Single-crystal ternary cathode material and preparation method and application thereof

Abstract

This application relates to the field of lithium battery technology, and in particular to a single-crystal ternary cathode material, its preparation method, and its application. The preparation method of the single-crystal ternary cathode material includes: mixing a first transition metal oxide with a ternary cathode material precursor and a lithium source, and then sintering the mixture once in an oxygen-containing atmosphere to obtain the single-crystal ternary cathode material; the first sintering conditions are: heating to 830℃~900℃ at a heating rate of 1.8℃ / min~2.8℃ / min, holding at that temperature for t1, then cooling to 720℃~780℃ and holding at that temperature for t2, where t1:t2 is (0.22~0.35):1. The single-crystal ternary cathode material prepared by the above method has high lithium penetration and a high degree of single crystallization.

Description

Technical Field

[0001] This application relates to the field of lithium battery technology, and in particular to a single-crystal ternary cathode material, its preparation method, and its application. Background Technology

[0002] The increasing demand for high-energy-density lithium batteries has driven the development of high-nickel ternary cathode materials. Increasing the nickel content and decreasing the cobalt content can improve the specific capacity of high-nickel ternary cathode materials. However, excessively high Ni content leads to a decrease in the lifespan and safety performance of these materials.

[0003] Compared to high-nickel agglomerated ternary cathode materials, high-nickel single-crystal small-particle cathode materials have the characteristics of high pressure resistance. During charge and discharge, they can reduce the pulverization phenomenon between particles, thereby effectively reducing the side reactions at the interface between the high-nickel ternary cathode material and the electrolyte, and improving the cycle performance of lithium batteries. Currently, the preparation of ultra-high nickel single-crystal materials has the following problems: 1) High-nickel single-crystal materials prepared by conventional methods have poor uniformity and roundness between particles, resulting in low lithium penetration; 2) The lithium-nickel mixing degree of high-nickel single-crystal materials is relatively high, resulting in a high retention rate of impurity lithium on the material surface. Summary of the Invention

[0004] Therefore, it is necessary to provide a single-crystal ternary cathode material that can improve lithium penetration and single-crystalization degree, and reduce lithium-nickel mixing degree to enhance electrochemical performance, as well as its preparation method and application.

[0005] In a first aspect, this application provides a method for preparing a single-crystal ternary cathode material, comprising the following steps:

[0006] The compound containing the first transition metal element is mixed with a ternary cathode material precursor and a lithium source, and then sintered once in an oxygen-containing atmosphere to obtain the single-crystal ternary cathode material; the conditions for the first sintering are as follows:

[0007] First, heat the material to 830℃~900℃ at a heating rate of 1.8℃ / min~2.8℃ / min, hold it at that temperature for t1, then cool it down to 720℃~780℃ and hold it at that temperature for t2, where t1:t2 is (0.22~0.35):1.

[0008] In some implementations, 3.4h≤t1≤4.8h, 13.7h≤t2≤15.1h.

[0009] In some embodiments, the chemical formula of the ternary cathode material precursor is Ni. x Co y Mn 1-x-y (OH)2, where 0.9≤x≤0.98, 0.005≤y≤0.1, and x+y<1.

[0010] In some embodiments, the mass ratio of the ternary cathode material precursor, the lithium source, and the compound containing the first transition metal element is 100:(42-52):(1.0-1.4).

[0011] In some embodiments, after the first sintering, the method further includes mixing the single-crystal ternary cathode material with a compound containing a second transition metal element and performing a second sintering under an oxygen-containing atmosphere to coat the surface of the single-crystal ternary cathode material with the second transition metal element.

[0012] Optionally, the mass ratio between the ternary cathode material and the compound containing the second transition metal element is 100:(0.36 to 0.56);

[0013] Optionally, the secondary sintering temperature is 300℃~500℃, and the holding time is 6h~11h.

[0014] In some embodiments, the compound containing a first transition metal element and the compound containing a second transition metal element each independently include one or more of zirconium oxide, titanium oxide, magnesium oxide, aluminum oxide, tungsten oxide, vanadium oxide, yttrium oxide, and strontium oxide.

[0015] In some embodiments, before mixing the single-crystal ternary cathode material with a compound containing a second transition metal element, the method further includes a step of crushing and sieving the single-crystal ternary cathode material to control the particle size D50 of the single-crystal ternary cathode material to be between 3.0 μm and 4.0 μm.

[0016] Secondly, this application also provides a single-crystal ternary cathode material, which is prepared by the method for preparing single-crystal ternary cathode materials as described in the first aspect of this application.

[0017] Thirdly, this application further provides a lithium battery comprising the single-crystal ternary cathode material described in the second aspect of this application.

[0018] Fourthly, this application provides an electrical device that includes the lithium battery described in the third aspect of this application.

[0019] The method for preparing single-crystal ternary cathode material provided in this application first involves molding at a high temperature and then repairing at a lower temperature. This improves the lithium penetration degree of the single-crystal ternary cathode material and the degree of single crystallization of primary particles in the single-crystal ternary cathode material, thereby achieving the purpose of stabilizing the internal crystal structure of the single-crystal ternary cathode material, reducing the retention rate of impurity lithium on its surface, and obtaining a single-crystal ternary cathode material with low impurity lithium and long cycle life.

[0020] In addition, shortening the time t1 required for high-temperature molding and simultaneously increasing the time t2 required for low-temperature repair can help to further improve the lithium penetration of single-crystal ternary cathode materials, reduce the retention of impurity lithium on the surface of single-crystal ternary cathode material particles, and thus stabilize the crystal structure of single-crystal ternary cathode materials. Attached Figure Description

[0021] To more clearly illustrate the technical solutions in the specific embodiments of this application or the prior art, the drawings used in the description of the specific embodiments or the prior art will be briefly introduced below. Obviously, the drawings described below are some embodiments of this application. For those skilled in the art, other drawings can be obtained from these drawings without creative effort.

[0022] Figure 1 These are scanning electron microscope (SEM) images of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-4 and Comparative Examples 1-3.

[0023] Figure 2 The graph shows the lithium impurity data of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1 and 2.

[0024] Figure 3 The graph shows the lithium impurity data of the high-nickel single-crystal ternary cathode materials prepared in Examples 1 and 4 and Comparative Example 3.

[0025] Figure 4 The graph shows a comparison of the cycle performance of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1 and 2.

[0026] Figure 5 The graph shows a comparison of the cycle performance of the high-nickel single-crystal ternary cathode materials prepared in Examples 1 and 4 and Comparative Example 3. Detailed Implementation

[0027] To facilitate understanding of this application, a more complete description will be provided below with reference to the accompanying drawings. Preferred embodiments of this application are shown in the drawings. However, this application can be implemented in many different forms and is not limited to the embodiments described herein. Rather, these embodiments are provided to provide a thorough and complete understanding of the disclosure of this application.

[0028] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the application. The term "and / or" as used herein includes any and all combinations of one or more of the associated listed items.

[0029] Traditional methods for preparing ultra-high nickel single-crystal materials often suffer from poor single-crystalization, low lithium penetration, high lithium-nickel mixing, and high surface impurity lithium retention. Therefore, this application provides a method for preparing a single-crystal ternary cathode material to improve upon these problems.

[0030] In a first aspect, this application provides a method for preparing a single-crystal ternary cathode material, including step a.

[0031] The above-mentioned method for preparing single-crystal ternary cathode material first involves molding at a high temperature and then repairing at a lower temperature. This improves the lithium penetration degree of the single-crystal ternary cathode material and the degree of single crystallization of primary particles in the single-crystal ternary cathode material, thereby achieving the goal of stabilizing the internal crystal structure of the single-crystal ternary cathode material, reducing the retention rate of impurity lithium on its surface, and obtaining a single-crystal ternary cathode material with low impurity lithium and long cycle life.

[0032] In addition, shortening the time t1 required for high-temperature molding and simultaneously increasing the time t2 required for low-temperature repair can help to further improve the lithium penetration of single-crystal ternary cathode materials, reduce the retention of impurity lithium on the surface of single-crystal ternary cathode material particles, and thus stabilize the crystal structure of single-crystal ternary cathode materials.

[0033] Step a: The compound containing the first transition metal element is mixed with the ternary cathode material precursor and the lithium source, and then sintered once in an oxygen-containing atmosphere to obtain the single-crystal ternary cathode material; wherein the conditions for the first sintering are as follows:

[0034] First, heat the material to 830℃~900℃ at a heating rate of 1.8℃ / min~2.8℃ / min, hold it at that temperature for t1, then cool it down to 720℃~780℃ and hold it at that temperature for t2, where t1:t2 is (0.22~0.35):1.

[0035] In this application, the heating rate can be any value between 1.8℃ / min and 2.8℃ / min, and can also be 1.9℃ / min, 2℃ / min, 2.1℃ / min, 2.2℃ / min, 2.3℃ / min, 2.4℃ / min, 2.5℃ / min, 2.6℃ / min, or 2.7℃ / min. Controlling the heating rate within the above range can improve the uniformity of single-crystal formation of particles; if the heating rate is further increased, the uniformity of the single-crystal particles of the material deteriorates, and even agglomeration-like phenomena may occur.

[0036] In this application, the holding time t1:t2 is any value between (0.22~0.35):1, and t1:t2 can also be 0.23:1, 0.24:1, 0.25:1, 0.26:1, 0.27:1, 0.28:1, 0.29:1, 0.30:1, 0.31:1, 0.32:1, 0.33:1, or 0.34:1. By adjusting the ratio of t1 and t2 within the above range (adjusting t1 to be less than t2), that is, by extending the time required for low-temperature repair compared to the time used for high-temperature forming, it is beneficial to improve the lithium penetration of the single-crystal ternary cathode material, reduce the retention of impurity lithium on the surface of the single-crystal ternary cathode material particles, and thus stabilize the crystal structure of the single-crystal ternary cathode material.

[0037] Furthermore, 3.4h≤t1≤4.8h, 13.7h≤t2≤15.1h.

[0038] In some embodiments, the compound containing the first transition metal element includes one or more of zirconium oxide, titanium oxide, magnesium oxide, aluminum oxide, tungsten oxide, vanadium oxide, yttrium oxide, and strontium oxide.

[0039] In this application, the ternary cathode material precursor specifically refers to a high-nickel ternary cathode material precursor. In some embodiments, the chemical formula of the ternary cathode material precursor is Ni. x Co y Mn 1-x-y (OH)2, where 0.9≤x≤0.98, 0.005≤y≤0.1, and x+y<1.

[0040] In some embodiments, the mass ratio between the ternary cathode material precursor, the lithium source, and the compound containing the first transition metal element is 100:(42-52):(1.0-1.4).

[0041] In some implementations, the cooling rate required to cool to 720°C to 780°C is 0.45°C / min to 1.25°C / min.

[0042] In some embodiments, the compound containing the first transition metal element is present in the sintered material at a mass percentage of 0.96% to 1.35%.

[0043] In some implementations, the oxygen-containing atmosphere in step a is specifically an oxygen-enriched atmosphere, which means that oxygen accounts for at least 99% of the total gas mass.

[0044] In this application, the method and conditions for mixing the compound containing the first transition metal element with the ternary cathode material precursor and the lithium source are not limited, as long as uniform mixing is achieved. As an example, the mixing method includes any of the following:

[0045] Method 1: Mix the compound containing the first transition metal element, the ternary cathode material precursor, and the lithium source together;

[0046] Method 2: First, mix the compound containing the first transition metal element with the ternary cathode material precursor, and then add a lithium source for further mixing. Method 2 is preferred.

[0047] Furthermore, the mixing speed of the compound containing the first transition metal element with the ternary cathode material precursor is 200 rpm / min to 400 rpm / min, and the mixing time is 5 min to 10 min; after adding the lithium source, the mixing speed is 400 rpm / min to 1000 rpm / min, and the mixing time is 20 min to 40 min.

[0048] In some embodiments, the preparation method further includes step c.

[0049] Step c: The ternary cathode material obtained in step a is mixed with a compound containing a second transition metal element, and then subjected to secondary sintering in an oxygen-containing atmosphere to coat the second transition metal element onto the surface of the ternary cathode material. It should be noted that the second transition metal element is coated onto the surface of the ternary cathode material in the form of an oxide and / or lithium oxide.

[0050] In some embodiments, the compound containing a second transition metal element includes one or more of zirconium oxide, titanium oxide, magnesium oxide, aluminum oxide, tungsten oxide, vanadium oxide, yttrium oxide, and strontium oxide. Preferably, the compound containing a second transition metal element includes one or more of zirconium oxide, titanium oxide, magnesium oxide, aluminum oxide, tungsten oxide, and vanadium oxide.

[0051] In some embodiments, the mass ratio between the ternary cathode material and the compound containing the second transition metal element is 100:(0.36 to 0.56).

[0052] In some embodiments, the secondary sintering temperature is 300℃~500℃, and the holding time is 6h~11h.

[0053] In some implementations, the oxygen-containing atmosphere in step c specifically refers to an atmosphere containing oxygen, such as an oxygen atmosphere or an air atmosphere.

[0054] In some embodiments, step b is included before step c. Step b involves crushing and sieving the single-crystal ternary cathode material obtained in step a to control the particle size D50 of the single-crystal ternary cathode material to be between 3.0 μm and 4.0 μm. Controlling the particle size of the single-crystal ternary cathode material within this range during the crushing process ensures that the particles do not adhere together, achieving a high degree of deagglomeration and minimal particle damage. It also reduces the amount of fine powder generated during crushing, thereby improving the product yield. In this application, any method known in the art can be used to crush the single-crystal ternary cathode material; for example, air jet milling can be used.

[0055] According to a specific implementation method, the preparation method of single-crystal ternary cathode material includes the following steps:

[0056] Step S10: First, mix the first transition metal oxide with the ternary cathode material precursor, then add a lithium source and mix again. Then, perform a single sintering under an oxygen-containing atmosphere to obtain a ternary cathode material doped with the first transition metal element. The conditions for the single sintering are as follows:

[0057] First, heat the material to 830℃~900℃ at a heating rate of 1.8℃ / min~2.8℃ / min, hold it at that temperature for t1, then cool it down to 720℃~780℃ and hold it at that temperature for t2, where t1:t2 is (0.22~0.35):1;

[0058] Step S20: The ternary cathode material obtained in step S10 is crushed and sieved to control the particle size D50 of the ternary cathode material within 3.0 μm to 4.0 μm;

[0059] Step S30: The ternary cathode material obtained in step S20 is mixed with a compound containing a second transition metal element and sintered again in an oxygen-containing atmosphere to coat the second transition metal element onto the surface of the ternary cathode material.

[0060] Secondly, this application also provides a single-crystal ternary cathode material, which is prepared by the method for preparing single-crystal ternary cathode materials as described in the first aspect of this application.

[0061] The aforementioned single-crystal ternary cathode material has a high degree of single crystallization and a low surface impurity lithium retention rate, resulting in higher compaction density and lithium penetration.

[0062] Thirdly, this application further provides a lithium battery comprising the single-crystal ternary cathode material described in the second aspect of this application.

[0063] It is understood that the lithium battery provided in this application may also include other necessary structures, such as a negative electrode, an electrolyte, and a separator.

[0064] As an example, the negative electrode can be a carbon-based negative electrode material or a combination of a carbon-based negative electrode material and a negative electrode current collector. The carbon-based negative electrode material includes one or more of artificial graphite, natural graphite, graphitized carbon fiber, graphitized carbon microspheres, fullerene, and amorphous carbon. The negative electrode current collector can be an aluminum current collector.

[0065] The electrolyte can be a solid electrolyte or an electrolyte solution. Specifically, it can be an electrolyte solution formed by lithium salt and organic solvent. The lithium salt can be one or more of LiPF6, LiBF4, LiSbF6 and LiAsF6. The organic solvent is mainly selected from carbonate solvents, such as ethylene carbonate (EC), ethyl methyl carbonate (EMC) and diethyl carbonate (DEC).

[0066] The primary function of the separator is to prevent short circuits between the positive and negative electrodes and to provide a channel for lithium ions. Separators that meet the requirements can include known separators, which can be selected from polyolefin-based polymer membranes. The polyolefin-based polymer can include polypropylene and polyethylene. It is understood that the polyolefin-based polymer membrane can specifically be a multilayer membrane, a microporous membrane, a woven fabric, or a nonwoven fabric.

[0067] Fourthly, this application provides an electrical device that includes the lithium battery described in the third aspect of this application.

[0068] In some implementations, the electrical device may specifically be a device powered by a lithium secondary battery. For example, the electrical device may be a small electronic device (mobile phone, PDA, laptop, camera, etc.), a vehicle, or a power tool, such as an electric drill, electric hammer, electric saw, or cutting machine.

[0069] The present application will be further described in detail below with reference to specific embodiments.

[0070] Example 1

[0071] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. .H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.3℃ / min and held for 4.1 h (t1); then, the temperature was decreased to 760℃ after 1 h and held for 14.4 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.28. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0072] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0073] Example 2

[0074] The preparation method of Example 2 is basically the same as that of Example 1, except that the ratio of the holding time t1 / t2 in step 1) is reduced from 0.28 to 0.22. The specific steps are as follows:

[0075] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. . H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.3℃ / min and held for 3.4 h (t1); then, the temperature was decreased to 760℃ after 1 h and held for 15.1 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.22. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0076] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0077] Example 3

[0078] The preparation method of Example 3 is basically the same as that of Example 1, except that the ratio of the holding time t1 / t2 in step 1) is increased from 0.28 to 0.35. The specific steps are as follows:

[0079] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. . H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.3℃ / min and held for 4.8 h (t1); then, the temperature was decreased to 760℃ after 1 h and held for 13.7 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.35. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0080] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0081] Example 4

[0082] The preparation method of Example 4 is basically the same as that of Example 1, except that the heating rate in step 1) is increased from 2.3℃ / min to 2.8℃ / min. The specific steps are as follows:

[0083] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. . H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.8℃ / min and held for 4.1 h (t1); then, the temperature was decreased to 760℃ after 1 h and held for 14.4 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.28. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0084] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0085] Comparative Example 1

[0086] The preparation method of Comparative Example 1 is basically the same as that of Example 1, except that the ratio of the holding time t1 / t2 in step 1) is reduced from 0.28 to 0.18. The specific steps are as follows:

[0087] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. .H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.3℃ / min and held for 2.8 h (t1), then cooled to 760℃ after 1 h and held for 15.7 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.18. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0088] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0089] Comparative Example 2

[0090] The preparation method of Comparative Example 2 is basically the same as that of Example 1, except that the ratio of the holding time t1 / t2 in step 1) is increased from 0.28 to 0.41. The specific steps are as follows:

[0091] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm / min for 10 min; then 469 g of LiOH·H₂O was added, and the mixture was further mixed at 700 rpm / min for 30 min to form a mixture. Subsequently, a first sintering was performed in an oxygen-enriched atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 2.3℃ / min and held for 5.4 h (t1); then, the temperature was decreased to 760℃ after 1 h and held for 13.1 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.41. Then, an airflow crusher was used to crush the sintered material to obtain high-nickel single-crystal cathode material particles doped with Al, Y and Zr with a particle size D50 of 3.5μm. The particles had good dispersion, no adhesion, and minimal surface damage.

[0092] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0093] Comparative Example 3

[0094] The preparation method of Comparative Example 3 is basically the same as that of Comparative Example 1, except that the heating rate in step 1) is increased from 2.3℃ / min to 3.8℃ / min. The specific steps are as follows:

[0095] 1) Put 1kg Ni 0.96 Co 0.03 Mn 0.01 The (OH)₂ precursor and 11.8 g of dopant (including alumina, yttrium oxide, and zirconium oxide in a mass ratio of 8.7:0.42:2.68) were mixed in a high-speed mixer at 250 rpm for 10 min; then 469 g of LiOH was added. . H2O was added and mixed at 700 rpm for 30 minutes to form a mixture. Then, a first sintering was performed in an oxygen-rich atmosphere. The specific process parameters for the first sintering were as follows: first, the temperature was increased to 873℃ at a rate of 3.8℃ / min and held for 4.1 h (t1), then cooled to 760℃ for 1 h and held for 14.4 h (t2), i.e., t1 + t2 = 18.5 h and t1 / t2 = 0.28. The sintered material was then crushed using an airflow crusher to obtain high-nickel single-crystal cathode material particles doped with Al, Y, and Zr with a particle size D50 of 3.5 μm. The particles exhibited good dispersion, no adhesion, and minimal surface damage.

[0096] 2) Take 500g of the high-nickel single-crystal cathode material particles obtained in step 1) and mix them evenly with 2.05g of coating agent (including alumina and tungsten oxide in a mass ratio of 0.67:1.38), and sinter them again at 400℃ for 8h to coat Al and W elements onto the surface of the high-nickel single-crystal cathode material particles, thus obtaining a high-nickel single-crystal ternary cathode material (LiNi). 0.954 Co 0.035 Mn 0.011 O2).

[0097] The high-nickel single-crystal ternary cathode materials prepared in Examples 1-4 and Comparative Examples 1-3 were subjected to relevant performance tests.

[0098] Acetylene black was used as a conductive agent and PVDF as a binder. The test sample, conductive agent, and binder were weighed out in a mass ratio of 90:5:5 and stirred evenly to prepare a paste-like positive electrode mixture. This positive electrode mixture was coated onto the surface of aluminum foil and dried at high temperature. Test electrodes of appropriate size were cut out and pressed to the required thickness using a calendering method, then dried for later use. CR2032 coin cells were selected for the test, and lithium metal sheets were used as the negative electrode. A separator was sandwiched between the positive and negative electrodes, and the positive electrode, separator, and negative electrode were assembled using a stacked assembly process.

[0099] 1) Capacity test:

[0100] After the button cell batteries were left to stand for 12 hours, charge and discharge tests were performed according to a specific charging and discharging method. The specific charging and discharging method and steps are as follows:

[0101] a) Constant current charging: Charging current is 0.2 ItA, cutoff voltage (4.25V vs. Li / Li) + );

[0102] b) Constant voltage charging: Charging voltage is 4.25V vs. Li / Li + Cut-off current: 0.005 ItA;

[0103] h) Let stand for 5 minutes;

[0104] i) Constant current discharge: Discharge current is 0.2 ItA, cutoff voltage (2.5V vs. Li / Li) + );

[0105] j) Let stand for 5 minutes.

[0106] 2) Cyclic performance test:

[0107] After the button cell battery has been left to stand for 12 hours, the charging and discharging steps described above are repeated according to a certain charging and discharging mode. The relevant parameters are recorded after 50 cycles of "charging-discharging".

[0108] The capacity and cycle performance test results of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-4 and Comparative Examples 1-3 are shown in Table 1.

[0109] Table 1

[0110] Example 1 214.6 88.46 91.50 Example 2 214.5 88.53 91.63 Example 3 214.0 88.36 91.39 Example 4 214.2 88.51 91.27 Comparative Example 1 214.8 88.47 91.03 Comparative Example 2 213.5 88.19 90.86 Comparative Example 3 213.8 88.27 90.93

[0111] Scanning electron microscope (SEM) images of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-4 and Comparative Examples 1-3 are shown below. Figure 1 As shown in (a) to (f). From Figure 1It can be seen that the high-nickel single-crystal ternary cathode materials prepared in Examples 1 to 4 have similar roundness and uniformity of single-crystalization of particles; however, due to the short high-temperature molding time in Comparative Example 1, the uniformity of single-crystalization of particles in the high-nickel single-crystal ternary cathode material is poor, and the number of small particles increases; while due to the long high-temperature molding time in Comparative Example 2, the number of large single crystal particles increases; and due to the excessively fast heating rate in Comparative Example 3, the amount of lithium source penetrating into the lattice is less, resulting in a decrease in the degree of single-crystalization of particles.

[0112] Figure 2 The graph shows the lithium impurity data of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1 and 2. Figure 3 This is a graph showing the lithium impurity data for the high-nickel single-crystal ternary cathode materials prepared in Examples 1 and 4 and Comparative Example 3. Figure 2 It can be seen that the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 all have low surface lithium impurity content; however, the high-nickel single-crystal ternary cathode material prepared in Comparative Example 2 has a significantly increased surface lithium impurity content. This indicates that as the ratio of high-temperature forming time to low-temperature repair increases, the amount of lithium participating in single-crystal forming decreases, that is, the amount of lithium penetrating from the surface into the crystal lattice decreases, and more remains on the surface of the cathode material as free Li. + It exists. (By) Figure 3 It can be seen that as the heating rate increases (Comparative Example 3), the effective time for lithium to penetrate from the surface into the lattice decreases, resulting in more lithium remaining on the surface of the cathode material.

[0113] Figure 4 The graph shows a comparison of the cycle performance of the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 and Comparative Examples 1 and 2. Figure 5 This is a comparison of the cycle performance of the high-nickel single-crystal ternary cathode materials prepared in Examples 1 and 4 and Comparative Example 3. Figure 4 It can be seen that the high-nickel single-crystal ternary cathode materials prepared in Examples 1-3 all have good cycle performance, while those in Comparative Examples 1 and 2 are poor. This indicates that the ratio of high-temperature forming time to low-temperature repair time is within the range of this application, which can result in a better cycle retention rate of the cathode material. Conversely, it will affect the stability of the lattice structure of the cathode material, thereby leading to instability in the lithium extraction-intercalation process in the lattice. Meanwhile, through... Figure 5 It can be seen that as the heating rate increases (Comparative Example 3), the cycle retention rate of the cathode material decreases. This is mainly because the increased heating rate reduces the effective time for lithium to penetrate into the crystal lattice, resulting in increased lithium-nickel mixing in the cathode material and decreased crystal structure stability, thus affecting the high-temperature cycle performance of the cathode material.

[0114] The technical features of the above embodiments can be combined in any way. For the sake of brevity, not all possible combinations of the technical features in the above embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0115] The embodiments described above are merely illustrative of several implementation methods of this application, and while the descriptions are relatively specific and detailed, they should not be construed as limiting the scope of the invention patent. It should be noted that those skilled in the art can make various modifications and improvements without departing from the concept of this application, and these all fall within the protection scope of this application. Therefore, the protection scope of this patent application should be determined by the appended claims, and the specification and drawings can be used to interpret the scope of the claims.

Claims

1. A method for preparing a single-crystal ternary cathode material, characterized in that, Includes the following steps: The compound containing the first transition metal element is mixed with a ternary cathode material precursor and a lithium source, and then sintered once in an oxygen-containing atmosphere to obtain the single-crystal ternary cathode material; the conditions for the first sintering are as follows: First, the temperature is increased to 830℃~900℃ at a heating rate of 1.8℃ / min~2.8℃ / min, and held at that temperature for t1. Then, the temperature is decreased to 720℃~780℃ and held at that temperature for t2. The ratio of t1 to t2 is (0.22~0.35):1, where 3.4 h≤t1≤4.8 h and 13.7 h≤t2≤15.1 h. The oxygen-containing atmosphere is characterized by oxygen comprising at least 99% of the total gas mass.

2. The method for preparing the single-crystal ternary cathode material as described in claim 1, characterized in that, The chemical formula of the ternary cathode material precursor is Ni x Co y Mn 1-x-y (OH)2, wherein 0.9≤x≤0.98, 0.005≤y≤0.1, and x+y<1.

3. The method of producing a single-crystal ternary cathode material according to claim 1 or 2, characterized in that, The mass ratio of the ternary cathode material precursor, the lithium source, and the compound containing the first transition metal element is 100:(42~52):(1.0~1.4).

4. The method for preparing the single-crystal ternary cathode material as described in claim 1 or 2, characterized in that, The process further includes, after the first sintering, mixing the single-crystal ternary cathode material with a compound containing a second transition metal element and performing a second sintering under an oxygen-containing atmosphere, so as to coat the second transition metal element onto the surface of the single-crystal ternary cathode material.

5. The method for preparing the single-crystal ternary cathode material as described in claim 4, characterized in that, The mass ratio between the ternary cathode material and the compound containing the second transition metal element is 100:(0.36~0.56).

6. The method for preparing the single-crystal ternary cathode material as described in claim 4, characterized in that, The secondary sintering temperature is 300℃~500℃, and the holding time is 6 h~11 h.

7. The method for preparing the single-crystal ternary cathode material as described in claim 4, characterized in that, The compound containing a first transition metal element and the compound containing a second transition metal element each independently include one or more of zirconium oxide, titanium oxide, magnesium oxide, aluminum oxide, tungsten oxide, vanadium oxide, yttrium oxide, and strontium oxide.

8. The method for preparing the single-crystal ternary cathode material as described in claim 4, characterized in that, Before mixing the single-crystal ternary cathode material with a compound containing a second transition metal element, the process further includes a step of crushing and sieving the single-crystal ternary cathode material to control the particle size D50 of the single-crystal ternary cathode material to be 3.0 μm to 4.0 μm.

9. A single-crystal ternary cathode material, characterized in that, It is prepared by the method for preparing single-crystal ternary cathode material as described in any one of claims 1 to 8.

10. A lithium battery, characterized in that, Including the single-crystal ternary cathode material as described in claim 9.

11. An electrical appliance, characterized in that, Including the lithium battery of claim 10.

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