Lithium-nickel-cobalt-manganese positive electrode material and preparation method therefor, positive electrode and battery

Abstract

A lithium-nickel-cobalt-manganese positive electrode material and a preparation method therefor, a positive electrode and a battery, relating to the technical field of battery materials. The lithium-nickel-cobalt-manganese positive electrode material comprises a lithium-nickel-cobalt-manganese single crystal and a modification layer located at an internal interface of the lithium-nickel-cobalt-manganese single crystal. The modification layer is generated by a reaction of Li, A, B and oxygen, wherein element A is selected from at least one of elements W, Mo and Re, and element B is selected from at least one of Ba and Ca. The preparation method for the lithium-nickel-cobalt-manganese positive electrode material comprises: uniformly mixing a nickel-cobalt-manganese precursor, a lithium source, an additive A and an additive B, and sintering the mixture. According to the preparation method, a lithium-nickel-cobalt-manganese positive electrode material can be prepared. The preparation method is simple, and the prepared positive electrode material has good electrochemical performance.

Description

Lithium nickel cobalt manganese positive electrode material and preparation method thereof, positive electrode and battery

[0001] CROSS-REFERENCE TO RELATED APPLICATIONS

[0002] This application claims priority to Chinese patent application number 2024100693865 filed with the Patent Office of China on January 17, 2024, entitled “Lithium Nickel Cobalt Manganese Positive Electrode Material, Preparation Method, Positive Electrode and Battery”, the entire contents of which are incorporated herein by reference. Technical Field

[0003] The present application relates to the field of battery material technology, and in particular to lithium nickel cobalt manganese positive electrode materials, preparation methods thereof, positive electrodes and batteries. Background Art

[0004] Lithium-ion batteries are widely used in new energy vehicles, and safety is the main challenge currently facing lithium-ion batteries. Polycrystalline cathodes can develop severe microcracks during long cycles, causing rapid capacity decay. Single-crystal cathode materials can effectively inhibit the formation of microcracks, alleviate side reactions between the cathode surface and the electrolyte, and extend cycle life. Therefore, single-crystal ternary materials are of great research significance in improving their cycling performance and safety. However, single-crystal cathode materials also have some problems during the charge and discharge process. For example, during high-voltage charge and discharge, the cracking of internal grain boundaries exposes new interfaces, which can cause side reactions with the electrolyte, thus affecting cyclability and safety.

[0005] Currently known methods for preparing single-crystal multi-component cathode materials include mixing a multi-component cathode material matrix with a grain boundary stabilizer and sintering the mixture to produce a single-crystal multi-component cathode material. While this approach does not emphasize the preparation of the multi-component cathode material matrix, the process from precursor to finished product requires a two-step sintering process, making the method less streamlined.

[0006] Summary of the Invention

[0007] The purpose of this application is to provide a lithium nickel cobalt manganese positive electrode material and a preparation method thereof, a positive electrode and a battery.

[0008] This application is implemented as follows:

[0009] In a first aspect, the present application provides a lithium nickel cobalt manganese positive electrode material, which includes a lithium nickel cobalt manganese single crystal and a modified layer located at the inner interface of the lithium nickel cobalt manganese single crystal, the modified layer being generated by the reaction of Li, A and B and oxygen, the A element being selected from at least one of W, Mo and Re elements; and the B element being selected from at least one of Ba and Ca elements.

[0010] In an optional embodiment, the ratio of element A to the lithium nickel cobalt manganese positive electrode material is 1500ppm to 6000ppm, and the ratio of element B to the lithium nickel cobalt manganese positive electrode material is 500ppm to 6000ppm.

[0011] In an optional embodiment, the chemical formula of the lithium nickel cobalt manganese single crystal is LiNi x Co y Mn 1-x-y O2, where 0<x<1, 0<y<1, 0<x+y<1.

[0012] In a second aspect, the present application provides a method for preparing a lithium nickel cobalt manganese positive electrode material, comprising:

[0013] The nickel-cobalt-manganese precursor, the lithium source, the additive A and the additive B are uniformly mixed and then sintered;

[0014] Additive A is a simple substance of element A or a compound of element A, and element A is at least one selected from the group consisting of W, Mo, and Re; additive B is a simple substance of element B or a compound of element B, and element B is at least one selected from the group consisting of Ba and Ca;

[0015] Additive A has a BET of 5m 2 / g~10m 2 / g; BET of additive B is 5m 2 / g~10m 2 / g, and the BET of additive A is less than or equal to the BET of additive B;

[0016] Additive A is added according to the ratio of element A to the target lithium nickel cobalt manganese positive electrode material generated being less than or equal to 6000 ppm, and additive B is added according to the ratio of element B to the target lithium nickel cobalt manganese positive electrode material generated being less than or equal to 6000 ppm.

[0017] In an optional embodiment, additive A is added at a ratio of 1500ppm to 6000ppm of element A to the target lithium nickel cobalt manganese positive electrode material, and additive B is added at a ratio of 500ppm to 6000ppm of element B to the target lithium nickel cobalt manganese positive electrode material.

[0018] In an optional embodiment, the lithium source is selected from at least one of lithium hydroxide and lithium carbonate;

[0019] Optionally, the lithium source involved in sintering is fed in a molar ratio of lithium element to metal element in the nickel-cobalt-manganese precursor of 1 to 1.07:1;

[0020] Alternatively, the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn 1-x-y (OH)2 or Nix Co y Mn 1-x-y CO3, 0<x<1, 0<y<1, 0<x+y<1.

[0021] In an optional embodiment, the sintering includes high temperature stage sintering;

[0022] When you x Co y Mn 1-x-y When 0<x≤0.4, 0<x+y<1 in (OH)2, the sintering conditions in the high temperature stage are: oxygen atmosphere or mixed atmosphere with oxygen, oxygen volume proportion is 20~100%, temperature is 900℃~950℃, and sintering time is 7.5~8.5h;

[0023] When you x Co y Mn 1-x-y When (OH)2 is 0.4<x≤0.6, 0.4<x+y<1, the sintering conditions in the high temperature stage are: oxygen atmosphere or mixed atmosphere with oxygen, oxygen volume proportion is 30~100%, temperature is 880℃~930℃, and sintering time is 9.5~10.5h;

[0024] When you x Co y Mn 1-x-y When (OH)2 is 0.6<x≤0.7, 0.6<x+y<1, the sintering conditions in the high temperature stage are: oxygen atmosphere or mixed atmosphere with oxygen, oxygen volume proportion is 60~100%, temperature is 870℃~920℃, and sintering time is 9.5~10.5h;

[0025] When you x Co y Mn 1-x-y When 0.7<x<1, 0.7<x+y<1 in (OH)2, the sintering conditions in the high temperature stage are: oxygen atmosphere or mixed atmosphere with oxygen, oxygen volume proportion is 70~100%, temperature is 830℃~900℃, and sintering time is 11.5~12.5h;

[0026] Optionally, the sintering further includes low-temperature sintering. The conditions for the low-temperature sintering are: adding a low-temperature sintering stage before the high-temperature sintering stage, the sintering temperature is 400° C. to 500° C., and the sintering time is 4 to 6 hours.

[0027] In an optional embodiment, after sintering, a primary positive electrode material is obtained, and after obtaining the primary positive electrode material, the process further comprises:

[0028] The primary positive electrode material is crushed from D50=5~10μm to D50=2~10μm.

[0029] In a third aspect, the present application provides a positive electrode, which is made using the positive electrode material of any one of the aforementioned embodiments or the positive electrode material prepared by the preparation method of any one of the aforementioned embodiments.

[0030] In a fourth aspect, the present application provides a battery comprising a positive electrode as described in the aforementioned embodiment.

[0031] This application has the following beneficial effects:

[0032] The modified layer at the inner grain boundary of the lithium nickel cobalt manganese cathode material provided in the embodiments of the present application can inhibit side reactions with the electrolyte caused by the rupture of the inner grain boundary during the preparation or high-voltage charging and discharging process. In addition, the modified layer not only protects the inner grain boundary but also acts as a fast ion conductor, thereby improving the capacity, rate, cycle, and storage performance at higher voltages. Therefore, the lithium nickel cobalt manganese cathode material provided in the embodiments of the present application has excellent electrochemical properties.

[0033] The preparation method of the lithium nickel cobalt manganese cathode material provided in the embodiment of the present application selects additives A and B with appropriate BET and addition amount for preparation, which can achieve that element B first reacts with the lithium compound during the low-temperature sintering process to form a Li-BO compound, and then reacts with element A to form a Li-BAO compound modification layer. When the grains in the high-temperature section begin to fuse and develop, the Li-BAO compound modification layer is only enriched at the inner grain boundaries and does not enter the interior of the crystal. The reaction proceeds spontaneously, thereby obtaining a cathode material with a modification layer at the inner grain boundaries. The cathode material has good electrochemical properties. In addition, the preparation method provided by the present application is simple, and the target cathode material can be obtained by only one sintering. BRIEF DESCRIPTION OF THE DRAWINGS

[0034] In order to more clearly illustrate the technical solutions of the embodiments of the present application, the following is a brief introduction to the drawings required for use in the embodiments. It should be understood that the following drawings only show certain embodiments of the present application and therefore should not be regarded as limiting the scope. For ordinary technicians in this field, other relevant drawings can be obtained based on these drawings without creative work.

[0035] FIG1 is a flow chart of a preparation method provided by an embodiment of the present invention;

[0036] FIG2 is a cross-sectional view of the positive electrode material particles prepared in Example 3 of the present application under a scanning electron microscope;

[0037] FIG3 is a SEM-EDS image of the positive electrode material prepared in Example 3 of the present application;

[0038] FIG4 is a high-temperature cycle curve diagram of button batteries prepared in the examples and comparative examples of the present application. DETAILED DESCRIPTION

[0039] To make the purpose, technical solutions and advantages of the examples of the present application clearer, the technical solutions in the examples of the present application will be described clearly and completely below. Where specific conditions are not specified in the examples, conventional conditions or conditions recommended by the manufacturer are used. Where the manufacturer of the reagents or instruments is not specified, they are all conventional products that can be purchased commercially.

[0040] The following is a detailed description of the lithium nickel cobalt manganese positive electrode material, its preparation method, positive electrode and battery provided in the embodiments of the present application.

[0041] The lithium nickel cobalt manganese positive electrode material provided in the embodiment of the present application includes a lithium nickel cobalt manganese single crystal and a modified layer located at the inner interface of the lithium nickel cobalt manganese single crystal, and the modified layer is generated by the reaction of Li, A and B and oxygen, the A element is selected from at least one of W, Mo and Re elements; the B element is selected from at least one of Ba and Ca.

[0042] The modified layer at the inner grain boundary of the lithium nickel cobalt manganese cathode material provided in the embodiments of the present application can inhibit side reactions with the electrolyte caused by the rupture of the inner grain boundary during the preparation or high-voltage charging and discharging process. In addition, the modified layer not only protects the inner grain boundary but also acts as a fast ion conductor, thereby improving the capacity, rate, cycle, and storage performance at higher voltages. Therefore, the lithium nickel cobalt manganese cathode material provided in the embodiments of the present application has excellent electrochemical properties.

[0043] Optionally, to ensure that the lithium nickel cobalt manganese positive electrode material provided in the embodiment of the present application has better electrochemical properties, the ratio of element A to the lithium nickel cobalt manganese positive electrode material is 1500ppm~6000ppm, and the ratio of element B to the lithium nickel cobalt manganese positive electrode material is 500ppm~6000ppm.

[0044] Alternatively, the chemical formula of the lithium nickel cobalt manganese single crystal is LiNi x Co y Mn 1-x-y O2, where 0<x<1, 0<y<1, 0<x+y<1.

[0045] The method for preparing the lithium nickel cobalt manganese positive electrode material provided in the embodiment of the present application includes:

[0046] The nickel-cobalt-manganese precursor, the lithium source, the additive A and the additive B are uniformly mixed and then sintered;

[0047] Additive A is a simple substance of element A or a compound of element A, and element A is at least one selected from the group consisting of W, Mo, and Re; additive B is a simple substance of element B or a compound of element B, and element B is at least one selected from the group consisting of Ba and Ca;

[0048] Additive A has a BET of 5m 2 / g~10m2 / g; BET of additive B is 5m 2 / g~10m 2 / g, and the BET of additive A is less than or equal to the BET of additive B;

[0049] Additive A is added according to the ratio of element A to the target lithium nickel cobalt manganese positive electrode material generated being less than or equal to 6000 ppm, and additive B is added according to the ratio of element B to the target lithium nickel cobalt manganese positive electrode material generated being less than or equal to 6000 ppm.

[0050] The preparation method provided in the embodiment of the present application first reacts with the lithium compound during the low temperature sintering process to form a Li-BO compound, and then reacts with the A element to form a Li-BAO compound modification layer, so that the Li-BAO compound modification layer is only enriched at the inner grain boundary and does not enter the interior of the crystal. The reaction proceeds spontaneously. During preparation, the specific surface area of ​​additives A and B is required to be 5m 2 / g~10m 2 / g, and the specific surface area of ​​additive A is not greater than that of additive B. If the specific surface area of ​​additives A and additives B (hereinafter referred to as additives) is less than 5m 2 / g, it is not conducive to the reaction of element A and element B with lithium; if the specific surface area of ​​the additive is greater than 10m 2 / g, it may cause the additive to react with elements other than lithium; if the specific surface area of ​​additive A is greater than the specific surface area of ​​additive B, A may react with the lithium compound in advance. In the cases outside the above three required ranges, it is impossible to form a coating layer containing Li compounds only at the inner grain boundaries. In addition, this scheme also requires that additive A be fed in such a way that the ratio of element A to the target lithium nickel cobalt manganese positive electrode material generated is less than or equal to 6000ppm, and additive B be fed in such a way that the ratio of element B to the target lithium nickel cobalt manganese positive electrode material generated is less than or equal to 6000ppm. If the content of the additive is higher than the required range, the reaction product of the additive and the lithium compound will enter the interior of the crystal, which will destroy the internal structure of the crystal.

[0051] Therefore, the preparation method provided in the embodiment of the present application can produce a lithium nickel cobalt manganese positive electrode material with good electrochemical performance.

[0052] Optionally, additive A is added at a ratio of 1500ppm to 6000ppm (e.g., 1500ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm or 6000ppm) between element A and the target lithium nickel cobalt manganese positive electrode material generated, and additive B is added at a ratio of 500ppm to 6000ppm (e.g., 500ppm, 1000ppm, 1500ppm, 2000ppm, 3000ppm, 4000ppm, 5000ppm or 6000ppm) between element B and the target lithium nickel cobalt manganese positive electrode material generated.

[0053] The addition amount of additive element A is 1500ppm to 6000ppm, and the addition amount of additive element B is 500ppm to 6000ppm. If the addition amount of additive A and additive B is lower than the above optional range, the reaction products of A, B and lithium cannot spontaneously form a sufficiently thick coating layer at the inner grain boundary, and the side reaction with the electrolyte after the inner grain boundary rupture cannot be effectively suppressed.

[0054] As shown in Figure 1, the preparation method is specifically as follows:

[0055] S1. Mixed sintering

[0056] First, a nickel-cobalt-manganese precursor, a lithium source, and an additive are uniformly mixed to obtain a mixture, wherein the additive includes additive A and additive B.

[0057] Alternatively, the chemical formula of the nickel-cobalt-manganese precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Mn 1-x-y CO3, 0<x<1, 0<y<1, 0<x+y<1.

[0058] Optionally, the lithium source is selected from at least one of lithium hydroxide and lithium carbonate;

[0059] Optionally, the lithium source involved in sintering is fed in a molar ratio of lithium element to metal element in the nickel-cobalt-manganese precursor of 1.00 to 1.07:1 (eg, 1:1, 1.02:1, 1.04:1, 1.05:1 or 1.07:1).

[0060] Then, the mixture is placed in an atmosphere containing oxygen for sintering, and the sintering includes low-temperature sintering. The sintering conditions of the low-temperature sintering are: the sintering atmosphere is an air atmosphere, an oxygen atmosphere or a mixed atmosphere of oxygen and air, the volume proportion of oxygen is 20% to 100% (for example, 20%, 40%, 60%, 80% or 100%), the sintering temperature is 400°C to 500°C (for example, 400°C, 430°C, 450°C, 480°C or 500°C), and the sintering time is 4 to 6 hours (for example, 4 hours, 5 hours or 6 hours).

[0061] Furthermore, the sintering process further includes a high-temperature sintering stage. The conditions for the high-temperature sintering stage are as follows: based on the low-temperature sintering process, the sintering temperature is increased to 830°C to 950°C (e.g., 830°C, 850°C, 880°C, 900°C, or 950°C), and the sintering time is 7.5 hours to 12.5 hours (e.g., 7.5 hours, 8 hours, 10 hours, 12 hours, or 12.5 hours), to obtain a primary positive electrode material.

[0062] The high temperature sintering process selects different sintering conditions according to different metal element ratios, such as:

[0063] When you x Co y Mn 1-x-y When 0<x≤0.4 and 0<x+y<1 in (OH)2, the sintering conditions in the high temperature stage are: an oxygen atmosphere or a mixed atmosphere containing oxygen, wherein the volume proportion of oxygen is 20-100% (e.g., 20%, 40%, 60%, 80% or 100%), a temperature of 900°C to 950°C (e.g., 900°C, 910°C, 920°C, 930°C or 950°C), and a sintering time of 7.5-8.5h (e.g., 7.5h, 8h or 8.5h);

[0064] When you x Co y Mn 1-x-y When 0.4<x≤0.6 and 0.4<x+y<1 in (OH)2, the sintering conditions in the high temperature stage are: an oxygen atmosphere or a mixed atmosphere containing oxygen, wherein the volume proportion of oxygen is 30-100% (e.g., 30%, 40%, 60%, 80% or 100%), a temperature of 880°C to 930°C (e.g., 880°C, 890°C, 900°C, 920°C or 930°C), and a sintering time of 9.5-10.5h (e.g., 9.5h, 10h or 10.5h);

[0065] When you x Co y Mn 1-x-yWhen 0.6<x≤0.7 and 0.6<x+y<1 in (OH)2, the sintering conditions in the high temperature stage are: an oxygen atmosphere or a mixed atmosphere containing oxygen, wherein the volume proportion of oxygen is 60-100% (e.g., 60%, 70%, 80%, 90% or 100%), a temperature of 870°C to 920°C (e.g., 870°C, 880°C, 890°C, 900°C or 920°C), and a sintering time of 9.5-10.5 h (e.g., 9.5 h, 10 h or 10.5 h);

[0066] When you x Co y Mn 1-x-y When 0.7<x<1 and 0.7<x+y<1 in (OH)2, the sintering conditions in the high temperature section are: oxygen atmosphere or a mixed atmosphere with oxygen, the volume proportion of oxygen is 70-100% (for example, 70%, 80%, 90% or 100%), the temperature is 830℃~900℃ (for example, 830℃, 850℃, 870℃, 890℃ or 900℃), and the sintering time is 11.5~12.5h (for example, 11.5h, 12h or 12.5h).

[0067] Setting a low-temperature sintering stage before the high-temperature sintering stage can enable the additives to react fully, which is conducive to forming more modified layers on the inner interface, thereby further improving the electrochemical performance of the positive electrode material.

[0068] In order to obtain a positive electrode material with uniform particle size distribution and better electrochemical performance, the following step S2 is also performed:

[0069] S2, Crushing

[0070] The positive electrode material is initially crushed by jaw crusher, roller crusher and air crusher, and the positive electrode material is crushed from D50=5-10 μm to D50=2-10 μm to obtain a lithium nickel cobalt manganese single crystal positive electrode material with a modified layer on the inner interface.

[0071] The positive electrode provided in the embodiments of the present application is made using the positive electrode material provided in the embodiments of the present application or the positive electrode material prepared using the preparation method provided in the embodiments of the present application. Since the positive electrode includes the positive electrode material provided in the embodiments of the present application, it has better electrochemical performance.

[0072] Specifically, the positive electrode includes a current collector and a coating material disposed on the surface of the current collector. The coating material includes the positive electrode material provided in the embodiments of the present application, a conductive material, and a binder. The preparation method of the positive electrode includes: dispersing the positive electrode material, the conductive material, and the binder in a solvent in a certain proportion, uniformly mixing to obtain a dispersion, then coating the dispersion on the current collector, drying, and slicing to obtain the positive electrode.

[0073] The battery provided in the embodiment of the present application includes the positive electrode provided in the embodiment of the present application. Since the battery includes the positive electrode provided in the embodiment of the present application, it has better electrochemical performance.

[0074] Specifically, the battery includes a positive electrode, a negative electrode, a separator disposed between the positive electrode and the negative electrode, and an electrolyte.

[0075] The features and performance of the present application are further described in detail below with reference to the embodiments.

[0076] Example 1

[0077] Lithium hydroxide, chemical formula Ni 0.4 Co 0.3 Mn 0.3 The nickel-cobalt-manganese precursor of (OH)2, additive A and additive B are mixed by a ball mill mixer to obtain a mixture. 0.4 Co 0.3 Mn 0.3 The molar ratio of the metal elements in (OH)2 is 1.07:1. Additive A is WO3, and the addition amount (ratio to the prepared positive electrode material) is 6000ppm; Additive B is Ba(OH)2, and the addition amount (ratio to the prepared positive electrode material) is 2000ppm; The BET of additives A and B is 8m 2 / g.

[0078] The mixture was sintered in a high-temperature roller sintering furnace at 450°C for 5 hours in an atmosphere of approximately 20% oxygen (air), then raised to 950°C and held for 8 hours. The sintered agglomerates were then crushed using a jaw crusher and a roller mill, followed by air flow crushing to produce a lithium nickel cobalt manganese single crystal cathode material with a D50 of 5μm and a modified internal interface layer.

[0079] Example 2

[0080] This embodiment is basically the same as the first embodiment, except that:

[0081] The chemical formula of the nickel-cobalt-manganese precursor is changed to Ni 0.6 Co 0.2 Mn 0.2 (OH)2, lithium in lithium hydroxide and Ni 0.6 Co 0.2 Mn 0.2 The molar ratio of the metal elements in (OH)2 is 1.05:1, the oxygen concentration is 60%, the sintering temperature is 500℃ and kept for 4h, then the temperature is raised to 930℃ and kept for 10h.

[0082] Additive A has a BET of 10m 2 / g, the BET of additive B is 5m2 / g.

[0083] Example 3

[0084] This embodiment is basically the same as the first embodiment, except that:

[0085] The chemical formula of the nickel-cobalt-manganese precursor is changed to Ni 0.7 Co 0.1 Mn 0.2 (OH)2, lithium in lithium hydroxide and Ni 0.7 Co 0.1 Mn 0.2 The molar ratio of the metal elements in (OH)2 is 1.03:1, the oxygen concentration is 80%, the sintering temperature is 450℃ and kept for 5h, then the temperature is raised to 890℃ and kept for 10h.

[0086] The prepared precursor is shown in Figures 2 and 3.

[0087] Example 4

[0088] This embodiment is basically the same as the first embodiment, except that:

[0089] The chemical formula of the nickel-cobalt-manganese precursor is changed to Ni 0.8 Co 0.1 Mn 0.1 (OH)2, lithium in lithium hydroxide and Ni 08 Co 0.1 Mn 0.1 The molar ratio of the metal elements in (OH)2 is 1.01:1, the oxygen concentration is 100%, the sintering temperature is 400℃ and kept for 6h, then the temperature is raised to 830℃ and kept for 12h.

[0090] Additive A has a BET of 5m 2 / g, the BET of additive B is 5m 2 / g.

[0091] Example 5

[0092] This embodiment is basically the same as embodiment 3, except that the additive B is Ca(OH)2.

[0093] Example 6

[0094] This embodiment is basically the same as embodiment 3, except that additive A is MoO 3 and additive B is Ca(OH) 2 .

[0095] Example 7

[0096] This embodiment is basically the same as embodiment 3, except that the additive A is NH4ReO4.

[0097] Example 8

[0098] This embodiment is substantially the same as embodiment 3, except that the amount of additive A added is 1500 ppm, and the amount of additive B added is 500 ppm.

[0099] Example 9

[0100] This embodiment is substantially the same as embodiment 3, except that the amount of additive A added is 3000 ppm, and the amount of additive B added is 3000 ppm.

[0101] Example 10

[0102] This embodiment is substantially the same as embodiment 3, except that the amount of additive A added is 2000 ppm, and the amount of additive B added is 6000 ppm. Other aspects are the same as embodiment 3.

[0103] Example 11

[0104] This embodiment is basically the same as embodiment 3, except that the sintering temperature is 900°C.

[0105] Example 12

[0106] This embodiment is basically the same as embodiment 3, except that the sintering temperature is 880°C.

[0107] Example 13

[0108] This embodiment is basically the same as embodiment 3, with the only difference being that the oxygen concentration is 60%.

[0109] Example 14

[0110] This embodiment is basically the same as embodiment 3, except that no low-temperature sintering is performed. That is, the sintering conditions are: oxygen concentration 80%, sintering temperature 890° C., and sintering is completed at a temperature of 10 hours.

[0111] Comparative Example 1

[0112] This comparative example is basically the same as Example 3, except that additive A and additive B are not added.

[0113] Comparative Example 2

[0114] This comparative example is basically the same as Example 3, except that additive A is not added.

[0115] Comparative Example 3

[0116] This comparative example is basically the same as Example 3, except that additive B is not added.

[0117] Comparative Example 4

[0118] This comparative example is substantially the same as Example 3, except that the amount of additive A added is 7000 ppm.

[0119] Comparative Example 5

[0120] This comparative example is basically the same as Example 10, except that the addition amount of additive B is 7000 ppm.

[0121] Comparative Example 6

[0122] This comparative example is basically the same as Example 3, except that the BET of additive A is 15m 2 / g, the BET of additive B is 15m 2 / g.

[0123] Comparative Example 7

[0124] This comparative example is basically the same as Example 4, except that the BET of additive A is 3m 2 / g, the BET of additive B is 3m 2 / g.

[0125] Comparative Example 8

[0126] This comparative example is basically the same as Example 3, except that:

[0127] Additive A has a BET of 10m 2 / g, the BET of additive B is 5m 2 / g.

[0128] Experimental example

[0129] The button-type batteries of the positive electrode materials prepared in Examples 1 to 14 and Comparative Examples 1 to 8 were tested to measure their electrochemical properties.

[0130] The specific preparation method of the button battery is as follows: the above-mentioned positive electrode material, carbon black and adhesive are mixed in a certain mass ratio, placed in a defoaming machine for mixing to obtain an electrode material; then the electrode material is coated on an aluminum foil by blade coating, and then vacuum dried, and then rolled to obtain a positive electrode.

[0131] The binder may be polyvinylidene fluoride (PVDF), for example. The mass ratio of the positive electrode material, carbon black, and the binder may be 94:3:3.

[0132] The electrode pieces of Examples 1 to 15 and Comparative Examples 1 to 8 were assembled to produce button cells. The test environment temperature was 25°C, and the charge and discharge test rate was 0.1C. The capacity retention was tested at a high temperature of 45°C and a charge and discharge rate of 1C. The results are shown in Table 1.

[0133] The test results are recorded in Table 1 and Figure 4.

[0134] Table 1 Electrochemical performance test of each embodiment and comparative example

[0135] It can be seen from Table 1 and Figure 4 that the positive electrode materials prepared in various embodiments of the present application all have good electrochemical properties.

[0136] Comparing Example 3 with Comparative Examples 1-3, Example 3 has significantly higher initial discharge specific capacity and significantly lower impedance, indicating that the simultaneous addition of additives A and B can significantly improve the electrochemical performance of the positive electrode material.

[0137] Comparing Example 3 with Comparative Example 4, the capacity of Comparative Example 4 is worse and the impedance is increased, indicating that when the amount of additive A added exceeds the range required by this application, additive A may enter the interior of the single crystal and destroy the crystal structure, thereby causing a decrease in electrochemical performance.

[0138] Comparing Example 10 with Comparative Example 5, the capacity of Comparative Example 5 is worse and the impedance is increased, indicating that when the amount of additive B added exceeds the range required by this application, additive B may enter the interior of the single crystal and destroy the crystal structure, thereby causing a decrease in electrochemical performance.

[0139] Comparing Example 3 with Comparative Example 6, the capacity and impedance of Comparative Example 6 are both poor, indicating that when the BET of the additive is greater than the range required by this application, the additive may not react sufficiently with lithium, and an effective modification layer may not be formed, resulting in a decrease in electrochemical performance;

[0140] Comparing Example 4 with Comparative Example 7, the capacity of Comparative Example 7 is lower and the impedance is significantly increased, indicating that when the BET of the additive is less than the range required by this application, the additive may react with metals other than lithium and fail to form an effective modification layer, resulting in a decrease in electrochemical performance.

[0141] Comparing Example 3 with Comparative Example 8, the impedance of Comparative Example 8 is worse, indicating that the BET of Additive A cannot be greater than that of Additive B. If the BET of Additive A is greater, it is possible that A reacts with lithium in advance and fails to form an effective modification layer.

[0142] Comparing Example 3 with Examples 11 to 13, the electrochemical performance of Example 3 is better, while the sintering temperature and oxygen content of Examples 13 to 15 are not sintered under the most suitable sintering conditions for the corresponding precursor compared to Example 3, which shows that for the precursor Ni 0.7 Co 0.1 Mn 0.2(OH)2, the best sintering conditions are sintering temperature 890℃ and oxygen content 80%. Sintering under this condition can obtain positive electrode materials with better performance.

[0143] Comparing Example 3 with Example 14, Example 3 has better electrochemical performance and lower impedance, indicating that the low temperature section is conducive to the reaction of the additives and can enable the generated modified layer to better protect the inner grain boundaries.

[0144] FIG3 is a high-temperature cycle curve diagram of Example 3 of the present application and Comparative Example 1. As can be seen from the figure, the positive electrode material obtained in Example 3 has the best high-temperature cycle performance.

[0145] In summary, the modified layer at the inner grain boundary of the lithium nickel cobalt manganese cathode material provided in the embodiment of the present application can inhibit the side reaction between the material and the electrolyte caused by the rupture of the inner grain boundary and the exposure of the new interface during the preparation or high-voltage charging and discharging process. In addition, the modified layer protects the inner grain boundary while also acting as a fast ion conductor, thereby improving the capacity, rate, cycle and storage performance at higher voltages. Therefore, the lithium nickel cobalt manganese cathode material provided in the embodiment of the present application has excellent electrochemical properties.

[0146] The preparation method of the lithium nickel cobalt manganese positive electrode material provided in the embodiment of the present application is to add additives A and B during preparation. The role of element B is to first react with the lithium compound during the low temperature sintering process to form a Li-BO compound, and then react with element A to form a Li-BAO compound modification layer, so that the Li-BAO compound modification layer is only enriched at the inner grain boundary and does not enter the interior of the crystal. The reaction proceeds spontaneously. During preparation, the specific surface area of ​​additives A and additive B is required to be 5m 2 / g~10m 2 / g, and the specific surface area of ​​additive A is not greater than that of additive B. If the specific surface area of ​​additives A and additives B (hereinafter referred to as additives) is less than 5m 2 / g, it is not conducive to the reaction of element A and element B with lithium; if the specific surface area of ​​the additive is greater than 10m 2 / g, it may cause the additive to react with elements other than lithium; if the specific surface area of ​​additive A is greater than the specific surface area of ​​additive B, A may react with the lithium compound in advance. In the cases outside the above three required ranges, it is impossible to form a coating layer containing Li compounds only at the inner grain boundaries. In addition, this scheme also requires that additive A be fed in such a way that the ratio of element A to the target lithium nickel cobalt manganese positive electrode material generated is less than or equal to 6000ppm, and additive B be fed in such a way that the ratio of element B to the target lithium nickel cobalt manganese positive electrode material generated is less than or equal to 6000ppm. If the content of the additive is higher than the required range, the reaction product of the additive and the lithium compound will enter the interior of the crystal, which will destroy the internal structure of the crystal.

[0147] The above are merely optional embodiments of the present application and are not intended to limit the present application. Various modifications and variations are possible for those skilled in the art. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the present application shall be included within the scope of protection of the present application. Industrial Applicability

[0148] The lithium nickel cobalt manganese cathode material provided in this application includes a lithium nickel cobalt manganese single crystal and a modified layer located at the inner interface of the lithium nickel cobalt manganese single crystal. The modified layer is formed by the reaction of Li, A, B, and oxygen, wherein the element A is selected from at least one of W, Mo, and Re; and the element B is selected from at least one of Ba and Ca. The preparation method of the lithium nickel cobalt manganese cathode material comprises: uniformly mixing a nickel cobalt manganese precursor, a lithium source, additives A, and additives B, followed by sintering. The present application provides a preparation method capable of producing the lithium nickel cobalt manganese cathode material provided in this application. The preparation method is simple, and the resulting cathode material has excellent electrochemical properties.

Claims

1. A lithium nickel cobalt manganese cathode material, characterized in that, It includes a lithium nickel cobalt manganese single crystal and a modification layer located at the inner interface of the lithium nickel cobalt manganese single crystal. The modification layer is formed by the reaction of Li, A, B and oxygen. Element A is selected from at least one of the elements W, Mo and Re; Element B is selected from at least one of Ba and Ca.

2. The lithium nickel cobalt manganese cathode material according to claim 1, wherein The ratio of Element A to the lithium nickel cobalt manganese cathode material is 1500 ppm to 6000 ppm, and the ratio of Element B to the lithium nickel cobalt manganese cathode material is 500 ppm to 6000 ppm.

3. The lithium nickel cobalt manganese cathode material according to claim 1 or 2, characterized in that, The chemical formula of the lithium nickel cobalt manganese single crystal is LiNi x Co y Mn 1-x-y O2, where 0 < x < 1, 0 < y < 1, and 0 < x + y < 1.

4. A preparation method of a lithium nickel cobalt manganese cathode material, characterized in that, It includes: Mixing a nickel cobalt manganese precursor, a lithium source, additive A and additive B evenly and then sintering; Additive A is an element A single substance or a compound of element A, and element A is selected from at least one of the elements W, Mo and Re; Additive B is an element B single substance or a compound of element B, and element B is selected from at least one of Ba and Ca; The BET of the additive A is 5 m 2 / g to 10 m 2 / g; the BET of the additive B is 5 m 2 / g to 10 m 2 / g, and the BET of the additive A is less than or equal to the BET of the additive B; Additive A is fed according to the ratio of element A to the target lithium nickel cobalt manganese cathode material to be generated less than or equal to 6000 ppm, and additive B is fed according to the ratio of element B to the target lithium nickel cobalt manganese cathode material to be generated less than or equal to 6000 ppm.

5. The preparation method according to claim 4, characterized in that, Additive A is fed according to the ratio of element A to the target lithium nickel cobalt manganese cathode material to be generated of 1500 ppm to 6000 ppm, and additive B is fed according to the ratio of element B to the target lithium nickel cobalt manganese cathode material to be generated of 500 ppm to 6000 ppm.

6. The preparation method according to claim 4 or 5, characterized in that, The lithium source is selected from at least one of lithium hydroxide and lithium carbonate; Optionally, the lithium source participating in the sintering is fed according to the molar ratio of lithium element to the metal element in the nickel cobalt manganese precursor of 1 to 1.07:1; Optionally, the chemical formula of the nickel cobalt manganese precursor is Ni x Co y Mn 1-x-y (OH)2 or Ni x Co y Mn 1-x-y CO3, where 0 < x < 1, 0 < y < 1, and 0 < x + y < 1.

7. The preparation method according to any one of claims 4 to 6, characterized in that, Sintering includes high-temperature sintering; When Ni x Co y Mn 1-x-y In (OH)2, when 0 < x ≤ 0.4 and 0 < x + y < 1, the sintering conditions in the high-temperature stage are as follows: oxygen atmosphere or a mixed atmosphere with oxygen, the volume fraction of oxygen is 20 - 100%, the temperature is 900°C - 950°C, and the sintering time is 7.5 - 8.5 h; When Ni x Co y Mn 1-x-y In (OH)2, when 0.4 < x ≤ 0.6 and 0.4 < x + y < 1, the sintering conditions in the high-temperature stage are as follows: oxygen atmosphere or a mixed atmosphere with oxygen, the volume ratio of oxygen is 30 - 100%, the temperature is 880°C - 930°C, and the sintering time is 9.5 - 10.5 h; When Ni x Co y Mn 1-x-y in (OH)2, when 0.6 < x ≤ 0.7 and 0.6 < x + y < 1, the sintering conditions in the high-temperature stage are as follows: an oxygen atmosphere or a mixed atmosphere with oxygen, the volume ratio of oxygen is 60-100%, the temperature is 870°C-920°C, and the sintering time is 9.5-10.5 h; When Ni x Co y Mn 1-x-y When 0.7 < x < 1 and 0.7 < x + y < 1 in (OH)₂, the sintering conditions in the high-temperature stage are as follows: oxygen atmosphere or a mixed atmosphere containing oxygen, with the volume ratio of oxygen being 70 - 100%, the temperature being 830°C - 900°C, and the sintering time being 11.5 - 12.5 h; Optionally, the sintering further includes low-temperature sintering. The low-temperature sintering conditions are: adding a section of low-temperature sintering before the high-temperature sintering, the sintering temperature is 400 °C to 500 °C, and sintering for 4 to 6 h.

8. The preparation method according to any one of claims 4-7, characterized in that, After sintering, a primary cathode material is obtained. After obtaining the primary cathode material, it further includes: Crushing the primary cathode material from D50 = 5 - 10 μm to D50 = 2 - 10 μm.

9. A positive electrode, characterized in that, It is prepared by using the cathode material described in any one of claims 1 to 3 or the cathode material prepared by the preparation method described in any one of claims 4 to 8.

10. A battery, characterized in that, It includes the cathode described in claim 9.

Images