Positive electrode material and preparation method and application thereof

Abstract

The invention relates to a positive electrode material and a preparation method and application thereof. The positive electrode material comprises secondary particles formed by aggregating primary particles; the size variable coefficient CV of the primary particles is less than or equal to 25%; the primary particles comprise an active material with a chemical formula of LiNixCoyMnzMkRjO2-aXa, x + y + z + k + j = 1, 0.8 < = x < = 0.98, 0.01 < = y < = 0.2, 0.01 < = z < = 0.2, 0 < = a < = 0.025, 0 < a + k < = 0.025, and 0 < j < = 0.01; m comprises one or more of W, Mo, Nb, Ta, Sn, Sb, Y, B and P; x comprises one or more of S and F; r comprises one or more of Zr, Al, Ti, Mg and Sr. Based on the specific doping modification, the size of the primary particles of the positive electrode material has a relatively low size variation coefficient, so that the stability of a crystal structure is enhanced while the size uniformity is improved, and the long-term cycle capacity retention rate of the positive electrode material is remarkably improved.

Description

Technical Field

[0001] This application relates to the field of lithium-ion batteries, and in particular to cathode materials, their preparation methods, and applications. Background Technology

[0002] The grain boundaries between primary particles in polycrystalline ternary cathode materials are weak links in lithium-ion transport. Uneven primary particle size can lead to significant differences in properties such as specific surface area, surface energy, and diffusion path. This can easily cause local polarization at high rates and phase transitions during cycling, resulting in decreased rate performance and capacity decay. Summary of the Invention

[0003] Based on this, this application provides a cathode material, its preparation method, and its application. This cathode material is formed from primary particles with a low coefficient of size variation, exhibiting high specific capacity and excellent long-term cycle capacity retention.

[0004] In a first aspect, this application provides a cathode material.

[0005] A cathode material includes secondary particles formed by the agglomeration of primary particles; the primary particles include those with the chemical formula LiNi. x Co y Mn z M k R j O 2-a X a The active material, wherein x+y+z+k+j=1, 0.8≤x≤0.98, 0.01≤y≤0.2, 0.01≤z≤0.2, 0≤a≤0.025, 0<a+k≤0.025, 0<j≤0.01; M includes one or more of W, Mo, Nb, Ta, Sn, Sb, Y, B, and P; X includes one or more of S and F; R includes one or more of Zr, Al, Ti, Mg, and Sr.

[0006] In some embodiments, M is one or more of W, Nb, Sn, and Sb.

[0007] In some implementations, 0.002 < a ≤ 0.008, 0.002 < k ≤ 0.01; and / or

[0008] R is one or more of Zr and Al.

[0009] In some embodiments, the average particle size of the primary particles is 100 nm to 800 nm.

[0010] In some embodiments, the coefficient of variation (CV) of the primary particle is ≤25%; and / or

[0011] (003) The proportion of crystal face orientation particles is ≥60%.

[0012] In a second aspect, this application provides a method for preparing the above-mentioned cathode material.

[0013] A method for preparing the above-mentioned cathode material includes the following steps:

[0014] The raw materials are mixed in molar ratio to prepare the first powder;

[0015] The first powder was sintered in an oxygen atmosphere;

[0016] The raw materials include a lithium source, a nickel-cobalt-manganese precursor, and a doping source; the doping source includes an R source, and at least one of an M source and an X source; the R source includes one or more of a Zr source, an Al source, a Ti source, a Mg source, and a Sr source; the M source includes one or more of a W source, a Mo source, a Nb source, a Ta source, a Sn source, a Sb source, a Y source, a B source, and a P source; and the X source includes one or more of a S source and a F source.

[0017] In some embodiments, the sintering process includes the following steps:

[0018] The first powder is subjected to a first sintering treatment to prepare the second powder;

[0019] The second powder is subjected to a second sintering treatment;

[0020] The temperature of the first sintering treatment is 700℃~800℃, and the time is 5h~10h;

[0021] The second sintering treatment is performed at a temperature of 850℃~950℃ for 12h~20h.

[0022] In a third aspect, this application provides a positive electrode sheet.

[0023] A positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, wherein the positive active layer contains the positive electrode material described above or the positive electrode material prepared by the preparation method described above.

[0024] In a fourth aspect, this application provides a battery comprising the aforementioned positive electrode.

[0025] In a fifth aspect, this application provides an electrical device including the battery described above.

[0026] Studies have found that the varying degrees of side reactions and stress experienced by primary particles of different sizes exacerbate the propagation of microcracks in the grain boundary structure, leading to increased interfacial impedance and capacity decay. The primary particles of the aforementioned cathode material include those with the chemical formula LiNi. x Coy Mn z M k R j O 2-a X a By using specific M and X doping elements to modify the cathode material, the uniformity of crystal growth and grain boundary migration can be improved. Simultaneously, the use of R doping elements helps to enhance the stability of the crystal structure while improving size uniformity. Based on these specific doping modifications, the primary particles of the cathode material exhibit a low coefficient of variation (CV), which helps to mitigate interfacial side reactions and stress differences caused by primary particles of different sizes. This results in a cathode material with high specific capacity while significantly improving its long-term cycle capacity retention. Attached Figure Description

[0027] To more clearly illustrate the technical solutions in the embodiments of this application, the accompanying drawings used in the description of the embodiments will be briefly introduced below. Obviously, the accompanying drawings described below are only some embodiments of this application. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.

[0028] Figure 1 This is a scanning electron microscope image of the primary particles of the cathode material in Example 3 of this application.

[0029] Figure 2 The results are from a single particle size test of the cathode material in Example 3 of this application.

[0030] Figure 3 This is a scanning electron microscope image of the primary particles of the cathode material of Comparative Example 1 of this application.

[0031] Figure 4 The results are from a single particle size test of the cathode material of Comparative Example 1 of this application. Detailed Implementation

[0032] To make the above-mentioned objectives, features, and advantages of this application more apparent and understandable, a detailed description of specific embodiments of this application is provided below. Many specific details are set forth in the following description to provide a thorough understanding of this application. However, this application can be implemented in many other ways different from those described herein, and those skilled in the art can make similar modifications without departing from the spirit of this application. Therefore, this application is not limited to the specific embodiments disclosed below.

[0033] In the description of this application, "multiple" means at least two, such as two, three, etc., unless otherwise explicitly specified. In this application, "at least one" means one or more, such as one, two, or more than two. "Multiple" or "several" means at least two, such as two, three, etc.

[0034] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0035] When a numerical range is disclosed herein, the range is considered continuous and includes the minimum and maximum values ​​of the range, as well as every value between the minimum and maximum values. Furthermore, when the range refers to integers, it includes every integer between the minimum and maximum values ​​of the range. Additionally, when multiple ranges are provided to describe a feature or characteristic, the ranges may be combined. In other words, unless otherwise specified, all ranges disclosed herein should be understood to include any and all subranges to which they are incorporated.

[0036] Unless otherwise specified, all steps in this application may be performed sequentially or randomly. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the method may also include step (c), indicating that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0037] In this application, "above" or "below" includes the stated number. For example, "below 1" includes 1.

[0038] Unless otherwise specified, the temperature parameters in this application are permitted to be either constant-temperature treatment or variations within a certain temperature range. It should be understood that the constant-temperature treatment allows temperature fluctuations within the precision range of the instrument control, such as ±5℃, ±4℃, ±3℃, ±2℃, or ±1℃.

[0039] The grain boundaries between primary particles in polycrystalline ternary cathode materials are weak points for lithium-ion transport. Inhomogeneous primary particle sizes lead to significant differences in specific surface area, surface energy, and diffusion paths. For example, small-sized primary particles with high specific surface areas are prone to significant interfacial side reactions; large-sized primary particles have long diffusion paths, resulting in poor electrical performance at high rates and a higher likelihood of microcrack formation. Due to these issues, traditional cathode materials are prone to phase transitions during cycling and localized polarization at high rates, leading to decreased rate performance and capacity decay.

[0040] Currently, traditional technologies control the secondary particle size through spray drying or template methods, but these methods struggle to address the grain boundary problems caused by uneven primary particle size within the grain. Furthermore, introducing Al... 3+ Mg 2+ While cation doping stabilizes the crystal structure, its ability to control the primary particle size distribution is limited by other effects caused by the amount of doping, making it difficult to fundamentally solve the cycle decay caused by uneven grain size.

[0041] Based on this, the first aspect of this application provides a cathode material. This cathode material is formed from primary particles with a low coefficient of size variation and exhibits excellent long-term cycle capacity retention.

[0042] For example, one embodiment of this application provides a cathode material. The cathode material includes secondary particles formed by the agglomeration of primary particles. The size variation coefficient (CV) of the primary particles is ≤25%, and the primary particles include particles with the chemical formula LiNi. x Co y Mn z M k R j O 2-a X a The active material, wherein x+y+z+k+j=1, 0.8≤x≤0.98, 0.01≤y≤0.2, 0.01≤z≤0.2, 0≤a≤0.025, 0<a+k≤0.025, 0<j≤0.01; M includes one or more of W, Mo, Nb, Ta, Sn, Sb, Y, B, and P; X includes one or more of S and F; R includes one or more of Zr, Al, Ti, Mg, and Sr.

[0043] In the cathode material of this embodiment, by using specific M and X doping elements to modify the cathode material, the uniformity of crystal growth and grain boundary migration can be improved; at the same time, the use of R doping element helps to stabilize the crystal structure while improving size uniformity. Based on the above specific doping modification, the primary particles of the cathode material have a low coefficient of variation (CV), which helps to alleviate the differences in interfacial side reactions and stress caused by primary particles of different sizes, and significantly improves the long-term cycle capacity retention of the cathode material.

[0044] Understandably, x represents the amount of nickel doping in the active material. Optionally, the value of x can be, but is not limited to, 0.8, 0.82, 0.84, 0.86, 0.88, 0.9, 0.92, 0.84, 0.96, 0.98, or other values ​​within the range of 0.8 to 0.98. Maintaining a high nickel content helps provide high specific capacity and high energy density, but excessive content can easily lead to the formation of microcracks, which in turn leads to deterioration of cycle performance. This application, based on the combination of multiple doping elements, helps to alleviate the stability of the grain boundary structure in high-nickel-content active materials.

[0045] Understandably, y represents the amount of cobalt doping in the active material. Optionally, the value of y can be, but is not limited to, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.15, 0.2, or other values ​​in the range of 0.01 to 0.2. Maintaining a certain amount of cobalt doping helps reduce the cation mixing degree of the crystal lattice and helps improve conductivity and rate performance.

[0046] Understandably, z represents the amount of manganese doping in the active material. Optionally, the value of z can be, but is not limited to, 0.01, 0.02, 0.03, 0.04, 0.05, 0.1, 0.15, 0.2, or other values ​​in the range of 0.01 to 0.2. Maintaining a certain amount of manganese doping helps to obtain good cycle capacity retention.

[0047] Understandably, the active material is LiNi x’ Co y’ Mn z’ O2 is the base material, where x'+y'+z'=1. Doping elements replace some of these elements, thus doping LiNi. x’ Co y’ Mn z’ In the O2 lattice.

[0048] Understandably, k represents the doping amount of element M in the active material, and a represents the doping amount of element X in the active material. Optionally, the value of a+k can be, but is not limited to, 0.005, 0.01, 0.012, 0.014, 0.016, 0.018, 0.02, 0.025, or other values ​​within the range of 0 to 0.025. Maintaining a certain amount of manganese doping helps to obtain good cycle capacity retention. Studies have found that maintaining the doping of the aforementioned elements M and R helps to suppress crystal growth rate and regulate grain boundary migration behavior, thereby reducing the CV value of primary particles.

[0049] It can be understood that 0≤a≤0.025 indicates that the maximum value of k is 0.025 and the minimum value is 0.

[0050] Studies have shown that different inhibitors exhibit significant specificity in regulating the CV of primary particles due to differences in atomic radius, electronegativity, and properties relative to the active material.

[0051] In some embodiments, M includes one or more of a first type of doping element, a second type of doping element, a third type of doping element, and a fourth type of doping element.

[0052] The first type of doping elements includes W, Mo, Nb, and Ta. These first-type doping elements have relatively large atomic radii, similar to Ni in the active material. 2+ Mn 3+ Co 3+ The significant difference in ionic radii helps to reduce grain boundary energy, making grain growth rates more uniform and reducing the formation of abnormally large particles. Optionally, the amount of the first type of dopant added is 0%~0.625 at%.

[0053] Type II doping elements include Sn and Sb. The atomic radii of Type II doping elements are between those of Type I doping elements and Ni. 2+ Mn 3+ Co 3+ The difference in ionic radii also helps to reduce grain boundary energy, and when introduced together with type I dopants, it helps to further reduce the CV value. Optionally, the amount of type II dopants added is 0%~0.625 at%.

[0054] The third type of dopant includes Y, which can suppress grain growth and help reduce cation mixing and improve thermal stability. Optionally, the amount of the third type of dopant added is 0% to 0.1 at%.

[0055] The fourth type of doping element includes B and P. The fourth type of doping element helps to control the growth direction of the crystal, helps to promote the growth of high nickel materials along the (003) crystal plane, and makes the primary particles transform from plate-like to spherical, reducing the size inhomogeneity caused by the difference in crystal plane growth rate.

[0056] In some embodiments, M is one or more of W, Nb, Sn, and Sb. This ensures good lattice matching between the above-mentioned dopant element combination and the active material, resulting in better size control.

[0057] In some embodiments, X includes one or more of S and F, and adding a certain amount of X helps to make grain growth more uniform. Optionally, the amount of X added is 0% to 1 at%.

[0058] Understandably, j represents the doping amount of element R in the active material. Optionally, the value of j can be, but is not limited to, 0.001, 0.002, 0.003, 0.004, 0.005, 0.006, 0.007, 0.008, 0.009, 0.01, or other values ​​in the range of 0 to 0.01. Maintaining a certain amount of element R doping helps to obtain good cycling capacity retention.

[0059] In some of these implementations, R includes a fifth type of doping element and a sixth type of doping element.

[0060] The fifth type of doping element includes one or more of Zr and Ti. The radii of Zr and Ti are similar to those of the active material's metal ions, making them readily enter the crystal lattice to form solid solutions, thereby controlling the concentration of lattice defects. Zr doping increases the dislocation density in the crystal lattice, inhibiting excessively rapid grain growth, while Ti helps enhance the stability of the grain boundary structure. Optionally, the amount of the fifth type of doping element added is 0%~0.25 at%.

[0061] The sixth type of dopant includes one or more of Al, Mg, and Sr. Al doping helps reduce cation mixing and suppress irreversible phase transitions, thus improving cycle stability. Optionally, the amount of the sixth type of dopant added is 0–0.25 at%.

[0062] In some embodiments, R is one or more of Zr and Al. Studies have shown that the combination of Zr and Al with W, Nb, Sn, and Sb has a better effect and can effectively reduce the size variation coefficient of primary particles.

[0063] In some embodiments, 0.002 < a ≤ 0.008, 0.002 < k ≤ 0.01. Studies have shown that modification by combining one or more of W, Nb, Sn, and Sb with one or two of S and F can effectively reduce the size variation coefficient of primary particles.

[0064] In some embodiments, the coefficient of variation (CV) of the primary particles is ≤20%. Maintaining this coefficient of variation reduces stress concentration and microcrack formation between particles, and helps to construct more ordered lithium-ion diffusion channels, reducing the transport resistance of lithium ions within and between particles, thereby improving the rate performance and charge / discharge efficiency of the battery. Furthermore, primary particles with good size uniformity can better inherit the structural characteristics of the precursor during sintering, forming a more stable layered crystal structure, reducing lattice distortion and structural defects, and improving the thermal and chemical stability of the material. Further, the coefficient of variation (CV) of the primary particles is ≤15%.

[0065] In some embodiments, the average particle size of the primary particles is 100 nm to 800 nm. Optionally, the average particle size of the primary particles can be, but is not limited to, 100 nm, 200 nm, 300 nm, 400 nm, 500 nm, 600 nm, 700 nm, 800 nm, or other values ​​within the range of 100 nm to 800 nm. Maintaining the above-mentioned average particle size range of the primary particles helps to obtain a cathode material with stable structure, moderate specific surface area, and short ion diffusion paths. Further, the average particle size of the primary particles is 300 nm to 500 nm.

[0066] In some embodiments, the proportion of (003) crystal plane-oriented particles in a primary particle is ≥60%. Further, the proportion of (003) crystal plane-oriented particles is ≥70%. Even further, the proportion of (003) crystal plane-oriented particles is ≥80%. The radially ordered (003) planes can alleviate the internal strain during the phase transition process and improve the capacity retention rate after long-term cycling.

[0067] In a second aspect, this application provides a method for preparing the above-mentioned cathode material.

[0068] For example, a method for preparing a cathode material includes the following steps:

[0069] The raw materials are mixed in molar ratio to prepare the first powder;

[0070] The first powder is sintered in an oxygen atmosphere;

[0071] The raw materials include lithium source, nickel-cobalt-manganese precursor and doping source; the doping source includes R source, and at least one of M source and X source; R source includes one or more of Zr source, Al source, Ti source, Mg source and Sr source, M source includes one or more of W source, Mo source, Nb source, Ta source, Sn source, Sb source, Y source, B source and P source, and X source includes one or more of S source and F source.

[0072] In some embodiments, the dopant source is one or more of oxides, carbonates, hydroxides, oxalates, and fluorides.

[0073] In some of these implementations, the Zr source includes zirconium dioxide.

[0074] In some embodiments, the Al source includes one or more of aluminum oxide, aluminum nitrate, aluminum hydroxide, aluminum sulfate, and their hydrates.

[0075] In some of these implementations, the Ti source includes titanium dioxide.

[0076] In some embodiments, the Mg source includes one or more of magnesium oxide, magnesium hydroxide, and their hydrates.

[0077] In some embodiments, the Sr source includes one or more of strontium carbonate and strontium nitrate.

[0078] In some of these embodiments, the W source includes tungsten trioxide.

[0079] In some of these implementations, the Mo source includes molybdenum trioxide.

[0080] In some of these embodiments, the Nb source comprises niobium pentoxide.

[0081] In some of these implementations, the Ta source includes tantalum pentoxide.

[0082] In some of these implementations, the Sn source comprises tin dioxide.

[0083] In some of these embodiments, the Sb source comprises antimony trioxide.

[0084] In some embodiments, the Y source includes one or more of yttrium trioxide and yttrium nitrate.

[0085] In some embodiments, the source B includes one or more of boron trioxide and boric acid.

[0086] In some of these embodiments, the P source includes one or more of ammonium dihydrogen phosphate and phosphorus pentoxide.

[0087] In some embodiments, the S source includes one or more of lithium sulfate, aluminum sulfate, sodium sulfate, potassium sulfate, and lithium sulfide.

[0088] In some embodiments, the F source includes one or more of lithium fluoride and ammonium fluoride.

[0089] In some embodiments, the nickel-cobalt-manganese precursor includes Ni x’ Co y’ Mn z’(OH)2. Where, 0.8≤x'≤0.98, 0.01≤y'≤0.2, 0.01≤z'≤0.2, and x'+y'+z'=1.

[0090] In some embodiments, the lithium source includes one or more of lithium carbonate, lithium dihydrogen phosphate, lithium hydroxide, and lithium oxalate.

[0091] In some embodiments, the molar ratio of lithium source to nickel-cobalt-manganese precursor is (1~1.1):1.

[0092] In some embodiments, the sintering process includes the following steps:

[0093] The first powder is subjected to a first sintering treatment to prepare the second powder;

[0094] The second powder is subjected to a second sintering treatment;

[0095] The temperature of the first sintering treatment is 700℃~800℃, and the time is 5h~10h;

[0096] The second sintering treatment is carried out at a temperature of 850℃~950℃ for 12h~20h. It can be understood that after the first and second sintering treatments, the sintered material is crushed to prepare the second powder and the cathode material.

[0097] In some embodiments, the sintering process includes the following steps:

[0098] The first powder is subjected to a first sintering treatment to prepare the second powder;

[0099] The second powder is subjected to a second sintering treatment to prepare the third powder;

[0100] The third powder is subjected to a third sintering treatment.

[0101] The third sintering treatment is carried out at a temperature of 600℃~800℃ for 5h~10h.

[0102] It is understandable that after the first sintering treatment, the second sintering treatment, and the third sintering treatment, the sintered material is crushed to prepare the second powder, the third powder, and the cathode material.

[0103] By controlling one or more parameters in the sintering process within the aforementioned range, it is beneficial to better regulate the particle size distribution of the primary particles.

[0104] In a third aspect, this application provides a positive electrode sheet.

[0105] For example, the positive electrode sheet includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, wherein the positive active layer contains the positive electrode material described above or the positive electrode material prepared by the preparation method described above.

[0106] In a fourth aspect, this application provides a battery comprising the aforementioned positive electrode. Optionally, the battery comprises a positive electrode, a negative electrode, a separator, and an electrolyte, wherein the positive electrode comprises the aforementioned positive electrode material.

[0107] In a fifth aspect, this application provides an electrical device including the aforementioned battery. The electrical device may include mobile devices and electric vehicles. The mobile device may be a mobile phone, a laptop computer, etc.; the electric vehicle may be a pure electric vehicle, a hybrid electric vehicle, a plug-in hybrid electric vehicle, etc.

[0108] The present application will be further described in detail below with reference to specific embodiments.

[0109] Unless otherwise specified, the raw materials used in the following specific embodiments and comparative examples are all commercially available products; the instruments used are all commercially available products; and the processes used are all conventionally selected by those skilled in the art unless otherwise specified.

[0110] Example 1

[0111] This embodiment provides a cathode material Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.98 W 0.01 Nb 0.005 Al 0.005 O2.

[0112] The preparation method of the cathode material is as follows:

[0113] Ni 0.8 Co 0.1 Mn 0.1 (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.05. WO3 was added at a rate of 1 mol%W, Nb2O5 at a rate of 0.5 mol%Nb, and Al2(SO4)3 at a rate of 0.5 mol%Al. The mixture was ball-milled for 2 hours and then dried to obtain the first powder.

[0114] The first powder was sintered in an oxygen atmosphere, and the specific process is as follows:

[0115] The first powder was sintered at 780℃ for 10 hours to obtain the second powder;

[0116] The second powder was sintered at 920℃ for 15 hours to obtain the cathode material;

[0117] The cathode material is crushed and sieved.

[0118] Example 2

[0119] This embodiment provides a cathode material Li(Ni) 0.88 Co 0.08 Mn 0.04 ) 0.983 Mo 0.008 Ta 0.005 Ti 0.004 O2.

[0120] The preparation method of the cathode material is as follows:

[0121] Ni 0.88 Co 0.08 Mn 0.04 (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.03. Mo2O3 was added at a ratio of 0.8 mol% Mo, Ta2O5 at a ratio of 0.5 mol% Ta, and TiO2 at a ratio of 0.4 mol% Ti. The mixture was ball-milled for 2 hours and then dried to obtain the first powder.

[0122] The first powder was sintered in an oxygen atmosphere, and the specific process is as follows:

[0123] The first powder was sintered at 760℃ for 8 hours to obtain the second powder;

[0124] The second powder was sintered at 900℃ for 12 hours to obtain the third powder;

[0125] The second powder was sintered at 750℃ for 5 hours to obtain the cathode material;

[0126] The cathode material is crushed and sieved.

[0127] Example 3

[0128] This embodiment provides a cathode material Li(Ni) 0.9 Co 0.05 Mn 0.05 ) 0.97 Sn 0.02 Mg 0.01 O2.

[0129] The preparation method of the cathode material in this embodiment is basically the same as that in Example 1, except that: Ni is used... 0.9 Co 0.05 Mn 0.05The (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.07. SnO2 was added at a rate of 2 mol% Sn and MgSO4 was added at a rate of 1 mol% Mg.

[0130] Example 4

[0131] This embodiment provides a positive electrode material.

[0132] This embodiment provides a cathode material Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.98 W 0.01 Al 0.01 O 1.97 F 0.03 .

[0133] The preparation method of the cathode material is as follows:

[0134] Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.05. WO3 was added at a rate of 1 mol%W, and AlF3 was added at a rate of 1 mol%Al.

[0135] Example 5

[0136] This embodiment provides a positive electrode material.

[0137] This embodiment provides a cathode material Li(Ni) 0.8 Co 0.1 Mn 0.1 ) 0.98 Nb 0.005 Al 0.005 O 1.99 F 0.01 .

[0138] The preparation method of the cathode material is as follows:

[0139] Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.05. Nb2O5 was added according to the mass of 0.5 mol% Nb, Al2(SO4)3 was added according to the mass of 0.5 mol% Al, and LiF was added according to the mass of 1 mol% F.

[0140] Comparative Example 1

[0141] This comparative example provides a cathode material.

[0142] The preparation method of the cathode material in this comparative example is basically the same as that in Example 1, except that no modifier or dopant element is added.

[0143] Comparative Example 2

[0144] This comparative example provides a cathode material.

[0145] The preparation method of the cathode material in this comparative example is basically the same as that in Example 3, except that 3 mol% Mg is added with the corresponding mass of MgSO4.

[0146] Comparative Example 3

[0147] This comparative example provides a cathode material.

[0148] The preparation method of the cathode material in this comparative example is basically the same as that in Example 1, except that: Nb2O5 is added according to the mass of 0.5 mol% Nb, and Al2(SO4)3 is added according to the mass of 0.5 mol% Al.

[0149] Comparative Example 4

[0150] This comparative example provides a cathode material.

[0151] The preparation method of the cathode material in this comparative example is basically the same as that in Example 5, except that:

[0152] Ni 0.8 Co 0.1 Mn 0.1 The (OH)2 precursor and LiOH·H2O were mixed in a molar ratio of 1:1.05. The corresponding mass of Nb2O5 was added for 1 mol% Nb, the corresponding mass of Al2(SO4)3 was added for 0.5 mol% Al, and the corresponding mass of LiF was added for 3 mol% F.

[0153] Test case

[0154] The cathode materials of the embodiments and comparative examples were characterized and assembled into batteries for electrical performance testing.

[0155] Specifically, the positive electrode material, acetylene black, and polyvinylidene fluoride (PVDF) were mixed in a mass ratio of 90:5:5, and N-methylpyrrolidone was added to grind them into a slurry. The slurry was then uniformly coated onto aluminum foil and vacuum dried at 120°C for 12 hours to obtain the positive electrode sheet. The positive electrode sheet was rolled and cut into circular sheets, and then assembled into a half-cell using lithium metal as the negative electrode and 1M LiPF6 solution as the electrolyte in an argon atmosphere glove box.

[0156] Test method description:

[0157] Primary particle size distribution analysis: The cross-section of the material was observed by scanning electron microscopy (SEM), and the size (major axis length) of at least 100 primary particles was counted. The mean, standard deviation and CV value were calculated.

[0158] Crystal orientation analysis: The crystal orientation of primary particles was characterized by electron backscatter diffraction (EBSD) and the proportion of particles with (003) crystal plane orientation was statistically analyzed.

[0159] Microcrack analysis: The proportion of microcrack area is calculated using SEM images of the cross-section of the material after cycling.

[0160] Structural stability assessment: In-situ XRD was used to monitor phase transitions and structural changes during the charging and discharging process.

[0161] Initial discharge specific capacity test: room temperature, 2.8V~4.3V, 0.1CC / CD.

[0162] Cyclic test: 45℃, 2.8V~4.3V, 1CC / CD, 100 cycles.

[0163] The test results are shown in Table 1 and Figures 1-4 ,in, Figures 1-2 Scanning electron microscope (SEM) images of the primary particles of the cathode material corresponding to Example 3, and the size test results of the primary particles. Figures 3-4 Scanning electron microscope images of the primary particles of the cathode material in Comparative Example 1, and the size test results of the primary particles.

[0164] Table 1 Performance test results of the cathode materials in the examples and comparative examples

[0165]

[0166] As shown in Table 1, the CV values ​​of the cathode materials in Examples 1-5 are significantly lower than those in Comparative Example 1, and the proportion of (003) oriented particles is significantly improved, indicating that the grain structure of the primary particles in the cathode materials has been optimized. Furthermore, the cathode materials in Examples 1-5 exhibit stable performance improvements in microcrack area and DSC exothermic initiation temperature, indicating that the uniform size distribution of primary particles helps improve the stability between primary particles, thereby enabling the high-nickel ternary cathode material to achieve a higher specific capacity while maintaining a superior long-term cycle capacity retention rate. Among them, Examples 4 and 5 show extremely low microcrack area ratios after long-term cycling, with a long-term cycle capacity retention rate exceeding 97%, demonstrating excellent stability. As seen in the examples and Comparative Examples 2-4, using a single type of element doping makes it difficult to simultaneously achieve low CV and high structural stability, ultimately resulting in poor specific capacity and long-term cycle stability. However, using a specific ratio of different types of dopants can effectively improve the grain structure of the primary particles, enabling the battery to exhibit a superior capacity retention rate and a smaller microcrack area after long-term cycling.

[0167] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0168] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this invention patent should be determined by the appended claims, and the specification can be used to interpret the content of the claims.

Claims

1. A positive electrode material, characterized in that, Includes secondary particles formed by the agglomeration of primary particles; the primary particles include those with the chemical formula LiNi. x Co y Mn z M k R j O 2-a X a The active material, wherein x+y+z+k+j=1, 0.8≤x≤0.98, 0.01≤y≤0.2, 0.01≤z≤0.2, 0≤a≤0.025, 0<a+k≤0.025, 0<j≤0.01; M includes one or more of W, Mo, Nb, Ta, Sn, Sb, Y, B, and P; X includes one or more of S and F; R includes one or more of Zr, Al, Ti, Mg, and Sr.

2. The cathode material according to claim 1, characterized in that, M is one or more of W, Nb, Sn, and Sb.

3. The cathode material according to claim 2, characterized in that, 0.002 < a ≤ 0.008, 0.002 < k ≤ 0.01; and / or R is one or more of Zr and Al.

4. The cathode material according to claim 1, characterized in that, The average particle size of the primary particles is 200nm~500nm.

5. The cathode material according to any one of claims 1 to 4, characterized in that, The size variation coefficient (CV) of the primary particles is ≤25%; and / or In the primary particles, the proportion of particles with (003) crystal plane orientation is ≥60%.

6. A method for preparing the cathode material according to any one of claims 1 to 5, characterized in that, Includes the following steps: The raw materials are mixed in molar ratio to prepare the first powder; The first powder was sintered in an oxygen atmosphere; The raw materials include a lithium source, a nickel-cobalt-manganese precursor, and a doping source; the doping source includes an R source, and at least one of an M source and an X source; the R source includes one or more of a Zr source, an Al source, a Ti source, a Mg source, and a Sr source; the M source includes one or more of a W source, a Mo source, a Nb source, a Ta source, a Sn source, a Sb source, a Y source, a B source, and a P source; and the X source includes one or more of a S source and a F source.

7. The method for preparing the cathode material according to claim 6, characterized in that, The sintering process includes the following steps: The first powder is subjected to a first sintering treatment to prepare the second powder; The second powder is subjected to a second sintering treatment; The temperature of the first sintering treatment is 700℃~800℃, and the time is 5h~10h; The second sintering treatment is performed at a temperature of 850℃~950℃ for 12h~20h.

8. A positive electrode sheet, characterized in that, It includes a positive current collector and a positive active layer located on at least one surface of the positive current collector, wherein the positive active layer contains the positive electrode material according to any one of claims 1 to 5 or the positive electrode material prepared by the preparation method according to any one of claims 6 to 7.

9. A battery, characterized in that, Includes the positive electrode sheet as described in claim 8.

10. An electrical appliance, characterized in that, Includes the battery as described in claim 9.

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