co+Mn+M) of the lithium element in the lithium source to the sum of the amounts of nickel element in the positive electrode material precursor, cobalt element in the positive electrode material precursor and manganese element in the positive electrode material precursor is 1.2-1.6:

1.

24. A lithium ion battery, characterized in that: The positive electrode material comprises the positive electrode material according to any one of claims 1 to 12.

25. An electrical device, characterized in that: Including the lithium ion battery according to claim 24.

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