Modified ternary positive electrode material and preparation method therefor

Abstract

A modified ternary positive electrode material, comprising a substrate and a coating layer coated on the outer surface of the substrate, wherein the substrate comprises a ternary positive electrode material and a doping agent, the ternary positive electrode material comprises a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the doping agent comprises a phosphate, and the material of the coating layer comprises CexGd2-2xO3-x, wherein 0.4≤x≤0.8.

Description

A modified ternary cathode material and preparation method thereof

[0001] Related applications

[0002] This application claims priority to Chinese patent application number 202311244853.5, filed on September 25, 2023, entitled “A modified ternary positive electrode material and its preparation method,” the entire text of which is hereby incorporated by reference. Technical Field

[0003] The present application relates to the field of lithium-ion batteries, and in particular to a phosphate-doped, rare earth-coated ternary cathode material and a preparation method thereof. Background Art

[0004] As one of the secondary reversible green energy sources, the development of lithium-ion batteries depends largely on the continuous improvement of the performance of positive electrode materials. The overcharge performance of positive electrode materials has a significant impact on the safety of lithium-ion batteries. At present, ternary positive electrode materials still have shortcomings in overcharge safety. When the battery is charged to a higher voltage, especially under overcharge conditions, the excessive amount of lithium released from the positive electrode material will lead to structural instability. A large amount of active oxygen is released in the form of O2, accompanied by heat release. The precipitated O2 reacts with the electrolyte and the negative electrode of the battery in succession to generate heat, which can easily cause thermal runaway of the battery and cause fire and explosion. Slowing down the release of oxygen from positive electrode materials during overcharge is one of the effective measures to improve the safety of lithium-ion batteries. Currently, the means to slow down the release of oxygen from positive electrode materials during overcharge include modifying the surface and internal phase of the positive electrode material, which correspond to improving the early and late stages of overcharge of the battery, respectively.

[0005] Related art discloses a rare earth composite metaphosphate-coated lithium positive electrode material and a preparation method thereof, the method comprising the following steps: thoroughly mixing the lithium positive electrode material and the rare earth composite metaphosphate by ball milling, calcining at high temperature, grinding, and screening to obtain the rare earth composite metaphosphate-coated lithium positive electrode material. This method can prevent the surface of the lithium positive electrode material from being corroded by the electrolyte by coating with the rare earth composite metaphosphate, so that the lithium positive electrode material has better cycle performance and thermal stability at a voltage of 4.50V or even higher. However, when the positive electrode material is overcharged and the degree of delithiation continues to increase, the degree of material structure damage and oxygen release will gradually extend to the interior of the bulk phase, thereby exacerbating side reactions.

[0006] Related technologies also disclose a boron-doped phosphite-coated nickel-based positive electrode material for lithium-ion all-solid-state batteries and its preparation method and application. The method comprises a boron-doped lithium-ion battery nickel-based positive electrode material and a material surface-coated phosphite, wherein the surface-coated polyanion salt compound LiLa 1-y M y(PO3)4 helps to improve the stability of the interface and the lithium ion transport capacity. However, the electronic conductivity of the compound itself is low, and its application in the current large-scale lithium-ion batteries with liquid organic electrolytes has certain limitations. In addition, for the deeply delithiated ternary cathode materials, the highly active Ni 4+ It often captures electrons in the lattice oxygen, which intensifies the cation mixing, causes phase change in the material structure, and releases oxygen to generate heat, leading to thermal runaway. The surface is coated with polyanion salt compound LiLa 1-y M y (PO3)4, since La ions do not have many high-orbital extranuclear electrons, their effect in ultimately stabilizing lattice oxygen is not significant, and they cannot effectively slow down the overcharge and oxygen release of the positive electrode material.

[0007] Summary of the Invention

[0008] Some embodiments of the present application provide a modified ternary positive electrode material and also disclose a method for preparing the modified ternary positive electrode material.

[0009] In a first aspect, a modified ternary positive electrode material is provided, the modified ternary positive electrode material comprising: a substrate and a coating layer coated on the outer surface of the substrate; the substrate comprises: a ternary positive electrode material and a dopant, wherein the ternary positive electrode material comprises: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the dopant comprises: a phosphate; the material of the coating layer comprises: Ce x Gd 2-2x O 3-x , where 0.4≤x≤0.8.

[0010] Optionally, when the ternary positive electrode material includes: nickel-cobalt-aluminum ternary positive electrode material, the doping molar amount of P element in the phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

[0011] Optionally, the doping molar amount of the P element in the phosphate accounts for 0.1% to 1% of the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

[0012] Optionally, when the ternary positive electrode material includes: nickel-cobalt-manganese ternary positive electrode material, the doping molar amount of P element in the phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese ternary positive electrode material.

[0013] Optionally, the doping molar amount of the P element in the phosphate accounts for 0.1% to 0.4% of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese ternary positive electrode material.

[0014] Optionally, 0.5≤x≤0.6.

[0015] In a second aspect, a method for preparing a modified ternary cathode material is provided, comprising:

[0016] preparing a substrate;

[0017] forming a coating layer on the outer surface of the substrate to prepare a modified ternary positive electrode material;

[0018] The matrix includes: a ternary positive electrode material and a dopant, the ternary positive electrode material includes: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the dopant includes: phosphate; the coating layer material includes: Ce x Gd 2-2x O 3-x , where 0.4≤x≤0.8.

[0019] Optionally, preparing a substrate comprises:

[0020] Mixing a ternary cathode material precursor, a lithium source, and a phosphorus source in proportion to obtain a mixture;

[0021] The mixed material is sintered once to prepare a matrix.

[0022] Optionally, the lithium source is selected from one or more of anhydrous lithium hydroxide and lithium hydroxide monohydrate;

[0023] and / or,

[0024] The phosphorus source is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, aluminum phosphate, and lithium phosphate.

[0025] Optionally, the molar ratio of the lithium source to the ternary cathode material precursor is 0.9 to 1.2.

[0026] Optionally, the primary sintering is performed in an oxygen atmosphere at a temperature of 720° C. to 780° C. for 8 hours to 20 hours.

[0027] Optionally, forming a coating layer on the outer surface of the substrate to prepare a modified ternary cathode material includes:

[0028] The matrix is ​​mixed with cerium oxide and gadolinium oxide, and then subjected to secondary sintering to obtain a modified ternary positive electrode material.

[0029] Optionally, when the ternary positive electrode material includes: nickel-cobalt-aluminum ternary positive electrode material, the molar addition amount of cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt and aluminum in the matrix, and the molar addition amount of gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt and aluminum in the matrix.

[0030] Optionally, when the ternary positive electrode material includes: nickel, cobalt and manganese ternary positive electrode material, the molar addition amount of cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt and manganese in the matrix, and the molar addition amount of gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt and manganese in the matrix.

[0031] Optionally, the secondary sintering is performed in an oxygen atmosphere, the secondary sintering temperature is 640-690° C., and the time is 3 h to 12 h.

[0032] The details of one or more embodiments of the present application are set forth in the following drawings and description. Other features, objects, and advantages of the present application will become apparent from the description, drawings, and claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0033] In order to more clearly illustrate the embodiments of the present application or the technical solutions in the conventional technology, the following briefly introduces the drawings required for use in the embodiments or the conventional technology descriptions. Obviously, the drawings described below are merely embodiments of the present application. For ordinary technicians in this field, other drawings can be obtained based on the disclosed drawings without any creative work.

[0034] FIG1 is an electron microscope image of the modified ternary cathode material prepared in Example 1 of the present application;

[0035] FIG2 is an electron microscope image of the ternary cathode material prepared in Comparative Example 1 of the present application;

[0036] FIG3 is an EPMA (Electron Probe Micro Analysis) image of the secondary spherical cross section corresponding to the P element distribution of the modified ternary cathode material prepared in Example 1;

[0037] Figure 4 is a curve diagram of the surface temperature change of the soft-pack battery prepared using the modified ternary positive electrode material in Example 1 and Comparative Example 1 of the present application during charging from 0% SOC to 130% SOC through a 1C constant current. DETAILED DESCRIPTION

[0038] To make the above-mentioned objects, features, and advantages of the present application more clearly understood, the specific embodiments of the present application are described in detail below with reference to the accompanying drawings. The following description sets forth many specific details to facilitate a full understanding of the present application. However, the present application can be implemented in many other ways than those described herein, and those skilled in the art can make similar improvements without violating the scope of the present application. Therefore, the present application is not limited to the specific embodiments disclosed below.

[0039] Unless the context requires otherwise, throughout the specification and claims, the term "including" is to be interpreted as having an open, inclusive meaning, that is, "including, but not limited to." In the description of the specification, the terms "one embodiment," "some embodiments," "exemplary embodiments," "exemplarily," or "some examples" are intended to indicate that specific features, structures, materials, or characteristics associated with the embodiment or example are included in at least one embodiment or example of the present disclosure. The schematic representations of the above terms do not necessarily refer to the same embodiment or example. In addition, the specific features, structures, materials, or characteristics may be included in any one or more embodiments or examples in any appropriate manner.

[0040] Exemplary embodiments are described herein with reference to cross-sectional and / or plan views that are idealized exemplary drawings. In the drawings, the thicknesses of layers and regions are exaggerated for clarity. Therefore, variations in shape relative to the drawings due to, for example, manufacturing techniques and / or tolerances are contemplated. Therefore, the exemplary embodiments should not be construed as limited to the shapes of the regions shown herein, but rather include deviations in shape due to, for example, manufacturing. For example, an etched region shown as a rectangle will typically have curved features. Therefore, the regions shown in the drawings are schematic in nature, and their shapes are not intended to illustrate the actual shape of regions of the device and are not intended to limit the scope of the exemplary embodiments.

[0041] As used herein, unless otherwise specified, "one or more" means one or more than two.

[0042] As used herein, the terms "for example," "such as," "example," and "for instance" are used for descriptive purposes to indicate that the preceding and following technical solutions are related in terms of their coverage, but should not be construed as limiting the preceding technical solution or the scope of protection herein. As used herein, unless otherwise specified, "A (such as B)" means that B is a non-limiting example of A, and it should be understood that A is not limited to B.

[0043] As used herein, "optionally," "optional," and "optional" mean optional or dispensable, meaning that the option is selected from either of two parallel options: "optional" or "optional." If a technical solution contains multiple "optional" clauses, each "optional" clause is considered independent unless otherwise specified and there are no conflicts or constraints.

[0044] In this document, the terms "first", "second", "third", "fourth", etc. in "first aspect", "second aspect", "third", "fourth", etc. are used for descriptive purposes only and cannot be understood as indicating or implying relative importance or quantity, nor can they be understood as implicitly indicating the importance or quantity of the indicated technical features.

[0045] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as those commonly understood by those skilled in the art to which this application pertains. The terms used herein in the specification of this application are for the purpose of describing specific embodiments only and are not intended to limit this application.

[0046] In this article, the technical features described in an open manner include closed technical solutions composed of the listed features, and also include open technical solutions containing the listed features.

[0047] Herein, when referring to a numerical interval (i.e., a numerical range), unless otherwise specified, the distribution of the optional numerical values ​​within the numerical interval is considered continuous and includes the two numerical endpoints (i.e., the minimum and maximum values) of the numerical interval, and each numerical value between the two numerical endpoints. Unless otherwise specified, when a numerical interval refers only to integers within the numerical interval, including the two endpoint integers of the numerical range, and each integer between the two endpoints, is equivalent to directly listing each integer. When multiple numerical ranges are provided to describe features or characteristics, these numerical ranges can be merged. In other words, unless otherwise specified, the numerical ranges disclosed herein should be understood to include any and all subranges included therein. The "numerical value" in the numerical interval can be any quantitative value, such as a number, a percentage, a ratio, etc. "Numerical interval" allows for broad inclusion of numerical interval types such as percentage intervals, ratio intervals, and ratio intervals.

[0048] In this document, if a method flow involves multiple steps, unless otherwise specified herein, there is no strict order restriction on the execution of these steps, and they can be performed in an order other than the order described. Moreover, any step can include multiple sub-steps or multiple stages, and these sub-steps or stages do not necessarily need to be completed at the same time, but can be performed at different times, and their execution order does not necessarily need to be sequential, but can be performed in rotation, alternation, or simultaneously with other steps or parts of sub-steps or stages of other steps.

[0049] To facilitate understanding of the present application, the present application will be described in more comprehensive and detailed form below in conjunction with the accompanying drawings and preferred embodiments of the specification, but the scope of protection of the present application is not limited to the following specific embodiments.

[0050] Unless otherwise defined, all technical terms used hereinafter have the same meanings as those generally understood by those skilled in the art. The technical terms used herein are only for the purpose of describing specific embodiments and are not intended to limit the scope of protection of this application.

[0051] Unless otherwise specified, all reagents and raw materials used in this application are commercially available products or products that can be prepared by known methods.

[0052] In a first aspect, some embodiments of the present application provide a modified ternary positive electrode material, the modified ternary positive electrode material comprising: a substrate and a coating layer coated on the outer surface of the substrate; the substrate comprises: a ternary positive electrode material and a dopant, wherein the ternary positive electrode material comprises: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the dopant comprises: a phosphate; the material of the coating layer comprises: Ce x Gd 2-2x O 3-x , where 0.4≤x≤0.8.

[0053] In the modified ternary cathode material provided in the embodiment of the present application, Ce is coated on the surface of the matrix of the ternary cathode material. x Gd 2-2x O 3-x The coating layer has abundant oxygen vacancies, which increases the activation energy of lattice oxygen loss by capturing active oxygen ions on the surface of the material, alleviates the lattice oxygen release and heat release caused by excessive lithium removal during overcharging, reduces the corrosion of the electrolyte on the lithium positive electrode material and other side reaction heat release, thereby reducing the overall temperature rise of the battery cell in the late overcharging period and enhancing the safety of the battery cell. On the other hand, during the preparation process, Ce x Gd 2-2x O 3-x Part of Ce in the coating layer 4+ and Gd 3+ It will disperse into the lattice of the ternary positive electrode material, reducing the mixing of lithium and nickel, and forming stronger Ce-O and Gd-O bonds, which can minimize the damage to the near-surface structure of the positive electrode material. On the other hand, by doping phosphate into the matrix of the ternary positive electrode material, the phosphate contains stable PO bonds. Therefore, the P element in the phosphate is doped into the material and easily combines with the bulk lattice oxygen to form a bond, which is beneficial to the stability of the bulk structure of the material during overcharging. At the same time, since phosphate is incompletely doped, a very small amount will remain on the surface of the matrix after sintering. If it is sintered multiple times, the phosphate will be doped with Ce and Gd respectively. x Gd 2-2x O 3-x Ce in 3+ 、Gd 3+ Combined to form LiGdP2O7, LiCeP2O7 structure, the structure has good ionic conductivity, which is conducive to Li + At the same time, it can prevent the surface of the positive electrode material from being corroded by the electrolyte, further improving the thermal stability and safety of the positive electrode material.

[0054] In some embodiments, when the ternary positive electrode material includes: nickel-cobalt-aluminum ternary positive electrode material, the doping molar amount of P element in phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

[0055] In some embodiments, the doping molar amount of the P element in the phosphate is 0.1% to 1% of the total molar amount of nickel, cobalt, and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

[0056] In some embodiments, when the ternary positive electrode material includes: a nickel-cobalt-manganese ternary positive electrode material, the doping molar amount of the P element in the phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary positive electrode material.

[0057] In some embodiments, the doping molar amount of the P element in the phosphate is 0.1% to 0.4% of the total molar amount of nickel, cobalt, and manganese in the nickel-cobalt-manganese ternary positive electrode material.

[0058] In some embodiments, 0.5≤x≤0.6.

[0059] In a second aspect, a method for preparing a modified ternary cathode material is provided, comprising:

[0060] preparing a substrate;

[0061] forming a coating layer on the outer surface of the substrate to prepare a modified ternary positive electrode material;

[0062] The matrix includes: a ternary positive electrode material and a dopant, the ternary positive electrode material includes: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the dopant includes: phosphate; the coating layer material includes: Ce x Gd 2-2x O 3-x , where 0.4≤x≤0.8.

[0063] In some embodiments, preparing a substrate comprises:

[0064] Mixing a ternary cathode material precursor, a lithium source, and a phosphorus source in proportion to obtain a mixture;

[0065] The mixed material is sintered once to prepare a matrix.

[0066] In these embodiments, phosphate can be doped into the ternary cathode material. x Gd 2-2x O 3-x Part of Ce in the coating layer 4+ and Gd 3+ It will disperse into the lattice of the ternary positive electrode material, reducing the mixing of lithium and nickel, and at the same time forming stronger Ce-O and Gd-O bonds, which can minimize the damage to the near-surface structure of the positive electrode material.

[0067] In some embodiments, the lithium source is selected from one or more of anhydrous lithium hydroxide and lithium hydroxide monohydrate;

[0068] and / or,

[0069] The phosphorus source is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, aluminum phosphate, and lithium phosphate.

[0070] In some embodiments, the molar ratio of the lithium source to the ternary cathode material precursor is 0.9 to 1.2.

[0071] In some embodiments, the primary sintering is performed in an oxygen atmosphere at a temperature of 720° C. to 780° C. for a time of 8 h to 20 h.

[0072] In some embodiments, forming a coating layer on the outer surface of the substrate to prepare a modified ternary cathode material includes:

[0073] The matrix is ​​mixed with cerium oxide and gadolinium oxide, and then subjected to secondary sintering to obtain a modified ternary positive electrode material.

[0074] In these embodiments, Ce can be coated on the outer surface of the substrate. x Gd 2-2x O 3-x The preparation method is simple. After the phosphate is doped in the ternary cathode material, since the phosphate is incompletely doped, a very small amount of phosphate will remain on the surface of the substrate after the first sintering, and will react with Ce in the second sintering process. x Gd 2-2x O 3-x Ce in 3+ 、Gd 3+ Combined to form LiGdP2O7, LiCeP2O7 structure, the structure has good ionic conductivity, which is conducive to Li + At the same time, it can prevent the surface of the positive electrode material from being corroded by the electrolyte, further improving the thermal stability and safety of the positive electrode material.

[0075] In some embodiments, when the ternary positive electrode material includes: nickel-cobalt-aluminum ternary positive electrode material, the molar addition amount of cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt, and aluminum in the matrix, and the molar addition amount of gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt, and aluminum in the matrix.

[0076] In some embodiments, when the ternary positive electrode material includes: nickel, cobalt, and manganese ternary positive electrode material, the molar addition amount of cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt, and manganese in the matrix, and the molar addition amount of gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt, and manganese in the matrix.

[0077] In some embodiments, the secondary sintering is performed in an oxygen atmosphere at a temperature of 640-690° C. and for a time of 3 h to 12 h.

[0078] In these embodiments, Ce can be formed on the surface of the substrate by controlling the secondary sintering temperature to 640-690°C. x Gd 2-2x O 3-x Structure, convenient for Ce x Gd 2-2x O 3-x The structure is coated on the substrate, which can capture active oxygen ions on the surface of the material, alleviate the release of lattice oxygen and heat release caused by excessive lithium removal during overcharging, and enhance the safety of the battery cell. When the sintering temperature is too low, cerium oxide and gadolinium oxide exist mainly in the form of floating powder on the surface of the material. Due to insufficient temperature, it is difficult for cerium oxide and gadolinium oxide to interpenetrate into each other's crystal lattices, and they exist more in the form of cerium oxide and gadolinium oxide crystal phases; when the sintering temperature is too high, cerium oxide and gadolinium oxide may also form Ce during the insulation period. x Gd 2-2x O 3-x However, due to the high sintering temperature, the structure will continue to enter the matrix phase, which is equivalent to conventional element doping, so there will be no pure Ce on the matrix surface. x Gd 2-2x O 3-x The coating layer lacks abundant oxygen vacancies, so it cannot achieve the purpose of oxygen fixation, and there is still a risk of oxygen release during overcharging. x Gd 2-2x O 3-x Part of Ce in the coating layer 4+ and Gd 3+ It will disperse into the lattice of the ternary positive electrode material, reducing the mixing of lithium and nickel, and at the same time forming stronger Ce-O and Gd-O bonds, which can minimize the damage to the near-surface structure of the positive electrode material.

[0079] It can be seen that compared with the related art, this application has the following beneficial technical effects:

[0080] (1) This application covers the surface of the ternary cathode material matrix with CexGd 2-2x O 3-x The coating layer has abundant oxygen vacancies, which increases the activation energy of lattice oxygen loss by capturing active oxygen ions on the surface of the material, alleviates the lattice oxygen release and heat release caused by excessive lithium removal during overcharging, reduces the corrosion of the electrolyte on the lithium positive electrode material and other side reaction heat release, thereby reducing the overall temperature rise of the battery cell in the later stage of overcharging and enhancing the safety of the battery cell. On the other hand, Ce during sintering x Gd 2-2x O 3-x Part of Ce in the coating layer 4+ and Gd 3+It will disperse into the lattice of the ternary positive electrode material, reducing the mixing of lithium and nickel, and at the same time forming stronger Ce-O and Gd-O bonds, which can minimize the damage to the near-surface structure of the positive electrode material.

[0081] (2) The present application dopes phosphate into the matrix of the ternary positive electrode material. Phosphate contains stable PO bonds. Therefore, the P element in the phosphate is doped into the material and easily combines with the bulk lattice oxygen to form bonds, which is beneficial to the stability of the bulk structure of the material during overcharging.

[0082] (3) The phosphate in this application is incompletely doped, and a very small amount will remain on the surface of the substrate after sintering. During the secondary sintering process, it will react with Ce x Gd 2-2x O 3-x Ce in 3+ 、Gd 3+ Combined to form LiGdP2O7, LiCeP2O7 structure, the structure has good ionic conductivity, which is conducive to Li + At the same time, it can prevent the surface of the positive electrode material from being corroded by the electrolyte, further improving the thermal stability and safety of the positive electrode material.

[0083] (4) The preparation process of the present application is simple to operate and has low requirements on production equipment.

[0084] In summary, the present invention doped phosphate into the matrix of the ternary cathode material, and the surface of the matrix was coated with Ce. x Gd 2- 2x O 3-x The two layers work together to improve the shortcomings of overcharge safety of existing ternary positive electrode materials, so that the positive electrode materials can better adapt to some extreme conditions and avoid safety hazards during application.

[0085] Example 1:

[0086] A modified ternary cathode material, the modified ternary cathode material is based on Li 1.03 Ni 0.9 Co 0.08 Al 0.02 P 0.003 O2 is the matrix, the matrix is ​​doped with phosphate, the molar number of P element in the phosphate accounts for 0.3% of the total molar number of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material, and the surface of the matrix is ​​covered with Ce. 0.6 Gd 0.8 O 2.4 layer.

[0087] The preparation method of the modified ternary cathode material in this embodiment includes the following steps:

[0088] (1) Lithium hydroxide and ternary cathode precursor Ni were weighed according to the molar ratio of Li:Me=1.03. 0.9 Co 0.08 Al 0.02 (OH)2, and then weighing diammonium hydrogen phosphate in an amount such that the doping molar ratio of P to Me in the ternary positive electrode material matrix is ​​0.3%, and mixing the weighed materials evenly, wherein Me refers to nickel, cobalt and aluminum;

[0089] (2) placing the mixed material after step (1) into an oxygen atmosphere furnace for primary sintering, keeping the temperature at 760° C. for 12 h, then cooling with the furnace and sieving to obtain a phosphate-doped ternary cathode material matrix;

[0090] (3) uniformly mixing the material obtained in step (2) with cerium oxide and gadolinium oxide, wherein the molar addition amounts of cerium oxide and gadolinium oxide are 0.03% and 0.02% of the total molar amounts of nickel, cobalt, and aluminum in the phosphate-doped ternary cathode material matrix, respectively;

[0091] (4) The mixed material obtained in step (3) is placed in an oxygen atmosphere furnace for secondary sintering, and the secondary sintering is kept at 680°C for 8 hours, and then cooled and sieved with the furnace to obtain a finished modified ternary positive electrode material.

[0092] Example 2:

[0093] A modified ternary cathode material, the modified ternary cathode material is a nickel-cobalt-aluminum ternary cathode material Li 1.03 Ni 0.9 Co 0.08 Al 0.02 P 0.005 O2 is the matrix, which is doped with phosphate. The molar number of P element in the phosphate accounts for 0.5% of the total molar number of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material. The surface of the matrix is ​​covered with Ce. 0.7 Gd 0.6 O 2.3 layer.

[0094] The preparation method of the modified ternary cathode material in this embodiment includes the following steps:

[0095] (1) Lithium hydroxide and ternary cathode precursor Ni were weighed according to the molar ratio of Li:Me=1.03. 0.9 Co 0.08 Al 0.02 (OH)2, and then weighing diammonium hydrogen phosphate according to the doping molar ratio of P to Me in the ternary positive electrode material matrix of 0.5%, and mixing the weighed materials evenly, wherein Me refers to nickel, cobalt and aluminum;

[0096] (2) placing the mixed material after step (1) into an oxygen atmosphere furnace for primary sintering, keeping the temperature at 780° C. for 12 h, then cooling with the furnace and sieving to obtain a phosphate-doped ternary cathode material matrix;

[0097] (3) uniformly mixing the material obtained in step (2) with cerium oxide and gadolinium oxide, wherein the molar addition amounts of cerium oxide and gadolinium oxide are 0.035% and 0.015% of the total molar amounts of nickel, cobalt, and aluminum in the phosphate-doped ternary cathode material matrix, respectively;

[0098] (4) The mixed material obtained in step (3) is placed in an oxygen atmosphere furnace for secondary sintering, and the secondary sintering is kept at 690°C for 8 hours, and then cooled and sieved with the furnace to obtain a finished modified ternary positive electrode material.

[0099] Example 3:

[0100] A modified ternary positive electrode material, the modified ternary positive electrode material is a nickel-cobalt-manganese ternary positive electrode material Li 1.03 Ni 0.9 Co 0.08 Al 0.02 P 0.0005 O2 is the matrix, the matrix is ​​doped with phosphate, the molar number of P element in the phosphate accounts for 0.05% of the total molar number of nickel, cobalt and aluminum in the nickel-cobalt-manganese ternary positive electrode material, and the surface of the matrix is ​​coated with Ce. 0.5 GDJ 2.5 layer.

[0101] The preparation method of the modified ternary cathode material in this embodiment includes the following steps:

[0102] (1) Lithium hydroxide and ternary cathode precursor Ni were weighed according to the molar ratio of Li:Me=1.03. 0.9 Co 0.08 Al 0.02 (OH)2, and then weighing diammonium hydrogen phosphate according to the doping molar ratio of P to Me in the ternary positive electrode material matrix of 0.05%, and mixing the weighed materials evenly, wherein Me refers to nickel, cobalt and aluminum;

[0103] (2) placing the mixed material after step (1) into an oxygen atmosphere furnace for primary sintering, keeping the temperature at 720° C. for 12 h, then cooling with the furnace and sieving to obtain a phosphate-doped ternary cathode material matrix;

[0104] (3) uniformly mixing the material obtained in step (2) with cerium oxide and gadolinium oxide, wherein the molar addition amounts of cerium oxide and gadolinium oxide are 0.025% and 0.025% of the total molar amounts of nickel, cobalt and aluminum in the phosphate-doped ternary cathode material matrix, respectively;

[0105] (4) The mixed material obtained in step (3) is placed in an oxygen atmosphere furnace for secondary sintering, and the secondary sintering is kept at 640°C for 8 hours, and then cooled and sieved with the furnace to obtain a finished modified ternary positive electrode material.

[0106] Comparative Example 1:

[0107] The difference between this comparative example and Example 1 is that diammonium hydrogen phosphate is not added in step (1), and cerium oxide and gadolinium oxide are not added in step (3). Other conditions are consistent with Example 1, and a finished ternary positive electrode material is obtained.

[0108] Comparative Example 2:

[0109] The difference between this comparative example and Example 1 is that no cerium oxide or gadolinium oxide is added in step (3), and there is no Ce on the outer surface of the substrate. 0.6 Gd 0.8 O 2.4 The coating layer and other conditions were kept consistent with those in Example 1 to obtain a finished phosphate-doped ternary positive electrode material.

[0110] Comparative Example 3:

[0111] The difference between this comparative example and Example 1 is that the coating temperatures of cerium oxide and gadolinium oxide are different during the preparation process, that is, the uniformly mixed materials in step (4) are kept at 600°C for 8 hours, and the other conditions are consistent with Example 1, thereby obtaining a phosphate-doped cerium gadolinium oxide-coated ternary positive electrode material product.

[0112] Comparative Example 4:

[0113] The difference between this comparative example and Example 1 is that during the preparation process, gadolinium oxide in the coating material is replaced with lanthanum oxide, and other conditions are consistent with Example 1 to obtain a phosphate-doped cerium lanthanum oxide-coated ternary positive electrode material.

[0114] The SEM picture of the modified cathode material obtained in Example 1 is shown in FIG1 . As can be seen from FIG1 , the modified cathode material is densely packed with primary particles to form secondary balls with a relatively rough surface. The rare earth oxide nanoparticles are mainly deposited on the surface of the cathode material to form Ce x Gd 2-2x O 3-x Coating layer. The EPMA image of the P element distribution in the cross-section of the secondary sphere of the modified cathode material is shown in Figure 3. The two dotted circles in Figure 3 represent the secondary sphere particles, and the bright white area represents the P element in the phosphate. As can be seen from Figure 3, the P element in the phosphate is mainly distributed in the bulk phase inside the secondary sphere, with a small amount remaining on the surface of the secondary sphere.

[0115] The SEM image of the modified positive electrode material obtained in Comparative Example 1 is shown in FIG2 . Because it has no rare earth oxide coating layer, the surface of the secondary spheres is smooth and the boundaries of the primary particles are clear.

[0116] The modified ternary cathode materials finally obtained in each embodiment and comparative example were made into soft-pack batteries for evaluation and testing:

[0117] (1) Perform 1C discharge and DCR tests at room temperature and a voltage range of 2.8 to 4.2 V, and record the discharge capacity and initial DCR.

[0118] (2) The soft-pack battery cell was charged and discharged once at a rate of 1C under the condition of 2.8-4.2V, and then charged to 130% SOC at a constant current of 1C. The surface temperature of the battery cell was detected by a thermocouple, the maximum temperature reached on the surface of the battery cell was recorded, and the fire condition of the battery cell was observed. The surface temperature change curves of the battery cells of Example 1 and Comparative Example 1 are shown in Figure 4.

[0119] The specific data of the ternary positive electrode materials of the above embodiments and comparative examples are shown in Table 1 below.

[0120] Table 1 Performance of modified ternary cathode materials in various embodiments and comparative examples

[0121] As shown in Table 1, the phosphate doping and Ce x Gd 2-2x O 3-x The overcharged cells coated with ternary positive electrode materials did not catch fire, and the surface temperature of the cells was better than (that is, lower than) that of comparative examples 1 to 4, indicating that the phosphate-doped, Ce- x Gd 2-2x O 3-x The coated ternary cathode material has excellent overcharge safety performance. Although the coating material of Comparative Example 3 uses cerium oxide and gadolinium oxide, the sintering temperature is too low and no Ce x Gd 2-2x O 3- x The coating layer is a mixed coating layer of CeO2 and Gd2O3. The experimental data show that the surface temperature of the overcharged core in Comparative Example 3 is significantly higher than that in Example 1, indicating that Ce x Gd 2-2x O 3-x The overcharge safety of the coated ternary cathode material is superior to that of a mixed CeO2 and Gd2O3-coated ternary cathode material. Comparative Example 2 shows no significant loss in discharge capacity compared to Comparative Example 1, and the overcharged cell did not catch fire. However, the cell surface temperature was still higher than that of the Example. This indicates that phosphate doping allows the phosphorus element to form bonds with the lattice oxygen of the cathode material, stabilizing the bulk structure of the material and reducing heat generation from structural collapse and other side reactions during overcharge. However, its effectiveness in improving overcharge safety is far less pronounced than that of the Example.

[0122] It can also be seen from the experimental data in Table 1 that phosphate doping and Ce x Gd 2-2x O 3-x The coating layer improves the overcharge safety of the positive electrode material, and the simultaneous presence of both is more significant. Comparing Example 4 with Example 1, the battery cell ignited and exploded during overcharge. Although the lanthanum in the coating layer is a rare earth element, it has far fewer high-orbital electrons than gadolinium, making it far inferior to Example 1 in stabilizing lattice oxygen.

[0123] In summary, the present invention doped phosphate into the matrix of the ternary cathode material, and the surface of the matrix was coated with Ce. x Gd 2- 2x O 3-x The two layers work together to improve the shortcomings of overcharge safety of existing ternary positive electrode materials, so that the positive electrode materials can better adapt to some extreme conditions and avoid safety hazards during application.

[0124] The technical features of the above-mentioned embodiments can be combined arbitrarily. In order to make the description concise, not all possible combinations of the technical features in the above-mentioned 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.

[0125] The above-described embodiments merely represent several implementation methods of the present application. While the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the patent application. It should be noted that a person of ordinary skill in the art may make various modifications and improvements without departing from the spirit of the present application, and these modifications and improvements fall within the scope of protection of the present application. Therefore, the scope of protection of the present patent application shall be determined by the appended claims.

Claims

1. A modified ternary cathode material, comprising: A substrate, the substrate comprising: a ternary positive electrode material and a dopant, wherein the ternary positive electrode material comprises: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, and the dopant comprises: a phosphate; and A coating layer is coated on the outer surface of the substrate, and the material of the coating layer includes: Ce x G 2-2x O 3-x , where 0.4≤x≤0.

8.

2. The modified ternary cathode material according to claim 1, wherein: When the ternary positive electrode material includes: a nickel-cobalt-aluminum ternary positive electrode material, the doping molar amount of the P element in the phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

3. The modified ternary cathode material according to claim 2, wherein: The doping molar amount of the P element in the phosphate accounts for 0.1% to 1% of the total molar amount of nickel, cobalt and aluminum in the nickel-cobalt-aluminum ternary positive electrode material.

4. The modified ternary cathode material according to any one of claims 1 to 3, wherein: When the ternary positive electrode material comprises a nickel-cobalt-manganese ternary positive electrode material, the doping molar amount of the P element in the phosphate accounts for 0.05% to 3% of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese ternary positive electrode material.

5. The modified ternary cathode material according to claim 4, wherein: The doping molar amount of the P element in the phosphate accounts for 0.1% to 0.4% of the total molar amount of nickel, cobalt and manganese in the nickel-cobalt-manganese ternary positive electrode material.

6. The modified ternary cathode material according to any one of claims 1 to 5, wherein: 0.5≤x≤0.6。 7. A method for preparing a modified ternary cathode material, wherein: include: preparing a substrate; Forming a coating layer on the outer surface of the substrate to prepare the modified ternary positive electrode material; The matrix includes: a ternary positive electrode material and a dopant, the ternary positive electrode material includes: a nickel-cobalt-aluminum ternary positive electrode material and / or a nickel-cobalt-manganese ternary positive electrode material, the dopant includes: phosphate; the material of the coating layer includes: Ce x G 2-2x O 3-x , where 0.4≤x≤0.

8.

8. The preparation method according to claim 7, wherein the preparation of the substrate comprises: The ternary cathode material precursor, the lithium source and the phosphorus source are mixed in proportion to prepare a mixed material; The mixed material is sintered once to prepare the matrix.

9. The preparation method according to claim 8, wherein The lithium source is selected from one or both of anhydrous lithium hydroxide and monohydrate lithium hydroxide; and / or, The phosphorus source is selected from one or more of diammonium hydrogen phosphate, ammonium dihydrogen phosphate, aluminum phosphate, and lithium phosphate.

10. The preparation method according to claim 8 or 9, wherein: The molar ratio of the lithium source to the ternary positive electrode material precursor is 0.9 to 1.

2.

11. The preparation method according to any one of claims 8 to 10, wherein: The primary sintering is carried out in an oxygen atmosphere at a temperature of 720° C. to 780° C. for a time of 8 h to 20 h.

12. The preparation method according to any one of claims 7 to 11, wherein: The method of forming a coating layer on the outer surface of the substrate to prepare the modified ternary positive electrode material comprises: The matrix is ​​mixed with cerium oxide and gadolinium oxide, and then subjected to secondary sintering to obtain the modified ternary positive electrode material.

13. The preparation method according to claim 12, wherein: When the ternary positive electrode material includes: nickel-cobalt-aluminum ternary positive electrode material, the molar addition amount of the cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt and aluminum in the matrix, and the molar addition amount of the gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt and aluminum in the matrix.

14. The preparation method according to claim 12 or 13, wherein: When the ternary positive electrode material includes: nickel-cobalt-manganese ternary positive electrode material, the molar addition amount of the cerium oxide is 0.025% to 0.035% of the total molar amount of nickel, cobalt and manganese in the matrix, and the molar addition amount of the gadolinium oxide is 0.015% to 0.025% of the total molar amount of nickel, cobalt and manganese in the matrix.

15. The preparation method according to any one of claims 12 to 14, wherein: The secondary sintering is performed in an oxygen atmosphere at a temperature of 640° C. to 690° C. for a time of 3 h to 12 h.

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