A ternary cathode material and its preparation method, and a battery

Abstract

This invention belongs to the field of cathode materials, and provides a ternary cathode material, its preparation method, and a battery. The tungsten content of the ternary cathode material provided by this invention gradually decreases along a direction perpendicular to the surface of the ternary cathode material towards the interior, and the tungsten element in the ternary cathode material is mainly distributed within a depth range of 100 nm. The tungsten element material on the outer surface of the ternary active material includes tungsten oxide and lithium tungstate. The formed lithium tungstate consumes the residual lithium on the surface of the ternary active material, reducing the residual lithium content on the surface of the ternary cathode material. In the preparation method of the ternary cathode material provided by this invention, tungsten chloride with a low melting point is deposited on the surface of the ternary active material, and then the tungsten chloride is oxidized to tungsten oxide using an oxidation reaction to obtain the ternary cathode material. This reduces heat consumption while ensuring that the tungsten element is uniformly distributed on the surface of the ternary cathode material, thereby obtaining a ternary cathode material with high compressive strength, low surface residual lithium content, and good cycle performance.

Description

Technical Field

[0001] This invention relates to the field of cathode materials, specifically to a ternary cathode material, its preparation method, and a battery. Background Technology

[0002] Against the backdrop of global carbon neutrality, countries around the world are accelerating the development of green new energy sources. Lithium-ion batteries, as devices for storing and releasing electrical energy, play a crucial role in the development of new energy sources.

[0003] Lithium nickel manganese oxide (LiCO), a ternary cathode material in lithium-ion batteries, is considered the most likely candidate for widespread application in power batteries due to its advantages such as high discharge capacity, low production cost, stable layered structure, and good thermal stability. However, it still suffers from problems such as low capacity retention, large irreversible phase transitions, poor cycle performance, and poor high-temperature thermal stability. Surface coating is considered a simple and effective method to improve multiple properties of the material. Common coating elements include Al, B, Mg, W, Zr, and Ti. Among them, W oxide (WO3) is an acidic oxide that can neutralize residual alkali on the cathode material surface. Furthermore, the W compound formed on the surface can effectively protect the cathode material from electrolyte corrosion, improve its compressive strength, and enhance its cycle performance. Additionally, the Li2WO4 formed by WO3 and residual alkali has certain ionic conductivity, which can increase the ionic conductivity of the cathode material and improve its rate performance.

[0004] Currently, WO3 coating generally uses a dry coating process. Although the dry coating process is simple to operate, it is difficult to guarantee the uniformity of the coating. Low coating uniformity cannot effectively protect the cathode material from electrolyte corrosion, cannot effectively improve the compressive strength of the cathode material, and cannot effectively neutralize residual alkali on the surface of the cathode material, ultimately failing to effectively improve cycle performance.

[0005] In view of this, the present invention is proposed. Summary of the Invention

[0006] The present invention aims to provide a ternary cathode material and its preparation method, as well as a battery, thereby increasing the compressive strength of the ternary cathode material, reducing the surface residual alkali content, and improving cycle performance.

[0007] To achieve the above objectives, the present invention provides a ternary cathode material in a first aspect, wherein the tungsten content of the ternary cathode material gradually decreases along a direction perpendicular to the surface of the ternary cathode material and pointing inward;

[0008] The tungsten content accumulated at a depth of 50 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 60%-90% of the total tungsten content of the ternary cathode material.

[0009] The tungsten content accumulated at a depth of 100 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 80%-95% of the total tungsten content of the ternary cathode material.

[0010] In some embodiments, the ternary cathode material satisfies: 30% ≤ (D v10 -D v10 ') / D v10 ×100%≤55%;

[0011] And / or, the ternary cathode material satisfies: 15% ≤ (D v50 -D v50 ') / D v50 ×100%≤25%;

[0012] And / or, the ternary cathode material satisfies: 8% ≤ (D v90 -D v90 ') / D v90 ×100%≤20%;

[0013] Among them, D v10 D v50 and D v90 These represent the particle sizes, in μm, corresponding to when the volumetric cumulative distribution of the ternary cathode material reaches 10%, 50%, and 90%; D v10 '、D v50 'and D v90 'These are the particle sizes corresponding to the cumulative volume distribution of the ternary cathode material after being pressed under 30kN pressure, reaching 10%, 50%, and 90%, respectively, in μm.

[0014] In a second aspect, the present invention provides a method for preparing a ternary cathode material, comprising the following steps:

[0015] A ternary active material and tungsten chloride are reacted by vapor phase deposition to obtain a ternary cathode material precursor;

[0016] The ternary cathode material precursor is oxidized to obtain the ternary cathode material.

[0017] In some embodiments, the vapor deposition reaction includes: spreading the ternary active material flat on the side of the tubular reactor near the exhaust pipe, placing the tungsten chloride in a ceramic boat and placing it on the side of the tubular reactor near the air inlet, introducing an inert gas into the tubular reactor, and then evacuating the tubular reactor; rotating the tubular reactor and performing a first reaction at a first reaction temperature to obtain a ternary cathode material precursor.

[0018] In some embodiments, the oxidation includes: sequentially introducing an inert gas and oxygen into the tubular reactor, performing a second reaction at a second reaction temperature, and obtaining a ternary cathode material.

[0019] In some embodiments, the tungsten chloride is at least one of WCl6 and WCl5; and / or, the inert gas is at least one of N2, Ar and He.

[0020] In some embodiments, the mass ratio of the ternary active material to tungsten chloride is 100:1.5-2.5.

[0021] In some embodiments, the vacuuming refers to bringing the vacuum level inside the tubular reactor to -0.09 MPa to -0.05 MPa;

[0022] And / or, the rotational speed is 10~60 rpm.

[0023] In some embodiments, the first reaction temperature includes the temperature T1 of the region where tungsten chloride is located, the temperature T2 of the region where the ternary active material is located, and the temperature T3 of the remaining regions in the tubular reactor; the second reaction temperature includes a first-stage reaction temperature T4 and a second-stage reaction temperature T5; the second reaction includes a first-stage reaction at the first-stage reaction temperature T4 and a second-stage reaction at the second-stage reaction temperature T5.

[0024] Wherein, the temperature T1 is 280℃~400℃;

[0025] And / or, the temperature T2 is 150℃~300℃;

[0026] And / or, the temperature T3 is 250℃~400℃;

[0027] And / or, the duration of the first reaction is 1 to 5 hours;

[0028] And / or, the temperature T4 is 150℃~300℃;

[0029] And / or, the temperature T5 is 300℃~700℃;

[0030] And / or, a portion of the second reaction lasts for 0.5 to 2 hours;

[0031] And / or, the reaction time for the two stages in the second reaction is 0.5~2.5h.

[0032] In a third aspect, the present invention provides a battery comprising the ternary cathode material described in the first aspect, or the ternary cathode material obtained by the preparation method of the ternary cathode material described in the second aspect.

[0033] The beneficial effects of this invention include:

[0034] In the ternary cathode material provided by this invention, tungsten is mainly distributed within a depth of 100 nm in a direction perpendicular to the surface of the ternary cathode material and pointing inward, which can effectively increase the compressive strength of the ternary cathode material. The tungsten material on the outer surface of the ternary active material includes tungsten oxide and lithium tungstate. The formed lithium tungstate consumes the residual lithium on the surface of the ternary active material, reduces the residual lithium content on the surface of the ternary cathode material, and thus improves the cycle performance of the cathode material.

[0035] In the preparation method of ternary cathode material provided by the present invention, tungsten chloride with a low melting point is deposited on the surface of ternary active material, and then tungsten chloride is oxidized to tungsten oxide by oxidation reaction to obtain ternary cathode material. This reduces heat consumption while making tungsten element uniformly distributed on the surface of ternary cathode material. Attached Figure Description

[0036] To more clearly illustrate the technical solutions of the embodiments of the present invention, the accompanying drawings used in the embodiments will be briefly introduced below. It should be understood that the following drawings only show some embodiments of the present invention and should not be regarded as a limitation on the scope. For those skilled in the art, other related drawings can be obtained based on these drawings without creative effort.

[0037] Figure 1 This is a schematic diagram of the tubular reactor used in an embodiment of the present invention;

[0038] Figure 2 (a) is a SEM image of the ternary cathode material obtained in Comparative Example 4 of this invention; Figure 2 (b) is a SEM image of the ternary cathode material obtained in Example 1; Figure 2 (c) is a SEM image of the ternary cathode material obtained in Example 2; Figure 2 (d) is the SEM image of the ternary cathode material obtained in Comparative Example 1; Figure 2 (e) is a SEM image of the ternary cathode material obtained in Comparative Example 2; Figure 2 (f) is a SEM image of the ternary cathode material obtained in Comparative Example 3;

[0039] Figure 3 (a)-(b) are 3D time-of-flight secondary ion mass spectrometry images of tungsten in different micro-regions of the ternary cathode material obtained in Example 1; Figure 3 (c)-(d) are time-of-flight secondary ion mass spectrometry (3D) images of tungsten in different micro-regions of the ternary cathode material obtained in Comparative Example 1. Figure 3 (e)-(f) are time-of-flight secondary ion mass spectrometry (3D) images of tungsten in different micro-regions of the ternary cathode material obtained in Comparative Example 2; Figure 3(g)-(h) are 3D time-of-flight secondary ion mass spectra of tungsten in different micro-regions of the ternary cathode material obtained in Comparative Example 3;

[0040] Figure 4 The graph shows the trend of tungsten element accumulation in different micro-regions of the ternary cathode materials obtained in Example 1 and Comparative Examples 1-3 along the direction perpendicular to the surface of the ternary cathode material and pointing inward.

[0041] Figure 5 The graph shows a comparison of the cycle performance of Examples 1-2 and Comparative Examples 1-5. Detailed Implementation

[0042] The following detailed description, with appropriate reference to the accompanying drawings, discloses a ternary cathode material, its preparation method, and a battery according to the present invention. However, unnecessary detailed descriptions may be omitted. For example, detailed descriptions of well-known matters and repetitive descriptions of essentially the same structures may be omitted. This is to avoid unnecessarily lengthy descriptions and to facilitate understanding by those skilled in the art. Furthermore, the accompanying drawings and the following description are provided to enable those skilled in the art to fully understand this application and are not intended to limit the subject matter of the claims.

[0043] The "range" disclosed in this application is defined by a lower limit and an upper limit. A given range is defined by selecting a lower limit and an upper limit, which define the boundaries of the specific range. Specifically, "()", ")", "[", and "]" represent intervals, where "()" or ")" represents an open interval, meaning the endpoints of the interval are not included; and "[" and "]" represent a closed interval, meaning the endpoints of the interval are included. A range defined in this way can include endpoints or not, and can be arbitrarily combined, meaning any lower limit can be combined with any upper limit to form a range.

[0044] Specifically, for example, if the ranges 60-120 and 80-110 are listed for a specific parameter, it is understood that the ranges 60-110 and 80-120 are also expected. Furthermore, if the minimum range values ​​are listed as 1 and 2, and if the maximum range values ​​are listed as 3, 4, and 5, then the following ranges are all expected: 1-3, 1-4, 1-5, 2-3, 2-4, and 2-5. In this application, unless otherwise stated, the numerical range “ab” represents a shortened representation of any combination of real numbers between a and b, where a and b are real numbers. For example, the numerical range “0-5” means that all real numbers between “0-5” have been listed herein, and “0-5” is merely a shortened representation of these numerical combinations. Additionally, when a parameter is stated as an integer ≥ 2, it is equivalent to disclosing that the parameter is, for example, an integer 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, etc. If (10, 20) is listed, it is understood as any value in the interval 10-20 excluding 10 and 20; (10, 20] is understood as any value in the interval 10-20 excluding 10 but including 20.

[0045] Unless otherwise specified, all embodiments and optional embodiments of this application can be combined to form new technical solutions.

[0046] Unless otherwise specified, all technical features and optional technical features of this application may be combined to form new technical solutions.

[0047] Unless otherwise specified, all steps in this application may be performed sequentially or randomly, preferably sequentially. For example, the method includes steps (a) and (b), indicating that the method may include steps (a) and (b) performed sequentially, or it may include steps (b) and (a) performed sequentially. For example, the mention that the method may also include step (c) indicates that step (c) may be added to the method in any order. For example, the method may include steps (a), (b), and (c), or it may include steps (a), (c), and (b), or it may include steps (c), (a), and (b), etc.

[0048] Unless otherwise specified, the terms "comprising" and "including" as used in this application can be open-ended or closed-ended. For example, "comprising" and "including" can mean that other components not listed may also be included, or that only the listed components may be included.

[0049] Unless otherwise specified, the term "or" is inclusive in this application. For example, the phrase "A or B" means "A, B, or both A and B". More specifically, the condition "A or B" is satisfied by any of the following conditions: A is true (or exists) and B is false (or does not exist); A is false (or does not exist) and B is true (or exists); or both A and B are true (or exist).

[0050] The first aspect of the present invention provides a ternary cathode material, wherein the tungsten content of the ternary cathode material gradually decreases along a direction perpendicular to the surface of the ternary cathode material and pointing inward;

[0051] The tungsten content accumulated at a depth of 50 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 60%-90% of the total tungsten content of the ternary cathode material.

[0052] The tungsten content accumulated at a depth of 100 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 80%-95% of the total tungsten content of the ternary cathode material.

[0053] Depth is the length of the ternary cathode material from the surface to the interior along a direction perpendicular to the surface of the ternary cathode material, measured in nm.

[0054] In ternary cathode materials, tungsten is mainly distributed within a depth of 100 nm in a direction perpendicular to the surface of the ternary cathode material and pointing inward. This ensures the effective content of tungsten on the outer surface of the ternary active material, effectively improving the compressive strength of the ternary cathode material, reducing residual lithium on the surface, and improving the cycle performance of the material.

[0055] In some embodiments, the ternary cathode material satisfies: 30% ≤ (D v10 -D v10 ') / D v10 ×100%≤55%;

[0056] And / or, the ternary cathode material satisfies: 15% ≤ (D v50 -D v50 ') / D v50 ×100%≤25%;

[0057] And / or, the ternary cathode material satisfies: 8% ≤ (D v90 -D v90 ') / D v90 ×100%≤20%;

[0058] Among them, D v10 D v50 and D v90These represent the particle sizes, in μm, corresponding to when the volumetric cumulative distribution of the ternary cathode material reaches 10%, 50%, and 90%; D v10 '、D v50 'and D v90 'These are the particle sizes corresponding to the cumulative volume distribution of the ternary cathode material after being pressed under 30kN pressure, reaching 10%, 50%, and 90%, respectively, in μm.

[0059] The ternary cathode material provided by this invention has good mechanical strength and minimal particle size change after pressing, thus exhibiting high compressive strength and good structural stability.

[0060] A second aspect of the present invention provides a method for preparing a ternary cathode material, characterized by comprising the following steps:

[0061] A ternary active material and tungsten chloride are reacted by vapor phase deposition to obtain a ternary cathode material precursor;

[0062] The ternary cathode material precursor is oxidized to obtain the ternary cathode material.

[0063] In some embodiments, the vapor deposition reaction includes: spreading the ternary active material flat on the side of the tubular reactor near the exhaust pipe, placing the tungsten chloride in a ceramic boat and placing it on the side of the tubular reactor near the air inlet, introducing an inert gas into the tubular reactor, and then evacuating the tubular reactor; rotating the tubular reactor and performing a first reaction at a first reaction temperature to obtain a ternary cathode material precursor.

[0064] In some embodiments, the oxidation includes: sequentially introducing an inert gas and oxygen into the tubular reactor, performing a second reaction at a second reaction temperature, and obtaining a ternary cathode material.

[0065] In some embodiments, the tungsten chloride is first uniformly deposited on the surface of the ternary active material, and then oxygen is introduced under heating conditions, causing the tungsten chloride to oxidize to tungsten oxide. The reaction mechanism includes:

[0066] 2WCl6 + 3O2 = 2WO3 + 6Cl2

[0067] 2WCl5 + 3O2 = 2WO3 + 5Cl2

[0068] The above process ensures uniform deposition of oxides on the surface of the ternary active material. Simultaneously, some tungsten oxide reacts with residual lithium on the active material surface to form lithium tungstate, ultimately resulting in tungsten on the surface of the ternary cathode material existing in the form of tungsten oxide or lithium tungstate. By employing low-temperature vapor deposition followed by oxidation, the uniformity of tungsten on the outer surface of the ternary active material and its effective content are ensured, effectively improving the compressive strength of the ternary cathode material, reducing residual lithium on the surface, and enhancing the material's cycle performance.

[0069] In some embodiments, the first reaction temperature includes the temperature T1 of the region where tungsten chloride is located, the temperature T2 of the region where the ternary active material is located, and the temperature T3 of the remaining regions in the tubular reactor; the second reaction temperature includes a first-stage reaction temperature T4 and a second-stage reaction temperature T5; the second reaction includes a first-stage reaction at the first-stage reaction temperature T4 and a second-stage reaction at the second-stage reaction temperature T5.

[0070] Wherein, the temperature T1 is 280℃~400℃;

[0071] And / or, the temperature T2 is 150℃~300℃;

[0072] And / or, the temperature T3 is 250℃~400℃;

[0073] And / or, the duration of the first reaction is 1 to 5 hours;

[0074] And / or, the temperature T4 is 150℃~300℃;

[0075] And / or, the temperature T5 is 300℃~700℃;

[0076] And / or, a portion of the second reaction lasts for 0.5 to 2 hours;

[0077] And / or, the reaction time for the two stages in the second reaction is 0.5~2.5h.

[0078] The above-mentioned vapor deposition reaction has a low temperature and a short oxidation time, so the heat consumption of the entire ternary cathode material preparation process is low.

[0079] In some embodiments, the tubular reactor is rotatable and has an inlet pipe, an exhaust pipe, and a vacuum pipe at each end; the tubular reactor has a section that can be heated individually along its length axis.

[0080] The following describes embodiments of this application. The embodiments described below are exemplary and are only used to explain this application, and should not be construed as limiting this application. Where specific techniques or conditions are not specified in the embodiments, they are performed according to the techniques or conditions described in the literature in this field or according to the product instructions. Reagents or instruments used, unless otherwise specified, are all conventional products that can be obtained commercially.

[0081] For tubular reactors, please refer to Figure 1 The features and performance of the present invention will be further described in detail below with reference to embodiments. It should be understood that these embodiments are for illustrative purposes only and are not intended to limit the scope of the invention.

[0082] Example 1

[0083] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 2.2 g of WCl6 was loaded into a ceramic boat and placed on the inlet side.

[0084] (2) Introduce N2 into the tubular reactor until the chamber is full of N2, close the inlet valve and the outlet valve, turn on the vacuum pump and open the vacuum valve. After the vacuum degree in the tubular reactor reaches -0.09 MPa, close the vacuum valve. Repeat the above steps 3 times to maintain the vacuum degree in the tubular reactor at -0.09 MPa.

[0085] (3) The tubular reactor is rotated at a speed of 15 rpm, and the temperature T1 of the tungsten chloride area is set to 380℃, the temperature T2 of the ternary active material area is set to 250℃, and the temperature T3 of the remaining areas is set to 380℃. After each area reaches the set temperature, it is kept warm for 2 hours.

[0086] (4) After the heat preservation in step (3) is completed, maintain the set temperature of each area and continuously introduce N2 into the tubular reactor, and open the exhaust valve to discharge the residual WCl6 gas in the tubular reactor.

[0087] (5) After the residual WCl6 gas in the tubular reactor is completely discharged, stop the N2 supply, switch to O2 supply, and set the temperature T4 of all areas in the tubular reactor to 250℃. After the temperature of each area stabilizes, keep it at that temperature for 1 hour. Then set the temperature T5 of all areas in the tubular reactor to 600℃ and keep it at that temperature for 2 hours.

[0088] (6) After the heat preservation is completed, stop heating, continue to introduce O2, and after the tubular reactor cools to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0089] Example 2

[0090] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 2.0 g of WCl5 was loaded into a ceramic boat and placed on the inlet side.

[0091] (2) Introduce N2 into the tubular reactor until the chamber is full of N2, close the inlet valve and the outlet valve, turn on the vacuum pump and open the vacuum valve. After the vacuum degree in the tubular reactor reaches -0.09 MPa, close the vacuum valve. Repeat the above steps 3 times to maintain the vacuum degree in the tubular reactor at -0.09 MPa.

[0092] (3) After the vacuum in the tubular reactor stabilizes, the tubular reactor is rotated at a speed of 20 rpm. The temperature T1 in the area where tungsten chloride is located is set to 310℃, the temperature T2 in the area where the ternary active material is located is set to 230℃, and the temperature T3 in the other areas is set to 310℃. After each area reaches the set temperature, it is kept warm for 3 hours.

[0093] (4) After the heat preservation in step (3) is completed, maintain the set temperature of each area and continuously introduce N2 into the tubular reactor, and open the exhaust valve to discharge the residual WCl5 gas in the tubular reactor.

[0094] (5) After the residual WCl5 gas in the tubular reactor is completely discharged, stop the N2 supply, switch to O2 supply, and set the temperature T4 of all areas in the tubular reactor to 230℃. After the temperature of each area stabilizes, keep it at that temperature for 1.5h. Then set the temperature T5 of all areas in the tubular reactor to 650℃ and keep it at that temperature for another 2.5h.

[0095] (6) After the heat preservation is completed, stop heating, continue to introduce O2, and after the tubular reactor cools to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0096] Example 3

[0097] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 1.5 g of WCl6 was loaded into a ceramic boat and placed on the inlet side.

[0098] (2) Introduce N2 into the tubular reactor until the chamber is full of N2, close the inlet valve and the outlet valve, turn on the vacuum pump and open the vacuum valve. After the vacuum degree in the tubular reactor reaches -0.09 MPa, close the vacuum valve. Repeat the above steps 3 times to maintain the vacuum degree in the tubular reactor at -0.09 MPa.

[0099] (3) The tubular reactor is rotated at a speed of 10 rpm, and the temperature T1 of the tungsten chloride area is set to 360℃, the temperature T2 of the ternary active material area is set to 150℃, and the temperature T3 of the remaining areas is set to 360℃. After each area reaches the set temperature, it is kept warm for 2 hours.

[0100] (4) After the heat preservation in step (3) is completed, maintain the set temperature of each area and continuously introduce N2 into the tubular reactor, and open the exhaust valve to discharge the residual WCl6 gas in the tubular reactor.

[0101] (5) After the residual WCl6 gas in the tubular reactor is completely discharged, stop the N2 supply, switch to O2 supply, and set the temperature T4 of all areas in the tubular reactor to 150℃. After the temperature of each area stabilizes, keep it at the temperature for 1 hour, and then set the temperature T5 of all areas in the tubular reactor to 400℃ and continue to keep it at the temperature for 2 hours.

[0102] (6) After the heat preservation is completed, stop heating, continue to introduce O2, and after the tubular reactor cools to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0103] Comparative Example 1

[0104] WO3 was coated with 5000 ppm of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 After thoroughly mixing with O2, the material is kept at 600 °C for 6 hours in an oxygen atmosphere to obtain the WO3-coated cathode material.

[0105] Comparative Example 2

[0106] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 2.2 g of WCl6 was loaded into a ceramic boat and placed on the inlet side.

[0107] (2) Rotate the tubular reactor at a speed of 15 rpm and introduce air to remove water and CO2 into the tubular reactor, and open the exhaust valve. After the air in the tubular reactor has been replaced,

[0108] (4) Set the temperature T1 of the tungsten chloride area to 380℃, the temperature T2 of the ternary active material area to 250℃, and the temperature T3 of the remaining areas to 380℃. After each area reaches the set temperature, keep it warm for 2 hours.

[0109] (3) After the heat preservation is completed, stop the air supply to remove water and CO2, keep the exhaust valve open, switch to O2 supply, and set all areas to 600℃. After each area reaches the set temperature, continue heat preservation for 2 hours.

[0110] (4) After the heat preservation is completed, stop heating and continue to introduce O2. After the tubular reactor cools down to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0111] Comparative Example 3

[0112] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1 O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 2.2 g of WCl6 was loaded into a ceramic boat and placed on the inlet side.

[0113] (2) Rotate the tubular reactor at a speed of 15 rpm and introduce air that has been dewatered and de-CO2ed into the tubular reactor. Close the exhaust valve, turn on the vacuum pump and open the vacuum valve. Adjust the vacuum valve to make the vacuum degree inside the tubular reactor reach -0.085 MPa and maintain it stably, so that the tubular reactor maintains a state of continuous air supply and vacuum degree.

[0114] (3) Set the temperature T1 of the tungsten chloride area to 300℃, the temperature T2 of the ternary active material area to 150℃, and the temperature T3 of the remaining areas to 300℃. After each area reaches the set temperature, keep it warm for 2 hours.

[0115] (4) After the heat preservation is completed, close the vacuum valve and vacuum pump, stop the air supply, switch to O2 supply, open the exhaust valve, and set the temperature of all areas T4 in the tubular reactor to 250℃. After the temperature of each area stabilizes, keep it warm for 1 hour, and then set the temperature of all areas T5 in the tubular reactor to 600℃ and continue to keep it warm for 2 hours.

[0116] (7) After the heat preservation is completed, stop heating, continue to introduce O2, and after the tubular reactor cools down to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0117] Comparative Example 4

[0118] Untreated ternary active materials.

[0119] Comparative Example 5

[0120] (1) 100.0 g of ternary active material LiNi 0.8 Co 0.1 Mn 0.1O2 was spread evenly on one side of the exhaust port of the tubular reactor, and then 2.2 g of WCl6 was loaded into a ceramic boat and placed on the inlet side.

[0121] (2) Introduce dehydrated and CO2-free air into the tubular reactor until the chamber is full. Close the inlet and outlet valves, turn on the vacuum pump and open the vacuum valve. After the vacuum level in the tubular reactor reaches -0.09 MPa, close the vacuum valve.

[0122] (3) The tubular reactor is rotated at a speed of 15 rpm, and the temperature T1 of the tungsten chloride area is set to 380℃, the temperature T2 of the ternary active material area is set to 250℃, and the temperature T3 of the remaining areas is set to 380℃. After each area reaches the set temperature, it is kept warm for 2 hours.

[0123] (4) After the heat preservation in step (3) is completed, maintain the set temperature of each area and continuously introduce air to remove water and CO2 into the tubular reactor, and open the exhaust valve to discharge the residual WCl6 gas in the tubular reactor.

[0124] (5) After the residual WCl6 gas in the tubular reactor is completely discharged, stop the air that removes water and CO2, switch to O2, and set the temperature T4 of all areas in the tubular reactor to 250℃. After the temperature of each area stabilizes, keep it at that temperature for 1 hour, and then set the temperature T5 of all areas in the tubular reactor to 600℃ and keep it at that temperature for 2 hours.

[0125] (6) After the heat preservation is completed, stop heating, continue to introduce O2, and after the tubular reactor cools to room temperature, stop introducing O2 into the tubular reactor and stop rotating the tubular reactor to obtain the ternary cathode material.

[0126] Example of effect 1:

[0127] The morphology of the cathode materials obtained in Examples 1-2 and Comparative Examples 1-4 was examined using scanning electron microscopy.

[0128] from Figure 2 (a) It can be seen that the surface of the uncoated ternary active material is smooth.

[0129] from Figure 2 (b)-(c) and Figure 2 As can be seen from (e)-(f), the ternary cathode material obtained by vapor deposition has a relatively smooth surface.

[0130] from Figure 2 (d) It can be seen that the ternary cathode material obtained by direct dry coating with tungsten oxide has a lot of dot-like coatings on the surface and does not form a uniform and effective coating layer.

[0131] Example 2:

[0132] (1) Using a time-of-flight secondary ion mass spectrometer, the time-of-flight secondary ion mass spectrometry 3D images of tungsten in different micro-regions of the ternary cathode materials provided in Example 1 and Comparative Examples 1-3 were obtained.

[0133] from Figure 3 As can be seen from (a)-(b), the preparation scheme provided by the present invention yields a ternary cathode material with a uniform coating layer in different micro-regions.

[0134] from Figure 3 As can be seen from (c)-(d), the ternary cathode material obtained by dry coating with tungsten oxide has a large difference in tungsten content in different micro-regions, and cannot obtain a uniformly coated ternary cathode material.

[0135] from Figure 3 (e)-(f) and Figure 3 (g)-(h) show that not vacuuming the tubular reactor or using inert gas to protect the tungsten chloride gasification process will result in the inability to form a coating layer of uniform depth on the surface of the ternary cathode material.

[0136] (2) Calculation method of tungsten accumulation at different depths: The distribution value of tungsten signal intensity along the radial direction (direction perpendicular to the particle surface and pointing inward) of the ternary cathode material particles was obtained by time-of-flight secondary ion mass spectrometry, and the relationship curve of tungsten accumulation with depth was further calculated. At least 3 micro-regions were selected for measurement for each sample, and the average value of tungsten accumulation at a certain depth was calculated as the tungsten accumulation at that depth. Using time-of-flight secondary ion mass spectrometry, the proportion of tungsten accumulation at different depths in the total tungsten content of the ternary cathode materials provided in Examples 1-3 and Comparative Examples 1-3 along the direction perpendicular to the ternary cathode material surface and pointing inward was measured. The results are shown in Table 1.

[0137] Table 1 shows the percentage of accumulated tungsten at different depths along a direction perpendicular to the surface of the ternary cathode material, pointing inwards, relative to the total tungsten content.

[0138]

[0139] As can be seen from Table 1, the tungsten content accumulated at a depth of 50 nm in the direction perpendicular to the surface of the ternary cathode material and pointing inward in the ternary cathode material is 60%-90% of the total tungsten content of the ternary cathode material; the tungsten content accumulated at a depth of 100 nm in the direction perpendicular to the surface of the ternary cathode material and pointing inward in the ternary cathode material is 80%-95% of the total tungsten content of the ternary cathode material.

[0140] Figure 4This figure shows the cumulative tungsten content in different micro-regions obtained in Examples 1 and Comparative Examples 1-3, along a direction perpendicular to the surface of the ternary cathode material and pointing inwards, as a function of depth. The figure shows that in the ternary cathode material of Example 1, the tungsten is mainly concentrated within a depth of 100 nm; while in the ternary cathode materials of Comparative Examples 1-3, the tungsten is uniformly distributed throughout the entire test depth range. The ternary cathode material obtained in Example 1 has an effective tungsten coating layer on its surface, which effectively protects it, increases its compressive strength, and enhances its pressure resistance.

[0141] Example of effect 3:

[0142] The strength performance tests of the cathode materials obtained in Examples 1-3 and Comparative Examples 1-5 are shown in Table 2.

[0143] The testing steps include: first, using a Malvern laser particle size analyzer to test the particle size distribution of the cathode material to obtain the original particle size distribution; then, pressing the cathode material with a pressure of 30 kN to obtain the pressed cathode material; and finally, using a Malvern laser particle size analyzer to test the particle size distribution of the pressed cathode material to obtain the pressed cathode material particle size distribution.

[0144] Particle size breakage rate = (D vx -D vx ') / D vx ×100%, where D vx The particle size, D, corresponds to the cumulative volume distribution of the original ternary cathode material reaching x%. vx 'Refers to the particle size corresponding to the cumulative volume distribution of the ternary cathode material after pressing reaching x%.

[0145] Table 2 Strength performance tests of Examples 1-3 and Comparative Examples 1-5

[0146]

[0147] As can be seen from Table 2, the breakage rates of the ternary cathode materials in Examples 1-3 when the cumulative volume distribution reaches 10%, 50% and 90% are 48%-54.1%, 18.7%-23.8% and 15.1%-19.3%, respectively.

[0148] Compared with Example 1, the breakage rate of the ternary cathode materials in Comparative Examples 1-3 when the volume cumulative distribution reaches 10%, 50% and 90% is higher. This is because the tungsten content accumulated in different micro-regions of the ternary cathode materials obtained in Comparative Examples 1-3 at a depth of 50nm or 100nm in the direction perpendicular to the surface of the ternary cathode material and pointing inward is lower. Therefore, its compressive strength and pressure resistance are lower.

[0149] Compared with Examples 1-3 and Comparative Examples 1-3, the breakage rate of the ternary cathode material in Comparative Example 4 when the volume cumulative distribution reaches 10%, 50% to 90% is higher. This is because the ternary cathode material has not undergone vapor deposition and oxidation treatment and is a pure ternary active material, thus it has the lowest compressive strength and the lowest pressure resistance.

[0150] Compared to Example 1, the breakage rate of the ternary cathode material in Comparative Example 5 was slightly higher when the volume cumulative distribution reached 10%, 50%, and 90%. This is because air with dehydrated and CO2-free properties was used instead of N2 during the vacuuming process, and the vacuuming step was not repeated. Therefore, some oxygen remained in the tubular reactor after vacuuming, causing some tungsten chloride to be directly oxidized to tungsten oxide during the vapor-phase deposition reaction of the ternary active material and tungsten chloride, reducing the uniformity of tungsten element dispersion on the surface of the ternary active material. Consequently, its compressive strength and pressure resistance were slightly lower.

[0151] Example of effect 4:

[0152] Surface residual lithium content test: The residual lithium content in Examples 1-3 and Comparative Examples 1-5 was tested by potentiometric titration, and the results are shown in Table 3.

[0153] Table 3. Residual lithium test results of Examples 1-3 and Comparative Examples 1-5

[0154]

[0155] As can be seen from Table 3, the residual lithium content in Examples 1-3 is significantly lower than that in Comparative Examples 1-5.

[0156] Example 5:

[0157] Battery preparation method: The prepared positive electrode material, acetylene black, and PVDF were weighed at a mass ratio of 90:5:5. These three substances were added to NMP solvent and thoroughly mixed. After ultrasonic dispersion, a slurry was prepared. The slurry was uniformly coated onto aluminum foil and then transferred to a vacuum oven at 120 °C for drying. After 12 h, the dried electrode was removed and rolled, then punched to obtain a circular positive electrode with a diameter of 14 mm. A lithium metal sheet was used as the negative electrode, with a concentration of 1 mol·L⁻¹. -1 A LiPF6 organic solution (EC:DEC:DMC = 1:1:1, volume ratio) was used as the electrolyte, and a Celgrd 2400 polypropylene microporous membrane was used as the separator. Coin cells were assembled in a glove box protected by high-purity argon. After assembly, the cells were allowed to stand for 4 hours, and then their electrical performance was tested using a LAND battery testing system.

[0158] Electrochemical performance testing: The cathode materials obtained in Examples 1-3 and Comparative Examples 1-5 were respectively fabricated into coin cells. The initial discharge specific capacity at 0.1C, the initial efficiency at 0.1C, and the discharge specific capacity at 5C were tested at 25°C. The performance changes after 100 cycles were tested at 45°C. The cycle performance test conditions were: using a LAND charge-discharge apparatus, 2.8~4.30V, 1C charge-discharge. The discharge capacity retention rate after 100 cycles is shown in Table 4.

[0159] Comparison of cycle performance of batteries in Examples 1-2 and Comparative Examples 1-5 Figure 5 As shown in the figure, the capacity retention rate of the lithium-ion battery containing the cathode material of the present invention decreases slowly, and the capacity retention rate is high after 100 cycles.

[0160] Table 4 Comparison of electrochemical performance of Examples 1-3 and Comparative Examples 1-5

[0161]

[0162] As can be clearly seen from Table 4, the rate performance of Examples 1-3 is significantly higher than that of Comparative Examples 1-5, the capacity retention of Examples 1-3 after 100 cycles is significantly higher than that of Comparative Examples 1-5, and the electrochemical performance of Examples 1-3 is significantly better than that of Comparative Examples 1-5.

[0163] It should be noted that this application is not limited to the above-described embodiments. The above embodiments are merely examples, and any embodiments with the same structure and effect as the technical concept within the scope of this application are included in the technical scope of this application. Furthermore, various modifications that can be conceived by those skilled in the art to the embodiments, and other ways of constructing by combining some of the constituent elements of the embodiments, without departing from the spirit of this application, are also included in the scope of this application.

Claims

1. A ternary cathode material, characterized in that, The tungsten content of the ternary cathode material gradually decreases along the direction perpendicular to the surface of the ternary cathode material and pointing inward; The tungsten content accumulated at a depth of 50 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 60%-90% of the total tungsten content of the ternary cathode material. The tungsten content accumulated at a depth of 100 nm along a direction perpendicular to the surface of the ternary cathode material and pointing inward is 80%-95% of the total tungsten content of the ternary cathode material.

2. The ternary cathode material according to claim 1, characterized in that, The ternary cathode material satisfies: 30% ≤ (D v10 -D v10 ') / D v10 ×100%≤55%; And / or, the ternary cathode material satisfies: 15% ≤ (D v50 -D v50 ') / D v50 ×100%≤25%; And / or, the ternary cathode material satisfies: 8% ≤ (D v90 -D v90 ') / D v90 ×100%≤20%; Among them, D v10 D v50 and D v90 These represent the particle sizes, in μm, corresponding to when the volumetric cumulative distribution of the ternary cathode material reaches 10%, 50%, and 90%; D v10 '、D v50 'and D v90 'These are the particle sizes corresponding to the cumulative volume distribution of the ternary cathode material after being pressed under 30kN pressure, reaching 10%, 50%, and 90%, respectively, in μm.

3. A method for preparing a ternary cathode material according to claim 1 or 2, characterized in that, Includes the following steps: A ternary active material and tungsten chloride are reacted by vapor phase deposition to obtain a ternary cathode material precursor; The ternary cathode material precursor is oxidized to obtain the ternary cathode material.

4. The method for preparing the ternary cathode material according to claim 3, characterized in that, The vapor deposition reaction includes: spreading the ternary active material on the side of the tubular reactor near the exhaust pipe, placing the tungsten chloride in a ceramic boat and placing it on the side of the tubular reactor near the air inlet, introducing inert gas into the tubular reactor, and then evacuating the tubular reactor; rotating the tubular reactor and performing a first reaction at a first reaction temperature to obtain a ternary cathode material precursor.

5. The method for preparing the ternary cathode material according to claim 4, characterized in that, The oxidation process includes sequentially introducing an inert gas and oxygen into the tubular reactor, performing a second reaction at a second reaction temperature, and obtaining a ternary cathode material.

6. The method for preparing the ternary cathode material according to any one of claims 3-5, characterized in that, The tungsten chloride is at least one of WCl6 and WCl5; And / or, the inert gas is at least one of N2, Ar and He.

7. The method for preparing the ternary cathode material according to claim 4 or 5, characterized in that, The mass ratio of the ternary active material to tungsten chloride is 100:1.5-2.

5.

8. The method for preparing the ternary cathode material according to claim 4, characterized in that, The vacuuming refers to bringing the vacuum level inside the tubular reactor to -0.09 MPa to -0.05 MPa; And / or, the rotational speed is 10~60 rpm.

9. The method for preparing the ternary cathode material according to claim 5, characterized in that, The first reaction temperature includes the temperature T1 of the region where tungsten chloride is located, the temperature T2 of the region where the ternary active material is located, and the temperature T3 of the remaining regions in the tubular reactor; the second reaction temperature includes a first-stage reaction temperature T4 and a second-stage reaction temperature T5; the second reaction includes a first-stage reaction at the first-stage reaction temperature T4 and a second-stage reaction at the second-stage reaction temperature T5. Wherein, the temperature T1 is 280℃~400℃; And / or, the temperature T2 is 150℃~300℃; And / or, the temperature T3 is 250℃~400℃; And / or, the duration of the first reaction is 1 to 5 hours; And / or, the temperature T4 is 150℃~300℃; And / or, the temperature T5 is 300℃~700℃; And / or, a portion of the second reaction lasts for 0.5 to 2 hours; And / or, the reaction time for the two stages in the second reaction is 0.5~2.5h.

10. A battery, characterized in that, The battery comprises the ternary cathode material according to any one of claims 1-2, or the ternary cathode material obtained by the preparation method of any one of claims 3-9.

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