A highly dispersed medium-high nickel single-crystal ternary cathode material, its preparation method, and a lithium-ion battery.

Abstract

This invention relates to a highly dispersed medium-high nickel single-crystal ternary cathode material, its preparation method, and a lithium-ion battery. The medium-high nickel single-crystal ternary cathode material comprises single-crystal matrix particles, a symbiotic intermediate layer enriched at the interface of the single-crystal matrix particles, and a lithium fluorine-cobalt compound coating layer covering the surface of the symbiotic intermediate layer. The preparation method includes: mixing a nickel-cobalt-manganese hydroxide precursor, a lithium source, and a high-valence dopant, sintering, cooling, crushing, and sieving to obtain a highly dispersed primary sintered material; then mixing the obtained primary sintered material with a coating agent, sintering, crushing, and sieving to obtain the highly dispersed medium-high nickel single-crystal ternary cathode material. This invention can prevent excessive fusion at the interface of the single-crystal matrix particles, ensure that the primary sintered material is easily crushed and dissociated, avoid affecting subsequent coating processes, and avoid the wastewater problems caused by molten salt washing and the problems of short cycle life and low capacity under high voltage and high temperature due to particle interface degradation.

Description

Technical Field

[0001] This invention relates to the field of battery technology, and in particular to a highly dispersed medium-high nickel single-crystal ternary cathode material, its preparation method, and a lithium-ion battery. Background Technology

[0002] With the rapid development of new energy vehicles, portable electronic devices, and large-scale energy storage systems, lithium-ion batteries, as core energy carriers, face increasingly higher requirements for energy density and cycle life. The choice of cathode material for lithium-ion batteries directly affects battery performance. As a leading cathode material for lithium-ion batteries, ternary materials (often abbreviated as NCM) have attracted much attention due to their superior energy density. When the nickel content in this material reaches or exceeds 0.6%, it is classified as a medium-high nickel ternary cathode material. This type of material has become a research hotspot in recent years.

[0003] High-nickel ternary cathode materials primarily achieve higher energy density by increasing the cutoff voltage. To maintain stability under high-voltage systems, single-crystalization is often necessary to achieve longer cycle life. Currently, single-crystal ternary cathode materials are mainly prepared through high-temperature solid-state sintering, followed by deagglomeration via airflow fragmentation. However, single-crystal ternary materials prepared by traditional high-temperature solid-state methods often suffer from severe agglomeration and excessive fusion at the particle interface, preventing complete dissociation of single-crystal particles and affecting subsequent coating effects, thus leading to a decline in the material's electrical performance. Alternatively, single-crystal ternary cathode materials can be prepared using molten salt synthesis. This method primarily uses molten salt to lower the melting point of the reaction system to prepare highly dispersed ternary cathode materials. However, this method often requires water washing to remove molten salt impurities from the particle surface, increasing production costs and often causing structural lithium to leach out during washing, degrading the interface and resulting in a decrease in the material's electrical performance. Summary of the Invention

[0004] The purpose of this invention is to provide a highly dispersed medium-high nickel single-crystal ternary cathode material, its preparation method, and a lithium-ion battery, aiming to solve the problems of short cycle life and low capacity of current medium-high nickel ternary cathode materials under high voltage and high temperature.

[0005] To achieve the above objectives, the present invention adopts the following technical solution: Firstly, the present invention proposes a highly dispersed, medium-high nickel single-crystal ternary cathode material, comprising single-crystal matrix particles, a symbiotic intermediate layer enriched at the interface of the single-crystal matrix particles, and a lithium-fluorine-cobalt compound coating layer covering the surface of the symbiotic intermediate layer; the chemical formula of the single-crystal matrix particles is LiNi. x Co y Mn 1-x-yO2, 0.60≤x≤0.95, 0.05≤y≤0.20, and x+y<1; the chemical formula of the intermediate layer of the symbiotic structure is Li2MO4-Li 4+z Ni 1-z MO6, 0≤z≤0.1, where M is selected from at least one of W, Mo, Mn and Cr.

[0006] Through extensive experiments, the inventors discovered that in medium-to-high nickel systems, high-valence doping element M is difficult to completely dope into the bulk phase. It can only form a symbiotic intermediate layer (equivalent to a shallow doping and coating structure). The symbiotic intermediate layer enriched at the interface of single-crystal matrix particles can not only prevent excessive fusion at the single-crystal matrix particle interface, but also effectively suppress harmful phase transitions in ternary cathode materials during charge and discharge, reduce lattice shrinkage and microcrack formation, and enhance the mechanical stability and electrochemical activity of ternary cathode materials, thereby improving the cycle life and capacity of ternary cathode materials under high temperature and high voltage.

[0007] Preferably, the particle size distribution span of the single-crystal matrix particles [(D90-D10) / D50] < 1.0. The single-crystal matrix particles are uniform in size and highly dispersed, which is beneficial for constructing a more complete coating layer, has high mechanical strength, and facilitates more uniform Li+ insertion / extraction during high-voltage charge and discharge processes, thus extending the cycle life of the single-crystal ternary cathode material.

[0008] Preferably, the thickness of the intermediate layer of the symbiotic structure is 1~10nm.

[0009] Preferably, the thickness of the lithium fluorine cobalt compound coating layer is 1~100 nm.

[0010] Secondly, this invention proposes a method for preparing the highly dispersed, high-nickel single-crystal ternary cathode material, comprising the following steps: mixing a nickel-cobalt-manganese hydroxide precursor, a lithium source, and a high-valence dopant; after mixing, transferring the mixture into an alumina crucible, placing it in a muffle furnace, heating it to 500-800°C at a heating rate of 3°C / min, holding it at that temperature for 3-5 hours, heating it to 900-1100°C at a heating rate of 3°C / min, holding it at that temperature for 1-3 hours, and then cooling it down at a rate of 3°C / min. The material is cooled to 650-850℃ and held at that temperature for 6-8 hours, then allowed to cool naturally to room temperature. It is then removed, crushed, and sieved to obtain highly dispersed primary sintered material. This primary sintered material is mixed with a coating agent. After mixing, the mixture is transferred to a corundum sagger and placed in a muffle furnace. The temperature is increased to 450-850℃ at a rate of 2℃ / min and held for 6-12 hours. The material is then removed, crushed, and sieved to obtain secondary sintered material, i.e., highly dispersed medium-high nickel single-crystal ternary cathode material.

[0011] This invention employs a high-temperature solid-state sintering method to prepare highly dispersed, medium-to-high nickel single-crystal ternary cathode materials. During the preparation process, the lithium source reacts with a high-valence dopant to obtain Li₂MO₄, and the lithium source, high-valence dopant, and Ni on the surface of the nickel-cobalt-manganese hydroxide precursor react to obtain Li. 4+x Ni 1-x MO6 and the other two are enriched in a symbiotic structure at the particle interface of the single crystal matrix, which prevents excessive fusion of the particle interface, ensures that the material sintered in the first stage is easy to crush and dissociate, avoids affecting the subsequent coating process, and avoids the wastewater problem caused by molten salt washing and the problem of electrical performance degradation caused by particle interface deterioration.

[0012] Preferably, the molar ratio of total nickel, cobalt, and manganese metals (Me) to Li in the nickel-cobalt-manganese hydroxide precursor is 1.000:1.000~1.090, i.e., Li / Me=1.000~1.090.

[0013] Preferably, the amount of the high-valence dopant added is 500~8000ppm, and the high-valence dopant is selected from WO2, WO3, H2WO4, Li2WO4, Na2WO4, CaWO4, (NH4)6W7O. 26 *6H2O, MoO3, H2MoO4, Na2MoO4, (NH4)6Mo7O 26 *At least one of the following: 6H₂O, K₂MnO₄, Na₂MnO₄, Li₂MnO₄, BaMnO₄, Na₂CrO₄, K₂CrO₄, SrCrO₄, BaCrO₄, (NH₄)₂Cr₂O₇, and CrO₃. When the amount of high-valence dopant added is too small, its effect on improving excessive fusion at the particle interface is poor. Conversely, when the amount of high-valence dopant added is too large, its effect on improving excessive fusion at the particle interface is too strong, resulting in excessively small particle sizes. This leads to degradation of the particle interface during cycling, thereby causing a decrease in electrical performance.

[0014] Preferably, the lithium source is one or a mixture of Li₂CO₃ and LiOH. More preferably, the lithium source is LiOH. As a strong base, LiOH reacts more readily with H₂WO₄. Furthermore, due to its lower melting point, LiOH can carry M element into the particle interface during the reaction, allowing the symbiotic intermediate layer to be more uniformly distributed at the single-crystal matrix particle interface.

[0015] Preferably, the coating agent comprises nano-fluoride, low-melting-point lithium compound, and nano-cobalt compound; the nano-fluoride is selected from one or two of LiF, NaF, CaF2, MgF2, and AlF3, and the coating amount is 500-5000 ppm; the low-melting-point lithium compound is selected from one of LiOH, LiNO3, LiCl, LiBr, and LiI, and the coating amount is 500-10000 ppm; the nano-cobalt compound is selected from one of CoOOH, Co(OH)2, CoCO3, CoC2O4, and Co(CH3COO)2*4H2O, and the coating amount is 1000-50000 ppm. The nano-fluoride acts as a passivator, protecting the material from HF corrosion; the low-melting-point lithium compound melts the coating agent, making the coating layer more uniform and repairing surface defects caused by breakage; the nano-cobalt compound enriches the surface with cobalt, improving the material's conductivity, increasing its capacity, and reducing the impact of the fluoride passivation layer on the reduction of material capacity.

[0016] Thirdly, the present invention proposes a lithium-ion battery comprising the aforementioned highly dispersed medium-high nickel single-crystal ternary cathode material.

[0017] The beneficial effects of this invention are as follows: This invention uses a high-temperature solid-state sintering method to prepare highly dispersed medium-high nickel single-crystal ternary cathode material. During the preparation process, the high-valence dopant reacts with the lithium source to obtain Li₂MO₄, and simultaneously, the high-valence dopant reacts with the lithium source and Ni on the surface of the nickel-cobalt-manganese hydroxide precursor to obtain Li. 4+x Ni 1-x MO6 and its components coexist in a symbiotic structure at the interface of single-crystal matrix particles, preventing excessive fusion at the particle interface and ensuring easy crushing and dissociation of the primary sintered material, thus avoiding impact on subsequent coating processes. Furthermore, the symbiotic intermediate layer enriched at the single-crystal matrix particle interface effectively suppresses harmful phase transitions in the ternary cathode material during charge and discharge, reduces lattice shrinkage and microcrack formation, and enhances the mechanical stability and electrochemical activity of the ternary cathode material, thereby improving its cycle life and capacity under high temperature and high voltage. In addition, this invention also coats the primary sintered material to form a uniform and complete lithium fluorine cobalt compound coating layer, which improves both the material's conductivity and capacity. Attached Figure Description

[0018] Figure 1 This is a scanning electron microscope image of the product (unbroken) obtained after sintering the material and coating agent in Comparative Example 5.

[0019] Figure 2 This is a scanning electron microscope image of the product (unbroken) obtained after sintering the material and coating agent in Example 11.

[0020] Figure 3This is a scanning electron microscope image of the single-crystal ternary cathode material (broken) in Comparative Example 5;

[0021] Figure 4 This is a scanning electron microscope image of the single-crystal ternary cathode material (broken) in Example 11. Detailed Implementation

[0022] The present invention will be further described in detail below with reference to specific embodiments and accompanying drawings, but the embodiments of the present invention are not limited thereto.

[0023] Example 1

[0024] A method for preparing a highly dispersed, high-nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24 (OH)2 and lithium source LiOH were mixed with 5000 ppm of high-valence dopant H2WO4 at a Li / Me ratio of 1.050. After uniform mixing, the mixture was transferred to a corundum crucible and placed in a muffle furnace. The temperature was increased to 500℃ at a rate of 3℃ / min and held for 3 hours. Then, the temperature was increased to 1000℃ at a rate of 3℃ / min and held for 1 hour. Finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 9 hours. The mixture was then allowed to cool naturally to room temperature. Afterward, it was removed, crushed, and sieved to obtain... A highly dispersed primary sintering material was obtained. The obtained primary sintering material was mixed with coating agents LiF (coating amount of 1000ppm), LiOH (coating amount of 1000ppm), and CoOOH (coating amount of 5000ppm). After mixing, the mixture was transferred into a corundum sagger and placed in a muffle furnace. The temperature was increased to 680℃ at a heating rate of 2℃ / min and held at that temperature for 9 hours. The mixture was then allowed to cool naturally to room temperature. It was then removed, crushed, and sieved to obtain a highly dispersed medium-high nickel single crystal ternary cathode material.

[0025] Example 2

[0026] Unlike Example 1, in this example, the amount of high-valence dopant H2WO4 added is 3000ppm, and Li / Me = 1.020.

[0027] The rest is the same as in Example 1, and will not be repeated here.

[0028] Example 3

[0029] Unlike Example 1, in this example, the amount of high-valence dopant H2WO4 added is 3000ppm, and Li / Me = 1.080.

[0030] The rest is the same as in Example 1, and will not be repeated here.

[0031] Example 4

[0032] Unlike Example 1, in this example, the amount of high-valence dopant H2WO4 added is 8000ppm, and Li / Me = 1.020.

[0033] The rest is the same as in Example 1, and will not be repeated here.

[0034] Example 5

[0035] Unlike Example 1, in this example, the amount of high-valence dopant H2WO4 added is 8000ppm, and Li / Me = 1.080.

[0036] The rest is the same as in Example 1, and will not be repeated here.

[0037] Example 6

[0038] Unlike Example 1, in this example, the lithium source is Li2CO3.

[0039] The rest is the same as in Example 1, and will not be repeated here.

[0040] Example 7

[0041] Unlike Example 1, in this example, the lithium source is Li2CO3 and the high-valence dopant is MoO3.

[0042] The rest is the same as in Example 1, and will not be repeated here.

[0043] Example 8

[0044] Unlike Example 1, in this example, the lithium source is Li2CO3 and the high-valence dopant is WO3.

[0045] The rest is the same as in Example 1, and will not be repeated here.

[0046] Example 9

[0047] Unlike Example 1, in this example, the high-valence dopant is Li2WO4.

[0048] The rest is the same as in Example 1, and will not be repeated here.

[0049] Example 10

[0050] Unlike Example 1, in this example, the high-valence dopant is a mixture of H2WO4 and MoO3 in a mass ratio of 1:1.

[0051] The rest is the same as in Example 1, and will not be repeated here.

[0052] Example 11

[0053] Unlike Example 1, in this example, the coating agent LiF is replaced by a mixture of LiF and MgF2 in a mass ratio of 1:1.

[0054] The rest is the same as in Example 1, and will not be repeated here.

[0055] Example 12

[0056] Unlike Example 1, in this example, the coating agent LiOH is replaced with LiNO3.

[0057] The rest is the same as in Example 1, and will not be repeated here.

[0058] Comparative Example 1

[0059] A method for preparing a medium-high nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24 (OH)2 and lithium source LiOH are mixed at a ratio of Li / Me=1.050. After uniform mixing, the mixture is transferred to a corundum crucible and placed in a muffle furnace. The temperature is increased to 500℃ at a heating rate of 3℃ / min and held for 3 hours. The temperature is then increased to 1000℃ at a heating rate of 3℃ / min and held for 1 hour. The temperature is then decreased to 800℃ at a cooling rate of 3℃ / min and held for 9 hours. The mixture is then allowed to cool naturally to room temperature. After that, it is taken out, crushed, and sieved to obtain a medium-high nickel single crystal ternary cathode material.

[0060] Comparative Example 2

[0061] A method for preparing a medium-high nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24 (OH)2 and lithium source LiOH are mixed at a ratio of Li / Me = 1.050. After uniform mixing, the mixture is transferred to an alumina crucible and placed in a muffle furnace. The temperature is increased to 500℃ at a rate of 3℃ / min and held for 3 hours. Then, the temperature is increased to 1000℃ at a rate of 3℃ / min and held for 1 hour. Finally, the temperature is decreased to 800℃ at a rate of 3℃ / min and held for 9 hours. The mixture is then allowed to cool naturally to room temperature. After cooling, the mixture is removed, crushed, and sieved to obtain the primary sintered material. The primary sintered material is then mixed with a coating agent LiF (coating amount of 1000ppm). After mixing, the mixture is transferred to an alumina crucible and placed in a muffle furnace. The temperature is increased to 680℃ at a rate of 2℃ / min and held for 9 hours. The mixture is then allowed to cool naturally to room temperature. After cooling, the mixture is removed, crushed, and sieved to obtain LiF-coated medium-high nickel single crystal ternary cathode material.

[0062] Comparative Example 3

[0063] A method for preparing a medium-high nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24 (OH)2 and lithium source LiOH were mixed at a ratio of Li / Me = 1.050. After uniform mixing, the mixture was transferred to an alumina crucible and placed in a muffle furnace. The temperature was increased to 500℃ at a rate of 3℃ / min and held for 3 hours. Then, the temperature was increased to 1000℃ at a rate of 3℃ / min and held for 1 hour. Finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 9 hours. The mixture was then allowed to cool naturally to room temperature. The material was then removed, crushed, and sieved to obtain the primary sintered material. The primary sintered material was then mixed with a coating agent MgF2 (coating amount of 1000ppm). After mixing, the mixture was transferred to an alumina crucible and placed in a muffle furnace. The temperature was increased to 680℃ at a rate of 2℃ / min and held for 9 hours. The mixture was then allowed to cool naturally to room temperature. The material was then removed, crushed, and sieved to obtain MgF2-coated medium-high nickel single crystal ternary cathode material.

[0064] Comparative Example 4

[0065] A method for preparing a medium-high nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24 (OH)2 and lithium source LiOH are mixed at a ratio of Li / Me=1.050. After uniform mixing, the mixture is transferred to a corundum sagger and placed in a muffle furnace. The temperature is increased to 500℃ at a heating rate of 3℃ / min and held for 3 hours. The temperature is then increased to 1000℃ at a heating rate of 3℃ / min and held for 1 hour. The temperature is then decreased to 800℃ at a cooling rate of 3℃ / min and held for 9 hours. The mixture is then allowed to cool naturally to room temperature. After that, it is taken out, crushed, and sieved to obtain the primary sintered material.

[0066] The obtained primary sintered material was mixed with coating agents MgF2 (coating amount of 1000ppm) and LiOH (coating amount of 1000ppm). After mixing, the mixture was transferred into a corundum sagger and placed in a muffle furnace. The temperature was increased to 680℃ at a heating rate of 2℃ / min and held at that temperature for 9 hours. After naturally cooling to room temperature, the material was removed, crushed, and sieved to obtain a medium-high nickel single crystal ternary cathode material coated with MgF2 and LiOH.

[0067] Comparative Example 5

[0068] A method for preparing a medium-high nickel single-crystal ternary cathode material includes the following steps: preparing a nickel-cobalt-manganese hydroxide precursor Ni... 0.69 Co 0.07 Mn 0.24(OH)2 and lithium source LiOH were mixed at a Li / Me ratio of 1.050. After uniform mixing, the mixture was transferred to a corundum crucible and placed in a muffle furnace. The temperature was increased to 500℃ at a rate of 3℃ / min and held for 3 hours. Then, the temperature was increased to 1000℃ at a rate of 3℃ / min and held for 1 hour. Finally, the temperature was decreased to 800℃ at a rate of 3℃ / min and held for 9 hours. The mixture was then allowed to cool naturally to room temperature. Afterward, it was removed, crushed, and sieved to obtain the primary sintered material. The primary sintering material was mixed with coating agents MgF2 (1000ppm), LiOH (1000ppm), and CoOOH (5000ppm). After mixing, the mixture was transferred to a corundum sagger and placed in a muffle furnace. The temperature was increased to 680℃ at a rate of 2℃ / min and held at that temperature for 9 hours. The mixture was then allowed to cool naturally to room temperature. It was then removed, crushed, and sieved to obtain a medium-high nickel single-crystal ternary cathode material coated with Mg, F, and Co.

[0069] Comparative Example 6

[0070] Unlike Example 1, in this comparative example, the high-valence dopant H2WO4 is replaced with dopant MgO.

[0071] The rest is the same as in Example 1, and will not be repeated here.

[0072] Comparative Example 7

[0073] Unlike Example 1, in this comparative example, the high-valence dopant H2WO4 is replaced with dopant Al2O3.

[0074] The rest is the same as in Example 1, and will not be repeated here.

[0075] Comparative Example 8

[0076] The difference from Example 1 is that in this comparative example, the sintering process of the sintered material is as follows: heating at a rate of 3°C / min to 500°C, holding at that temperature for 3 hours, heating at a rate of 3°C / min to 1000°C, holding at that temperature for 1 hour, and cooling at a rate of 3°C / min to 750-850°C, holding at that temperature for 8 hours. This is replaced by heating at a rate of 3°C / min to 500°C, heating at a rate of 3°C / min to 950°C, and holding at that temperature for 10 hours.

[0077] The rest is the same as in Example 1, and will not be repeated here.

[0078] Comparative Example 9

[0079] Unlike Example 1, in this comparative example, the nickel-cobalt-manganese hydroxide precursor Ni 0.69 Co 0.07 Mn 0.24 (OH)2 is replaced with Ni0.33 Co 0.33 Mn 0.33 (OH)2.

[0080] The rest is the same as in Example 1, and will not be repeated here.

[0081] 1. Particle size test

[0082] Take 0.5g of the ternary cathode material prepared in Examples 1-12 and Comparative Examples 1-9 respectively and place it in a beaker. Add deionized water and sodium hexametaphosphate dispersant and stir evenly. After sonication for 2 minutes, use an Omec particle size analyzer to test it. D50 represents the particle size corresponding to the cumulative distribution ratio of 50% in the system. PSD represents the particle size distribution. The smaller the value, the more uniform the particle size and the better the degree of particle dissociation.

[0083] 2. Electrical performance testing

[0084] The ternary cathode materials prepared in Examples 1-12 and Comparative Examples 1-9 were ground thoroughly with conductive carbon black and binder PVDF in a mass ratio of 92:5:3 (total mass 15g). Then, 12mL of NMP was added and ground into a slurry. The slurry was then uniformly coated onto aluminum foil to form an electrode sheet. The electrode sheet was placed in a 120℃ drying oven and baked for 12h. It was then rolled and punched into the required size of the positive electrode sheet for the coin cell.

[0085] Using lithium metal sheets as the counter electrode, ternary cathode materials, commonly used electrolytes, and double-sided ceramic-coated separators, CR2016 button batteries were assembled in an argon-filled glove box.

[0086] The coin cell batteries were subjected to electrical performance tests. The capacity test was conducted at a rate of 0.1C, with a test temperature of 25℃ and a charge / discharge range of 3.0 to 4.5V. The high-temperature cycle performance test was conducted at a rate of 1C, with a test temperature of 45℃ and a charge / discharge range of 3.0 to 4.5V.

[0087] The performance test results are shown in Table 1.

[0088]

[0089] As shown in Table 1, the particle size distribution of the medium-high nickel single-crystal ternary cathode material prepared by the method of this invention is relatively small. This means that the medium-high nickel single-crystal ternary cathode material of this invention has uniform particle size, good particle dissociation, and high dispersibility. Furthermore, the lithium-ion batteries prepared using the highly dispersed medium-high nickel single-crystal ternary cathode materials of Examples 1-12 of this invention also have relatively high discharge capacity and cycle retention. A comparison of the examples shows that when at least one of the lithium source, high-valence dopant, and its content is different, the performance of the prepared medium-high nickel ternary cathode material also varies. Specifically, a comparison of Examples 1 and 6 shows that when the lithium source is LiCO3, the particle size distribution is significantly increased. This means that the particle size is not as uniform as in Example 1. This is because Example 1 uses LiOH as the lithium source. LiOH has a low melting point and, as a strong alkali, its reaction with H2WO4 is the most extensive. Due to the low melting point of LiOH, it can carry M element to penetrate the particle interface during the reaction, allowing the symbiotic intermediate layer to be more uniformly distributed at the single-crystal matrix particle interface. Furthermore, a comparison between Examples 1 and Examples 2-5 shows that when the amount of high-valence dopant added is too small, its improvement effect is not obvious, while when the amount of high-valence dopant added is too large, its melting resistance is too strong, and the generated medium-high nickel single crystal ternary cathode material particles are too small, which will lead to particle interface deterioration during cycling, and thus lead to a decrease in electrical performance.

[0090] Specifically, a comparison between Example 1 and Comparative Example 1 shows that the medium-high nickel single-crystal ternary cathode material prepared without the addition of high-valence dopants and coating agents exhibits a significantly increased particle size distribution and a significantly reduced capacity retention. This is because Comparative Example 1 failed to form a symbiotic intermediate layer and a lithium fluorine cobalt compound coating layer on the surface of the single-crystal matrix particles, resulting in excessive fusion at the particle interface, hindering dispersion and dissociation, leading to particle agglomeration, poor dispersibility, and further degradation of the particle interface, which in turn causes a decrease in electrical performance.

[0091] Similarly, a comparison of Example 1 and Comparative Examples 2-5 shows that the particle size distribution of the medium-high nickel single-crystal ternary cathode material prepared without the addition of high-valence dopants is significantly increased. However, unlike Comparative Example 1, Comparative Examples 2-5 involved surface coating treatment, therefore, their capacity retention rate only decreased slightly. In other words, surface coating of single-crystal matrix particles can improve the electrical performance of the material.

[0092] As can be seen from the comparison between Example 1 and Comparative Examples 6-7, when conventional metal dopants are added instead of high-valence dopants during preparation, the low-valence metal ions have small radii and tend to be bulk doped, and cannot form an intermediate phase structure at the interface. Therefore, they cannot protect the particle interface and prevent excessive fusion of the single crystal matrix particle interface.

[0093] Furthermore, a comparison between Example 1 and Comparative Example 8 shows that the D50 value and cycle capacity retention of Comparative Example 8 are significantly smaller. This is because, in the medium-high nickel system, high-valence dopants are difficult to completely dop into the bulk phase and can only form a symbiotic intermediate layer (equivalent to a shallow doping and coating structure). At this time, the symbiotic intermediate layer at the enrichment interface mainly plays the role of preventing particle fusion and growth. When the sintering reaction temperature is increased, it can promote particle growth. However, Comparative Example 8 uses a conventional sintering process, which does not reach 1000°C and is held at that temperature for 1 hour. Therefore, its particles are smaller, and the side reactions between the particles and the electrolyte increase, resulting in poorer cycle performance.

[0094] As can be seen from the comparison between Example 1 and Comparative Example 9, the performance of the nickel-cobalt-manganese hydroxide precursor deteriorates significantly when the contents of Ni, Co, and Mn are changed. The inventors discovered during the experiment that, with increased Co and Mn contents, the high-valence dopants completely diffuse into the interior of the single-crystal matrix particles, failing to form a symbiotic intermediate layer. This results in an inability to effectively suppress harmful phase transitions in the ternary cathode material during charge and discharge, reduce lattice shrinkage and microcrack formation, and consequently lead to performance degradation.

[0095] In addition, by Figure 1 and Figure 2 A comparison of the two shows that the high-nickel single-crystal ternary cathode material in Example 11 exhibits significant interface separation after doping with high-valence elements, with the "grooves" between particles becoming deeper and more pronounced; similarly, the high-nickel single-crystal ternary cathode material in Example 11 shows... Figure 3 and Figure 4 A comparison of the two materials shows that the high-nickel single-crystal ternary cathode material of Example 11 exhibits higher particle dispersion after doping with high-valence elements, while the high-nickel single-crystal ternary cathode material of Comparative Example 5, without high-valence elements, shows more severe particle adhesion and lower dispersion compared to Example 11. This is because, during the primary sintering material preparation process, the high-valence dopant reacts with the lithium source to form Li₂MO₄, and simultaneously, the high-valence dopant reacts with the lithium source and Ni on the surface of the nickel-cobalt-manganese hydroxide precursor to form Li. 4+x Ni 1-x MO6 and the other two are enriched in a symbiotic structure at the interface of single crystal matrix particles, preventing excessive fusion of the particle interface and ensuring that the material sintered in one step is easy to crush and dissociate.

[0096] Based on the disclosure and teachings of the foregoing specification, those skilled in the art can make changes and modifications to the above embodiments. Therefore, the present invention is not limited to the specific embodiments described above, and any obvious improvements, substitutions, or modifications made by those skilled in the art based on the present invention are within the scope of protection of the present invention. Furthermore, although some specific terms are used in this specification, these terms are only for convenience of explanation and do not constitute any limitation on the present invention.

Claims

1. A highly dispersed, medium-high nickel single-crystal ternary cathode material, characterized in that, It includes single-crystal matrix particles, a symbiotic intermediate layer enriched at the interface of the single-crystal matrix particles, and a lithium-fluorine-cobalt compound coating layer covering the surface of the symbiotic intermediate layer; the chemical formula of the single-crystal matrix particles is LiNi. x Co y Mn 1-x-y O2, 0.60≤x≤0.95, 0.05≤y≤0.20, and x+y<1; the chemical formula of the intermediate layer of the symbiotic structure is Li2MO4-Li 4+z Ni 1-z MO6, 0≤z≤0.1, M is selected from at least one of W, Mo, Mn and Cr; the thickness of the intermediate layer of the symbiotic structure is 1~10nm.

2. The highly dispersed, high-nickel single-crystal ternary cathode material according to claim 1, characterized in that, The particle size distribution span of the single crystal matrix particles [(D90-D10) / D50] < 1.

0.

3. The highly dispersed, high-nickel single-crystal ternary cathode material according to claim 1, characterized in that, The thickness of the lithium fluorine cobalt compound coating layer is 1~100 nm.

4. A method for preparing a highly dispersed, medium-high nickel single-crystal ternary cathode material according to any one of claims 1 to 3, characterized in that, The process includes the following steps: mixing a nickel-cobalt-manganese hydroxide precursor, a lithium source, and a high-valence dopant; after mixing, transferring the mixture into a corundum crucible and placing it in a muffle furnace; heating at a rate of 3°C / min to 500-800°C and holding at that temperature for 3-5 hours; then heating at a rate of 3°C / min to 900-1100°C and holding at that temperature for 1-3 hours; finally cooling at a rate of 3°C / min to 650-850°C and holding at that temperature for 6-8 hours; and finally allowing it to cool naturally to room temperature. The resulting material is then removed, crushed, and sieved to obtain a highly dispersed primary sintered material. The primary sintering material is mixed with the coating agent. After mixing, the mixture is transferred to a corundum sagger and placed in a muffle furnace. The temperature is increased to 450℃~850℃ at a rate of 2℃ / min and held at this temperature for 6~12 hours. The mixture is then removed, crushed, and sieved to obtain the secondary sintering material, namely, a highly dispersible medium-high nickel single crystal ternary cathode material. The amount of high-valence dopant added is 500~8000ppm, and the high-valence dopant is selected from WO2, WO3, H2WO4, Li2WO4, Na2WO4, CaWO4, and (NH4)6W7O. 26 *6H2O, MoO3, H2MoO4, Na2MoO4, (NH4)6Mo7O 26 At least one of the following: *6H2O, K2MnO4, Na2MnO4, Li2MnO4, BaMnO4, Na2CrO4, K2CrO4, SrCrO4, BaCrO4, (NH4)2Cr2O7, and CrO3.

5. The method for preparing the highly dispersed, high-nickel single-crystal ternary cathode material according to claim 4, characterized in that, The ratio of the total molar number of nickel, cobalt, and manganese (Me) in the nickel-cobalt-manganese hydroxide precursor to the molar number of Li is 1.000:1.000~1.090, i.e., Li / Me=1.000~1.

090.

6. The method for preparing the highly dispersed, high-nickel single-crystal ternary cathode material according to claim 4, characterized in that, The lithium source is one or a mixture of Li2CO3 and LiOH.

7. The method for preparing the highly dispersed, high-nickel single-crystal ternary cathode material according to claim 4, characterized in that, The coating agent includes nano-fluoride, low-melting-point lithium compound, and nano-cobalt compound; the nano-fluoride is selected from one or two of LiF, NaF, CaF2, MgF2, and AlF3, and the coating amount is 500-5000ppm; the low-melting-point lithium compound is selected from one of LiOH, LiNO3, LiCl, LiBr, and LiI, and the coating amount is 500-10000ppm; the nano-cobalt compound is selected from one of CoOOH, Co(OH)2, CoCO3, CoC2O4, and Co(CH3COO)2*4H2O, and the coating amount is 1000-50000ppm.

8. A lithium-ion battery, characterized in that, Including the highly dispersed medium-high nickel single-crystal ternary cathode material as described in any one of claims 1 to 3.

Images